Development of new chiral 1,2,4-triazole-3-thiones and 1,3,4-thiadiazoles with promising in vivo anticonvulsant activity targeting GABAergic system and voltage-gated sodium channels (VGSCs).

Antiepileptic drugs (AEDs) are used in the treatment of epilepsy, a neurodegenerative disease characterized by recurrent and untriggered seizures that aim to prevent seizures as a symptomatic treatment. However, they still have significant side effects as well as drug resistance. In recent years, especially 1,3,4-thiadiazoles and 1,2,4-triazoles have attracted attention in preclinical and clinical studies as important drug candidates owing to their anticonvulsant properties. Therefore, in this study, which was conducted to discover AED candidate molecules with reduced side effects at low doses, a series of chiral 2,5-disubstituted-1,3,4-thiadiazoles (4a-d) and 4,5-disubstituted-1,2,4-triazole-3 thiones (5a-d) were designed and synthesized starting from l-phenylalanine ethyl ester hydrochloride. The anticonvulsant activities of the new chiral compounds were assessed in several animal seizure models in mice and rats for initial (phase I) screening after their chemical structures including the configuration of the chiral center were elucidated using spectroscopic methods and elemental analysis. First, all chiral compounds were pre-screened using acute seizure tests induced electrically (maximal electroshock test, 6 Hz psychomotor seizure model) and induced chemically (subcutaneous metrazol seizure model) in mice and also their neurotoxicity (TOX) was determined in the rotorad assay. Two of the tested compounds were used for quantitative testing, and (S)-(+)5-[1-(4-fluorobenzamido)-2-phenylethyl]-4-(4-fluorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5b) and (S)-(+)-(5-[1-(4-fluorobenzamido)-2-phenylethyl]-4-(4-methoxyphenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (5c) emerged as the most promising anticonvulsant drug candidates and also showed low neurotoxicity. The antiepileptogenic potential of these compounds was determined using a chronic seizure induced electrically corneal kindled mouse model. Furthermore, all chiral compounds were tested for their neuroprotective effect against excitotoxic kainic acid (KA) and N-methyl-d-aspartate (NMDA) induced in vitro neuroprotection assay using an organotypic hippocampal slice culture. The KA-induced neuroprotection assay results revealed that compounds 5b and 5c, which are the leading compounds for anticonvulsant activity, also had the strongest neuroprotective effects with IC50 values of 103.30 ± 1.14 and 113.40 ± 1.20 µM respectively. Molecular docking studies conducted to investigate the molecular binding mechanism of the tested compounds on the GABAA receptor showed that compound 5b exhibits a strong affinity to the benzodiazepine (BZD) binding site on GABA. It also revealed that the NaV1.3 binding interactions were consistent with the experimental data and the reported binding mode of the ICA121431 inhibitor. This suggests that compound 5b has a high affinity for these specific binding sites, indicating its potential as a ligand for modulating GABAA and NaV1.3 receptor activity. Furthermore, the ADME properties displayed that all the physicochemical and pharmacological parameters of the compounds stayed within the specified limits and revealed a high bioavailability profile.

An efficient eco-friendly, simple, and green synthesis of some new spiro-N-(4-sulfamoyl-phenyl)-1,3,4-thiadiazole-2-carboxamide derivatives as potential inhibitors of SARS-CoV-2 proteases: drug-likeness, pharmacophore, molecular docking, and DFT exploration.

INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic has caused a global health crisis. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly contagious virus that can cause severe respiratory illness. There is no specific treatment for COVID-19, and the development of new drugs is urgently needed. PROBLEM STATEMENT: The SARS-CoV-2 main protease (Mpro) enzyme is a critical viral enzyme that plays a vital role in viral replication. The inhibition of Mpro enzyme can be an effective strategy for developing new COVID-19 drugs. METHODOLOGY: An efficient operationally simple and convenient green synthesis method had been done towards a series of novel spiro-N-(4-sulfamoylphenyl)-2-carboxamide derivatives, in ethanol at room temperature in green conditions, up to 90% yield. The molecular structures of the synthesized compounds were verified using spectroscopic methods.The title compounds were subjected to in silico analysis, including Lipinski's rule and ADMET prediction, in addition to pharmacophore modeling and molecular docking against the active site of SARS-CoV-2 target main protease (Mpro) enzyme (6LU7). Furthermore, both of the top-ranked compounds (5 and 6) and the standard Nirmatrelvir were subjected to DFT analysis. FINDINGS: The synthesized compounds exhibited good binding affinity to SARS-CoV-2 Mpro enzyme, with binding energy scores ranging from - 7.33 kcal/mol (compound 6) and - 7.22kcal/mol (compound 5) to - 6.54 kcal/mol (compounds 8 and 9). The top-ranked compounds (5 and 6) had lower HOMO-LUMO energy difference (ΔE) than the standard drug Nirmatrelvir. This highlights the potential and relevance of charge transfer at the molecular level. RECOMMENDATION: These findings suggest that the synthesized spiro-N-(4-sulfamoylphenyl)-2-carboxamide derivatives could be potential candidates for COVID-19 drug development. To confirm these drugs' antiviral efficacy in vivo, more research is required. With very little possibility of failure, this proven method could aid in the search for the SARS-CoV-2 pandemic's desperately needed medications.

New Antibacterial 1,3,4-Thiadiazole Derivatives With Pyridine Moiety.

1,3,4-Thiadiazole compounds were synthesized using pyridine carboxylic acid derivatives and thiosemicarbazide derivatives. The molecular structures of the resulting compounds were characterized by spectroscopic methods such as ATR-FTIR, 1H-NMR, and elemental analysis. Its compounds were also examined for their antibacterial properties against some strains of bacteria. Five synthesized compounds showed varying antibacterial effects on Escherichia coli, Salmonella kentucky, Bacillus substilis and Klebsiella pneumoniae. This result revealed that some of the resulting compounds could be antibacterial agents.

Synthesis, Structural Characterization, and Biological Activities of 1,3,4- Thiadiazole Derivatives Containing Sulfonylpiperazine Structures.

To develop novel bacterial biofilm inhibiting agents, a series of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures were designed, synthesized, and characterized using 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR), and high-resolution mass spectrometry. Meanwhile, their biological activities were evaluated, and the ensuing structure-activity relationships were discussed. The bioassay results showed the substantial antimicrobial efficacy exhibited by most of the compounds. Among them, compound A24 demonstrated a strong efficacy with an EC50 value of 7.8 µg/mL in vitro against the Xanthomonas oryzae pv. oryzicola (Xoc) pathogen, surpassing commercial agents thiodiazole copper (31.8 µg/mL) and bismerthiazol (43.3 µg/mL). Mechanistic investigations into its anti-Xoc properties revealed that compound A24 operates by increasing the permeability of bacterial cell membranes, inhibiting biofilm formation and cell motility, and inducing morphological changes in bacterial cells. Importantly, in vivo tests showed its excellent protective and curative effects on rice bacterial leaf streak. Besides, molecular docking showed that the hydrophobic effect and hydrogen-bond interactions are key factors between the binding of A24 and AvrRxo1-ORF1. Therefore, these results suggest the utilization of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures as a bacterial biofilm inhibiting agent, warranting further exploration in the realm of agrochemical development.

Synthesis and Antifungal Activity of Chalcone Derivatives Containing 1,3,4-Thiadiazole.

24 chalcone derivatives containing 1,3,4-thiadiazole were synthesized. The results of bioactivity tests indicated that some of the target compounds exhibited superior antifungal activities in vitro. Notably, the EC50 value of D4 was 14.4 µg/mL against Phomopsis sp, which was significantly better than that of azoxystrobin (32.2 µg/mL) and fluopyram (54.2 µg/mL). The in vivo protective activity of D4 against Phomopsis sp on kiwifruit (71.2 %) was significantly superior to azoxystrobin (62.8 %) at 200 µg/mL. The in vivo protective activities of D4 were 74.4 and 57.6 % against Rhizoctonia solani on rice leaf sheaths and rice leaves, respectively, which were slightly better than those of azoxystrobin (72.1 and 49.2 %) at 200 µg/mL. Scanning electron microscopy (SEM) results showed that the mycelial surface collapsed, contracted and grew abnormally after D4 treatment. Finally, the results were further verified by in vivo antifungal assay, fluorescence microscopy (FM) observation, determination of relative conductivity, membrane lipid peroxidation degree assay, and determination of cytoplasmic content leakage. Molecular docking results suggested that D4 could be a potential SDHI.

