Opioid peptides. Structure-activity relationships in [OGly4] dermorphin tetrapeptides. X.

We describe the synthesis and preliminary in vitro and in vivo pharmacological tests of four [OGly4] tetrapeptide analogues of the opioid heptapeptide dermorphin H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2. The modification obtained by substituting aminoxy-acetic acid (OGly) for Gly4 provided analogues with substantial reduction of activity.