Background: Nitric oxide (NO) has been linked to the pathogenesis of asbestos-related pleural diseases, including an extremely aggressive cancer called malignant pleural mesothelioma (MPM). Given that MPM cells are characterized by a higher expression of NO synthases and elevated NO production relative to normal cells, the use of NO-donor compounds could potentially saturate the cancerous cells with NO, triggering their death. Methods: We developed a novel class of NO prodrugs by merging two NO-releasing components, 1,2,5-oxadiazole 2-oxides (furoxans) and 1,2,4-oxadiazoles, and studied their NO-releasing characteristics in a time-dependent manner using the Griess assay. The cytotoxicity against two human MPM cell lines and non-cancerous lung fibroblasts was evaluated using a colorimetric MTT assay. Results: All compounds exhibited excellent NO-donating properties, surpassing the capacity of two reference NO donor compounds, 3-carbamoyl-4-(hydroxymethyl)furoxan (CAS-1609) and 4-ethoxy-3-phenylsulphonylfuroxan (CHF-2363), by at least 1.5–3 times. All oxadiazole hybrids demonstrated high cytotoxicity against MPM cell lines in a low micromolar range, comparable or higher than the cytotoxicity of the standard-of-care drug cisplatin. Conclusions: Notably, the novel compounds displayed a markedly greater selectivity towards cancerous cells than cisplatin when compared with non-cancerous lung fibroblasts, aligning with the intended design.

A facile and efficient method for the regioselective [3 + 2] cycloaddition of 4-azidofuroxans to 1-dimethylamino-2-nitroethylene under p-TSA catalysis affording (4-nitro-1,2,3-triazolyl)furoxans was developed. This transformation is believed to proceed via eliminative azide–olefin cycloaddition resulting in its complete regioselectivity. The developed protocol has a broad substrate scope and enables a straightforward assembly of the 4-nitro-1,2,3-triazole motif. Moreover, synthesized (4-nitro-1,2,3-triazolyl)furoxans were found to be capable of NO release in a broad range of concentrations, thus providing a novel platform for future drug design and related biomedical applications of heterocyclic NO donors.

Nitrogen heterocycles hold leading positions in the field of medicinal chemistry and targeted search for next-generation pharmaceuticals. Among the enormous set of available heterocyclic structures, oxadiazole derivatives attract attention of scientists due to a wide range of pharmacological activity, including antimicrobial, antiinflammatory, antiproliferative, and other types of activity. This review summarizes the achievements in the field of synthesis and biological activity of oxadiazole derivatives over the past 10 years. Methods for the synthesis of various therapeutic agents based on 1,2,3- 1,2,4- and 1,2,5-oxadiazoles are considered, and new approaches to the fabrication of hybrid molecules (hybrids) consisting of two or more pharmacophore moieties are systematized. The review provides the first comprehensive consideration of the key structure–property relationships for each type of oxadiazole derivatives, which can serve as guidelines for specialists in various fields who develop strategies for the design of new pharmaceuticals. The bibliography includes 173 references.

A series of new high-nitrogen energetic salts comprising linearly linked 1,2,4-triazole, furoxan and N -hydroxytetrazole scaffolds were synthesized.

Background: Malignant pleural mesothelioma (MPM) is an aggressive, asbestos-associated cancer characterized by dysregulated nitric oxide (NO) signaling and increased NO levels that facilitate tumor progression. Paradoxically, this aberrant NO environment creates a therapeutic vulnerability that can be exploited by NO-donor prodrugs, which overwhelm cellular defenses with cytotoxic concentrations of NO, inducing nitrosative stress and apoptosis. Within this framework, oxadiazole-based scaffolds have emerged as a promising platform for prodrug development owing to their versatile chemistry and potential as novel NO donors or synergistic agents. In our previous studies, we developed several series of hybrid architectures incorporating 1,2,5-oxadiazole 2-oxide (furoxan) and 1,2,4-oxadiazole scaffolds, producing compounds with diverse and tunable NO-donor activities. We further observed that the cytotoxicity of these hybrids was significantly influenced by the substituents introduced at position 3 of the furoxan ring. Methods: We designed and synthesized a series of bis(1,2,4-oxadiazolyl)furoxans to systematically investigate their NO-donating capacity, cytotoxicity against MPM cell lines, selectivity over healthy lung fibroblasts, and underlying anticancer mechanisms. Results: The bis(1,2,4-oxadiazolyl)furoxans exhibited lower overall cytotoxicity but significantly higher selectivity compared with previously studied 3-cyano-4-(1,2,4-oxadiazolyl)furoxans. Their NO-releasing properties showed a strong correlation with their ability to induce mitochondrial damage, as evidenced by membrane depolarization. Moreover, the incorporation of specific substituents, such as a furan ring, on the 1,2,4-oxadiazole moiety introduced an additional mechanism of action through the induction of reactive oxygen species. Conclusions: Analysis of cancer cell death confirmed that these compounds acted through a multimodal mechanism dependent on both NO release and the specific substituents on the 1,2,4-oxadiazole moiety.