Cascade radical cyclisations leading to polycyclic diterpenes. Total synthesis of (±)-spongian-16-one

Article abstract of DOI:10.1039/a708042e

A cascade of three consecutive 6-endo-trig radical cyclisations from the polyene acyl radical intermediate 12 derived from the selenoate 11 is used to construct the trans,anti,trans,anti,cis-tetracyclic keto lactone 20 in one step. Manipulation of the ketone function in 20 to the corresponding gem-dimethyl substituted carbon then completed a concise synthesis of the marine metabolite spongian-16-one 1.