Synthesis and antioxidant properties of organosulfur and organoselenium compounds derived from 5-substituted-1,3,4-oxadiazole/thiadiazole-2-thiols

Total Synthesis of an Epothilone Analogue Based on the Amide-Triazole Bioisosterism

Epothilones are 16-membered macrolides that act as microtubule-targeting agents to tackle cancer. Many synthetic analogues have been investigated for their activity, yet often based on macrolide structures. A notable exception is Ixabepilone, an azalide whose metabolic stability and pharmacokinetics are significantly improved. Exploiting the amide-triazole bioisosterism, in this work we report the synthesis of the first generation of epothilones lacking the macrolide or azalide structure, with the ester or amide linkage replaced by a triazole unit. Together with the synthesis of this new analogue, computational and biological evaluations have been performed too.

Abd Razik. Synthesizing, Studying Molecular Docking, Characterizing, and Preliminary Evaluating Anti-Bacterial Effects of Derivatives of Serotonin Contain Imidazolidine Ring

This study included synthesis of new serotonin derivatives in which imidazolidine rings are present in their structures. The final imidazolidine derivatives compounds were synthesized by reaction of synthesized   Schiff bases derivatives of serotonin with the glycine (NH2-CH2COOH) in presence of tetrahydrofuran (THF) as a solvent. The imidazolidine derivatives were identified by physical characteristics, FT-IR spectroscopy and 1H- NMR spectroscopy. Biological activities against two Gram negative (Klebsiella and E. coli) and two Gram positive (Streptococcus pyogenes and Staphylococcus aureus) bacteria were also distinguished. All the synthesized compounds III(a-d) exhibit moderate activities on four types of bacteria comparing with the activity of standard drug (Trimethoprim) but the highest activities of these compounds occur on Streptococcus pyogenes and their least activities occur on E. coli. The synthesized compounds were studied for the molecular docking to know the interaction and affinity of binding between them and bacteria  

Rational design of 1,2,3-triazole hybrid structures as novel anticancer agents: synthesis, biological evaluation and molecular docking studies

New hybrid compounds belonging to the class of 1,4-disubstituted 1,2,3-triazoles were synthesized. The structural characterization of the synthesized compounds was performed using IR, ¹H-NMR, ¹³C NMR and elemental analysis techniques. Diarylketones 1a and 1b were used as starting compounds for the synthesis of triazoles. The corresponding diarylmethanol derivatives (2a,b) were obtained from reduction of ketone units with NaBH₄. Oxyalkynes (3a,b) were obtained by treating the hydroxyl group with NaH in anhydrous THF and then with propargylbromide. The target hybrid structures 6a-n were obtained from the metal-catalyzed "click reaction" of the arylazide and alkyne units. The newly synthesized compounds were structurally analysed using ¹H-NMR, ¹³C-NMR, elemental analysis, LC-MS and FT-IR. The antioxidant and anticancer activities of all compounds were investigated. It has been determined that the new hybrid structures have very good antioxidant and anticancer activities according to the standards. In particular, compounds 6b, 6h, 6i and 6j (IC₅₀: 1.87, 12.5, 7.22, 8.04 µM) showed excellent activity compared to standard 5-Fu (IC₅₀: 40.89 µM). According to the results of molecular docking of compounds 6b and 6i with the highest cancer activity, MetAP-2 was found to have a high affinity through exposed polar and apolar contacts with fundemental residues in the binding pocket.Communicated by Ramaswamy H. Sarma.

