Opioid peptides

Abstract

Opioid peptides including those of the formula ##STR1## in which A.sub.1 is the identifying group of an amino acid selected from 3,4-dihydroxyphenylalanine, 3,4-dimethoxyphenylalanine, azatyrosine, and 2,6-dimethyltyrosine; A.sub.2 is the identifying group of an amino acid selected from D-Ala and D-Arg; A.sub.3 is H, or the identifying group of an amino acid selected from of 3,4-dihydroxyphenylalanine and 3,4-dimethoxyphenylalanine, A.sub.4 is H, cyclohexylmethyl, the identifying group of an amino acid selected from 3,4-dihydroxyphenylalanine, 3,4-dimethoxyphenylalanine, Phe, and substituted Phe with its benzene ring substituted by halogen, NO.sub.2, OH, or CH.sub.3 ; A.sub.5 is the identifying group of a D- or L-amino acid selected from Leu, Nle, Lys, Met and Met(O), or is deleted together with R.sub.4 --CH attached thereto; each R.sub.1 and R.sub.2 is --H, --C(NH.sub.2).dbd.NH, or C.sub.1-12 alkyl; R.sub.3 is ##STR2## R.sub.4 is ##STR3## and R.sub.5 is --(CH.sub.2).sub.n+1 OH, ##STR4## wherein m is 0-6, n is 0-6, and X is H, C.sub.1-12 alkyl, C.sub.6-12 aryl, C.sub.7-18 aralkyl, C.sub.7-18 alkaryl, C.sub.7-18 alkayl, C.sub.6-17 pyridylalkyl, or C.sub.6-17 alkylpyridyl; provided that when one of R.sub.1 and R.sub.2 is --C(NH.sub.2).dbd.NH, the other must be H; or a pharmaceutically acceptable salt thereof.