Synthesis and Evaluation of Novel 6′,6′-Difluoro 5′-Deoxycarbocyclic Phosphonic Acid Nucleosides as Antiviral Agents

The authors describe highly efficient synthetic routes for the preparation of novel 6′,6′-difluoro 5′-deoxycarbocyclic phosphonic acid nucleosides from 1,4-dihydroxy-2-butene. The discovery that the 6′-fluorinated carbocyclic nucleoside (2, EC₅₀ = 0.16 μM) is a potent anti-HSV-1 agent led to the syntheses and biological evaluations of 6′-modified 5′-deoxyversions of carbocyclic phosphonate nucleosides. The synthesized nucleoside analogues 15, 18, 22, and 25 were tested for anti-HIV activity and for cytotoxicity. However, none of them showed significant anti-HIV-1 activity or cytotoxicity at concentrations up to 100 μM.     

Synthesis of Novel 2′-Fluoro-3′-Hydroxymethyl-5′-Deoxythreosyl Phosphonic Acid Nucleoside Analogues As Antiviral Agents

A series of purine 5′-deoxyphosphonate analogues were designed and synthesized to mimic naturally occurring purine monophosphate from 1,3-dihydroxyacetone as starting material. The discovery of threosyl phosphonate nucleoside (PMDTA, EC₅₀ = 2.53 μM) as a potent anti-HIV agent has led to the synthesis and biological evaluation of 2′,3′-modified 5′-deoxyversions of the threosyl phosphonate nucleosides. The synthesized 2′-fluoro-3′-hydroxymethyl 5′-deoxythreosyl phosphonic acid nucleoside analogues 14, 18, 23, and 27 were tested for anti-HIV activity as well as cytotoxicity. The adenine analogue 18 exhibits weak in vitro anti-HIV-1 activity (EC₅₀ = 19.2 μM).     

Synthesis of Novel 2′,3′-Difluorinated 5′-Deoxythreosyl Phosphonic Acid Nucleosides as Antiviral Agents

A novel route for the synthesis of 2′,3′-difluorinated 5′-deoxythreosyl phosphonic acid nucleosides from glyceraldehyde using the Horner-Emmons reaction in the presence of triethyl α-fluorophosphonoacetate is described. The second fluorination at the 2′-position was an electrophilic reaction performed using N-fluorodibenzenesulfonimide. Glycosylation reactions between the nucleosidic bases and glycosyl donor 9 generated nucleosides that were further phosphonated and hydrolyzed to produce the desired nucleoside analogues. The synthesized nucleoside analogues 13, 16, 20, and 23 were tested for anti- human immunodeficiency virus (HIV) activity as well as cytotoxicity. Adenine derivative 16 showed significant anti-HIV activity up to 100 μM.     

Design and Synthesis of Novel Threosyl-5′- Deoxyphosphonic Acid Purine Analogues as Potent Anti-Hiv Agents

The discovery of threosyl phosphonate nucleoside (PMDTA, EC₅₀ = 2.53 μM) as a potent anti-HIV agent has led to the synthesis and biological evaluation of 5 ′-deoxyversions of threosyl phosphonate nucleosides from 1,4-dihydroxy-2-butene. The synthesized nucleoside phosphonic acid analogues 14 and 19 were tested for anti-HIV activity as well as cytotoxicity. The adenine analogue 14 exhibits moderate in vitro anti-HIV-1 activity (EC₅₀ = 12.6 μM).     

Design and Synthesis of Novel 1′,3′-Dioxolane 5′-Deoxyphosphonic Acid Purine Analogues as Potent Antiviral Agents

Electronic parameters of 1′,3 ′-oxygen play significant roles in steering the conformation of nucleoside phosphonic acid analogues. To investigate the relationship of two oxygen atoms with antiviral enhancement, novel 1′,3 ′-dioxolane 5 ′-deoxyphosphonic acid purine analogues were synthesized via de novo acyclic stereoselective route from acrolein and glycolic acid. The synthesized nucleoside phosphonic acid analogues 14 and 19 were subjected to antiviral screening against several viruses, such as HIV-1, HSV-1, HSV-2, and HCMV. The guanine analogue 19 exhibits in vitro anti-HIV-1 activity similar to that of 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA) in MT-4 cells.     

