Imidazole-4,5-dicarboxamide derivatives with antiproliferative activity against HL-60 cells

Synthesis of 5-(trifluoroacetyl)imidazoles from Bromoenones and Benzimidamides via Aza-Michael Initiated Ring Closure Reaction

INTRODUCTION

A simple method for the preparation of 5-(trifluoroacetyl)imidazoles was elaborated.

METHODS

The reaction of trifluoromethyl(α-bromoalkenyl)ketones with benzimidamides was employed to afford the target heterocycles in good yields.

RESULTS

The assembly of imidazole core proceeds via aza-Michael adduct formation followed by intramolecular nucleophilic substitution and spontaneous aromatization as an oxidation sequence.

CONCLUSION

The yields of target imidazoles can be improved by the use of soft oxidizing agents.

Synthesis and anticancer activity of podophyllotoxin derivatives with nitrogen-containing heterocycles

Three series of podophyllotoxin derivatives with various nitrogen-containing heterocycles were designed and synthesized. The antitumor activity of these podophyllotoxin derivatives was evaluated in vitro against a panel of human tumor cell lines. The results showed that podophyllotoxin-imidazolium salts and podophyllotoxin-1,2,4-triazolium salts a1-a20 exhibited excellent cytotoxic activity. Among them, a6 was the most potent cytotoxic compound with IC₅₀ values of 0.04-0.29 μM. Podophyllotoxin-1,2,3-triazole derivatives b1-b5 displayed medium cytotoxic activity, and podophyllotoxin-amine compounds c1-c3 has good cytotoxic activity with IC₅₀ value of 0.04-0.58 μM. Furthermore, cell cycle and apoptosis experiments of compound a6 were carried out and the results exhibited that a6 could induce G2/M cell cycle arrest and apoptosis in HCT-116 cells.

Synthesis of Fully Substituted 5-(o-Hydroxybenzoyl)imidazoles via Iodine-Promoted Domino Reaction of Aurones with Amidines

An iodine-promoted domino reaction of aurones with amidines has been successfully explored. The reaction proceeds in a consecutive manner containing Michael addition, iodination, cyclization from intramolecular nucleophilic substitution, and dehydrogenative aromatization from spiro ring opening. Following this novel strategy, a variety of 1,2,4-trisubstituted 5-(o-hydroxybenzoyl)imidazoles were efficiently synthesized in moderate to good yields from readily available starting materials. A plausible mechanism has been proposed.

Synthesis and antitumor activity of novel hybrid compounds between 1,4-benzodioxane and imidazolium salts

A series of novel hybrid compounds between 1,4-benzodioxane and imidazolium salts was designed and prepared. The compounds were evaluated in vitro against a panel of human tumor cell lines (K562, SMMC-7721, and A-549). The structure-activity relationship results demonstrated that the 2-methyl-benzimidazole or 5,6-dimethyl-benzimidazole ring and substitution of the imidazolyl-3-position with a 4-phenylphenacyl substituent were critical for promoting cytotoxic activity. Particularly, compound 25 was found to be the most potent compound with IC₅₀ values of 1.06-8.31 μM against the three human tumor cell lines and exhibited higher selectivity to K562 and SMMC-7721 cells with IC₅₀ values 4.5- and 4.7-fold lower than cisplatin. Moreover, compound 25 inhibited cell proliferation by inducing the G0/G1 cell cycle arrest and apoptosis in SMMC-7721 cells.

TMSOTf-catalyzed synthesis of trisubstituted imidazoles using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions

In the process of drug discovery and development, an efficient and expedient synthetic method for imidazole-based small molecules from commercially available and cheap starting materials has great significance. Herein, we developed a TMSOTf-catalyzed synthesis of trisubstituted imidazoles through the reaction of 1,2-diketones and aldehydes using hexamethyldisilazane as a nitrogen source under microwave heating and solvent-free conditions. The chemical structures of representative trisubstituted imidazoles were confirmed using X-ray single-crystal diffraction analysis. This synthetic method has several advantages including the involvement of mild Lewis acid, being metal- and additive-free, wide substrate scope with good to excellent yields and short reaction time. Furthermore, we demonstrate the application of the methodology in the synthesis of biologically active imidazole-based drugs.

Trisubstituted imidazoles are synthesized efficiently from the readily available 1,2-diketones and aldehydes using hexamethyldisilazane as a new and stable nitrogen source under TMSOTf-catalysis system, microwave heating and solvent-free conditions.

