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Chirality

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https://www.readbyqxmd.com/read/28730706/chromatographic-profiles-of-tryptophan-and-kynurenine-enantiomers-derivatized-with-s-4-3-isothiocyanatopyrrolidin-1-yl-7-n-n-dimethylaminosulfonyl-2-1-3-benzoxadiazole-using-lc-ms-ms-on-a-triazole-bonded-column
#1
Hideaki Iizuka, Takahiro Harashima, Shuhei Takahashi, Ryosuke Kuwabara, Yoko Naito, Tatsuya Sakamoto, Mayu Onozato, Hideaki Ichiba, Takeshi Fukushima
d- and l-Tryptophan (Trp) and d- and l-kynurenine (KYN) were derivatized with a chiral reagent, (S)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole (DBD-PyNCS), and were separated enantiomerically by high-performance liquid chromatography (HPLC) equipped with a triazole-bonded column (Cosmosil HILIC) using tandem mass spectrometric (MS/MS) detection. Effects of column temperature, salt (HCO2 NH4 ) concentration, and pH of the mobile phase in the enantiomeric separation, followed by MS detection of (S)-DBD-PyNCS-d,l-Trp and -d,l-KYN, were investigated...
July 21, 2017: Chirality
https://www.readbyqxmd.com/read/28715084/synthesis-of-cupf6-s-binap-loaded-resin-and-its-enantioselectivity-toward-phenylalanine-enantiomers
#2
Xiong Liu, Wenqi Zhou, Longqi Xu
A type of resin-anchored CuPF6 -(S)-BINAP was synthesized and identified. The PS-CuPF6 -(S)-BINAP resin was used to adsorb the phenylalanine enantiomers. The results showed that the adsorption capacity of PS-CuPF6 -(S)-BINAP resin toward L-phenylalanine was higher than that of resin toward D-phenylalanine. PS-CuPF6 -(S)-BINAP resin exhibited good enantioselectivity toward L-phenylalanine and D-phenylalanine. The influence of phenylalanine concentration, pH, adsorption time, and temperature on the enantioselectivity of the resin were investigated...
July 17, 2017: Chirality
https://www.readbyqxmd.com/read/28710844/reliable-hplc-separation-vibrational-circular-dichroism-spectra-and-absolute-configurations-of-isoborneol-enantiomers
#3
Rui-Qi Gao, Jun Fan, Qi Tan, Dong Guo, Tao Chen, Ru-Jian He, Dan Li, Hui Zhang, Wei-Guang Zhang
Resolution of chiral compounds has played an important role in the pharmaceutical field, involving detailed studies of pharmacokinetics, physiological, toxicological, and metabolic activities of enantiomers. Herein, a reliable method by high-performance liquid chromatography (HPLC) coupled with an optical rotation detector was developed to separate isoborneol enantiomers. A cellulose tris(3, 5-dimethylphenylcarbamate)-coated chiral stationary phase showed the best separation performance for isoborneol enantiomers in the normal phase among four polysaccharide chiral packings...
July 15, 2017: Chirality
https://www.readbyqxmd.com/read/28710791/origin-of-enhanced-vcd-in-amyloid-fibril-spectra-effect-of-deuteriation-and-ph
#4
Markéta Pazderková, Tomáš Pazderka, Maruda Shanmugasundaram, Rina K Dukor, Igor K Lednev, Laurence A Nafie
Supramolecular chirality of amyloid fibrils, protein aggregates related to many neurodegenerative diseases, is a remarkable property associated with fibril structure and polymorphism. Since its discovery almost 10 years ago there is still little understanding of this phenomenon, including the cause of the highly enhanced vibrational circular dichroism (VCD) intensity arising from fibril supramolecular chirality. In this study, VCD spectra, enhanced by filament supramolecular chirality, are presented for lysozyme and insulin fibrils above and below pH 2 and after deuterium exchange, above and below pD 2...
July 15, 2017: Chirality
https://www.readbyqxmd.com/read/28710781/functionalities-tuned-enantioselectivity-of-phenylcarbamate-cyclodextrin-clicked-chiral-stationary-phases-in-hplc
#5
Jian Tang, Yuzhou Lin, Bo Yang, Jie Zhou, Weihua Tang
The mixed chloro- and methyl- functionalities can greatly modulate the enantioselectivities of phenylcarbamate cyclodextrin (CD) clicked chiral stationary phases (CSPs). A comparison study is herein reported for per(4-chloro-3-methyl)phenylcarbamate and per(2-chloro-5-methyl)phenylcarbamate β-CD clicked CSPs (i.e., CCC4M3-CSP and CCC2M5-CSP). The enantioselectivity dependence on column temperature was studied in both normal-phase and reversed-phase mode high performance liquid chromatography (HPLC). The thermodynamic study revealed that the stronger intermolecular interactions can be formed between CCC4M3-CSP and chiral solutes to drive the chiral separation...
