Enhancement by pyrazolones of colistin efficacy against mcr-1-expressing E. coli: an in silico and in vitro investigation.

Owing to the emergence of antibiotic resistance, the polymyxin colistin has been recently revived to treat acute, multidrug-resistant Gram-negative bacterial infections. Positively charged colistin binds to negatively charged lipids and damages the outer membrane of Gram-negative bacteria. However, the MCR-1 protein, encoded by the mobile colistin resistance (mcr) gene, is involved in bacterial colistin resistance by catalysing phosphoethanolamine (PEA) transfer onto lipid A, neutralising its negative charge, and thereby reducing its interaction with colistin. Our preliminary results showed that treatment with a reference pyrazolone compound significantly reduced colistin minimal inhibitory concentrations in Escherichia coli expressing mcr-1 mediated colistin resistance (Hanpaibool et al. in ACS Omega, 2023). A docking-MD combination was used in an ensemble-based docking approach to identify further pyrazolone compounds as candidate MCR-1 inhibitors. Docking simulations revealed that 13/28 of the pyrazolone compounds tested are predicted to have lower binding free energies than the reference compound. Four of these were chosen for in vitro testing, with the results demonstrating that all the compounds tested could lower colistin MICs in an E. coli strain carrying the mcr-1 gene. Docking of pyrazolones into the MCR-1 active site reveals residues that are implicated in ligand-protein interactions, particularly E246, T285, H395, H466, and H478, which are located in the MCR-1 active site and which participate in interactions with MCR-1 in ≥ 8/10 of the lowest energy complexes. This study establishes pyrazolone-induced colistin susceptibility in E. coli carrying the mcr-1 gene, providing a method for the development of novel treatments against colistin-resistant bacteria.

Pyrazolones Potentiate Colistin Activity against MCR-1-Producing Resistant Bacteria: Computational and Microbiological Study.

The polymyxin colistin is a last line antibiotic for extensively resistant Gram-negative bacteria. Colistin binding to lipid A disrupts the Gram-negative outer membrane, but mobile colistin resistance (mcr) gene family members confer resistance by catalyzing phosphoethanolamine (PEA) transfer onto lipid A, neutralizing its negative charge to reduce colistin interactions. Multiple mcr isoforms have been identified in clinical and environmental isolates, with mcr-1 being the most widespread and mcr-3 being common in South and East Asia. Preliminary screening revealed that treatment with pyrazolones significantly reduced mcr-1, but not mcr-3, mediated colistin resistance. Molecular dynamics (MD) simulations of the catalytic domains of MCR-1 and a homology model of MCR-3, in different protonation states of active site residues H395/H380 and H478/H463, indicate that the MCR-1 active site has greater water accessibility than MCR-3, but that this is less influenced by changes in protonation. MD-optimized structures of MCR-1 and MCR-3 were used in virtual screening of 20 pyrazolone derivatives. Docking of these into the MCR-1/MCR-3 active sites identifies common residues likely to be involved in protein-ligand interactions, specifically the catalytic threonine (MCR-1 T285, MCR-3 T277) site of PEA addition, as well as differential interactions with adjacent amino acids. Minimal inhibitory concentration assays showed that the pyrazolone with the lowest predicted binding energy (ST3f) restores colistin susceptibility of mcr-1, but not mcr-3, expressing Escherichia coli. Thus, simulations indicate differences in the active site structure between MCR-1 and MCR-3 that may give rise to differences in pyrazolone binding and so relate to differential effects upon producer E. coli. This work identifies pyrazolones as able to restore colistin susceptibility of mcr-1-producing bacteria, laying the foundation for further investigations of their activity as phosphoethanolamine transferase inhibitors as well as of their differential activity toward mcr isoforms.

Iridium(I) complexes with bidentate NHC ligands as catalysts for dehydrogenative directed C-H silylation.

A series of (NHC)(cod)Ir(I) complexes bearing NHC-carboxylate ligands were efficiently synthesized and fully characterized. Their solid-state structures confirmed the bidentate coordination mode of these LX-type NHC ligands. These unprecedented iridium(I) complexes demonstrated efficient catalytic activities in dehydrogenative directed C-H silylation of arenes, and allowed for excellent ortho-selectivity control with aromatic silylating agents.

Quinoxalinones as A Novel Inhibitor Scaffold for EGFR (L858R/T790M/C797S) Tyrosine Kinase: Molecular Docking, Biological Evaluations, and Computational Insights.

