N-(N, N'-Dicarbobenzoxy-L-cystinyl)-diglycine (111) was prepared'and converted to N-(S- benzyl-L-cysteiny1)-glycine (IV). 2 IV could be crystallized from water as recommended by Loring and du Vigneaud2 providing the temperature of the water was kept below 80'. Above 80'IV was converted rapidly to L-benzylmercaptomethyldiketopipera-zine (V). Compound IV reacted with phenylacetyl chloride to give N-(N-phenylacetyl-S-benzylcys-teiny1)-glycine ( ...
