Synthesis and antimicrobial activity of pyrimidinyl 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and 1,2,4-triazoles

Antifungal Activity of Novel Indole Derivatives Containing 1,3,4-Thiadiazole

In this study, 24 indole derivatives containing 1,3,4-thiadiazole were discovered and synthesized. The target compounds' antifungal efficacy against 14 plant pathogenic fungal pathogens was then determined in vitro. With an EC50 value of 2.7 μg/mL, Z2 demonstrated the highest level of bioactivity among them against Botrytis cinerea (B.c.), exceeding the concentrations of the control prescription drugs azoxystrobin (Az) (EC50 = 14.5 μg/mL) and fluopyram (Fl) (EC50 = 10.1 μg/mL). Z2 underwent in vivo testing on blueberry leaves in order to evaluate its usefulness in real-world settings. A reasonable protective effect was obtained with a control effectiveness of 93.0% at 200 μg/mL, which was superior to those of Az (83.0%) and Fl (52.0%). At 200 μg/mL, this chemical had an efficacy of 84.0% in terms of curative efficacy. These figures outperformed those of Az (69.0%) and Fl (48.0%). Scanning electron microscopy (SEM) experiments and light microscopy experiments showed that Z2 altered the integrity of the cell wall and cell membrane of the pathogenic fungus B.c., which led to an increase in the content of malondialdehyde (MDA), cellular leakage, and cellular permeability. Enzyme activity assays and molecular docking studies indicated that Z2 could act as a potential succinate dehydrogenase inhibitor (SDHI). It was hypothesized that Z2 could cause disruption of mycelial cell membranes, which in turn leads to mycelial death. According to the research, indole derivatives containing 1,3,4-thiadiazole were expected to evolve into new fungicides due to their significant antifungal effects on plant fungi.

Design, Synthesis, and Mode of Action of Thioacetamide Derivatives as the Algicide Candidate Based on Active Substructure Splicing Strategy

Lakes and reservoirs worldwide are experiencing a growing problem with harmful cyanobacterial blooms (HCBs), which have significant implications for ecosystem health and water quality. Algaecide is an effective way to control HCBs effectively. In this study, we applied an active substructure splicing strategy for rapid discovery of algicides. Through this strategy, we first optimized the structure of the lead compound S5, designed and synthesized three series of thioacetamide derivatives (series A, B, C), and then evaluated their algicidal activities. Finally, compound A3 with excellent performance was found, which accelerated the process of discovering and developing new algicides. The biological activity assay data showed that A3 had a significant inhibitory effect on M. aeruginosa. FACHB905 (EC50 = 0.46 μM) and Synechocystis sp. PCC6803 (EC50 = 0.95 μM), which was better than the commercial algicide prometryn (M. aeruginosa. FACHB905, EC50 = 6.52 μM; Synechocystis sp. PCC6803, EC50 = 4.64 μM) as well as better than lead compound S5 (M. aeruginosa. FACHB905, EC50 = 8.80 μM; Synechocystis sp. PCC6803, EC50 = 7.70 μM). The relationship between the surface electrostatic potential, chemical reactivity, and global electrophilicity of the compounds and their activities was discussed by density functional theory (DFT). Physiological and biochemical studies have shown that A3 might affect the photosynthesis pathway and antioxidant system in cyanobacteria, resulting in the morphological changes of cyanobacterial cells. Our work demonstrated that A3 might be a promising candidate for the development of novel algicides and provided a new active skeleton for the development of subsequent chemical algicides.

Thiadiazole and Thiazole Derivatives as Potential Antimicrobial Agents

BACKGROUND

This review summarizes data on heterocyclic systems with thiadiazole and thiazole fragments in molecules as promising antimicrobial agents.

INTRODUCTION

Thiadiazole and thiazole backbones are the most favored and well-known heterocycles, a common and essential feature of various drugs. These scaffolds occupy a central position and are the main structural components of numerous drugs with a wide spectrum of action. These include antimicrobial, antituberculous, anti-inflammatory, analgesic, antiepileptic, antiviral, and anticancer agents.

METHOD

The research is based on bibliosemantic and analytical methods using bibliographic and abstract databases, as well as databases of chemical compounds.

