MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Chirality' source. Mon, 06 Feb 2012 16:52:03 +0100 http://www.medworm.com/index.php?rid=5638956&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278758%26dopt%3DAbstract Authors: Pham NH, Wenzel TJ Abstract A sulfonated calix[4]resorcinarene containing L-pipecolinic acid groups is investigated as a water-soluble chiral NMR solvating agent. Aromatic substrates with phenyl, indole, indane, naphthyl, and pyridyl rings are analyzed. The substrates, which are water soluble because of ammonium, hydroxyl, or carboxylate functional groups, form host-guest complexes by insertion of the aromatic ring into the cavity of the calix[4]resorcinarene. Enantiomeric discrimination with the calix[4]resorcinarene derivative with L-pipecolinic acid is compared with similar reagents with proline, hydroxyproline, and α-methylproline moieties that have previously been reported. The derivative with L-pipecolinic acid often produces the best enantiomeric discrimination for... Chirality journals http://www.medworm.com/rss/comments.php?id=5638956 Wed, 25 Jan 2012 05:00:00 +0100 5638956 http://www.medworm.com/index.php?rid=5638955&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278775%26dopt%3DAbstract Authors: Enders D, Ludwig M, Raabe G Abstract The synthesis of planar chiral strong Brønsted acid organocatalysts derived from [2.2]paracyclophane is described. Resolution was accomplished according to a modified protocol involving pseudo-ortho-substituted [2.2]paracyclophane-based sulfoxides for the synthesis of three new sulfonic acids. The first planar chiral phosphoric acid diester was obtained from the corresponding phenyl-substituted diol derived from enantiopure 4-bromo-12-hydroxy [2.2]paracyclophane. These new classes of catalysts were tested in an enantioselective Friedel-Crafts reaction as well as in a direct asymmetric Mannich reaction and gave yields of up to 93% and ee-values of up to 38%. Chirality, 2012. © 2012 Wiley Periodicals, Inc. PMID: 22278775 [PubMed - a... Chirality journals http://www.medworm.com/rss/comments.php?id=5638955 Wed, 25 Jan 2012 05:00:00 +0100 5638955 http://www.medworm.com/index.php?rid=5638954&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278809%26dopt%3DAbstract Authors: Li W, Song B, Bhadury PS, Li L, Wang Z, Zhang X, Hu D, Chen Z, Zhang Y, Bai S, Wu J, Yang S Abstract A cinchona alkaloid-derived thiourea catalyst has been designed to access new asymmetric β-amino esters bearing benzothiazole moiety by utilizing a Mannich reaction between an imine and a malonate. A simultaneous activation of the two imine functionalities and malonate by the bifunctional chiral organocatalyst is proposed to account for the good yields (71-91%) and high enantiomeric excess (89.4-98.5%) under mild conditions. Chirality © 2012 Wiley Periodicals, Inc. PMID: 22278809 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5638954 Wed, 25 Jan 2012 05:00:00 +0100 5638954 http://www.medworm.com/index.php?rid=5638953&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278831%26dopt%3DAbstract Authors: Wang J, Lao J, Du Q, Nie S, Hu Z, Yan M Abstract A series of chiral pyrrolidine-sulfamides were prepared and examined as the catalysts for conjugate addition of ketones to nitroalkenes. Benzoic acid was identified as the most efficient additives for the transformation. Excellent enantioselectivities, diastereoselectivities, and yields were achieved for the reaction of cyclohexanone with β-aryl nitroethylenes under solvent free conditions. β-Isopropyl nitroethylene is also applicable and the product could be obtained with excellent enantioselectivity after extended reaction time. A comparison of the catalytic behaviors of pyrrolidine-sulfamide organocatalysts with different side chains demonstrates that the enantioselectivity is mainly controlled by the chiral pyrrolidine... Chirality journals http://www.medworm.com/rss/comments.php?id=5638953 Wed, 25 Jan 2012 05:00:00 +0100 5638953 http://www.medworm.com/index.php?rid=5638952&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278901%26dopt%3DAbstract Authors: Weng J, Ai HB, Luo RS, Lu G Abstract Several pyrrolidine-camphor derived organocatalysts were designed and synthesized. These organocatalysts were used for direct Michael reaction of aldehydes with nitroalkenes to give the desired γ-nitrocarbonyl compounds in high yields (up to 99%), high diastereoselectivities (syn:anti up to 92:8), and good to excellent enantioselectivities (up to 94% ee). Possible transition-state model was also proposed for this asymmetric transformation, which may involve hydrogen-bond interactions between the nucleophilic enamine formed in situ and the nitroalkenes. Chirality, 2012. © 2012 Wiley Periodicals, Inc. PMID: 22278901 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5638952 Wed, 25 Jan 2012 05:00:00 +0100 5638952 http://www.medworm.com/index.php?rid=5638951&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278909%26dopt%3DAbstract Authors: Zhang P, Dang Z, Shen Z, Zhu W, Xu X, Liu D, Zhou Z Abstract Hexaconazole [(RS)-2-(2,4-dichlorophenyl)-1-(1H-1,2,4-triazol-1-yl) hexan-2-ol] is a potent triazole fungicide and consists of a pair of enantiomers. Enantioselective degradation of hexaconazole was investigated in rat hepatic microsomes in vitro. Concentrations of (-)- and (+)-hexaconazole and enantiomer fraction were determined by high performance liquid chromatography with a cellulose-tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase. The t(1/2) of (-)-hexaconazole and (+)-hexaconazole were 23.70 and 13.95 min for rac- hexaconazole and 44.18 and 23.54 for enantiomers examined separately. Furthermore, hexaconazole is configurationally stable in rat hepatic microsomes, demonstrating no chiral inve... Chirality journals http://www.medworm.com/rss/comments.php?id=5638951 Wed, 25 Jan 2012 05:00:00 +0100 5638951 http://www.medworm.com/index.php?rid=5638950&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278928%26dopt%3DAbstract Authors: Sánchez-Carnerero EM, Engel TD, Maroto BL, Cerero SD Abstract The screening of the catalytic activity in the diethylzinc reaction of a series of easily accessible (1S)-ketopinic-acid derived hydroxyamides, designed by key structure modifications of a parent highly active related bis(hydroxyamide), has allowed to find the first case of dual stereoselection in highly structurally close ligands of such interesting chemically sustainable typology. The found striking dual stereoselection is explained on the basis of empiric models for the acting zinc catalysts and involved controlling transition states, which are supported by additional specific experimental structure-activity tests. Chirality, 2012. © 2012 Wiley Periodicals, Inc. PMID: 22278928 [PubMed - as supplied by p... Chirality journals http://www.medworm.com/rss/comments.php?id=5638950 Wed, 25 Jan 2012 05:00:00 +0100 5638950 http://www.medworm.com/index.php?rid=5638949&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22278951%26dopt%3DAbstract Authors: Li J, Dong F, Xu J, Liu X, Li Y, Shan W, Zheng Y Abstract A simple chiral high-performance liquid chromatography method with diode array detector was developed and validated for stereoselective determination of tetraconazole enantiomers in cucumber, muskmelon, and soils. Good separation was achieved at 20°C using cellulose tris-(4-methylbenzoate) as chiral stationary phase, a mixture of n-hexane and ethanol (90:10) as mobile phase at a flow rate of 0.8 ml/min. The assay method was linear over a range of concentrations (0.5-50 μg/ml) and the mean recoveries in all samples were more than 85% for the two enantiomers. The limits of detection for both enantiomers in plant and soil samples were 0.06 and 0.12 μg/g, respectively. Then, the proposed method was successfully appli... Chirality journals http://www.medworm.com/rss/comments.php?id=5638949 Wed, 25 Jan 2012 05:00:00 +0100 5638949 http://www.medworm.com/index.php?rid=5638962&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22271571%26dopt%3DAbstract In this study, a rapid and sensitive sampling method using headspace solid-phase microextraction (SPME) coupled to chiral gas chromatography was developed for the "on-line" analysis of chiral molecules in the IL solvent. Three different SPME sorbent coatings, namely polydimethylsiloxane, polyacrylate, and a polymeric ionic liquid-based fiber, were examined in this study. The analytical performance of the developed method was evaluated in terms of reproducibility, slope of calibration curve, linear range, calibration linearity, and the determination of detection limits. The SPME method was successfully applied in the determination of enantiomeric excess from selected mixtures of chiral molecules. A preliminary study was performed using an "on-fiber" derivatization approach revealing that th... Chirality journals http://www.medworm.com/rss/comments.php?id=5638962 Tue, 24 Jan 2012 05:00:00 +0100 5638962 http://www.medworm.com/index.php?rid=5638961&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22271587%26dopt%3DAbstract Authors: Poggi JC, Da Silva FG, Coelho EB, Marques MP, Bertucci C, Lanchote VL Abstract Carvedilol is an antihypertensive drug available as a racemic mixture. (-)-(S)-carvedilol is responsible for the nonselective β-blocker activity but both enantiomers present similar activity on α(1) -adrenergic receptor. To our knowledge, this is the first study of carvedilol enantiomers in human plasma using a chiral stationary phase column and liquid chromatography with tandem mass spectrometry. The method involves plasma extraction with diisopropyl ether using metoprolol as internal standard and direct separation of the carvedilol enantiomers on a Chirobiotic T® (Teicoplanin) column. Protonated ions [M + H](+) and their respective ion products were monitored at transitions of 407 > 100 ... Chirality journals http://www.medworm.com/rss/comments.php?id=5638961 Tue, 24 Jan 2012 05:00:00 +0100 5638961 http://www.medworm.com/index.php?rid=5638960&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22271601%26dopt%3DAbstract Authors: Zhang Y, Shi K, Wen J, Fan G, Chai Y, Hong Z Abstract Tetrahydroberberine (THB), a racemic mixture of (+)- and (-)-enantiomer, is a biologically active ingredient isolated from a traditional Chinese herb Rhizoma corydalis (yanhusuo). A chiral high performance liquid chromatography method has been developed for the determination of THB enantiomers in rat plasma. The enantioseparation was carried out on a Chiral®-AD column using methanol:ethanol (80:20, v/v) as the mobile phase at the flow rate 0.4 ml/min. The ultraviolet detection was set at 230 nm. The calibration curves were linear over the range of 0.01-2.5 μg/ml for (+)-THB and 0.01-5.0 μg/ml for (-)-THB, respectively. The lower limit of quantification was 0.01 μg/ml for both (+)-THB and (-)-THB. The stereoselective... Chirality journals http://www.medworm.com/rss/comments.php?id=5638960 Tue, 24 Jan 2012 05:00:00 +0100 5638960 http://www.medworm.com/index.php?rid=5638959&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22271616%26dopt%3DAbstract Authors: Ibrahim WA, Wahib SM, Hermawan D, Sanagi MM, Aboul-Enein HY Abstract A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) technique has been developed for enantioseparation of vinpocetine using an inexpensive 2-hydroxypropyl-β-CD (HP-β-CD) as the chiral selector (CS). The best chiral separation was achieved using 40 mM HP-β-CD as the CS in 50 mM phosphate buffer (pH 7.0) consisting of 40 mM sodium dodecyl sulfate (SDS) at a separation temperature and separation voltage of 25°C and 25 kV, respectively. To the author's best knowledge, this is the first CD-MEKC study able to successfully separate the four stereoisomer of vinpocetine in separation time of 9.5 min and resolution of 1.04-3.87. Chirality, 2012. © 2012 Wiley Periodicals, Inc. PMID: 222... Chirality journals http://www.medworm.com/rss/comments.php?id=5638959 Tue, 24 Jan 2012 05:00:00 +0100 5638959 http://www.medworm.com/index.php?rid=5638958&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22271626%26dopt%3DAbstract Authors: Deng X, De Cock B, Vervoort R, Pamperin D, Adams E, Van Schepdael A Abstract A chiral capillary electrophoresis method has been developed for the quantification of 0.1% of the enantiomeric impurity (dextrocetirizine) in levocetirizine and determination of both in pharmaceuticals using sulfated-β-cyclodextrins (CDs) as chiral selector. Several parameters affecting the separation were studied such as the type and concentration of chiral selectors, buffer composition and pH, organic modifier, mixtures of two CDs in a dual system, voltage, and temperature. The optimal separation conditions were obtained using a 50 mM tetraborate buffer (pH 8.2) containing 1% (w/v) sulfated-β-CDs on a fused-silica capillary. Under these conditions, the resolution of two enantiomers was higher... Chirality journals http://www.medworm.com/rss/comments.php?id=5638958 Tue, 24 Jan 2012 05:00:00 +0100 5638958 http://www.medworm.com/index.php?rid=5638957&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22271632%26dopt%3DAbstract Authors: Kumar BN, Murugesan V, Prakasam T, Srinivasan PS, Ramana DV Abstract (1R,2R)-1-Phenyl-1-alkyl/arylamino-2-(N-alkylamino)propane hydrochloride salts have been synthesized with high degree of enantiomeric purity from (1S,2R)-(+)-1-phenyl-2-(N-alkylamino)-1-propanol through the corresponding chloro derivatives. This reaction sequence involves three inversions with overall inversion of configuration at C-1. Chirality, 2012. © 2012 Wiley Periodicals, Inc. PMID: 22271632 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5638957 Mon, 23 Jan 2012 05:00:00 +0100 5638957 http://www.medworm.com/index.php?rid=5620817&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22253063%26dopt%3DAbstract We report the first preparation of cis-5,6-dihydro-1,10-phenanthroline derivatives by reacting triphenyl borate with the corresponding epoxide precursor. We found that solvent and temperature choice determined the stereoselectivity of the epoxide opening giving rise to the cis (14:1 dr) or trans (99:1 dr) product. Racemates of each stereoisomeric mixture, cis- and trans-phenoxy alcohol, were separated via highly enantioselective transesterifications with lipase PSCI from Burkholderia cepacia (97% ee, E > 200). Stereochemical assignments were carried out using CD and X-ray analyses in conjunction with NMR studies of α-methoxy-α-(trifluoromethyl)phenylacetic acid and α-methoxyphenylacetic acid esters. Chirality, 2012. © 2012 Wiley Periodicals, Inc. PMID: 22253063 [PubMed - as supp... Chirality journals http://www.medworm.com/rss/comments.php?id=5620817 Wed, 18 Jan 2012 05:00:00 +0100 5620817 http://www.medworm.com/index.php?rid=5512735&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139818%26dopt%3DAbstract Authors: Shen Z, Zhu W, Liu D, Xu X, Zhang P, Zhou Z Abstract The aim of this study was to assess the stereoselectivity of two tebuconazole [(RS)-1-p-chlorophenyl-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)pentan-3-ol] enantiomers in in vitro system (rat liver microsomes). The analytes were extracted with acetic ether and concentrations were determined by high performance liquid chromatography (HPLC) with a cellulose tris(3,5-dimethylphenylcarbamate)-based chiral stationary phase. The degradation of rac-tebuconazole (15 μM) followed first-order kinetics, and the degradation of the S-tebuconazole (t(1/) (2) = 22.31 min) was faster than that of the R-tebuconazole (t(1/) (2) = 48.76 min), but no significant difference between the enantiomers was found in the respective i... Chirality journals http://www.medworm.com/rss/comments.php?id=5512735 Sat, 17 Dec 2011 13:31:01 +0100 5512735 http://www.medworm.com/index.php?rid=5512734&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139827%26dopt%3DAbstract This study was aimed to explore the metabolic mechanism of chiral inversion of S-MA in vitro. S-MA was converted to R-MA in rat hepatocytes, whereas MA enantiomers remained unchanged in acidic and neutral phosphate buffers, HepG2 cells, and intestinal flora. In addition, the synthesized S-MA-CoA thioester was rapidly racemized and hydrolyzed to R-MA by rat liver homogenate and S9, cytosolic and mitochondrial fractions. The data suggest that chiral inversion of S-MA may involve the hydrolysis of S-MA-CoA, and its metabolic mechanism could be the same as that of 2-arylpropionic acid (2-APA) drugs. Chirality 24:86-95, 2012. © 2011 Wiley Periodicals, Inc. PMID: 22139827 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5512734 Sat, 17 Dec 2011 13:30:51 +0100 5512734 http://www.medworm.com/index.php?rid=5512733&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22139855%26dopt%3DAbstract On chirality transfer in electron donor-acceptor complexes. A prediction for the sulfinimine···BF(3) system. Chirality. 