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Chirality

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https://www.readbyqxmd.com/read/28332282/chirally-sensitive-collision-induced-dissociation-of-proton-bound-diastereomeric-complexes-of-tryptophan-and-2-butanol
#1
Oleksii Rebrov, Kostiantyn Kulyk, Mauritz Ryding, Richard D Thomas, Einar Uggerud, Mats Larsson
In this work we report the stereo-dependent collision-induced dissociation (CID) of proton-bound complexes of tryptophan and 2-butanol. The dissociation efficiency was measured as a function of collision energy in single collision mode. The homochiral complex was found to be less stable against CID than a heterochiral one. Additional gas dependence measurements were performed with diastereomeric complexes that confirm the findings.
March 23, 2017: Chirality
https://www.readbyqxmd.com/read/28328107/chiral-exploration-of-6-12-diphenyldibenzo-b-f-1-5-diazocine-with-stable-conformation
#2
Zheng-Yi Li, Yong Pan, Lin-Lin Jin, Yue Yin, Bao-Zhu Yang, Xiao-Qiang Sun
A first optical resolution of 6,12-diphenyldibenzo[b,f][1,5]diazocine with stable boat conformation was achieved by chiral supercritical fluid chromatography (SFC). The absolute configurations of enantiomers were first assigned and determined by X-ray crystal structure based on CIP-rules. The high optical rotation and circular dichroism spectrum were well explained by electronic helix theory. Owing to the high stabilization of boat conformation, the chiral configuration could be maintained at very high temperature, more than 200 °C, which was proved by Density Functional Theory calculations...
March 22, 2017: Chirality
https://www.readbyqxmd.com/read/28321927/enantioseparation-and-enantioselective-behavior-of-trichlorfon-enantiomers-in-sediments
#3
Xiao-Feng Gao, Jing Nie, Xiao-Kun Ouyang, Yang-Guang Wang, Wei-Jian Wu
Trichlorfon (TF), an organophosphorus insecticide, has been widely used in seawater aquaculture; it is easily degraded to the highly toxic insecticide, dichlorvos (DDVP). In this study, the enantioseparation of TF enantiomers, as well as their degradation behavior and product (DDVP) formation in mariculture pond sediments, was investigated. The results show that both TF enantiomers degrade into DDVP, which is the main degradation product. Furthermore, S-(+)-TF is preferentially degraded under natural conditions, suggesting that TF enantiomers degrade enantioselectively...
March 21, 2017: Chirality
https://www.readbyqxmd.com/read/28079923/vibrational-circular-dichroism-of-a-2-5-diketopiperazine-dkp-peptide-evidence-for-dimer-formation-in-cyclo-ll-or-ld-diphenylalanine-in-the-solid-state
#4
Ariel Pérez-Mellor, Anne Zehnacker
The diastereomer diketopiperazine (DKP) peptides built on phenylalanine, namely, cyclo diphenylalanine LPhe-LPhe and LPhe-DPhe, were studied in the solid phase by vibrational circular dichroism (VCD) coupled to quantum chemical calculations. The unit structure of cyclo LPhe-LPhe in KBr pellets is a dimer bridged by two strong NH…O hydrogen bonds. The intense bisignate signature in the CO stretch region is interpreted in terms of two contributions arising from the free COs of the dimer and the antisymmetrical combination of the bound COs...
January 12, 2017: Chirality
https://www.readbyqxmd.com/read/28028832/design-of-experiment-assisted-concurrent-enantioseparation-of-bupropion-and-hydroxybupropion-by-high-performance-thin-layer-chromatography
#5
Nejal M Bhatt, Vijay D Chavada, Mallika Sanyal, Pranav S Shrivastav
A simple and efficient high-performance thin-layer chromatographic method was developed for chiral separation of rac-bupropion (BUP) and its active metabolite rac-hydroxybupropion (HBUP). Design of experiment (DoE)-based optimization was adopted instead of a conventional trial-and-error approach. The Box-Behnken design surface response model was used and the operating variables were optimized based on 17 trials design. The optimized method involved impregnation of chiral reagent, L(+)-tartaric acid, in the stationary phase with simultaneous addition in the mobile phase, which consisted of acetonitrile : methanol : dichloromethane : 0...
December 28, 2016: Chirality
https://www.readbyqxmd.com/read/28052591/homo-c-nucleoside-analogs-iv-synthesis-of-4-2-5-anhydro-d-altro-pentitol-1-yl-2-phenyl-2h-1-2-3-triazole-homo-c-nucleoside-cd-assignment-of-the-absolute-configuration-of-the-carbon-bridge
#6
Mohammed A E Sallam
Dehydrative cyclization of 4-(D-altro-pentitol-1-yl)2-phenyl-2H-1,2,3-triazole in basic medium with one moler equivalent of p-toluene sulfonyl chloride in pyridine solution gave the homo-C-nucleoside 4-(2,5-anhydro-D-altro-1-yl)-2-phenyl-2H-1,2,3-triazole. The structure and anomeric configuration was determined by acylation, nuclear magnetic resonance (NMR), and mass spectroscopy. The stereochemistry at the carbon bridge of homo-C-nucleoside 2-phenyl-2H-1,2,3-triazoles was determined by circular dichroism (CD) spectroscopy...
