Synthesis of (+)-Brefeldin-A.

Two routes to (+)-brefeldin A have been investigated. In one the bicyclic ketone 2 was transformed into the hydroxy lactone 7. Subsequent reduction, opening of the heterocyclic ring and epimerization furnished the aldehyde 13. Further steps towards the natural product from this late stage intermediate 13 were not investigated. In the second route, the readily available hydroxy lactone 17 was converted into the enone 22. Conjugate addition of the requisite cuprate reagent to this enone afforded the 3,4-disubstituted cyclopentanone 24 which was converted into brefeldin-A 29 in five steps.