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951.
Abstract Chiral crystals of tryptamine and achiral carboxylic acids such as p-chlorobenzoic acid, cinnamic acid, p-chlorocinnarnic acid and p-methylcinnamic acid were prepared by crystallization from the solutions of both components. All the crystals belonged to typical chiral space group P212121. The crystal chirality is generated through the formation of a unidirectional twofold helix between the two components through quaternary ammonium salt interaction and hydrogen bonding in the lattice. This kind of spontaneous crystallization necessarily gives crystals of both clockwise and counterclockwise helicites. Here, pseudo-seeding based on utilizing these crystals as seed crystals was examined, resulting in successful helicity control in crystallization from solutions of tryptamine and different carboxylic acids. 相似文献
952.
o-Dihyroxy-3-phenylchromenone derivatives, namely, 6,7-dihydroxy-3-(3′,4′-dimethoxyphenyl)chromenone and 6,7-dimethoxy-3-(3′,4′-dihydroxyphenyl)chromenone, were obtained from 2,4,5-trihydroxybenzaldehyde/3,4-dimethoxyphenylacetic acid and 2-hydroxy-4,5-dimethoxybenzaldehyde/3,4-dihydroxyphenylacetic acid, respectively, in the presence of acetic anhydride and sodium acetate under an inert atmosphere, after treatment with MeOH/HCl(aq). The chromenone-crown ethers were prepared from cyclic condensation of o-dihydroxy-3-phenylchromenones with poly(ethylene glycol) ditosylates in the presence of CH3CN/alkali metal carbonates. The chromatographically purified novel chromenone-crown ethers were identified by 1H NMR, MALDI-TOF mass spectrometry and elemental analysis. The fluorescence and UV–vis spectroscopic properties of the obtained chromenone-crown ethers and their complexes with Li+, Na+ and K+ perchlorate salts were estimated in acetonitrile. The quantum yields of novel chromenone-crown ethers were determined by the comparative method. 相似文献
953.
Baohua Li Xuemei Yang Xiaojun Wu Zengwei Luo Cheng Zhong 《Supramolecular chemistry》2013,25(6):507-513
The enantioselectivity of chiral macrocyclic polyamides 1–3 derived from L-/D-tartaric acid was investigated by using 1H NMR. All the macrocycles exhibited certain chiral recognition towards the enantiomers of the racemic carboxylic acids we had chosen. As a chiral solvating agent, the compound 3 has the excellent enantiomeric discriminating ability for mandelic acids and its derivatives, containing an α-OH at the chiral carbon, while the compound 2 has the best enantioselectivity towards dibenzoyltartaric acid. The molar ratio and the association constants of the compound 3 with each of the enantiomers of some guest molecules were determined by using the Job's plots and a nonlinear leastsquares fitting method, respectively. The effect of the structure of the hosts or guests on the enantioselectivity of the compound 1–3 has been explored. 相似文献
954.
Heterocycles derived from Tröger's base were shown to complex with metal salts in 2:1 ligand:salt ratios as monodentate or bidentate ligands depending on structure. 相似文献
955.
Ivan I. Stoikov Dina S. Ibragimova Nadezhda V. Shestakova Dmitry B. Krivolapov Igor A. Litvinov Igor S. Antipin 《Supramolecular chemistry》2013,25(7):564-571
The preparation of partially substituted thiacalix[4]arenes 2–6 has been accomplished by conducting the reaction of the thiacalixarene 1 with N-(p-nitrophenyl)-α-bromoacetamide in acetone or acetonitrile in the presence of M2CO3 (M = Na, K and Cs). The influence of the reaction conditions (temperature, time, solvent, ratio of the reagents and the nature of the alkali metal carbonate) on regio- and stereoselectivity of this reaction is described. 相似文献
956.
C. Bauvais F. Barbault Y. Zhu M. Petitjean 《SAR and QSAR in environmental research》2013,24(3):253-264
A theoretical investigation was carried out on the retention and separation of enantiomeric molecules including nonsteroidal anti-inflammatory drugs, anti-neoplastic compounds and N-derivatized amino acids by capillary electrophoresis using macrocyclic antibiotics, a new class of chiral selectors, as stationary phase. Firstly docking methods were used to study the enantiorecognition in chiral electrophoresis. The molecular dynamics simulations of the two diastereoisomer complexes were then performed in order to understand how these antibiotics recognize the enantiomers. Another approach was applied in this study to establish a quantitative structure-enantioselectivity relationship (QSER) model, able to describe the resolution of a series of chiral compounds in capillary electrophoresis using vancomycin as the resolving agent. 相似文献
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