New mustard-linked 2-aryl-bis-benzimidazoles with anti-proliferative activity

Symmetric bis-benzimidazoles as DNA minor groove-binding agents with anti-tumour and antibacterial activity, and the evolution of the drug ridinilazole for the treatment of Clostridium difficile infections

We report the synthesis of a range of symmetrical bis-benzimidazoles (BBZ) which possess anticancer and antibacterial activities. One of these BBZs has specific activity against Clostridium difficile and is currently in a phase 3 clinical evaluation as the drug ridinilazole. X-ray and computer modelling studies showed that BBZs typically exhibit high specificity for oligonucleotide sequences that occur in the minor groove of DNA.

Cyanoacetylenic Alcohols: Molecules of Interstellar Relevance in the Synthesis of Essential Heterocycles, Amino Acids, Nucleobases and Nucleosides

Cyanoacetylenic alcohols, R1R2C(OH)C≡C–CN, the closest derivatives of cyanoacetylene, an abundant interstellar molecule, are now becoming important compounds in the area of modern organic synthesis that tends to mimic Nature. The presence of highly reactive C≡C and C≡N bonds in close proximity to a hydroxy group endows cyanoacetylenic alcohols with a chemical trinity of mutually influencing functions, leading to a myriad number of chemical transformations. All reactions of cyanoacetylenic alcohols parallel modern organic synthesis, whilst being biomimetic. To react, they do not need transition metals (and in most cases, no metals at all, except for physiologically indispensable Na+ and K+), proceed at ambient temperature and often in aqueous media. Fundamentally, their reactions are 100% atom-economic because they are almost exclusively addition processes. Typically, the cyano, acetylene and hydroxy functions of cyanoacetylenic alcohols behave as an inseparable entity, leading to reaction products with multiple functional groups. This allows hydroxy, carbonyl, carboxylic, imino, amino, amido, cyanoamido, cyano, various P-containing, ether and ester functions, along with double bonds, different fundamental heterocycles (furans, furanones, pyrazoles, oxazoles, pyridines, pyrimidines, purines, etc.) and diverse polycyclic systems to be integrated in a single molecular architecture. This review focuses on an analysis and generalization of the knowledge that has accumulated on the chemistry of cyanoacetylenic alcohols, mostly over the past 15 years.

1 Introduction

2 Nucleophilic Addition to Cyanoacetylenic Alcohols and Subsequent Transformations of the Adducts

3 Annulation with Nonaromatic Nitrogen Heterocycles

4 Annulation with Aromatic Nitrogen Heterocycles

5 Modification of Amino Acids

6 Modifications of Nucleobases

7 Modification of Nucleosides

8 Conclusion

Governing the DNA-binding mode of styryl dyes by the length of their alkyl substituents – from intercalation to major groove binding

The length of alkyl substituents governs the DNA binding mode of mono- and bis-chromophoric styryl dyes.

Benzimidazole Scaffold as Anticancer Agent: Synthetic Approaches and Structure-Activity Relationship

Cancer, also known as malignant neoplasm, is a dreadful disease which involves abnormal cell growth having the potential to invade or spread to other parts of the body. Benzimidazole is an organic compound that is heterocyclic and aromatic in nature. It is a bicyclic compound formed by the fusion of the benzene and imidazole ring systems. It is an important pharmacophore and a privileged structure in medicinal chemistry. According to the World Health Organisation (2015 survey), one in six deaths is due to cancer around the globe, accounting for 8.8 million deaths of which 70% of the cases were from low- and middle-income countries. In the efforts to develop suitable anticancer drugs, medicinal chemists have focussed on benzimidazole derivatives. This review article covers the current development of benzimidazole-based anticancer agents along with the synthetic approaches and structure-activity relationships (SAR).

2,3-Dihydrobenz[4,5]imidazo[2,1-b]thiazole

The asymmetric unit of the title compound, C9H8N2S, consists of two independent molecules (AandB) differing in the conformation of the thiazole ring: twisted for moleculeAand planar for moleculeB. In the crystal, molecules stack along thecaxis in alternatingAandBlayers. Within the layers, molecules are linked by C—H...π interactions, and inversion-relatedBmolecules are linked by offset π–π interactions [inter-centroid distance = 3.716 (1) Å]. The two molecules are also linked by a C—H...N hydrogen bond, which results finally in the formation of a three-dimensional structure.

