Monosaccharide etherification

Abstract Polyfunctionality of carbohydrates and their low solubility in conventional organic solvents make rather complex their conversion to higher value added chemicals. Therefore, innovative processes are now strongly needed in order to increase the selectivity of these reactions. Here, we report an overview of the different heterogeneously-catalyzed processes described in the literature. In particular, hydrolysis, dehydration, oxidation, esterification, and etherification of carbohydrates are presented. We shall discuss the main structural parameters that need to be controlled and that permit the conversion of carbohydrates to bioproducts with good selectivity. The conversion of monosaccharides and disaccharides over solid catalysts, as well as recent advances in the heterogeneously-catalyzed conversion of cellulose, will be presented. 

Here we report an overview of the different heterogeneously-catalyzed pathways designed for the selective conversion of carbohydrates. On the basis of these results, we shall try to determine the key parameters allowing a better control of the reaction selectivity. Water being commonly used as solvent in carbohydrate chemistry, we will also discuss the stability of solid catalysts in the aqueous phase. In this review, heterogeneously-catalyzed hydrolysis, dehydration, oxidation, esterification, and etherification of monosaccharides and polysaccharides are reported. 

Ethers are important derivatives of both monosaccharides and polysaccharides. Etherification is often used in the determination of structures and types of linkages between sugars in oligo- and polysaccharides. Table 2-2 gives examples of the preparation of ethers. Ethers are very stable against both acids and bases. 

In this context, a one-pot regioselective protection of persilylated monosaccharides, using copper(ii) triflate as a single catalyst was able to promote acetalation-reductive etherification-acylation reactions. In the same way, the easy to handle, cheap and environment-friendly FeCls 6H2O complex was a very efficient catalyst to promote regioselective acetalation and reductive etherification on glucopyranosides. Hence, treatment of per-O-silylated a-methyl-u-glucopyranoside 50 with benzaldehyde (3 equiv) and triethylsilane (1.1 equiv) in the presence of... 

It was stated earlier (p. 9) that internal etherification of monosaccharides yields anhydro-sugars. 1,2-, 2,3-(CC), 34-, and 5,6-epoxide rings, 2,4- and 3,5-propylene oxides (2,4-anhydro-D-glucose (CCI), and 3,5-anhydro-D-xylo-P3Tanose), and 1,4-, 2,5-, and 3,6- (CCII) butylene oxide rings are known. 

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