- HSAB-driven chemoselective N1-alkylation of pyrimidine bases and their 4-methoxy- or 4-acetylamino-derivatives
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The lithium salts of the conjugated bases of 4-methoxy- and 4-acetylamino-2(1H)-pyrimidinones 1-3 undergo highly chemoselective N1-methylation or ethylation when treated with methyl- or ethylsulfate (hard electrophiles) in dry dioxane, while the use of DMF as solvent results in competitive O2-alkylation. Potassium salts of the same bases in DMF undergo prevalent O2-attack. Under the same conditions, a similar but less chemoselective behaviour is observed in alkylation of thymine and uracil, where some N3-attack occurs. This can be rationalised in terms of the HSAB principle.
- Gambacorta, Augusto,Tofani, Daniela,Loreto, Maria Antonietta,Gasperi, Tecla,Bernini, Roberta
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p. 6848 - 6854
(2007/10/03)
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- Photochemical synthesis of benzopyrimidosemibullvalenesfrom benzopyrimidobarrelenes
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UV irradiation (λ=254 nm) of 5-fluoro-1,3-dimethyluracil with naphthalene afforded a novel benzopyrimidosemibullvalene derivative with H and F atoms remaining intact on the newly constructed moiety. It was found that the semibullvalene could be derived from the initially produced barrelene derivative during irradiation.
- Ohkura, Kazue,Kudo, Mikiko,Ishihara, Tetsuya,Nishijima, Ken-ichi,Seki, Koh-ichi
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p. 2583 - 2586
(2007/10/03)
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- Facile synthesis of thymidine derivatives by cross-coupling of 5-halogenouridine derivatives with trimethylaluminum
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An efficient method for the introduction of a methyl group in the 5-position of uridine derivatives is described. This method involves three steps: protection of 5-halogenouridines 4 and 5 with hexamethyldisilazane, a palladium-catalyzed cross-coupling of the pertrimethylsilylated nucleosides with trimethylaluminum, and subsequent deprotection to afford the corresponding thymidine derivatives 6 in high overall yields.
- Hirota,Kitade,Kanbe,Isobe,Maki
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p. 213 - 215
(2007/10/02)
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- Model studies of the thymidylate synthase reaction. The mechanism of reduction of 5-uracilylmethylenepyridinium salts by benzyl thiol
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The reduction of 5-uracilylmethylenepyridinium salts by benzyl thiols, to the corresponding thymine derivatives, involves an exocyclic methylene intermediate, which appears to be reduced by a radical mechanism. The overall reaction constitutes a mechanist
- Meissner,Pandit
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p. 2999 - 3002
(2007/10/02)
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- Reactions with Dimethyl Carbonate, 5 Methylation of the Pyrimidine Bases of Nucleic Acids
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The methylation of the pyrimidine bases of nucleic acids by dimethyl carbonate is described compared to dimethyl sulphate.The reaction needs higher temperature, a base and the help of 18-crown-6 and DMF as cosolvent. - Keywords: Dimethyl Carbonate, Methylations, Pyrimidine Bases of Nucleic Acids
- Jansen, Helmut in de Wal,Lissel, Manfred
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p. 863 - 865
(2007/10/02)
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- Oxidation of Thymines by Peroxosulfate Ions in Water
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Oxidation of thymines by sodium peroxodisulfate in water at 85 deg C gave the corresponding 5-(hydroxymethyl)uracils and 5-formyluracils.The reaction may proceed via thymine cation radicals.On the other hand, oxidation of thymines by potassium peroxomonosulfate in water gave the corresponding cis-5,6-dihydroxy-5,6-dihydrothymines and 5-hydroxy-5-methylbarbituric acids.Furthermore, treatment of thymine with both potassium peroxomonosulfate and hydrogen peroxide in water gave cis-6-hydroperoxy-5-hydroxy-5,6-dihydrothymine.
- Itahara, Toshio,Fujii, Yukiko,Tada, Miki
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p. 3421 - 3424
(2007/10/02)
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