Diastereoselective Synthesis of 2'-Dihalopyrimidine Ribonucleoside Inhibitors of Hepatitis C Virus Replication.

We present a newly developed synthetic route to 2-bromo-2-fluoro ribolactone based on our published 2-chloro-2-fluoro ribolactone synthesis. Stereoselective fluorination is key to controlling the 2-diastereoselectivity. We also report a substantially improved glycosylation reaction with both the 2-bromo-2-fluoro and 2-chloro-2-fluoro sugars. These improvements allowed us to prepare 2'-dihalo nucleosides 13 and 14 in an overall 15-20% yield.

Discovery of a Series of 2'-α-Fluoro,2'-ß-bromo-ribonucleosides and Their Phosphoramidate Prodrugs as Potent Pan-Genotypic Inhibitors of Hepatitis C Virus.

Hepatitis C virus (HCV) nucleoside inhibitors display pan-genotypic activity, a high barrier to the selection of resistant virus, and are some of the most potent direct-acting agents with durable sustained virologic response in humans. Herein, we report, the discovery of ß-d-2'-Br,2'-F-uridine phosphoramidate diastereomers 27 and 28, as nontoxic pan-genotypic anti-HCV agents. Extensive profiling of these two phosphorous diastereomers was performed to select one for in-depth preclinical profiling. The 5'-triphosphate formed from these phosphoramidates selectively inhibited HCV NS5B polymerase with no inhibition of human polymerases and cellular mitochondrial RNA polymerase up to 100 µM. Both are nontoxic by a variety of measures and display good stability in human blood and favorable metabolism in human intestinal microsomes and liver microsomes. Ultimately, a preliminary oral pharmacokinetics study in male beagles showed that 28 is superior to 27 and is an attractive candidate for further studies to establish its potential value as a new clinical anti-HCV agent.

Synthesis and anti-HCV activity of ß-d-2'-deoxy-2'-α-chloro-2'-ß-fluoro and ß-d-2'-deoxy-2'-α-bromo-2'-ß-fluoro nucleosides and their phosphoramidate prodrugs.

We report herein the synthesis and evaluation of a series of ß-d-2'-deoxy-2'-α-chloro-2'-ß-fluoro and ß-d-2'-deoxy-2'-α-bromo-2'-ß-fluoro nucleosides along with their corresponding phosphoramidate prodrugs. Key intermediates, lactols 11 and 12, were obtained by a diastereoselective fluorination of protected 2-deoxy-2-chloro/bromo-ribonolactones 7 and 8. All synthesized nucleosides and prodrugs were evaluated with a hepatitis C virus (HCV) subgenomic replicon system.

Synthesis and characterization of various 5'-dye-labeled ribonucleosides.

Hitherto unknown chromophoric nucleosides are reported. This novel set of visibly coloured dye-labeled 5'-nucleosides, including 1,2,4,5-tetrazine, dicyanomethylene-4H-pyran, benzophenoxazinone, 9,10-anthraquinone and azobenzene chromophores, were prepared mainly under Cu-catalyzed azide-alkyne cycloaddition (CuAAC). The design criteria are outlined. Several derivatives possess in supplement a fluorescence property. The absorption and fluorescence spectra of all coloured nucleosides were recorded to study their potential as visible-range probes. Such nucleodyes are of great interest for future competitive lateral flow test MIP-based strips.

Synthesis of (2S)-2-Chloro-2-fluororibolactone via Stereoselective Electrophilic Fluorination.

A novel and efficient route for the preparation of (2S)-2-chloro-2-fluorolactone 29 is described. This approach takes advantage of a highly efficient diastereoselective electrophilic fluorination reaction (94% yield; >50:1 dr).

Metabolism of Nucleosides and Nucleotides Prodrugs.

BACKGROUND: Modified nucleoside and nucleotide analogs are now the cornerstone of antiviral and anticancer chemotherapies. However, these compounds are not active on their own and need, after entering the cell, to be metabolized to their active 5'-triphosphate form. METHOD: Limitations of these metabolic processes led to development of nucleoside/nucleotide prodrugs in which nucleosides are masked with different groups that can be intracellularly cleaved either chemically or enzymatically. RESULTS: Several prodrug approaches have been successfully developed in order to increase the efficacy, bioavailability, penetration in target organ, and selectivity of nucleoside/nucleotide analogs. CONCLUSION: The concept of nucleoside/nucleotide prodrug is now a well-established approach that led to the approval of numerous drugs for the treatment of HIV, HBV, HCV, HSV and cancer.

Olefin cross-metathesis for the synthesis of alkenyl acyclonucleoside phosphonates.

The detailed synthetic protocol for the straightforward, efficient synthesis of various alkenyl acyclonucleosides, including challenging trisubstituted alkenyl acyclonucleoside phosphonates, is described. The key step of those syntheses is an olefin cross-metathesis reaction between two olefins selected based on their reactivity using well-defined ruthenium alkylidene catalysts.

Artificial receptors for the extraction of nucleoside metabolite 7-methylguanosine from aqueous media made by molecular imprinting.

A series of imprinted polymers targeting nucleoside metabolites, prepared using a template analogue approach, are presented. These were prepared following selection of the optimum functional monomer by solution association studies using (1)H NMR titrations whereby methacrylic acid was shown to be the strongest receptor with and affinity constant of 621±51Lmol(-1)vs. 110±16Lmol(-1) for acrylamide. The best performing polymers were prepared using methanol as porogenic co-solvent and although average binding site affinities were marginally reduced, 2.3×10(4)Lmol(-1)vs. 2.7×10(4)Lmol(-1) measured for a polymer prepared in acetonitrile, these polymers contained the highest number of binding sites, 5.27µmolg(-1)vs. 1.64µmolg(-1), while they also exhibited enhanced selectivity for methylated guanosine derivatives. When applied as sorbents in the extraction of nucleoside derivative cancer biomarkers from synthetic urine samples, significant sample clean-up and recoveries of up to 90% for 7-methylguanosine were achieved.

Fluorophosphonylated nucleoside derivatives as new series of thymidine phosphorylase multisubstrate inhibitors.

The synthesis of new class of potential TPase inhibitors containing a difluoromethylphosphonate function as phosphate mimic is reported. This new series was prepared from a readily available fluorinated building block in few steps. Two series were evaluated as potential inhibitors: a linear series and a conformational constrained series. The activity of these multisubstrate inhibitors depends on the size of the spacer introduced between the pyrimidine ring and the phosphonate function. Best results were observed from triazolyl derivatives, easily obtained from propargylthymine and corresponding azides.