Combating acquired drug resistance of EGFR tyrosine kinase (TK) is a great challenge and an urgent necessity in the management of non-small cell lung cancers. The advanced EGFR (L858R/T790M/C797S) triple mutation has been recently reported, and there have been no specific drugs approved for this strain. Therefore, our research aimed to search for effective agents that could impede the function of EGFR (L858R/T790M/C797S) TK by the integration of in silico and in vitro approaches. Our in-house quinoxalinone-containing compounds were screened through molecular docking and their biological activity was then verified by enzyme- and cell-based assay. We found that the four quinoxalinone-containing compounds including CPD4, CPD15, CPD16, and CPD21 were promising to be novel EGFR (L858R/T790M/C797S) TK inhibitors. The IC50 values measured by the enzyme-based assay were 3.04 ± 1.24 nM; 6.50 ± 3.02 nM,10.50 ± 1.10 nM; and 3.81 ± 1.80 nM, respectively, which are at a similar level to a reference drug; osimertinib (8.93 ± 3.01 nM). Besides that, they displayed cytotoxic effects on a lung cancer cell line (H1975) with IC50 values in the range of 3.47 to 79.43 µM. In this proposed study, we found that all screened compounds could interact with M793 at the hinge regions and two mutated residues including M790 and S797; which may be the main reason supporting the inhibitory activity in vitro. The structural dynamics revealed that the screened compounds have sufficient non-native contacts with surrounding amino acids and could be well-buried in the binding site's cleft. In addition, all predicted physicochemical parameters were favorable to be drug-like based on Lipinski's rule of five, and no extreme violation of toxicity features was found. Altogether, this study proposes a novel EGFR (L858R/T790M/C797S) TK inhibitor scaffold and provides a detailed understanding of compounds' recognition and susceptibility at the molecular level.

Ruthenium-NHC complex-catalyzed P(III)-directed C-H borylation of arylphosphines.

(NHC)(arene)Ru(II) complexes with bidentate LX-type NHC-carboxylate ligands were efficiently synthesized and fully characterized including solid-state structures. The strong coordination of the NHC carboxylate ligand and the labile character of the arene ligand are highlighted. These unprecedented Ru(II) complexes demonstrated efficient catalytic activities in the selective P(III)-directed C-H borylation at the ortho position of arylphosphines, representing the first report of the use of a ruthenium-NHC based catalyst in C-H borylation.

Discovery of JAK2/3 Inhibitors from Quinoxalinone-Containing Compounds.

Janus kinases (JAKs) are involved in a wide variety of cell signaling associated with T-cell and B-cell mediated diseases. The pathogenesis of common lymphoid-derived diseases and leukemia cancer has been implicated in JAK2 and JAK3. Therefore, to decrease the risk of these diseases, targeting this pathway using JAK2/3 inhibitors could serve as a valuable research tool. Herein, we used a combination of the computational and biological approaches to identify the quinoxalinone-based dual inhibitors of JAK2/3. First, an in-house library of 49 quinoxalinones was screened by molecular docking. Then, the inhibitory activities of 17 screened compounds against both JAKs as well as against two human erythroleukemia cell lines, TF1 and HEL were examined. The obtained results revealed that several quinoxalinones could potentially inhibit JAK2/3, and among them, ST4j showed strong inhibition against JAKs with the IC50 values of 13.00 ± 1.31 nM for JAK2 and 14.86 ± 1.29 nM for JAK3, which are better than ruxolitinib and tofacitinib. In addition, ST4j potentially inhibited TF1 cells (IC50 of 15.53 ± 0.82 µM) and HEL cells (IC50 of 17.90 ± 1.36 µM), similar to both tofacitinib ruxolitinib. Mechanistically, ST4j inhibited JAK2 autophosphorylation and induced cell apoptosis in dose- and time-dependent manners. From molecular dynamics simulations, ST4j was mainly stabilized by van der Waals interactions, and its hydroxyl group could form hydrogen bonds in the hinge region at residues S936 and R938 of JAK2. This research highlights the potential of ST4j to be a novel therapeutic agent for the treatment of lymphoid-derived diseases and leukemia cancer.

Pharmacophore-Based Virtual Screening and Experimental Validation of Pyrazolone-Derived Inhibitors toward Janus Kinases.

Janus kinases (JAKs) are nonreceptor protein tyrosine kinases that play a role in a broad range of cell signaling. JAK2 and JAK3 have been involved in the pathogenesis of common lymphoid-derived diseases and leukemia cancer. Thus, inhibition of both JAK2 and JAK3 can be a potent strategy to reduce the risk of these diseases. In the present study, the pharmacophore models built based on the commercial drug tofacitinib and the JAK2/3 proteins derived from molecular dynamics (MD) trajectories were employed to search for a dual potent JAK2/3 inhibitor by a pharmacophore-based virtual screening of 54 synthesized pyrazolone derivatives from an in-house data set. Twelve selected compounds from the virtual screening procedure were then tested for their inhibitory potency against both JAKs in the kinase assay. The in vitro kinase inhibition experiment indicated that compounds 3h, TK4g, and TK4b can inhibit both JAKs in the low nanomolar range. Among them, the compound TK4g showed the highest protein kinase inhibition with the half-maximal inhibitory concentration (IC50) value of 12.61 nM for JAK2 and 15.80 nM for JAK3. From the MD simulations study, it could be found that the sulfonamide group of TK4g can form hydrogen bonds in the hinge region at residues E930 and L932 of JAK2 and E903 and L905 of JAK3, while van der Waals interaction also plays a dominant role in ligand binding. Altogether, TK4g, found by virtual screening and biological tests, could serve as a novel therapeutical lead candidate.

