Heterocyclic Benzimidazole Research Articles

Solid-phase synthesis of amidine-substituted phenylbenzimidazoles and incorporation of this DNA binding and recognition motif into amino acid and peptide conjugates

Amidine-substituted phenylbenzimidazoles are well-established DNA-binding structural motifs that have contributed to the development of diverse classes of DNA-targeted agents; this ring system not only assists in increasing the overall DNA affinity of an agent, but can also influence its site selectivity. Seeking a means to conveniently exploit these attributes, a protocol for the on-resin synthesis of amino acid- and peptide-phenylbenzimidazole-amidine conjugates was developed to facilitate installation of phenylbenzimidazole-amidines into peptide chains during the course of standard solid-phase syntheses. Building from a resin-bound amino acid or peptide on Rink amide resin, 4-formyl benzoic acid was coupled to the resin-bound free amine followed by introduction of 3,4-diamino-N'-hydroxybenzimidamide (in the presence of 1,4-benzoquinone) to construct the benzimidazole heterocycle. Finally, the resin-bound N'-hydroxybenzimidamide functionality was reduced to an amidine via 1 M SnCl2·2H2O in DMF prior to resin cleavage to release final product. This procedure permits the straightforward synthesis of amino acids or peptides that are N-terminally capped by a phenylbenzimidazole-amidine ring system. Employing this protocol, a series of amino acid-phenylbenzimidazole-amidine (Xaa-R) conjugates was synthesized as well as dipeptide conjugates of the general form Xaa-Gly-R (where R is the phenylbenzimidazole-amidine and Xaa is any amino acid).

A benzimidazole functionalised DO3A chelator showing pH switchable coordination modes with lanthanide ions.

The synthesis of a new macrocyclic chelator incorporating a benzimidazole heterocycle is reported. Lanthanide complexes with macrocyclic chelators based on 1,4,7,10-tetra(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DOTA) and 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DO3A) are of interest in luminescent, radiopharmaceutical and magnetic resonance (MR) biomedical imaging applications. The benzimidazole DO3A chelator allows for sensitisation of europium(iii), terbium(iii) and ytterbium(iii) luminescence by the heterocycle and also shows a pH dependent coordination change due to protonation of the chelator (pKa = 4.1 for the europium(iii) complex). The thermodynamic stability of the complexes has been investigated by potentiometric titration with the gadolinium(iii) complex showing significantly higher stability than the zinc(ii) complex, where log βZnLH = 28.1 and log βGdLH = 32.1.

English

Nitrites and morpholine are ubiquitous environmental contaminants found in drinking water and food. NMOR can be formed endogenously from nitrite and morpholine. Increased levels of reactive oxygen species/ reactive nitrite species (ROS/RNS) are involved in the mechanism of NMOR toxicity. Certain antimicrobial, antifungal and antioxidant potential were observed in heterocyclic benzimidazole derivatives and dimethyl sulfoxide (DMSO). This study was designed to evaluate the biological potential of 3-aminothiazolo[3-2a]benzimadzole-2-carbonitrile in the protection of lung and colon tissues against the increased levels of ROS/RNS that are induced by administration of nitrite and morpholine in drinking water for 15 weeks. Forty adult male rats were categorized into 4 groups, 10 rats each. The results showed a significant increase in NO, lipid peroxidation (LPO), total peroxides (TPO), superoxide anion (O2-) and DNA fragmentation in lung and colon tissues of rats treated with nitrite and morpholine compared to the control group. Moreover, histological observation of the lung and colon tissues showed cell necrosis, increase in the leukocyte infiltration and blood vessel congestion. Immunostaining for inducible nitric oxide synthase (iNOS) showed positive reaction for lung and colon tissues. After the co-treatment of rats with DEMSO and 3-aminothiazolo[3-2a]benzimadzole-2-carbonitrile, all the previous biochemical changes were reduced in addition to the relative improvement in the morphological changes of both lung and colon. In conclusion, the injury in lung and colon tissues induced by nitrite and morpholine may return to the increased production of ROS and to the alterations in the levels of antioxidants. Co-treatment of rats with 3-aminothiazolo[3-2a]benzimadzole-2-carbonitrile and DMSO may protect them against nitrite and morpholine toxicity. Key words: Nitrite, morpholine, nitrosomorpholine (NMOR), inducible nitric oxide synthase (iNOS), benzimidazole derivatives, dimethyl sulfoxide (DMSO), colon, lung, rat.

