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At least 289 records · Page 16Linked to original sources
PubMed2004

Nucleosides. LXV. Synthesis of new pteridine-N8-nucleosides.

A general synthetic approach to various isoxanthopterin-nucleosides starting from 6-methyl-2-methylthio-4(3H),7(8H)-pterdinedione (1) has been developed. Ribosylation with 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose via the silyl-method led to 2 and reaction with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-D-ribofuranose using the DBU-method afforded 28. Protection of the amide function at O4 by benzylation to 5 and by a Mitsunobu reaction with 2-(4-nitrophenyl)ethanol to 29 gave soluble intermediates which can be oxidized to the corresponding 2-methylsulfonyl derivatives 8 and 30, respectively. Nucleophilic displacement reactions of the highly reactive 2-methylsulfonyl functions by various amines proceeded under mild conditions to isoxanthopterin-N8-ribo- (11-17) and 2'-deoxyribomucleosides (31-33). Debenzylation can be achieve by Pd-catalyzed hydrogenation (9 to 19) and cleavage of the npe-protecting group (31, 32 to 34, 35) works well with DBU by beta-elimination.

Nucleosides↗
PubMed1998

Design and racemic synthesis of conformationally restricted carbocyclic pyrimidine nucleoside analogs based on the structure of the L-nucleoside residue in heterochiral DNA.

Carbocyclic pyrimidine nucleoside analogs which have restricted glycosidic conformation at chi approximately 180 degrees were designed, based on the conformational features of the L-nucleotide residue in heterochiral DNA, and synthesized. The synthesis of (+/-)-carbocyclic 6,6'-O-cyclo-2'-deoxyuridine was achieved via bromination and subsequent intramolecular cyclization of carbocyclic 6'beta-hydroxy-2'-deoxyuridine. (+/-)-Carbocyclic 6,6'-O-cyclo-2'-deoxycytidine was synthesized from protected carbocyclic 6,6'-O-cyclo-2'-deoxyuridine via the 4-triazole intermediate.

Anti-HIV Agents↗
PubMed1976

Changes in the activities of nucleoside triphosphatases and nucleoside kinases in Vero cells infected with Simian virus 40.

Changes in the activities of three enzymes involved in nucleotide metabolism were studied following infection of Vero cells with SV40. The results showed that SV40 infection enhanced the activities of uridine phosphokinase and UMP phosphokinase involved in nucleotide synthesis and suppressed the activity of nucleoside triphosphatases involved in nulceotide degradation. These SV40-induced enzyme activity changes probably served to somehow increase the quantity of nucleotides for virus proliferation.

Animals↗
PubMed1989

Nucleoside analogues. 9. Seco-nucleoside analogues of some 5-fluorouracil/nitrosourea molecular combinations having uracil as base: synthesis and anti-tumour activity.

The synthesis of representative seco-nucleoside analogues of 5-fluorouracil (5-FU)/nitrosourea molecular combinations having uracil (U) as base instead of 5-FU is described. The anti-tumour activity of corresponding pairs of drugs is compared in experimental tumours of the mouse colon, lung and breast. These studies have demonstrated that the presence of a hydrogen or fluorine atom at pyrimidine C-5 is unimportant for the activity shown against most of the experimental tumours employed, rather that the pyrimidine cyclic urea and/or alkylthio functionalities may constitute the critical factors. One exception is the prototypical compound B.3839 and its U analogue B.3912. B.3839 is highly active against colon 38 adenocarcinoma, a tumour which is highly responsive to 5-FU, whereas most of the activity is lost in B.3912. The 5-FU release profile of some of these molecular combinations could be adequate or effective in treatment of slow-growing clinical tumours.

Adenocarcinoma↗
PubMed1993

Nucleoside analogues. 13. The effect on anti-tumour activity of varying the uracil 5-substituent and the point of attachment (N1 or N3) of the uracil moiety in seco-nucleoside nitrosoureas.

The high activity against colon tumours in the mouse of nitrosoureas linked to seco-nucleosides with 5-fluorouracil or uracil as base component led us to synthesize and test similar drugs carrying other 5-substituted uracils attached by either N1 or N3. Not only were some of the new drugs active against the solid MAC 13 and against mammary and lung tumours, but unlike earlier compounds were particularly effective (especially N3 and alkoxy drugs like B.4083) against the ascitic MAC 15A, causing some cures. Further, these agents are valuable tools in the study, using modern techniques, of bifunctional alkylation of biological macromolecules, a vital principle of experimental cancer chemotherapy about which our knowledge is still very incomplete.

Animals↗
PubMed1977

[Imidazole nucleosides, III. Nucleosides of 4(5)-aminoimidazole-5(4)-carboxamide (author's transl)].

