Synthesis and anti-HSV-1 activity of quinolonic acyclovir analogues

Exploring 4-quinolone-3-carboxamide derivatives: A versatile framework for emerging biological applications

4-Quinolones are a pivotal class of compounds derived from the quinoline core, recognized for their broad therapeutic applications. Originating from the synthesis of chloroquine, their discovery led to nalidixic acid, the first quinolone analog to exhibit antibacterial activity, catalyzing the development of fluoroquinolones. Beyond their role as antibiotics, 4-quinolone derivatives have emerged as versatile scaffolds with demonstrated antitumor, antiviral, and antiparasitic activities, among others. Concurrently, the carboxamide functional group has gained prominence in medicinal chemistry due to its structural versatility and bioisosteric potential. Its unique properties, such as conformational stability and dual hydrogen bond capabilities, enable diverse pharmacodynamic interactions. The combination of these two structural fragments has proven to be a powerful tool for the discovery of new bioactive prototypes. This review consolidates advancements in the exploration of 4-quinolone-3-carboxamide derivatives, emphasizing their multifaceted biological activities and the innovative strategies driving their optimization. Key highlights include their potential as kinase inhibitors, antiviral agents, and anticancer therapeutics. By synthesizing insights from recent studies, this review underscores the relevance of this framework in addressing contemporary medicinal challenges.

Ring expansion of 3-hydroxyoxindoles to 4-quinolones via palladium-catalyzed C-C(acyl) bond cleavage

We report herein the construction of 4-quinolones via palladium-catalyzed regioselective β-acyl elimination of 3-hydroxyoxindoles and a subsequent Camps cyclization process. This protocol is highly efficient and various 4-quinolone derivatives are obtained in high yields. The construction of the core skeleton of the 4-quinolone antibiotics demonstrated the synthetic utility of this method.

Hydrogen Bond Assisted Three-Component Tandem Reactions to Access N-Alkyl-4-Quinolones

Hydrogen-bonding catalytic reactions have gained great interest. Herein, a hydrogen-bond-assisted three-component tandem reaction for the efficient synthesis of N-alkyl-4-quinolones is described. This novel strategy features the first proof of polyphosphate ester (PPE) as a dual hydrogen-bonding catalyst and the use of readily available starting materials for the preparation of N-alkyl-4-quinolones. The method provides a diversity of N-alkyl-4-quinolones in moderate to good yields. The compound 4h demonstrated good neuroprotective activity against N-methyl-ᴅ-aspartate (NMDA)-induced excitotoxicity in PC12 cells.

A green and efficient synthetic methodology towards the synthesis of 1-allyl-6-chloro-4-oxo-1,4-dihydroquinoline-3-carboxamide derivatives

Quinolone is a privileged scaffold in medicinal chemistry and 4-Quinolone-3-Carboxamides have been reported to harbor vast therapeutic potential. However, conversion of N-1 substituted 4-Quinolone 3-Carboxylate to its corresponding carbamates is highly restrictive. This motivated us to adopt a much simpler, scalable and efficient methodology for the synthesis of highly pure N-1 substituted 4- Quinolone-3-Carboxamides with excellent yields. Our adopted methodology not only provides a robust pathway for the convenient synthesis of N-1 substituted 4- Quinolone-3-Carboxamides which can then be explored for their therapeutic potential, this may also be adaptable for the derivatization of other such less reactive carboxylate species.

Inhibitory properties of crude microalgal extracts on the in vitro replication of cyprinid herpesvirus 3

Microalgae are possible sources of antiviral substances, e.g. against cyprinid herpesvirus 3 (CyHV-3). Although this virus leads to high mortalities in aquacultures, there is no treatment available yet. Hence, ethanolic extracts produced with accelerated solvent extraction from six microalgal species (Arthrospira platensis, Chlamydomonas reinhardtii, Chlorella kessleri, Haematococcus pluvialis, Nostoc punctiforme and Scenedesmus obliquus) were examined in this study. An inhibition of the in vitro replication of CyHV-3 could be confirmed for all six species, with the greatest effect for the C. reinhardtii and H. pluvialis crude extracts. At still non-cytotoxic concentrations, viral DNA replication was reduced by over 3 orders of magnitude each compared to the untreated replication controls, while the virus titers were even below the limit of detection (reduction of 4 orders of magnitude). When pre-incubating both cells and virus with C. reinhardtii and H. pluvialis extracts before inoculation, the reduction of viral DNA was even stronger (> 4 orders of magnitude) and no infectious viral particles were detected. Thus, the results of this study indicate that microalgae and cyanobacteria are a promising source of natural bioactive substances against CyHV-3. However, further studies regarding the isolation and identification of the active components of the extracts are needed.

