Potent DNA gyrase inhibitors; novel 5-vinylpyrazole analogues with Gram-positive antibacterial activity

Revisiting the Chemistry of Vinylpyrazoles: Properties, Synthesis, and Reactivity

Vinylpyrazoles, also known as pyrazolyl olefins, are interesting motifs in organic chemistry but have been overlooked. This review describes the properties and synthetic routes of vinylpyrazoles and highlights their versatility as building blocks for the construction of more complex organic molecules. Concerning the reactivity of vinylpyrazoles, the topics surveyed herein include their use in cycloaddition reactions, free-radical polymerizations, halogenation and hydrohalogenation reactions, and more recently in transition-metal-catalyzed reactions, among other transformations. The current state of the art about vinylpyrazoles is presented with an eye to future developments regarding the chemistry of these interesting compounds. Styrylpyrazoles were not considered in this review, as they were the subject of a previous review article published in 2020.

Synthesis, evaluation and modeling of some triazolothienopyrimidinones as anti-inflammatory and antimicrobial agents

AIM

New triazolotetrahydrobenzothienopyrimidinone derivatives were synthesized.

EXPERIMENTAL

Their structures were confirmed, and their anti-inflammatory, antimicrobial activities and ulcerogenic potentials were evaluated.

RESULTS

Compounds 7a, 10a and 11a showed minimal ulcerogenic effect and high selectivity toward human recombinant COX-2 over COX-1 enzyme with IC₅₀ values of 1.39, 1.22 and 0.56 μM, respectively. Their docking outcome correlated with their biological activity and confirmed the high selectivity binding toward COX-2. Compound 12b displayed antimicrobial activity comparable to that of ampicillin against Escherichia coli while compounds 6 and 11c were similar to ampicillin against Staphylococcus aureus. In addition, compounds 7a, 9a, 10b and 11c showed dual anti-inflammatory/antimicrobial activities.

CONCLUSION

This work represents a promising matrix for developing new potential anti-inflammatory, antimicrobial and dual antimicrobial/anti-inflammatory candidates. [Formula: see text].

Lipophilicity Studies on Thiosemicarbazide Derivatives

The lipophilicity of two series of thiosemicarbazide derivatives was assessed by the RP-HPLC method with the RP-18 chromatographic column and the methanol–water mixture as the mobile phase. Distribution coefficients logP_HPLC were compared to calculated values generated by commonly used AClogP software and quantum chemical calculations. The reliability of the predictions was evaluated using the correlation matrix and PCA. For 4-benzoylthiosemicarbazides, a high correlation between theoretical and experimental logP parameters was obtained using the XlogP3 algorithm, while for 4-aryl/(cyclohexyl)thiosemicarbazides, the XlogP2 parameter was strongly correlated with the experimentally obtained logP.

New N-phenyl-4,5-dibromopyrrolamides and N-Phenylindolamides as ATPase inhibitors of DNA gyrase

Following the withdrawal of novobiocin, the introduction of a new ATPase inhibitor of DNA gyrase to the clinic would add the first representative of this mechanistic class to the antibacterial pipeline. This would be of great importance because of the well-known problems associated with antibacterial resistance. Using structure-based design and starting from the recently determined crystal structure of the N-phenyl-4,5-dibromopyrrolamide inhibitor-DNA gyrase B complex, we have prepared 28 new N-phenyl-4,5-dibromopyrrolamides and N-phenylindolamides and evaluated them against DNA gyrase from Escherichia coli. The most potent compound was 2-((4-(4,5-dibromo-1H-pyrrole-2-carboxamido)phenyl)amino)-2-oxoacetic acid (9a), with an IC50 of 0.18 μM against E. coli gyrase. A selected set of compounds was evaluated against DNA gyrase from Staphylococcus aureus and against topoisomerase IV from E. coli and S. aureus, but the activities were weaker. The binding affinity of 2-((4-(4,5-dibromo-1H-pyrrole-2-carboxamido)phenyl)amino)-2-oxoacetic acid (9a) to E. coli gyrase was studied using surface plasmon resonance. In the design of the present series, the focus was on the optimisation of biological activities of compounds - especially by varying their size, the position and orientation of key functional groups, and their acid-base properties. The structure-activity relationship (SAR) was examined and the results were rationalised with molecular docking.

