1.3- Dicyclohexylcarbodiimide phosphate esters

The synthesis of the methyl ester of 9-0-glycyl-N-acetylneuraminic acid has been reported by Derevitskaya et al. (1965 b). The methyl ester of N-acetylneuraminic acid was coupled with N-benzyloxycarbonylglycine in the presence of dicyclohexylcarbodiimide subsequently the benzyloxycarbonyl group was removed by hydrogenolysis. The 9-phosphate esters of N-acetylneuraminic acid and N-glycolylneuraminic acid were prepared enzymatically (Roseman et al. 1961, Warren and Felsenfeld 1961, Watson et al. 1966a,b). Also a chemical... 

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. 

Protective group for nucleosides. Stepwise synthesis of oligonucleotides utilizing 2-cyanoethyl phosphate (1, 172-173) requires protection of the 3 -hydroxyl group which can be cleaved under essentially neutral conditions, since a methoxy-trityl ether is sensitive to acid and a /3-cyanoethyl phosphoric ester is sensitive to alkali. The /3-benzoylpropionyl group meets these requirements, since it is quantitatively cleaved by dilute solutions of hydrazine hydrate in pyridine-acetic acid. The esters are prepared by condensation with DCC (dicyclohexylcarbodiimide). Definitive paper R. L. Letsinger and P. S. Miller, Am. Soc., 91, 3356 (1969)... 

An entirely different ester is D-fructosyl phosphate, both ring forms of which, (14) and (15), were synthesized, isolated, and identified. Important as a possible intermediate in the biochemical synthesis and breakdown of the fructans, the pyridine salt of the 1-phosphate (12) was treated with dicyclohexylcarbodiimide, to form the cyclic 1,2-ester (13), which is very labile and is hydrolyzed to a mixture of both forms, (14) and (15), of the 2-phosphoric ester. This cycUzation mechanism was first mentioned by Khorana and coworkers, and later confirmed. Separation was effected... 

A very useful reagent for the preparation of esters and particularly of nucleoside pyrophosphates is dicyclohexylcarbodiimide (DCC). Its mechanism of action has been studied by Smith et al and is shown in Fig. I. On reaction of DCC (I) with a monophosphate (II) an intermediate believed to have structure (III) is formed. With another molecule of monophosphate (II) a symmetrical pyrophosphate (IV) is formed together with dicyclohexyl urea (V). The reaction can be carried out in a partially aqueous solution because water is a poor nucleophilic agent as compared with the phosphate anion. If the reaction mixture contains excess of an alcohol (VI)... 

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