Synthesis, fungicidal activity, and sterol 14α-demethylase binding interaction of 2-azolyl-3,4-dihydroquinazolines on Penicillium digitatum

Direct Formation of C-C, C-N, and C-O Bonds in Dihydroquinazolines via Hypervalent Iodine(III)-Mediated sp3 C-H Functionalization

A hypervalent iodine(III)-mediated cross-dehydrogenative coupling reaction for the direct formation of C-C, C-N, and C-O bonds in dihydroquinazolines has been developed. This one-pot method allows for the synthesis of C4-disubstituted dihydroquinazolines as well as C4-spirolactam, spirolactone, and spiroindene dihydroquinazolines in moderate to high yields.

Palladium-catalyzed [4 + 2] cycloaddition of 2-methylidenetrimethylene carbonate or methylene cyclic carbamate with sulfamate-derived cyclic imines

A palladium-catalyzed [4 + 2] cycloaddition of 2-methylidenetrimethylene carbonate or methylene cyclic carbamate with sulfamate-derived cyclic imines has been successfully developed under mild reaction conditions, affording pharmacologically interesting oxazine or hydropyrimidine derivatives in high yields (up to 99% yield). Furthermore, the cycloaddition reactions could be efficiently scaled up and several synthetic transformations were accomplished for the construction of other useful 1,3-oxazine and hydropyrimidinone derivatives.

Synthesis of 4-Tetrazolyl-Substituted 3,4-Dihydroquinazoline Derivatives with Anticancer Activity via a One-Pot Sequential Ugi-Azide/Palladium-Catalyzed Azide-Isocyanide Cross-Coupling/Cyclization Reaction

A new one-pot preparation of 4-tetrazolyl-3,4-dihydroquinazolines has been reported. The Ugi-azide reactions of 2-azidobenzaldehydes, amines, trimethylsilyl azide, and isocyanides produced azide intermediates without separation, which were treated with isocyanides to give 4-tetrazolyl-3,4-dihydroquinazoline derivatives through a sequential Palladium-catalyzed azide-isocyanide cross-coupling/cyclization reaction in moderate to good yields. The biological evaluation demonstrated that compound 6c inhibited breast cancer cells well and displayed broad applications for synthesis and medicinal chemistry.

Antitubercular, Cytotoxicity, and Computational Target Validation of Dihydroquinazolinone Derivatives

A series of 2,3-dihydroquinazolin-4(1H)-one derivatives (3a–3m) was screened for in vitro whole-cell antitubercular activity against the tubercular strain H37Rv and multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB) strains. Compounds 3l and 3m with di-substituted aryl moiety (halogens) attached to the 2-position of the scaffold showed a minimum inhibitory concentration (MIC) of 2 µg/mL against the MTB strain H37Rv. Compound 3k with an imidazole ring at the 2-position of the dihydroquinazolin-4(1H)-one also showed significant inhibitory action against both the susceptible strain H37Rv and MDR strains with MIC values of 4 and 16 µg/mL, respectively. The computational results revealed the mycobacterial pyridoxal-5′-phosphate (PLP)-dependent aminotransferase (BioA) enzyme as the potential target for the tested compounds. In vitro, ADMET calculations and cytotoxicity studies against the normal human dermal fibroblast cells indicated the safety and tolerability of the test compounds 3k–3m. Thus, compounds 3k–3m warrant further optimization to develop novel BioA inhibitors for the treatment of drug-sensitive H37Rv and drug-resistant MTB.

Recent research progress and outlook in agricultural chemical discovery based on quinazoline scaffold

The discovery of new scaffolds and targets for pesticides is still a huge challenge facing the sustainable development of modern agriculture. In recent years, quinazoline derivatives have achieved great progress in drug discovery and have attracted great attention. Quinazoline is a unique bicyclic scaffold with a variety of biological activities, which increases the possibilities and flexibility of structural modification, showing enormous appeal in the discovery of new pesticides. Therefore, the agricultural biological activities, structure-activity relationships (SAR), and mechanism of action of quinazoline derivatives in the past decade were reviewed systematically, with emphasis on SAR and mechanism. Then, we prospected the application of the quinazoline scaffold as a special structure in agricultural chemical discovery, hoping to provide new ideas for the rational design and mechanism of novel quinazoline agricultural chemicals in the future.

New efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines through a Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution sequence

A new efficient synthesis of polysubstituted 3,4-dihydroquinazolines and 4H-3,1-benzothiazines via sequential Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution reaction has been developed. The three-component Passerini reactions of 2-azidobenzaldehydes 1, benzoic acid (2), and isocyanides 3 produced the azide intermediates 4, which were treated sequentially with triphenylphosphine, isocyanates (or CS₂), and secondary amines to give polysubstituted 3,4-dihydroquinazolines 8 and 4H-3,1-benzothiazines 11 in good overall yields through consecutive Passerini/Staudinger/aza-Wittig/addition/nucleophilic substitution reactions.

A Concise and Efficient CuI-catalyzed Synthesis of Diimino Dihydroquinazoline Derivatives from Isocyanides and Guanidines Derivatives Through Intramolecular C-H Activation

:

A novel series of diimino dihydroquinazoline derivatives were synthesized from isocyanides and guanidine analogs in quantitative yields by applying an efficient, inexpensive, one-pot copper-catalyzed intramolecular C-H activation reaction under mild conditions. The structures were confirmed on the basis of IR, 1HNMR, 13C NMR, mass spectral and elemental analysis data. The protocol offers advantages like short reaction time, simple workup process, high yields, and an environmentally benign methodology. Interestingly, better results (yield = 82%) were observed in terms of the yield obtained by using a mixture of CuI, Cs2CO3 and acetonitrile as the catalyst, base and solvent, respectively. The data also suggested that compound 5i is produced with the highest yield (87%) from the corresponding diisopropyl carbon diimide, 4-nitroaniline and phenyl isocyanide. Finally, a mechanistic explanation for the reaction promoted by cuprous iodide (CuI) was proposed on the basis of previous investigations and our experimental observations.

Advances in Proteasome Enhancement by Small Molecules

The proteasome system is a large and complex molecular machinery responsible for the degradation of misfolded, damaged, and redundant cellular proteins. When proteasome function is impaired, unwanted proteins accumulate, which can lead to several diseases including age-related and neurodegenerative diseases. Enhancing proteasome-mediated substrate degradation with small molecules may therefore be a valuable strategy for the treatment of various neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington's diseases. In this review, we discuss the structure of proteasome and how proteasome's proteolytic activity is associated with aging and various neurodegenerative diseases. We also summarize various classes of compounds that are capable of enhancing, directly or indirectly, proteasome-mediated protein degradation.

A bifunctional iminophosphorane squaramide catalyzed enantioselective synthesis of hydroquinazolines via intramolecular aza-Michael reaction to α,β-unsaturated esters

An efficient synthesis of enantioenriched hydroquinazoline cores via a novel bifunctional iminophosphorane squaramide catalyzed intramolecular aza-Michael reaction of urea-linked α,β-unsaturated esters is described. The methodology exhibits a high degree of functional group tolerance around the forming hydroquinazoline aryl core and wide structural variance on the nucleophilic N atom of the urea moiety. Excellent yields (up to 99%) and high enantioselectivities (up to 97 : 3 er) using both aromatic and less acidic aliphatic ureas were realized. The potential industrial applicability of the transformation was demonstrated in a 20 mmol scale-up experiment using an adjusted catalyst loading of 2 mol%. The origin of enantioselectivity and reactivity enhancement provided by the squaramide motif has been uncovered computationally using density functional theory (DFT) calculations, combined with the activation strain model (ASM) and energy decomposition analysis (EDA).

The activation of both aromatic and aliphatic ureas as N-centered nucleophiles in intramolecular Michael addition reactions to α,β-unsaturated esters was achieved under bifunctional iminophosphorane squaramide superbase catalysis.

