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101.
(+)-Goniothalamin has been synthesized by lipase catalyzed resolution of (1E)-1-phenylhexa-1,5-dien-3-ol using vinyl acrylate as acyl donor followed by ring closing metathesis of the formed (1R)-1-[(E)-2-phenylvinyl]but-3-enyl acrylate. The unreacted alcohol from the resolution, (1E,3S)-1-phenylhexa-1,5-dien-3-ol, was esterified non-enzymatically, and used for synthesis of (−)-goniothalamin. 相似文献
102.
Binding energies of helium, neon and atomic hydrogen encapsulated inside a C20 cage were calculated using an ab initio method at the B3LYP/6-31+G⋆ level of theory. The standard equilibrium constants for
the reactions of noble-gas atoms going into the C20 molecular cage have also been studied. The transition states for the reactions of C20 with hydrogen and helium were further obtained with an ab initio method at the B3LYP/6-31+G⋆ level and the rate constants
were estimated by using conventional transition-state theory. It was found that the hydrogen and helium atoms are extremely
difficult to put into the C20 cage. Once inside the cage, a helium atom can hardly get out, while a hydrogen atom can easily escape from the cage. The
results are expected to enrich fullerene science and be helpful for fullerene applications such as storage.
Received: 2 November 2002 / Accepted: 19 December 2002 /
Published online: 30 April 2003
Correspondence to: R. Q. Zhang, e-mail: aprqz@cityu.edu.hk
Acknowledgements. The work described in this paper was jointly supported by a grant from the City University of Hong Kong (project no. 7001222)
and a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (project no. 9040633/CityU,
1011/01P]. 相似文献
103.
104.
The kinetics of the esterification of lauric acid with geraniol catalyzed by a commercially immobilized lipase preparation
fromMucor miehei, Lipozyme, was studied in well-stirred flasks under conditions of no external mass transfer limitations. It was shown that
the reaction is inhibited by lauric acid and the reaction mechanism can be described as a Ping-Pong Bi-Bi with Dead-End inhibition
caused by lauric acid. 相似文献
105.
固定化脂肪酶催化合成6,6'-海藻糖月桂酸酯 总被引:6,自引:0,他引:6
以吸附在硅藻土上的假丝酵母(Candidasp.1619)脂肪酶为催\r\n化剂,在无溶剂体系中,研究了月桂酸与海藻糖的酯化反应.结果表明\r\n,反应温度为47℃,pH为7.0,月桂酸与海藻糖的摩尔比大于6时酯化\r\n反应的转化率较高.在3.2mmol(0.64g)月桂酸、0.2mmol(0.07\r\n6g,即53μl浓度为1.43g/ml的糖溶液)海藻糖和200mg固定化脂肪酶\r\n(1000U)组成的反应体系中,于47℃振荡反应36h,以海藻糖月桂酸双\r\n酯计算,酯化程度达95%以上.用有机溶剂提取的反应产物经薄层色谱\r\n提纯后进行13CNMR分析,结果表明,产物主要是6,6’-海藻糖月桂酸\r\n酯,其纯度为90%~95%. 相似文献
106.
Influence of the support on the reaction course of tributyrin hydrolysis catalyzed by soluble and immobilized lipases 总被引:1,自引:0,他引:1
Cristina Otero Eitel Pastor Victor M. Fernández Antonio Ballesteros 《Applied biochemistry and biotechnology》1990,23(3):237-247
Lipases from different origins have been immobilized in supports chosen by its different aquaphilicity and used as biocatalysts for the hydrolysis of tributyrin. The changes of the concentration of tri-, di-, monobutyrin, glycerol, and butyric acid during the reactions catalyzed by soluble, as well as immobilized, lipases were evaluated by gas chromatography. The experimental data were fitted to a simple kinetic model for the sequential reaction of tributyrin hydrolysis. The calculated apparent rate constants were different for the biocatalysts used and were apparently related to diffusional effects and aquaphilicity of the supports. Maximal yields of dibutyrin were found with the soluble Candida lipase, whereas the highest yield of monobutyrin (90%) was obtained with the least aquaphylic derivative (Candida-Celite). 相似文献
107.
Immobilizing enzymes: how to create more suitable biocatalysts 总被引:8,自引:0,他引:8
Bornscheuer UT 《Angewandte Chemie (International ed. in English)》2003,42(29):3336-3337
108.
《Green Chemistry Letters and Reviews》2013,6(4):539-543
Abstract Lipase-catalyzed transesterification was used as an efficient tool for the interconversion of β-ketoesters. Catalytic activity of commercial lipase B from Candida antarctica (Novozym 435) was evaluated in systems involving non activated acyl donors, and enhanced using microwave irradiation. Interestingly, the combination of CAL B in microwave irradiation worked excellent in solvent-free conditions, thus assuring a highly competitive and environment-friendly process with high yields (up to 96%) in competitive times (< 2h). The combination of biocatalysis with solvent-free systems and microwave assistance is currently scarcely used, and may represent a powerful synergy for preparative reactions. 相似文献
109.
110.
Magnetic Fe3O4/SiO2 particles with rod-like structure and hollow interior have been constructed by a template method. During this procedure, β-FeOOH was firstly synthesized as the rod-like template to fabricate β-FeOOH/SiO2 core/shell-like particles. These β-FeOOH/SiO2 nanorods could be further transformed to Fe3O4/SiO2 via the decomposition-reducing method. These particles showed ferromagnetic behavior at room temperature with high coercivity and may provide potential applications in biological area. 相似文献