Opioid peptide. Structure-activity relationships in dermorphin tetrapeptide-amides. II

Preliminary pharmacological data and the characterization of sixteen synthetic tetrapeptide-amide analogs of dermorphin (opioid heptapeptide) are reported. N,N-dialkylamides displayed reduced or no activity; on the contrary, derivatization of H-Tyr-D-Ala-Phe-Gly-OH C-terminus by suitable amide moieties (1-adamantanamine, 1-adamantane-methylamino, or D-alpha-methylbenzylamine) produced potent analogues with peripheral and central opioid activities comparable to, or higher than those of dermorphins.