Monosaccharides modified

Different approaches have been used for the hydrosilylation of allylglycosides with various H-functional polysiloxanes [71, 78, 85-87], Glucopyranosyl- and cellobiosyl-terminated oligodimethylsiloxanes with thioether or ether linkages have been prepared and tested as transdermal penetration enhancers [87], The monosaccharide-modified compounds exhibited a pronounced permeation acceleration for antipyrine, while the disaccharide ether siloxane had no enhancing activity. 

Note 1. The term glycal is a non-preferred, trivial name for cyclic enol ether derivatives of sugars having a double bond between carbon atoms 1 and 2 of the ring. It should not be used or modified as a class name for monosaccharide derivatives having a double bond in any other position. 

This is a modified form of the 1980 recommendations [4]. Priority is now given to naming cyclic forms, since in most cases branched-chain monosaccharides will form cyclic hemiacetals or hemiketals. 

Fischer projection, monosaccharides acyclic form, 56-57 cyclic forms, 59-60 modified, 60-61 Fluorine chemistry, 18-19 D-Fructofuranosides, degradation, 445 Fructofuranosyl cation, 217 Fructofuranosyl fluorides, 217 Fructose... 

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. 

Aldonolactones are useful starting materials for the synthesis of modified sugars. They have also been used as chiral templates in synthesis of natural products. Some of them are inexpensive, commercially available products or they may be obtained readily from the respective monosaccharides. The purpose of this chapter is to survey the main reactions of aldonolactones. Previous reviews on the subject include articles on gulono-1,4-lactones (1) and D-ribonolactone (2). Methods of synthesis, conformational analysis, and biological properties are not discussed in this chapter. 

In many cases the monosaccharides found in these complex structures are present as one of their chemical derivatives, which may be an oxidation or reduction product, a phosphate or sulphate ester or an amino derivative, etc. However, these modified forms of monosaccharides may themselves have important biochemical roles and are not always found incorporated in polysaccharides. 

On Ca +-form columns, some separation of monosaccharides is possible and, for the separation of galactose and glucose in dairy products, this is the column of choice. The separation of several disaccharides, such as sucrose plus maltose plus lactose, in sweetened dairy products cannot be accomplished on single-resin columns, however, and separation on amine-modified silica gel or on dual-resin columns " is recommended. These columns are capable of separating the five major food sugars, namely, D-glucose, D-fructose, sucrose, maltose, and lactose, but are subject to rapid degradation if proper precautions are not used (see Section II,2,a). 

Because carbohydrates are so frequently used as substrates in kinetic studies of enzymes and metabolic pathways, we refer the reader to the following topics in Ro-byt s excellent account of chemical reactions used to modify carbohydrates formation of carbohydrate esters, pp. 77-81 sulfonic acid esters, pp. 81-83 ethers [methyl, p. 83 trityl, pp. 83-84 benzyl, pp. 84-85 trialkyl silyl, p. 85] acetals and ketals, pp. 85-92 modifications at C-1 [reduction of aldehydes and ketones, pp. 92-93 reduction of thioacetals, p. 93 oxidation, pp. 93-94 chain elongation, pp. 94-98 chain length reduction, pp. 98-99 substitution at the reducing carbon atom, pp. 99-103 formation of gycosides, pp. 103-105 formation of glycosidic linkages between monosaccharide residues, 105-108] modifications at C-2, pp. 108-113 modifications at C-3, pp. 113-120 modifications at C-4, pp. 121-124 modifications at C-5, pp. 125-128 modifications at C-6 in hexopy-ranoses, pp. 128-134. 

Polythiophenes functionalized with monosaccharides have been evaluated for their ability to detect the influenza virus and E. coli (Baek et al. 2000). Copolymers of thiophene acetic acid 10 and carbohydrate-modified thiophenes 11 have been prepared via iron(III) chloride mediated polymerization. Addition of influenza virus to a sialic acid containing copolymer resulted in a blue shift of the polymer absorption maximum, resulting in an orange to red chromatic transition. Mannose-containing polythiophenes underwent color changes upon the addition of the lectin ConA or E. coli cells that contain cell surface mannose-binding receptors. A similar biotinylated pol5hhiophene afforded a streptavidin responsive material (Paid and Leclerc 1996). 

---