A new C-nucleoside analogue of tiazofurin: synthesis and biological evaluation of 2-beta-D-ribofuranosylimidazole-4-carboxamide (imidazofurin)

New imidazole-2-thiones linked to acenaphythylenone as dual DNA intercalators and topoisomerase II inhibitors: structural optimization, docking, and apoptosis studies

In this article, a new series of 2-((3,5-disubstituted-2-thioxo-imidazol-1-yl)imino)acenaphthylen-1(2H)-ones were synthesized. Imidazole-2-thione with acenaphthylen-one gave a hybrid scaffold that integrated key structural elements essential for DNA damage via direct DNA intercalation and inhibition of the topoisomerase II enzyme. All the synthesized compounds were screened to detect their DNA damage using a terbium fluorescent probe. Results demonstrated that 4-phenyl-imidazoles 5b and 5e in addition to 4-(4-chlorophenyl)imidazoles 5h and 5j would induce detectable potent damage in ctDNA. The four most potent compounds as DNA intercalators were further evaluated for their antiproliferative activity against HepG2, MCF-7 and HCT-116 utilizing the MTT assay. The highest anticancer activity was recorded with compounds 5b and 5h against the breast cancer cell line MCF-7 which were 1.5- and 3- folds more active than doxorubicin, respectively. Therefore, imidazole-2-thione tethered acenaphthylenone derivatives can be considered as promising scaffold for the development of effective dual DNA intercalators and topoisomerase II inhibitors.

Understanding the mechanism and regio- and stereo selectivity of [3 + 2] cycloaddition reactions between substituted azomethine ylide and 3,3,3-trifluoro-1-nitroprop-1-ene, within the molecular electron density theory

The selectivity and the nature of the molecular mechanism of the [3 + 2] cycloaddition (32CA) reaction between 2-(dimethylamino)-1H-indene-1,3(2H)-dione (AY11) and trans(E)-3,3,3-trifluoro-1-nitroprop-1-ene(FNP10) has been studied, in which the molecular electron density theory using density functional theory methods at the MPWB1K/6-31G(d) computational level was used. Analysis of the global reactivity indices permits us to characterize FNP10 as a strong electrophile and AY11 as a strong nucleophile. Four reactive pathways associated with the ortho/meta regioselective channels and endo/exo stereoselective approaches modes have been explored and characterized in the gas phase and in the benzene solvent. The analysis of the relative energies associated with the different reaction pathways indicates that the 32CA reactions of the azomethine ylide (AY) with the nitroalkene (FNP) is meta regioselective with high endo stereoselectivity. This result is in good agreement with the experimental observations. electron localization function topological analysis of the most favored reactive pathways allows for characterizing the mechanism of this 32CA reactions as a non-concerted two-stage one-step mechanism. Finally, non-covalent interactions and quantum theory of atoms in molecule analyses at the meta/endo transition state structure indicate that the presence of different several weak interactions, namely, CF and NH contributed in favoring the formation of a meta-endo cycloadduct.

5-Aryl-1-Arylideneamino-1H-Imidazole-2(3H)-Thiones: Synthesis and In Vitro Anticancer Evaluation

A novel series of N-1 arylidene amino imidazole-2-thiones were synthesized, identified using IR, ¹H-NMR, and ¹³C-NMR spectral data. Cytotoxic effect of the prepared compounds was carried out utilizing three cancer cell lines; MCF-7 breast cancer, HepG2 liver cancer, and HCT-116 colon cancer cell lines. Imidazole derivative 5 was the most potent of all against three cell lines. DNA flow cytometric analysis showed that, imidazoles 4d and 5 exhibit pre-G1 apoptosis and cell cycle arrest at G2/M phase. The results of the VEGFR-2 and B-Raf kinase inhibition assay revealed that compounds 4d and 5 displayed good inhibitory activity compared with reference drug erlotinib.

Improved preparation of 4(5)-aryl-2-(β-d-glucopyranosyl)-imidazoles, the most efficient glucose analogue inhibitors of glycogen phosphorylase

Large scale (up to 20 g) preparation ofIandIIallowed the best inhibitors of glycogen phosphorylaseIIIto be synthesized in close to 60% overall yields fromI.

C-Nucleosides To Be Revisited

Two new C-nucleoside analogues, BCX4430, an imino-C-nucleoside, and GS-6620, a phosphoramidate derivative of 1'-cyano-2'-C-methyl-4-aza-7,9-dideazaadenosine C-nucleoside, have been recently described as effective against filovirus infections (Marburg) and hepatitis C virus (HCV), respectively. The first C-nucleoside analogues were described about half a century ago. The C-nucleoside pseudouridine is a natural component of RNA, and various other C-nucleoside analogues have been reported previously for their antiviral and/or anticancer potential, the most prominent being pyrazofurin, tiazofurin, and selenazofurin. In the meantime, showdomycin, formycin, and various triazole, pyrazine, pyridine, dihydroxyphenyl, thienopyrimidine, pyrazolotriazine, and porphyrin C-nucleoside analogues have been described. It would be worth revisiting these C-nucleosides and derivatives thereof, including their phosphoramidates, for their therapeutic potential in the treatment of virus infections and, where appropriate, cancer as well.

