Next Article in Journal
Anionic Water Cluster Polymers [(H2O)18(OH)2]n2n− Is Stabilized by Bis(2,2′-bipyridine) Cupric Chloride [Cu(bipy)2Cl]−
Previous Article in Journal
Regioselective Synthesis of Procyanidin B6, A 4-6-Condensed (+)-Catechin Dimer, by Intramolecular Condensation
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Molecules
Volume 23
Issue 1
10.3390/molecules23010199
molecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Synthesis and Antimicrobial Activity of 4-Substituted 1,2,3-Triazole-Coumarin Derivatives

by
Priscila López-Rojas
1,
Monika Janeczko
2,
Konrad Kubiński
2,
Ángel Amesty
1,*,
Maciej Masłyk
2,* and
Ana Estévez-Braun
1,*
1
Instituto Universitario de Bio-Orgánica Antonio González (CIBICAN), Departamento de Química Orgánica, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez 2, 38206 La Laguna, Tenerife, Spain
2
Department of Molecular Biology, The John Paul II Catholic University of Lublin, ul. Konstantynów 1i, 20-708 Lublin, Poland
*
Authors to whom correspondence should be addressed.
Molecules 2018, 23(1), 199; https://doi.org/10.3390/molecules23010199
Submission received: 18 December 2017 / Revised: 15 January 2018 / Accepted: 15 January 2018 / Published: 18 January 2018
(This article belongs to the Section Medicinal Chemistry)
Browse Figures
Versions Notes

Abstract

:
A new series of coumarin-1,2,3-triazole conjugates with varied alkyl, phenyl and heterocycle moieties at C-4 of the triazole nucleus were synthesized using a copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction of corresponding O-propargylated coumarin (3) or N-propargylated coumarin (6) with alkyl or aryl azides. Based on their minimal inhibitory concentrations (MICs) against selected microorganisms, six out of twenty-six compounds showed significant antibacterial activity towards Enterococcus faecalis (MIC = 12.5–50 µg/mL). Moreover, the synthesized triazoles show relatively low toxicity against human erythrocytes.

1. Introduction

Antimicrobial resistance has been listed by the World Health Organization (WHO) as one of the biggest threats to global health today [1]. The antibiotic resistance crisis has been attributed to the overuse and misuse of these medications, as well as a lack of new drug development by the pharmaceutical industry due to reduced economic incentives and challenging regulatory requirements [2,3,4,5,6]. Over the past decade, it has become apparent that several highly resistant bacterial pathogens have acquired clever mechanisms to negate the effectiveness of numerous therapeutic agents [7]. Staphylococcus aureus is one bacterial pathogen that has emerged as a significant concern to healthcare professionals worldwide. In this sense, isolated strains of S. aureus have exhibited resistance to several classes of antibacterial drugs, including β-lactam antibiotics [8], macrolides [9], fluoroquinolones [10,11,12], glycopeptides [13] and oxazolidinones [14]. Enterococci were previously considered commensal organisms of little clinical importance but have emerged as serious nosocomial pathogens responsible for e.g. endocarditis and infections of the urinary tract, bloodstream, meninges, wounds and the biliary tract [15]. Recent surveillance data indicate that Enterococcus is the third most commonly isolated nosocomial pathogen (12% of all hospital infections), only behind coagulase-negative Staphylococcus and Staphylococcus aureus [16]. The clinical importance of the genus Enterococcus is directly related to its antibiotic resistance, which contributes to the risk of colonization and infection. Enterococci are intrinsically resistant to many commonly used antimicrobial agents (penicillins, ampicillins, cephalosporins, clindamycin) and exhibit native resistance to clinically achievable concentrations of aminoglycosides. Although E. faecalis is naturally resistant to quinupristin-dalfopristin, this combination is highly active against E. faecium strains that lack specific resistance determinants. Enterococci are tolerant to the (normally) bactericidal activity of cell-wall active agents, such as β-lactam antibiotics and vancomycin. Tolerance implies that the bacteria can be inhibited by clinically achievable concentrations of the antibiotic but will only be killed by concentrations far in excess of the inhibitory concentration [17]. The emergence of multi-resistant E. faecalis strains, complicating the treatment, means that it is important to search for and identify new treatment strategies.
All the information mentioned above highlights the urgent need to develop novel antibacterial agents devoid of cross-resistance to marketed antibiotics.
The use of privileged structures in drug discovery has proven to be an effective strategy allowing the generation of innovative hits⁄leads and successful optimization processes [18,19]. Coumarins are considered to be privileged structures due to their broad range of biological properties including anticoagulant [20], anti-neurodegenerative [21], antioxidant [22], anticancer [23] and antimicrobial activities [24,25,26,27,28]. These interesting properties of coumarins can be ascribed to the chemical attributes of the 2H-chromen-2-one core; its aromatic ring can establish a series of hydrophobic, π–π, CH–π and cation–π interactions and the two oxygen atoms in the lactone ring can hydrogen-bond to a series of amino acid residues in different classes of enzymes and receptors. Additionally, the double bond in the lactone helps to make the planar system, allows charge delocalization between the carbonyl group of the lactone and the aromatic ring and confers the characteristic fluorescence of this class of compounds.
On the other hand, 1,2,3-triazoles are nitrogen heterocycles capable of forming hydrogen bonds, which improves their solubility and ability to interact with biomolecular targets [29]. The 1,2,3-triazoles are highly stable to metabolic degradation, compared to other compounds containing three adjacent nitrogen (N) atoms [29]. The triazoles have been used for broad therapeutic applications due to their diverse biological activities [30], i.e. antimicrobial [31,32,33], antiviral [34], anti-inflammatory [35], analgesic [35], anticancer [36,37,38], antifungal [39] and anticonvulsant [40] activities.
Taking into consideration the antimicrobial activity shown by some coumarins and 1,2,3-triazols mentioned above and as a continuation of our project on searching for new antibacterial molecules [41,42,43,44,45], we envisaged that the linkage of coumarin and 1,2,3-triazole pharmacophores through –OCH2– or –NCH2– linkers would generate novel hybrid molecules with promising antibacterial activities.
Therefore, we herein report the synthesis and antibacterial activity of coumarin-1,2,3-triazole conjugates with varied alkyl, phenyl and heterocycle moieties at C-4 of the triazole nucleus in order to evaluate their contribution to the antimicrobial activity.

2. Results and Discussion

2.1. Chemistry

The required acetylenic dipolarophiles 3 and 6 were obtained as shown in Scheme 1. Thus, the treatment of 4-hydroxy-coumarin (1) with 3-bromoprop-1-yne (2) employing potassium carbonate in anhydrous acetone yielded the O-propargylated coumarin (3) in 55% yield. The N-propargylated coumarin (6) was obtained in 63% yield from 4-bromo-coumarin (4) through nucleophilic substitution with prop-2-yn-1-amine (5) in dimethylformamide (DMF).
The 4-substituted 1,2,3-triazole-coumarin derivatives were synthesized using a copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction [46] of the corresponding O-propargylated coumarin (3) or N-propargylated coumarin (6) with alkyl or aryl azides (Scheme 2).
Azides 7a–7j were prepared from the corresponding boronic acids and sodium azide, in the presence of CuSO4 in ethanol (EtOH), at room temperature (Table 1 and Scheme 3) [47,48].
Azides 7k–7m were obtained from the corresponding alkyl bromide or aryl bromide and sodium azide in DMF (Table 2 and Scheme 4) [49,50].
Following the reaction shown in Scheme 2 and using azides 7a–7m, compounds 8a–8m and 9a–9m were obtained as illustrated in Figure 1.
As can be seen, two isosteric series of coumarin derivatives were obtained (X=O, X=NH). Each series presents different substituents at the triazole moiety in order to evaluate their influence on the antimicrobial activity. Thus, coumarin derivatives with an aromatic ring having electron-donating groups or electron-withdrawing groups were prepared (8a–8h, 9a–9h). Coumarin-triazole derivatives with alkyl moieties (8k, 9k, 8l, 9l) and coumarin-indole hybrids (8i, 9i) were synthesized as well. Moderate yields were obtained with aromatic azides while the use of the more stable aliphatic azides (7k, 7l and 7m) led to high yields, in agreement with the more favourable HOMO of the dipole in the 1,3-dipolar cycloaddition. The structures of all adducts were determined by spectroscopic studies. All of them showed the characteristic proton of the triazol ring in the 1H-NMR spectral region between δ 7.63 and 9.31. The hydrogen of the coumarin nucleus was detected as a singlet at δ 5.18–6.22 and the methylene hydrogens in the oxygenated series appeared as a singlet at δ 5.35–5.59 and as a doublet at δ 4.66–4.46 (J = 5.6 Hz) in the nitrogenated series.
The best yields were obtained from the N-propargylated coumarin (6) and from the aliphatic azides (7k, 7l and 7m).

2.2. Biology

Since some coumarins and 1,2,3-triazoles have shown potential as antibacterial drugs [41,42,43,44,45,51], these combined pharmacophores could offer some advantages e.g. in overcoming drug resistance as well as improving their biological potency.
The in vitro antimicrobial activity of the novel coumarin-1,2,3-triazole conjugates was tested against the yeast Candida albicans, Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis and Gram-negative bacteria Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa. The minimum inhibitory concentrations (MICs) were determined and given in Table 3. As can be seen, most of the coumarin-triazole hybrids did not exhibit considerable activity against the tested microorganisms. The best results were obtained with conjugates 8a, 8b, 8f, 9h and 9k, which displayed promising activity against Enterococcus faecalis at MICs ranging from 12.5 to 50.0 µg/mL. Compound 8b having a 2-OMe–Ph group attached at the triazol nucleus and an –OCH2– linker was the best of the series, while the corresponding isoster 9b (–NHCH2–) turned out to be 64-fold less active than 8b. The position of the OMe group in the phenyl ring also plays an important role in the activity, since compounds 8c (3-OMe–Ph) and 8d (4-OMe–Ph) showed an 8- and 16-fold lower antibacterial activity, respectively, than 8b. In the nitrogenated series, compounds 9h (3-NO2–Ph) and 9k having an undecyl chain showed the best activities.
In other studies, menthyl 1,4-disubstituted 1,2,3-triazole derivatives of hydroxybenzaldehydes, phenols and bile acids showed a strong inhibitory effect against E. faecium with the minimum inhibitory concentration (MIC) values in the range of 1–3 μM [52]. Kant and co-workers reported that 1,2,3-triazole linked chalcone and flavone hybrids showed activity against Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Shigella boydii, Klebsiella pneumoniae) with MIC values in the range of 6.25–100 µg/mL [53]. In turn, 1,2,4-triazolo[3,4a]phthalazine derivatives showed inhibitory activity against Staphylococcus aureus (MIC 16–128 µg/mL) [54].
In order to verify if the newly synthesized triazoles could be considered as potential antimicrobial therapeutics, the most active compounds, namely 8a, 8b, 8f, 9h and 9k were examined in terms of their haemolytic activity against human erythrocytes. The results are shown in Figure 2.
Compounds 8b, 8f and 9h exhibit minimal toxicity towards human blood cells (1.6–3.1% of lysed cells) in MIC. Although compound 8b appears to be the most active antimicrobial agent, simultaneously it moderately affects the erythrocytes (6.9% of lysed cells) in MIC. The presence of an undecyl chain in the triazole ring (9k) results in a drastic increase in the haemolytic activity (94% of lysed cells) in MIC.

