The Synthesis of 3,4-Benzpyrene-5-C'4 and

The introduction of the tracer technic as a new tool for the elucidation of the metabolism of can cinogens has provided an impetus for reinvestiga tions and new researches in this field. The first compound to be so used was 1,2,5,6-dibenzan thracene-9,10-C'4(6), and considerable work has been devoted to a study of its metabolism (7—10, 17). Shortly thereafter, 20-methylcholanthrene 11-C'4 was synthesized (2), and its distribution in the mouse was investigated (3). 3,4-Benzpyrene is an extremely powerful and rapidly acting can cinogenie hydrocarbon, and its chemical and bio logical properties, especially its metabolic behav ior, have been investigated very thoroughly. These studies depended on changes observed in the fluorescence and ultraviolet spectra during the course of metabolism. We decided to label this compound with radioactive carbon in order to provide a more critical test of the advantages of the tracer technic oven optical methods than has been obtained with the other compounds thus far studied, because of the considerable body of infor mation already available about the metabolism of benzpyrene. Another interesting carcinogen, 2-acetylamino fluorene, has been labeled by Ray and Geiser (16), and its metabolism is being investigated by Morris and the Weisburgers (15). Because of the relatively low specific activity of the 2-acetylaininofluorene 9-C'4 prepared by Ray and Geisen, it seemed im portant to us to undertake the preparation of the compound with considerably higher specific ac tivity, so that certain projected metabolic expeni ments might be undertaken. The synthetic scheme of Ray and Geisen (16) was followed, but the im provement in yield in several of the steps was so significant that we are prompted to report the re sults of our synthesis at the present time.