5-alkylvinyl-1,2,4-triazole nucleosides: Synthesis and biological evaluation

Abstract

Some 5-substituted ribavirin analogues have a high antiviral and anticancer activity, but their mechanisms of action are obviously not the same as their parent compound. The SAR studies performed on 3 (5)-substituted 1,2,4-triazole nucleosides have shown a high dependency between the structure of the 3 (5)-substituent and the level of antiviral/anticancer activity. The most active substances of the row contain coplanar with the 1,2,4-triazole ring aromatic substituent which is connected by a rigid ethynyl bond. However, the compounds with the trans-vinyl linker also had antiviral activity. We decided to study the antitumor activity of ribavirin analogues with alkyl/aryl vinyl substituents in the 5th position of the 1,2,4-triazole ring. Protected nucleoside analogues with various 5-alkylvinyl substituents were obtained by Horner-Wadsworth-Emmons reaction from the common precursor and converted to the nucleosides. Arylvinyl nucleosides were synthesised according the reported procedures. All compounds did not show significant antiproliferative activity on several tumour cell lines. Coplanar aromatic motif in the 5-substituent for the anticancer activity manifestation was confirmed.     

Synthesis and antiviral activity of amino acid esters of ribavirin

The synthesis and antiviral activity of amino acid esters of 1-(β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (ribavirin,1) is described.     

Discovery of 3-(3-cyano-4-pyridyl)-5-(4-pyridyl)-1,2,4-triazole,FYX-051-a xanthine oxidoreductase inhibitor for the treatment of hyperuricemia

Our previous study identified 2-[2-(2-methoxy-ethoxy)-ethoxy]-5-[5-(2-methyl-4-pyridyl)-1H-[1,2,4]triazol-3-yl]-benzonitrile (2) as a safe and potent xanthine oxidoreductase (XOR) inhibitor for the treatment of hyperuricemia. Here, we synthesized a series of 3,5-dipyridyl-1,2,4-triazole derivatives and, in particular, examined their in vivo activity in lowering the serum uric acid levels in rats. As a result, we identified 3-(3-cyano-4-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (FYX-051, compound 39) to be one of the most potent XOR inhibitors; it exhibited an extremely potent in vivo activity, weak CYP3A4-inhibitory activity and a better pharmacokinetic profile than compound 2. Compound 39 is currently being evaluated in a phase 2 clinical trial.     

Design, synthesis, and biological evaluation of substituted 3-alkylthio-4,5-diaryl-4H-1,2,4-triazoles as selective COX-2 inhibitors

A new type of 4,5-diaryl-4H-1,2,4-triazole, possessing C-3 thio and alkylthio (SH, SMe or SEt) substituents, was designed and synthesized for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors with in vivo anti-inflammatory activity. The compound, 3-ethylthio-5-(4-fluorophenyl)-4-(4-methylsulfonylphenyl)-4H-1,2,4-triazole (10d), exhibited a high in vitro selectivity (COX-1 IC50=20.5 nM; COX-2 IC50=1.8 nM; SI=11.39) relative to the reference drug celecoxib (COX-1 IC50=3.7 nM; COX-2 IC50=2.2 nM; SI=1.68) and also showed good anti-inflammatory activity compared to celecoxib in a carrageenan-induced rat paw edema assay.     

Discovery of 4,5-diphenyl-1,2,4-triazole derivatives as a novel class of selective antagonists for the human V(1A) receptor

In the search for a novel class of selective antagonists for the human V(1A) receptor, high-throughput screening (HTS) of the Yamanouchi chemical library using CHO cells expressing the cloned human V(1A) (hV(1A)) receptor led to the discovery of 5-(4-biphenyl)-4-(2-methoxyphenyl)-3-methyl-1,2,4-triazole (3) which possessed the novel 4,5-diphenyl-1,2,4-triazole structure. Subsequent structure-activity relationships studies on a series of the 4,5-diphenyl-1,2,4-triazole derivatives related to 3 revealed that the 4,5-diphenyl-1,2,4-triazole structure played an essential role in exerting high affinity for the hV(1A) receptor and that introduction of a basic amine moiety to the methoxy part of the 4-phenyl ring was effective in the improvement of both affinity for the hV(1A) receptor and selectivity versus the hV(2) receptor. Compound 3 and the 2-(morphorino)ethoxy derivative (11b) were shown to be antagonists for the hV(1A) receptor, from their effects on AVP-induced [Ca(2+)](i) response in CHO cells expressing the hV(1A) receptor.     