From ribavirin to NAD analogues and back to ribavirin in search for anticancer agents

Ribavirin, a broad-spectrum antiviral agent is used in the clinic alone or in combination with other antivirals and/or interferons. Numerous structural analogues of ribavirin have been developed, among them tiazofurin, which is inactive against viruses but is a potent anticancer drug. Tiazofurin was found to inhibit nicotinamide adenine dinucleotide (NAD)-dependent inosine monophosphate dehydrogenase (IMPDH) after metabolic conversion into tiazofurin adenine dinucleotide (TAD), which binds well but could not serve as IMPDH cofactor. TAD showed high selectivity against human IMPDH vs. other cellular dehydrogenases. Mycophenolic acid (MPA) was even more specific, binding at the cofactor-binding domain of IMPDH. Ribavirin adenine dinucleotide, however, did not show any significant inhibition at the enzymatic level. We synthesized numerous NAD analogues in which natural nicotinamide riboside was replaced by tiazofurin, MPA moiety, or benzamide riboside, and the adenosine moiety as well as the pyrophosphate linker were broadly modified. Some of these compounds were found to be low nanomolar inhibitors of the enzyme and sub-micromolar inhibitors of cancer cell line proliferation. The best were as potent as tyrosine kinase inhibitor gleevec heralded as a ‘magic bullet’ against chronic myelogenous leukemia. In recent years, ribavirin was rediscovered as a potential anticancer agent against number of tumors including leukemia. It was clearly established that its antitumor activity is related to the inhibition of an oncogene, the eukaryotic translation initiation factor (eIF4E).

Synthesis of novel aza-analogues of tiazofurin with 2-[5,5-bis(hydroxymethyl)pyrrolidin-2-yl] framework as sugar mimic

The novel aza-analogues of tiazofurin (TZF) with 2-[5,5-bis(hydroxymethyl)pyrrolidin-2-yl] moiety, as sugar mimic, were synthesized from O,O-cyclohexylidene derivative of 4,4-bis(hydroxymethyl)-4-nitrobutanal in multi-gram scale. The synthetic route consisted of three stages: (i) the synthesis of corresponding derivative of 5,5-bis(hydroxymethyl)pyrrolidine-2-carbonitrile, (ii) the construction of ethyl thiazole-2-carboxylate part by the conversion of the pyrrolidine-2-carbonitrile into the N-trifluoroacetyl derivative followed by cyclocondensation with L-cysteine ethyl ester and then by dehydrogenation, and (iii) the final transformation of the ethyl thiazole-4-carboxylate into the aza-analogues of TZF. The TZF aza-analogues were evaluated for their antiviral activities in cell-culture-based assays.

Synthesis and antitumour activity of new tiazofurin analogues bearing a 2,3-anhydro functionality in the furanose ring

This paper describes a divergent de novo synthesis of 2-(2,3-anhydro-beta-dribofuranosyl)thiazole-4-carboxamide (2',3'-anhydro-tiazofurin) and the corresponding alpha- and beta-homo-C-nucleosides, as well as evaluation of their antitumour activities in vitro.

One-pot synthesis of 2-C-glycosylated benzimidazoles from the corresponding methanal dimethyl acetals

A series of 2-glycosyl-benzimidazoles with alpha-d-arabinopyranosyl, beta-d-galactopyranosyl, beta-d-glucopyranosyl, beta-d-mannopyranosyl, and beta-l-rhamnopyranosyl configurations were obtained in 52-73% yields from the corresponding C-glycosylmethanal dimethyl acetals and o-phenylenediamine under catalysis with hydrogen chloride or a strongly acidic cation-exchange resin. Intermediate benzimidazolines were spontaneously oxidized by air to produce the final products in the one-pot procedure. The prepared compounds did not show any inhibitory effect on the growth of 12 strains of five different species of pathogenic yeasts.

Synthesis and biological activity of some new 5′-O-acyl tiazofurin derivatives

Three new 5'-O-acyl tiazofurin derivatives 2-4 were synthesized and evaluated for their antiproliferative activity against different tumour cell lines as well as for their ability to induce apoptosis in C6 cells in vitro. Apart of the antitumour assays, the cell membrane permeation of 2-4 and their intracellular metabolism in C6 cells in vitro was also studied in order to evaluate their potential as possible tiazofurin bioisosteres or prodrugs.

Zinc(II) Triflate-Controlled 1,3-Dipolar Cycloadditions of C-(2-Thiazolyl)nitrones: Application to the Synthesis of a Novel Isoxazolidinyl Analogue of Tiazofurin

[reaction: see text] The cycloaddition reaction between C-(2-thiazolyl) nitrones and allylic alcohol takes place with complete exo selectivity when the reactions are carried out in the presence of 1 equiv of zinc triflate. The rate of the reaction is increased enormously under microwave irradiation. The use of a chiral dipolarophile allowed application of the methodology to the synthesis of a hitherto unknown enantiomerically pure isoxazolidinyl analogue of the C-nucleoside tiazofurin.

De novo synthesis of two new cytotoxic tiazofurin analogues with modified sugar moieties

A divergent synthesis of two novel tiazofurin analogues, 2-(3-deoxy-3-fluoro-beta-D-xylofuranosyl)thiazole-4-carboxamide (2) and 2-(3-acetamido-3-deoxy-beta-D-xylofuranosyl)thiazole-4-carboxamide (3), has been achieved starting from D-glucose. Both nucleoside analogues were evaluated for their in vitro cytotoxicity against several human leukaemia and solid tumour cell lines.