Discovery of new acetamide derivatives of 5-indole-1,3,4-oxadiazol-2-thiol as inhibitors of HIV-1 Tat-mediated viral transcription

Human immunodeficiency virus-1 (HIV-1) encodes a transcriptional factor called Tat, which is critical for viral transcription. Tat-mediated transcription is highly ordered apart from the cellular manner; therefore, it is considered a target for developing anti-HIV-1 drugs. However, drugs targeting Tat-mediated viral transcription are not yet available. Our high-throughput screen of a compound library employing a dual-reporter assay identified a 1,3,4-oxadiazole scaffold against Tat and HIV-1 infection. Furthermore, a serial structure-activity relation (SAR) study performed with biological assays found 1,3,4-oxadiazole derivatives (9 and 13) containing indole and acetamide that exhibited potent inhibitory effects on HIV-1 infectivity, with half-maximal effective concentrations (EC50) of 0.17 (9) and 0.24 µM (13), respectively. The prominent derivatives specifically interfered with the viral transcriptional step without targeting other infection step(s) and efficiently inhibited the HIV-1 replication cycle in the T cell lines and peripheral blood mononuclear cells infected with HIV-1. Additionally, compared to the wild type, the compounds exhibited similar potency against anti-retroviral drug-resistant HIV-1 strains. In a series of mode-of-action studies, the compounds inhibited the ejection of histone H3 for facilitating viral transcription on the long-terminal repeat (LTR) promoter. Furthermore, SAHA (a histone deacetylase inhibitor) treatment abolished the compound potency, revealing that the compounds can possibly target Tat-regulated epigenetic modulation of LTR to inhibit viral transcription. Overall, our screening identified novel 1,3,4-oxadiazole compounds that inhibited HIV-1 Tat, and subsequent SAR-based optimization led to the derivatives 9 and 13 development that could be a promising scaffold for developing a new class of therapeutic agents for HIV-1 infection.

New oxadiazole and pyrazoline derivatives as anti-proliferative agents targeting EGFR-TK: design, synthesis, biological evaluation and molecular docking study

Two new series of oxadiazole and pyrazoline derivatives were designed and synthesized as promising EGFR-TK inhibitors. The in vitro antiproliferative activity was studied against three human cancer cell lines; HCT116, HepG-2 and MCF7 using MTT assay. Compound 10c showed the most potent anticancer activity against all cancer cell lines, with IC50 range of 1.82 to 5.55 μM, while proving safe towards normal cells WI-38 (IC50 = 41.17 μM) compared to the reference drug doxorubicin (IC50 = 6.72 μM). The most active candidates 5a, 9b, 10a, 10b and 10c were further assessed for their EGFR-TK inhibition. The best of which, compounds 5a and 10b showed IC50 of 0.09 and 0.16 μM respectively compared to gefitinib (IC50 = 0.04 μM). Further investigation against other EGFR family members, showed that 5a displayed good activities against HER3 and HER4 with IC50 values 0.18 and 0.37 µM, respectively compared to gefitinib (IC50 = 0.35 and 0.58 µM, respectively). Furthermore, 5a was evaluated for cell cycle distribution and apoptotic induction on HepG-2 cells. It induced mitochondrial apoptotic pathway and increased accumulation of ROS. Molecular docking study came in agreement with the biological results. Compounds 5a and 10b showed promising drug-likeness with good physicochemical properties.

Andrographis paniculata and Andrographolide - A Snapshot on Recent Advances in Nano Drug Delivery Systems against Cancer

Cancer is one of the deadliest illnesses of the 21st century. Chemotherapy and radiation therapies both have considerable side effects. Antitumor antibiotics are one of them. Coughs, common colds, fevers, laryngitis, and infectious disorders have all been treated with Andrographis paniculata for centuries. Extracts of Andrographis effectively treat various ailments, as well as cancer. The most active molecule in Andrographis paniculata is andrographolide a, diterpene, and lactone. Andrographis paniculata and its derivatives have long been used to treat various ailments. Anti-inflammatory and cancerfighting characteristics have been observed in Andrographolide. Andrographolide, a diterpene lactone separated from Andrographis paniculata, has also been shown to have important criticalessential biological protective properties. It has also been suggested that it could be used to treat major human diseases like-rheumatoid like rheumatoid, colitis, and Parkinsons disease. This summary aims to highlight Andrographolide as a promising cancer treatment option. Several databases were searched for andrographolides cytotoxic/anti-cancer effects in pre-clinical and clinical research to serve this purpose. Several studies have shown that Andrographolide is helpful in cancer medication, as detailed in this review.

Hybrids of Benzimidazole-oxadiazole: A New Avenue for Synthesis, Pharmacological Activity and Recent Patents for the Development of More Effective Ligands

BACKGROUND

Two significant families of compounds i.e. 1,3,4-oxadiazole and benzimidazole, have undergone extensive investigation into their pharmacological characteristics and possible therapeutic applications. Both classes have shown their potential in a variety of applications, and because of their synergistic interactions, they may have an even better therapeutic impact when combined.

OBJECTIVES

To produce a specific molecule with potent therapeutic properties, it is now common methods to combine at least two pharmacophores. This facilitates interaction with several targets, enhances biological functions, or eliminates adverse effects associated with them.

