Concise synthesis of a highly functionalized cyclopentane segment: toward the total synthesis of kansuinine A

Kansuinine A, isolated from the plant Euphorbia kansui Liou, is one of a series of jatrophane diterpenes that have novel structural features, which include contiguous stereocenters, a highly oxygenated carbon framework, and a tricyclic ring system. We describe here a short and concise synthesis of the cyclopentane segment of kansuinine A via SmI2-mediated cyclization of δ-iodoester as a key construction method.