Synthetic routes to β, β‐diaryl‐α‐amino acids via nitrogen hetercycles

Abstract β, β‐Diphenylalanine and its ring‐substituted analogs are prepared from oxazolones, thiazolones, imidazolones, hydantoins, thiohydantoins, and piperazine 2,5‐diones by alkaline ring opening followed by acid cleavage of the N‐benzoyl group. The oxazolone approach, with its variations, offers the most advantageous route to these compounds. Several new amino acids are described.