Recent progress on the discovery of antiamoebic agents

A large number of protozoans infect humans but Entamoeba histolytica is the only organism responsible for causing amoebiasis, a deadly disease after malaria. Numerous heterocycle-based antiamoebic agents have been previously synthesized as E. histolytica inhibitors and while some of these agents have shown moderate activity, the search for a novel and ideal antiamoebic compound is still ongoing. In this digest Letter, we present the latest data on antiamoebic agents from 2011 to 2016 based on the different classes of heterocyclic agents.

Application of Resin-Bound Reagents for the Synthesis of Benzimidazole Derivatives

In an efficient exploitation of solid-phase chemistry, this work describes the preparation of the new resin-bound 4-( N-arylamino)-3-aminobenzoates and their successful cyclocondensations with the sodium bisulfite adducts of different aldehydes and triethyl orthoformate or triethyl orthoacetate, followed by resin cleavage to produce the target 1,2-diaryl- and 1-aryl-2-(un)substituted benzimidazole-5-carboxylic acid derivatives, respectively. In another variation, the cyclocondensation of the resin-bound 4-( N-arylamino)-3-aminobenzoates with carbon disulfide afforded the corresponding resin-bound thioxobenzimidazoles, which upon cleavage gave the corresponding 2-thioxobenzimidazoles. S-Alkylation of the resin-bound thioxobenzimidazoles with benzyl chloride and 4-bromophenacyl bromide furnished 2-benzylsulfanyl benzimidazoles and 4-bromophenyl-2-oxoethylsulfanyl-benzimidazoles, respectively. Reacting the resin-bound 4-( N-arylamino)-3-aminobenzoates with phenyl isothiocyanate gave the open-form 4-(arylamino)-3-(3-phenylthioureido) benzoic acids. Moreover, the reaction of the resin-bound 4-( N-arylamino)-3-aminobenzoates with N,N-carbonyldiimidazole yielded the corresponding 2-bezimidazolones.

DNA Cleavage and Condensation Activities of Mono- and Binuclear Hybrid Complexes and Regulation by Graphene Oxide

Hybrid complexes with N,N'-bis(2-benzimidazolylmethyl)amine and cyclen moieties are novel enzyme mimics and controlled DNA release materials, which could interact with DNA through three models under different conditions. In this paper, the interactions between plasmid DNA and seven different complexes were investigated, and the methods to change the interaction patterns by graphene oxide (GO) or concentrations were also investigated. The cleavage of pUC19 DNA promoted by target complexes were via hydrolytic or oxidative mechanisms at low concentrations ranging from 3.13 × 10(-7) to 6.25 × 10(-5) mol/L. Dinuclear complexes 2a and 2b can promote the cleavage of plasmid pUC19 DNA to a linear form at pH values below 7.0. Furthermore, binuclear hybrid complexes could condense DNA as nanoparticles above 3.13 × 10(-5) mol/L and partly release DNA by graphene oxide with π-π stacking. Meanwhile, the results also reflected that graphene oxide could prevent DNA from breaking down. Cell viability assays showed dinuclear complexes were safe to normal human hepatic cells at relative high concentrations. The present work might help to develop novel strategies for the design and synthesis of DNA controllable releasing agents, which may be applied to gene delivery and also to exploit the new application for GO.

The discovery of a novel antibiotic for the treatment of Clostridium difficile infections: a story of an effective academic-industrial partnership

The story of the discovery of the bis-benzimidazole derivative SMT19969, which is currently in clinical trials against the pathogen Clostridium difficile.

Academic drug discovery is playing an increasingly important role in the identification of new therapies for a wide range of diseases. There is no one model that guarantees success. We describe here a drug discovery story where chance, the ability to capitalise on chance, and the assembling of a range of expertise, have all played important roles in the discovery and subsequent development of an antibiotic chemotype based on the bis-benzimidazole scaffold, with potency against a number of current therapeutically challenging diseases. One compound in this class, SMT19969, has recently entered Phase 2 human clinical trials for the treatment of Clostridium difficile infections.

Synthesis, crystal structure, and DNA-binding studies of different coordinate binuclear silver(i) complexes with benzimidazole open-chain ether ligands

Three new binuclear silver(i) complexes with bis-benzimidazole ligands have been developed and they bind to CT-DNA in an intercalation mode.

