Oxidation of Sugar Alcohols

No reaction occurs between glycerol and sodium hypochlorite unless a trace of cobalt acetate is added with this catalyst present, formaldehyde is formed at low temperatures. With neutral hypochlorite, even in the presence of cobalt acetate, no reaction occurs. The same formation of formaldehyde is observed with calcium hypochlorite and cobalt acetate. 

In the case of the oxidation of glycerol, D,L-glyceric acid has also been isolated. Hlasiwetz and Habermann treated glycerol with chlorine water and obtained the acid as the main product. From the action of bromine water on glycerol, Barth obtained glyceric acid, bromoform and carbon dioxide. In the absence of water, bromine converted glycerol to dibromohydrin and bromoacetic acid. The former decomposed to hydrogen bromide and acrolein. 

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The chemical oxidation of sugar alcohols to ketoses may be successful when only one unsubstituted hydroxyl group is present. Thus, 6-0-benzoyl-1,3 2,4-di-0-ethylidene-D-glucitol is oxidized to the corresponding L-sor-bose derivative by the action of chromic acid dissolved in glacial acetic... 

Oxidation of ascorbate (reduction of 02 to H20) Oxidation of primary alcohols to aldehydes in sugars (reduction of 02 to 11202) Removal of amines and diamines Electron-transfer... 

Abstract This is one of the most important classes of oxidation effected by Ru complexes, particnlarly by RnO, [RuO ] , [RnO ] and RuCljCPPhj), though in fact most Ru oxidants effect these transformations. The chapter covers oxidation of primary alcohols to aldehydes (section 2.1), and to carboxylic acids (2.2), and of secondary alcohols to ketones (2.3). Oxidation of primary and secondary alcohol functionalities in carbohydrates (sugars) is dealt with in section 2.4, then oxidation of diols and polyols to lactones and acids (2.5). Finally there is a short section on miscellaneous alcohol oxidations in section 2.6. 

Structurally, these acids are cunsidered to be the oxidation products of polyhydric alcohols. However, a number of them can be formed from the oxidation of sugars. The careful oxidation of glycerol will yield a syrupy liquid, glyceric acid, an example of a dihydroxymonobasic carboxylic acid. 

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 development of methods18,17 for the mild, specific oxidation of secondary alcohols has led to the availability of a variety of oxidized sugars 18 these can be reduced in a similar way. 

Acetic Fermentation.—Acetic acid in addition to its occurrence in nature in the form of esters is produced on the large scale by the acid fermentation (oxidation) of the alcohol obtained as the result of fermenting fruit juices which contain sugar, especially apple juice or cider, and wine. When the sugar present in cider is fermented, dueTo the action of the enzyme zymase, alcohol is produced (p. 95). This alcohol is then oxidized through the activity of an aerobic bacterial organism Bacterium aceti, which is present naturally in the fruit juice. The product is acetic acid. 

Continuing, one carbon homologation of 96 was easily achieved by oxidation of the alcohol to the corresponding ketone and a subsequent enolisation-formylation sequence. The last lacking carbon was introduced by nucleophilic addition on the complex keto-sugar 97 using vinyl magnesium bromide in the presence of cerium salts. The diol 98 was further elaborated into a relay compound already prepared from squalestatin [88]. 

Electrochemical oxidation of sugars and alditols is a kinetically controlled process where the rate-determining step is the abstraction of hydrogen from the carbon atom in the a position with respect to the alcohol group, the overall electrochemical process being significantly influenced by molecular dimensions, preferred orientation, and steric hindrance as first described by Konaka et al. (1969). 

Another general method for the preparation of ketones was also applied to sugars, i.e. the oxidation of secondary alcohols by ruthenium tetroxide, RUO4. Only catalytic quantities of this very costly compound are used which is regen-... 

Among the most important C-disaccharide syntheses reported in 1989 is the preparation of C-sucrose. This analog of table sugar is interesting in that unlike natural sucrose, it cannot be metabolized to lower sugars. An actual synthesis of C-sucrose was reported by Nicotra, et ai.,22>23 and is illustrated in Scheme 8.7.5. As shown, the C-glucoside, prepared as discussed in Chapter 2, was converted to a metallated alcohol in 97% yield. Subsequent oxidation of the metal with iodine followed by oxidation of the alcohol to a ketone and... 

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