Stereoselective Total Synthesis of (±)-5- epi-Cyanthiwigin I via an Intramolecular Pauson-Khand Reaction as the Key Step.

A convenient approach to the construction of the 5-6-7 tricarbocyclic fused core structure of cyanthiwigins via a Co-mediated Pauson-Khand reaction as a key step has been developed. The cyathane core intermediate obtained by this strategy was used in the concise synthesis of (±)-5- epi-cyanthiwigin I. The developed chemistry paves the way for the total synthesis of structurally diverse cyanthiwigins.