Chemoenzymatic selective formation of C–N bonds in a benzimidazole heterocycle

A novel and efficient method for the chemoenzymatic selective formation of C–N bonds in the synthesis of a 2-substituted benzimidazole heterocycle, catalyzed by lipase from porcine pancreas (PPL), has been developed. A series of 2-substituted benzimidazole derivatives were synthesized under mild conditions, with high yields (89–96%) and high selectivity. The blank and control experiments reveal that PPL plays an important catalytic role during the selective C–N bond formation process. The results demonstrate that PPL has a broad catalytic tolerance towards different aldehydes containing electron-donating or -withdrawing groups in this reaction. This study provides an efficient tool for the selective formation of C–N bonds in the synthesis of 2-substituted benzimidazole derivatives.

Benzimidazole Heterocycle as a Privileged Scaffold in Antiviral Agents

Benzimidazole Heterocycle as a Privileged Scaffold in Antiviral Agents

Synthesis and Anti‐Hepatitis B Virus Activity of a Novel Class of Thiazolylbenzimidazole Derivatives

Recently, heterocyclic benzimidazole derivatives have been investigated and validated as a promising class of antiviral agents. In this paper, a series of novel thiazolylbenzimidazole derivatives was synthesized and evaluated for their anti-hepatitis B virus (HBV) activity and cytotoxicity on the HepG2.2.15 cell line. Afterwards, the preliminary structure-activity relationship (SAR) was discussed. Compound 8b, with IC(50) = 1.1 µM and SI > 90.9, was the most promising compound and could be selected as a benchmark compound for further investigation.

Synthesis of new aramid fiber

A new aramid fiber designed for the fabrication of heat-and-fire-resistant textile products is synthesized. The chemical structure of the initial polymer is a copolymer based on three aromatic diamines—5(6)-amino-2-(p-aminophenyl)benzimidazole, m-phenylenediamine, and p-phenylenediamine—and terephthaloyl chloride. The synthesis of this copolymer and its main features are described. The new fibers are characterized by higher resistance to fire and higher hygroscopicity than the known m-aramid fibers. This circumstance is due to the presence of benzimidazole heterocycles in the molecular chains of aramid. In contrast to m-aramid fibers, the undesirable step of thermal strengthening can be excluded in the manufacture of the new fiber, since it is characterized by high strength and high stability against heat shrinkage in the as-spun state. These properties are due to the semi-rigid-chain character of the initial copolyamide. According to Papkov’s concepts, the phase transition into the ordered liquid-crystalline state can proceed in these polymers during the spinning of fiber at the stage of polymer precipitation.

ChemInform Abstract: New Synthesis of Heterocyclic Benzimidazole Derivatives.

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Halogenated benzimidazole carboxamides target integrin alpha4beta1 on T-cell and B-cell lymphomas.

Integrin alpha(4)beta(1) is an attractive but poorly understood target for selective diagnosis and treatment of T-cell and B-cell lymphomas. This report focuses on the rapid microwave preparation, structure-activity relationships, and biological evaluation of medicinally pertinent benzimidazole heterocycles as integrin alpha(4)beta(1) antagonists. We documented tumor uptake of derivatives labeled with (125)I in xenograft murine models of B-cell lymphoma. Molecular homology models of integrin alpha(4)beta(1) predicted that docked halobenzimidazole carboxamides have the halogen atom in a suitable orientation for halogen-hydrogen bonding. The high-affinity halogenated ligands identified offer attractive tools for medicinal and biological use, including fluoro and iodo derivatives with potential radiodiagnostic ((18)F) or radiotherapeutic ((131)I) applications, or chloro and bromo analogues that could provide structural insights into integrin-ligand interactions through photoaffinity, cross-linking/mass spectroscopy, and X-ray crystallographic studies.

