Reduction of carbohydrates

Fig. 2.1. Reduction of carbohydrate in an aeration tank at various air flow rates.

Even if the main focus on the research activities were directed towards structural studies on carbohydrates of natural origin, the synthesis of model substances, deriva-tization of oligo- and poly-saccharides, oxidation, and reduction of carbohydrates, and identification of the products all were performed during this time. 

In 1904, Schardinger discovered the bacteriological formation of acetone from carbohydrates, and Pringsheim, in the years 1905-1909, described the reduction of carbohydrates to isopropyl alcohol and n-butyl alcohol. The subsequent work of Fernbach and Weizmann led to the development of an industry for the production of these substances by the fermentation of carbohydrates. ... 

Day 1 Reduction of Carbohydrates with Sodium Borohydride and Enzymatic Determination of Glucose... 

Lithium aluminum hydride, effect of solvents on reduction of carbohydrate sulfonic esters, 269 Lutease, 380 Luteic acid, fungal, 378 Lyxitol, 1-acetamido-l-deoxy-L-, 170 Lyxofuranose, 5 - acetamido - 5 - deoxy-D-, 171... 

Furthermore, superhydride is used as an alternative to LAH in the reduction of carbohydrate epoxides (equation 18), In this example, the C—O bond away from the hydroxy group is selectively cleaved, but a tosyloxy group is also reduced in epoxides having a hydroxy group protected with tosyl. A kinetic study of reductions with superhydride has been reported. ... 

The reduction of carbohydrate epoxides has also been examined with the sodium borohydride/dibo-rane system. As shown in Table 5, the corresponding alcohols are obtained in good yields, although the... 

Table 5 Reduction of Carbohydrate Epwxides with NaBH4/BH3 ...

Numerous reduction procedures are available in organic s)uithesis [154] and many of these can be applied for the reduction of carbohydrates. 

The reduction of carbohydrate absorption from the intestine of rats with a saccharide supplemented by EGCG or green tea is based upon suppression of the activity of intestinal a-amylase, sucrase, or a-glucosidase. Also, green tea enhances insulin sensitivity of normal and fructose-fed rats as demonstrated by increased glucose uptake by muscle cells. ... 

We already know from our earlier mapping of the path of carbon in photosynthesis that we need not only a reducing agent for the reduction of carbohydrate but also, in addition, a rather specific type of chemical. Since we know the exact steps for carbon reduction, we were able to... 

The imine formed on hydrolysis yields o-phenylenediamine and the corresponding carbonyl compound, and, depending on the pH of the medium, can also undergo further chemical and electrochemical reactions. By this reduction of carbohydrate derivatives of quinoxaline, the corresponding deoxy saccharides would be formed. For 1,2-dihydro-2,3-dimethylquinoxaline in an alkaline medium, the decrease in the height of wave i2 and the appearance of an anodic wave, ia, with increasing pH value prove that only its protonated form is reduced to the corresponding quinoxaline derivative, whereas its nonprotonated form is capable of oxidation to the initial 2,3-dimethylquinoxaline, as shown in Scheme 13. 

The chemistry of carbohydrates has sometimes been referred to as a marriage between the chemistry of alcohols and that of aldehydes and ketones. In the preceding sections, we examined oxidations and reductions of carbohydrates, cyanohydrin formation, Fischer glycosidation, and processes that involve enolization. All of these reactions involve carbonyl groups in carbohydrates. In this section, we will consider the reactions of the hydroxyl groups of carbohydrates, starting with their conversion to esters. 

Numerous enzymes exist in living tissues which in vivo or in vitro catalyze the oxidation (and reduction) of carbohydrates, and are important in their metabolism. Usually these are dehydrogenations (or hydrogenations). These enzymes are discussed in detail in Chapter XIII. 

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