Metal-free regioselective direct thiolation of 2-pyridones.

A highly regioselective metal-free direct C-H thiolation of 2-pyridones with disulfides or thiols has been developed. A combination of persulfate and a commercially available halide source such as LiCl, NCS or I2 enables the successful direct incorporation of a sulfide moiety into the 5-position of pyridone under mild conditions, providing a useful and convenient approach for the preparation of a diverse array of 5-thio-substituted pyridones in moderate to excellent yields.

Persulfate-promoted oxidative C-N bond coupling of quinoxalinones and NH-sulfoximines.

The persulfate-meditated oxidative C-N bond coupling of the C-H bond of quinoxalinones and the N-H bond of NH-sulfoximines is reported. The reaction proceeds smoothly under transition metal-free conditions and provides good to excellent yields of sulfoximidoyl-functionalized quinoxalinone products under mild conditions. The optimized conditions were found to be suitable for a range of sulfoximine and quinoxalinone substrates. This reaction offers a new and convenient strategy to directly install the sulfoximine moiety into the C3 position of quinoxalinone.

DABCO-catalyzed silver-promoted direct thiolation of pyrazolones with diaryl disulfides.

A highly efficient protocol for a direct thiolation of N-substituted pyrazolones with diaryl disulfides is described. Using a combination of DABCO and silver(i) acetate, the C-S bond formation proceeds smoothly at room temperature under mild and easy to handle conditions. This synthetic strategy offers a convenient and direct modification of antipyrine and other pyrazolone substrates, giving a series of aryl sulfide-substituted pyrazolone products in moderate to excellent yields.

Copper-catalyzed oxidative decarboxylative coupling of α-keto acids and sulfoximines.

A copper-catalyzed oxidative decarboxylative coupling of α-keto acids with NH-sulfoximines has been developed. With CuBr as the catalyst and K2S2O8 as the oxidant, this reaction enables the formation of a C-N bond and gives N-aroylsulfoximine products in moderate to excellent yields. The reaction mechanism is likely to involve the generation of a reactive aroyl radical intermediate.

Iodine-catalyzed expeditious synthesis of sulfonamides from sulfonyl hydrazides and amines.

A new synthesis of sulfonamides has been developed via an iodine-catalyzed sulfonylation of amines with arylsulfonyl hydrazides. This metal-free strategy employs readily accessible and easy to handle starting materials, catalysts and oxidants, and can be easily conducted under mild conditions, providing a convenient access to a wide range of sulfonamides in moderate to excellent yields within a short reaction time.

Iodine-catalyzed oxidative cross-coupling of indoles and azoles: regioselective synthesis of N-linked 2-(azol-1-yl)indole derivatives.

A highly efficient iodine-catalyzed regioselective oxidative cross-coupling of an indole C-H bond and azole N-H bond is described. This metal-free reaction can be easily carried out at room temperature under mild and environmentally friendly conditions and provides a series of N-linked 2-(azol-1-yl)indole derivatives in moderate to excellence yields.

Synthesis of multicyclic pyridine and quinoline derivatives via intramolecular C-H bond functionalization.

An efficient method is reported for the preparation of multicyclic pyridines and quinolines by a rhodium-catalyzed intramolecular C-H bond functionalization process. The method shows good scope for branched and unbranched alkyl substituents on the pyridine ring and at the R position of the tethered alkene group. Starting materials capable of undergoing olefin isomerization to provide terminal 1,1-disubstituted alkenes also proved to be effective substrates.

Application of Daugulis copper-catalyzed direct arylation to the synthesis of 5-aryl benzotriazepines.

A method for the direct arylation of benzotriazepines is reported, employing an aryl iodide as the coupling partner, copper iodide as the catalyst, and lithium tert-butoxide as the base. A variety of electron-rich, electron-poor, and sterically hindered aryl iodides are compatible with the reaction conditions. The arylation reaction can also be performed outside a glovebox in air without a significant decrease in yield. Furthermore, convenient microwave conditions for carrying out this transformation are reported.

The use of aminoglycoside derivatives to study the mechanism of aminoglycoside 6'-N-acetyltransferase and the role of 6'-NH2 in antibacterial activity.

Aminoglycoside antibiotics act by binding to 16S rRNA. Resistance to these antibiotics occurs via drug modifications by enzymes such as aminoglycoside 6'-N-acetyltransferases (AAC(6')s). We report here the regioselective and efficient synthesis of N-6'-acylated aminoglycosides and their use as probes to study AAC(6')-Ii and aminoglycoside-RNA complexes. Our results emphasize the central role of N-6' nucleophilicity for transformation by AAC(6')-Ii and the importance of hydrogen bonding between 6'-NH(2) and 16S rRNA for antibacterial activity.