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enantiomer separation

Pengfei Zhao, Zhaokun Wang, Xun Gao, Xingjie Guo, Longshan Zhao
This paper presents a novel multi-residue method for the enantioselective analysis of 22 chiral pesticides in cucumber, tomato, cabbage, grape, mulberry, apple and pear at enantiomeric levels. Pesticides were efficiently extracted by magnetic solid-phase extraction based on graphene as sorbent. Response surface methodology was used to assist the multivariable optimization. The perfect chiral separation of the enantiomers was achieved on a Chiralpak IG column within 47 min by reversed-phase liquid chromatography coupled with tandem mass spectrometry, which is a significant improvement to resolve a large group of chiral compounds under one set of conditions...
March 30, 2019: Food Chemistry
Emmanuelle Lipka, Anca-Elena Dascalu, Yasmine Messara, Eka Tsutsqiridze, Tivadar Farkas, Bezhan Chankvetadze
In this short communication preliminary results are reported on the separation of enantiomers of underivatized amino acids on polysaccharide-based chiral columns in sub/super-critical fluid chromatography (SFC). Racemic mixtures of 14 amino acids were used to evaluate the chiral recognition ability of 8 different polysaccharide-based chiral columns with coated or covalently immobilized chiral selectors. Among the studied columns, the one based on cellulose (3,5-dichlorophenylcarbamate) exhibited the most universal chiral recognition ability providing baseline resolution for the enantiomers of 10 studied amino acids...
November 22, 2018: Journal of Chromatography. A
Lu Feng, Attila Mándi, Chunping Tang, Tibor Kurtán, Shuai Tang, Chang-Qiang Ke, Ning Shen, Ge Lin, Sheng Yao, Yang Ye
(±)-Cryptomeriolide, a pair of racemic bis- seco-abietane diterpenoids, were isolated from the bark of Cryptomeria fortunei. The separation of enantiomers was achieved by using chiral stationary phase HPLC. Their structures including the absolute configuration and conformations in solution and solid state were determined by extensive analysis of spectroscopic data, single-crystal X-ray diffraction, and comparison of calculated and experimental electronic circular dichroism data. A bioinspired one-pot enantiomeric synthesis of 1a and 1b was accomplished via a readily made intermediate orthoquinone from sugiol...
November 28, 2018: Journal of Natural Products
Xue Xiao, Jia Wu, Zhenqun Li, Li Jia
Chiral separation of low concentrations of pharmaceuticals in biofluids is a challenge task. In this study, a method is developed to enantioseparate trace amount of racemic ofloxacin in urine and bovine blood by combining magnetic solid phase extraction (MSPE) and chiral capillary electrophoresis (CE). Poly(3,4-dihydroxyphenylalanine) modified magnetic nanoparticles (polyDOPA-MNPs) are prepared and used as the adsorbents in MSPE to extract ofloxacin. The polyDOPA-MNPs are spherical, about 130 nm in diameter and the polyDOPA shell is about 3 nm...
November 16, 2018: Journal of Chromatography. A
Umut Salgin Goksen, Sevgi Sarigul, Patrick Bultinck, Wouter Herrebout, Ilknur Dogan, Kemal Yelekci, Gulberk Ucar, Nesrin Gokhan Kelekci
A new racemic pyrazoline derivative was synthesized and resolved to its enantiomers using analytic and semipreparative high-pressure liquid chromatography. The absolute configuration of both fractions was established using vibrational circular dichroism. The in vitro monoamine oxidase (MAO) inhibitory profiles were evaluated for the racemate and both enantiomers separately for the two isoforms of the enzyme. The racemic compound and both enantiomers were found to inhibit hMAO-A selectively and competitively...
November 23, 2018: Chirality
Michael Ramharter, Matthias Schwab, Ghyslain Mombo-Ngoma, Rella Zoleko Manego, Daisy Akerey-Diop, Arti Basra, Jean-Rodolphe Mackanga, Heike Würbel, Jan-Georg Wojtyniak, Raquel Gonzalez, Ute Hofmann, Mirjam Geditz, Pierre-Blaise Matsiegui, Peter G Kremsner, Clara Menendez, Reinhold Kerb, Thorsten Lehr
Introduction Mefloquine is evaluated as an alternative for intermittent preventive treatment of malaria in pregnancy (IPTp) due to increasing resistance against the first line drug sulfadoxine-pyrimethamine (SP). This study determined the pharmacokinetic characteristics of the mefloquine stereoisomers and its metabolite carboxymefloquine (CMQ) when given as IPTp in pregnant women. Also, the relationship between plasma concentrations of the three analytes and cord samples was evaluated and potential covariates influencing the pharmacokinetic properties were assessed...
