Of monosaccharides

Disaccharides are sugars which yield two molecules of monosaccharides upon hydrolysis. The four of greatest practical interest are ... 

The most general methods for the syntheses of 1,2-difunctional molecules are based on the oxidation of carbon-carbon multiple bonds (p. 117) and the opening of oxiranes by hetero atoms (p. 123fl.). There exist, however, also a few useful reactions in which an a - and a d -synthon or two r -synthons are combined. The classical polar reaction is the addition of cyanide anion to carbonyl groups, which leads to a-hydroxynitriles (cyanohydrins). It is used, for example, in Strecker s synthesis of amino acids and in the homologization of monosaccharides. The ff-hydroxy group of a nitrile can be easily substituted by various nucleophiles, the nitrile can be solvolyzed or reduced. Therefore a large variety of terminal difunctional molecules with one additional carbon atom can be made. Equally versatile are a-methylsulfinyl ketones (H.G. Hauthal, 1971 T. Durst, 1979 O. DeLucchi, 1991), which are available from acid chlorides or esters and the dimsyl anion. Carbanions of these compounds can also be used for the synthesis of 1,4-dicarbonyl compounds (p. 65f.). 

The stmcture of monosaccharides is often written in the acycHc form although only very minor amounts of it ever occur in that form. Because the interconversions are rapid, the carbonyl groups of sugars can and do react both as if they are free and as if they are in a hemiacetal ring form. 

Isomerization. Both the carbonyl group and the adjacent hydroxyl group are involved in isomerization of monosaccharides. This reaction can be catalyzed by either a base or an enzyme. By this reaction, an aldose is converted into another aldose and a ketose, and a ketose is converted into two... 

COLLECTION AND IDENTIFICATION OF BIOACTIVE ORGANIC COMPOUNDS OCCURRING IN RIVERS AND LAKES. ADSORPTION SELECTIVITY OF MONOSACCHARIDES ONTO HYDROUS METAL OXIDES... 

As a possible method of concentrating trace amounts of bioactive organic compounds occurring in the hydrosphere, adsorption properties of various compounds have been explored by employing hydrous metal oxides as the adsorbents. To date, a family of organophosphoms compounds and carbonic acids were adsorbed onto hydrous iron oxide, along with the adsoi ption of monosaccharides onto hydrous zirconium oxide. 

In the course of the study, we found that a family of monosaccharides exhibited a definite adsoi ption selectivity (Langmuir s isotherm adsoi ption constant), reflecting their molecular stmctures. 

All of the structures shown in Figures 7.2 and 7.3 are D-configurations, and the D-forms of monosaccharides predominate in nature, just as L-amino acids do. These preferences, established in apparently random choices early in evolution, persist uniformly in nature because of the stereospecificity of the enzymes that synthesize and metabolize these small molecules. 

Storage polysaccharides are an important carbohydrate form in plants and animals. It seems likely that organisms store carbohydrates in the form of polysaccharides rather than as monosaccharides to lower the osmotic pressure of the sugar reserves. Because osmotic pressures depend only on numbers of molecules, the osmotic pressure is greatly reduced by formation of a few polysaccharide molecules out of thousands (or even millions) of monosaccharide units. 

Anomeric effect of monosaccharides and their derivatives insights from the new QVBMM (quantized valence bond molecular mechanisms) molecular mechanics force field 98H(48)2389. 

Because monosaccharides contain only two kinds of functional groups, hydroxyls and carbonyls, most of the chemistry of monosaccharides is the familiar chemistry of these two groups. Alcohols can be converted to esters and ethers... 

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. 

Reaction of hydrazine 165 with a number of monosaccharides give hydrazones 166 (92BCJ546). Their acetylations gave peracetyl derivatives 167. The same reactions were extended to the /V-methyl and the 7-methyl derivatives of 165 (93 JPROO). That compounds 166 exist as open-chain structures was based on a 2D NMR study (93MI1) (Scheme 35). 

Homopolysaccharides contain only one type of monosaccharide, whereas... 

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