Synthesis and opioid activity of novel tetrapeptides analogous to sequence (1-4) of dermorphin

Seven new tetrapeptides analogous to (1-4) sequence of dermorphin were synthesized and evaluated for their opioid activity. The peptides were synthesized by the solution phase method. Their opioid activity revealed that peptides II and V were the most potent in the analgesia test as well as in the peripheral assays. Peptide II was most active in the guinea pig ileum assay, whereas peptide VI was 2763 times more selective for mu-receptors.