Dual targeting DNA gyrase B (GyrB) and topoisomerse IV (ParE) inhibitors: A review

GyrB and ParE are type IIA topoisomerases and found in most bacteria. Its function is vital for DNA replication, repair and decatenation. The highly conserved ATP-binding subunits of DNA GyrB and ParE are structurally related and have been recognized as prime candidates for the development of dual-targeting antibacterial agents with broad-spectrum potential. However, no natural product or small molecule inhibitors targeting ATPase catalytic domain of both GyrB and ParE enzymes have succeeded in the clinic. Moreover, no inhibitors of these enzymes with broad-spectrum antibacterial activity against Gram-negative pathogens have been reported. Availability of high resolution crystal structures of GyrB and ParE made it possible for the design of many different classes of inhibitors with dual mechanism of action. Among them benzimidazoles, benzothiazoles, thiazolopyridines, imidiazopyridazoles, pyridines, indazoles, pyrazoles, imidazopyridines, triazolopyridines, pyrrolopyrimidines, pyrimidoindoles as well as related structures are disclosed in literatures. Unfortunately most of these inhibitors are found to be active against Gram-positive pathogens. In the present review we discuss about studies on novel dual targeting ATPase inhibitors.

A New-Class Antibacterial-Almost. Lessons in Drug Discovery and Development: A Critical Analysis of More than 50 Years of Effort toward ATPase Inhibitors of DNA Gyrase and Topoisomerase IV

The introduction into clinical practice of an ATPase inhibitor of bacterial DNA gyrase and topoisomerase IV (topo IV) would represent a new-class agent for the treatment of resistant bacterial infections. Novobiocin, the only historical member of this class, established the clinical proof of concept for this novel mechanism during the late 1950s, but its use declined rapidly and it was eventually withdrawn from the market. Despite significant and prolonged effort across the biopharmaceutical industry to develop other agents of this class, novobiocin remains the only ATPase inhibitor of gyrase and topo IV ever to progress beyond Phase I. In this review, we analyze the historical attempts to discover and develop agents within this class and highlight factors that might have hindered those efforts. Within the last 15 years, however, our technical understanding of the molecular details of the inhibition of the gyrase and topo IV ATPases, the factors governing resistance development to such inhibitors, and our knowledge of the physical properties required for robust clinical drug candidates have all matured to the point wherein the industry may now address this mechanism of action with greater confidence. The antibacterial spectrum within this class has recently been extended to begin to include serious Gram negative pathogens such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. In spite of this recent technical progress, adverse economics associated with antibacterial R&D over the last 20 years has diminished industry's ability to commit the resources and perseverance needed to bring new-class agents to launch. Consequently, a number of recent efforts in the ATPase class have been derailed by organizational rather than scientific factors. Nevertheless, within this context we discuss the unique opportunity for the development of ATPase inhibitors of gyrase and topo IV as new-class antibacterial agents with broad spectrum potential.

Novel pyrazole integrated 1,3,4-oxadiazoles: synthesis, characterization and antimicrobial evaluation

A novel series of 2-(5-methyl-1,3-diphenyl-1H-pyrazol-4-yl)-5-phenyl-1,3,4-oxadiazoles 7(a-m) were synthesized either by cyclization of N'-benzoyl-5-methyl-1,3-diphenyl-1H-pyrazole-4-carbohydrazide 4a using POCl3 at 120°C or by oxidative cyclization of hydrazones derived from various arylaldehyde and (E)-N'-benzylidene-5-methyl-1,3-diphenyl-1H-pyrazole-4-carbohydrazide 5(a-d) using chloramine-T as oxidant. Newly synthesized compounds were characterized by analytical and spectral (IR, (1)H NMR, (13)C NMR and LC-MS) methods. The synthesized compounds were evaluated for their antimicrobial activity and were compared with standard drugs. The compounds demonstrated potent to weak antimicrobial activity. Among the synthesized compounds, compound 7m emerged as an effective antimicrobial agent, while compounds 7d, 7f, 7i and 7l showed good to moderate activity. The minimum inhibitory concentration of the compounds was in the range of 20-50μgmL(-1) against bacteria and 25-55μgmL(-1) against fungi. The title compounds represent a novel class of potent antimicrobial agents.

