Glycosides between

O-glycosidation between O-silylated glycosyl acceptors and several 1-substituted sugars, glycopyranosyl or furanosyl silyl ethers [79a], fluorides [80], phosphates [81], and trichloroacetimidates [82a] has been examined to develop other efficient and stereoselective procedures catalyzed by silicon Lewis acids. The trichloroacetimidate glycosyl donors are fairly reliable and were used for the synthesis of eanelioside GD by Ogawa (Fig. l)[82b]. 

Polysaccharides are glycosides between sugars. The name given to the polysaccharide is dependent on the size of the molecule ... 

Al-glycosidic, between the reducing end monosaccharide and the side chain amide group of asparagine (Al-glycans),... 

The alkamines isolated directly from plant material or obtained by acid or enzymatic hydrolysis of naturally occurring glycosides between 1967 and 1979 are summarized in Table III. Physical me ods are of increasing importance in structure elucidation. Recent papers have dealt with IR spectra (173), H NMR (174,175), NMR (176-178,357,358), EPR (179), ORD (180-183), and MS (184,351,352) of Solanum alkamines. Some X-ray analyses have been carried out since 1967 (58, 81, 149, 185-189, 359). Tables rV-VI survey the characteristic features of H NMR, NMR, and MS of Solanum alkaloids. Silver nitrate-containing adsorption layers were shown to be useful in TLC separation of 5a-saturated and S-unsaturated alkamines (194,195). High-pressure liquid chromatography has been applied successfully for the separation of steroidal Solanum and Veratrum alkamines (373). 

Kato Y, Yasue M 1984 Studies on the constituents of Lyonia ovalifolia Drude van elliptica Hand.-Mazz. XXL The difference of flavonoid glycosides between individuals. Shoyakugaku Zasshi 37 412-417... 

Maltose obtained by the hydrolysis of starch and cellobiose by the hydrolysis of cellulose are isomenc disaccharides In both maltose and cellobiose two d glucopyra nose units are joined by a glycosidic bond between C 1 of one unit and C 4 of the other The two are diastereomers differing only m the stereochemistry at the anomeric carbon of the glycoside bond maltose is an a glycoside cellobiose is a (3 glycoside... 

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... 

Nikkomycins. The nikkomycins (141—159), isolated from S. tendae are nucleoside-peptide antibiotics (1,4,244,245) as shown in Table 8. Nikkomycins X and Z are stmcturaHy identical to neopolyoxins A and C, respectively. Compound (141) is a competitive inhibitor of chitin synthetase. Two new nikkomycins, nikkomycin pseudo-Z and pseudo-J (158, 159), contain a C-glycosidic bond between C-5 of uracil and C-1 of... 

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. 

RNA is relatively resistant to the effects of dilute acid, but gentle treatment of DNA with 1 mM HCl leads to hydrolysis of purine glycosidic bonds and the loss of purine bases from the DNA. The glycosidic bonds between pyrimidine bases and 2 -deoxyribose are not affected, and, in this case, the polynucleotide s sugar-phosphate backbone remains intact. The purine-free polynucleotide product is called apurinic acid. 

Disaccharides contain a glycosidic acelal bond between the anomeric carbon of one sugar and an -OH group at any position on the other sugar. A glycosidic bond between Cl of the first sugar and the -OH at C4 of the second sugar is particularly common. Such a bond is called a 1—>4 link. 

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