A-Disaccharides

D (+) Galactose is a constituent of numerous polysaccharides It is best obtained by acid hydrolysis of lactose (milk sugar) a disaccharide of d glucose and d galactose L (—) Galactose also occurs naturally and can be prepared by hydrolysis of flaxseed gum and agar The principal source of d (+) mannose is hydrolysis of the polysaccharide of the ivory nut a large nut like seed obtained from a South American palm... 

Sucrose (Section 25 14) A disaccharide of glucose and fruc tose in which the two monosacchandes are joined at their anomenc positions... 

Rhamsan Gum. Rhamsan gum, produced y lcaligenes strain (ATCC 31961) (91), has the same backbone as geUan and welan gums, but it carries a disaccharide sidechain (92). 

La.ctose, Lactose [63-42-3] (milk sugar), 20, makes up about 5% of cow s milk. Lactose is a disaccharide composed of D-glucose... 

Suciose [57-50-1] (P-D-fructofuianosyl-a-D-glucopyianoside), 0 2 22, fomiula weight 342.3, is a disaccharide composed of glucose and fmctose residues joined by an a,P-glycosidic bond (Fig. 1). 

Among the various types of sugars marketed, the mass consumption of sucrose far outweighs by volume the consumption of other products. Sucrose, also called table sugar, is a disaccharide which, upon hydrolysis, yields two monosaccharides glucose and fmctose. Various types of sugar vary in sweetness (1). 

Dextrose (D-glucose) is by far the most abundant sugar in nature. It occurs either in the monosaccharide form (free state) or in a polymeric form of anhydrodextrose units. As a monosaccharide, dextrose is present in substantial quantities in honey, fmits, and berries. As a polymer, dextrose occurs in starch, cellulose (qv), and glycogen. Sucrose is a disaccharide of dextrose and fmctose. 

DP refers to degree of polymerization, where DP-1 is dextrose, DP-2 is a disaccharide, etc. DE = dextrose equivalent. 

Lactose is a disaccharide constituting 2-6% of milk and is known as milk sugar. It differs from maltose and cellobiose in that only one of its monosaccharide units is D-glucose. The other monosaccharide unit, the one that contributes its anomeric carbon to the glycoside bond, is D-galactose. Like cellobiose, lactose is a p-glycoside. 

Cellobiose (Section 25.14) A disaccharide in which two glucose units are joined by a (3(1,4) linkage. Cellobiose is obtained by the hydrolysis of cellulose. 

Lactose (Section 25.14) Milk sugar a disaccharide formed by a (3-glycosidic linkage between C-4 of glucose and C-1 of galactose. 

FIGURE 6.20 A disaccharide of galactose and glucose is covalently linked to the 5-hydroxyl group of hydroxylysines in collagen by the combined action of the enzymes galactosyl transferase and glucosyl transferase. 

Sucrose, in contrast, is a disaccharide of almost universal appeal and tolerance. Produced by many higher plants and commonly known as table sugar, it is one of the products of photosynthesis and is composed of fructose and glucose. Sucrose has a specific optical rotation, of +66.5°, but an... 

Trehalose, a disaccharide produced in fungi, has the following structure ... 

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. 

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. 

Although glucose can exist as a simple sugar, it is most often found in nature in combined form, as a disaccharide or polysaccharide. Several glucose-containing disaccharides are known. We will consider two of these, maltose and sucrose. 

The two sugars we have discussed are monosaccharides—they have a single, simple sugar unit in each molecule. The sugar on your table is a disaccharide—it has two units. One molecule of sucrose contains one molecule of glucose and one of fructose hooked together (losing a... 

Several new exopolysaccharides such as welan and rhamsan produced by Alcaltngettes spp may supercede xanthan for some industrial applications. These are based on the same repeat tetrasaccharide backbone of glucose, glucuronic acid, glucose and rhamnose but differ in the substituents rhamsan has a disaccharide side chain and welan a monosaccharide. Both are stable at high temperature and have excellent pseudoplastic properties. 

Lactose is a disaccharide, two simple sugars in one molecule. In this case, the sugars are galactose and glucose. 

On either side of the crocetin molecule is a disaccharide molecule called beta-gentiobiose, and the result is the molecule that gives saffron its yellow color. 

A disaccharide is a compound in which two monosaccharide units are joined by a... 

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. 

The E. coli M41 mutant CPS (46) has a complex chemical sequence. Its repeating unit is an anionic hexamer a tetrasaccharide -A-B-C-D- in the main chain and a disaccharide -F-E- side chain, E attached to C (Table II). Polycrystalline and oriented fibers of the sodium salt of 46 have produced good diffraction data, with reflections up to 3 A resolution. Careful X-ray analysis60 has shown that the polymer forms a left-handed, smooth and sinuous, 2-fold helix of pitch 30.4 A. As shown in Fig. 39a, the main chain is fairly close to the helix axis. A notable observation is that side chain E-F, turned up toward the non-re-... 

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