Introduction: The determination of biotransformation products is an essential part of the preclinical trial of original medicines. These studies have not been conducted before for the new drug 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide. Identification and synthesis of metabolite substances are necessary for subsequent tests of bioavailability, linearity of pharmacokinetics, accumulation, distribution and excretion. Materials and methods: The study was carried out on Wistar rats and rabbits of the Soviet Chinchilla breed. The substance of the drug was administered to animals intraperitoneally. The collection of animal blood samples was performed before administration and 1 h, 2 h, 4 h, 24 h after administration into K3EDTA-tubes. A part of each sample was centrifuged to separate the plasma. Rat urine samples were taken before administration and at intervals of 0-2 h, 2-4 h, 4-6 h, 6-24 h after administration of the drug. The HPLC-MS/MS method was used to identify metabolites in biological fluids. The assumed biotransformation products were synthesized after preliminary analysis. The structure of the obtained substances was confirmed by NMR spectroscopy and high-resolution mass spectrometry. Then, a comparison was carried out with the compounds identified in biological fluids by retention time, ratios of chromatographic peak areas at the main MRM-transitions using HPLC-MS/MS. Results and discussion: A metabolite formed by addition an oxygen atom to a drug molecule, as well as an acylated metabolite were detected during the analysis of plasma and blood samples. A compound with an increased molecular weight of 1 dalton compared to the drug substance was also present in a rat urine. N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide, 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonic acid, which could potentially be obtained during biotransformation, as well as N-acetyl-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide were synthesized. Repeated HPLC-MS/MS tests confirmed the correctness of the initial hypothesis. It was found that a sulfonic acid derivative is formed in urine as a result of decomposition of N-hydroxymetabolite during sample collection. Conclusion: The studied drug is metabolized by formation of two metabolites: N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide and N-acetyl-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide. N-hydroxymetabolite is able to decompose in biological fluids samples with formation of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonic acid.

Introduction: 3-(2-butyl-5-chloro-1H-imidazole-4-yl)-N-[4-methoxy-3-(trifluoromethyl)phenyl]-4,5-dihydro-1,2-oxazole-5-carboxamide is new antirheumatic drug. It is necessary to identify and synthesize the biotransformation products for its complete pharmacokinetic study. Materials and Methods: A biotransformation study was carried out by intraperitoneal administration of the drug to Wistar rats and Soviet Chinchilla breed rabbits. Animal blood sampling was performed before the injection and 0.5 h, 1 h, 2 h, 4 h, 24 h after the injection of the investigated compound. The samples were immediately centrifuged for plasma separation. Urine was simultaneously collected from rats before the administration and at intervals of 0-2 h, 2-4 h, 4-6 h, 6-24 h after administration, faeces – before administration and at intervals of 0-12 h and 12-24 h after administration. The samples were analyzed by HPLC-MS/MS after immediate preparation by adding acetonitrile. Results and Discussion: 3-(2-butyl-5-chloro-1H-imidazole-4-yl)-4,5-dihydro-1,2-oxazole-5-carboxylic acid and 4-methoxy-3-(trifluoromethyl)aniline – hydrolysis products of the active substance were found during the analysis of plasma, urine and fecal samples. The 4,5-dihydro-1,2-oxazole-5-carboxylic acid derivative has been synthesized. The second metabolite is a raw material for production of active pharmaceutical substance. During comparative tests, no significant difference between the retention times, ratio areas of chromatographic peaks at the main MRM-transitions and mass spectra of these metabolites on chromatograms of standard and animal samples was found, which indicates the correct identification of biotransformation products. Conclusion: The studied drug undergoes biotransformation by hydrolysis to form two main metabolites: 3-(2-butyl-5-chloro-1H-imidazole-4-yl)-4,5-dihydro-1,2-oxazole-5-carboxylic acid and 4-methoxy-3-(trifluoromethyl)aniline. The structure of the metabolites was confirmed by comparison with the synthesized standard samples using HPLC-MS/MS.

