4(3H)-Quinazolinone derivatives: Promising antibacterial drug leads

Rhodium(III)-Catalyzed Annulation Synthesis of Difluorinated Quinazolinone Derivatives Using an Amide Carbonyl as the Directing Group

The use of amide carbonyl groups of substrates as weakly coordinating directing groups has received a significant amount of attention. Recently, difluoromethylene alkynes have been successfully used in fluorination reactions, resulting in the preparation of various fluorine-containing compounds. This work describes a [4+2] annulation method for creating a range of fluorinated quinolino[2,1-b]quinazolinone derivatives. The derivatives are formed through Rh(III)-catalyzed cascade cyclization of 3-phenylquinazolinones and gem-difluoromethylene alkynes.

Oxalic acid as a dual C1 surrogate for heterogeneous palladium-catalyzed tandem four-component quinazolinone synthesis

Herein, a heterogeneous Pd/C-catalyzed direct one-step four-component double carbonylative approach for cascade synthesis of 2-aryl quinazolinones has been reported for the first time starting from 2-iodoaniline derivatives and aryl iodides. The given reaction involves the simultaneous implementation of two different gaseous surrogates i.e., ammonium carbamate as an NH3 precursor and oxalic acid as a bi-functional reagent acting as a CO as well as a C-atom surrogate under ligand-free conditions.

Visible-light-induced three-component reactions of α-diazoesters, quinazolinones and cyclic ethers toward quinazoline-based hybrids

An effective approach for the construction of 4-short-chain ether attached carbonyl group-substituted quinazolines was developed. Visible-light-induced three-component reactions of α-diazoesters, quinazolinones, and cyclic ethers, with a broad substrate scope and excellent functional group tolerance, under extremely mild conditions without the need for any additional additives and catalysts, selectively led to quinazoline-based hybrids in good to excellent yields. The synthesized hybrids, which are a conglomeration of a quinazoline, a short-chain ether, and a carbonyl group in one molecular skeleton, have potential for application in the development of new drugs or drug candidates.

Design, synthesis, in-silico studies and apoptotic activity of novel amide enriched 2-(1H)- quinazolinone derivatives

Cancer is a broad classification of diseases that can affect any organ or body tissue due to aberrant cellular proliferation for unknown reasons. Many present chemotherapeutic drugs are highly toxic and have little selectivity. Additionally, they lead to the development of medication resistance. Therefore, developing tailored chemotherapeutic drugs with minimal side effects and good selectivity is crucial for cancer treatment. 2-(1H)-Quinazolinone is one of the vital scaffold and anticancer activity is one of the prominent biological activities of this class. Here we report the novel set of amide-enriched 2-(1H)-quinazolinone derivatives (7a-j) and their apoptotic activity with the help of MTT assay method against four human cancer cell lines: PC3 (prostate cancer), DU-145 (prostate cancer), A549 (lung cancer), and MCF7 (breast cancer). When compared to etoposide, every synthetic test compound (7a-j) exhibited moderate to excellent activity. The IC50 values of the new amide derivatives (7a-j) varied from 0.07 ± 0.0061 μM to 10.8 ± 0.69 μM. While the positive control, etoposide, exhibited 1.97 ± 0.45 μM to 3.08 ± 0.135 μM range. Among the novel amide derivatives (7a-j), in particular, 7i and 7j showed strong apoptotic activity against MCF7; 7h showed against PC3, and 7g showed against DU-145. Molecular docking studies of test compounds (7a-j) with the EGFR tyrosine kinase domain (PDB ID: 1M17) protein provided the significant docking scores for each test compound (7a-j) (-9.00 to -9.67 kcal/mol). Additionally, DFT investigations and MD simulations validated the predictions of molecular docking. According to the findings of the ADME analysis, oral absorption by humans is anticipated to be higher than 85 % for all test compounds.

Unveiling the Untapped Potential of Bertagnini's Salts in Microwave-Assisted Synthesis of Quinazolinones

Microwave-assisted organic synthesis (MAOS) has emerged as a transformative technique in organic chemistry, significantly enhancing the speed, efficiency, and selectivity of chemical reactions. In our research, we have employed microwave irradiation to expedite the synthesis of quinazolinones, using water as an eco-friendly solvent and thereby adhering to the principles of green chemistry. Notably, the purification of the product was achieved without the need for column chromatography, thus streamlining the process. A key innovation in our approach is using aldehyde bisulfite adducts (Bertagnini's salts) as solid surrogates of aldehydes. Bertagnini's salts offer several advantages over free aldehydes, including enhanced stability, easier purification, and improved reactivity. Green metrics and Eco-Scale score calculations confirmed the sustainability of this approach, indicating a reduction in waste generation and enhanced sustainability outcomes. This methodology facilitates the synthesis of a diverse array of compounds, offering substantial contributions to the field, with potential for widespread applications in pharmaceutical research and beyond.

