Diol epoxides types

A novel formal inverse-electron-demand hetero-Diels-Alder reaction between 2-aryl-a,/3-unsaturated aldehydes and ketones produces dihydropyran derivatives stereo-specifically.161 The inverse-electron-demand Diels-Alder reaction of 3,4-r-butylthio-phene 1-oxide with electron-rich dienophiles shows vyn-jr-face and endo selectivity.162 (g) The inverse-electron-demand Diels-Alder reaction of dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate with a variety of dienophiles produces phthalazine-type dihydrodiol and diol epoxides which were synthesized as possible carcinogens.163... 

Estrogens induce tumors in animals, a fact that probably depends on the formation of catechol-type A rings. Arene oxides and/or semiquinones may then be formed, which react as cross-linkers in the same way as polycyclic hydrocarbons, such as benzopyrene, which is oxidized in the body to a diol-epoxide. Electroreduction of the corresponding ortho-quimm to the semiquinone radical, the same product that would be formed upon oxygen oxidation of the catechol, in the presence of adenine, does indeed produce a covalent adduct in 14% yield (Scheme 3.4.5)... 

A novel ring-opening reaction of oxirans, catalysed by copper and pyridine, generates c/s-diols under mild conditions. The bicyclic epoxides (186 = 1 or 2) yield (187 n = 1) (95%) and (187 = 2) (85%) in neutral, phosphate-buffered, solution. This type of reaction may have some relevance to the metabolic pathways for fused aromatic compounds, which are thought to proceed via arene oxides and diol epoxides. The catalyst system may be used to add OH", Cr, or MeO regiospecifically to the benzylic centre of indene oxide, with proton addition to the oxygen atom of oxiran. 

Oxiranes from yic-dioh. Epoxidation with a peracid of a double bond in the presence of a triple bond is often not successful. However, 1 -alkynylOxiranes can be obtained in yields of about 80% by treatment of t /c-diols of type 1 with 1 equiv. of tosyl chloride in monoglyme followed by reaction with powdered sodium... 

The way these carcinogens produce cancer is now fairly well understood. Unsubstituted PAHs are not very soluble, so to eliminate hydrocarbons, the body usually oxidizes them to render them more water soluble and then excretes them in urine. The metabolic oxidation products seem to be the real culprits in causing cancer. For example, one of the most potent carcinogens of this type is benzo[a]pyrene. Enzymatic oxidation converts it to the diol-epoxide shown below. The diol-epoxide reacts with cellular DNA, causing mutations... 

According to Ross and Nesnow (1999), the identification of specific mutations in the ras gene makes possible to diagnose which adduct induced the alterations. The authors reported that transversion mutations of the A- T type, in the codon 61, are related to the deoxyadenosime adducts action, while transversions G- -T, in the codon 12, are frequently induced by the diol-epoxide, which binds to deoxyguanosine and to cyclopenta-ring oxides, inducing transversions G—>C, in the codon 12. 

Compound types Aromatics Olefins Alcohols Nitriles Acids CHC12 CC13 CH2C1 NO, Diols Ketones Ethers Aldehydes N(Me), Esters Epoxides Nitromethane Nitrogroups Pyridine Dioxane Aromatic bases... 

Epoxide hydrolase A type of enzyme that converts epoxides to diols by the addition of water. 

There are many ways to categorize the oxidation of double bonds as they undergo a myriad of oxidative transformations leading to many product types including epoxides, ketones, diols, endoperoxides, ozonides, allylic alcohols and many others. Rather than review the oxidation of dienes by substrate type or product obtained, we have chosen to classify the oxidation reactions of dienes and polyenes by the oxidation reagent or system used, since each have a common reactivity profile. Thus, similar reactions with each specific oxidant can be carried out on a variety of substrates and can be easily compared. 

Payne rearrangement. The Payne rearrangement2 of a primary cts-2,3-epoxy alcohol to a secondary 1,2-epoxy alcohol usually requires a basic aqueous medium, but it can be effected with BuLi in THF, particularly when catalyzed by lithium salts. As a consequence, the rearrangement becomes a useful extension of the Sharpless epoxidation, with both epoxides available for nucleophilic substitutions. Thus the more reactive rearranged epoxide can be trapped in situ by various organometallic nucleophiles. Cuprates of the type RCu(CN)Li are particularly effective for this purpose, and provide syn-diols (3).3... 

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