ENZYMES IN ORGANIC SYNTHESIS .26. SYNTHESIS OF ENANTIOMERICALLY ENRICHED 2,3-DIMETHYLPENTAN-5-OLIDES AND 3,4-DIMETHYLPENTAN-5-OLIDES BY LIPASE-CATALYZED REGIOSELECTIVE AND ENANTIOSELECTIVE ALCOHOLYSIS OF CIS-2,3-DIMETHYLPENTANEDIOIC AND TRANS-2,3-DIMETHYLPENTANEDIOIC ANHYDRIDES

The enzyme-catalyzed regio- and enantioselective alcoholysis of racemi c cis- nd trans-2,3-dimethylpentanedioic anhydride in the presence of Novozym 435 from Candida antarctica afforded two of the eight possible monoesters with an enantiomeric excess higher than 90%. Regioselectiv e reductions of these monoesters with lithium borohydride or borane/di methyl sulfide furnished four enantiomerically highly enriched dimethy lpentan-5-olides, which are versatile chiral intermediates.