Muscarinic agonist, (±)-quinuclidin-3-yl-(4-fluorophenethyl)(phenyl)carbamate: High affinity, but low subtype selectivity for human M ₁ – M ₅ muscarinic acetylcholine receptors

Novel quinuclidinyl N-phenylcarbamate analogs were synthesized, and binding affinities at M ₁ -M ₅ muscarinic acetylcholine receptor (mAChR) subtypes were determined using Chinese hamster ovary (CHO) cell membranes stably expressing one specific subtype of human mAChR. Although not subtype selective, the lead analog (±)-quinuclidin-3-yl-(4-fluorophenethyl)(phenyl)carbamate (3c) exhibited the highest affinity (K _i = 2.0, 13, 2.6, 2.2, 1.8 nM) at each of the M ₁ -M ₅ mAChRs, respectively. Based on results from the [ ³ H]dopamine release assay using rat striatal slices, 3c acted as an agonist at mAChRs. The effect of 3c was inhibited by the nonselective mAChR antagonist, scopolamine, and 3c augmented release evoked by oxotremorine. A potent analog from the same scaffold, (±)-quinuclidin-3-yl-(4-methoxyphenethyl)(phenyl)-carbamate (3b) exhibited the greatest selectivity (17-fold) at M ₃ over M ₂ mAChRs. These analogs could serve as leads for further discovery of novel subtype-selective muscarinic ligands with the goal of providing therapeutics for substance use disorders and chronic obstructive pulmonary disease.