Synthesis, In Vivo Anticonvulsant Activity Evaluation and In Silico Studies of Some Quinazolin-4(3H)-One Derivatives

Two series, "a" and "b", each consisting of nine chemical compounds, with 2,3-disubstituted quinazolin-4(3H)-one scaffold, were synthesized and evaluated for their anticonvulsant activity. They were investigated as dual potential positive allosteric modulators of the GABAA receptor at the benzodiazepine binding site and inhibitors of carbonic anhydrase II. Quinazolin-4(3H)-one derivatives were evaluated in vivo (D1-3 = 50, 100, 150 mg/kg, administered intraperitoneally) using the pentylenetetrazole (PTZ)-induced seizure model in mice, with phenobarbital and diazepam, as reference anticonvulsant agents. The in silico studies suggested the compounds act as anticonvulsants by binding on the allosteric site of GABAA receptor and not by inhibiting the carbonic anhydrase II, because the ligands-carbonic anhydrase II predicted complexes were unstable in the molecular dynamics simulations. The mechanism targeting GABAA receptor was confirmed through the in vivo flumazenil antagonism assay. The pentylenetetrazole experimental anticonvulsant model indicated that the tested compounds, 1a-9a and 1b-9b, present a potential anticonvulsant activity. The evaluation, considering the percentage of protection against PTZ, latency until the onset of the first seizure, and reduction in the number of seizures, revealed more favorable results for the "b" series, particularly for compound 8b.

Design and synthesis of new quinazolinone derivatives: investigation of antimicrobial and biofilm inhibition effects

New quinazolin-4-ones 9-32 were synthesized in an attempt to overcome the life-threatening antibiotic resistance phenomenon. The antimicrobial screening revealed that compounds 9, 15, 16, 18, 19, 20 and 29 are the most broad spectrum antimicrobial agents in this study with safe profile on human cell lines. Additionally, compounds 19 and 20 inhibited biofilm formation in Pseudomonas aeruginosa, which is regulated by quorum sensing system, at sub-minimum inhibitory concentrations (sub-MICs) with IC50 values 3.55 and 6.86 µM, respectively. By assessing other pseudomonal virulence factors suppression, it was found that compound 20 decreased cell surface hydrophobicity compromising bacterial cells adhesion, while both compounds 19 and 20 curtailed the exopolysaccharide production which constitutes the major component of the matrix binding biofilm components together. Also, at sub-MICs Pseudomonas cells twitching motility was impeded by compounds 19 and 20, a trait which augments the cells pathogenicity and invasion potential. Molecular docking study was performed to further evaluate the binding mode of candidates 19 and 20 as inhibitors of P. aeruginosa quorum sensing transcriptional regulator PqsR. The achieved results demonstrate that both compounds bear promising potential for discovering new anti-biofilm and quorum quenching agents against Pseudomonas aeruginosa without triggering resistance mechanisms as the normal bacterial life cycle is not disturbed.

A Phosphine-Free Air-Stable Mn(II)-Catalyst for Sustainable Synthesis of Quinazolin-4(3H)-ones, Quinolines, and Quinoxalines in Water

The synthesis, characterization, and catalytic application of a new phosphine-free, well-defined, water-soluble, and air-stable Mn(II)-catalyst [Mn(L)(H2O)2Cl](Cl) ([1]Cl) featuring a 1,10-phenanthroline based tridentate pincer ligand, 2-(1H-pyrazol-1-yl)-1,10-phenanthroline (L), in dehydrogenative functionalization of alcohols to various N-heterocycles such as quinazolin-4(3H)-ones, quinolines, and quinoxalines are reported here. A wide array of multisubstituted quinazolin-4(3H)-ones were prepared in water under air following two pathways via the dehydrogenative coupling of alcohols with 2-aminobenzamides and 2-aminobenzonitriles, respectively. 2-Aminobenzyl alcohol and ketones bearing active methylene group were used as coupling partners for synthesizing quinoline derivatives, and various quinoxaline derivatives were prepared by coupling vicinal diols and 1,2-diamines. In all cases, the reaction proceeded smoothly using our Mn(II)-catalyst [1]Cl in water under air, affording the desired N-heterocycles in satisfactory yields starting from cheap and readily accessible precursors. Gram-scale synthesis of the compounds indicates the industrial relevance of our synthetic strategy. Control experiments were performed to understand and unveil the plausible reaction mechanism.

Critical view on antimicrobial, antibiofilm and cytotoxic activities of quinazolin-4(3H)-one derived schiff bases and their Cu(II) complexes

A series of nine 2,3-disubstituted-quinazolin-4(3H)-one derived Schiff bases and their three Cu(II) complexes was prepared and tested for their antimicrobial activities against reference strains Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 and resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant E. faecalis (VRE). All the substances were tested in vitro against Mycobacterium tuberculosis H37Ra ATCC 25177, M. kansasii DSM 44162 and M. smegmatis ATCC 700084. While anti-enterococcal and antimycobacterial activities were insignificant, 3-[(E)-(2-hydroxy-5-nitrobenzylidene)amino]-2-(2-hydroxy-5-nitrophenyl)-2,3-dihydroquinazolin-4(1H)-one (SB3) and its Cu(II) complex (SB3-Cu) demonstrated bacteriostatic antistaphylococcal activity. In addition, both compounds, as well as the other two prepared complexes, showed antibiofilm activity, which resulted in a reduction of biofilm formation and eradication of mature S. aureus biofilm by 80% even at concentrations lower than the values of their minimum inhibitory concentrations. In addition, the compounds were tested for their cytotoxic effect on the human monocytic leukemia cell line THP-1. The antileukemic efficiency was improved by the preparation of Cu(II) complexes from the corresponding non-chelated Schiff base ligands.

