Dale L. Whalen

Effects of pH and salt concentration on the hydrolysis of a benzo[a]pyrene 7,8-diol-9,10-epoxide catalyzed by DNA and polyadenylic acid

The time-dependent absorbance change that occurs when benzo[alpha]pyrene 7,8-diol-9,10-epoxide is added to solutions of calf thymus DNA has been shown, by an unequivocal chromatographic method, to correspond to DNA-catalyzed hydrolysis of the diol-epoxide. At 25 degrees C and mu = 0.10, the kinetics of the reaction of the diol-epoxide with polyadenylic acid or DNA are consistent with preequilibrium formation of a non-covalent complex between the diol-epoxide and the polynucleotide or DNA, followed by hydrolysis of the bound epoxide by a process that is first-order in hydronium ions. Cacodylic acid also catalyzes the hydrolysis of the epoxide bound to polyadenylic acid. The rate of the DNA-catalyzed hydrolysis exhibits little or no enantiomeric selectivity for the diol-epoxide. DNA catalyzed hydrolysis of the diol-epoxide is extraordinarily sensitive to the salt concentration in the reaction medium: the rate of hydrolysis of the bound epoxide at pH 7 is retarded by a factor of approximately 45 in the presence of 0.1 M sodium chloride compared to a 1 mM buffer containing no added salt. Thus, studies of the interactions of DNA with carcinogenic diol-epoxides must take into account the ionic environment of DNA within the cell.

Conformational effects in the hydrolyses of benzo-ring diol epoxides that have bay-region diol groups

Etude realisee sur des diol epoxydes des benzo [a] anthracene, triphenylene et benzo [e] pyrene dans lesquels les equilibres entre les conformations alignees et non alignees sont modifies par la localisation du groupe diol dans une region baie de la molecule

Internal Hydrogen Bond Formation in a syn-Hydroxyepoxide

The existence of an internal hydrogen bond in a compound representative of a syn diol epoxide (a possible intermediate in chemical carcinogenesis by certain polycyclic aromatic hydrocarbons) has been demonstrated by x-ray crystallographic and nuclear magnetic resonance studies. This internal hydrogen bond was found in 3,4-epoxy-2-methyl-1,2,3,4-tetrahydro-1-naphthol and was shown to persist in dioxane-water solutions containing up to 80 mole percent water. In this structure, the 1-hydroxy and 2-methyl groups are shown to occupy axial positions. In the anti diol epoxide, which has no internal hydrogen bond, analogous groups are equatorial. Crystals of the compound were unstable in the x-ray beam while the data were being collected (even at low temperatures), presumably as a result of decomposition.

Hydrogen bonding incis-2,3-epoxycyclooctanol

Hydrogen bonding and the electron-withdrawing or electron-donating characteristics of substituent groups that are neighboring to epoxide groups can affect the reactivity of the epoxide ring. The crystal structure ofcis-2,3-epoxycyclooctanol has been determined as a saturated eight-membered ring compound in which a hydroxyl group is attached to the C(1) atom that is adjacent to a 2,3-fused epoxy ring. The findings are that the longer epoxide C-O bond (and hence the one expected to be more readily broken) is the one farther from the hydroxyl group [1.462(1) å versus 1.447(1) å] and that the optimal hydrogen bonding is to an adjacent molecule radier than within the molecule. The shortest C-C bond is that of the epoxide group; the bond adjacent to it (on the side farther from the hydroxyl group) is the next shortest.

Mechanism of the “spontaneous” reaction of p-methoxystyrene oxide in aqueous solution

An 1H NMR study of the spontaneous reaction of p-methoxy-trans-β-deutereostyrene oxide and its cis-β-deutereo isomer has provided evidence that the trans-β-D and cis-β-D have equal migrating aptitudes in the aldehyde-forming reaction.

Mechanisms of Solution Reactions of Cyclo-Penta[cd]Pyrene Oxide and Acenaphthylene Oxide

Abstract Rates and products of the acid-catalyzed and spontaneous reactions of cyclopenta[cd]pyrene oxide (2) and acenaphthalene oxide (3) in 1:3 dioxane-water and water, respectively, have been determined. Both 2 and 3 undergo acid-catalyzed hydrolyses to yield cis diol as the major product, and undergo spontaneous reactions to yield predominantly ketone products. The mechanisms of these reactions are discussed.

Quantitative Aspects of the Effects of Halide and Azide Ions on the Acid-Catalyzed Hydrolysis of (±)-7β,8α-Dihydroxy-9α,10α-Epoxy-7,8,9,10-Tetrahydrobenzo[a]Pyrene

Abstract Mechanisms of the acid-catalyzed reactions of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (1) in 1:9 dioxane-water solutions containing varying concentrations of KCl, KBr, NaI, NaN3 and NaClO4 are discussed.

Ring pucker in dihydroaromatic epoxides: The molecular structure ofr-1-hydroxy-t-2-methyl-t,t-3,4-epoxy-1,2,3,4-tetrahydronaphthalene

The crystal structure of the derivative of tetrahydronaphthalene with substituent epoxy, hydroxyl, and methyl groups in the more saturated ring (r-1-hydroxy-t-2-methyl-t,t-3,4-epoxy-1,2,3,4-tetrahydronaphthalene) has been determined. The hydroxyl and methyl groups are both found to beequatorial. The crystal structure is characterized by chains of molecules linked by O-H ⋯ O hydrogen bonds involving the hydroxyl groups; these hydrogen bonds lie approximately parallel to theb axis. The conformations of the epoxide-bearing rings in various hydroxy epoxides are compared and shown to be similar.