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Chiral separation

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https://www.readbyqxmd.com/read/27916126/general-screening-and-optimization-strategy-for-fast-chiral-separations-in-modern-supercritical-fluid-chromatography
#1
Lucie Nováková, Michal Douša
High throughput general chiral screening method using supercritical fluid chromatography was developed. This method takes an advantage of very fast gradient screening (3 min + 1 min isocratic hold) and generic enantioselectivity of the combined additive formed by 0.1% trifluoroacetic (TFA) acid and 0.1% diethylamine (DEA). The TFA/DEA combined additive was systematically added to organic modifiers methanol and isopropanol. Among five tested polysaccharide-based chiral stationary phases, amylose tris(3,5-dimethylphenylcarbamate) and cellulose tris(3,5-dimethylphenylcarbamate) provided the best enantioseparation success rate...
January 15, 2017: Analytica Chimica Acta
https://www.readbyqxmd.com/read/27911555/electromagnetic-signatures-of-the-chiral-anomaly-in-weyl-semimetals
#2
Edwin Barnes, J J Heremans, Djordje Minic
Weyl semimetals are predicted to realize the three-dimensional axial anomaly first discussed in particle physics. The anomaly leads to unusual transport phenomena such as the chiral magnetic effect in which an applied magnetic field induces a current parallel to the field. Here we investigate diagnostics of the axial anomaly based on the fundamental equations of axion electrodynamics. We find that materials with Weyl nodes of opposite chirality and finite energy separation immersed in a uniform magnetic field exhibit an anomaly-induced oscillatory magnetic field with a period set by the chemical potential difference of the nodes...
November 18, 2016: Physical Review Letters
https://www.readbyqxmd.com/read/27908928/development-and-validation-of-a-normal-phase-chiral-hplc-method-for-analysis-of-afoxolaner-using-a-chiralpak%C3%A2-ad-3-column
#3
Jinyou Zhuang, Satish Kumar, Abu Rustum
Afoxolaner is a new antiparasitic molecule from the isoxazoline family that acts on the insect acarine gamma-aminobutyric acid and glutamate receptors. Isoxazoline family of compounds has been employed as active pharmaceutical ingredient in drug products prescribed for control of fleas and ticks in dogs. Afoxolaner with a chiral center at isoxazoline ring exists as a racemic mixture. A normal phase chiral high performance liquid chromatography analytical method has been developed to verify that afoxolaner is a racemic mixture as demonstrated by specific rotation, as well as to determine enantiomeric purity of single enantiomer samples...
November 2016: Journal of Chromatographic Science
https://www.readbyqxmd.com/read/27897331/a-convenient-and-validated-enantiomer-separation-of-chiral-aliphatic-amines-as-nitrobenzoxadiazole-derivatives-on-polysaccharide-derived-chiral-stationary-phases-under-simultaneous-ultraviolet-and-fluorescence-detection
#4
Suraj Adhikari, Jong Seong Kang, Wonjae Lee
A convenient method using a fluorogenic agent, 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl), was developed for enantiomer separation of chiral aliphatic amines including amino alcohols by normal high-performance liquid chromatography. The enantiomer separation of chiral aliphatic amines as NBD derivatives was performed on six covalently bonded and four coated-type polysaccharide-derived chiral stationary phases (CSPs) under simultaneous ultraviolet (UV) and fluorescence detection (FLD). Among the covalently bonded CSPs, Chiralpak IE showed the best enantiomer separation for most analytes...
December 2016: Chirality
https://www.readbyqxmd.com/read/27897327/high-performance-liquid-chromatography-evaluation-of-the-enantiomeric-purity-of-amino-acids-by-means-of-automated-precolumn-derivatization-with-ortho-phthalaldehyde-and-chiral-thiols
#5
Raphael Kühnreich, Ulrike Holzgrabe
The use of ortho-phthalaldehyde (OPA) for the derivatization of amino acids (AA) is well known. It enables the separation of the derivatives on common reversed phase columns and improves the sensitivity with fluorescence detection. With the use of a chiral thiol an indirect enantioseparation of chiral amines and AAs is feasible. The major drawback of the OPA-derivatization is the poor stability of the products. Here, a method with an in-needle derivatization procedure is optimized to facilitate a quantitative conversion of the AA with OPA and the chiral thiols N-acetyl-L-cysteine or N-isobutyryl-L-cysteine, followed by a subsequent analysis, eluding the stability issue...