January 2017: Chirality
https://www.readbyqxmd.com/read/27901292/differential-in-radiosensitizing-potency-of-enantiomers-of-the-fatty-acid-synthase-inhibitor-c75
#7
Colin Rae, John W Babich, Robert J Mairs
The elevated activity of fatty acid synthase has been reported in a number of cancer types. Inhibition of this enzyme has been demonstrated to induce cancer cell death and reduce tumor growth. In addition, the fatty acid synthase inhibitor drug C75 has been reported to synergistically enhance the cancer-killing ability of ionizing radiation. However, clinical use of C75 has been limited due to its producing weight loss, believed to be caused by alterations in the activity of carnitine palmitoyltransferase-1...
January 2017: Chirality
https://www.readbyqxmd.com/read/28019704/isolation-of-the-major-chiral-compounds-from-bubonium-graveolens-essential-oil-by-hplc-and-absolute-configuration-determination-by-vcd
#8
Mohammed El-Amin Said, Isabelle Bombarda, Jean-Valère Naubron, Pierre Vanloot, Marion Jean, Abdelkrim Cheriti, Nathalie Dupuy, Christian Roussel
The chirality issues in the essential oils (EOs) of leaves and flowers from Bubonium graveolens were addressed by chiral high-performance liquid chromatography (HPLC) with polarimetric detection and vibrational circular dichroism (VCD). The chemical compositions of the crude oils of three samples were established by gas chromatography / mass spectrometry (GC/MS). The well-known cis-chrysanthenyl acetate (1), oxocyclonerolidol (2), and the recently disclosed cis-acetyloxychrysanthenyl acetate (3), the three major chiral compounds, were isolated by preparative HPLC...
December 26, 2016: Chirality
https://www.readbyqxmd.com/read/28019695/determination-of-enantiomeric-excess-of-nipecotic-acid-as-1-7-nitrobenzo-c-1-2-5-oxadiazol-4-yl-derivatives
#9
Simone K Schmidt, Georg Höfner, Klaus T Wanner
For the enantiopure synthesis of novel chiral GABA uptake inhibitors, nipecotic acid (1) is an important key precursor. To characterize accurately the pharmacological activity of these interesting target compounds, the determination of the correct enantiomeric purity of nipecotic acid as the starting material is indispensable. In this report, a sensitive high-performance liquid chromatography (HPLC) based method for the separation and quantitation of both enantiomers of nipecotic acid as 1-(7-nitrobenzo[c][1,2,5]oxadiazol-4-yl) derivatives (5) on a Chiralpak ID-3 column (Daicel, Illkirch, France) was established...
December 26, 2016: Chirality
https://www.readbyqxmd.com/read/28019677/chirality-specific-lift-forces-of-helix-under-shear-flows-helix-perpendicular-to-shear-plane
#10
Qi-Yi Zhang
Chiral objects in shear flow experience a chirality-specific lift force. Shear flows past helices in a low Reynolds number regime were studied using slender-body theory. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius, pitch length, number of turns, and helix phase angle. Its analytical formula is given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow...
December 26, 2016: Chirality
https://www.readbyqxmd.com/read/28009446/distribution-of-enantiomers-of-volatile-organic-compounds-in-selected-fruit-distillates
#11
Olga Vyviurska, Helena Zvrškovcová, Ivan Špánik
The enantiomer ratios of chiral volatile organic compounds in fruit distillates were determined by multidimensional gas chromatography using solid-phase microextraction (SPME) as a sample treatment procedure. Linalool and its oxides, limonene, α-terpineol, and nerolidol, were present at the highest concentration levels, while significantly lower amounts of β-citronellol and lactones were found in the studied samples. However, almost all terpenoids mainly occur as a racemic or near-racemic mixture; enantiomer distribution of some chiral organic compounds in fruit distillates correlated to a botanical origin...
December 23, 2016: Chirality
https://www.readbyqxmd.com/read/28009445/stereoselective-bioaccumulation-transformation-and-toxicity-of-triadimefon-in-scenedesmus-obliquus
#12
Peng Xu, Ledan Huang
In this study the stereoselective bioaccumulation and transformation of triadimefon and the toxicity of triadimefon and its metabolite triadimenol to the green algae Scenedesmus obliquus were studied. In growth inhibition experiments, triadimenol was more toxic than triadimefon, and (1S,2R)-triadimenol, which has the largest fungicidal activity, presented the highest toxicity to the algae. In bioaccumulation experiments, triadimefon was rapidly taken up by algae cells, and the decrease in the concentration of triadimefon was accompanied by an increase in triadimenol...