5-(2-Pyrimidinyl)-imidazo[1,2-a]pyridines are antibacterial agents targeting the ATPase domains of DNA gyrase and topoisomerase IV

Dual inhibitors of bacterial gyrB and parE based on a 5-(2-pyrimidinyl)-imidazo[1,2-a]pyridine template exhibited MICs (microg/mL) of 0.06-64 (Sau), 0.25-64 (MRSA), 0.06-64 (Spy), 0.06-64 (Spn), and 0.03-64 (FQR Spn). Selected examples were efficacious in mouse sepsis and lung infection models at <50mg/kg (PO dosing).

Synthesis and biological evaluation of novel pyrazoles and pyrazolo[3,4-d]pyrimidines incorporating a benzenesulfonamide moiety

Synthesis and biological evaluation of novel pyrazoles and pyrazolo[3,4-d]pyrimidines are reported. Fourteen compounds were selected by the NCI and tested for their preliminary in-vitro anticancer activity, whereas all the synthesized compounds were evaluated for their in-vitro antimicrobial activity. Compound 12a was proven to possess the highest anticancer activity with a broad spectrum profile. It showed particular effectiveness towards leukemia HL-60 (TB), K-562, non-small cell lung cancer NCI-H23, and colon cancer HT 29, KM 12 cell lines (GI(50) = 6.59, 4.44, 1.37, 3.33, and 9.63 muM, respectively). Out of the synthesized compounds, thirteen derivatives were found to display pronounced antimicrobial activity especially against P. aeruginosa. Compounds 2c, 5b, 10, 11b, 17b, 18b, and 19 were proven to be the most active with a broad spectrum of activity. Compound 19 was found to be equipotent to ampicillin against B. subtilis, whereas compounds 11b and 19 were four times superior to ampicillin against P. aeruginosa, while compounds 5b and 18b were equipotent to ampicillin against the same organism. Moreover, compounds 2c, 10, and 11b were nearly equipotent to ampicillin against E. coli. On the other hand, compounds 2c, 5b, 10, 11a, 17b, and 18b exerted nearly half the activity of clotrimazole against C. albicans.

Synthesis of some pyrazolyl benzenesulfonamide derivatives as dual anti-inflammatory antimicrobial agents

Four series of pyrazolylbenzenesulfonamide derivatives were synthesized and evaluated for their anti-inflammatory activity using cotton pellet induced granuloma and carrageenan-induced rat paw edema bioassays. Moreover, COX-1 and COX-2 inhibitory activity, ulcerogenic effect and acute toxicity were also determined. Furthermore, the target compounds were screened for their in-vitro antimicrobial activity against Eischerichia coli, Staphylococcus aureus and Candida albicans. Compounds 4-(3-Phenyl-4-cyano-1H-pyrazol-1-yl)benzenesulfonamide 9a and 4-(3-Tolyl-4-cyano-1H-pyrazol-1-yl)benzenesulfonamide 9b were not only found to be the most active dual anti-inflammatory antimicrobial agents in the present study with good safety margin and minimal ulcerogenic effect but also exhibited good selective inhibitory activity towards COX-2. A docking pose for 9a and 9b separately in the active site of the human COX-2 enzyme was also obtained. Therefore, these compounds would represent a fruitful matrix for the development of dual anti-inflammatory antimicrobial candidates with remarkable COX-2 selectivity.