Synthesis of 1,2,4-triazole C-nucleosides from hydrazonyl chlorides and nitriles

A series of 1,3-diaryl-5-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)-1H-1,2,4-triazole nucleosides (3a-f) were synthesized via the intermolecular cyclization of hydrazonyl chlorides with peracylated ribofuranosyl cyanide catalyzed by Yb(OTf)3 or AgNO3, respectively. Similarly, the 1,2,4-triazole of glucopyranosyl C-nucleosides 5a,b were prepared from the hydrazonyl chlorides and the nitrile 4. Alternatively, the 1,2,4-triazole N-nucleoside 8 was obtained from cyclization of the unsymmetrical bis[alpha-(4-methoxyphenyl)aminobenzylidene]-hydrazine with peracylated 1-amino-D-manno-pentitol.     

Ribavirin can be mutagenic for arenaviruses

Arenaviruses include several important human pathogens, and there are very limited options of preventive or therapeutic interventions to combat these viruses. An off-label use of the purine nucleoside analogue ribavirin (1-β-d-ribofuranosyl-1-H-1,2,4-triazole-3-carboxamide) is the only antiviral treatment currently available for arenavirus infections. However, the ribavirin antiviral mechanism action against arenaviruses remains unknown. Here we document that ribavirin is mutagenic for the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) in cell culture. The mutagenic activity of ribavirin on LCMV was observed under single- and multiple-passage regimes and could not be accounted for by a decrease of the intracellular GTP pool promoted by ribavirin-mediated inhibition of inosine monophosphate dehydrogenase (IMPDH). Our findings suggest that the antiviral activity of ribavirin on arenaviruses might be exerted, at least partially, by lethal mutagenesis. Implications for antiarenavirus therapy are discussed.     

Design,synthesis, and pharmacological and pharmacokinetic evaluation of 3-phenyl-5-pyridyl-1,2,4-triazole derivatives as xanthine oxidoreductase inhibitors

In an effort to find a potent xanthine oxidoreductase (XO) inhibitor, we discovered the best compound 2-[2-(2-methoxy-ethoxy)-ethoxy]-5-[5-(2-methyl-pyridin-4-yl)-1H-[1,2,4]triazol-3-yl]-benzonitrile 28. Here, we describe the following: (1) the design, synthesis, and structure–activity relationship of a series of 3-phenyl-5-pyridyl-1,2,4-triazole derivatives by in vitro studies of XO inhibitory activity in bovine milk and in vivo studies of serum uric acid (UA) reductive activity in rats, (2) a drug interaction study by a cytochrome P450 3A4 (CYP3A4) assay, and (3) a pharmacokinetic (PK) study. Compound 28 exhibits potent XO inhibitory activity, serum UA-lowering activity in rats, weak CYP3A4 inhibitory activity, and moderate PK profile.     

Synthesis and biological evaluation of novel 7-hydroxy-4-phenylchromen-2-one–linked to triazole moieties as potent cytotoxic agents

A new series of novel 7-hydroxy-4-phenylchromen-2-one (1a)–linked 1,2,4-triazoles were synthesised using a click chemistry approach. All derivatives were subjected to 3-(4,5-dimethylthiazol-yl)-diphenyl tetrazolium bromide (MTT) cytotoxicity screening against a panel of six different human cancer cell lines (AGS, MGC-803, HCT-116, A-549, HepG2, and HeLa) to assess their cytotoxic potential. Among the tested molecules, some of the analogues showed better cytotoxic activity than that shown by the 7-hydroxy-4-phenylchromen-2-one (1a). Of the synthesised 1,2,4-triazoles,the 7-((4-(4-Chlorophenyl)-4H-1,2,4-triazol-3-yl)methoxy)-4-phenyl-2H-chromen-2-one (4d) showed the best activity, with an IC₅₀ of 2.63?±?0.17?µM against AGS cells. Further flow cytometry assays demonstrated that compound 4d exerts its antiproliferative effects by arresting cells in the G2/M phase of the cell cycle and by inducing apoptosis. Collectively, our results indicate that the 1,2,4-triazole derivatives have a significantly stronger antitumour activity than 1,2,3-triazole derivatives. Most of the compounds exhibited better antitumour activity than the positive control drug 5-fluorouracil.     