Tail-approach based design, synthesis, and molecular modeling of benzenesulfonamides carrying thiadiazole and urea moieties as novel carbonic anhydrase inhibitors.

We synthesized herein 16 compounds (SUT1-SUT16) as potential carbonic anhydrase (CA) inhibitors utilizing the tail-approach design. Based on this strategy, we connected benzenesulfonamide, the zinc-binding scaffold, to different urea moieties with the 1,3,4-thiadiazole ring as a linker. We obtained the target compounds by the reaction of 4-(5-amino-1,3,4-thiadiazol-2-yl)benzenesulfonamide with aryl isocyanates. Upon confirmation of their structures, the compounds were screened for their ability to inhibit the tumor-related human (h) isoforms human carbonic anhydrase (hCA) IX and XII, as well as the physiologically dominant hCA I and II. Most of the molecules demonstrated Ki values ≤ 10 nM with different selectivity profiles. The binding modes of SUT9, SUT10, and SUT5, the most effective inhibitors of hCA II, IX, and XII, respectively, were predicted by molecular docking. SUT16 (4-{5-[3-(naphthalen-1-yl)ureido]-1,3,4-thiadiazol-2-yl}benzenesulfonamide) was found to be the most selective inhibitor of the cancer-associated isoforms hCA IX and XII over the off-target isoforms, hCAI and II. The interaction dynamics and stability of SUT16 within hCA IX and XII were investigated by molecular dynamics simulations as well as dynophore analysis. Based on computational data, increased hydrophobic contacts and hydrogen bonds in the tail part of these molecules within hCA IX and XII were found as favorable interactions leading to effective inhibitors of cancer-related isoforms.

Cooperativity of ESPT and Aggregation-Induced Emission Effects-An Experimental and Theoretical Analysis of a 1,3,4-Thiadiazole Derivative.

4-[5-(Naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol (NTBD) was extensively studied through stationary UV-vis absorption and fluorescence measurements in various solvents and solvent mixtures and by first-principles quantum chemical calculations. It was observed that while in polar solvents (e.g., methanol) only a single emission band emerged; the analyzed 1,3,4-thiadiazole derivative was capable of producing dual fluorescence signals in low polarity solvents (e.g., n-hexane) and certain solvent mixtures (e.g., methanol/water). As clearly follows from the experimental spectroscopic studies and theoretical modeling, the specific emission characteristic of NTBD is triggered by the effect of enol → keto excited-state intramolecular proton transfer (ESIPT) that in the case of solvent mixture is reinforced by aggregation of thiadiazole molecules. Specifically, the restriction of intramolecular rotation (RIR) due to environmental hindrance suppresses the formation of non-emissive twisted intramolecular charge transfer (TICT) excited keto* states. As a result, this particular thiadiazole derivative is capable of simultaneously producing both ESIPT and aggregation-induced emission (AIE).

Design, Synthesis, Antibacterial, and Antifungal Evaluation of Phenylthiazole Derivatives Containing a 1,3,4-Thiadiazole Thione Moiety.

To effectively control the infection of plant pathogens, we designed and synthesized a series of phenylthiazole derivatives containing a 1,3,4-thiadiazole thione moiety and screened for their antibacterial potencies against Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, as well as their antifungal potencies against Sclerotinia sclerotiorum, Rhizoctonia solani, Magnaporthe oryzae and Colletotrichum gloeosporioides. The chemical structures of the target compounds were characterized by 1H NMR, 13C NMR and HRMS. The bioassay results revealed that all the tested compounds exhibited moderate-to-excellent antibacterial and antifungal activities against six plant pathogens. Especially, compound 5k possessed the most remarkable antibacterial activity against R. solanacearum (EC50 = 2.23 µg/mL), which was significantly superior to that of compound E1 (EC50 = 69.87 µg/mL) and the commercial agent Thiodiazole copper (EC50 = 52.01 µg/mL). Meanwhile, compound 5b displayed the most excellent antifungal activity against S. sclerotiorum (EC50 = 0.51 µg/mL), which was equivalent to that of the commercial fungicide Carbendazim (EC50 = 0.57 µg/mL). The preliminary structure-activity relationship (SAR) results suggested that introducing an electron-withdrawing group at the meta-position and ortho-position of the benzene ring could endow the final structure with remarkable antibacterial and antifungal activity, respectively. The current results indicated that these compounds were capable of serving as promising lead compounds.