2012 Jan;24(1):5-16 Authors: Rode JE, Dobrowolski JC Abstract Stabilization energies of the electron donor-acceptor sulfinimine···BF(3) complexes calculated at either the B3LYP/aug-cc-pVTZ or the MP2/aug-cc-pVTZ level do not allow to judge, whether the N- or O-atom in sulfinimine is stronger electron-donor to BF(3) . The problem seems to be solvable because chirality transfer phenomenon between chiral sulfinimine and achiral BF(3) is expected to be vibrational circular dichroism (VCD) active. Moreover, the bands associated with the achiral BF(3) molecule are predicted to be the most intense in the entire spectrum. However, the VCD band robustness ana... Chirality journals http://www.medworm.com/rss/comments.php?id=5512733 Sat, 17 Dec 2011 13:30:41 +0100 5512733 http://www.medworm.com/index.php?rid=5512732&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22144292%26dopt%3DAbstract Authors: Payagala T, Armstrong DW Abstract In recent years, the field of chiral ionic liquids (CILs) has undergone exponential growth. As the technology has advanced, new ways of synthesizing stable and structurally diverse ionic liquids have been established. This has led to heretofore unknown applications of CILs as well as in improving efficiency of previously identified applications. In this review article we have compiled a comprehensive database containing structures and physical properties of notable CILs that have been synthesized during the last 6 years. Their applications in the fields of asymmetric organic synthesis, spectroscopy, and chromatography are also illustrated. This is an expansion of our previous review, which covered the literature before 2005. Chirality, 201... Chirality journals http://www.medworm.com/rss/comments.php?id=5512732 Sat, 17 Dec 2011 13:30:31 +0100 5512732 http://www.medworm.com/index.php?rid=5512731&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22173987%26dopt%3DAbstract Authors: He Q, Rohani S, Zhu J, Gomaa H Abstract The chiral discrimination mechanism in the resolution of sertraline with mandelic acid was investigated by examining the weak intermolecular interactions (such as hydrogen bond, CH/π, and van der Waals interactions) and molecular packing difference in crystal structures of the resulting diastereomeric salts. A new one-dimensional chain-like hydrogen-bonding network and unique supramolecular packing mode are disclosed. The investigation demonstrated that stable hydrogen-bonding pattern, herringbone-like arrangement of aromatic rings, and planar boundary surface in the hydrophobic region are the three most important structural characteristics expected in less soluble diastereomeric salts. The existence and magnitude of hydrogen bond, ... Chirality journals http://www.medworm.com/rss/comments.php?id=5512731 Fri, 16 Dec 2011 05:00:00 +0100 5512731 http://www.medworm.com/index.php?rid=5512730&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22173997%26dopt%3DAbstract In this study, repeated preferential crystallization of p-toluenesulfonate valine benzyl ester with a 20% e.e. in 2-propanol gave a 94% e.e. on sonication. Sonication accelerated crystallization rate, but there was not a big difference in e.e. between with and without sonication. However, this research demonstrates the first preferential crystallization of p-toluenesulfonate of valine benzyl esters with an acceleration of crystallization using sonication. Chirality, 2011. © 2011 Wiley Periodicals, Inc. PMID: 22173997 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5512730 Fri, 16 Dec 2011 05:00:00 +0100 5512730 http://www.medworm.com/index.php?rid=5455424&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22121064%26dopt%3DAbstract Authors: Sorrenti A, Altieri B, Ceccacci F, Di Profio P, Germani R, Giansanti L, Savelli G, Mancini G Abstract The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities. Chirality, 2011. © 2011 Wiley Periodicals, Inc. PMID: 22121064 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5455424 Sat, 26 Nov 2011 05:00:00 +0100 5455424 http://www.medworm.com/index.php?rid=5455423&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22121071%26dopt%3DAbstract Authors: Rasulev B, Turabekova M, Gorska M, Kulig K, Bielejewska A, Lipkowski J, Leszczynski J Abstract In this work, the enantioseparation of 15 structurally similar chiral solutes is studied, and analysis of the retention factors is performed using a genetic algorithm and multiple linear regression analysis technique. The present quantitative structure-enantioselective retention relationship model generated for retention factors' data has confirmed the importance of a number of descriptors altering the retention behavior and enantioselectivity of the studied compounds. Thus, fragment-based descriptor PSA, which encodes polar surface area, has confirmed the crucial role of heteroatoms in the retention behavior exhibited by pyrroliddin-2-ones. The presence of E(LUMO) descriptor, wh... Chirality journals http://www.medworm.com/rss/comments.php?id=5455423 Sat, 26 Nov 2011 05:00:00 +0100 5455423 http://www.medworm.com/index.php?rid=5455422&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22121077%26dopt%3DAbstract Authors: Schafer W, Hamilton SE, Pirzada Z, Welch CJ Abstract A simple approach to the automated screening of four different columns on a single gas chromatography (GC) instrument is used for rapid chiral GC method development. Configuration of a conventional GC instrument with a second autosampler and several inexpensive Y-splitters enables simultaneous evaluation of two different columns, allowing a total of four different columns to be evaluated in two automated back to back runs. The resulting system affords a simple and effective approach to chiral GC method development that speeds analysis while eliminating the need for slow and tedious manual interchange of columns. An example of developing a rapid isothermal GC method from the screening results obtained by the instrument is... Chirality journals http://www.medworm.com/rss/comments.php?id=5455422 Sat, 26 Nov 2011 05:00:00 +0100 5455422 http://www.medworm.com/index.php?rid=5379373&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22012790%26dopt%3DAbstract In this study, enantioselective degradation of warfarin in a turfgrass and a groundcover soils was examined in aerobic and ambient temperature conditions. An enantioselective analytical method was established using a novel triproline chiral stationary phase in high performance liquid chromatography. Unusual peak profile patterns, i.e., first peak (S(-)) broadening/second peak (R(+)) compression with hexane (0.1%TFA)/2-propanol (92/8, v/v) mobile phase, and first peak compression/second peak broadening with the (96/4, v/v) mobile phase, were observed in enantioseparation. This unique tunable peak property was leveraged in evaluating warfarin enantioselective degradation in two types of soil. Warfarin was extracted in high recovery from soil using methylene chloride after an aqueous phase ba... Chirality journals http://www.medworm.com/rss/comments.php?id=5379373 Thu, 20 Oct 2011 04:00:00 +0100 5379373 http://www.medworm.com/index.php?rid=5379372&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22012845%26dopt%3DAbstract Authors: Kao MF, Lu PY, Kao JY, Wang PY, Wu AC, Tsai SW Abstract The best reaction condition of Candida antartica lipase B as biocatalyst, 3-(2-pyridyl)pyrazole as leaving azole, and water-saturated methyl t-butyl ether as reaction medium at 45°C were first selected for performing the hydrolytic resolution of (R,S)-2-(4-chlorophenoxyl) azolides (1-4). In comparison with the kinetic resolution of (R,S)-2-phenylpropionyl 3-(2-pyridyl)pyrazolide or (R,S)-α-methoxyphenylacetyl 3-(2-pyridyl)pyrazolide at the same reaction condition, excellent enantioselectivity with more than two order-of-magnitudes higher activity for each enantiomer was obtained. The resolution was then extended to other (R,S)-3-(2-pyridyl)pyrazolides (5-7) containing 2-chloro, 3-chloro, or 2,4-dichloro substituent,... Chirality journals http://www.medworm.com/rss/comments.php?id=5379372 Thu, 20 Oct 2011 04:00:00 +0100 5379372 http://www.medworm.com/index.php?rid=5325870&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21997862%26dopt%3DAbstract Authors: Kudo M, Azumaya I, Kagechika H, Tanatani A Abstract Aromatic N,N'-dimethylated urea exists in (cis, cis) form, both in the crystal and in solution, and this structure can be utilized to construct intramolecular aromatic multilayered oligomers. These structures show helical conformation with all-R or all-S axis chirality, when the benzene rings are connected at the meta positions. To investigate the dynamic conformational behavior of such aromatic multilayered ureas in various solvents, we synthesized tetra(m-phenylurea) 3 bearing two chiral N-2-(methoxyethoxyethoxy)propyl groups and six N-methoxyethoxyethyl groups. The high solubility of compound 3 enabled its analysis in various solvents, including water. The CD spectra of compound 3 showed broad electronic absorption wit... Chirality journals http://www.medworm.com/rss/comments.php?id=5325870 Fri, 14 Oct 2011 04:00:00 +0100 5325870 http://www.medworm.com/index.php?rid=5325868&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21997886%26dopt%3DAbstract Authors: Kimura T, Kido S, Kamiyama T, Fujisawa M Abstract Enthalpies of mixing of R- and S-limonene in non-polar solvents in the entire range of mole fractions were measured at 298.15 K. The enthalpies of mixing were negative for all concentrations in dilute concentration, but increased by increasing the concentration of limonenes in solutions. Ultimately positive excess enthalpies were shown in high concentration. Enthalpies of mixing were compared with theoretical estimation by COSMO-RS. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21997886 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5325868 Fri, 14 Oct 2011 04:00:00 +0100 5325868 http://www.medworm.com/index.php?rid=5325867&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21997897%26dopt%3DAbstract We report here the application of subcritical water in chiral separations on two popular polysaccharide chiral stationary phases (CSPs): Chiralpak AD and Chiralcel OD. The behavior of these two CSPs was studied under reversed phase conditions at room temperature to discover the maximum percentage of water in the mobile phase, which provided the separation of enantiomers of flavanone and benzoin, respectively, in a reasonable time (i.e., less than 1 h). Then, the stability of Chiralpak AD and Chiralcel OD versus temperature was investigated and discussed. Chiralcel OD separation of flavanone racemate was obtained at 120°C with water and 2-propanol (80/20) as the mobile phase, while benzoin racemate was separated in pure water at 160°C. Separations of several racemates were also presented,... Chirality journals http://www.medworm.com/rss/comments.php?id=5325867 Fri, 14 Oct 2011 04:00:00 +0100 5325867 http://www.medworm.com/index.php?rid=5325866&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21997932%26dopt%3DAbstract Authors: Hamzic M, Pietruszka J, Sandkuhl D Abstract Enantioselective reductions are a key to successful target-oriented syntheses. Finding the most suitable conditions is often a tedious work that is especially hampered by the time-consuming analytical investigation. A possible solution is the combined use of high-performance liquid chromatography and circular dichroism to find a suitable system for providing enantiomerically pure alcohols. This investigation led to an efficient protocol for the alcohol dehydrogenase-catalyzed reduction of 1-phenyl-2-propyn-3-trimethylsilyl-1-on (1). Chirality, 2011. © 2011Wiley-Liss, Inc. PMID: 21997932 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5325866 Fri, 14 Oct 2011 04:00:00 +0100 5325866 http://www.medworm.com/index.php?rid=5229270&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21919076%26dopt%3DAbstract Authors: Bertucci C, Superchi S, Berova N PMID: 21919076 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5229270 Mon, 19 Sep 2011 09:32:38 +0100 5229270 http://www.medworm.com/index.php?rid=5229269&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21919077%26dopt%3DAbstract The objective of this study is to investigate the utility of a new class of melamine-bridged Zn-porphyrin tweezers as sensitive AC reporters. A combined approach based on an experimental CD analysis and a theoretical prediction of the prevailing interporphyrin helicity demonstrates that these tweezers display favorable properties for chiral recognition. Herein, we discuss the application of the melamine-bridged tweezer to the chiral recognition of a diverse set of chiral guests, such as 1,2-diamines, α-amino-esters and amides, secondary alcohols, and 1,2-amino-alcohols. The bulky periphery and the presence of a rigid porphyrin linkage lead, in some cases, to a more enhanced CD sensitivity than that reported earlier with other tweezers. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 2... Chirality journals http://www.medworm.com/rss/comments.php?id=5229269 Mon, 19 Sep 2011 09:32:29 +0100 5229269 http://www.medworm.com/index.php?rid=5229268&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21919078%26dopt%3DAbstract Authors: Bertucci C, De Simone A, Pistolozzi M, Rosini M Abstract Lipocrine has been selected as an effective candidate for in vivo investigation because of its multiple biological properties, namely inhibition of AChE and BChE activities, inhibition of AChE-induced Aβ aggregation, and ability to protect cells against reactive oxygen species. To evaluate the possibility for lipocrine to become a lead and to be developed as a multipotent drug for the treatment of Alzheimer's disease, ADMET (absorption, distribution, metabolism, excretion, and toxicity) parameters need to be determined. Among ADMET parameters, distribution plays a key role in determining the lead drugability, and the drug binding to plasma proteins greatly influences the drug distribution. Here, the human serum albu... Chirality journals http://www.medworm.com/rss/comments.php?id=5229268 Mon, 19 Sep 2011 09:32:20 +0100 5229268 http://www.medworm.com/index.php?rid=5229267&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21919079%26dopt%3DAbstract Authors: Cicchi S, Pescitelli G, Lascialfari L, Ghini G, Bari LD, Brandi A, Bussotti L, Atsbeha T, Marcelli A, Foggi P, Berti D, Mannini M Abstract In this work, we present the characterization of an enantiomeric pair of fluorescent dye organogelators and the properties of their stable gel at low concentration in organic solvents. The gels of both enantiomers and of their mixtures were analyzed by differential scanning calorimetry, circular dichroism (CD), atomic force microscopy, UV-vis absorption, and fluorescence. The acquired data were supported by molecular modeling of the helical assembly of the gelators and by the simulation of their CD spectra by means of DeVoe method, and suggested the occurrence of an enantiomeric discrimination process during the formation of the gels. C... Chirality journals http://www.medworm.com/rss/comments.php?id=5229267 Mon, 19 Sep 2011 09:32:11 +0100 5229267 http://www.medworm.com/index.php?rid=5218680&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21898605%26dopt%3DAbstract Authors: Abbate S, Longhi G, Gangemi F, Gangemi R, Superchi S, Caporusso AM, Ruzziconi R Abstract The IR and Near infrared (NIR) vibrational circular dichroism (VCD) spectra of molecules endowed with noncentral chirality have been investigated. Data for fundamental, first, and second overtone regions of (S)-2,3-pentadiene, exhibiting axial chirality, and methyl-d(3) (R)- and (S)-[2.2]paracyclophane-4-carboxylate, exhibiting planar chirality have been measured and analyzed. The analysis of NIR and IR VCD spectra was based on the local-mode model and the use of density functional theory (DFT), providing mechanical and electrical anharmonic terms for all CH-bonds. The comparison of experimental and calculated spectra is satisfactory and allows one to monitor fine details in the asymme... Chirality journals http://www.medworm.com/rss/comments.php?id=5218680 Wed, 07 Sep 2011 04:00:00 +0100 5218680 http://www.medworm.com/index.php?rid=5157187&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21858877%26dopt%3DAbstract This article relates the results that we obtained in the field of the total synthesis of indolizidines from α-amino acids, based on the rhodium-catalyzed hydroformylation of N-allylpyrroles intermediates. The formed pyrrolylbutanals undergo an intramolecular cyclodehydration to 5,6-dihydroindolizines, which are fully hydrogenated to indolizidines. All reaction sequences are stereocontrolled: indeed, the chiral center in the starting amino acid is transferred into 5,6-dihydroindolizine moiety with complete stereochemical integrity and the new stereogenic center at C9 carbon atom in the final indolizidines is generated in only one configuration.Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21858877 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5157187 Thu, 18 Aug 2011 23:00:00 +0100 5157187 http://www.medworm.com/index.php?rid=5157188&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21853474%26dopt%3DAbstract We describe herein the investigation of the stereodynamic processes occurring in a series of 1-aryl-2,2-dimethylindanols, by dynamic NMR. When the aryl moiety is a mesityl or a 2-methyl-1-naphthyl, the rotational barrier exceeds the 25 kcal/mol, so that stable atropisomers are observed. In two cases, all the chiral-atropisomeric species have been separated by enantioselective HPLC, and the comparison between theoretical and experimental electronic circular dichroism spectra allowed the absolute configuration assignment of all the isolated species to be obtained. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21853474 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=5157188 Wed, 17 Aug 2011 23:00:00 +0100 5157188 http://www.medworm.com/index.php?rid=5004171&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21695735%26dopt%3DAbstract Authors: Arjmand F, Sharma GC, Muddassir M, Tabassum S To evaluate the biological preference of chiral drug candidates for molecular target DNA, new potential metal-based chemotherapeutic agents 1-3 (a and b) of late 3d transition metals Ni(II), Cu(II), and Zn(II), respectively, derived from (R)- and (S)-2-amino-2-phenylethanol with CH(2) CH(2)  linker were synthesized and thoroughly characterized. Interaction studies of 1-3 (a and b) with calf thymus DNA in Tris buffer were studied by electronic absorption titrations, luminescence titrations, cyclic voltammetry, and circular dichroism. The results reveal that the extent of DNA binding of R-enantiomer of copper 1a was highest in comparison to rest of the complexes via electrostatic interaction mode. The nuclease activity of 1(... Chirality journals http://www.medworm.com/rss/comments.php?id=5004171 Thu, 07 Jul 2011 18:00:10 +0100 5004171 http://www.medworm.com/index.php?rid=5004170&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21710506%26dopt%3DAbstract We describe a test system with the chiral tris(ethylenediamine)Co(III) complex dissolved in water trapped inside sephadex particles, suspended in 1-butanol. Independent measurements of particle size distribution, volume fraction, and the absorbance of the suspension are used to calculate the required CD correction. The corrected CD signal is found to agree rather well with that for the same amount of Co-complex dispersed uniformly throughout the sample cell. This holds for different particle volume fractions and Co-complex concentrations inside the particles. The correction seems to work despite a substantial scattering contribution to the absorbance, which is not considered in the theoretical models. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21710506 [PubMed - in process] (Sourc... Chirality journals http://www.medworm.com/rss/comments.php?id=5004170 Thu, 07 Jul 2011 18:00:06 +0100 5004170 http://www.medworm.com/index.php?rid=4910308&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21633977%26dopt%3DAbstract Authors: Mori K Mori's synthetic works on bioactive natural products in general and pheromones in particular started about 40 years ago to establish their absolute configurations and also to clarify their stereochemistry-bioactivity relationships. Results indicate that bioactive natural products are not always enantiomerically pure, and the stereochemistry-bioactivity relationships are not simple but complicated. For example, neither (R)- nor (S)-sulcatol, the aggregation pheromone of an ambrosia beetle, is behaviorally bioactive, whereas their mixture is active. In the case of olean, the sex pheromone of the olive fruit fly, its (R)-isomer is active against the males and the (S)-isomer is active against the females. Recent synthesis of two new insect pheromones is discussed to illustr... Chirality journals http://www.medworm.com/rss/comments.php?id=4910308 Wed, 08 Jun 2011 23:00:10 +0100 4910308 http://www.medworm.com/index.php?rid=4910311&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21618614%26dopt%3DAbstract Authors: Pietropaolo A, Parrinello M PMID: 21618614 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4910311 Wed, 25 May 2011 23:00:00 +0100 4910311 http://www.medworm.com/index.php?rid=4910310&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21618615%26dopt%3DAbstract Authors: Jozwiak K, Plazinska A, Toll L, Jimenez L, Woo AY, Xiao RP, Wainer IW The β(2) adrenergic receptor (β(2) -AR) is a model system for studying the ligand recognition process in G protein-coupled receptors. Fenoterol (FEN) is a β(2) -AR selective agonist that has two centers of chirality and exists as four stereoisomers. Radioligand binding studies determined that stereochemistry greatly influences the binding affinity. Subsequent Van't Hoff analysis shows very different thermodynamics of binding depending on the stereoconfiguration of the molecule. The binding of (S,x')-isomers is almost entirely enthalpy controlled whereas binding of (R,x')-isomers is purely entropy driven. Stereochemistry of FEN molecule also affects the coupling of the receptor to different G proteins. In ... Chirality journals http://www.medworm.com/rss/comments.php?id=4910310 Wed, 25 May 2011 23:00:00 +0100 4910310 http://www.medworm.com/index.php?rid=4910309&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21618616%26dopt%3DAbstract Authors: Tominaga M, Azumaya I PMID: 21618616 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4910309 Wed, 25 May 2011 23:00:00 +0100 4910309 http://www.medworm.com/index.php?rid=4804582&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21462270%26dopt%3DAbstract Authors: Mirgane NA, Karnik AV (S)-(-)-2-(α-hydroxyethyl)-benzimidazole and (S)-(+)-2-(α-hydroxybenzyl)-benzimidazole work as chiral Brønsted bases (BBs) in Diels-Alder reaction between anthrone and maleimides under mild reaction condition. These chiral BBs cause asymmetric induction. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21462270 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4804582 Sat, 30 Apr 2011 23:00:00 +0100 4804582 http://www.medworm.com/index.php?rid=4804581&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21465569%26dopt%3DAbstract Authors: Marinho VR, Ramalho JP, Rodrigues AI, Burke AJ Two simple hemilabile P,O-coordinating phosphinoamidoester ligands 6a and 6b were synthesized and studied in the Pd(0)-catalyzed asymmetric allylic alkylation of rac-1,3-diphenylpropenyl acetate affording a highest ee of 83% ee with 6a. To gain an insight into the actual mechanism of this catalytic reactions, which had previously been investigated with a first generation family of P,O-coordinating phosphinoamido-alcohol ligands-4a and 4b-a semiempirical computational study was carried out with the Pd-allyl complexes formed from both 4a and 6a including Hitchcock's phosphinoamido-alcohol ligand 5 (R(1) = H, R(2) = Ph). The results of this study substantiate a working model that has previously been proposed for this reaction using h... Chirality journals http://www.medworm.com/rss/comments.php?id=4804581 Sat, 30 Apr 2011 23:00:00 +0100 4804581 http://www.medworm.com/index.php?rid=4804580&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21465570%26dopt%3DAbstract Authors: Cai YF, Li L, Luo MX, Yang KF, Lai GQ, Jiang JX, Xu LW A detailed experimental investigation of an aza-Michael reaction of aniline and chalcone is presented. A series of Cinchona alkaloid-derived organocatalysts with different functional groups were prepared and used in the aza-Michael and retro-aza-Michael reaction. There was an interesting finding that a complete reversal of stereoselectivity when a benzoyl group was introduced to the cinchonine and cinchonidine. The chirality amplification vs. time proceeds in the quinine-derived organocatalyst containing silicon-based bulky group, QN-TBS, -catalyzed aza-Michael reaction under solvent-free conditions. In addition, we have demonstrated for the first time that racemization was occurred in suitable solvents under mild conditio... Chirality journals http://www.medworm.com/rss/comments.php?id=4804580 Sat, 30 Apr 2011 23:00:00 +0100 4804580 http://www.medworm.com/index.php?rid=4804579&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21472783%26dopt%3DAbstract Authors: de Diego HL, Bond AD, Dancer RJ The X-ray powder diffractograms of racemic citalopram oxalate and (S)-citalopram oxalate are very similar, but the melting point of the racemate is higher than that of the pure enantiomer. The higher melting point indicates that the racemate is a racemic compound, rather than a conglomerate. The crystal structure of the enantiomer contains two molecules of (S)-citalopram in the asymmetric unit. The conformation of the two molecules is different but they approximate mirror images of each other if the aromatic groups are interchanged. The crystal structure of the racemate is essentially isostructural with that of the enantiomer, having almost the same cell parameters but containing a crystallographic inversion centre that is not retained in the en... Chirality journals http://www.medworm.com/rss/comments.php?id=4804579 Sat, 30 Apr 2011 23:00:00 +0100 4804579 http://www.medworm.com/index.php?rid=4804577&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21488103%26dopt%3DAbstract Authors: Vandenbussche S, Reisse J, Bartik K, Lievin J Amino-acid enantiomeric excesses (ee's) have been detected in different types of carbonaceous chondrites, all in favor of the L enantiomer. In this article, we discuss possible deterministic causes to the presence of these amino-acid ee's in meteorites and evaluate in particular enantioselective photolysis by circularly polarized light (CPL). The electronic circular dichroism spectra of a set of amino- and hydroxy-acids, all detected in chondritic matter but some with ee's and others without ee's, were calculated and compared. The spectra were calculated for the most stable conformation(s) of the considered molecules using quantum mechanical methods (density functional theory). Our results suggest that CPL photolysis in the gas pha... Chirality journals http://www.medworm.com/rss/comments.php?id=4804577 Sat, 30 Apr 2011 23:00:00 +0100 4804577 http://www.medworm.com/index.php?rid=4804576&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21488104%26dopt%3DAbstract Authors: Oztürk G, Colak M, Demirel N Chiral Schiff-bases 3a-f based on ferrocene were designed and synthesized using solvent-free methods by mixing ferrocene carbaldehyde 1 with amino alcohols and amines 2a-f under microwave irradiation and classical method for the enantioselective nitroaldol (Henry) reaction. The Schiff-bases were obtained in shorter reaction times and improved yield under microwave irradiation method over classical method. The highest enantioselectivity was observed in ligand 3e (95% ee) when CH(2) Cl(2) was used as solvent. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21488104 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4804576 Sat, 30 Apr 2011 23:00:00 +0100 4804576 http://www.medworm.com/index.php?rid=4804575&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21488105%26dopt%3DAbstract Authors: Ma C, Xu XL, Ai P, Xie SM, Lv YC, Shan HQ, Yuan LM This work reports the chiral separation of D,L-mandelic acid with cellulose membranes. Cellulose was chosen as membrane material because it possesses multichiral carbon atoms in its molecular structure unit. The flux and permselective properties of membrane using aqueous solutions of D,L-mandelic acid as feed solution was studied. The top surface and cross-section morphology of the resulting membrane were examined by scanning electron microscopy. When the membrane was prepared with 8.1 wt % cellulose and 8.1 wt % LiCl in the DMA casting solution, and the operating pressure and feed concentration of racemate were 0.0125 MPa and 0.5 mg/ml, respectively, over 90% of enantiomeric excess could be obtained. This is the first report ... Chirality journals http://www.medworm.com/rss/comments.php?id=4804575 Sat, 30 Apr 2011 23:00:00 +0100 4804575 http://www.medworm.com/index.php?rid=4804564&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21538573%26dopt%3DAbstract Authors: Qin L, Li L, Yi L, Da CS, Zhou YF Nitroso compounds have two reactive nitrogen and oxygen atoms. It is interesting and important to perform a nitrogen or oxygen selective reaction with interesting substrates. These atom specific reactions are crucial to specifically synthesis of specific compounds. An enantioselective N-specific reaction of nitrosobenzene with unmodified aldehydes was successfully achieved catalyzed first by a variety of primary amine-based organocatalysts with higher yield and enantioselectivity. The bulkier substituted groups of the organocatalyst and two hydrogen bonds from the organocatalyst and the oxygen atom of nitrosobenzene make the reaction preferentially N-specific and predominantly afford R products. Chirality, 2011. © 2011 Wiley-Liss, Inc. PM... Chirality journals http://www.medworm.com/rss/comments.php?id=4804564 Thu, 28 Apr 2011 23:00:00 +0100 4804564 http://www.medworm.com/index.php?rid=4804566&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21538571%26dopt%3DAbstract Authors: Watanabe K, Sakamoto T, Nakano T 2,7-Bis(4-t-butylphenyl)fluoren-9-ylmethyl methacrylate (BBPFMMA) was synthesized as a new candidate of a bulky monomer suitable for asymmetric anionic polymerization (IUPAC nomenclature: asymmetric helix-chirogenic polymerization) leading to a preferred-handed helical, optically active polymer. The new monomer was polymerized using the complex of 9-fluorenyllithium and (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine in toluene at -78°C. As opposed to the original intention to obtain a polymethacrylate, the monomer seemed to undergo structural transition (decomposition) giving 2,7-bis(4-t-butylphenyl)dibenzofulvene and the obtained polymer was most probably a terpolymer of BBPFMMA, 2,7-bis(4-t-butylphenyl)dibenzofulvene, and methacrylic acid. The ... Chirality journals http://www.medworm.com/rss/comments.php?id=4804566 Wed, 27 Apr 2011 23:00:00 +0100 4804566 http://www.medworm.com/index.php?rid=4804565&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21538572%26dopt%3DAbstract Authors: Onimura K, Shintaku K, Rattanatraicharoen P, Yamabuki K, Oishi T Optically active 4-alkyl-2-ethynyloxazoline derivatives (BnEOx) were polymerized with rhodium catalysts. The polymerization in toluene produced polymer with the highest absolute values of specific rotation ([α](D) = -77.3°). The yields, molecular weights, and specific rotations of poly(BnEOx)s were influenced by polymerization conditions. The copolymerization with phenylacetylene (PA) was effective to increase the molecular weight of the copolymer. It is interesting to note that the copolymers exhibited positive specific rotations ([α](D) = +4.7° to +62.5°) despite the fact that [α](D) s of BnEOx and the homopolymer are negative sign. The chiroptical properties were investigated by the chiral/achiral copoly... Chirality journals http://www.medworm.com/rss/comments.php?id=4804565 Wed, 27 Apr 2011 23:00:00 +0100 4804565 http://www.medworm.com/index.php?rid=4804563&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21538575%26dopt%3DAbstract Authors: Fukuyama T, Matsuo K, Gekko K The electronic circular dichroism (ECD) spectra of three L-hydroxy acids (L-lactic acid, (+)-(S)-2-hydroxy-3-methylbutyric acid, and (-)-(S)-2-hydroxyisocaproic acid) were measured down to 160 nm in aqueous solution using a vacuum-ultraviolet ECD spectrophotometer. To assign the two positive peaks around 210 and 175 nm and the one negative peak around 190 nm in the observed spectra, the ECD spectrum of L-lactic acid was calculated using time-dependent density functional theory (DFT) for the optimized structures by DFT and a continuum model. The observed ECD spectrum was successfully reproduced as the average spectrum for four optimized structures with seven water molecules that localized around the COO(-) and OH groups of L-lactic acid. The positi... Chirality journals http://www.medworm.com/rss/comments.php?id=4804563 Wed, 27 Apr 2011 23:00:00 +0100 4804563 http://www.medworm.com/index.php?rid=4804567&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21523831%26dopt%3DAbstract Authors: Sánchez-Carnerero EM, de Las Casas Engel T, Lora Maroto B, de la Moya Cerero S Asymmetric bis(hydroxyamide)-based zinc-chelate catalysts are able to promote the enantioselective addition of diethylzinc to benzaldehyde in the absence of titanium with yields and ees comparable, or inclusively superior, to their C(2) -symmetric analogues. This unexpected fact demonstrates that the previously established assumption on the necessity of using C(2) -symmetric bis(hydrdoxyamides) to generate C(2) -symmetric zinc-chelate catalysts can be discarded, which expand the possibilities for designing new ligands based on the interesting hydroxyl-amide functional grouping. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21523831 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4804567 Mon, 25 Apr 2011 23:00:00 +0100 4804567 http://www.medworm.com/index.php?rid=4804570&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21506167%26dopt%3DAbstract This study used chiral columns packed with 3-μm and 5-μm particles to comparatively separate enantiomers of 9 triazole fungicides, and Lux Cellulose-1 columns with chiral stationary phase of cellulose-tris-(3,5-dimethylphenylcarbamate) were used on reverse-phase high-performance liquid chromatography with flow rates of 0.3 and 1.0 mL min(-1) for 3-μm and 5-μm columns, respectively. The (+)-enantiomers of hexaconazole (1), tetraconazole (4), myclobutanil (7), fenbuconazole (8) and the (-)-enantiomers of flutriafol (2), diniconazole (3), epoxiconazole (5), penconazole (6), triadimefon (9) were firstly eluted from both columns, the elution orders identified with an optical rotation detector didn't change with variety of column particles and mobile phases (acetronitrile/water and methanol/... Chirality journals http://www.medworm.com/rss/comments.php?id=4804570 Mon, 18 Apr 2011 23:00:00 +0100 4804570 http://www.medworm.com/index.php?rid=4804569&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21506168%26dopt%3DAbstract Authors: Guo HM, Li JG, Qu GR, Zhang XM, Yuan WC A novel enantioselective Michael addition of malononitrile to trans-β-nitroolefins in the presence of bifunctional amine thiourea organocatalyst is developed. The Michael reaction catalyzed by amine thioureas containing both central and axial chiral elements proceeded smoothly and provided the desired adducts with high yields (up to 96% yield) and moderate enantioselectivities (up to 83% enantiomeric excess). Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21506168 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4804569 Mon, 18 Apr 2011 23:00:00 +0100 4804569 http://www.medworm.com/index.php?rid=4804568&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21506169%26dopt%3DAbstract Authors: Morrison C, J Smith F, Tomaszewski T, Stawiarska K, Biziuk M The aim of this study was to develop a chiral gas chromatographic method for the separation of compounds likely to be found in the EMDE synthesis of methylamphetamine, a heavily abused stimulant drug. Here we describe the separation of the enantiomers of ephedrine, pseudoephedrine, chlorinated intermediates and methylamphetamine using fluorinated acid anhydrides as chemical derivatization reagents prior to gas chromatographic analysis on a 2,3-di-O-methyl-6-t-butyl silyl-β-cyclodextrin stationary phase (CHIRALDEX™ B-DM). Separation of the enantiomers of pseudoephedrine, methylamphetamine and chloro-intermediates was achieved using PFPA derivatization, and enantiomers of ephedrine using TFAA derivatization, in run ... Chirality journals http://www.medworm.com/rss/comments.php?id=4804568 Mon, 18 Apr 2011 23:00:00 +0100 4804568 http://www.medworm.com/index.php?rid=4804574&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21500285%26dopt%3DAbstract Authors: Lai C, Lin G, Wang W, Luo H Glyoxal and methylglyoxal are two endogenous and mutagenic 1,2-dicarbonyl compounds, which can readily form adducts with guanosine. The molecular structures of cyclic guanosine-glyoxal (G-g) and guanosine-methylglyoxal (G-mg) mono-adducts have been extensively studied before. However, diastereoisomers of these adducts have not yet been studied in detail. In this work, one pair of G-g and two pairs of G-mg diastereoisomers were baseline separated by reverse phase HPLC, whose structures were identified as the previously reported cyclic forms, and their absolute configurations were determined by circular dichroism, the octant rule, and molecular modeling. According to the HPLC elution order, configurations of two G-g (as well as trans G-mg) were (6R,7R... Chirality journals http://www.medworm.com/rss/comments.php?id=4804574 Thu, 14 Apr 2011 23:00:00 +0100 4804574 http://www.medworm.com/index.php?rid=4804573&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21500286%26dopt%3DAbstract Authors: Zhou S, Zhou Y, Xing Y, Wang N, Cao L An improved method of the synthesis of flavanones catalyzed by pyrrolidine and BF(3) ·Et(2) O has been developed and a lot of flavanones could be easily synthesized via this method. The asymmetric synthesis of flavanone from benzaldehyde and 5-fluoro-2-hydroxyacetophenone has been studied and flavanone with moderate enantioselectivity was obtained in one step. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21500286 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4804573 Thu, 14 Apr 2011 23:00:00 +0100 4804573 http://www.medworm.com/index.php?rid=4804572&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21500287%26dopt%3DAbstract Authors: Sayago FJ, Pueyo MJ, Calaza MI, Jiménez AI, Cativiela C An efficient methodology for the preparation of the α-tetrasubstituted proline analog (S,S,S)-2-methyloctahydroindole-2-carboxylic acid, (S,S,S)-(αMe)Oic, and its enantiomer, (R,R,R)-(αMe)Oic, has been developed. Starting from easily available substrates and through simple transformations, a racemic precursor has been synthesized in excellent yield and further subjected to HPLC resolution using a cellulose-derived chiral stationary phase. Specifically, a semipreparative (250 mm × 20 mm ID) Chiralpak® IC column has allowed the efficient resolution of more than 4 g of racemate using a mixture of n-hexane/tert-butyl methyl ether/2-propanol as the eluent. Multigram quantities of the target amino acids have been isolated... Chirality journals http://www.medworm.com/rss/comments.php?id=4804572 Thu, 14 Apr 2011 23:00:00 +0100 4804572 http://www.medworm.com/index.php?rid=4804571&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21500288%26dopt%3DAbstract Authors: Kawamura H, Takeyama Y, Yamamoto M, Kurihara H, Morino K, Yashima E A novel, optically active, cis-transoidal poly(phenylacetylene) bearing an L-proline residue as the pendant group (poly-1) was prepared by the polymerization of the corresponding monomer using a rhodium catalyst in water, and its chiroptical property was investigated using circular dichroism spectroscopy. Poly-1 showed intense Cotton effects in the UV-visible region of the polymer backbone in water, resulting from the prevailing one-handed helical conformation induced by the covalent-bonded chiral L-proline pendants and exhibited a unique helix-sense inversion in response to external, achiral, and chiral stimuli, such as the solvent and interactions with chiral small molecules. We found that poly-1 could enant... Chirality journals http://www.medworm.com/rss/comments.php?id=4804571 Thu, 14 Apr 2011 23:00:00 +0100 4804571 http://www.medworm.com/index.php?rid=4804578&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21472784%26dopt%3DAbstract Authors: Naziroglu HN, Durmaz M, Bozkurt S, Sirit A Four proline-derived chiral receptors 5-8 were readily synthesized starting from L-proline. The enantiomeric recognition ability of chiral receptors was examined with a series of carboxylic acids by (1) H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that the hosts form 1:1 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. Among the chiral receptors used in this study, prolinamide 6 was found to be the best chiral shift reagent and is e... Chirality journals http://www.medworm.com/rss/comments.php?id=4804578 Tue, 05 Apr 2011 23:00:00 +0100 4804578 http://www.medworm.com/index.php?rid=4580401&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384434%26dopt%3DAbstract Authors: Godoy AL, De Moraes NV, Martinez EZ, Carvalho TM, Marques MP, Lanchote VL Tramadol (T) is available as a racemic mixture of (+)-trans-T and (-)-trans-T. The main metabolic pathways are O-demethylation and N-demethylation, producing trans-O-desmethyltramadol (M1) and trans-N-desmethyltramadol (M2) enantiomers, respectively. The analgesic effect of T is related to the opioid activity of (+)-trans-T and (+)-M1 and to the monoaminergic action of (+/-)-trans-T. This is the first study using tandem mass spectrometry as a detection system for the simultaneous analysis of trans-T, M1, and M2 enantiomers. The analytes were resolved on a Chiralpak® AD column using hexane:ethanol (95.5:4.5, v/v) plus 0.1% diethylamine as the mobile phase. The quantitation limits were 0.5 ng/ml for trans... Chirality journals http://www.medworm.com/rss/comments.php?id=4580401 Mon, 14 Mar 2011 04:03:02 +0100 4580401 http://www.medworm.com/index.php?rid=4580400&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384435%26dopt%3DAbstract Authors: Horáková H, Grüner B, Vespalec R The structural chirality is an inherent feature of fully synthetic boron cluster compounds that sometimes exhibit unique biochemical effects. HPLC studies with zwitter-ionic cluster boron compounds and electrophoretic studies with boron cluster anions reveal that the chiral separability of these species is remarkably dissimilar to that of organic species, if uncharged cyclodextrins are used as chiral selectors. Furthermore, marked differences were found between the analytical characteristics of the chiral separations of the boron cluster species and those of the organic species with uncharged cyclodextrins. The present-day experimental database indicates that the rules valid for the chiral separations of the organic species cannot be applied... Chirality journals http://www.medworm.com/rss/comments.php?id=4580400 Mon, 14 Mar 2011 04:02:55 +0100 4580400 http://www.medworm.com/index.php?rid=4580399&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384436%26dopt%3DAbstract Authors: Dubey R, Dutta D, Shami TC, Bhasker Rao KU Optically active polyaniline (PANI) salts were readily generated in solution via the enantioselective acid doping of neutral emeraldine base (EB) form of PANI with either (+) or (-)-2-pyrrolidone-5-carboxylic acid (PCA) in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solvents. Strong mirror imaged circular dichroism (CD) spectra were obtained for the deep green polymer solutions obtained with (+) or (-) PCA, suggesting that the acid doping is enantioselective, with one helical screw of the polymer chain being preferentially produced depending on the nature of enantiomer. It was observed that molar concentration of PCA as well as nature of solvent plays a very important role in the generation of optically active PANI. The gener... Chirality journals http://www.medworm.com/rss/comments.php?id=4580399 Mon, 14 Mar 2011 04:02:32 +0100 4580399 http://www.medworm.com/index.php?rid=4580398&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384437%26dopt%3DAbstract Authors: Kodama K, Kimura Y, Shitara H, Yasutake M, Sakurai R, Hirose T Solvent-induced chirality control in the enantioseparation of 1-phenylethylamine 1 by N-(p-toluenesulfonyl)-(S)-phenylalanine 2 via diastereomeric salt formation was studied. (S)-1·(S)-2 was preferentially crystallized as a less-soluble salt from aqueous alcohol, while (R)-1·(S)-2 salt was mainly obtained by addition of solvents with a six-membered ring such as dioxane, cyclohexane, tetrahydropyran, and cyclohexene to 2-propanol. Further investigations were carried out from the viewpoints of molecular structures, optical rotation measurement, and X-ray crystallographic analyses. Crystallographic analyses have revealed that incorporation of the six-membered ring solvent molecule in (R)-1·(S)-2 without hydrogen bo... Chirality journals http://www.medworm.com/rss/comments.php?id=4580398 Mon, 14 Mar 2011 04:01:45 +0100 4580398 http://www.medworm.com/index.php?rid=4580397&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384438%26dopt%3DAbstract Authors: Hefnawy MM, Asiri YA, Al-Zoman NZ, Mostafa GA, Aboul-Enein HY Enantiomeric resolution of teratolol was achieved on a vancomycin macrocyclic antibiotic chiral stationary phase known as Chirobiotic V with UV detection set at 220 nm. The polar ionic mobile phase (PIM) consisted of methanol-glacial acetic acid-triethylamine (100:0.01:0.015, v/v/v) has been used at a flow rate of 0.8 ml min(-1) . The calibration curves in plasma were linear over the range of 5-500 ng ml(-1) for each enantiomer with detection limit of 2 ng ml(-1) . The proposed method was validated in compliance with the international conference on harmonization (ICH) guidelines. The developed method applied for the trace analyses of tertatolol enantiomers in plasma and for the pharmacokinetic study of tertatolol en... Chirality journals http://www.medworm.com/rss/comments.php?id=4580397 Mon, 14 Mar 2011 04:01:27 +0100 4580397 http://www.medworm.com/index.php?rid=4580396&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384439%26dopt%3DAbstract Authors: Vega-Villa KR, Remsberg CM, Takemoto JK, Ohgami Y, Yáñez JA, Andrews PK, Davies NM The chirality of flavonoids has been overlooked in the majority of pharmacokinetic studies of homoeriodictyol, isosakuranetin, and taxifolin. The stereospecific pharmacokinetic disposition of these xenobiotics in male Sprague-Dawley rats is described for the first time. Validated HPLC methods were used to analyze serum and urine samples of rats following intravenous administration of each flavonoid via jugular vein cannulation and to determine their content in selected fruits. The characterization and interpretation of the pharmacokinetic disposition profiles of homoeriodictyol, isosakuranetin, and taxifolin are described. A discrepancy exists between half-lives in serum and urine which may be... Chirality journals http://www.medworm.com/rss/comments.php?id=4580396 Mon, 14 Mar 2011 04:00:51 +0100 4580396 http://www.medworm.com/index.php?rid=4580395&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384440%26dopt%3DAbstract Authors: Cho EN, Li Y, Kim HJ, Hyun MH A new colorimetric chiral sensor material consisting of three different functional sites such as chromophore (2,4-dinitrophenylazophenol dye), binding site (crown ether), and chiral barrier (3,3'-diphenyl-1,1'-binaphthyl group) was prepared and applied to the recognition of the two enantiomers of primary amino alcohols and amines. Among five primary amino alcohols and two primary amines tested, the two enantiomers of phenylalaninol show the highest difference in the absorption maximum wavelength (Δλ(max) = 43.5 nm) and in the association constants (K(S) /K(R) = 2.51) upon complexation with the colorimetric chiral sensor material and, consequently, the two enantiomers of phenylalaninol were clearly distinguished from each other by the color diffe... Chirality journals http://www.medworm.com/rss/comments.php?id=4580395 Mon, 14 Mar 2011 04:00:33 +0100 4580395 http://www.medworm.com/index.php?rid=4580394&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384441%26dopt%3DAbstract Authors: Julínek O, Lindner W, Urbanová M The stereoselective complexation of tert-butylcarbamoyl quinine and tert-butylcarbamoyl quinidine selectors (SOs) with 3,5-dinitrobenzoyl (DNB) derivatives of D- and L-alpha amino acids (DNB-Ala, DNB-Val, DNB-Leu, and DNB-Ile) as well as achiral DNB-Gly has been studied by vibrational circular dichroism (VCD) spectroscopy in the spectral region of CH stretching vibrations. All the complexes of SOs and sterically compatible enantiomers of derivatized amino acid selectands (SAs) showed induced circular dichroism (ICD) bands in the region of aromatic CH stretching vibrations, indicating the occurrence of a π-π interaction between the aromatic moieties of SA and SO. To our knowledge, this is the first report in which a π-π interaction w... Chirality journals http://www.medworm.com/rss/comments.php?id=4580394 Mon, 14 Mar 2011 04:00:27 +0100 4580394 http://www.medworm.com/index.php?rid=4580393&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21384442%26dopt%3DAbstract Authors: Hsu LC, Kim H, Yang X, Ross D There are several approaches to produce enantiomerically pure drug substances, such as recrystallization, catalytic process (ligand and enzyme), indirect chromatographic resolution, and direct chromatographic resolution. However, the use of preparative chromatography with chiral stationary phases seems to be most effective for early phase projects, where the time and resources on the developments need to be minimized to get the drug candidates into the clinical studies. We showed that by following a well-defined process, chiral chromatography can be easily scaled up from an analytical system to a pilot plant system. We also used the results from a multicolumn continuous chromatography (MCC) study to conclude that MCC can be a cost-effective produc... Chirality journals http://www.medworm.com/rss/comments.php?id=4580393 Mon, 14 Mar 2011 04:00:21 +0100 4580393 http://www.medworm.com/index.php?rid=4580392&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21387418%26dopt%3DAbstract Authors: Lu Y, Diao J, Gu X, Zhang Y, Xu P, Wang P, Zhou Z Stereoselective degradation of Diclofop-methyl (DM) has been found in alcohol fermentation of grape must and sucrose solution with dry yeast. A method was developed for separation and determination the two enantiomers of DM during the fermentation process by high-performance liquid chromatography based on cellulose tri-(3,5-dimethylphenyl-carbamate) chiral stationary phase. The results showed that the enantiomers of DM degraded following the first-order kinetics in the sucrose solution and the degradation of DM enantiomers in grape must were biphasic (slow-fast-slow process). In the sucrose solution, half lives of (+)-(R)-DM and (-)-(S)-DM were calculated to be 8.5 h and 3.1 h, respectively. In the grape must, half life of (+)-... Chirality journals http://www.medworm.com/rss/comments.php?id=4580392 Tue, 08 Mar 2011 00:00:00 +0100 4580392 http://www.medworm.com/index.php?rid=4580402&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21365690%26dopt%3DAbstract Authors: Park JY, Cho HS, Hyun MH The two enantiomers of N-acyl amide and N-ureide derivatives of 3-amino-5-phenyl-1,4-benzodiazepin-2-ones, which have been known to show anti-respiratory syncytial virus (RSV) activity, were resolved on seven different Pirkle-type chiral stationary phases (CSPs) with the use of 10% isopropyl alcohol in hexane as a mobile phase. Among the seven Pirkle-type CSPs, the one based on (S)-leucine derivative named as N-Phe-L-Leu was found to be most successful, the separation factors (α) and the resolutions (R(S) ) for seven analytes being in the range of 1.78-4.21 and 5.94-15.08, respectively. By resolving N-benzyloxycarbonyl derivatives of 3-amino-5-phenyl(or 5-methyl)-1,4-benzodiazepin-2-ones on Pirkle-type CSPs, the phenyl ring at the 5-position and the N... Chirality journals http://www.medworm.com/rss/comments.php?id=4580402 Tue, 01 Mar 2011 00:00:00 +0100 4580402 http://www.medworm.com/index.php?rid=4338391&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21213244%26dopt%3DAbstract Authors: Hsu LC, Kim H, Yang X, Ross D There are several approaches to produce enantiomerically pure drug substances, such as recrystallization, catalytic process (ligand and enzyme), indirect chromatographic resolution, and direct chromatographic resolution. However, the use of preparative chromatography with chiral stationary phases seems to be most effective for early phase projects, where the time and resources on the developments need to be minimized to get the drug candidates into the clinical studies. We showed that by following a well-defined process, chiral chromatography can be easily