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Chirality

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https://www.readbyqxmd.com/read/29920777/enantiomeric-separation-of-novel-psychoactive-substances-by-capillary-electrophoresis-using-18-crown-6-tetracarboxylic-acid-as-chiral-selector
#1
Johannes S Hägele, Martin G Schmid
In the recent years, hundreds of Novel Psychoactive Substances (NPS) have entered both the European and the global drug market. These drugs, which are mainly used for recreational matters, have caused serious social problems. Every year, the spectrum of these misused drugs is enlarged by new derivatives, which are produced by modifications of basic structures of already well-known substances. Additionally, a lot of them possess a stereogenic center which leads to 2 enantiomeric forms. The fact that the pharmacological effects and potencies of the enantiomers of these chiral NPS may differ can be assumed from a broad spectrum of active pharmaceutical ingredients...
June 19, 2018: Chirality
https://www.readbyqxmd.com/read/29885046/utilization-of-deep-sea-microbial-esterase-phe21-to-generate-chiral-sec-butyl-acetate-through-kinetic-resolutions
#2
Yilong Wang, Yongkai Xu, Yun Zhang, Aijun Sun, Yunfeng Hu
We previously identified and characterized 1 novel deep-sea microbial esterase PHE21 and used PHE21 as a green biocatalyst to generate chiral ethyl (S)-3-hydroxybutyrate, 1 key chiral chemical, with high enantiomeric excess and yield through kinetic resolution. Herein, we further explored the potential of esterase PHE21 in the enantioselective preparation of secondary butanol, which was hard to be resolved by lipases/esterases. Despite the fact that chiral secondary butanols and their ester derivatives were hard to prepare, esterase PHE21 was used as a green biocatalyst in the generation of (S)-sec-butyl acetate through hydrolytic reactions and the enantiomeric excess, and the conversion of (S)-sec-butyl acetate reached 98% and 52%, respectively, after process optimization...
June 8, 2018: Chirality
https://www.readbyqxmd.com/read/29873852/c-2-symmetric-sulfonamides-as-homogeneous-and-heterogeneous-organocatalysts-that-mimic-enzymes-in-enantioselective-michael-additions
#3
Harold Cruz, Felipe A Servín, Domingo Madrigal, Daniel Chávez, Sergio Perez-Sicairos, Gerardo Aguirre, Andrew L Cooksy, Ratnasamy Somanathan
Herein, we report the synthesis of C2 -symmetric sulfonamides as homogeneous and heterogeneous organocatalysts and their application in the enantioselective conjugate 1,4-Michael addition of carbonylic nucleophiles to β-nitrostyrene. Organocatalysts hydrogen bond to β-nitrostyrene and enamine in the transition state, mimicking an enzyme leading to final products in high yields (up to 98%) and good enantioselectivities (up to 96%). In addition, these results were supported by density functional calculations...
June 6, 2018: Chirality
https://www.readbyqxmd.com/read/29864196/the-development-of-biphasic-chiral-recognition-in-chiral-separation
#4
REVIEW
Xin-Yi Huang, Kai-Jun Quan, Dong Pei, Jian-Fei Liu, Duo-Long Di
In chiral separation, enantioseparation factor is an important parameter which influences the resolution of enantiomers. In this current overview, a biphasic chiral recognition method is introduced to the readers. This method can significantly improve the enantioseparation factor in two-phase solvent through adding lipophilic and hydrophilic chiral selectors which have opposite chiral recognition ability to organic and aqueous phases, respectively. This overview presents the development and applications of biphasic chiral recognition in liquid-liquid extraction and counter current chromatography...
June 4, 2018: Chirality
https://www.readbyqxmd.com/read/29863761/atropisomerism-in-rilpivirine-hydrochloride-spectroscopic-characterization-of-rilpivirine-and-related-impurities
#5
Senthilkumar Natarajan, Hiriyanna Salmara Ganeshbhat, Sujeet Shrivastava, Srimurugan Sankareswaran, Pramod Kumar
Nuclear magnetic resonance (NMR) technique has been used to find the property of atropisomerism in Rilpivirine hydrochloride by variable temperature analysis and various 2D techniques. Both the Rilpivirine hydrochloride (E-isomer) and Impurity-A (Z-isomer) isomers have been differentiated and confirmed by NMR and ultraviolet techniques. Preparative high-performance liquid chromatography isolation for Impurity-A is followed by spectroscopic (NMR, mass spectra, and infrared) investigation that provides a perfect solution for determination of the structure of Rilpivirine and related impurities...
