Direct Construction of 1,4-Dihydropyridazines and Pyrazoles via Annulation of Alkyl 2-Aroyl-1-chlorocyclopropanecarboxylates

An efficient and chemodivergent synthesis of highly functionalized 1,4-dihydropyridazines and pyrazoles has been accomplished via base-promoted annulation between hydrazones and alkyl 2-aroyl-1-chlorocyclopropanecarboxylates, respectively. This transition-metal-free domino reaction proceeded rapidly under mild basic conditions, affording potentially bioactive 1,4-dihydropyridazine and pyrazole derivatives in moderate yields. The conversion of 1,4-dihydropyridazine to pyrazole was confirmed by adjusting the quantity of the base.

Novel Small Molecule Growth Inhibitors of Xanthomonas spp. Causing Bacterial Spot of Tomato

Bacterial spot (BS) of tomato, caused by Xanthomonas gardneri, X. perforans, X. vesicatoria, and X. euvesicatoria, is difficult to control because of the high prevalence of copper- and streptomycin-resistant strains and the lack of resistance cultivars and effective bactericides. The objective of this study was to identify novel growth inhibitors of BS-causing Xanthomonas (BS-X) species by using small molecules (SM; n = 4,182). Several SMs (X1, X2, X5, X9, X12, and X16) completely inhibited the growth of BS-X isolates (n = 68 X. gardneri, 55 X. perforans, 4 X. vesicatoria, and 32 X. euvesicatoria) at ≥12.5 µM by disrupting Xanthomonas cell integrity through weakening of the cell membrane and formation of pores. These SMs were also effective against biofilm-embedded, copper- and streptomycin-resistant Xanthomonas strains while having minimal impact on other plant pathogenic (n = 20) and beneficial bacteria (n = 12). Furthermore, these SMs displayed equivalent antimicrobial activity against BS-X in seeds and X. gardneri in seedlings compared with conventional control methods (copper sulfate and streptomycin) at similar concentrations while having no detectable toxicity to tomato tissues. SMs X2, X5, and X12 reduced X. gardneri, X. perforans, X. vesicatoria, and X. euvesicatoria populations in artificially infested seeds ≤3.4-log CFU/seed 1 day postinfection (dpi) compared with the infested untreated control (P ≤ 0.05). SMs X1, X2, X5, and X12 reduced disease severity ≤72% and engineered bioluminescent X. gardneri populations ≤3.0-log CFU/plant in infected seedlings at 7 dpi compared with the infected untreated control (P ≤ 0.05). Additional studies are needed to increase the applicability of these SMs for BS management in tomato production.

Chemoselective synthesis of fully substituted pyrroles via a one-pot four-component isocyanide-based reaction

Small-ring heterocycles comprising pyrrole and pyrazole are well known for their rich biological properties. In this article, an efficient green sonochemical approach was designed for the synthesis of novel, fully substituted pyrroles connected to pyrazole scaffolds via a one-pot, four-component isocyanide-based sequential reaction. This reaction was carried out using various 5-amino-pyrazoles, aldehydes, dialkyl acetylenedicarboxylates and isocyanides for the synthesis of fully functionalized pyrroles with high chemoselectivity in the presence of a catalytic amount of PTSA·H2O, in good to excellent yields under ultrasound irradiation. This waste-free (-H2O) reaction exhibited a high atom economy and step economy via creating four new bonds, including two C-N and two C-C bonds, and the formation of two five-member heterocycles which are connected in a single operation. The mechanism of this four-component domino process involved sequential imination-dipolar cyclization-[1,5]-H shift reactions. The synthesized compounds possess interesting fluorescence features, and the bioactive scaffolds might attract great interest in the fields of clinical diagnostics and biomedical research in the future.

Recent advancements in the medicinal chemistry of bacterial type II topoisomerase inhibitors

Replication proteins are sought as a potential targets for antimicrobial agents. Despite their promising target characteristics, only topoisomerase II inhibitors targeting DNA gyrase and/or topoisomerase IV have reached clinical use. Topoisomerases are the enzymes that are essential for cellular functions and various biological activities. A wide range of natural and synthetic compounds have been identified as potential topoisomerase inhibitors but the resistance is most commonly found in these drugs. The emergence of FQ resistance has increased the need for the development of novel topoisomerase inhibitors with efficacy and high potency against FQ-resistant strains. Besides structural modifications of existing FQ scaffolds, novel non-quinolone topoisomerase II inhibitors, known as novel bacterial topoisomerase inhibitors, have been developed which showed remarkable inhibitory activity against DNA gyrase/topoisomerase IV or both with an improved spectrum of antibacterial potency including drug-resistant strains. This review aims to summarize various recent advancements in the medicinal chemistry of topoisomerase inhibitors with the following objectives: (1) To represent inclusive data on types of topoisomerases and various marketed topoisomerase inhibitors as drugs; (2) To discuss the recent advances in the medicinal chemistry of various topoisomerase inhibitors (DNA gyrase and topo IV) belonging to different structural classes as potential antibacterial agents; (3) To summarizes the structure activity relationship (SAR) including in silico and mechanistic studies to afford ideas and to provide focused direction for the development of new chemical entities which are effective against drug-resistant bacterial pathogens and biofilms.

