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Chiral separation

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https://www.readbyqxmd.com/read/28811101/chiral-stationary-phase-optimized-selectivity-liquid-chromatography-a-strategy-for-the-separation-of-chiral-isomers
#1
Ravindra Suryakant Hegade, Maarten De Beer, Frederic Lynen
Chiral Stationary-Phase Optimized Selectivity Liquid Chromatography (SOSLC) is proposed as a tool to optimally separate mixtures of enantiomers on a set of commercially available coupled chiral columns. This approach allows for the prediction of the separation profiles on any possible combination of the chiral stationary phases based on a limited number of preliminary analyses, followed by automated selection of the optimal column combination. Both the isocratic and gradient SOSLC approach were implemented for prediction of the retention times for a mixture of 4 chiral pairs on all possible combinations of the 5 commercial chiral columns...
August 2, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28809873/generating-broadband-vortex-modes-in-ring-core-fiber-by-using-a-plasmonic-q-plate
#2
Jingfu Ye, Yan Li, Yanhua Han, Duo Deng, Xiaoya Su, He Song, Jianmin Gao, Shiliang Qu
A mode convertor was proposed and investigated for generating vortex modes in a ring-core fiber based on a plasmonic q-plate (PQP), which is composed of specially organized L-shaped resonator (LSR) arrays. A multicore fiber was used to transmit fundamental modes, and the LSR arrays were used to modulate phases of these fundamental modes. Behind the PQP, the transmitted fundamental modes with gradient phase distribution can be considered as the incident lights for generating broadband vortex modes in the ring-core fiber filter...
August 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28809483/discrimination-and-enantiomeric-excess-determination-of-chiral-primary-amines-based-on-a-chiral-at-metal-ir-iii-complex-using-nmr-spectroscopy
#3
Li-Ping Li, Bao-Hui Ye
A three-component protocol involving enantiopure Δ-[Ir(ppy)2(MeCN)2](PF6) (ppy is 2-phenylpyridine) and salicylaldehyde as chiral auxiliaries was successfully applied to discriminate the absolute configuration and determine the enantiopurity of primary amines and amine alcohols via (1)H NMR spectroscopy. The assembly reaction is rapid and quantitative, generating a pair of diastereomers that can be determined directly without physical separation. Single crystal structural analyses indicate that the shielding effects on the ligands imposed by a pair of diastereomers are different and generate sufficient resolution NMR signals for identification...
August 15, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28806704/chiral-pharmaceuticals-a-review-on-their-environmental-occurrence-and-fate-processes
#4
REVIEW
Edmond Sanganyado, Zhijiang Lu, Qiuguo Fu, Daniel Schlenk, Jay Gan
More than 50% of pharmaceuticals in current use are chiral compounds. Enantiomers of the same pharmaceutical have identical physicochemical properties, but may exhibit differences in pharmacokinetics, pharmacodynamics and toxicity. The advancement in separation and detection methods has made it possible to analyze trace amounts of chiral compounds in environmental media. As a result, interest on chiral analysis and evaluation of stereoselectivity in environmental occurrence, phase distribution and degradation of chiral pharmaceuticals has grown substantially in recent years...
August 5, 2017: Water Research
https://www.readbyqxmd.com/read/28806570/chiral-separation-of-terbutaline-and-non-steroidal-anti-inflammatory-drugs-by-using-a-new-lysine-bridged-hemispherodextrin-in-capillary-electrophoresis
#5
V Cucinotta, M Messina, A Contino, G Maccarrone, S Orlandini, A Giuffrida
A method for the separation of a mixture of terbutaline and non-steroidal anti-inflammatory drugs was developed using capillary electrophoresis with a new hemispherodextrin, ad hoc designed, the lysine - bridged hemispherodextrin (THLYSH). The use of lysine residues to bridge the trehalose capping unit moiety to the cyclodextrin cavity gives rise to a receptor with two long chains with amine nitrogen atoms, whose charge can be easily tuned as a function of the solution pH. The new hemispherodextrin was accurately characterised by ESI-MS and NMR spectroscopy, also highlighting its protonation behaviour...
