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Chiral separation

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https://www.readbyqxmd.com/read/28918632/analysis-and-sensory-evaluation-of-the-stereoisomers-of-a-homologous-series-c5-c10-of-4-mercapto-2-alkanols
#1
Svenja Nörenberg, Christiane Kiske, Bastian Reichardt, Verena Andelfinger, Anne Pfeiffer, Franziska Schmidts, Wolfgang Eisenreich, Karl-Heinz Engel
A homologous series of 4-mercapto-2-alkanols (C5-C10) was used to investigate the impact of the stereochemistry on the sensory properties of a class of naturally occurring polyfunctional thiols having a 1,3-oxygen-sulfur functionality. Stereoisomers were obtained via syntheses of racemic mixtures and subsequent lipase-catalyzed kinetic resolutions. Analytical separations of the stereoisomers were achieved by capillary gas chromatography (GC) using chiral stationary phases. The absolute configurations were assigned via NMR analysis...
September 17, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28917599/enantiomeric-separation-of-some-chiral-analytes-using-amylose-3-5-dimethylphenylcarbamate-covalently-immobilized-on-silica-by-nano-liquid-chromatography-and-capillary-electrochromatography
#2
Giovanni D'Orazio, Chiara Fanali, Marina Karchkhadze, Bezhan Chankvetadze, Salvatore Fanali
A new experimental chiral stationary phase containing amylose 3,5-dimethylphenylcarbamate immobilized onto silica gel (i-ADMPC) was packed in 100μm I.D. fused silica capillary and used for the chiral separation of eight selected flavanone derivatives in polar organic mobile phase by using different miniaturized techniques, such as nano-liquid chromatography (nano-LC), capillary electrochromatography (CEC) and pressure-assisted CEC (pCEC). A comparative study of different elution modes in terms of chromatographic efficiency, analysis time and enantiomeric resolution was carried out...
September 8, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28914062/-separation-of-phenylalanine-and-methionine-enantiomers-by-hplc-method-a%C3%A2-comparison-of-stationary-phase-types
#3
Katarína Hroboňová, Anna Lomenova, Jozef Čižmárik, Jozef Lehotay
The paper deals with enantioselective separation of amino acids by the high performance liquid chromatography method. Separations of enantiomeric forms were tested on the chiral stationary phases based on β-cyclodextrine, isopropyl carbamate cyclofructan 6, and the macrocyclic antibiotic teicoplanin. The best enantioseparation was obtained on the teicoplanin-based chiral stationary phase in the reversed-phase mode. UV spectrophotometric detection at 210 nm was used for detection of amino acids. The method was validated with respect to linearity, precision, limit of detection, limit of quantitation, and recovery...
2017: Ceská a Slovenská Farmacie
https://www.readbyqxmd.com/read/28911942/new-perspectives-in-high-efficient-and-ultrafast-chiral-liquid-chromatography-through-zwitterionic-teicoplanin-based-2-%C3%AE-m-superficially-porous-particles
#4
Omar H Ismail, Michela Antonelli, Alessia Ciogli, Claudio Villani, Alberto Cavazzini, Martina Catani, Simona Felletti, David S Bell, Francesco Gasparrini
With the aim of pushing forward the limits of high efficient and ultrafast chiral liquid chromatography, a new Chiral Stationary Phase (CSP) has been prepared by covalently bonding the teicoplanin selector on 2.0μm Superficially Porous Particles (SPPs). An already validated bonding protocol, which permits to achieve teicoplanin-based CSPs exhibiting zwitterionic behaviour, has been employed to prepare not only the 2.0μm version of the CSP but also two other analogous CSPs based, respectively, on 2.7μm SPPs and 1...
September 6, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28905405/bioassay-determination-and-separation-of-enantiomers-of-atenolol-by-direct-and-indirect-approaches-using-liquid-chromatography-a-review
#5
REVIEW
Sonika Batra, Ravi Bhushan
Atenolol, a β-adrenergic receptor antagonist, is a chiral compound used for the treatment of cardiovascular diseases and to treat hypertension, coronary heart disease, arrhythmias, sinus tachycardia and myocardial infarction, where it acts preferentially upon the β-adrenergic receptors in the heart. It is marketed as a racemate, but only (S)-enantiomer of (RS)-atenolol is responsible for the β-adrenoceptor blocking activity. Different chromatographic methods have been applied for separation and determination of enantiomers...
