Sugar structures

Therapeutic Function Fluid and nutrient replenisher Chemical Name Fructose Common Name Levulose and fruit sugar Structural Formula h... 

Most secreted and membrane-embedded proteins are modified by addition of sugar structures (glycosylation) to the side chains of some amino acids. 

By convention, one of these two forms is designated the d isomer, the other the l isomer. As for other biomolecules with chiral centers, the absolute configurations of sugars are known from x-ray crystallography. To represent three-dimensional sugar structures on paper, we often use Fischer projection formulas (Fig. 7 2). 

W. A. Szarek, A. Zamojski, A. R. Gibson, D. M. Vyas, and J. K. N. Jones, Selective, reductive dechlorination of chlorodeoxy sugars. Structural determination of chlorodeoxy and deoxy sugars by l3C nuclear magnetic resonance spectroscopy, Can. J. Chem. 54 3783 (1976). 

Sugar Structure and the Boric Acid-Diol Reactions... 

The study of the structure of the sugars in solution can be approached chemically if the chemistry used is as sensitive to sugar structure as sugars are diverse in their structure. The boric acid-sugar reaction could serve this purpose if some of the fundamental aspects of this reaction were understood. Priority should probably be given to (1) the determination of the structure of the borate-sugar complex, (2) the evaluation of the stability constants for these complexes, and (3) the determination of the mechanism of the reaction. 

Many more examples of the relation between sugar structure and taste could be given. Birch et al (10) have studied a number of free sugars, sugar derivatives, and substituted sugars. 

Many lectins combine preferentially with a single sugar structure, for example g-galactose or L-fucose. For some lectins the specificity is broader and includes several closely related sugars, e.g., D-man-nose, g-glucose and g-arabinose other lectins-interact only with complex carbohydrate structures such as those that occur in glycoproteins, glycolipids,... 

Sugar Structure Thresh- old (molar) < ,r> Kd (molar) Maximum response N... 

Let s now consider concerted skeletal rearrangements which allow the direct transformation of a sugar structure into a carbocyde. The Claisen rearrangement has been used for the direct conversion of sugar C-glycosides to eight membered carbocycles, respectively. The reaction has precedents in the transformation of 2-methylene-6-vinyl-tetrahydropyrans to cyclooctenone derivatives, a transformation that has been applied in the synthesis of several natural products [54],... 

Sugar Structures Describe the common structural features and the differences for each pair ... 

Before spectroscopy, one of the best ways to identify ketones and aldehydes was conversion to crystalline hydrazones, especially phenylhydrazones and 2,4-dinitro-phenylhydrazones (Section 18-16). In his exploratory work on sugar structures, Emil Fischer often made and used phenylhydrazone derivatives. In fact, his constant use of phenylhydrazine ultimately led to Fischer s death in 1919 from chronic phenyl-hydrazine poisoning. 

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