July 15, 2017: Chirality
https://www.readbyqxmd.com/read/28696072/comparison-of-three-s-%C3%AE-cds-with-different-degrees-of-substitution-for-the-chiral-separation-of-12-drugs-in-capillary-electrophoresis
#6
Zhaokun Wang, Qiongwen Zhang, Linda Luo, Tiemin Sun, Xingjie Guo
Three kinds of sulfated β-cyclodextrin (S-β-CD), including a single isomer, heptakis-6-sulfato-β-cyclodextrin (HS-β-CD), degree of substitution (DS) of 7, which was synthesized in our laboratory and another two commercialized randomly substituted mixtures, a sulfated β-cyclodextrin with DS of 7 to 11, as well as a highly sulfated-β-cyclodextrin with DS of 12 to 15, were used for the enantioresolution of 12 drugs (the β-blockers, phenethylamines, and anticholinergic agents) in capillary electrophoresis...
July 11, 2017: Chirality
https://www.readbyqxmd.com/read/28677874/enantioresolution-and-stereochemical-characterization-of-two-chiral-sulfoxides-endowed-with-cox-2-inhibitory-activity
#7
Roccaldo Sardella, Federica Ianni, Alessandro Di Michele, Angela Di Capua, Andrea Carotti, Maurizio Anzini, Benedetto Natalini
The capacity of nonsteroidal antiinflammatory drugs (NSAIDs) to prevent prostanoids biosynthesis through the inhibition of COX-2 enzyme is related to their structural backbone, based on the fusion of a cis-stilbene unit with a variety of heterocyclic and carbocyclic rings. By this route, a series of new selective COX-2 inhibitors was developed, by maintaining the 4-methylsulfone or 4-methylsulfonamide substituent on the phenyl moiety, essential for their activity. In this frame, two novel propyl sulfoxide derivatives were synthesized, which proved selective and sufficiently potent COX-2 inhibition activity when tested as racemates...
July 5, 2017: Chirality
https://www.readbyqxmd.com/read/28677844/enantioselective-analysis-of-ibuprofen-enantiomers-in-mice-plasma-and-tissues-by-high-performance-liquid-chromatography-with-fluorescence-detection-application-to-a-pharmacokinetic-study
#8
Katarzyna Przejczowska-Pomierny, Monika Włodyka, Agnieszka Cios, Elżbieta Wyska
A direct fluorometric high-performance liquid chromatography (HPLC) method was developed and validated for the analysis of ibuprofen enantiomers in mouse plasma (100 μl) and tissues (brain, liver, kidneys) using liquid-liquid extraction and 4-tertbutylphenoxyacetic acid as an internal standard. Separation of enantiomers was accomplished in a Chiracel OJ-H chiral column based on cellulose tris(4-methylbenzoate) coated on 5 μm silica-gel, 250 x 4.6 mm at 22 °C with a mobile phase composed of n-hexane, 2-propanol, and trifluoroacetic acid that were delivered in gradient elution at a flow rate of 1 ml min(-1) ...
July 5, 2017: Chirality
https://www.readbyqxmd.com/read/28675534/emergent-chemodiversity-the-case-of-stereoisomerism-in-acyclic-alkanes
#9
Bernard Testa
The objective of this pen-and-paper study is to witness the emergence of stereoisomeric properties when comparing lower to higher families of homologs. Specifically, the study compares all acyclic hexanes (five constitutional isomers, a.k.a. regioisomers), all nine heptanes, all 18 octanes, all 35 nonanes, and all 75 decanes. The first part of the work examines the nature and number of stereoisomeric properties seen to emerge in chemical structures featuring one chiral center (i.e., enantiomerism) or two such centers, in which case more complex stereoisomeric features emerge (enantiomerism, diastereoisomerism, pseudoasymmetry, and meso-isomers)...