RESULT

This review reports on thiadiazole and thiazole derivatives, which have important pharmacological properties. We are reviewing the structural modifications of various thiadiazole and thiazole derivatives, more specifically, the antimicrobial activity reported over the last years, as we have taken this as our main research area. 80 compounds were illustrated, and various derivatives containing hydrazone bridged thiazole and pyrrole rings, 2-pyridine and 4-pyridine substituted thiazole derivatives, compounds containing di-, tri- and tetrathiazole moieties, spiro-substituted 4- thiazolidinone-imidazoline-pyridines were analyzed. Derivatives of 5-heteroarylidene-2,4- thiazolidinediones, fluoroquinolone-thiadiazole hybrids, and others.

CONCLUSION

1,3,4-thiadiazoles and thiazoles are valuable resource for researchers engaged in rational drug design and development in this area.

Recent advances in 1,2,3- and 1,2,4-triazole hybrids as antimicrobials and their SAR: A critical review

With the widespread use and sometimes even abuse of antibiotics, the problem of bacterial resistance to antibiotics has become very serious, and it is posing a great threat to global health. Therefore, development of new antibiotics is imperative. Triazoles are five-membered, nitrogen-containing aromatic heterocyclic scaffolds, with two isomeric forms, i.e. 1,2,3-triazole and 1,2,4-triazole. Triazole-containing compounds have a wide range of biological activities such as antibacterial, antifungal, anticancer, antioxidant, antitubercular, antimalarial, anti-HIV, anticonvulsant, anti-inflammatory, antiulcer, analgesic, and etc. The bioactivities and the diversity of triazole-containing drugs have attracted wide interest in these heterocycles. Various antibiotic triazole hybrids have been developed, and most of which have shown potent antimicrobial activities. In this review, we summarized the recent advances in triazole hybrids as potential antibacterial agents and their structure-activity relationships (SARs). The information gained through SAR studies will provide further insights into the development of new triazole antimicrobials.

An Understanding of Mechanism-Based Approaches for 1,3,4-Oxadiazole Scaffolds as Cytotoxic Agents and Enzyme Inhibitors

The world's health system is plagued by cancer and a worldwide effort is underway to find new drugs to treat cancer. There has been a significant improvement in understanding the pathogenesis of cancer, but it remains one of the leading causes of death. The imperative 1,3,4-oxadiazole scaffold possesses a wide variety of biological activities, particularly for cancer treatment. In the development of novel 1,3,4-oxadiazole-based drugs, structural modifications are important to ensure high cytotoxicity towards malignant cells. These structural modification strategies have shown promising results when combined with outstanding oxadiazole scaffolds, which selectively interact with nucleic acids, enzymes, and globular proteins. A variety of mechanisms, such as the inhibition of growth factors, enzymes, and kinases, contribute to their antiproliferative effects. The activity of different 1,3,4-oxadiazole conjugates were tested on the different cell lines of different types of cancer. It is demonstrated that 1,3,4-oxadiazole hybridization with other anticancer pharmacophores have different mechanisms of action by targeting various enzymes (thymidylate synthase, HDAC, topoisomerase II, telomerase, thymidine phosphorylase) and many of the proteins that contribute to cancer cell proliferation. The focus of this review is to highlight the anticancer potential, molecular docking, and SAR studies of 1,3,4-oxadiazole derivatives by inhibiting specific cancer biological targets, such as inhibiting telomerase activity, HDAC, thymidylate synthase, and the thymidine phosphorylase enzyme. The purpose of this review is to summarize recent developments and discoveries in the field of anticancer drugs using 1,3,4-oxadiazoles.

