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Here it is described the synthesis, antioxidant and antimicrobial activity determination of novel rel-([Formula: see text])-6-benzoyl-7-phenyl-2-oxo-3,5,6,7-tetrahydro-2H-thiopyrano[2,3-d]thiazole-5-carboxylic acids. The target compounds were obtained in good yields from 5-arylidene-4-thioxo-2-thiazolidinones and [Formula: see text]-aroylacrylic acids via regio- and diastereoselective hetero-Diels-Alder reaction. The stereochemistry of the cycloaddition was confirmed by NMR spectra. The antioxidant and antimicrobial activity screening identified 7 compounds (3c, 3e, 3f, 3g, 3k, 3l, 3p) with a high level of free radical scavenging (43-77% DPPH assay), and compounds with significant influence on Staphylococcus aureus, Bacillus subtilis and Candida albicans (MIC 3.13-6.25 [Formula: see text]), but slight effect on Escherichia coli.

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To study the antimicrobial properties of 2-thioxo-4-thiazolidinone enaminone derivatives with a L-β-phenyl-α-alanine fragment in molecule. Methods. Diffusion in agar; serial dilutions in agar. Clinical isolates of microorganisms: methicillin-sensitive strain of Staphylococcus aureus (MSSA), methicillin-resistant strain of Staphylococcus aureus (MRSA), methicillinresistant strain of Staphylococcus haemolyticus (MRSH), Escherichia coli; Pseudomonas aeruginosa, ESβL + Klebsiella pneumonia, Candida albicans, Candida tropicalis. Results. Screening of antimicrobial activity of 13 new2-thioxo-4-thiazolidinone derivatives was carried out. The methicillin-resistant strain of Staphylococcus aureus (MRSA) was the most sensitive to the tested compounds. A number of derivatives exhibit synergism in combination with amoxicillin against the ESβL+ Klebsiella pneumonia strain. The structure-antimicrobial activity relationshipis was analyzed in detail. Conclusions. The tested 5-R-aminomethylene derivatives of ethyl 2-(4-oxo-2-thioxothiazolidin-3-yl)-3-phenylpropionic acid exhibit the

4-(1H-[1,2,4]-Triazol-5-ylsulfanyl)-1,2-dihydropyrazol-3-one (4) was synthesized with a yield of 55% via ring-switching hydrazinolysis of 5-ethoxymethylidenethiazolo[3,2-b][1,2,4] triazol-6-one (3) in ethanol medium. The initial 1H-[1,2,4]-triazole-3-thiol (1) was modified via a two-step reaction: S-alkylation with chloroacetic acid under Williamson reaction conditions, and further one-pot cyclization–condensation with triethylorthoformate in the acetic anhydride medium, yielding compound 3. The structures of compounds 3 and 4 were confirmed by LC-MS, NMR spectra and a single X-ray diffraction analysis (for compound 4).