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

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.

EmbedDTI: Enhancing the Molecular Representations via Sequence Embedding and Graph Convolutional Network for the Prediction of Drug-Target Interaction

The identification of drug-target interaction (DTI) plays a key role in drug discovery and development. Benefitting from large-scale drug databases and verified DTI relationships, a lot of machine-learning methods have been developed to predict DTIs. However, due to the difficulty in extracting useful information from molecules, the performance of these methods is limited by the representation of drugs and target proteins. This study proposes a new model called EmbedDTI to enhance the representation of both drugs and target proteins, and improve the performance of DTI prediction. For protein sequences, we leverage language modeling for pretraining the feature embeddings of amino acids and feed them to a convolutional neural network model for further representation learning. For drugs, we build two levels of graphs to represent compound structural information, namely the atom graph and substructure graph, and adopt graph convolutional network with an attention module to learn the embedding vectors for the graphs. We compare EmbedDTI with the existing DTI predictors on two benchmark datasets. The experimental results show that EmbedDTI outperforms the state-of-the-art models, and the attention module can identify the components crucial for DTIs in compounds.

In Vitro Anti-Toxoplasma gondii Activity Evaluation of a New Series of Quinazolin-4(3H)-one Derivatives

Toxoplasmosis post serious threaten to human health, leading to severely eye and brain disease, especially for immunocompromised patients and pregnant women. The multiple side effects and long dosing period of current main treatment regiments calls for high effective and low toxicity anti-toxoplasmosis drugs. Herein, we report our efforts to synthesize a series of 2-(piperazin-1-yl)quinazolin-4(3H)-one derivatives and investigate their activity against Toxoplasma gondii tachyzoites in vitro based on cell phenotype screening. Among the 26 compounds, 8w and 8x with diaryl ether moiety at the side chain of piperazine exhibited good efficacy to inhibit T. gondii, with IC₅₀ values of 4 μM and 3 μM, respectively. Structure-activity relationship (SAR) studies implies that hydrophobic aryl at the side chain would be preferred for improvement of activity. Molecular docking study reveals these two compounds appeared high affinity to TgCDPK1 by interaction with the hydrophobic pocket of ATP-binding cleft.

In silico study and biological screening of benzoquinazolines as potential antimicrobial agents against methicillin-resistant Staphylococcus aureus, carbapenem-resistant Klebsiella pneumoniae, and fluconazole-resistant Candida albicans

Globally, antibiotic-resistant pathogens have become a serious threat to public health. The use of drugs having structures different from those applied in the clinical treatments of bacterial infections is a well-known potential solution to the antibiotic resistance crisis. Benzo-[g]-quinazolines were identified by our research group as a new class of antimicrobial agents. Herein, to follow-up the research on such compounds, three benzo-[g]-quinazolines (1-3) were studied, as in vitro antibacterial candidates against methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Klebsiella pneumoniae, and fluconazole-resistant Candida albicans, as well. The minimum inhibitory concentration (MIC) assay for benzoquinazolines was carried out via the calorimetric broth microdilution method using the XTT assay in comparison with vancomycin, ciprofloxacin, and ketoconazole as reference drugs. The target compounds 1-3 revealed high variation in their activity against the examined resistant microbial strains. Benzoquinazoline 3 exhibited a more potent effect against the resistant strains compared with the reference drugs. A docking study was performed to identify the interactions between the benzoquinazolines 1-3 and ligand proteins (OXA-48 carbapenemase, β-lactamase, and sterol 14-alpha demethylase (CYP51)) at the active sites. Benzoquinazolines 1-3 showed very weak cytotoxicity against human lung fibroblast normal cells (WI-38). The targets showed promising antimicrobial effects against the three resistant strains. These findings may inform future inhibitor discoveries targeting penicillin-binding proteins.

Chemoselective Reactions of Isocyanates with Secondary Amides: One-Pot Construction of 2,3-Dialkyl-Substituted Quinazolinones

A facile method for the preparation of 2,3-dialkyl-substituted quinazolinones from readily available N-arylamides and commercial isocyanates was developed. This one-pot procedure involves the chemoselective activation of the secondary amide with Tf₂O/2-Br-Pyr, the sequential addition of isocyanate, and cyclization. The mild reaction is general for a wide range of substrates and can be run on a gram scale.

