Total Syntheses of (+)-Aquatolide and Related Humulanolides

The short, efficient total synthesis of (+)-aquatolide was achieved by a biomimetic transannular [2+ 2] photocycloaddition, and provides the first example of constructing a 5/5/4/8-ring system from asteriscunolides. Furthermore, the reaction leading to a 5/4/4/7-ring system, the originally proposed structure of aquatolide, was also developed. This strategy achieved syntheses of five more humulanolides, ()-asteriscunolides A, C, D, and I, and (+)-tetradehydroasteriscanolide.