Exploration of electronic properties, radical scavenging activity and QSAR of oxadiazole derivatives by molecular docking and first-principles approaches

Eight new oxadiazole derivatives were designed then geometries for ground state were optimized through Density Functional Theory (DFT) at B3LYP/6-31G** level. Single electron transfer mechanism has been studied to understand the antioxidant ability of the oxadiazole derivatives. Then molecular electrostatic potential and quantitative structure–activity relationship (QSAR) was probed. Additionally, we shed light on different molecular descriptors, e.g., electrophilicity(ω), electronegativity(χ), electrophilicity indices(ωi), hardness(η), softness(S) and chemical potential(μ).The smaller value of ionization potential for 5a is showing that it might be efficient antioxidant candidate. The electrophilic reactive sites in 2a, 3a, 4a, 5a and 7a derivatives might be a good choice for reactivity that would be advantageous to improve the biological activity. The polar surface area of 3a, 4a and 5a derivatives was found < 60 A² which is enlightening that these drugs might be suitable as orally active and for brain penetration. First-principles calculations and molecular docking results revealed that 5a would lead to superior antioxidant activity.

Ultrasound-assisted, low-solvent and acid/base-free synthesis of 5-substituted 1,3,4-oxadiazole-2-thiols as potent antimicrobial and antioxidant agents

One of the goals of green chemistry is to use environmentally friendly solvents or remove and reduce the volume of harmful spent solvents. In this study, a novel process for the synthesis of 5-substituted 1,3,4-oxadiazole-2-thiol derivatives was proposed via ultrasound-assisted reaction of aryl hydrazides with CS2 (1:1 molar ratio) in some drops of DMF in the absence of basic or acidic catalysts. They were produced in good to excellent yields under easy workup and purification conditions. In order to prove the usefulness of the prepared compounds, their antioxidant, antibacterial, and antifungal potentials were screened by DPPH free radical scavenging, serial twofold microdilution and streak plate methods. Acceptable to significant inhibitory activities were observed with synthesized heterocycles. The results showed that 5-(4-fluorophenyl)-1,3,4-oxadiazole-2-thiol (3c) is an broad-spectrum antimicrobial agent. Many of them displayed remarkable antioxidant properties comparable to standard controls (ascorbic acid and α-tocopherol). Synthesized 1,3,4-oxadiazoles are also potent candidates to treat cancer, Parkinson, inflammatory, and diabetes diseases. Eighteen 5-substituted 1,3,4-oxadiazole-2-thiol derivatives as potent antimicrobial and antioxidant agents were prepared via a new, efficient and green procedure.

Design, computational studies, synthesis and in vitro antimicrobial evaluation of benzimidazole based thio-oxadiazole and thio-thiadiazole analogues

Background

Two series of benzimidazole based thio-oxadiazole and thio-thiadiazole analogues were designed and synthesised as novel antimicrobial drugs through inhibition of phenylalanyl-tRNA synthetase (PheRS), which is a promising antimicrobial target. Compounds were designed to mimic the structural features of phenylalanyl adenylate (Phe-AMP) the PheRS natural substrate.

Methods

A 3D conformational alignment for the designed compounds and the PheRS natural substrate revealed a high level of conformational similarity, and a molecular docking study indicated the ability of the designed compounds to occupy both Phe-AMP binding pockets. A molecular dynamics (MD) simulation comparative study was performed to understand the binding interactions with PheRS from different bacterial microorganisms. The synthetic pathway of the designed compounds proceeded in five steps starting from benzimidazole. The fourteen synthesised compounds 5a-d, 6a-c, 8a-d and 9a-c were purified, fully characterised and obtained in high yield.

Results

In vitro antimicrobial evaluation against five bacterial strains showed a moderate activity of compound 8b with MIC value of 32 μg/mL against S. aureus, while all the synthesised compounds showed weak activity against both E. faecalis and P. aeruginosa (MIC 128 μg/mL).

Conclusion

Compound 8b provides a lead compound for further structural development to obtain high affinity PheRS inhibitors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13065-021-00785-8.

