文摘
A biomimetic synthesis of the triterpene (¡À)-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.