The synthesis and activities of novel mononuclear or dinuclear cyclen complexes bearing azole pendants as antibacterial and antifungal agents

A series of novel compounds containing 1,4,7,10-tetraazacyclododecane and azoles were synthesized and characterized by (1)H NMR, MS and elemental analysis. Bioactive assay manifested that some target compounds, such as 11a, 11b and 11d, displayed good and broad spectrum antimicrobial activities with relative low MIC values against most of tested strains. These dinuclear complexes gave comparable or even better antimicrobial efficiencies than the reference drugs Fluconazole and Chloromycin. The result showed that the metal ions were the key factors to enhance the antimicrobial activities for mononuclear or dinuclear complexed in varying degrees. The interaction evaluation of compound 11b with bovine serum albumin (BSA) as an example was tested by fluorescence method. The thermodynamic parameters indicated that the hydrogen bonds and van der waals forces played the major roles in the strong association between dinuclear compound and BSA. The CCK-8 tests also confirmed the safeties of these dinuclear compounds in vitro.

Synthesis, antitumor activity and SAR study of novel [1,2,4]triazino[4,5-a]benzimidazole derivatives

A series of novel 1,2,3,4-tetrahydro[1,2,4]triazino[4,5-a]benzimidazoles carrying variety of aryl and heteroaryl groups at position 1 were synthesized. The newly synthesized compounds were tested in vitro on human breast adenocarcinoma cell line (MCF7). Some of the test compounds showed potent antitumor activity, especially compound 3c [1-(2-chlorophenyl) derivative] which displayed the highest activity among the test compounds.

Synthesis of glycal-based chiral benzimidazoles by VO(acac)2-CeCl3 combo catalyst and their self-aggregated nanostructured materials

VO(acac)(2)-CeCl(3) combo catalyst has been developed for chemoselective cyclocondensation cum oxidation under mild reaction conditions toward synthesis of a new class of optically pure compounds, 2-(2'-C-3',4',6'-tri-O-benzyl/methyl-glycal)-1H-benzimidazoles. It involves an operationally simple synthetic protocol efficient for the syntheses of a wide range of chiral benzimidazoles in high yields without formation of undesired 1,2-disubstituted and pseudoglycal byproducts. Vanadium(V) is found as active oxidant for the chemical processes which is investigated by UV absorption spectroscopy. Highly ordered one-dimensional low molecular mass organic nanostructured materials are fabricated by nanocrystallization of the chiral nanoscale building blocks. Theoretical calculation by the B3LYP/6-31G** level of theory of the glycal-based chiral benzimidazoles shows out of planar geometry of the 1H-anthra[1,2-d]imidazole-6,11-dione moiety, which is responsible for the strong self-aggregation to generate ultralong nanostructured materials. We have also found nice agreement between the theoretical results with the experimental observation in 2D-NOESY experiments. The photophysical property of the solid nanostructured materials is also reported.

Benzothiazole bipyridine complexes of ruthenium(II) with cytotoxic activity

A series of benzothiazole-substituted trisbipyridine ruthenium(II) analogues {[Ru(bpy)(2)(4,5'-bbtb)](2+), [Ru(bpy)(2)(5,5'-bbtb)](2+) and [Ru(bpy)(2)(5-mbtb)](2+) [bpy is 2,2'-bipyridine, bbtb is bis(benzothiazol-2-yl)-2,2'-bipyridine, 5-mbtb is 5-(benzothiazol-2-yl),5'-methyl-2,2'-bipyridine]} have been prepared and compared with the complex [Ru(bpy)(2)(4,4'-bbtb)](2+) reported previously. From the UV-vis spectral studies, substitution at the 5-position of the bpy causes the ligand-centred transitions to occur at considerably lower energy than for those with the functionality at the 4-position, while at the same time causing the emission to be effectively quenched. However, substitution at the 4-position causes the metal-to-ligand charge transfer to occur at lower energies. Fluorescent intercalator displacement studies indicate that the doubly substituted complexes displace ethidium bromide from a range of oligonucleotides, with the greater preference shown for bulge and hairpin sequences by the Lambda enantiomer. Since the complexes only show small variation in the UV-vis spectra on the introduction of calf thymus DNA and a small increase in fluorescence they do not appear to be intercalators, but appear to associate within one of the grooves. All of the reported bisbenzothiazole complexes show reasonable cytotoxicity against a range of human cancer cell lines.