Synthetic Studies toward the Hamigerans with a 6-7-5 Tricyclic Core.

An approach toward the 6-7-5 tricyclic carbon skeleton of the hamigeran natural products was developed. The key steps include a benzyne-β-ketoester annulative ring expansion to form the 7-membered ring, a Nazarov reaction to form the 5-membered ring, a Ni-catalyzed conjugate methyl addition or a Corey-Chaykovsky reaction to install the all-carbon quaternary center, and a Suzuki cross coupling followed by reduction to introduce the isopropyl group.