β-Lactams against the Fortress of the Gram-Positive Staphylococcus aureus Bacterium

The biological diversity of the unicellular bacteria-whether assessed by shape, food, metabolism, or ecological niche-surely rivals (if not exceeds) that of the multicellular eukaryotes. The relationship between bacteria whose ecological niche is the eukaryote, and the eukaryote, is often symbiosis or stasis. Some bacteria, however, seek advantage in this relationship. One of the most successful-to the disadvantage of the eukaryote-is the small (less than 1 μm diameter) and nearly spherical Staphylococcus aureus bacterium. For decades, successful clinical control of its infection has been accomplished using β-lactam antibiotics such as the penicillins and the cephalosporins. Over these same decades S. aureus has perfected resistance mechanisms against these antibiotics, which are then countered by new generations of β-lactam structure. This review addresses the current breadth of biochemical and microbiological efforts to preserve the future of the β-lactam antibiotics through a better understanding of how S. aureus protects the enzyme targets of the β-lactams, the penicillin-binding proteins. The penicillin-binding proteins are essential enzyme catalysts for the biosynthesis of the cell wall, and understanding how this cell wall is integrated into the protective cell envelope of the bacterium may identify new antibacterials and new adjuvants that preserve the efficacy of the β-lactams.

Unconventional Antibacterials and Adjuvants

The need for new classes of antibacterials is genuine in light of the dearth of clinical options for the treatment of bacterial infections. The prodigious discoveries of antibiotics during the 1940s to 1970s, a period wistfully referred to as the Golden Age of Antibiotics, have not kept up in the face of emergence of resistant bacteria in the past few decades. There has been a renewed interest in old drugs, the repurposing of the existing antibiotics and pairing of synergistic antibiotics or of an antibiotic with an adjuvant. Notwithstanding, discoveries of novel classes of these life-saving drugs have become increasingly difficult, calling for new paradigms. We describe, herein, three strategies from our laboratories toward discoveries of new antibacterials and adjuvants using computational and multidisciplinary experimental methods. One approach targets penicillin-binding proteins (PBPs), biosynthetic enzymes of cell-wall peptidoglycan, for discoveries of non-β-lactam inhibitors. Oxadiazoles and quinazolinones emerged as two structural classes out of these efforts. Several hundred analogs of these two classes of antibiotics have been synthesized and fully characterized in our laboratories. A second approach ventures into inhibition of allosteric regulation of cell-wall biosynthesis. The mechanistic details of allosteric regulation of PBP2a of Staphylococcus aureus, discovered in our laboratories, is outlined. The allosteric site in this protein is at 60 Å distance to the active site, whereby ligand binding at the former makes access to the latter by the substrate possible. We have documented that both quinazolinones and ceftaroline, a fifth-generation cephalosporin, bind to the allosteric site in manifestation of the antibacterial activity. Attempts at inhibition of the regulatory phosphorylation events identified three classes of antibacterial adjuvants and one class of antibacterials, the picolinamides. The chemical structures for these hits went through diversification by synthesis of hundreds of analogs. These analogs were characterized in various assays for identification of leads with adjuvant and antibacterial activities. Furthermore, we revisited the mechanism of bulgecins, a class of adjuvants discovered and abandoned in the 1980s. These compounds potentiate the activities of β-lactam antibiotics by the formation of bulges at the sites of septum formation during bacterial replication, which are points of structural weakness in the envelope. These bulges experience rupture, which leads to bacterial death. Bulgecin A inhibits the lytic transglycosylase Slt of Pseudomonas aeruginosa as a likely transition-state mimetic for its turnover of the cell-wall peptidoglycan. Once damage to cell wall is inflicted by a β-lactam antibiotic, the function of Slt is to repair the damage. When Slt is inhibited by bulgecin A, the organism cannot cope with it and would undergo rapid lysis. Bulgecin A is an effective adjuvant of β-lactam antibiotics. These discoveries of small-molecule classes of antibacterials or of adjuvants to antibacterials hold promise in strategies for treatment of bacterial infections.

