Synthesis and biological activity of the first cyclic biphalin analogues

Biphalin is a linear octapeptide with strong opioid activity. Its structure is based on two identical sequences derived from enkephalins joined C-terminal to C-terminal by an hydrazide bridge (Tyr-D-Ala-Gly-Phe-NH-NH ← Phe ← Gly ← D-Ala ← Tyr). In this study we present the design, synthesis, and biological evaluation of the first cyclic biphalin analogues. d-Alanine residues in positions 2, 2′ of the parent peptide were replaced by d- and l-cysteine and an intramolecular disulfide bond between the cysteine thiol groups was introduced. We obtained two cyclic analogues with quite different biological profiles.

Design, synthesis, and biological evaluation of the first cyclic biphalin analogues are reported. d-Alanine residues in positions 2, 2′ of the parent peptide were replaced by d- and l-cysteine and an intramolecular disulfide bridge has been established. Two cyclic biphalin analogues, with quite different biological profiles, have been described.Figure optionsDownload as PowerPoint slide