June 4, 2018: Chirality
https://www.readbyqxmd.com/read/29856908/cellulose-type-chiral-stationary-phase-based-on-reduced-graphene-oxide-silica-gel-for-the-enantiomer-separation-of-chiral-compounds
#6
Yuanyuan Li, Qiang Li, Nan Zhu, Zhuxian Gao, Yulong Ma
The graphene oxide (GO) was covalently coupled to the surfaces of silica gel (SiO2 ) microspheres by amide bond to get the graphene oxide@silica gel (GO@SiO2 ). Then, the GO@SiO2 was reduced with hydrazine to the reduced graphene oxide@silica gel (rGO@SiO2 ), and the cellulose derivatives were physically coated on the surfaces of rGO@SiO2 to prepare a chiral stationary phase (CSP) for high performance liquid chromatography. Under the optimum experimental conditions, eight benzene-enriched enantiomers were separated completely, and the resolution of trans-stilbene oxide perfectly reached 4...
June 1, 2018: Chirality
https://www.readbyqxmd.com/read/29856893/urea-derivative-catalyzed-enantioselective-aldol-reaction-of-isatins-with-ketones
#7
Li Ming Wang, Mei Jun Zhao, Zhe Chen, Hong Wen Mu, Ying Jin
Urea derivative has been used to catalyze the asymmetric aldol reaction of isatins with ketones. The resulting 3-alkyl-3-hydroxy-indolin-2-ones products were obtained in good yields (70%-94%) with high enantioselectivities (up to 87%ee).
June 1, 2018: Chirality
https://www.readbyqxmd.com/read/29852522/functionalization-of-nanostructured-gold-substrates-with-chiral-chromophores-for-sers-applications-the-case-of-5-aza-5-helicene
#8
Chiara Zanchi, Andrea Lucotti, Damiano Cancogni, Francesca Fontana, Sebastiano Trusso, Paolo M Ossi, Matteo Tommasini
Nanostructured gold thin films can be fabricated by controlled pulsed laser deposition to get efficient sensors, with uniform morphology and optimized plasmon resonance, to be employed as plasmonic substrates in surface enhanced Raman scattering spectroscopy. By attaching 5-aza[5]helicen-6-yl-6-hexanethiol to such gold nanostructures, used in a previous work for label-free drug sensing with biomedical purposes, we successfully prepared functionalized substrates with remarkable surface enhanced Raman scattering activity...
May 31, 2018: Chirality
https://www.readbyqxmd.com/read/29791052/high-performance-liquid-chromatography-quantification-of-enantiomers-of-a-dihydroxylated-tetrahydrofuran-natural-product
#9
Ke Li, Skye D Fissette, Tyler J Buchinger, Zoe E Middleton, Alistair Boyer, Weiming Li
Both enantiomers of petromyroxol are putative pheromones in sea lamprey (Petromyzon marinus). Here, we describe the separation and quantification of the petromyroxol enantiomers using high-performance liquid chromatography tandem mass spectrometry. The separation was tested on a wide range of chiral columns with normal phases, and effects of the chromatographic parameters such as mobile phase and temperature on the separation were optimized. The AD-H column showed the best separation of enantiomers with n-hexane and ethanol as the mobile phase...
May 23, 2018: Chirality
https://www.readbyqxmd.com/read/29791038/special-issue-proceedings-of-16th-international-conference-on-chiroptical-spectroscopy-rennes-2017
#10
Jeanne Crassous, Narcis Avarvari, Nina Berova, John Caldwell
No abstract text is available yet for this article.
May 23, 2018: Chirality
https://www.readbyqxmd.com/read/29782670/surface-enhanced-chiroptical-spectroscopy-with-superchiral-surface-waves
#11
Giovanni Pellegrini, Marco Finazzi, Michele Celebrano, Lamberto Duò, Paolo Biagioni
No abstract text is available yet for this article.
