{Synthesis and biological evaluation of (3-aryl-1,2-oxazol-5-yl)methyl 6-fluoro-4-oxo-4H-chromene-2-carboxylates as antioxidant and antimicrobial agents} J. Serb. Chem. Soc. 82 (1) 1–12 (2017) UDC 547.786/.787+547.814.1: JSCS–4942 615.279–188:615.28–188 Original scientific paper 1 Synthesis and biological evaluation of (3-arylisoxazol-5-yl)methyl 6-fluoro-4-oxo-4H-chro- mene-2-carboxylates as antioxidant and antimicrobial agents KUMARASWAMY BATTULA1, SIRASSU NARSIMHA1, VASUDEVA REDDY NAGAVELLI1* and MUTHENENI SRINIVASA RAO2 1Department of Chemistry, Kakatiya University, Warangal-506009, Telangana, India and 2Chemical Biology Laboratory, Indian Institute of Chemical Technology, Hyderabad-500007, India (Received 22 December 2015, revised 6 September, accepted 27 September 2016) Abstract: A series of novel (3-arylisoxazol-5-yl)methyl 6-fluoro-4-oxo-4H- -chromene-2-carboxylate derivatives (C1–C12) were synthesized by the Cu(I)- -catalyzed reaction of in situ generated nitrile oxides with prop-2-ynyl 6-flu- oro-4-oxo-4H-chromene-2-carboxylate in good yields and their antioxidant and antimicrobial activities were investigated. Among all the synthesized com- pounds, C1 (IC50: 16.43±0.57 µM) and C12 (IC50:15.98±0.72 µM) registered good antioxidant activity as compared to the standard drug trolox. Compounds C1, C3 and C6 registered very good inhibition against all the tested Gram-posi- tive and Gram-negative bacterial strains with MIC values ranging from 9.375 to 37.5 µg mL-1. Compounds C7–C11 registered good inhibition against Bacil- lus subtilis and Staphylococcus aureus with MIC values ranging from 18.75 to 37.5 µg mL-1. Compounds C10 and C11 against Pseudomonas aeroginosa showed more prominent activity than the standard drug penicillin (MIC: 12.5 µg mL-1) with an MIC value of 9.375 µg mL-1 (≈1.33-fold more potent than penicillin). Compounds C7–C9 registered good to moderate antifungal activity against the four tested fungal strains with MIC values ranging from 18.75 to 37.5 µg mL-1. Keywords: isoxazole; chromene; antioxidant; antimicrobial activity. INTRODUCTION Isoxazole and its derivatives have attracted much awareness because of their unique structure and applications.1 The isoxazole ring system is a five-membered heterocyclic ring structure composed of nitrogen and oxygen atoms at the 1,2 positions and is used in the synthesis of pharmaceuticals.2,3 The isoxazole moiety is a versatile lead molecule in pharmaceutical development and has a wide range * Corresponding author. E-mail: vasujac3@gmail.com doi: 10.2298/JSC151222088B 2 BATTULA et al. of biological activities. In the past few years, the therapeutic interest of isoxazole derivatives in the pharmaceutical and medicinal fields has been given great attention by medicinal chemist.4,5 A literature survey revealed that isoxazole derivatives are well known to exhibit antibacterial,6 GABAA antagonist,7 anti- cancer,8 antidiabetic9 and anti-HIV activities.10 The synthesis of isoxazole deri- vatives is obviously an important assignment in modern medicinal chemistry research. Isoxazole is the basic moiety for several drugs, such as zonisamide (Z, an anti-convulsant), leflunomide (L, a disease-modifying antirheumatic drug, DMARD) and valdecoxib (V, a COX-2 inhibitor), Fig. 1. Although a number of synthetic methods are available,11 the copper(I)-catalyzed union of terminal alk- ynes and oximes to give 3,5-disubstituted isoxazole