In-vitro Anti-trypanosomal and Cytotoxicity Evaluation of 3-methyl-3,4-dihydroquinazolin-2(1H)-one Derivatives

Sleeping sickness, caused by trypanosomes, is a debilitating, neglected tropical disease wherein current treatments suffer from several drawbacks such as toxicity, low activity, and poor pharmacokinetic properties, and hence the need for alternative treatment is apparent. To this effect, we screened in vitro a library of 2-quinazolinone derivatives for antitrypanosomal activity against T.b. brucei and cytotoxicity against HeLa cells. Seven compounds having no overt cytotoxicity against HeLa cells exhibited antitrypanosomal activity in the range of 0.093-45 µM were identified. The activity data suggests that the antitrypanosomal activity of this compound class is amenable to substituents at N1 and C6 positions. Compound 14: having a molecular weight of 238Da, ClogP value of 1 and a total polar surface area of 49 was identified as the most active, exhibiting an IC₅₀ value of 0.093 µM Graphical Abstract.

Activity-directed expansion of a series of antibacterial agents

The feasibility of using activity-directed synthesis to drive antibacterial discovery was investigated. An array of 220 Pd-catalysed microscale reactions was executed, and the crude product mixtures were evaluated for activity against Staphylococcus aureus. Scale-up of the hit reactions, purification and evaluation, enabled expansion of a class of antibacterial quinazolinones. The novel antibacterials had MICs from 0.016 μg mL-1 (i.e. 38 nM) to 2-4 μg mL-1 against S. aureus ATCC29213.

Expeditious Approach to Indoloquinazolinones via Double Annulations of o-Aminoacetophenones and Isocyanates

A novel procedure for a one-pot cascade reaction of o-aminoacetophenones and aryl/aliphatic isocyanates catalyzed/oxidized by the [Pd]/[Ag] system was developed. The reaction involves two C-N bond and one C-C bond formations during the double annulation process and the desired indoloquinazolinones and derivatives were afforded up to 81% yields from readily available substrates with a tolerance of a broad variety.

Metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates at room temperature

Herein, we describe the novel reactivity of hexafluoroisopropyl 2-aminobenzoates. The metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates has been developed at room temperature. These procedures feature good functional group tolerance, mild reaction conditions, and excellent yields. The newly formed products can readily be converted to other useful N-heterocycles. Moreover, the products and their derivatives showed potent anticancer activities in vitro by MTT assay.

A metal-free synthesis of 1,4-benzodiazepines and quinazolinones from hexafluoroisopropyl 2-aminobenzoates has been developed at room temperature.

Recent advances in quinazolinones as an emerging molecular platform for luminescent materials and bioimaging

This review summarized recent advances relating to the luminescence properties of quinazolinones and their applications in fluorescent probes, biological imaging and luminescent materials. Their future outlook is also included.

Rhodium(iii)-catalyzed annulation of 3-arylquinazolinones with alkynes via double C–H activation: an efficient route for quinolino[2,1-b]quinazolinones

An effective method for the synthesis of quinolino[2,1-b]quinazolinones has been described.

Synthesis and biofilm inhibition studies of 2-(2-amino-6-arylpyrimidin-4-yl)quinazolin-4(3H)-ones

Synthesis of novel 4(3H)-quinazolinonyl aminopyrimidine derivatives has been achieved via quinazolinonyl enones which in turn were obtained from 2-acyl-4(3H)-quinazolinone. They have been assayed for biofilm inhibition against Gram-positive (methicillin-resistant Staphylococcus aureus (MRSA)) and Gram-negative bacteria (Acinetobacter baumannii). The analogues with 2,4,6-trimethoxy phenyl, 4-methylthio phenyl, and 3-bromo phenyl substituents (5h, 5j & 5k) have been shown to inhibit biofilm formation efficiently in MRSA with IC50 values of 20.7-22.4 μM). The analogues 5h and 5j have demonstrated low toxicity in human cells in vitro and can be investigated further as leads.

Design, synthesis and molecular modeling studies of 2-styrylquinazoline derivatives as EGFR inhibitors and apoptosis inducers

