Synthesis and antitumor activity of fused quinoline derivatives. V. Methylindolo[3,2-b]quinolines

Indolo[3,2-b]quinoline derivatives (1b-i) with a methyl group at each possible position have been synthesized. The 1-methyl (1b) and 9-methyl (1i) derivatives were inactive, but the 3-methyl (1d), 4-methyl (1e), and 6-methyl (1f) derivatives exhibited high treatment/control (T/C) value and cure rates against leukemia P388 in mice. These results indicated that modification of indolo[3,2-b]quinoline derivatives at 3, 4, and 6 positions may be useful approach for lead optimization.