Discovery of fused azetidines as novel selective α4β2 neuronal nicotinic receptor (NNR) agonists

An efficient synthesis of (1R,5S)-6-(5-cyano-3-pyridinyl)-3,6-diaza-bicyclo[3.2.0]heptane A-366833, a novel potent selective neuronal nicotinic receptor (NNR) agonist, is described. The enantiomerically pure pharmacophore benzyl (1S,5S)-3,6-diaza-bicyclo[3.2.0]heptane-3-carbamate was successfully constructed from benzyl N-allyl-N-(2-hydroxyimino-ethyl)-carbamate through a convenient approach including an intramolecular [1,3]-dipolar cycloaddition, reductive ring-opening reaction, chiral resolution, and intramolecular cyclization. Subsequent N-arylation of the pharmacophore with 3-bromo-5-cyanopyridine and N-Cbz deprotection with trifluoroacetic acid furnished A-366833.