Recent advances in developing modified C14 side chain pleuromutilins as novel antibacterial agents

Owing to the increasing resistance to most existing antimicrobial drugs, research has shifted towards developing novel antimicrobial agents with mechanisms of action distinct from those of current clinical options. Pleuromutilins are antibiotics known for their distinct mechanism of action, inhibiting bacterial protein synthesis by binding to the peptidyl transferase center of the ribosome. Recent studies have revealed that pleuromutilin derivatives can disrupt bacterial cell membranes, thereby enhancing antibacterial efficacy. Both marketed pleuromutilin derivatives and those in clinical trials have been developed by structurally modifying the pleuromutilin C14 side chain to improve their antimicrobial activity. Therefore, this review aims to review advancement in the chemical structural characteristics, antibacterial activities, and structure-activity relationship studies of pleuromutilins, specifically focusing on modifications made to the C14 side chain in recent years. These findings provide a valuable reference for future research and development of pleuromutilins.

Construction of Indium(III)-Organic Framework Based on a Flexible Cyclotriphosphazene-Derived Hexacarboxylate as a Reusable Green Catalyst for the Synthesis of Bioactive Aza-Heterocycles

The constant demand for eco-friendly methods of synthesizing complex organic compounds inspired researchers to design and develop modern, highly efficient heterogeneous catalytic systems. Herein, In-HCPCP metal-organic framework (SRMIST-1), a heterogeneous Lewis acid catalyst containing less toxic indium and eco-friendly robust cyclotriphosphazene and exhibiting notable chemical and thermal stability, durable catalytic activity, and exceptional reusability was produced through the reaction between indium(III) nitrate hydrate and hexakis(4-carboxylatophenoxy)-cyclotriphosphazene. In the SRMIST-1 structure, secondary building units {InO7} are assembled by a connection of η2- and η1-carboxylic oxo atoms from different HCPCP ligands, forming a three-dimensional network. The occurrence of regularly distributed In(III) sites in SRMIST-1 confers superior reactivity on the catalyst toward the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and 3,4-dihydro-2H-1,2,4-benzothiadiazine-1,1-dioxides by the cyclization reaction of 2-aminobenzamides and 2-aminobenzenesulphonamides with aldehydes under optimized reaction conditions, respectively. The notable features of this method include broad functional group compatibility, low catalyst loading (1-5 mol %), mild reaction conditions, easy workup procedures, good to excellent reaction yields, ethanol as a green solvent, reusability of the catalyst (five cycles), and economic attractiveness, which is mainly due to sustainability of SRMIST-1 as a reusable green catalyst. Our findings demonstrate that the highly reactive and reusable green catalyst finds widespread applications in medicinal chemistry.

Access to CF2COR-Containing Quinazolinones via Visible-Light-Induced Domino Difluoroalkylation/Cyclization of N-Cyanamide Alkenes

A green and highly efficient visible-light-induced radical cascade difluoroalkylation/cyclization reaction of N-cyanamide alkenes has been developed. A variety of CF2COR-containing quinazolinones have been obtained in high yields with cheap non-metallic 4CzIPN as the photocatalyst. This photocatalytic reaction provides rapid, facile, and practical access to valuable polycyclic quinazolinone, and it is amenable to the gram scale.

Cyclizations of Alkenyl(Alkynyl)-Functionalized Quinazolinones and their Heteroanalogues: A Powerful Strategy for the Construction of Polyheterocyclic Structures

Quinazolin-4-one, its heteroanalogues, and derivatives represent an outstandingly important class of compounds in modern organic, medicinal, and pharmaceutical chemistry, as these molecular structures are noted for their wide synthetic and pharmacological potential. In the last years, ever-increasing research attention has been paid to quinazolinone derivatives bearing alkenyl and alkynyl substituents on the pyrimidinone nucleus. The original structural combination of synthetically powerful endocyclic amidine (or amidine-related) and exocyclic unsaturated moieties provides a driving force for cyclizations, which offer an efficient toolkit to construct a variety of fused pyrimidine systems with saturated N- and N,S-heterocycles. In this connection, the present review article is mainly aimed at systematic coverage of the progress in using alkenyl(alkynyl)quinazolinones and their heteroanalogues as convenient bifunctional substrates for regioselective annulation of small- and medium-sized heterocyclic nuclei. Much attention is paid to elucidating the structural and electronic effects of reagents on the regio- and stereoselectivity of the cyclizations as well as to clarifying the relevant reaction mechanisms.

Synthesis of Selenium-Containing N-Quinazolinyl Acroleins via a 3,3-Radical Rearrangement Cascade Reaction

An effective approach for the construction of 2-aryl-3-(3-oxo-1-aryl-2-(organoselanyl)prop-1-en-1-yl)quinazolin-4(3H)-ones was developed. Excellent to almost quantitative yields were obtained by the cascade reaction of propargyl quinazoline-4-yl ethers, diselenides, and 70% tert-butyl hydrogen peroxide aqueous solution under metal-free and mild conditions. The synthesized hybrids, with conglomeration of quinazolinone, organoselenium, aldehyde, and fully substituted alkene moieties in one molecule, will have the potential for applications in development of new drugs or drug candidates.