December 2016: Chirality
https://www.readbyqxmd.com/read/27897117/enantiomeric-resolution-of-rs-naproxen-and-application-of-s-naproxen-in-the-direct-and-indirect-enantioseparation-of-racemic-compounds-by-liquid-chromatography-a-review
#6
Sonika Batra, Ravi Bhushan
(S)-Naproxen (Npx), an α-aryl propionic acid derivative, belongs to class of Non-Steroidal Anti-Inflammatory Drugs and is easily available in pure (S)-form. (S)-Npx has been used as a chiral selector for chromatographic separation of a variety of racemates, using both direct and indirect methods, and has been found to be useful and successful as a basic chiral moiety. This review article describes methods for enantioseparation of (RS)-Npx, development of chiral stationary phases based on (S)-Npx and preparation of novel chiral derivatizing reagents synthesized from (S)-Npx along with their application for enantioseparation of several pharmaceutically important racemates...
November 28, 2016: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/27894124/extensive-degeneracy-coulomb-phase-and-magnetic-monopoles-in-artificial-square-ice
#7
Yann Perrin, Benjamin Canals, Nicolas Rougemaille
Artificial spin-ice systems are lithographically patterned arrangements of interacting magnetic nanostructures that were introduced as way of investigating the effects of geometric frustration in a controlled manner. This approach has enabled unconventional states of matter to be visualized directly in real space, and has triggered research at the frontier between nanomagnetism, statistical thermodynamics and condensed matter physics. Despite efforts to create an artificial realization of the square-ice model-a two-dimensional geometrically frustrated spin-ice system defined on a square lattice-no simple geometry based on arrays of nanomagnets has successfully captured the macroscopically degenerate ground-state manifold of the model...
November 28, 2016: Nature
https://www.readbyqxmd.com/read/27888567/chiral-separation-of-benzothiazole-derivatives-of-amino-acids-using-capillary-zone-electrophoresis
#8
Zuzana Nováková, Vladimír Pejchal, Jan Fischer, Petr Česla
A method for the separation of enantiomers of leucine and phenylalanine benzothiazole derivatives as potential antimicrobial agents was developed using capillary zone electrophoresis with a dual cyclodextrin system. The best resolution of enantiomers was achieved in 100 mmol.L(-1) phosphate background electrolyte pH 3.5 with dual cyclodextrin system consisting of 10 mmol.L(-1) of β-cyclodextrin with 10 mmol.L(-1) of 2-hydroxypropyl-β-cyclodextrin for leucine derivative and 10 mmol.L(-1) of 2-hydroxypropyl-γ-cyclodextrin for phenylalanine derivative, respectively...
November 26, 2016: Journal of Separation Science
https://www.readbyqxmd.com/read/27888525/breaking-sad-unleashing-the-breakthrough-potential-of-ketamine-s-rapid-antidepressant-effects
#9
David Feifel
Preclinical Research The surprising results of a small clinical trial on the effects of low dose ketamine, a 65-year old anesthetic drug that is also used off-label for chronic pain and recreationally as a club drug, in eight depressed subjects unleashed the most significant advance in antidepressant drug development in decades. That study and subsequent ones have demonstrated that low dose, infused ketamine is able to induce a remission of depression in patients who have failed conventional medications, within 24 h...
November 26, 2016: Drug Development Research
https://www.readbyqxmd.com/read/27886776/synthesis-and-performance-of-chiral-ferrocene-modified-silica-gel-for-mixed-mode-chromatography
#10
Lijun Qiao, Xiaohua Zhou, Xue Li, Wenrui Du, Ajuan Yu, Shusheng Zhang, Yangjie Wu
A brush-type chiral stationary phase, N-ferrocenyl benzoyl-(1S, 2R)-1, 2-diphenyl ethanol-bonded on the silica gel (NFcBEs) for high performance liquid chromatography (HPLC), was prepared using γ-glycidoxypropyltrimethoxysilane as coupling reagent. The structure of this novel material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Mechanism involved in the chromatographic separation is the multi-interaction including hydrophobic, π-π, hydrogen-bonding, π-charge transfer, dipole-dipole and acid-base equilibrium interactions...