July 4, 2017: Chirality
https://www.readbyqxmd.com/read/28649773/synthesis-and-pka-determination-of-new-enantiopure-dimethyl-substituted-acridino-crown-ethers-containing-a-carboxyl-group-useful-candidates-for-enantiomeric-recognition-studies
#10
Tamás Németh, Gergő Dargó, József Levente Petró, Zsófia Petrik, Sándor Lévai, Balázs Krámos, Zoltán Béni, József Nagy, György Tibor Balogh, Péter Huszthy, Tünde Tóth
New enantiopure dimethyl-substituted acridino-18-crown-6 and acridino-21-crown-7 ethers containing a carboxyl group at position 9 of the acridine ring [(S,S)-8, (S,S)-9, (R,R)-10] were synthesized. The pKa values of the new crown ethers [(S,S)-8, (S,S)-9, (R,R)-10] and of an earlier reported macrocycle [(R,R)-2] were determined by UV-pH titrations. Crown ether (S,S)-8 was attached to silica gel by covalent bonds and the enantiomeric separation ability of the newly prepared chiral stationary phase [(S,S)-CSP-12] was studied by high-performance liquid chromatography (HPLC)...
June 26, 2017: Chirality
https://www.readbyqxmd.com/read/28649696/amaryllidaceae-alkaloids-absolute-configuration-and-biological-activity
#11
REVIEW
Alessio Cimmino, Marco Masi, Marco Evidente, Stefano Superchi, Antonio Evidente
Plants belonging to the Amaryllidaceae family are well known for their ornamental and medicinal use. Plant members of this group are distributed through both tropical and subtropical regions of the world and are dominant in Andean South America, the Mediterranean basin, and southern Africa. Amaryllidaceae plants have been demonstrated to be a good source of alkaloids with a large spectrum of biological activities, the latter being strictly related to the absolute stereochemistry of the alkaloid scaffold. Among them, great importance for practical applications in medicine has galanthamine, which has already spawned an Alzheimer's prescription drug as a potent and selective inhibitor of the enzyme acetylcholinesterase...
June 26, 2017: Chirality
https://www.readbyqxmd.com/read/28644553/structural-insights-into-the-inclusion-complexes-between-clomiphene-citrate-and-%C3%AE-cyclodextrin-the-mechanism-of-preferential-isomeric-selection
#12
Arti Maheshwari, Harish Saraswat, Santosh Kumar Upadhyay
A major challenge in pharmaceuticals for clinical applications is to alter the solubility, stability, and toxicity of drug molecules in living systems. Cyclodextrins (CDs) have the ability to form host-guest inclusion complexes with pharmaceuticals for further development of new drug formulations. The inclusion complex of clomiphene citrate (CL), a poorly water-soluble drug, with native β-cyclodextrin (β-CD) was characterized by a one and two-dimensional nuclear magnetic resonance (NMR) spectroscopic approach and also by molecular docking techniques...
June 23, 2017: Chirality
https://www.readbyqxmd.com/read/28635069/exciton-coupling-between-enones-quassinoids-revisited
#13
Gennaro Pescitelli, Lorenzo Di Bari
The electronic circular dichroism (ECD) spectra of two previously reported quassinoids containing a pair of enone chromophores are revisited to gain insight into the consistency and applicability of the exciton chirality method. Our study is based on time-dependent Density Functional Theory calculations, transition and orbital analysis, and numerical exciton coupling calculations. In quassin (1) the enone/enone exciton coupling is quasi-degenerate, yielding strong rotational strengths that account for the observed ECD spectrum in the enone π-π* region...
June 21, 2017: Chirality
https://www.readbyqxmd.com/read/28635058/preparation-and-evaluation-of-regioselectively-substituted-amylose-derivatives-for-chiral-separations
#14
Shouwan Tang, Zhaolei Jin, Baishen Sun, Fang Wang, Wenyuan Tang
Six novel regioselectively substituted amylose derivatives with a benzoate at 2-position and two different phenylcarbamates at 3- and 6-positions were synthesized and their structures were characterized by (1) H nuclear magnetic resonance (NMR) spectroscopy. Their enantioseparation abilities were then examined as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after they were coated on 3-aminopropyl silica gels. Investigations indicated that the substituents at the 3- and 6-positions played an important role in chiral recognition of these amylose 2-benzoate serial derivatives...
June 21, 2017: Chirality
https://www.readbyqxmd.com/read/28627023/cinchona-alkaloid-derivatives-catalyzed-asymmetric-aza-friedel-crafts-reaction-of-%C3%AE-naphthols-with-aryl-aldimines
#15
Ya Wei Li, Li Ming Wang, Ying Jin, Sheng Chang
Cinchona alkaloid derivatives as organocatalysts were applied in the asymmetric aza-Friedel-Crafts reaction of α-naphthol with aryl aldimines. The desired chiral aminoarylnaphthols were obtained in 85% enantiomeric excess.
