Total Synthesis of (+)-Boronolide, (+)-Deacetylboronolide, and (+)-Dideacetylboronolide

Total synthesis of (+)-boronolide, (+)-deacetylboronolide, and (+)-dideacetylboronolide has been achieved from a single intermediate 26, which was synthesized in 11 steps from a d-mannitol-derived intermediate 8 in an overall yield of 10%. The key steps in the synthesis are inversion of a chiral center by taking an advantage of the inherent mechanism involved in the ring closing to an epoxide via intramolecular S(N)2 reaction and lactonization of a diol using Fetizons reagent. The strategy is amenable to preparation of analogues of (+)-boronolide in sufficient amount for further screening of biological activity.