May 21, 2018: Chirality
https://www.readbyqxmd.com/read/29782664/stereoselective-hplc-separation-of-alvimopan-on-cellulose-based-immobilized-polysaccharide-as-a-chiral-stationary-phase
#12
Nitin H Dhekale, Dattatray B Gunjal, Anil H Gore, Yagnakirankumar Komaravolu, K Hima Bindu, Govind B Kolekar
Chiral separation by normal phase high performance liquid chromatography is one of the most powerful technique to quantify the chiral purity of the compounds. In this study, a novel, simple, and specific analytical method was proposed to ascertain the chiral purity of alvimopan (ALV). The normal phase HPLC method was developed based on cellulose tris (3,5-dichlorophenylcarbamate) stationary phase. The separation of ALV isomers achieved by using column CHIRALPAK IC (250 × 4.6 mm, 5 μm), mobile phase n-hexane: isopropyl alcohol: ethanol: diethylamine (650:200:150:5 v/v), column oven temperature 30°C, flow rate 1...
May 21, 2018: Chirality
https://www.readbyqxmd.com/read/29752740/how-do-reaction-conditions-affect-the-enantiopure-synthesis-of-2-substituted-1-4-benzodioxane-derivatives
#13
Valentina Straniero, Andrea Casiraghi, Laura Fumagalli, Ermanno Valoti
Several biologically active compounds structurally include the enantiopure 2-substituted-1,4-benzodioxane scaffold. The straightforward racemization that affects reactions involving most of the common chemical reactives is thus a crucial issue. The developing of a completely stereo-controlled synthetic route that does not affect the enantiomeric excess is consequently mandatory. It is also important to set up a reliable chiral HPLC method, able to follow the reaction, and to improve the synthetic performances...
May 12, 2018: Chirality
https://www.readbyqxmd.com/read/29752732/hplc-ecd-and-tddft-ecd-study-of-hexahydropyrrolo-1-2-a-quinoline-derivatives
#14
László Tóth, Attila Mándi, Dániel Váradi, Tibor Kovács, Anna Szabados, Attila Kiss-Szikszai, Qi Gong, Haiyan Zhang, Péter Mátyus, Sándor Antus, Tibor Kurtán
Synthesis of racemic hexahydropyrrolo[1,2-a]quinoline derivatives (1-8) was performed by utilizing the Knoevenagel-[1,5]-hydride shift-cyclization domino reaction. Separation of the enantiomers of the chiral products (1-8) was carried out by chiral high-performance liquid chromatography, and online high-performance liquid chromatography-electronic circular dichroism (ECD) spectra were recorded to elucidate the absolute configuration by comparing the experimental and time-dependent density functional theory-ECD spectra obtained at various theoretical levels...
May 12, 2018: Chirality
https://www.readbyqxmd.com/read/29746716/-r-metacycloprodigiosin-hcl-chiroptical-properties-and-structure
#15
Daniela Peixoto, Elisabete P Ferreira, Ana M Lourenço, Jordan L Johnson, Ana M Lobo, Prasad L Polavarapu
(R)-Metacycloprodigiosin can exist in three different tautomeric forms, each with hydrogens at C9' and C12 in syn or anti orientation. With the addition of HCl, this structural diversity reduces to syn-(R)-metacycloprodigiosin-HCl (1a) and anti-(R)-metacycloprodigiosin-HCl (1b), each with multiple conformers. Energetics and chiroptical properties, namely, electronic circular dichroism (ECD) and specific optical rotation (SOR), of (R)-metacycloprodigiosin-HCl have been investigated at B3LYP/6-311++G(2d,2p) level...
May 10, 2018: Chirality
https://www.readbyqxmd.com/read/29733469/isotope-chirality-in-long-armed-multifunctional-organosilicon-cephalopod-molecules
#16
Béla Barabás, Róbert Kurdi, Claudia Zucchi, Gyula Pályi
Long-armed multifunctional organosilicon molecules display self-replicating and self-perfecting behavior in asymmetric autocatalysis (Soai reaction). Two representatives of this class were studied by statistical methods aiming at determination of probabilities of natural abundance chiral isotopomers. The results, reported here, show an astonishing richness of possibilities of the formation of chiral isotopically substituted derivatives. This feature could serve as a model for the evolution of biological chirality in prebiotic and early biotic stereochemistry...
