Replacement of the peptide-backbone amides connecting Tyr-Gly and Gly-Gly in leucine-enkephalin with ketomethylene groups: Synthesis and biological activity

Article abstract of DOI:10.1021/jm00368a003

A peptide analogue of Leu-enkephalin was synthesized in which the amide linkages between Tyr-Gly and Gly-Gly were replaced by ketomethylene groups. The resulting analogue, x, had 1/4000th and 1/2400th the opiate receptor binding activity of Leu-enkephalin