Polycyclic aromatic hydrocarbons stereoselectivity

Stereoselective Metabolism and Activations of Polycyclic Aromatic Hydrocarbons... 

Figure 7. Steric model proposed by Jerina, et al. for the catalytic binding site of cytochrome P-450c (P-448) to account for the stereoselective metabolism of polycyclic aromatic hydrocarbons (48). The boundary should be enlarged in the directions shown to accommodate substrates whose mechanism of stereoselective oxygenation does not fit the steric model originally proposed.

The microsomal epoxide hydrolases (microsomal EH, mEH), predominantly found in the endoplasmic reticulum, regio- and stereoselectively catalyze the hydration of both alkene and arene oxides, including oxides of polycyclic aromatic hydrocarbons. These enzymes have been purified to homogeneity from various species and tissues [22] [41 - 46], The human microsomal EH contains 455 amino acids (Mr 52.5 kDa) and is the product of the EPHX1 gene [47] (also known as HYL1 [48]). 

M. Shou, F. J. Gonzalez, H. V. Gelboin, Stereoselective Epoxidation and Hydration at the K-Region of Polycyclic Aromatic Hydrocarbons by cDNA-Expressed Cytochromes P450 1A1, 1A2, and Epoxide Hydrolase , Biochemistry 1996, 35, 15807 - 15813. 

S. K. Yang, M. Mushtaq, P. L. Chiu, Stereoselective Metabolism and Activation of Polycyclic Aromatic Hydrocarbons , in Polycyclic Hydrocarbons and Carcinogenesis , Ed. R. G. Harvey, American Chemical Society, Washington, 1985, p. 19 - 34. 

Even the 1,2-dihydrodiol derivatives of polycyclic aromatic hydrocarbons are converted to the corresponding epoxydiols with MCPBA. The reaction is stereoselective only in some cases. The trans-dihydrodiols (6) give the antiepoxide (7), whereas the cfs-dihydrodiols (8) give a mixture of anti- (9) and syn-epoxy compounds (10). The anti- and syn-diol epoxides of benz[a]anthracene and benzo[a]pyrene have been prepared by this method.10... 

Yang, S. K. (1988). Stereoselectivity of Cytochrome P-450 Isozymes and Epoxide Hydrolase in the Metabolism of Polycyclic Aromatic Hydrocarbons, Biochetn. Pharmacol, 37 61-70. 

Yang SK. 1988. Stereoselectivity of cytochrome P-450 isozymes and epoxide hydrolase in the metabolism of polycyclic aromatic hydrocarbons. Biochem Pharmacol 37(1) 61-70. 

Polycyclic aromatic hydrocarbons are also known to undergo ort/zo-photocycloaddi-tions.805 For example, the reaction of the chrysene derivative 204 with the electron-deficient methyl cinnamate 205 affords the adduct 206 as the major product (Scheme 6.82).821 The high stereoselectivity observed has been explained by the formation of an electronically favourable sandwich-type singlet exciplex 207. 

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