Alcohols disaccharide

Low-caloric Sugar alcohols Disaccharides Isomalt Lactitol Maltitol... 

Fig. 3. Structures of disaccharide alcohols (a) maltitol, (b) lactitol, (c) a-D-glucopyraiiosyl-l,l-D-maiinitol(dihydrate), and (d)...

We saw in Section 25.6 that reaction of a monosaccharide with an alcohol yields a glycoside in which the anomeric -OH group is replaced by an -OR substituent. If the alcohol is itself a sugar, the glycosidic product is a disaccharide. 

A disaccharide in which one glycosyl unit has replaced the hydrogen atom of an alcoholic hydroxy group of the other is named as a glycosylglycose. The locants of the glycosidic linkage and the anomeric descriptor(s) must be given in the full name. 

Hydrogenation of the carbonyl group of a mono- or disaccharide gives the corresponding sugar alcohol. On paper, this reaction is simple, and it can schematically be written as O... 

In an fermentation process of a solution containing sucrose, the enzyme in-vertase, present in yeast, acts as a catalyst to convert sucrose into a 1 1 mixture of glucose and fructose. Thus, sucrose is a disaccharide that hydrolyzes in the presence of certain bacteria to yield glucose and fructose. The ether linkage in sucrose is broken to yield two alcohols ... 

KEY TERMS carboxylic acid alcohol oxidation disaccharide... 

The disaccharide component was not maltose the value of the rotation at the end of the first stage (+64°) excluded that sugar. The fairly pure, though amorphous, disaccharide, which he freed largely from D-glucose by the use of alcohol, was considered to be a new disaccharide, to which Alekhine gave the name turanose, from Turan, the old Persian... 

Alekhine had mentioned that turanose reacts with phenylhydrazine. Maquenne prepared the phenylosazone and described its precipitation from water in the flocculent or gel condition that is so very characteristic of the substance, but he did not report an analysis. A year after Ma-quenne s publication, Emil Fischer16 examined a small sample of amorphous turanose which had been sent by Dr. Konowaloff of Moscow. Its phenylosazone was prepared in good crystalline form by several recrystallizations from aqueous alcohol the analysis of these crystals proved conclusively the disaccharide formula for turanose which Alekhine had proposed from the analysis of amorphous substances. The writer had occasion recently to prepare turanose phenylosazone in considerable quantity its very characteristic properties and those of the derived phenylosotriazole are described on pages 27 and 28. 

Various fully-acetylated monosaccharides and disaccharides or sugar alcohols are readily separable by chromatographic adsorption on Mag-nesol (a hydrated magnesium acid silicate)111 and the unacetylated substances may be separated on clay columns.112... 

Although aliphatic alcohols are typically poor acceptors in the Mitsunobu-type glycosylation, Szarek and coworkers have highlighted one advance to this end [95]. For the triphenylphosphine and diethylazodicarboxylate promoted glycosylation of a monosaccharide acceptor, the addition of mercuric bromide is necessary to promote the reaction. For example, the (1,6)-disaccharide 44 was obtained in 80% yield using this modified Mitsunobu protocol. Unlike previous examples with phenol or N-acceptors, preactivation of the hemiacetal donor was performed for 10 min at room temperature prior to addition of the aliphatic alcohol nucleophile. 

Kusumoto and coworkers have found that the treatment of hemiacetal 1 with trifluoro- or trichloroacetic anhydride 94 (1 equiv) and trimethylsilyl perchlorate (0.2 equiv) selectively provides the corresponding anomeric ester intermediate 91 [152], Hemiacetal acylation occurs even in the presence of the alcohol acceptor. With Lewis acid assistance, the glycosyl ester intermediate is displaced to provide disaccharide products in good yields. This transformation allowed the synthesis of disaccharides 98 (81%) and 99 (91%). In some cases, acetic anhydride has been used as the electrophilic activator of hemiacetal donors and the reaction with thiol acceptors yields S-linked glycosides [153,154],... 

---