Herein, we report the synthesis of novel 2-substituted styrylquinazolines conjugated with aniline or sulfonamide moieties, anticipated to act as potent anticancer therapeutic agents through preferential EGFR inhibition. In doing so, all the synthesized compounds were screened for their in vitro anticancer activities (nine subpanels) at the National Cancer Institute (NCI), USA. The resulting two most active anticancer compounds (7b and 8c) were then chemically manipulated to investigate feasible derivatives (12a-e and 15a-d). MTT cytotoxicity, in vitro cell free EGFR and anti-proliferative activity against EGFR/ A549 cell line evaluation for the most active broadly spectrum candidates (7a/b, 8c/e, 12b and 15d) was conducted. Promising results were obtained for the styrylquinazoline-benzenesulfonamide derivative 8c (IC50 = 8.62 µM, 0.190 µM and = 79.25%), if compared to lapatanib (IC50 = 11.98 µM, 0.190 µM, and 79.25%), respectively. Moreover, its apoptotic induction potential was studied through cell cycle analysis, Annexin-V and caspase-3 activation assays. Results showed a clear cell arrest at G2/M phase, a late apoptotic increase (76 folds) and a fruitful caspase-3 expression change (8 folds), compared to the control. Finally, molecular docking studies of compounds 7a/b, 8c/e, 12b and 15d revealed proper fitting into the active site of EGFR with a low binding energy score for compound 8c (-13.19 Kcal/mole), compared to lapatanib (-14.54 Kcal/mole).

Design, synthesis, molecular docking study, and antibacterial evaluation of some new fluoroquinolone analogues bearing a quinazolinone moiety

BACKGROUND

Increasing bacterial resistance to quinolones is concerning. Hence, the development of novel quinolones by chemical modifications to overcome quinolone resistance is an attractive perspective in this context.

OBJECTIVE

In this study, it is aimed to design and synthesize a novel series of functionalized fluoroquinolones using ciprofloxacin and sarafloxacin cores by hybridization of quinazolinone derivatives. This objective was tested by a comprehensive set of in vitro antibacterial assays in addition to SAR (structure-activity relationship) characterisation studies.

METHODS

A nucleophilic reaction of ciprofloxacin and sarafloxacin with 2-(chloromethyl)quinazolin-4(3H)-one in the presence of NaHCO₃ in dimethylformamide (DMF) was performed to obtain the desired compounds 5a-j. Novel compounds were characterised by ¹H, ¹³C- NMR and IR spectroscopy, MS and elemental analysis. In silico pharmacokinetics prediction assays and molecular docking studies were performed to explore the binding characteristics and interactions. Antibacterial activities of the novel compounds were evaluated by Broth microdilution, well diffusion and disc diffusion assays against three gram-positive (Methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus and Enterococcus faecalis) and three gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli).

RESULTS

The compounds exhibited moderate to good activities against gram-positive bacteria and weak to moderate activities against gram-negative bacteria. Amongst all ciprofloxacin-derivatives, compound 5d was the most potent agent with high antibacterial activity against gram-positive bacteria, including MRSA and S. aureus ((minimum inhibitory concentration (MIC) = 16 nM for both), that is 60 times more potent than ciprofloxacin as parent drug. Compound 5i from sarafloxacin-derivatives was the most potent compound against MRSA and S. aureus (MIC = 0.125 μM). Well diffusion and disk diffusion assay results demonstrated confirmatory outcomes for the quantitative broth microdilution assay. Molecular docking study results were in accordance with the results of antibacterial activity assays.

CONCLUSION

The results of the current study demonstrated that the novel ciprofloxacin and sarafloxacin derivatives synthesized here have promising antibacterial activities. Particularly, compounds 5d and 5i have potential for wider antibacterial applications following further analysis.

Construction of Binuclear Benzimidazole-Fused Quinazolinones and Pyrimidinones Using Aryl Isocyanates as Building Blocks by Transition-Metal-Free C(sp2)-N Coupling

A class of binuclear N-fused hybrid scaffolds was constructed by the reaction of 2-(2-bromoaryl)- and 2-(2-bromovinyl)benzimidazoles with aryl isocyanates as building blocks in the presence of a base under microwave irradiation. A nucleophilic addition followed by an unprecedented transition-metal-free C(sp²)-N coupling is proposed as a reaction pathway of this green process.

1,2,3-Triazole-containing hybrids with potential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA), as a classic reason for genuine skin and flimsy tissues diseases, is a worldwide general wellbeing risk and has already tormented humanity for a long history, creating a critical need for the development of new classes of antibacterials. 1,2,3-Triazole moiety, readily interact with diverse enzymes and receptors in organisms through weak bond interaction, is among the most common frameworks present in the bioactive molecules. 1,2,3-Triazole derivatives, especially 1,2,3-triazole-containing hybrids, possess broad-spectrum activity against a panel of clinically important bacteria including drug-resistant pathogens, so rational design of 1,2,3-triazole derivatives may open a door for the opportunities on the development of novel anti-MRSA agents. This review is an endeavour to highlight the current scenario of 1,2,3-triazole-containing hybrids with potential anti-MRSA activity, covering articles published between 2010 and 2020.

