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Lu-Ning Sun, Yi-Wen Shen, Yu-Wen Ying, Duo Li, Teng-Fei Li, Xue-Hui Zhang, Ping Zhao, Li Ding, Yong-Qing Wang
Rabeprazole is an effective proton pump inhibitor to treat acid-related diseases. To achieve the simultaneous determination of rabeprazole enantiomers in human plasma, a chiral LC-MS/MS method was developed and validated. Acetonitrile including 0.1% ammonium were used as protein precipitating agent. Analytes were separated within 8 minutes on a Chiralpak IC column (4.6 mm × 150 mm, 5 μm). The mobile phase was 10 mM ammonium acetate including 0.2% acetic acid-acetonitrile (35:65, v/v). An API 4000 mass spectrometer was used as detector for the analysis, and the multiple reactions monitoring transitions of m/z 360...
October 15, 2018: Chirality
Imran Ali, Mohd Suhail, Leonid Asnin
New chiral high-performance liquid chromatography (HPLC) method for the enantiomeric resolution of quinolones is developed and described. The column used was Chirobiotic T (150 × 4.6 mm, 5.0 μm). Three mobile phases used were MeOH:ACN:Water:TEA (70:10:20:0.1%), (60:30:10:0.1%), and (50:30:20:0.1%). The flow rate of the mobile phases was 1.0 mL/min with UV detection at different wavelengths. The values of retention, resolution, and separation factors ranged from 1.5 to 6.0, 1.80 to 2.25, and 2.86 to 6...
October 15, 2018: Chirality
Nabila Braia, Mounia Merabet-Khelassi, Louisa Aribi-Zouioueche
No abstract text is available yet for this article.
October 8, 2018: Chirality
Yingying Liu, Ling Ye, Zhichuan Shi, Xuejun Yang, Zhigang Zhao, Xuefeng Li
A highly enantioselective (91- > 99% ee) Michael addition of α-nitroacetate to α,β-unsaturated pyrazolamide was developed in the presence of a bifunctional squaramide. Satisfactory isolated yields (42%-99%) have been achieved with a wide range of α,β-unsaturated pyrazolamides, albeit acceptor of this type displayed poor reactivity in the precedent reports. The adducts resulting from this protocol are useful synthetic intermediates for further synthetic modification.
October 4, 2018: Chirality
Ashish Dixit, Pramod Kumar, Surendra Singh
Chiral salalen ligands derived from (S)-proline and derivatives of salicyaldehydes were synthesized, and their in-situ generated Cu (II) complexes were evaluated in the asymmetric Henry reaction. Salalen ligand of different substituents on the phenyl moiety showed remarkable effect on the enantioselectivity of nitro-aldol product of 4-nitrobenzaldehyde and nitromethane. Cu (II) complex generated in situ with (S)-2-(tert-butyl)-6-((2-(((2-hydroxy-3-methylbenzylidene)amino)methyl)pyrrolidin-1-yl)methyl) phenol (10 mol%) and Cu (OAc)2 ...
September 20, 2018: Chirality
Cheng Cheng, Rui Ma, Yuele Lu, Chunxiao Liu, Wenjun Zhang, Shanshan Di, Li Chen, Jinling Diao, Zhiqiang Zhou, Yuxia Hou
Research on the enantioselective environmental behavior of chiral pesticides has been a hot spot of environmental chemistry recently. In this study, the acute toxicity and digestion of furalaxyl enantiomers were determined on the aquatic algae Scendesmus obliquus. After exposure for 96 hours, the EC50 values for (S)-furalaxyl and (R)-furalaxyl were 13.59 and 15.26 mg/L, respectively. In addition, enantioselectivity was observed from the determined chlorophyll contents and antioxidant enzyme (CAT and SOD) activities of algae cells after exposure to furalaxyl enantiomers for 96 hours...
September 20, 2018: Chirality
Jiawei Ding, Ming Zhang, Huixue Dai, Chunmian Lin
Mandelic acid and its derivatives are important chiral analogs which are widely used in the pharmaceutical synthetic industry. The present study investigated the enantiomeric separation of six mandelic acids (mandelic acid, 2-chloromandelic acid, 3-chloromandelic acid, 4-chloromandelic acid, 4-bromomandelic acid, 4-methoxymandelic acid) on the Chiralpak AD-3 column by supercritical fluid chromatography. The influences of volume fraction of trifluoroacetic acid, type and percentage of modifier, column temperature, and backpressure on the separation efficiency were investigated...
