Methylated Polycyclic Aromatic Hydrocarbons Research Articles

2,9-Dimethylpicene: Synthesis, Mutagenic Activity, and Identification in Natural Samples

Abstract 2,9-Dimethylpicene (2,9-DMPic) has been conveniently synthesized via a new route involving oxidative photocyclization of suitable substituted diarylethylenes and has been characterized by high-resolution 400-MHz 1H-NMR spectroscopy. Furthermore, 2,9-DMPic exhibits a typical line narrowed emission spectrum in n-decane matrix frozen at 15 K (Shpol'skii effect). Its unambiguous identification in a natural sample has been performed by this technique, providing strong evidence for the formation of this compound through aromatization of triterpenoid natural precursors. The mutagenicity of this naturally occurring methylated polycyclic aromatic hydrocarbon (PAH) has been examined in six his − strains of Salmonella typhimurium (TA 97, TA 98, TA 100, TA 102, TA 104, TA 1537) in the presence of a hepatic xenobiotic-metabolizing system. While carcinogenic PAH, used as positive controls, showed potent effects in this system, 2,9-DMPic proved completely inactive.

Chemical reactivities and mutagenicities of a series of chloromethylbenzo[ a]pyrenes

The chemical and mutagenic properties of a series of chloromethylbenzo[ a]pyrenes (chloromethyl-BaP) (chloromethyl groups in position 1-, 4-, 5-, 6-, 10-, 11- or 12-) were studied in order to address the question of the importance of arylmethyl carbocations as possible ultimate carcinogens of methylated polycyclic aromatic hydrocarbons (PAH). The rates of solvolysis of the series of chloromethyl-BaP in 50% aqueous acetone decrease in the order: 6 > 1 ⪢ 4 > 12 > 5 > 10 > 11. There is a rough correlation ( r = −0.80, P < 0.05) between rates of solvolysis and the carbon chemical shifts of the methylene carbons. There is a good correlation ( r = 0.98, P < 0.001) between the rates of solvolysis and the gas phase stabilities of the carbocations, (M + − 35), obtained from mass spectral analysis. The mutagenicities of the series of chloromethyl-BaP in the Ames assay with strains TA98 and TA100 showed strong to very strong mutagenicities for the 4-, 5-, 10-, 11- and 12-isomers and weak mutagenicities for the 1- and 6-isomers. The corresponding hydroxymethyl-BaP were not mutagenic. The mutagenicities of some of the chloromethyl-BaP are among the highest reported for direct-acting (not requiring microsomal activation) mutagens in the Ames assay.

Quantitative structure-carcinogenic activity relationship of methyl, alkyl, cyclopentano, cyclohexano polycyclic aromatic hydrocarbons and cholanthrene series.

By applying the di-region theory, in this paper, the quantitative structure-carcinogenic activity relationship of methyl, alkyl, cyclopentano, cyclohexano polycyclic aromatic hydrocarbons (PAH) and cholanthrene series totalling 187 alkyl-substituted PAH compounds is established reasonably and systematically for the first time. The consistent ratio between calculation and experiment is more than 95%. In the metabolic course of methyl PAH, which one is the so-called "ultimate carcinogen", the bay-region carbonium ion situated on the angular ring or methylene carbonium ion produced from the methyl group, is still in dispute at present. Now, the afore-mentioned disputable viewpoints have been successfully integrated by the di-region theory.

Alkyl Aromatic Synthesis: Nucleophilic Alkyl Lithium Addition

Abstract Alkylated and, in particular, methylated polycyclic aromatic hydrocarbons and heteroaromatic compounds associated with increased coal utilization may be considerably more carcinogenic than the corresponding parent system.1,2 The availability of these alkylated compounds as standards for structural comparison or for biological testing is therefore of some importance. The report describes improvements on methodology for the synthesis of alkyl aromatic compounds by using a nucleophilic addition of an alkyl lithium (often enhanced by UV irradiation)3–11 in combination with the subsequent addition of iodine to conveniently regenerate the aromatic system (Scheme I, Table I).