Quinazoline-based VEGFR-2 inhibitors as potential anti-angiogenic agents: A contemporary perspective of SAR and molecular docking studies

Angiogenesis, the formation of new blood vessels from the existing vasculature, is pivotal in the migration, growth, and differentiation of endothelial cells in normal physiological conditions. In various types of tumour microenvironments, dysregulated angiogenesis plays a crucial role in supplying oxygen and nutrients to cancerous cells, leading to tumour size growth. VEGFR-2 tyrosine kinase has been extensively studied as a critical regulator of angiogenesis; thus, inhibition of VEGFR-2 has been widely used for cancer treatments in recent years. Quinazoline nucleus is a privileged and versatile scaffold with a broad range of pharmacological activity, especially in the field of tyrosine kinase inhibitors with more than twenty small molecule inhibitors approved by the US Food and Drug Administration in the last two decades. As of now, the U.S. FDA has approved eleven small chemical inhibitors of VEGFR-2 for various types of malignancies, with a prime example being vandetanib, a quinazoline derivative, which is a multi targeted kinase inhibitor used for the treatment of late-stage medullary thyroid cancer. Despite of prosperous discovery and development of VEGFR-2 down regulator drugs, there still exists limitations in clinical efficacy, adverse effects, a high rate of clinical discontinuation and drug resistance. Therefore, there is an urgent need for the design and synthesis of more selective and effective inhibitors to tackle these challenges. Through the gathering of this review, we have strived to broaden the extent of our view over the entire scope of quinazoline-based VEGFR-2 inhibitors. Herein, we give an overview of the importance and advancement status of reported structures, highlighting the SAR, biological evaluations and their binding modes.

H2O2-Mediated Synthesis of a Quinazolin-4(3H)-one Scaffold: A Sustainable Approach

A quinazolin-4(3H)-one ring system is a privileged heterocyclic moiety with distinctive biological properties. From this perspective, the development of an efficient strategy for the synthesis of quinazolin-4(3H)-one has always been in demand for the synthetic chemistry community. In this report, we envisaged an efficient protocol for the synthesis of quinazolin-4(3H)-one using substituted 2-amino benzamide with dimethyl sulfoxide (DMSO) as a carbon source and H2O2 as an effective oxidant. Mechanistically, the reaction proceeds through the radical approach with DMSO as one carbon source. To further substantiate the synthetic claim, the synthetic protocol has been extended to the synthesis of the anti-endotoxic active compound 3-(2-carboxyphenyl)-4-(3H)-quinazolinone.

Discovery, SAR Study of GST Inhibitors from a Novel Quinazolin-4(1H)-one Focused DNA-Encoded Library

The DNA-encoded library (DEL) is a powerful hit-generation tool in drug discovery. This study describes a new DEL with a privileged scaffold quinazolin-4(3H)-one developed by a robust DNA-compatible multicomponent reaction and a series of novel glutathione S-transferase (GST) inhibitors that were identified through affinity-mediated DEL selection. A novel inhibitor 16 was subsequently verified with an inhibitory potency value of 1.55 ± 0.02 μM against SjGST and 2.02 ± 0.20 μM against hGSTM2. Further optimization was carried out via various structure-activity relationship studies. And especially, the co-crystal structure of the compound 16 with the SjGST was unveiled, which clearly demonstrated its binding mode was quite different from the known GSH-like compounds. This new type of probe is likely to play a different role compared with the GSH, which may provide new opportunities to discover more potent GST inhibitors.

An Oxidant-Free and Mild Strategy for Quinazolin-4(3H)-One Synthesis via CuAAC/Ring Cleavage Reaction

An oxidant-free and highly efficient synthesis of phenolic quinazolin-4(3H)-ones was achieved by simply stirring a mixture of 2-aminobenzamides, sulfonyl azides, and terminal alkynes. The intermediate N-sulfonylketenimine underwent two nucleophilic additions and the sulfonyl group eliminated through the power of aromatization. The natural product 2-(4-hydroxybenzyl)quinazolin-4(3H)-one can be synthesized on a large scale under mild conditions with this method.

Novel Thiazolylketenyl Quinazolinones as Potential Anti-MRSA Agents and Allosteric Modulator for PBP2a

Bacterial infections caused by methicillin-resistant Staphylococcus aureus have seriously threatened public health. There is an urgent need to propose an existing regimen to overcome multidrug resistance of MRSA. A unique class of novel anti-MRSA thiazolylketenyl quinazolinones (TQs) and their analogs were developed. Some synthesized compounds showed good bacteriostatic potency. Especially TQ 4 was found to exhibit excellent inhibition against MRSA with a low MIC of 0.5 μg/mL, which was 8-fold more effective than norfloxacin. The combination of TQ 4 with cefdinir showed stronger antibacterial potency. Further investigation revealed that TQ 4, with low hemolytic toxicity and low drug resistance, was not only able to inhibit biofilm formation but also could reduce MRSA metabolic activity and showed good drug-likeness. Mechanistic explorations revealed that TQ 4 could cause leakage of proteins by disrupting membrane integrity and block DNA replication by intercalated DNA. Furthermore, the synergistic antibacterial effect with cefdinir might be attributed to TQ 4 with the ability to induce PBP2a allosteric regulation of MRSA and further trigger the opening of the active site to promote the binding of cefdinir to the active site, thus inhibiting the expression of PBP2a, thereby overcoming MRSA resistance and significantly enhancing the anti-MRSA activity of cefdinir. A new strategy provided by these findings was that TQ 4, possessing both excellent anti-MRSA activity and allosteric effect of PBP2a, merited further development as a novel class of antibacterial agents to overcome increasingly severe MRSA infections.