Development of Oxadiazole-Sulfonamide-Based Compounds as Potential Antibacterial Agents

In this work, substituted 1,2,4-oxadiazoles (OX1-OX27) were screened against five bacterial strains, identified to be OX7 and OX11 as growth inhibitors with minimum inhibitory concentration (MIC) values of 31.25 and 15.75 μg/mL, respectively. The growth inhibitory property of OX7 and OX11 was further validated by disk diffusion, growth curve, and time kill curve assays. Both disrupted biofilm formation with 92-100% reduction examined by the XTT assay were further visualized by scanning electron microscopy analysis. These compounds in combination with ciprofloxacin also exhibit synergy against Escherichia coli cells. With insignificant cytotoxic behavior on HEK293 cells, human red blood cells, and Galleria mellonella larvae, OX11 was tested against 28 multidrug resistant environmental isolates of bacteria and showed inhibition of Kluyvera georgiana and Citrobacter werkmanii strains with 32 and 16 μg/mL MIC values, respectively. The synergistic behavior of OX11 with ampicillin showed many fold reductions in MIC values against K. georgiana and Klebsiella pneumoniae multidrug resistant strains. Further, transmission electron microscopy analysis of OX11-treated E. coli cells showed a significantly damaged cell wall, which resulted in the loss of integrity and cytosolic oozing. OX11 showed significant changes in the secondary structure of human serum albumin (HSA) in the presence of OX11, enhancing HSA stability. Overall, the study provided a suitable core for further synthetic alterations and development as an antibacterial agent.

Selanzylimidazopyridine abolishes inflammation- and stress-induced depressive-like behaviors and decreases oxidonitrosative stress in the prefrontal cortex and hippocampus of mice

The 3-[(4-methoxyphenyl)selanyl]-2-phenylimidazo[1,2-a] pyridine (MPI), a novel organic selenium compound, has been receiving increased attention due to its antioxidant effects and its ability to protect against depression-like behaviours. However, it remains elusive whether MPI is able to reverse depressive-like symptoms and biochemical alterations in mice. In the present work, we explored the ability of MPI (10 mg/kg, i.g.) to reverse inflammation- and stress-induced depression-like behaviours in mice injected with tumour necrosis factor (TNF-α) or submitted to acute restraint stress. Depression-like behaviours were evaluated by the tail suspension and splash test and the open field test was used to evaluate the locomotor activity of mice. The prefrontal cortex and hippocampus of mice were used for the evaluation of parameters of oxidonitrosative stress. Here, we showed that a single administration of MPI abolished the depressive-like behaviours induced by TNF-α and acute restraint stress without having an effect per se. The oxidative and nitrosative stress presented in mice with depression-like behaviours were also decreased by MPI in the prefrontal cortex and hippocampus. Our findings suggest that MPI presents antidepressant-like activity which is associated with the biochemical regulation of oxidative stress in the prefrontal cortex and hippocampus of mice, arising as a promising strategy for the management of depressive symptoms.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Assessing Methodologies to Synthesize α-Sulfenylated Carbonyl Compounds by Green Chemistry Metrics

α-Sulfenylated carbonyl compounds are important both as active pharmaceutical ingredients and as intermediates in organic synthesis. Owing to their relevance in synthetic organic chemistry, this Minireview focuses on assessing the most relevant synthetic procedures based on green chemistry metrics. The Minireview starts with the traditional routes and then focuses on more recently developed methodologies. These routes include sulfenylating reagents using organocatalysis, cross-dehydrogenative couplings using in situ halogenations to prevent reactive intermediates in high concentrations, oxidative couplings using terminal oxidants such as DDQ or TEMPO, and redox-neutral couplings using transition metal catalysis. These methodologies have been evaluated on the basis of atom economy, E factor, and the safety and toxicity of the transformations and the solvents used. Besides using green metrics to evaluate these novel methodologies, the synthetic utility is also assessed with regard to the availability of starting materials and the generality of the reactions. This Minireview aims to inspire researchers to apply green assessments to other methodologies and also for them to take measures to increase the greenness of their developed transformations.

