Construction of the Tetracyclic Core of Harziandione via Gold(I) Catalysis

Harziandione is a diterpenoid natural product featuring a 6/5/7/4 tetracyclic core with four contiguous stereocenters, two of which are quaternary. Herein, we report the rapid assembly of its tetracyclic framework in just nine steps from commercially available cyclopentenone, strategically enabled by gold(I) catalysis. The strained bicyclo[5.2.0]nonene motif was assembled via a gold(I)-catalyzed formal [2 + 2] cycloaddition, while the congested bridged [3.2.1] ring system was constructed through a gold(I)-catalyzed Conia-ene reaction. Subsequently, the pivotal C11 enone was installed using a sequence featuring olefin dihydroxylation and Babler-Dauben oxidation as key transformations.