Synthesis and biological activity of 3-substituted 3-desoxynaltrindole derivatives

The 3-unsubstituted and substituted analogs of naltrindole (NTI) were synthesized using palladium-catalyzed transformations, and their binding affinity to opioid receptors was determined. Although the 3-desoxy analog showed comparable δ selectivity with that of NTI, all of the novel compounds possessed low affinity for δ receptors indicating the important role of the 3-oxygen atom of NTI for interaction with δ-opioid receptors.