4'-C-modified nucleosides: synthesis and antiviral properties

The synthetic methods for 4'-C-modified nucleosides as well as structure activity relationship of obtained compounds towards hepatitis C virus are reviewed.     

Stereoselective synthesis of novel thioiso dideoxy nucleosides with exocyclic methylene as potential antiviral agents

Novel thioiso pyrimidine and purine nucleosides substituted with exocyclic methylene have been synthesized, starting from D-xylose. Cyclization of the dimesylate to the 4-thiosugar 6a proceeded in pure SN2 reaction in the presence of allylic functional group.     

5-substituted arabinofuranosyluracil nucleosides: synthesis and antiviral properties

A number of 5-alkyl (ethyl, propyl, isopropyl, butyl) analogues of araU, their alpha-anomers and N3-isomers have been synthesized by a number of different procedures, based on the catalytic condensation of the appropriate 5-alkyl-2,4-bis-(trimethylsilyloxy)-pyrimidine with 2,3,5-tri-O-benzyl-alpha-D-arabinofuranosyl chloride. The resulting protected nucleosides were deblocked by a new procedure based on the use of BF3 X Et2O in C2H5SH. The chloromercuri derivative of araU, on reaction with allyl chloride in the presence of Li2PdCl4, gave the 5-allyl derivative, which was catalytically reduced to the corresponding 5-propyl analogue. The antiviral activities of these compounds have been evaluated. 5-Allyl-araU showed moderate specific activity (MIC 20 micrograms/ml) against herpes simplex type 1 virus in PRK cell cultures. Structure-activity relationships are discussed for the 5-alkyl deoxy- and arabino- uracil nucleoside series.     

Homologues of isomeric dideoxynucleosides as potential antiviral agents: synthesis of isodideoxynucleosides with a furanethanol sugar moiety.

The synthesis of a homologues series of compounds related to (R, S)-isodideoxynucleosides has been completed by coupling a variety of natural purine and pyrimidine bases with a modified sugar intermediate. This sugar precursor was prepared regiospecifically and stereospecifically from D-glucose.     

Simple synthesis of novel acyclic (e)-bromovinyl nucleosides as potential antiviral agents

In these study, novel acyclic (E)-bromovinyl nucleosides were synthesized as potential antiviral agents. The coupling of the allylic bromide 9 with bases (thymine, uracil, 5-fluorouracil, 5-iodouracil, cytosine, adenine) afforded a series of novel acyclic nucleosides. The synthesized compounds were evaluated for their antiviral activity against various viruses such as HIV-1, HSV-1, HSV-2, and HCMV. 5-Iodouracil analogue 19 showed weak anti-HIV-1 activity.     

Short synthesis and antiviral evaluation of C-fluoro-branched cyclopropyl nucleosides

A series of novel fluorocyclopropyl nucleosides were synthesized using the Simmons-Smith reaction as a key reaction starting from 1,3-dihydroxyacetone. All the nucleosides synthesized were assayed against several viruses. Among the compounds synthesized, the 5-fluorouracil analogue 15 showed significant anti-HCMV activity (9.22 microM).     

The Ugi reaction in the generation of new nucleosides as potential antiviral and antileishmanial agents

5-Formyl-2'-deoxyuridine-3',5'-diacetate was converted to a small library of 5-substituted pyrimidine nucleoside N-acylamino acid amides by means of a Ugi multicomponent reaction. The reaction allowed introduction of various substituents at the acyl moiety, at the amino acid alpha-amide group, and at the amino acid carboxyl function. Evaluation of these novel 5-substituted nucleosides against vaccinia virus and cowpox virus provided one compound with discernable activity against cowpox virus but five- to eightfold less active than the Cidofovir standard. More promising activity was seen for the inhibition of Leishmania donovani promastigotes. Several synthetic products showed antileishmanial activity in the 10(-5)M range. When compared to earlier studies demonstrating anti-orthopoxviral and antileishmanial activity of 5-substituted pyrimidine nucleosides, these results imply that the 5-(N-acylamino acid amide)-derivatized pyrimidine nucleosides may possess more steric bulk, greater hydrophobicity, and more flexibility than is compatible with these particular biological activities.     

