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enantiomer separation

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https://www.readbyqxmd.com/read/30340763/mechanistic-study-on-the-high-selectivity-enantioseparation-of-amino-acids-using-a-chiral-crown-ether-bonded-stationary-phase-and-acidic-highly-organic-mobile-phase-by-liquid-chromatography-time-of-flight-mass-spectrometry
#1
Yutaka Konya, Moyu Taniguchi, Masahiro Furuno, Yosuke Nakano, Nobuo Tanaka, Eiichiro Fukusaki
The separation mechanism of amino acid enantiomers using a chiral crown ether-bonded stationary phase, CROWNPAK CR-I(+), and acetonitrile (ACN)-rich mobile phases (MPs) was studied. The retention factors of proteinogenic l-amino acids (except proline) formed U-shaped plots against the ACN content in the MP with a sharp increase at a high ACN content, while d-amino acids showed much smaller increases or monotonous decreases in retention within the same range. The use of an acidic, highly organic MP with trifluoroacetic acid (TFA) provided a high enantioselectivity with a short separation time from the contribution of the increased binding of the ammonium group of the analytes to the crown ether functionality of the stationary phase and electrostatic repulsion counteracting the hydrophilic partition mechanism...
October 9, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/30340337/enantioseparation-stereochemical-assignment-and-chiral-recognition-mechanism-of-sulfoxide-containing-drugs
#2
Fei Xiong, Bei-Bei Yang, Jie Zhang, Li Li
The distinct pharmacodynamic and pharmacokinetic properties of enantiopure sulfoxide drugs have stimulated us to systematically investigate their chiral separation, stereochemical assignment, and chiral recognition mechanism. Herein, four clinically widely-used sulfoxide drugs were chosen and optically resolved on various chiral stationary phases (CSPs). Theoretical simulations including electronic circular dichroism (ECD) calculation and molecular docking were adopted to assign the stereochemistry and reveal the underlying chiral recognition mechanism...
October 18, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/30321480/stereoselective-pharmacokinetics-of-r-and-s-rabeprazole-in-human-using-chiral-lc-ms-ms-after-administration-of-rabeprazole-sodium-enteric-coated-tablet
#3
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
https://www.readbyqxmd.com/read/30321474/chiral-separation-and-modeling-of-quinolones-on-teicoplanin-macrocyclic-glycopeptide-antibiotics-csp
#4
REVIEW
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
https://www.readbyqxmd.com/read/30311251/inverse-cationic-isotachophoresis-for-separation-of-methadone-enantiomers-with-sulfated-%C3%AE-cyclodextrin-as-chiral-selector
#5
Saara Mikkonen, Jitka Caslavska, Petr Gebauer, Wolfgang Thormann
Chiral ITP of the weak base methadone using inverse cationic configurations with H+ as leading component and multiple isomer sulfated β-CD (S-β-CD) as leading electrolyte (LE) additive, has been studied utilizing dynamic computer simulation, a calculation model based on steady-state values of the ITP zones, and capillary ITP. By varying the amount of acidic S-β-CD in the LE composed of 3-morpholino-2-hydroxypropanesulfonic acid and the chiral selector, and employing glycylglycine as terminating electrolyte (TE), inverse cationic ITP provides systems in which either both enantiomers, only the enantiomer with weaker complexation, or none of the two enantiomers form cationic ITP zones...
October 12, 2018: Electrophoresis
https://www.readbyqxmd.com/read/30307111/enhanced-enantioselectivity-of-native-%C3%AE-cyclodextrins-by-the-synergy-of-chiral-ionic-liquids-in-capillary-electrophoresis
#6
Qi Zhang, Jian Zhang, Song Xue, Mengjie Rui, Bin Gao, Ang Li, Jiashuai Bai, Zhichao Yin, Anochie Ebubedike Mitchelle
In the cyclodextrins family, the native α-cyclodextrin has almost been abandoned in CE chiral separation due to its much weaker enantioselectivity compared with β-cyclodextrin and their derivatives. In this work, several amino acid chiral ionic liquids were selected to establish synergistic enantioseparation systems with native α-cyclodextrin. Enhanced enantioselectivities were observed in the chiral ionic liquids/α-cyclodextrin synergistic systems compared with single α-cyclodextrin system. A series of comparison experiments were performed to demonstrate the superiority of the synergistic systems...
October 11, 2018: Journal of Separation Science
https://www.readbyqxmd.com/read/30298475/comparison-of-in-vitro-stereoselective-metabolism-of-bupropion-in-human-monkey-rat-and-mouse-liver-microsomes
#7
Chandrali Bhattacharya, Danielle Kirby, Michael Van Stipdonk, Robert E Stratford
BACKGROUND AND OBJECTIVES: Bupropion is an atypical antidepressant and smoking cessation aid associated with wide intersubject variability. This study compared the formation kinetics of three phase I metabolites (hydroxybupropion, threohydrobupropion, and erythrohydrobupropion) in human, marmoset, rat, and mouse liver microsomes. The objective was to establish suitability and limitations  for subsequent use of nonclinical species to model bupropion central nervous system (CNS) disposition in humans...