Synthesis and pharmacological evaluation of condensed heterocyclic 6-substituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives of naproxen

Some 6-substituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (4a-f and 5a-d) have been synthesized by cyclisation of 4-amino-5-[1-(6-methoxy-2-naphthyl)ethyl]-3-mercapto-(4H)-1,2,4-triazole (3) with various substituted aromatic acids and aryl/alkyl isothiocyanates, through a single step reaction. The target compounds were pharmacologically evaluated for their anti-inflammatory and analgesic potentials by known experimental models. Several of these showed significant activity. Very low ulcerogenic index was observed for potent compounds.     

Synthesis of acyclic analogs of ribavirin

A number of ribavirin analogues were prepared in which the ribose moiety was replaced with acyclic substituents imitating some fragments of the ribose ring: 2,3-dihydroxy-prop-1-yl, 3-hydroxymethyl-4-hydroxy-2-oxabut-1-yl, 4,5-dihydroxy-2-oxapent-1-yl and 1,5-dihydroxy-3-oxapent-2-yl. These analogues were synthesized by direct alkylation of ethyl 1,2,4-triazole-3-carboxylate with suitable agents followed by ammonolysis. New convenient methods for preparing the alkylating agents were developed.     

Synthesis and characterisation of a series of mononuclear ruthenium(II) carbonyl complexes of heterocycle-based asymmetric bidentate ligands

In this contribution, the synthesis and characterisation of a series of complexes of the type [Ru(L-L′)(CO)₂Cl₂] are reported, where L-L′ are the chelating ligands L1-L8, 2-(4H-[1,2,4]triazol-3′-yl)-pyridine (L1); 2-(4H-[1,2,4]triazol-3′-yl)-pyrazine; (L2); 2-(1-methyl-4H-[1,2,4]-triazol-3-yl)pyridine (L3); 2-(5-pyridin-2-yl-4H-[1,2,4]-triazole-3-yl)phenol (L4); 3-(5-methylphenyl)-pyridin-2-yl-1,2,4-triazole (L5); 3-(4-methylphenyl)-pyridin-2-yl-1,2,4-triazole (L6); 3-(4-methoxyphenyl)-pyridin-2-yl-1,2,4-triazole (L7); 3,6-bis[(4-methoxyphenyl)iminomethyl]pyridazine (L8). L1-L7 are triazole-based ligands, which provide two distinct bidentate coordinate modes (via N2 or N4 of the triazole) whereas L8 is pyridazine-based and contains two identical bidentate binding pockets. The products obtained are analysed using infrared and NMR spectroscopy. The X-ray and molecular structures of the complexes with the ligands L2, L6, L7 and L8 are reported. These structures are the first to be reported for triazole based ruthenium chloro and ruthenium pyridazine imine complexes. The data show that the triazole ring in L2, L6 and L7 is coordinated via the N2 atom, and that the pyridazine-based ligand L8 uses only one binding pocket hence accommodating only one ruthenium(II) centre. For all compounds the cis(CO)transCl conformation is obtained. The results obtained are compared with those obtained for other similar compounds.     

Effect of cytosine, arabinoside, iododeoxyuridine, ethyldeoxyuridine, thiocyanatodeoxyuridine, and ribavirin on tail lesion formation in mice infected with vaccinia virus.

Mice infected intravenously with vaccinia virus develop characteristic lesions over the entire tail surface. This experimental virus infection presents a highly sensitive and reliable model for evaluating the antivaccinia activity of antiviral compounds. Ara-C (1-beta-D-arabinofuranosylcytosine), ribavirin (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), IUdR (5-iodo-2'-deoxyuridine) as well as two novel analogs of IUdR, EtUdR (5-ethyl-2'-deoxyuridine), and NCSUdR (5-thiocyanato-2'-deoxyuridine), were found to inhibit the formation of vaccinia tail lesions, when administered intraperitoneally once daily for 7 days starting immediately after virus infection. The order of (decreasing) activity was: ara-C greater than IUdR greater than NCSUdR greater than ribavirin greater than EtUdR. Various drug combinations, involving IUdR + ara-C, NCSUdR + ara-C, NCSUdR + IUdR, NSCUdR + ribavirin, etc., were evaluated but none proved more efficacious than either compound administered alone.     

