Synthesis and antimycobacterial evaluation of N'-(E)-heteroaromaticpyrazine-2-carbohydrazide derivatives

Towards Novel 3-Aminopyrazinamide-Based Prolyl-tRNA Synthetase Inhibitors: In Silico Modelling, Thermal Shift Assay and Structural Studies

Human cytosolic prolyl-tRNA synthetase (HcProRS) catalyses the formation of the prolyl-tRNA^Pro, playing an important role in protein synthesis. Inhibition of HcProRS activity has been shown to have potential benefits in the treatment of fibrosis, autoimmune diseases and cancer. Recently, potent pyrazinamide-based inhibitors were identified by a high-throughput screening (HTS) method, but no further elaboration was reported. The pyrazinamide core is a bioactive fragment found in numerous clinically validated drugs and has been subjected to various modifications. Therefore, we applied a virtual screening protocol to our in-house library of pyrazinamide-containing small molecules, searching for potential novel HcProRS inhibitors. We identified a series of 3-benzylaminopyrazine-2-carboxamide derivatives as positive hits. Five of them were confirmed by a thermal shift assay (TSA) with the best compounds 3b and 3c showing EC₅₀ values of 3.77 and 7.34 µM, respectively, in the presence of 1 mM of proline (Pro) and 3.45 µM enzyme concentration. Co-crystal structures of HcProRS in complex with these compounds and Pro confirmed the initial docking studies and show how the Pro facilitates binding of the ligands that compete with ATP substrate. Modelling 3b into other human class II aminoacyl-tRNA synthetases (aaRSs) indicated that the subtle differences in the ATP binding site of these enzymes likely contribute to its potential selective binding of HcProRS. Taken together, this study successfully identified novel HcProRS binders from our anti-tuberculosis in-house compound library, displaying opportunities for repurposing old drug candidates for new applications such as therapeutics in HcProRS-related diseases.

A study of antituberculosis activities and crystal structures of (E)-2-[2-(arylidene)hydrazinyl]pyrimidine and (E)-N 1-(arylidene)pyrimidine-2-carbohydrazide derivatives

A study of the anti-tuberculosis activity against Mycobacterium tuberculosis ATTC 27294 and an X-ray structural determination of (E)-2-[2-(arylidene)hydrazinyl]pyrimidine, 1, and (E)-N 1-(arylidene)pyrimidine-2-carbohydazide, 2, derivatives are presented. The effect of the substituents in the aryl moiety on the antituberculosis (anti-TB) activities of 1 and 2 is compared with that of other heteroaryl hydrazonyl and acylhydrazonyl derivatives. The biological activities of 1 do not depend on the coordinating ability of the substituted aryl group: in 2, the most effective aryl group is 5-nitrofuranyl. The structure determinations of (E)-2-((2-(pyrimidin-2-yl)hydrazono)methyl)-phenol, (E)-N′-(2,5-dihydroxybenzylidene)pyrimidine-2-carbohydrazide and of the hydrate of (E)-N′-(2-hydroxy-4-methylbenzylidene)pyrimidine-2-carbohydrazide, and a literature search of related structures in the CCDC data base, allowed an examination of the more important interactions, including the occurrence of X–Y⋯π interactions.

When biomolecules meet 2-hydrazinopyrazine: from theory through experiment to molecular levels using a wide spectrum of techniques

The design of drug structures that are non-toxic, easily transported and permeable to cellular barriers is currently one of the most growing research trends. Indeed, the structural similarity of 2-hydrazinopyrazine (2HP) to pyrazinamide, which has been successfully used in anti-tuberculosis therapy, makes 2HP a promising research object. Thus, herein, a complete analysis of the structure of 2HP and its physicochemical and cytotoxic properties was performed. Calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) binding studies were conducted, which demonstrated the higher affinity of 2HP to BSA. Furthermore, cytotoxicity tests were performed, which proved that 2HP was non-toxic to human skin keratinocyte cells. Accordingly, 2HP was initially classified as a compound with potential application. Physicochemical investigations were performed using a wide range of experiments, which were supported by DFT calculations using the B3LYP functional and 6-311+G** basis set. The good correlation, high quality and correctness of the obtained parameters were proven although the data was obtained using independent techniques. Additionally, 42 tautomeric (prototrophic) forms of 2HP were found by searching the conformational hyperspace. The most energy stable 2HP conformer structure and the partial charge distribution were established. The preferred 2HP ionic forms preferred were presented, and models of the equilibrium occurring in aqueous solution were proposed. The hydrophilic character of 2HP was established based on the partition coefficient values determined by both experiment and theory. The PCM and SMD solvent models of water and n-octanol were used.

Structure, ionic forms, hydrophilic and non-cytotoxic character of 2-hydrazinopyrazine with stronger affinity to BSA than DNA were proved.

Crystal structure of 1-(2H-1,3-benzodioxol-5-yl)-3-(1H-imidazol-1-yl)propan-1-one, C13H12N2O3

C13H12N2O3, monoclinic, P21/n (no. 14), a = 7.3322(5) Å, b = 8.0341(5) Å, c = 19.4479(14) Å, β = 95.775(2)°, V = 1139.82(13) Å3, Z = 4, R gt(F) = 0.0533, wR ref(F 2) = 0.1335, T = 293(2) K.

