Synthesis of conformationally constrained spirodihydrofuropyridine analogues of epibatidine

Conformationally constrained spirofuropyridine analogues of epibatidine, syn-2 and anti-2, in which the 7-azabicyclo[2.2.1]heptane system and the 2-chloropyridine ring are held rigidly with the shorter and longer N–N distances, respectively, were synthesized from N-Boc-7-azabicyclo[2.2.1]heptan-2-one. The preliminary binding studies suggested that syn-2 has stronger binding affinity for nAChRs than anti-2.