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Chiral separation

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https://www.readbyqxmd.com/read/28527527/small-scale-separation-of-isoxazole-structurally-related-analogues-by-chiral-supercritical-fluid-chromatography
#1
Yasmine Zehani, Lucas Lemaire, Regis Millet, Emmanuelle Lipka
Chromatographic preparative enantioseparation is now the preferred method to obtain milligram amounts of pure enantiomers in the first step of the development of a therapeutic molecule. Supercritical fluid chromatography has many advantages over liquid chromatography and was therefore chosen for the small scale enantioseparation of four original 3-carboxamido-5-aryl isoxazole molecules, ligands of the CB2 cannabinoid receptors. The preparation of about 10mg of each of the eight enantiomers was achieved successfully on a Chiralpak(®) AD-H (tris-3,5-dimethylphenylcarbamate of amylose) polysaccharide based stationary phase with various percentages of ethanol as a co-solvent, through mixed-stream injections and touching-band approach...
May 12, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28520466/development-and-validation-of-a-highly-sensitive-gradient-chiral-separation-of-pramipexole-in-human-plasma-by-lc-ms-ms
#2
Marco Michi, Massimo Breda, Justin Keane Belardi, Steven Dworetzky, Lara Solazzo
AIM: Development of a high-sensitivity chiral LC-MS/MS method was required to evaluate a combination of pramipexole (S-PPX) and its enantiomer dexpramipexole (R-PPX) in a proposed clinical trial. The previously available methods suffered from low sensitivity for the (S)-enantiomer in the presence of the more abundant (R)-enantiomer. Based on the projected dosing regimen in the clinical trial, a 5000-fold improvement in sensitivity was required for the (S)-enantiomer. METHODOLOGY: Spiked human plasma samples were extracted by liquid-liquid extraction using ethyl acetate and injected onto a CHIRALPAK ID column under pH gradient conditions...
May 18, 2017: Bioanalysis
https://www.readbyqxmd.com/read/28518201/a-general-diastereoselective-synthesis-of-highly-functionalized-ferrocenyl-ambiphiles-enabled-on-a-large-scale-by-electrochemical-purification
#3
Emmanuel Lerayer, Patrice Renaut, Julien Roger, Nadine Pirio, Hélène Cattey, Charles H Devillers, Dominique Lucas, Jean-Cyrille Hierso
A general synthesis of highly functionalized ferrocenes, which include (P,B)- and (N,B)-ambiphiles, has been developed at a multigram scale. Diastereoselective stepwise modification of di-tert-butylated ferrocenes included the unprecedented separation of electroactive species. Bulky alkyl groups on ferrocenes ensure planar chirality of ambiphiles and enforce closer proximity of antagonist Lewis functions.
May 18, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28517365/enantioselective-dissipation-of-pyriproxyfen-in-soils-and-sand
#4
Hui Liu, Peng Wang, Zhiqiang Zhou, Donghui Liu
Under normal conditions, the environmental behaviors of pesticides are affected by complex environmental factors and the manner of administration together with constraints. In order to meet the actual needs, we imitated the experiment and found that the degradation rate of pyriproxyfen in soils rendered complex changes. Rac-pyriproxyfen was successfully chiral separated on an AZ-H column and the residue analysis method was in accord with the demand of pesticide analysis. The results indicated that pyriproxyfen dissipated at a faster rate in Heilongjiang soil and Hainan soil, while at a much slower speed in another three soils and sand...
May 18, 2017: Chirality
https://www.readbyqxmd.com/read/28513743/adsorption-differences-between-low-coverage-enantiomers-of-alanine-on-the-chiral-cu-421-r-surface
#5
Michael J Gladys, Jeong Woo Han, Therese S Pedersen, Anton Tadich, Kane M O'Donnell, Lars Thomsen
Chiral separation using heterogeneous methods has long been sought after. Chiral metal surfaces have the potential to make it possible to model these systems using small amino acids, the building blocks for proteins. A comparison of submonolayer concentrations of alanine enantiomers adsorbed onto Cu{421}(R) has revealed a large geometrical differences between the two molecules as compared to the saturated coverage. Large differences were observed in HR-XPS and NEXAFS and complemented by theoretical DFT calculations...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28510993/chiral-separation-of-quinolones-by-liquid-chromatography-and-capillary-electrophoresis
#6
REVIEW
Imran Ali, Mohd Suhail, Leonid Asnin
The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for pre-clinical or clinical trials, respective chiral separation methods are urgently needed...