scaled up from an analytical system to a pilot plant system. We also used the results from a multicolumn continuous chromatography (MCC) study to conclude that MCC can be a cost-effective produc... Chirality journals http://www.medworm.com/rss/comments.php?id=4338391 Thu, 06 Jan 2011 00:00:00 +0100 4338391 http://www.medworm.com/index.php?rid=4338390&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21213245%26dopt%3DAbstract Authors: Oztürk G, Colak M, Demirel N Chiral Schiff-bases 3a-f based on ferrocene were designed and synthesized using solvent-free methods by mixing ferrocene carbaldehyde 1 with amino alcohols and amines 2a-f under microwave irradiation and classical method for the enantioselective nitroaldol (Henry) reaction. The Schiff-bases were obtained in shorter reaction times and improved yield under microwave irradiation method over classical method. The highest enantioselectivity was observed in ligand 3e (95% ee) when CH(2)Cl(2) was used as solvent. Chirality, 2011. © 2011 Wiley-Liss, Inc. PMID: 21213245 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4338390 Thu, 06 Jan 2011 00:00:00 +0100 4338390 http://www.medworm.com/index.php?rid=4338394&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21210457%26dopt%3DAbstract Authors: Mori K Mori's synthetic works on bioactive natural products in general and pheromones in particular started about 40 years ago to establish their absolute configurations and also to clarify their stereochemistry-bioactivity relationships. Results indicate that bioactive natural products are not always enantiomerically pure, and the stereochemistry-bioactivity relationships are not simple but complicated. For example, neither (R)- nor (S)-sulcatol, the aggregation pheromone of an ambrosia beetle, is behaviorally bioactive, whereas their mixture is active. In the case of olean, the sex pheromone of the olive fruit fly, its (R)-isomer is active against the males and the (S)-isomer is active against the females. Recent synthesis of two new insect pheromones is discussed to illustr... Chirality journals http://www.medworm.com/rss/comments.php?id=4338394 Wed, 05 Jan 2011 00:00:00 +0100 4338394 http://www.medworm.com/index.php?rid=4338393&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21210458%26dopt%3DAbstract Authors: Ma C, Xu XL, Ai P, Xie SM, Lv YC, Shan HQ, Yuan LM This work reports the chiral separation of D,L-mandelic acid with cellulose membranes. Cellulose was chosen as membrane material because it possesses multichiral carbon atoms in its molecular structure unit. The flux and permselective properties of membrane using aqueous solutions of D,L-mandelic acid as feed solution was studied. The top surface and cross-section morphology of the resulting membrane were examined by scanning electron microscopy. When the membrane was prepared with 8.1 wt % cellulose and 8.1 wt % LiCl in the DMA casting solution, and the operating pressure and feed concentration of racemate were 0.0125 MPa and 0.5 mg/ml, respectively, over 90% of enantiomeric excess could be obtained. This is the first report ... Chirality journals http://www.medworm.com/rss/comments.php?id=4338393 Wed, 05 Jan 2011 00:00:00 +0100 4338393 http://www.medworm.com/index.php?rid=4338392&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21210459%26dopt%3DAbstract Authors: Vandenbussche S, Reisse J, Bartik K, Lievin J Amino-acid enantiomeric excesses (ee's) have been detected in different types of carbonaceous chondrites, all in favor of the L enantiomer. In this article, we discuss possible deterministic causes to the presence of these amino-acid ee's in meteorites and evaluate in particular enantioselective photolysis by circularly polarized light (CPL). The electronic circular dichroism spectra of a set of amino- and hydroxy-acids, all detected in chondritic matter but some with ee's and others without ee's, were calculated and compared. The spectra were calculated for the most stable conformation(s) of the considered molecules using quantum mechanical methods (density functional theory). Our results suggest that CPL photolysis in the gas pha... Chirality journals http://www.medworm.com/rss/comments.php?id=4338392 Wed, 05 Jan 2011 00:00:00 +0100 4338392 http://www.medworm.com/index.php?rid=4251330&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21125685%26dopt%3DAbstract Authors: Wijeratne AB, Yang SH, Gracia J, Armstrong DW, Schug KA The effect of solvent systems on previously-reported ESI-MS based proton-assisted enantioselective molecular recognition phenomena of tartar emetic, L-antimony(III)-tartrate, was evaluated. This was achieved by carrying out a series of competitive binding experiments using chiral selectors, bis(sodium) D- and -L-antimony(III)-tartrates with chiral selectands, neutral side-chain amino acid enantiomeric isotopomers of alanine (Ala), valine (Val), leucine (Leu) and phenylalanine (Phe), in three different solvent systems, ACN/H(2) O (75/25 v/v), H(2) O (100%) and H(2) O/MeOH (25/75 v/v). Observations from these experiments suggest that the effect of solvent systems on previously reported proton-assisted chiral recognition cap... Chirality journals http://www.medworm.com/rss/comments.php?id=4251330 Sun, 12 Dec 2010 08:50:34 +0100 4251330 http://www.medworm.com/index.php?rid=4251329&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21125686%26dopt%3DAbstract We report the synthesis of a series of novel structurally related protic chiral ionic liquids (PCILs) derived from ephedrines. Enantiopure norephedrine, ephedrine, and methylephedrine were neutralized by use of fluorinated acids, bis(trifluoromethanesulfonyl)imide, and bis(pentafluoroethanesulfonyl)imide to afford six PCILs with protonated primary, secondary, and tertiary amines. The goal of this study is to investigate the influence of structure on both chiral recognition abilities and physicochemical properties of these closely related PCILs. The newly synthesized PCILs were characterized by use of nuclear magnetic resonance (NMR), thermal gravimetric analysis, differential scanning calorimetry, circular dichroism (CD), mass spectrometry, and elemental analysis. The PCILs were thermally ... Chirality journals http://www.medworm.com/rss/comments.php?id=4251329 Sun, 12 Dec 2010 08:50:30 +0100 4251329 http://www.medworm.com/index.php?rid=4251328&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21125687%26dopt%3DAbstract "The β(1) -selective adrenoceptor agonist dobutamine": A fallacy being perpetuated. Chirality. 2011 Jan;23(1):63-4 Authors: Waldeck B Dobutamine is a cardiotonic agent, developed as a racemate more than 30 years ago. The compound soon got the label "the β(1) -selective adrenoceptor agonist". However, a closer examination of the enantiomers showed that (+)-dobutamine is predominantly a β(1) - and β(2) -adrenoceptor agonist with modest selectivity whereas (-)-dobutamine is predominantly an α(1) -adrenoceptor agonist. Nevertheless, rac dobutamine is still frequently used as a tool for classification of β-adrenoceptors. This ignorance of chiralilty may lead to erroneous conclusions and consolidate false labels. Chirality, 2011. © 2010 Wiley-Liss, Inc. PMID: 21125687 [Pub... Chirality journals http://www.medworm.com/rss/comments.php?id=4251328 Sun, 12 Dec 2010 08:50:26 +0100 4251328 http://www.medworm.com/index.php?rid=4251327&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21125688%26dopt%3DAbstract Authors: Chen L, Cheng F, Jia L, Zhang A, Wu J, Tang N Two new chiral dinuclear Mn(III)-Salen complexes with inherent phase-transfer capability have been synthesized, which serve as catalysts in the asymmetric epoxidation of nonfunctionalized alkenes. Experimental results show these complexes are effective catalysts for the asymmetric epoxidation of some cyclic alkenes and the catalysts have certain inherent phase-transfer capability during the epoxidation because of their weak water solubility. In general, good enantioselectivity and acceptable yields were achieved when NaClO was used as oxidant under three different reaction systems. Among these alkenes, the catalyst 6a gave the highest ee (94%) for 6-chloro-2,2-dimethylchromene in the presence of ionic liquid 2. Additionally, the re... Chirality journals http://www.medworm.com/rss/comments.php?id=4251327 Sun, 12 Dec 2010 08:50:21 +0100 4251327 http://www.medworm.com/index.php?rid=4251326&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21125689%26dopt%3DAbstract Authors: Kureshy RI, Kumar M, Agrawal S, Khan NU, Dangi B, Abdi SH, Bajaj HC The active catalysts for the enantioselective ring opening (ARO) of meso-stilbene oxide, cis-butene oxide, cyclohexene oxide, cyclopentene oxide, and cyclooctene oxide with various substituted anilines were generated in situ by the reaction of Ti(O(i) Pr)(4) with poly-[(R,R)-N,N'-bis-{3-(1,1-dimethylethyl)-5-methylene salicylidene} cyclohexane-1,2-diamine]-1 and (1R,2R)-N,N'-bis[3,5-di(tert-butyl)salicylidene] cyclohexane-1,2-diamine-2. These catalysts in the presence of nonracemic imine as an additive provided β-amino alcohol in excellent yield (99%) and chiral purity (enantiomeric excess (ee) up to 99%) for the ARO of meso-stilbene oxide with aniline. The same protocol was less effective for the ARO of cycl... Chirality journals http://www.medworm.com/rss/comments.php?id=4251326 Sun, 12 Dec 2010 08:50:15 +0100 4251326 http://www.medworm.com/index.php?rid=4251325&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21125690%26dopt%3DAbstract In this study, circular dichroism (CD) and UV/Visible (UV/Vis) absorption spectroscopy techniques were used to investigate the interactions between N-methyl-N'-(7-chloro-4-quinolyl)-1,3-diaminopropane (QD), an achiral, bicyclic compound similar to previously investigated antimalarial drugs, and heparin, a complex GAG that is frequently used as a clinical anticoagulant. Relatively intense heparin-induced CD features were observed for QD and were noted to be radically different from previous studies using related chiral drugs, underscoring the importance of the Pfieffer effect on this and similar heparin research. Additionally, the induced CD for QD was observed to be highly dependent upon drug concentration, heparin concentration, system pH, equilibration time, and ionic strength. These res... Chirality journals http://www.medworm.com/rss/comments.php?id=4251325 Sun, 12 Dec 2010 08:50:09 +0100 4251325 http://www.medworm.com/index.php?rid=4218385&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21117144%26dopt%3DAbstract Authors: Horáková H, Grüner B, Vespalec R The structural chirality is an inherent feature of fully synthetic boron cluster compounds that sometimes exhibit unique biochemical effects. HPLC studies with zwitter-ionic cluster boron compounds and electrophoretic studies with boron cluster anions reveal that the chiral separability of these species is remarkably dissimilar to that of organic species, if uncharged cyclodextrins are used as chiral selectors. Furthermore, marked differences were found between the analytical characteristics of the chiral separations of the boron cluster species and those of the organic species with uncharged cyclodextrins. The present-day experimental database indicates that the rules valid for the chiral separations of the organic species cannot be applied... Chirality journals http://www.medworm.com/rss/comments.php?id=4218385 Mon, 29 Nov 2010 00:00:00 +0100 4218385 http://www.medworm.com/index.php?rid=4218384&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21117146%26dopt%3DAbstract Authors: Godoy AL, De Moraes NV, Martinez EZ, Carvalho TM, Marques MP, Lanchote VL Tramadol (T) is available as a racemic mixture of (+)-trans-T and (-)-trans-T. The main metabolic pathways are O-demethylation and N-demethylation, producing trans-O-desmethyltramadol (M1) and trans-N-desmethyltramadol (M2) enantiomers, respectively. The analgesic effect of T is related to the opioid activity of (+)-trans-T and (+)-M1 and to the monoaminergic action of (+/-)-trans-T. This is the first study using tandem mass spectrometry as a detection system for the simultaneous analysis of trans-T, M1, and M2 enantiomers. The analytes were resolved on a Chiralpak® AD column using hexane:ethanol (95.5:4.5, v/v) plus 0.1% diethylamine as the mobile phase. The quantitation limits were 0.5 ng/ml for trans... Chirality journals http://www.medworm.com/rss/comments.php?id=4218384 Mon, 29 Nov 2010 00:00:00 +0100 4218384 http://www.medworm.com/index.php?rid=4185610&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21077185%26dopt%3DAbstract Authors: Kodama K, Kimura Y, Shitara H, Yasutake M, Sakurai R, Hirose T Solvent-induced chirality control in the enantioseparation of 1-phenylethylamine 1 by N-(p-toluenesulfonyl)-(S)-phenylalanine 2 via diastereomeric salt formation was studied. (S)-1·(S)-2 was preferentially crystallized as a less-soluble salt from aqueous alcohol, while (R)-1·(S)-2 salt was mainly obtained by addition of solvents with a six-membered ring such as dioxane, cyclohexane, tetrahydropyran, and cyclohexene to 2-propanol. Further investigations were carried out from the viewpoints of molecular structures, optical rotation measurement, and X-ray crystallographic analyses. Crystallographic analyses have revealed that incorporation of the six-membered ring solvent molecule in (R)-1·(S)-2 without hydrogen bo... Chirality journals http://www.medworm.com/rss/comments.php?id=4185610 Fri, 12 Nov 2010 00:00:00 +0100 4185610 http://www.medworm.com/index.php?rid=4166479&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21069787%26dopt%3DAbstract Authors: Vega-Villa KR, Remsberg CM, Takemoto JK, Ohgami Y, Yáñez JA, Andrews PK, Davies NM The chirality of flavonoids has been overlooked in the majority of pharmacokinetic studies of homoeriodictyol, isosakuranetin, and taxifolin. The stereospecific pharmacokinetic disposition of these xenobiotics in male Sprague-Dawley rats is described for the first time. Validated HPLC methods were used to analyze serum and urine samples of rats following intravenous administration of each flavonoid via jugular vein cannulation and to determine their content in selected fruits. The characterization and interpretation of the pharmacokinetic disposition profiles of homoeriodictyol, isosakuranetin, and taxifolin are described. A discrepancy exists between half-lives in serum and urine which may be... Chirality journals http://www.medworm.com/rss/comments.php?id=4166479 Wed, 10 Nov 2010 00:00:00 +0100 4166479 http://www.medworm.com/index.php?rid=4139654&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21046639%26dopt%3DAbstract Authors: Dubey R, Dutta D, Shami TC, Bhasker Rao KU Optically active polyaniline (PANI) salts were readily generated in solution via the enantioselective acid doping of neutral emeraldine base (EB) form of PANI with either (+) or (-)-2-pyrrolidone-5-carboxylic acid (PCA) in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solvents. Strong mirror imaged circular dichroism (CD) spectra were obtained for the deep green polymer solutions obtained with (+) or (-) PCA, suggesting that the acid doping is enantioselective, with one helical screw of the polymer chain being preferentially produced depending on the nature of enantiomer. It was observed that molar concentration of PCA as well as nature of solvent plays a very important role in the generation of optically active PANI. The gener... Chirality journals http://www.medworm.com/rss/comments.php?id=4139654 Tue, 02 Nov 2010 00:00:00 +0100 4139654 http://www.medworm.com/index.php?rid=4139653&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21046641%26dopt%3DAbstract We report the synthesis of a series of novel structurally related protic chiral ionic liquids (PCILs) derived from ephedrines. Enantiopure norephedrine, ephedrine, and methylephedrine were neutralized by use of fluorinated acids, bis(trifluoromethanesulfonyl)imide, and bis(pentafluoroethanesulfonyl)imide to afford six PCILs with protonated primary, secondary, and tertiary amines. The goal of this study is to investigate the influence of structure on both chiral recognition abilities and physicochemical properties of these closely related PCILs. The newly synthesized PCILs were characterized by use of nuclear magnetic resonance (NMR), thermal gravimetric analysis, differential scanning calorimetry, circular dichroism (CD), mass spectrometry, and elemental analysis. The PCILs were thermally ... Chirality journals http://www.medworm.com/rss/comments.php?id=4139653 Tue, 02 Nov 2010 00:00:00 +0100 4139653 http://www.medworm.com/index.php?rid=4139652&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21046642%26dopt%3DAbstract Authors: Hefnawy MM, Asiri YA, Al-Zoman NZ, Mostafa GA, Aboul-Enein HY Enantiomeric resolution of teratolol was achieved on a vancomycin macrocyclic antibiotic chiral stationary phase known as Chirobiotic V with UV detection set at 220 nm. The polar ionic mobile phase (PIM) consisted of methanol-glacial acetic acid-triethylamine (100:0.01:0.015, v/v/v) has been used at a flow rate of 0.8 ml min(-1). The calibration curves in plasma were linear over the range of 5-500 ng ml(-1) for each enantiomer with detection limit of 2 ng ml(-1). The proposed method was validated in compliance with the international conference on harmonization (ICH) guidelines. The developed method applied for the trace analyses of tertatolol enantiomers in plasma and for the pharmacokinetic study of tertatolol enan... Chirality journals http://www.medworm.com/rss/comments.php?id=4139652 Tue, 02 Nov 2010 00:00:00 +0100 4139652 