Synthesis and Biological Evaluation of 3-(Pyridine-3-yl)-2-Oxazolidinone Derivatives as Antibacterial Agents

In this research, a series of 3-(pyridine-3-yl)-2-oxazolidinone derivatives was designed, synthesized, and evaluated for in vitro antibacterial activity, which included bacteriostatic, morphological, kinetic studies, and molecular docking. The results demonstrated that compounds 21b, 21d, 21e and 21f exhibited strong antibacterial activity similar to that of linezolid toward five Gram-positive bacteria. After observing the effect of the drug on the morphology and growth dynamics of the bacteria, the possible modes of action were predicted by molecular docking. Furthermore, the antibiofilm activity and the potential drug resistance assay was proceeded. These compounds exhibited universal antibiofilm activity and compound 21d showed significant concentration-dependent inhibition of biofilm formation. Compound 21d also showed a stable effect on S. pneumoniae (ATCC 49619) with less drug resistance growth for 15 days, which is much longer than that of linezolid. Overall, these results can be used to guide further exploration of novel antimicrobial agents.

Synthesis, crystal structure, DFT and molecular docking studies of N-acetyl-2,4-[diaryl-3-azabicyclo[3.3.1]nonan-9-yl]-9-spiro-4'-acetyl-2'-(acetylamino)-4',9-dihydro-[1',3',4']-thiadiazoles: A potential SARS-nCoV-2 Mpro (COVID-19) inhibitor

In this paper, we describe the synthesis and crystal structure analysis of N-acetyl-2,4-[diphenyl-3-azabicyclo[3.3.1]nonan-9-yl]-9-spiro-4′-acetyl-2′-(acetylamino)-4′,9-dihydro-[1′,3′,4′]-thiadiazole (3a) and N-acetyl- 2,4-[bis(p-methoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-yl]-9-spiro-4′-acetyl-2′-(acetylamino)-4′,9-dihydro-[1′,3′,4′]-thiadiazole (3b). The title compounds 3a and 3b are characterized by 1D NMR and single crystal x-ray diffraction analysis. Non-covalent interactions in a molecule were identified by Hirshfeld surface (d_norm contacts and 2D fingerprint plot) analysis. In addition, the existence of chalcogen bond (S•••O bond) in the molecular structures (3a and 3b) are described by NCI-RDG and QTAIM analysis. NBO analysis is employed to describe the orbital interactions and electron transfer between sulfur and oxygen atoms. Molecular docking is carried out for compounds 3a and 3b with COVID-19 viral protein SARS-nCoV-2 M^pro (PDB ID: 6LU7).

Comparative Study of the Synthetic Approaches and Biological Activities of the Bioisosteres of 1,3,4-Oxadiazoles and 1,3,4-Thiadiazoles over the Past Decade

The bioisosteres of 1,3,4-oxadiazoles and 1,3,4-thiadiazoles are well-known pharmacophores for many medicinally important drugs. Throughout the past 10 years, 1,3,4-oxa-/thiadiazole nuclei have been very attractive to researchers for drug design, synthesis, and the study of their potential activity towards a variety of diseases, including microbial and viral infections, cancer, diabetes, pain, and inflammation. This work is an up-to-date comparative study that identifies the differences between 1,3,4-thiadiazoles and 1,3,4-oxadiazoles concerning their methods of synthesis from different classes of starting compounds under various reaction conditions, as well as their biological activities and structure–activity relationship.

1,3,4-Thiadiazole Scaffold: As Anti-Epileptic Agents

A wide range of biological activities is exhibited by 1,3,4-thiadiazole moiety such as antidiabetic, anticancer, anti-inflammatory, anticonvulsant, antiviral, antihypertensive, and antimicrobial. To date, drugs such as butazolamide, and acetazolamide. Several modifications have been done in the 1,3,4-thiadiazole moiety which showed good potency as anticonvulsant agents which are highly effective and have less toxicity. After in-depth literature survey in this review, we have compiled various derivatives of 1,3,4-thiadiazole scaffold as anticonvulsant agents.

3-Imino derivative-sulfahydantoins: Synthesis, in vitro antibacterial and cytotoxic activities and their DNA interactions