January 15, 2017: Talanta
https://www.readbyqxmd.com/read/27884429/development-of-separation-methods-for-the-chiral-resolution-of-hexahelicenes
#11
Jan Storch, Květa Kalíková, Eva Tesařová, Vítězslav Maier, Jan Vacek
In this short communication we report optimized procedures for the chiral separation of non-charged [6]helicene (1) and cationic derivative 1-butyl-3-(2-methyl[6]helicenyl)-imidazolium bromide (2) using high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) methods. The possibility of using capillary electrophoresis (CE) was also tested. The satisfactory results were obtained with SFC, where the highly selective resolution of four enantiopure 1 and 2 helicenes was achieved in a single run within 5min...
December 9, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/27881063/membrane-bioreactors-for-pharmaceutical-applications-optically-pure-enantiomers-production
#12
Emma Piacentini, Rosalinda Mazzei, Lidietta Giorno
In biological systems, recognition at molecular level is governed by chiral interactions. Therefore, optical isomers have very different effect in natural systems. For example, one can have beneficial effect while the other can be very harmful. For these reasons, chiral drugs nowadays are mainly admitted in the optically pure form. Given these requirements, it is clear why demand for chiral drugs has grown dramatically and the single-enantiomer drug segment has become an important part of the overall pharmaceutical market...
November 23, 2016: Current Pharmaceutical Design
https://www.readbyqxmd.com/read/27873184/-%C3%A2-evodiakine-a-pair-of-rearranged-rutaecarpine-type-alkaloids-from-evodia-rutaecarpa
#13
Yan-Hong Li, Yu Zhang, Li-Yan Peng, Xiao-Nian Li, Qin-Shi Zhao, Rong-Tao Li, Xing-De Wu
(±)-Evodiakine (1a and 1b), a pair of rearranged rutaecarpine-type alkaloids with an unprecedented 6/5/5/7/6 ring system, were isolated from the nearly ripe fruits of Evodia rutaecarpa. Separation of the enantiomers have been achieved by chiral HPLC column. The structures of (±)-evodiakine were unambiguously elucidated by 1D and 2D NMR spectra, mass spectrometry, and single-crystal X-ray diffraction. Their absolute configurations were determined by comparison of experimental and calculated electronic circular dichroism spectra...
December 2016: Natural Products and Bioprospecting
https://www.readbyqxmd.com/read/27872920/ultrafast-chiral-separations-for-high-throughput-enantiopurity-analysis
#14
Chandan L Barhate, Leo A Joyce, Alexey A Makarov, Kerstin Zawatzky, Frank Bernardoni, Wes A Schafer, Daniel W Armstrong, Christopher J Welch, Erik L Regalado
Recent developments in fast chromatographic enantioseparations now make high throughput analysis of enantiopurity on the order of a few seconds achievable. Nevertheless, routine chromatographic determinations of enantiopurity to support stereochemical investigations in pharmaceutical research and development, synthetic chemistry and bioanalysis are still typically performed on the 5-20 min timescale, with many practitioners believing that sub-minute enantioseparations are not representative of the molecules encountered in day to day research...
November 22, 2016: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/27869770/direct-separation-of-pregabalin-enantiomers-using-a-zwitterionic-chiral-selector-by-high-performance-liquid-chromatography-coupled-to-mass-spectrometry-and-ultraviolet-detection
#15
Lakshmi Narayana Chennuru, Thirupathi Choppari, Ramakrishna Prasad Nandula, Tong Zhang, Pilar Franco
The chromatographic resolution of pregabalin enantiomers has been often achieved by derivatization of the molecule, in order to reach enough sensitivity at low concentrations of the minor enantiomer present in the active principle. In the present article, the development and optimization of two liquid chromatographic methods are presented for the direct resolution of pregabalin enantiomers on a chiral stationary phase (CSP) containing a zwitterionic selector derived from cinchona alkaloid and sulfonic acid (CHIRALPAK ZWIX)...