http://www.medworm.com/index.php?rid=4004042&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872663%26dopt%3DAbstract Authors: Perraud O, Raytchev PD, Martinez A, Dutasta JP The racemic hemicryptophane molecular cage 2 was resolved by semipreparative HPLC on Whelk-O1 column. The absolute configuration of each isolated enantiomer was established from the analysis of their circular dichroism spectra and assigned as P-(+)-2 and M-(-)-2. Chirality, 2010. © 2010 Wiley-Liss, Inc. PMID: 20872663 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4004042 Wed, 29 Sep 2010 09:47:00 +0100 4004042 http://www.medworm.com/index.php?rid=4003986&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872664%26dopt%3DAbstract Authors: Xin YF, Gu LQ, Zhang S, Bai YS, Zhou GL, You ZQ, Xuan YX In the present study, we analyzed the stereospecific pharmacodynamics and inversion of N(G)-nitro-arginine by an intravenous blous injection of L-N(G)-nitro-arginine (L-NNA) or D-N(G)-nitro-arginine (D-NNA) (10 mg/kg) in beagle dogs. Significant pressor responses were observed for both substances, though a similar maximum response induced by L-NNA was reached at 120 min slower as compared with D-NNA. The rise in mean arterial pressure (MAP) of D-NNA dogs was also shown to be slower than the L-NNA group. Our data showed that D-NNA had no impact on MAP within 60 min after its injection. Plasma L-NNA started to appear after 45 min posterior to the i.v. bolus injection of D-NNA. This chiral inversion is unidirectional becaus... Chirality journals http://www.medworm.com/rss/comments.php?id=4003986 Wed, 29 Sep 2010 09:45:07 +0100 4003986 http://www.medworm.com/index.php?rid=4003923&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872665%26dopt%3DAbstract Authors: Ishii K, Ogaya T, Song Z, Iizuka H, Fukushima T An aqueous solution of enantiomerically pure tryptophan (Trp), namely, D-Trp or L-Trp (100 mg/kg), was administered intraperitoneally to male Sprague-Dawley rats. The time-course profiles of the rat plasma concentrations of D-kynurenine (KYN), L-KYN, and kynurenic acid (KYNA), which are metabolites of D- or L-Trp, were investigated using high-performance liquid chromatography (HPLC) systems that were reported in our previous study. The plasma D-KYN concentration increased after the administration of D-Trp, but this increase was not observed after the administration of L-Trp. The plasma L-KYN concentration increased after the administration of L-Trp, but no significant change was observed after the administration of D-Trp. The pla... Chirality journals http://www.medworm.com/rss/comments.php?id=4003923 Wed, 29 Sep 2010 09:42:44 +0100 4003923 http://www.medworm.com/index.php?rid=4003851&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872666%26dopt%3DAbstract Authors: Lente G Three different general strategies are proposed for kinetic models of the emergence of homochirality in open systems: flow-through reactors, photochemical energy input, and chemical energy input from a sacrificial reagent. Using a simple, second-order chiral autocatalytic core model, it is shown that all these scenarios lead to similar mathematical description despite the fundamentally different chemical background and practically complete homochirality is reached in all of these cases. It is also argued that the photochemical energy input scenario might not be compatible with a sunlight-driven natural process. Chirality, 2010. © 2010 Wiley-Liss, Inc. PMID: 20872666 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=4003851 Wed, 29 Sep 2010 09:39:49 +0100 4003851 http://www.medworm.com/index.php?rid=4003759&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872667%26dopt%3DAbstract Authors: Liu P, He W, Qin XY, Sun XL, Chen H, Zhang SY A novel single isomer of positively charged β-cyclodextrin, mono-6-deoxy-6-((2S,3S)-(+)-2,3-O-isopropylidene-1,4-tetramethylenediamine)-β-CD (MIPTACD) was designed and synthesized in seven steps starting from commercially available (2R,3R)-tartaric acid. The chiral resolution abilities of the new cationic chiral selector were studied by capillary electrophoresis using 10 different dansyl (Dns)-amino acids and N-acetylphenylalanine (N-Ac-Phe) as model analytes. The effects of running buffer pH and chiral selector concentration on the separation selectivity, resolutions, and migration times of analytes were studied in detail. MIPTACD shows a very good chiral recognition ability even at very low concentrations at the investigate... Chirality journals http://www.medworm.com/rss/comments.php?id=4003759 Wed, 29 Sep 2010 09:36:45 +0100 4003759 http://www.medworm.com/index.php?rid=4003553&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872668%26dopt%3DAbstract Authors: Yan TQ, Orihuela C, Preston JP, Xia F The use of phase appropriate technologies is critical for efficiently moving drug candidates forward in the early stages of drug discovery and development. Phase appropriate purification technology develops the analytical method and subsequently scales up the method and turns the sample around quickly (Kennedy et al., J Chromatogr A 2004; 1046:55). In this article, separation results and conditions from supercritical fluid chromatography (SFC), high-performance liquid chromatography (HPLC), and steady-state recycling (SSR) for the resolutions of three pharmaceutical intermediates in the early stage of the drug development are discussed. The first study used SFC and SSR to separate an impurity for a Good Manufacturing Practice (GMP) campaig... Chirality journals http://www.medworm.com/rss/comments.php?id=4003553 Wed, 29 Sep 2010 03:48:25 +0100 4003553 http://www.medworm.com/index.php?rid=4003521&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20872669%26dopt%3DAbstract Authors: Grudniewska A, Gniłka R, Wawrzeńczyk C The biotransformation of racemic piperitone ((±)-1) was investigated using four strains of fungi selected in the screening procedure. The substrate was transformed by Botrytis cinerea AM235, Absidia cylindrospora AM336, Absidia coerulea AM93, and Absidia glauca AM177 into more polar metabolites. The transformation of racemic piperitone ((±)-1) catalyzed by B. cinerea AM235 gave 7-hydroxypiperitone (2) as the only product. The biotransformation of (±)-1 by A. cylindrospora AM336 afforded mixture of three products: (-)-(R)-7-hydroxypiperitone ((-)-2), (+)-(4S,6R)-trans-6-hydroxypiperitone ((+)-3), and (+)-(4R,6R)-cis-6-hydroxypiperitone ((+)-4). The transformation of this substrate ((±)-1) by A. coerulea AM93 gave (±)-7... Chirality journals http://www.medworm.com/rss/comments.php?id=4003521 Wed, 29 Sep 2010 00:03:07 +0100 4003521 http://www.medworm.com/index.php?rid=3915420&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803742%26dopt%3DAbstract Authors: Cannazza G, Carrozzo MM, Battisti U, Braghiroli D, Parenti C, Troisi A, Troisi L Benzothiadiazines differently substituted at the sulfonamidic nitrogen atom, at the stereogenic carbon atom and at the anilinic nitrogen atom have been synthesized and fully characterized. Enantioseparation of these compounds has revealed rapid on-column enantiomerization. The recently developed software DCXplorer has been successfully applied to calculate enantiomerization kinetic parameters. Enantiomerization barriers of 3-phenyl substituted benzothiadiazines, calculated in this work, have indicated a higher enantiomerization rate suggesting that the aromatic substituent exerts a strong effect on the enantiomerization process. Methyl substitution on N(2) position led to higher free energy barrie... Chirality journals http://www.medworm.com/rss/comments.php?id=3915420 Tue, 31 Aug 2010 10:12:39 +0100 3915420 http://www.medworm.com/index.php?rid=3915419&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803743%26dopt%3DAbstract Authors: Marom H, Agranat I The pyramidal inversion mechanisms of the 6-methoxy and the 5-methoxy tautomers of (S)-omeprazole were studied, employing ab initio and DFT methods. The conformational space of the model molecule (S)-2-[(3-methyl-2-pyridinyl)methyl]sulfinyl-1H-benzimidazole was calculated, with respect to rotations around single bonds, at the B3LYP/6-311G(d,p) level. All of the resulting conformations were used as starting points for full optimizations of (S)-omeprazole, at B3LYP/6-31G(d), B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), B3LYP/6-311G(2df,2pd), MP2/6-31G(d), and MP2/6-311G(d,p) levels. Four distinct pathways were found for enantiomerization via the pyramidal inversion mechanism for each of the tautomers of (S)-omeprazole. Each transition state, in which the sulfur, th... Chirality journals http://www.medworm.com/rss/comments.php?id=3915419 Tue, 31 Aug 2010 10:12:35 +0100 3915419 http://www.medworm.com/index.php?rid=3915418&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803744%26dopt%3DAbstract Authors: Kühnle M, Kreidler D, Holtin K, Czesla H, Schuler P, Schurig V, Albert K The hyphenation of enantioselective capillary gas chromatography and mass spectrometry is not always sufficient to distinguish between structural isomers, thus requiring peak identification by NMR spectroscopy. Here the first online coupling of enantioselective capillary gas chromatography with proton nuclear resonance spectroscopy is described for the unfunctionalized chiral alkane 2,4-dimethylhexane resolved on octakis(6-O-methyl-2,3-di-O-pentyl)-gamma-cyclodextrin at 60 degrees C. NMR allows constitutional and configurational isomers (diastereomers and enantiomers) to be distinguished. Enantiomers display identical spectra at different retention times, which enable an indirect identification of thes... Chirality journals http://www.medworm.com/rss/comments.php?id=3915418 Tue, 31 Aug 2010 10:12:31 +0100 3915418 http://www.medworm.com/index.php?rid=3915417&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803745%26dopt%3DAbstract Authors: Sun H, Zhang D, Zhang C, Liu C The Michael addition of cyclohexanone with trans-beta-nitrostyrene catalyzed by a chiral ionic liquid (CIL) pyrrolidine-imidazolium bromide, which represents a prototype of CIL-promoted asymmetric syntheses, has been investigated by performing density functional theory calculations. We show the details of the mechanism and energetics, the influence of the acid additive on the reactivity, and the functional role of the CIL in the asymmetric addition. It is found that the reaction proceeds via two stages, i.e., the initial enamine formation, where the imine complex is first created and then isomerizes into the enamine intermediate, and the subsequent Michael addition involving a three-step mechanism. The calculations show that the presence of the a... Chirality journals http://www.medworm.com/rss/comments.php?id=3915417 Tue, 31 Aug 2010 10:12:28 +0100 3915417 http://www.medworm.com/index.php?rid=3915416&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803746%26dopt%3DAbstract Authors: Zhang ZG, Dong ZB, Li JS A series of (S)-BINOL ligands substituted at the 3 position with some five-membered nitrogen-containing aromatic heterocycles were effectively prepared and their catalytic abilities were evaluated in the asymmetric addition of diethylzinc to benzaldehyde in the presence of titanium tetraisopropoxide. Under the optimized reaction conditions, titanium complex of (S)-3-(1H-benzimidazol-1-yl)-1,1'-bi-2-naphthol was found to be the most efficient catalyst for asymmetric ethylation of various aldehydes to generate the corresponding secondary alcohols in up to 99% yield and 91% ee. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803746 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915416 Tue, 31 Aug 2010 10:12:25 +0100 3915416 http://www.medworm.com/index.php?rid=3915415&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803747%26dopt%3DAbstract Authors: Wang H The enantiomeric atropoisomers of 1,1'-binaphthyl-2,2'-diol (BINOL) have become one of the most widely used chiral ligands and auxiliaries for asymmetric synthesis. This review provides an overview of enantioselective synthesis of optical active BINOLs by straightforward asymmetric oxidative coupling of identical 2-naphthol and its substituted derivatives. Chirality 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803747 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915415 Tue, 31 Aug 2010 10:12:22 +0100 3915415 http://www.medworm.com/index.php?rid=3915414&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803748%26dopt%3DAbstract Authors: Marathias VM, Tate PA, Papaioannou N, Massefski W By using a combination of inverse gated (1)H decoupled (13)C-NMR experiments1 with short acquisition times and NMR Cryo-probe technology, the sample requirements and experimental times necessary to accurately measure enantiomeric excess of small chiral molecules has been reduced 16-fold. Quality (13)C-NMR spectra can now be obtained from a 1 to 5 mg sample in 12 minutes. The enantiomeric excess determination achieved from the average integration of all the (13)C-resonances in the spectrum is comparable to enantiomeric excess measured by chiral SFC. The advantage of the NMR method is that enantiomeric excess can rapidly be measured in situ on practical amounts of enantioselective reaction products without the need for chromatogr... Chirality journals http://www.medworm.com/rss/comments.php?id=3915414 Tue, 31 Aug 2010 10:12:18 +0100 3915414 http://www.medworm.com/index.php?rid=3915413&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803749%26dopt%3DAbstract Authors: Gavrilov KN, Benetsky EB, Boyko VE, Rastorguev EA, Davankov VA, Schäffner B, Börner A (S)-6-Br-BINOL-derived phosphoramidite, a simple monodentate ligand with a stereogenic center at the phosphorus atom, was synthesized for the first time. This stereoselector generated a high level of enantioselectivity (80-95% ee) in the rhodium-catalyzed hydrogenation of alpha-dehydrocarboxylic acid esters and was also successfully employed in the asymmetric palladium-catalyzed allylic substitution of (E)-1,3-diphenylallyl acetate. The optical yield also showed significant dependence with reaction type: up to 70% ee for allylic amination, up to 75% ee for allylic sulfonylation, and up to 90% ee for allylic alkylation. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803749 [PubMe... Chirality journals http://www.medworm.com/rss/comments.php?id=3915413 Tue, 31 Aug 2010 10:12:14 +0100 3915413 http://www.medworm.com/index.php?rid=3915412&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803750%26dopt%3DAbstract Authors: Zilbeyaz K, Kurbanoglu EB Ninety isolates of microorganisms belonging to different taxonomical groups (30 bacteria, 20 yeast, and 40 fungi) were previously isolated from various samples. These isolates were screened as reducing agents for acetophenone 1a to phenylethanol 2a. It was found that the isolate EBK-10 was the most effective biocatalyst for the enantioselective bioreduction of acetophenone. This isolate was identified as Rhodotorula glutinis by the VITEK 2 Compact system. The various parameters (pH 6.5, temperature 32 degrees C, and agitation 200 rpm) of the bioreduction reaction was optimized, which resulted in conversions up to 100% with >99% enantiomeric excesses (ee) of the S-configuration. The preparative scale bioreduction of acetophenone 1a by R. glutinis EB... Chirality journals http://www.medworm.com/rss/comments.php?id=3915412 Tue, 31 Aug 2010 10:12:11 +0100 3915412 http://www.medworm.com/index.php?rid=3915411&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803751%26dopt%3DAbstract Authors: Miao S, Bai J, Yang J, Zhang Y A series of new highly efficient chiral aliphatic-aromatic diamine catalysts have been designed and successfully applied to the asymmetric Michael addition of cyclohexanone with nitroolefins under solvent-free conditions without any acidic additives. The desired adducts were obtained in high yields with excellent enantio- and diastereoselectivities of syn products (up to >99% ee, >99:1 dr). Chirality 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803751 [PubMed - in process] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915411 Tue, 31 Aug 2010 10:12:06 +0100 3915411 http://www.medworm.com/index.php?rid=3915425&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803490%26dopt%3DAbstract Authors: Caglioti L, Micskei K, Pályi G Origin(s) of biological chirality appear(s) to be intimately connected to origin(s) of life. Prebiotic evolution toward these important turning points can be traced back to single chiral molecules. These can be small (monomeric) units as amino acids or monosaccharides or oligomers as oligo-RNA type molecules. Earlier speculations about these two kinds of entries to biological chirality are critically reviewed. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803490 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915425 Thu, 26 Aug 2010 23:00:00 +0100 3915425 http://www.medworm.com/index.php?rid=3915424&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803492%26dopt%3DAbstract In this study, an empirical algorithm was developed to estimate alpha at isocratic conditions based upon information collected from a gradient elution. The algorithm was validated for SFC applications and has been shown to accurately predict enantioselectivity for a wide variety of racemic test analytes eluted on different chiral column and mobile phase conditions. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803492 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915424 Thu, 26 Aug 2010 23:00:00 +0100 3915424 http://www.medworm.com/index.php?rid=3915423&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803494%26dopt%3DAbstract Authors: Tóth GK, Hetényi A, Ilisz I, Péter A Meso diaminopimelic acid is an important noncoded amino acid found in Gram-negative bacterial peptidoglycan. In spite of its importance, this stereoisomer is not available commercially. A simple, economical procedure was developed for the isolation of pure meso diaminopimelic acid via an high-performance liquid chromatography separation. In our new approach, the underivatized three isomers of diaminopimelic acid were separated on a crown ether-based chiral stationary phase. For the structure identification, (1)H NMR spectroscopy was applied. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803494 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915423 Thu, 26 Aug 2010 23:00:00 +0100 3915423 http://www.medworm.com/index.php?rid=3915422&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803495%26dopt%3DAbstract Conclusion: The results indicate that (R)- and (S)-ketamine and (R)- and (S)-norketamine plasma concentrations do not explain the antinociceptive activity of the drug in patients suffering from CRPS. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20803495 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3915422 Thu, 26 Aug 2010 23:00:00 +0100 3915422 http://www.medworm.com/index.php?rid=3915421&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20803496%26dopt%3DAbstract This article explores the reasons of this micro/macro difference as well as the size borderline between the two regimes. There are two major demarcation lines, both related to the object's chaotic thermal motion. The first one is due to destruction of the necessary spatial orientation by the fast rotational diffusion. Only particles larger than 1 mum can maintain their original orientation for 1 sec or longer. For smaller particles, an additional external orienting factor, e.g., a strong electric field has to be applied. The second limitation is defined by the ratio of the hydrodynamic separation of the enantiomers (which is directly proportional to time) to their displacement due to the translational Brownian motion (which is proportional to square root of time). On the laboratory time sc... Chirality journals http://www.medworm.com/rss/comments.php?id=3915421 Thu, 26 Aug 2010 23:00:00 +0100 3915421 http://www.medworm.com/index.php?rid=3758994&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20623583%26dopt%3DAbstract Authors: Wang L, Cheng S, Chen R, Chang J Axially chiral biphenyls such as (M,S)-3k have been conveniently obtained by crystallization of their diastereomeric mixtures, which were synthesized from racemic 4,4'-dimethoxy-5,6,5',6'-bis(methylenedioxy)-2-carboxylester-2'-carboxyl-biphenyls 4 and chiral amino alcohols (R)-alaninol, (S)-alaninol, (S)-valinol, and (S)-phenylalaninol. A crystallization-induced configuration transformation of the biphenyls was thus achieved. It was found that amide formation of an (S)-valinol or (S)-phenylalaninol at the 2'-position of the biphenyl usually induced the deposition of crystals with the (M)-configuration from ethanol in yields higher than 50%. The absolute configurations (ACs) of two crystalline biphenyls have been determined by X-ray crystallogra... Chirality journals http://www.medworm.com/rss/comments.php?id=3758994 Fri, 16 Jul 2010 23:12:11 +0100 3758994 http://www.medworm.com/index.php?rid=3758993&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20623585%26dopt%3DAbstract Authors: Martínez AG, Vilar ET, Fraile AG, Cerero Sde L, Ruiz PM, Morillo CD A new set of optically active 2,3,3- and 2,7,7-trimethyl-substituted gamma-aminonorbornan-2-ols have been obtained from 2-methylenenorbornane-1-carbonitriles derived from (+)-camphor and (-)-fenchone and probed as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde. This has allowed the study of the structural factors influencing the chirality transfer, such as variation of the relative configuration at C(2) and steric hindrance at C(2), C(3), and C(7) positions of norbornane, which result in the observance of the important role played by the gem-dimethyl position in gamma-aminonorbornan-2-exo-ols. An empirical rationalization of the obtained experimental results has been realize... Chirality journals http://www.medworm.com/rss/comments.php?id=3758993 Fri, 16 Jul 2010 23:12:08 +0100 3758993 http://www.medworm.com/index.php?rid=3719410&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20589938%26dopt%3DAbstract Authors: Gal J Louis Pasteur resolved sodium ammonium (+/-)-tartrate in 1848, thereby discovering molecular chirality. Although hindered by the primitive state of organic chemistry, he introduced new terminology and nomenclature for his new science of molecular and crystal chirality. He was well prepared for this task by his rigorous education and innate abilities, and his linguistic achievements eventually earned him membership in the supreme institution for the French language, the Académie française. Dissymmetry had been in use in French from the early 1820s for disruption or absence of symmetry or for dissimilarity or difference in appearance between two objects, and Pasteur initially used it in the latter connotation, without any reference to handedness or enantiomorphism. S... Chirality journals http://www.medworm.com/rss/comments.php?id=3719410 Mon, 28 Jun 2010 23:00:00 +0100 3719410 http://www.medworm.com/index.php?rid=3673001&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20549711%26dopt%3DAbstract Authors: Damas A, Moussa J, Rager MN, Amouri H The chiral octahedral bimetallic assemblies [(bpy)(2)Ru(o-L(Ir))][CF(3)SO(3)](2) (2), [(ppy)(2)Rh(o-L(Ir))][NO(3)] (7) and [(ppy)(2)Ir(o-L(Ir))][NO(3)] (8) featuring chelating organometallic linker [Cp*Ir(eta(4)-o-benzoquinone)] (o-L(Ir)) have been prepared and fully characterized. Anion metathesis following a convenient procedure allowed the preparation of the related diastereomers [Delta-(bpy)(2)Ru(o-L(Ir))][Delta-TRISPHAT](2) (2a) and [Lambda-(bpy)(2)Ru(o-L(Ir))][Delta-TRISPHAT](2) (2b) as well as the octahedral rhodium [(Delta, Lambda)-(ppy)(2)Rh(o-L(Ir))][Delta-TRISPHAT] (7a, 7b) and iridium [(Delta, Lambda)-(ppy)(2)Ir(o-L(Ir))][Delta-TRISPHAT] (8a, 8b) bimetallic assemblies. (1)H NMR studies in solution carried out on these compounds... Chirality journals http://www.medworm.com/rss/comments.php?id=3673001 Sun, 13 Jun 2010 23:00:00 +0100 3673001 http://www.medworm.com/index.php?rid=3673000&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20549777%26dopt%3DAbstract Authors: Gou S, Judeh ZM New amino acid-based modular chiral ligands were readily synthesized and used to catalyze the asymmetric conjugate addition of Et(2)Zn to various cyclic enones in the presence of a variety of copper sources. Moderately high ee of up to 72% were obtained using ligand (S)-1e under mild conditions. Chirality 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20549777 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3673000 Sun, 13 Jun 2010 23:00:00 +0100 3673000 http://www.medworm.com/index.php?rid=3673003&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20544700%26dopt%3DAbstract Authors: Zhang P, Zhu W, Dang Z, Shen Z, Xu X, Huang L, Zhou Z Benalaxyl (BX), methyl-N-phenylacetyl-N-2,6-xylyl alaninate, is a potent acylanilide fungicide and consist of a pair of enantiomers. The stereoselective metabolism of BX was investigated in rat and rabbit microsomes in vitro. The degradation kinetics and the enantiomer fraction (EF) were determined using normal high-performance liquid chromatography with diode array detection and a cellulose-tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). The t(1/2) of (-)-R-BX and (+)-S-BX in rat liver microsomes were 22.35 and 10.66 min of rac-BX and 5.42 and 4.03 of BX enantiomers. However, the t(1/2) of (-)-R-BX and (+)-S-BX in rabbit liver microsomes were 11.75 and 15.26 min of rac-BX and 5.66 and 9.63 of ... Chirality journals http://www.medworm.com/rss/comments.php?id=3673003 Thu, 10 Jun 2010 23:00:00 +0100 3673003 http://www.medworm.com/index.php?rid=3673002&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20544701%26dopt%3DAbstract Authors: Zheng C, Zhang D, Wu Q, Lin X A series of novel designed mexiletine derivatives and its analogs were prepared, the structures were confirmed by Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), and Electrospray Ionization-Mass Spectrometry (ESI-MS), and the enantioseparations were performed on polysaccharide-based chiral stationary phase (CSP), Chiralcel OD-H, and Chiralcel OJ-H, under normal-phase mode. The effects of the concentration of isopropanol in the mobile phase were studied, seven of the eight enantiomers got baseline separation on Chiralcel OD-H, and five of the eight enantiomers got successfully separation on Chiralcel OJ-H. The effects of structural features were also discussed. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 2... Chirality journals http://www.medworm.com/rss/comments.php?id=3673002 Thu, 10 Jun 2010 23:00:00 +0100 3673002 http://www.medworm.com/index.php?rid=3379701&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20235280%26dopt%3DAbstract Authors: Uncuta C, Bartha E, Gherase D, Teodorescu F, Draghici C, Cavagnat D, Daugey N, Liotard D, Buffeteau T Six enantiomeric pairs of TADDOL-s gathered in two series with either methyl (series A) or phenyl (series B) substituent in 2-position of the dioxolane ring were studied by vibrational circular dichroism (VCD). Experimental IR and VCD spectra associated with density functional theory (DFT) calculations showed that the two series exhibit quite different conformations in solution. In series A, the conformer with anti C--O bonds and stabilized by intramolecular OHOH hydrogen bonding prevails, whereas in series B the conformer with gauche C--O bonds and intramolecular OHpi hydrogen bonding is favored. The shape and sign of the VCD bands in the O--H stretching region revealing the ... Chirality journals http://www.medworm.com/rss/comments.php?id=3379701 Tue, 16 Mar 2010 00:00:00 +0100 3379701 http://www.medworm.com/index.php?rid=3379700&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20235281%26dopt%3DAbstract This study provides not only the novel insights into the planar chirality of substituted [2.2]paracyclophanes but also a basis for the potential application of such dramatic CD spectral difference between the acid-base pair to the chiroptical pH-sensors. Chirality 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20235281 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3379700 Tue, 16 Mar 2010 00:00:00 +0100 3379700 http://www.medworm.com/index.php?rid=3362614&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20222142%26dopt%3DAbstract Authors: Liang J, Canary JW A tetradentate tripodal ligand containing a chiral center and three different coordinating arms was designed and synthesized. Its complexation properties with Zn(II) and Cu(I) were studied by NMR and optical spectroscopy. NMR experiments demonstrated the formation of two diastereomers, indicating the stabilization of the central tertiary amine configuration by metal coordination. The inversion of pyramidalization of the central tertiary amine of the ligand was found to be highly dependent upon metal ion, solvent, and temperature. Dynamic NMR measurements were used to estimate the energy of activation required for nitrogen atom inversion. Finally, absorption and circular dichroism measurements confirmed the expectation that metal complexes of the ligand gave ... Chirality journals http://www.medworm.com/rss/comments.php?id=3362614 Wed, 10 Mar 2010 00:00:00 +0100 3362614 http://www.medworm.com/index.php?rid=3362613&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20222143%26dopt%3DAbstract We report that 3,3'-diaryl-BINOL phosphoric acids are effective enantioselective extractants in chiral separation methods based on reactive liquid-liquid extraction. These new extractants are capable of separating racemic benzylic primary amine substrates. The effect of the nature of the substituents at the 3,3'-positions of the host were examined as well as the structure of the substrate, together with important parameters such as the organic solvent, the pH of the aqueous phase, and the host stoichiometry. Titration of the substrate with the host was monitored by FTIR, NMR, UV-Vis, and CD spectroscopy, which provided insight into the structure of the host-guest complex involved in extraction. Chirality 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20222143 [PubMed - as supplied by publisher]... Chirality journals http://www.medworm.com/rss/comments.php?id=3362613 Wed, 10 Mar 2010 00:00:00 +0100 3362613 http://www.medworm.com/index.php?rid=3315754&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20186757%26dopt%3DAbstract Authors: Merten C, Amkreutz M, Hartwig A Chiral alpha-methylbenzyl amine is a well known and often used chiral auxiliary, e.g., in the resolution of racemates or asymmetric catalysis. In this work, alpha-methylbenzyl amine and its derivatives N,alpha-dimethylbenzyl amine, N,N,alpha-trimethylbenzyl amine, and bis[alpha-methylbenzyl] amine were investigated by vibrational circular dichroism (VCD) spectroscopy and density functional theory (DFT). For all compounds, stable low energy conformers were obtained by the DFT calculations and based on those, the theoretical vibrational absorption (VA) and VCD spectra were calculated and compared with experimental spectra. Hence, the absolute configurations and conformational preferences were determined. A qualitative comparison of all the experim... Chirality journals http://www.medworm.com/rss/comments.php?id=3315754 Mon, 22 Feb 2010 00:00:00 +0100 3315754 http://www.medworm.com/index.php?rid=3315753&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20186758%26dopt%3DAbstract Authors: Merten C, Jalkanen KJ, Weiss VC, Hartwig A Vibrational circular dichroism (VCD) spectroscopy and density functional theory (DFT) calculations are used to investigate the keto-enol equilibrium of 3-(trifluoroacetyl)-camphor (TFC) and to study the interaction of TFC with chiral amines in deuterated Chloroform. It is shown that the VCD spectra of the enol- and keto forms of TFC can clearly be distinguished and that the enol form is favored. By deprotonation of the TFC enol with chiral amines, no indication of a mutual diasteriomeric influence on the VCD spectra induced by transfer of stereochemical information between the chiral ionic species is found, neither experimentally nor theoretically. Chirality 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20186758 [PubMed - as supplied by p... Chirality journals http://www.medworm.com/rss/comments.php?id=3315753 Mon, 22 Feb 2010 00:00:00 +0100 3315753 http://www.medworm.com/index.php?rid=3315752&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20186759%26dopt%3DAbstract Authors: PMID: 20186759 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3315752 Mon, 22 Feb 2010 00:00:00 +0100 3315752 http://www.medworm.com/index.php?rid=3276802&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20155823%26dopt%3DAbstract Authors: Vass E, Majer Z, Kőhalmy K, Hollósi M The optical spectroscopic characterization of gamma-turns in solution is uncertain and their distinction from beta-turns is often difficult. This work reports systematic ECD and vibrational circular dichroism (VCD) spectroscopic studies on gamma-turn model cyclic tetrapeptides cyclo(Ala-beta-Ala-Pro-beta-Ala) (1), cyclo(Pro-beta-Ala-Pro-beta-Ala) (2) and cyclo(Ala-beta-Ala-Ala-beta-Ala) (3). Conformational analysis performed at the 6-31G(d)/B3LYP level of theory using an adequate PCM solvent model predicted one predominant conformer for 1-3, featuring two inverse gamma-turns. The ECD spectra in ACN of 1 and 2 are characterized by a negative n-->pi* band near 230 nm and a positive pi-->pi* band below 200 nm with a long wave... Chirality journals http://www.medworm.com/rss/comments.php?id=3276802 Fri, 12 Feb 2010 00:00:00 +0100 3276802 http://www.medworm.com/index.php?rid=3263064&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143410%26dopt%3DAbstract Authors: Jiang X, Zhang B, Zhang Y, Lin L, Yan W, Wang R Although the organocatalytic direct asymmetric Michael reactions of carbonyl compounds to nitroalkenes have been investigated intensely, the Michael reaction of the thioether-based donors remains a rather undeveloped field. This work concerns the asymmetric Michael addition of aryl sulfanyl-propan-2-one to nitroalkenes with benzoic acid as an additive, and chiral amine-thiourea as a bifunctional organocatalyst. The reactions provided the highly functionalized chiral adducts with excellent enantioselectivities (up to 96% ee) and good yields. Moreover, the further transformed products exhibited excellent diastereoselectivity. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20143410 [PubMed - as supplied by publisher] (Source: ... Chirality journals http://www.medworm.com/rss/comments.php?id=3263064 Mon, 08 Feb 2010 00:00:00 +0100 3263064 http://www.medworm.com/index.php?rid=3263063&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143411%26dopt%3DAbstract Authors: He Q, Gomaa H, Rohani S, Zhu J, Jennings M The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine were determined and are presented herein. The structure comparison between less soluble salts and more soluble salts shows that weak interactions such as CH/pi interactions and van der Waals gain importance and contribute to chiral recognition when the hydrogen bonding patterns are very similar. