Synthesis, anti-inflammatory and analgesic activity evaluation of some mercapto pyrimidine and pyrimidobenzimidazole derivatives

4-Aminoantipyrine and 1,4-diaminobutane react with 4-isothiocyanato-4-methy lpentan-2-one to give condensation products 1 and 2 respectively. Condensat ion of p-nitroaniline with 4-isothiocyanatobutan-2-one gave thiourea deriva tive 3 however coupling with 4-methyl-2-nitroaniline and 4-methoxy-2-nitroa niline gave cyclized products 5 and 6. 3,4-Diaminobenzophenone on condensat ion with 4-isothiocyanato-4-methylpentan-2-one in the presence of THF gave product 7 whereas the same reaction using methanol as solvent gave a mixtur e of hydroxy and methoxy compounds i.e. 8 which on treatment with acid unde r reflux temp. of MeOH gave pyrimidobenzimidazole derivative 9 in good yiel ds. S-Methyl pyrimidobenzimidazole derivative 10 was obtained by treating 9 with methanol under strongly acidic conditions. Pyrimidobenzimidazole 9 on reaction with methyl bromoacetate and ethyl bromoacetate gave compounds 11 and 12 respectively. Anti-inflammatory activity was carried out at 100 mg /kg p.o. of compounds 1-3 and 5-12. Compounds 5, 6, 8 and 10 showed 11,18,2 5 and 22% activity respectively whereas all other compounds were found to b e inactive. Analgesic activity evaluation of 1, 2, 7-9 and 12 showed that c ompounds 2, 7 and 12 exhibited 50, 25 and 60% at 100 mg/kg p.o. and 50, 25 and 40% activity at 50 mg/kg p.o. respectively where as compounds 1, 8 and 9 were found to be inactive.