Quinoline Derivatives with Potential Activity Against Multidrug-resistant Tuberculosis

Synthesis of S-Alkyl Dithiocarbamates via Multicomponent Reaction of Cyclic Sulfonium Salts with CS2 and Amines

A convenient and practical method for the synthesis of various S-alkyl dithiocarbamates through three-component reaction of sulfonium salts, CS2 and amines has been developed. The reaction proceeds efficiently without any catalyst and additive under mild and open-air conditions, making it potential applications in pharmaceutical chemistry and sulfur chemistry.

Machine learning-based drug design for identification of thymidylate kinase inhibitors as a potential anti-Mycobacterium tuberculosis

The rise of antibiotic-resistant Mycobacterium tuberculosis (Mtb) has reduced the availability of medications for tuberculosis therapy, resulting in increased morbidity and mortality globally. Tuberculosis spreads from the lungs to other parts of the body, including the brain and spine. Developing a single drug can take several decades, making drug discovery costly and time-consuming. Machine learning algorithms like support vector machines (SVM), k-nearest neighbor (k-NN), random forest (RF) and Gaussian naive base (GNB) are fast and effective and are commonly used in drug discovery. These algorithms are ideal for the virtual screening of large compound libraries to classify molecules as active or inactive. For the training of the models, a dataset of 307 was downloaded from BindingDB. Among 307 compounds, 85 compounds were labeled as active, having an IC50 below 58 mM, while 222 compounds were labeled inactive against thymidylate kinase, with 87.2% accuracy. The developed models were subjected to an external ZINC dataset of 136,564 compounds. Furthermore, we performed the 100-ns dynamic simulation and post trajectories analysis of compounds having good interaction and score in molecular docking. As compared to the standard reference compound, the top three hits revealed greater stability and compactness. In conclusion, our predicted hits can inhibit thymidylate kinase overexpression to combat Mycobacterium tuberculosis.Communicated by Ramaswamy H. Sarma.

Ts2O mediated deoxygenative C2-dithiocarbamation of quinoline N-oxides with CS2 and amines

A general, efficient and practical protocol for Ts2O promoted deoxygenative dithiocarbamation of quinoline N-oxides with in situ generated dithiocarbamic acids from CS2 and amines is reported. The reaction proceeded well under transition-metal free conditions to obtain a variety of novel quinoline-dithiocarbamate compounds with wide functional group tolerance and good to high yields.

Ts2O Promoted Deoxygenative C-H Dithiocarbonation of Quinoline N-Oxides with Potassium O-Alkyl Xanthates

A simple, efficient, and practical method for the synthesis of S-quinolyl xanthates was developed via Ts2O-promoted deoxygenative C-H dithiocarbonation of quinoline N-oxides with various potassium O-alkyl xanthates. The reaction performed well under transition-metal-free, base-free, and room-temperature conditions with wide substrate tolerance. Employing potassium O-tert-butyl xanthate (tBuOCS2K) as a nucleophile, some valuable quinoline-2-thiones were unexpectedly obtained in a one-pot reaction without any additional base.

TsCl promoted deoxygenative phosphorothiolation of quinoline N-oxides towards S-quinolyl phosphorothioates

A convenient, efficient and practical approach for the synthesis of S-quinolyl phosphorothioates via cheap TsCl promoted deoxygenative C2-H phosphorothiolation of quinoline N-oxides with readily available triethylammonium O,O-dialkylphosphorothioates was developed. The reaction performed well under transition-metal-free conditions at room temperature with a very short reaction time (10-20 min). Preliminary studies showed that the current transformation underwent a nucleophilic substitution process.

Ball milling synthesis of S-quinolyl xanthates via coupling of haloquinolines with potassium O-alkyl xanthates

An environmentally benign protocol that provides various S-quinolyl xanthates via a ball milling enabled cross coupling reaction of haloquinolines and readily available potassium O-alkyl xanthates is first reported. The reaction proceeded well under mild, transition metal- and solvent-free conditions, making it an attractive method for the introduction of xanthates into the quinoline scaffold.

Quinolone: a versatile therapeutic compound class

The discovery of nalidixic acid is one pinnacle in medicinal chemistry, which opened a new area of research that has led to the discovery of several life-saving antimicrobial agents (generally referred to as fluoroquinolones) for over decades. Although fluoroquinolones are frequently encountered in the literature, the utility of quinolone compounds extends far beyond the applications of fluoroquinolones. Quinolone-based compounds have been reported for activity against malaria, tuberculosis, fungal and helminth infections, etc. Hence, the quinolone scaffold is of great interest to several researchers in diverse disciplines. This article highlights the versatility of the quinolone pharmacophore as a therapeutic agent beyond the fluoroquinolone profile.

