Asymmetric Synthesis of the Balanol Heterocycle via a Palladium-Mediated Epimerization and Olefin Metathesis

The enantioselective formal synthesis of balanol, a potent protein kinase C inhibitor, was accomplished from d-serine utilizing a Pd-catalyzed equilibration of diastereomeric 5-vinyloxazolines to set the stereochemistry of the vicinal amino and hydroxyl groups. A ruthenium-catalyzed ring-closing metathesis was employed to form the seven-membered nitrogen heterocyle.