Synthesis and immunotropic activity of some 2-aminobenzimidazoles, Part 4.

2-Aminobenzimidazole reacted with selected esters of alpha, beta-unsaturated acids and alpha, beta-unsaturated ketones to form derivatives of 1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-2-ones, 1,4-dihydropyrimido[1,2-a]benzimidazoles, and 2-acetylaminobenzimidazole. 2-Cinnamoylaminobenzimidazole, 4-phenyl-1,2,3,4-tetrahydropyrimido[1,2,-a]benzimidazol-2-on e, 4-(benzimidazol-2-ylamino)-4-phenylbutan-2-one, and 4-methyl-2-phenyl-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole were tested for their potential activity in immunological assays in the mouse model. Compound 1, at a dose of 100 micrograms/mouse, significantly inhibited the humoral immune response and, at the same time, stimulated the cellular type of that response. The proliferative response of mouse splenocytes to concanavalin A was inhibited only at a higher dose (2 micrograms/ml). The immunotropic activity of 4, on the other hand, was uniformly strongly inhibitory in all applied tests. The suppressive activity of 4 was lower in the cellular immune response and proliferation tests than that of cyclosporin A.