Guanosine 2’-deoxy

Rj = NHj Re = OH Guanine Guanosine Deoxy guanosine R4 = NH2 R5 = H Cytosine Cytidine Deoxycytidine... 

FIGURE 12.14 Comparison of the deoxy-guanosine conformation in B- and Z-DNA. In B-DNA, the Cl -N-9 glycosyl bond is always in the anti position (lefi). In contrast, in the left-handed Z-DNA structure, this bond rotates (as shown) to adopt the syn conformation. 

All NRTIs, as exemplified for AZT (Fig. 7), act in a similar fashion following their uptake by the cells, they are phosphorylated successively to their 5 -monophosphate, 5 -diphosphate, and 5 -triphosphate form (De Clercq 2002). Unlike the first phosphorylation step in the metabolic pathway of the acyclic guanosine analogues (see above), which is carried out by a virus-encoded enzyme (thymidine kinase), the first as well as the subsequent phosphorylations of the 2, 3 -dideoxynucleosides are carried out by cellular enzymes, that is, a 2 -deoxynucleoside (e.g., dThd) kinase, a 2 -deoxynucleotide (e.g., dTMP) kinase, and a (2 -deoxy)nucleoside 5 -diphosphate (NDP) kinase. 

The 2 -C-methyl-substituted ribonucleosides 2 -C-methyladenosine and -guanosine were also found to inhibit the replication of flaviviruses other than HCV, such as bovine viral diarrhea virus (BVDV), yellow fever virus, and West Nile virus (Mighaccio et al. 2003). Other 2 -C-methylribonucleosides such as P-D-2 -deoxy-2 -lluoro-2 -C-methylcytidine (PSl-6130), however, showed little if any activity against BVDV, West Nile virus, or yellow fever virus (Stuyver et al. 2006). 

By analogy with the conversion of uridine 1 into cytidines 6, the conventional amination of inosine 235a, guanosine 235b, or xanthosine 235c and their 2 -deoxy analogues to the adenosines 237 requires ... 

Devasagayam, T.P.A., Steenken, S., Obendorf, M.S.W., Schultz, W.A. and Sies, H. (1991). Formation of 8-hydroxy(deoxy)guanosine and generation of strand breaks at guanine residues in DNA by singlet oxygen. Biochemistry 30, 6283-6289. 

Recently, Switzer and co-workers have further extended the multi-stranded motifs for nucleic acids with the formation of a quintet assembly with oligonucleotides containing 2,deoxy-iso-guanosine (74). To support the quintet, metal ions larger than those appropriate for quartet stabilization were required, and Cs+ ions were found to best meet this requirement. From modeling studies, a structure in which a central Cs+ interacts with ten 02 iG atoms at a distance of 3.5 A was proposed. 

It should be emphasized that benzyloxycarbonylimidazolium salts are effective agents for the direct mono-iV-protection of deoxynucleosides as their benzyloxycarbonyl derivatives. No over-acylation occurs. However, bis(ter/-butyldimethylsilyl)-deoxy-guanosine failed to react with this reagent.[189]... 

A nucleoside consists of a purine or pyrimidine base linked to a pentose, either D-ribose to form a ribonucleo-side or 2-deoxy-D-ribose to form a deoxyribonucleoside. Three major purine bases and their corresponding ribo-nucleosides are adenine/adenosine, guanine/guanosine and hypoxanthine/inosine. The three major pyrimidines and their corresponding ribonucleosides are cytosine/ cytodine, uracil/uradine and thymine/thymidine. A nucleotide such as ATP (Fig. 17-1) is a phosphate or polyphosphate ester of a nucleoside. 

Guanine Guanosine-5 -phosphate (GMP) Deoxy guanosine-5 -phosphate (dGMP)... 

Fig. 15A,B Modified motif of the adenovirus pre-mRNA substrates studied by Son-theimer et al. [151] A in the Ad5-lS, the guanosine at 5 splice site position was substituted by 2 -deoxy-3 -thiouridine B in the Ad3-lS, the guanosine at 3 splice site position was substituted by 3 -thioinosine...

Guanosine 5 -(a-D-rhamnopyranosyl pyrophosphate) (23) was shown to be a product of enzymic reduction of the mannosyl ester (17) in the presence of a plant extract93 or an enzyme preparation from an unidentified strain of Gram-negative bacteria.94,95 In the latter example, the 6-deoxy-D-talosyl ester, presumably 24, is also produced. 

Enzyme preparations that can convert a-D-mannopyranosyl or 6-deoxy-a-D-Zt/xo-hexopyranosyl-4-ulose esters of guanosine 5 -pyro-phosphate into the /3-L-fucopyranosyl ester were obtained from Aerobacter aerogenes,99 432 Escherichia coli,100 Salmonella strains,433 higher plants,92 and animal tissues.434 Further purification of these enzymes will be necessary for mechanistic studies. 

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