Catalytic Epoxypolyene Cyclization via Radicals: Highly Diastereoselective Formal Synthesis of Puupehedione and 8-epi-Puupehedione

A catalytic and highly stereoselective synthesis of a common building block for the marine natural product puupehedione (1) and its biologically more active 8-epimer is described. Our approach features a copper-catalyzed allylic substitution reaction of epoxyfarnesyl acetate and a diastereoselective titanocene-catalyzed epoxypolyene cyclization via radicals. The formal syntheses of 1 and 2 are completed by highly diastereoselective ring closures to the required benzodihydropyran units.