exhibits a remarkably broad scope and exquisite selectivity.12 In recent years, extensive studies have been focused on isoxazole derivatives because of their diverse chemical reactivity, accessibility and wide range of biological activities. Fig. 1. Structures of isoxazole-congaing drugs. Chromone and its derivatives are reported to be physiologically and pharma- cologically active and find applications in the treatment of several diseases. Chro- mone derivatives are a broad class of chemical compounds with many important pharmacological properties.13,14 Substituted chromone derivatives play a signific- ant role in the medical field with many pharmacological activities, such as anti- -HIV,15 antimicrobial,16 anticancer,17,18 antiviral,19 antioxidant,20 cytotoxic act- ivities21 and anti-inflammatory activity.22 Based on the above considerations and in continuation of ongoing research on biologically potent azole derivatives,23–31 herein, the synthesis of (3-arylisoxazol-5-yl)methyl 6-fluoro-4-oxo-4H-chromene- 2-carboxylate hybrids and their antioxidant and antimicrobial activities are reported. EXPERIMENTAL All the reagents and solvents were purchased from Sigma–Aldrich or S.D. Fine Chem- icals and used without further purification. Thin-layer chromatography (TLC) was performed using Merck silica gel 60 F254 pre-coated plates (0.25 mm) and silica gel (particle size 60–120 mesh) was used for column chromatography. Melting points were determined using a Cintex apparatus and are uncorrected. FTIR spectra were recorded using a Bruker spectrometer and are reported on the frequency of absorption (cm-1). Elemental analysis was performed using a CHROMENE-DERIVED ISOXAZOLES AS ANTIOXIDANT AND ANTIMICROBIAL AGENTS 3 Perkin Elmer 2400 CHN elemental analyzer. The 1H-NMR spectra were recorded on a Varian Gemini 400 MHz spectrometer and the 13C-NMR spectra on a Bruker 100 MHz spectrometer. CDCl3 was used as the solvent. The 1H-NMR spectra are reported relative to Me4Si (δ 0.0 ppm). Coupling constants (J) values are presented in Hz and spin multiples are given as s (singlet), d (doublet), t (triplet), dd (doublet of doublets) and m (multiplet). The mass spectral analysis was recorded on a Bruker HCT mass spectrometer using the electrospray ionization mass spectrometry (ESI-MS) technique. Analytical and spectral data of the synthesized compounds are given in Supplementary material to this paper. Synthesis of ethyl 6-fluoro-4-oxo-4H-chromene-2-carboxylate (2) To a stirred solution of 1-(5-fluoro-2-hydroxyphenyl)ethanone (10 g, 64.93 mmol, 1 eq) and diethyl oxalate (194.79 mmol, 3 eq) in ethanol (200 mL) was added Na metal (389.58 mmol, 6 eq) and the reaction mixture was refluxed under a nitrogen atmosphere for 4 h. After completion of the reaction (TLC), the reaction mixture was cooled, 6 M HCI (100 mL) was added and the product was extracted with CH2CI2 (3×200 mL). The combined organic layer was washed with brine, dried over anhydrous Na2SO4 and evaporated under reduced pressure to afford the crude compound. Recrystallization of the crude compound from ethyl acetate and diethyl ether afforded compound 2 (13.5 g, 88 %) as a light yellow solid. Synthesis of 6-fluoro-4-oxo-4H-chromene-2-carboxylic acid (3) Ethyl 6-fluoro-4-oxo-4H-chromene-2-carboxylate (10 g, 42.37 mmol) was dissolved in 50 % aqueous NaOH solution and stirred at room temperature for 5 h. After completion of the reaction (TLC) the reaction mixture was neutralized with dilute HCl and extracted with ethyl acetate (3×50 mL). The combined organic layer was washed with brine, dried over anhydrous Na2SO4 and evaporated under reduced pressure to afford compound 3 (6.34 g, 72 %) as a light yellow powder. Synthesis of prop-2-ynyl 6-fluoro-4-oxo-4H-chromene-2-carboxylate (4) To a stirred solution of 6-fluoro-4-oxo-4H-chromene-2-carboxylic acid (3) (5 g, 24.03 mmol) in DMF (50 mL) was added t-BuOK (48.06 mmol, 2 eq) portion-wise over a 10 min period. Then, propargyl bromide (31.25 mmol, 1.3 eq) was added to the reaction mixture and stirred at room temperature for 4 h. The progress of the reaction was monitored by TLC. After the completion of the reaction, ice-cold water (100 mL) was added to the reaction mixture and extracted with ethyl acetate (3×50 mL). The combined organic layer was washed with brine, dried over Na2SO4 and evaporated under reduced pressure to afford compound 4 (4.73 g, 80 % yield) as a yellow solid. Typical experimental procedure for synthesis of 3,5-disubstituted isoxazoles (C1–C12) as exemplified by the reaction of prop-2-ynyl 6-fluoro-4-oxo-4H-chromene-2-carboxylate and nicotinaldehyde Nicotinaldehyde (500 mg, 4.67 mmol) was added to a solution of hydroxylamine hyd- rochloride (322 mg, 5.14 mmol) in 10 mL of 1:1 t-BuOH:H2O. To this was added NaOH (205 mg, 5.14 mmol), and after stirring for 30 min at ambient temperature, TLC analysis indicated that the oxime formation was complete. Chloramine-T trihydrate (1.47 g, 5.14 mmol) was added in small portions over 10 min, followed by CuI (44 mg, 0.233 mmol). Compound 4 (1.26 g, 5.14 mmol) was added, the pH was adjusted to 6 by the addition of a few drops of 1 M NaOH, and stirring was continued for a further 8 h. The reaction mixture was poured into cold water (50 mL), and 5 mL of dilute NH4OH was added to remove all copper salts. Isox- 4 BATTULA et al. azole C2 was collected by filtration, redissolved, and passed through a short plug of silica gel (ethyl acetate: hexanes 1:6, RF = 0.5) affording 3.6 g (72 %) of [3-(pyridin-3-yl)-isoxazol- -5-yl]methyl 6-fluoro-4-oxo-4H-chromene-2-carboxylate as an off-white solid. Antioxidant activity assay All the synthesized compounds C1–C12 were investigated for their in vitro antioxidant activity in terms of hydrogen donating or radical scavenging ability by the rapid and con- venient 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay technique32 using trolox and ascorbic acid as standard drugs. Methanol (95 %), DPPH solution and standard drugs were used as the blank, control and references, respectively. The absorbance was measured at 517 nm (at an absorption maximum of DPPH) after keeping a mixture of 100 mL of the synthesized com- pounds at a concentration 10 µg mL-1 (dissolved in DMSO) and 900 mL of DPPH radical sol- ution (0.004 % solution of DPPH in methanol) in the dark for 30 min incubation. The anti- oxidant activity was evaluated as the IC50 value in µM (the effective concentration at which 50 % of the radicals were scavenged). In vitro antimicrobial activity assay All the synthesized compounds (C1–C12) were examined for their in vitro antibacterial activity against Gram-positive organisms, i.e., Bacillus subtilis (MTCC 441), Staphylococcus aureus (MTCC 96) and Staphylococcus epidermidis (MTCC 2639), and Gram-negative organisms, i.e., Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 