May 7, 2018: Chirality
https://www.readbyqxmd.com/read/29733458/revisiting-polarimetry-near-the-isotropic-point-of-an-optically-active-non-enantiomorphous-molecular-crystal
#17
Alexander T Martin, Melissa Tan, Shane M Nichols, Emily Timothy, Bart Kahr
Accurate polarimetric measurements of the optical activity of crystals along low symmetry directions are facilitated by isotropic points, frequencies where dispersion curves of eigenrays cross and the linear birefringence disappears. We report here the optical properties and structure of achiral, uniaxial (point group D2d ) potassium trihydrogen di-(cis-4-cyclohexene-1,2-dicarboxylate) dihydrate, whose isotropic point was previously detected (S. A. Kim, C. Grieswatch, H. Küppers, Zeit. Krist. 1993; 208:219-222) and exploited for a singular measurement of optical activity normal to the optic axis...
May 7, 2018: Chirality
https://www.readbyqxmd.com/read/29727500/computational-simulation-of-vibrationally-resolved-spectra-for-spin-forbidden-transitions
#18
Franco Egidi, Marco Fusè, Alberto Baiardi, Julien Bloino, Xiaosong Li, Vincenzo Barone
In this computational study, we illustrate a method for computing phosphorescence and circularly polarized phosphorescence spectra of molecular systems, which takes into account vibronic effects including both Franck-Condon and Herzberg-Teller contributions. The singlet and triplet states involved in the phosphorescent emission are described within the harmonic approximation, and the method fully takes mode-mixing effects into account when evaluating Franck-Condon integrals. Spin-orbit couplings, which are responsible for these otherwise forbidden phenomena, are accounted for by means of a relativistic two-component time-dependent density functional theory method...
May 4, 2018: Chirality
https://www.readbyqxmd.com/read/29722457/enantiomeric-composition-of-nicotine-in-tobacco-leaf-cigarette-smokeless-tobacco-and-e-liquid-by-normal-phase-high-performance-liquid-chromatography
#19
Hongfei Zhang, Yongqiang Pang, Yanbo Luo, Xiangyu Li, Huan Chen, Shulei Han, Xingyi Jiang, Fengpeng Zhu, Hongwei Hou, Qingyuan Hu
Evaluating the source of nicotine in e-liquid is a problem. Tobacco-derived nicotine contains predominantly (S)-(-)-nicotine, whereas tobacco-free nicotine products may not. Thus, we developed a new normal phase high-performance liquid chromatography method to determinate the enantiomeric composition of nicotine in 10 kinds of flue-cured tobacco, 3 kinds of burley, 1 kind of cigar tobacco, 2 kinds of oriental tobacco, 5 kinds of Virginia cigarette, 5 kinds of blend cigarette, 10 kinds of e-liquid, and 4 kinds of smokeless tobacco...
May 3, 2018: Chirality
https://www.readbyqxmd.com/read/29676476/kinetic-resolution-of-n-acetyl-dl-alanine-methyl-ester-using-immobilized-escherichia-coli-cells-bearing-recombinant-esterase-from-bacillus-cereus
#20
Jianyong Zheng, Xing Lan, Lijuan Huang, Yinjun Zhang, Zhao Wang
D-alanine is widely used in medicine, food, additives, cosmetics, and other consumer items. Esterase derived from Bacillus cereus WZZ001 exhibits high hydrolytic activity and stereoselectivity. In this study, we expressed the esterase gene in Escherichia coli BL21 (DE3). We analyzed the biocatalytic resolution of N-acetyl-DL-alanine methyl ester by immobilized whole E. coli BL21 (DE3) cells, which were prepared through embedding and cross-linking. We analyzed biocatalytic resolution under the optimal conditions of pH of 7...
April 20, 2018: Chirality
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