June 18, 2017: Chirality
https://www.readbyqxmd.com/read/28608629/enantioselective-cytotoxicity-of-zns-mn-quantum-dots-in-a549-cells
#16
V A Kuznetsova, A K Visheratina, A Ryan, I V Martynenko, A Loudon, C M Maguire, F Purcell-Milton, A O Orlova, A V Baranov, A V Fedorov, A Prina-Mello, Y Volkov, Y K Gun'Ko
Chirality strongly influences many biological properties of materials, such as cell accumulation, enzymatic activity, and toxicity. In the past decade, it has been shown that quantum dots (QDs), fluorescent semiconductor nanoparticles with unique optical properties, can demonstrate optical activity due to chiral ligands bound on their surface. Optically active QDs could find potential applications in biomedical research, therapy, and diagnostics. Consequently, it is very important to investigate the interaction of QDs capped with chiral ligands with living cells...
June 13, 2017: Chirality
https://www.readbyqxmd.com/read/28608589/new-chiral-stationary-phases-based-on-xanthone-derivatives-for-liquid-chromatography
#17
Carla Fernandes, Maria Elizabeth Tiritan, Sara Cravo, Ye' Zaw Phyo, Anake Kijjoa, Artur M S Silva, Quezia B Cass, Madalena M M Pinto
Six chiral derivatives of xanthones (CDXs) were covalently bonded to silica, yielding the corresponding xanthonic chiral stationary phases (XCSPs). The new XCSPs were packed into stainless-steel columns with 150 x 4.6 mm i.d. Moreover, the greening of the chromatographic analysis by reducing the internal diameter (150 x 2.1 mm i.d.) of the liquid chromatography (LC) columns was also investigated. The enantioselective capability of these phases was evaluated by LC using different chemical classes of chiral compounds, including several types of drugs...
June 13, 2017: Chirality
https://www.readbyqxmd.com/read/28560736/enantioseparation-of-ofloxacin-and-its-four-related-substances-with-ligand-exchange-micellar-electrokinetic-chromatography-using-copper-ii-l-isoleucine-complex-as-chiral-selector
#18
Yongjing Liu, Xiaoying Wang
A ligand-exchange micellar electrokinetic capillary electrophoresis system with copper(II)-L-isoleucine complexes as the chiral selector incorporated in micelles of sodium dodecyl sulfate (SDS) was developed for the enantioseparation of ofloxacin and its four related substances (impurities A, C, E, and F). The effects of important parameters affecting separation such as buffer pH, SDS concentration, chiral selector concentration, and organic additive were investigated in detail. Under optimum experimental conditions, enantioseparation of ofloxacin, impurities A, C, E, and F enantiomers was accomplished with resolutions of 4...
May 31, 2017: Chirality
https://www.readbyqxmd.com/read/28560831/stereochemical-assignment-of-fusiccocadiene-from-nmr-shielding-constants-and-vibrational-circular-dichroism-spectroscopy
#19
Christian Merten, Michael Dirkmann, Frank Schulz
The absolute configuration (AC) of the common precursor of the fusicoccane family of terpenoids, fusicocca-2,10(14)-diene (FCdiene), had only been deduced by a lengthy total synthesis, or indirectly from crystal structures of fusicoccin A. However, in particular the AC determinations based on downstream products of the terpene synthase intrinsically overlook potential epimerization reactions. In this contribution, we confirm the relative stereochemistry of FCdiene by comparison of experimental and predicted (13) C-NMR chemical shifts, and finally determine the absolute configuration from an analysis of its infrared and vibrational circular dichroism spectra...
May 30, 2017: Chirality
https://www.readbyqxmd.com/read/28543776/a-surface-molecularly-imprinted-polymer-as-chiral-stationary-phase-for-chiral-separation-of-1-1-binaphthalene-2-naphthol-racemates
#20
Hongxing Dong, Danxia Zhang, Hailong Lin, Yudan Wang, Lijia Liu, Meixia Zheng, Xiaobo Li, Chunhong Zhang, Junqing Li, Peng Zhang, Juhyok So
Acrylamide (AM) was copolymerized with ethylene glycol dimethacrylate (EGDMA) in the presence of (R)-1,1'-binaphthalene-2-naphthol (BINOL) as the template molecules on the surface of silica gel by a free radical polymerization to produce a chiral stationary phase based on the surface molecularly imprinted polymer (SMIP-CSP). The SMIP-CSP showed a much better separation factor (α = 4.28) than the CSP based on the molecularly imprinted polymer (MIP-CSP) without coating on the silica gel (α = 1.96) during the chiral separation of BINOL enantiomers by high-performance liquid chromatography...
May 25, 2017: Chirality
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