741) and Klebsiella pneumoniae (MTCC 618), using the broth dilution method.33-37 In vitro antifungal activity of synthesized compounds was evaluated against the fungal strains Candida albicans (MTCC 227), Saccharomyces cerevisiae (MTCC 36), Aspergillus niger (MTCC 282) and Aspergillus flavus (MTCC 92) by the agar well diffusion method.38 The standard pathogenic microbial cultures were procured from the Microbial Type Culture Collection (MTCC), Chan- digarh, India. The antimicrobial activity was evaluated in terms of the minimum inhibitory concentration (MIC) value (which corresponds to the lowest concentration that inhibits visible microbial growth) by the broth dilution method recommended by the National Committee for Clinical Laboratory (NCCL), standard protocol in liquid medium (nutrient agar) distributed in 96-well plates. The test compounds were dissolved in dimethylformamide (DMF) and further dilutions were made at the required concentrations of 300, 150, 75, 37.5, 18.75, 9.75, 6.25, 3.125 and 1.56 g mL-1. Streptomycin and penicillin were used as reference standards for the antibacterial activity and amphotericin B was the reference standard for antifungal activity. RESULTS AND DISCUSSION Chemistry In this work, a series of 3,5-disubstituted isoxazoles (C1–C12) were synthe- sized by employing Cu(I)-catalyzed cyclization between in situ generated nitrile oxide and the terminal alkyne as shown in Scheme 1. 1-(5-Fluoro-2-hydroxy- phenyl)ethanone was treated with diethyl oxalate in the presence of NaOEt in EtOH under refluxing condition to afford compound 2. The latter, on treated with 50 % NaOH solution at room temperature, afforded 6-fluoro-4-oxo-4H-chro- mene-2-carboxylic acid in good yield. In initial experiments, the outlined react- ion of 6-fluoro-4-oxo-4H-chromene-2-carboxylic acid with propargyl bromide CHROMENE-DERIVED ISOXAZOLES AS ANTIOXIDANT AND ANTIMICROBIAL AGENTS 5 using K2CO3 in DMF at room temperature was investigated.39 This reaction afforded prop-2-ynyl 6-fluoro-4-oxo-4H-chromene-2-carboxylate in low yield (23 %). Then, propargylation was performed using t-BuOK in DMF at room tem- perature for 4 h, which afforded the corresponding prop-2-ynyl 6-fluoro-4-oxo- -4H-chromene-2-carboxylate in good yield (80 %). Further, other aldehydes were converted to the corresponding aldoximes using hydroxylammonium chloride and 1 M NaOH in t-BuOH:H2O at room temperature. These aldoximes were converted to the corresponding nitrile oxide using chloramine-T trihydrate.40 The in situ generated nitrile oxide and alkyne in the presence of copper(I) catalyst at room temperature yielded 3,5-disubstitued isoxazoles (C1–C12) in good yields, Table I. Scheme 1. Reagents and reaction conditions: i) diethyl oxalate / NaOEt, EtOH, reflux, 4 h; ii) 50 % NaOH, r.t., 5h; iii) propargyl bromide / t-BuOK, DMF, r.t., 4h; iv) a) Ar-CHO, NH2OH⋅HCl, NaOH, t-BuOH:H2O, r.t., 30 min. b) chloramine-T trihydrate, Cu(I), r.t., 8–10 h. TABLE I. Synthesized 3,5-disubstituted isoxazoles C1–C12 from various aldehydes Entry Ar-CHO Time, h Product Yield, % C1 8.5 68 C2 9 70 C3 10 68 6 BATTULA et al. Table I. Continued Entry Ar-CHO Time, h Product Yield, % C4 10 65 C5 8.5 70 C6 9 65 C7 Cl O 8.5 66 C8 8.5 68 C9 8.5 66 C10 9 65 C11 10 62 C12 O 9 68 Spectral analysis All the synthesized compounds were well characterized by spectral and ana- lytical studies, such as 1H-NMR, 13C-NMR, FTIR, ESI-MS