Glycosyl phosphates, preparation

Several cases have been documented in which a different, naturally occurring, glycosyl phosphate substitutes for the true substrate of the pyrophosphorylase. Adenosine 5 -(a-D-xylopyranosyl pyrophosphate) was prepared by the action of the pyrophosphorylase of adenosine 5 -(a-D-glucopyranosyl pyrophosphate) from wheat flour,218... 

Nucleoside 5 -phosphates are employed as starting materials to prepare the activated derivatives (56). Their synthesis has been discussed in a Chapter in this Series.266 The methods used most frequently for preparing glycosyl phosphates involve the interaction of protected glycosyl bromides with diphenyl phosphate and subsequent removal of the protective groups,267 or by fusion of the peracetylated monosaccharides with anhydrous phosphoric acid.268... 

A related method, of preparative value, was subsequently developed.323 It makes use of the 2-hydroxypyridyl esters (74), of nucleoside 5 -phosphates, which can readily be obtained from nucleoside 5 -phosphates and 2-pyridinol. The reaction of the derivative (74) with glycosyl phosphates in anhydrous pyridine gives rise to the... 

In the late fifties, the N. I.H. started the Visiting Program under this, young scientists were invited to work for one or two years at the Institutes under the direction of staff members. Dr. Fletcher actively participated in this program. It was as a Visitor in Dr. Fletcher s laboratory that Dr. Donald L. MacDonald became interested in the preparation of phosphoric esters of carbohydrates, and his work eventually led to the MacDonald method of synthesizing glycosyl phosphates. 

Several chemical and enzymatic methods are available for the synthesis of glycosyl phosphates. The required nucleoside triphosphates (NTPs) are most conveniently prepared by enzymatic routes. In general, these methods involve the sequential use of two kinases to transform NMPs to NTPs, by the corresponding NDPs (Fig. 2, see a recent review [12] for more details). 

The first stage of the synthesis is the preparation of the substrate for enzymatic polymerization, the polyprenyl pyrophosphate-galactosy1-rhamnosy1-mannose XXI. Since the most convenient way to control the polycondensation reaction is the use of isotopic methods, a procedure for incorporation of tritium into trisaccharide I was developed (2 5). Labelled trisaccharide was then converted into the glycosyl phosphate XIX through interaction of its peracetate III with anhydrous phosphoric acid (26). Conditions were found under which the reaction is accompanied by minimal destruction and yields the Ot-phosphate of the trisaccharide. 

Figure 4. Preparation of glycosyl phosphates by the oxazoline procedure.

The 4 -monophosphate was also prepared from the same compound as above (Figure 5). Although the 4 -hydroxyl group in 12 has rather low reactivity, its phosphorylation could be performed with phenyl phosphate and dicyclohexylcarbodiimide (DCC) in pyridine. The reaction product was converted into the benzyl phenyl ester ( ) to facilitate purification. In contrast to the above dibenzyl ester of the glycosyl phosphate, the benzyl phenyl ester of the 4 -phosphate was stable and could be purified by silica gel column chromatography after removal of the propenyl group without decomposition. Hydrogenolytic deprotection of (first with Pd-black then with PtC>2) afforded the 4 -monophosphate 17. 

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