Synthesis of Phthalide Derivatives of Podocarpic Acid Via Directed ortho Metalation: a Route to Highly Substituted Octahydrochrysene Derivatives

Two phthalide derivatives (7) and (8) have been prepared from podocarpic acid (1) via directed ortho metallation. The ring-c aromatic 16-oxa-17-oxo androstane analogue (8) was reacted with dimethyl acetylenedicarboxylate to give the 1,4-epoxy decahydrochrysene derivatives (9) and (10). The stereoisomer (10) was aromatized under acidic conditions to give the chrysen-1-ol derivative (11).