In vitro inhibition and molecular docking of a new ciprofloxacin-chalcone against SARS-CoV-2 main protease

Background/Aim

SARS‐CoV‐2 is one of the coronavirus families that emerged at the end of 2019. It infected the respiratory system and caused a pandemic worldwide. Fluoroquinolones (FQs) have been safely used as antibacterial agents for decades. The antiviral activity of FQs was observed. Moreover, substitution on the C‐7 position of ciprofloxacin enhanced its antiviral activity. Therefore, this study aims to investigate the antiviral activity of 7‐(4‐(N‐substituted‐carbamoyl‐methyl)piperazin‐1yl)‐chalcone in comparison with ciprofloxacin against SARS‐CoV‐2 main protease (M^pro).

Materials and methods

Vero cells were infected with SARS‐CoV‐2. After treatment with ciprofloxacin and the chalcone at the concentrations of 1.6, 16, 160 nmol/L for 48 h, SARS‐CoV‐2 viral load was detected using real‐time qPCR, SARS‐CoV‐2 infectivity was determined using plaque assay, and the main protease enzyme activity was detected using in vitro 3CL‐protease inhibition assay. The activity of the chalcone was justified through molecular docking within SARS‐CoV‐2 M^pro, in comparison with ciprofloxacin.

Results

The new chalcone significantly inhibited viral load replication where the EC50 was 3.93 nmol/L, the plaque formation ability of the virus was inhibited to 86.8% ± 2.47. The chalcone exhibited a significant inhibitory effect against SARS‐CoV‐2 M^pro in vitro in a dose‐dependent manner. The docking study into SARS‐CoV‐2 M^pro active site justified the importance of adding a substitution to the parent drug. Additionally, the assessment of the drug‐likeness properties indicated that the chalcone might have acceptable ADMET properties.

Conclusion

The new chalcone might be useful and has new insights for the inhibition of SARS‐CoV‐2 M^pro.

Antiviral activity of 1,4-disubstituted-1,2,3-triazoles against HSV-1 in vitro

BACKGROUND

Herpes simplex virus 1 (HSV-1) affects a large part of the adult population. Anti-HSV-1 drugs, such as acyclovir, target thymidine kinase and viral DNA polymerase. However, the emerging of resistance of HSV-1 alerts for the urgency in developing new antivirals with other therapeutic targets. Thus, this study evaluated a series of 1,4-disubstituted-1,2,3-triazole derivatives against HSV-1 acute infection and provided deeper insights into the possible mechanisms of action.

METHODS

Human fibroblast cells (HFL-1) were infected with HSV-1 17syn+ and treated with the triazole compounds at 50 μM for 24 h. The 50% effective drug concentration (EC₅₀) was determined for the active compounds. Their cytotoxicity was also evaluated in HFL-1 with the 50% cytotoxic concentration (CC₅₀) determined using CellTiter-Glo^® solution. The most promising compounds were evaluated by virucidal activity and influence on virus egress, DNA replication and transcription, and effect on an acyclovir-resistant HSV-1 strain.

RESULTS

Compounds 3 ((E)-4-methyl-N'-(2-(4-(phenoxymethyl)-1H-1,2,3-triazol1yl)benzylidene)benzenesulfonohydrazide) and 4 (2,2'-(4,4'-((1,3-phenylenebis(oxy))bis(methylene))bis(1H-1,2,3-triazole-4,1 diyl)) dibenzaldehyde) were the most promising, with an EC₅₀ of 16 and 21 μM and CC₅₀ of 285 and 2,593 μM, respectively. Compound 3 was able to inhibit acyclovir-resistant strain replication and to interfere with virus egress. Both compounds did not affect viral DNA replication, but inhibited significantly the expression of ICP0, ICP4 and gC. Compound 4 also affected the transcription of UL30 and ICP34.5.

CONCLUSIONS

Our findings demonstrated that these compounds are promising antiviral candidates with different mechanisms of action from acyclovir and further studies are merited.