Rhodium-Catalyzed Merging of 2-Arylquinazolinone and 2,2-Difluorovinyl Tosylate: Diverse Synthesis of Monofluoroolefin Quinazolinone Derivatives

An efficient method for the synthesis of 2-(o-monofluoroalkenylaryl)quinazolinone derivatives was developed. In this context, the quinazolinone ring served as the inherent directing group, 2,2-difluorovinyl tosylate was used as the monofluoroolefin synthon, and Rh(III)-catalyzed C-H bond difluorovinylation of 2-arylquinazolinons was performed to give the corresponding monofluoroalkene-containing quinazolinons in yields of 65-92%. The method is characterized by broad synthetic utility, mild conditions, and high efficiency.

Synthesis and Spectral Characterization of 4,7-Dichloro-6-nitroquinazoline

Afatinib is a 4-anilinoquinazoline tyrosine kinase inhibitor (TKI) in the form of a dimaleate salt which is indicated for the treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC). The most scalable route for the synthesis of this drug was reported in two Boehringer Ingelheim patents, in which the title compound, 4,7-dichloro-6-nitroquinazoline (IV), is an important intermediate. Compound IV is also present in a number of synthetic pathways for various 4,7-disubstituted quinazoline derivatives displaying high therapeutic potential. However, no detailed characterization of this popular compound has been reported, possibly due to its high instability. In this paper, IV was prepared in an overall yield of 56.1% by a 3-step process (condensation, nitration, and chlorination) from 2-amino-4-chlorobenzoic acid (I). The target compound has been for the first time fully characterized by melting point, mass-spectrometry, FT-IR, 1H-NMR and 13C-NMR spectroscopies.

Microwave Assisted Synthesis of 4-Phenylquinazolin-2(1H)-one Derivatives that Inhibit Vasopressor Tonus in Rat Thoracic Aorta

Quinazolinones have pharmacological effects on vascular reactivity through different mechanisms. We synthesized 4-phenylquinazolin-2(1H)-one derivatives under microwave irradiation and tested them on the rat thoracic aorta. The prepared compounds 2a–2f were obtained in about 1 h with suitable yields (31–92%). All derivatives produced vasorelaxant effects with IC₅₀ values ranging from 3.41 ± 0.65 µM to 39.72 ± 6.77 µM. Compounds 2c, 2e and 2f demonstrated the highest potency in endothelium-intact aorta rings (IC₅₀ 4.31 ± 0.90 µM, 4.94 ± 1.21 µM and 3.41 ± 0.65 µM respectively), and they achieved around 90% relaxation (30 μM). In aorta rings without an endothelium, the effect of compound 2f was abolished. Using the MTT assay to test for cell viability, only compound 2b induced cytotoxicity at the maximum concentration employed (30 µM). The results show that vasorelaxation by 4-phenylquinazolin-2(1H)-one derivatives might depend on the activation of a signalling pathway triggered by endothelium-derived factors.

Synthesis of the quinazolinone derivatives using an acid-functionalized magnetic silica heterogeneous catalyst in terms of green chemistry

In this research, the synthesis of the quinazolinone derivatives by the reaction of diaminoglyoxime with anthranilic acid or methyl 2-amino benzoate over an acetic acid-functionalized magnetic silica-based catalyst in water was described. The acetic acid-functionalized catalyst was prepared using a three-step procedure from magnetite NPs that initially coated with a layer of silica through the sol-gel process, modified with an aminosilane layer and functionalized with bromoacetic acid. The catalyst was characterized by means of spectroscopic and microscopic techniques, and its activity was investigated for the synthesis of the quinazolinones, bisquinazolinone and oxadiazole quinazolinones obtained from diaminoglyoxime in water at room temperature.

α-Hydroxy acid as an aldehyde surrogate: metal-free synthesis of pyrrolo[1,2-a]quinoxalines, quinazolinones, and other N-heterocycles via decarboxylative oxidative annulation reaction

A metal-free and efficient procedure for the synthesis of pyrrolo[1,2-a]quinoxalines, quinazolinones, and indolo[1,2-a]quinoxaline has been developed. The key features of our method include the in situ generation of aldehyde from α-hydroxy acid in the presence of TBHP (tert-butyl hydrogen peroxide), and further condensation with various amines, followed by intramolecular cyclization and subsequent oxidation to afford the corresponding quinoxalines, quinazolinones derivatives in moderate to high yields.