3. Materials and Methods

3.1. Compounds Synthesis

3.1.1. General Experimental Procedures

IR spectra were obtained using a Fourier Transform Infrared spectrometer. NMR spectra were recorded in CDCl3 or DMSO at 500 or 600 MHz for 1H NMR and 125 or 150 MHz for 13C-NMR. Chemical shifts are given in (δ) parts per million and coupling constants (J) in hertz (Hz). 1H- and 13C-spectra were referenced using the solvent signal as an internal standard. Melting points were taken on a capillary melting point apparatus and are uncorrected. Microwave reactions were conducted in sealed glass vessels (capacity 5 mL) using a CEM Discover microwave reactor. HREIMS were recorded using a high-resolution magnetic trisector (EBE) mass analyser. The analytical thin-layer chromatography plates used were Polygram-Sil G/UV254. Preparative thin-layer chromatography was carried out with Analtech (Newark, NJ, USA) silica gel GF plates (20 × 20 cm, 1000 Microns) using appropriate mixtures of ethyl acetate and hexanes. All solvents and reagents were purified by standard techniques reported in [55] or used as supplied from commercial sources. All compounds were named using the ACD40 Name-Pro program, which is based on IUPAC rules. Azides 7a–7m were synthesized according to procedures previously described in the literature [47,48,49,50,56].
4-(Prop-2-yn-1-yloxy)-2H-chromen-2-one (3). 259 µL (2.4 mmol) of propargyl bromide were slowly added to a mixture of 330.9 mg (2.0 mmol) of 4-hydroxycoumarin and 552.8 mg (4.0 mmol) of K2CO3 in 15 mL of acetone. The reaction mixture was refluxed for 8 h until disappearance of the starting coumarin. Then, the solvent was eliminated under reduced pressure, 30 mL of H2O were added and the mixture was extracted with AcOEt (3 × 30 mL). The organic phases were collected, washed with H2O (20 mL) and brine (20 mL) and dried over anhydrous MgSO4. After filtration and elimination of the solvent, the crude extract was purified by silica gel column chromatography using DCM as an eluent and 224.7mg (55%) of compound 3 were obtained as an amorphous white solid. Compound 3 showed identical spectroscopic data to those described in the literature [57].
4-(Prop-2-yn-1-ylamino)-2H-chromen-2-one (6). 47 µL (0.72 mmol) of prop-2-yn-1-amine were slowly added to 200 mg (0.89 mmol) of 4-bromocoumarin in 2 mL of dimethylformamide (DMF) under argon atmosphere. The reaction mixture was stirred at room temperature for 18 h. Then water was added and the N-propargylated coumarin precipitated. After filtration, 111.8 mg (63%) of compound (6) was obtained as an amorphous white solid. m.p. 223–224 °C; 1H-NMR (600 MHz, (CDCl3) δ 7.57 (1H, t, J = 8.1 Hz), 7.46 (1H, d, J = 8.1 Hz), 7.37 (1H, d, J = 8.1 Hz), 7.30 (1H, t, J = 8.1 Hz), 5.46 (1H, s), 5.28 (1H, bs), 4.11 (2H, dd, J = 5.5, 2.5 Hz), 2.41 (1H, t, J = 2.5 Hz); 13C-NMR (150 MHz, (CDCl3) δ 162.5 (C=O), 153.6 (C), 151.8 (C), 132.0 (CH), 123.6 (CH), 119.9 (CH), 118.1 (CH), 113.9 (C), 85.9 (CH), 77.6 (C), 73.6 (CH2), 32.9(CH) ppm; EIMS m/z 199 ([M+], 71); 198 (61); 197 (13); 171 (100); 170 (53); 144 (13); 143 (22); 142 (27); 119 (12); 118 (16); 115 (15); 90 (11); 77 (18); 63 (14); 51 (14); HREIMS 199.0638 (calcd. for C12H9NO2 [M+] 199.0633); FT-IR (ATR) νmax 3325, 3259, 3093, 3074, 2934, 2122, 1807, 1668, 1612, 1552, 1484, 1445, 1389, 1354, 1328, 1271, 1192, 1147, 1045, 983, 937, 865, 811 cm−1.