Synthesis and biological activity of new bisbenzofuran-imidazolium salts

A series of novel bisbenzofuran-imidazolium salts were designed and prepared. The in vitro antitumor activity of these derivatives was evaluated against a panel of human tumor cell lines (A549, HL-60, MCF-7, SMMC-7721 and SW480). Results demonstrated that 2-methyl-benzimidazole ring and substitution of the imidazolyl-3-position with a 4-methoxyphenacyl or 2-naphthylacyl substituent were important for promoting cytotoxic activity. Notably, compound 23 was found to be the most potent compound with IC₅₀ values of 0.64-1.47 μM against five human tumor cell lines, and exhibited higher selectivity to MCF-7 and SW-480 cell lines with IC₅₀ values 15.3-fold and 9.1-fold lower than DDP.

Synthesis and biological evaluation of novel 3-benzylcoumarin-imidazolium salts

A series of novel 3-benzylcoumarin-imidazolium salts were prepared and evaluated in vitro against a panel of human tumor cell lines. The results showed that the existence of 5,6-dimethyl-benzimidazole ring and substitution of the imidazolyl-3-position with a naphthylacyl group were vital for modulating cytotoxic activity. Notably, compound 38 was found to be the most potent derivative with IC₅₀ values of 2.04-4.51 μM against five human tumor cell lines, while compound 34 were more selective to SW-480 cell lines with IC₅₀ value 40.0-fold lower than DDP. Mechanism of action studies indicated that compound 38 can cause the G0/G1 phase cell cycle arrest and apoptosis in SMMC-7721 cell lines.

An Inhibitor of Fatty Acid Synthase Thioesterase Domain with Improved Cytotoxicity against Breast Cancer Cells and Stability in Plasma

It is well recognized that many cancers are addicted to a constant supply of fatty acids (FAs) and exhibit brisk de novo FA synthesis. Upregulation of a key lipogenic enzyme, fatty acid synthase (FASN), is a near-universal feature of human cancers and their precursor lesions, and has been associated with chemoresistance, tumor metastasis, and diminished patient survival. FASN inhibition has been shown to be effective in killing cancer cells, but progress in the field has been hindered by off-target effects and poor pharmaceutical properties of candidate compounds. Our initial hit (compound 1) was identified from a high-throughput screening effort by the Sanford-Burnham Center for Chemical Genomics using purified FASN thioesterase (FASN-TE) domain. Despite being a potent inhibitor of purified FASN-TE, compound 1 proved highly unstable in mouse plasma and only weakly cytotoxic to breast cancer (BC) cells in vitro. An iterative process of synthesis, cytotoxicity testing, and plasma stability assessment was used to identify a new lead (compound 41). This lead is more cytotoxic against multiple BC cell lines than tetrahydro-4-methylene-2S-octyl-5-oxo-3R-furancarboxylic acid (the literature standard for inhibiting FASN), is stable in mouse plasma, and shows negligible cytotoxic effects against nontumorigenic mammary epithelial cells. Compound 41 also has drug-like physical properties based on Lipinski's rules and is, therefore, a valuable new lead for targeting fatty acid synthesis to exploit the requirement of tumor cells for fatty acids. SIGNIFICANCE STATEMENT: An iterative process of synthesis and biological testing was used to identify a novel thioesterase domain FASN inhibitor that has drug-like properties, is more cytotoxic to breast cancer cells than the widely used tetrahydro-4-methylene-2S-octyl-5-oxo-3R-furancarboxylic acid, and has negligible effects on the growth and proliferation of noncancerous mammary epithelial cells. Our studies have confirmed the value of using potent and selective FASN inhibitors in the treatment of BC cells and have shown that the availability of exogenous lipoproteins may impact both cancer cell FA metabolism and survival.

Imidazole synthesis by transition metal free, base-mediated deaminative coupling of benzylamines and nitriles

An unprecedented transition metal free, base-mediated deaminative coupling of benzylamines and nitriles is reported. This protocol provides a practical strategy for the synthesis of 2,4,5-tri-substituted imidazoles with liberation of NH₃.