2′,3′-Dideoxyuridine triphosphate conjugated to SiO2 nanoparticles: Synthesis and evaluation of antiproliferative activity

A conjugate of triphosphorylated 2′,3′-dideoxyuridine (ddU) with SiO₂ nanoparticles was obtained via the CuAAC click chemistry between a γ-alkynyl ddU triphosphate and azido-modified SiO₂ nanoparticles. Assessment of cytotoxicity in human breast adenocarcinoma MCF7 cells demonstrated that ddU triphosphate conjugated to SiO₂ nanoparticles exhibited a 50% decrease in cancer cell growth at a concentration of 183?±?57?µg/mL, which corresponds to 22?±?7?µM of the parent nucleotide, whereas the parent nucleoside, nucleotide and alkynyl triphosphate precursor do not show any cytotoxicity. The data provide an example of remarkable potential of novel conjugates of SiO₂ nanoparticles with phosphorylated nucleoside analogues, even those, which have not been used previously as therapeutics, for application as new anticancer agents.     

Efficient Electrophilic Fluorination for the Synthesis of Novel 2′-Fluoro-3′-Methyl-5′-Deoxyphosphonic Acid Apiosyl Nucleoside Analogues

Novel 5′-deoxyapiosyl purine phosphonic acid analogues with a 2′-electropositive moiety, such as, a fluorine atom were designed and synthesized from commercially available hydroxylacetone. Condensation of a glycosyl donor 10 with purines under Vorbruggen conditions and cross-metathesis give the desired nucleoside phosphonic acid analogues 14, 17, 21, and 24. The synthesized nucleoside analogues were subjected to antiviral screening against HIV-1, and the adenine analogue 17 exhibited weak in vitro anti-HIV-1 activity (EC₅₀ = 26.6 μM)     

Synthesis,characterization and biological evaluation of C5′-N-cyclopropylcarboxamido-C6-amino-C2-alkynylated purine nucleoside analogues

In an effort to develop potent antibacterial and anticancer agents, a series of C5′-N-cyclopropylcarboxamido-C6-amino-C2-alkynylated purine nucleoside analogues 11a-g were synthesized through a Sonogashira cross-coupling reaction. The nine-step synthesis is easy to perform, and employs commercially available reagents. 2-Iodo-5′-N-cyclopropylcarboxamidoadenosine (9) was used as the starting intermediate for the synthesis of title derivatives 11a-g. Synthetic intermediates (2–9) and final products (11a-g) were appropriately characterized by IR, ¹H NMR, ¹³C NMR and mass spectroscopy. The synthesized purine nucleoside analogues (11a-g) were evaluated for their in vitro antibacterial activity against two gram-positive and two gram-negative bacteria. They were then tested for cytotoxicity against MDA-MB-231 and Caco-2 cancer cell lines to determine their anti-cancer activity. Among the tested compounds, compounds 11c and 11g showed most potent antibacterial activity against S.aureus and P.aeruginosa bacterial strains. Compounds 11b and 11e displayed considerable IC₅₀^s of 7.9 and 6.8 µg/mL, respectively, vs MDA-MB-231 cell lines of 7.5 and 8.3 µg/mL, respectively, against the Caco-2 cell lines.     

Synthesis of Novel 3′-Hydroxymethyl 5′-Deoxythreosyl Phosphonic Acid Nucleoside Analogues as Potent Antiviral Agents

A very efficient synthetic route to novel 3′-hydroxymethyl 5′-deoxythreosyl phosphonic acid nucleosides was described. The discovery of threosyl phosphonate nucleoside (PMDTA, EC₅₀ = 2.53 μM) as a potent antihuman immunodeficiency virus (anti-HIV) agent has led to the synthesis and biological evaluation of 3′-modified 5′-deoxy versions of the threosyl phosphonate nucleosides. 3′-Hydroxymethyl 5 ′-deoxythreosyl phosphonic acid nucleoside analogues 15, 19, 24, and 28 were synthesized from 1,3-dihydroxyacetone and tested for anti-HIV activity as well as cytotoxicity. The adenine analogue 19 exhibits moderate in vitro anti-HIV-1 activity (EC₅₀ = 10.2 μM).     

