Discovery of the First N-Substituted 4β-Methyl-5-(3-hydroxyphenyl)morphan To Possess Highly Potent and Selective Opioid δ Receptor Antagonist Activity

A structurally novel opioid δ receptor selective antagonist has been identified. This compound, (+)-5-(3-hydroxyphenyl)-4-methyl-2-(3-phenylpropyl)-2-azabicyclo[3.3.1]non-7-yl-(1-phenyl-1-cyclopentane)carboxamide [(+)-KF4, (+)-4], showed a K e value of 0.15 nM in the [35S]GTPγS functional assay. (+)-KF4 is also a δ inverse agonist with an IC50 value of 1.8 nM. To our knowledge, this is the first potent and selective δ opioid receptor antagonist from the 5-phenylmorphan class of opioids.