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固定化假丝酵母99-125脂肪酶催化酯化脂肪酸低碳醇酯反应条件的研究 总被引:9,自引:2,他引:9
以硅藻土和纺织品为载体 ,采用吸附法制备固定化脂肪酶 ,研究了固定化假丝酵母 99 1 2 5脂肪酶在有机溶剂中催化脂肪酸低碳醇酯酯化合成过程中 ,有机溶剂性质、脂肪酸与低碳醇的结构、pH值、反应温度和体系含水量、低碳醇的抑制作用等因素对酯化过程的影响。试验结果表明 :底物低碳醇需要采用流加方式加入体系 ,石油醚是最适宜的有机溶剂 ,脂肪酸与醇的碳链越长 ,越易于酯化 ;固定化脂肪酶对直链醇的选择性优于支链醇。以石油醚为有机溶剂 ,在反应温度为 40℃、pH值为 7时 ,硬脂酸与甲醇的酯化率达 95 % ;反应后期应除去体系中的水以避免酶失活。固定化酶间歇催化油酸与甲醇的酯化时 ,重复使用 1 5次 (每次 2 4h) ,其操作半衰期约为 360h。 相似文献
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脂肪酶主要催化醇、酸、内酯的酯化反应,脂肪酶催化反应可在非水溶剂中进行,并且反应条件温和,被认为是制备单一对映异构体的有效方法。文中利用固定化脂肪酶Novozym 435催化3-TBDMSO戊二酸酐不对称醇解制备3-TBDMSO戊二酸甲酯,通过高效液相色谱考察了不同反应条件对底物转化率、产物选择性的影响规律。实验研究了四氢呋喃、乙酸乙酯、乙醚、甲基叔丁基醚和甲苯5种溶剂对酶催化反应的影响,结果表明:在甲基叔丁基醚溶剂中,Novozym 435的催化效果最好。最优反应条件:温度25℃,酶质量浓度30 mg/mL,醇与3-TBDMSO戊二酸酐摩尔比1.0,酸酐浓度100 mmol/L,pH值为6.5,水活度0.66,反应时间6 h。实验采用萃取的方法分离出反应产物,通过结晶纯化得到无色晶体,利用核磁氢谱证明产物为3-TBDMSO戊二酸甲酯,通过圆二色光谱说明合成产物为对映体过剩产品。 相似文献
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醛化酶又称醇氰裂酶或Hnls,用于催化由氰氢酸与醛类或酮类等化合物合成氰醇的可逆反应(图1)。最早涉及Hnls酶应用的报道是:从杏仁中提取的粗酶(苦杏仁酶)用于催化苯醛和氢氰酸的反应以合成苯乙醇腈。当时并没有引起人们多大的注意,一直到二十世纪六十年代,有人分离得到这一酶,对它的特性进行了研究,并被应用于从芳香族和脂肪族醛类化合物制备高含量的对是映体(R)-氰醇。 相似文献
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通过多级催化法用脂肪酶N435催化不同碳数脂肪族二醇与二酯反应,合成直链聚酯。结果表明:短链二醇与短链二酯难以被脂肪酶催化发生反应,长链二醇与二酯易被催化发生反应。采用脂肪酶N435催化己二酸二乙酯与1,4-丁二醇反应可以获得重均分子量为24 816,相对分子质量分布为1.09的聚酯。脂肪酶催化二醇、二酯与甘油共聚合可以获得重均分子量较高、相对分子质量分布窄的共聚物。 相似文献
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近年来,酶的催化多功能性广泛应用与有机合成反应中。我国关于生物催化有机合成的报道日益增多,本文综述了近两年来国内有关酶多功能催化有机合成的报道。 相似文献
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Dendrimers, well-defined hyper-branched macromolecules with characteristic globular structures, have inspired chemists and
chemical engineers to develop new materials and several applications have been explored. The dendritic molecule has emerged
as an attractive material in the field of catalysis and various dendrimer catalysts have been applied not only to catalytic
reactions but also to non-catalytic ones such as nanoscale reactor systems. This article presents a review of research work
on the dendrimer-based catalysis involving the rational design of homogeneous or heterogeneous chiral dendrimer catalysts
for enantioselective reactions and the synthesis of catalytically active bimetallic nanoparticles in the presence of dendrimer
as a template.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
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The discovery and development of the catalysis of stannane-mediated radical chain reactions by benzeneselenol, generated in situ by reduction of diphenyl diselenide with tributyltin hydride, are described. The catalytic sequence is discussed in terms of polarity reversal catalysis of radical chain reactions, and applications to synthesis are presented. These include the prevention of numerous radical rearrangement reactions, the ability to intervene in certain multistep radical rearrangements, especially aryl and vinyl radical cyclizations, at intermediate stages with advantages to the product profile, and the effective trapping of allyl-, benzyl-, and cyclohexadienyl-type radicals, permitting inter alia the isolation of aryl cyclohexadienes and their application in synthesis. 相似文献
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Daniel Pflästerer Matthias Rudolph A. Stephen K. Hashmi 《Israel journal of chemistry》2018,58(5):622-638
This contribution summarizes the application of homogeneous gold catalysis in hydrofunctionalization and spiroketalization reactions in total synthesis, the most frequent applications of gold catalysis in that sector. 相似文献
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构筑手性金属有机骨架的方法及其在不对称催化中的应用 总被引:1,自引:0,他引:1
手性金属有机骨架(MOF)具有独特的结构、不对称催化和手性拆分等性能,引起了催化学者的极大重视.系统地介绍了国内外有关手性MOF的合成方法,即:①非手性物质在晶体生长过程中自组装;②使用手性化合物来诱导合成;③通过手性有机基团与金属离子配位将手性成分嵌入金属有机骨架;④表面修饰的方法,第3种方法是最常用的合成手性MOF的方法.重点阐述了近年来手性MOF在不对称催化领域的最新研究成果,希望能为手性MOF研究者设计、合成更优良的手性MOF催化剂提供参考.未来手性MOF催化的主要目标在于合成性能更加高效、稳定的新型手性MOF催化剂,并应用于大规模工业生产中,在温和条件下实现较高的转化数和对映体选择性. 相似文献
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Phase-transfer catalysis (PTC) has been widely used for the synthesis of organic compounds for more than three decades. The scope and mechanistic features of PTC have been the aim of numerous studies. This review focuses on the application of phase transfer catalysis in synthesis of phosphorus compounds. 相似文献
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Over the last years, gold catalysis has gained considerable significance in organic synthesis, since it allows atom economy and synthetic efficiency for the transformation of relatively simple substrates into valuable, highly complex molecular architectures. The gold-catalyzed polycyclization reactions of alkynes and enynes have been particularly successful toward the synthesis of natural products. This review highlights the recent developments in polycyclization area according to the key gold-catalyzed step. 相似文献