Intramolecular Cyclobutadiene Cycloaddition/Cyclopropanation/Thermal Rearrangement: An Effective Strategy for the Asymmetric Syntheses of Pleocarpenene and Pleocarpenone

The first total synthesis of the guaiane sesquiterpene natural products pleocarpenone and pleocarpenene is described. An intramolecular cycloaddition of cyclobutadiene, followed by cyclopropanation and thermal fragmentation of the resulting highly strained intermediate, is the strategy used to achieve this synthesis. The asymmetric route allowed for confirmation of the absolute stereochemistry of these natural products.