Sugars selective oxidation

Various substituted N-hiomo- and A/-chloroureas have also been prepared (97). These compounds are useful for synthesis of oxazoUdinones, and also hydrazine, hydrazo, and azo compounds. A/-Bromourea [51918-81 -1] is useful for selective oxidation of sugar derivatives (98). 

When used at room temperature in the presence of an active platinum catalyst in an inert solvent, e.g., acetone or ethyl acetate, oxygen will oxidize nonhindered, saturated hydroxyl groups and exposed allylic alcohols. This reagent has found extensive use in sugar chemistry and is particularly suited for the selective oxidation of either 3a- or 3j -alcohols of steroids. Other hydroxyl groups on the steroid skeleton are much less sensitive to oxidation. As a result, this reaction has been used extensively in research on polyhydroxy cardiac-active principles, e.g., the cardenolides and bufadienolides, where the 3-hydroxyl group is easily oxidized without extensive oxidation or dehydration of other hydroxyl groups. The ordinarily difficult selective oxidation of the... 

Uronic acids are found in nature, but they are formed enzymically by selective oxidation of the primary alcohol function of a sugar. Oxidation takes place not on the free sugar, but on UDPsugar... 

Lead tetraacetate is used as a highly selective oxidizing agent in organic synthesis. This includes oxidation of glycols into aldehydes, preparation of cyclohexyl acetate, production of oxahc acid, and in structural analysis of sugars. 

Levulinic acid is formed by the treatment of six-carbon sugar carbohydrates from starch or lignocellulosics with acids, or by add treatment plus a reductive step of five-carbon sugars derived from hemicellulose. Levulinic add can serve as a building block for the synthesis of many derivatives of interest may be the selective oxidation to succinic and acrylic add. [i-Acetylacrylic add could be used in the production of new acrylate polymers. 

The 6-dcoxy-/J-D-c -c//hHohexofuranoside-5-ulose, a constituent of the sugar-cinnamate unit 234 of the antibiotic hygromycin, and several related analogues, have been synthesized from 6-deoxy-/J-D-glucofuranosides via a 2,3-epoxide and selective oxidation at C-5 with the Jones reagent.445... 

In contrast, if a single aqueous liquid phase is used, and if the aldehyde product has a tendency to be hydrated, the reaction proceeds smoothly to the carboxylic acid salt (413,414). It is believed that the RC(OH)2 hydration product of the aldehyde is the actual reagent. This reaction is highly useful for the selective oxidation of primary alcohol groups in sugars such as methyl-a-D-glucopyranoside to the uronic salt ... 

The most dramatic results obtained so far with gold catalysts have been with the liquid phase processes. They are conducted with oxygen or air, often using water as solvent, and are therefore felt to be environmentally benign. Particular success has been obtained with reducing sugars (Section 8.3.2) and other aldehydes (Section 8.3.3), and with alcohols and other hydroxy-compounds (Sections 8.3.4-8.3.7). Reactions that use soluble gold complexes to catalyse selective oxidation are reported in Chapter 12. 

Most of these liquid phase catalytic oxidations have been used for the selective oxidation of carbohydrates. In the oxidation of a sugar such as glucose, four basic types of selective oxidation are possible. ... 

As depicted in Scheme 21.1 for the oxidation of glucose, three general types of acids can be produced by the oxidation of a sugar aldonic acids in which only the aldehyde of the parent aldose has been oxidized to the acid aldaric acids that are dicarboxylic acids with one carboxy group coming from the oxidation of the aldehyde and the other from the primary alcohol at the other end of the carbon chain or uronic acids derived from the selective oxidation of the primary alcohol without the oxidation of the aldehyde. 

This chapter is intended to provide a selective overview of the most recent developments in EFC research. Several excellent and comprehensive reviews focused on aspects of EFC research have appeared over the past few years [7, 10-16]. We focus here on developments that may lead to deployment of an implantable glucose-oxidizing, oxygen-reducing EFC, as an example of the extensive research on EFC bioelectrochemistry. Developments, focused on using other fuels, such as hydrogen, alcohols, or other sugars, or oxidants will not be considered in detail. 

Another 3,6-dldeoxy-sugar glycoside, methyl a-D-paratoslde (6), has been synthesized from methyl 3 6-dl- -plvaloyl-a-D-mannopyrano-slde by sequential selective oxidation-reduction at C-2, followed... 

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