Schiff bases 2–6 obtained from 2-aminobenzimidazole 1 with p-(N,N-diethylamino)-, p-chloro-, p-bromo-, 2,4-dimethoxy-, and 3,4-dimethoxybenzaldehyde were subjected to the reaction with 1,3-ketoester: methyl-, ethyl-, benzyl-, and t-butylacetoacetate to form derivatives of pyrimido[1,2-a]benzimidazole 7–23. 1H NMR spectra recorded for the compounds 20–23 in DMSO solution indicate the presence of two conformational forms. Compounds 2, 7–23 were examined for their antiproliferative activity in vitro against the cells of human lung cancer cell lines A549.
A series of pyrimido[1,2-a]benzimidazole derivatives has been synthesized in the reactions of 2-aminobenzimidazole Schiff bases 1-6 with selected _-diketones; acetylacetone 7-12 or benzoylacetone 13-18. The structures 4, 7-18 were confirmed by the results of elemental analysis and their IR, 1H NMR and MS spectra. Compounds 4, 7-18 were examined for their antiproliferative activityin vitro against 3 cancer cell lines: P338 (mice leukemia), A549 (non-small cell lung carcinoma), SW707 (rectal adenocarcinoma), using SRB (sulphorhodamine B) or MTT (3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl tetrazolium bromide) technique. The Schiff base 4 and tricyclic derivatives 9, 14, 16 exhibited the highest cytotoxic activity in vitro.
A series of 2-methylpyrimido[1,2-a]benzimidazole derivatives has been synthesized in the reactions of 2-aminobenzimidazole (1) with selected halogeno _-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 _-chloro- and _- 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.
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