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At least 469 records · Page 26Linked to original sources
PubMed1991

Nucleosides and nucleotides. 94. Radical deoxygenation of tert-alcohols in 1-(2-C-alkylpentofuranosyl) pyrimidines: synthesis of (2'S)-2'-deoxy-2'-C-methylcytidine, an antileukemic nucleoside.

(2'S and 2'R)-2'-Deoxy-2'-C-methylcytidine (1i and 15) and (2'S)-2'-deoxy-2'-C-ethylcytidine (1j) have been synthesized from the corresponding 2'-C-alkylarabinofuranosyl- or -ribofuranosylpyrimidine derivatives 3 and 4 by radical deoxygenation of the methyl oxalyl esters of the 2'-tert-alcohol, followed by sequential deblocking and amination at the 4-position. (2'S)-2'-Deoxy-2'-C-methyl-5-methyluridine (8) has also been synthesized in a similar manner. Among them, compound 1i exhibits the most potent cytotoxicity to L1210 cells with potency comparable to that of 1-beta-D-arabinofuranosylcytosine (1a). The size of the 2'-substituents and the configuration at the 2'-position are the most important for the cytotoxicity. Cytotoxicity in vitro of 1i against various human cancer cell lines was also examined and compared with that of 1a and 5-fluorouracil.

Animals↗
PubMed2000

Molecular characterization of two genes from Streptomyces tendae Tü901 required for the formation of the 4-formyl-4-imidazolin-2-one-containing nucleoside moiety of the peptidyl nucleoside antibiotic nikkomycin.

The genes nikQ and nikR were identified by sequencing DNA of the nikkomycin biosynthetic gene cluster from Streptomyces tendae Tü901/8c. The nikQ gene encodes a P450 cytochrome, and the predicted NikR gene product shows 48-56% sequence identity with uracil phosphoribosyltransferases from eukaryotic organisms. The nikQ and nikR genes were inactivated separately by insertion of a kanamycin-resistance cassette. Inactivation of the nikQ gene abolished synthesis of nikkomycins containing 4-formyl-4-imidazolin-2-one as the base (nikkomycins X and I), whereas production of nikkomycins containing uracil (nikkomycins Z and J) was not affected. Nikkomycin X and I production could be restored by feeding 4-formyl-4-imidazolin-2-one to the nikQ mutants, indicating that NikQ is responsible for its formation from L-histidine. Disruption of the nikR gene resulted in formation of decreased amounts of nikkomycins X and I, whereas nikkomycins Z and J were synthesized at wild-type levels. A fluorouracil-resistant nikR mutant lacking uracil phosphoribosyltransferase (UPRTase) activity did not synthesize nikkomycins X and I and accumulated 4-formyl-4-imidazolin-2-one in its culture filtrate, whereas formation of nikkomycins Z and J was unimpaired. The mutant was complemented to nikkomycin X and I production by nikR expressed from the mel promoter of plasmid pIJ702. The nikR gene expressed in Escherichia coli led to the production of UPRTase activity. Our results indicate that NikR converts 4-formyl-4-imidazolin-2-one to yield 5'-phosphoribosyl-4-formyl-4-imidazolin-2-one, the precursor of nikkomycins containing this base.

Aminoglycosides↗
PubMed1992

Treatment of HIV infection: the antiretroviral nucleoside analogues. Nucleoside analogues: combination therapy.

Combination antiretroviral therapy is an important development in the management of HIV infection. AZT with ddC is the first such combination to be approved for clinical use. Several issues remain, however, including the precise clinical benefit and toxicity of combination therapy, its effect on drug resistance, and the development of ever more effective therapeutic strategies.

Acquired Immunodeficiency Syndrome↗
PubMed1975

Reaction of a nucleoside 2, 4-dinitrophenyl phosphate with fluoride; a convenient method for the preparation of the nucleoside phosphorfluoridate.

Examination of the reaction of 2, 4-dinitrofluorobenzene with thymidine-5' phosphate in detail reveals that the initial product is the 2, 4-dinitrophenyl ester. This reacts with fluoride to produce thymidine-5' phosphorfluoridate. This second reaction provides the basis for the conversion of preformed thymidine-5' 2, 4-dinitrophenyl phosphate to thymidine-5' phosphorofluoridate.

Binding Sites↗
PubMed2003

A new, but old, nucleoside analog: the first synthesis of 1-deaza-2'-deoxyguanosine and its properties as a nucleoside and as oligodeoxynucleotides.

The first synthesis of 5-amino-3-(2'-deoxy-beta-D-ribofuranosyl)imidazo[4,5-b]pyridin-7-one (1-deaza-2'-deoxyguanosine) is described. The compound was converted from the known AICA-deoxyriboside. The tautomeric structure of the base moiety was determined by theoretical calculation to be a hydroxyl form. Although the analog was found to be labile to acidic conditions, 1-deaza-2'-deoxyguanosine was successfully converted into a phosphoramidite derivative, which was incorporated into oligodeoxynucleotides by the standard phosphoramidite method. Thermal stabilities of oligodeoxynucleotides containing 1-deaza-2'-deoxyguanosine were investigated by thermal denaturing experiments. Also, a triphosphate analog of 1-deaza-2'-deoxyguanosine was synthesized for polymerase extension reactions. Single nucleotide insertion reactions using a template containing 1-deaza-2'-deoxyguanosine, as well as 1-deaza-2'-deoxyguanosine triphosphate, were performed using the Klenow fragment (exonuclease minus) polymerase and other polymerases. No hydrogen bonded base pairs, even a 1-deaza-2'-deoxyguanosine:cytidine base pair, were indicated by thermal denaturing studies. However, though less selective and less effective than the natural guanosine counterpart, the polymerase extension reactions suggested the formation of a base pair of 1-deaza-2'-deoxyguanosine with cytidine during the insertion reactions.

Base Pairing↗