Crystal Correlation Of Heterocyclic Imidazo[1,2-a]pyridine Analogues and Their Anticholinesterase Potential Evaluation

Imidazo[1,2-a]pyridine-based compounds are clinically important to the treatments of heart and circulatory failures, while many are under development for pharmaceutical uses. In this study, a series of imidazo[1,2-a]pyridine-based derivatives 2(a-o) were synthesized by reacting a-haloketones with 2-aminopyridines in a basic media at ambient temperature. Single crystal X-ray diffraction studies suggest that with low degree-of-freedom, the introduction of bulky adamantyl or electron-rich biphenyl moiety into the imidazopyridine derivatives will not affect its structural occupancy. Imidazo[1,2-a]pyridine-based derivatives with biphenyl side chain are potential AChE inhibitors. Compound 2h which bears a biphenyl side chain and methyl substituent at the position R4 of the imidazo[1,2-a]pyridine ring showed the strongest AChE inhibition with an IC50 value of 79 µM. However, imidazo[1,2-a]pyridine derivatives with phenyl side chain exhibit better BChE inhibition effect among the series. Compound 2j with 3,4-dichlorophenyl side chain and unsubstituted imidazo[1,2-a]pyridine ring appears to be the strongest BChE inhibitor with an IC50 value of 65 µM and good selectivity. The inhibitory effects of active compounds were further confirmed by computational molecular docking studies. The results unveiled that peripheral anionic sites of AChE and acyl pocket of BChE were the predominated binding sites for the subjected inhibitors.