October 8, 2018: European Journal of Drug Metabolism and Pharmacokinetics
https://www.readbyqxmd.com/read/30294058/investigation-of-chiral-recognition-by-molecular-micelles-with-molecular-dynamics-simulations
#8
Kevin F Morris, Eugene J Billiot, Fereshteh H Billiot, Jordan A Ingle, Stephanie R Zack, Kevin B Krauss, Kenny B Lipkowitz, William M Southerland, Yayin Fang
Molecular dynamics simulations were used to characterize the binding of the chiral drugs chlorthalidone and lorazepam to the molecular micelle poly-(sodium undecyl-(L)-leucine-valine). The project's goal was to characterize the nature of chiral recognition in capillary electrophoresis separations that use molecular micelles as the chiral selector. The shapes and charge distributions of the chiral molecules investigated, their orientations within the molecular micelle chiral binding pockets, and the formation of stereoselective intermolecular hydrogen bonds with the molecular micelle were all found to play key roles in determining where and how lorazepam and chlorthalidone enantiomers interacted with the molecular micelle...
2018: Journal of Dispersion Science and Technology
https://www.readbyqxmd.com/read/30277076/chiral-control-in-pentacoordinate-systems-the-case-of-organosilicates
#9
Leon J P van der Boon, Laurens van Gelderen, Tim R de Groot, Martin Lutz, J Chris Slootweg, Andreas W Ehlers, Koop Lammertsma
Chirality at the central element of pentacoordinate systems can be controlled with two identical bidentate ligands. In such cases the topological Levi-Desargues graph for all the Berry pseudorotations (BPR, max. 20) reduces to interconnected inner and outer "circles" that represent the dynamic enantiomer pair. High enough barriers of the BPR crossovers between the two circles is all what is needed to ascertain chiral integrity. This is illustrated computationally and experimentally for the organosilicates 7 and 10 that carry besides a Me (a), Et (b), Ph (c), or F (d) group two bidentate 2-(phenyl)benzo[ b]-thiophene or 2-(phenyl)naphthyl ligands, respectively...
October 2, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/30276925/direct-differentiation-of-stereoisomers-of-ezetimibe-ambrisentan-atorvastatin-and-their-mechanism-study-by-electrospray-ionization-quadurupole-time-of-flight-mass-spectrometry
#10
Lu Wang, Yali Wang, Lushan Yu, Cuirong Sun, Yu Kang, Zeng Su
A mass spectrometric method is introduced for rapid and accurate chiral quantification by examining a trimeric metal complex into which a chiral reference is incorporated with the analyte. Several metal ions (CuII, NiII, MgII, MnII, CoII, ZnII) were selected as the central metal ion, and chiral drugs ezetimibe (EZM) and ambrisentan (AMB) were used as the reference to each other for isomeric differentiation by using electrospray ionization quadrupole time-of-flight mass spectrometry. Doubly charged trimeric cluster ions instead of the singly charged clusters were applied in this study...
October 1, 2018: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/30273816/capillary-electrophoresis-method-for-the-determination-of-r-dapoxetine-3s-3-dimethylamino-3-phenyl-1-propanol-s-3-amino-3-phenyl-1-propanol-and-1-naphthol-as-impurities-of-dapoxetine-hydrochloride
#11
Henrik Harnisch, Gerhard K E Scriba
A capillary electrophoresis method was developed and validated for the determination of the purity of dapoxetine with regard to the related substances (3S)-3-amino-3-phenylpropan-1-ol, (3S)-3-(dimethylamino)-3-phenylpropan-1-ol, 1-naphthol and the enantiomer (R)-dapoxetine. The separation was based on a dual selector system, which was optimized by a fractional factorial resolution V + design followed by a central composite face centered design with star distance 1 and Monte Carlo simulations for defining the design space...
September 19, 2018: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/30271773/%C3%AE-glucosidase-inhibitors-from-the-coral-associated-fungus-aspergillus-terreus
#12
Mengting Liu, Changxing Qi, Weiguang Sun, Ling Shen, Jianping Wang, Junjun Liu, Yongji Lai, Yongbo Xue, Zhengxi Hu, Yonghui Zhang
Nine novel butenolide derivatives, including four pairs of enantiomers, named (±)-asperteretones A-D ( 1a/1b-4a/4b ), and a racemate, named asperteretone E ( 5 ), were isolated and identified from the coral - associated fungus Aspergillus terreus . All the structures were established based on extensive spectroscopic analyses, including HRESIMS and NMR data. The chiral chromatography analyses allowed the separation of (±)-asperteretones A-D, whose absolute configurations were further confirmed by experimental and calculated electronic circular dichroism (ECD) analysis...