Regioselective synthesis of phenanthridine-fused quinazolinones using a 9-mesityl-10-methylacridinium perchlorate photocatalyst

Herein, we demonstrate a regioselective intramolecular C-N cross-coupling for the synthesis of 14H-quinazolino[3,2-f]phenanthridin-14-one by using 9-mesityl-10-methylacridinium perchlorate as the visible-light (450-470 nm) photocatalyst. The experiments with BHT, TEMPO, and Stern-Volmer quenching studies helped to rationalize a radical pathway via a SET mechanism.

Advances in the development of phosphodiesterase 7 inhibitors

Phosphodiesterase 7 (PDE7) specifically hydrolyzes cyclic adenosine monophosphate (cAMP), a second messenger that plays essential roles in cell signaling and physiological processes. Many PDE7 inhibitors used to investigate the role of PDE7 have displayed efficacy in the treatment of a wide range of diseases, such as asthma and central nervous system (CNS) disorders. Although PDE7 inhibitors are developed more slowly than PDE4 inhibitors, there is increasing recognition of PDE7 inhibitors as potential therapeutics for no nausea and vomiting secondary. Herein, we summarized the advances in PDE7 inhibitors over the past decade, focusing on their crystal structures, key pharmacophores, subfamily selectivity, and therapeutic potential. Hopefully, this summary will lead to a better understanding of PDE7 inhibitors and provide strategies for developing novel therapies targeting PDE7.

Design, Synthesis, Antibacterial Evaluation, Three-Dimensional Quantitative Structure-Activity Relationship, and Mechanism of Novel Quinazolinone Derivatives

Plant bacterial illnesses are common and cause dramatic damage to agricultural goods all over the world, yet there are few efficient bactericides to alleviate them at present. To discover novel antibacterial agents, two series of quinazolinone derivatives with novel structures were synthesized and their bioactivity against plant bacteria was tested. Combining CoMFA model search and the antibacterial bioactivity assay, D32 was identified as a potent antibacterial inhibitor against Xanthomonas oryzae pv. Oryzae (Xoo), with an EC₅₀ value of 1.5 μg/mL, much better in inhibitory capacity compared to bismerthiazol (BT) and thiodiazole copper (TC) (31.9 and 74.2 μg/mL). The activities of compound D32 against rice bacterial leaf blight in vivo were 46.7% (protective activities) and 43.9% (curative activities), better than commercial drug thiodiazole copper (29.3% protective activities and 30.6% curative activities). Flow cytometry, proteomics, reactive oxygen species, and key defense enzymes were used to further investigate the relevant mechanisms of action of D32. The identification of D32 as an antibacterial inhibitor and revelation of its recognition mechanism not only open the possibility of developing new therapeutic strategies for treatment of Xoo but also provide clues for elucidation of the acting mechanism of quinazolinone derivative D32, which is a possible clinical candidate worth in-depth study.

Design and synthesis of novel quinazolin-4(1H)-one derivatives as potent and selective inhibitors targeting AKR1B1

Inhibition of aldose reductase (AKR1B1) is a promising option for the treatment of diabetic complications. However, most of the developed small molecule inhibitors lack selectivity or suffer from low bioactivity. To address this limitation, a novel series of quinazolin-4(1H)-one derivatives as potent and selective inhibitors of AKR1B1 were designed and synthesized. Aldose reductase inhibitory activities of the novel compounds were characterized by IC₅₀ values ranging from 0.015 to 31.497 μM. Markedly enhanced selectivity of these derivatives was also recorded, which was further supported by docking studies. Of these inhibitors, compound 5g exhibited the highest inhibition activity with selectivity indices reaching 1190.8. The structure-activity relationship highlighted the importance of N1-acetic acid and N3-benzyl groups with electron-withdrawing substituents on the quinazolin-4(1H)-one scaffold for the construction of efficient and selective AKR1B1 inhibitors.

