Quinazoline clubbed thiazole and 1,3,4-oxadiazole heterocycles: synthesis, characterization, antibacterial evaluation, and molecular docking studies

An Overview of the Structure-Activity Relationship in Novel Antimicrobial Thiazoles Clubbed with Various Heterocycles (2017-2023)

Antimicrobial resistance is an increasing problem for global public health. One of the strategies to combat this issue is the synthesis of novel antimicrobials through rational drug design based on extensive structure-activity relationship studies. The thiazole nucleus is a prominent feature in the structure of many authorized antimicrobials, being clubbed with different heterocycles. The purpose of this review is to study the structure-activity relationship in antimicrobial thiazoles clubbed with various heterocycles, as reported in the literature between 2017 and 2023, in order to offer an overview of the last years in terms of antimicrobial research and provide a helpful instrument for future research in the field.

Synthesis, Antifungal Ergosterol Inhibition, Antibiofilm Activities, and Molecular Docking on β-Tubulin and Sterol 14-Alpha Demethylase along with DFT-Based Quantum Mechanical Calculation of Pyrazole Containing Fused Pyridine-Pyrimidine Derivatives

Multidrug-resistant fungal infections have become much more common in recent years, especially in immune-compromised patients. Therefore, researchers and pharmaceutical professionals have focused on the development of novel antifungal agents that can tackle the problem of resistance. In continuation to this, a novel series of pyrazole-bearing pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives (4a-4o) have been developed. These compounds have been screened against Candida albicans, Aspergillus niger, and Aspergillus clavatus. The synthesized compounds were characterized by well-known spectroscopic techniques, i.e., IR, 1H NMR, 13C NMR, and mass spectrometry. In vitro antifungal results revealed that compound 4n showed activity against C. albicans having MIC value of 200 μg/mL. To know the plausible mode of action, the active derivatives were screened for anti-biofilm and ergosterol biosynthesis inhibition activities. The compounds 4h, 4j, 4k, and 4n showed greater ergosterol biosynthesis inhibition than the control DMSO. To comprehend how molecules interact with the receptor, studies of molecular docking of 4k and 4n have been performed on the homology-modeled protein of β-tubulin. The molecular docking revealed that the active compounds 4h, 4j, 4k, 4l, and 4n interacting with the active site amino acid of sterol 14-alpha demethylase (PDB ID: 5v5z) indicate one of the possible modes of action of ergosterol inhibition activity. The synthesized compounds 4c, 4e, 4h, 4i, 4j, 4k, 4l, and 4n inhibited biofilm formation and possessed the potential for anti-biofilm activity. DFT-based quantum mechanical calculations were carried out to optimize, predict, and compare the vibration modes of the molecule 4a.

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.

Oxadiazole: A highly versatile scaffold in drug discovery

As a pharmacologically important heterocycle, oxadiazole paved the way to combat the problem associated with the confluence of many commercially available drugs with different pharmacological profiles. The present review focuses on the potential applications of five-membered heterocyclic oxadiazole derivatives, especially 1,2,4-oxadiazole, 1,2,5-oxadiazole, and 1,3,4-oxadiazole, as therapeutic agents. Designing new hybrid molecules containing the oxadiazole moiety is a better solution for the development of new drug molecules. The designed molecules may accumulate a biological profile better than those of the drugs currently available on the market. The present review will guide the way for researchers in the field of medicinal chemistry to design new biologically active molecules based on the oxadiazole nucleus. Antitubercular, antimalarial, anti-inflammatory, anti-HIV, antibacterial, and anticancer activities of various oxadiazoles have been reviewed extensively here.

The antibacterial activity of quinazoline and quinazolinone hybrids

Bacterial infections cause substantial morbidity and mortality across the world and pose serious threats to humankind. Drug resistance, especially multidrug resistance resulting from different defensive mechanisms in bacteria, is the leading cause of failure the chemotherapy, making it an urgent need to develop more effective antibacterials. Quinazoline and quinazolinone frameworks have received considerable attention due to their diversified therapeutic potential. In particular, quinazoline/quinazolinone hybrids could exert antibacterial activity through various mechanisms and are useful scaffolds for the discovery of novel antibacterials. This review principally emphases on the antibacterial potential, structure-activity relationships (SARs), and mechanism of action of quinazoline and quinazolinone hybrids, covering articles published between 2017 and 2021.