2016 Volume 64 Issue 10 Pages 1499-1504
A series of 2-azolylchromone derivatives were synthesized and their monoamine oxidase (MAO) A and B inhibitory activities were evaluated. Of the synthesized compounds, compounds 1b, 2b, 4a–c, 5b and 7b showed potent inhibitory activities against MAO-A (IC50 values, 1b: 0.32 µM; 2b: 0.14 µM; 4a: 0.11 µM; 4b: 0.023 µM; 4c: 0.15 µM; 5b: 0.59 µM; 7b: 0.19 µM) and 4a, c, 5a, c, 6c and 8c for MAO-B (IC50 values, 4a: 0.028 µM; 4c: 0.019 µM; 5a: 0.73 µM; 5c: 0.28 µM; 6c: 0.28 µM; 8c: 0.27 µM). These data suggest that 6-methoxy substitution favors MAO-A inhibition and 7-methoxy substitution favors MAO-B inhibition. In addition, compound 4b was the most potent inhibitor for MAO-A, and compound 4c for MAO-B. This is the first report identifying 2-azolylchromone derivatives as potent monoamine oxidase inhibitors. These results suggest that the 2-triazolylchromone structure may be a useful scaffold for the design and development of novel monoamine oxidase inhibitors, as evidenced by the activities of 4a–c and 5a–c.
4H-1-Benzopyran-4-ones (chromones) are an important class of oxygenated heterocyclic compounds that have attracted the attention of organic chemists and biochemists due to their biological activities. The chromone core structure is found in flavones and isoflavones, which are secondary metabolites that are ubiquitous in nature and especially in the plant kingdom, and are present in notable amounts in several species of plants. The chromone scaffold is the pharmacophore of a large number of bioactive molecules of either natural or synthetic origin. The biological effects of these bioactive molecules include anti-inflammatory, anti-tumor and anti-microbial activities, and inhibitory activities towards cyclooxygenases, kinases, phosphatases, aromatases, acetylcholinesterases, and monoamine oxidases.1,2)
The monoamine oxidases A and B (EC 1.4.3.4; MAO-A and MAO-B) are flavoenzymes that play an important role in the oxidative degradation of neurotransmitters such as dopamine, serotonin, and epinephrine. MAOs are found in the outer mitochondrial membrane of various mammalian cell types. MAO-A and MAO-B share approximately 70% sequence identity at the amino acid level and were identified based on their substrate selectivities and inhibitor sensitivities. MAO-A preferentially deaminates serotonin, norepinephrine, and epinephrine and is irreversibly inhibited by clorgyline, whereas MAO-B preferentially deaminates dopamine, β-phenetylamine, and benzylamine and is irreversibly inhibited by R-(−)-deprenyl. MAO inhibitors are important in the treatment of several neurodegenerative diseases. Selective MAO-A inhibitors are used as anti-depressant and anti-anxiety drugs whereas selective MAO-B inhibitors are used to treat Parkinson’s disease.3–5)
Recently, several research groups have reported chromone derivatives substituted at different positions of the chromone ring and their inhibitory effects towards MAO-A and MAO-B.2,6–12) These reports suggested that structural changes induced by the substitutions on the chromone ring can increase the biological activity of the compound.
Azoles such as pyrrole,13) pyrazole,14) indole15) and benzazole16) containing compounds have also been reported as potent MAO inhibitors. We therefore proposed that chromones bearing an azole moiety should display interesting monoamine oxidase inhibitory activities.
In this report we explored promising lead compounds for developing MAO inhibitors by synthesizing a series of 2-azoylchromone derivatives for the first time and investigating their MAO inhibitory activities.
The 2-azolylchromone derivatives presented in this study were synthesized by conjugated addition reactions of 3-iodochromone derivatives (III) with azoles according to the method of Sugita and Yokoe17) (Chart 1). This required preparation of the 3-iodochromone derivatives IIIa–c (R1, R2=H and OMe, respectively). These compounds were synthesized from 2-hydroxyacetophenone derivatives (I) via enaminoketone derivatives (II) according to the method of Vasselin et al.18) Satisfactory yields were obtained in all cases.
