Primary -Glycosylation

In bacteria, primary glycosyl nucleotides include14 22 UDP-Glc, as well as other nucleotide derivatives of the same monosaccharide. Important representatives of this class are16"21,23"25 dTDP-Glc and17"19,21,26 29 CDP-Glc, which serve as precursors for a number of secondary glycosyl nucleotides, whereas similar enzymic reactions have not been demonstrated for GDP-Glc,1819,21,30 and ADP-Glc17 19,21-31"38 seems to participate only in the biosynthesis of bacterial glycogen, a subject that is beyond the scope of this article. 

Guanosine (D-mannosyl diphosphate) (GDP-Man, 4)39-42 and uridine (2-acetamido-2-deoxy-D-glucosyl diphosphate) (UDP-GlcNAc, 5)43,44 are other important examples of primary glycosyl nucleotides. Although formation of ADP and dTDP derivatives of the latter monosaccharide was observed,17 their functions remain obscure.45... 

The symbol X in the Table means that an activated form of the monosaccharide is not known a dash shows that the monosaccharide has not been identified as a component of bacterial polysaccharides. For references, see the text. 6 See Ref. 101 for abbreviations. c Primary glycosyl nucleotide. 4 See comments in the text. 

The key intermediates in the biosynthesis of 6-deoxy sugars are the nucleoside 6-deoxyhexosyl-4-ulose diphosphates (7), formed through enzymic reactions catalyzed by NDP-sugar 4,6-dehydratases (EC 4.2.1.45-47) from primary glycosyl nucleotides. These reactions were observed... 

In this group of monosaccharide components of bacterial polysaccharides, a primary glycosyl nucleotide is ADP-D-g/ycero-D-manno-heptose (9), identified in extracts of a mutant strain of Shigella sonnei.231... 

Rhamnogalacturonan 11 (RG-11) is a structurally complex, pectic polysaccharide that is present in the primary cell-walls of higher plants. It is composed of 60 glycosyl residues, and is a very complex molecule indeed. For example, on acid hydrolysis, at least ten different monosaccharides are formed, including the novel aceric acid (30), which is the only branched-... 

Disarmed glycosyl trichloro- and /V-(phenyI)trifluoroacetimidates were efficiently activated by the system I2/Et3SiH for the rapid and high-yield glycosylation of primary and secondary saccharide acceptors, and it was observed that the presence of AW 4 A MS was decisive for achieving high reaction yields.62... 

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