Synthesis of a Bicyclic g-Lactam Dipeptide Analogue

The asymmetric synthesis of a bicydlic y-lactarn analogue of a dipeptide, in which the key step was the bis-alkylation of an optically active diphenyloxazinone c h i d glycine anion equivalent is described.In recent years both ourselvesl and others2 have synthesised y-lactams designed to act as antibacterials by the inhibition of aanspeptidases.Some of these compounds have displayed interesting biological activities.3As a result of a desire to extend the use of y-lactams for the inhibition of therapeutically important proteases we wished to synthesise conformationally restricted analogues of Phe-Pro or Tyr-Pro, which are cleavage sites for the HIV protease.4In this communication we describe the asymmetric synthesis of a bicyclic analogue of Phe-Pro (I), in which the key step was the dialkylation of a chual diphenyloxazinone glycine anion equivalent.'