3.1.2. General Procedures for the Preparation of 4-Substituted 1,2,3-Triazole-Coumarin Derivatives

Method A. Corresponding boronic acid (0.24 mmol) and 78.5 mg (1.2 mmol) of sodium azide in 1.5 mL of H2O were added to a vigorously stirred mixture of 3.4 mg (0.0241 mmol) of Cu2O in 0.06 mL of 20% of NH3 and 0.12 mL of H2O. The reaction mixture was stirred for 16 h at room temperature under an oxygen atmosphere. Then, 0.14 mmol of propargylated coumarin (3 or 6), 8.11 mg (0.041 mmol) of sodium ascorbate, 1.5 mL of H2O and 3 mL of acetone were added. The reaction was left at room temperature for 48h. Then, the reaction mixture was extracted with EtOAc. The aqueous phase was acidified with 5% HCl until pH = 2 and extracted with EtOAc (3 × 15 mL). The organic phases were collected, dried over anhydrous MgSO4 and after elimination of the solvent, the corresponding residue was purified by silica gel CC or TLC-preparative with DCM or 5% DCM/MeOH.
Method B. To a solution of 0.28 mmol of the corresponding azide in 3 mL of DCM, 0.14 mmol of propargylated coumarin (3 or 6), 3.6 mg (0.02 mmol) of sodium ascorbate, 1.2 mg (0.004 mmol) of CuSO4·5H2O and 3 mL of H2O, were added. The reaction mixture was stirred for 48 h at room temperature. The reaction mixture was extracted with EtOAc (3 × 15 mL). The organic phases were collected, dried over anhydrous MgSO4 and after elimination of the solvent, the corresponding residue was purified by silica gel CC or TLC-preparative with DCM or 5% DCM/MeOH.
4-((1-Phenyl-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8a). Following the experimental procedure described in method A, from 31.2 mg (0.24 mmol) of phenyl boronic acid and 28.0 mg (0.14 mmol) of O-propargylated coumarin (3), 10.9 mg (24%) of compound 8a were obtained as an amorphous orange solid [58]. m.p. 193–194 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 9.09 (1H,s), 7.95 (2H, d, J = 7.5 Hz), 7.83 (1H, dd, J = 7.9, 1.5 Hz), 7.65–7.63 (3H, m), 7.52 (1H, t, J = 7.4 Hz), 7.41 (1H, dd, J = 8.3, 0.7 Hz), 7.34 (1H, t, J = 7.6 Hz), 6.21 (1H, s), 5.53 (2H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 164.4 (C=O), 161.6 (C), 152.8 (C), 142.3 (C), 136.5 (C), 132.9 (CH), 129.9 (2CH), 128.9 (CH), 124.2 (CH), 123.4 (CH), 123.1 (CH), 120.3 (2CH), 116.5 (CH), 115.1 (C), 91.5 (CH), 62.8 (CH2) ppm; EIMS m/z 319 ([M+], 26); 131 (11); 130 (100); 103 (11); 77 (47); 51 (12); HREIMS319.0967 (calcd. for C18H13N3O3 [M+] 319.0957); FT-IR (ATR) νmax 3386, 3146, 3097, 1716, 1621, 1563, 1494, 1460, 1397, 1367, 1337, 1243, 1208, 1186, 1136, 1100, 1029, 925, 835 cm−1.
4-((1-(2-Methoxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8b). Following the experimental procedure described in method B, from 42.3 mg (0.28 mmol) of 1-azido-2-methoxybenzene and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 14.2 mg (27%) of compound 8b were obtained as an amorphous white solid. m.p. 200–201 °C; 1H-NMR (500 MHz, CDCl3) δ 8.33 (1H, s), 7.84 (2H, dd, J = 7.9, 1.3 Hz), 7.56 (1H, t, J = 8.5 Hz), 7.47 (1H, t, J = 8.5 Hz), 7.32 (1H, dd, J = 8.3, 0.6 Hz), 7.25 (1H, td, J = 7.8, 1.1 Hz), 7.16–7.11 (2H, m), 5.93 (1H, s), 5.43 (2H, s), 3.93 (3H, s) ppm; 13C-NMR (125 MHz, CDCl3) δ 165.2 (C=O), 162.8 (C), 153.4 (C), 151.1 (C), 140.8 (C), 132.6 (CH), 130.6 (CH), 126.0 (C), 125.9 (CH), 125.5 (CH), 124.0 (CH), 123.4 (CH), 121.4 (CH), 116.8 (CH), 115.6 (C), 112.4 (CH), 91.2 (CH), 62.8 (CH2), 56.2 (CH3) ppm; EIMS m/z 349 ([M+], 37); 161 (12); 160 (100); 145 (28); 120 (14); 92 (11); 77 (16); HREIMS 349.1050 (calcd. for C19H15N3O4 [M+] 349.1063); FT-IR (ATR) νmax 3400, 3129, 3093, 3009, 2942, 2841, 2287, 1707, 1617, 1563, 1507, 1493, 1477, 1460, 1410, 1368, 1233, 1186, 1136, 1103, 1052, 1018, 970, 930, 883, 868, 811 cm−1.
4-((1-(3-Methoxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8c). Following the experimental procedure described in method B, from 42.3 mg (0.28 mmol) of 1-azido-2-methoxybenzene and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 26.8 mg (51%) of compound 8c were obtained as an amorphous white solid. m.p. 188–189 °C; 1H-NMR (500 MHz, CDCl3) δ 8.16 (1H, s), 7.82 (1H, d, J = 7.6 Hz), 7.56 (1H, t, J = 7.4 Hz), 7.45 (1H, t, J = 8.1 Hz), 7.37 (1H, s), 7.33 (1H, d, J = 8.1 Hz), 7.30–7.21 (2H, m), 7.00 (1H, d, J = 7.8 Hz), 5.91 (1H, s), 5.43 (2H, s), 3.90 (3H, s) ppm;13C-NMR (125 MHz, CDCl3) δ 165.1 (C=O), 162.7 (C), 160.8 (C), 153.5 (C), 142.2 (C), 137.9 (C), 132.7 (CH), 130.8 (CH), 124.1 (CH), 123.3 (CH), 121.9 (CH), 116.9 (CH), 115.6 (C), 115.2 (CH), 112.7 (CH), 106.7 (CH), 91.4 (CH), 62.7 (CH2), 55.8 (CH3) ppm; EIMS m/z 349 ([M+], 49); 160 (100); 145 (18); 130 (16); 117 (12); 107 (14); 92 (18); 77 (21); HREIMS 349.1078 (calcd. for C19H15N3O4 [M+] 349.1063); FT-IR (ATR) νmax 3401, 3148, 3093, 2933, 2838, 1719, 1620, 1610, 1565, 1493, 1456, 1400, 1368, 1337, 1237, 1189, 1158, 1103, 1044, 1004, 931, 833 cm−1.
4-((1-(4-Methoxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8d). Following the experimental procedure described in method B, from 42.3 mg (0.28 mmol) of 1-azido-4-methoxybenzene and 28.0 mg (0.14 mmol) of O-propargylated coumarin (3), 27.7 mg (53%) of compound 8d were obtained as an amorphous white solid. m.p. 195–196 °C; 1H-NMR (500 MHz, CDCl3) δ 8.07 (1H, s), 7.83 (1H, d, J = 8.0 Hz), 7.66 (2H, d, J = 8.9 Hz), 7.56 (1H, t, J = 7.8 Hz), 7.33 (1H, d, J = 8.3 Hz), 7.4 (1H, t, J = 7.9 Hz), 7.05 (2H, d, J = 8.9 Hz), 5.91 (1H, s), 5.42 (2H, s), 3.89 (3H, s) ppm; 13C-NMR (125 MHz, CDCl3) δ 165.1 (C=O), 162.7 (C), 160.3 (C), 153.5 (C), 142.1 (C), 132.7 (CH), 130.3 (C), 124.1 (CH), 123.3 (CH), 122.5 (2CH), 121.9 (CH), 116.9 (CH), 115.6 (C), 115.0 (2CH), 91.4 (CH), 62.8 (CH2), 55.8 (CH3) ppm; EIMS m/z 349 ([M+], 29); 161 (12); 160 (100); 145 (13); 92 (12); 77 (13); HREIMS 349.1061 (calcd. for C19H15N3O4 [M+] 349.1063); FT-IR (ATR) νmax 3140, 3095, 3006, 2942, 2840, 2381, 2055, 1719, 1619, 1564, 1519, 1457, 1400, 1369, 1257, 1240, 1185, 1137, 1102, 1030, 927, 824 cm−1.
4-((1-(3-Fluoro-4-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8e). Following the experimental procedure described in method B, from 47.4 mg (0.28 mmol) of 1-azido-3-fluoro-4-methoxybenzene and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 25.3 mg (46%) of compound 8e were obtained as an amorphous white solid. m.p. 190–191 °C; 1H-NMR (600 MHz, CDCl3) δ 8.07 (1H, s), 7.82 (1H, dd, J = 8.0, 1.0 Hz), 7.60–7.51 (2H, m), 7.48 (1H, d, J = 8.8 Hz), 7.33 (1H, d, J = 8.3 Hz), 7.24 (1H, t, J = 7.9 Hz), 7.11 (1H, t, J = 8.7 Hz), 5.91 (1H, s), 5.42 (2H, s), 3.97 (3H, s) ppm; 13C-NMR (150 MHz, CDCl3) δ 165.1 (C=O), 162.7 (C), 153.4 (C), 152.3 (J1C–F = 249.1 Hz), 148.6 (C, J2C–F = 28.7 Hz), 142.4 (C), 132.8 (CH), 124.1 (CH), 123.3 (CH), 121.8 (CH), 117.0 (CH), 116.8 (CH, J3C–F = 3.6 Hz), 115.6 (C), 114.0 (CH, J3C–F = 1.9 Hz), 110.0 (CH, J2C–F = 22.6 Hz), 91.5 (CH), 62.7 (CH2), 56.7 (CH3) ppm; EIMS m/z 367 ([M+], 27); 179 (12); 178 (100); 163 (21); HREIMS367.0898 (calcd. for C19H14N3O4F [M+] 367.0968); FT-IR (ATR) νmax 3488, 3143, 3089, 2976, 2944, 2844, 2361, 1715, 1620, 1565, 1527, 1493, 1451, 1401, 1368, 1328, 1287, 1243, 1233, 1186, 1159, 1133, 1104, 1017, 952, 933, 880, 833, 808 cm−1.
4-((1-(4-Fluoro-phenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8f). Following the experimental procedure described in method A, from 34.8 mg (0.24 mmol) of 4-fluorophenyl boronic acid and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 22.1 mg (43%) of compound 8f were obtained as an amorphous white solid. m.p. 233–235 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 9.07 (1H, s), 8.02–7.98 (2H, m), 7.83 (1H, dd, J = 7.9, 1.5 Hz), 7.67 (1H, ddd, J = 8.7, 7.4, 1.6 Hz), 7.49 (2H, t, J = 8.8 Hz), 7.42 (1H, dd, J = 8.3, 0.6 Hz), 7.35 (1H, t, J = 7.6 Hz), 6.20 (1H, s), 5.52 (2H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 164.3 (C=O), 161.5 (C), 161.4 (C, J1C–F = 245.7 Hz), 152.7 (C), 142.3 (C), 133.0 (C, J4C–F = 3.4 Hz), 132.9 (CH), 124.2 (CH), 123.6 (CH), 123.0 (CH), 122.7 (2 CH, J3C–F = 8.6 Hz), 116.8 (2 CH, J2C–F = 24.1 Hz), 116.5 (CH), 115.1 (C), 91.5 (CH), 62.8 (CH2); EIMS m/z 337 ([M+], 23); 149 (11); 148 (100); 95 (25); HREIMS 337.0859 (calcd. for C18H12N3O3F [M+] 337.0863). FT-IR (ATR) νmax 3148, 3098, 2384, 2294, 2050, 1718, 1624, 1567, 1516, 1496, 1465, 1454, 1401, 1370, 1233, 1184, 1105, 1051, 1022, 951, 931, 833 cm−1.
4-((1-(3-Trifluoromethyl-phenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8g). Following the experimental procedure described in method B, from 53.2 mg (0.28 mmol) of 1-azido-3-trifluoromethylbenzene and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 24.0 mg (41%) of compound 8g were obtained as an amorphous white solid. m.p. 192–193 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 9.27 (1H, s), 8.34 (1H, s), 8.32 (1H, d, J = 8.2 Hz), 7.93–7.86 (2H, m), 7.85 (1H, dd, J = 8.0, 1.5 Hz), 7.68 (1H, ddd, J = 8.8, 7.4, 1.6 Hz), 7.43 (1H, d, J = 7.7 Hz), 7.37 (1H, t, J = 7.6 Hz), 6.22 (1H, s), 5.56 (2H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 164.3 (C=O), 165.1 (C), 152.7 (C), 142.5 (C), 136.9 (C), 132.8 (CH), 131.3 (CH), 130.5 (C, J2C–F = 29.6 Hz), 125.4 (CH, J3C–F = 4.1 Hz), 124.2 (CH), 124.1 (CH), 123.5 (C, J1C–F = 276.4 Hz), 123.7 (CH), 123.0 (CH), 116.9 (CH, J3C–F = 4.5 Hz), 116.4 (CH), 115.0 (C), 91.5 (CH), 62.7 (CH2);EIMS m/z 387 ([M+], 12); 386 (42); 358 (23); 357 (45); 329 (10); 199 (12); 198 (100); 159 (26); 145 (50); HREIMS 387.0846 (calcd. for C19H12N3O3F3 [M+] 387.0831); FT-IR (ATR) νmax 3531, 3409, 1685, 1618, 1559, 1069, 972 cm–1.
4-((1-(3-Nitro-phenyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8h). Following the experimental procedure described in method B, from 46.6 mg (0.28 mmol) of 1-azido-3-nitrobenzene and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 23.1 mg (43%) of compound 8g were obtained as an amorphous white solid. m.p. 215–217 °C; 1H-NMR (600 MHz, (CD3)2SO) δ 9.31 (1H, s), 8.78 (1H, s), 8.45 (1H, d, J = 7.8 Hz), 8.36 (1H, d, J = 7.9 Hz), 7.93 (1H, t, J = 8.1 Hz), 7.85 (1H, d, J = 7.8 Hz), 7.67 (1H, t, J = 7.6 Hz), 7.42 (1H, d, J = 8.3 Hz), 7.36 (1H, t, J = 7.5 Hz), 6.21 (1H, s), 5.56 (2H, s) ppm; 13C-NMR (150 MHz, (CD3)2SO) δ 164.4 (C=O), 161.6 (C), 152.8 (C), 148.6 (C), 142.8 (C), 137.1 (C), 133.0 (CH), 131.7 (CH), 126.4 (CH), 124.3 (CH), 123.9 (CH), 123.4 (CH), 123.1 (CH), 116.5 (CH), 115.2 (CH), 115.1 (C), 91.6 (CH), 62.8 (CH2) ppm; EIMS m/z 364 ([M+], 59); 176 (11); 175 (100); 162 (23); 145 (14); 129 (92); 128 (37); 121 (14); 120 (39); 92 (18); 77 (11); 76 (37); HREIMS 364.0820 (calcd. for C18H12N4O5 [M+] 364.0808); FT-IR (ATR) νmax 3431, 3146, 3091, 2925, 1713, 1617, 1565, 1531, 1493, 1464, 1406, 1352, 1245, 1185, 1138, 1104, 1045, 1009, 980, 952, 929, 830 cm–1.
