4-Step Total Synthesis of (−)-Pavidolide B

(−)-Pavidolide B is a complex tetracyclic diterpenoid with seven contiguous stereocenters, and classical total syntheses have recently been reported. In this work, an annulation strategy of carbanion cascade reaction is formulated for accomplishing an asymmetric total synthesis of (−)-pavidolide B in just 4 linear steps. The key reaction is a tandem intramolecular Michael addition, which constructs two 5-membered rings and five stereocenters in a highly selective fashion in one step. This work represents one of the most efficient cases of total synthesis and demonstrates that synthetic access to complex therapeutic natural product can be greatly simplified.