Synthesis and CYP26A1 inhibitory activity of 1-[benzofuran-2-yl-(4-alkyl/aryl-phenyl)-methyl]-1H-triazoles

Methodology previously described by our group was applied to the preparation of a series of 4-alkyl/aryl-substituted 1-[benzofuran-2-yl-phenylmethyl]-1H-triazoles. The [1,2,4]-triazole derivatives were prepared for a range of alkyl and aryl substituents, and for the 4-methyl, 4-ethyl, 4-(i)propyl, 4-(t)butyl, 4-phenyl and 4-chlorophenyl derivatives, the minor [1,3,4]-triazole isomer also isolated. All the triazole derivatives were evaluated for CYP26A1 inhibitory activity using a MCF-7 cell-based assay. The 4-ethyl and 4-phenyl-1,2,4-triazole derivatives displayed inhibitory activity (IC(50) 4.5 and 7 microM, respectively) comparable with that of the CYP26 inhibitor liarozole (IC(50) 7 microM). Using a CYP26A1 homology model (based on CYP3A4) template, docking experiments were performed with MOE with multiple hydrophobic interactions observed in addition to coordination between the triazole nitrogen and the haem transition metal.     

Double-headed acyclo C-nucleoside analogues. Functionalized 1,2-bis-(1,2,4-triazol-3-yl)ethane-1,2-diol

Reaction of L-tartaric acid with thiocarbohydcrazide afforded (1R, 2S)-1,2-bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)-ethane-1,2-diol (3). The functional groups in 3 allowed the construction of fused heterocycles on the 1,2,4-triazole rings, mainly of the 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine type as in 4, 5, 7, 10, 13 and 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole type as in 14.     

Synthesis of some new hybride molecules containing several azole moieties and investigation of their biological activities

1,2,4-Triazole-3-one prepared from tryptamine was converted to the corresponding carbothioamides by several steps. Their treatment with ethyl bromoacetate or 4-chlorophenacyl bromide produced the corresponding 5-oxo-1,3-thiazolidine or 3-(4-chlorophenyl)-1,3-thiazole derivatives. Acetohydrazide derivative that was obtained starting from tryptamine, was converted to the corresponding Schiff basis and sulfonamide by the treatment with suitable aldehydes and benzensulphonyl chloride, respectively. 2-[(4-Amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-yl)methyl]-4-[2-(1H-indole-3-yl)ethyl]-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-one was synthesized starting from hydrazide via the formation of the corresponding 1,3,4-oxadiazole compound, while the other bitriazole compounds were obtained by intramolecular cyclisation of carbothioamides in basic media. The treatment of 1,2,4-triazole or 1,3,4-oxadiazole compound with several amines generated the corresponding Mannich bases. Ethyl (2-amino-1,3-thiazole-4-yl)acetate was converted to the corresponding 1,3,4-oxadiazole derivative, arylidenehydrazides, 1,2,4-triazole-3-one and 5-oxo-1,3-oxazolidine derivatives by several steps. The structural assignments of new compounds were based on their elemental analysis and spectral (FT IR, ¹H NMR, ¹³C NMR and LC-MS) data. The antimicrobial, antilipase and antiurease activity studies revealed that some of the synthesized compounds showed antimicrobial, antilipase and/or antiurease activity.     

Synthesis and properties of new substituted 1,2,4-triazoles: potential antitumor agents

Cycloaddition of the reactive intermediates 4 with 1-(cyanomethyl)benzotriazole (5) and its N-2 isomer 9 furnished, after spontaneous rearrangements, the 1,2,4-triazole derivatives 8 and 10. Analogously, reaction of 4 with ethyl cyanoacetate lead to the 1,3,5-trisubstituted 1,2,4-triazoles 12, which gave on treatment with hydrazine the corresponding hydrazides 13. Treatment of 13d with galactose or phenyl isothiocayanate gave the 1-D-galactose-acylhydrazone 14 and the 1,2,4-triazole derivative 15, respectively. Compounds 8c; 10b,c; 13a,c and 14 were selected for the antitumor screening, whereby 8c, 13a, and 13c showed remarkable activity against leukemia, ovarian, renal and lung cancers (8c with Gl(50) of 0.70 microM, 0.07 microM against leukemia (CCRF-CEM and RPMI-8226), 0.02 microM against ovarian (OVCAR-3) and 0.60 microM against renal (CARKI-1) and lung cancers, respectively).     