September 20, 2018: Chirality
Yinjun Zhang, Feifei Cheng, Hongde Yan, Jianyong Zheng, Zhao Wang
The kinetic resolution of (R,S)-1-(4-chlorophenyl)ethylamine was accomplished using a commercial lipase from Candida antarctica (Novozym 435). The performance of this lipase was investigated for the enantioselective amidation of (R,S)-1-(4-chlorophenyl)ethylamine, leaving the target product (S)-1-(4-chlorophenyl)ethylamine in its unreacted form. The effects of various types of solvents and an acyl donor, the molar ratio of the substrate to the acyl donor, and the reaction temperature were studied. The optimum reaction conditions were found to result in amidation with methyl 2-tetrahydrofuroate at 40°C in methyl tert-butyl ether, with a substrate/acyl donor molar ratio of 1:2...
November 2018: Chirality
Jidong Yang, Xuanping Tan, Yanmei Zhao
A novel and simple method for simultaneous determination of chiral carnitine (CA) enantiomers was proposed. In this work, the rhodamine B (RhB) could react with D-CA and L-CA, and new resonance Rayleigh scattering (RRS) peaks were generated. According to the polarization experiments, it could be testified that scattering peak of this system was composed of resonance fluorescence and scattering light. The RRS intensity of the RhB could be enhanced with the addition of D- or L-CA. However, The RRS signal with L-CA had greater degree increased...
November 2018: Chirality
Ming-Yeh Yang, Aye Aye Khine, Jen-Wei Liu, Hui-Chen Cheng, Anren Hu, Hao-Ping Chen, Tzenge-Lien Shih
Borneol is a plant terpene commonly used in traditional Chinese medicine. Optically pure (+)-borneol and (-)-borneol can be obtained by extraction from the plants Dipterocarpaceae and Blumea balsamifera, respectively. "Synthetic borneol" is obtained from the reduction of (±)-camphor to lead to four different stereoisomers: (+)-isoborneol, (-)-isoborneol, (+)-borneol, and (-)-borneol. In contrast, "semi-synthetic borneol" is produced from the reduction of natural camphor, (+)-camphor, to afford two isomers: (-)-isoborneol and (+)-borneol...
November 2018: Chirality
Masahiro Kawada, Kosuke Nakashima, Shin-Ichi Hirashima, Toru Sakagami, Yuji Koseki, Tsuyoshi Miura
In this study, stereoselective conjugate addition of ketones to alkylidene malonates using organocatalyst has been developed. The reaction in the presence of 20 mol% of a novel thiourea-sulfonamide organocatalyst afforded conjugate adducts in moderate to high yields (up to 81%) under mild reaction conditions. Excellent diastereoselectivity (up to 98:2 dr) and enantioselectivity (up to 88% ee) were achieved.
November 2018: Chirality
Jordan L Johnson, Vijay Raghavan, Alessio Cimmino, Arash Moeini, Ana G Petrovic, Ernesto Santoro, Stefano Superchi, Nina Berova, Antonio Evidente, Prasad L Polavarapu
No abstract text is available yet for this article.
November 2018: Chirality
Eman I El-Kimary, Marwa A A Ragab
Stereospecific separation method of (±) betaxolol, (±) carvedilol, and (±) sotalol using High Performance Thin Layer Chromatography (HPTLC) and β-cyclodextrin as chiral selector has been developed and validated. The Box-Behnken surface response design was selected for optimizing the operating variables based on 15 trials design. The optimized method involves separation on Fluka HPTLC silica gel plates 60 F254 (20 × 10 cm) using acetonitrile-methanol-acetic acid-water (3.4:3.6:0.18:1 v/v) as a mobile phase containing 0...
November 2018: Chirality
Huimin Zang, Shun Yao, Yingjie Luo, Dan Tang, Hang Song
As one kind of functionalized green medium, chiral ionic liquids (CILs) have been widely applied in fields of asymmetric catalysis, enantioseparation, and so on. In this study, four kinds of amino acid-based CILs were synthesized by using trimethylamine, N-methylpyrrolidine, N-methylimidazole, and tropine as cationic nucleus, respectively. Then their specific optical rotation and solubility in common solvents were determined for further resolution application. The effect of different cations in these CILs was explored on the separation of racemic phenylalanine in complex-precipitation way...