4-Oxoquinoline Derivatives as Antivirals: A Ten Years Overview

4-Oxoquinoline derivatives constitute an important family of biologically important substances, associated with different bioactivities, which can be synthesized by different synthetic methods, allowing the design and preparation of libraries of substances with specific structural variations capable of modulating their pharmacological action. Over the last years, these substances have been extensively explored by the scientific community in efforts to develop new biologically active agents, with greater efficiency for the treatment of a variety of diseases. Viral infections have been one of the targets of these studies, although to a lesser extent than other diseases such as cancer and bacterial infections. Nevertheless, the literature provides examples that corroborate with the fact that these substances may act on different pharmacological targets in different viral pathogens. This review provides a compilation of some of the major studies published in recent years showing the discovery and/or development of new antiviral oxoquinoline agents, highlighting, whenever possible, their mechanisms of action.

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

We present a short and efficient way of synthesizing two synthetically versatile 4-quinolone-3-carboxylate building blocks by cyclopropanation-ring expansion of 3-chloroindoles with α-halodiazoacetates as the key step. This novel transformation was applied towards the synthesis of the antibiotic drug norfloxacin.

Rhodium(iii)-catalyzed [3 + 3] annulation reactions of N-nitrosoanilines and cyclopropenones: an approach to functionalized 4-quinolones

We report Rh(iii)-catalyzed [3 + 3] annulation reactions for the preparation of functionalized 4-quinolones from available N-nitrosoanilines and cyclopropenones.

Ubiquitous Nature of Fluoroquinolones: The Oscillation between Antibacterial and Anticancer Activities

Fluoroquinolones are synthetic antibacterial agents that stabilize the ternary complex of prokaryotic topoisomerase II enzymes (gyrase and Topo IV), leading to extensive DNA fragmentation and bacteria death. Despite the similar structural folds within the critical regions of prokaryotic and eukaryotic topoisomerases, clinically relevant fluoroquinolones display a remarkable selectivity for prokaryotic topoisomerase II, with excellent safety records in humans. Typical agents that target human topoisomerases (such as etoposide, doxorubicin and mitoxantrone) are associated with significant toxicities and secondary malignancies, whereas clinically relevant fluoroquinolones are not known to exhibit such propensities. Although many fluoroquinolones have been shown to display topoisomerase-independent antiproliferative effects against various human cancer cells, those that are significantly active against eukaryotic topoisomerase show the same DNA damaging properties as other topoisomerase poisons. Empirical models also show that fluoroquinolones mediate some unique immunomodulatory activities of suppressing pro-inflammatory cytokines and super-inducing interleukin-2. This article reviews the extended roles of fluoroquinolones and their prospects as lead for the unmet needs of "small and safe" multimodal-targeting drug scaffolds.

Efficient synthesis of novel N-substituted 2-carboxy-4-quinolones via lithium bis(trimethylsilyl)amide (LiHMDS)-induced in situ cyclocondensation reaction

Efficient synthesis ofN-aryl-2-carboxy-substituted 4-quinolones with broad substrate scope and high regioselectivity.

Photo-Fries rearrangement of aryl acetamides: regioselectivity induced by the aqueous micellar green environment

NMR spectroscopy shows the location of acetanilides within the shells and hydrophobic cores in micellar solutions. Irradiation of acetanilides in aqueous micellar solutions involves C–N homolytic cleavage to yield singlet radical pairs that selectively provide 2-aminoacetophenone derivatives.

A new route for the synthesis of highly substituted 4-aminoquinoline drug like molecules via aza hetero–Diels–Alder reaction

A new route has been developed for the synthesis of 4-aminoquinoline drug like moleculesviaaza hetero–Diels–Alder reaction starting from 2H-indazole as a diene for the first time.

Design, synthesis, molecular docking, and antibacterial evaluation of some novel flouroquinolone derivatives as potent antibacterial agent

Objective. Quinolone moiety is an important class of nitrogen containing heterocycles widely used as key building blocks for medicinal agents. It exhibits a wide spectrum of pharmacophores and has bactericidal, antiviral, antimalarial, and anticancer activities. In view of the reported antimicrobial activity of various fluoroquinolones, the importance of the C-7 substituents is that they exhibit potent antimicrobial activities. Our objective was to synthesize newer quinolone analogues with increasing bulk at C-7 position of the main 6-fluoroquinolone scaffold to produce the target compounds which have potent antimicrobial activity. Methods. A novel series of 1-ethyl-6-fluoro-4-oxo-7-{4-[2-(4-substituted phenyl)-2-(substituted)-ethyl]-1-piperazinyl}-1,4-dihydroquinoline-3-carboxylic acid derivatives were synthesized. To understand the interaction of binding sites with bacterial protein receptor, the docking study was performed using topoisomerase II DNA gyrase enzymes (PDB ID: 2XCT) by Schrodinger's Maestro program. In vitro antibacterial activity of the synthesized compounds was studied and the MIC value was calculated by the broth dilution method. Results. Among all the synthesized compounds, some compounds showed potent antimicrobial activity. The compound 8g exhibited good antibacterial activity. Conclusion. This investigation identified the potent antibacterial agents against certain infections.