CONCLUSION

The synthesis of benzimidazole-1,3,4-oxadiazole hybrid compounds has recently involved the use of several synthetic techniques, all of which are detailed in the literature along with the advantages and disadvantages. It has been noted that the structure-activity relationship relates their pharmacological actions to their molecular structure. In order to set the stage for future research, the study aims to provide researchers with an effective toolbox and an understanding of benzimidazole and 1,3,4-oxadiazole hybrid compounds.

An Overview of the Pharmacological Activities and Synthesis of Benzothiophene Derivatives

One important class of organic compounds having many uses, especially in medical chemistry, is benzothiophene and its derivatives. This review examines the biological activity of benzothiophene derivatives and summarizes the synthetic methods used in their production. The effectiveness of several synthetic pathways, such as cyclization techniques, functional group modifications, and reactions catalyzed by transition metals, in gaining access to benzothiophene scaffolds has been examined. Additionally, a broad spectrum of therapeutic domains, such as antiinflammatory, antibacterial, antidiabetic, anticancer, antimicrobial, anti-leishmanial, antifungal, antimalarial, and antitubercular activities, are covered by the pharmacological activities that are being explored. The synthesis and pharmacological potential of benzothiophene derivatives are well-explained in this thorough review, which opens up new options for medicinal chemistry and drug discovery study. Overall, this study is a useful resource for scientists working on drug development and discovery as it sheds light on the pharmacological potential of benzothiophene derivatives. This review includes the synthesis and bioactivities of the years 2002-2024. The goal of this review is to compile the existing information on benzothiophene derivatives and provide guidance for future research and development as well as insights into their possible medicinal uses.

1,3,4-Oxadiazole Scaffold in Antidiabetic Drug Discovery: An Overview

Diabetes mellitus is one of the biggest challenges for the scientific community in the 21st century. With the increasing number of cases of diabetes and drug-resistant diabetes, there is an urgent need to develop new potent molecules capable of combating this cruel disease. Medicinal chemistry concerns the discovery, development, identification, and interpretation of the mode of action of biologically active compounds at the molecular level. Oxadiazole-based derivatives have come up as a potential option for antidiabetic drug research. Oxadiazole is a five-membered heterocyclic organic compound containing two nitrogen atoms and one oxygen atom in its ring. Oxadiazole hybrids have shown the ability to improve glucose tolerance, enhance insulin sensitivity, and reduce fasting blood glucose levels. The mechanisms underlying the antidiabetic effects of oxadiazole involve the modulation of molecular targets such as peroxisome proliferator-activated receptor gamma (PPARγ), α-glucosidase, α-amylase and GSK-3β which regulate glucose metabolism and insulin secretion. The present review article describes the chemical structure and properties of oxadiazoles and highlights the antidiabetic activity through action on different targets. The SAR for the oxadiazole hybrids has been discussed in this article, which will pave the way for the design and development of new 1,3,4-oxadiazole derivatives as promising antidiabetic agents in the future. We expect that this article will provide comprehensive knowledge and current innovation on oxadiazole derivatives with antidiabetic potential and will fulfil the needs of the scientific community in designing and developing efficacious antidiabetic agents.

A Bird's Eye Review of Recent Reports on 1,3,4-oxadiazoles' Anti-inflammatory Insights Perspectives

Anti-inflammatory agents suppress inflammatory mediators such as prostaglandins, prostacyclins, cytokines, thromboxane, histamine, bradykinins, COX-I and COX-II, 5-LOX, and other substances. These inflammatory chemicals create inflammatory responses when tissue is injured by trauma, bacteria, heat, toxins, or other factors. These inflammatory reactions may result in fluid flow from the blood vessels into the tissues, resulting in swelling. When the therapeutic importance of these clinically beneficial medications in treating inflammation was recognized, it spurred the invention of even more powerful and important molecules. Oxadiazole derivatives are exceptionally potent NSAIDs, and they are widely used. Comprehensive biochemical, structure-activity-relationship and pharmacological investigations have demonstrated that these 1,3,4-oxadiazole compounds exhibit anti-inflammatory properties. This review article outlines the synthesis scheme for 1,3,4-oxadiazole used in treating inflammation.

Podophyllotoxin: Recent Advances in the Development of Hybridization Strategies to Enhance Its Antitumoral Profile

Podophyllotoxin is a naturally occurring cyclolignan isolated from rhizomes of Podophyllum sp. In the clinic, it is used mainly as an antiviral; however, its antitumor activity is even more interesting. While podophyllotoxin possesses severe side effects that limit its development as an anticancer agent, nevertheless, it has become a good lead compound for the synthesis of derivatives with fewer side effects and better selectivity. Several examples, such as etoposide, highlight the potential of this natural product for chemomodulation in the search for new antitumor agents. This review focuses on the recent chemical modifications (2017-mid-2023) of the podophyllotoxin skeleton performed mainly at the C-ring (but also at the lactone D-ring and at the trimethoxyphenyl E-ring) together with their biological properties. Special emphasis is placed on hybrids or conjugates with other natural products (either primary or secondary metabolites) and other molecules (heterocycles, benzoheterocycles, synthetic drugs, and other moieties) that contribute to improved podophyllotoxin bioactivity. In fact, hybridization has been a good strategy to design podophyllotoxin derivatives with enhanced bioactivity. The way in which the two components are joined (directly or through spacers) was also considered for the organization of this review. This comprehensive perspective is presented with the aim of guiding the medicinal chemistry community in the design of new podophyllotoxin-based drugs with improved anticancer properties.

