STRUCTURE-ACTIVITY-RELATIONSHIPS OF ANALOGS OF HIGHLY POTENT OPIOID PEPTIDE BIPHALIN

For SAR study of biphalin [(Tyr-D-Ala-Gly-PheNH-)(2)] we have synthesized several analogues with modifications of amino acid residues in position 3 and 4. The introduction of halogenated phenylalanine residues in position 4 increases affinity to delta receptors. Introducing basic aromatic amino acid residues in position 4 resulted in decrease in affinity to mu receptors, but preserve affinity to delta receptors.