A Metabolic Activation Mechanism of 7 H -Dibenzo[ c,g ]carbazole Via o -Quinone. Part 1: Synthesis of 7 H -Dibenzo[ c,g ]carbazole-3,4-dione and Reactions with Nucleophiles

7 H -Dibenzo[ c,g ]carbazole (DBC) is a potent carcinogen present in the environment. The metabolic activation pathway of DBC has not been completely understood. The formation of the DBC- o -quinone was proposed and the novel DBC-3,4-dione was chemically synthesized from 4-OH- or 3-OH-DBC, using the Fremy's salt at room temperature. The DBC-3,4-dione was found to react readily with model nucleophile, 2-mercaptoethanol, to afford 1-(2'-hydroxyethylthio)-DBC-3,4-dione through 1,4-Michael addition. An adduct of DBC-3,4-dione with adenine was obtained; adducts formed with other DNA bases and nucleosides were partially characterized and are under further analysis. Under the same conditions, DBC-3,4-dione with guanine did not yield an adduct. These results are encouraging for further studies on DNA binding of DBC through 3,4-dione in vitro and in vivo.