Sulfahydantoins are five-membered rings found in the structure of chemicals that exhibit antibacterial, anti-inflammatory, and anticonvulsant properties. They also activate serine protease enzymes that catalyze the hydrolysis of peptide bonds. Five 3-imino sulfahydantoin compounds were synthesized by using Strecker synthesis reaction with minor modifications. We used reflux of various aldehydes with excess sulfamide in 85% methanol in the presence of sodium cyanide. The spectroscopic properties of these compounds were studied in detail. Antibacterial activities of all synthesized new compounds against four Gram-positive (Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Streptococcus mutans) and four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella Enteritidis) bacteria were investigated by disc diffusion and microdilution method. pBR322 plasmid DNA binding abilities of compounds were investigated in vitro by agarose gel electrophoresis. In addition, the cytotoxic activities of the compounds against the human malignant pleural mesothelioma (SPC212) cell line were determined by the MTT method. The remarkable result in this study is that the synthesized compounds, especially 4b, 4d, and 4e, have significant biological activities. It has been demonstrated that these compounds, which cause DNA damage, also have an important antibacterial effect on both Gram-negative and Gram-positive bacteria when results compared with the control group antibiotics. Compound 4e exhibited the highest antibacterial potency against Streptococcus mutans (24.33 ± 0.57) from Gram-positive bacteria and Pseudomonas aeruginosa (24.66 ± 1.15) from Gram-negative bacteria. At the same time, MTT results determined that compounds 4b, 4d, and 4e showed cytotoxic activity against the SPC212 cells. In particular, compound 4b had a high cytotoxic effect, and the IC₅₀ value was determined as 6.25 µM.

Ultrasound-assisted synthesis of pyrimidines and their fused derivatives: A review

The pyrimidine scaffold is present in many bioactive drugs; therefore, efficient synthetic routes that provide shorter reaction times, higher yields, and site-selective reactions are constantly being sought. Ultrasound (US) irradiation has emerged as an alternative energy source in the synthesis of these heterocyclic scaffolds, and over the last ten years there has been a significant increase in the number of publications mentioning US in either the construction or derivatization of the pyrimidine core. This review presents a detailed summary (with 140 references) of the effects of US (synergic or not) on the construction and derivatization of the pyrimidine core through classical reactions (e.g., multicomponent, cyclocondensation, cycloaddition, and alkylation reactions). The main points that were taken into consideration are as follows: chemo- and regioselectivity issues, and the results of conventional heating methods compared to US and mechanistic insights that are also presented and discussed for key reactions.

Green synthesis of novel antifungal 1,2,4-triazoles effective against γ-irradiated Candida parapsilosis

This study reports the green synthesis of 11 novel 3-substituted-4-amino-5-mercapto-1,2,4-triazole derivatives using water as a readily available nontoxic solvent. Evaluation of their antimicrobial potential against several clinical pathogenic microorganisms was carried out. The newly synthesized cysteine derivative 6 showed promising antifungal activity against both γ-irradiated and nonirradiated Candida parapsilosis 216, with the lowest MIC (minimum inhibitory concentration) value of 3.125 µg/ml, probably through inhibition of 14α-demethylase. In addition, compound 6 showed complete inhibition of gelatinase, a virulence enzyme of C. parapsilosis. Also, scanning electron microscopy was carried out. Interestingly, compound 6 acted as a dual agent as it also showed good antibacterial activity against strains of Gram-positive bacteria used in the study. The synthesized compounds showed no cytotoxicity.

1,2,4-Triazoles as Important Antibacterial Agents

The global spread of drug resistance in bacteria requires new potent and safe antimicrobial agents. Compounds containing the 1,2,4-triazole ring in their structure are characterised by multidirectional biological activity. A large volume of research on triazole and their derivatives has been carried out, proving significant antibacterial activity of this heterocyclic core. This review is useful for further investigations on this scaffold to harness its optimum antibacterial potential. Moreover, rational design and development of the novel antibacterial agents incorporating 1,2,4-triazole can help in dealing with the escalating problems of microbial resistance.

New Application of 1,2,4-Triazole Derivatives as Antitubercular Agents. Structure, In Vitro Screening and Docking Studies

