RESOLUTION OF DERIVATIVES OF 1,2-PROPANEDIOL WITH LIPASE-B FROM CANDIDA-ANTARCTICA - EFFECT OF SUBSTRATE STRUCTURE, MEDIUM, WATER ACTIVITY AND ACYL DONOR ON ENANTIOMERIC RATIO

The glycerol-related racemic derivatives 1a-15a and 1b-15b have been r esolved by hydrolysis and transesterifications using lipase B from Can dida antarctica. Influence of substrate structure for the enantiomeric ratio E has been explained on the basis of previous molecular modelli ng. E values and equilibrium constants K-eq have been calculated on th e basis of ee(s) and ee(p) 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 activit y, a(w). For some substrates addition of 30% acetone to the hydrolysis reaction gave a large increase of E. High water activity gave for som e substrates an increase of E, but was unfavourable for the reversibil ity. However, this did not significantly influence the ee of product f raction. The influence of the alkoxy part of various butanates as acyl donors has been studied with respect to E and K-eq. It was generally found that 2-chloroethyl butanate gave higher E than vinyl butanate; h owever, the latter gave irreversible conditions. (C) 1998 Elsevier Sci ence Ireland Ltd. All rights reserved.