The synthesis and properties of 13 nucleosides derived from 5-aminoimidazole-4-carboxamide and from 4-aminoimidazole-5-carboxamide are described. The isomers were oriented by comparison of their spectra and colour reactions. All compounds were tested for anticancer activity. 4-Amino-1-(alpha-D-arabinopyranosyl)-imidazole-5-carboxamide significantly inhibits the growth of Ehrlich ascites carcinoma (fluid form) in mice.

Aminoimidazole Carboxamide↗
PubMed2001

The self-assembly of a lipophilic guanosine nucleoside into polymeric columnar aggregates: the nucleoside strucutre contains sufficient information to drive the process towards a strikingly regular polymer.

Lipophilic guanosine derivatives act as self-assembled ionophores. In the presence of alkali metal ions in organic solvents, these G derivatives can form tubular polymeric structures. The molecular aggregates formed by 3',5'-didecanoyl-2'-deoxyguanosine (1) have been characterised by SANS and NMR spectroscopy. The polymer is structured as a pile of stacked G quartets held together by the alkali metal ions that occupy the column's central channel. The deoxyribose moieties, with their alkyl substituents, surround the stacked G quartets, and the nucleoside's long-chain alkyl tails are in intimate contact with the organic solvent. In this polymeric structure, there is an amazing regularity in the rotamers around the glycosidic bond within each G quartet and in the repeat sequence of the G quartets along the columns. In hydrocarbon solvents, these columnar aggregates form lyomesophases of the cholesteric and hexagonal types.

Biopolymers↗
PubMed1985

Reversed-phase high-performance liquid chromatographic determination of tricyclic nucleoside and tricyclic nucleoside 5'-phosphate in biological specimens.

An isocratic, sensitive, high-performance liquid chromatographic assay was developed for the determination of the tricyclic nucleoside 1,4,5,6,8-pentaazaacenaphthylene -3-amino-1,5-dihydro-5-methyl-1-beta-D-ribofuranosyl 5'-monophosphate (TCN-P; NSC 280594) and its dephosphorylated metabolite TCN (NSC 154020). Separation was obtained using a C18 Sep-Pak precolumn, a reversed-phase column, and a mobile phase of phosphate buffer--methanol (87.5:12.5, v/v) containing 0.0025 M tetrabutylammonium hydroxide. The absorbance of both TCN and TCN-P was monitored at 280 nm with a sensitivity limit of 10 ng/ml. The recovery was 54 +/- 6% and 51 +/- 8% (mean +/- S.D.) from plasma for TCN and TCN-P, respectively. Rapid enzymatic dephosphorylation of TCN-P in plasma and tissue samples was prevented by adding a large excess of adenosine 5'-monophosphate. The assay was used to determine plasma and tissue concentrations of TCN-P and TCN after administration of TCN-P to cancer patients in a Phase I clinical study.

Acenaphthenes↗
PubMed2000

Inhibitory effect of cycloSaligenyl-nucleoside monophosphates (cycloSal-NMP) of acyclic nucleoside analogues on HSV-1 and EBV.

The in vitro antiviral activity of a new series of cycloSal-pro-nucleotides derived from the acyclic nucleoside analogues aciclovir and penciclovir against herpes simplex virus type 1 (HSV-1), thymidine kinase deficient (TK-) HSV-1, and Epstein-Barr virus (EBV) was evaluated. Using the XTT-based tetrazolium reduction assay EZ4U, the cycloSal derivatives were examined for their antiviral and cytotoxic effects in HSV-1 as well as HSV-1-TK--infected Vero cells. The anti-EBV activity was assessed by means of an EBV DNA hybridization assay using a digoxigenin-labeled probe specific for the Bam H1-W-fragment of the EBV genome and by measuring viral capsid antigen (VCA) expression in P3HR-1 cells by indirect immunofluorescence. Among the new cycloSal-phosphotriesters the three aciclovir monophosphates proved to be potent and selective inhibitors of HSV-1 replication, EBV DNA synthesis and EB-VCA expression. Of interest is the retention of activity of the aciclovir monophosphates in HSV-1-TK--infected cells. Particularly 3-methyl-cycloSal-aciclovir monophosphate retained the same effectiveness, as compared to the wild type virus strain. In contrast to the aciclovir pro-nucleotides the penciclovir cycloSal-phosphotriesters exhibited at best only a marginal antiviral effect on HSV and EBV replication.

Acyclovir↗
PubMed1998

Nucleosides and nucleotides. 176. 2'-Deoxy-2'-hydroxylaminocytidine: a new antitumor nucleoside that inhibits DNA synthesis although it has a ribonucleoside structure.