August 3, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28801961/recent-advances-in-microscale-separation
#6
Yuanyuan Liu, Weiwei Wang, Mengqi Jia, Rangdong Liu, Qing Liu, Han Xiao, Jing Li, Yun Xue, Yan Wang, Chao Yan
This review focuses on the recent advances on microscale separation technology, particularly on the new development on column and detection technologies in electrophoretic and chromatographic separation modes (i.e., CE, CEC, cLC, etc.). Representative examples illustrate also applications on the small molecules, peptides, proteins, polysaccharides, chiral and so on. 247 relevant articles are cited covering the literature published from 2013 to May, 2017. This article is protected by copyright. All rights reserved...
August 12, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28799177/racemic-and-enantiopure-forms-of-3-ethyl-3-phenylpyrrolidin-2-one-adopt-very-different-crystal-structures
#7
Arcadius V Krivoshein, Sergey V Lindeman, Tatiana V Timofeeva, Victor N Khrustalev
3-Ethyl-3-phenylpyrrolidin-2-one (EPP) is an experimental anticonvulsant based on the newly proposed α-substituted amide group pharmacophore. These compounds show robust activity in animal models of drug-resistant epilepsy and are thus promising for clinical development. In order to understand pharmaceutically relevant properties of such compounds, we are conducting an extensive investigation of their structures in the solid state. In this article, we report chiral high-performance liquid chromatography (HPLC) separation, determination of absolute configuration of enantiomers, and crystal structures of EPP...
August 11, 2017: Chirality
https://www.readbyqxmd.com/read/28796348/anion-%C3%AF-catalysts-with-axial-chirality
#8
Chao Wang, Stefan Matile
The idea of anion-π catalysis is to stabilize anionic transition states by anion-π interactions on aromatic surfaces. For asymmetric anion-π catalysis, π-acidic surfaces have been surrounded with stereogenic centers. This manuscript introduces the first anion-π catalysts that operate with axial chirality. Bifunctional catalysts with tertiary amine bases next to π-acidic naphthalenediimide planes are equipped with a bulky aromatic substituent in the imide position to produce separable atropisomers. The addition of malonic acid half thioesters to enolate acceptors is used for evaluation...
August 10, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28794492/unusual-inner-salt-guaiazulene-alkaloids-and-bis-sesquiterpene-from-the-south-china-sea-gorgonian-muriceides-collaris
#9
Pinglin Li, Xiaoling Liu, Hongyan Zhu, Xuli Tang, Xuefeng Shi, Yonghong Liu, Guoqiang Li
Three new guaiazulene alkaloids muriceidines A-C (1-3) and one new bis-sesquiterpene muriceidone A (4), were isolated from the South China Sea gorgonian Muriceides collaris. Muriceidines are the first examples structurally architected by guaiazulene coupling with an inner-salt Δ (1)-pipecolic acid via a unique sp(2) methine-bridged linkage, and the bis-sesquiterpene was comprised by a guaiazulene and a indene units linked through a unprecedented carbon-carbon σ-bond between the high steric bridgehead carbon C-10 of guaiazulene moiety and C-2' of indene moiety...
August 9, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28791799/reducing-the-flexibility-of-type-ii-dehydroquinase-enzyme-for-inhibition-a-fragment-based-approach-and-molecular-dynamics-simulation-study
#10
Antonio Peón, Adrián Robles, Beatriz Blanco, Marino Convertino, Paul Thompson, Alastair R Hawkins, Amedeo Caflisch, Concepcion Gonzalez-Bello
A multidisciplinary approach was used to identify and optimize a quinazolinedione-based ligand that would reduce the flexibility of the substrate-covering loop (catalytic loop) of the type II dehydroquinase from Helicobacter pylori. This enzyme, which is essential for the survival of this bacterium, is involved in the biosynthesis of the aromatic amino acids. A computer-aided fragment-based protocol (ALTA) was first employed to identify the aromatic fragments able to block the interface pocket that separates two neighbor enzyme subunits and is located at the active site entrance...