Imidazole and Imidazolium Antibacterial Drugs Derived from Amino Acids

The antibacterial activity of imidazole and imidazolium salts is highly dependent upon their lipophilicity, which can be tuned through the introduction of different hydrophobic substituents on the nitrogen atoms of the imidazole or imidazolium ring of the molecule. Taking this into consideration, we have synthesized and characterized a series of imidazole and imidazolium salts derived from L-valine and L-phenylalanine containing different hydrophobic groups and tested their antibacterial activity against two model bacterial strains, Gram-negative E. coli and Gram-positive B. subtilis. Importantly, the results demonstrate that the minimum bactericidal concentration (MBC) of these derivatives can be tuned to fall close to the cytotoxicity values in eukaryotic cell lines. The MBC value of one of these compounds toward B. subtilis was found to be lower than the IC₅₀ cytotoxicity value for the control cell line, HEK-293. Furthermore, the aggregation behavior of these compounds has been studied in pure water, in cell culture media, and in mixtures thereof, in order to determine if the compounds formed self-assembled aggregates at their bioactive concentrations with the aim of determining whether the monomeric species were in fact responsible for the observed antibacterial activity. Overall, these results indicate that imidazole and imidazolium compounds derived from L-valine and L-phenylalanine—with different alkyl lengths in the amide substitution—can serve as potent antibacterial agents with low cytotoxicity to human cell lines.

One-Pot Tandem Assembly of Amides, Amines, and Ketones: Synthesis of C4-Quaternary 3,4- and 1,4-Dihydroquinazolines

A multicomponent tandem assembly procedure for the synthesis of diverse C4-quaternary 3,4-dihydroquinazolines from amides, amines, and ketones has been developed. The one-pot reaction involves successive triflic anhydride mediated amide dehydration, ketimine addition, and Pictet-Spengler-like cyclization processes and affords products in up to 92% yield. Conversion of 3,4-dihydroquinazolines to the corresponding 1,4-dihydroquinazolines via a two-step N1 dealkylation and regioselective N3 functionalization protocol, including computational rationale for the observed regioselectivity, is also described.

Larvicidal Activities of 2-Aryl-2,3-Dihydroquinazolin -4-ones against Malaria Vector Anopheles arabiensis, In Silico ADMET Prediction and Molecular Target Investigation

Malaria, affecting all continents, remains one of the life-threatening diseases introduced by parasites that are transmitted to humans through the bites of infected Anopheles mosquitoes. Although insecticides are currently used to reduce malaria transmission, their safety concern for living systems, as well as the environment, is a growing problem. Therefore, the discovery of novel, less toxic, and environmentally safe molecules to effectively combat the control of these vectors is in high demand. In order to identify new potential larvicidal agents, a series of 2-aryl-1,2-dihydroquinazolin-4-one derivatives were synthesized and evaluated for their larvicidal activity against Anopheles arabiensis. The in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of the compounds were also investigated and most of the derivatives possessed a favorable ADMET profile. Computational modeling studies of the title compounds demonstrated a favorable binding interaction against the acetylcholinesterase enzyme molecular target. Thus, 2-aryl-1,2-dihydroquinazolin-4-ones were identified as a novel class of Anopheles arabiensis insecticides which can be used as lead molecules for the further development of more potent and safer larvicidal agents for treating malaria.

Triflic anhydride mediated synthesis of 3,4-dihydroquinazolines: a three-component one-pot tandem procedure

A one-pot three-component tandem reaction involving a key Pictet-Spengler-like annulation step has been developed, providing an efficient method for the synthesis of 3,4-dihydroquinazolines in moderate to good yields from amides, aldehydes, and amines. The multicomponent triflic anhydride mediated reaction tolerates the installation of numerous functional groups, affording extensive diversity about the heterocyclic scaffold.

