title: Absolute stereochemistry of the trans-dihydrodiols formed from benzo[a]anthracene by liver microsomes.
abstract: Through application of the exciton chirality method, absolute stereochemistry has been assigned to the (+)-and (-)-enantiomers of four of the five metabolically possible trans-dihydrodiols of the polycyclic hydrocarbon benzo[a]anthracene (BA). The (+)- and (-)-enantiomers of each of these dihydrodiols can be separated as their diastereomeric bis-esters with (-)-alpha-methoxy-alpha-trifluoromethylphenylacetic acid by high pressure liquid chromatography (HPLC). BA 3,4-, 5,6-, 8,9- and 10,11-dihydrodiol are formed in 38%, 36%, 78% and 66% enantiometric purity, respectively, by liver microsomes from phenobarbital-treated rats, whereas the liver microsomes from 3-methylcholanthrene(MC)-treated rats form BA 5,6-, 8,9- and 10,11-dihydrodiols with higher optical purity (62%, 96% and 96%, respectively). BA 3,4-dihydrodiol is formed from (+/-)-BA 3,4-oxide by microsomal epoxide hydrase in very high enantiometric purity (78%). The major enantiomer of the BA dihydrodiols formed by liver enzymes has R,R absolute stereochemistry in each case. In parallel with previous studies on the metabolism of benzo[a]pyrene, the more tumorigenic (-)-enantiomer is the predominant isomer of BA 3,4-dihydrodiol formed by liver microsomes from BA.
mesh_terms: D000818:Animals; D001551:Benz(a)Anthracenes / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004851:Epoxide Hydrolases / Q000378:metabolism; D004852:Epoxy Compounds / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D051381:Rats; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D001551:Benz(a)Anthracenes; D004852:Epoxy Compounds; D004851:Epoxide Hydrolases