A series of 1,2,4-triazole derivatives were synthesized and assigned as potential anti-tuberculosis substances. The molecular and crystal structures for the model compounds C1, C12, and C13 were determined using X-ray analysis. The X-ray investigation confirmed the synthesis pathway and the assumed molecular structures for analyzed 1,2,4-triazol-5-thione derivatives. The conformational preferences resulting from rotational degrees of freedom of the 1,2,4-triazole ring substituents were characterized. The lipophilicity (logP) and electronic parameters as the energy of frontier orbitals, dipole moments, NBO net charge distribution on the atoms, and electrostatic potential distribution for all structures were calculated at AM1 and DFT/B3LYP/6-311++G(d,p) level. The in vitro test was done against M. tuberculosis H37Ra, M. phlei, M. smegmatis, and M. timereck. The obtained results clearly confirmed the antituberculosis potential of compound C4, which turned out to be the most active against Mycobacterium H37Ra (MIC = 0.976 μg/mL), Mycobaterium pheli (MIC = 7.81 μg/mL) and Mycobacerium timereck (62.6 μg/mL). Satisfactory results were obtained with compounds C8, C11, C14 versus Myc. H37Ra, Myc. pheli, Myc. timereck (MIC = 31.25-62.5 μg/mL). The molecular docking studies were carried out for all investigated compounds using the Mycobacterium tuberculosis cytochrome P450 CYP121 enzyme as molecular a target connected with antimycobacterial activity.

Synthesis of Novel 3-(4-tert-Butylphenyl)-5-Cylopropyl-4H-1,2,4-Triazole Derivatives with Antioxidative and Antimicrobial Activities

Background:

In this work, new heterocyclic compounds containing 3-(4-tertbutylphenyl)- 5-cyclopropyl-4H-1,2,4-triazole ring were synthesized, starting from iminoester hydrochlorides and 4-tert-butylbenzhyrazide.

Methods:

Ethyl N-[(4-tert-butylphenyl)carbonyl]cyclopropanecarbohydrazonoate was used to synthesize 4-amino-3-(4-tert-butylphenyl)-5-cyclopropyl-4H-1,2,4-triazole, 3-(4-tert-butylphenyl)-5- cyclopropyl-4-(arylmethyleneamino)-4H-1,2,4-triazole, 3-(4-tert-butylphenyl)-5-cyclopropyl-4- (arylmethylamino)-4H-1,2,4-triazole and their phthalonitrile derivatives sequentially.

Results:

Seventeen new 3-(4-tert-butylphenyl)-5-cyclopropyl-4H-1,2,4-triazole derivatives were synthesized and their antioxidant and antimicrobial activities were determined.

Conclusion:

Imine and amine derivatives were better antioxidants than phthalonitrile derivatives. Doubly fluorination compounds appeared to result in higher activity. The compounds tested with five microorganisms showed better activity against B. subtilis with the antimicrobial activity of two far exceeding that of ampicillin. Imine and amine derivatives were better antimicrobials than phthalonitrile derivatives.

The origin of the longer wavelength emission in 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole and its analogue 2-phenylamino-5-(2-hydroxybenzono)-1,3,4-thiadiazole† ‡

In aqueous solution, 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT) was found to emit dual emission and the longer wavelength emission was assigned to the combination of aggregation and conformational change. In a number of molecules that possess an intramolecular hydrogen bond between the proton donor and the acceptor, the longer wavelength emission is often observed due to the emission from the tautomer formed by excited state intramolecular proton transfer (ESIPT). Therefore, an analogue of FABT, 2-phenylamino-5-(2-hydroxybenzono)-1,3,4-thiadiazole (PHBT), was synthesized to determine the origin of the longer wavelength emission. The luminescence of PHBT and its methoxy derivatives was studied and compared with that of FABT. Theoretical calculations were also performed on both FABT and PHBT. Based on the experimental and theoretical investigations, the nonexistence of the keto tautomer in the ground state and the origin of the longer wavelength emission are divulged.

Preparation of 2,6-diurea-chitosan oligosaccharide derivatives for efficient antifungal and antioxidant activities

In this study, 2-urea-chitosan oligosaccharide derivatives (2-urea-COS derivatives) and 2,6-diurea-chitosan oligosaccharide derivatives (2,6-diurea-COS derivatives) were successfully designed and synthesized via intermediate 2-methoxyformylated chitosan oligosaccharide. All samples were characterized and compared based on FT-IR, ¹H NMR spectroscopy, and elemental analysis. The antifungal effects of COS derivatives were tested against Fusarium oxysporum f. sp. niveum, Phomopsis asparagus, and Botrytis cinereal. Their antioxidant properties, including superoxide radicals' scavenging activity, hydroxyl radicals' scavenging activity, and DPPH radicals' scavenging activity were also explored within different concentrations. COS derivatives bearing urea groups showed improved bioactivity compared with pristine COS and 2,6-diurea-COS derivatives had a higher biological activity than 2-urea-COS derivatives in tested concentrations. Additionally, L929 cells were used to carry out cytotoxicity test of COS and COS derivatives by CCK-8 assay. The results indicated that some of samples showed low cytotoxicity. These findings offered a suggestion that COS derivatives bearing urea groups are promising biological materials.

