title: Free radicals in quinone containing antitumor agents. The nature of the diaziquone (3,6,-diaziridinyl-2,5-bis(carboethoxyamino)-1,4-benzoquinone) free radical.
abstract: The enzymatically generated free radical of the antitumor agent diaziquone is analyzed with the help of two analogs where either the aziridine rings (RQ14) or the carboethoxyamino groups (RQ2) were substituted by chlorine atoms. The hyperfine couplings observed in the diaziquone free radical are due to the nitrogens in the aziridine group. Unresolved coupling and hindered rotation contribute to line broadening. We find that diaziquone free radicals are more stable than RQ14 but less stable than RQ2 free radicals. The reason for this is that the carboethoxyamino groups make the aromatic ring unstable, while the aziridines contribute to its stability. The free radical observed in diaziquone is in all probability that of the parent compound and not that of an intermediate metabolite.
mesh_terms: D000970:Antineoplastic Agents; D001388:Aziridines; D001389:Azirines; D016227:Benzoquinones; D001711:Biotransformation; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D007700:Kinetics; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D001388:Aziridines; D001389:Azirines; D016227:Benzoquinones; D005609:Free Radicals; D009251:NADPH-Ferrihemoprotein Reductase; C029108:diaziquone