4-((1-(1H-Indole-5-yl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8i). Following the experimental procedure described in method B, from 44.9 mg (0.28 mmol) of 5-azido-1H-indol and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 18.1 mg (33%) of compound 8i were obtained as an amorphous white solid. m.p. 191–193 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 11.46 (1H, s), 8.99 (1H, s), 8.05 (1H, s), 7.84 (1H, d, J = 7.1 Hz), 7.67 (1H, t, J = 7.2 Hz), 7.63–7.57 (2H, m), 7.53–7.51 (1H, m), 7.42 (1H, d, J = 8.3 Hz), 7.35 (1H, t, J = 7.5 Hz), 6.59 (1H, s), 6.22 (1H, s), 5.52 (2H, s); 13C NMR (125 MHz, (CD3)2SO) 164.4 (C=O), 161.6 (C), 152.8 (C), 141.8 (C), 135.6 (C), 132.9 (CH), 129.3 (C), 127.8 (CH), 127.6 (C), 124.3 (CH), 123.7 (CH), 123.1 (CH), 116.5 (CH), 115.1 (C), 114.4 (CH), 112.4 (CH), 112.3 (CH), 102.0 (CH), 91.4 (CH), 62.9 (CH2) ppm; EIMS m/z 358 ([M+], 28); 169 (100); 168 (19); 162 (30); 121 (13); 120 (39); 116 (28); 92 (14); HREIMS 358.1068 (calcd. for C20H14N4O3 [M+] 358.1066); FT-IR (ATR) νmax 3399, 3299, 1699, 1685, 1616, 1563, 1494, 1403, 1350, 1327, 1228, 1097, 1048, 1025, 993 cm–1.
4-((1-(Furan-3-yl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8j). Following the experimental procedure described in method A, from 34.8 mg (0.24mmol) of 3-furylboronic acid and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 8.1 mg (18%) of compound 8j were obtained as an amorphous white solid. m.p. 189–190 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.88 (1H,s), 8.48 (1H, s), 7.91 (1H, t, J = 1.9 Hz), 7.80 (1H, dd, J = 7.9, 1.5 Hz), 7.67 (1H, t, J = 7.6Hz), 7.42 (1H, dd, J = 8.3, 0.7 Hz), 7.35 (1H, t, J = 7.8 Hz), 7.16 (1H, dd, J = 2.0, 0.9 Hz), 6.19 (1H, s), 5.51 (2H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 164.4 (C=O), 161.6 (C), 152.8 (C), 144.9 (CH), 141.9 (C), 134.3 (CH), 132.9 (CH), 125.9 (C), 124.3 (CH), 124.2 (CH), 123.0 (CH), 116.5 (CH), 115.1 (C), 105.3 (CH), 91.5 (CH), 62.7 (CH2) ppm; EIMS m/z 309 ([M+], 59); 279 (25); 198 (21); 159 (23); 120 (100); 94 (18); 65 (13); HREIMS 309.0662 (calcd. for C16H11N3O4 [M+] 309.0671). FT-IR (ATR) νmax 3514, 3399, 3084, 2924, 2387, 2094, 2064, 1992, 1696, 1619, 1606, 1563, 1492, 1450, 1410, 1365, 1270, 1248, 1193, 1105, 1053, 1023, 942, 911, 871, 839 cm−1.
4-((1-Undecyl-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8k). Following the experimental procedure described in method B, from 56.1 mg (0.28mmol) of 1-azido-undecane and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 51.4 mg (86%) of compound 8k were obtained as an amorphous white solid. m.p. 144–145 °C; 1H-NMR (500 MHz, CDCl3) δ 7.78 (1H, dd, J = 13.2, 6.5 Hz), 7.75 (1H, s), 7.54 (1H, t, J = 7.5 Hz), 7.30 (1H, d, J = 7.9 Hz), 7.24 (1H, t, J = 7.6 Hz), 5.87 (1H, s), 5.34 (1H, s), 4.41 (2H, t, J = 7.3 Hz), 1.96 (2H, t, J = 7.2 Hz), 1.38–1.23 (16H, m), 0.87 (3H, t, J = 6.9 Hz) ppm; 13C-NMR (125 MHz, CDCl3) δ 165.1 (C=O), 162.7 (C), 153.4 (C), 141.4 (C), 132.6 (CH), 124.0 (CH), 123.4 (CH), 123.2 (CH), 116.8 (CH), 115.5 (C), 91.2 (CH), 62.8 (CH2), 50.7 (CH2), 31.9 (CH2), 30.3 (CH2), 29.6 (CH2), 29.5 (CH2), 29.4 (CH2), 29.3 (CH2), 29.0 (CH2), 26.6 (CH2), 22.7 (CH2), 14.2 (CH3) ppm; EIMS m/z 397 ([M+], 18); 236 (17); 209 (15); 208 (100); 68 (21); 57 (16); 55 (15); HREIMS 397.2351 (calcd. for C23H31N3O3 [M+] 397.2365); FT-IR (ATR) νmax 3134, 3075, 2918, 2849, 1725, 1623, 1610, 1566, 1492, 1458, 1424, 1381, 1328, 1272, 1248, 1187, 1154, 1138, 1106, 1059, 1031, 979, 931, 882, 851, 814 cm−1.
4-((1-Benzyl-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8l). Following the experimental procedure described in method B, from 40.8 mg (0.28 mmol) of benzylazide and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 47.0 mg (94%) of compound 8l were obtained as an amorphous white solid. m.p. 210–211 °C; 1H-NMR (500 MHz, CDCl3) δ 7.76 (1H, dd, J = 7.9, 1.5 Hz), 7.63 (1H, s), 7.56–7.52 (1H, t, J = 7.6 Hz), 7.47–7.36 (3H, m), 7.35–7.28 (3H, m), 7.23 (1H, t, J = 7.6 Hz), 5.84 (s, 1H), 5.59 (s, 2H), 5.31 (2H, d, J = 3.8 Hz) ppm; 13C-NMR (125 MHz, CDCl3) δ 165.1 (C=O), 162.5 (C), 153.7 (C), 142.1 (C), 134.4 (C), 132.6 (CH), 129.5 (2CH), 129.2 (CH), 128.4 (2CH), 124.0 (CH), 123.3 (CH), 123.2 (CH), 117.0 (CH), 115.8 (C), 91.5 (CH), 62.9 (CH2), 54.6 (CH2) ppm; EIMS m/z 333 ([M+], 39); 172 (13); 144 (62); 104 (11); 92 (14); 91 (100); HREIMS 333.1116 (calcd. for C19H15N3O3[M+] 333.1113); FT-IR (ATR) νmax 3075, 1722, 1625, 1569, 1498, 1459, 1421, 1377, 1331, 1277, 1250, 1187, 1141, 1111, 1063, 1035, 983, 933, 885, 849, 814 cm−1.
4-((1-Tetradecyl-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (8m). Following the experimental procedure described in method B, from 68.0 mg (0.28 mmol) of 1-azido-tetradecane and 28 mg (0.14 mmol) of O-propargylated coumarin (3), 61.3 mg (93%) of compound 8m were obtained as an amorphous white solid. m.p. 146–147 °C; 1H-NMR (500 MHz, CDCl3) δ 7.79 (1H, dt, J = 7.9, 1.5 Hz), 7.72 (1H, s), 7.54 (1H, tt, J = 9.1, 1.7 Hz), 7.31 (1H, dd, J = 8.4, 1.5 Hz), 7.24 (1H, t, J = 7.6 Hz), 5.87 (1H, s), 5.35 (2H, s), 4.41 (2H, t, J = 7.3 Hz), 1.96 (2H, t, J = 7.1 Hz), 1.38–1.23 (22H, m), 0.88 (3H, t, J = 6.9 Hz) ppm; 13C-NMR (125 MHz, CDCl3) δ 165.1 (C=O), 162.8 (C), 153.4 (C), 141.4 (C), 132.6 (CH), 124.0 (CH), 123.4 (CH), 123.3 (CH), 116.8 (CH), 115.6 (C), 91.2 (CH), 62.8 (CH2), 50.8 (CH2), 32.0 (CH2), 31.0 (CH), 30.4 (CH2), 29.9 (CH2), 29.8 (CH2), 29.7 (2CH2), 29.6 (CH2), 29.5 (CH2), 29.4 (CH2), 29.1 (CH2), 26.6 (CH2), 22.8 (CH2), 14.2 (CH3) ppm; EIMS m/z 439 ([M+], 11); 278 (26); 251 (19); 250 (100); 215 (20); 120 (10); 71 (14); 70 (12); 68 (23); 57 (22); 56 (10); 55 (19); HREIMS 439.2852 (calcd. for C26H37N3O3 [M+] 439.2835); FT-IR (ATR) νmax 3135, 3075, 2918, 2849, 1817, 1726, 1624, 1567, 1468, 1423, 1381, 1328, 1273, 1248, 1185, 1154, 1139, 1107, 1058, 979, 931, 882, 851, 814 cm−1.
4-(((1-Phenyl-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9a). Following the experimental procedure described in method A, from 31.2 mg (0.24 mmol) of phenyl boronic acid and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 13.8 mg (28%) of compound 9a were obtained as an amorphous white solid. m.p. 194–195 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.82 (1H, s), 8.31 (1H, t, J = 5.6 Hz), 8.10 (1H, dd, J = 8.0, 1.0 Hz), 7.90 (2H, d, J = 7.6 Hz), 7.61–7.56 (3H, m), 7.48 (1H, t, J = 7.4 Hz), 7.36–7.30 (2H, m), 5.30 (1H, s), 4.64 (2H, d, J = 5.6 Hz) ppm; 13C-NMR (125 MHz,(CD3)2SO) δ 161.5 (C=O), 153.1 (C),153.0 (C), 144.6 (C), 136.6 (C), 132.0 (CH), 130.0 (CH), 128.7 (CH), 123.4 (CH), 122.6 (CH), 121.5 (CH), 120.0 (CH), 117.0 (CH), 114.5 (C), 82.5 (CH), 37.8 (CH2) ppm; EIMS m/z 318([M+], 64); 290 (21); 289 (44); 261 (16); 198 (15); 159 (22); 130 (100); 77 (56); HREIMS 318.1117 (calcd. for C18H14N4O2 [M+] 318.1117); FT-IR (ATR) νmax 3500, 3297, 3138, 3082, 2940, 1707, 1609, 1557, 1503, 1480, 1146, 1377, 1340, 1321, 1188, 1054, 954, 922, 861, 823 cm−1.
4-(((1-(2-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9b). Following the experimental procedure described in method B, from 68.0 mg (0.28 mmol) of 1-azido-2-methoxybenzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 16.9 mg (32%) of compound 9b were obtained as an amorphous white solid. m.p. 187–189 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.36 (1H, s), 8.09 (1H, t, J = 5.5 Hz), 8.01 (1H, dd, J = 8.1, 1.2 Hz), 7.54 (1H, dd, J = 7.9, 1.6 Hz), 7.51 (1H, dd, J = 11.3, 4.2 Hz), 7.44 (1H, t, J = 7.9 Hz), 7.27–7.20 (m, 3H), 7.06 (1H, td, J = 7.7, 1.0 Hz, ), 5.30 (1H, s), 4.56 (2H, d, J = 5.7 Hz), 3.77 (3H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.2 (C=O), 153.0 (C), 152.8 (C), 151.4 (C), 142.9 (C), 131.7 (CH), 130.4 (CH), 125.7 (C), 125.4 (CH), 125.1 (CH), 123.1 (CH), 122.4 (CH), 120.8 (CH), 116.7 (CH), 114.4 (C), 113.0 (CH), 82.5 (CH), 56.0 (CH3), 37.5 (CH2) ppm; EIMS m/z 348 ([M+], 20); 320 (17); 319 (20); 160 (100); 159 (20); 145 (11); 120 (11); 77 (19); HREIMS 348.1228 (calcd. for C19H16N4O3 [M+] 348.1222); FT-IR (ATR) νmax 3524, 3318, 3173, 3085, 2944, 2847, 2376, 1649, 1607, 1555, 1505, 1476, 1446, 1384, 1327, 1290, 1260, 1244, 1197, 1120, 1044, 1017, 957, 937, 865 cm−1.
4-(((1-(3-Methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9c). Following the experimental procedure described in method B, from 42.3 mg (0.28 mmol) of 1-azido-3-methoxybenzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 26.9 mg (51%) of compound 9c were obtained as an amorphous white solid. m.p. 246–248 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.71 (1H, s), 8.08 (1H, t, J = 5.5 Hz), 8.02 (1H, dd, J = 8.1, 1.2 Hz), 7.52 (1H, t, J = 7.8 Hz), 7.44–7.36 (3H, m), 7.27 (1H, d, J = 0.8 Hz), 7.24 (1H, t, J = 7.7 Hz), 6.97 (1H, dt, J = 6.8, 2.5 Hz), 5.25 (1H, s), 4.57 (2H, d, J = 5.6 Hz), 3.78 (3H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.2 (C=O), 160.1 (C), 153.0 (C), 152.7 (C), 144.3 (C), 137.5 (C), 131.7 (CH), 130.6 (CH), 123.1 (CH), 123.0 (CH), 121.5 (CH), 116.7 (CH), 114.4 (C), 114.2 (CH), 111.9 (CH), 105.7 (CH), 82.5 (CH), 55.5 (CH3), 37.7 (CH2) ppm; EIMS m/z 348 ([M+], 40); 319 (25); 291 (10); 198 (11); 161 (13); 160 (100); 159 (30); 123 (11); 107 (24); 92 (19); 77 (26); HREIMS 348.1221 (calcd. for C19H16N4O3 [M+] 348.1222); FT-IR (ATR) νmax 3297, 3143, 3085, 3000, 2936, 2830, 1708, 1609, 1558, 1483, 1446, 1373, 1322, 1246, 1192, 1158, 1142, 1118, 1048, 954, 922, 859, 846, 819 cm−1.
4-(((1-(4-Methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9d). Following the experimental procedure described in method B, from 42.3 mg (0.28 mmol) of 1-azido-4-methoxybenzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 29.6 mg (56%) of compound 9d were obtained as an amorphous white solid. m.p. 246–248 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.58 (1H, s), 8.07 (1H, t, J = 5.4 Hz), 8.01 (1H, dd, J = 8.1, 1.1 Hz), 7.74–7.69 (2H, m), 7.52 (1H, t, J = 7.8 Hz), 7.24 (2H, dd, J = 14.4, 7.6 Hz), 7.07–7.01 (2H, m), 5.25 (1H, s), 4.55 (2H, d, J = 5.6 Hz), 3.75 (3H, s) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.2 (C=O), 159.2 (C), 153.0 (C), 152.8 (C), 144.1 (C), 131.7 (CH), 130.0 (C), 123.1 (CH), 122.4 (CH), 121.6 (2CH), 121.3 (CH), 116.7 (CH), 114.7 (2CH), 114.4 (C), 82.5 (CH), 55.4 (CH3), 37.7 (CH2) ppm; EIMS m/z 348 ([M+], 21); 320 (14); 319 (22); 161 (12); 160 (100); 159 (26); 123 (10); 77 (15); HREIMS 348.1225 (calcd. for C19H16N4O3 [M+] 348.1222); FT-IR (ATR) νmax 3528, 3285, 3137, 3081, 3067, 3003, 2945, 2924, 2829, 2310, 2051, 1700, 1609, 1556, 1517, 1446, 1378, 1307, 1247, 1187, 1140, 1055, 1041, 989, 953, 920, 860, 822 cm−1.
