Of D-glucitol

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],... 

Alkyl derivatives of D-glucitol and D-mannitol also display a wide variety of mesophases (Fig. 3c, [11]). Predictive rules for the occurrence of various phases in relation with geometric parameters were established for 3 c... 

Oxidation of secondary or primary alcohols by dehydrogenases is usually not performed biocatalytically. The reaction destroys a stereocentre, it is thermodynamically not favoured and product inhibition is a problem. It is attractive only in cases where it is necessary to discern between several hydroxy groups in a molecule. Microbial oxidation of D-glucitol to yield L-sorbose is the key step in production of vitamin C (Reichstein and Griissner, 1934). 

Fig. 4. —Conformations of D-Glucitol. (a, Planar b, nonplanar, after rotation about C-2-C-3 c, nonplanar, after rotation about C-3-C-4 and C-4-C-5.)...

G. J. F. Chittenden, Some aspects of the isopropylidenation of D-glucitol under neutral conditions, Carbokydr. Res. 708 81 (1982). 

Adducts of alkali metal salts prepared in anhydrous alcoholic media generally retain very little alcohol of solvation after being dried under vacuum at room temperature (see Table I). The unusual ability of adducts of D-glucitol to retain alcohol is probably due largely to the great ability of D-glucitol itself to retain solvent. Adducts of alkaline-earth metal salts, however, are more strongly solvated by alcohol than adducts of alkali metal salts. For example,21 lactose CaClj 4 MeOH is relatively stable at 60° at atmospheric pressure under vacuum (< 19 mm. of Hg), a molecule releases only two of the four molecules of methanol. From aqueous alcoholic media, adducts of alkaline-earth metal salts tend to crystallize as hydrates. 

Figure 1. Stereoscopic view of the molecular packing in the crystal structure of D-glucitol. The molecules, indicated by circles linked by heavy lines, are viewed down the carbon chain axis. The thin lines are the intermodular H-bonds.

Pyrolysis of cellobiitol at 350 in vacuo yields — 32% of levoglucosan (1,6-anhydro-/ -D-glucopyranose) and 70% of a mixture of D-glucitol and its anhydrides." Preparation of mono- and di-anhydrohexitols, mixed with linear polyols and polymers, were claimed by application of particular noble metal catalysts, coated with copper, on catalytic hydrogenation of D-glucitol and D-mannitol.9"... 

For the conversion of D-glucitol (24) into L-xty/o-2-hexulosonic acid (28), several other methods, that do not proceed by way of L-sorbose, have been reported. 

Anodic oxidation of a 1,3 2,4-diacetal of D-glucitol led to the 3,5 4,6-diacetal of 2-keto-L-gulonic acid, which gave L-ascorbic acid directly on... 

P. A. Garcia, R. Velasco, and F. Barba, Role of trace metal ions. Kinetic and mechanism of the copper(II)-catalyzed oxidation of ascorbic acid (vitamin C) from protected derivatives of D-glucitol, Synth. Commun., 21 (1991) 1153-1161. 

Further studies verified the intermediate formation of free radicals, as demonstrated by the electron-spin resonance spectra obtained during autooxidation of cellulose,75 and hydrogen peroxide was identified as a byproduct in the autooxidation of D-glucitol. Similar oxidations of cellulose in the presence of alkenic monomers afforded graft copolymers. The autooxidation of cellulose and of the cello-oligosaccharides was shown to be more extensive in the presence of transition-metal cations. 

Platinum-catalyzed oxidation of D-glucitol affords L-gulose and D-glucose. The specificity of this reaction is probably due to both statistical and steric factors. A related example is the conversion of L-sorbose into L-vy/o-2-hexulosonic acid in 62% yield (see Ref. 1, p. 1129). Similar oxidation of 1,2-acetals of a-D-glucofuranose and a-D-xylofuranose affords the respective glycuronic acids whereas, under more drastic conditions, the former acetal is converted into 1,2-O-isopropylidene-o -D-vy/o-hexofuranos-5-ulosono-6,3-lactone, a synthetic precursor of ascorbic acids. 

Using Fischer projection formulas, we can write the structures of D-glucitol (eq 16.9) and D-mannitol (see the answer to Problem 16.9). 

Alternatively, a procedure that specifically removes the tritium by ionization, or oxidation to water-t, can be used. Thus, the presence of isotopic hydrogen at C-l of aldoses was confirmed by oxidation, either by re-isolation of the aldonic acid,7 or by measurement of the isotope appearing in the water.26 Other oxidative procedures have involved oxidation to D-glucaric acid,75 the platinum-catalyzed oxidation19 of mt/o-inositol-2-f, bacterial oxidation75 of D-glucitol-5-t, and osazone formation.76... 

Fig. 13.1. The molecular environment of the molecule of D-glucitol [GLUCIT01]. Stereo view down the carbon chain axis in the crystal structure showing molecular packing and hydrogen bonding...

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