Concise Synthesis of the Erythrina Alkaloid 3-Demethoxyerythratidinone via Combined Rhodium Catalysis

The total synthesis of the erythrina alkaloid 3-demethoxyerythratidinone has been achieved via a strategy based on combined rhodium catalysis. The catalytic tandem cyclization effected by the interplay of allrynyl and vinylidene rhodium species allows for efficient access to the A and B rings of the tetracyclic erythrinane skeleton in a single step. The synthesis also features rapid preparation of the requisite precursor for the double ring closure and thus has been completed in only 7 total steps in 41% overall yield.