Rational Optimization and Action Mechanism of Novel Imidazole (or Imidazolium)-Labeled 1,3,4-Oxadiazole Thioethers as Promising Antibacterial Agents against Plant Bacterial Diseases

The emergence and widespread occurrence of plant bacterial diseases that cause global production constraints have become major challenges to agriculture worldwide. To promote the discovery and development of new bactericides, imidazole-labeled 1,3,4-oxadiazole thioethers were first fabricated by integrating the crucially bioactive scaffolds of the imidazole motif and 1,3,4-oxadiazole skeleton in a single molecular architecture. Subsequently, a superior antibacterial compound A₆ was gradually discovered possessing excellent competence against plant pathogens Xanthomonas oryzae pv oryzae and Xanthomonas axonopodis pv citri with EC₅₀ values of 0.734 and 1.79 μg/mL, respectively. These values were better than those of commercial agents bismerthiazol (92.6 μg/mL) and thiodiazole copper (77.0 μg/mL). Further modifying the imidazole moiety into the imidazolium scaffold led to the discovery of an array of potent antibacterial compounds providing the corresponding minimum EC₅₀ values of 0.295 and 0.607 μg/mL against the two strains. Moreover, a plausible action mechanism for attacking pathogens was proposed based on the concentration dependence of scanning electron microscopy, transmission electron microscopy, and fluorescence microscopy images. Given the simple molecular structures, easy synthetic procedure, and highly efficient bioactivity, imidazole (or imidazolium)-labeled 1,3,4-oxadiazole thioethers can be further explored and developed as promising indicators for the development of commercial drugs.

Synthesis of dihydroquinazolines from 2-aminobenzylamine: N 3 -aryl derivatives with electron-withdrawing groups

The sequential N-functionalization of 2-aminobenzylamine (2-ABA) followed by cyclodehydration allowed for a straightforward and efficient synthesis of 3,4-dihydroquinazolines with N-aryl substituents bearing electron-withdrawing groups. The sequence involves an initial S_NAr displacement, N-acylation and MW-assisted ring closure. Remarkably, the uncatalyzed N-arylation of 2-ABA led to the monosubstitution product using equimolar amounts of both reagents. The individual steps were optimized achieving good to excellent overall yields of the desired heterocycles, avoiding additional protection and deprotection steps. A mechanistic interpretation for the cyclodehydration reaction promoted by trimethylsilyl polyphosphate (PPSE) is also proposed on the basis of literature data and our experimental observations.

Access to Chiral Hydropyrimidines through Palladium-Catalyzed Asymmetric Allylic C-H Amination

A palladium-catalyzed asymmetric intramolecular allylic C-H amination controlled by a chiral phosphoramidite ligand was established for the preparation of various substituted chiral hydropyrimidinones, the precursors of hydropyrimidines, in high yields with high enantioselectivities. In particular, dienyl sodium N-sulfonyl amides bearing an arylethene-1-sulfonyl group underwent a sequential allylic C-H amination and intramolecular Diels-Alder (IMDA) reaction to produce chiral fused tricyclic tetrahydropyrimidinone frameworks in high yields and with high levels of stereoselectivity. Significantly, this method was used as the key step in an asymmetric synthesis of letermovir.

Synthesis of novel (E)-2-(4-(1H-1,2,4-triazol-1-yl)styryl)-4- (alkyl/arylmethyleneoxy)quinazoline derivatives as antimicrobial agents

A series of novel (E)-2-(4-(1H-1,2,4-triazol-1-yl)styryl)-4-(alkyl/arylmethyleneoxy)quinazoline derivatives (4a-4s) were synthesized in good to excellent yields, and their structures were fully characterized by [Formula: see text] NMR, [Formula: see text] NMR, HRMS and IR spectra. The structure of compound 4b was further confirmed via single-crystal X-ray diffraction analysis. The bioassay results indicated that compounds 4s, 4q and 4n inhibit phytopathogenic bacterium Xanthomonas axonopodis pv. citri (Xac) more potently than commercial bactericide bismerthiazol. However, not a single compound can effectively inhibit three pathogenic fungi tested at 50 [Formula: see text].

