Amidoalkylation of mercaptans with glyoxylic acid derivatives

The synthesis of α-alkyl mercaptohippuric acid (3a–d), N-benzyloxycarbonyl-α-methylthioglycine (3e) and their methyl esters (5a–d) by the amido-alkylation of mercaptans with α-hydroxyhippuric acid (2a), α-hydroxy-N-benzyloxycarbonylglycine (2b) and their methoxymethyl ester derivatives 4a and 4b is described. Oxidation with m-chloroperbenzoic acid afforded the corresponding sulfoxides and sulfones and treatment with N-bromosuccinimide in methanol or chlorine in carbon tetrachloride solution exchanged the sulfur containing side chain for a methoxy or a chloro group respectively. (4a, 8).