Assessment of without prescription antibiotic dispensing at community pharmacies in Hazara Division, Pakistan: A simulated client's study

Antibiotics dispensing without a prescription is an irrational practice and can increase the risk of antibiotic resistance, which is a significant public health concern around the globe. This study was aimed to determine the extent to which antibiotics are supplied without prescription in the community pharmacies (CPs) at Hazara Division from November 2020 to February 2021. The simulated client method (SCM) was used, and the data were gathered, recorded, and analyzed through different statistical methods with descriptive and inferential techniques. The antibiotic dispensing was observed in CPs (90.5%), the most dispensed antibiotics were azithromycin (29.4%) and ciprofloxacin (46.5%) respectively. Furthermore, visited medical stores/ drug outlets, 9.5% of the visited stores denied dispensing of antibiotics because they preferred a referral to visit physicians (23. 9%) and (12.8%) did not had the antibiotics at the time of visits. Antibiotics were more obtainable in retail medical stores (AOR = 8.6, 95 percent Cl: 3.0–24.7; p = 0.001) than in pharmacies. In rural areas antibiotics dispensing was more (p = 0.004) as compared to urban areas. Staff members also had asked about patient’s (17.7%) symptoms and drug allergies (12.3% and 3.9%), and (1.5%) they consoled them about their medications. The findings of this study indicate that nonprescription antibiotic sales are very common, despite national rules prohibiting this activity. When the simulated Client requested for any medication to relieve his or her discomfort, many antibiotics were given out without a prescription. Pharmacies/medical stores in Hazara Division selling antibiotics without a prescription are worrying and need immediate action by regulators.

Metal-free, one-pot synthesis of 2-styrylquinolines via Friedländer annulation and sp3 C–H activation using 1,3-dimethylurea and l-tartaric acid (3 : 1) as a deep eutectic solvent

Functionalized 2-styrylquinolines are prepared using DMU + l-(+)-tartaric acid as deep eutectic solvent. DFT calculations supported the experimental results on role of DES as catalyst. The absorption-emission spectra indicating that these compounds can be useful as fluorescent probes.

Pyridine appended 2-hydrazinylthiazole derivatives: design, synthesis, in vitro and in silico antimycobacterial studies

An array of pyridine appended 2-hydrazinylthiazole derivatives has been synthesized to discover novel chemotherapeutic agents for Mycobacterium tuberculosis (Mtb). The drug-likeness of pyridine appended 2-hydrazinylthiazole derivatives was validated using the Lipinski and Veber rules. The designed thiazole molecules have been synthesized through Hantzsch thiazole methodologies. The in vitro antimycobacterial studies have been conducted using Luciferase reporter phage (LRP) assay. Out of thirty pyridine appended 2-hydrazinylthiazole derivatives, the compounds 2b, 3b, 5b, and 8b have exhibited good antimycobacterial activity against Mtb, an H37Rv strain with the minimum inhibitory concentration in the range of 6.40–7.14 μM. In addition, in vitro cytotoxicity of active molecules has been observed against Human Embryonic Kidney Cell lines (HEK293t) using MTT assay. The compounds 3b and 8b are nontoxic and their cell viability is 87% and 96.71% respectively. The in silico analyses of the pyridine appended 2-hydrazinylthiazole derivatives have been studied to find the mode of binding of the active compounds with KasA protein of Mtb. The active compounds showed a strong binding score (−5.27 to −6.23 kcal mol⁻¹).

Thirty novel pyridine-appended 2-hydrazinylthiazole derivatives have been synthesized and tested for their antimycobacterial activity against Mictrobactrium tuberculosis, H37Rv strain.

Advances in the application of 1,2,4-triazole-containing hybrids as anti-tuberculosis agents

Tuberculosis is a deadly communicable disease caused by the bacillus Mycobacterium tuberculosis (MTB), and pulmonary tuberculosis accounts for over 80% of the total cases. The 1,2,4-triazole is a privileged structure in the discovery of new drugs, and its derivatives act on various targets in MTB. In particular, 1,2,4-triazole hybrids can not only exert dual or multiple antitubercular mechanisms of action but also have the potential to enhance efficacy and reduce side effects. The present work aims to summarize the current status of 1,2,4-triazole hybrids as potential antitubercular agents, covering articles published between 2010 and 2020, to aid the further rational design of novel potential drug candidates endowed with higher efficacy, better compliance and fewer side effects.

