Convenient synthesis of indeno[1,2-c]isoquinolines as constrained forms of 3-arylisoquinolines and docking study of a topoisomerase I inhibitor into DNA–topoisomerase I complex

11-Hydroxyindeno[1,2-c]isoquinolines 12a–c were prepared as constrained forms of 3-arylisoquinolines through an intramolecular cyclization reaction. Among the synthesized compounds, the 11-ibutoxy analog 15l displayed potent in vitro cytotoxicity against four different tumor cell lines as well as topoisomerase 1 inhibitory activity. A FlexX docking study was performed to explain the topoisomerase 1 activity of 15l.