Total Synthesis of (−)-Graminin A Based on Asymmetric Cyclization Carbonylation of Propargyl Acetate

The first total synthesis of (−)-graminin A is described. Key features of our synthetic approach involve a palladium-catalyzed asymmetric cyclization carbonylation of prochiral propargylic acetate, conversion of the orthoester product into methyl 4-oxo-3-furancarboxylate, and copper complex-mediated aldol condensation of (+)-gregatin B bearing a diene moiety. A new synthesis of (+)-gregatin B and the first synthesis of (−)-graminin A were achieved.