November 19, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/27866846/determination-of-enantiomeric-vigabatrin-by-derivatization-with-diacetyl-l-tartaric-anhydride-followed-by-ultra-high-performance-liquid-chromatography-quadrupole-time-of-flight-mass-spectrometry
#16
Jing Zhao, Yujin Shin, Yan Jin, Kyung Min Jeong, Jeongmi Lee
Vigabatrin, one of the most widely used antiepileptic drugs, is marketed and administered as a racemic mixture, while only S-enantiomer is therapeutically effective. In the present study, diacetyl-l-tartaric acid anhydride was used as an inexpensive and effective chiral derivatization reagent to produce tartaric acid monoester derivatives of vigabatrin enantiomers that could be readily resolved by reversed phase chromatography. Derivatization conditions were statistically optimized by response surface methodology, resulting in an optimal reaction temperature of 44°C and an optimal reaction time of 30min...
November 10, 2016: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/27866254/heart-cut-achiral-chiral-lc-lc-method-development-using-factorial-design-application-to-the-chiral-separation-of-ketoprofen
#17
Miguel Peñín-Ibáñez, María Jesús Santos-Delgado, Luis María Polo-Díez
A two-dimensional achiral-chiral LC-LC method in heart-cut mode for ketoprofen and its enantiomeric fraction determination was proposed. A C8 column was used in the first dimension, and the chiral column was an α1-acid glycoprotein. The mobile phase of the chiral system was optimized by a factorial design. The effect of temperature on retention and on enantiomeric resolution was studied. Particular attention was paid to mobile phase compatibility for the two columns and to transferring time, using ketoprofen standards...
November 19, 2016: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/27863711/n-acylated-chitosan-bis-arylcarbamate-s-a-class-of-promising-chiral-separation-materials-with-powerful-enantioseparation-capability-and-high-eluents-tolerability
#18
Sheng Tang, Jian-De Liu, Qin Bin, Ke-Qin Fu, Xiao-Chen Wang, Ying-Bin Luo, Shao-Hua Huang, Zheng-Wu Bai
In order to comprehensively understand the influence of coordination of the substituent at 2-position with those at 3- and 6-positions on the properties of chitosan derivatives, a series of chitosan 3,6-bis(arylcarbamate)-2-(amide)s (CACAs) and the related chiral stationary phases (CSPs) were prepared and reported in the present study. Specifically, chitosan was N-acylated with carboxylic acid anhydrides, and then further derivatized with various aryl isocyanates to afford CACAs, from which a class of coated-type CSPs were prepared...
December 9, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/27845761/eluent-tolerance-and-enantioseparation-recovery-of-chiral-packing-materials-based-on-chitosan-bis-phenylcarbamate-n-octyl-urea-s-for-high-performance-liquid-chromatography
#19
Jing Wang, Shao-Hua Huang, Wei Chen, Zheng-Wu Bai
The goal of the present work was to study the influence of the swelling of chitosan derivatives on the enantioseparation and the separation performance recovery of chiral stationary phases (CSPs) based on these derivatives. Therefore, six chitosan bis(phenylcarbamate)-(n-octyl urea)s were synthesized, which were coated on macroporous 3-aminopropyl silica gel affording new CSPs. Most of the CSPs demonstrated strong enantioseparation capability for the tested chiral compounds. The swelling capacity of the chitosan bis(phenylcarbamate)-(n-octyl urea)s in ethyl acetate, acetone and tetrahydrofuran (THF) was evaluated...
November 13, 2016: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/27844416/two-synthetic-methods-for-preparation-of-chiral-stationary-phases-using-crystalline-degradation-products-of-vancomycin-column-performance-for-enantioseparation-of-acidic-and-basic-drugs
#20
Assem Abdollahpour, Rouhollah Heydari, Mojtaba Shamsipur
Two chiral stationary phases (CSPs) based on crystalline degradation products (CDPs) of vancomycin by using different synthetic methods were prepared and compared. Crystalline degradation products of vancomycin were produced by hydrolytic loss of ammonia from vancomycin molecules. Performances of two chiral columns prepared with these degradation products were investigated using several acidic and basic drugs as model analytes. Retention and resolution of these analytes on the prepared columns, as two main parameters, in enantioseparation were studied...
November 14, 2016: AAPS PharmSciTech
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