Design, synthesis and cholinesterase inhibitory activity of novel spiropyrrolidine tethered imidazole heterocyclic hybrids

Active site of hAChE showing the docked compounds, (6f) and (6i) in the binding pocket of enzyme. [Display omitted] A small library of structurally fascinating spiropyrrolidine tethered imidazole heterocylic hybrids has been synthesized regioselectively in good yields employing [bmim]Br mediated 1,3-diplar cycloaddition strategy. The new class of azomethine ylide generated in situ from l-histidine and 11H-indeno[1,2-b]quinoxalin-11-one reacts with various substituted β-nitrostyrenes affording the spiropyrrolidine tethered imidazole heterocylic hybrids. Compounds thus synthesized were assessed for their in vitro cholinesterase (ChEs) inhibitory activities, among them compounds possessing 4-methyl and 4-methoxy substituents on the aryl ring showed potent activities with IC50 values of 2.02 ± 0.05 and 2.05 ± 0.06 μM against AChE and 12.40 ± 0.14 and 11.45 ± 0.28 μM against BChE enzyme, respectively. In addition, the most active compounds were performed for their molecular docking simulation and the results revealed interesting binding templates to the active site channel of cholinesterase enzymes.