Synthesis of 2',3'-dideoxy-3'-fluoro-L-ribonucleosides as potential antiviral agents from D-sorbitol

Phytoestrogen β-Sitosterol Exhibits Potent In Vitro Antiviral Activity against Influenza A Viruses

Influenza is a contagious infection in humans that is caused frequently by low pathogenic seasonal influenza viruses and occasionally by pathogenic avian influenza viruses (AIV) of H5, H7, and H9 subtypes. Recently, the clinical sector in poultry and humans has been confronted with many challenges, including the limited number of antiviral drugs and the rapid evolution of drug-resistant variants. Herein, the anti-influenza activities of various plant-derived phytochemicals were investigated against highly pathogenic avian influenza A/H5N1 virus (HPAIV H5N1) and seasonal low pathogenic human influenza A/H1N1 virus (LPHIV H1N1). Out of the 22 tested phytochemicals, the steroid compounds β-sitosterol and β-sitosterol-O-glucoside have very potent activity against the predefined influenza A viruses (IAV). Both steroids could induce such activity by affecting multiple stages during IAV replication cycles, including viral adsorption and replication with a major and significant impact on the virus directly in a cell-free status "viricidal effect". On a molecular level, several molecular docking studies suggested that β-sitosterol and β-sitosterol-O-glucoside exhibited viricidal effects through blocking active binding sites of the hemagglutinin surface protein, as well as showing inhibitory effects against replication through the binding with influenza neuraminidase activity and blocking the active sites of the M2 proton channel activity. The phytoestrogen β-sitosterol has structural similarity with the active form of the female sex hormone estradiol, and this similarity is likely one of the molecular determinants that enables the phytoestrogen β-sitosterol and its derivative to control IAV infection in vitro. This promising anti-influenza activity of β-sitosterol and its O-glycoside derivative, according to both in vitro and cheminformatics studies, recommend both phytochemicals for further studies going through preclinical and clinical phases as efficient anti-influenza drug candidates.

Design, synthesis, and biological evaluation of new 2'-deoxy-2'-fluoro-4'-triazole cytidine nucleosides as potent antiviral agents

A series of 4'-[1,2,3]triazole-2'-deoxy-2'-fluoro-β-d-arabinofuranosylcytosines (9-17) were prepared by Cu(I)-mediated [3 + 2] cycloaddition reactions (CuAAC) of 1-(4'-azido-2'-deoxy-2'-fluoro-β-d-arabinofuranosyl)cytosine (1) with appropriate alkynes in good yields. Their structures were fully established by (1)H NMR, (13)C NMR, HRMS, and elemental analysis. Most of these nucleoside analogs exhibited potent anti-HIV-1 activity with no cytotoxicity observed at the highest tested concentration up to 25 μM. Among them, compounds 9, 10 and 13 exhibited extremely potent antiviral activity, thus had a great potential for further development as novel nucleoside reverse transcriptase inhibitors (NRTIs) for the treatment of HIV-1 infection. Besides, the anti-HBV activity of compounds 10, 11 and 17 had been investigated.

Synthesis, antiviral activity, cytotoxicity and cellular pharmacology of l-3'-azido-2',3'-dideoxypurine nucleosides

Microwave-assisted optimized transglycosylation reactions were used to prepare eleven modified l-3'-azido-2',3'-dideoxypurine nucleosides. These l-nucleoside analogs were evaluated against HIV and hepatitis B virus. The l-3'-azido-2',3'-dideoxypurines nucleosides were metabolized to nucleoside 5'-triphosphates in primary human lymphocytes, but exhibited weak or no antiviral activity against HIV-1. The nucleosides were also inactive against HBV in HepG2 cells. Pre-steady state kinetic experiments demonstrated that the l-3'-azido-2',3'-dideoxypurine triphosphates could be incorporated by purified HIV-1 reverse transcriptase, although their catalytic efficiency (k(pol)/K(d)) of incorporation was low. Interestingly, a phosphoramidate prodrug of l-3'-azido-2',3'-dideoxyadenosine exhibited anti-HIV-1 activity without significant toxicity.

