beta-carbolinedione derivatives as topoisomerase I inhibitors

Pyrrolo[3,4-c]-beta-carbolinedione dimers 5-14 were synthesized from furo[3 ,4-c]-beta-carbolinediones and diamines by solvent-free TaCl5/silica cataly zed reaction under microwave irradiation. The inhibitory property of these target compounds, the starting materials 2, 31, 32, and the N-alkylated pyr rolo[3,4-c]-beta-carbolinediones 16, 17, 20-30 was tested against the relax ation of supercoiled pRB322 DNA by calf thymus topoisomerases I and II. Som e of these compounds, especially 7 and 23 proved to be selective inhibitors of topoisomerase I.