Structure-Activity Study on the Phe Side Chain Arrangement of Endomorphins Using Conformationally Constrained Analogues

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Endomorphins-1 and -2 were substituted with all the β-MePhe stereoisomers in their Phe residues to generate a conformationally constrained peptide set. This series of molecules was subjected to biological assays, and for β-MePhe4 -endomorphins-2, a conformational analysis was performed. Incorporation of (2S,3S)-β-MePhe4 resulted in the most potent analogues of both endomorphins with enhanced enzymatic stability. Their μ opioid affinities were 4-times higher than the parent peptides, they stimulated [35S]GTPγS binding, and they were found to be full agonists. NMR experiments revealed that C-terminal (2S,3S)-β-MePhe in endomorphin-2 strongly favored the gauche (-) spatial orientation which implies the presence of the χ1 = -60° rotamer of Phe4 in the binding conformer of endomorphins. Our results emphasize that the appropriate orientation of the C-terminal aromatic side chain of endomorphins is substantial for binding to the μ opioid receptor.

Original languageEnglish
Pages (from-to)735-743
Number of pages9
JournalJournal of Medicinal Chemistry
Issue number3
Publication statusPublished - Jan 29 2004


ASJC Scopus subject areas

  • Molecular Medicine
  • Drug Discovery

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