Solid phase synthesis and opioid receptor binding activities of (D-Ala2,D-Leu5)enkephalin analogs containing a fluorinated aromatic amino acid.

Abstract
Five [D-Ala2, D-Leu55]enkephalin (DADLE) analogs containing fluorinated Tyr1 or Phe4 residue, that is, [Phe(2F)4](I), [Phe(3F)4] (II), [Tyr(3F)1] (IV) and [Try(2F)1] (V), were synthesized by the solid phase method and their opioid receptor affinities were examined. Affinity profiles of five derivatives for the .mu.- and .delta.-receptor were similar to those of DADLE, and the affinity for .kappa.-receptor was zero or negligible.