May 16, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28510451/mechanisms-and-origins-of-selectivities-of-the-lewis-acid-catalyzed-diels-alder-reactions-between-aryl-allenes-and-acrylates
#7
Peiyuan Yu, Wei Li, Kendall N Houk
The mechanisms of recently reported Lewis acid-catalyzed Diels-Alder reactions of aryl allenes and acrylates were studied using density functional theory calculations. A stepwise mechanism involving short-lived zwitterion intermediates is established. The reaction is endo-selective in the presence of Lewis acid catalyst. The [2+2] cycloaddition is not observed because of the greater charge separation in the first step of the [2+2] cycloaddition. The origins of chirality transfer in the Diels-Alder reaction using chiral aryl allenes are uncovered, and the absolute stereochemistry of the product is predicted...
May 16, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28505281/application-of-partially-substituted-3-5-dimethylphenylcarbamate-3-2-o-%C3%AE-cyclodextrin-2-hydroxypropoxy-propylsilyl-appended-silica-particles-as-chiral-stationary-phase-for-multi-mode-high-performance-liquid-chromatography
#8
Mingxuan Ma, Qunli Wei, Min Meng, Jiale Yin, Lei Du, Xia Zhu, Mengjun Min, Xueyan Zhou, Xiaoxing Yin, Yinhan Gong
A new type of partially substituted 3,5-dimethylphenylcarbamate-(3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (MP-CD-HPS) have been prepared by a convenient post-immobilization derivazition procedure. The MP-CD-HPS has been successfully used as chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) under normal phase, reversed phase and polar organic mobile phase conditions. The chromatographic evaluation results show that the MP-CD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of some chiral compounds...
May 13, 2017: Journal of Chromatographic Science
https://www.readbyqxmd.com/read/28493436/enantioselective-analysis-of-bambuterol-in-human-plasma-using-microwave-assisted-chiral-derivatization-coupled-with-ultra-high-performance-liquid-chromatography-and-tandem-mass-spectrometry
#9
Ting Zhou, Jing Zeng, Ting Zhao, Qisheng Zhong, Yang Yang, Wen Tan
In this study, an enantioselective analytical method based on microwave-assisted chiral derivatization coupled with ultra high performance liquid chromatography and tandem mass spectrometry was developed for the determination of bambuterol enantiomers in human plasma. The chiral derivatization reaction was greatly accelerated by microwave irradiation. Under the optimized conditions, both the derivatization time and separation time on column was only 3 min, and the lower limit of quantification was 2.5 pg mL(-1) ...
May 11, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28489373/scalemic-caged-xanthones-isolated-from-the-stem-bark-extract-of-garcinia-propinqua
#10
Teerayut Sriyatep, Raymond J Andersen, Brian O Patrick, Stephen G Pyne, Chatchai Muanprasat, Sawinee Seemakhan, Suparerk Borwornpinyo, Surat Laphookhieo
Seven new caged xanthones, doitunggarcinones E-K (1-7), all as scalemic mixtures and 10 known compounds (8-17), were isolated from the stem bark extract of Garcinia propinqua. The structures were elucidated on the basis of spectroscopic methods. The separation of the enantiomers of 1-6 was achieved by semipreparative chiral HPLC. The absolute configuration of compound (+)-1 was determined by single-crystal X-ray crystallographic analysis using Cu Kα radiation. The absolute configurations of the other related compounds were determined from comparisons of their ECD spectra with that of compound (+)-1...
