Glycosides linkages

FIGURE 25 6 Molecu lar models of the disaccha rides maltose and cellobiose Two D glucopyranose units are connected by a glycoside linkage between C 1 and C 4 The glycosidic bond has the a orientation in maltose and IS p in cellobiose Mai tose and cellobiose are diastereomers... 

One of the most important differences between cellulose and starch is that animals can digest starch Because the glycosidic linkages m starch are a an animal s a glycosidase enzymes can catalyze then hydrolysis to glucose When more glucose is... 

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... 

Derivatives. Many derivatives of acylated phlorogluciaols that bear a benzene ring substituent or an ether or glycoside linkage occur ia aature. Examples are cotoia [479-21-0] (52) ia coto bark and conglomerone [480-25-1] (53) ia Eucalyptus conglomerata. 

Neosidomycin (63) and SF-2140 (64) are indole N-glycosides produced by S. hjgroscopicus A.ctinomadura respectively (195,196). A revised stmcture for (63) has appeared (197). Compound (64) contains an a-N-glycoside linkage. Both (63) and (64) show activity against gram-positive bacteria, yeast, fungi, and vimses. 

Fig. 1. Primary stmctures of some common polysaccharides, (a) Alpha-glycoside linkages characterize amylose, amylopectin, and glycogen (b) cellulose has...

Fig. 1. Stmctural diagram of (a) P-cyclodextrin and (b) two of the glucopyranose units illustrating details of the a-(l,4) glycosidic linkage, C-1 (d) chair...

The small change in stereochemistry between cellulose and amylose creates a large difference in their overall shape and in their properties. Some of this difference can be seen in the strorcture of a short portion of fflnylose in Figure 25.9. The presence of the a-glycosidic linkages imparts a twist to the fflnylose chain. Where the main chain is roughly linear- in cellulose, it is helical in anylose. Attractive forces between chains are weaker in fflnylose, and fflnylose does not form the same kind of strong fibers that cellulose does. 

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. 

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