Disaccharide nonreducing

Trehalose is a nonreducing disaccharide that is hydrolyzed by aqueous acid to yield 2 equivalents of D-glucose. Methylation followed by hydrolysis yields 2 equivalents of 2,3,4,6-tetra-O-methylglucose. How many structures are possible for trehalose ... 

A nonreducing disaccharide gives an octamethyl derivative with dimethyl sulfate and alkali. On acid hydrolysis, this derivative yields 1 mol of 2,3,4,6-tetramethyl-D-glucose and 1 mol of 2,3,4,6-tetramethyl-D-galactose. The disaccharide is hydrolyzed rapidly by either maltase or lactase (a P-galactosidase). 

In general, we find that the nonreducing disaccharides give none of the carbonyl reactions observed for glucose, such as mutarotation and osazone formation, except when the conditions are sufficiently acidic to hydrolyze the acetal linkage. 

It was found122 that 2,3 5,6-di-0-isopropylidene-D-mannose reacts with p-toluenesulfonyl chloride in pyridine, but the only product isolated was the corresponding mannofuranosylpyridinium p-toluenesulfonate. On the other hand, when 2 moles of the sodium salt of 2,3 5,6-di-0-iso-propylidene-D-mannose, dissolved in dry petroleum ether, were treated with one mole of p-toluenesulfonyl chloride, there apparently resulted the nonreducing-disaccharide derivative, 2,3 5,6-di-0-isopropylidene-D-mannofuranosyl 2,3 5,6-di-0-isopropylidene-D-mannofuranoside (a compound later prepared121 by condensation of 2,3 5,6-di-0-isopropylidene-D-mannosyl chloride with 2,3 5,6-di-0-isopropylidene-D-mannose). Presumably, the following reactions had taken place (Ip = isopropylidene) ... 

The 4,6-anhydro derivative 93 has been reportedly prepared from ethyl 2,3-dideoxy-o -D-t/zreo-hex-2-enopyranoside by mesylation at C-6 to give 92 and action of base 354 in a similar way a 4,6-anhydro-a-D-galactopyranosyl component was built into a nonreducing disaccharide.355... 

A disaccharide is formed when two monosaccharides become joined by a glycosidic bond. The bond may be an a- or (3-bond depending on the configuration of the anomeric carbon atom involved in the bond. Usually the anomeric carbon atom of only one of the two monosaccharides is involved in the bond so that the disaccharide still has one free aldehyde or ketone group and is still reducing. However, in sucrose both anomeric carbon atoms are bonded together so that sucrose is a nonreducing disaccharide. 

Trehalose is a nonreducing disaccharide (C12H22O11) isolated from the poisonous mushroom Amanita muscaria. Treatment with an a-glucosidase converts trehalose to two molecules of glucose, but no reaction occurs when trehalose is treated with a j3-glucosidase. When trehalose is methylated by dimethyl sulfate in mild base and then hydrolyzed, the only product is 2,3,4,6-tetra-O-methylglucose. Propose a complete structure and systematic name for trehalose. 

Trehalose occurs as a nonhygroscopic, white, crystalline powder. It is obtained through enzymatic conversion of food-grade starch into a stable, nonreducing disaccharide with two glucose molecules linked in an a,a-1,1 configuration. The powder is freely soluble or readily dispersible in water. Trehalose is typically used in its dihydrate form. 

The nature of the sugars in a nonenzymic browning reaction determines their reactivity. Reactivity is related to their conformational stability or to the amount of open-chain structure present in solution. Pentoses are more reactive than hexoses, and hexoses more than reducing disaccharides. Nonreducing disaccharides only react after hydrolysis has taken place. The order of reactivity of some of the aldohexoses is mannose is more reactive than galactose, which is more reactive than glucose. 

FIGURE 2.41 The three possible nonreducing disaccharides of D-glucofuranose. 

FIGURE 2.42 The three possible nonreducing disaccharides of D-glu opy 7,006 by Taylor Francis Group LLC... 

The monosaccharide units can be present in both their furanose and pyranose forms, and the anomeric configuration can be both a and (3 in the case of nonreducing disaccharides. When both monosaccharides have the same configuration (e.g., D-glucose), there are several variations. When both monosaccharide units form furanose rings, three isomers — two symmetric... 

Lemer, L M, Ferric chloride-molecular sieve-catalyzed formation of a nonreducing disaccharide derivative, Carbohydr. Res., 207, 138-141, 1990. 

Trehalose is a nonreducing disaccharide that is hydrolyzed by aqueous acid to]... 

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