Antifolate and antibacterial activities of 5-substituted 2,4-diaminoquinazolines

Fungicidal activity of novel quinazolin-6-ylcarboxylates and mode of action on Botrytis cinerea

BACKGROUND

Fungal diseases remain important causes of crop failure and economic losses. As the resistance toward current selective fungicides becomes increasingly problematic, it is necessary to develop efficient fungicides with novel chemotypes.

RESULTS

A series of novel quinazolin-6-ylcarboxylates which combined the structures of pyridine or heterocyclic motif and the N-(3-chloro-4-fluorophenyl)quinazolin-4-amine moiety, a binding group of ATP-binding site of gefitinib, were evaluated for their fungicidal activity on different phytopathogenic fungi. Most of these compounds showed excellent fungicidal activities against Botrytis cinerea and Exserohilum rostratum, especially compound F17 displayed the highest activity with EC50 values as 3.79 μg mL-1 against B. cinerea and 2.90 μg mL-1 against E. rostratum, which was similar to or even better than those of the commercial fungicides, such as pyraclostrobin (EC50 , 3.68, 17.38 μg mL-1 ) and hymexazol (EC50 , 4.56, 2.13 μg mL-1 ). Moreover, compound F17 significantly arrested the lesion expansion of B. cinerea infection on tomato detached leaves and strongly suppressed grey mold disease on tomato seedlings in greenhouse. The abilities of compound F17 to induce cell apoptosis of the non-germinated spores, to limit oxalic acid production, to reduce malate dehydrogenase (MDH) expression, and to block the active pocket of MDH protein were demonstrated in B. cinerea.

CONCLUSION

The novel quinazolin-6-ylcarboxylates containing ATP-binding site-directed moiety, especially compound F17, could be developed as a potential fungicidal candidate for further study. © 2023 Society of Chemical Industry.

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.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Optimization of the 2,4-substituents

The emergence of bacterial resistance has triggered a multitude of efforts to develop new antibacterial agents. There are many compounds in literature that were reported as potent antibacterial agents, however, they lacked the required safety to mammalian cells or no clear picture about their toxicity profile was presented. Inspired by discovered hit from our in-house library and by previously reported 2,4-diaminosubstituted quinazolines, we describe the design and synthesis of novel 2,4-disubstituted-thioquinazolines (3-13 and 36), 2-thio-4-amino substituted quinazolines (14-33) and 6-substituted 2,4-diamonsubstituted quinazolines (37-39). The synthesized compounds showed potent antibacterial activity against a panel of Gram-positive, efflux deficient E.coli and Mycobacterium smegmatis. The panel also involved resistant strains including methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae, vancomycin-resistant Enterococcus faecalis and vancomycin-resistant Enterococcus faecium, in addition to Mycobacterium smegmatis. The newly synthesized compounds revealed MIC values against the tested strains ranging from 1 to 64 µg/mL with a good safety profile. Most of the 2-thio-4-amino substituted-quinazolines showed significant antimycobacterial activity with the variations at position 2 and 4 offering additional antibacterial activity against the different strains. Compared to previously reported 2,4-diaminosubstituted quinazolines, the bioisosteric replacement of the 2-amino with sulfur offered a successful approach to keep the high antibacterial potency while substantially improving safety profile as indicated by the reduced activity on different cell lines and a lack of hemolytic activity.

Synthesis, in vitro antitumour activity, and molecular docking study of novel 2-substituted mercapto-3-(3,4,5-trimethoxybenzyl)-4(3H)-quinazolinone analogues

