Sugar Alcohols Alditols

The sugar alcohols of greatest interest are sorbitol and mannitol, and their derivatives 60). (See Chapter V.) Mannitol is the most abundant of 

D-Mannitol is only slightly utilized if at all by higher animals and man 60, 61), and dulcitol (galactitol) is definitely inactive in the rat (57). 

Unquestionably sorbitol (n-glucitol) is utilized by various higher animals as a source of energy 60, 62). When it is administered to dogs and to rabbits, there is only a moderate amount of sorbitol in the blood, but there is a prompt increase in blood reducing sugar. The sugar is D-fructose, and it is supposed that the ketose is formed directly from sorbitol 62). 

Because mannitol and sorbitol are both moderately sweet and relatively inexpensive, they have been considered as special dietary constituents 63). The content of sorbitol in diabetic foods should be counted as available carbohydrate, and the label of foods containing sorbitol should indicate the amount present. Probably owing to the slow intestinal absorption of sorbitol, doses greater than 50 g. are laxative in humans, but smaller doses are well tolerated. Care needs to be exercised in determining more fully the possible harmful effect of ingesting considerable amounts of sugar alcohols, before their general use as food additives is accepted. 

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Sugar Alcohols (Alditols) as Model Cooperative Hydrogen-Bonded Structures... 

Formaldehyde, as the most reactive aldehyde, undergoes Cannizzaro reaction even with aldehydes that have a hydrogen atom at the carbon. Formaldehyde also reacts to some extent with aldoses that are reduced to sugar alcohols (alditols) and formaldehyde is oxidised to formic acid (Figure 4.69). Reaction of formaldehyde with D-glucose yields D-glucitol, reaction with D-glyceraldehyde... 

The aldo or keto groups of carbohydrates can be readily reduced in aqueous solution at pH values between 6 and 10 with sodium borohydride to give sugar alcohols (alditols, reaction 4.35). The rate of the reduction can be accelerated by heating at 50°C. The reduction of ketoses results in two epimeric alditols (reaction 4.36). Use of tritiated sodium borohydride gives a tritium atom attached to C-1. 

Reduction. Mono- and oligosaccharides can be reduced to polyols (polyhydroxy alcohols) termed alditols (glycitols) (1) (see Sugar alcohols). Common examples of compounds in this class ate D-glucitol (sorbitol) [50-70-4] made by reduction of D-glucose and xyhtol [87-99-0] made from D-xylose. Glycerol [56-87-5] is also an alditol. Reduction of D-fmctose produces a mixture of D-glucitol and D-mannitol [69-65-8],... 

The catalytic hydrogenation of nitro alcohol to amino alcohol has been applied to the synthesis of an intermediate leading to sugar alcohols. The condensation of ni-tromethane with pentoses in the presence of sodium methoxide, followed by hydrogenation over platinum oxide and deamination with nitric acid, gave the alditols with one more carbon atom.22 The reaction sequence is as follows pentose — 2-epimeric sodio aci-nitro alcohols —> 2-epimeric hexitylamines —> 2-epimeric hexitols + 2-epi-meric 1,4-anhydrohexitols. The 2-epimeric sodio a -nitro alcohols were hydrogenated to 2-epimeric hexitylamines over platinum oxide in acetic acid. An example is shown in eq. 9.8 with D-ribose. 

Electrochemical oxidation of sugars and alditols is a kinetically controlled process where the rate-determining step is the abstraction of hydrogen from the carbon atom in the a position with respect to the alcohol group, the overall electrochemical process being significantly influenced by molecular dimensions, preferred orientation, and steric hindrance as first described by Konaka et al. (1969). 

Sugar alcohols and reducing sugars, added to agar culture media for the purpose of identifying specific Gram-negative bacteria, have been determined by g.l.c. as their alditol acetates and aldononitrile acetates, respectively. ... 

Ing retention of "free" water in the resin. While the Ca -form resin retained even less "free" water, polyols and ribose were strongly retained due to complex formation. It was confirmed that the best separation of hexoses and pentoses is obtained with the Ca -form resin, while for sugar alcohols and polyols, the -form was best. Specific applications of cation-exchange resin columns include the determination of low levels of monosaccharides, alditols, and cyclltols in sheep plasma on a Ca -form column with u.v. detection at 190 nm, an extension of this involving collection... 

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