Synthesis of (±)- and (+)-perovskone

A biomimetic synthesis of the triterpene (±)-perovskone was achieved featuring a remarkable polycyclization process in which three rings, four bonds, and five stereocenters were created in a single operation in 82% yield. This convergent synthesis required 16 steps, starting from vanillin, and proceeded in 9% overall yield. A second route to prepare optically active quinone 2 took 15 steps in 36% overall yield and featured a palladium-catalyzed reductive allylic transposition to establish the C-5 chirality stereospecifically. Quinone (−)-2 was converted to (+)-perovskone (1) via a polycyclization cascade, which created four rings, five bonds, and six stereocenters in a single operation in 50% yield.