Antibacterial activity evaluation of pleuromutilin derivatives with 4(3H)-quinazolinone scaffold against methicillin-resistant Staphylococcusaureus

Growing antibiotic resistance is causing a health care crisis, leading to an urgent need for new antibiotics to tackle serious hospital and community infections. Pleuromutilin, a naturally occurring product with moderate antibacterial activity, has a unique structure that has attracted great efforts to modify its scaffold to obtain lead compounds. Herein, we report the synthesis of a series of novel pleuromutilin derivatives with a scaffold of 4(3H)-quinazolinone or its analogues at the C-14 side chain and investigated their in vitro activity against Staphylococcus aureus and Staphylococcus epidermidis as well as Gram-negative bacteria (Escherichia coli and Salmonella enterica subsp. enterica serovar pullorum). Structure-activity relationship (SAR) studies showed that the substituents on the benzene ring of 4(3H)-quinazolinone was not as important as the substituted position to improve antibacterial activity while the substituted groups on the N-3 position of 4(3H)-quinazolinone had strong impact on the efficacy. The replacement of the benzene moiety of 4(3H)-quinazolinone with other rings (pyridine, pyrrole, thiophene, or cyclopentyl) also showed high antibacterial efficacy, meaning the benzene ring was dispensable for exerting powerful antibacterial properties. In vitro pharmacokinetics investigations and cytotoxicity assays indicated that 2-mercapto-4(3H)-quinazolinone scaffold was superior to 2-(piperazin-1-yl)quinazolin-4(3H)-one. Among this series of pleuromutilin analogues, compound 23 with a structure of 2-mercapto-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one displayed the best in vitro antibacterial activity against MRSA (MIC = 0.063 μg/mL) and low cytotoxicity to RAW 264.7 cells (IC50＞100 μM) and was demonstrated to inhibit MRSA effectively in a mouse thigh infection model, outperforming the comparator, tiamulin.

Transition-metal-free radical difluorobenzylation/cyclization of unactivated alkenes: access to ArCF2-substituted ring-fused quinazolinones

A mild and efficient transition-metal-free radical difluorobenzylation/cyclization of unactivated alkenes toward the synthesis of difluorobenzylated polycyclic quinazolinone derivatives with easily accessible α,α-difluoroarylacetic acids has been developed. This transformation has the advantages of wide functional group compatibility, a broad substrate scope, and operational simplicity. This methodology provided a highly attractive access to pharmaceutically valuable ArCF₂-containing polycyclic quinazolinones.

Algorithm-driven activity-directed expansion of a series of antibacterial quinazolinones

Activity-directed synthesis (ADS) is a structure-blind, function driven approach that can drive the discovery of bioactive small molecules. In ADS, arrays of reactions are designed and executed, and the crude product mixtures are then directly screened to identify reactions that yield bioactive products. The design of subsequent reaction arrays is then informed by the hit reactions that are discovered. In this study, algorithms for reaction array design were developed in which the reactions to be executed were selected from a large set of virtual reactions; the reactions were selected on the basis of similarity to reactions known to yield bioactive products. The algorithms were harnessed to design arrays of photoredox-catalysed alkylation reactions whose crude products were then screened for inhibition of growth of S. aureus ATCC29213. It was demonstrated that the approach enabled expansion of a series of antibacterial quinazolinones. It is envisaged that such algorithms could ultimately enable fully autonomous activity-directed molecular discovery.

Palladium-Catalyzed Synthesis of Novel Quinazolinylphenyl-1,3,4-thiadiazole Conjugates

Two novel series of symmetrical and unsymmetrical conjugates, in which 1,3,4-thiadiazole and 4-N,N-dimethylaminoquinazoline scaffolds were connected via 1,4-phenylene linker, were synthetized in high yields by Suzuki cross-coupling reactions. The elaborated protocol makes use of bromo-substituted quinazolines, boronic acid pinacol ester or diboronic acid bis(pinacol)ester of 2,5-diphenyl-1,3,4-thiadiazole, catalytic amounts of [1,10-bis(diphenylphosphino)ferrocene]dichloropalladium(II) Pd(dppf)Cl2, sodium carbonate, and tetrabutylammonium bromide, which plays the role of a phase-transfer catalyst. The structures of prepared compounds were confirmed by 1H NMR, 13C NMR, UV-VIS, IR and HRMS. For the target compounds, the fluorescence spectra were measured to determine their quantum yields and Stokes shifts. The study revealed that among the tested compounds, two highly-conjugated derivatives (8a, 9a), in which 1,3,4-thiadiazole core is connected to 4-(N,N-dimethylamino)quinazoline via a double 1,4-phenylene linker, exhibit high quantum yields of fluorescence and strong fluorescence emission.

In Vitro Anticancer Activity of Methanolic Extract of Justicia adhatoda Leaves with Special Emphasis on Human Breast Cancer Cell Line

Natural products are being targeted as alternative anticancer agents due to their non-toxic and safe nature. The present study was conducted to explore the in vitro anticancer potential of Justicia adhatoda (J. adhatoda) leaf extract. The methanolic leaf extract was prepared, and the phytochemicals and antioxidant potential were determined by LCMS analysis and DPPH radical scavenging assay, respectively. A docking study performed with five major alkaloidal phytoconstituents showed that they had a good binding affinity towards the active site of NF-κB. Cell viability assay was carried out in five different cell lines, and the extract exhibited the highest cytotoxicity in MCF-7, a breast cancer cell line. Extract-treated cells showed a significant increase in nitric oxide and reactive oxygen species production. Cell cycle analysis showed an arrest in cell growth at the Sub-G0 phase. The extract successfully inhibited cell migration and colony formation and altered mitochondrial membrane potential. The activities of superoxide dismutase and glutathione were also found to decrease in a dose-dependent manner. The percentage of apoptotic cells was found to increase in a dose-dependent manner in MCF-7 cells. The expressions of caspase-3, Bax, and cleaved-PARP were increased in extract-treated cells. An increase in the expression of NF-κB was found in the cytoplasm in extract-treated cells. J. adhatoda leaf extract showed a potential anticancer effect in MCF-7 cells.

