Total Synthesis of (+)-Niduenes A and B

Niduenes A and B, two tetraquinane sesterterpenoids, possess a complex and intriguing 5/5/5/5/6 pentacyclic skeleton with eight contiguous stereocenters. We have achieved the first total synthesis of niduenes A and B in 16 and 14 steps, respectively. The synthesis features a Pauson-Khand reaction to generate the 5/5 bicycle, a Pd-catalyzed oxidative cyclization to construct the congested triquinane framework, and a radical cyclization to assemble the tetraquinane skeleton.