Uracil nucleosides

Figure 10. Synthesis of a bicyclic uracil nucleoside related to the octosyl acids.

In a recent paper, Kim and Ryu have demonstrated that the reaction of some stable nitrile oxides with uracil nucleosides cleanly gave products of 1,3 addition (Scheme 34). The 5-aroylpyrimidine nucleoside oximes 57-64 were prepared in moderate to good yield by the reaction of hydroximoyl chlorides 55a-e with the corresponding pyrimidine nucleosides 56a-d. 

G.W.M. Visser, P. Noordhuis, O. Zwaagstra, J.D.M. Herscheid, A. Hoekstra, A simplified synthesis of F-labelled cytosine- and uracil-nucleosides, Appl. Radiat. Isot. 37 (1986) 1074-1076. 

The syntheses of both l-(3-deoxy-/ -D-g/i/cm>-pentofuranosyl-2-ulose)uracil (25c) and l-(3-deoxy-/ -D-g/ /cm>-pentofuranosyl-2-ulose)cytosine (30b) by selective elimination reactions have been reported.4,5 Thus, the reaction of sulfonyl derivatives of the cytosine nucleoside 26, and uracil nucleosides 23a, 23c, and 28, with sodium benzoate in N,N-dimethylformamide (DMF) leads to 3 -deoxy-2 -ke-tonucleosides by way of such (presumed) unsaturated intermediates as 24a, 24c, 29a, and 29b. However, in one instance, the intermediate... 

Scheme 39 Synthesis of pyrimidine or uracil nucleosides of phospha sugars...

The facility with which the bromo, chloro and iodo analogues undergo reduction, with maintenance of the 5,6-double bond and replacement of the halogen by hydrogen, has been exploited for the electrochemical synthesis of 5-(3H)-uracil by conducting the reaction in tritiated water121). This procedure should be equally effective for the synthesis of labelled uracil nucleosides and nucleotides. 

This reaction has been extended to a range of different heterocyclic compounds, e.g. uracil nucleosides, pyrimidin-2-one. pyrimidin-2-one nucleosides 6, A -mcthylpyr-folidone 7 and isoquinoline 8." "... 

Uracil nucleosides react with 1-methylimidazole in the presence of phosphoryl chloride to give 4-substituted pyrimidin-2-(l/()-one nucleosides via quaternized imidazole species <85CPB2575>. Quaternary salts are believed to be intermediates in the thermal isomerization of 5- to 4-nitroimidazoles in the presence of catalytic quantities of iodomethane (Scheme 12) <88TL536i>. There is a similar transposition of l,2-dimethylimidazole-5-nitrile. 

The degradation of hexopyranosyl cytosine nucleosides in buffers of acid, neutral and alkaline pH has been followed by HPLC. The compounds were found to degrade by hydrolysis to cytosine and/or deamination to the corresponding uracil nucleosides. ... 

Deoxyuridine and thymidine are substrates for pyrimidine nucleoside phosphorylases, but deoxycytidine (and cytidine) is generally regarded as being inert to phosphorolysis (7) Tarris demonstration of deoxycytidine formation from cytosine in extracts of fish milt is an exception to this generalization (8). Catabolism of C3rtosine nucleosides is initiated by deamination to form uracil nucleosides which can be phosphorolyzed. 

The most studied nuclear imaging based reporter gene has involved the use of the HSVl-TK enzyme (or mutant versions of this enzyme) and a variety of reporter probes. In general, these probes have consisted of uracil nucleoside derivatives radiolabeled with iodine isotopes for PET and SPECT imaging or acycloguano-sine derivatives radiolabeled with for PET imaging. These probes are... 

Cech and Holy (104) gave Rf information on 30+ compounds related to the preparation of 2-pyrimininone nucleosides from uracil nucleosides and its 5- substituted derivatives on silica with benzene-ethyl acetate (3 1) and several other solvents. 

Silver fluoride in pyridine is frequently used in the dehydrohalogenation of 5 -deoxy-5 -iodo-nucleosides for example, the theophylline and uracil nucleosides (383) and (384) respectively, were prepared in this way (see Scheme 89), whereas 3, 5 -dideoxy-3, 5 -di-iodothymidine gave the diene (236) when treated with silver fluoride in pyridine. However, 9-(2,5-dideoxy-j8-D- /ycero-pent-4-enofuranosyl)adenine (385) was best prepared by the action of DBU on 3 -0-acetyl-5 -bromo-2, 5 -dideoxyadenosine. In a synthesis of the 2, 3 -unsaturated... 

A total synthesis of nikkomycin B from a uracil nucleoside precursor has been reported. The stereoisomers (37a) of 4, 5 -... 

In a synthesis of 3 -C-carbomethoxymethyl-3 -deoxythymidine, and related nucleosides, the cyclization of bromide (113), induced by BusSnH-AIBN, was the key step. 134 Thymine nucleosides (114, X=OH, H) have been made by a-selective attack of ethynylmagnesium bromide on 3 -keto-derivatives.135 A variety of C-3 branched uracil nucleosides (115) have been prepared by a sequence involving conjugate additions of cuprates to an... 

Asakura and Robins described a mild procedure for the regioselective halogenation of uracil derivatives at the C-5 position with ammonium hexanitratocerate(IV) and elemental iodine, lithium halides or hydrochloric acid (scheme 35) (Asakura and Robins, 1988, 1990). The solvent for this type of reactions is methanol or acetonitrile. The reaction is very useful for the conversion of (protected) uracil nucleosides into (protected) 5-halouracil nucleosides. 4-Iodopyrazoles can be prepared by iodination of N-H and A-benzylpyrazoles with elemental iodine in presence of ammonium hexanitratocerate(IV) (scheme 36) (Rodriguez-Franco et al., 2001). The reaction works well, even with electron-withdrawing groups. Firouzabadi and coworkers reported that micellar solutions of sodium dodecyl sulfate catalyze the regios-... 

Uridine, uracil nucleoside, is obtained from uracil nucleotide, which occurs along with cytosine nucleotide in yeast-nucleic acid. 

L. Pichat, J. Godbillon, and M. Herbert, Lithiation par le n-butyllithium de bromo-5 uracile nucleosides silylds. Preparation de methyl ( C-5) et methyl ( -6) uridine, de desoxy-2 -ethyl (l C-5) uridine et desoxy-2 -ethyl ( C-ti) uridine, B H. Soc. Chim. Fr. 2712 (1973). 

Y. F. Shealy and C. A. O Dell, Synthesis of the carbocyclic analogs of uracil nucleosides,... 

---