Synthesis of 3'-trifluoromethyl nucleosides as potential antiviral agents

1,2-Di-O-acetyl-3-deoxy-3-trifluoromethyl-5-O-benzoyl-beta-D-ribofuranos e was synthesized from the precursor keto sugar by the use of Ruppert's reagent (CF3SiMe3) as the source of a nucleophilic trifluoromethyl group. Coupling of this trifluoromethyl sugar with nucleobases and elaboration gave novel deoxy and dideoxynucleosides. A single crystal X-ray analysis confirmed the structure and stereochemistry. The deoxynucleosides were converted through an elimination reaction to their dideoxydidehydro derivatives.     

New approaches to the synthesis of antiviral nucleosides.

There is a pressing, worldwide need for new antiviral agents. The chemical synthesis of novel nucleosides for chemotherapeutic screening usually involves multistage processes which can be time consuming. The application of enzymatic methods for the synthesis and modification of antiviral nucleosides shows great promise because of the simplicity and high specificity of enzymatic reactions.     

Phosphoralaninate pronucleotides of pyrimidine methylenecyclopropane analogues of nucleosides: synthesis and antiviral activity

The Z- and E-thymine and cytosine pronucleotides 3d, 4d, 3e, and 4e of methylenecyclopropane nucleosides analogues were synthesized, evaluated for their antiviral activity against human cytomegalovirus (HCMV), herpes simplex virus 1 and 2 (HSV-1 and HSV-2), varicella zoster virus (VZV), Epstein-Barr virus (EBV), human immunodeficiency virus type 1 (HSV-1), and hepatitis B virus (HBV) and their potency was compared with the parent compounds 1d, 2d, 1e, and 2e. Prodrugs 3d and 4d were obtained by phosphorylation of parent analogues 1d or 2d with reagent 8. A similar phosphorylation of N4-benzoylcytosine methylenecyclopropanes 9a and 9b gave intermediates 11a and 11b. Deprotection with hydrazine in pyridine-acetic acid gave pronucleotides 3e and 4e. The Z-cytosine analogue 3e was active against HCMV and EBV The cytosine E-isomer 4e was moderately effective against EBV.     

Concise synthesis and antiviral activity of novel unsaturated acyclic pyrimidine nucleosides

Novel acyclic nucleoside analogues were designed and synthesized as open-chain analogues of neplanocin A. The coupling of the allylic bromide with pyrimidine bases using cesium carbonate afforded a series of novel acyclic nucleosides. The synthesized compounds 15-22 were evaluated for their antiviral activity against various viruses such as HIV, HSV-1, HSV-2, and HCMV.     

Novel bicyclic sugar modified nucleosides: synthesis, conformational analysis and antiviral evaluation

Methodology previously described by us was applied to the formation of novel conformationally restrained bicyclic sugar modified nucleosides, with introduction of an oxazole and a thiocarbamate ring at the 2('),3(')-positions of the ribonucleosides. Two novel alkyl derivatives of 2('),3(')-dideoxy-2('),3(')-oxazole-beta-d-uridine and a novel uridine 2('),3(')-thiocarbamate were successfully synthesised. Conformational evaluation of all the synthesised compounds was conducted using the theoretical potential energy calculation via the macromodel v.6.0 molecular modelling programme. The conformationally restrained nucleosides described were evaluated against a wide range of DNA and RNA viruses. None of the compounds showed specific antiviral effects at subtoxic concentrations.     

Novel imidazo[1,2-c]pyrimidine base-modified nucleosides: synthesis and antiviral evaluation

The preparation of a series of novel 6-(beta-D-ribofuranosyl)-2-alkyl/aryl-6H-imidazo[1,2-c]pyrimidin-5-one nucleosides and the 2-nitrile nucleosides, 6-(beta-D-ribofuranosyl)-5-oxo-5,6-dihydro-imidazo[1,2-c]pyrimidine-2-carbonitrile and 2R and 2S isomers of 6-(beta-D-ribofuranosyl)-5-oxo-2,3,5,6-tetrahydro-imidazo[1,2-c]pyrimidine-2-carbonitrile, is described using two synthetic approaches. The nucleoside mimetics described were evaluated against a wide range of viral types and strains in cell culture. With the exception of one nucleoside, which displayed anti-CMV activity at toxic concentrations, none of the compounds showed antiviral activity most likely due to a lack of substrate recognition by viral and/or cellular nucleoside kinases.     