and elemental CHROMENE-DERIVED ISOXAZOLES AS ANTIOXIDANT AND ANTIMICROBIAL AGENTS 7 analysis. For convenience, compound C1 is discussed for spectral analysis. The presence of absorption bands at 3061 (C–H, Ar), 1740 (C=O, ester), 1657 (C=O, chromene), 1608 (C=N, isoxazole) and 1220, 1130 cm–1 (Ar-C–O–CH3) in the FTIR spectrum confirmed the required functional groups present in compound C1. From its 1H-NMR spectrum, the presence of three multiplet signals (ppm) in the region δ 7.46–7.86 (3H, Ar-H), two doublet signals at δ 7.37 (2H, Ar-H) and δ 7.12 (2H, Ar-H), two singlet signals at δ 7.15 (1H, chromene-H) and δ 6.82 (1H, isoxazole CH), and two singlet signals at δ 5.62 (2H, O–CH2) and 3.82 (3H, O–CH3) confirmed the formation of compound C1. Similarly, from the 13C- -NMR spectrum, the presence of characteristic carbon peaks at (ppm) 178.6 (C=O, ester), 168.7, (C=N, isoxazole), 162.3 (O–C=C), 162.1 (C=O, chromene), 100.1 (C–H, isoxazole), 61.9 (O–CH3) and 58.8 (CH2, ester) confirmed the pre- sence of the characteristic carbon peaks in compound C1. The presence of the fluorine atom was confirmed by the additional carbon splitting pattern in the C-NMR spectra of C1 with a doublet coupling constant, J, values 245.6, 29.3, 10.5, and 9.2 Hz, respectively. In addition, the molecular ion peak [396.0 (M+H)] from the ESI-MS spectrum and elemental analysis (CHN) data (C, 63.88 %; H, 3.50 %; N, 3.57 %) were further evidence for the formation of compound C1. Antioxidant activity The evaluation of antioxidant activity results (Table II) revealed that some of the tested compounds exhibited good to moderate antioxidant activity as com- pared with the positive controls trolox and ascorbic acid. Among them, com- pounds possessing the 4-methoxyphenyl and 1-napthyl group on the isoxazole ring (C1 and C12, respectively) registered very good antioxidant activity with IC50 values of 16.43±0.57 and 15.98±0.72 µM, respectively. Compounds bearing 4-butylphenyl, 2,3-dimethylphenyl and 3,5-dimethyl- phenyl groups on the isoxazole ring (C5, C10 and C11, respectively) exhibited a moderate scavenging ability with IC50 values of 23.78±1.42, 27.15±1.47 and 18.87±0.82 µM, respectively. The remaining compounds exhibited moderate to poor antioxidant activity with IC50 values ranging from 34.66±2.10 to 82.31±3.02 µM. The potential scavenging ability may be attributed to the pre- sence of pharmacologically active groups, such as 4-methoxyphenyl and 1-napthyl groups on the isoxazole ring. In vitro antibacterial activity The antibacterial screening results (Table III) revealed that some of the syn- thesized compounds exhibited excellent to moderate inhibition against the tested bacterial strains. Compounds bearing 4-methoxyphenyl (C1), 2-(trifluoromethyl)- phenyl (C3) and 2-hydroxyphenyl (C6) groups on the isoxazole core registered pro- 8 BATTULA et al. TABLE II. Antioxidant activity of (3-arylisoxazol-5-yl)methyl 6-fluoro-4-oxo-4H-chromene- 2-carboxylates (C1–C12) determined by the DPPH method Product IC50 / µM C1 16.43±0.57 C2 82.31±3.02 C3 54.62±1.37 C4 66.17±2.21 C5 23.78±1.42 C6 45.30±1.31 C7 34.66±2.10 C8 77.40±1.88 C9 68.02±1.54 C10 27.15±1.47 C11 18.87±0.82 C12 15.98±0.72 Trolox 13.24±0.80 Ascorbic acid 3.54±0.40 TABLE III. In vitro antibacterial activity (MIC / µg mL-1) of (3-arylisoxazol-5-yl)methyl 6- -fluoro-4-oxo-4H-chromene-2-carboxylates (C1–C12) against various bacterial strains Compound