Introduction: 4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonamide is a new selective type II carbonic anhydrase inhibitor with local action through instillation into the eyes. For a complete pharmacokinetic study of this drug, it is necessary to detect and synthesize its metabolites for their systemic exposure evaluation. Materials and Methods: The investigation was performed on 6 Wistar rats and 6 Soviet Chinchilla rabbits. The drug in the form of a 1% suspension was administered by intraperitoneal injection. Blood was sampled in a volume of 0.2 mL at the following time points: before administration and 1 h, 2 h, 4 h, 24 h after administration. Then 150 µL of each sample was centrifuged to produce plasma. Urine was simultaneously sampled in rats using metabolic cells: before administration and at intervals of 0-2 h, 2-4 h, 4-6 h, 6-24 h after administration of the drug. The identification of metabolites in these objects was performed using HPLC-MS/MS. Then the detected biotransformation products were synthesized. The structure of the obtained substances was confirmed by NMR spectroscopy and high-resolution mass spectrometry. At the final stage, animal biological fluids and model samples with the addition of the synthesized compounds were analyzed using HPLC-MS/MS to establish the structure of metabolites.Results and Discussion: N-hydroxy-4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonamide, 4-(5-(hydroxymethyl)-1,3,4-oxadiazole-2-yl)-benzenesulfonamide and 4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonic acid were identified and synthesized. The complete coincidence of the structure of metabolites and the synthesized substances was established as a result of their comparison in retention time, the ratio of the areas of chromatographic peaks at the main MRM transitions, as well as mass spectra.Conclusion: N-hydroxy-4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonamide and 4-(5-(hydroxymethyl)-1,3,4-oxadiazole-2-yl)-benzenesulfonamide are products of biotransformation of the studied drug. It was found that 4-(5-methyl-1,3,4-oxadiazole-2-yl)-benzenesulfonic acid is formed by decomposition of N-hydroxymetabolite in urine samples during the collection process.

Methods were developed for the synthesis of a series of new thioethers, interesting for medical chemistry, by reacting 4-fluorothiophenol, 2-mercaptobenzoxazole and 5-methoxy-2-mercaptobenzimidazole with 3-aryl-5-(chloromethyl)-1,2,4-oxadiazoles. The conditions for the oxidation of the obtained thioethers into the corresponding sulfones were selected. Analysis of the results of screening of the prepared derivatives against sensitive strains of Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Bacillus cereus and Candida albicans showed the presence of high and moderate antibacterial activity in a number of compounds in drug concentrations up to 250 μg/mL.

A preparative procedure has been developed for the synthesis of a series of new medicinally relevant 3-aryl-5-(aryloxymethyl)-1,2,4-oxadiazoles in 46–66% yields by alkylation of substituted phenols with 3-aryl-5-(chloromethyl)-1,2,4-oxadiazoles in the system K₂CO₃/KI/DMF. Poorly studied 3-R-4H-1,2,4-oxadiazin-5(6H)-ones were synthesized by a new method based on the reaction of methyl chloroacetate with amidoximes in the superbasic system t-BuONa/DMSO. The synthesized compounds at concentrations of up to 250 μg/mL showed no antibacterial activity against sensitive strains of Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas fluorescens, which supposedly suggests their low toxicity for human intestinal and mucous microflora.

A one-pot synthesis of 2-(3-iminoisoindol-1-ylidene)-2-arylacetonitriles in yields of up to 95% by the cascade condensation of phthalonitrile with arylacetonitriles in a superbasic NaOH/DMSO medium was proposed. A method for the synthesis of (E)-2-(3-oxoisoindol-1-ylidene)-2-arylacetonitriles by the hydrolysis of 2-(3-iminoisoindol-1-ylidene)-2-arylacetonitriles in acetic acid was developed. The obtained (E)-2-(3-iminoisoindol-1-ylidene)-2-arylacetonitriles were shown to be active inhibitors of human monoamine oxidase [IC₅₀(MAO-A) for (E)-2-(3-iminoisoindol-1-ylidene)-2-(4-methylphenyl)acetonitrile 3.26 µM].