Enzyme-mediated preparation of enantiomerically pure p-menthan-3, 9-diols and their use for the synthesis of natural p-menthane lactones and ethers

The diasiereoselective preparation of the p-menthane-3,9-diols (+/-)-12, (+/-)-13a, (+/-)-13b, and (+/-)-18 and the study of their enzymic resolution is described (Scheme 1). The corresponding enantiomer-enriched diols obtained by means of the lipase-mediated kinetic acetylation of the racemic diols are suitable synthetic precursors of many relevant p-menthane monoterpenes. Their usefulness is shown in the preparation of different natural products of this class that are interesting for industrial purposes because of their odor qualities, i.e., of the enantiomeric form of 3-hydroxy-p-menthan-9-oic acid lactone 1, of mintlactone 2, of the 3,9-epoxy-p-menth-1,8(10)-diene 10, and of the pheromone vesperal 11 (Schemes 2 and 3).