Parallel synthesis of 1,2,4-oxadiazoles using CDI activation

Computational design, synthesis, and assessment of 3-(4-(4-(1,3,4-oxadiazol-2-yl)-1H-imidazol-2-yl)phenyl)-1,2,4-oxadiazole derivatives as effective epidermal growth factor receptor inhibitors: a prospective strategy for anticancer therapy

The epidermal growth factor receptor (EGFR) enzyme plays a critical role in governing the cell cycle, positioning it as a promising target for the development of anticancer drugs. In this study, we endeavored to design and synthesize innovative EGFR inhibitors with potential applications in anticancer therapy. A novel series of compounds, namely 3-(4-(4-(1,3,4-oxadiazol-2-yl)-1H-imidazol-2-yl)phenyl)-1,2,4-oxadiazoles (30a-j), were meticulously designed using FBDD efforts and synthesized. The synthesized compounds underwent thorough characterization using 1HNMR, 13CNMR, HRMS, and mass spectrum analyses. The in vitro anticancer activities of the newly developed compounds (30a-j) were evaluated against four human cancer cell lines such as prostate cancer (PC3 & DU-145), lung cancer (A549), and liver cancer (HEPG2) using the MTT method. The results, expressed as IC50 values, demonstrated significant anticancer activity for several compounds, with five compounds (30a, 30b, 30c, 30i, and 30j) exhibiting superior potency compared to the established anticancer drug etoposide. Notably, compound 30a emerged as the most promising compound, displaying potent cytotoxicity. We also conducted a screening of the compounds on the normal Vero cell line, revealing a pronounced selectivity of the compounds against cancer cell lines, with no observable impact on the normal cell lines. Moreover, the synthesized compounds were investigated for their impact on enzyme EGFR activity. The findings revealed a robust inhibitory effect against the EGFR wild-type enzyme and a 10-fold inferior potency against the mutant form of EGFR. This observation underscores the potential of the new derivatives as effective EGFRWT inhibitors with substantial anticancer efficacy. Further studies, including cell cycle analysis and apoptosis assays in HEPG2 cell lines, revealed cell cycle arrest at G1/G0 and G2 phases. We also evaluated the potential influence of compound 30a on the EGFR pathway using western blot analysis, revealing a significant inhibition of EGFR autophosphorylation in HEPG2 cells. In conclusion, our findings highlight the promise of these novel compounds as potent EGFR inhibitors, encouraging further investigation and development for the creation of novel and effective anticancer therapeutics.

Electrochemical synthesis of 1,2,4-oxadiazoles from amidoximes through dehydrogenative cyclization

A convenient and efficient method for the generation of the iminoxy radical through anodic oxidation was developed for the synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from N-benzyl amidoximes. The transformation proceeds through 1.5-Hydrogen Atom Transfer (1,5-HAT) and intramolecular cyclization. The process features simple operation, mild conditions, broad substrate scope and high functional group compatibility, and provides a facile and practical way for the preparation of 1,2,4-oxadiazoles.

Synthesis and SAR studies of novel 1,2,4-oxadiazole-sulfonamide based compounds as potential anticancer agents for colorectal cancer therapy

A diverse series of 1,2,4-oxadiazoles based substituted compounds were designed, synthesized and evaluated as anticancer agents targeting carbonic anhydrase IX (CAIX). Initial structure-activity analysis suggested that the thiazole/thiophene-sulfonamide conjugates of 1,2,4-oxadiazoles exhibited potent anticancer activities with low μM potencies. Compound OX12 exhibited antiproliferative activity (IC₅₀ = 11.1 µM) along with appreciable inhibition potential for tumor-associated CAIX (IC₅₀ = 4.23 µM) isoform. Therefore, OX12 was structurally optimized and its SAR oriented derivatives (OX17-27) were synthesized and evaluated. This iteration resulted in compound OX27 with an almost two-fold increase in antiproliferative effect (IC₅₀ = 6.0 µM) comparable to the clinical drug doxorubicin and significantly higher potency against CAIX (IC₅₀ = 0.74 µM). Additionally, OX27 treatment decreases the expression of CAIX, induces apoptosis and ROS production, inhibited colony formation and migration of colon cancer cells. Our studies provide preclinical rational for the further optimization of identified OX27 as a suitable lead for the possible treatment of CRC.