Synthesis of new 7-amino-3,4-dihydroquinolin-2(1H)-one-peptide derivatives and their carbonic anhydrase enzyme inhibition, antioxidant, and cytotoxic activities

Six new monopeptides, seven new dipeptides, and two deprotected monopeptide dihydroquinolinone conjugates were prepared by the benzothiazole-mediated method and their structures were confirmed by nuclear magnetic resonance, mass, infrared spectroscopy, and elemental analysis methods. The human carbonic anhydrase (hCA) I and hCA II enzyme inhibition activities of the compounds were determined using the stopped-flow instrument. The synthesized peptide-dihydroquinolinone conjugates 2, 3, 6, 10, 13, and 15 showed inhibition against the hCA II enzyme in the range of 15.7-65.7 µM. However, none of the compounds showed inhibition of hCA I at a concentration of 100 µM. The antioxidant activities of the compounds were also examined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method at concentrations of 12.5-125 µg/ml, but when compared with the standard antioxidant compounds α-tocopherol and butylated hydroxyanisole (BHA), weak antioxidant activities were detected. The cytotoxic effects of four compounds against the A549 and BEAS-2B cell lines were also investigated. Among the compounds studied, compound 7 was found to be most effective, with the IC₅₀ values on the A549 cells for 48 and 72 h being 26.87 and 9.979 µg/ml, respectively, and the IC₅₀ values on the BEAS-2B cells being >100 µg/ml. None of the tested compounds showed antimicrobial activity in the concentration range (800-1.56 µg/ml) studied.

Iodothiophenes and Related Compounds as Coupling Partners in Copper-Mediated N-Arylation of Anilines

N-Arylation of various 2-acylated anilines with different electron-rich heteroaryl iodides (2- and 3-iodothiophenes, 2- and 3-iodobenzothiophenes­, 2-iodobenzofuran) was achieved by using activated copper and potassium carbonate in dibutyl ether at reflux. The reactivity of the different heteroaryl iodides and anilines employed was discussed and rationalized on the basis of their electronic features. Subsequent cyclization by aromatic electrophilic substitution easily took place in the case of C2-free (benzo)thienyl or C3-free (benzo)furyl derivatives­, affording original tri- and tetracycles. The antiproliferative activity of most of them was evaluated in A2058 melanoma cells and revealed four chlorinated tetracycles as effective growth inhibitors.

Triazole-containing hybrids with anti-Mycobacterium tuberculosis potential - Part I: 1,2,3-Triazole

Tuberculosis regimens currently applied in clinical practice require months of multidrug therapy, which imposes a major challenge of patient compliance and drug resistance development. Moreover, because of the increasing emergence of hard-to-treat tuberculosis, this disease continues to be a significant threat to the human population. 1,2,3-triazole as a privileged structure has been widely used as an effective template for drug discovery, and 1,2,3-triazole-containing hybrids that can simultaneously act on dual or multiple targets in Mycobacterium tuberculosis have the potential to circumvent drug resistance, enhance efficacy, reduce side effects and improve pharmacokinetic as well as pharmacodynamic profiles. Thus, 1,2,3-triazole-containing hybrids are useful scaffolds for the development of antitubercular agents. This review aims to highlight recent advances of 1,2,3-triazole-containing hybrids with potential activity against various forms of M. tuberculosis, covering articles published between 2015 and 2020. The structure-activity relationship and the mechanism of action are also discussed to facilitate further rational design of more effective drug candidates.

Preparation, carbonic anhydrase enzyme inhibition and antioxidant activity of novel 7-amino-3,4-dihydroquinolin-2(1H)-one derivatives incorporating mono or dipeptide moiety

New dipeptide–dihydroquinolinone derivatives were successfully synthesised by benzotriazole mediated nucleophilic acyl substitution reaction and their structures were elucidated by spectroscopic and analytic techniques. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was determined against four human (h) isoforms, hCA I, hCA II, hCA IX and hCA XII. While all compounds showed moderate to good in vitro CA inhibitory properties against hCA IX and hCA XII with inhibition constants in the micromolar level (37.7–86.8 and 2.0–8.6 µM, respectively), they did not show inhibitory activity against hCA I and hCA II up to 100 µM concentration. The antioxidant capacity of the peptide–dihydroquinolinone conjugates was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. Most of the synthesised compounds showed low antioxidant activities compared to the control antioxidant compounds BHA and α-tocopherol.

