Synthesis and Anti Bacterial and Anti-ulcer Evaluation of New S-mannich Bases of 4,6-diaryl-3,4-dihydropyrimidin-2(1H)-thiones

The synthesis of title compounds were accomplished by synthetic sequence shown in Scheme 1. Chalcones on cyclocondensation with thiourea in ethanol and potassium hydroxide under reflux yielded the respective dihydropyramidin-2(1H)-thiones. Each of the dihydropyrimidin thiones was, then subjected to the Mannich condensation in alkaline medium using three different secondary amines, viz., dimethylamine, diethylamine and morpholine to obtain a new series of S-Mannich bases. All the synthesised compounds ($C_1-C_{15}$) were evaluated for their antiulcer and antibacterial activities. Compounds $C_4$, $C_5$, $C_6$, $C_{14}$ and $C_{15}$ exhibited relatively more potent antiulcer activity but not comparable to the standard; Omeprazole, while $C_1$, $C_2$, $C_3$ and $C_{13}$ were moderate in activity at 100 mg/kg p.o. All the compounds ($C_1-C_{15}$) showed mild to moderate activity against both Gram-positive (S.aureus, L.delbrueckii) and Gram-negative (P.vulgaris, E.coli) bacteria. Amongst the compounds tested, only $C_6$, $C_9$, $C_{12}$ and $C_{15}$ were found to be potent.