Disaccharide Pyrimidine Nucleosides and Their Derivatives: A Novel Group of Cell-Penetrating Inhibitors of Poly(ADP-Ribose) Polymerase 1

Nearly 30 synthetic nucleosides were tested with human recombinant poly(ADP-ribose) polymerase 1 as potential inhibitors of this enzyme. The most active compounds were some disaccharide analogues of thymidine: 3′-O-β-D-ribofuranosyl-5-iodo-dUrd (2d; IC₅₀ = 45 μM), 3′-O-β-D-ribofuranosyl-2′-deoxythymidine (2e; IC₅₀ = 38 μM), and 3′-O-β-D-ribofuranosyl-2′-deoxythymidine oxidized (4; IC₅₀ = 25 μM). These compounds also reduced H₂O₂-induced synthesis of poly(ADP-ribose) in cultured human ovarian carcinoma (SKOV-3) cells in a dose-dependent manner. Furthermore, compounds 2d or 2e until a concentration of 1 mM did not affect growth of SKOV-3 cells, whereas dialdehyde compound 4, as well as thymidine, exhibited a significant cytotoxicity.     

Synthesis and Anti-HIV Activity of Novel 4′-Trifluoromethylated 5′-Deoxycarbocyclic Nucleoside Phosphonic Acids

Efficient synthetic route to novel 4′-trifluoromethylated 5′-deoxycarbocyclic nucleoside phosphonic acids was described from α-trifluoromethyl-α,β-unsaturated ester. Coupling of purine nucleosidic bases with cyclopentanol using a Mitsunobu reaction gave the nucleoside intermediates which were further phosphonated and hydrolyzed to reach desired nucleoside analogs. Synthesized nucleoside analogs were tested for anti-HIV activity as well as cytotoxicity. Adenine analog 22 shows significant anti-HIV activity (EC₅₀ = 8.3 μM) up to 100 μM.     

Screening of bromotyramine analogues as antifouling compounds against marine bacteria

Rapid and efficient synthesis of 23 analogues inspired by bromotyramine derivatives, marine natural products, by means of CuSO₄-catalysed [3+2] alkyne–azide cycloaddition is described. The final target was then assayed for anti-biofilm activity against three Gram-negative marine bacteria, Pseudoalteromonas ulvae (TC14), Pseudoalteromonas lipolytica (TC8) and Paracoccus sp. (4M6). Most of the synthesised bromotyramine/triazole derivatives are more active than the parent natural products Moloka’iamine (A) and 3,5-dibromo-4-methoxy-β-phenethylamine (B) against biofilm formation by the three bacterial strains. Some of these compounds were shown to act as non-toxic inhibitors of biofilm development with EC₅₀ < 200 μM without any effect on bacterial growth even at high concentrations (200 μM).     

Preparation and Properties of a New Type of Acyclic,Achiral Nucleoside Analogue

Abstract

Preparation of the nucleoside analogues 1 and incorporation of 1, B = T, in deoxyribooligonucleotides by the phosphoramidite method is described. A two-step deprotection procedure was developed to reduce cleavage of the modified allylic unit. The binding properties of the modified oligonucleotides towards complementary DNA and RNA has been evaluated by T_m measurements showing a ΔT_m of ?2 to ?6.5°C per modification. An oligonucleotide with two modifications at the 3′-end showed considerable resistance towards cleavage by a 3′-exonuclease. No antiviral activity against HIV-1 or HSV-1 was found for 1, B = G or T, or for any of the trihydroxy derivatives 5.     

Potential application of thymidylate kinase in nucleoside analogue activation in Plasmodium falciparum

Plasmodium falciparum thymidylate kinase (PfTMPK) shows a broad range of substrate tolerance when compared to the corresponding human enzyme. Besides 2′-deoxythymidine monophosphate (dTMP), PfTMPK can phosphorylate 3′-azido-2′,3′-dideoxythymidine monophosphate (AZTMP) very efficiently. In contrast, human thymidylate kinase (hTMPK) is 200 times less active towards AZTMP. We were interested to see if we could use PfTMPK to activate 3′-azido-2′,3′-deoxythymidine (AZT) derivatives as a strategy to treat malaria. P. falciparum lacks a pyrimidine nucleoside kinase which usually activates nucleoside and nucleoside analogues to the corresponding monophosphates. Therefore, several prodrug analogues of AZT and related nucleoside monophosphates were prepared and analysed for antiparasitic activity. The prodrugs showed an increase in activity over the parent nucleoside analogues, which showed no inhibition of parasite growth at the concentration tested. The evidence here reported provides a strategy that could be exploited for further anti-malarial design.     

