Of 1,2-disaccharide

Maltose and cellobiose (Section 25 14) are examples of disaccharides denved from D glucopyranosyl units... 

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

Sections Disaccharides are carbohydrates in which two monosaccharides are 25.14-25.15 joined by a glycoside bond. Polysaccharides have many monosaccharide units connected through glycosidic linkages. Complete hydrolysis of disaccharides and polysaccharides cleaves the glycoside bonds, yielding the free monosaccharide components. 

A disaccharide is added to a pyridine SO3 complex solution, which is prepared by reacting 5 to 6 times the molar amount of liquid SO3 as much as that of disaccharide with 5 to 10 times the amount of pyridine as that of the disaccharide at 0°C to 5°C, for sulfation at 50°C to 70°C for 3 to 7 hours. After the completion of sulfation, the greater part of pyridine Is removed by decantation. The obtained solution exhibits an acidity that is so strong that it is improper to apply the reaction with aluminum ion and, therefore, sodium hydroxide is added for neutralization. After the remaining pyridine is removed by concentration, 100 unit volumes of water per unit volume of the residue is added thereto. To the solution is then added aluminum ion solution mainly containing aluminum dihydroxychloride, the pH of which is 1.0 to 1.2, in such an amount that the aluminum ion Is present in an amount of 4 to 6 molar parts of the amount of disaccharide to provide a pH of 4 to 4.5. The mixture is reacted under stirring at room temperature and the formed disaccharide poly sulfate-aluminum compound is allowed to precipitate. After filtration, the residue is washed with water and dried. 

An important metabolic reaction of disaccharides is the reverse of (5). Water, in the presence of H+(aq), reacts with sucrose to give glucose and fructose. This process is called hydrolysis, meaning reaction with water."... 

In contrast with the monotonous monosaccharide repeat and the same type of linkage in the polysaccharide structures (1 to 21) described in Sections IV and V, this section deals with rather more complex polymers (23 to 39), which are composed of disaccharide repeats. Further, combining two types of linkages enhances the formation of exotic morphologies not amenable to the former set. The sequence listed in Table II is referred to as -A-B- in Table V while listing... 

Scheme 34 Introduction of disaccharides into the pyrazinone skeleton ...

Figure 10.32 Applications of bidirectional chain extension for the synthesis of disaccharide mimetics and of annulated and spirocyclic oligosaccharide mimetics using tandem enzymatic aldol additions, including racemate resolution under thermodynamic control.

Nonselective Spin-Lattice Relaxation Rates (s )° for the Anomeric Protons of Disaccharides, Oligosaccharides, and Polysaccharides... 

Carbohydrates are classified based upon the products formed when they are hydrolyzed. Monosaccharides are simple sugars that cannot be broken down into simpler sugars upon hydrolysis. Examples of monosaccharides are glucose, ribose, deoxyribose, and fructose. Disaccharides contain two monosaccharide units and yield two monosaccharides upon hydrolysis. Examples of disaccharides are lactose, maltose, and sucrose. Polysaccharides are polymers of monosaccharide units and yield many individual monosaccharides upon hydrolysis. Examples of polysaccharides are starch, glycogen, and cellulose. 

Conclusive evidence for the a-L configuration of the idosyluronic-to-hexosamine bond was provided by 1H-n.m.r. studies on disaccharide 7, obtained as the major product ( 75% yield) of the cleavage of heparin by heparinase.106 This configuration is consistent also with the 1H- and 13C-n.m.r. spectra of disaccharide 6 (the major product from nitrous acid cleavage of heparin103-106) and of unmodified heparin.82-84... 

Both positional linkages (uronic acid to hexosamine and hexosamine to uronic acid) were established as being (1 — 4) by structural analysis of the previously mentioned (see Section IV), crystalline disaccharides containing D-glucuronic acid, isolated from an acid hydrolyzate of carboxyl-reduced heparin.128-129 Further evidence was obtained from the structure of the D-glucuronic acid-containing counterpart of disaccharides 6 and 8, obtained as minor products from pig-mucosal heparin following nitrous acid deamination,1110 136-138 and acid hydrolysis followed by N-acetylation,130 respectively. 

Fic. 6.—Proposed Distribution of Disaccharide Units Along an Average Heparin Chain.151 [For simplicity, possible linkage regions and antithrombin-binding sequences are not considered. For notations, see legend and footnote to Scheme 1. Arrows indicate possible insertion of units G-Ana.]... 

Martin has used this strategy for the preparation of (3-(l,6) and P,(3-(l,l) hnked C-disaccha-rides, as shown in Scheme 7.7.73 Such C-disaccharides are a class of nonhydrolyzable mimics of disaccharide and potential glycosidase inhibitors in the treatment of metabolic diseases (Scheme 7.7). 

Huang, S.S., Yu, H. and Chen, X. (2007) Disaccharides as sialic acid aldolase substrates synthesis of disaccharides containing a sialic acid at the reducing end. Angewandte Chemie-International Edition, 46, 2249-2253. 

An early report from Shukla et al.129 showed efficient hydrolysis and isomerization reactions of disaccharides, including cellobiose, maltose, and lactose, over zeolites type A, X, and Y. Abbadi et al.130 studied the hydrolysis of maltose, amylose, and starch over the zeolitic materials H-mordenite, H-beta, and mesoporous MCM-41. The effect of temperature and pressure, as well as that of the Si/Al ratio of H-mordenite and H-beta zeolites, on their catalytic activity was investigated for the... 

M. Wilstermann and G. Magnusson, Synthesis of disaccharide glycosyl donors suitable for introduction of the /i-D-Galp-0 >3)-a- and -jS-D-GalpNAc groups, Carbohydr. Res., 272 (1995) 1-7. 

Maurer62 investigated briefly the ability of the reducing unit of disaccharides to form a 7-pyrone nucleus without cleavage of the glycosidic linkage. Hepta-0-acetyl-(2-hydroxycellobial) (LIII) and hepta-O-acetyl-... 

The anomeric natures of two sugar residues in 36 are evident from the characterization of disaccharides 32 and 33. The other anomeric... 

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