Synthesis of nucleosides having unusual branched sugars as potential antiviral agents.

Enantiomerically pure novel nucleosides having unusual branched sugars were synthesized in a stereospecific manner from a common chiral pool of (S, S)-1,4-bis(benzyloxy)-2,3-epoxybutane and evaluated for antiviral activity.     

3-Trifluoromethylpyrazolones derived nucleosides: Synthesis and antiviral evaluation

Dengue (DENV) viral infection is a global public health problem that infrequently develops life threatening diseases such as dengue hemorrhagic fever (DFS) and dengue shock syndrome (DSS). Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human corona virus with 38% fatality rate of infected patients. A series of 4-arylhydrazono-5-trifluoromethyl-pyrazolones, their ribofuranosyl, and 5′-deoxyribofuranosyl nucleosides were synthesized, geometry optimized using Density functional theory (DFT), and evaluated for their antiviral activity. 2-Nitrophenylhydrazonopyra-zolone derivative 5 showed significant activity against MERS-CoV (EC₅₀ = 4.6?μM). The nucleoside analog 8 showed moderate activity against DENV-2 (EC₅₀ = 10?μM), while the activity was abolished with the corresponding 5′-deoxyribonucleoside analogs. The identified hits in this study set this category of compounds for further future optimizations.     

Mass spectrometry based methods for analysis of nucleosides as antiviral drugs and potential tumor biomarkers

The intracellular analysis of the phosphorylated metabolites of some anti-HIV nucleosides by liquid chromatography or capillary electrophoresis coupled with tandem mass spectrometry (LC-MS/MS or CE-MS/MS) has been realized on human peripheral blood mononuclear cells (PBMC), with limit of quantitation (LOQ) that allow them to be quantitated intracellularly. We described also the analysis of modified urinary nucleosides as potential tumor biomarkers.     

Synthesis of novel 3'-deoxy-3'-C-hydroxymethyl nucleosides with conformationally rigid sugar moiety as potential antiviral agents

Based on the fact that the ring expanded 3'-C-hydroxymethyl analogue of oxetanocin A exhibited potent antiviral activity, two types of conformationally rigid 3'-C-hydroxymethyl derivatives in which 2'-hydroxyl group is linked to the 4'-position or to the 6'-position were synthesized starting from 1,2;5,6-di-O-isopropylidene-D-glucose, respectively.     

Synthesis of 2',3'-dideoxy-2'-fluoro-L-threo-pentofuranosyl nucleosides as potential antiviral agents

A series of 2',3'-dideoxy-2'-fluoro-L-threo-pentofuranosyl nucleosides has been synthesized as potential antiviral agents. The synthesized compounds were evaluated against HIV-1, HBV, HSV-1, and HSV-2. Among the synthesized analogues, only the cytosine derivative showed moderate antiviral activity against HIV and HBV.     

Nucleic acid components and their analogues: new synthesis of bicyclic thiopyrimidine nucleosides

A novel synthesis of condensed bicyclic thiopyrimidine glycosides utilising 1H-cyclopentapyrimidine-2(3H)-thiones and alpha-bromoglucose or alpha-bromogalactose tetraacetate as starting components is described.     

A new approach to the synthesis of benzothiazole, benzoxazole, and pyridine nucleosides as potential antitumor agents

A modified nitrogen and sulfur glycosylation reaction involving benzothiazole benzoxazole and pyridine nucleoside bases with furanose and pyranose sugars are described. Conformational analysis has been studied by homo- and heteronuclear two-dimensional NMR methods (2D DFQ-COSY, HMQC and HMBC). The N and S sites of glycosylation were determined from the 1H, 13C heteronuclear multiple-quantum coherence (HMQC) experiments. All the deprotected nucleosides were tested for their potential antitumor activity.