From Penicillin to Penem and Carbapenem. VIII. Introduction of an Allyl Group at the C-4 Position of the Azetidinone Molecule, and the Synthesis of Dethiathienamycin

A new C3-unit introduction reaction at the C-4 position of 4-acetoxy-2-azetidinone derivatives using tetraallyltin in the presence of 1/10 equiv of boron trifluoride etherate in dichloromethane is described. Dethiathienamycin was synthesized from (3S,4R)-4-allyl-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone via the ylide intermediate.