Rigidified acetylcholine mimics: conformational requirements for binding to neuronal nicotinic receptors

Rigidified derivatives have been designed and synthesized assuming the g+t conformer of acetylcholine (N–C–C–O=+60°, C–C–O–C=180°) as active conformation for binding to cytisine sensitive neuronal nicotinic receptors. The SAR of the compounds evaluated, along with those of more flexible analogues, support the g+t conformer hypothesis and highlight the stringent steric limitation of this nicotinic receptor sub-type. Compound 3e has low μM affinity for cytisine sensitive nicotinic receptor binding sites while being selective with regard to the α-bungarotoxin sensitive subclass. We also report few compounds with μM affinity for the α-bungarotoxin sensitive subclass.