Sorbitol isosorbide

Fig. 4. AnhydriZation of sorbitol (1) to 1,4-sorbitan (2), 3,6-sorbitan (3), 2,5-ahydro-L-iditol (4), and isosorbide (5). Also shown are isomannide (6) and...

Reaction of olefin oxides (epoxides) to produce poly(oxyalkylene) ether derivatives is the etherification of polyols of greatest commercial importance. Epoxides used include ethylene oxide, propylene oxide, and epichl orohydrin. The products of oxyalkylation have the same number of hydroxyl groups per mole as the starting polyol. Examples include the poly(oxypropylene) ethers of sorbitol (130) and lactitol (131), usually formed in the presence of an alkaline catalyst such as potassium hydroxide. Reaction of epichl orohydrin and isosorbide leads to the bisglycidyl ether (132). A polysubstituted carboxyethyl ether of mannitol has been obtained by the interaction of mannitol with acrylonitrile followed by hydrolysis of the intermediate cyanoethyl ether (133). 

Isomerization of sorbitol, D-mannitol, L-iditol, and dulcitol occurs in aqueous solution in the presence of hydrogen under pressure and a nickel—kieselguhr catalyst at 130—190°C (160). In the case of the first three, a quasiequiUbrium composition is obtained regardless of starting material. Equilibrium concentrations are 41.4% sorbitol, 31.5% D-mannitol, 26.5% L-iditol, and 0.6% dulcitol. In the presence of the same catalyst, the isohexides estabUsh an equihbrium at 220—240°C and 15.2 MPa (150 atm) of hydrogen pressure, having the composition 57% isoidide, 36% isosorbide, and 7% isomannide (161). 

Manufacture of vitamin C starts with the conversion of sorbitol to L-sorbose. Sorbitol and xyHtol have been used for parenteral nutrition following severe injury, bums, or surgery (246). An iron—sorbitol—citric acid complex is an intramuscular bematinic (247). Mannitol administered intravenously (248) and isosorbide administered orally (249) are osmotic diuretics. Mannitol hexanitrate and isosorbide dinitrate are antianginal dmgs (see Cardiovascular agents). 

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. 

Sorbitol forms a crystalline dianhydride, namely isosorbide this in contrast to isomannide was not described fully until recent times. Montgomery and Wiggins61 fully described it in 1946 but other authors had referred to it previously. In 1927 Muller and Hoffman62 described a liquid dianhydro-D-sorbitol which was probably an impure form of isosorbide. In 1940, Bell, Carr and Krantz63 described experiments with a crystalline dianhydro-D-sorbitol. Montgomery and Wiggins61... 

The simultaneous preparation of both isosorbide and isomannide from sucrose has been achieved.57 This process entailed the hydrogenation of sucrose to a mixture of D-mannitol and D-sorbitol and the subjection of this mixture to dehydration in the presence of acid catalysts followed by fractional distillation.68... 

Since no other stereoisomer but that of iditol, mannitol or sorbitol can exist in the as-fused ring series of l,4 3,6-dianhydrohexitols and since amination experiments on the ditosyl derivatives of each isomer have given three different amino derivatives, it is reasonable to assume that the two diamines which have been isolated are of the same configuration as their parent dianhydrohexitols. These two diamines LXXIV and LXXV on treatment with nitrous acid suffered deamination as expected but instead of obtaining in one case isomannide and in the other isosorbide, only one dianhydrohexitol was isolated and that was dian-hydro-L-iditol. The deamination must of course lead to the transitory carbonium cation LXXVIII and this on hydroxylation can take on any of the configurations, L-iditol, D-mannitol or D-sorbitol. That it preferentially takes on the configuration of L-iditol indicates that this is in some ways a more stable structure than the others. This behavior is paralleled... 

The hexitol anhydrides also have medicinal uses.97 Carr and Krantz98 found that l,4 3,6-dianhydro-D-mannitol was quite non-toxic to man and was a valuable diuretic. The dinitrates of both isomannide and isosorbide" have possible uses as agents for lowering blood pressure, though Burn and Stephenson100 found that the D-sorbitol derivative was twice as active as the D-mannitol derivative in this respect. 2,5-Diam-ino-2,5-didesoxy-l,4 3,6-dianhydro-D-mannitol and -D-sorbitol have been prepared and their sulfanilamido derivatives obtained.101 These however showed no outstanding bacteriostatic activity. 

Sorbitol easily dehydrates into its 1 4-3 6-dianhydro derivative, isosorbide (III), in the presence of an acid catalyst such as sulfuric, hydrochloric, or toluenesul-fonic acid or a cation exchange resin in a one-step preparation in high yield (75-85%)(1) ... 

Scheme 13 Acid catalyzed conversion of sorbitol to dilauryl isosorbide...

Jacobs and coworkers reported the catalytic activity of a mesoporous silica-supported sulfonic sites in the esterification of sorbitol with lauric acid [130]. This reaction affords in a one step process the dilauryl isosorbide (dehydration of sorbitol/esterification). In contrast to zeolites, it is found that mesoporous silica-supported sulfonic sites afford the corresponding dilauryl isosorbide with 95% selectivity at 33% conversion (Scheme 13). 

In order to avoid the acid-catalyzed dehydration of sorbitol to isosorbide, Corma et al. reported a new innovative three-step cascade route involving (1) an acetaUza-tion of sorbitol, (2) an esterification of sorbitol, and (3) a deacetalization of sorbitol esters (Scheme 14) [131]. In this case, esters of sorbitol were obtained. At 408 K, between 70 and 90% of conversion of sorbitol was obtained. Activity of the zeolites employed (H-Beta, mordenite, and dealuminated zeolite ITQ-2) was dependent on both their acidity and pore structure. The modemite catalyst has emerged as the most efficient. 

Sorbitol. Sorbitol is the sugar alcohol obtained by reduction of glucose and it can be dehydrated to either isosorbide or to 1,4- and 2,5-sorbitan in acid or base catalyzed processes, respectively. Using sulfonic acid functionalized MCM-41 type materials lauric acid esters of isosorbide can be achieved quite selectively starting from sorbitol (>95% selectivity towards isosorbide dilaurate at 33% lauric acid conversion) in a dehydration-esterification... 

Isosorbide and isomannide are important by-products of the starch industry, arising from dehydration of D-sorbitol and D-mannitol. These commercial starting materials provide an easy and inexpensive access to optically pure functionalized tetrahydrofurans like 04,05-isopropylidene-1-iodo-3,6-anhydro-1-deoxy-D-glucitol and 04,05-isopropylidene-l-iodo-3,6-anhydro-1-deoxy-Q-mannitol. This procedure describes a preparation of the former compound and the epoxide derived therefrom. 

Glucitol ("sorbitol") is converted at the initial rates of 0,135 x 10"4mol.min g cai.at 493 K and 8,8 x 10 mol.min g cat. at 533 K. The main path is its cyclization into, first, 1,4-anhydro-D-glucitol and then to 1,4-3,6-dianhydro-D-glucitol (isosorbide) (figure 1). Two secondary ways of conversion are observed leading to 2,5-anhydro-L-iditol and 2,5-anhydro-D-mannitol. 

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