Pyrimidine riboside

One of the more difficult prebiotic syntheses is that of the nucleosides. Heating of ribose and purines at 100°C gives fair yields (2-20%) of a mixture of isomers of the purine ribosides, with some of the correct 13-isomer being produced.45 However, a mixture of pyrimidines and ribose gives no detectable yield of nucleosides. Whether the inability to synthesize pyrimidine ribosides is a matter of not trying the correct conditions or whether pyrimidine nucleosides were not involved in the first organisms remains to be determined. 

It has been found that extracts of Salmonella typhimurium transform both purine and pyrimidine ribosides and ribonucleotides to the corresponding 2-deoxy-D-ribose compounds. 

PI. Paege, L. M., and Schlenk, F., Pyrimidine riboside metabolism. Arch. Biochem. Biophys. 28, 348-358 (1950). 

Pyrimidine ribosides, adenosine and, IX, 92 Pyrithiamine, VII, 104 thiamine and, VI, 169 VII, 104 iso-Pyrocalciferol, optical rotation, VIII, 279 Pyrogens,... 

In the above experiment, there was no conversion of the administered pyrimidine ribosides to PNA purines. Strangely enough, the DNA purines, especially adenine, were labeled to such a large extent after cytidine administration that some specific interrelationship between the purines and pyrimidines of DNA was suggested. Since N Mabeled cytidine was used, it is possible that the isotope in DNA adenine was located solely in the amino group, and may have been the result of some transamination reaction. It Avill be possible to accept this as a conversion of the pyrimidine ring to a purine ring only when it has been demonstrated with carbon-labeled cytidine. 

Since Hammarsten s results showed that not only the pyrimidines of PNA but also those of DNA were labeled after administration of labeled cytidine, it was concluded that this was indirect evidence for the conversion of a pyrimidine riboside to a pyrimidine desoxyriboside. The reason for this was that cytidine could not have been split to cytosine and then reincorporated into desoxycytidine, since it had been shown earlier that the free base, cytosine, could not be utilized for the synthesis of nucleic acid pyrimidines. The possibility should not be overlooked, however, that the above conversion may possibly occur at the nucleotide level thus, cytidylic acid, in which the phosphate is attached to the nucleoside, may be the intermediate in the transformation of PNA to DNA pyrimidines. 

Glycoside C-N bond hydrolyses (purine and 1 6 pyrimidine ribosides) 10 0,571... 

Chemical and enzymatic ribosidization of the aza analogs of the pyrimidine bases thus take different routes. These results and independent earlier studies of the alkylation of 6-azauraciE led to the conclusion that, in order to achieve ribosidization in position 1 (i.e., position 2 of the triazine ring), the position 3 (4 of the triazine ring) must be protected. ... 

Although pyridines and quinolines were first produced during the carbonization of coal, they are now available by synthesis in quantities that far exceed those by the former. Phosphorylated ribosides of hydroxylated and aminated pyrimidines and purines make up the basic structure of ribonucleic and deoxyribonucleic acids. The polycyclic oxaarenes are plant metabolites, while thiaarenes are primarily important components of high-sulfur petroleum that must be removed. 

A major recent growth point in substitution reactions has been the synthesis of pteridine glycosides, especially ribosides for study as probes in DNA chemistry taking advantage of the fluorescent properties of pteridines (see Section 10.18.12.4). Typically these reactions are developments of standard methods of glycosylation used with purines and pyrimidines as nucleophiles. In these and in other cases, the ambident nucleophiles within the pterin... 

NUCLEOSIDE. A compound of importance in physiological and medical research, obtained during partial decomposition (hydrolysis) of nucleic acids and containing a purine, oi pyrimidine base linked to either tf-ribose, forming ribosides, or rf-deoxyribose, forming deoxynbosides. They are nucleotides minus the phosphorus group. See also Adenosine and Nucleic Acids... 

Because of the great interest in the naturally occurring nucleosides, studies of the synthesis of D-ribosides of purines and pyrimidines have been numerous. The first attempt in this direction was made by Levene and Sobotka146 who condensed the silver salt of theophylline with tri-acetyl- 8-D-ribopyranosyl bromide to obtain what was probably triacetyl-7- 8-D-ribopyranosyl theophylline (LXXVI). Subsequently Hilbert and Rist94 condensed 2,4-diethoxypyrimidine (LXXVII) with triacetyl-0-D-ribopyranosyl bromide (LXXVIII) to form ethyl bromide and 1-triacetyl-D-ribopyranosyl-4-ethoxyuracil (LXXX), which, on deacetylation with hydrogen chloride, gave 1-D-ribopyranosyluracil (LXXIX), an isomer of... 

THIO-6-PROPYL-l,3-PYRIMIDIN-4-ONE see PNXOOO 6-THIO-4-PROPYLURACIL see PNXOOO P-THIOPSEUDOUREA see ISROOO 6-THIOPURINE RIBONUCLEOSIDE see MCQ500 6-THIOPURINE RIBOSIDE see MCQ500... 

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