A TBHP mediated, metal-free approach for the synthesis of quinoxalines, quinazolinones, and indolo quinoxaline was developed from alpha hydroxy acids via decarboxylation followed by condensation.

Synthesis of C-Ring-Substituted Vasicinones and Luotonins via Regioselective Aza-Nazarov Cyclization of Quinazolinonyl Enones

A facile synthesis of C-ring substituted luotonins and vasicinones has been realized via a super-acid-mediated aza-Nazarov cyclization of quinazolinonyl enones. The regioselectivity of the cyclization is highly dependent on proton availability in the reaction medium.

Susceptibility of Methicillin-Resistant Staphylococcus aureus to Five Quinazolinone Antibacterials

The in vitro activities of five quinazolinone antibacterials, compounds Q1 to Q5, were tested against 210 strains of methicillin-resistant Staphylococcus aureus (MRSA). The MIC₅₀/MIC₉₀ values (in μg/ml) were as follows: Q1, 0.5/2; Q2, 1/4; Q3, 2/4; Q4, 0.06/0.25; and Q5, 0.125/0.5.

The in vitro activities of five quinazolinone antibacterials, compounds Q1 to Q5, were tested against 210 strains of methicillin-resistant Staphylococcus aureus (MRSA). The MIC₅₀/MIC₉₀ values (in μg/ml) were as follows: Q1, 0.5/2; Q2, 1/4; Q3, 2/4; Q4, 0.06/0.25; and Q5, 0.125/0.5. Several strains with high MIC values (from 8 to >32 μg/ml) for some of these compounds exhibited amino acid changes in the penicillin-binding proteins, which are targeted by these antibacterials.

Catalyst-free cyclization of anthranils and cyclic amines: one-step synthesis of rutaecarpine

An efficient synthesis of a variety of quinazolinone derivatives via a direct cyclization reaction between commercially available anthranils and cyclic amines is described. The developed transformation proceeds with the merits of high step- and atom-efficiency, a broad substrate scope, and good to excellent yields, without additional catalysts, and offers a practical way for the preparation of rutaecarpine and its derivatives with structural diversity.

A Simple Metal-Free Cyclization for the Synthesis of 4-Methylene-3-Substituted Quinazolinone and Quinazolinthione Derivatives: Experiment and Theory

A new series of 3-substituted 4-methylene-quinazolinthiones and 4-methylene-quinazolinones were synthesized in moderate to excellent yield through a simple reaction of 2-aminoacetophenones with isocyanates or isothiocyanates. The reaction shows good tolerance of many important functional groups in the presence of air and water under metal-free conditions. Only water is produced as a coproduct, rendering this “green” methodology a highly versatile and eco-friendly alternative to the existing methods for the construction of the quinazolinone/quinazolinthione framework. We have interpreted the reaction mechanism by use of quantum chemical calculations on the basis of state-of-the-art computational methods SMD-B3LYP-D3(BJ)/BS1//B3LYP/BS1.

Cp*CoIII-catalyzed formal [4+2] cycloaddition of benzamides to afford quinazolinone derivatives

A Cp*Co^III-catalyzed arene C–H bond amidation/annulation of benzamides was developed to afford quinazolinone derivatives in one-pot with high yields and broad substrate scope.

Facile synthetic approach towards vasorelaxant active 4-hydroxyquinazoline-4-carboxamides

A Facile synthetic approach is reported towards 4-hydroxyquinazoline-4-carboxamides 13a–i through ring expansion of 2,3-dioxoindoline-1-carboxamides 10a–c during secondary amine 11a–d nucleophilic reaction. Single crystal X-ray studies of 10c and 13d support the structures. Some of the synthesized quinazolinecarboxamides 13 show promising vasorelaxant properties with potency higher than that of Doxazosin through the pre-contracted (norepinephrine hydrochloride) rat aorta standard bioassay. Good molecular models (2D-QSAR, pharmacophore) describe the biological observations.

A set of vasorelaxant active 4-hydroxyquinazoline-4-carboxamides was obtained in a novel synthetic approach via secondary amine nucleophilic reaction with 2,3-dioxoindoline-1-carboxamides.

Transition metal-free synthesis of quinazolinones using dimethyl sulfoxide as a synthon

Biologically important quinazolinones have been synthesized from 2-aminobenzamides and DMSO.