Antimicrobial and Cytotoxic Activities of Water-Soluble Isoxazole-Linked 1,3,4-Oxadiazole with Delocalized Charge: In Vitro and In Vivo Results

The distinct structure of cationic organic compounds plays a pivotal role in enhancing their water solubility, which in turn influences their bioavailability. A representative of these compounds, which contains a delocalized charge, is 5-amino-2-(5-amino-3-methyl-1,2-oxazol-4-yl)-3-methyl-2,3-dihydro-1,3,4-oxadiazol-2-ylium bromide (ED). The high-water solubility of ED obviates the need for potentially harmful solvents during in vitro testing. The antibacterial and antifungal activities of the ED compound were assessed in vitro using the microtiter plate method and a biocellulose-based biofilm model. Additionally, its cytotoxic effects on wound bed fibroblasts and keratinocytes were examined. The antistaphylococcal activity of ED was also evaluated using an in vivo larvae model of Galleria mellonella. Results indicated that ED was more effective against Gram-positive bacteria than Gram-negative ones, exhibiting bactericidal properties. Furthermore, ED demonstrated greater efficacy against biofilms formed by Gram-positive bacteria. At bactericidal concentrations, ED was non-cytotoxic to fibroblasts and keratinocytes. In in vivo tests, ED was non-toxic to the larvae. When co-injected with a high load of S. aureus, it reduced the average larval mortality by approximately 40%. These findings suggest that ED holds promise for further evaluation as a potential treatment for biofilm-based wound infections, especially those caused by Gram-positive pathogens like S. aureus.

Multicomponent Domino Reaction for Concise Access to 2-Amino-Substituted 1,3,4 Oxadiazoles via Smiles Rearrangement

A multicomponent domino reaction has been developed for the preparation of N-substituted 2-amino-1,3,4-oxadiazoles directly from various hydrazides (32 examples). The formation of 2-amino-1,3,4-oxadiazole involves the Smiles rearrangement of thiazolidinone, which results in the formation of carbodiimide intermediate that concomitantly undergoes amide-imidic acid tautomerism followed by cyclization. The protocol developed has wide applicability and provides the desired 2-amino-1,3,4-oxadiazole in excellent yields. The GSD studies of NMR spectra of aliphatic substrates (4di, 4dh) revealed the formation of three products, whereas, in the case of allylic and benzylic substrates, thiazolidinones were obtained as the sole products. Furthermore, to elucidate the plausible mechanism, DFT studies were performed affirming carbodiimide as the crucial intermediate for the interconversion of thiazolidinone to oxadiazole.

Design, Synthesis, Characterization and Computational Studies of Mannich Bases Oxadiazole Derivatives as New Class of Jack Bean Urease Inhibitors

Mannich bases consisting of 1,3,4-oxadiazole-2-thione (3 a-3 l) bearing various substituents were synthesized and found potent jack bean urease inhibitors. The prepared compounds showed significantly good inhibitory activities with IC50 values from 9.45±0.05 to 267.42±0.23 μM. The compound 3 k containing 4-chlorophenyl (-R) and 4-hydroxyphenyl (-R') was most active with IC50 9.45±0.05 μM followed by 3 e (IC50 22.52±0.15 μM) in which -R was phenyl and -R' was isopropyl group. However, when both -R and -R' were either 4-chlorophenyl groups (3 l) or only -R' was 4-nitrophenyl (3 i), both compounds were found inactive. The detailed binding affinities of the produced compounds with protein were explored through molecular docking and data-supported in-vitro enzyme inhibition profiles. Drug likeness was confirmed by in silico ADME investigations and molecular orbital analysis (HOMO-LUMO) and electrostatic potential maps were got from DFT calculations. ESP maps exposed that there are two potential binding sites with the most positive and most negative parts.

Rapid Assembly of Pyrrole-Ligated 1,3,4-Oxadiazoles and Excellent Antibacterial Activity of Iodophenol Substituents

Pyrrole-ligated 1,3,4-oxadiazole is a very important pharmacophore which exhibits broad therapeutic effects such as anti-tuberculosis, anti-epileptic, anti-HIV, anti-cancer, anti-inflammatory, antioxidant, and antibacterial activities. A one-pot Maillard reaction between D-Ribose and an L-amino methyl ester in DMSO with oxalic acid at 2.5 atm and 80 °C expeditiously produced pyrrole-2-carbaldehyde platform chemicals in reasonable yields, which were utilized for the synthesis of pyrrole-ligated 1,3,4-oxadiazoles. Benzohydrazide reacted with the formyl group of the pyrrole platforms to provide the corresponding imine intermediates, which underwent I₂-mediated oxidative cyclization to the pyrrole-ligated 1,3,4-oxadiazole skeleton. The structure and activity relationship (SAR) of the target compounds with varying alkyl or aryl substituents of the amino acids and electron-withdrawing or electron-donating substituents on the phenyl ring of benzohydrazide were evaluated for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Acinetobacter baumannii as representative Gram(-) and Gram(+) bacteria. Branched alkyl groups from the amino acid showed better antibacterial activities. Absolutely superior activities were observed for 5f-1 with an iodophenol substituent against A. baumannii (MIC < 2 μg/mL), a bacterial pathogen that displays a high resistance to commonly used antibiotics.

