60968-03-8Relevant academic research and scientific papers
Conformational Effects in the Hydrolyses of Benzo-Ring Diol Epoxides That Have Bay-Region Diol Groups
Sayer, J. M.,Whalen, D. L.,Friedman, S. L.,Paik, A.,Yagi, H.,et al.
, p. 226 - 233 (1984)
Kinetics of the hydronium ion catalyzed(KH) and pH-independent (k0) hydrolyses of several benzo-ring diol epoxides, derived from polycyclic aromatic hydrocarbons, that possess bay-region trans diol groups have been investigated in 1:9 dioxane-water at 25 deg C.These epoxides are 1,2,3,4-tetrahydrobenzanthracene-1,2-diol 3,4-epoxide, 1,2,3,4-tetrahydrotriphenylene-1,2-diol 3,4-epoxide, and 9,10,11,12-tetrahydrobenzopyrene-9,10-diol 11,12-epoxide.Both possible diastereomers of the diol epoxides in which the two hydroxyl groups are trans to each other were investigated: isomer 1, in which the benzylic hydroxyl group is cis to the epoxide oxigen, and isomer 2, in which this hydroxyl group and the epoxide oxygen are trans.The corresponding tetrahydro epoxides that lack a diol group were also investigated.For comparison, isomers 1 and 2 of 1,2,3,4-tetrahydrobenzanthracene-3,4-diol 1,2-epoxide, a bay-region epoxide with a non-bay-region trans diol group, and the corresponding benzanthracene tetrahydro epoxide were also studied.The most striking feature of the reactions of the diol epoxides that possess a bay-region diol group is a reversal of the relative reactivity of isomers 1 and 2 in the k0 reaction, when compared with diol epoxides whose diol group is not in a bay region.This reversal of reactivity, which causes k0 to be larger for isomer 2 than for isomer 1 when the diol is in a bay region, is explained by changes in conformational equilibria involving the cyclohexene ring due to steric crowding of the bay-region diol.Preference of this diol group for a pseudodiaxial conformation favors a conformation of isomer 2 which the benzylic C-O bond of the epoxide is more or less aligned with the ? orbitals of the aromatic system and strongly disfavors this aligned conformation of isomer 1.Reaction via the k0 process is faster for the aligned than for the nonaligned conformer; thus for epoxides with bay-region diol groups, k0 for isomer 2 is faster than k0 for isomer 1.The pH-independent reaction of isomer 2 of 1,2,3,4-tetrahydrobenzanthracene-1,2-diol 3,4-epoxide via the aligned conformer gives, in addition to cis and trans tetraol products, substantial quantitites of a keto diol, whereas no keto diol was detected from the corresponding isomer 1.This also represents a reversal of the pattern of product formation generally observed with diol epoxides that lack a bay region in the vicinity of the diol group.Rate constants for hydronium ion catalyzed hydrolysis (kH) are much less sensitive to conformational factors than k0.The distribution of cis and trans tetraol products from hydronium ion catalyzed hydrolysis of the 1,2,3,4-tetrahydrobenzanthracene-1,2-diol 3,4-epoxides and the 1,2,3,4-tetrahydrotriphenylene-1,2-diol 3,4-epoxides can be explained by preferential pseudoaxial attack of water upon the benzylic cations formed from these epoxides.On the basis of these observations and previous findings with non-bay-region diol, bay-region epoxides, rules for predicting the effects of conformation on rates...
Synthesis and Absolute Configuration of the Bacterial cis-1,2-, cis-8,9-, and cis-10,11-Dihydrodiol Metabolites of Benzanthracene Formed by a Strain of Beijerinckia
Jerina, D. M.,Bladeren, P. J. van,Yagi, H.,Gibson, D. T.,Mahadevan, V.,et al.
, p. 3621 - 3628 (2007/10/02)
Metabolism of the environmental contaminant benzanthracene has been examined with the bacterium Beijerinckia B8/36.This organism is a mutant strain of the wild type, which lacks the ability to oxidize further initially formed cis-dihydrodiol metabolites of aromatic hydrocarbons.The main isolated metabolites of benzanthracene consist of the cis-1,2-, cis-8,9-, and cis-10,11-dihydrodiols in a ratio of 73:15:12, respectively.Synthesis of the dihydrodiols in optically pure form from precursors whose configurations were previously known or have been assigned in thepresent study has established that the metabolites are of very high enantiomeric purity and have 1R,2S, 8R,9S, and 10S,11R absolute configurations.In the course of these assignments, the (+)-isomer of 1,2-epoxy-1,2,3,4-tetrahydrobenzanthracene has been established to have 1R,2S absolute configuration, and a prior assignment of (-)-trans-(1R,2R)-1,2-dihydroxy-1,2-dihydrobenzanthracene has been confirmed.The chemical interrelationships of absolute configuration have been done in such a manner that the cis-1,2-, cis-8,9-, and cis-10,11-dihydrodiols formed by the bacterium are tied directly to structures which have been used to assign the corresponding trans-1,2-, trans-8,9-, and trans-10,11-dihydrodiols formed from benzanthracene in mammalian liver.