Bacteria B. subtilis S. aureus S. epidermidis E. coli P. aeruginosa K. pneumoniae C1 9.375 18.75 18.75 37.5 18.75 37.5 C2 75 75 150 75 75 150 C3 9.375 37.5 18.75 37.5 18.75 18.75 C4 75 75 75 150 75 150 C5 37.5 37.5 75 75 18.75 18.75 C6 9.375 18.75 18.75 37.5 18.75 37.5 C7 37.5 37.5 75 75 75 75 C8 18.75 37.5 75 75 75 75 C9 37.5 18.75 150 75 75 75 C10 37.5 37.5 75 75 9.375 37.5 C11 18.75 37.5 75 75 9.375 18.75 C12 37.5 75 75 75 18.75 75 Penicillin 1.562 1.562 3.125 12.5 12.5 6.25 Streptomycin 6.25 6.25 3.125 6.25 1.562 3.125 minent inhibition against all the tested Gram-positive and Gram-negative micro- organisms with MIC values ranging from 9.375 to 37.5 µg mL–1, as compared with the standard drugs penicillin and streptomycin. Compounds possessing 4-butylphenyl (C5), 3-chlorophenyl (C7), 4-chlorophenyl (C8), 4-bromophenyl (C9), 2,3-dimethylphenyl (C10) and 3,5-dimethylphenyl (C11) groups on the iso- xazole core registered good inhibition against B. subtilis and S. aureus bacterial strains, with MIC values ranging from 18.75 to 37.5 µg mL–1. Compounds C10 and C11 showed prominent activity against P. aeruginosa, greater than the stan- CHROMENE-DERIVED ISOXAZOLES AS ANTIOXIDANT AND ANTIMICROBIAL AGENTS 9 dard drug penicillin (MIC: 12.5 µg mL–1) with an MIC value of 9.375 µg mL–1 (≈1.33 fold more potent than penicillin). Compounds C10 and C11 also showed moderate inhibition against K. pneu- moniae, with MIC values of 37.5 and 18.75 µg mL–1, respectively. Similarly, compound C5 also registered moderate inhibition against P. aeruginosa and K. pneumoniae, with an MIC value 18.75 µg mL–1. Compound C12 registered mod- erate inhibition against B. subtilis and P. aeruginosa, with MIC values of 37.5 and 18.75 µg mL–1, respectively. The remaining compounds (C2 and C4) showed poor activity against all the bacterial strains. From the above observations, it is obvious that the presence of pharmaco- logically active moieties, such as 4-methoxyphenyl, 2-(trifluoromethyl)phenyl, 2-hydroxyphenyl, 2,3-dimethylphenyl and 3,5-dimethylphenyl groups, on the isoxazole core increased the antibacterial activity. In vitro antifungal activity The antifungal activity screening results (Table IV) revealed that some of the synthesized compounds registered good to moderate activity against the tested microorganisms. Compound C7, C8, and C9 showed better antifungal activity than the other synthesized compounds against the four fungal strains with MIC values ranging from 18.75 and 37.5 µg mL–1. Compounds C2 and C5 showed moderate activity against C. albicans and S. cerevisiae, with an MIC value of 37.5 µg mL–1. Compound C10 and C11 showed moderate antifungal activity against C. albicans and A. flavus, with MIC values ranging from 18.75 to 37.5 µg mL–1. The remain- ing compounds (C1, C3, C4, C6 and C12) exhibited poor inhibition against all the tested fungal strains. From the above observations, it is obvious that the presence TABLE IV. In vitro anti-fungal activity (MIC / µg mL-1) of (3-arylisoxazol-5-yl)methyl 6- -fluoro-4-oxo-4H-chromene-2-carboxylates (C1–C12) against various fungal strains Compound Fungi C. albicans S. cerevisiae A. niger A. flavus C1 150 75 150 75 C2 37.5 37.5 75 75 C3 75 150 75 75 C4 75 75 150 150 C5 37.5 37.5 75 75 C6 75 75 150 150 C7 18.75 37.5 18.75 37.5 C8 37.5 18.75 37.5 37.5 C9 37.5 37.5 37.5 37.5 C10 37.5 75 75 37.5 C11 18.75 75 75 37.5 C12 150 150 150 150 Amphotericin B 6.25 