Stereoselective Synthesis of the Core Ring Systemof Lancifonins A–D

A 5/5/7 tricyclic intermediate bearing an oxa-bridged hemiketal ring was successfully synthesized from dihydrocarvone in 14 steps, which is a common intermediate of various <i>Schisandra</i> nortriterpenoids. Subsequently, the core structure of lancifonins A–D, characterized by a 5/5/7/8 fused ring system, was constructed in seven steps. The route employs key transformations, including the aldol reaction, Mukaiyama hydration, Mn(III)-mediated cyclization, the Suzuki reaction, and McMurry coupling.