Anthonsen T, Hoff B H
Department of Chemistry, Rosenborg, Norwegian University of Science and Technology, Trondheim, Norway.
Chem Phys Lipids. 1998 Jun;93(1-2):199-207. doi: 10.1016/s0009-3084(98)00043-7.
The glycerol-related racemic derivatives 1a-15a and 1b-15b have been resolved by hydrolysis and transesterifications using lipase B from Candida antarctica. Influence of substrate structure for the enantiomeric ratio E has been explained on the basis of previous molecular modelling. E values and equilibrium constants Keq have been calculated on the basis of ees and eep measured throughout the reaction, and ping-pong bi-bi mechanism using the computer program E&K calculator. Medium effects have been studied for hydrolysis with organic co-solvents and transesterifications in different solvents with varying water activity, aw. For some substrates addition of 30% acetone to the hydrolysis reaction gave a large increase of E. High water activity gave for some substrates an increase of E, but was unfavourable for the reversibility. However, this did not significantly influence the ee of product fraction. The influence of the alkoxy part of various butanates as acyl donors has been studied with respect to E and Keq. It was generally found that 2-chloroethyl butanate gave higher E than vinyl butanate; however, the latter gave irreversible conditions.
利用来自南极假丝酵母的脂肪酶B，通过水解和酯交换反应拆分了甘油相关的外消旋衍生物1a - 15a和1b - 15b。基于先前的分子模型解释了底物结构对对映体比例E的影响。根据整个反应过程中测得的对映体过量值ees和对映体过量百分比eep，使用计算机程序E&K计算器，并采用乒乓双底物双产物机制，计算了E值和平衡常数Keq。研究了在水解反应中添加有机共溶剂以及在不同水活度aw的不同溶剂中进行酯交换反应时的介质效应。对于某些底物，在水解反应中添加30%的丙酮会使E大幅增加。高水活度对某些底物会使E增加，但不利于反应的可逆性。然而，这对产物馏分的对映体过量没有显著影响。研究了各种丁酸酯作为酰基供体的烷氧基部分对E和Keq的影响。通常发现，丁酸2 - 氯乙酯比丁酸乙烯酯给出更高的E；然而，后者给出不可逆的反应条件。
