Enzyme mediated polyester synthesis with the lipase from Candida rugosa - Preparation of an enantiomerically enriched polymer from an A-B monomer

We have previously demonstrated an efficient polyester synthesis of omega-h ydroxyacids catalysed by the Candida rugosa lipase in dry hexane (1,2). Thi s method is now extended to the polymerisation of racemic 10-hydroxyundecan oic acid to explore the polymerisation of a secondary alcohol and the abili ty of the lipase to display stereoselectivity, The resultant polyester (sim ilar to 1000 Mwt) contained monomer units with an average enantiomeric exce ss of 60%ee favouring the (S) enantiomer. The residual monomer was recovere d with a 33%ee favouring the (R) enantiomer. The origin of this stereoselec tivity has been evaluated and it has been shown to arise due to the immedia te chiral environment surrounding the esterification event between the acyl ated enzyme and the secondary alcohol nucleophile. It is not due to recogni tion of the remote secondary alcohol functional group by the enzyme during initial acylation.