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Angel E. Kaifer Pablo A. Quintela Jodi M. Schuette 《Journal of inclusion phenomena and macrocyclic chemistry》1989,7(1):107-115
N-ethyl-N-hexadecyl-4,4-bipyridinium bromide (C16VBr2) andN-ethyl-N-octadecyl-4,4-bipyridinium bromide (C18VBr2) were used as electroactive probes to assess the interactions between surfactants and cyclodextrins. Cyclic voltammetry, visible spectroscopy, fluorescence spectroscopy and surface tension techniques were used to detect the formation of complexes between the surfactant viologen probes and- and-cyclodextrins. The voltammetric results suggest the formation of inclusion compounds in which the hydrophobic tail of the surfactant viologens penetrate the cyclodextrin cavity. The dimerization of the viologen cation radicals is essentially suppressed by the presence of-cyclodextrin (ACD) while no effects are observed in the presence of-cyclodextrin (BCD). The observed results are best explained by the relative solubility in aqueous media of each of the inclusion complexes in the several accessible viologen oxidation states. 相似文献
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A. K. Chatjigakis Ph. J. P. Cardot A. W. Coleman H. Parrot-Lopez 《Chromatographia》1993,36(1):174-178
Summary In the course of systematic studies on the solubility, hydrophobicity and complexation properties of cyclodextrins and modified cyclodextrins, the retention behavior of , , and of some glycosylated cyclodextrins has been examined by means of reverse phase HPLC. Mobile phase mixtures containing large amounts of water have been used because of the possible application of such systems to biological studies. Mobile phase mixtures with both methanol and acetonitrile show a linear relationship between the volume fraction of the organic part of the mobile phase and the logarithm of the capacity factor. The extrapolation of capacity factors to a total aquous system are used and compared to other techniques (including solubility) in order to evaluate the hydrophobic properties of the cyclodextrins. In particular, the solubility of cyclodextrins has been explored for a wide range of organic solvent/water mixtures. Whilst cyclodextrins are definitely the most hydrophobic, followed by glycosylated cyclodextrins, the others behave differently in the two mobile phase systems. The differences observed in the results are related to the chemical nature of the organic phase. Comparisons between chromatographic and solubility methods are given and interpretations are proposed. Some cyclodextrins have been modified to increase or modify not only the hydrophobicity but also the solubility, the complexation and the molecular recognition of drugs. The most important aim of this study was to define conditions and rules for further drug vectorization by cyclodextrin-drug complexation. 相似文献
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Dr. Hiromichi Egami Prof. Dr. Yoshitaka Hamashima 《Chemical record (New York, N.Y.)》2023,23(7):e202200285
Fluorine is an attractive element in the field of pharmaceutical and agrochemical chemistry due to its unique properties. Considering the chiral environment in nature, where enantiomers often show different biological activities, the introduction of fluorine atom(s) into organic molecules to make chiral fluorinated compounds is an important subject. Herein, we describe the story of the development of our chiral carboxylate-based phase-transfer catalysts and their applications for asymmetric fluorocyclizations of alkenes bearing a carboxylic acid, an amide, and an oxime as an internal nucleophile with a dicationic fluorinating reagent, Selectfluor. We also describe dearomative fluorinations of indole derivatives, 2-naphthols, and resorcinols. 相似文献
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催化不对称反应新发展: 不对称活化 总被引:7,自引:1,他引:7
介绍了催化不对称催化反应中的一个新概念-不对称活化(asymmetricactivation)及其研究的最新发展。运用不对称活化策略,一个光学活性的整或者甚至外消旋的催化剂可以被另一种手性活化剂(chiralactivator)选择性的活化,从而催化反应生成非外消旋产物。该方法较不对称活化(asymmetricactivation)方法的优点是被活化的催化剂能够产生较使用光学纯催化剂更高对映体过量的产物。 相似文献
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重点从立体选择性和催化机理方面,总结了不同的有机小分子催化剂在烯酮的[2+2]和[4+2]不对称环加成反应中的应用. 相似文献
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本文综述了近年来在无溶剂条件下进行的一些不对称催化反应的进展, 着重介绍了无溶剂条件下的不对称Aldol反应、环氧化合物不对称开环反应、外消旋环氧化合物的拆分、不对称Diels-Alder反应、金属有机试剂对醛酮的不对称加成反应、不对称氢化反应、不对称氢甲酰化反应、不对称烯烃复分解反应、不对称Michael加成反应、不对称氧化反应、不对称Friedel-Crafts反应等, 同时展望了无溶剂不对称催化反应的研究前景。 相似文献
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In(III) complexes efficiently catalyse asymmetric Mannich-type reactions in ionic liquids with high diastereoselectivity and good yield. 相似文献
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综述了钯-手性膦配体催化剂在烯烃的不对称氢氰化、不对称羰基化、不对称交叉偶联、不对称氢化硅氢化等方面的研究进展。参考文献36篇。 相似文献
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The Biginelli reaction, known for over 100 years, is an important multicomponent reaction for accessing dihydropyrimidinones (DHPMs). The individual enantiomers of DHPMs exhibit different or even opposite pharmaceutical activities, which require synthetic methods to easily access the optically pure DHPMs. In recent decades, many efforts have focused on developing procedures for the preparation of optically active Biginelli products. In this article, we will summarize the developments in the synthetic methods to access optically active DHPMs with an emphasis on the recent advances in the asymmetric catalytic Biginelli reactions, along with concepts to design the organocatalytic asymmetric variants. 相似文献
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