Monosaccharides esters

Horvat, S., Roscic, M., Varga-Defterdarovic, L., Horvat, J. Intramolecular rearrangement of the monosaccharide esters of an opioid pentapeptide formation and identification of novel Amadori compounds related to fructose and tagatose. J. Chem. Soc., Perkin Trans. 1 1998, 909-914. 

I. Jeric, L. Simicic, M. Stipetic, and S. Horvat, Synthesis and reactivity of the monosaccharide esters of amino acids as models of teichoic acid fragment,... 

Wood resists hydrolysis by dilute mineral acids at room temperature but reaction occurs with increased concentration or higher temperature. The cellulose component is hydrolysed by 85% H3PO4 although the rate of reaction is considerably slower than that with 60% H2SO4. Almost complete conversion to monosaccharide esters can eventually be achieved with these acids, with most of the lignin remaining as an insoluble residue. 

What would be the structures of the monosaccharide esters obtained from hydrolysis of Olestra ( A Word about Fat Substitutes from Carbohydrates, page 482) with an aqueous acid ... 

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.). 

Phosphate esters of glucose, fructose, and other monosaccharides are important metabolic intermediates, and the ribose moiety of nucleotides such as ATP and GTP is phosphorylated at the 5 -position (Figure 7.13). 

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... 

Monosaccharides behave as simple alcohols in much of their chemistry. For example, carbohydrate -OH groups can be converted into esters and ethers, which are often easier to work with than the free sugars. Because of their many hydroxyl groups, monosaccharides are usually soluble in water but insoluble in organic solvents such as ether. They are aiso difficult to purify and have a tendency to form syrups rather than crystals when water is removed. Ester and ether derivatives, however, are soluble in organic solvents and are easily purified and crystallized. 

Easily prepared from the appropriate monosaccharide, a glycal is an unsatu-rated sugar with a C1-C2 double bond. To ready it for use in potysaccharide synthesis, the primary -OH group of the glycal is first protected at its primary -OH group by formation of a silvl ether (Section 17.8) and at its two adjacent secondary - OH groups by formation of a cyclic carbonate ester. Then, the protected glycal is epoxidized. 

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. 

Of special biochemical importance are the esters of monosaccharides with phosphoric acid. They are generally termed phosphates (e.g. glucose 6-phosphate). In biochemical use, the term phosphate indicates the phosphate residue regardless of the state of ionization or the counter ions. 

REACTIONS OF MONOSACCHARIDES WITH BE TA -KETONIC ESTERS AND RELATED SUBSTANCES... 

REACTIONS OF MONOSACCHARIDES WITH BETA-KETONIC ESTERS 101... 

REACTIONS OF MONOSACCHARIDES WITH BBTA-KETONIC ESTERS 105... 

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