Traceless Solid-Phase Organic Synthesis

Traceless solid-phase synthesis represents an ultimate sophisticated synthetic strategy on insoluble supports. Compounds synthesized on solid supports can be released without a trace of the linker that was used to tether the intermediates during the synthesis. Thus, the target products are composed only of the components (atoms, functional groups) inherent to the target core structure. A wide variety of synthetic strategies have been developed to prepare products in a traceless manner, and this review is dedicated to all aspects of traceless solid-phase organic synthesis. Importantly, the synthesis does not need to be carried out on a linker designed for traceless synthesis; most of the synthetic approaches described herein were developed using standard, commercially available linkers (originally devised for solid-phase peptide synthesis). The type of structure prepared in a traceless fashion is not restricted. The individual synthetic approaches are divided into eight sections, each devoted to a different methodology for traceless synthesis. Each section consists of a brief outline of the synthetic strategy followed by a description of individual reported syntheses.

One-pot synthesis of 3,5-diaryl substituted-1,2,4-oxadiazoles using gem-dibromomethylarenes

1,2,4-Oxadiazole is one of the most promising heterocyclic ring systems in medicinal chemistry. In the present paper, we report the method for an efficient one-pot synthesis of 3,5-diaryl substituted 1,2,4-oxadiazoles using a two-component reaction of gem-dibromomethylarenes with amidoximes in good yields. In this method, gem-dibromomethylarenes are used as benzoic acid equivalents for the efficient synthesis of aryl-substituted 1,2,4-oxadiazoles. It is anticipated that this methodology will have versatile applications in the practical syntheses of various molecules of both medicinal and material chemistry importance.

Synthesis of novel methyl jasmonate derivatives and evaluation of their biological activity in various cancer cell lines

Warburg hypothesized that the energy consumption of cancer cells is different than the normal cells. When compared to normal conditions, cancer cells do not undergo tricarboxylic acid (TCA) cycle therefore resulting in more lactate in the cells. Glycolysis pathway is a way of cancer cells to provide energy. The first step in glycolysis is the phosphorylation of glucose to glucose-6-phosphate. This reaction is catalyzed by the hexokinase-II enzyme (HK-II) which is known to be overexpressed in tumor cells. The feeding of cancer cells can be prevented by inhibiting the hexokinase-II enzyme in the first step of aerobic glycolysis. In literature, Methyl Jasmonate (MJ) is known as a Hexokinase-II inhibitor since it disposes VDAC and HK-II interaction on mitochondrial membrane. In our study, we aimed to increase the activity by synthesizing the novel MJ analogues with appropriate modifications. Here we report Hexokinase-2 enzyme and cell viability study results in different cancer cells. Based on the three different cancer cell lines we investigated, our novel MJ analogues proved to be more potent than the original molecule. Thus this research may provide more efficacious/novel HK-II inhibitors and may shed light to develop new anti-cancer agents.

Recent Developments in the Synthesis, Chemistry and Applications of the Fully Unsaturated 1,2,4-Oxadiazoles

Recent major developments in the synthesis (including solid phase methodologies), chemistry and applications of the fully unsaturated 1,2,4-oxadiazole nucleus are reviewed. The review covers the years 1995–2000.

A Straightforward and High-Yielding Synthesis of 1,2,4-Oxadiazoles from Chiral N-Protected α-Amino Acids and Amidoximes in Acetone-Water: An Eco-Friendly Approach

A straightforward and high-yielding methodology for the synthesis of a high structural diversity of 1,2,4-oxadiazoles from different chiral N-protected α-amino acids and amidoximes under microwave (MW) irradiation is described herein. This greener approach gives the desired products using acetone/water as solvent in very short reaction times.

Expanding Synthesizable Space of Disubstituted 1,2,4-Oxadiazoles

One-pot synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from carboxylic acids and nitriles was optimized to parallel chemistry. The method was validated on a 141 member library; the desired products were recovered with a high success rate and in moderate yields. Practical application of the approach was demonstrated in the synthesis of bioactive compound pifexole and agonists of free fatty acid receptor 1. A library of 4 948 100 synthesizable drug-like 3,5-disubstituted 1,2,4-oxadiazoles was enumerated based on the method and available validated reagents.