Structure-Activity Relationships Among a New Class of Antiviral Heterosubstituted 2′,3′-Dideoxynucleoside Analogues

Abstract

3′-Oxa-4′-thiocytidine nucleoside analogues 14–17 were prepared from oxathiolanes 10 and 11, and evaluated for activity against HIV-1 and HBV in vitro. The nucleoside analogues were found to possess potent activities against HIV-1 in a panel of cell lines. Compound 16 is moderately active against HBV in 2.2.15 cells.     

A novel entecavir analogue constructing with a spiro[2.4]heptane core structure in the aglycon moiety: Its synthesis and evaluation for anti-hepatitis B virus activity

Synthesis of a novel 2′-deoxy-guanine carbocyclic nucleoside 4 constructed with spiro[2.4]heptane core structure in the aglycon moiety was carried out. Radical-mediated 5-exo-dig mode cyclization and following cyclopropanation proceeded efficiently to furnish the spiro alcohol 10. Subsequent Mitsunobu-type glycosylation between 13 and 14, deoxygenation of the 2′-hydroxyl group of 16 and deprotection of 17 gave the title compound 4. Compound 4 demonstrated moderate anti-HBV activity (EC₅₀ value of 0.12 ± 0.02 µM) and no cytotoxicity against HepG2 cells was observed up to 100 µM.     

Chemistry and Anti-HIV Activity of 2′-β-Fluoro-2′,3′-dideoxyguanosine

Abstract

The 2′-β-fluoro analogue of 2′,3′-dideoxyguanosine has been prepared by two synthetic routes. This compound and two analogues have anti-HIV activity in at least two of three host cell systems used (ATH8, CEM, PBL). These compounds, as well as their ddGuo parents, have been characterized with regard to their acid-stabilities, octanol-water partition coefficients, and enzyme substrate properties for adenosine deaminase and purine nucleoside phosphorylase. F-ddGuo analogues are less potent but more stable than their non-fluorinated parent compounds.     

3′-O- and 5′-O-Propargyl Derivatives of 5-Fluoro-2′-Deoxyuridine: Synthesis,Cytotoxic Evaluation and Conformational Analysis

A series of new 3′-O- and 5′-O-propargyl derivatives of 5-fluoro-2′-deoxyuridine (1–4) was synthesized by means of propargyl reaction of properly blocked nucleosides (2,4), followed by the deprotection reaction with ammonium fluoride. The synthesized propargylated 5-fluoro-2′-deoxyuridine analogues (1–4) were evaluated for their cytotoxic activity in three human cancer cell lines: cervical (HeLa), oral (KB) and breast (MCF-7), using the sulforhodamine B (SRB) assay. The highest activity and the best SI coefficient in all of the investigated cancer cells were displayed by 3′-O-propargyl-5-fluoro-2′-deoxyuridine (1), and its activity was higher than that of the parent nucleoside. The other new compounds exhibited moderate activity in all of the used cell lines.     

Synthesis and Anti-HIV Activity of Novel 2′-Deoxy-2′-β-Fluoro-Threosyl Nucleoside Phosphonic Acid Analogues

Novel 2′-deoxy-2′-β-fluoro-threose purine phosphonic acid analogues were designed and racemically synthesized from 2-propanone-1,3-diacetate. Condensation successfully proceeded from a glycosyl donor 9 under Vorbrüggen conditions. Cross-metathesis of vinyl analogues 13 and 23 with diethyl vinylphosphonate yielded the desired nucleoside phosphonate analogues 14 and 24, respectively. Ammonolysis and hydrolysis of phosphonates yielded the nucleoside phosphonic acid analogues 16, 19, 26, and 29. The synthesized nucleoside analogues were subjected to antiviral screening against human immunodeficiency virus (HIV)-1. Adenine analogue 18 exhibited weak in vitro activities against human immunodeficiency virus (HIV)-1.     

Extended exposure to substrate regulates the human equilibrative nucleoside transporter 1 (hENT1)

ABSTRACT

Human equilibrative nucleoside transporter 1 (hENT1) is a major route of entry of nucleosides and nucleoside analog drugs. The regulation of hENT1 is poorly understood in spite of its clinical importance as a drug transporter. Immunofluorescence microscopy and fluorescence-activated cell sorting suggested that cytidine pre-treatment (40 μM, 6 h) promotes hENT1 internalization in a way that does not affect either hENT1-mediated nucleoside uptake or gemcitabine-induced cytotoxicity. The Scatchard plot analyses of our NBTI binding data support previous speculations that hENT1 proteins exist as two sub-populations, and suggest that cytidine pre-treatment leads to the internalization of one population.