Pyridine analogs of (−)-cytisine and varenicline: cholinergic receptor probes

A series of bicyclic pyridine containing alkaloids related to (−)-cytisine and varenicline are described. Synthetic access via regioisomeric metalation of alkoxy- and halo-pyridines gains entry to all four isomeric [3.3.1]-bicyclic targets. Regioselective and sequential oxidative cleavage of dicyclopentadiene generates a related [3.2.1]-bicyclic analog.