Regioselective synthesis of pyrazolo[4,5-g]pyrido[1,2-a]benzimidazoles: cytotoxic derivatives of pyrido[1,2-a]benzimidazolic ring system

N-1 and N-2 substituted pyrazolo[4,5-g]pyrido[1,2-a]benzimidazoles were prepared regioselectively, and cytotoxicities evaluated in vitro against K562 and HL60 cells. All compounds displayed weaker activity than doxorubicin against sensitive lines, but showed the same activity against resistant cell lines (multidrug resistance+, (MDR+); K562R and HL60R) indicating no resistance phenomena.