Enantiospecific Total Synthesis of the Highly Strained (-)-Presilphiperfolan-8-ol via a Pd-Catalyzed Tandem Cyclization.

A rare element of high strain in molecules of natural origin is a 1,2-trans fusion of 5-membered rings within a [3.3.0]-bicycle, a motif present in (-)-presilphiperfolan-8-ol. This molecule also possesses a 1,3-trans stereochemical arrangement of substituents on one of its 5-membered rings, a pattern shared by a number of other terpenes. Herein, we disclose the first total synthesis of this highly strained target in 13 steps. The key operation is a Pd-catalyzed tandem cyclization that directly establishes the requisite 1,3-trans stereochemical arrangement on one ring while concurrently setting the stage for the controlled generation of the highly strained 1,2-trans ring fusion of the final architecture.