Synthesis of Daucane Natural Products Enabled by a Gold(I)-Catalyzed Tandem Cycloisomerization/(4 + 3) Cycloaddition

A divergent synthesis of three members of the daucane family of natural products is reported, enabled by a gold(I)-catalyzed cycloisomerization/formal (4 + 3) cycloaddition as the key step. The synthesis of penigrisacid A features a vanadium-catalyzed tandem epoxidation/SN2′ cyclization, whereas a Suárez radical cyclization enables the synthesis of aspterric acid. This work has also led to the reassignment of the structure of penigrisacid A as well as a short formal synthesis of schisanwilsonene A.