Free radical scavenging mechanism of 1,3,4-oxadiazole derivatives: thermodynamics of O-H and N-H bond cleavage

The thermodynamics of free radical scavenge of 1,3,4-oxadiazole derivatives towards oxygen-centred free radicals were investigated by the density functional theory (DFT) method in the gas phase and aqueous solution. Three mechanisms of free radical scavenge namely, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were considered. The antioxidant descriptors that characterize these mechanisms such as, bond dissociation enthalpy (BDE), adiabatic ionization potential (AIP), proton dissociation enthalpy (PDE), proton affinity (PA) and electron transfer enthalpy (ETE) were evaluated. The sequence of electron donation as predicted by the HOMO results were in good agreement with the sequence of ETE for the considered molecules at their favoured sites of free radical scavenge. The reaction Gibbs free energy for inactivation of the selected peroxyl radicals, show that 1,3,4-oxadiazole antioxidants are more efficient radical scavengers by HAT and SPLET mechanisms than SET-PT mechanism in vacuum. In aqueous solution, the SET-PT mechanism was observed to be the dominant reaction pathway.

Regioselective Sulfenylation of α'-CH3 or α'-CH2 Groups of α,β-Unsaturated Ketones with Heterocyclic Thiols

A rare regioselective sulfenylation of α'-CH₃ or α'-CH₂ bonds adjacent to α,β-unsaturated ketones using dimethyl sulfoxide as an oxidant and a substoichiometric amount of aq HI as an additive is described. This methodology employs a strong acid such as aq HI or iodine and exhibits a high regioselectivity without undergoing conjugate addition, which is difficult to achieve under the cross dehydrogenative coupling method.

Antioxidant, anticancer and electrochemical redox properties of new bis(2,3-dihydroquinazolin-4(1H)-one) derivatives

In this paper, a series of bis(2,3-dihydroquinazolin-4(1H)-one) derivatives (4a-i, 10a-k) were synthesized by the one-pot pseudo-five-component reaction of isatoic anhydride with aromatic aldehydes and aromatic amines under reflux in glacial acetic acid. The synthesized compounds were screened for their antioxidant properties using the DPPH radical scavenging method. Compounds 4i and 10h showed potent radical scavenging activities at 20 [Formula: see text] compared to BHA and ascorbic acid. The anticancer activity of compound 4f was evaluated against human breast cancer cell line (MCF 7), and the observed [Formula: see text] was found to be 11.4 [Formula: see text]. The redox behaviour of some analogues was evaluated by cyclic voltammetric methods, and it is found that compound 7d possesses the maximum redox potential.

Synthesis and Antiviral Activity of Novel 1,4-Pentadien-3-one Derivatives Containing a 1,3,4-Thiadiazole Moiety

1,4-Pentadien-3-one derivatives derived from curcumin possess excellent inhibitory activity against plant viruses. On the basis of this finding, a series of novel 1,4-pentadien-3-one derivatives containing a 1,3,4-thiadiazole moiety were designed and synthesized, and their structures confirmed by IR, ¹H-NMR, and ¹³C-NMR spectroscopy and elemental analysis. The antiviral activities of the title compounds were evaluated against tobacco mosaic virus (TMV) and cucumber mosaic virus (CMV) in vivo. The assay results showed that most of compounds had remarkable antiviral activities against TMV and CMV, among which compounds 4b, 4h, 4i, 4k, 4o, and 4q exhibited good curative, protection, and inactivation activity against TMV. Compounds 4h, 4i, 4k, 4l, 4o, and 4q exhibited excellent protection activity against TMV, with EC₅₀ values of 105.01, 254.77, 135.38, 297.40, 248.18, and 129.87 μg/mL, respectively, which were superior to that of ribavirin (457.25 µg/mL). In addition, preliminary SARs indicated that small electron-withdrawing groups on the aromatic ring were favorable for anti-TMV activity. This finding suggests that 1,4-pentadien-3-one derivatives containing a 1,3,4-thiadiazole moiety may be considered as potential lead structures for discovering new antiviral agents.

Synthesis and electrochemical and antioxidant properties of chalcogenocyanate oxadiazole and 5-heteroarylchalcogenomethyl-1H-tetrazole derivatives

This article presents the 5-heteroarylchalcogenomethyl-1H-tetrazoles, which were synthesized in high yields.