4-(((1-(3-Fluoro-4-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9e). Following the experimental procedure described in method B, from 47.4 mg (0.28 mmol) of 1-azido-3-fluoro-4-methoxybenzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 27.3 mg (49 %) of compound 9e were obtained as an amorphous white solid. m.p. 204–205 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.76 (1H, s), 8.29 (1H, t, J = 5.7 Hz), 8.09 (1H, dd, J = 8.1, 1.2 Hz), 7.87 (1H, dd, J = 12.1, 2.6 Hz), 7.72 (1H, ddd, J = 8.9, 2.5, 1.4 Hz), 7.60 (1H, t, J = 7.8 Hz), 7.39–7.30 (3H, m), 5.28 (1H, s), 4.62 (2H, d, J = 5.6 Hz), 3.90 (3H, s); 13C-NMR (125 MHz, (CD3)2SO) δ 162.4 (C=O), 153.7 (C), 153.4 (C), 151.6 (C, J1C–F = 247.8 Hz), 147.7 (C, J2C–F = 20.3 Hz), 144.9 (C), 132.7 (CH), 129.9 (C, J3C–F = 9.0 Hz), 124.1 (CH), 122.8 (CH), 122.1 (CH), 117.4 (CH), 117.0 (CH,J3C–F = 2.8 Hz), 114.9 (C), 114.7 (CH), 109.2 (CH, J2C–F = 22.5 Hz), 82.8 (CH), 56.7 (CH3), 38.0 (CH2) ppm; EIMS m/z 366 ([M+], 30); 338 (16); 337 (22); 198 (15); 179 (13); 178 (100); 159 (22); HREIMS 366.1138 (calcd. for C19H15N4O3F [M+] 366.1128); FT-IR (ATR) νmax 3301, 3133, 3078, 3009, 2936, 2849, 1699, 1609, 1557, 1518, 1477, 1446, 1377, 1317, 1184, 1123, 1082, 1053, 953, 921, 884, 859, 817 cm−1.
4-(((1-(4-Fluoro-phenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9f). Following the experimental procedure described in method A, from 34.8 mg (0.24mmol) of 4-fluoro-phenyl boronic acid and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 15.2 mg (30 %) of compound 9f were obtained as an amorphous white solid. m.p. 212–213 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.79 (1H, s), 8.32 (1H, t, J = 6.0 Hz), 8.16 (1H, d, J = 7.8 Hz), 7.97–7.91 (2H, m), 7.61 (1H, t, J = 8.4 Hz), 7.45 (2H, t, J = 8.8 Hz), 7.35–7.30 (2H, m), 5.30 (1H, s), 4.6 (2H, d, J = 5.5 Hz) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.4 (C=O), 153.1 (C), 153.0 (C), 144.7 (C), 133.1 (C), 132.0 (CH), 123.4 (CH), 122.6 (CH), 122.3 (2CH, J3C–F = 9.1 Hz), 121.7 (C), 116.9 (CH), 116.7 (2CH, J2C–F = 23.9 Hz), 114.5 (C), 82.6 (CH), 37.4 (CH2) ppm; EIMS m/z 336 ([M+], 54); 308 (19); 307 (36); 198 (15); 159 (27); 148 (100); 95 (38); HREIMS 336.1030 (calcd. for C18H13N4O2F [M+] 336.1023); FT-IR (ATR) νmax 3537, 3417, 3307, 3143, 3084, 2454, 2288, 2167, 2051, 1985, 1707, 1610, 1558, 1541, 1516, 1481, 1447, 1377, 1230, 1183, 1051, 993, 957, 920, 825 cm−1.
4-(((1-(3-Trifluoromethylphenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9g). Following the experimental procedure described in method B, from 53.2 mg (0.28 mmol) of 1-azido-3-trifluoromethylbenzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 26.2 mg (45 %) of compound 9g were obtained as an amorphous white solid. m.p. 231–232 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 9.00 (1H, s), 8.32 (1H, t, J = 5.7 Hz), 8.29–8.24 (2H, m), 8.09 (1H, dd, J = 8.1, 1.2 Hz), 7.88–7.80 (2H, m), 7.60 (1H, dd, J = 15.6, 1.4 Hz), 7.34 (2H, ddd, J = 9.2, 8.2, 1.0 Hz), 5.29 (1H, s), 4.66 (2H, d, J = 5.7 Hz) ppm; 13C-NMR (125MHz, (CD3)2SO) δ 161.5 (C=O), 153.1 (C), 153.0 (C), 145.0 (C), 137.1 (C), 132.0 (CH), 131.4 (CH), 130.5 (C, J2C–F = 32.5 Hz), 125.2(CH, J3C–F = 3.1 Hz), 123.9 (CH), 123.6 (C, J1C–F = 272.5 Hz), 123.4 (CH), 122.6 (CH), 121.8 (CH), 117.0 (CH), 116.7 (CH, J3C-F= 3.8 Hz), 114.5 (C), 82.6 (CH), 37.8 (CH2); EM-IE m/z 386 ([M+], 72); 358 (26); 357 (50); 198 (100); 159 (29); 145 (49); HREIMS 386.0977 (calcd. for C19H13N4O2F3 [M+] 386.0991); FT-IR (ATR) νmax 3425, 3318, 3142, 3085, 2942, 1701, 1610, 1557, 1540, 1482, 1448, 1377, 1342, 1321, 1298, 1266, 1248, 1172, 1142, 1110, 1070, 1046, 955, 923, 896, 861, 819 cm–1.
4-(((1-(3-Nitrophenyl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9h). Following the experimental procedure described in method B, from 46.6 mg (0.28 mmol) of 1-azido-3-nitrobenzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 21.2 mg (39 %) of compound 9h were obtained as an amorphous white solid. m.p. 240–241 °C; 1H-NMR (600 MHz, (CD3)2SO) δ 9.06 (1H, s), 8.73 (1H, t, J = 1.9 Hz), 8.42 (1H, d, J = 7.8 Hz), 8.32 (2H, dd, J = 8.2, 2.1 Hz), 8.10 (1H, d, J = 7.9 Hz), 7.93–7.83 (1H, m), 7.61 (1H, t, J = 7.4 Hz), 7.37–7.27 (2H, m), 5.29 (1H, s), 4.67 (2H, d, J = 5.4 Hz) ppm; 13C-NMR (150 MHz, (CD3)2SO) δ 161.4 (C=O), 153.1 (C), 153.0 (C), 148.6 (C), 145.2 (C), 137.1 (C), 132.0 (CH), 131.5 (CH), 126.0 (CH), 123.4 (CH), 123.1 (CH), 122.5 (CH), 122.0 (CH), 116.9 (CH), 114.7 (CH), 114.5 (C), 82.61 (CH), 37.7 (CH2) ppm; EIMS m/z 363 ([M+], 48); 335 (31); 334 (69); 333 (100); 286 (23); 242 (30); 198 (28); 197 (31); 175 (40); 161 (38); 159 (31); 129 (40); 92 (27); 76 (30); 65 (27); HREIMS 363.0983 (calcd. for C18H13N5O4 [M+] 363.0968); FT-IR (ATR) νmax 3426, 3137, 3106, 3082, 2927, 1707, 1614, 1561, 1531, 1481, 1448, 1352, 1315, 1269, 1189, 1142, 1119, 1043, 1001, 960, 925, 863, 818 cm−1.
4-(((1-(1H-Indole-5-yl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9i). Following the experimental procedure described in method B, from 44.9 mg (0.28 mmol) of 5-azido-1H-indole and 28.0 mg (0.14 mmol) of N-propargylated coumarin (6), 20.7 mg (37 %) of compound 9i were obtained as an amorphous white solid. m.p. 236–237 °C;1H-NMR (500 MHz, (CD3)2SO) δ 11.42 (1H, bs), 8.72 (1H, s), 8.29 (1H, t, J = 5.6 Hz), 8.11 (1H, d, J = 7.2 Hz), 8.00 (1H, s), 7.63–7.53 (3H, m), 7.50 (1H, s), 7.33 (2H, dd, J = 12.4, 7.8 Hz), 6.55 (1H, s, J = 2.1 Hz), 5.34 (1H, s), 4.63 (2H, d, J = 5.6 Hz) ppm; 13C-NMR (125 MHz, (CD3)2SO)δ162.4 (C=O), 161.5 (C), 153.1 (C), 153.0(C), 144.1 (C), 135.5 (C), 132.0 (CH), 129.5 (C), 127.7 (CH), 127.6 (C), 123.4 (CH), 122.6 (CH), 121.9 (CH), 116.9 (CH), 114.5 (C), 114.2 (CH), 112.3 (CH), 111.9 (CH), 101.9 (CH), 82.5 (CH), 37.9 (CH2); EIMS m/z 357 ([M+], 27); 329 (14); 328 (23); 170 (16); 169 (100); 168 (30); 156 (23); 132 (21); 116 (57); 115 (16); 89 (19); HREIMS 357.1217 (calcd. for C20H15N5O2 [M+] 357.1226); FT-IR (ATR) νmax 3522, 3397, 3324, 1682, 1616, 1562, 1486, 1354, 1092, 1053, 886 cm−1.
4-(((1-(Furan-3-yl)-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9j). Following the experimental procedure described in method A, from 21.3 mg (0.24 mmol) of 3-furyl boronic acid and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 5.4 mg (12%) of compound 9j were obtained as an amorphous white solid. m.p. 198–199 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.58 (1H, s), 8.42 (1H, d, J = 0.8 Hz), 8.30 (1H, t, J = 5.6 Hz), 8.08 (1H, d, J = 6.9 Hz), 7.86 (1H, t, J = 1.8 Hz), 7.60 (1H, t, J = 7.8 Hz), 7.32 (2H, dd, J = 8.1, 4.6 Hz), 7.12 (1H, dd, J = 2.0, 0.8 Hz), 5.27 (1H, s), 4.62 (2H, d, J = 5.6 Hz) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.4 (C=O), 153.1 (C), 153.0 (C), 144.8 (CH), 144.3 (C), 133.9 (CH), 132.0 (CH), 126.0 (C), 123.4 (CH), 122.6 (CH), 122.2 (CH), 117.0 (CH), 114.5 (C), 105.1 (CH), 82.5 (CH), 37.7 (CH2) ppm; EIMS m/z 308 ([M+], 99); 120 (67); 93 (28); 91 (12); 66 (23); 65 (100); 58 (17); HREIMS 308.1000 (calcd. for C16H12N4O3 [M+] 308.0988); FT-IR (ATR) νmax 3293, 3134, 3083, 2924, 2853, 2285, 1706, 1610, 1557, 1480, 1446, 1378, 1323, 1262, 1230, 1191, 1143, 1118, 1089, 1039, 1017, 955, 921, 867, 821 cm−1.
4-(((1-Undecyl-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9k). Following the experimental procedure described in method B, from 56.1 mg (0.28 mmol) of 1-azido-undecane and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 50.3 mg (84%) of compound 9k were obtained as an amorphous white solid. m.p. 154–156 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.08–7.93 (3H, m), 7.51 (1H, t, J = 7.7 Hz), 7.25 (1H, s), 7.22 (1H, t, J = 7.9 Hz), 5.18 (1H, s), 4.46 (2H, d, J = 5.6 Hz), 4.24 (2H, t, J = 7.0 Hz), 1.80–1.59 (2H, m), 1.14 (16H, s), 0.78 (3H, t, J = 6.9 Hz) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.1 (C=O), 153.0 (C), 152.7 (C), 143.1 (C), 131.6 (CH), 123.1 (CH), 122.8 (CH), 122.3 (CH), 116.7 (CH), 114.4 (C), 82.3 (CH), 49.2 (CH2), 37.7 (CH2), 31.0 (CH2), 29.4 (CH2), 28.7 (CH2), 28.6 (CH2), 28.6 (CH2), 28.4 (CH2), 28.1 (CH2), 25.6 (CH2), 21.8 (CH2), 13.6 (CH3) ppm; EIMS m/z 396 ([M+], 88); 395 (16); 368 (40); 367 (100); 339 (15); 297 (18); 283 (17); 235 (20); 227 (37); 199 (23); 198 (21); 162 (19); 57 (19); 55 (23); HREIMS 396.2504 (calcd. for C23H32N4O2 [M+] 396.2525); FT-IR (ATR) νmax 3523, 3399, 3325, 3127, 3069, 2955, 2920, 2849, 1679, 1607, 1553, 1481, 1465, 1446, 1376, 1096, 1055 cm−1.
4-(((1-Benzyl-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9l). Following the experimental procedure described in method B, from 56.1 mg (0.28 mmol) of azidomethyl-benzene and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 45.5 mg (91%) of compound 9l were obtained as an amorphous white solid. m.p. 217–219 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.03 (2H, d, J = 8.7 Hz), 7.96 (1H, dd, J = 8.0, 1.2 Hz), 7.50 (1H, t, J = 7.8 Hz), 7.31–7.19 (7H, m), 5.50 (2H, s), 5.19 (1H, s), 4.47 (2H, d, J = 5.8 Hz) ppm; 13C-NMR (125 MHz, (CD3)2SO) δ 161.2 (C=O), 153.0 (C), 152.8 (C), 143.5 (C), 135.9 (C), 131.7 (CH), 128.5 (2CH), 127.9 (CH), 127.7 (2CH), 123.2 (CH), 123.1 (CH), 122.3 (CH), 116.7 (CH), 114.3 (C), 82.4 (CH), 52.7 (CH2), 37.6 (CH2) ppm; EIMS m/z 332 ([M+], 41); 303 (14); 213 (18); 144 (13); 91 (100); 65 (11); HREIMS 332.1279 (calcd. for C19H16N4O2 [M+] 332.1273); FT-IR (ATR) νmax 3283, 3141, 3075, 2922, 2852, 2366, 2323, 1697, 1608, 1557, 1482, 1446, 1380, 1322, 1262, 1222, 1188, 1124, 1058, 955, 920, 861, 827 cm−1.
4-(((1-Tetradecyl-1H-1,2,3-triazol-4-yl)methyl)amino)-2H-chromen-2-one (9m). Following the experimental procedure described in method B, from 68.0 mg (0.28 mmol) of 1-azido-tetradecane and 28 mg (0.14 mmol) of N-propargylated coumarin (6), 63.5 mg (96%) of compound 9m were obtained as an amorphous white solid. m.p. 156–157 °C; 1H-NMR (500 MHz, (CD3)2SO) δ 8.23 (1H, t, J = 5.7 Hz), 8.07 (1H, s), 8.05 (1H, d, J = 8.1 Hz), 7.58 (1H, d, J = 7.5 Hz), 7.33–7.29 (2H, m), 5.24 (1H, s), 4.53 (2H, d, J = 5.7 Hz), 4.31 (2H, t, J = 7.0 Hz), 1.75 (2H, t, J = 7.3 Hz ), 1.23–1.13 (22H, m), 0.85 (3H, t, J = 6.9 Hz) ppm; 13C-NMR (150 MHz, (CD3)2SO) δ 161.8 (C=O), 153.5 (C), 153.3 (C), 143.7 (C), 132.4 (CH), 123.8 (CH), 123.5 (CH), 122.9 (CH), 117.4 (CH), 114.9 (C), 82.8 (CH), 49.7 (CH2), 31.7 (CH2), 30.1 (CH2), 29.5 (2CH2), 29.4 (2CH2), 29.3 (2CH2), 29.1 (CH2), 28.7 (CH2), 26.2 (CH2), 22.5 (CH2), 14.4 (CH3) ppm; EIMS m/z 438 ([M+], 92); 410 (55); 409 (100); 367 (37); 227 (51); 199 (44); 198 (60); 162 (39); 57 (42); 55 (47); HREIMS 438.2978 (calcd. for C26H38N4O2 [M+] 438.2995); FT-IR (ATR) νmax 3320, 3127, 3070, 2918, 2848, 2416, 2167, 2051, 1983, 1658, 1606, 1550, 1467, 1377, 1322, 1258, 1202, 1150, 1118, 1055, 966, 938, 867, 835 cm−1.

