Approach to the Synthesis of Briarane Diterpenes through a Dianionic Claisen Rearrangement and Ring-Closing Metathesis

The synthesis of the briarane–brianthein A core has been accomplished utilizing an extension of the dianionic Ireland–Claisen rearrangement to establish the C1 quaternary carbon and the adjacent C10 ring juncture stereocenters. Two sequential ring-closing metathesis reactions were exploited to construct the 6–10 trans fused ring system.