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

A straightforward strategy for the synthesis of dihydroquinazolines is presented, which allows for the preparation of 3,4- and 1,4-dihydroquinazolines with different substitution patterns from 2-aminobenzylamine (2-ABA) as common precursor. The required functionalization of both amino groups present in 2-ABA was achieved by different routes involving selective N-acylation and cesium carbonate-mediated N-alkylation reactions, avoiding protection/deprotection steps. The heterocycles were efficiently synthesized in short reaction times by microwave-assisted ring closure of the corresponding aminoamides promoted by ethyl polyphosphate (PPE).

Pharmacophore-Based Virtual Screening of Novel Inhibitors and Docking Analysis for CYP51A from Penicillium italicum

Sterol 14α-demethylases from Cytochrome P450 family (CYP51s) are essential enzymes in sterol biosynthesis and well-known as the target of antifungal drugs. The 3D structure of CYP51A from Penicillium italicum (PiCYP51A) was constructed through homology modeling based on the crystal structure of human CYP51A (PDB: 3LD6). Molecular dynamics (MD) simulation was operated to relax the initial model and followed by quality assessment using PROCHECK program. On the basis of the docking information on the currently available CYP51s with the patent demethylase inhibitors (DMIs), pharmacophore-based virtual screening combined with docking analysis was performed to pick out twelve new compounds from ZINC database. Six hits revealed in the ligand database suggested potential ability to inhibit PiCYP51A. Compared to patent fungicide triazolone, the top three lead compounds had similar or higher affinity with the target enzyme, and accordingly, exhibited comparable or lower EC50 values to P. italicum isolates. The results could provide references for de novo antifungal drug design.

Design, synthesis and biological evaluation of novel 3-alkylsulfanyl-4-amino-1,2,4-triazole derivatives

Based on our previous work, a series of novel 3-alkylsulfanyl-4-amino-1,2,4-triazole derivatives were designed, synthesized and evaluated for their antiproliferative activities. The results indicated that some compounds possessed significant antiproliferative activities against four cancer cell lines, HepG2, HCT116, PC-3, and Hela. Particularly, the most promising compound 8d displayed 184-, 18-, and 17-fold improvement compared to fluorouracil in inhibiting HCT116, Hela and PC-3 cell proliferation with IC50 values of 0.37, 2.94, and 31.31μM, respectively. Most interestingly, the compound did not affect the normal human embryonic kidney cells, HEK-293. Moreover, mechanistic investigation showed that the representative compound 8d induced apoptosis and blocked cell cycle in G2/M phase in Hela cells in a dose-dependent manner. These findings suggest that compound 8d may have potential to be developed as a promising lead for the design of novel anticancer small-molecule drugs.

Design, synthesis and structure-activity relationship of novel oxime ether strobilurin derivatives containing substituted benzofurans

BACKGROUND

Strobilurins are one of the most important classes of agricultural fungicides. To discover new strobilurin analogues with broad spectrum and high activity, a series of novel oxime ether strobilurin derivatives containing substituted benzofurans in the side chain were synthesised and bioassayed.

RESULTS

The synthesised compounds were characterised by (1) H NMR, (13) C NMR, MS and HRMS. Bioassays demonstrated that most target compounds possessed good or excellent fungicidal activities, especially against Erysiphe graminis and Pyricularia oryzae. Furthermore, methyl 3-methoxypropenoate oxime ethers exhibited remarkably higher activities against E. graminis, Colletotrichum lagenarium and Puccinia sorghi Schw. Notably, (E,E)-methyl 3-methoxy-2-{2-[({[5-fluoro-1-(benzofuran-2-yl)ethylidene]amino}oxy)methyl]phenyl}propenoate (BSF2) and (E,E)-methyl 3-methoxy-2-{2-[({[5-chloro-1-(benzofuran-2-yl)ethylidene]amino}oxy)methyl]phenyl}propenoate (BSF3) were identified as the most promising candidates for further study.