August 9, 2017: ChemMedChem
https://www.readbyqxmd.com/read/28783369/helical-oligourea-foldamers-as-powerful-hydrogen-bonding-catalysts-for-enantioselective-c-c-bond-forming-reactions
#11
Diane Bécart, Vincent Diemer, Arnaud Salaün, Mikel Oiarbide, Yella-Reddy Nelli, Brice Kauffmann, Lucile Fischer, Claudio Palomo, Gilles Guichard
Substantial progress has been made towards the development of metal-free catalysts of enantioselective transformations, yet the discovery of organic catalysts effective at low catalyst loadings remains a major challenge. Here we report a novel synergistic catalyst combination system consisting of a simple tertiary amine and a peptide-inspired chiral helical (thio)urea oligomer that is able to promote the Michael reaction between enolizable carbonyl compounds and nitroolefins with excellent enantio-selectivities at exceptionally low (1/10000) chiral catalyst/substrate molar ratios...
August 7, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28783341/synthesis-of-mechanically-planar-chiral-rac-2-rotaxanes-by-partitioning-of-an-achiral-2-rotaxane-stereoinversion-induced-by-shuttling
#12
Yuta Mochizuki, Katsuhiko Ikeyatsu, Yuichiro Mutoh, Shoichi Hosoya, Shinichi Saito
Mechanically planar chiral [2]rotaxanes were synthesized by the introduction of bulky pyrrole moieties into the axle component of an achiral [2]rotaxane. The enantiomers were separated by chiral HPLC. The shuttling of the ring component between the two compartments at high temperature induced the stereoinversion of the mechanically planar chiral [2]rotaxane. The rate of the stereoinversion was studied quantitatively, and the kinetic parameters were determined.
August 7, 2017: Organic Letters
https://www.readbyqxmd.com/read/28779767/polysaccharide-derivatives-as-unique-chiral-selectors-for-enantioselective-chromatography
#13
Eric R Francotte
From the beginning of the 1980s, the life science industry increasingly recognized the importance of chirality in biological interaction processes, but the methods for preparing optically pure drugs were still limited. Most of the syntheses of chiral compounds were performed starting from optically active building blocks (chiral pool), mainly from natural sources, or by resolution of the enantiomers via formation of diastereomers. In this context, there was a growing interest for enantioselective processes, such as synthetic methodologies and separation techniques for accessing optically pure substances in an effective manner...
August 9, 2017: Chimia
https://www.readbyqxmd.com/read/28766240/determination-of-s-lansoprazole-in-dexlansoprazole-preparation-by-capillary-zone-electrophoresis
#14
Hyun Kyu Chung, Quoc-Ky Truong, Xuan-Lan Mai, Yusung Choi, Jong-Seong Kang, Woongchon Mar, Kyeong Ho Kim
Capillary zone electrophoresis was successfully applied to the enantiomeric purity determination of dexlansoprazole using sulfobutyl ether-β-cyclodextrin and methyl-β-cyclodextrin as chiral selectors. Separations were carried out in a 50 μm, 64/56 cm fused-silica capillary. The optimized conditions included 90 mM phosphate buffer, pH 6.0, containing 30 mM sulfobutyl ether-β-cyclodextrin, 20 mM methyl-β-cyclodextrin as background electrolyte, an applied voltage of 25 kV and a temperature of 16 °C, detection was at 280 nm...
August 1, 2017: Archives of Pharmacal Research
https://www.readbyqxmd.com/read/28762520/nanomaterials-as-stationary-phases-and-supports-in-liquid-chromatography
#15
REVIEW
Sandya R Beeram, Elliott Rodriguez, Suresh Doddavenkatanna, Zhao Li, Allegra Pekarek, Darin Peev, Kathryn Goerl, Gianfranco Trovato, Tino Hofmann, David S Hage
The development of various nanomaterials over the last few decades has led to many applications for these materials in liquid chromatography (LC). This review will look at the types of nanomaterials that have been incorporated into LC systems and the applications that have been explored for such systems. A number of carbon-based nanomaterials and inorganic nanomaterials have been considered for use in LC, ranging from carbon nanotubes, fullerenes and nanodiamonds to metal nanoparticles and nanostructures based on silica, alumina, zirconia and titanium dioxide...