Investigations of p-tolyloxy-1,3,4-oxadiazole propionamides as soybean 15-lipoxygenase inhibitors in comforting with in vitro and in silico studies

Inflammatory disorders are the prime contributor to public health issue and the development of more effective and safer anti-inflammatory drugs in addition to other therapeutic alternatives to treat inflammatory illnesses, particularly chronic inflammatory diseases, is one of the foremost current issues. In this regard, our present work is concerned with the synthesis of a new series of N-alkyl/aralkyl/aryl derivatives (7a-o) of 5-((p-tolyloxymethyl)-4H-1,3,4-oxadiazole-2-ylthio)propionamide which was instigated by the successive conversions of p-tolyloxyacetic acid into ester, hydrazide and 5-(p-tolyloxymethyl)-4H-1,3,4-oxadiazole-2-thiol. The planned compounds (7a-o) were attained by the reaction of 5-(p-tolyloxymethyl)-4H-1,3,4-oxadiazole-2-thiol with variety of N-alkyl/aralkyl/aryl electrophiles in potassium hydroxide and were characterized by FTIR, 1H-, 13C-NMR spectroscopy, EI-MS and HR-EI-MS spectrometry and probed for their inhibiting potential against soybean 15-lipoxygenase (15-LOX) enzyme. The compounds 7a, 7n, 7 g, 7e, 7h, 7i, 7j and 7b promulgated the potent inhibiting potential with IC50 values 9.43 ± 0.45, 16.75 ± 0.49, 19.45 ± 0.37, 21.32 ± 0.46, 22.64 ± 0.56, 23.53 ± 0.62, 24.32 ± 0.45 and 29.15 ± 0.57 µM, respectively, while excellent to good inhibitory activities were shown by 7o, 7 m, 7k, 7f, 7c, 7 l and 7d with IC50 values in the range 30.29 ± 0.56 to 52.54 ± 0.64 µM. Compounds 7i-o maintained 91.12 ± 1.5 to 98.23 ± 1.2% blood mononuclear cells (MNCs) viability at 0.25 mM by MTT assay whilst compounds 7d-h observed 46.51 ± 1.3 to 57.12 ± 1.4% viability where as the most toxic compounds were 7b (12.51 ± 1.4%), 7a (28.12 ± 1.5%) and 7c (38.23 ± 1.5%) as compared with controls. Pharmacokinetic profiles predicted good oral bioavailability and drug-likeness properties of molecules as per rule of five. Molecular docking studies displayed hydrogen bonding between the compounds and the enzyme with Arg378 which was common in 7n, 7 g, 7h and baicalein. In 7a and quercetin, hydrogen bonding was established through Asn375; Tyr512 and Val589 were also involved in bonding with other analogues. RMSD (root mean square deviation) values exhibited good inhibitory profiles in the order quercetin (0.73 Å)<7 g (0.98 Å) Collapse

Key Words

• 15-Lipoxygenase inhibition
• ADME studies
• DFT calculations
• MTT assay
• characterization
• in silico studies
• synthesis
• tolyloxyoxadiazole propionamides

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MESH Headings

• Structure-Activity Relationship
• Molecular Docking Simulation
• Lipoxygenase Inhibitors/pharmacology
• Glycine max
• Quercetin
• Anti-Inflammatory Agents/pharmacology
• Sulfhydryl Compounds
• Molecular Structure

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Grants Collapse

Affiliation(s)

Bushra Bashir Institute of Chemistry, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Naheed Riaz Institute of Chemistry, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Syeda Abida Ejaz Department of Pharmaceutical Chemistry, Faculty of Pharmacy, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Muhammad Saleem Institute of Chemistry, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Ambar Iqbal Institute of Chemistry, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan Department of Biochemistry, Institute of Biochemistry, Biotechnology and Bioinformatics (IBBB), Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Muhammad Ashraf Institute of Chemistry, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Samina Ejaz Department of Biochemistry, Institute of Biochemistry, Biotechnology and Bioinformatics (IBBB), Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Aziz-Ur -Rehman Department of Chemistry, Government College University Lahore, Lahore, Pakistan
Mubashir Aziz Department of Pharmaceutical Chemistry, Faculty of Pharmacy, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
Keshab Bhattarai Department of Pharmaceutical Biology, University of Tuebingen, Tuebingen, Germany

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Exploring Probenecid Derived 1,3,4-Oxadiazole-Phthalimide Hybrid as α-Amylase Inhibitor: Synthesis, Structural Investigation, and Molecular Modeling

1,3,4-Oxadiazole moiety is a crucial pharmacophore in many biologically active compounds. In a typical synthesis, probenecid was subjected to a sequence of reactions to obtain a 1,3,4-oxadiazole–phthalimide hybrid (PESMP) in high yields. The NMR (1H and 13C) spectroscopic analysis initially confirmed the structure of PESMP. Further spectral aspects were validated based on a single-crystal XRD analysis. Experimental findings were confirmed afterwards by executing a Hirshfeld surface (HS) analysis and quantum mechanical computations. The HS analysis showed the role of the π⋯π stacking interactions in PESMP. PESMP was found to have a high stability and lower reactivity in terms of global reactivity parameters. α-Amylase inhibition studies revealed that the PESMP was a good inhibitor of α-amylase with an s value of 10.60 ± 0.16 μg/mL compared with that of standard acarbose (IC50 = 8.80 ± 0.21 μg/mL). Molecular docking was also utilized to reveal the binding pose and features of PESMP against the α-amylase enzyme. Via docking computations, the high potency of PESMP and acarbose towards the α-amylase enzyme was unveiled and confirmed by docking scores of −7.4 and −9.4 kcal/mol, respectively. These findings shine a new light on the potential of PESMP compounds as α-amylase inhibitors.