November 19, 2018: Antimicrobial Agents and Chemotherapy
Athina G Nicolaou, Maria C Mavroudi, Ioannis J Stavrou, Choyce A Weatherly, Constantina P Kapnissi-Christodoulou
The combined use of chiral ionic liquids (CILs) and conventional chiral selectors (CSs) in CE, to establish a synergistic system, has proven to be an effective approach for the separation of enantiomeric pairs. In this study, a new CE method was developed, employing a binary system of a CS, either a cyclodextrin (CD) or a cyclofructan (CF), and a chiral amino acid ester-based ionic liquid (AAIL), for the chiral separation of four basic, acidic and zwitterionic drug compounds. In particular, the enantioseparation of two anticoagulants, warfarin (WAR) and coumachlor (COU), a non-opioid analgesic, nefopam (NEF) and a third-generation antihistamine, fexofenadine (FXD), was examined, by supporting the BGE with a CS and the chiral AAIL L-alanine tert butyl ester lactate (L-AlaC4 Lac)...
November 18, 2018: Electrophoresis
Lu Huang, Qi Lin, Yanxia Li, Guocai Zheng, Yiting Chen
Two new chiral membranes were prepared by modification of gold nanochannel membranes with D-penicillamine and N-acetyl-L-cysteine and were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of key factors such as the gold deposition time, the pH, and the concentration of sodium dihydrogen phosphate on the separation factor are discussed. Chiral resolution of amino acid enantiomers by the chiral membranes was investigated. The experimental results show that the D-penicillamine-modified membrane has good enantioselectivity toward tyrosine and phenylalanine enantiomers, whereas the N-acetyl-L-cysteine-modified membrane has good enantioselectivity toward tyrosine and tryptophan enantiomers...
November 19, 2018: Analytical and Bioanalytical Chemistry
Yu-Xi Wang, Bin Lin, Le Zhou, Zhi-Yang Yan, Han Zhang, Xiao-Xiao Huang, Shao-Jiang Song
The phytochemical investigation on the twigs and leaves of Archidendron clypearia (Jack) I.C.N. led to the isolation of three pairs of furolactone-type lignans enantiomers, including a pair of new compounds (1R,5S,6S)-Kachiranol (1a) and (1S,5R,6R)-Kachiranol (1b) and four known compounds (2a/2b and 3a/3b). Separation of the furolactone-type lignans enantiomeric mixtures was achieved using chiral HPLC for the first time. Their structures were determined by spectroscopic analysis and comparison between the experimental and calculated electronic circular dichroism (ECD) spectra...
November 16, 2018: Natural Product Research
Guojun Yao, Jing Gao, Chuntao Zhang, Wenqi Jiang, Peng Wang, Xueke Liu, Donghui Liu, Zhiqiang Zhou
Alpha-cypermethrin (α-cypermethrin), an important chiral pyrethroid insecticide, is frequently detected in human samples. Because of the possible human health risks caused by α-cypermethrin, we studied dynamics, residues, and metabolism of α-cypermethrin in five common vegetables (tomato, cucumber, rape, cabbage, and pepper) on enantiomeric levels after foliar spray. α-Cypermethrin was qualified by a HP-5 column and its enantiomers could be separated by gas chromatograph (GC) using a BGB-172 chiral column...
November 15, 2018: Environmental Science and Pollution Research International
Kai-Jun Quan, Xin-Yi Huang, Yuan Gong, Dong Pei, Wen-Da Duan, Duo-Long Di
In this work, to further verify and develop the novel counter-current chromatography modified column separate mode, a melamine modified counter-current chromatography column was prepared. Meanwhile, the modified counter-current chromatography column was used to separate stevioside and rebaudioside A with the same partition coefficient in chosen solvent system to evaluate its separation efficiency. The results show that because the presence of intermolecular forces between melamine and model compounds, better separation could be achieved on the modified column while it's almost impossible to be separated on the unmodified column...
November 14, 2018: Journal of Separation Science
Narayan Balaji, Bhavesh Babulal Gabani, Umesh Todmal, Suresh P Sulochana, Neeraj Kumar Saini, Rajesh Chandran, Ramesh Mullangi
We developed and validated a simple, sensitive, selective and reliable LC-MS/MS-ESI method for direct quantitation of dropropizine enantiomers namely levodropropizine (LDP) and dextrodropropizine (DDP) in rat plasma without a need of derivatization as per regulatory guideline. Dropropizine enantiomers and carbamazepine (internal standard; IS) were extracted from 50 μL rat plasma using ethyl acetate. LDP and DDP resolved with good baseline separation (Rs = 4.45) on a Chiralpak IG-3 column. The mobile phase consisted of methanol with 0...
November 13, 2018: Biomedical Chromatography: BMC
Guogang Liu, Tobias Koch, Yan Li, Nikos L Doltsinis, Zhaohui Wang
A novel kind of nanographene imides, namely pentaperylene decaimides (PPD) featuring dual core sixfold [5]helicenes and ten imide groups, was efficiently obtained. Among the possible 28 stereoisomers, which include 14 pairs of enantiomers, only one pair of enantiomers was obtained selectively which could be separated by chiral HPLC. Single-crystal X-ray diffraction analyses revealed that it exhibits a D2-symmetric "four-bladed propeller" conformation composed of conjoined double "three-bladed propeller", which is very stable and could not convert to other conformations even when heated up to 200 ºC...
