Synthesis of novel 2-nitroimidazole-tethered tricyclic quinolines, bearing a second heteroatom, and their in vitro evaluation as hypoxia-selective cytotoxins and radiosensitizers

Two novel nitroimidazole-based bioreductive compounds, 10-[3-(2-nitroimidazolyl)-propylamino]-3,4-dihydro-1H-thiopyrano[4,3-b]quinoline hydrochloride (8a) and 10-[3-(2-nitroimidazolyl)propylamino]-2-methyl-1,2,3,4-tetrahydro-benzo[b]-1,6-naphthyridine hydrochloride (8b) have been synthesized and evaluated in V79 cells as hypoxia-selective cytotoxins and radiosensitizers that target DNA through weak intercalation. Both compounds were relatively good radiosensitizers (C1.6 values of 40.0±0.8 and 59.0±0.4 μM for 8a and 8b, respectively) but neither of the compounds was superior to 2 which does not carry a second heteroatom in the DNA-intercalating chromophore.