Natural p-menthene monoterpenes: Synthesis of the enantiomeric forms of wine lactone, epi-wine lactone, dill ether, and epi-dill ether starting from a common intermediate.

A concise synthesis of the enantiomeric forms of wine lactone (5), epi-wine lactone (14), dill ether (6), and epi-dill ether (15) was accomplished starting from the enantiomeric forms of p-mentha-1,8(10)-diene-3,9-diol (8) (Scheme 3). The latter compounds were previously prepared in high optical purity by means of lipase-mediated kinetic resolution, and they were the common building blocks for this divergent synthesis. The key steps were a number of chemo- and diastereoselective reactions of which the oxidation of 8 to the lactone 7 (see Table 1), the diastereoselective reduction of 7 to the lactones 14 and 5 (see 7 Table 2), and the reduction of enol-ether 16 to ether 15 were studied comprehensively. The effectiveness of this new synthetic approach allows the preparation of the title p-menthane monoterpenes, which are of considerable interest to the perfume industry, in high yield and in a few simple experimental steps.