Reactions of α-Substituted Glycine Derivatives With Stannanes in the Presence of Disulfides

Reactions of α- bromo -, α- benzoyloxy - and α- methoxy -substituted glycine derivatives with stannanes afforded the corresponding α- centred glycinyl radical, which reacted with di -t-butyl disulfide and diphenyl disulfide by homolytic substitution to give the corresponding α-t- butylthio- and α-phenylthio -substituted glycine derivatives, respectively. The glycinyl radical reacted with dibenzyl disulfide by displacement of benzyl radical to give a mixed disulfide, which was subsequently reduced to the corresponding α- benzylthio-substituted glycine derivative. In related reactions of a cystine derivative the corresponding S-glycinylcysteine derivative was produced, indicating that, while the chemical integrity of disulfide bonds in cystine derivatives is likely to be affected in radical reactions of peptides, the reactions are suitable for exploitation in the synthesis of cross-linked amino acid derivatives.