Dihydropyrazinoquinazolinones via SN2 Sulfamidate Ring-Opening and a Sequential Quinazolinone-Amidine Rearrangement Strategy (SQuAReS)

A synthesis of dihydropyrazino-[2,1-b]-quinazolinones is described using a 2-alkylaminoquinazolinone-mediated ring opening of a-/chiral sulfamidates, followed by a tandem quinazolinone-amidine rearrangement termed SQuAReS. This approach takes advantage of sulfamidates whose regioselective ring opening, after hydrolysis, appends an optimally distanced nucleophilic amine to a quinazolinone such that subsequent domino rearrangements are favored, integrating unique substitution patterns on a privileged core. This three-step protocol integrated five telescoped transformations and generated 20 pyrazinoquinazolinones in up to 74% yield with high enantiomeric fidelity and diastereoselectivity.

Unexpected assembly machinery for 4(3H)-quinazolinone scaffold synthesis

4(3H)-quinazolinone is the core scaffold in more than 200 natural alkaloids and numerous drugs. Many chemosynthetic methodologies have been developed to generate it; however, investigation of its native enzymatic formation mechanism in fungi has been largely limited to fumiquinazolines, where the two nitrogen atoms come from anthranilate (N-1) and the α-NH₂ of amino acids (N-3). Here, via biochemical investigation of the chrysogine pathway, unexpected assembly machinery for 4(3H)-quinazolinone is unveiled, which involves a fungal two-module nonribosomal peptide synthase ftChyA with an unusual terminal condensation domain catalysing tripeptide formation; reveals that N-3 originates from the inorganic ammonium ions or the amide of L-Gln; demonstrates an unusual α-ketoglutarate-dependent dioxygenase ftChyM catalysis of the C-N bond oxidative cleavage of a tripeptide to form a dipeptide. Our study uncovers a unique release and tailoring mechanism for nonribosomal peptides and an alternative route for the synthesis of 4(3H)-quinazolinone scaffolds.

Design and Synthesis of Quinazolinone-Triazole Hybrids as Potent Anti-Tubercular Agents

A straightforward and convenient methodology has been developed for the reaction of 2-aminobenzamide and carbonyls affording 2,3-dihydroquinazolin-4(1H)-ones using aqueous solution of [C12Py][FeCl3Br]. The developed methodology was applied for the synthesis of 25 quinazolinone-triazole hybrids followed by evaluation of their in vitro anti-tubercular (TB) activity. The results revealed that 8 quinazolinone-triazole hybrids displayed promising activity having MIC values of 0.78-12.5 μg/mL. The compound 3if with MIC 0.78 μg/mL was found to be the lead nominee among the series, better than Ethambutol, a first line anti-TB drug and comparable with Rifampicin. The active compounds with MIC values ≤ 6.25 μg/mL were subjected to in vitro cytotoxicity and found nontoxic. In drug-drug interaction, compounds 3ia and 3ii interacted synergistically with all the three anti-TB drugs, INH, RFM, and EMB. Other 3 compounds interacted either in synergistic or additive manners. Important information on the binding interaction of the target compounds with the active sites of 1DQY Antigen 85C from Mycobacterium tuberculosis and Enoyl acyl carrier protein reductase (InhA) enzymes was obtained from molecular docking studies. Screening of the drug-likeness properties and bioactivity score indicates that synthesized molecules could be projected as potential drug candidates. Based on the current study, quinazolinone-triazole hybrids framework can be useful in drug development for TB.

Directed Evolution of Flavin-Dependent Halogenases for Site- and Atroposelective Halogenation of 3-Aryl-4(3H)-Quinazolinones via Kinetic or Dynamic Kinetic Resolution

In this study, we engineer a variant of the flavin-dependent halogenase RebH that catalyzes site- and atroposelective halogenation of 3-aryl-4(3H)-quinazolinones via kinetic or dynamic kinetic resolution. The required directed evolution uses a combination of random and site-saturation mutagenesis, substrate walking using two probe substrates, and a two-tiered screening approach involving the analysis of variant conversion and then enantioselectivity of improved variants. The resulting variant, 3-T, provides >99:1 e.r. for the (M)-atropisomer of the major brominated product, 25-fold improved conversion, and 91-fold improved site selectivity relative to the parent enzyme on the probe substrate used in the final rounds of evolution. This high activity and selectivity translate well to several additional substrates with varied steric and electronic properties. Computational modeling and docking simulations are used to rationalize the effects of key mutations on substrate binding. Given the range of substrates that have been used for atroposelective synthesis via electrophilic halogenation in the literature, these results suggest that flavin-dependent halogenases (FDHs) could find many additional applications for atroposelective catalysis. More broadly, this study highlights how RebH can be engineered to accept structurally diverse substrates that enable its use for enantioselective catalysis.