Synthesis, Structure, and Antibacterial Activity of Novel 5-Arylpyrazole Derivatives

A series of novel 1-(acetyl,carboxamide,carbothioamide)substituted-5-(substituted-phenyl)-3-methy-4,5-dihydropyrazole derivatives have been synthesized and characterized by 1H NMR, IR, ESI-MS, and elemental analysis. Compounds 6h and 6q were further characterized by single crystal X-ray structural analysis. All of the compounds have been screened for their antibacterial potential in vitro against Bacillus subtilis ATCC 6633, Escherichia coli ATCC 35218, Pseudomonas fluorescens ATCC 13525, and Staphylococcus aureus ATCC 6538. Among the tested compounds, some of them display significant activity against the tested strains, and compounds 5ac and 6h show potent activity with a minimum inhibitory concentration value of 1.562 μg mL–1 against B. subtilis ATCC 6633, which is comparable to the positive control penicillin. Structure–effect relationships are also discussed based on the experimental data.

Antibacterial drug discovery and structure-based design

Bacterial resistance continues to develop and pose a significant threat, both in hospitals and, more recently, in the community. A focus on other therapeutic areas by the larger pharmaceutical companies has left a shortfall in the pipeline of novel antibacterials. Recently, many new structures have been studied by structure-genomics initiatives, delivering a wealth of targets to consider. Using the tools of structure-based design, antibacterial discovery must exploit these targets to accelerate the process of drug discovery.

Crystallizing new approaches for antimicrobial drug discovery

Over the past decade, the sequences of microbial genomes have accumulated, changing the strategies for the discovery of novel anti-infective agents. Targets have become plentiful, yet new antimicrobial agents have been slow to emerge from this effort. In part, this reflects the long discovery and development times needed to bring new drugs to market. In addition, bottlenecks have been revealed in the antimicrobial drug discovery process at the steps of identifying good leads, and optimizing those leads into drug candidates. The fruit of structural genomics may provide opportunities to overcome these bottlenecks and fill the antimicrobial pipeline, by using the tools of structure guided drug discovery (SGDD).

Synthesis and Biological Evaluation of Some Hydroxypyrazole Derivatives as Anti-inflammatory-Antimicrobial Agents

Some hydroxypyrazole derivatives 2-7 were synthesized by cyclocondensation of the keto-ester 1 with hydrazines hydrate or substituted hydrazines followed by reduction and acylation with acetic anhydride or trifluoroacetic anhydride. The newly synthesized compounds were evaluated for their anti-inflammatory, antimicrobial activities. In addition, the ulcerogenic and acute toxicity profiles were determined. Compounds N-(4-(5-hydroxy-1-trifluoroacetyl-1H-pyrazol-3-yl)phenyl) trifluoroacetamide 4b, 3-(4-nitrophenyl)-1-(4-methoxyphenyl)-1H-pyrazol-5-ol 5b, and N-(4-(5-hydroxy-1-methyl-1H-pyrazol-3-yl)phenyl)trifluoroacetamide 7b were proved to be the most active anti-inflammatory, antimicrobial agents in the present study with a good safety margin and minimal or no ulcerogenic effect.

Synthesis and antibacterial activity of novel and potent DNA gyrase inhibitors with azole ring

The 4-piperidyl moiety and the pyrazole ring in 1-(3-chlorophenyl)-5-(4-phenoxyphenyl)-3-(4-piperidyl)pyrazole 2, which has previously shown improved DNA gyrase inhibition and target-related antibacterial activity, were transformed to other groups and the in vitro antibacterial activity of the synthesized compounds was evaluated. The selected pyrazole, oxazole and imidazole derivatives showed moderate inhibition against DNA gyrase and topoisomerase IV with similar IC(50) values (IC(50)=9.4-25 microg/mL). In addition, many of the pyrazole, oxazole and imidazole derivatives synthesized in this study exhibited potent antibacterial activity against quinolone-resistant clinical isolates and coumarin-resistant laboratory isolates of Gram-positive bacteria with minimal inhibitory concentration values equivalent to those against susceptible strains.