Ribonucleoside synthesis

Mikhailopulo, I. A. Pricota, T. I. Sivets, G. G. Altona, C. 2 -Chloro-2, 3 -dideoxy-3 -fluoro-D-ribonucleosides synthesis, stereospecificity, some chemical transformations, and conformational analysis./. Org. Chem. 2003, 68, 5897-5908. 

Kline PC, Serianni AS (1990) 13C-enriched ribonucleosides synthesis and application of 13C-1H and 13C-13C spin-coupling constants to asses furanose and iV-glycoside bond conformations. J Am Chem Soc 112 7373, 7381... 

Conversion of purines, their ribonucleosides, and their deoxyribonucleosides to mononucleotides involves so-called salvage reactions that require far less energy than de novo synthesis. The more important mechanism involves phosphoribosylation by PRPP (structure II, Figure 34-2) of a free purine (Pu) to form a purine 5 -mononucleotide (Pu-RP). 

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). 

Chandra and Brown66 investigated the synthesis of x-ribonucleosides as mimetics of the lower axial ligand in coenzyme B12. Reaction of unprotected indolines with... 

T. Chandra and K. L. Brown, Direct glycosylation Synthesis of a-indoline ribonucleosides, Tetrahedron Lett., 46 (2005) 2071-2074. 

Using guanosine or 2 -deoxyguanosine as starting material for the synthesis of ribonucleosides or deoxyribonucleosides respectively, the reaction can be driven towards completion by precipitation of the highly insoluble guanine co-product. This approach has... 

These enzymes use DNA as a template and the ribonucleotide substrates must be present in the nucleus, i.e. ATP, GTP, CTP and UTP. Similarly, for the synthesis of DNA, the deoxyribonucleotides dATP, dGTP, dCTP and dTTP must be present in the nucleus. In addition, since the ribonucleoside diphosphates are required for synthesis of deoxyribonucleotides, these diphosphates must also be present. The concentrations of these various nucleotides have not been measured in the nucleus but it may be assumed that the concentrations of the ribonucleotides will be similar in the nucleus to those in the cytosol. 

Example 37 the 4-cyano-2-butenyl protecting group has been described by Ravikumar et al. in the synthesis of oligodeoxy ribonucleosides by the phosphoroamidite approach [70]. This group is resistant to acids conditions and its removal proceeds under mild basic conditions by aqueous ammonia. 

A. R. Hernandez and E. T. Kool, The components of xRNA Synthesis and fluorescence of a full genetic set of size-expanded ribonucleosides, Org. Lett., 13 (2011) 676-679. 

L. A. Paquette and S. Z. Dong, Stereoselective synthesis of beta-anomeric 4 -thiaspirocyclic ribonucleosides carrying the full complement of RNA-level hydroxyl substitution,./. Org. Chem., 70 (2005) 5655-5664. 

RNA polymerase, and the triphosphates of the purine ribonucleosides, uridine, and cytidine, and otherwise the same conditions, will prime the synthesis of RNA. The amounts of synthetic DNA or RNA are many fold greater than the amount of primer DNA the DNA product is nearly the same in most measurable ways as the primer DNA. The efficiency of the DNA in initiating these syntheses is known as the primer activity of the DNA, and can be affected by alterations of the bases which compose the nucleic acid, and by other factors. 

Purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1) catalyzes the reversible phosphorylysis of ribonucleosides and 2 -deoxyribonucleosides of guanine, hypoxanthine, and related nucleoside analogs [1]. It normally acts in the phosphorolytic direction in intact cells, although the isolated enzyme catalyzes the nucleoside synthesis under equilibrium conditions. Figure 1 shows the chemical reaction. 

Transcription is catalyzed by DNA-dependent RNA polymerases, which use ribonucleoside 5 -triphosphates to synthesize RNA complementary to the template strand of duplex DNA. Transcription occurs in several phases binding of RNA polymerase to a DNA site called a promoter, initiation of transcript synthesis, elongation, and termination. 

Transfer RNA precursors may undergo further posttranscriptional processing. The 3 -terminal trinucleotide CCA(3 ) to which an amino acid will be attached during protein synthesis (Chapter 27) is absent from some bacterial and all eukaryotic tRNA precursors and is added during processing (Fig. 26-23). This addition is carried out by tRNA nucleotidyltransferase, an unusual enzyme that binds the three ribonucleoside triphosphate precursors in separate active sites and catalyzes formation of the phosphodiester bonds to produce the CCA(3 ) sequence. The creation of this defined sequence of nucleotides is therefore not dependent on a DNA or RNA template—the template is the binding site of the enzyme. 

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