6, 11-Dihydro-pyrido [2, 3-b] phenazine-6, 11-diones and 6, 11-dihydro-benzo [2, 3-b] phenazine-6, 11-diones were synthesized from 6, 7-dichloro-5, 8-quinolinedione and 2, 3- dichloro-1, 4-naphthoquinone. The study on the cytotoxicity on these products revealed that the pyridophenazinediones, tetracyclic heteroquinone analogues with three nitrogen atoms exhibited a high cytotoxicity on several human tumor cell lines. Compound 9c and 9e ...