Syntheses and Reactions of N-(Phenylpyruvoyl) Amino Acids

Abstract α-Ethoxy- and α-acetoxycinnamoyl chlorides were synthesized by treatments of α-ethoxy-and α-acetoxycinnamic acid with thionyl chloride and oxalyl chloride, respectively, and reactions of ammo acid esters with the cinnamoyl chlorides were investigated in order to seek for a synthetic method of N-(phenylpyruvoyl) amino acids. N-Hydroxy- or N-benzyloxy-Dl-alanine esters prepared from 2-bromopropionic esters and hydroxylamine or benzyloxyamine were treated with α-ethoxycinnamoyl chloride to give the corresponding N-(α-ethoxycinnamoyl) derivatives. Treatment of l-leucine ethyl ester with α-acetoxycinnamoyl chloride afforded N-(α-acetoxycinnamoyl)-l-leucine ethyl ester, the removal of the acetyl group from which was readily accomplished under mild, basic conditions, and N-(phenylpyruvoyl)-l-leucine ester was obtained. Treatment of the ester with ammonia yielded 3-benzylidene-6-isobutyl-2,5-piperazinedione.