Synthesis and Pharmacological Characterization of Metronidazole-Oxadiazole Derivatives

Background

The use of antibiotics with or without prescription is increasing worldwide. With certain limitations, metronidazole (MTZ) is extensively used as an antibacterial and antiparasitic drug. Derivatives of 1,2,4-oxadiazole (ODZ) are used to modify the chemical structure of drugs. The present study aimed to synthesize new MTZ-ODZ derivatives that could potentially lead to new medications.

Methods

The reaction of MTZ with ethyl chloroacetate and potassium carbonate anhydrous was used to produce compound 7. This compound was treated with hydrazine hydrate in methanol to obtain compound 8. Carbon disulfide and potassium hydroxide were then added to obtain compound 9, which was then mixed with various α-haloketones to obtain compounds 10a to 10f. Subsequently, the structures of the new MTZ-ODZ derivatives were determined.

Results

All new compounds exhibited excellent activity against all tested organisms. The synthesized compounds showed a significant radical scavenging activity. The IC₅₀ value for compounds 10a, 10b, 10c, 10d, 10e, and 10f was 70.42±0.15, 70.52±0.54, 85.21±0.85, 80.10±0.46, 82.52±0.13, and 70.45±0.12 g/mL, respectively. In terms of antigiardial activity, the IC₅₀ value for compounds 10a,10b, 10c, and 10d ranged from 1.31±0.11 µM to 2.26±0.49 µM. In contrast, the IC₅₀ for MTZ was 3.71±0.27 µM. Compound 10f showed the highest antigiardial activity with an IC₅₀ value of 0.88±0.52 µM.

Conclusion

Most of the MTZ-ODZ derivatives showed high radical scavenging activity in the benzene ring due to the activation of certain groups, such as OCH₃, NO₂, and OH. The results suggest that the newly synthesized compounds could be used as an antiparasitic drug.

Crystal structure of ethyl 4-{[5-(adamantan-1-yl)-2-sulfanylidene-2,3-dihydro-1,3,4-oxadiazol-3-yl]methyl}piperazine-1-carboxylate, C20H30N4O3S

C20H30N4O3S, orthorhombic, P212121 (no. 19), a = 7.7152(3) Å, b = 10.6132(2) Å, c = 25.5990(7) Å, V = 2096.12(11) Å3, Z = 4, R gt(F) = 0.0579, wR ref(F 2) = 0.1216, T = 293 K.

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.

BTEAC Catalyzed Ultrasonic-Assisted Synthesis of Bromobenzofuran-Oxadiazoles: Unravelling Anti-HepG-2 Cancer Therapeutic Potential through In Vitro and In Silico Studies

In this work, BTEAC (benzyl triethylammonium chloride) was employed as a phase transfer catalyst in an improved synthesis (up to 88% yield) of S-alkylated bromobenzofuran-oxadiazole scaffolds BF1-9. These bromobenzofuran-oxadiazole structural hybrids BF1-9 were evaluated in vitro against anti-hepatocellular cancer (HepG2) cell line as well as for their in silico therapeutic potential against six key cancer targets, such as EGFR, PI3K, mTOR, GSK-3β, AKT, and Tubulin polymerization enzymes. Bromobenzofuran structural motifs BF-2, BF-5, and BF-6 displayed the best anti-cancer potential and with the least cell viabilities (12.72 ± 2.23%, 10.41 ± 0.66%, and 13.08 ± 1.08%), respectively, against HepG2 liver cancer cell line, and they also showed excellent molecular docking scores against EGFR, PI3K, mTOR, and Tubulin polymerization enzymes, which are major cancer targets. Bromobenzofuran-oxadiazoles BF-2, BF-5, and BF-6 displayed excellent binding affinities with the active sites of EGFR, PI3K, mTOR, and Tubulin polymerization enzymes in the molecular docking studies as well as in MMGBSA and MM-PBSA studies. The stable bindings of these structural hybrids BF-2, BF-5, and BF-6 with the enzyme targets EGFR and PI3K were further confirmed by molecular dynamic simulations. These investigations revealed that 2,5-dimethoxy-based bromobenzofuran-oxadiazole BF-5 (10.41 ± 0.66% cell viability) exhibited excellent cytotoxic therapeutic efficacy. Moreover, computational studies also suggested that the EGFR, PI3K, mTOR, and Tubulin polymerization enzymes were the probable targets of this BF-5 scaffold. In silico approaches, such as molecular docking, molecular dynamics simulations, and DFT studies, displayed excellent association with the experimental biological data of bromobenzofuran-oxadiazoles BF1-9. Thus, in silico and in vitro results anticipate that the synthesized bromobenzofuran-oxadiazole hybrid BF-5 possesses prominent anti-liver cancer inhibitory effects and can be used as lead for further investigation for anti-HepG2 liver cancer therapy.