Solvent free synthesis, anti-inflammatory and anticancer activity evaluation of tricyclic and tetracyclic benzimidazole derivatives

Heterocyclic benzimidazole derivatives 3a– h, 5a– c and 7a– d have been synthesized by condensation of succinic acid ( 1) homophthalic acid ( 4) and 2,3-pyrazinedicarboxlic acid ( 6) with various substituted diamines under microwave irradiation in good yields. Structures assigned to 3a– h, 5a– c and 7a– d are fully supported by spectral data. All these compounds were screened for anti-inflammatory and anticancer activities. At a dose of 50 mg/kg po compounds 3b (39.4%) and 3c (39.2%) exhibited anti-inflammatory activity, comparable to standard ibuprofen which showed 39% activity at 50 mg/kg po and compound 7c exhibit good anticancer activity against ovary (IGR-OV-1), breast (MCF-7) and CNS(SF-295) human cancer cell lines.

The synthesis and characterization of novel coumarin dyes derived from 1,4-diethyl-1,2,3,4-tetrahydro-7-hydroxyquinoxalin-6-carboxaldehyde

1,4-Diethyl-1,2,3,4-tetrahydro-7-hydroxyquinoxalin-6-carboxaldehyde was synthesized and condensed with substituted active methylene compounds to obtain a series of novel coumarin compounds. Solutions of the dyes in various solvents exhibited an orange hue and brilliant fluorescence and displayed high thermal stability, as determined using thermogravimetric analysis. The dye having a heterocyclic benzimidazole ring as an electron withdrawing system was selected as a representative compound for comparison of its spectral characteristics with known analogues.

Design, synthesis and antibacterial activity of novel actinonin derivatives containing benzimidazole heterocycles

A series of novel actinonin derivatives containing a benzimidazole heterocycle linked as amide isostere have been designed and synthesized. The structures of all the synthesized compounds were confirmed by analytical and spectroscopic methods. All the compounds were evaluated in vitro against Staphylococcus aureus, Klebsiella pneumoniae, and Sarcina lutea. Among them, compound 1a with unsubstituted benzimidazole ring exhibited potent antibacterial activities.

Efficient synthesis and solid state analysis of 3-(1 H-pyrrol-2-yl)quinoxalin-2(1 H)-one and 2-(1 H-pyrrol-2-yl)-1 H-benzo[ d]imidazole from pyrrolo-2-ylglyoxyl acid

The synthesis of new pyrrole-functionalized quinoxalines and benzimidazole is described. Our methodology involves the condensation between 2-oxo-2-(1 H-pyrrol-2-yl)acetic acid and differently substituted 1,2-phenylene diamines. Depending on the substitution and on the reaction conditions, the synthesis leads to either the pyrrolyl-quinoxaline or -benzimidazole heterocycles. Further insights concerning the structural arrangement of the pyrrolyl-quinoxaline were obtained by solid state analysis, revealing an inverted pyrrole similar to that observed for 2,3-dipyrrolyl quinoxalines. This observation accounts for the fact that strong dipolar interactions or intermolecular H-bonds may govern the structural arrangement in the solid state.

Intramolecular Cycloaddition of Azomethine Ylides in the Preparation of Pyrrolidino[2‘,3‘:3,4]pyrrolidino[1,2- a]benzimidazoles

The parent pyrrolidino[2',3':3,4]pyrrolidino[1,2-a]benzimidazole heterocycle as well as a series of novel analogues have been synthesized utilizing a microwave-assisted intramolecular cycloaddition of azomethine ylides as the key transformation. A variety of diversity groups were added to explore the scope of this reaction and to provide a number of new compounds for biological screening.

Synthesis, Antiviral and Antitumor Activity of 2‐Substituted‐5‐amidino‐benzimidazoles.

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Synthesis and second-order nonlinear optical properties of new chromophores containing benzimidazole, thiophene, and pyrrole heterocycles

A new series of thermally stable benzimidazole-based nonlinear optical (NLO) chromophores 4 and 5 have been developed. These chromophores possess a thienylpyrrolyl π-conjugated system attached to functionalized benzimidazole heterocycles. This feature leads to robust chromophores with excellent solvatochromic properties, high thermal stabilities and good molecular optical nonlinearities.

