Sugar alcohols hexitols

Polarimetric analysis of sorbitol and mannitol in the presence of each other and of sugars is possible because of their enhanced optical rotation when molybdate complexes are formed and the higher rotation of the mannitol molybdate complex under conditions of low acidity (194). The concentration of a pure solution of sorbitol may be determined by means of the refractometer (195). Mass spectra of trimethylsilyl ethers of sugar alcohols provide unambiguous identification of tetritols, pentitols, and hexitols and permit determination of molecular weight (196). 

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. 

In this review of the metabolism of the sugar alcohols emphasis will be centered mainly on the isomeric hexitols. Substances such as methyl alcohol and ethylene glycol are studied under categories other than the sugar alcohols. Furthermore, in common parlance, the term, sugar alcohol, as a rule, refers to the hexahydric alcohols and their availability as food in the human diet warrants special study of their metabolic patterns. 

Methyloxime-acetyl derivatives of sugar alcohols that avoid interference due to monosaccharides and resolve isomeric hexitols have been described. The procedure is as follows 0.5 ml of methoxylamine hydrochloride in pyridine (10 mg ml ) is added to dried samples containing polyols, and then incubated at 70°C for 30 min. The specimens are acetylated by adding 0.5 ml of acetic anhydride for a further 10 min at 70°C. Two drops of methanol are added and solvents evaporated in a water bath at 30°C vm-der a stream of air. The residues are desiccated for at least 1 h and then dissolved in 50 pi of methanol to be chromatographed. The column was filled with 3% XE-60 (80-100 mesh) and the chromatograph operated at a column temperature of 230°C with nitrogen as carrier gas at a flow of 50 ml min Figure 3... 

These two hexitols readily form mono- and di-anhydrides. The majority of sugar alcohols readily form acetal and ketal derivatives . When the terminal groups in aldoses are made alike, loss of asymmetry of the molecules often occurs the resulting aldaric acids and alditols, as for example, xylaric acid and galactitol, are optically inactive, non-resolvable meso forms. Fischer made use of this fact in his assignment of sterciochemical formulae to the monosaccharides. 

Lespieau, R., Synthesis of Hexitols and Pentitols from Unsaturated Poly-hydric Alcohols, II, 107-118 Levi, Irving, and Purves, Clifford B., The Structure and Configuration of Sucrose (oipta-D-Glucopyranosyl beta-D-Fructofuranoside), IV, 1-35 Liggett, R. W., and Deitz, Victor R., Color and Turbidity of Sugar Products, IX, 247-284... 

Although the polyhydric alcohols derived from sugars have been the subject of numerous investigations over many years, the inner ethers or anhydrides of these substances have been for the most part neglected, despite the fact that many of them were isolated and some description of their properties recorded before the advent of the twentieth century. In recent years, however, the anhydrides of polyhydric alcohols derived from sugars have received marked attention in several countries. Some indeed have achieved importance in chemical industry. Most interest has been centered on the anhydrides of pentitols and hexitols and this article will be restricted to a discussion of the chemistry of these substances. 

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