2018: Frontiers in Chemistry
https://www.readbyqxmd.com/read/30270614/highly-enantioselective-graphene-based-chemical-sensors-prepared-by-chiral-noncovalent-functionalization
#13
Xiaobo Shang, Cheol Hee Park, Gwan Yeong Jung, Sang Kyu Kwak, Joon Hak Oh
As a basic characteristic of the natural environment and living matter, chirality has been used in various scientific and technological fields. Chiral discrimination is of particular interest owing to its importance in catalysis, organic synthesis, biomedicine, and pharmaceutics. However, it is still very challenging to effectively and selectively sense and separate different enantiomers. Here, enantio-differentiating chemosensor systems have been developed through spontaneous chiral functionalization of the surface of graphene field-effect transistors (GFETs)...
October 1, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/30253829/metal-ion-free-chiral-analysis-of-amino-acids-as-small-as-proline-using-high-definition-differential-ion-mobility-mass-spectrometry
#14
J Diana Zhang, K M Mohibul Kabir, William A Donald
The chiral analysis of enantiomers is important because bioactivity can depend strongly on stereochemistry as ligand-protein binding motifs are typically chiral. Ion mobility mass spectrometry-based methods are emerging for the rapid and sensitive chiral analysis of molecules. However, such methods are typically limited by the use of metal-bound trimers, which can be challenging to form owing to ion suppression and the need for extensive pre-screening experiments to identify suitable metal ions. Moreover, the chiral separation of very small molecules, such as cysteine and proline, using ion mobility has remained challenging...
December 7, 2018: Analytica Chimica Acta
https://www.readbyqxmd.com/read/30238493/enantioseparation-of-chiral-mandelic-acid-derivatives-by-supercritical-fluid-chromatography
#15
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
https://www.readbyqxmd.com/read/30224280/preparative-enantioseparation-of-synephrine-by-conventional-and-ph-zone-refining-counter-current-chromatography
#16
Yang Zhang, Shanshan Wang, Jianguang Luo, Yaolan Lin, Xiao Xu, Chao Han, Lingyi Kong
Synephrine, a chiral adrenergic agonist, exists as R- (more active) and S-enantiomers (less active) that are difficult to separate because of their alkalinity and high polarity. Herein, we show that although this enantioseparation can hardly be achieved by high-performance liquid chromatography, acceptable preparative separation can be realized using high-speed counter-current chromatography (HSCCC) and pH-zone-refining counter-current chromatography (CCC) under optimal conditions. Specifically, 23.0 mg of S-synephrine and 25...
September 7, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/30223142/sfc-for-chiral-separations-in-bioanalysis
#17
REVIEW
Lukas C Harps, Jan F Joseph, Maria K Parr
This review covers literature investigating methods for enantioselective chromatography using supercritical fluids as mobile phase constituents (SFC) in the field of bioanalysis. It provides an overview on method development and screening approaches published in scientific literature 2014-2018. Chiral stationary phases are used to create a chiral environment that allows for discrimination of enantiomers. Especially polysaccharide-based stationary phases are used in methods of recent investigations. In comparison to HPLC chiral SFC separation provides more selective cavity effects of inclusion-type chiral separation phases...
September 3, 2018: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/30222211/resolution-of-isoborneol-and-its-isomers-by-gc-ms-to-identify-synthetic-and-semi-synthetic-borneol-products
#18
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
https://www.readbyqxmd.com/read/30216709/an-environmentally-friendly-method-for-the-enantioseparation-and-determination-of-benalaxyl-in-tobacco-and-soil-by-ultra-performance-convergence-chromatography-with-tandem-mass-spectrometry
#19
Fei Yang, Gangling Tang, Zhonghao Li, Ziyan Fan, Ying Wang, Shanshan Liu, Zhaoyang Bian, Huimin Deng
For the purpose of chiral separation and determination of benalaxyl enantiomers in tobacco and soil, we developed a rapid, green and sensitive method using ultra-performance convergence chromatography with tandem mass spectrometry. The samples were extracted and purified by quick, easy, cheap, effective, rugged and safe method before injection. The baseline separation was obtained on a chiral column in 5 min with carbon dioxide and ethanol as mobile phase. Separation parameters were optimized for the best separation efficiency...
September 14, 2018: Journal of Separation Science
https://www.readbyqxmd.com/read/30213446/improving-visualization-of-trace-components-for-quantification-using-a-power-law-based-integration-approach
#20
Garrett Hellinghausen, M Farooq Wahab, Daniel W Armstrong
In some cases, trace component analysis only requires a sensitive and high-resolution mass spectrometer. However, enantiomers must be completely separated to be differentiated with a mass spectrometer, which is highly dependent on the stationary-mobile phase composition. In case of a challenging chiral separation, instead of trying new columns for screening purpose, resolution enhancement techniques could be used to resolve partially overlapping peaks. A well-known enhancement method is the power law, which increases the linear dynamic range of each analyte and reduces excessive noise...
September 1, 2018: Journal of Chromatography. A
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