Synthesis and cytotoxic activities of a new benzo[c]phenanthridine alkaloid, 7-hydroxynitidine, and some 9-oxygenated benzo[c]phenanthridine derivatives

[formula: see text] A new benzo[c]phenanthridine alkaloid, 7-hydroxynitidine, was synthesized by a novel synthetic procedure. The cytotoxic activity of this compound against HeLa S3 cells was strong, but not greater than those of its mother compounds, nitidine and NK109. We also synthesized other 9-oxygenated benzo[c]phenanthridine alkaloids, 7-methoxynitidine, 9-demethylnitidine, nitidine, and fagaronine, and tested their cytotoxic activities. These results suggest that the 7-hydroxy group enhances antitumor activity and an 8- or 9-hydroxy group weakens this activity.