A Brief Synthesis of (−)-Englerin A

Englerins A and B are guaiane sesquiterpenes that were isolated from the bark of Phyllanthus engleri, a plant indigenous to east Africa. The englerins consist of a 5-6-5 fused tricyclic structure with an ether bridge and two ester-bearing stereogenic centers, including a highly unusual glycolate residue. Englerin A is a potent and selective inhibitor of the growth of six human renal cancer cell lines. We report herein an efficient, eight-step synthesis of englerin A that leverages simple carbonyl-enabled carbon−carbon bond formations. Our route is amenable to the production of a diverse series of analogues for structure−function studies and determination of the mode of action of these natural products.