November 12, 2018: Angewandte Chemie
Sudhakar Jakkaraj, Victor G Young, Gunda I Georg
Two synthetic methods were developed for the synthesis of PDE3A inhibitor ORG9935. The first one proceeds in six steps and 34% overall yield and the second one in five steps and an overall yield of 69% starting from commercially available starting material 5,6-dimethoxybenzo[ b ]thiophene-2-carboxylic acid ( 6 ). The enantiomers of ORG9935 were separated by chiral column chromatography and the absolute stereochemistry of the (+)-enantiomer, ORG20865 was determined by X-ray crystallography to possess the ( S) -configuration...
May 31, 2018: Tetrahedron
Jose I Santos, Iván Rivilla, Fernando P Cossío, Jon M Matxain, Marek Grzelczak, Shobeir K S Mazinani, Jesus M Ugalde, Vladimiro Mujica
NMR-based techniques are supposed to be incapable of distinguishing pure crystalline chemical enantiomers. However, through systematic studies of cross-polarization magic angle spinning (CP-MAS) NMR in a series of amino acids, we have found a rather unexpected behavior in the intensity pattern of optical isomers in hydrogen/nitrogen nuclear polarization transfer that would allow the use of CP NMR as a nondestructive enantioselective detection technique. In all molecules considered, the d isomer yields higher intensity than the l form, while the chemical shift for all nuclei involved remains unchanged...
November 27, 2018: ACS Nano
Lie-Ding Shiau
Stripping crystallization (SC) is introduced in this work for chiral purification of R -phenylglycinol from the enantiomer mixture with an initial concentration ranging from 0.90 to 0.97. As opposed to the solid⁻liquid transformation in melt crystallization, the three-phase transformation occurs in SC at low pressures during the cooling process. SC combines melt crystallization and vaporization to produce a crystalline product and mixture vapor from a mixture melt due to the three-phase transformation. Thermodynamic calculations were applied to determine the operating pressure for the three-phase transformation during the cooling process in the SC experiments...
November 7, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Xinzhong Zhang, Yuechen Zhao, Xinyi Cui, Xinru Wang, Huishan Shen, Zongmao Chen, Chun Huang, Narendra Meruva, Li Zhou, Fang Wang, Luchao Wu, Fengjian Luo
A chiral separation and residue determination method for diniconazole enantiomers in tea, apple, and grape was developed and validated by supercritical fluid chromatography coupled with quadrupole-time-of-flight mass spectrometry (SFC-Q-TOF/MS). The two diniconazole enantiomers were separated on a Chiral CCA column, and the chromatographic conditions (mobile phase proportion and modifier, column temperature, backpressure, and auxiliary solvent) were optimized. The optimal SFC-Q-TOF/MS conditions were selected as a mobile phase of CO2 /isopropanol (IPA) (v/v, 96/4), flow rate at 2...
October 31, 2018: Journal of Chromatography. A
Marília Cristina Oliveira Souza, Maria Paula Marques, Geraldo Duarte, Vera Lucia Lanchote
Bupivacaine, a drug used in obstetric anesthesia and analgesia, is commercially available as a racemic mixture of the R-bupivacaine and S-bupivacaine enantiomers, which show differences in pharmacokinetics, efficacy and toxicity. Changes in bupivacaine plasma protein binding is of clinical relevance considering its high protein binding (approximately 95%) and its classification as an intermediate hepatic extraction ratio drug (E = 0.38). Furthermore, the plasma protein binding of bupivacaine is also of clinical relevance considering that pregnancy is a physiological condition associated with reduced plasma albumin concentration...
October 23, 2018: Journal of Pharmaceutical and Biomedical Analysis
Patricia Schaaf, Thomas Bayer, Moumita Koley, Michael Schnürch, Uwe T Bornscheuer, Florian Rudroff, Marko D Mihovilovic
In this study, we present a concurrent chemo/biocatalytic one pot reaction cascade by combining a metal (Pd/Cu) assisted Liebeskind-Srogl (L-S) coupling with an enantioselective enzymatic reduction for the production of chiral amines and alcohols. The latter transformation was realized by applying enantiocomplementary alcohol dehydrogenases from Lactobacillus kefir (R-selective) and Rhodococcus ruber (S-selective). Compatibility issues were solved by investigating first the L-S-coupling protocol in water at room temperature...
November 15, 2018: Chemical Communications: Chem Comm
Bob W J Pirok, Dwight R Stoll, Peter J Schoenmakers
Liquid chromatography (LC) is an incredibly successful analytical separation tool. Its versatility is unprecedented, because of the many different separation modes (reversed-phase LC, ion-exchange chromatography, size-exclusion chromatography, etc.) and because almost all samples can be dissolved in some kind of solvent, ranging from water to organic solvents to strong acids or bases. Conditions (mobile and stationary phases, additives, pH, temperatures, etc.) can be found to separate almost all pairs of analytes...
November 1, 2018: Analytical Chemistry
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