September 14, 2017: Biomedical Chromatography: BMC
https://www.readbyqxmd.com/read/28899554/construction-of-a-new-hydrazone-linked-chiral-covalent-organic-framework-silica-composite-as-the-stationary-phase-for-high-performance-liquid-chromatography
#6
Kai Zhang, Song-Liang Cai, Yi-Lun Yan, Zi-Hao He, Hui-Mei Lin, Xiao-Ling Huang, Sheng-Run Zheng, Jun Fan, Wei-Guang Zhang
Covalent organic frameworks (COFs), as an emerging class of crystalline porous organic polymers, have great potential for applications in chromatographic separation owning to their fascinating crystalline structures and outstanding properties. However, development of COF materials as novel stationary phases in high performance liquid chromatography (HPLC) is just in its infancy. Herein, we report the design and construction of a new hydrazone-linked chiral COF, termed BtaMth COF, from a chiral hydrazide building block (Mth) and present a one-pot synthetic method for the fabrication of BtaMth@SiO2 composite for HPLC separation of isomers...
September 5, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28894621/stereospecific-assay-of-r-and-s-goitrin-in-commercial-formulation-of-radix-isatidis-by-reversed-phase-high-performance-liquid-chromatography
#7
Lixing Nie, Zhong Dai, Shuangcheng Ma
Radix isatidis (Banlangen) is a widely used traditional Chinese medicine for treating fever and removing toxic heat. Pharmacological studies have indicated that (R)-goitrin (epigoitrin) is one of the main constituents accounting for its antiviral activity, while (S)-goitrin (goitrin) is known as an antithyroid factor. To better control the quality of radix isatidis and its formulations, it is imperative to enantiomerically determine the contents of R- and S-goitrin. In this study, an enantioselective method based on reversed phase chromatography was developed for the assay of (R, S)-goitrin enantiomers...
2017: Journal of Analytical Methods in Chemistry
https://www.readbyqxmd.com/read/28887486/propagation-of-superconducting-coherence-via-chiral-quantum-hall-edge-channels
#8
Geon-Hyoung Park, Minsoo Kim, Kenji Watanabe, Takashi Taniguchi, Hu-Jong Lee
Recently, there has been significant interest in superconducting coherence via chiral quantum-Hall (QH) edge channels at an interface between a two-dimensional normal conductor and a superconductor (N-S) in a strong transverse magnetic field. In the field range where the superconductivity and the QH state coexist, the coherent confinement of electron- and hole-like quasiparticles by the interplay of Andreev reflection and the QH effect leads to the formation of Andreev edge states (AES) along the N-S interface...
September 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28886938/enantioselective-determination-of-r-zopiclone-and-s-zopiclone-eszopiclone-in-human-hair-by-micropulverized-extraction-and-chiral-liquid-chromatography-high-resolution-mass-spectrometry
#9
Hajime Miyaguchi, Kenji Kuwayama
Zopiclone and its (S)-enantiomer (eszopiclone) are commonly prescribed for insomnia. Despite the high demand for enantioselective differentiation, the chiral analysis of zopiclone in hair has not been reported. In this study, a method for the enantioselective quantification of zopiclone in human hair was developed. The extraction medium and duration were optimized using real eszopiclone-positive hair samples. Specifically, micropulverized extraction with 3.0M ammonium phosphate buffer (pH 8.4) involving salting-out assisted liquid-liquid extraction with acetonitrile was utilized to minimize the degradation of zopiclone and for rapid and facile operation...
August 24, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28885007/stereoselective-differences-between-the-reinforcing-and-motivational-effects-of-cathinone-derived-4-methylmethcathinone-mephedrone-in-self-administering-rats
#10
Helene L Philogene-Khalid, Steven J Simmons, Sunil Nayak, Rose M Martorana, Shu H Su, Yohanka Caro, Brona Ranieri, Kathryn DiFurio, Lili Mo, Taylor A Gentile, Ali Murad, Allen B Reitz, John W Muschamp, Scott M Rawls
Mephedrone (4-methylmethcathinone (4-MMC)) (MEPH) is a new psychoactive substance (NPS) of the synthetic cathinone class. MEPH has a chiral center and exists as two enantiomers (R-,S-MEPH), yet stereospecific effects of MEPH have not been extensively investigated in preclinical assays. Because significant behavioral and neurochemical differences can exist between enantiomers, probing effects of stereochemistry on biological activity enables separation of adverse and therapeutic effects. Our prior work showed that R-MEPH, relative to S-MEPH, produced greater locomotor activation, place preference and facilitation of brain reward thresholds in rodents...
