Synthesis of the angiotensin converting enzyme inhibitor (-)-A58365A via an isomunchnone cycloaddition reaction

The angiotensin converting enzyme inhibitor (-)-A58365A (1) was synthesized by a process based on the [3 + 2]-cycloaddition reaction of a phenylsulfon yl substituted isomunchnone intermediate. The starting material for this pr ocess was prepared from L-pyroglutamic acid and involved using a diazo-phen ylsulfonyl substituted pyrrolidine imide. Treatment of the diazoimide with Rh-2(OAc)(4) in the presence of methyl vinyl ketone afforded a 3-hydroxy-2- pyridone derivative which was subsequently converted to the ACE inhibitor i n six additional steps.