Epoxidation of fatty acids

The epoxidation of fatty acid methyl esters (FAME) is traditionally conducted in strong acidic media, e.g., with peracetic acid in sulfuric acid solutions. These reactions can be conducted by an environmentally benign route, however, in the... 

Catalytic Processes for the Selective Epoxidation of Fatty Acids More Environmentally Benign Routes... 

In contrast to the relative chemical stability of mono-epoxides, diol epoxides of fatty acids (10.52), which are formed from di-epoxides by EH, are subject to a different fate. In such metabolites, intramolecular nucleophilic substitution may occur, such that oxirane opening is accompanied by formation of a tetrahydrofuran ring [134], Such reactions of intramolecular nucleophilic substitution are discussed in detail in Sect. 11.9. In the case of diol epoxides of fatty acids, the resulting tetrahydrofuran-diols (10.53) are part of a much larger ensemble of oxygenated metabolites of fatty acids, the potential cytotoxicities of which are being evaluated [135]. 

Most transgenic oilseeds with altered fatty acid composition remain research subjects, with commercial introduction limited to two crops, neither of which have yet achieved success in the marketplace. The expected benefits from transgenic crops with altered fatty acid composition include improved stability properties enhanced nutritive value expanded use of renewable resources to replace petroleum derived materials replacement of chemical processes, such as epoxidation of fatty acid double bonds and gradual expansion of agriculture as a chemical industry, a concept long ago known as chemurgy. It is possible to predict some issues that... 

Use Bleaching textiles, paper, oils, waxes, starch polymerization catalyst bactericide and fungicide, especially in food processing epoxidation of fatty acid esters and epoxy resin precursors reagent in making caprolactam, synthetic glycerol. 

Epoxidation of various olefins by cytochrome P-450 enzymes has been studied using rat liver microsomes [29,30] as well as using enzymes from microbial origin. For example, Ruettinger and Fulco [31] reported the epoxidation of fatty acids such as palmitoleic acid by a cytochrome P-450 from Bacillus megaterium. Their results indicate that both the epoxidation and the hydroxylation processes are catalyzed by the same NADPH-dependent monooxygenase. More recently, other researchers demonstrated that the cytochrome P-450cam from Pseudomonas putida, which is known to hydroxylate camphor at a non-activated carbon atom, is also responsible for stereoselective epoxidation of cis- -methylstyrene [32]. The (lS,2R)-epoxide enantiomer obtained showed an enantiomeric purity (ee) of 78%. This result fits the predictions based on a theoretical approach (Fig. 2). 

Debal, A., G. Rafaralahitsimba, and E. Ucciani, Epoxidation of Fatty Acid Methyl Esters with Organic Hydroperoxides and Molybdenum Oxide, FatSci. Technol. 95 236-239 (1993). 

Piazza JG, Nunes A, Foglia TA. Epoxidation of fatty acids, fatty methyl esters, and alkenes by immobilized oat seed peroxygenase. J Mol Catal B Enzym 2003 21 143-151. 

These bacteria also have epoxide hydrolase activity, and can form e.g. 9, 10-dihydroxy 18 0 from 9,10-epoxy 18 0. Many eubacteria have an 02-dependent monooxygenase (cytochrome P450) that can catalyze hydroxylation and epoxidation of fatty acids and hydrocarbons Ai-alkanes are metabolized to primary alcohols, fatty acids to co-OH compounds, and unsaturated hydrocarbons to epoxides (282). 

Epoxide resins can be esterified with fatty acids to give media ranging from air-drying to stoving types. The presence of fatty acid reduces the chemical resistance to the same order as that of the alkyds. It is nevertheless sometimes found advantageous to use an epoxy ester for certain specialised purposes. 

There is an informative parallel to be drawn between the metabolism of fatty acids and that of valproic acid (VA), a well-known anti-epileptic drug. One of the metabolites of VA is A4-valproic acid (10.54, Fig. 10.16), which undergoes a number of metabolic transformations, including oxygenation to epoxide 10.55. Rather than being a substrate for EH, this epoxide reacts by intramolecular nucleophilic attack of the carboxylate anion at the internal C-... 

Studies on the biosynthesis of lactones have shown that epoxidation of unsaturated fatty acids like, e.g., linoleic and linolenic acid may represent a common pathway to oxygenated derivatives of fatty acids. Epoxy fatty acid hydrolases were identified as key enzymes that exhibit high regioselectivity and enantiose-lectivity [25, 26]. 