A novel series of 2-substituted mercapto-3-(3,4,5-trimethoxybenzyl)-4(3H)-quinazolinones 1–20 was synthesised and evaluated for in vitro antitumour activity. N-(4-Chlorophenyl)-2-[(3-(3,4,5-trimethoxybenzyl)-4(3H)-quinazolinon-2-yl)thio)acetamide (7) and N-(3,4,5 trimethoxybenzyl)-2-[(3-(3,4,5-trimethoxybenzyl)-4(3H)-quinazolinon-2-yl)thio]propanamide (19) exhibited excellent antitumour properties, with mean growth inhibitory concentration (GI₅₀) of 17.90 and 6.33 µΜ, respectively, compared with those of 5-fluorouracil 5-FU, gefitinib, and erlotinib (mean GI₅₀: 18.60, 3.24, and 7.29 µΜ, respectively). Comparison of the GI₅₀ (µM) values of compounds 7 and 19 versus those of 5-FU, gefitinib, and erlotinib against an in vitro subpanel of tumour cells lines showed that compounds 7 and 19 have activities almost equal to or higher than that of those standard drugs, especially against lung, CNS, and breast cancer cells. However, compounds 5, 10, 14, 15, 16, 17, and 20 exhibited effective antitumour activity against the different cell lines tested, with growth inhibition percentage (MGI%) of 19, 24, 19, 17, 16, 15, and 16, respectively. A modelling study was performed for compounds 7 and 19 by docking them into the EGFR kinase enzyme to study their mode of binding with the putative binding site.

Characterizing the Antimicrobial Activity of N2,N4-Disubstituted Quinazoline-2,4-Diamines toward Multidrug-Resistant Acinetobacter baumannii

We previously reported a series of N²,N⁴-disubstituted quinazoline-2,4-diamines as dihydrofolate reductase inhibitors with potent in vitro and in vivo antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. In this work, we extended our previous study to the Gram-negative pathogen Acinetobacter baumannii We determined that optimized N²,N⁴-disubstituted quinazoline-2,4-diamines are strongly antibacterial against multidrug-resistant A. baumannii strains when the 6-position is replaced with a halide or an alkyl substituent. Such agents display potent antibacterial activity, with MICs as low as 0.5 μM, while proving to be strongly bactericidal. Interestingly, these compounds also possess the potential for antibiofilm activity, eradicating 90% of cells within a biofilm at or near MICs. Using serial passage assays, we observed a limited capacity for the development of resistance toward these molecules (4-fold increase in MIC) compared to existing folic acid synthesis inhibitors, such as trimethoprim (64-fold increase) and sulfamethoxazole (128-fold increase). We also identified limited toxicity toward human cells, with 50% lethal doses (LD₅₀s) of ≤23 μM for lead agents 4 and 5. Finally, we demonstrated that our lead agents have excellent in vivo efficacy, with lead agent 5 proving more efficacious than tigecycline in a murine model of A. baumannii infection (90% survival versus 66%), despite being used at a lower dose (2 versus 30 mg kg^-1). Together, our results demonstrate that N²,N⁴-disubstituted quinazoline-2,4-diamines have strong antimicrobial and antibiofilm activities against both Gram-positive organisms and Gram-negative pathogens, suggesting strong potential for their development as antibacterial agents.

Design, synthesis of 2,3-disubstitued 4(3H)-quinazolinone derivatives as anti-inflammatory and analgesic agents: COX-1/2 inhibitory activities and molecular docking studies

A new series, 2-substituted mercapto-3-[2-(pyridin-2-yl)ethyl]-4(3H)-quinazolinone 1-21, was synthesized and evaluated for in vivo anti-inflammatory and analgesic activities and in vitro COX-1/COX-2 inhibition. Compounds 1, 4, 5, 6, 8, 10, 13, 14, 15, 16, and 17 exhibited potent anti-inflammatory and analgesic properties, with ED50 values of 50.3-112.1mg/kg and 12.3-111.3mg/kg, respectively. These values may be compared with those of diclofenac sodium (ED50=112.2 and 100.4mg/kg) and celecoxib (ED50=84.3 and 71.6mg/kg). Compounds 4 and 6 possessed strong COX-2 inhibitory activity with IC50 (0.33μM and 0.40μM, respectively) and selectivity index (SI>303.0 and >250.0, respectively) values that are similar to those of the reference drug celecoxib (IC50 0.30μM and COX-2 SI>333). Compounds 5, 8, and 13 demonstrated effective COX-2 inhibitory activity with IC50 values of 0.70-0.80μM and COX-2 SI>125-142. Potent COX-2 inhibitors, such as compounds 4, 6, and 13, were docked into the active site pockets of COX-1 and COX-2, with the greatest recognition occurring at the COX-2 binding site and insignificant interactions at the binding site of the COX-1 pocket.