November 2018: Chirality
Pierluigi Reveglia, Alessio Cimmino, Marco Masi, Paola Nocera, Nina Berova, George Ellestad, Antonio Evidente
Plants and fungi are seemingly inexhaustible sources of interesting natural products with remarkable structural and biological diversity. One of the most important groups is the terpenes, ubiquitous natural products that are generated by 2 now well-established biosynthetic pathways: the older mevalonate and the more recently discovered 1-deoxyxylulose-5-phosphate. Among the diterpenes, the pimarane diterpenes are a very representative subgroup with several and interesting biological activities resulting from different functional group modifications...
October 2018: Chirality
Elahe Naghdi, Ali Reza Fakhari
The stereoselective analysis and separation of racemic drugs play an important role in pharmaceutical industry to eliminate the unwanted isomer and find the right therapeutic control for the patient. Present study suggests a maltodextrin-modified capillary electrophoresis method for a single-run chiral separation of two closely similar opiate pain relief drugs: tramadol (TRA) and methadone (MET). The best separation method possible for the both enantiomers was achieved on an uncoated fused-silica capillary at 25°C using 100 mM phosphate buffer (pH 8...
October 2018: Chirality
Risa Sawada, Masayuki Gon, Jun Nakamura, Yasuhiro Morisaki, Yoshiki Chujo
A new type of planar chiral (Rp )- and (Sp )-4,7,12,15-tetrasubstituted [2.2]paracyclophanes was prepared from racemic 4,7,12,15-tetrabromo[2.2]paracyclophane as the starting substrate. Regioselective lithiation and transformations afforded racemic bis-(para)-pseudo-meta-type [2.2]paracyclophane (4,15-dibromo-7,12-dihydroxy[2.2]paracyclophane). Its optical resolution was performed by the diastereomer method using a chiral camphanoyl group as the chiral auxiliary. The diastereoisomers were readily isolated by simple silica gel column chromatography, and the successive hydrolysis afforded (Rp )- and (Sp )-bis-(para)-pseudo-meta-type [2...
October 2018: Chirality
Golo Storch, Oliver Trapp
We present rhodium catalysts that contain stereodynamic axially chiral biphenol-derived phosphinite ligands modified with non-stereoselective amides for non-covalent interactions. A chirality transfer was achieved with (R)- or (S)-acetylphenylalanine methyl amide, and the interaction mechanism was investigated by NMR measurements. These interactions at the non-stereoselective interaction sites and the formation of supramolecular complexes result in an enrichment of either the (Rax )- or (Sax ) enantiomer of the tropos catalysts, which in turn provide the (R)- or (S)-acetylphenylalanine methyl ester in the hydrogenation of (Z)-methyl-α-acetamidocinnamate...
October 2018: Chirality
Cemil Aydoğan
A novel chiral porous-layer stationary phase was developed for use in open-tubular nano liquid chromatography. The stationary phase was prepared by an in-situ polymerization of 3-chloro-2-hydroxypropylmethacrylate (HPMA-Cl) and ethylene dimethacrylate (EDMA). The reactive chloro groups at the surface of the porous stationary phase were reacted with β-Cyclodextrin (β-CD). The resulting morphology was characterized by using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR)...
October 2018: Chirality
Vera Yu Kuksenok, Victoria V Shtrykova, Victor D Filimonov, Alexandr G Druganov, Alexandr A Bondarev, Ksenia S Stankevich
For the first time, a method for enantiomer resolution of the anticonvulsant Galodif (1-((3-chlorophenyl)(phenyl)methyl) urea) by chiral HPLC was developed, whereas the enantiomeric composition of 1-((3-chlorophenyl)(phenyl)methyl) amine-precursor in Galodif synthesis-cannot be resolved by this method. However, starting 1-((3-chlorophenyl)(phenyl)methyl) amine quantitatively forms diastereomeric N-((3-chlorophenyl)(phenyl)methyl)-1-camphorsulfonamides in reaction with chiral (1R)-(+)- or (1S)-(-)-camphor-10-sulfonyl chlorides...
October 2018: Chirality
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