Pyranose ring structures

In 1947, L-rhamnose was first recognized by Stacey as a constituent of Pneumococcus Type II specific polysaccharide. This finding was confirmed, in 1952, by Kabat et al. and in 1955 again by Stacey when 2,4- and 2,5-di-O-methyl-L-rhamnose were synthesized and the former was shown to be identical with a di-O-methylrhamnose, obtained by hydrolysis of the methylated polysaccharide. This result indicated a pyranose ring structure for the rhamnose units in the polysaccharide. Announcement of the identification of D-arabinofuranose as a constituent of a polysaccharide from M. tuberculosis aroused considerable interest. The L-enantiomer had been found extensively in polysaccharides, but reports of the natural occurrence of D-arabinose had been comparatively rare. To have available reference compounds for comparison with degradation products of polysaccharides, syntheses of derivatives (particularly methyl ethers) of both d- and L-arabinose were reported in 1947. 

The indifference of /3-fructofuranosidase towards substitution in the afructon part of sucrose is contrasted by its extreme sensitivity towards any change in the structure and configuration of the fructon. Change from the furanose to the pyranose ring structure in methyl /3-D-fructoside is incompatible with the action of /3-fructofuranosidase.60... 

Nojirimycin (5-amino-5-deoxy-D-glucose) is an antibiotic used in studies of the biosynthesis of glycoproteins. Write its open-chain and pyranose ring structures. 

Periodate oxidations of N-acetyldidesoxydihydrostreptobiosamine indicated a pyranose ring structure for the N-methyl-n-glucosamine por-... 

As in the case of glycosides, the sugar residue of a nucleoside is presumed to have either the furanose or the pyranose ring-structure. 

MUTAROTATION The a- and /T forms of monosaccharides are readily interconverted when dissolved in water. This spontaneous process, called mutarotation, produces an equilibrium mixture of a- and /1-forms in both furanose and pyranose ring structures. The proportion of each form differs with each sugar type. Glucose, for example, exists primarily as a mixture of a- (38%) and j8- (62%) pyranose forms (Figure 7.11). Fructose is predominantly found in the a-and /J-furanose forms. The open chain formed during mutarotation can participate in oxidation-reduction reactions. 

Haworth receives the Nobel prize in chemistry for his work in carbohydrates, including describing the pyranose ring structure of the monosaccharides N-sulfation of heparin identified... 

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