Synthesis and biological evaluation of dehydroabietic acid-pyrimidine hybrids as antitumor agents

A series of novel dehydroabietic acid derivatives containing pyrimidine moieties were designed and synthesized. Some of them displayed more potent inhibitory activities compared with 5-FU.

Dinuclear cobalt and nickel complexes of a mercaptoacetic acid substituted 1,2,4-triazole ligand: syntheses, structures and urease inhibitory studies

Because of its versatile coordination modes and strong coordination ability, the mercaptoacetic acid substituted 1,2,4-triazole 2-{[5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetic acid (H₂L) was synthesized and characterized. Treatment of H₂L with cobalt and nickel acetate afforded the dinuclear complexes {μ-3-[(carboxylatomethyl)sulfanyl]-5-(pyridin-2-yl)-4H-1,2,4-triazol-4-ido-κ²N¹,N⁵:N²,O}bis[aqua(methanol-κO)cobalt(II)] methanol disolvate, [Co₂(C₉H₆N₄O₂S)₂(CH₃OH)₂(H₂O)₂]·2CH₃OH (1), and {μ-3-[(carboxylatomethyl)sulfanyl]-5-(pyridin-2-yl)-4H-1,2,4-triazol-4-ido-κ²N¹,N⁵:N²,O}bis[diaquanickel(II)] methanol disolvate dihydrate, [Ni₂(C₉H₆N₄O₂S)₂(H₂O)₄]·2CH₃OH·2H₂O (2), respectively. Complex 1 crystallized in the monoclinic space group P2₁/c, while 2 crystallized in the tetragonal space group I4₁/a. Single-crystal X-ray diffraction studies revealed that H₂L is doubly deprotonated and acts as a tetradentate bridging ligand in complexes 1 and 2. For both of the obtained complexes, extensive hydrogen-bond interactions contribute to the formation of their three-dimensional supermolecular structures. Hirshfeld surface analysis was used to illustrate the intermolecular interactions. Additionally, the urease inhibitory activities of 1, 2 and H₂L were investigated against jack bean urease, where the two complexes revealed strong urease inhibition activities.

Two New 1,3,4-Oxadiazoles With Effective Antifungal Activity Against Candida albicans

Candida infections have become a serious public health problem with high mortality rates, especially in immunocompromised patients, since Candida albicans is the major opportunistic pathogen responsible for systemic or invasive candidiasis. Commercially available antifungal agents are restricted and fungal resistance to such drugs has increased; therefore, the development of a more specific antifungal agent is necessary. Using assays for antifungal activity, here we report that two new compounds of 1,3,4-oxadiazoles class (LMM5 and LMM11), which were discovered by in silico methodologies as possible thioredoxin reductase inhibitors, were effective against C. albicans. Both compounds had in vitro antifungal activity with MIC 32 μg/ml. Cytotoxicity in vitro demonstrated that LMM5 and LMM11 were non-toxic in the cell lines evaluated. The kinetic of the time-kill curve suggested a fungistatic profile and showed an inhibitory effect of LMM5 and LMM11 in 12 h that remained for 24 and 36 h, which is better than fluconazole. In the murine systemic candidiasis model by C. albicans, the two compounds significantly reduced the renal and spleen fungal burden. According to the SEM and TEM images, we hypothesize that the mechanism of action of LMM5 and LMM11 is directly related to the inhibition of the enzyme thioredoxin reductase and internally affect the fungal cell. In view of all in vitro and in vivo results, LMM5 and LMM11 are effective therapeutic candidates for the development of new antifungal drugs addressing the treatment of human infections caused by C. albicans.