14C labeled benzo [rst] pentaphene ( V ) known as 3 , 4 , 9,IO-dibenzpyrene, 14C labeled benzo [rst] pentaphene-5,8-diol, diacetate ( V I ) and l4C labeled benzo [rst] pentaphene-5,8-dione ( I V ) have been synthesized jor the study of the distribution, Ihe metabolic ,fate and the mode of action of the carcinogenic hydrocarbon dibenzpyrene, which appears to difSer from other known carcinogens with regard to these factors[l, 21.
Benzo [rst] pentaphene (3, 4, 9, 10-dibenzpyrene) when injected subcutaneously in mice has been found not to be excreted in urine or feces [l, 21. These results have been obtained by the use of the ultraviolet absorption technique. In order to confirm these data and to show that not even trace amounts of the carcinogen are excreted or metabolized, benzo [rst] pentaphene-5,1 5-14C was synthesized. The results of the biological experiments obtained will be reported elsewhere. l'he labeled carcinogen and its oxidation products (1V and VI) are also being used for the study of the mechanism of carcinogenesis of DP and for the study of the possible metabolism of DP by TPNH-dependent inductive hydroxylases in liver and the gastro-intestinal tract [3].
The synthesis of DPJ4C involved eight steps and started with the commercially available phthalic anh~dride-7;~C as source of radioactivity. Cotldensation with benzene gave o-benzoyl benzoic acid [4] ("C equally distributed between carbonyl and carboxylic carbons). Ring closure yielded anthra-quin0ne-9,1~C [ 5 ] . The latter substance was partially reduced with copper to *