Ribonucleosides phosphorylation

While mammahan cells reutilize few free pyrimidines, salvage reactions convert the ribonucleosides uridine and cytidine and the deoxyribonucleosides thymidine and deoxycytidine to their respective nucleotides. ATP-dependent phosphoryltransferases (kinases) catalyze the phosphorylation of the nucleoside diphosphates 2 "-de-oxycytidine, 2 -deoxyguanosine, and 2 -deoxyadenosine to their corresponding nucleoside triphosphates. In addition, orotate phosphoribosyltransferase (reaction 5, Figure 34-7), an enzyme of pyrimidine nucleotide synthesis, salvages orotic acid by converting it to orotidine monophosphate (OMP). 

A. Mononucleotides.—A new journal has appeared in the past year consisting of abstracts of papers published in the nucleotide and nucleic acid fields. The use of nucleosides and nucleotides as potential therapeutic agents has been reviewed. Nucleotides which have been prepared recently using conventional methods of phosphorylation include those derived from 6-methylthiopurine ribonucleoside (la), 5-methylsulphonyluridine (lb), l-(jS-D-ribofuranosyl)-2-pyrimidone (Ic), 3-(jS-D-ribofuranosyl)-4-pyrimidone (Id), and various thionucleosides. - O-Phosphorylated 3 -amino-3 -deoxythymidine (2a) and 5 -amino-5 -deoxythymidine (2b)... 

Additional information <1> (<1>, the deletion mutants rDm-dNKAClO and rDm-dNKAC20 show the same substrate activity pattern as the recombinant wild-type enzyme. Relative phosphorylation of 2 -deoxycytidine and 2-chloro-2 -deoxyadenosine increases with increasing C-terminal truncation. The relative activities of rDm-dNKAClO and rDm-dNKAC20 with deoxyribonucleosides remains largely unchanged, whereas there is a substantial decrease in the phosphorylation of the purine ribonucleosides adenosine and guanosine, as well as of all dideoxyribonucleosides and 3 -azido-2 ,3 -dide-oxythymidine. The relative activities with the pyrimidine ribonucleosides and l-/l-D-arabinofuranosylcytosine and l-/i-D-arabinofuranosylthymine are not affected by the C-terminal deletions [4]) [4]... 

In the 1960s, Schwartz described the phosphorylation of adenosine with trimetaphosphate to yield 2 - and 3 -AMP. The strong alkaline conditions used for this transformation were not likely to occur on the primitive Earth [137]. Similarly, all natural ribonucleosides were phosphory-lated to corresponding 2 - and 3 -nucleotide monophosphates with sodium trimetaphosphate at high pH and temperature [138,139]. When the reaction was performed under similar experimental conditions at lower pH, 2/,3/-cyclic phosphate nucleotides were recovered as the major products [140]. Magnesium ion catalyzes this transformation in neutral water solution [141]. 

Ribonucleotides Ribonucleic acid consists of ribonucleosides bonded together into a polymer. This polymer cannot be bonded by glycosidic linkages like those of other polysaccharides because the glycosidic bonds are already used to attach the heterocyclic bases. Instead, the ribonucleoside units are linked by phosphate esters. The 5 -hydroxyl group of each ribofuranoside is esterified by phosphoric acid. A ribonucleoside that is phosphorylated at its 5 carbon is called a ribonucleotide ( tied to phosphate). The four common ribonucleotides, shown in Figure 23-23, are simply phosphorylated versions of the four common ribonucleosides. 

A method for the synthesis of pApUp that uses the triester method has appeared,324 and the concept of phosphorylating preformed oligonucleotides has been extended to the synthesis of 5 -phosphates of di(ribonucleoside) monophosphates by way of phosphoric triester intermediates 325 The terminal 3 -hydroxyl group was protected with the... 

