(R)-3′-(3-methylbenzo[b]thiophen-5-yl)spiro[1-azabicyclo[2,2,2]octane-3,5′-oxazolidin]-2′-one, a novel and potent α7 nicotinic acetylcholine receptor partial agonist displays cognitive enhancing properties

Recent studies have suggested that the alpha 7 nicotinic acetylcholine receptors play important roles in learning and memory. Herein, we describe our research of the structure-activity relationships (SAR) in a series of (S)-spiro[1-azabicyclo[2.2.2]octane-3,5'-oxazolidin]-2'-ones bearing various bicyclic moieties to discover novel alpha 7 receptor agonists. Through a number of SAR studies on the series, we have found out that inhibition of CYP 2D6 isozyme, which was a primary obstacle for the previously identified compound, was avoidable by the introduction of bicyclic moieties. Chemical optimization of the series led to the identification of a novel and potent alpha 7 nicotinic acetylcholine receptor partial agonist 23. This compound not only possessed high binding affinity (K-i) 3 nmol/L) toward the alpha 7 receptor but also showed agonistic activity even at a concentration of 0.1 mu mol/L. In addition, compound 23 improved cognition in several rat models, which might suggest the potential of the alpha 7 receptor partial agonist for the treatment of neurological disorders including cognitive dysfunction.