(A) A new route of α-mercapto-β-amino-α, β-disubtituted carboxylic acids has been presented. By condensing 5-methyl-2-thiothiazolidine-4-one and benzylidene-N, N- bisacetamide, 5-methyl-5-[α-acetylaminobenzyl]-2-thiothiazolidine-4-one was obtained and this was converted through its oxime into the corresponding thiazolidine-2, 4-dione. By the action of alkali the thiazolidine ring was cleaved and α-methyl-β-phenylisocysteine and its ...