Transition metal-free one-pot synthesis of 2-substituted 3-carboxy-4-quinolone and chromone derivatives

A novel one-pot synthesis of the 2-substituted 3-carboxy-4-quinolone/chromone derivatives from readily available 3-oxo-3-arylpropanoates and amides/acyl chlorides is reported, without any transition metal aid.

Synthesis and anti-HSV-1 activity of new 1,2,3-triazole derivatives

In this work, a new series of arysulfonylhydrazine-1H-1,2,3-triazole derivatives were synthesized, and their ability to inhibit the in vitro replication of HSV-1 was evaluated. Among the 1,2,3-triazole derivatives, 1-[(5″-methyl-1″-(4‴-fluorophenylamino)-1H-1,2,3-triazol-4″-yl)carbonyl]-2-(4'-methylphenylsulfonyl)hydrazine and 1-[(5'-methyl-1'-(2″,5″-dichlorophenylamino)-1H-1,2,3-triazol-4'-yl)carbonyl]-2-(phenylsulfonyl)hydrazine, with IC(50) values of 1.30 and 1.26 μM, respectively, displayed potent activity against HSV-1. Because these compounds have low cytotoxicity, their selectivity indices are high. Under the assay conditions, they have better performance than does the reference compound acyclovir. The structures of all of the compounds were confirmed by one- and two-dimensional NMR techniques ((1)H, (13)C-APT, COSY-(1)H×(1)H and HETCOR (1)J(CH)) and by elemental analysis.

Synthesis of 2,3-Dihydro-4(1H)-quinolones and the Corresponding 4(1H)-Quinolones via Low-Temperature Fries Rearrangement of N-Arylazetidin-2-ones

N-Arylazetidin-2-ones of the general form 1, which are readily prepared by Goldberg–Buchwald-type copper-catalyzed coupling of N-unsubstituted azetidin-2-ones with the relevant aryl halide or using Mitsunobu cyclization processes, undergo smooth Fries-rearrangement in triflic acid at 0–18°C to give the isomeric 2,3-dihydro-4(1H)-quinolones (2). Dehydrogenation of the latter compounds using 10% Pd on C in 1.0 M aqueous sodium hydroxide/propan-2-ol mixtures at ca. 82°C provides the corresponding 4(1H)-quinolones (3).

Synthesis and structure-activity relationships of antimalarial 4-oxo-3-carboxyl quinolones

Malaria is endemic in tropical and subtropical regions of Africa, Asia, and the Americas. The increasing prevalence of multi-drug-resistant Plasmodium falciparum drives the ongoing need for the development of new antimalarial drugs. In this light, novel scaffolds to which the parasite has not been exposed are of particular interest. Recently, workers at the Swiss Tropical Institute discovered two novel 4-oxo-3-carboxyl quinolones active against the intra-erythrocytic stages of P. falciparum while carrying out rationally directed low-throughput screening of potential antimalarial agents as part of an effort directed by the World Health Organization. Here we report the design, synthesis, and preliminary pharmacologic characterization of a series of analogues of 4-oxo-3-carboxyl quinolones. These studies indicate that the series has good potential for preclinical development.

(E)-1-Ethyl-4-oxo-N'-(4-pyridylmethyl-ene)-1,4-dihydroquinoline-3-carbo-hydrazide

In the title compound, C₁₈H₁₆N₄O₂, the plane defined by the ethyl C atoms and the attached N atom is inclined to the adjacent pyridine ring at an angle of 67.87 (16)°. The dihedral angle between the two heterocyclic rings is 3.33 (16)°. The mol­ecular conformation is stabilized by an intra­molecular N—H⋯O hydrogen bond and the crystal structure by inter­molecular C—H⋯O hydrogen bonds, forming a one-dimensional structure.