Glucitols

D[Pg.367]

Another name for glucitol obtained by reduction of d glucose is sorbitol it is used as a sweetener especially in special diets required to be low in sugar Reduction of D fructose yields a mixture of glucitol and mannitol corresponding to the two possi ble configurations at the newly generated chirality center at C 2... 

Fig. 2. Structures of hexitols (a) allitol, (b) sorbitol (D-glucitol), (c) D-maimitol, (d) dulcitol, (e) L-iditol, and (f) D-altritol.

Maltitol (4-0-a-D-glucopyranosyl-D-glucitol) formed by catalytic hydrogenation of maltose (97), has been obtained both as a noncrystalline powder and a viscous Hquid (98). Stmctures of disacchatide alcohols are shown ia Figure 3. 

Lactitol (4-0-p -D-galactopyranosyl-D-glucitol) is obtained by sodium borohydride reduction (99,100) or catalytic hydrogenation (101) of lactose. Potentially large quantities of this sugar alcohol are available from lactose obtained from whey. 

Loss of a second molecule of water occurs on heating (1) (106,107), (2), or (3) (108) with concentrated sulfuric or hydrochloric acid forming 1,4 3,6-dianhydro-D-glucitol (isosorbide) (5). Mannitol and iditol anhydrize under similar conditions to isomannide (6) and isoidide (7), respectively. In (6), both hydroxyl groups are oriented toward each other (endo) ia (7), both are oriented away from each other (exo) and ia isosorbide (5), one hydroxyl is endo and the other exo. XyUtol loses two moles of water to form l,3 2,5-dianhydrox5litol (109). 

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],... 

A series of sorbitol-based nonionic surfactants are used ia foods as water-ia-oil emulsifiers and defoamers. They are produced by reaction of fatty acids with sorbitol. During reaction, cycHc dehydration as well as esterification (primary hydroxyl group) occurs so that the hydrophilic portion is not only sorbitol but also its mono- and dianhydride. The product known as sorbitan monostearate [1338-41 -6] for example, is a mixture of partial stearic and palmitic acid esters (sorbitan monopalmitate [26266-57-9]) of sorbitol, 1,5-anhydro-D-glucitol [154-58-8] 1,4-sorbitan [27299-12-3] and isosorbide [652-67-5]. Sorbitan esters, such as the foregoing and also sorbitan monolaurate [1338-39-2] and sorbitan monooleate [1338-43-8], can be further modified by reaction with ethylene oxide to produce ethoxylated sorbitan esters, also nonionic detergents FDA approved for food use. 

Chemical DesignationsD-Glucitol Hexahydric alcohol 1,2,3,4,5,6-Hexanehexol Sorbit Sorbo Sorbol Chemical Formula CH20H(CH0H)4CHj0H. 

D-Glucitol D-Mannitol D-Xylitol D-Glycerol myo- Inositol D-Ribitol... 

An aqueous syrup of 1,4 3,6-dlanhydro-D-glucitol is slowly added to a cooled mixture of HNO3 and H2M4. After standing a few minutes the mixture is poured into cold water and the precipitated product is collected and recrystallized from ethanol. 

Treatment of l,4 3,6-dianhydro-D-glucitol with boron trichloride gives l,6-dichloro-l,6-dideoxy-D-glucitol (20). Although methyl 6-chloro-6-deoxy-a-D-glucopyranoside (isolated as the tribenzoate) could be isolated from the reaction of methyl 3,6-anhydro-a-D-glucopyranoside with boron trichloride (21), the application to the isomeric furanoside derivative led to complex results. 

D-Glucitol, the alditol produced by reduction of D-glucose, is itself a naturally occurring substance present in many fruits and berries. It is used under its alternative name, D-sorbitol, as a sweetener and sugar substitute in foods. 

Problem 25.17 I Reduction of D-glucose leads to an optically active alditol (D-glucitol), whereas reduc-I tion of D-galactose leads to an optically inactive alditol. Explain. 

Problem 25.18 I Reduction of L-gulose with NaBH4 leads to the same alditol (D-glucitol) as reduction of D-glucose. Explain. 

GC separation of the acetate derivatives rhamnitol, fucitol. ribi-tol, arabinitol, mannitol, galacitol, glucitol, and inositol... 

D-glucitol. See sorbitol D-mannitol. See mannitol Dactylopius coccus, 111... 

Amino-sugars and Related Compounds. Part VII. 2-Amino-2-deoxy-1,3,4,5-tetra-O-methyl-D-glucitol, 2-Amino-2-deoxy-L-threitol and Certain Derivatives Thereof, A. B. Foster, D. Horton,... 

Anhydro-2,3,4,6-tetra-0-methyl-D-glucitol-1-ide 2-Carb-32.4. Radical ions... 

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