Novel and potent 6-chloro-3-pyridinyl ligands for the α4β2 neuronal nicotinic acetylcholine receptor

Article abstract of DOI:10.1021/jm980721x

1-[(6-Chloro-3-pyridinyl)methyl]-2-imidazolidine (1), the N-desnitro metabolite of the major insecticide imidacloprid, is known to have similar potency to that of (-)-nicotine as an inhibitor of [³H](-)-nicotine binding at the rat recombinant α4β2 neuronal nicotinic acetylcholine receptor (nAChR); IC₅₀ values in the present study are 3.8 nM for (-)-nicotine, 6.0 nM for 1, and 155 nM for imidacloprid. Synthesis of new analogues of 1, modified only in the heterocyclic moiety (five-, six-, or seven-membered rings with NH, S, O, and CH₂ substituents), gave compounds varying from 4- fold higher potency (2-iminothiazole analogue 10) to > 6000-fold less active than (-)-nicotine. Other potent N-[(6-chloro-3-pyridinyl)methyl] compounds are those in which the heterocyclic imine is replaced with pyrrolidine (19) (IC₅₀ 9 nM) or trimethylammonium (22) (IC₅₀ 18 nM). A novel conversion of (-)-nicotine to its 6-chloro analogue increased the potency 2-fold. These 6- chloro-3-pyridinyl compounds are of interest as novel nAChR probes and potential metabolites of candidate insecticides.