Sugar substitutes, polyols

Polyols are frequently used sugar substitutes and are particularly suited to situations where their different sensory and functional properties are attractive. In addition to sweetness, some of the polyols have other useful properties. For example, although it contains the same number of calories/gram as other sweeteners, sorbitol is absorbed more slowly from the digestive tract than is sucrose. It is, therefore, useful in making foods intended for special diets. When consumed in large quantities (1-2 oz 25,059 g)/dav, sorbitol can have a laxative effect, apparently because of its comparatively slow intestinal absorption. 

To achieve sugar-free preparations, polyols (sugar alcohol) are replacing sucrose as bulk sugar substitutes. They are not fermented by oral bacteria, hence noncariogenic. However, they are slowly hydrolyzed by the enzymes of the small intestine into their constituent monomers, which are only slowly and incompletely absorbed compared with... 

Another class of polyol compounds that have been widely used as sugar substitutes is that of sugar alcohols. The most important of these sugar substitutes are erythritol, glycerol, mannitol (hexane-1,2,3,4,5,6-hexol), and sorbitol. Figure 1 shows the molecular models of glycerol and sorbitol. It can be appreciated that sorbitol has a chemical constitution very similar to that of monosaccharides, yet it has been used as sugar substitute since the body metabolizes it slowly. 

Etherification. The reaction of alkyl haUdes with sugar polyols in the presence of aqueous alkaline reagents generally results in partial etherification. Thus, a tetraaHyl ether is formed on reaction of D-mannitol with aHyl bromide in the presence of 20% sodium hydroxide at 75°C (124). Treatment of this partial ether with metallic sodium to form an alcoholate, followed by reaction with additional aHyl bromide, leads to hexaaHyl D-mannitol (125). Complete methylation of D-mannitol occurs, however, by the action of dimethyl sulfate and sodium hydroxide (126). A mixture of tetra- and pentabutyloxymethyl ethers of D-mannitol results from the action of butyl chloromethyl ether (127). Completely substituted trimethylsilyl derivatives of polyols, distillable in vacuo, are prepared by interaction with trim ethyl chi oro s il an e in the presence of pyridine (128). Hexavinylmannitol is obtained from D-mannitol and acetylene at 25.31 MPa (250 atm) and 160°C (129). 

At one time the idea of recording a mass spectrum of a nucleic acid would have been considered utopic and futuristic. Nucleic acids are practically nonvolatile and usually possess a molecular weight of several million atomic mass units (amu) (fi) often expressed in daltons up to 10 daltons where 1 dalton = 1.67 X 10 g. They possess their own mass spectra. In general they are esters of phosphoric acid and polyols, such as the sugars ribose and 2 -deoxyribose, which are themselves substituted with heteroaromatic purine or pyrimidine bases. Consequently, fragment ions characteristic of all these structural elements can be found in the mass spectra of nucleic acids. 

The principle of exciton coupling between vicinal benzoate chromophores has been extended to other aromatic carboxylic acid derivatives , including those of ring-substituted benzoic acids, 9-anthranoic acid (141) and p-methoxycinnamic acid (142). These derivatives have been widely used for the determination of the absolute stereochemistry in polyol natural products. The circular dichroism of the A -p-bromobenzoyl group combined with various 0-, 0,0 -di- and 0,0, 0"-tii-(p-bromobenzoyl) derivatives of 2-amino-2-deoxygalactopyranoside and an iV-anthranoyl group combined with tri-, tetra- and penta-p-methoxycinnamoyl derivatives of acyclic 1-amino polyols were studied to improve and develop microscale CD methods for the structural study of amino sugars. 

Alkoxides are readily formed from partially substituted polyols and sugars by treatment with sodium naphthalenide 19) in 1,2-dimethoxy-ethane solution and subsequent reaction with alkyl halides then produces ethers 20). The reaction sequence is simple to apply, and the method deserves further investigation. 

Other saccharides (sugar alcohols) also include cycHtols (alicyclic polyols), because they have similar properties, although they are not derived from sugars by simple reduction. CycHtols are cycloalkanes, in which at least three ring carbon atoms are substituted (each of them only once) by hydroxyl or alkoxyl groups. 

Studies, which have substituted nonfermentable sugar alcohols or polyols such eis sorbitol or xylitol for some or all of the sweeteners (sugar) used in the diet, have shown a reduction in caries. 

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