Synthesis and Evaluation of Novel S-alkyl Phthalimide- and S-benzyl-oxadiazole-quinoline Hybrids as Inhibitors of Monoamine Oxidase and Acetylcholinesterase

New S-alkyl phthalimide 5a-f and S-benzyl 6a-d analogs of 5-(2-phenylquinolin-4-yl)-1,3,4-oxadiazole-2-thiol (4) were prepared by reacting 4 with N-bromoalkylphthalimide and CF₃-substituted benzyl bromides in excellent yields. Spectroscopic techniques were employed to elucidate the structures of the synthesized molecules. The inhibition activity of newly synthesized molecules toward MAO-A, MAO-B, and AChE enzymes, was also assessed. All these compounds showed activity in the submicromolar range against all enzymes. Compounds 5a and 5f were found to be the most potent compounds against MAO-A (IC₅₀ = 0.91 ± 0.15 nM) and MAO-B (IC₅₀ = 0.84 ± 0.06 nM), while compound 5c showed the most efficient acetylcholinesterase inhibition (IC₅₀ = 1.02± 0.65 μM). Docking predictions disclosed the docking poses of the synthesized molecules with all enzymes and demonstrated the outstanding potency of compounds 5a, 5f, and 5c (docking scores = -11.6, -15.3, and -14.0 kcal/mol against MAO-A, MAO-B, and AChE, respectively). These newly synthesized analogs act as up-and-coming candidates for the creation of safer curative use against Alzheimer's illness.

Crystal structure of 2-({[5-(adamantan-2-yl)-2-sulfanylidene-1,3,4-oxadiazolidin-3-yl]methyl}amino)benzonitrile, C20H22N4OS

C20H22N4OS, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 6.8528(3) Å, b = 11.3498(5) Å, c = 13.3896(9) Å, α = 114.083(5)°, β = 104.326(4)°, γ = 90.369(3)°, V = 914.38(9) Å3, Z = 2, R gt (F) = 0.0844, wR ref (F 2) = 0.2217, T = 160 K.

1,3,4-Oxadiazole-naphthalene hybrids as potential VEGFR-2 inhibitors: design, synthesis, antiproliferative activity, apoptotic effect, and in silico studies

In the current work, some 1,3,4-oxadiazole-naphthalene hybrids were designed and synthesised as VEGFR-2 inhibitors. The synthesised compounds were evaluated in vitro for their antiproliferative activity against two human cancer cell lines namely, HepG-2 and MCF-7. Compounds that exhibited promising cytotoxicity (5, 8, 15, 16, 17, and 18) were further evaluated for their VEGFR-2 inhibitory activities. Compound 5 showed good antiproliferative activity against both cell lines and inhibitory effect on VEGFR-2. Besides, it induced apoptosis by 22.86% compared to 0.51% in the control (HepG2) cells. This apoptotic effect was supported by a 5.61-fold increase in the level of caspase-3 compared to the control cells. Moreover, it arrested the HepG2 cell growth mostly at the Pre-G1 phase. Several in silico studies were performed including docking, ADMET, and toxicity studies to predict binding mode against VEGFR-2 and to anticipate pharmacokinetic, drug-likeness, and toxicity of the synthesised compounds.

Crystal structure of 2-(adamantan-1-yl)-5-(3,5-dinitrophenyl)-1,3,4-oxadiazole, C18H18N4O5

C18H18N4O5, monoclinic, P21/c (no. 14), a = 11.7553(8) Å, b = 6.4876(4) Å, c = 22.3442(15) Å, β = 91.263(7)°, V = 1703.64(19) Å3, Z = 4, Rgt (F) = 0.0531, wRref (F 2) = 0.1376, T = 160 K.

Assessing p-tolyloxy-1,3,4-oxadiazole acetamides as lipoxygenase inhibitors assisted by in vitro and in silico studies

The underlying correlation between the inflammation, innate immunity and cancer is extensively familiar and linked through a process mediated by three enzymes; cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (CYP₄₅₀). The ever increase in the reported side effects of the antiinflammatory drugs against the targeted enzymes and the resistance developed afterwards compels the researchers to synthesize new effective molecules with safer profile. On the basis of these facts, our ongoing research on 1,3,4-oxadiazole derivatives deals with the synthesis of a new series of N-alkyl/aralky/aryl derivatives of 5-((p-tolyloxymethyl)-4H-1,3,4-oxadiazole-2-ylthio)acetamide (6a-o) which were developed by the sequential conversion of p-tolyloxyacetic acid (a) into ester (1) hydrazide (2) and 5-(p-tolyloxymethyl)-4H-1,3,4-oxadiazole-2-thiol (3). The designed compounds (6a-o) were acquired by the reaction of 1,3,4-oxadiazole (3) with numerous electrophiles (5a-o) in KOH. The synthesized analogues (6a-o) were characterized by FTIR, ¹H-, ¹³C NMR spectroscopy, EI-MS and HR-EI-MS spectrometry, and were further assessed for their inhibitory potential against the soybean 15-LOX enzyme. The results showed excellent inhibitory potential of the compounds against the said enzyme, specifically 6o, 6b, 6n and 6e with inhibitory values (IC₅₀ ± SEM) of 21.5 ± 0.76, 24.3 ± 0.45, 29.1 ± 0.65 and 31.3 ± 0.78 µM, respectively. These compounds displayed < 55 % blood mononuclear cells (MNCs) cellular viability as measured by MTT assay at 0.25 mM concentration. Other compounds demonstrated moderate inhibitory activities with IC₅₀ values in the range of 33.2 ± 0.78 to 96.3 ± 0.73 µM and exhibited little cellular viability against MNCs except 6i, 6j, 6 m and 6 k that showed 61-79 % cellular viability. It was observed that most of the compounds (6o, 6b, 6n, 6e) were found more toxic towards MNCs at studied concentration of 0.25 mM. SAR studies revealed that the positions and nature of substituents accompanying phenyl ring have great influence on 15-LOX inhibitory activity. In the most active compound 6o, the amino acids Asp768 and Val126 were involved in hydrogen bonding, Thr529 was linked with π-anion interaction and π-sulphur interaction was displayed with Tyr525 and two π-alkyl interactions were formed with the benzene ring and amino acid residues Pro530 and Arg533. The in silico pharmacokinetics profiles and density functional theory calculations of the compounds further supported the in vitro findings. Further work on the synthesis of more oxadiazole derivatives is in progress in search for potential 'leads' for the drug discovery as LOX inhibitors.