Structure-based design of new DHFR-based antibacterial agents: 7-aryl-2,4-diaminoquinazolines

Dihydrofolate reductase (DHFR) inhibitors such as trimethoprim (TMP) have long played a significant role in the treatment of bacterial infections. Not surprisingly, after decades of use there is now bacterial resistance to TMP and therefore a need to develop novel antibacterial agents with expanded spectrum including these resistant strains. In this study, we investigated the optimization of 2,4-diamnoquinazolines for antibacterial potency and selectivity. Using structure-based drug design, several 7-aryl-2,4-diaminoquinazolines were discovered that have excellent sub-100 picomolar potency against bacterial DHFR. These compounds have good antibacterial activity especially on gram-positive pathogens including TMP-resistant strains.

Synthesis and biological evaluation of novel 2,4-diaminoquinazoline derivatives as SMN2 promoter activators for the potential treatment of spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) is an autosomal recessive disorder characterized by death of motor neurons in the spinal cord that is caused by deletion and/or mutation of the survival motor neuron gene ( SMN1). Adjacent to SMN1 are a variable number of copies of the SMN2 gene. The two genes essentially differ by a single nucleotide, which causes the majority of the RNA transcripts from SMN2 to lack exon 7. Although both SMN1 and SMN2 encode the same Smn protein amino acid sequence, the loss of SMN1 and incorrect splicing of SMN2 have the consequence that Smn protein levels are insufficient for the survival of motor neurons. The therapeutic goal of our medicinal chemistry effort was to identify small-molecule activators of the SMN2 promoter that, by up-regulating gene transcription, would produce greater quantities of full-length Smn protein. Our initial medicinal chemistry effort explored a series of C5 substituted benzyl ether based 2,4-diaminoquinazoline derivatives that were found to be potent activators of the SMN2 promoter; however, inhibition of DHFR was shown to be an off-target activity that was linked to ATP depletion. We used a structure-guided approach to overcome DHFR inhibition while retaining SMN2 promoter activation. A lead compound 11a was identified as having high potency (EC50 = 4 nM) and 2.3-fold induction of the SMN2 promoter. Compound 11a possessed desirable pharmaceutical properties, including excellent brain exposure and long brain half-life following oral dosing to mice. The piperidine compound 11a up-regulated expression of the mouse SMN gene in NSC-34 cells, a mouse motor neuron hybrid cell line. In type 1 SMA patient fibroblasts, compound 11a induced Smn in a dose-dependent manner when analyzed by immunoblotting and increased the number of intranuclear particles called gems. The compound restored gems numbers in type I SMA patient fibroblasts to levels near unaffected genetic carriers of SMA.

Structure-activity relationship of triazafluorenone derivatives as potent and selective mGluR1 antagonists

SAR (structure-activity relationship) studies of triazafluorenone derivatives as potent mGluR1 antagonists are described. The triazafluorenone derivatives are non-amino acid derivatives and noncompetitive mGluR1 antagonists that bind at a putative allosteric recognition site located within the seven-transmembrane domain of the receptor. These triazafluorenone derivatives are potent, selective, and systemically active mGluR1 antagonists. Compound 1n, for example, was a very potent mGluR1 antagonist (IC50 = 3 nM) and demonstrated full efficacy in various in vivo animal pain models.

Pyrrolo[1,2-a][1,4]benzodiazepine: a novel class of non-azole anti-dermatophyte anti-fungal agents

Broad screening revealed compound 1a to be a novel anti-fungal agent with high specificity towards dermatophytes. The anti-fungal structure-activity relationship of this novel class of 5,6-dihydro-4H-pyrrolo[1,2-a][1,4]benzodiazepines is described together with its mode of action that appeared to be the inhibition of squalene epoxidase. Preliminary in vivo results of the most active compounds are also reported.

Novel and efficient synthesis of 4-dimethylamino-2-glycosylaminoquinazolines by cyclodesulfurization of glycosyl thioureas with dimethylcyanamide

4-dimethylamino-2-glycosylaminoquinazoline derivatives were synthesized by cyclodesulfurization of N-aryl-N'-glycosyl thioureas with dimethylcyanamide in the presence of silver triflate in good yields.