6.25 1.562 6.25 10 BATTULA et al. of 3-chlorophenyl, 4-chlorophenyl, and 4-bromophenyl groups on the isoxazole core influenced the antifungal activity of the synthesized compounds. CONCLUSIONS In conclusion, a series of novel (3-arylisoxazol-5-yl)methyl 6-fluoro-4- -oxo-4H-chromene-2-carboxylates was synthesized by the Cu(I)-catalyzed react- ion between in situ generated nitrile oxides and prop-2-ynyl 6-fluoro-4-oxo- -4H-chromene-2-carboxylate in good yields. All the synthesized compounds were investigated for their antioxidant and antimicrobial activities. Compounds C1 and C12 exhibited very good antioxidant activity. Compounds C1, C3 and C6 registered marked antibacterial activity against all bacterial strains, and C10 and C11 against P. aeroginosa. Similarly, compounds C7, C8 and C9 showed better antifungal activity than remaining synthesized compounds. The biological acti- vity of these compounds suggests that the synthesized compounds could be good candidates for future investigations. SUPPLEMENTARY MATERIAL Analytical and spectral data for the synthesized compounds are available electronically at the pages of journal website: http://www.shd.org.rs/JSCS/, or from the corresponding authors on request. Acknowledgements. The authors are thankful to the Head of Department of Chemistry, Kakatiya University, Warangal, India, for providing the facilities and S. N. thanks CSIR-UGC New Delhi, for the award of a senior research fellowship. И З В О Д СИНТЕЗА (3-АРИЛИЗОКСАЗОЛ-5-ИЛ)МЕТИЛ-6-ФЛУОР-4-ОКСО-4H-ХРОМЕН-2- -КАРБОКСИЛАТА И ИСПИТИВАЊЕ ЊИХОВЕ АНТИОКСИДАТИВНЕ И АНТИМИКРОБНЕ АКТИВНОСТИ KUMARASWAMY BATTULA1, SIRASSU NARSIMHA1, VASUDEVA REDDY NAGAVELLI1 и MUTHENENI SRINIVASA RAO2 1 Department of Chemistry, Kakatiya University, Warangal-506009, Telangana, India и 2 Chemical Biology Laboratory, Indian Institute of Chemical Technology, Hyderabad-500007, India Синтетисана је серија (3-арилизоксазол-5-ил)метил-6-флуор-4-оксо-4H-хромен- -2-карбоксилата (C1–C12) у добром приносу, у реакцији in situ формираног нитрил-ок- сида са проп-2-инил-6-флуор-4-оксо-4H-хромен-2-карбоксилатом у присуству Cu(I) као катализатора. Испитана је антiиоксидативна и антимикробна активност синтетисаних једињења. Од свих синтетисаних једињења, C1 (IC50: 16,43±0,57 μM) и C12 (IC50: 15,98±0,72 μM) имају добру антиоксидативну активност у поређењу са тролоксом, стандардним леком. Једињења C1, C3 и C6 имају добру инхибиторну активност према свим грам-позитивним и грам-негативним бактеријама, са MIC вредностима у опсегу од 9,375 до 37,5 μg mL-1. Једињења C7–C11 имају добру инхибиторну активност према Bacillus subtilis и Staphylococus. aureus са MIC вредностима у опсегу од 18,75 до 37,5 μg mL-1. Једињења C10 и C11 показују истакнуту активност према Pseudomonas aeruginosa у поређењу са пеницилином, као стандардним леком: MIC, 12,5 μg mL-1 према 9,375 μg mL-1 (~1,33 активније од пеницилина). Једињења C7–C9 CHROMENE-DERIVED ISOXAZOLES AS ANTIOXIDANT AND ANTIMICROBIAL AGENTS 11 имају добре до умерене антифунгалне активности према четири испитивана соја гљива са MIC вредностима у опсегу од 18,75 до 37,5 μg mL-1. (Примљено 22. децембра 2015, ревидирано 6. септембра, прихваћено 27. септембра 2016) REFERENCES 1. D. Simoni, M. Roberti, F. P. Invidiata, R. Rondanin, R. Baruchello, C. Malagutti, M. Rossi, A. Mazzali, S. Grimaudo, F. Capone, L. Dusonchet, M. Meli, M. V. 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