Synthesis and properties of dermorphin and an analog of β‐endorphin containing the dermorphin sequence

Abstract
Dermorphin (I) and [D-Ala2, Phe3, Gly4, Tyr5, Pro6]-.beta.c-EP (camel .beta.-endorphin II) were synthesized by the solid-phase method. Positions 1 through 7 of II correspond to the sequence of .LAMBDA.. Relative potencies of synthetic peptides in the mouse tail-flick test for analgesia by the intracerebroventricular route were: human .beta.-endorphin, 100; .beta.c-EP, 164; I, 450; II, 440. I was .apprx. 670 times more potent than morphine in the assay. Peptide II represents a rare instance where the enkephalin moiety of .beta.-endorphin was altered to produce a more potent analgesic.