A novel class of imidazo [1, 2-a] pyridines as melatonin receptor ligands is designed and synthesized. The affinities of 3-(6-methoxy-2-phenylimidazo [1, 2-a] pyridine-3-yl)-N-methyl- propionamide 8, N-[2-(6-methoxy-2-phenylimidazo [1, 2-a] pyridine-3-yl)-ethyl]-acetamide 13 and N-(1-hydroxy-3-(5-methoxy-2-phenyl-1H-indol-3-yl) propan-2-yl) acetamide 18 are evaluated for binding on melatonin receptors. Compound 8 present good selectivity for ...