Functionalization of 2-Mercapto-5-methyl-1,3,4-thiadiazole: 2-(ω-Haloalkylthio) Thiadiazoles vs. Symmetrical Bis-Thiadiazoles.

A study on the functionalisation of 2-mercapto-5-methyl-1,3,4-thiadiazole has been conducted, yielding two series of products: 2-(ω-haloalkylthio)thiadiazoles and symmetrical bis-thiadiazoles, with variable chain lengths. The experimental conditions were optimised for each class of compounds by altering the base used and the reagents' proportions, leading to the development of separate protocols tailored to their specific reactivity and purification needs. The target halogenide reagents and bis-thiadiazole ligands were obtained either as single products or as mixtures easily separable by chromatography. Characterisation of the products was performed using 1D and 2D NMR spectra in solution, complemented by single crystal X-ray diffraction (XRD) for selected samples, to elucidate their structural properties.

In vitro evaluation of 2-(1H-pyrazol-1-yl)-1,3,4-thiadiazole derivatives against replicative and infective stages of Trypanosoma cruzi.

Current treatment of Chagas disease (CD) is based on two substances, nifurtimox (NT) and benzonidazole (BZ), both considered unsatisfactory mainly due to their low activities and high toxicity profile. One of the main challenges faced in CD management concerns the identification of new drugs active in the acute and chronic phases and with good pharmacokinetic profiles. In this work, we studied the bioactivity of twenty 2-(1H-pyrazol-1-yl)-1,3,4-thiadiazole derivatives against Trypanosoma cruzi epimastigotes and trypomastigotes. We identified seven derivatives with promising activity against epimastigote forms with IC50 values ranging from 6 µM to 44 µM. Most of the compounds showed no significant toxicity against murine macrophages. Our initial investigation on the mechanism of action indicates that this series of compounds may exert their anti-parasitic effect, inducing cell membrane damage. The results in trypomastigotes showed that one derivative, PDAN 78, satisfactorily inhibited metabolic alteration at all concentrations. Moreover, we used molecular modeling to understand how tridimensional and structural aspects might influence the observed bioactivities. Finally, we also used in silico approaches to assess the potential pharmacokinetic and toxicological properties of the most active compounds. Our initial results indicate that this molecular scaffold might be a valuable prototype for novel and safe trypanocidal compounds.

Design and synthesis of thiadiazole-oxadiazole-acetamide derivatives: Elastase inhibition, cytotoxicity, kinetic mechanism, and computational studies.

Considering the biological significance of 1,3,4-thiadiazole/oxadiazole heterocyclic scaffolds, a novel series of 1,3,4-thiadiazole-1,3,4-oxadiazole-acetamide derivatives (7a-j) was designed and synthesized using molecular hybridization. The inhibitory effects of the target compounds on elastase were evaluated, and all of these molecules were found to be potent inhibitors compared to the standard reference oleanolic acid. Compound 7f exhibited the excellent inhibitory activity (IC50 = 0.06 ± 0.02 µM), which is 214-fold more active than oleanolic acid (IC50 = 12.84 ± 0.45 µM). Kinetic analysis was also performed on the most potent compound (7f) to determine the mode of binding with the target enzyme, and it was discovered that 7f inhibits the enzyme in a competitive manner. Furthermore, the MTT assay method was used to assess their toxicity on the viability of B16F10 melanoma cell lines, and all compounds did not display any toxic effect on the cells even at high concentrations. The molecular docking studies of all compounds also justified with their good docking score and among them, compound 7f had a good conformational state with hydrogen bond interactions within the receptor binding pocket, which is consistent with the experimental inhibition studies.

Synthesis, antifungal activity and mechanism of action of novel chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole.

