Anti-inflammatory, analgesic and antiamoebic activity evaluation of pyrimido[1,6-a]benzimidazole derivatives synthesized by the reaction of ketoisothiocyanates with mono and diamines.

(UN) substituted o-phenylenediamines 1a-g reacted with 3-isothiocyanatobutanal to give pyrimidobenzimidazole derivatives, 2a-g, respectively. Products 4, 6 and 8, 10 were obtained by condensation of 3-isothiocyanatobutanal with 2,3-diaminopyridine, 1,4-diaminobutane and 3-isothiocyanatopropanal with 4,5-dimethyl-1,2-phenylenediamine, o-nitroaniline, respectively. S-Methylation of 2f and 11b gave products 12a and 12b, respectively. Anti-inflammatory and analgesic activity evaluations of 2a-g and 12b were carried out at 50 mg kg(-1) p.o. Compound 2c exhibited good anti-inflammatory (46%) and mild analgesic activity (50%). Antiamoebic activity evaluations (using microdilution method) of 2a-g against Entamoeba-histolytica (strain HM1: IMSS) were carried out and compounds 2a, 2b, 2d and 2g exhibited good antiamoebic activity in vitro.