May 10, 2017: Journal of Natural Products
https://www.readbyqxmd.com/read/28489362/atropisomerism-and-conformational-equilibria-impact-on-pi3k%C3%AE-inhibition-of-2-6-amino-9h-purin-9-yl-methyl-5-methyl-3-o-tolyl-quinazolin-4-3h-one-ic87114-and-its-conformationally-restricted-analogs
#11
Alessio Lodola, Serena Bertolini, Matteo Biagetti, Silvia Capacchi, Fabrizio Facchinetti, Paola Maria Gallo, Alice Pappani, Marco Mor, Daniele Pala, Silvia Rivara, Filippo Visentini, Mauro Corsi, Anna Maria Capelli
IC87114 [compound 1, (2-((6-amino-9H-purin-9-yl)methyl)-5-methyl-3-(o-tolyl)quinazolin-4(3H)-one)] is a potent PI3K inhibitor selective for the δ isoform. As predicted by molecular modelling calculations, rotation around the bond connecting the quinazolin-4(3H)-one nucleus to the o-tolyl is sterically hampered, which leads to separable conformers with axial chirality (i.e. atropisomers). After verifying that the aS and aR isomers of compound 1 do not interconvert in solution, we investigated how biological activity is influenced by axial chirality and conformational equilibrium...
May 10, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28489105/chirality-as-a-tool-for-function-in-porous-organic-cages
#12
T Hasell, M A Little, S Y Chong, M Schmidtmann, M E Briggs, V Santolini, K E Jelfs, A I Cooper
The control of solid state assembly for porous organic cages is more challenging than for extended frameworks, such as metal-organic frameworks. Chiral recognition is one approach to achieving this control. Here we investigate chiral analogues of cages that were previously studied as racemates. We show that chiral cages can be produced directly from chiral precursors or by separating racemic cages by co-crystallisation with a second chiral cage, opening up a route to producing chiral cages from achiral precursors...
May 10, 2017: Nanoscale
https://www.readbyqxmd.com/read/28487120/surface-anchored-counterions-on-weak-chiral-anion-exchangers-accelerate-separations-and-improve-their-compatibility-for-mass-spectrometry-hyphenation
#13
Ulrich Woiwode, Adrian Sievers-Engler, Aleksandra Zimmermann, Wolfgang Lindner, Orlando L Sánchez-Muñoz, Michael Lämmerhofer
In the present work we propose new variants of chiral stationary phases (CSP) with tert-butylcarbamoylquinine (tBuCQN) as chiral selector molecule. Four tBuCQN-CSPs with distinct bonding chemistries are compared in terms of their pH-dependent surface charge by ζ-potential determinations, by achiral and chiral liquid chromatographic tests and LC-ESI-MS hyphenation. In one embodiment tBuCQN was immobilized on 3-mercaptopropylmethylsilyl-modified silica by thiol-ene click reaction (brush type CSP with selector coverage of 0...
April 28, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28481510/chiral-at-metal-phosphorescent-square-planar-pt-ii-complexes-from-an-achiral-organometallic-ligand
#14
Thorben Rüdiger Schulte, Julian J Holstein, Lennard Krause, Reent Michel, Dietmar Stalke, Eri Sakuda, Keisuke Umakoshi, Giovanna Longhi, Sergio Abbate, Guido H Clever
The synthesis and characterization of a new kind of cis- and trans-cyclometalated square-planar platinum(II) com- plexes is reported. Uncharged organometallic compounds carrying one or two of the C^N-donor ligand LCN were prepared. Due to the heterobidentate coordination of the achiral chelate ligand, the formed [PtLCNCl(SEt2)], cis- and trans-[PtLCN2] complexes are chiral with the metal serving as the stereo center. The enantiomers of complex trans-[PtLCN2] could be separated and their absolute configuration was determined by anomalous X-ray diffraction, in accordance with CD spectroscopic results and TD-DFT calcula- tions...
May 8, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28481008/chiral-selective-transport-of-proteins-by-cysteine-enantiomer-modified-nanopores
#15
Fan Zhang, Yue Sun, Demei Tian, Haibing Li
Chirality is an intriguing and intrinsic feature of life and is highly associated with many significant biological processes. However, whether it influences the translocation behavior of proteins remains unclear. Herein, based on biomimetic strategies, we made chiral nanopores modified with cysteine enantiomers, and studied the chirality gating effects on protein transport. The results show that protein is preferentially transported through nanopores modified with l-cysteine because of chiral interaction, indicating chirality strongly influences protein transport process...
