α,β-Unsaturated Carboxylic Acid Derivatives. IX. The Cyclization of α-(N-Acyl-hydroxyamino) Acid Esters with Ammonia or Hydroxylamine

A new type of cyclization reaction of α-(N-acyl-hydroxyamino) acid esters to imidazolidine-4-one derivatives and the synthesis of several 2,5-piperazinedione derivatives are described. The treatment of β-methoxy-α-(N-chloroacetyl- or N-phthaloylglycyl-hydroxyamino) acid esters with ammonia gave 2-carbamoyl-2-(1-methoxy)alkyl-or aralkyl-imidazolidine-4-ones, while a similar cyclization of α-(N-haloacetylamino) or α-(N-haloacyl-hydroxyamino) acid esters with ammonia or hydroxylamine gave 2,5-piperazinedione, 1-hydroxy-2,5-piperazinedione or 1,4-dihydroxy-2,5-piperazinedione derivatives. The difference in the formation mechanisms between the imid-azolidine-4-one and 2,5-piperazinedione and their structural assignment were discussed.