Synthetic studies on basmane diterpenes. enantiospecific total synthesis of (+)-7,8-epoxy -2-basmen-6-one by claisen ring expansion

Article abstract of DOI:10.1021/ja00007a039

The first of an is described. The enantiospecific pathway by transforming optically pure aldehyde 10 into bicyclic 39. Methylenation of 39 by of the Tebbe reaction allows for opration of a Claisen that completely by way of transition 44 to the 42. Regiospecific cyclopentannulation with installation of four additional stereogenic centers rested upon sucessful introduction of a functionalized four-carbon chain as in 48, facially controlled hydrogenation of the conjugated double bond, cyclization, and hydroxyl-directed epoxidation. Finally, Swern oxidation led to the target molecule 3, whose three-dimensional structural features confirmed by X-ray crystallography.