Opioid peptides. Structure-activity relationships in [beta-Ala4]dermorphin tetrapeptides. V

We describe the synthesis and preliminary in vitro and in vivo pharmacological tests of six [beta-Ala4]tetrapeptides analogs of the opioid heptapeptide dermorphin H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2. The modification obtained by substituting beta-Ala4 for Gly4 provided further analogues with significant opioid activity.