3.2. Microbial Strains

Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (PCM 2673), Escherichia coli (ATCC 8739), Klebsiella pneumoniae (PCM1, Pseudomonas aeruginosa (PCM 2562) and yeast Candida albicans (ATCC 10231) were obtained from the Department of Molecular Biology, The John Paul II Catholic University of Lublin, Poland.

3.3. MIC Determination

The in vitro antimicrobial studies were carried out with the microbroth dilution method against test organisms, as described previously [59,60]. The bacterial strains were inoculated in Mueller Hinton Broth medium (Biocorp, Warsaw, Poland) and the Candida strain was inoculated in Sabouraud Dextrose liquid medium (Biocorp, Poland) and incubated at 37 °C and at 30 °C, respectively, with vigorous shaking (200 rpm) for 24 h. Bacterial cell suspensions at initial inoculums of 5 × 105 in Mueller-Hinton liquid medium and adequate yeast suspensions at initial inoculums of 3 × 103 cfu/mL in Sabouraud Dextrose Broth were exposed to the examined compound at relevant concentrations (range 0.001–2 mg/mL) for 24 h at 37 °C for the bacteria and for 48 h at 30 °C in the case of the fungi. Simultaneously, the standard antibiotics, chloramphenicol for antibacterial activity and ketoconazole for antifungal activity (as a positive control), were tested against the pathogens. The MIC was the lowest concentration of the compounds that inhibited the visible growth of the microorganism. The experiments were performed in triplicate.

3.4. Haemolytic Assay

Haemolytic properties of the selected compounds were determined according to the method described previously [45]. The human blood samples were centrifuged at 500× g for 10 min at 4 °C and the supernatant was discarded. Next, the erythrocytes were resuspended with PBS buffer (10 mM phosphate, pH 7.5; 150 mM NaCl) and centrifuged as previously. The washing procedure was repeated until a transparent supernatant was obtained. The washed erythrocytes were finally resuspended in PBS buffer to a final concentration of 2%. Simultaneously, appropriate concentrations (5, 10, 25, 50, 100 and 500 µg/mL for 8a, 8f, 9h and 9k, or 2, 5, 12.5, 50, 125 and 250 µg/mL for 8b) of the examined compounds were prepared in a final volume of 50 mL DMSO. The compounds prepared in this way were mixed with 450 mL of 2% erythrocyte suspension and incubated for 1 h at 37 °C. Then, the samples were centrifuged at 5000× g for 10 min and absorbance at wavelength 415 nm was measured.

4. Conclusions

In conclusion, twenty-eight coumarin-triazole conjugates were synthesized through a copper(I)-catalysed Huisgen 1,3-dipolar cycloaddition reaction of the corresponding O-propargylated coumarin (3) or N-propargylated coumarin (6) with alkyl or aryl azides. Five of them (8a, 8b, 8f, 9h and 9k) displayed promising activity against Enterococcus faecalis at MICs ranging from 12.5 to 50.0 µg/mL. Compound 8b having a 2-OMe-Ph group attached at the triazol nucleus and an –OCH2– linker was the best of the series. The most active compounds showed minimal toxicity towards human blood cells.

Supplementary Materials

The following are available online: 1H-NMR and 13C-NMR spectra of compounds 6, 8a–8m and 9a–9m.

Acknowledgments

We gratefully acknowledge the financial support from the Spanish MINECO SAF 2015-65113-C2-1-R to A.E.B. This project is also co-funded by the European Regional Development Fund (FEDER). PLR thanks to Spanish MINECO for a pre-doctoral grant (FPU-Program).

