wide spectrum of 5-aminomethylene barbituric/ thiobarbituric acidderivatives was synthesized and evaluated for their Jack bean urease inhibitory activity. Methods: Among the synthesized compounds, 5-cyclohexylaminomethylene barbituricacid (3a) showed the most potent activity (IC50 = 25.8 µM), 4 times more potent than hydroxyurea (IC50 = 100.0 µM) and a similar activity to thiourea (IC50 = 22.0 µM), both