Application of peptidyl radicals into a new radical cascade leading to unsaturated gamma-lactams

Radical cyclization of dipeptides 1a-h proceeds smoothly to give five- and seven-membered rings in good to moderate total yields using Stork's catalytic tin hydride method. A radical is generated on a protecting group and translocated to the peptide moiety. Following a cyclization reaction, the vinyl radical can abstract hydrogen from a benzyl group on an amine, which results in elimination of the protected amine group. Encouraging results have notably been obtained with amino acids other than glycine.