Author Contributions

Ana Estévez-Braun, Ángel Amesty, and Maciej Masłyk conceived and designed the experiments; Priscila López-Rojas, Monika Janeczko, Konrad Kubiński, and Ángel Amesty performed the experiments; Ana Estévez-Braun, Ángel Amesty and Maciej Masłyk wrote the paper.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Holpuch, A. UN meeting tackles the “fundamental threat” of antibiotic-resistant superbugs. Guardian 2016. [Google Scholar]
  2. Viswanathan, V.K. Off-label abuse of antibiotics by bacteria. Gut Microbes 2014, 5, 3–4. [Google Scholar] [CrossRef] [PubMed]
  3. Read, A.F.; Woods, R.J. Antibiotic resistance management. Evol. Med. Public Health 2014, 2014, 147. [Google Scholar] [CrossRef] [PubMed]
  4. The antibiotic alarm. Nature 2013, 495, 151.
  5. Lushniak, B.D. Antibiotic resistance: A public health crisis. Public Health Rep. 2014, 129, 314–316. [Google Scholar] [CrossRef] [PubMed]
  6. Michael, C.A.; Dominey-Howes, D.; Labbate, M. The antimicrobial resistance crisis: Causes, consequences, and management. Front. Public Health 2014, 2, 145. [Google Scholar] [CrossRef] [PubMed]
  7. Laxminarayan, R.; Duse, A.; Wattal, C.; Zaidi, A.K.; Wertheim, H.F.; Sumpradit, N.; Vlieghe, E.; Hara, G.L.; Gould, I.M.; Goossens, H.; et al. Antibiotic resistance-the need for global solutions. Lancet Infect. Dis. 2013, 13, 1057–1098. [Google Scholar] [CrossRef]
  8. Chambers, H.F. Community-associated MRSA—Resistance and virulence converge. N. Engl. J. Med. 2005, 352, 1485–1487. [Google Scholar] [CrossRef] [PubMed]
  9. Moran, G.J.; Krishnadasan, A.; Gorwitz, R.J.; Fosheim, G.E.; McDougal, L.K.; Carey, R.B.; Talan, D.A.; Group, E.I.N.S. Methicillin-resistant S. aureus infections among patients in the emergency department. N. Engl. J. Med. 2006, 355, 666–674. [Google Scholar] [CrossRef] [PubMed]
  10. Frazee, B.W.; Lynn, J.; Charlebois, E.D.; Lambert, L.; Lowery, D.; Perdreau-Remington, F. High prevalence of methicillin-resistant Staphylococcus aureus in emergency department skin and soft tissue infections. Ann. Emerg. Med. 2005, 45, 311–320. [Google Scholar] [CrossRef] [PubMed]
  11. Fridkin, S.K.; Hageman, J.C.; Morrison, M.; Sanza, L.T.; Como-Sabetti, K.; Jernigan, J.A.; Harriman, K.; Harrison, L.H.; Lynfield, R.; Farley, M.M.; et al. Methicillin-resistant Staphylococcus aureus disease in three communities. N. Engl. J. Med. 2005, 352, 1436–1444. [Google Scholar] [CrossRef] [PubMed]
  12. Moran, G.J.; Amii, R.N.; Abrahamian, F.M.; Talan, D.A. Methicillin-resistant Staphylococcus aureus in community-acquired skin infections. Emerg. Infect. Dis. 2005, 11, 928–930. [Google Scholar] [CrossRef] [PubMed]
  13. Hiramatsu, K. Vancomycin-resistant Staphylococcus aureus: A new model of antibiotic resistance. Lancet Infect. Dis. 2001, 1, 147–155. [Google Scholar] [CrossRef]
  14. Wilson, P.; Andrews, J.A.; Charlesworth, R.; Walesby, R.; Singer, M.; Farrell, D.J.; Robbins, M. Linezolid resistance in clinical isolates of Staphylococcus aureus. J. Antimicrob. Chemother. 2003, 51, 186–188. [Google Scholar] [CrossRef] [PubMed]
  15. Hollenbeck, B.L.; Rice, L.B. Intrinsic and acquired resistance mechanisms in enterococcus. Virulence 2012, 3, 421–433. [Google Scholar] [CrossRef] [PubMed]
  16. World Health Organization (WHO). Antimicrobial Resistance: Global Report on Surveillance; WHO: Geneva, Switzerland, 2014. [Google Scholar]
  17. Kristich, C.J.; Rice, L.B.; Arias, C.A. Enterococcal infection—Treatment and antibiotic resistance. In Enterococci: From Commensals to Leading Causes of Drug Resistant Infection; Gilmore, M., Clewell, D., Ike, Y., Eds.; Massachusetts Eye and Ear Infirmary: Boston, MA, USA, 2014. [Google Scholar]
  18. Hueso-Falcón, I.; Amesty, Á.; Anaissi-Afonso, L.; Lorenzo-Castrillejo, I.; Machín, F.; Estévez-Braun, A. Synthesis and biological evaluation of naphthoquinone-coumarin conjugates as topoisomerase II inhibitors. Bioorg. Med. Chem. Lett. 2017, 27, 484–489. [Google Scholar] [CrossRef] [PubMed]
  19. Jiménez-Alonso, S.; Pérez-Lomas, A.L.; Estévez-Braun, A.; Muñoz Martinez, F.; Chávez Orellana, H.; Ravelo, A.G.; Gamarro, F.; Castanys, S.; López, M. Bis-pyranobenzoquinones as a new family of reversal agents of the multidrug resistance phenotype mediated by P-glycoprotein in mammalian cells and the protozoan parasite Leishmania. J. Med. Chem. 2008, 51, 7132–7143. [Google Scholar] [CrossRef] [PubMed]
  20. Weigt, S.; Huebler, N.; Strecker, R.; Braunbeck, T.; Broschard, T.H. Developmental effects of coumarin and the anticoagulant coumarin derivative warfarin on zebrafish (Danio rerio) embryos. Reprod. Toxicol. 2012, 33, 133–141. [Google Scholar] [CrossRef] [PubMed]
  21. Jameel, E.; Umar, T.; Kumar, J.; Hoda, N. Coumarin: A privileged scaffold for the design and development of antineurodegenerative agents. Chem. Biol. Drug. Des. 2016, 87, 21–38. [Google Scholar] [CrossRef] [PubMed]
  22. Torres, F.C.; Brucker, N.; Andrade, S.F.; Kawano, D.F.; Garcia, S.C.; Poser, G.L.; Eifler-Lima, V.L. New insights into the chemistry and antioxidant activity of coumarins. Curr. Top. Med. Chem. 2014, 14, 2600–2623. [Google Scholar] [CrossRef] [PubMed]
  23. Kaur, M.; Kohli, S.; Sandhu, S.; Bansal, Y.; Bansal, G. Coumarin: A promising scaffold for anticancer agents. Anticancer. Agents Med. Chem. 2015, 15, 1032–1048. [Google Scholar] [CrossRef] [PubMed]
  24. Widelski, J.; Popova, M.; Graikou, K.; Glowniak, K.; Chinou, I. Coumarins from angelica lucida L.—Antibacterial activities. Molecules 2009, 14, 2729–2734. [Google Scholar] [CrossRef] [PubMed]
  25. Ouahouo, B.M.; Azebaze, A.G.; Meyer, M.; Bodo, B.; Fomum, Z.T.; Nkengfack, A.E. Cytotoxic and antimicrobial coumarins from Mammea africana. Ann. Trop. Med. Parasitol. 2004, 98, 733–739. [Google Scholar] [CrossRef] [PubMed]
  26. Walasek, M.; Grzegorczyk, A.; Malm, A.; Skalicka-Woźniak, K. Bioactivity-guided isolation of antimicrobial coumarins from Heracleum mantegazzianum Sommier & Levier (Apiaceae) fruits by high-performance counter-current chromatography. Food Chem. 2015, 186, 133–138. [Google Scholar] [PubMed]
  27. Tsassi, V.B.; Hussain, H.; Meffo, B.Y.; Kouam, S.F.; Dongo, E.; Schulz, B.; Greene, I.R.; Krohn, K. Antimicrobial coumarins from the stem bark of Afraegle paniculata. Nat. Prod. Commun. 2010, 5, 559–561. [Google Scholar] [PubMed]
  28. Baraza, L.D.; Neser, W.; Jackson, K.C.; Fredrick, J.B.; Dennis, O.; Wairimu, K.R.; Keya, A.O.; Heydenreich, M. Antimicrobial Coumarins from the Oyster Culinary-Medicinal Mushroom, Pleurotus ostreatus (Agaricomycetes), from Kenya. Int. J. Med. Mushrooms 2016, 18, 905–913. [Google Scholar] [CrossRef] [PubMed]
  29. Vatmurge, N.S.; Hazra, B.G.; Pore, V.S.; Shirazi, F.; Chavan, P.S.; Deshpande, M.V. Synthesis and antimicrobial activity of beta-lactam-bile acid conjugates linked via triazole. Bioorg. Med. Chem. Lett. 2008, 18, 2043–2047. [Google Scholar] [CrossRef] [PubMed]
  30. Agalave, S.G.; Maujan, S.R.; Pore, V.S. Click chemistry: 1,2,3-triazoles as pharmacophores. Chem. Asian J. 2011, 6, 2696–2718. [Google Scholar] [CrossRef] [PubMed]
  31. Prasad, D.J.; Ashok, M.; Karegoudar, P.; Poojary, B.; Holla, B.S.; Kumari, N.S. Synthesis and antimicrobial activities of some new triazolothiadiazoles bearing 4-methylthiobenzyl moiety. Eur. J. Med. Chem. 2009, 44, 551–557. [Google Scholar] [CrossRef] [PubMed]
  32. Holla, B.S.; Gonsalves, R.; Shenoy, S. Studies on some N-bridged heterocycles derived from bis-[4-amino-5-mercapto-1,2,4-triazol-3-yl] alkanes. Farmaco 1998, 53, 574–578. [Google Scholar] [CrossRef]
  33. Turan-Zitouni, G.; Kaplancikli, Z.A.; Yildiz, M.T.; Chevallet, P.; Kaya, D. Synthesis and antimicrobial activity of 4-phenyl/cyclohexyl-5-(1-phenoxyethyl)-3-[N-(2-thiazolyl)acetamido]thio-4H-1,2,4-triazole derivatives. Eur. J. Med. Chem. 2005, 40, 607–613. [Google Scholar] [CrossRef] [PubMed]
  34. Masuda, K.; Toga, T.; Hayashi, N. Synthesis of 3-morpholino-N-ethoxycarbonyl sydnonimine-5-14C (sin-10-14C). J. Labell. Compd. 1975, 11, 301–304. [Google Scholar] [CrossRef]
  35. Almasirad, A.; Tabatabai, S.A.; Faizi, M.; Kebriaeezadeh, A.; Mehrabi, N.; Dalvandi, A.; Shafiee, A. Synthesis and anticonvulsant activity of new 2-substituted-5-[2-(2-fluorophenoxy)phenyl]-1,3,4-oxadiazoles and 1,2,4-triazoles. Bioorg. Med. Chem. Lett. 2004, 14, 6057–6059. [Google Scholar] [CrossRef] [PubMed]
  36. Holla, B.S.; Poojary, K.N.; Rao, B.S.; Shivananda, M.K. New bis-aminomercaptotriazoles and bis-triazolothiadiazoles as possible anticancer agents. Eur. J. Med. Chem. 2002, 37, 511–517. [Google Scholar] [CrossRef]
  37. Shivarama Holla, B.; Veerendra, B.; Shivananda, M.K.; Poojary, B. Synthesis characterization and anticancer activity studies on some Mannich bases derived from 1,2,4-triazoles. Eur. J. Med. Chem. 2003, 38, 759–767. [Google Scholar] [CrossRef]
  38. Pingaew, R.; Mandi, P.; Nantasenamat, C.; Prachayasittikul, S.; Ruchirawat, S.; Prachayasittikul, V. Design, synthesis and molecular docking studies of novel N-benzenesulfonyl-1,2,3,4-tetrahydroisoquinoline-based triazoles with potential anticancer activity. Eur. J. Med. Chem. 2014, 81, 192–203. [Google Scholar] [CrossRef] [PubMed]
  39. Manclús, J.J.; Moreno, M.J.; Plana, E.; Montoya, A. Development of monoclonal immunoassays for the determination of triazole fungicides in fruit juices. J. Agric. Food Chem. 2008, 56, 8793–8800. [Google Scholar] [CrossRef] [PubMed]
  40. Amir, M.; Shikha, K. Synthesis and anti-inflammatory, analgesic, ulcerogenic and lipid peroxidation activities of some new 2-[(2,6-dichloroanilino)phenyl]acetic acid derivatives. Eur. J. Med. Chem. 2004, 39, 535–545. [Google Scholar] [CrossRef] [PubMed]
  41. Peña, R.; Martín, P.; Feresin, G.E.; Tapia, A.; Machín, F.; Estévez-Braun, A. Domino synthesis of embelin derivatives with antibacterial activity. J. Nat. Prod. 2016, 79, 970–977. [Google Scholar] [CrossRef] [PubMed]
  42. Casero, C.; Machín, F.; Méndez-Álvarez, S.; Demo, M.; Ravelo, Á.; Pérez-Hernández, N.; Joseph-Nathan, P.; Estévez-Braun, A. Structure and antimicrobial activity of phloroglucinol derivatives from Achyrocline satureioides. J. Nat. Prod. 2015, 78, 93–102. [Google Scholar] [CrossRef] [PubMed]
  43. Peña, R.; Jiménez-Alonso, S.; Feresin, G.; Tapia, A.; Méndez-Alvarez, S.; Machín, F.; Ravelo, Á.; Estévez-Braun, A. Multicomponent synthesis of antibacterial dihydropyridin and dihydropyran embelin derivatives. J. Org. Chem. 2013, 78, 7977–7985. [Google Scholar] [CrossRef] [PubMed]
  44. Casero, C.; Estévez-Braun, A.; Ravelo, A.G.; Demo, M.; Méndez-Álvarez, S.; Machín, F. Achyrofuran is an antibacterial agent capable of killing methicillin-resistant vancomycin-intermediate Staphylococcus aureus in the nanomolar range. Phytomedicine 2013, 20, 133–138. [Google Scholar] [CrossRef] [PubMed]
  45. Janeczko, M.; Demchuk, O.M.; Strzelecka, D.; Kubiński, K.; Masłyk, M. New family of antimicrobial agents derived from 1,4-naphthoquinone. Eur. J. Med. Chem. 2016, 124, 1019–1025. [Google Scholar] [CrossRef] [PubMed]
  46. Rostovtsev, V.V.; Green, L.G.; Fokin, V.V.; Sharpless, K.B. A stepwise huisgen cycloaddition process: copper(I)-catalyzed regioselective “ligation” of azides and terminal alkynes. Angew. Chem. Int. Ed. Engl. 2002, 41, 2596–2599. [Google Scholar] [CrossRef]
  47. Yang, H.; Li, Y.; Jiang, M.; Wang, J.; Fu, H. General copper-catalyzed transformations of functional groups from arylboronic acids in water. Chem. Eur. J. 2011, 17, 5652–5660. [Google Scholar] [CrossRef] [PubMed]
  48. Tao, C.-Z.; Cui, X.; Li, J.; Liu, A.-X.; Liu, L.; Guo, Q.-X. Copper-catalyzed synthesis of aryl azides and 1-aryl-1, 2, 3-triazoles from boronic acids. Tetrahedron Lett. 2007, 48, 3525–3529. [Google Scholar] [CrossRef]
  49. Yuhong, J.; Dalip, K.; Rajender, S.V. Revisiting nucleophilic substitution reactions: Microwave-Assisted synthesis of azides, thiocyanates, and sulfones in an aqueous medium. J. Org. Chem. 2006, 71, 6697–6700. [Google Scholar]
  50. Díaz, L.; Bujons, J.; Casas, J.; Llebaria, A.; Delgado, A. Click chemistry approach to new N-substituted aminocyclitols as potential pharmacological chaperones for Gaucher disease. J. Med. Chem. 2010, 53, 5248–5255. [Google Scholar] [CrossRef] [PubMed]
  51. Zhou, C.H.; Wang, Y. Recent researches in triazole compounds as medicinal drugs. Curr. Med. Chem. 2012, 19, 239–280. [Google Scholar] [CrossRef] [PubMed]
  52. Khaligh, P.; Salehi, P.; Bararjanian, M.; Aliahmadi, A.; Khavasi, H.R.; Nejad-Ebrahimi, S. Synthesis and in Vitro Antibacterial Evaluation of Novel 4-Substituted 1-Menthyl-1,2,3-triazoles. Chem. Pharm. Bull. 2016, 64, 1589–1596. [Google Scholar] [CrossRef] [PubMed]
  53. Kant, R.; Kumar, D.; Agarwal, D.; Gupta, R.D.; Tilak, R.; Awasthi, S.K.; Agarwal, A. Synthesis of newer 1,2,3-triazole linked chalcone and flavone hybrid compounds and evaluation of their antimicrobial and cytotoxic activities. Eur. J. Med. Chem. 2016, 113, 34–49. [Google Scholar] [CrossRef] [PubMed]
  54. Zhang, Q.R.; Xue, D.Q.; He, P.; Shao, K.P.; Chen, P.J.; Gu, Y.F.; Ren, J.L.; Shan, L.H.; Liu, H.M. Synthesis and antimicrobial activities of novel 1,2,4-triazolo [3,4-a] phthalazine derivatives. Bioorg. Med. Chem. Lett. 2014, 24, 1236–1238. [Google Scholar] [CrossRef] [PubMed]
  55. Perrin, D.D.; Armarego, W.L.F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon Press: Oxford, UK, 1988. [Google Scholar]
  56. Wan, X.; Wang, D.; Liu, S. Fluorescent pH-sensing organic/inorganic hybrid mesoporous silica nanoparticles with tunable redox-responsive release capability. Langmuir 2010, 26, 15574–15579. [Google Scholar] [CrossRef] [PubMed]
  57. Yu, B.; Qi, P.P.; Shi, X.J.; Huang, R.; Guo, H.; Zheng, Y.C.; Yu, D.Q.; Liu, H.M. Efficient synthesis of new antiproliferative steroidal hybrids using the molecular hybridization approach. Eur. J. Med. Chem. 2016, 117, 241–255. [Google Scholar] [CrossRef] [PubMed]
  58. Gupta, A.; Jamatia, R.; Mahato, M.; Pal, A.K. Metalloprotein-inspired ruthenium polymeric complex: A highly efficient catalyst in parts per million level for 1,3-dipolar huisgen’s reaction in aqueous medium at room temperature. Indust. Engin. Chem. Res. 2017, 56, 2375–2382. [Google Scholar] [CrossRef]
  59. Janeczko, M.; Kazimierczuk, Z.; Orzeszko, A.; Niewiadomy, A.; Krol, E.; Szyszka, R.; Maslyk, M. In Search of the Antimicrobial Potential of Benzimidazole Derivatives. Pol. J. Microbiol. 2016, 65, 359–364. [Google Scholar] [CrossRef] [PubMed]
  60. Janeczko, M.; Masłyk, M.; Kubiński, K.; Golczyk, H. Emodin, a natural inhibitor of protein kinase CK2, suppresses growth, hyphal development, and biofilm formation of Candida albicans. Yeast 2017, 34, 253–265. [Google Scholar] [CrossRef] [PubMed]
Sample Availability: Samples of the compounds 8a–l, and 9a–l are available from the authors.
Molecules 23 00199 sch001 550
Scheme 1. Formation of O-propargylated coumarin (3) and N-propargylated coumarin (6).
Scheme 1. Formation of O-propargylated coumarin (3) and N-propargylated coumarin (6).
Molecules 23 00199 sch001
Molecules 23 00199 sch002 550
Scheme 2. Formation of 4-substituted 1,2,3-triazole-coumarin derivatives 8 and 9.
Scheme 2. Formation of 4-substituted 1,2,3-triazole-coumarin derivatives 8 and 9.
Molecules 23 00199 sch002
Molecules 23 00199 sch003 550
Scheme 3. Preparation of azides 7a–7j.
Scheme 3. Preparation of azides 7a–7j.
Molecules 23 00199 sch003
Molecules 23 00199 sch004 550
Scheme 4. Preparation of azides 7k–7m.
Scheme 4. Preparation of azides 7k–7m.
Molecules 23 00199 sch004
Molecules 23 00199 g001a 550Molecules 23 00199 g001b 550
Figure 1. Structures of 4-substituted 1,2,3-triazole-coumarin derivatives (8a–8n) and (9a–9n).
Figure 1. Structures of 4-substituted 1,2,3-triazole-coumarin derivatives (8a–8n) and (9a–9n).
Molecules 23 00199 g001aMolecules 23 00199 g001b
Molecules 23 00199 g002 550
Figure 2. Haemolytic activity of compounds 8a, 8b, 8f, 9h and 9k. Tetracycline (TET) and chloramphenicol (CAM) in MIC concentrations were used as a control.
Figure 2. Haemolytic activity of compounds 8a, 8b, 8f, 9h and 9k. Tetracycline (TET) and chloramphenicol (CAM) in MIC concentrations were used as a control.
Molecules 23 00199 g002
Table
Table 1. Synthesized azides 7a–7j.
Table 1. Synthesized azides 7a–7j.
EntryAzideArYield a
17aPh58
27b2-OMe–Ph61
37c3-OMe–Ph97
47d4-OMe–Ph96
57e3-F, 4-OMe–Ph96
67f4-F–Ph41
77g3-CF3–Ph31
87h3-NO2–Ph82
97i5-1H-indol35
107j3-furyl- b
a Isolated yield; b It was not isolated but was reacted in situ.
Table
Table 2. Synthesized azides 7k–7m.
Table 2. Synthesized azides 7k–7m.
EntryAzideRYield a
17k(CH2)10CH386
27l(CH2)13CH373
37mCH2Ph82
a Isolated yield; b MW irradiation at 120 °C for 35 min was used.
Table
Table 3. Antimicrobial activity (MIC µg/mL) of the synthesized compounds.
Table 3. Antimicrobial activity (MIC µg/mL) of the synthesized compounds.
CompoundCandida albicansStaphylococcus aureusEnterococcus faecalisEscherichia coliKlebsiella pneumoniaePseudomonas aeruginosa
8a1600400501600-1600
8b80020012.5160016001600
8c160080010016008001600
8d--20016008001600
8e400400100200800800
8f16001600501600400800
8g8001600100800400800
8h80040040016008001600
8i16001600200160016001600
8j1600800800160016001600
8k--400160016001600
8l--40016001600800
9a1600160040016001600-
9b-160080016008001600
9c20080040016001600800
9d200400100800800800
9e200200100800800800
9f200-160016001600-
9g-200----
9h160010050800800800
9i1600160010016008001600
9j-80080016001600-
9k160020050---
9l1600-800160016001600
CAMn.d.551.255
KET8n.d.n.d.n.d.n.d.n.d.
no activity; n.d.—not determined, CAM—chloramphenicol; KET—ketoconazole.