Synthesis of 2-Imino-1,3,4-oxadiazolines from Acylhydrazides and Isothiocyanates via Aerobic Oxidation and a DMAP-Mediated Annulation Sequence

In this work, an efficient synthesis of 2-imino-1,3,4-oxadiazolines from acylhydrazides and isothiocyanates is described. In the presence of 4-dimethylaminopyridine (DMAP) and molecular oxygen, various 2-imino-1,3,4-oxadiazolines were produced in good to high yields. The developed method showed a broad substrate scope and was effective on the gram scale. On the basis of the mechanistic studies and previous literature, it was proposed that the mechanism consists of an aerobic oxidation of acylhydrazides facilitated by DMAP and isothiocyanates, followed by a DMAP-mediated annulation of the in situ generated acyldiazenes with isothiocyanates.

Synthesis, crystal structure and Hirshfeld surface analysis of a zinc(II) coordination polymer of 5-phenyl-1,3,4-oxa-diazole-2-thiol-ate

A new zinc coordination polymer with 5-phenyl-1,3,4-oxa-diazole-2-thiol-ate, namely, catena-poly[zinc(II)-bis-(μ2-5-phenyl-1,3,4-oxa-diazole-2-thiol-ato)-κ2 N 3:S;κ2 S:N 3], [Zn(C8H5N2OS)2] n , was synthesized. The single-crystal X-ray diffraction analysis shows that the polymeric structure crystallizes in the centrosymmetric monoclinic C2/c space group. The ZnII atom is coordinated to two S and two N atoms from four crystallographically independent (L) ligands, forming zigzag chains along the [001] direction. This polymer complex forms an eight-membered [Zn-S-C-N-Zn-S-C-N] chair-like ring with two ZnII atoms and two ligand mol-ecules. On the Hirshfeld surface, the largest contributions come from the short contacts such as van der Waals forces, including H⋯H, C⋯H and S⋯H. Inter-actions including N⋯H, O⋯H and C⋯C contacts were also observed; however, their contribution to the overall stability of the crystal lattice is minor.

Potential Synthetic Routes and Metal-Ion Sensing Applications of 1,3,4-Oxadiazoles: An Integrative Review

Oxadiazoles, especially 1,3,4-oxadiazole scaffolds, stand among the foremost heterocyclic fragments with a broad spectrum of applications in diverse fields, including pharmacology, polymers, material science, and organic electronics, among others. In this comprehensive review, we summarize the pivotal synthetic strategies for 1,3,4-oxadiazole derivatives including dehydrogenative cyclization of 1,2-diacylhydrazines, oxidative cyclization of acylhydrazones, condensation cyclization, C-H activation of oxadiazole ring, decarboxylative cyclization and oxidative annulation along with plausible mechanisms. The set of 1,3,4-oxadiazoles selected from the literature and discussed herein epitomize the ease of synthesis as well as the possibility of linking π-conjugated groups; thereby encouraging the use of these molecules as important starting building blocks for a wide variety of fluorescent frameworks, particularly in the development of potential chemosensors. High photoluminescent quantum yield, excellent thermal and chemical stability, and the presence of potential coordination (N and O donor atoms) sites make these molecules a prominent choice for metal-ions sensors. An overview of selective metal-ion sensing, the detection limit along with the sensing mechanisms (photo-induced electron transfer, excited-state intramolecular proton transfer, and complex formation) is also included.

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

Heterocycles of synthetic and natural origin are a well-established class of compounds representing a broad range of organic molecules that constitute over 60% of drugs and agrochemicals in the market or research pipeline. Considering the vast abundance of these structural motifs, the development of chemical processes providing easy access to novel complex target molecules by introducing environmentally benign conditions with the main focus on improving the cost-effectiveness of the chemical transformation is highly demanding and challenging. Accordingly, sonochemistry appears to be an excellent alternative and a highly feasible environmentally benign energy input that has recently received considerable and steadily increasing interest in organic synthesis. However, the involvement of transition-metal-catalyst(s) in a chemical process often triggers an unintended impact on the greenness or sustainability of the transformation. Consequently, enormous efforts have been devoted to developing metal-free routes for assembling various heterocycles of medicinal interest, particularly under ultrasound irradiation. The present review article aims to demonstrate a brief overview of the current progress accomplished in the ultrasound-assisted synthesis of pharmaceutically relevant diverse heterocycles using transition-metal-free catalysis.

