Information concerning the influence of alkyl substitution on the carcinogenic properties of cholanthrene is available with respect to only three positions. 20-Methylcholanthrene, the only one of the twelve possible monomethyl Tsomers hitherto known, corresponds closely with the parent hydrocarbon in potency, while the 15, 20-and 16, 20-dimethyl homologs show diminished activity associated with the presence of the added substituent in the five- ...
