The relative carcinogenic activities of a series of 5-methylchrysene derivatives.

The carcinogenicity of 1,11-dimethylchrysene (=5,7dimethylchrysene) and its 1,2,3,4-tetrahydro-, 3,4-dihydro-, and 1,2,3,4-tetrahydro-l-oxo derivatives was tested by mouse skin painting. Each mouse received 30 ¿/gof the chrysene on the dorsal skin twice weekly for one year, and the animals were observed for a second year. The 1-ketone was much more active than any of the hydrocarbons. Of the latter, the fully aromatic 1,11-di methylchrysene was fairly active, the 3,4-dihydro deriva tive was less so, while the 1,2,3,4-tetrahydro compound was a weak carcinogen. These results are discussed in connection with the carci nogenicity of the corresponding cyclopenta[a]phenanthrenes, which exhibit a similar structure-activity relation ship.