September 8, 2017: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/28880531/janus-nanocomposite-hydrogels-for-chirality-dependent-cell-adhesion-and-migration
#11
Andisheh Motealleh, Nermin Seda Kehr
Recently, there has been much interest in the chirality-dependent cell affinity to enantiomorphous nanomaterials (NMs), since, at the nanoscale level, enantiomers of (bio)molecules have different effects on cell behaviors. In this respect, this study used enantiomorphous NMs with which to generate the Janus nanocomposite (NC) hydrogels as multifunctional biomaterials for studying chirality-dependent cell adhesion and cell migration. These Janus NC hydrogels possess two enantiomorphous NC hydrogels, in which the different halves of the hydrogel contain the opposite enantiomers of a biopolymer functionalized nanomaterials...
September 7, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28880241/cyclodextrin-catalyzed-organic-synthesis-reactions-mechanisms-and-applications
#12
REVIEW
Chang Cai Bai, Bing Ren Tian, Tian Zhao, Qing Huang, Zhi Zhong Wang
Cyclodextrins are well-known macrocyclic oligosaccharides that consist of α-(1,4) linked glucose units and have been widely used as artificial enzymes, chiral separators, chemical sensors, and drug excipients, owing to their hydrophobic and chiral interiors. Due to their remarkable inclusion capabilities with small organic molecules, more recent interests focus on organic reactions catalyzed by cyclodextrins. This contribution outlines the current progress in cyclodextrin-catalyzed organic reactions. Particular emphases are given to the organic reaction mechanisms and their applications...
September 7, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28877441/development-of-large-scale-synthesis-of-tetrahydropyran-glycine-a-precursor-to-the-hcv-ns5a-inhibitor-bms-986097
#13
Arvind Mathur, Bei Wang, Daniel Smith, Jianqing Li, Joseph Pawluczyk, Jung-Hui Sun, Michael Kwok Wong, Subramaniam Krishnananthan, Dauh-Rurng Wu, Dawn Sun, Peng Li, Shiuhang Yip, Bang-Chi Cheng, Phil S Baran, Qi Chen, Omar D Lopez, Zhong Yong, John A Bender, Van N Nguyen, Jeffrey L Romine, Denis R St Laurent, Gan Wang, John F Kadow, Nicholas A Meanwell, Makonen Belema, Rulin Zhao
An efficient large scale synthesis of acid 1, a penultimate precursor to the HCV NS5A inhibitor BMS-986097, along with the final API step are described. Three routes were devised for the synthesis of 1 at the various stages of the program. The 3rd generation route, the one that proved scalable and is the main subject of this manuscript, features a one step Michael addition of t-butyl 2-((diphenylmethylene)amino)acetate 24 to (E)-benzyl 4-(1-hydroxycyclopropyl)but-2-enoate 28 followed by cyclization and chiral separation to form 27c, the core skeleton of cap piece 1...
September 6, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28877034/recent-progress-on-the-structure-separation-of-single-wall-carbon-nanotubes
#14
Jiaming Cui, Dehua Yang, Xiang Zeng, Naigen Zhou, Huaping Liu
The mass production of single-structure single-wall carbon nanotubes (SWCNTs) with identical properties is critical for their basic research and technical applications in the fields of electronics, optics and optoelectronics. Great efforts have been made to control the structures of SWCNTs since their discovery. Recently, the structure separation of SWCNTs has been made great progress. Various solution sorting methods have been developed to achieve not only the separation of metallic and semiconducting species, but also the sorting of distinct (n, m) single-chirality species and even their enantiomers...
September 6, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28876511/recent-progress-of-task-specific-ionic-liquids-in-chiral-resolution-and-extraction-of-biological-samples-and-metal-ions
#15
REVIEW
Datong Wu, Pengfei Cai, Xiaoyong Zhao, Yong Kong, Yuanjiang Pan
Ionic liquids have been functionalized for modern applications. The functional ionic liquids are also called task-specific ionic liquids. Various task-specific ionic liquids with certain groups have been constructed and exploited widely in the field of separation. To take advantage of their properties in separation science, task-specific ionic liquids are generally used in techniques such as liquid-liquid extraction, solid-phase extraction, gas chromatography, high-performance liquid chromatography and capillary electrophoresis...