A series of chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole was designed and synthesized. Structures of all compounds were characterized by 1H NMR, 13C NMR, 19F NMR, and HRMS. The biological activities of the compounds were determined with the mycelial growth rate method, and further studies showed that some compounds had good antifungal activities at the concentration of 100 µg/mL. The EC50 value of compound L31 was 15.9 µg/mL against Phomopsis sp., which were better than that of azoxystrobin (EC50 value was 69.4 µg/mL). In addition, the mechanism of action of compound L31 shown that compound can affect mycelial growth by disrupting membrane integrity against Phomopsis sp., and that the higher the concentration of the compound is, the greater the disruption of membrane integrity is.

1,3,4-Oxadiazole and 1,3,4-Thiadiazole Nortopsentin Derivatives against Pancreatic Ductal Adenocarcinoma: Synthesis, Cytotoxic Activity, and Inhibition of CDK1.

A new series of nortopsentin analogs, in which the central imidazole ring of the natural lead was replaced by a 1,3,4-oxadiazole or 1,3,4-thiadiazole moiety, was efficiently synthesized. The antiproliferative activity of all synthesized derivatives was evaluated against five pancreatic ductal adenocarcinoma (PDAC) cell lines, a primary culture and a gemcitabine-resistant variant. The five more potent compounds elicited EC50 values in the submicromolar-micromolar range, associated with a significant reduction in cell migration. Moreover, flow cytometric analysis after propidium iodide staining revealed an increase in the G2-M and a decrease in G1-phase, indicating cell cycle arrest, while a specific ELISA demonstrated the inhibition of CDK1 activity, a crucial regulator of cell cycle progression and cancer cell proliferation.

Design, synthesis and mechanism research of novel algicide based on bioactive fragments synthesis strategy.

The frequency and intensity of harmful cyanobacterial blooms (HCBs) are increasing all over the world, their prevention and control have become a great challenge. In this paper, a series of 1,3,4-thiadiazole thioacetamides (T series) were designed and synthesized as potential algaecides. Among them, the compound T3 showed its best algacidal activity against Synechocystis sp. PCC 6803 (PCC 6803, EC50 = 1.51 µM) and Microcystis aeruginosa FACHB 905 (FACHB905, EC50 = 4.88 µM), which was more effective than the lead compound L1 (PCC6803, EC50 = 7.7 µM; FACHB905, EC50 = 8.8 µM) and the commercially available herbicide prometryn (PCC6803, EC50 = 4.64 µM；FACHB905, EC50 = 6.52 µM). Meanwhile, T3 showed a lower inhibitory activity (EC50 = 12.76 µM) than prometryn (EC50 = 7.98 µM) to Chlorella FACHB1227, indicating that T3 had selective inhibition to prokaryotic algae (PCC6803, FACHB905) and eukaryotic algae (FACHB1227). Furthermore, the algacidal and anti-algae activities of T3 were significantly better than those of prometryn, while the toxicity of zebrafish and human cells was less than prometryn. Electron microscope, physiological, biochemical and metabonomic analysis showed that T3 interfered with light absorption and light conversion during photosynthesis by significantly reducing chlorophyll content, thus inhibited metabolic pathways such as the Calvin cycle and TCA cycle, and eventually led to the cell rupture of cyanobacteria. These results afforded further development of effective and safe algaecides.

Synthesis, characterization, biochemical, and molecular modeling studies of carvacrol-based new thiosemicarbazide and 1,3,4-thiadiazole derivatives.

