Monosaccharides alditol, reduced

Alditol The product formed when the C=0 group of a monosaccharide is reduced to a CHOH group. 

Much of the chemistry of monosaccharides is the familiar chemistry of alcohols and aldehydes/ketones. Thus, the hydroxyl groups of carbohydrates form esters and ethers. The carbonyl group of a monosaccharide can be reduced with NaBH4 to form an alditol, oxidized with aqueous Br2 to form an aldonic acid, oxidized with HNO3 to form an aldaric acid, oxidized enzymatically to form a uronic acid, or treated with an alcohol in the presence of acid to form a glycoside. Monosaccharides can also be chain-lengthened by the multistep Kiliani-Fischer synthesis and can be chain-shortened by the Wohl degradation. 

Reduce the monosaccharides in the filtered hydrolysates and controls to the corresponding alditols (see Basic Protocol 1, steps 11 to 13). Acetylate the alditols (see Basic Protocol 1, steps 14 to 22). 

Reduce monosaccharides to corresponding alditols (see Basic Protocol 1, steps 11 to 13). 

Preliminary examinations of dextran structures were conducted by optical rotation, infrared spectroscopy and periodate-oxidation reactions. More detailed results can be achieved by methylation analysis [19]. The hydroxyl groups are methylated with methyl iodide after activation with sodium methylsulfinyl carbanion (Fig. 2). The methyl dextran is hydrolysed to the corresponding different methylated monosaccharides, which are furthermore reduced and peracetylated. The resulting alditol acetates of methylated sugars are separated by gas chromatography and identified by their retention times. In particular, a combined capillary gas-liquid chromatography/mass... 

All monosaccharides and their derivatives that possess aldehyde or ketone groups (that is, excepting derivatives such as alditols and aldonic acids) will have reducing properties. Moreover, those with the appropriate number of carbon atoms can form rings occurring in two forms (anomers) and in which the potential reducing carbon is called the anomeric carbon. 

Treatment of a monosaccharide with NaBH, reduces it to a polyalcohol called an alditol. The redxiction occurs by interception of the open-chain form present in the aldehyde/ketone-hemiacctal equilibrium. Although only a small amount of the open-chain form is present at any given time, that small amount is reduced then more is produced by opening of the pyranose form and that additional amount is reduced and so on, until the entire sample has undergone reaction. 

Figure 11 GC/MS assay of alditol hexa-acetates quantified against inositol internal standard (IS), (a) In the chromatogram shown here the monosaccharides making up a plant cell wall are being quantified as their alditol acetates, using inositol (Ino) as the (IS). The GC separation of these reduced sugars is essential for their identification. The mass spectra of the alditol acetates of the hexoses, glucose (Glc) (b), galactose (Gal) (c), and mannose (Man), are essentially identical, as are the mass spectra of the alditol acetates of the pentoses, xylose (Xyl) and arabinose (Ara), and the deoxysugars, rhamnose (Rhm) and fucose (Fuc).

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