D-Ribose residue

This enzyme [EC 3.2.2.17], also known as deoxyribodi-pyrimidine endonucleosidase, catalyzes the hydrolysis of the A -glycosidic bond between the 5 -pyrimidine residue in cyclobutadipyrimidine (in the DNA) and the corresponding deoxy-D-ribose residue. 

The structure of an unusual compound isolated from spores of Ustilago avenue46 has not yet been completely clarified. According to data available,189 it seems to be a cytidine 5 -(D-glucosyl phosphate) derivative having a peptide chain attached to a hydroxyl group of the D-ribose residue. 

The attachment of the neosamine group to C-3 of the D-ribose residue and the linkage of the neobiosamine group to C-5 of 2-deoxystreptamine... 

Five pentoses, namely, D-ribose, d- and L-arabinose, and D- and L-xylose, have been found in hydrolyzates of bacterial polysaccharides. D-Riboseisthe most common of these, and is a component of different LPS, capsular polysaccharides, and teichoic acid type of polymers. In all these polymers, it occurs as the /I-furanosyl group or residue. 

Figure 1.40 The two forms of sugar residues commonly found in nucleic acids. 3-D-Ribose is the sugar constituent of RNA, while p-D-2-deoxyribose is a component of DNA.

Some bioactive compounds contain unusual pentoses in their molecules. This is the case of the antibiotic avilamycin, which contain a L-xylose. Quite recently Bechthold ct al. have biochemically characterized the genesis of this sugar and they have shown that enzyme AviE2 converted UDP-glucuronic acid to UDP-xylose via decarboxylation, indicating that the pentose residue of avilamycin A is derived from D-glucose and not from D-ribose [28]. 

Pyrimidine natural products are particularly important (Scheme lb). The nucleic acids contain pyrimidine and purine bases ribonucleic acids (RNA) contain D-ribose and uracil, deoxyribonucleic acids (DNA) contain 2-deoxy-D-ribose and thymine and both types contain phosphate residues,... 

Four sugars quite frequently occur as furanose residues in Nature. These sugars are D-fructose, n-arabinose, D-ribose, and 2-deoxy-n-erytAro-pentose D-Galactose, L-fucose, and D-psicose have also been found naturally in the furanose form. 

Baker s original work concerned the synthesis of 3-amino-3-deoxy-D-ribose, a component residue of the antibiotic puromycin.29 Two independent syntheses were achieved, starting from L-arabinose and D-xylose, respectively. The main steps in the reaction schemes are outlined in the following reaction sequences. 

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