Novel Quinazolinone–Isoxazoline Hybrids: Synthesis, Spectroscopic Characterization, and DFT Mechanistic Study

Quinazolinone and isoxazoline systems have attracted much attention due to their interesting pharmacological properties. The association of these two pharmacophores in a single hybrid structure can boost the biological activity or bring a new one. Inspired by this new paradigm, in the present work we report the synthesis and spectroscopic characterization of new quinazolinone–isoxazoline hybrids. The target compounds were obtained via 1,3-dipolar cycloaddition reactions of arylnitriloxides and N-allylquinazolinone. The synthesized compounds were characterized using spectroscopic techniques such as IR, 1D NMR (1H and 13C), 2D NMR (COSY and HSQC), and high-resolution mass spectrometry (HRMS). The spectral data show that this reaction leads only to the 3,5-disubstituted isoxazoline regioisomer, and that the observed regiochemistry is not affected by the nature of the substituents in the phenyl ring of the dipole. In addition, a theoretical study was performed using density functional theory (DFT) to support the experimental results in regard to the regiochemistry of the studied reactions. The computational mechanistic study was in good agreement with the experimental data.

tert-Butyl Hydroperoxide Promoted the Reaction of Quinazoline-3-oxides with Primary Amines Affording Quinazolin-4(3H)-ones

An efficient and facile approach for the synthesis of quinazolin-4(3H)-ones via the reaction of quinazoline-3-oxides with primary amines is described. This approach is demonstrated to be applicable for a broad range of substrates and proceeds efficiently under metal-free and mild reaction conditions employing easily available tert-butyl hydroperoxide as the oxidant. Remarkably, 3-(2-(1H-indol-3-yl) ethyl)quinazolin-4(3H)-one 3w, which was conveniently obtained by this process in 70% yield, was an excellent precursor for the synthesis of bioactive evodiamine and rutaempine.

Preparation of quinazolinones using biosynthesized silver nanoparticles

A silver nanocatalyst has been used as an effective catalyst for the preparation of quinazolinones under reflux conditions in ethanol. The catalyst was characterized by UV-VIS, FT-IR, XRD, SEM and EDS. Amongst the many benefits of this method are atom economy, reusability of the catalyst, low catalyst loading, applicability to a wide range of substrates, high yields of products, environmental friendliness and easy separation of products. Silver nanoparticles (Ag NPs) were prepared using Echium amoenum extract. The structures of the prepared quinazolinones were fully characterized by ¹H and ¹³C NMR, FT-IR spectra and elemental analysis.

Synthesis of quinazolinones using biosynthesized silver nanoparticles.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Modification of the benzenoid part

Bacterial resistance to currently used antibiotics demands the development of novel antibacterial agents with good safety margins and sufficient efficacy against multi-drug resistant isolates. We have previously described the synthesis of N-butyl-2-(butylthio)quinazolin-4-amine (I) as an optimized hit with broad-spectrum antibacterial activity and low cytotoxicity. In addition, we have identified a potential growing vector for this series of compounds. Herein, we describe further hit optimization which includes systematic diversifications of both the benzenoid part and the substituents at position 6 and 7 of compound I. Growing of the molecule beside the core modifications yielded several compounds with remarkable anti(myco)bacterial activity against a panel of pathogenic bacteria, including drug-resistant strains. Compound 12 showed a 2-4 fold improvement in activity than I against S. aureus Newman, S. pneumoniae DSM-20566 and E. faecalis DSM-20478. The compounds also showed a good safety profile towards human HepG2 cells.

Selective electrophilic di- and mono-fluorinations for the synthesis of 4-difluoromethyl and 4-fluoromethyl quinazolin(thi)ones by Selectfluor-triggered multi-component reaction

A simple and efficient domino protocol for the selective synthesis of 4-difluoromethyl and 4-fluoromethyl quinazolin(thi)ones was established from readily available 2-aminoacetophenones and iso(thio)cyanates mediated by Selectfluor. The reaction outcomes are...

Design and synthesis of novel quinazolinone-based fibrates as PPARα agonists with antihyperlipidemic activity

Aiming to discover new antihyperlipidemic agents, a new set of quinazolinone-fibrate hybrids 9a-r bearing the essential features for peroxisome proliferator-activated receptor-α (PPARα) agonistic activity was synthesized and the structures were confirmed by different spectral data. All the target compounds were screened for their PPARα agonistic activity. Compounds 9o and 9q exhibited potent activity, with EC₅₀ values better than that of fenofibrate by 8.7- and 27-fold, respectively. Molecular docking investigations were performed for all the newly synthesized compounds in the active site of the PPARα receptor to study their interactions and energies in the receptor. Moreover, the antihyperlipidemic and antioxidant activities of compounds 9o and 9q were determined using Triton WR-1339-induced hyperlipidemic rats. Compound 9q exhibited effective hypolipidemic activity in a dose-dependent manner, where it significantly reduced the serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, and very-low-density lipoprotein cholesterol and increased the level of high-density lipoprotein cholesterol. Furthermore, it possesses a powerful antioxidant profile where it significantly elevated the levels of reduced glutathione as well as the total antioxidant capacity and significantly decreased the malondialdehyde level. The histopathological studies revealed that compound 9q improved the aortic architecture and hepatic steatosis. These findings support that compound 9q could be a promising lead compound for the development of new antihyperlipidemic agents.