Double enantioselective transesterification of racemic carboxylic esters and cyclic meso-diols by lipase catalysis

Abstract

Lipase-catalysed double enantioselective transesterifications of racemic carboxylic esters and cyclic meso-diols to give the hydroxy esters 3, 6, 9, 11 and 14 have been investigated. The selectivity of this process is determined by the structure of both substrates and the origin of the lipase. In four of the five cases investigated, lipase SP 382 shows the highest activity and selectivity. In the products, excepting the acyl part of compounds 3, (S)-selectivity for both the alcohol and the acyl moiety has been observed. However, regarding the acyl part the selectivity is poor compared with that of the alcohol part. Application of this method allows us to prepare enantiomerically pure compounds with at least three asymmetric centres in one biocatalytic step if the reaction partners are matching and/or the products are easy to separate as found for compounds 9a, 9c and 11a for instance. The X-ray molecular structures of compounds 9a and 11a are reported.