Enantioselective Total Synthesis of the Reported Structures of (−)-9-epi-Presilphiperfolan-1-ol and (−)-Presilphiperfolan-1-ol: Structural Confirmation and Reassignment and Biosynthetic Insights

The first total synthesis of the reported structures of 9-epi-presilphiperfolan-1-ol and presilphiperfolan-1-ol has been achieved. Key steps are a catalytic asymmetric alkylation of a novel diene-containing electrophile followed by a two-carbon ring contraction and an intramolecular Diels–Alder cycloaddition to form the stereochemically dense tricyclic core. The synthetic work has resulted in the structural revision of presilphiperfolan-1-ol (see scheme)