May 8, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28475329/tolvaptan-type-vasopressin-receptor-ligands-important-role-of-axial-chirality-in-the-active-form
#16
Hidetsugu Tabata, Tetsuya Yoneda, Tetsuta Oshitari, Hideyo Takahashi, Hideaki Natsugari
The anti and syn isomers of tolvaptan-type compounds, N-benzoyl-5-hydroxy-1-benzazepines (5a-c), were prepared in a stereocontrolled manner by biasing the conformation with a methyl group at C9 and C6, respectively, and the enantiomeric forms were separated. Examination of the affinity at the human vasopressin receptors revealed that the axial chirality (aS) plays a more important role than the central chirality at C5 in receptor recognition, and the most preferable form was shown to be (E,aS,5S).
May 16, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28475218/immobilized-strychnine-as-a-new-chiral-stationary-phase-for-hplc
#17
David Sýkora, Jiří Vozka, Eva Tesařová, Květa Kalíková, Martin Havlík, Pavel Matějka, Vladimír Král
A new ion-exchanger type chiral stationary phase for high-performance liquid chromatography was prepared. The synthetic protocol is based on derivatization of silica with (3-iodopropyl)trimethoxysilane in the first step followed by immobilization of strychnine via quaternization of nitrogen atom of the alkaloid strychnine. The synthesized chiral stationary phase was chromatographically characterized. The main effort was headed towards the evaluation of the enantioselectivity of the novel sorbent. For that purpose a set of suitable chiral probes, specifically, binaphthyl derivatives, was employed...
May 5, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28474737/combination-of-large-volume-sample-stacking-with-an-electroosmotic-flow-pump-with-field-amplified-sample-injection-on-cross-channel-chips
#18
Fumihiko Kitagawa, Tatsuya Ishiguro, Misaki Tateyama, Isoshi Nukatsuka, Kenji Sueyoshi, Takayuki Kawai, Koji Otsuka
A combination of two online sample concentration techniques, large-volume sample stacking with an electroosmotic flow (EOF) pump (LVSEP) and field-amplified sample injection (FASI), was investigated in microchip electrophoresis (MCE) to achieve highly sensitive analysis. By applying reversed-polarity voltages on a cross-channel microchip, anionic analytes injected throughout a microchannel were first concentrated on the basis of LVSEP, followed by the electrokinetic stacking injection of the analytes from a sample reservoir by the FASI mechanism...
May 5, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28471055/a-novel-in-situ-strategy-for-the-preparation-of-a-%C3%AE-cyclodextrin-polydopamine-coated-capillary-column-for-capillary-electrochromatography-enantioseparations
#19
Heying Guo, Xiaoying Niu, Congjie Pan, Tao Yi, Hongli Chen, Xingguo Chen
Inspired by the chiral recognition ability of β-cyclodextrin and the natural adhesive properties of polydopamine under alkaline conditions, in this study, a rapid and in situ modification strategy was developed to fabricate β-cyclodextrin/polydopamine composite material coated-capillary columns for open tubular capillary electrochromatography. The results of scanning electron microscopy, FTIR spectroscopy, streaming potential and electro-osmotic flow studies indicated that β-cyclodextrin/polydopamine was successfully fixed on the inner wall of the capillary column...
May 4, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28470986/nickel-ii-assisted-enantiomeric-differentiation-and-quantitation-of-tadalafil-by-direct-electrospray-ionization-mass-spectrometry
#20
Lu Wang, Yali Wang, Yunfeng Chai, Yu Kang, Cuirong Sun, Su Zeng
A facile method based on electrospray mass spectrometry was established and validated for the differentiation of enantiomeric Tadalafil isomers without using chiral chromatographic separation. The enantiomers were coupled with a chiral selector to form diastereomeric complex ions. Nickel-Tadalafil complexes, [Ni(II) (Tadalafil)(L-Trp)-H](+) , produced a characteristic fragment ion at m/z 524 by loss of 1-methyl-1, 6-dihydropyrazine-2, 5-dione (MDD) via collision-induced dissociation (CID). The relative abundance of this fragment ion to the precursor contributed to differentiate Tadalafil enantiomers, and energy-resolved product-ion spectra were applied to determine molar composition of Tadalafil in the mixture (R, R and S, S) as well...
May 4, 2017: Journal of Mass Spectrometry: JMS
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