Norrisolide: Total Synthesis and Related Studies

A stereoselective synthesis of (+)‐norrisolide is presented. This natural product belongs to a family of marine spongiane diterpenes the structure of which is characterized by a fused γ‐lactone–γ‐lactol ring system attached to a bicyclic hydrophobic core. Our studies led to the development of a expedient synthesis of such γ‐lactone–γ‐lactol motifs based on ring expansion of a fused cyclopropyl ester. Highlights of the synthetic strategy toward norrisolide include the coupling of the two bicyclic systems by constructing a sterically demanding C9C10 bond and the installation of the C19 oxygen at the last step of the synthesis via a Baeyer–Villiger oxidation.