Synthesis, antiviral and antitumor activity of 2-substituted-5-amidino-benzimidazoles

We have prepared a set of heterocyclic benzimidazole derivatives bearing amidino substituents at C-5 of benzimidazole ring, by introducing various heterocyclic nuclei (pyridine, N-methyl-pyrrole or imidazole) at C-2, and evaluated their antitumor and antiviral activities. The most pronounced antiproliferative activity was shown with compounds 6 and 9, having imidazolinylamidino-substituent. Interestingly, all compounds show noticeable selectivity toward breast cancer cell line MCF-7. The most distinct and selective antiviral activity toward coxsackieviruses and echoviruses was observed with compounds having pyridine ring at C-2. Especially interesting was fairly strong activity of 4 and 8 toward adenoviruses, which could be considered as leads against adenoviral replication.

Cyanine dye–protein interactions: Looking for fluorescent probes for amyloid structures

We ascertained the ability to detect fibrillar β-lactoglobulin (BLG) of a series of mono-, tri-, penta-, and heptamethinecyanines based on benzothiazole and benzimidazole heterocycles, and of benzothiazole squaraine. Fluorescence properties of these cyanine dyes were measured in the unbound state and in the presence of monomeric and fibrillar BLG and compared with those for the commercially available benzothiazole dye Thioflavin T. The correlation between the chemical nature of the dye molecules and the ability of dyes to bind aggregated proteins was established. We found that meso-substituted cyanines with amino substituents in heterocycle in contrast to the corresponding unsubstituted dyes have a binding preference to fibrillar BLG and a noticeable fluorescence response in the presence of the aggregated protein. For the squaraines and benzimidazole penthamethinecyanines studied, fluorescence emission increased both in the presence of native and fibrillar protein. The trimethinecyanines T-49 and SH-516 exhibit specifically increased fluorescence in the presence of fibrillar BLG. These dyes demonstrated the same or higher emission intensity and selectivity to aggregated BLG as Thioflavin T, and are proposed for application in selective fluorescent detection of aggregated proteins.

Azole-linked coumarin dyes as fluorescence probes of domain-forming polymers

The binding of 7-aminocoumarins, substituted in the 3-position with heterocyclic benzimidazole or benzothiazole groups by domain-forming polymers in water has been studied. The acrylic polyelectrolyte, poly(methacrylic) acid (PMAA) was used as a solubilizing agent for coumarin dyes 6, 7, and 30 in water. The acid–base properties of these bound coumarin dyes were monitored spectroscopically on titration of aqueous solutions. Alterations in the fluorescence wavelength and intensity, quantum yields, lifetimes, and polarization are consistent with the preferential binding of the dyes in compact hydrophobic domains that form at a pH regime in which the polymer is in its protonated (uncharged) state. In this pH range (<4.0), coumarins 7 and 30 are bound as monocations, whereas coumarin 6 remains in its neutral form. Reduced quantum yields and lifetimes of fluorescence for cationic coumarins can be understood in terms of the imposition of a low-lying electron transfer state, an example of a twisted intramolecular charge transfer (TICT) intermediate. Effects of polymer microenvironment on the rate of TICT state decay (a reverse electron transfer) are observed. Coumarins of the azole type may find use as fluoroprobes of the microenvironments of proteins and other biological macromolecules and as agents for pH sensing.

Synthesis and preliminary antimicrobial screening of new benzimidazole heterocycles.

A series of 2-methylbenzimidazole incorporated to different heterocycles through ethyl or carbamoylethyl groups at position 1 of benzimidazole were synthesized. Also 3-(2-methylbenzimidazol-1-yl)propanoic acid hydrazide incorporated with semicarbazides and thiosemicarbazides were prepared. Moreover, the triazole 5e underwent Michael addition and alkylation reaction. Some of the newly synthesized compounds showed considerable antimicrobial activity against gram positive, negative bacteria and yeast.