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20143411 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3263063 Mon, 08 Feb 2010 00:00:00 +0100 3263063 http://www.medworm.com/index.php?rid=3263062&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143412%26dopt%3DAbstract Authors: Merlani M, Barbakadze V, Amiranashvili L, Gogilashvili L, Yannakopoulou E, Papadopoulos K, Chankvetadze B The racemic and enantioselective synthesis of a novel glyceric acid derivative, namely, 2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid as well as the antioxidant activities is described. The virtually pure enantiomers, (+)-(2R,3S)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid and (-)-(2S,3R)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid were synthesized for the first time via Sharpless asymmetric dihydroxylation of trans-caffeic acid derivatives using the enantiocomplementary catalysts, (DHQD)(2)-PHAL and (DHQ)(2)-PHAL. The determination of enantiomeric purity of the novel chiral glyceric acid derivatives was performed by high-performance liquid chromat... Chirality journals http://www.medworm.com/rss/comments.php?id=3263062 Mon, 08 Feb 2010 00:00:00 +0100 3263062 http://www.medworm.com/index.php?rid=3263061&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143413%26dopt%3DAbstract This article describes a simple and reliable analytical HPLC-PAD-CD method for simultaneous determination of catechin diastereomers both in infusions and extracts from the leaves of Byrsonima species. The direct separation of catechin, ent-catechin, epicatechin, and ent-epicatechin was obtained in normal phase by HPLC-PAD-CD using Chiralcel OD-H as chiral stationary phase and n-hexane/ethanol with 0.1% of TFA as mobile phase. Chirality, 2010. (c) 2010 Wiley-Liss, Inc. PMID: 20143413 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3263061 Mon, 08 Feb 2010 00:00:00 +0100 3263061 http://www.medworm.com/index.php?rid=3263055&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143415%26dopt%3DAbstract Authors: Yang G, Tran H, Fan E, Shi W, Lowary TL, Xu Y The absolute configurations of three synthesized anthracycline analogues have been determined using vibrational circular dichroism (VCD) spectroscopy and the density functional theory (DFT) calculations. The experimental VCD spectra of the three compounds have been measured for the first time in the film state, prepared from their CDCl(3) solutions. Conformational searches for the monomers and some dimers of the three compounds have been performed at the DFT level using the B3LYP functional and the 6-311G** and 6-311++G** basis sets. The corresponding vibrational absorption and VCD spectra have been calculated. The good agreement between the experimental and the calculated spectra allows one to assign the absolute configurations of... Chirality journals http://www.medworm.com/rss/comments.php?id=3263055 Mon, 08 Feb 2010 00:00:00 +0100 3263055 http://www.medworm.com/index.php?rid=3263053&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143416%26dopt%3DAbstract Authors: Ujj V, Bagi P, Schindler J, Madarász J, Fogassy E, Keglevich G A simple, efficient, and economical method based on the combination of the exceptional behavior of o,o'-dibenzoyl- or o,o'-di-p-toluyl-(2R,3R)-tartaric acid in chiral recognition processes, and the coordination ability of calcium or magnesium ion was developed for the resolution of phospholene oxides 1. The calcium or magnesium salt of (-)-o,o'-dibenzoyl-(2R,3R)-tartaric acid 2,4-6 or calcium hydrogen (-)-o,o'-di-p-toluyl-(2R,3R)-tartrate 3 may form crystalline diastereomeric coordination complexes with the appropriate antipode of substituted 3-phospholene oxides 1 that makes possible efficient resolutions. Optically active phospholene oxides 1 were prepared directly by simply crystallization and digestion of ... Chirality journals http://www.medworm.com/rss/comments.php?id=3263053 Mon, 08 Feb 2010 00:00:00 +0100 3263053 http://www.medworm.com/index.php?rid=3228275&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20120023%26dopt%3DAbstract Special issue "Advances in Chiroptical Methods" Chirality. 2010 Jan 29;21(S1):S2-S3 Authors: Polavarapu PL, Nafie LA, Berova N PMID: 20120023 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3228275 Fri, 29 Jan 2010 00:00:00 +0100 3228275 http://www.medworm.com/index.php?rid=3228274&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20120024%26dopt%3DAbstract Authors: PMID: 20120024 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3228274 Fri, 29 Jan 2010 00:00:00 +0100 3228274 http://www.medworm.com/index.php?rid=3146749&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20049972%26dopt%3DAbstract Authors: Nicu VP, Debie E, Herrebout W, Van der Veken B, Bultinck P, Baerends EJ Vibrational modes in an achiral molecule may acquire rotational strength by complexation to a chiral molecule, as happens for achiral solvent molecules complexed to a chiral solute. We investigate this transfer of chirality in vibrational circular dichroism for the pulegone molecule in CDCl(3) solvent from the point of view of the robustness concept introduced recently. It turns out that the transfer of chirality yields nonrobust modes, which means that, although they are observed in vibrational circular dichroism (VCD) experiments, the sign of these modes cannot be predicted reliably with standard (Density Functional Theory) VCD calculations. This limits the usefulness of the induced chirality phenomenon ... Chirality journals http://www.medworm.com/rss/comments.php?id=3146749 Mon, 04 Jan 2010 00:00:00 +0100 3146749 http://www.medworm.com/index.php?rid=3146748&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20049977%26dopt%3DAbstract Authors: Brazhe NA, Brazhe AR, Sosnovtseva OV, Abdali S The metalloprotein hemoglobin (Hb) was studied using surface enhanced resonance Raman spectroscopy (SERRS) and surface enhanced resonance Raman optical activity (SERROA). The SERROA results are analyzed and compared with the SERRS, and the later to the resonance Raman (RRS) performed on Hb. The SERRS measurements careful optimization, with respect to the concentration and volume ratio of the analyte to colloids, enables for the first time SERROA of this molecule. We observed that the most intense SERROA signals were attributed the nu(4), nu(20), and nu(21) vibrations, which are sensitive to the redox state of the heme's iron ion, and to the presence of its sixth site, bound to exogenous ligand; O(2), NO or CO. However, in this stu... Chirality journals http://www.medworm.com/rss/comments.php?id=3146748 Mon, 04 Jan 2010 00:00:00 +0100 3146748 http://www.medworm.com/index.php?rid=3122570&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20034018%26dopt%3DAbstract We report the first mid-infrared observation of vibrational circular birefringence (VCB) arising from individual chiral molecules. VCB can also be called vibrational optical rotatory dispersion (VORD) and is the Kramers-Kronig transform of vibrational circular dichroism (VCD). The method of measurement involves a simple change in the optical set-up and electronic processing of a VCD spectrometer such that the VCB spectrum appears at twice the polarization modulation frequency as a pseudo vibrational linear dichroism (VLD) spectrum. VCB spectra are also calculated with density function theory (DFT) for the first time using a commercially available program for rotational strengths where the calculated intensities are convolved with the real, dispersive part of a normalized complex Lorentzian... Chirality journals http://www.medworm.com/rss/comments.php?id=3122570 Wed, 23 Dec 2009 00:00:00 +0100 3122570 http://www.medworm.com/index.php?rid=3119454&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20029961%26dopt%3DAbstract Authors: Kubota T, Sawada N, Zhou L, Welch CJ The chiral recognition ability of the polysaccharide-based chiral columns (Chiralpak AD-RH, Chiralpak AS-RJ, Chiralpak IC, Chiralcel OD-RH, and Chiralcel OJ-RH) for the benzazoles and the benzanilides was evaluated under reversed phase conditions. The columns showed the high chiral recognition ability for a wide range of benzazoles and benzanilides. Twenty-one racemates were used for the evaluation, and 20 racemates were completely separated on at least one of the columns. In particular, AS-RH and OJ-RH showed the high chiral recognition ability for the benzazoles, and the AD-RH, IC, and OJ-RH were effective for the benzanilides. Chirality 2010. (c) 2009 Wiley-Liss, Inc. PMID: 20029961 [PubMed - as supplied by publisher] (Source: Chiral... Chirality journals http://www.medworm.com/rss/comments.php?id=3119454 Tue, 22 Dec 2009 00:00:00 +0100 3119454 http://www.medworm.com/index.php?rid=3032055&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19937957%26dopt%3DAbstract Authors: Urbanová M Vibrational circular dichroism (VCD) spectra are reliable indicators of the spatial structure of chiral molecules. The specific and characteristic feature of vibrational spectroscopy, and therefore also of VCD, where the energy of some vibrational modes is predominantly focused to a specific part of the molecule, enables monitoring both the structure of the molecule dissolved in different solvents and under different physicochemical conditions and molecular interactions. This minireview deals with recent contributions covering structural information on the bioinspired interactions obtained by means of VCD, especially in the following areas: interaction of DNA with biomolecules and biogenic metals, guanine tetramers and quadruplexes, biointeractions of bile pigm... Chirality journals http://www.medworm.com/rss/comments.php?id=3032055 Tue, 24 Nov 2009 00:00:00 +0100 3032055 http://www.medworm.com/index.php?rid=3032054&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19937959%26dopt%3DAbstract Authors: Ding S, Kolbanovskiy A, Durandin A, Crean C, Shafirovich V, Broyde S, Geacintov NE The usefulness of modern density functional theory (DFT) methods is considered for establishing the absolute configurations of DNA lesions by comparisons of computed and experimentally measured optical rotatory dispersion (ORD) and electronic circular dichroism (ECD) spectra. Two rigid, structurally different DNA lesions (two spiroiminodihydantoin stereoisomers and four equine estrogen 4-hydoxyequilenin-DNA stereoisomeric adducts) have been investigated. In all cases, the signs and shapes of the computed ORD spectra reproduced the experimentally measured ORD spectra, although the magnitudes of the computed and experimental ORD values do not coincide exactly. The computed ECD spectra also reprodu... Chirality journals http://www.medworm.com/rss/comments.php?id=3032054 Tue, 24 Nov 2009 00:00:00 +0100 3032054 http://www.medworm.com/index.php?rid=3015671&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19927373%26dopt%3DAbstract Authors: Abbate S, Castiglioni E, Gangemi F, Gangemi R, Longhi G The first well documented experiments of Near Infrared Vibrational Circular Dichroism (NIR-VCD) were performed around 1975. We review the thirty year history of NIR-VCD, encompassing both instrumental development and theoretical/computational methods that allow interpretation of experimental spectra, harvesting useful structural information therefrom. We hope to stimulate interest in this still scarcely explored spectroscopy of chiral molecules. Chirality, 2010. (c) 2009 Wiley-Liss, Inc. PMID: 19927373 [PubMed - as supplied by publisher] (Source: Chirality) Chirality journals http://www.medworm.com/rss/comments.php?id=3015671 Thu, 19 Nov 2009 00:00:00 +0100 3015671 http://www.medworm.com/index.php?rid=3015670&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19927374%26dopt%3DAbstract This report describes the strategies for gas-phase chiral and structural characterization of biomolecules using mass spectrometry (MS) and ion mobility-MS (IM-MS) techniques. Because both MS and IM-MS do not directly provide chiral selectivity, methodologies for adding a chiral selector are discussed in the context of (i) host-guest (H-G) associations, (ii) diastereomeric collision-induced dissociation (CID) methods, (iii) ion-molecule reactions, and (iv) the kinetic method. MS techniques for the analysis of proteins and protein complexes are briefly described. New advances in performing rapid 2D gas-phase separations on the basis of IM-MS are reviewed with a particular emphasis on the different forms of IM instrumentation and how they are used for chiral and/or structural biomolecular stu... Chirality journals http://www.medworm.com/rss/comments.php?id=3015670 Thu, 19 Nov 2009 00:00:00 +0100 3015670 http://www.medworm.com/index.php?rid=3015669&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19927375%26dopt%3DAbstract Authors: Zayit A, Pinsky M, Elgavi H, Dryzun C, Avnir D The web site, http://www.csm.huji.ac.il/, uses the Continuous Chirality Measure to evaluate quantitatively the degree of chirality of a molecule, a structure, a fragment. The value of this measure ranges from zero, the molecule is achiral, to higher values (the upper limit is 100); the higher the chirality value, the more chiral the molecule is. The measure is based on the distance between the chiral molecule and the nearest structure that is achiral. Questions such as the following can be addressed: by how much is one molecule more chiral than the other? how does chirality change along conformational motions? is there a correlation between chirality and enantioselectivity in a series of molecules? Both elementary and advanced fea... Chirality journals http://www.medworm.com/rss/comments.php?id=3015669 Thu, 19 Nov 2009 00:00:00 +0100 3015669 http://www.medworm.com/index.php?rid=3015668&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19927376%26dopt%3DAbstract Authors: Sun DL, Huang SD, Wu PS, Li J, Ye YJ, Jiang HD Tetrahydropalmatine (THP) is one of the active alkaloid ingredients of Rhizoma Corydalis. THP has a chiral center, and the stereoselective pharmacokinetics and tissue distribution have been reported. The aim of the present article is to study the stereoselective protein binding of THP using equilibrium dialysis followed by HPLC-UV analysis. The results showed that THP stereoselectively binds to human serum albumin (HSA), alpha(1)-acid glycoprotein (AGP), and proteins in human plasma. The fraction binding of (+)-THP was significantly higher than that of (-)-THP, whereas such stereoselectivity was not found in rat plasma. The affinity of HSA and AGP to (+)-THP, expressed as nK(A), were 9.0 x 10(3) M(-1) and 2.34 x 10(5) M(-1), respe... Chirality journals http://www.medworm.com/rss/comments.php?id=3015668 Thu, 19 Nov 2009 00:00:00 +0100 3015668 http://www.medworm.com/index.php?rid=2985247&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19902529%26dopt%3DAbstract Authors: Di Bari L, Ripoli S, Pradhan S, Salvadori P The interaction between quercetin, a popular antioxidant flavonoid, and human serum albumin (HSA) is investigated and characterized by means of induced circular dichroism and saturation transfer difference NMR. These techiques demonstrate the reversible binding of quercetin to the carrier protein, which is responsible for its dissolution in aqueous medium. Competition experiments with two classical probes for HSA binding sites, namely Ibuprofen and Warfarin (a common anticoagulant coumarin), demonstrate that quercetin has a primary binding site located in the subdomain IIA, where coumarins are hosted. The affinity for this site is large and we found that quercetin may effectively displace warfarin from HSA. This may have relevant con... Chirality journals http://www.medworm.com/rss/comments.php?id=2985247 Mon, 09 Nov 2009 00:00:00 +0100 2985247 http://www.medworm.com/index.php?rid=2985246&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19902530%26dopt%3DAbstract Authors: Pescitelli G, Kurtán T, Flörke U, Krohn K In this review article we examine state-of-the-art techniques for the structural elucidation of organic compounds isolated from natural sources. In particular, we focus on the determination of absolute configuration (AC), perhaps the most challenging but inevitable step in the whole process, especially when newly isolated compounds are screened for biological activity. Among the many methods employed for AC assignment that we review, special attention is paid to electronic circular dichroism (CD) and to the modern tools available for quantum-mechanics CD predictions, including TDDFT. In this context, we stress that conformational flexibility often poses a limit to practical CD calculations of solution CD spectra. Many crystal... Chirality journals http://www.medworm.com/rss/comments.php?id=2985246 Mon, 09 Nov 2009 00:00:00 +0100 2985246 http://www.medworm.com/index.php?rid=2977935&cid=s_38019_67_f&fid=38019&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19899143%26dopt%3DAbstract Authors: Roy A, Bouř P, Keiderling TA In this work, time dependent density functional theory (TD-DFT) is used to provide a reliable basis for interpretation of the electronic spectra of coupled tryptophan (Trp) residues, particularly those in a model Trpzip beta-hairpin peptide. Pairs of isolated indoles form chiral coupled chromophores whose computed electronic ultraviolet circular dichroism (CD) is in excellent agreement with observed transition wavelengths and intensities. The calculations were compared to experimental data for pairwise coupling in mutant Trpzip peptides that are recently available. A study of variation of the basis set, geometry optimization, and the solvent environment on the spectra showed limited impact on bandshapes. An alternative simplified computationa... Chirality journals http://www.medworm.com/rss/comments.php?id=2977935 Fri, 06 Nov 2009 00:00:00 +0100 2977935