A considerable amount of work haa been devoted to the catalytic reduction of fatty acid and fatty alcohol epoxides. Hydrogenation of is- and tran -Q, 1 tl-epoxyooUtbcanoic add, for example, has been reported108t-1887 1188 to give isomeric 10-hydroxyoctadecanoio acids exclusively (Eq. 344). Preferential attack of hydrogen on C< was... 

Lactone formation on treatment of uneatumted acids with pwox acids ib not confined to the field of fatty acid chemistry. Howell m l Taylor obtained a hydroxylactone, for instance, on adding perfoi nm acid to the indene derivative shown in Eq. 1 106). An epoxide < assumed to constitute the intermediate stage of this transformation. 

A considerable amount of knowledge has accumulated about how pheromone components are produced in female moths since the first pathway was identified some 20 years ago. It appears that most female moths produce their pheromone through modifications of fatty acid biosynthesis pathways. For moths that utilize aldehydes, alcohols, or esters biosynthesis occurs in the pheromone gland. The exceptions are those that utilize linoleic or linolenic acids, which must be obtained from the diet. However, modifications of these fatty acids occur in the gland. For moths that utilize hydrocarbons or epoxides of hydrocarbons, the hydrocarbon is produced in oenocyte cells and then transported to the pheromone gland where the epoxidation step takes place. 

These fatty acids and oils, as well as their derivatives, are applied in a broad range of products such as surfactants, lubricants and coatings, and, obviously, biodiesel. Upon epoxidation of the double bonds of the unsaturated fatty acids, very important compounds for the polymer industry are produced, which are used as plasticizers and stabilizers for a broad range of polymers such as polyvinyl chloride (PVC), polyesters, and polyurethanes [71]. Another interesting application has been found in the conversion of epoxidized soybean oil to carbonated soybean oil that can be reacted with ethylene diamine to obtain a polyurethane with interesting properties [72], Traditionally, stoichiometric reagents are used for the epoxidation of these oils and fats, albeit in some cases, with limited results. Therefore, the MTO/H2O2 system has been explored to epoxidize unsaturated fatty acids and oils. 

First, the use of two specific reactions — All desaturation and controlled 2 carbon chain shortening of fatty acid precursors to account for the biosynthesis of a large number of pheromones — has been an extremely fruitful approach. Even in a case where it seemed uncertain if this approach was appropriate (22)r it turned out that it was (23.). Other reactions should now be added to increase the range of products accounted for. Examples already mentioned include the A10 desaturase and the chain elongation of branched-chain starting materials. Other functional groups that appear in sex pheromones should also be accounted for, such as epoxides. 

Lipase has been employed to prepare peracids, usually in situ.m The lipase catalysed peracid production from carboxylic acids has been used for the mild epoxidation of alkenes.109 A number of immobilized lipases exist, including one from Candida Antarctica (Novozym 435), which catalyses the conversion of fatty acids to peroxy fatty acids.110... 

The benzofuran epoxides 70 are found to be the most reactive epoxides functioning as alkylative agents. Polyunsaturated free fatty acids, namely linoleic, arachidonic, and eicosatrienic acids, and also their methyl esters have been epoxidized using lb <2006HCA2243>. When the reaction is performed in water, it has been found that due to supramolecular organization of fatty acids into a micelle, the C=C bonds closest to the aqueous-micelle interface are most prone to epoxidation. 

Recent studies have attempted to improve the efficiency of epoxidation under milder conditions that minimize the formation of byproducts. Chemo-enzymatic epoxidation uses the immobilized lipase from Candida antartica (Novozym 435) (56) to catalyze conversion of fatty acids to peracids with 60% hydrogen peroxide. The fatty acid is then self-epoxidized in an intermolecular reaction. The lipase is remarkably stable under the reaction conditions and can be recovered and reused 15 times without loss of activity. Competitive lipolysis of triacylglycerols is inhibited by small amounts of fatty acid, allowing the reaction to be carried out on intact oils (57). Rapeseed oil with 5% of rapeseed fatty acids was converted to epoxidized rapeseed oil in 91% yield with no hydroxy byproducts. Linseed oil was epoxidized in 80% yield. Methyl esters are also epoxidized without hydrolysis under these conditions. 

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