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 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.