Share and Cite

MDPI and ACS Style

López-Rojas, P.; Janeczko, M.; Kubiński, K.; Amesty, Á.; Masłyk, M.; Estévez-Braun, A. Synthesis and Antimicrobial Activity of 4-Substituted 1,2,3-Triazole-Coumarin Derivatives. Molecules 2018, 23, 199. https://doi.org/10.3390/molecules23010199

AMA Style

López-Rojas P, Janeczko M, Kubiński K, Amesty Á, Masłyk M, Estévez-Braun A. Synthesis and Antimicrobial Activity of 4-Substituted 1,2,3-Triazole-Coumarin Derivatives. Molecules. 2018; 23(1):199. https://doi.org/10.3390/molecules23010199

Chicago/Turabian Style

López-Rojas, Priscila, Monika Janeczko, Konrad Kubiński, Ángel Amesty, Maciej Masłyk, and Ana Estévez-Braun. 2018. "Synthesis and Antimicrobial Activity of 4-Substituted 1,2,3-Triazole-Coumarin Derivatives" Molecules 23, no. 1: 199. https://doi.org/10.3390/molecules23010199

APA Style

López-Rojas, P., Janeczko, M., Kubiński, K., Amesty, Á., Masłyk, M., & Estévez-Braun, A. (2018). Synthesis and Antimicrobial Activity of 4-Substituted 1,2,3-Triazole-Coumarin Derivatives. Molecules, 23(1), 199. https://doi.org/10.3390/molecules23010199

Article Metrics

Back to TopTop