The design and synthesis of potential antitumor antimetabolites 2'-deoxy-2'-hydroxylaminouridine (2'-DHAU) and -cytidine (2'-DHAC) are described. We found that 2'-DHAC in neutral solution generated 2'-aminoxy radicals at room temperature. 2'-DHAC inhibited the growth of L1210 and KB cells, with IC50 values of 1.58 and 1.99 microM, respectively, more potently than 2'-DHAU, with IC50 values of 34.5 and 27.3 microM, respectively. 2'-DHAC was effective against 9 human cell lines, with IC50 values of in the micromolar range. The in vivo antitumor activity of 2'-DHAC was also examined using the mouse leukemia P388 model, which gave a T/C value 167%. Phosphorylation of 2'-DHAC by uridine/cytidine kinase was essential for its cytotoxicity, as suggested by a competition experiment using several common nucleosides. Inhibition of DNA synthesis was the predominant mechanism of action of 2'-DHAC, although it has a ribo-configuration.

Animals↗
PubMed2005

Structural effects of hypermodified nucleosides in the Escherichia coli and human tRNALys anticodon loop: the effect of nucleosides s2U, mcm5U, mcm5s2U, mnm5s2U, t6A, and ms2t6A.

Previous nuclear magnetic resonance (NMR) studies of unmodified and pseudouridine39-modified tRNA(Lys) anticodon stem loops (ASLs) show that significant structural rearrangements must occur to attain a canonical anticodon loop conformation. The Escherichia coli tRNA(Lys) modifications mnm(5)s(2)U34 and t(6)A37 have indeed been shown to remodel the anticodon loop, although significant dynamic flexibility remains within the weakly stacked U35 and U36 anticodon residues. The present study examines the individual effects of mnm(5)s(2)U34, s(2)U34, t(6)A37, and Mg(2+) on tRNA(Lys) ASLs to decipher how the E. coli modifications accomplish the noncanonical to canonical structural transition. We also investigated the effects of the corresponding human tRNA(Lys,3) versions of the E. coli modifications, using NMR to analyze tRNA ASLs containing the nucleosides mcm(5)U34, mcm(5)s(2)U34, and ms(2)t(6)A37. The human wobble modification has a less dramatic loop remodeling effect, presumably because of the absence of a positive charge on the mcm(5) side chain. Nonspecific magnesium effects appear to play an important role in promoting anticodon stacking. Paradoxically, both t(6)A37 and ms(2)t(6)A37 actually decrease anticodon stacking compared to A37 by promoting U36 bulging. Rather than stack with U36, the t(6)A37 nucleotide in the free tRNAs is prepositioned to form a cross-strand stack with the first codon nucleotide as seen in the recent crystal structures of tRNA(Lys) ASLs bound to the 30S ribosomal subunit. Wobble modifications, t(6)A37, and magnesium each make unique contributions toward promoting canonical tRNA structure in the fundamentally dynamic tRNA(Lys)(UUU) anticodon.

Adenosine↗
PubMed1999

Prediction of inhibitor binding free energies by quantum neural networks. Nucleoside analogues binding to trypanosomal nucleoside hydrolase.

A computational method has been developed to predict inhibitor binding energy for untested inhibitor molecules. A neural network is trained from the electrostatic potential surfaces of known inhibitors and their binding energies. The algorithm is then able to predict, with high accuracy, the binding energy of unknown inhibitors. IU-nucleoside hydrolase from Crithidia fasciculata and the inhibitor molecules described previously [Miles, R. W. Tyler, P. C. Evans, G. Furneaux R. H., Parkin, D. W., and Schramm, V. L. (1999) Biochemistry 38, xxxx-xxxx] are used as the test system. Discrete points on the molecular electrostatic potential surface of inhibitor molecules are input to neural networks to identify the quantum mechanical features that contribute to binding. Feed-forward neural networks with back-propagation of error are trained to recognize the quantum mechanical electrostatic potential and geometry at the entire van der Waals surface of a group of training molecules and to predict the strength of interactions between the enzyme and novel inhibitors. The binding energies of unknown inhibitors were predicted, followed by experimental determination of K(i)() values. Predictions of K(i)() values using this theory are compared to other methods and are more robust in estimating inhibitory strength. The average deviation in estimating K(i)() values for 18 unknown inhibitor molecules, with 21 training molecules, is a factor of 5 x K(i)() over a range of 660 000 in K(i)() values for all molecules. The a posteriori accuracy of the predictions suggests the method will be effective as a guide for experimental inhibitor design.

Animals↗
PubMed1993

Nucleosides and nucleotides. 123. Synthesis of 1-(2-deoxy-2-isocyano-beta-D-arabinofuranosyl)cytosine and related nucleosides as potential antitumor agents.