One-Pot Synthesis of 2,4,5-Trisubstituted Imidazoles via [2 + 2 + 1] Cycloannulation of 1,3-Bishet(aryl)-monothio-1,3-diketones, α-Substituted Methylamines and Sodium Nitrite through α-Nitrosation of Enaminones

An efficient one-pot synthesis of a series of diversely functionalized trisubstituted 4(5)het(aroyl)-2,5(4)-het(aryl)/alkylimidazoles from readily available 1,3-bishet(aryl)monothio-1,3-diketones has been reported. This novel sequential one-pot, three step protocol, wherein three new carbon nitrogen bonds are formed in contiguous fashion, involves in situ generation of enaminones by reaction of monothio-1,3-diketones with α-substituted methylamines, followed by their α-nitrosation with sodium nitrite and subsequent base mediated intramolecular heterocyclization of the resulting α-hydroxyiminoimines to trisubstituted imidazoles in high yields under mild conditions. These newly prepared 4(5)-het(aroyl)-5(4)-het(aryl)/alkylimidazoles are shown to exist as tautomeric mixture, however, their subsequent alkylation with methyl iodide in the presence of potassium carbonate affords 1-N-methy-2,5-bishet(aryl)-4-het(aroyl)imidazoles in highly regioselective fashion in most of the cases. Synthesis of few 4(5)-(2-hydroxyphenyl)-2,5(4)-substituted imidazoles, which are known to be good coordinating ligands, has also been reported. A probable mechanism for the formation of these imidazoles from hydroxyiminoimine intermediates has also been suggested.

A sequential one-pot approach to 1,2,4,5-tetrasubstituted-2H-imidazole synthesis from disubstituted alkynes

A sequential one-pot method was developed to prepare 2H-imidazole scaffolds from internal alkynes and various ketones with good substrate scope and high yields.

Synthesis and evaluation of imidazole-4,5- and pyrazine-2,3-dicarboxamides targeting dengue and yellow fever virus

The results of a high-throughput screening assay using the dengue virus-2 replicon showed that the imidazole 4,5-dicarboxamide (I45DC) derivative (15a) has a high dengue virus inhibitory activity. Based on 15a as a lead compound, a novel class of both disubstituted I45DCs and the resembling pyrazine 2,3-dicarboxamides (P23DCs) were synthesized. Here, we report on their in vitro inhibitory activity against dengue virus (DENV) and yellow fever virus (YFV). Some of these first generation compounds have shown activity against both viruses in the micromolar range. Within this series, compound 15b was observed to display the highest antiviral potency against YFV with an EC₅₀ = 1.85 μM. In addition, compounds 20a and 20b both potently inhibited replication of DENV (EC₅₀ = 0.93 μM) in Vero cells.

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Two new series of heterocycles were evaluated for Flavivirus inhibition.

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Activities at micromolar levels were noted for inhibition of dengue virus.

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Remarkable selective inhibitory properties for yellow fever virus were recorded.

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Imidazole-4,5-dicarboxylic amides provide an interesting scaffold for antivirals.

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Pyrazine-2,3-dicarboxylic amides likewise are endowed with anti-flavivirus activities.

Parallel synthesis of a library of symmetrically- and dissymmetrically-disubstituted imidazole-4,5-dicarboxamides bearing amino acid esters

The imidazole-4,5-dicarboxylic acid scaffold is readily derivatized with amino acid esters to afford symmetrically- and dissymmetrically-disubstituted imidazole-4,5-dicarboxamides with intramolecularly hydrogen bonded conformations that predispose the presentation of amino acid pharmacophores. In this work, a total of 45 imidazole-4,5-dicarboxamides bearing amino acid esters were prepared by parallel synthesis. The library members were purified by column chromatography on silica gel and the purified compounds characterized by LC-MS with LC detection at 214 nm. A selection of the final compounds was also analyzed by (1)H-NMR spectroscopy. The analytically pure final products have been submitted to the Molecular Library Small Molecule Repository (MLSMR) for screening in the Molecular Library Screening Center Network (MLSCN) as part of the NIH Roadmap.

Parallel synthesis of an imidazole-4,5-dicarboxamide library bearing amino acid esters and alkanamines

The imidazole-4,5-dicarboxylic acid scaffold is readily derivatized with amino acid esters and alkanamines to afford compounds with intramolecularly hydrogen bonded conformations that mimic substituted purines and therefore are hypothesized to be potential inhibitors of kinases through competitive binding to the ATP site. In this work, a total of 126 dissymmetrically disubstituted imidazole-4,5-dicarboxamides with amino acid ester and alkanamide substituents were prepared by parallel synthesis. The library members were purified by column chromatography on silica gel and the purified compounds characterized by LC-MS with LC detection at 214 nm. A selection of the final compounds was also analyzed by (1)H-NMR spectroscopy. The analytically pure final products have been submitted to the Molecular Library Small Molecule Repository (MLSMR) for screening in the Molecular Library Screening Center Network (MLSCN) as part of the NIH Roadmap.