CONCLUSION

The present work demonstrates that oxime ether strobilurin derivatives containing benzofurans can be used as possible lead compounds for developing novel fungicides.

A novel sterol regulatory element-binding protein gene (sreA) identified in penicillium digitatum is required for prochloraz resistance, full virulence and erg11 (cyp51) regulation

Penicilliumdigitatum is the most destructive postharvest pathogen of citrus fruits, causing fruit decay and economic loss. Additionally, control of the disease is further complicated by the emergence of drug-resistant strains due to the extensive use of triazole antifungal drugs. In this work, an orthologus gene encoding a putative sterol regulatory element-binding protein (SREBP) was identified in the genome of P. digitatum and named sreA. The putative SreA protein contains a conserved domain of unknown function (DUF2014) at its carboxyl terminus and a helix-loop-helix (HLH) leucine zipper DNA binding domain at its amino terminus, domains that are functionally associated with SREBP transcription factors. The deletion of sreA (ΔsreA) in a prochloraz-resistant strain (PdHS-F6) by Agrobacteriumtumefaciens-mediated transformation led to increased susceptibility to prochloraz and a significantly lower EC₅₀ value compared with the HS-F6 wild-type or complementation strain (COsreA). A virulence assay showed that the ΔsreA strain was defective in virulence towards citrus fruits, while the complementation of sreA could restore the virulence to a large extent. Further analysis by quantitative real-time PCR demonstrated that prochloraz-induced expression of cyp51A and cyp51B in PdHS-F6 was completely abolished in the ΔsreA strain. These results demonstrate that sreA is a critical transcription factor gene required for prochloraz resistance and full virulence in P. digitatum and is involved in the regulation of cyp51 expression.

Design, synthesis, and biological activity of oxime ether strobilurin derivatives containing indole moiety as novel fungicide

Twenty-one novel oxime ether strobilurins containing indole moiety, which employed an indole group to stabilize the E-styryl group in Enoxastrobin, were designed and synthesized. The biological assay indicated that most compounds exhibited potent fungicidal activities. The structure-activity relationship study demonstrated that the synthesized methyl 3-methoxypropenoate oxime ethers 7b-e exhibited remarkably high activities among all the synthesized oxime ether compounds 7. Moreover, the fungicidal activities of methyl α-(methoxyimino)benzeneacetate oxime ethers compounds 7f-i and N-methoxy-carbamic acid methyl esters compounds 7j-m showed significant differences compared to the corresponding products of ammonolysis.

Synthesis and fungistatic activity of bicyclic lactones and lactams against Botrytis cinerea, Penicillium citrinum, and Aspergillus glaucus

Six analogues of natural trans-4-butyl-cis-3-oxabicyclo[4.3.0]nonan-2-one (3) and three derivatives, 11, 12, and 13, of Vince lactam (10) were synthesized and tested as fungistatic agents against Botrytis cinerea AM235, Penicillium citrinum AM354, and six strains of Aspergillus. Moreover, bioresolution carried out by means of whole cell microorganisms and commercially available enzymes afforded opposite enantiomerically enriched (-) and (+) isomers of Vince lactam (10), respectively. The effect of compound structures and stereogenic centers on biological activity has been discussed. The highest fungistatic activity was observed for four lactones: 3, 4, 7, and 8 (IC50 = 104.6-115.2 μg/mL) toward B. cinerea AM235. cis-5,6-Epoxy-2-aza[2.2.1]heptan-3-one (13) indicated significant fungistatic activity (IC50 = 107.1 μg/mL) against Aspergillus glaucus AM211. trans-4-Butyl-cis-3-oxabicyclo[4.3.0]nonan-2-one (3) and trans-4-butyl-cis-3-oxabicyclo[4.3.0]non-7-en-2-one (7) exhibited high fungistatic activity (IC50 = 143.2 and 110.2 μg/mL, respectively) against P. citrinum AM354 as well.