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 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.