2'-Deoxy-2'-isocyano-1-beta-D-arabinofuranosylcytosine (8, NCDAC) has been synthesized as a potential antitumor antimetabolite from a corresponding 2'-azido-2'-deoxy-1-beta-D-arabinofuranosyluracil derivative 2a. Uracil and thymine analogues 6a and 6b of 8 were also prepared. Attempts to synthesize 2'-deoxy-2'-isocyanocytidine (14b) failed due to the insertion of the 2'-alpha isocyano group into the 3'-OH group, affording the 2',3'-oxazoline derivative 15b. Stability of the isocyano derivative 6a and 2',3'-oxazoline derivative 15a under basic and acidic conditions were examined. The isocyano group in 6a was stable in basic conditions but unstable even in weakly acidic conditions to furnish the corresponding 2'-beta formamide derivative 17. Compound 15a was easily hydrolyzed the corresponding 2'-alpha formamide derivative 16 on treatment with H2O at room temperature. The cytotoxicity of 8, 6a, and 6b was examined in mouse and human tumor cells in vitro and compared with that of ara-C. Of these nucleosides, 8 was moderately cytotoxic to these cell lines. In vivo antitumor activity of 8 against Lewis lung carcinoma cells was also investigated and 8 showed only moderate tumor volume inhibition.

Animals↗
PubMed1977

1,2,4-Triazole amino nucleosides. 1-beta-D-3'-Amino-3'-deoxyribofuranosyl-1,2,4-triazole-3-carboxamide and related nucleosides.

The synthesis of 1-beta-D-3'-amino-3'-deoxyribofuranosyl-1,2,4-triazole-3-carboxamide--the 3'-amino analogue of ribavirin--and five related nucleoside analogues is described. Each analogue exhibited LD50 concentrations greater than 100 microgram/mL against P-388 mouse lymphoid leukemia cells in tissue culture. Antiviral testing indicated that none of the compounds exhibited significant activity.

Animals↗
PubMed1998

Synthesis and antiviral activity of novel acyclic nucleosides: discovery of a cyclopropyl nucleoside with potent inhibitory activity against herpesviruses.

A series of acyclic nucleosides with two hydroxymethyl groups mimicking the 3'- and 5'-hydroxyl groups of the 2'-deoxyribose moiety were prepared and evaluated for their antiherpetic activity. Among those, 9-[[cis-1', 2'-bis(hydroxymethyl)cycloprop-1'-yl]methyl]guanine (3) showed extremely potent antiviral activity against herpes simplex virus type-1 (HSV-1) with good selectivity. Both enantiomers of 3 were synthesized starting from chiral epichlorohydrins, and only one of the enantiomers with 1'S,2'R-configuration (3a) exhibited strong antiherpetic activity (IC50 of 0.020 microg/mL against HSV-1 Tomioka vs 0.81 microg/mL for acyclovir). Enantiomer 3a was also more inhibitory than acyclovir against varicella-zoster virus (VZV) but ineffective against human immunodeficiency virus (HIV). Compound 3a is phosphorylated by HSV-1 thymidine kinase (TK) very efficiently. The relationship between conformation and antiherpetic activity in this series of compounds is discussed.

Acyclovir↗
PubMed2003

Acyclic, achiral enamide nucleoside analogues. The importance of the C=C bond in the analogue for its ability to mimic natural nucleosides.

The conformations of an acyclic, achiral enamide thymidine analogue 1 have been studied by model building and geometry calculations, as well as by NMR NOE and UV experiments. The results indicate that there are no significant barriers to rotation around any of the sigma bonds, in particular the N1-C1' enamide bond, and that the analogue should be able to accommodate conformations that mimic the conformations of natural nucleosides in A- and B-type helices quite well. For comparison the saturated analogue 2 has been prepared and built into oligonucleotides. It is shown that incorporation of 2 in oligonucleotides results in a much larger depression of the melting temperature (deltaTm -10 to -12.5 degrees C) than does incorporation of 1 (deltaTm -5 to -6.5 degrees C).

Biomimetic Materials↗
PubMedDate not supplied

Differential transport of cytosine-containing nucleosides by recombinant human concentrative nucleoside transporter protein hCNT1.

The transportability of cytosine-containing nucleosides by recombinant hCNT1 was investigated in transfected mammalian cells. Apparent K(m) values for hCNT1-mediated transport of uridine, cytidine and deoxycytidine were, respectively, 59, 140 and 150 microM. Uridine transport was inhibited 89, 32 and 11%, respectively, by 500 microM gemcitabine, cytarabine and lamivudine, demonstrating that, unlike gemcitabine (a high-affinity hCNT1 permeant), cytarabine and lamivudine are poor hCNT1 permeants.

Animals↗