Hydroperoxide-dependent epoxidation acid hydroperoxides

Labeque, R. and Marnett, L.J. (1988). Reaction of hematin with allylic fatty acid hydroperoxides identification of products and implications for pathways of hydroperoxide-dependent epoxidation of 7,8-dihydroxy-7,8-dihydrobenzo [a]pyrene. Biochemistry 27, 7060-7070. 

Hamberg, M. and Hamberg, G. Hydroperoxide-dependent epoxidation of unsaturated fatty acids in the broad bean (Vicia faba L.), Arch. Biochem. Biophys. 283(2) (1990), 409-416... 

Hydroperoxide-dependent peroxygenase (epoxygenase). This enzyme, detected in soybeans [7] and broad beans [8], controls the fatty acid hydroperoxide-dependent epoxidation of unsaturated fatty acids. Hydroperoxide molecule plays a role of oxygen donor for epoxidation. This pathway was proposed as the source of natural epoxides of linoleate, vemolic and coronaric acids, occurring in different amounts in many seed oils. 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

The first step in the formation of the leukotrienes is cleavage of arachidonic add from membrane phospholipids. 5-I.ipoxygcnasp, which is a calcium-dependent enzyme, catalyzes the introductionof Oi into the arachidonic add and the conversion of the resulting hydroperoxide to an epoxide. Leukotriene A, contains an epoxide group. Leukobiene (LTA ) can be converted to leukotriene B (LTB4) by enzymatic hydrolysis. LTB is a dihydroxy fatty acid it regulates the functions... 

The most dependable reagent for the epoxidation of unsaturated ketones is hydrogen peroxide, especially in alkaline media [142, 143, 149, 151]. Because the Baeyer-Villiger reaction is acid-catalyzed, it does not take place during epoxidations with alkaline hydrogen peroxide or its neutral derivatives, such as fe/ t-butyl hydroperoxide [220]. Most examples of epoxidation involve unsaturated ketones with conjugated double bonds. 

In 2010, Bryliakov reported on the use of a series of [(L)Mn(03SCF3)2] complexes (Scheme 13) for the epoxidatiOTi of olefins using peracetic acid, OT-chlorobenzoic acid, teri-butyl hydroperoxide, cumyl hydroperoxide, PhIO, and MesIO [59]. The enantioselectivities of the epoxidations varied depending on oxidant. Based on this finding, as well as other observations, iodosylarene [(L)Mn=0(OIAr)] complexes were proposed to be the active oxidizing species, similar to the intermediates proposed earlier by Goldberg [52]. 

Terpenic hydrocarbons are stable in the absence of air, but are easily oxidised in air, especially at higher temperatures. Their autoxidation proceeds by similar mechanisms as autoxidation of unsaturated fatty acids and depends greatly on the hydrocarbon structure. The primary autoxidation products are hydroperoxides. In branched hydrocarbons, the hydroperoxyl group mainly occurs in the secondary or tertiary carbon adjacent to the quaternary carbon of the double bond. The final autoxidation products are usually epoxides, alcohols and ketones. The primary site of attack in olefins is the carbon adjacent to the double bond, as in monounsaturated... 

Blee E and Schuber F. Efficient epoxidation of unsaturated fatty acids by a hydroperoxide-dependent oxygenase. J. Biol. Chem. 1990 265 12887-12894. 

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