N-Alkyl-octahydroisoquinolin-1-one-8-carboxamides: Selective and Nonbasic κ-Opioid Receptor Ligands

Herein, we report that N-alkyl-octahydroisoquinolin-1-one-8-carboxamides are a novel class of readily synthesized, selective K-opioid receptor (KOR) ligands. A striking feature of this class of compounds is the absence of any basic nitrogen atoms. Many of these compounds have demonstrated exclusive affinity for the KOR over not only the delta-opioid receptor and the mu-opioid receptor but also 38 other G protein-coupled receptor targets. The general binding affinity of this class of compounds for the KOR combined with a streamlined route for analogue synthesis provide strong motivation for pursuing this interesting new scaffold as a basis toward new probes targeting the KOR.