Recent advancements in the development of bioactive pyrazoline derivatives

Pyrazolines remain privileged heterocycles in drug discovery. 2-Pyrazoline scaffold has been proven as a ubiquitous motif which is present in a number of pharmacologically important drug molecules such as antipyrine, ramifenazone, ibipinabant, axitinib etc. They have been widely explored by the scientific community and are reported to possess wide spectrum of biological activities. For combating unprecedented diseases and worldwide increasing drug resistance, 2-pyrazoline has been tackled as a fascinating pharmacophore to generate new molecules with improved potency and lesser toxicity along with desired pharmacokinetic profile. This review aims to summarizes various recent advancements in the medicinal chemistry of pyrazoline based compounds with the following objectives: (1) To represent inclusive data on pyrazoline based marketed drugs as well as therapeutic candidates undergoing preclinical and clinical developments; (2) To discuss recent advances in the medicinal chemistry of pyrazoline derivatives with their numerous biological significances for the eradication of various diseases; (3) Summarizes structure-activity relationships (SAR) including in silico and mechanistic studies to afford ideas for the design and development of novel compounds with desired therapeutic implications.

Synthesis, structure, photophysical, electrochemical properties and antibacterial activity of brominated BODIPYs as an inhibitor of DNA gyrase B of S. aureus

BODIPYs with 3-thienyl and 4-acetamido phenyl groups substituted at the meso-position are subjected to regioselective bromination using three equivalents of [Formula: see text]-bromosuccinimide (NBS) to yield their 2-mono and 2,6-di bromoderivatives. Their photophysical, electrochemical and antimicrobial properties are investigated. This paper presents a mechanistic investigation of the antibacterial effect of brominated BODIPYs, particularly against Staphylococcus aureus. Fluorescence microscopic images reveal that the compounds are internalized effectively within the bacterial cells, making it an ideal antibacterial drug. Morphological analysis of the bacterial cells after the treatment with the test compounds showed that the compounds did not affect the cell membrane or cell wall and the antibacterial effect of these compounds is achieved via a different mechanism. The most effective compound was selected to explore the target of action. Molecular docking studies were performed on 22 selected proteins in S. aureus and the in silico results were validated by in vitro experiments. It was observed that the supercoiling activity of DNA gyrase was completely inhibited by the 2,6-dibromo-1,3,5,7-tetramethyl-8-(4-acetamido)-4-bora-3a,4a-diaza-[Formula: see text]-indacene, 3c by forming H-bonds with the ASP 81 residue of the enzyme.

A novel multicomponent quadruple/double quadruple domino reaction: highly efficient synthesis of polyheterocyclic architectures

A novel multicomponent quadruple domino reaction (MCQDR) for the assembly of structurally complex molecular architectures via the formation of three rings and three contiguous stereogenic centers has been accomplished with high regio- and diastereoselectivity. Solvents, catalysts and work-up were not required to obtain the target molecules. In addition, this new protocol is also extended for the multicomponent double quadruple domino reaction (MCDQDR) to create novel polyheterocyclic architectures in an orthogonal manner.

Design, Synthesis, and Evaluation of Novel Tyrosine-Based DNA Gyrase B Inhibitors

The discovery and synthesis of new tyrosine-based inhibitors of DNA gyrase B (GyrB), which target its ATPase subunit, is reported. Twenty-four compounds were synthesized and evaluated for activity against DNA gyrase and DNA topoisomerase IV. The antibacterial properties of selected GyrB inhibitors were demonstrated by their activity against Staphylococcus aureus and Enterococcus faecalis in the low micromolar range. The most promising compounds, 8a and 13e, inhibited Escherichia coli and S. aureus GyrB with IC₅₀ values of 40 and 30 µM. The same compound also inhibited the growth of S. aureus and E. faecalis with minimal inhibitory concentrations (MIC₉₀ ) of 14 and 28 µg/mL, respectively.

Review: biologically active pyrazole derivatives

Nitrogen-containing heterocyclic compounds and their derivatives have historically been invaluable as a source of therapeutic agents.

AgNO2 as the NO Source for the Synthesis of Substituted Pyrazole N-Oxides from N-Propargylamines

A straightforward method for synthesizing the pyrazole N-oxides from N-propargylamines and AgNO₂ through oxidation/cyclization reaction had been developed. AgNO₂ was used as the NO source for the first time to synthesize pyrazole N-oxides. Various substituted groups on N-propargylamines proceeded smoothly, and the desired products were obtained in good yields.

Radical Addition of Hydrazones by α-Bromo Ketones To Prepare 1,3,5-Trisubstituted Pyrazoles via Visible Light Catalysis

A novel efficient tandem reaction of hydrazones and α-bromo ketones is reported for the preparation of 1,3,5-trisubstituted pyrazoles by visible light catalysis. In this system, the monosubstituted hydrazones show wonderful reaction activity with alkyl radicals, generated from α-bromo ketones. A radical addition followed by intramolecular cyclization affords the important pyrazole skeleton in good to excellent yields. This efficient strategy under mild conditions with wide group tolerance provides a potential approach to the 1,3,5-trisubstituted pyrazoles.

Amphiphilic cationic copolymers with ciprofloxacin: preparation and antimicrobial activities

Amphiphilic copolymers with ciprofloxacin and primary amine salt copolymers applied to cellulose fibers showed excellent antimicrobial activities.

Benzo[α]phenoxazines and benzo[α]phenothiazine from vitamin K3: synthesis, molecular structures, DFT studies and cytotoxic activity

Novel benzo[α]phenoxazines and benzo[α]phenothiazine from vitamin K3 are cytotoxic against HeLa, MCF-7 cell lines and potential topoisomerase II inhibitors.

Dihydropyrazoles containing morpholine: design, synthesis and bioassay testing as potent antimicrobial agents

A series of dihydropyrazole derivatives were designed and synthesized as antimicrobial agents. In both docking simulation and bioassay tests, these compounds showed potent S. aureus TyrRS enzyme inhibition activity.