Synthesis and biological evaluation of imidazole derivatives as novel NOP/ORL1 receptor antagonists: Exploration and optimization of alternative pyrazole structure

Abstract Nonpeptidic small-molecule NOP/ORL1 receptor antagonists with an imidazole scaffold were designed and synthesized to investigate alternatives to the pyrazole analog. Systematic modification of the original pyrazole lead [Kobayashi et al., Bioorg. Med. Chem. Lett. 2009 , 19 , 3627; Kobayashi et al., Bioorg. Med. Chem. Lett. , in press] to change the heterocyclic core, substituted side chain, and pendant functional group demonstrated that examining the structure–activity relationship for novel templates allowed the identification of potent, fully substituted 4-aminomethyl-1 H -imidazole and 2-aminomethyl-1 H -imidazole. These compounds exhibited excellent potency for ORL1 receptor with minimal P-gp efflux and/or reduced hERG affinity.