August 1, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28760606/synthesis-analytical-characterization-and-capillary-electrophoretic-use-of-the-single-isomer-heptakis-6-o-sulfobutyl-beta-cyclodextrin
#16
Milo Malanga, Ida Fejős, Erzsébet Varga, Gábor Benkovics, András Darcsi, Julianna Szemán, Szabolcs Béni
This contribution reports the synthesis, characterization and capillary electrophoretic application of heptakis-(6-O-sulfobutyl-ether)-β-cyclodextrin sodium salt, (6-(SB)7-β-CD). The compound was obtained through a five-steps synthesis and it represents the first example of single-isomer sulfobutylated cyclodextrin that carries the negatively charged functions exclusively on its primary side and it is unmodified on the lower rim. The purity of each intermediate was determined by appropriate liquid chromatographic methods, while the isomeric purity of the final product was established by an ad-hoc developed HPLC method based on a CD-Screen-IEC column...
July 21, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28758711/enantioseparation-of-pheniramine-enantiomers-by-high-speed-counter-current-chromatography-using-%C3%AE-cyclodextrin-derivatives-as-a-chiral-selector
#17
Weifeng Xu, Shichuan Wang, Xiaojuan Xie, Panliang Zhang, Kewen Tang
The enantioselective separation of pheniramine was studied by a high-speed counter-current chromatography method using β-cyclodextrin derivatives as a chiral selector. Several key variables, for instance, type of organic solvent and chiral selector, concentration of chiral selector, pH value of aqueous phase and temperature on the enantioselectivity, were investigated systematically by liquid-liquid extraction experiments. Combining the results of extraction experiments and high-speed counter-current chromatography, the most suitable conditions for separation of pheniramine enantiomers were obtained with the two-phase system that consisted of isobutyl acetate/aqueous phase, containing 0...
July 31, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28756893/-or-1-9-fluorenyl-ethyl-chloroformate-as-chiral-derivatizing-agent-a-review
#18
REVIEW
Radu-Cristian Moldovan, Ede Bodoki, Anne-Catherine Servais, Jacques Crommen, Radu Oprean, Marianne Fillet
Over the last 30years, (±)-1-(9-fluorenyl)ethyl chloroformate ((±)-FLEC) was used as a chiral derivatizing agent in various analytical applications involving a wide range of endogenous, pharmaceutical and environmentally relevant molecules. This comprehensive review aims to present all the significant aspects related to the state of the art in FLEC labeling and subsequent chiral separation of the resulting diastereomers using LC, SFC and CE techniques.
July 16, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28753970/reversed-phase-uhplc-enantiomeric-separation-of-rasagiline-salts-using-a-chiralpak-%C3%A2-agp-column
#19
Nagarajan Balaji, Sayeeda Sultana
We report the first rapid ultra-high performance liquid chromatographic (UHPLC) enantiomeric reversed-phase separation of rasagiline mesylate and its tartrate salts using a Chiralpak(®) AGP column (50 mm × 2.1 mm, 5 μm) as a stationary phase. This method was developed as an alternative to the usage of previously reported normal-phase chiral LC columns for isomer separation. Our method is based on an isocratic approach using a mixture of ammonium acetate and isopropyl alcohol (90:10, v/v) as the mobile phase (0...
July 19, 2017: Scientia Pharmaceutica
https://www.readbyqxmd.com/read/28749545/optimization-of-throughput-in-semipreparative-chiral-liquid-chromatography-using-stacked-injection
#20
Mohammadreza Taheri, Mohsen Fotovati, Seyed-Kiumars Hosseini, Alireza Ghassempour
An interesting mode of chromatography for preparation of pure enantiomers from pure samples is the method of stacked injection as a pseudocontinuous procedure. Maximum throughput and minimal production costs can be achieved by the use of total chiral column length in this mode of chromatography. To maximize sample loading, often touching bands of the two enantiomers is automatically achieved. Conventional equations show direct correlation between touching-band loadability and the selectivity factor of two enantiomers...
July 27, 2017: Chirality
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