A series of carvacrol-based thiosemicarbazide (3a-e) and 1,3,4-thiadiazole-2-amine (4a-e) were designed and synthesized for the first time. The structures were characterized by nuclear magnetic resonance and high resolution mass spectroscopy techniques. All compounds were examined for some metabolic enzyme activities. Results indicated that all the synthetic molecules exhibited powerful inhibitory actions against human carbonic anhydrase I and II (hCAI and II), acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) enzymes compared to the standard molecules. Ki values of five novel thiosemicarbazides and five new 1,3,4-thiadiazole-2-amine derivatives (3a-e and 4a-e) for hCA I, hCA II, AChE, and BChE enzymes were obtained in the ranges 0.73-21.60, 0.42-15.08 µM, 3.48-81.48, 92.61-211.40 nM, respectively. After the experimental undertaking, an extensive molecular docking analysis was conducted to scrutinize the intricate details of interactions between the ligand and the enzyme in question. The principal focus of this investigation was to appraise the potency and efficacy of the most active compound. In this context, the calculated docking scores were noted to be remarkably low, with values of -8.65, -7.97, -8.92, and -8.32 kcal/mol being recorded for hCA I, hCA II, AChE, and BChE, respectively. These observations suggest a high affinity and specificity of the studied compounds toward the enzymes, as mentioned earlier, which may pave the way for novel therapeutic interventions aimed at modulating the activity of these enzymes.

Potent inhibitors of tumor associated carbonic anhydrases endowed with cathepsin B inhibition.

Twenty-one novel extended analogs of acetazolamide were synthesized and screened in vitro for their inhibition efficacy against human carbonic anhydrase (hCA) isoforms I, II, IX, XII, and cathepsin B. The majority of the compounds were found to be effective inhibitors of tumor-associated hCA IX and XII, and poor inhibitors of cytosolic hCA I. Despite the strong to moderate inhibition potential possessed by these compounds toward another cytosolic isoform hCA II, some of them demonstrated better potency against hCA IX and/or XII isoforms as compared to hCA II. Four compounds (11f, 11g, 12c, and 12g) effectively inhibited hCA IX and/or XII isoforms with considerable selectivity over the off-targets hCA I and II. Interestingly, five compounds, including 11f, 11g, 12c, 12d, and 12g, inhibited hCA IX even better than the clinically used acetazolamide. Some of the novel synthesized compounds exhibited higher anti-cathepsin B potential than acetazolamide, with % inhibition of around 50%, at a concentration of 10-7 M. Further, two compounds (12g and 12c) that showed effective and selective inhibition activity profiles against hCA IX and XII were additionally found to be effective inhibitors of cathepsin B.

Synthesis of 1,2,3-triazole-1,3,4-thiadiazole hybrids as novel α-glucosidase inhibitors by in situ azidation/click assembly.

α-Glucosidase inhibition is widely used in the oral management of diabetes mellitus (DM), a disease characterized by high blood sugar levels (hyperglycemia) and abnormal carbohydrate metabolism. In this respect, a series of 1,2,3-triazole-1,3,4-thiadiazole hybrids 7a-j were synthesized, inspired by a copper-catalyzed one-pot azidation/click assembly approach. All the synthesized hybrids were screened for inhibition of the α-glucosidase enzyme, displaying IC50 values ranging from 63.35 ± 0.72 to 613.57 ± 1.98 µM, as compared to acarbose (reference) with IC50 of 844.81 ± 0.53 µM. The hybrids 7h and 7e with 3-nitro and 4-methoxy substituents at the phenyl ring of the thiadiazole moiety were the best active hybrids of this series with IC50 values of 63.35 ± 0.72 µM, and 67.61 ± 0.64 µM, respectively. Enzyme kinetics analysis of these compounds revealed a mixed mode of inhibition. Moreover, molecular docking studies were also performed to gain insights into the structure-activity-relationships of the potent compounds and their corresponding analogs.

First X-ray Crystal Structure Characterization, Computational Studies, and Improved Synthetic Route to the Bioactive 5-Arylimino-1,3,4-thiadiazole Derivatives.

