Thymine nucleosides containing

Nucleosides containing deoxyfluoroglycopyranosyl residues were also prepared. 1-(6-Deoxy-6-fluoro-/ -D-gluco- and -galacto-pyranosyl)thymine (858 and 860) were obtained from l-/ -D-gluco- and -galacto-pyranosyl-thymine by the usual displacement reaction, or by the condensation method. 

The discovery of a small proportion of a nucleoside containing thymine42 in the ribonucleic acid of two strains of Escherichia coli, in Aerobacter aero-genes, and in commercial, yeast-ribonucleic acid emphasizes the point made previously,26-28 namely, that the nucleic acids may contain constituents other than those heretofore identified. Alkaline hydrolysis of the ribonucleic acid from E. coli gave nucleotides42 (probably the 2- and 3-phosphate esters) which were converted to the nucleoside with prostatic phospho-monoesterase.62 Enzymic hydrolysis of the nucleic acid preparation also led to the nucleoside, which was degraded further to thymine by hydrolysis with perchloric acid.42 There can be little doubt that this carbohydrate derivative of thymine is intimately bound as part of the polynucleotide chain of this particular ribonucleic acid. 

Boron-containing analogs of the biochemical precursors of nucleic acids, including purines, pyrimidines, thymines, nucleosides, and nucleotides, have been synthesized and several were evaluated in cellular and animal studies. Figure 10.8 shows several representative molecules of this class (35-42) containing carborane cages linked via various spacers to either the base or the carbohydrate... 

N -Fmoc serine benzyl ester 2, which could be prepared as shown or purchased commercially, was smoothly converted to the crystalHne O-methylthiomethyl (MTM) ether 3 in high yield via a Pummerer-Hke reaction using benzoyl peroxide and dimethyl sulfide in acetonitrile [39]. This common intermediate was used to synthesize both 5 and 8 [40]. Both Ogilvie [41] and Tsantrizos [42] had reported that I2 was an effective activator with similar MTM ether substrates. The H promoted nucleosidation reaction between O-MTM ether 3 and bis-silylated thymine 4 produced the nucleoamino acid 5 in 60% isolated yield (100% based on recovered 3). Hydrogenolytic deprotection of the benzyl ester with H2, Pd/C in MeOH gave the thymine-containing nucleoamino acid 6 in quantitative yield. 

Table XIX contains stability constants for complexes of Ca2+ and of several other M2+ ions with a selection of phosphonate and nucleotide ligands (681,687-695). There is considerably more published information, especially on ATP (and, to a lesser extent, ADP and AMP) complexes at various pHs, ionic strengths, and temperatures (229,696,697), and on phosphonates (688) and bisphosphonates (688,698). The metal-ion binding properties of cytidine have been considered in detail in relation to stability constant determinations for its Ca2+ complex and complexes of seven other M2+ cations (232), and for ternary M21 -cytidine-amino acid and -oxalate complexes (699). Stability constant data for Ca2+ complexes of the nucleosides cytidine and uridine, the nucleoside bases adenine, cytosine, uracil, and thymine, and the 5 -monophosphates of adenosine, cytidine, thymidine, and uridine, have been listed along with values for analogous complexes of a wide range of other metal ions (700). Unfortunately comparisons are sometimes precluded by significant differences in experimental conditions.

Phosphonated A.G-nucleosides (659) and (660), containing thymine (a), N -acetyleytosine (d) and fluorouracil (c) have been synthesized in good yields by the 1,3-dipolar cycloaddition methodology (Scheme 2.287) (152). 

Both DNA and RNA contain two major purine bases, adenine (A) and guanine (G), and two major pyrimidines. In both DNA and RNA one of the pyrimidines is cytosine (C), but the second major pyrimidine is not the same in both it is thymine (T) in DNA and uracil (U) in RNA Only rarely does thymine occur in RNA or uracil in DNA The structures of the five major bases are shown in Figure 8-2, and the nomenclature of their corresponding nucleotides and nucleosides is summarized in Table 8-1. 

DNA contains thymine (Thy) rather than uracil. The deoxyribose derivatives are thymidine (dThd or dT) and thymidine 5 -phosphate. The ribose derivatives of thymine are the nucleoside ribosylthymidine (Thd) and ribosylthy-midine 5 -phosphate (Thd-5 -P). 

Two types of heterocyclic N bases are found the pyrimidine bases (31), (32) and (33), and the purine bases (34) and (35). The pKt values are given in Table 10 as are the names of the compounds derived from the bases. One other difference between DNA and RNA is that the former is found to contain thymine, while the latter contains uracil. The average cell contains 2-5% of its dry weight as nucleic acids and nucleotides neither the heterocyclic bases nor the nucleosides occur as such in cells. 

With the exception of thymidine, these are the names of the ribonucleosides. Deoxyribonucleosides are indicated by the prefix deoxy in front of the nucleoside name thus deoxyadenosine contains deoxyribose instead of ribose. Thymidine indicates the deoxyribose derivative of thymine. Standard one-letter abbreviations are shown in parentheses. 

Do not confuse thiamine with thymine one of the pyrimidine bases on DNA. The DNA base thymine is Just a pyrimidine thymidine is the corresponding nucleoside. The coenzyme thiamineisa more complicated molecule, that contains a different pyrimidine. 

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