December 23, 2016: Chirality
https://www.readbyqxmd.com/read/28000946/direct-chiral-separations-of-the-enantiomers-of-phenylpyrazole-pesticides-and-the-metabolites-by-hplc
#13
Jing Gao, Han Qu, Chuntao Zhang, Weijia Li, Peng Wang, Zhiqiang Zhou
The enantiomeric separation of the enantiomers of three phenylpyrazole pesticides (fipronil, flufiprole, ethiprole) and two fipronil metabolites (amide-fipronil and acid-fipronil) were investigated by high-performance liquid chromatography (HPLC) with a CHIRALPAK(®) IB chiral column. The mobile phase was n-hexane or petroleum ether with 2-propanol or ethanol as modifier at a flow rate of 1.0 mL/min. The influences of mobile phase composition and column temperature between 15 and 35°C on the separations were studied...
December 21, 2016: Chirality
https://www.readbyqxmd.com/read/27992080/enantioseparation-of-nine-indanone-and-tetralone-derivatives-by-hplc-using-carboxymethyl-%C3%AE-cyclodextrin-as-the-mobile-phase-additive
#14
Xiaoyu Hu, Xin Guo, Shuo Sun, Bolin Zhu, Jia Yu, Xingjie Guo
High-performance liquid chromatography (HPLC) is a powerful method in the area of chiral separation. In this study, a method of HPLC using carboxymethyl-β-cyclodextrin (CM-β-CD) as chiral selector was developed for enantioseparation of nine indanone and tetralone derivatives. The separation was performed on a conventional C18 column. The optimal mobile phase was a mixture of methanol and 0.05 mol/L phosphate buffer at pH 1.8 (55:45, v/v) containing 22.9 mmol/L CM-β-CD. Under such conditions, the resolutions of all analytes were over 1...
December 19, 2016: Chirality
https://www.readbyqxmd.com/read/27992072/comparison-of-intestinal-permeability-and-p-glycoprotein-effects-on-the-intestinal-absorption-of-enantiomers-of-2-2-hydroxypropanamido-benzoic-acid-in-rats
#15
Qili Zhang, Meiyan Zhang, Danlin Wang, Yunli Zhao, Zhiguo Yu
The purpose of this study was to compare intestinal permeability between enantiomers of 2-(2-hydroxypropanamido) benzoic acid ((R)-/(S)-HPABA), a marine-derived antiinflammatory drug, using an in situ single-pass intestinal perfusion (SPIP) model in rats. Concentrations, isolated regions of small intestine, and p-glycoprotein (P-gp) inhibitor were performed to investigate their influences on the intestinal absorption of (R)-/(S)-HPABA. In addition, a molecular docking method was performed to illustrate our prediction...
December 19, 2016: Chirality
https://www.readbyqxmd.com/read/27933649/using-chiral-peptide-substitutions-to-probe-the-structure-function-relationship-of-a-key-residue-of-a%C3%AE-42
#16
Christopher J A Warner, Subrata Dutta, Alejandro R Foley, Eefei Chen, David S Kliger, Jevgenij A Raskatov
Amyloid beta-protein 42 plays an important role in the onset and progression of Alzheimer's disease. Familial mutations have identified the glutamate residue 22 as a hotspot with regard to peptide neurotoxicity. We introduce an approach to study the influence of systematic sidechain modification at this residue, employing chirality as a structural probe. Circular dichroism experiments reveal that charge-preserving alterations of the amino acid sidechain attenuate the characteristic random coil to β-sheet transition associated with the wildtype peptide...
December 8, 2016: Chirality
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
#17
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/27897330/bernard-l-feringa-nobel-prize-for-chemistry-2016
#18
EDITORIAL
David B Amabilino, Nina D Berova, John Caldwell
No abstract text is available yet for this article.
December 2016: Chirality
https://www.readbyqxmd.com/read/27897329/molecules-in-molecules-fragment-based-method-for-the-calculation-of-chiroptical-spectra-of-large-molecules-vibrational-circular-dichroism-and-raman-optical-activity-spectra-of-alanine-polypeptides
#19
K V Jovan Jose, Krishnan Raghavachari
The molecules-in-molecules (MIM) fragment-based method has recently been adapted to evaluate the chiroptical (vibrational circular dichroism [VCD] and Raman optical activity [ROA]) spectra of large molecules such as peptides. In the MIM-VCD and MIM-ROA methods, the relevant higher energy derivatives of the parent molecule are assembled from the corresponding derivatives of smaller fragment subsystems. In addition, the missing long-range interfragment interactions are accounted at a computationally less expensive level of theory (MIM2)...
December 2016: Chirality
https://www.readbyqxmd.com/read/27897328/solid-phase-extraction-with-metal-organic-frameworks-for-the-analysis-of-chiral-compounds
#20
Bo Tang, Jun-Hui Zhang, Min Zi, Xue-Xian Chen, Li-Ming Yuan
Metal-organic frameworks (MOFs) are excellent porous materials with nanoscale cavities and high surface areas, which make them promising as novel adsorbents in solid-phase extraction (SPE). In this article we report a new application of the chiral MOF [Zn2 (D-Cam)2 (4,4'-bpy)]n in SPE used for the measurement of the enantiomeric excess (ee) of (±)-1,1'-bi-2-naphthol. Several important experimental parameters that may influence the extraction efficiency were investigated and optimized. Under the optimum conditions, a good linearity (R(2)  > 0...
December 2016: Chirality
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