Azaguanine brought about a 60% increase in the lifespan of mice with leukemia L1210. However, its ribonucleoside was inactive because it did not become phosphorylated, whereas 8-azaguanine was transformed by HPRT (hypoxanthine phosphoribosyltransferase) into its nucleotide, which RNA can incorporate." On the other hand, 8-azaadenosine" and 8-azainosine (9-ribofuranosyl-8-azahypoxanthine)," " both of which dis-... 

Phosphorus oxychloride is a suitable reagent for preparation of the symmetrically substituted phospho-triesters of type (RO)3PO. The preparation is easily achieved by treatment of phosphorus oxychloride with 3 equiv. of alcohols or their metal salts. The reaction is generally promoted by a base or acid. Titanium trichloride is a particularly effective catalyst for the reaction. Conversion of POCI3 to unsymmetri-cally substituted phosphotriesters is achievable with difficulty. Phosphorochloridates and phosphorodichloridates have been used for the preparation of mixed tertiary phosphoric esters of type (ROlmPOfOROn (ffi = 1, n = 2, or m = 2, n = 1) in a very wide variety. Reaction of phosphorus oxychloride and 1 or 2 equiv. of alcohols followed by hydrolysis forms phosphomonoesters or phosphodi-esters, respectively. The hydrolysis may be generally effected by dilute aqueous alkali. Some phosphoFodichlori te intermediates are easily hydrolyzed by water. For example, the phosphorylation of a ribonucleoside (1 equation 4) with phosphorus oxychloride in an aqueous pyridine-acetonitrile mixture furnishes the nucleoside S -monophosphate (2) in excellent yield. ... 

Esterification of dialkyl phosphates is carried out with diethyl azodicarboxylate and triphenylphosphine (equation 46). This condensation is applicable to phosphorylation of pyrimidine nucleosides. The trichloromethanephosphonic acid derivative (69 equation 47) serves as a phosphorylating agent of ribonucleosides, affording the 2 - and 3 -monophosphates. ° Ethyl vinyl ether assisted the dimeric condensation of diethyl hydrogen phosphate giving tetraethyl pyrophosphate (equation 48). ... 

The ribonucleoside triphosphate 113 of 6-aminopyrazin-2(lH)-one has been prepared using salicyl chlorophosphite as the phosphorylating agent. Although the 6-aminopyrazin-2(lH)-one was found to base pair effectively with 5-aza-7-deazaisoguanine within a DNA duplex, 113 was not incorporated by T7 RNA polymerase opposite this latter base in a template. ... 

Phosphorylation of ribofuranosyl nucleosides7 Japanese chemists found that phosphoryl chloride is an excellent catalyst for the conversion of ribonucleosides into the 2, 3 -0-isopropylidene derivatives. These, on addition of pyridine, are esterified at the primary 5 -position. Aqueous hydrolysis then gives the nucleotide, The method can be used for a single-step conversion of ribonucleosides into ribonucleotides by using a combination of POCL, acetone, and pyridine without isolation of the isopropylidene derivative. 

In most of the syntheses of ribonucleoside 5 -phosphates that we have described thus far, 2, 3 -0-isopropylidene or 2, 3 -0-benzylidene acetals of nucleosides have been employed as starting materials, to permit selective phosphorylation on 0-5. Such protecting groups, in common with acetals generally, are removable with dilute, aqueous, mineral acid. In some cases, however, the marked instability of the nucleotide derivative to acid precludes the use of these acetals, as the conditions required for removal of the acetal group are too strong. p-Substituted benzylidene derivatives (97) or (98)122.146,146 have shown utility, as deacetalation of these derivatives is readily accomplished under milder acidic conditions. A series of... 

Ribonucleoside 2 3 -cyclic phosphate have been prepared by phosphorylation of the 5 -0-acyl derivatives of adenosine and uridine with P -diphenyl P -morpholino pyrophosphorochloridate (63), followed by treatment with dilute ammonium hydroxide. An interesting innovation... 

The thiolo isomer (97) is an efficient alkylating and phosphorylating agent, converting ribonucleosides to ribonucleoside 3, 5 -cyclic phosphate in the presence of cyclohexylamine (Eto et al., 1968 1971 1974). 

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