Recent updates on the anticancer activity of quinoxaline hybrids (Jan. 2017-Jan. 2022)

Abstract:

Cancer as one of the leading causes of death among non-communicable diseases has already posed a heavy burden on the world health system. Chemotherapy is one of the most effective approaches for cancer treatment, but multidrug resistance, lack of efficacy, and toxic side effects hamper efficacious cancer chemotherapy, creating an urgent need to develop novel, more effective and less toxic anticancer therapeutics. Quinoxalines as fascinating structures constitute an important class of heterocycles in drug discovery. Quinoxaline hybrids could exert anticancer activity through diverse mechanisms and possess profound in vitro and in vivo efficacy against various cancers including multidrug-resistant forms. Thus, quinoxaline hybrids represent useful templates for the control and eradication of cancer. The purpose of the present review article is to provide an emphasis on the recent developments (Jan. 2017-Jan. 2022) in quinoxaline hybrids with insights into their in vitro and in vivo anticancer potential as well as structure-activity relationships (SARs) to facilitate further rational design of more effective candidates.

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.

Advancement and recent trends in seeking less toxic and more active anti-cancer drugs: Insights into thiourea based molecules

The finding of potent anticancer agents with low toxicity and high selectivity has remained valuable for human health. Thiourea derivatives are the most significant organic compounds with integral and typical characteristics of numerous varieties of natural products and pharmaceutical agents. It exhibits various pharmacological properties, and its analogues confer a great deal of structural diversity that was proven to be the most advantageous in the search for novel therapeutic agents. Thiourea derivatives, which show beneficial antitumor activities, are typically considered the central core in various anticancer derivatives. They also have broad-ranging biological activities such as anti-inflammatory, antibacterial, antifungal, antitubercular, antihypertensive, antihistaminic, and antiviral activities. Several FDA-approved drugs of thiourea derivatives and their analogues in the market, currently in progress through various registration statuses or clinical stages, indicating that thiourea derivatives are the most promising drugs. The current review is intended to systematically provide comprehensive evidence in the recent developments of thiourea to treat numerous types of cancer. Furthermore, we hope that this review will be helpful for novel consideration in seeking rational designs of less toxic and more active drugs and more effective diagnostics agents.

New water-soluble isoxazole-linked 1,3,4-oxadiazole derivative with delocalized positive charge

Herein we present a synthesis and characterization of a new and unique low-weight heterocyclic compound 5-amino-2-(5-amino-3-methyl-1,2-oxazol-4-yl)-3-methyl-2,3-dihydro-1,3,4-oxadiazol-2-ylium bromide with the unusual electron charge delocalization owing the local positive charge at the carbon atom of oxadiazole moiety. X-ray single crystal of C7H10N5O2·Br- showed the molecule crystalized in monoclinic, space group P21/c. Both five membered rings are planar and twisted forming the ring motif with the counter ion where H⋯Br interactions are one of the dominant. The presented compound is characterized by high ionization efficiency in ESI-MS mode and undergoes dissociation within oxadiazole moiety under ESI-MS/MS conditions even under low collision energies. The presented compound is an interesting example of heterocyclic stable carbocation which may serve as a new lead structure.

Caspase-3: A primary target for natural and synthetic compounds for cancer therapy

Caspases, a group of protease enzymes (cysteine proteases), exist as inactive zymogens in the cells and execute apoptosis (programmed cell death). Caspase-3, an executioner caspase, plays an imperative role in apoptosis and becomes a primary target for cancer treatment. A number of analogues of quinazoline, quinazolinone, indoloquinazolines, quinone, naphthoquinones, pyrroloiminoquinones, styrylquinolines, tetheredtetrahydroquinoline, fluoroquinolone, thiosemicarbazones, benzotriazole, pyrimidines, chalcone, and carbazoles have been reported till date, representing caspase-3 mediated apoptosis for cancer therapy. Simultaneously, plant isolates, including lysicamine, podophyllotoxin, and majoranolide, have also been claimed for caspase-3-mediated apoptosis-induced cytotoxicity. Procaspase-activating compound-1 (PAC-1) is the first FDA approved orphan drug, and its synthetic derivative WF-208 also showed fascinating caspase-3 mediated anticancer activity. Till date, a large number of compounds have been reported and patented for their caspase-3-mediated cytotoxicity and now scientist is also focusing to introduce new compounds in market to encompass anticancer activity.

Discovery of Novel 1,2,4-Oxadiazole Derivatives as Potent Caspase-3 Activator for Cancer Treatment

In the present study, a quantitative structure–activity relationship (QSAR) and docking studies were accomplished on a series of 1,2,4-oxadiazoles. The results of QSARs are reliable and have high predictive ability for both the internal (q2 = 0.610) and external (pred_r2 = 0.553) datasets with least standard error (SE; i.e., 0.130) and four principal components, which signifies the reliability of the generated model. Molecular docking was also reported by the GOLD docking program, which showed that the hydrogen bonding may be responsible for the activity, and may be further increased upon adding high electronegative substitutions.