Epoxide functionality

Epichlorohydnn is the common name of an industrial chemical used as a component in epoxy cement The molecular formula of epichlorohydnn is C3H5CIO Epichlorohydnn has an epoxide functional group it does not have a methyl group Write a structural formula for epichloro hydrin... 

Section 16 14 Epoxide functions are present m a great many natural products and epox ide ring opening is sometimes a key step m the biosynthesis of other sub stances... 

An alternate way to make block copolymers involving PDMS blocks 124,125) is to have these chains fitted with epoxide functions at chain end, and to react them with a vinylic or dienic polymer carrying terminal COOH functions. Sequential addition of monomers has also been used, the ring opening polymerization of the cyclic trimer (D3) being initiated by the anionic site of a living polymer126). 

The principle of active-site-directed inactivation of glycosidases by gly-con-related epoxides can be extended to compounds having an exocyclic oxirane ring, either directly attached to the six-membered ring (32) or at some distance (33,34). Studies with -o-glucosidase from sweet almonds and intestinal sucrase-isomaltase revealed that, in spite of the higher intrinsic reactivity of these epoxides, this shift of the position of the epoxide function causes a 10- to 30-fold decrease of kj(max)/Ki, an effect which probably reflects the limited flexibility of the catalytic groups involved in the epoxide reaction. 

Seventy naturally occurring carotenoid epoxides have been referenced and 43 of them have been fully characterized. These compounds can be formally considered oxidation products as defined above, but they first have the status of carotenoids. They are indeed found in vivo and are possibly biosynthesized from the corresponding non-oxidized carotenoids. If carotenoids containing epoxide functions have been found in humans, the epoxidation reaction has not yet been proven to occur in humans. 

Epoxidation of the 1,2- and 7,8-dihydrodiols of 5-MC with m-chloroperbenzoic acid furnished the corresponding anti diol epoxides 26 and J27. Compound 26 was the first diol epoxide bearing a methyl group in the same bay region as the epoxide function to be synthesized. While the diol epoxide 26 is relatively reactive (104), it is more stable than the structurally analogous DMBA 1,2-diol-3,4-epoxide (21) it was obtained as a white crystalline solid. 

While the cytochrome P-450 monooxygenase reaction described in Eq. (1) often involves hydroxylation of carbon, many other reactions are catalyzed by these enzyme systems. These reactions include oxidation of nitrogen and sulfur, epoxidation, dehalogenation, oxidative deamination and desulfuration, oxidative N-, O-, and S-dealkylation, and peroxidative reactions (56). Under anaerobic conditions, the enzyme system will also catalyze reduction of azo, nitro, N-oxide, and epoxide functional groups, and these reductive reactions have been recently reviewed (56, 57). Furthermore, the NADPH-cytochrome P-450 reductase is capable of catalyzing reduction of quinones, quinonimines, nitro-aromatics, azoaromatics, bipyridyliums, and tetrazoliums (58). 

It is the thiol grouping that acts as a nucleophile, attacking the epoxide function of the toxin (see Box 6.6). In this way, the toxin becomes irreversibly bound to glutathione, and the additional polar functionalities in the adduct mean that the product becomes water soluble. The glutathione-toxin adduct can thus be excreted from the body. 

In the example shown overleaf where hydride attacks the epoxide function, the product is an alcohol, the reaction being completed by supplying a proton source, usually water. 

A series of bridged dinuclear [(bpy)2Ru(p-L)Ru(bpy)2] " and [(bpy)2Ru(/i-L)Os(bpy)2] complexes have been prepared in which the bridge coordination domains are phen ligands and the spacer is constructed by the stereoselective coupling of units through norbornene and epoxide functionalities. " " ... 

The epoxide functionality has tremendous versatihty in the preparation of complex molecules, since its treatment with a nucleophile affords an alcohol, two contiguous stereocenters, and a new carbon-carbon or carbon-heteroatom bond in a single step. 

In view of the efficient inhibition of a particular crystalline glycan hydrolase by the epoxylbutyl -cellobioside 7 (n = 2), we decided to prepare the deoxy iodo derivative 21 to aid in the X-ray crystallographic analysis. We soon found that, although the alkene 22 was easily available as a direct precursor to our target, the epoxide functionality had to be introduced indirectly using bromo-hydrin 23 technology any direct oxidation of 22 invariably led to some loss of the iodine atom [23]. 

Preparation of nonracemic epoxides has been extensively studied in recent years since these compounds represent useful building blocks in stereoselective synthesis, and the epoxide functionality constitutes the essential framework of various namrally occurring and biologically active compounds. The enantiomericaUy enriched a-fluorotropinone was anchored onto amorphous KG-60 silica (Figure 6.6) this supported chiral catalyst (KG-60-FT ) promoted the stereoselective epoxidation of several trans- and trisubstituted alkenes with ees up to 80% and was perfectly reusable with the same performance for at least three catalytic cycles. 

Epoxidaiion of HPL. Results from the epoxidation of HPL with ECH in the presence of KOH and QAS using methylene chloride (at room temperature) as solvent are shown in Figure 3. The degree of conversion of (aliphatic) hydroxy groups of HPL to epoxide functionality was monitored by titration. Parameters important to the success of this reaction included (a) stepwise addition of KOH, approximately paralleling the formation of KC1 by dechlorohydrogenation (b) presence of QAS in the reaction mixture (c) an at least five-fold stoichiometric excess of ECH over available... 

Distribution of amine functional groups equivalent to epoxide functionality. 

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