Cyclic glucose

The way we have represented some of these molecules may be unfamiliarto you we have shown stereochemistry (whether bonds come out of the paper or into it— the wiggly lines indicate a mixture of both) and, for the cyclic glucose, conformation (the actual shape the molecules adopt). These are very important in the sugars we devote Chapter 16 to stereochemistry and Chapter IB to conformation. 

FIGURE 7. (A) Crystal structure of xylose isomerase. The 8 a-helices comprised of the alji barrel are labeled A-H (PDB ID IXID, Plate XI). (B) The active site of xylose isomerase with a bound cyclic glucose (IXIF, Plate XII). (C) The active site of xylose isomerase with a bound xylose in linear form (8XIA) and the catalyticaUy important Lys and His (green, Plate XIII). (D) The active site of xylose isomerase with a bound ascorbate via its 3,4-enediolate site (IXID, Plate XIV)... 

FIGURE 23.17 Both starch (a) and cellulose (b) are polymers of glucose. In starch, all the cyclic glucose units are a-D-glucose. In cellulose, all the monomer units are /3-D-glucose. 

FIGURE 9.15 Schematics for the electrochemical oxidation of cyclic glucose forms. (From Domenech and Alarcon, 2007. Anal. Chem. 79, 6742-6751, with permission.)... 

Cyclodextrins are cyclic glucose oligomers consisting of six or more monomer units. The cyclodextrin structure is such that the hydrogens of C-H bonds are directed towards the inside of the cavity of the molecule and hydroxyl groups are directed towards the outside (Fig. 11-7). Therefore, the molecule has a hydrophobic cavity, which owing to its hydrophobicity can bind nonpolar molecules into host-guest complexes and transfer them into the polar phase. This property of cyclodextrins allows us to use them as components of catalytic systems in two-phase catalysis by metal complexes. [20-23, 182-196] this essentially increased the activity of these catalytic systems. 

Cyclodextrins (1) are cyclic glucose oligomers of cylindrical shape having primary hydroxyl groups at the... 

Cyclodextrins are cyclic glucose oligomers (da) having the shape roughly depicted in (6b), as a cylindrical form with the primary hydroxyl group at the more restricted end of the cylinder (most of the hydroxyl groups have been omitted from the drawing). 

On treatment with acid, glucose is liberated first, followed by a molecule of inorganic phosphate. The intermediate, uridine diphosphate, has been isolated. Uridine-5 -pho8phate is quite stable to acid. In alkali, the pyrophosphate linkage is cleaved, liberating the nucleotide plus a cyclic glucose monophosphate in which the phosphate is esterified both at Ci and another carbon atom, probably Cj. ... 

The four kelohexoses are fructose, sorbose, allulose and tagatose. See glucose for example of isomerization between open chain and cyclic structures in a typical hexose molecule. 

It is probable that many of the reactions of glucose in solution are due to the small amount of the open chain aldehyde present. If this reacts in a normal manner with a reagent, the equilibrium is disturbed, most of the cyclic form passes into (III) and ultimately the reaction proceeds to completion.-Fructose may be similarly formulated ... 

Lactam (Section 20 15) A cyclic amide Lactone (Section 19 15) A cyclic ester Lactose (Section 25 14) Milk sugar a disacchande formed by a p glycosidic linkage between C 4 of glucose and C 1 of galactose... 

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