Synthesis and antiproliferative activity in vitro of new 2-aminobenzimidazole derivatives. Part 2 [1]

A series of 2-methylpyrimido[1,2-a]benzimidazole derivatives has been synthesized in the reactions of 2-aminobenzimidazole (1) with selected halogeno β-diketones: 1,1,1-trifluoro- 2, 1-chloro-1,1-difluoro- 3, 3-chloro-2,4-pentadione- 4 and with 4-fluorobenzoylacetone 5. 2-Aminobenzimidazole (1) in the reactions with α-chloro- and α-bromocinnamaldehyde gave Schiff bases 10 and 11 which have been subjected to reduction using NaBH₄ and 3-benzylideno-1,2-dihydro- (12) and 3-benzylideno-1,2,9,10-tetrahydroimidazo[1,2-a]benzimidazole (13) were obtained. The structures 2-13 were identified by the results of elemental analysis and their IR, ¹H NMR and MS spectra. Compounds 2-13 were examined for their antiproliferative activity in vitro against the cells of 3 human cancer cell lines, using SRB (sulphorhodamine B) or MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) technique. Four out of all tested compounds revealed cytotoxic activity in vitro.