Glycosyl esters of nucleoside 5 -pyrophosphates

This sub-section is devoted to nucleotide derivatives that may participate in biosynthesis of certain polymers containing carbohydrate. They are generally included among the sugar nucleotides, although their structures differ somewhat from those of the glycosyl esters of nucleoside 5 -pyrophosphates so far discussed. 

Glycosyl esters of nucleoside 5 -pyrophosphates that have a hydrogen atom230 or an acetamido group9 instead of a hydroxyl group at C-2" are stable in alkali. 

From hen oviduct, enzymes have been isolated and purified that catalyze sulfation of glycosyl esters of nucleoside 5-pyrophosphates by the action of 3 -0-phosphono-5 -adenylyl hydrogen sulfate.448-449... 

III. Enzymic Synthesis of Glycosyl Esters of Nucleoside 5 -Pyrophosphates.. 358... 

Phosphorolysis of the glycosyl esters of sugar nucleotides leads to the corresponding nucleoside 5 -pyrophosphate and glycosyl phosphate. A wheat-germ enzyme specific for adenosine 5 -(a-D-glucopy-ranosyl pyrophosphate),462 and a yeast enzyme specific for guanosine 5 -(a-D-mannopyranosyl pyrophosphate),463,464 are known. 

Nucleoside 5 -phosphorothioates have also been employed as activated nucleotide derivatives for synthesis of pyrophosphates.321 The interaction of tributylammonium 2, 3 -di-0-benzoyluridine 5 -phosphorothioate (73) with silver a-D-glucopyranosyl and a-D-galac-topyranosyl phosphates in pyridine solution, with subsequent de-benzoylation, gave the corresponding glycosyl esters in 60-70% yield. This procedure can probably be classified as a variant of the mixed-anhydride method, the driving force of the reaction being the formation of insoluble silver sulfide. 

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