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Chirality

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https://www.readbyqxmd.com/read/28810058/estimation-of-optical-rotation-of-%C3%AE-alkylidenebutenolide-cyclopropylamine-cyclopropyl-methanol-and-cyclopropenone-based-compounds-by-a-density-functional-theory-dft-approach
#1
Iram Shahzadi, Aqsa Shaukat, Zeenat Zara, Muhammad Irfan, Bertil Eliasson, Khurshid Ayub, Javed Iqbal
Computing the optical rotation of organic molecules can be a real challenge, and various theoretical approaches have been developed in this regard. A benchmark study of optical rotation of various classes of compounds was carried out by Density Functional Theory (DFT) methods. The aim of the present research study was to find out the best-suited functional and basis set to estimate the optical rotations of selected compounds with respect to experimental literature values. Six DFT functional LSDA, BVP86, CAM-B3LYP, B3PW91, and PBE were applied on 22 different compounds...
August 15, 2017: Chirality
https://www.readbyqxmd.com/read/28799177/racemic-and-enantiopure-forms-of-3-ethyl-3-phenylpyrrolidin-2-one-adopt-very-different-crystal-structures
#2
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/28771847/chiral-dialkyl-ditellurides-conformation-of-chiral-chromophore-by-circular-dichroism-and-dft-calculation
#3
Jacek Ścianowski, Agata J Pacuła, Paweł Skowronek
The twisted structure of ditellurides, in a similar way as in other dichalcogenes, leads to different absorption of circularly polarized light by quasi-enantiomeric chiral orbitals. Chiral optically active ditellurides are not common compounds and this phenomenon is not widely reported. As chiral ditellurides found an application in asymmetric synthesis, their molecular structure, understood as their conformation, became an important factor for understanding their reactivity. Until now there are few examples of chiral ditellurides known and their structure was not analyzed in details...
August 3, 2017: Chirality
https://www.readbyqxmd.com/read/28771833/chirality-sensing-of-bioactive-compounds-with-amino-alcohol-unit-via-circular-dichroism
#4
Marcin Górecki, Grażyna Groszek, Jadwiga Frelek
The aim of the present work was to test various chiroptical techniques, including in particular the in situ dirhodium methodology, to assign the absolute configuration of 1,2- and 1,3-amino alcohols. As models, we selected mainly compounds that have both an additional strongly absorbing and interfering chromophoric system and application in medicinal chemistry. Determination of the absolute configuration (AC) of the tested molecules such as cinchona alkaloids, Tamiflu, and others was carried out using a combination of electronic and vibrational circular dichroism (ECD, VCD) spectroscopy...
August 3, 2017: Chirality
https://www.readbyqxmd.com/read/28771822/synthesis-and-cytotoxicity-of-r-and-s-ricinoleic-acid-amides-and-their-acetates
#5
Sylwia Matysiak, Agnieszka Chmiel, Janusz Skolimowski, Jozef Kula, Beata Pasternak, Alina Blaszczyk
An environment-friendly, free of solvent, process for the synthesis of (R)- and (S)-ricinoleic acid amides has been developed. Starting from methyl ricinoleates and pyrrolidine or ethanolamine, the corresponding amides were obtained with yields ranging from 83-88%. Among 12 synthesized derivatives of ricinoleic acid, including the starting methyl esters, amides, and their acetates, nine compounds were obtained and tested for the first time. Studies on ricinoleic acid derivatives cytotoxicity showed that methyl esters were the least cytotoxic compounds and modification of their structure resulted in increasing cytotoxicity of the obtained products against both cancer cells and normal lymphocytes...
August 3, 2017: Chirality
https://www.readbyqxmd.com/read/28749545/optimization-of-throughput-in-semipreparative-chiral-liquid-chromatography-using-stacked-injection
#6
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
https://www.readbyqxmd.com/read/28749538/fast-further-purification-of-diastereomeric-salts-of-a-nonracemic-acid-by-gas-antisolvent-fractionation
#7
Márton Kőrösi, János Madarász, Tamás Sohajda, Edit Székely
A novel, green possibility of the further purification of the diastereomeric salt of 4-chloromandelic acid and 1-phenylethane-1-amine was developed. Gas antisolvent method using supercritical carbon dioxide was applied for the first time to precipitate the diastereomeric salts with increased purity followed by the supercritical fluid extraction of the dissolved diastereomers. The RR-salt can be purified to >99%, while fractionation-based purification of the SR-salt is limited to ~80%. The limiting initial diastereomeric excess correlates strongly with the atmospheric melting eutectic composition of the same salts, which suggests that despite the fast precipitation, the diastereomeric excess of the solid product is not kinetically determined...
July 27, 2017: Chirality
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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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