Total synthesis of thienamycin analogs. II Synthesis of 2-alkyl and 2-aryl thienamycin nuclei

A new general synthesis leading to 2-alkyl and 2-aryl-1-carba-2-penem-3-carboxylic acids involves the preparation of a key thiolester intermediate 3. This is reacted with Me2CuLi or (C6H5)2MgCuX to give the corresponding methyl or phenyl ketone which undergoes a Wittig reaction to give the desired penems, which can be deblocked photolytically or by hydrogenolysis to give acids with good antibacterial activity.