Synthesis and cytotoxic activity of acronycine analogues in the benzo[c]pyrano[3,2-h]acridin-7-one and naphtho[1,2-b][1,7] and [1,10]-phenanthrolin-7(14H)-one series

Condensation of 1-bromo-2-naphthalenecarboxylic acid (9) with 7-methoxy-2,2-dimethyl-2H-1-benzopyran-5-ylamine (13) followed by acid-mediated cyclization afforded 6-methoxy-3,3-dimethyl-3,14-dihydro-7H-benzoc]pyrano3,2-h]acridin-7-one (15), which was further methylated into 6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzoc]pyrano3,2-h]acridin-7-one (benzoc]acronycine) (3) and 6,7-dimethoxy-3,3-dimethyl-3H-benzoc]pyrano3,2-h]acridine (4). Osmium tetroxide oxidation of 15 gave the (+/-)-cis-diol 16, which afforded the benzopyranoacridine and benzopyranoacridone esters 17-22 upon acylation. Condensation of 9 with suitable aminoquinolines 23-25 afforded the carboxylic naphthylquinolylamines 26-28. Cyclization gave the corresponding naphtho1,2-b]1,10]-phenanthrolin-7(14H)-ones 29 and 30, and naphtho1,2-b]1,7]-phenanthrolin-7(14H)-one 31, which were subsequently N-methylated to the desired 14-methylnaphtho1,2-b]1,10] and 1,7]-phenanthrolinones 6, 7, and 8. Benzoc]pyrano3,2-h]acridin-7-one derivatives 3, 16, and 22 displayed cytotoxic activities within the same range of magnitude as acronycine itself, whereas 7-alkoxybenzoc]pyrano3,2-h]acridine and 7-acyloxybenzoc]pyrano3,2-h]acridine derivatives 4 and 17-21 were less active when tested against L1210 murine leukemia cells in vitro. Naphthophenanthrolinones 6-8 were devoid of significant antiproliferative activity, but compounds 29-31 bearing no substituent on the nitrogen atom at position 14 were more potent.