September 6, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28875702/synthesis-structures-and-properties-of-hexapole-helicenes-assembling-six-5-helicene-substructures-into-highly-twisted-aromatic-systems
#16
Tomoka Hosokawa, Yusuke Takahashi, Tomoya Matsushima, Soichiro Watanabe, Shoko Kikkawa, Isao Azumaya, Akihiro Tsurusaki, Ken Kamikawa
Hexapole helicenes 1, which contain six [5]helicene substructures, were synthesized by Pd-catalyzed [2+2+2]cycloadditions of aryne precursor 6. Among the possible twenty stereoisomers, which include ten pairs of enantiomers, HH-1 was obtained selectively. Density functional theory (DFT) calculations identified HH-1 as the second most stable isomer that quantitatively isomerizes under thermal conditions into the most stable isomer (HH-2). Both enantiomers of HH-2 can be separated by chiral HPLC. Single-crystal X-ray diffraction analyses revealed a saddle-like structure for (P,M,P,P,M,P) HH-1 and a propeller-like structure for (P,M,P,M,P,M) HH-2...
September 6, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28872309/recent-progress-in-heterogeneous-asymmetric-hydrogenation-of-c%C3%A2-o-and-c%C3%A2-c-bonds-on-supported-noble-metal-catalysts
#17
Fabian Meemken, Alfons Baiker
The ease of separation, simple regeneration, and the usually high stability of solid catalysts facilitating continuous production processes have stimulated the development of heterogeneous asymmetric hydrogenation catalysis. The simplest and so far most promising strategy to induce enantioselectivity to solid metal catalysts is their modification by chiral organic compounds, as most prominently represented by the cinchona-modified Pt and Pd catalysts for the asymmetric hydrogenation of activated C═O and C═C bonds...
September 13, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28864189/high-performance-chiral-stationary-phases-based-on-chitosan-derivatives-with-a-branched-chain-alkyl-urea
#18
Shuang Liang, Shao-Hua Huang, Wei Chen, Zheng-Wu Bai
In this study, two series of chitosan 3,6-bis(arylcarbamate)-2-(isobutylurea)s and corresponding coated-type chiral stationary phases (CSPs) were prepared from two kinds of chitosans with different molecular weights. Most of the prepared CSPs demonstrated better enantioseparation performance than the homemade CSP of cellulose tris(3,5-dimethylphenylcarbamate). The CSPs of chitosan 3,6-bis(4-methylphenylcarbamate)-2-(isobutylurea) with higher molecular weight and chitosan 3,6-bis(3-chloro-4-methylphenylcarbamate)-2-(isobutylurea) with lower molecular weight possessed outstanding chiral recognition abilities which were at least as good as that of the commercialized CSP of Chiralcel OD-H towards the tested chiral analytes...
September 8, 2017: Analytica Chimica Acta
https://www.readbyqxmd.com/read/28863259/stereo-selective-analysis-and-degradation-of-pyrisoxazole-in-cabbage-pakchoi-and-pepper-by-liquid-chromatography-tandem-mass-spectrometry
#19
Xue Wei Yang, Pei Pei Qi, Xiangyun Wang, Zhi Wei Wang, Yu Han Sun, Lidong Wang, Xia Hong Xu, Hao Xu, Qiang Wang, Xin Quan Wang, Chang Shan Zhao
Pyrisoxazole is a chiral fungicide with high sterilizing activity to the plant pathogenic bacteria and thus can be used for protecting the vegetables from the gray mold, powdery mildew and brown rot. The present work aimed to explore its stereo-selective degradation in cabbage, pakchoi and pepper samples. The enantio-separation and analysis on chiral column Lux Cellulose-3 based on liquid chromatography tandem mass spectrometry was developed coupled to the QuEChERS method. The recoveries of the stereoisomers in various vegetables ranged from 72...
September 1, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28856822/resolution-of-r-and-s-enantiomers-of-clenbuterol-in-pharmaceutical-preparations-and-black-market-products-using-liquid-chromatography-tandem-mass-spectrometry
#20
Benjamín Velasco-Bejarano, Jahir Bautista, Ma Olivia Noguez, Evangelina Camacho, Martha E Rodríguez, Leonardo Rodríguez
Several banned substances are illegally used by athletes in racemic mixtures for performance enhancement. These include clenbuterol, methyl hexaneamine, methamphetamines, amphetamines. Clenbuterol is present in a large number of doping samples from Olympic and non-Olympic athletes that have adverse analytical findings. In some cases, the presence of these substance could be the result of consumption of meat contaminated with clenbuterol. In other cases, the origin is not clear. In this study, 27 products with racemic clenbuterol were evaluated using a new analytical methodology for the resolution of R-(-) and S-(+)-enantiomers of clenbuterol by Liquid Chromatography-Tandem Mass Spectrometry LC-MS/MS using a chiral column in 15 minutes with good separation...
August 30, 2017: Drug Testing and Analysis
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