Guanosine, synthesis

Guanine, 9-/3-D-ribofuranosyl-, 5, 536 Guanine, 6-thio-tautomerism, 5, 509 toxicity, 1, 141 Guanine, 8-trifluoromethyl-synthesis, 5, 574 Guanines, thio-synthesis, 5, 572 Guanosine arylation, 5, 538 dipole moment, 5, 522 free radical alkylation, 5, 543 hydrobromide... 

GTP is an essential component in protein synthesis, and it has been shown recently that another guanosine polyphosphate, guanosine 3, 5 -... 

Another triphosphate synthesis is described in reference [94], where a partially protected hexaribonucleotide derivative is converted by CDI into the imidazolide and subsequently condensed with a protected 7-methyl guanosine diphosphate to give the triphosphate. 

The poly(C)-directed oligoguanylate synthesis from guanosine 5 -phosphoric 2-methylimidazolide has been studied kinetically.11571 An intermediate elongation process on polycytidylate acting as template is illustrated schematically below. 

Not all analogues become active against cancer cells through incorporation into nucleic acid. Some analogues block the synthesis of normal purine and pyrimidine nucleotides for example, 8-azaguanine blocks guanosine monophosphate (GMP) synthesis and 6-mercaptopurine inhibits adenosine monophosphate (AMP) syn-thesis. 

Inoue and Orgel (1981) found that the oligomerisation of guanosine-5 -phosphoimidazolide on a poly(C) matrix can take place in the absence of Pb2+ or Zn2+, if guanosine-5 -phospho-2-methylimidazolide is used for the oligo-G synthesis. 

This chapter briefly describes the general methodology for making both series of ARCAs and describes in detail the synthesis of two representative compounds P1-guanosine-5/ P3-(7,3/-0-dimethylguanosine-5/) triphosphate (Fig. 11.1, compound 2) and P1-guanosine-5/ P3-(7,3/-0-dimethyl-guanosine-5 ) /by- methylene-triphosphate (Fig. 11.1, compound 5). 

Kadokura, M., Wada, T., Urashima, C., and Sekine, M. (1997). Efficient synthesis of g-methyl-capped guanosine. V-mphosphate as a SLtcrminal unique structure of U6 RNA via a new triphosphate bond formation involving activation of methyl phosphor-imidazolidate using ZnCl2 as a catalyst in DMF under anhydrous conditions. Tetrahedron Lett. 38, 8359-8362. 

Outstanding in this field has been the contribution of Todd and his co-workers. The significance of their work has been, first, that it has led to successful syntheses of adenosine, guanosine, cytidine, and uridine. Equally important, however, has been its contribution toward the final confirmation of the structures of the nucleosides. This may be illustrated in the following way. By the route I to V, which had been developed for the synthesis of pentosylpurines (purine 1-deoxypentosides), it was possible to obtain 9-/3-n-mannopyranosyladenine (V), in which the position of the carbohydrate residue was known with certainty.19 This nucleoside, on oxi-... 

The answer is e. (Katzung, p 842.) Ribavirin most likely interferes with guanosine triphosphate synthesis, resulting in inhibition of capping of viral messenger RNA and viral RN A-dependent RNA polymerase. It is effective in moderating infections with respiratory syncytial virus. 

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... 

Figure 20.10 The positions in the pathway for de novo purine nucleotide synthesis where GLUCOSE provides the ribose molecule and GLUTAMINE provides nitrogen atoms. The pathway begins with glucose which provides ribose 5-phosphate, via the pentose phosphate pathway (Chapter 6). Glutamine provides its amide nitrogen in two reactions formation of 5-phosphoribosylamine and formation of guanosine monophosphate (GMP) from xantho-sine 5-phosphate (XMP).

Mycophenolate sodium (62 Myfortic Norvatis, 2003) is an immunosuppressant drug used to prevent rejection in organ transplantation. It is a selective, noncompetitive, reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in the de novo pathway of guanosine nucleotide synthesis. Thus, mycophenolic acid (61), originally... 

Komori K, Tsujimura A, Takao T, Matsuoka Y, Miyagawa Y, Takada S, Nonomura N, Okuyama A. (2008) Nitric oxide synthesis leads to vascular endothelial growth factor synthesis via the NO/cyclic guanosine 3, 5-monophosphate (cGMP) pathway in human corpus cavemosal smooth muscle cells. J Sex Med 5 1623-1635. 

During the past 15 years data from experiments with different types of animal tissues and micro-organisms, using intact cells, crude extracts or purified enzymes, have firmly established the general occurrence of nucleotide reductases and have stressed their importance for DNA synthesis in essentially all types of rapidly growing cells [54]. It has been proposed that ribonucleotide diphosphates lose a hydroxide ion from C-2 to form a carbonium ion which is then stero-specifically reduced by a hydride ion derived from thioredoxin [54]. Adenosine diphosphate and guanosine diphosphate (as well as uridine and cytidine diphosphates) are reduced in this manner. 

Aminouracil produces a block in the mitotic cycle of various plants. For example, cessation of mitosis occurred in Vida faba roots incubated 24 h with this compound [392—394]. Depending on different experimental conditions, thymidine or thymidylic acid may or may not alleviate these effects [392—394]. It was concluded that 5-aminouracil depressed the rate of DNA synthesis, which led to an accumulation of cells in the S phase. After removal of the agent, DNA synthesis resumed. Similar results have been observed with Allium cepa and Haplopappus gracilis [395, 396]. Inhibition of guanosine incorporation into RNA of meristematic cells in Vida faba by 5-aminouracil was also reported [397]. 

The product succinyl-CoA is able to participate in ATP synthesis as an example of substrate-level phosphorylation - we met some other examples in the glycolytic pathway. Essentially, hydrolysis of succinyl-CoA liberates snfficient energy that it can be coupled to the synthesis of ATP from ADP. However, guanosine triphosphate (GTP) is the... 

The mechanism of the action of nitrates is not completely known, though it is reasonably likely that within smooth muscle cells, nitrates are transformed into nitrites, which then release NO. This, in turn, reacts with guanylatecyclase, causing increased synthesis of guanosine 3, 5 -monophosphate (cyclic GMP). As a result, a GMP-requiring protein kinase is activated, which results in less phosphorylation of muscle protein. Dephosphorylated muscle proteins are less able to contract, which ultimately results in a reduction of the heart s need for oxygen. 

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