An approach to the stereoselective synthesis of Sp-dinucleoside phosphorothioates using phosphotriester chemistry.

An approach to the stereoselective synthesis of Sp- dinucleoside phosphorothioates has been investigated which utilizes phosphotriester chemistry. The stereoselectivity of internucleotide bond formation between N4-benzoyl-5'-O-(4,4'-dimethoxytrityl)-2'-deoxycytidine-3'-O-(S2-cyano-e thyl) phosphorothioate (3) and 3'-O-acetylthymidine has been studied using either mesitylenesulphonyl-5-(pyridin-2-yl)tetrazole (MSPy) or 1-mesitylenesulphonyl-3-nitro-1,2,4-triazole (MSNT) as the activating agent. The removal of the cyanoethyl group from the protected dinucleoside phosphorothioate has been studied, and conditions are reported which provide rapid deprotection without concomittant desulphurisation.     

The synthesis and characterisation of Rh(III) complexes with pyridyl triazole ligands

A series of Rh(III) mixed ligand polypyridine type complexes have been prepared. Complexes of the form [Rh(L)₂(L^′)]ⁿ⁺, where n=2/3, L=2,2^′-bipyridine (bpy)/1,10-phenanthroline (phen) and L^′=3-(pyridin-2-yl)-1,2,4-triazole (Hpytr), 1-methyl-3-(pyridin-2-yl)-1,2,4-triazole (1M3pytr), 4-methyl-3-(pyridin-2-yl)-1,2,4-triazole (4Mpytr), 3,5-bis(pyridin-2-yl)-1,2,4-triazole (Hbpt), 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (NH₂bpt) and 3-(pyridin-2-yl)-5-phenyl-1,2,4-triazole (HPhpytr), have been prepared and their synthesis and characterisation are reported. Crystals of [Rh(bpy)₂(Phpytr)](PF₆)₂ and [Rh(phen)₂(NHbpt)](PF₆)₂ were obtained and their structures determined. Analysis of X-ray crystallographic data showed that coordination of the metal centre in [Rh(phen)₂(NHbpt)](PF₆)₂ occurs via the amine moiety and a nitrogen of the pyridine ring. NMR studies illustrated that coordination to the NH₂bpt ligand was also possible via a nitrogen of the triazole ring and the pyridine ring forming the complex [Rh(phen)₂(NH₂bpt)](PF₆)₃. The absorption and emission properties of the complexes studied were found to be π-π^* in nature and preliminary evidence suggests that all complexes with the exception of [Rh(phen)₂(NHbpt)](PF₆)₂ and [Rh(bpy)₂(NHbpt)](PF₆)₂ are dual emitting at 77 K.     

Novel synthesis of seco type of acyclo C-nucleosides of 1,2,4-triazole and 1,2,4-triazol

The seco C-nucleosides 3-(1,2,3,4,5-penta-O-acetyl-D-gluco- and D-galacto-pentitol-1-yl)-1H-1,2,4-triazoles (8 and 9) were obtained in a one pot by deamination and dethiolation of 4-amino-3-(D-gluco- and D-galacto-pentitol-1-yl)-5-mercapto-1,2,4-triazoles (1 and 2), respectively, using sodium nitrite in orthophosphoric acid and subsequent acetylation. Condensation of 1, 2, and 4-amino-3-(D-glycero-D-gulo-hexitol-1-yl)-5-mercapto-1,2,4-triazole (12) with phenacylbromide (11) afforded the corresponding 3-(D-gluco-, D-galactopentitol-1-yl) and 3-(D-glycero-D-gulo-hexitol-1-yl)-6-phenyl-7H-1,2,4-triazolo[3,4-b][1,3,4] thiadiazines (15, 16, and 17). Acetylation of 15-17 gave the penta- and hexa-O-acetyl derivatives 18-20, respectively. The structures were confirmed by using 1H, 13C, and 2D NMR spectra, DQFCOSY, HMQC, and HMBC experiments. The favored conformational structures were deduced from the vicinal coupling constants of the protons.