Synthesis, Structure-Activity Relationship, and Mechanistic Studies of Aminoquinazolinones Displaying Antimycobacterial Activity

Phenotypic whole-cell screening against Mycobacterium tuberculosis (Mtb) in glycerol–alanine–salts supplemented with Tween 80 and iron (GASTE-Fe) media led to the identification of a 2-aminoquinazolinone hit compound, sulfone 1 which was optimized for solubility by replacing the sulfone moiety with a sulfoxide 2. The synthesis and structure–activity relationship (SAR) studies identified several compounds with potent antimycobacterial activity, which were metabolically stable and noncytotoxic. Compound 2 displayed favorable in vitro properties and was therefore selected for in vivo pharmacokinetic (PK) studies where it was found to be extensively metabolized to the sulfone 1. Both derivatives exhibited promising PK parameters; however, when 2 was evaluated for in vivo efficacy in an acute TB infection mouse model, it was found to be inactive. In order to understand the in vitro and in vivo discrepancy, compound 2 was subsequently retested in vitro using different Mtb strains cultured in different media. This revealed that activity was only observed in media containing glycerol and led to the hypothesis that glycerol was not used as a primary carbon source by Mtb in the mouse lungs, as has previously been observed. Support for this hypothesis was provided by spontaneous-resistant mutant generation and whole genome sequencing studies, which revealed mutations mapping to glycerol metabolizing genes indicating that the 2-aminoquinazolinones kill Mtb in vitro via a glycerol-dependent mechanism of action.

Superacid-promoted synthesis of quinoline derivatives

A series of vinylogous imines have been prepared from anilines and cinnamaldehydes. These substrates react in superacidic media to provide quinolines and related compounds. A mechanism for the conversion is proposed which involves the cyclization of dicationic superelectrophilic intermediates. Aromatization of the quinoline ring is thought to occur by superacid-promoted elimination of benzene.

Synthesis of 3-sulfonylquinolines by visible-light promoted metal-free cascade cycloaddition involving N-propargylanilines and sodium sulfinates

A visible-light promoted radical cascade reaction of N-propargylanilines with sodium sulfinates as sulfonyl radical precursors was developed under metal-free conditions.

Copper-catalyzed cross-coupling and sequential allene-mediated cyclization for the synthesis of 1,2,3-triazolo[1,5-a]quinolines

In this paper, a tandem reaction involving copper-catalyzed cross-coupling and allene-mediated cyclization of 1-(2-ethynylaryl)-1,4-disubstituted-1,2,3-triazole with N-tosylhydrazone has been developed. This method features operational simplicity, excellent functional group compatibility, broad substrate scope, and easily available feedstock, providing an efficient and practical strategy for the synthesis of highly functionalized 1,2,3-triazolo[1,5-a]quinolines.

de Oliveira JP, A. Vasconcellos MLA, Zanatta N, G. Bonacorso H, Martins MAP. Substituent effects on the crystallization mechanisms of 7-chloro-4-substituted-quinolines

The crystallization mechanisms of a series of fourteen 7-chloro-4-substituted-quinolines were proposed based on a retrocrystallization approach using the supramolecular cluster as demarcation.

AgBF4-catalyzed deoxygenative C2-amination of quinoline N-oxides with isothiocyanates

A general, effective and convenient protocol for the direct synthesis of various 2-aminoquinolines (39 examples) through AgBF₄-catalyzed amination of quinoline N-oxides with isothiocyanates under base-, oxidant-free and mild conditions was developed.

Fluoroquinolone-isatin hybrids and their biological activities

Hybridization of different pharmacophores from various bioactive substances into a single molecule is the potential weapon to prevent the drug resistance since this strategy can provide new leads with complimentary activities and/or multiple pharmacological targets. Fluoroquinolone and isatin are common pharmacophores, and their derivatives possess various biological activities. Obviously, hybridization of these two pharmacophores into one molecule may result in novel candidates with broader spectrum, higher efficiency, lower toxicity as well as multiple mechanisms of action. Therefore, fluoroquinolone-isatin hybrids have the potential for clinical deployment in the control and eradication of various diseases. This review covers the recent advances of fluoroquinolone-isatin hybrids as potential anti-bacterial, anti-tubercular, anti-viral and anti-cancer agents. The structure-activity relationship is also discussed to pave the way for the further rational development of this kind of hybrids.