Total Syntheses of (+)-Sarcophytin, (+)-Chatancin, (-)-3-Oxochatancin, and (-)-Pavidolide B: A Divergent Approach.

A concise and divergent approach for the total syntheses of four cembrane diterpenoids, namely (+)-sarcophytin, (+)-chatancin, (-)-3-oxochatancin, and (-)-pavidolide B, has been developed, and it also led to the structural revision of (-)-isosarcophytin. The key steps of the strategy feature a double Mukaiyama Michael addition/elimination, a Helquist annulation, two substrate-controlled facial-selective hydrations, and a pinacol rearrangement. The described syntheses not only achieved these natural products in an efficient manner, but also provided insight into the biosynthetic relationship between the two different skeletons.