Synthesis of new 2'-deoxy-2'-fluoro-4'-azido nucleoside analogues as potent anti-HIV agents

We prepared 1-(4'-azido-2'-deoxy-2'-fluoro-β-D-arabinofuranosyl)cytosine (10) and its hydrochloride salt (11) as potential antiviral agents based on the favorable antiviral profiles of 4'-substituted nucleosides. Compounds 10 and 11 were synthesized from 1,3,5-O-tribenzoyl-2-deoxy-2-fluoro-D-arabinofuranoside in multiple steps, and their structures were unequivocally established by IR, (1)H NMR, (13)C NMR, and (19)F NMR spectroscopy, HRMS, and X-ray crystallography. Compounds 10 and 11 exhibited potent anti-HIV-1 activity (EC(50): 0.3 and 0.13 nM, respectively) without significant cytotoxicity in concentrations up to 100 μM. Compound 11 exhibited extremely potent anti-HIV activity against NL4-3 (wild-type), NL4-3 (K101E), and RTMDR viral strains, with EC(50) values of 0.086, 0.15, and 0.11 nM, respectively. Due to the high potency of 11, it was also screened against an NIH Reagent Program NRTI-resistant virus panel containing eleven mutated viral strains and for cytotoxicity against six different human cell lines. The results of this screening indicated that 11 is a novel NRTI that could be developed as an anti-AIDS clinical trial candidate to overcome drug-resistance issues.

Synthesis of L-2'-deoxypentofuranonucleoside derivatives of thymine from D-glucose

Convergent synthesis of L-2'-deoxypentofuranonucleoside derivatives of thymine was carried out from D-glucose via 6-O-toluoyl-3-deoxy-1,2-O-isopropylidene-beta-L-lyxo-hexofuranose as a key intermediate.

Antiviral activity of nucleoside analogues against SARS-coronavirus (SARS-coV)

The recent outbreak of severe acute respiratory syndrome (SARS), which is an acute respiratory illness, is caused by newly discovered SARS coronavirus (SARS-CoV). Herein we describe the antiviral activity of several classes of nucleoside analogues evaluated against SARS-CoV in Vero 76 cells, some of which exhibited moderate activity.

Synthesis and anti-HIV activity of beta-D-3'-azido-2',3'-unsaturated nucleosides and beta-D-3'-azido-3'-deoxyribofuranosylnucleosides

Since the discovery of 3'-azido-3'-deoxythymidine (AZT) and 2',3'-didehydro-2',3'-dideoxythymidine (d4T) as potent and selective inhibitors of the replication of human immunodeficiency virus (HIV), there has been a growing interest for the synthesis of 2',3'-didehydro-2',3'dideoxynucleosides with electron withdrawing groups on the sugar moiety. Here we described an efficient method for the synthesis of such nucleoside analogs bearing structural features of both AZT and d4T The key intermediate, 3-azido-1,2-bis-O-acetyl-5-O-benzoyl-3-deoxy-D-ribofuranose, 5 was synthesized from commercially available D-xylose in five steps, from which a series of pyrimidine and purine nucleosides were synthesized in high yields. The resultant protected nucleosides were converted to target nucleosides using appropriate chemical modifications. The final nucleosides were evaluated as potential anti-HIV agents.

Synthesis of 3‘-Fluoro-2‘,3‘-dideoxy-2‘,3‘-didehydro-4‘-ethynyl-d- and -l-furanosyl Nucleosides

An efficient procedure has been developed for the synthesis of 3'-fluoro-2',3'-dideoxy-2',3'-didehydro-4'-ethynyl D- and L-furanosyl nucleosides (1 and 2) starting from 2,3-O-isopropylidene-d-glyceraldehyde. The key intermediate 1-O-benzoyl-3E-fluoro-3,4-unsaturated-5,6-di(tert-butyldimethylsilyloxy)-2-hexanone 8 was obtained in nine steps with the overall yield of 22%. The alpha,beta-unsaturated ketone 8 was then treated with ethynylmagnesium bromide in a typical Grignard reaction procedure to afford the two intermediates 9 and 10, which after deprotection, oxidation, and acetylation gave the corresponding 4-ethynyl-substituted D- and L-sugar moieties 15 and 16, respectively. A series of D- and L-pyrimidine and purine nucleosides were prepared by the coupling of the sugar moieties with various silylprotected bases. The anomeric mixtures were obtained after condensation. After separation, the beta-isomers were further deprotected to yield the target nucleosides. All the newly synthesized 4'-substituted nucleosides were tested for their activities against HIV, among which the D-adenine derivative showed moderate anti-HIV activity (EC(50) = 25.1 microM) without significant cytotoxicity.

Synthesis and antiviral evaluation of 2'-deoxy-2'-C-trifiuoromethyl beta-D-ribonucleoside analogues bearing the five naturally occurring nucleic acid bases

2'-Deoxy-2'-C-trifluoromethyl-beta-D-ribonucleoside derivatives bearing the five naturally occurring acid bases have been synthesized. All these derivatives were prepared by glycosylation reactions of purine and pyrimidine bases with a suitable peracylated 2-deoxy-2-C-trifluoromethyl sugar precursor to afford anomeric mixtures of protected nucleosides. After separation and deprotection, the resulting beta-nucleoside analogues were tested for their activity against HIV, HBV and several RNA viruses. However, none of these compounds showed significant antiviral activity nor cytotoxicity.