3-Substituted N-Benzylpyrazine-2-carboxamide Derivatives: Synthesis, Antimycobacterial and Antibacterial Evaluation

A series of substituted N-benzyl-3-chloropyrazine-2-carboxamides were prepared as positional isomers of 5-chloro and 6-chloro derivatives, prepared previously. During the aminolysis of the acyl chloride, the simultaneous substitution of chlorine with benzylamino moiety gave rise to N-benzyl-3-(benzylamino)pyrazine-2-carboxamides as side products, in some cases. Although not initially planned, the reaction conditions were modified to populate this double substituted series. The final compounds were tested against four mycobacterial strains. N-(2-methylbenzyl)-3-((2-methylbenzyl)amino)pyrazine-2-carboxamide (1a) and N-(3,4-dichlorobenzyl)-3-((3,4-dichlorobenzyl)amino)pyrazine-2-carboxamide (9a) proved to be the most effective against Mycobacterium tuberculosis H37Rv, with MIC = 12.5 μg·mL^-1. Compounds were screened for antibacterial activity. The most active compound was 3-chloro-N-(2-chlorobenzyl)pyrazine-2-carboxamide (5) against Staphylococcus aureus with MIC = 7.81 μM, and Staphylococcus epidermidis with MIC = 15.62 μM. HepG2 in vitro cytotoxicity was evaluated for the most active compounds; however, no significant toxicity was detected. Compound 9a was docked to several conformations of the enoyl-ACP-reductase of Mycobacterium tuberculosis. In some cases, it was capable of H-bond interactions, typical for most of the known inhibitors.

Biological evaluation of isoniazid derivatives as an anticancer class

A series of thirty-two isoniazid derivatives have been evaluated for their activity against four human cancer cell lines with potent cytotoxicity (IC50 ranging from 0.61 to 3.36 μg/mL). The structure-activity relationship (SAR) analysis indicated the number, the positions, and the types of substituents attached to the aromatic ring as being critical factors for the biological activity. Briefly, we observed that the presence of a hydroxyl group on the benzene ring plays an important role in the anticancer activity of this series, especially when it is located in ortho-position. Among the thirty-two compounds, three displayed good cytotoxic activity when compared to the reference drug doxorubicin and are thus being considered leading compounds of this new class.

Comprehensive review in current developments of imidazole-based medicinal chemistry

Imidazole ring is an important five-membered aromatic heterocycle widely present in natural products and synthetic molecules. The unique structural feature of imidazole ring with desirable electron-rich characteristic is beneficial for imidazole derivatives to readily bind with a variety of enzymes and receptors in biological systems through diverse weak interactions, thereby exhibiting broad bioactivities. The related research and developments of imidazole-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous imidazole-based compounds as clinical drugs have been extensively used in the clinic to treat various types of diseases with high therapeutic potency, which have shown the enormous development value. This work systematically gives a comprehensive review in current developments of imidazole-based compounds in the whole range of medicinal chemistry as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents, together with their potential applications in diagnostics and pathology. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic imidazole-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes.

FiveN′-benzylidene-N-methylpyrazine-2-carbohydrazides

The compoundsN′-benzylidene-N-methylpyrazine-2-carbohydrazide, C13H12N4O, (IIa),N′-(2-methoxybenzylidene)-N-methylpyrazine-2-carbohydrazide, C14H14N4O2, (IIb),N′-(4-cyanobenzylidene)-N-methylpyrazine-2-carbohydrazide dihydrate, C14H11N5O·2H2O, (IIc),N-methyl-N′-(2-nitrobenzylidene)pyrazine-2-carbohydrazide, C13H11N5O3, (IId), andN-methyl-N′-(4-nitrobenzylidene)pyrazine-2-carbohydrazide, C13H11N5O3, (IIe), have dihedral angles between the pyrazine rings and the benzene rings in the range 55–78°. These methylated pyrazine-2-carbohydrazides have supramolecular structures which are formed by weak C—H...O/N hydrogen bonds, with the exception of (IIc) which is hydrated. There are π–π stacking interactions in all five compounds. Three of these structures are compared with their nonmethylated counterparts, which have dihedral angles between the pyrazine rings and the benzene rings in the range 0–6°.

Pyrazine derivatives: a patent review (2008 - present)

INTRODUCTION

Pyrazines derivatives are well-known and important two-nitrogen-containing six-membered ring aromatic heterocyclic compounds and can carry substituents at one or more of the four ring carbon atoms. Pyrazines are a class of compounds that occur in nature and various methods have been worked out for their synthesis. A large number of pyrazine derivatives have been found to possess diverse pharmacological properties, which has caused an increasing interest by researchers in this core.

AREA COVERED

This review provides a comprehensive review of the pyrazines derivatives patented between the years 2008 to 2012 as potential active compounds. The patent databases SciFinder and esp@cenet were used to locate patent applications that were published between 2008 to present. Information from articles published was also included.

EXPERT OPINION

The diversity of pyrazines derivatives found in organisms in nature with different applications began to arouse the interest of research in this nucleus. The pyrazines derivatives have numerous prominent pharmacological effects, such as antibacterial, antifungal, antimycobacterial, anti-inflammatory, analgesic, anticancer for different types, antidiabetic, treatment for arteriosclerosis, antiviral. It's the time to conduct further studies aimed at rationalizing the biological activities found in order to develop more effective and clinically interesting compounds.