Synthesis of Sugar Nucleotides

There is a second large gene duster, about 35kb, also involved in the synthesis of xanthan. The predse function is unknown but it is thought to encode for proteins involved in the synthesis of sugar nucleotide diphosphates. 

The first application of this reaction for the synthesis of sugar nucleotides was reported in 1958, when Moffatt and Khorana269 prepared uridine 5 -(a-D-glucopyranosyl pyrophosphate) (5) in 59% yield from uridine 5 -phosphoramidate (58). Other examples of similar... 

Timmons SC, Jakeman DL (2007) Stereoselective chemical synthesis of sugar nucleotides via direct displacement of acylated glycosyl bromides. Org Lett 9 1227... 

Mizanur RM, Zea CJ, Pohl NL (2004) Unusually broad substrate tolerance of a heat-stable archaeal sugar nucleotidyltransferase for the synthesis of sugar nucleotides. J Am Chem Soc 126 15993-15998... 

The most general mechanism for the synthesis of sugar nucleotides, first elucidated by Munch-Petersen and coworkers, involves the transfer of a nucleotidyl group from a nucleoside triphosphate to a glycosyl phosphate with the concomitant release of pyrophosphate. For instance, uridine 5-(a-D-glucopyranosyl pyrophosphate) is formed in numerous organ-isms by the following reaction. 

The several known enzymic mechanisms for the synthesis of sugar nucleotides have been previously reviewed. It was pointed out that the mechanism of epimerization, whereby the glycosyl moiety of the glycosyl ester of a nucleotide is transformed into one having a different group-configuration, was obscure. This process may be exemplified by one of the first such enzymic interconversions to be discovered ... 

The first hurdle which must be overcome in the chemical synthesis of sugar nucleotides is the preparation of anomerically pure sugar phosphates. In sialic acid there is no neighboring group which can control the stereoselective phosphorylation of the C-2 center to form the desired P-phosphates selectively. Optimization of protecting groups and phosphorylation protocols led to modest improvements only of the a/p ratios. This problem is not yet solved satisfactorily. 

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