N-arylcyanothioformamides are useful coupling components for building key chemical intermediates and biologically active molecules in an expedited and efficient manner. Similarly, substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides have been utilized in numerous one-step heteroannulation reactions to assemble the structural core of several different types of heterocyclic compounds. Herein, we demonstrate the effectiveness of the reaction of N-arylcyanothioformamides with various substituted (Z)-2-oxo-N-phenylpropanehydrazonoyl chlorides to produce, stereoselectively and regioselectively, a range of 5-arylimino-1,3,4-thiadiazole derivatives decorated with a multitude of functional groups on both aromatic rings. The synthetic methodology features mild room-temperature conditions, large substrate scope, wide array of functional groups on both reactants, and good to high reaction yields. The products were isolated by gravity filtration in all cases and structures were confirmed by multinuclear NMR spectroscopy and high accuracy mass spectral analysis. Proof of molecular structure of the isolated 5-arylimino-1,3,4-thiadiazole regioisomer was obtained for the first time by single-crystal X-ray diffraction analysis. Crystal-structure determination was carried out on (Z)-1-(5-((3-fluorophenyl)imino)-4-(4-iodophenyl)-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one and (Z)-1-(4-phenyl-5-(p-tolylimino)-4,5-dihydro-1,3,4-thiadiazol-2-yl)ethan-1-one. Similarly, the tautomeric structures of the N-arylcyanothioformamides and (Z)-geometries of the 2-oxo-N-phenylpropanehydrazonoyl chloride coupling partners were proven by X-ray diffraction studies. As representative examples, crystal-structure determination was carried out on (4-ethoxyphenyl)carbamothioyl cyanide and (Z)-N-(2,3-difluorophenyl)-2-oxopropanehydrazonoyl chloride. Density functional theory calculations at the B3LYP-D4/def2-TZVP level were carried out to rationalize the observed experimental findings.

Synergistic Antifungal Interactions between Antibiotic Amphotericin B and Selected 1,3,4-thiadiazole Derivatives, Determined by Microbiological, Cytochemical, and Molecular Spectroscopic Studies.

In recent years, drug-resistant and multidrug-resistant fungal strains have been more frequently isolated in clinical practice. This phenomenon is responsible for difficulties in the treatment of infections. Therefore, the development of new antifungal drugs is an extremely important challenge. Combinations of selected 1,3,4-thiadiazole derivatives with amphotericin B showing strong synergic antifungal interactions are promising candidates for such formulas. In the study, microbiological, cytochemical, and molecular spectroscopy methods were used to investigate the antifungal synergy mechanisms associated with the aforementioned combinations. The present results indicate that two derivatives, i.e., C1 and NTBD, demonstrate strong synergistic interactions with AmB against some Candida species. The ATR-FTIR analysis showed that yeasts treated with the C1 + AmB and NTBD + AmB compositions, compared with those treated with single compounds, exhibited more pronounced abnormalities in the biomolecular content, suggesting that the main mechanism of the synergistic antifungal activity of the compounds is related to a disturbance in cell wall integrity. The analysis of the electron absorption and fluorescence spectra revealed that the biophysical mechanism underlying the observed synergy is associated with disaggregation of AmB molecules induced by the 1,3,4-thiadiazole derivatives. Such observations suggest the possibility of the successful application of thiadiazole derivatives combined with AmB in the therapy of fungal infections.

Novel 1,3,4-Thiadiazole Derivatives: Synthesis, Antiviral Bioassay and Regulation the Photosynthetic Pathway of Tobacco against TMV Infection.

Tobacco mosaic virus (TMV) is a systemic virus that poses a serious threat to crops worldwide. In the present study, a series of novel 1-phenyl-4-(1,3,4-thiadiazole-5-thioether)-1H-pyrazole-5-amine derivatives was designed and synthesized. In vivo antiviral bioassay results indicated that some of these compounds exhibited excellent protective activity against TMV. Among the compounds, E2 (EC50 = 203.5 µg/mL) was superior to the commercial agent ningnanmycin (EC50 = 261.4 µg/mL). Observation of tobacco leaves infected with TMV-GFP revealed that E2 could effectively inhibit the spread of TMV in the host. Further plant tissue morphological observation indicated that E2 could induce the tight arrangement and alignment of the spongy mesophyll and palisade cells while causing stomatal closure to form a defensive barrier to prevent viral infection in the leaves. In addition, the chlorophyll content of tobacco leaves was significantly increased after treatment with E2, and the net photosynthesis (Pn) value was also increased, which demonstrated that the active compound could improve the photosynthetic efficiency of TMV-infected tobacco leaves by maintaining stable chlorophyll content in the leaves, thereby protecting host plants from viral infection. The results of MDA and H2O2 content determination revealed that E2 could effectively reduce the content of peroxides in the infected plants, reducing the damage to the plants caused by oxidation. This work provides an important support for the research and development of antiviral agents in crop protection.