Endomorphine mu opioid receptor agonist analogs

摘要

A cyclic peptide of formula I: (I) H-Tyr-c [X1-X2-X3-X4] -X5, wherein X1 and X4 each independently is an acidic amino acid or a basic amino acid; X2 is Trp; X3 is independently an aromatic amino acid; X5 is NHR, Ala-NHR, Arg-NHR, Asn-NHR, Asp-NHR, Cys-NHR, Glu-NHR, Gln-NHR, Gly-NHR, His-NHR, Ile-NHR, Leu-NHR, Met- NHR, Orn-NHR, Phe-NHR, Pro-NHR, Ser-NHR, Thr-NHR, Trp-NHR, Tyr-NHR, or Val-NHR, wherein R is H or an alkyl group; and there is an amide bond between an amino group and a carboxylic acid group in the side chains of amino acids X1 and X4; with the proviso that when X1 is an acidic amino acid, then X4 is a basic amino acid; and when X1 is a basic amino acid, then X4 is an acidic amino acid.