Novel 2-phenyl-5-[(E)-2-(thiophen-2-yl)ethenyl]-1,3,4-oxadiazole and 3-phenyl-5-[(E)-2-(thiophen-2-yl)ethenyl]-1,2,4-oxadiazole derivatives as dengue virus inhibitors targeting NS5 polymerase

Using a functional high-throughput screening (HTS) and subsequent SAR studies, we have discovered a novel series of non-nucleoside dengue viral polymerase inhibitors. We report the elaboration of SAR around hit compound 1 as well as the synthesis and antiviral evaluation of 3-phenyl-5-[(E)-2-(thiophen-2-yl)ethenyl]-1,2,4-oxadiazole and 5-phenyl-2-[2-(2-thienyl)ethenyl]-1,3,4-oxadiazole analogues derived from a rapid and easily accessible chemical pathway. A large number of compounds prepared by this method were shown to possess in vitro activity against the polymerase of dengue virus. The most potent inhibitors were tested against Dengue virus clinical isolates on infected cells model and exhibit submicromolar activity on the four dengue virus serotypes.

An efficient mEthod for the One-Pot Tandem Synthesis of 3,5-Disubstituted-1,2,4-Oxadiazoles from Benzyl Halides

The first example of a one-pot tandem approach for the synthesis of 3,5-disubstituted-1,2,4-oxadiazole derivatives from benzyl halides and amidoxime is reported. Derivatives of 3,5-disubstituted 1,2,4-oxadiazole were obtained in excellent yields under mild conditions using DMSO in the absence of an additional oxidant. Benzyl bromides bearing a range of substituents proved to be suitable substrates for this method which provides a very efficient and convenient application of the Kornblum oxidation.

Novel pyrazoline amidoxime and their 1,2,4-oxadiazole analogues: synthesis and pharmacological screening

A novel series of pyrazoline amidoxime (2a-d) and pyrazoly-1,2,4-oxadiazole (3a-p) and (4) of pharmacological significance have been synthesised. Structures of newly synthesised compounds were characterized by spectral studies. New compounds were screened for their in vitro antioxidant, antimicrobial and antiinflammatory activities. Among the synthesized compounds, compound 2a, 3l and 3o were found to be active antimicrobial agents in addition to having potent antioxidant activity, while the compound 3f showed promising antiinflammatory activity in comparison with standard drug.

2-Trifluoroacetylthiophene oxadiazoles as potent and selective class II human histone deacetylase inhibitors

Trifluoroacetylthiophene carboxamides have recently been reported to be class II HDAC inhibitors, with moderate selectivity. Exploration of replacements for the carboxamide with bioisosteric pentatomic heteroaromatic like 1,3,4-oxadiazoles, 1,2,4-oxadiazoles and 1,3-thiazoles, led to the discovery that 2-trifluoroacetylthiophene 1,3,4-oxadiazole derivatives are very potent low nanomolar HDAC4 inhibitors, highly selective over class I HDACs (HDAC 1 and 3), and moderately stable in HCT116 cell culture.

An Efficient One-Pot Synthesis of 5-(substituted amino)-1,2,4-thia- and -oxa-diazoles

A general protocol for the synthesis of 5-(substituted amino)-1,2,4-thiadiazoles by the cyclocondensation reaction of amidoximes with N-substituted thioureas in the presence of KF/Al2O3, and of 5-(cyclohexylamino)-1,2,4-oxadiazoles with DCC in the presence of KF/Al2O3 and thiourea, is described. The structures of the new compounds were elucidated by spectroscopic and physical data, and the crystal structure determination by X-ray diffraction of three examples.

Synthesis of glycosyl-triazole linked 1,2,4-oxadiazoles

The synthesis of four different types of oxadiazoles containing a terminal acetylenic group is described. Reaction of these oxadiazoles with various azidoglycosides via a copper-catalyzed [3+2] cycloaddition ('click chemistry') afforded the corresponding glycosyl-triazole linked 1,2,4-oxadiazoles in good yields.

Discovery of potent, selective, and orally bioavailable oxadiazole-based dipeptidyl peptidase IV inhibitors

A novel series of oxadiazole based amides have been shown to be potent DPP-4 inhibitors. The optimized compound 43 exhibited excellent selectivity over a variety of DPP-4 homologs.