Reagents and conditions: (a) DMF-DMA, 95°C; (b) Pyridine, I2, CHCl3; (c) Azole, K2CO3, DMF, 80°C
All the synthesized 2-azolylchromone derivatives were evaluated for MAO-A and MAO-B inhibitory activities. As shown in Table 1, different azole modifications and methoxy substitutions on the chromone ring revealed several interesting structure–activity relationships. The MAO-A inhibitory activities of the 2-azolylchromone derivatives were determined, with 7 of the 24 tested 2-azolylchromones displaying various degrees of potency. Compound 4b was the most potent inhibitor (IC50=0.023 µM). Compounds 1b, 2b, 4a, c, 5b and 7b showed potent inhibitory activities, with sub-micro molar IC50 values. Interestingly, 6-methoxy substituted compounds, such as 1b, 2b, 4b, 5b and 7b, also showed potent inhibitory activities against MAO-A. Compounds 3b, 6b and 8b showed selectivity for MAO-A compared with the unsubstituted or 7-methoxy substituted 2-azolylchromone derivatives.
| Compd. | R1 | R2 | IC50 (µM) | Selectivity index | ||
|---|---|---|---|---|---|---|
| MAO-A | MAO-B | For MAO-A | For MAO-B | |||
| 1a | H | H | 4.56 | >100 | >20 | — |
| 1b | MeO | H | 0.32 | >100 | >300 | — |
| 1c | H | MeO | 14.12 | 7.93 | — | — |
| 2a | H | H | 1.83 | 2.87 | — | — |
| 2b | MeO | H | 0.14 | >100 | >700 | — |
| 2c | H | MeO | 2.07 | 1.04 | — | — |
| 3a | H | H | 25.36 | 6.11 | — | 4 |
| 3b | MeO | H | 6.73 | 19.5 | 3 | — |
| 3c | H | MeO | 26.25 | 5.29 | — | 5 |
| 4a | H | H | 0.11 | 0.028 | — | 4 |
| 4b | MeO | H | 0.023 | 1.64 | 80 | — |
| 4c | H | MeO | 0.15 | 0.019 | — | 8 |
| 5a | H | H | 4.43 | 0.73 | — | 6 |
| 5b | MeO | H | 0.59 | 15.65 | 30 | — |
| 5c | H | MeO | 6.18 | 0.28 | — | 20 |
| 6a | H | H | 6.19 | 2.56 | — | — |
| 6b | MeO | H | 1.00 | 2.01 | — | — |
| 6c | H | MeO | >100 | 0.28 | — | >300 |
| 7a | H | H | 1.58 | >100 | >60 | — |
| 7b | MeO | H | 0.19 | >100 | >500 | — |
| 7c | H | MeO | 34.37 | 25.07 | — | — |
| 8a | H | H | >100 | >100 | — | — |
| 8b | MeO | H | 3.41 | 2.73 | — | — |
| 8c | H | MeO | >100 | 0.27 | — | >300 |
| Pargyline | — | — | 4.57 | 0.22 | — | 20 |
The MAO-B inhibitory activities of the 2-azolylchromone derivatives were also determined, with 6 of the 24 tested 2-azolylchromones displaying various degrees of potency. Compound 4c was the most potent inhibitor (IC50=0.019 µM). Compounds 4a, 5a, c, 6c and 8c showed potent inhibitory activities, with sub-micro molar IC50 values. 7-Methoxy substituted compounds, such as 4c, 5c, 6c and 8c, showed potent inhibitory activities against MAO-B, and compounds 1c, 2c, 3c and 7c also showed selectivity for MAO-B compared with the unsubstituted or 6-methoxy substituted 2-azolylchromone derivatives. These results suggested that introduction of a methoxy group on the chromone ring of 2-azolylchromone derivatives induced selectivities for MAO-A and MAO-B (Fig. 1).
In addition, compounds 1b, 2b and 7b showed higher selectivity for MAO-A, and compounds 6c and 8c showed higher selectivity for MAO-B. These differences might be due to the size of the active site cavity. The active site structures of MAO-A and MAO-B have been reported and the substrate cavity in MAO-A is smaller than the cavity in MAO-B.3–5)
Interestingly, compounds 4a–c and 5a–c showed potent inhibitory activities against both MAO-A and MAO-B, suggesting that the triazole moiety is recognized by MAOs. Thus, the 2-triazolylchromone structure might be a useful scaffold for the design of MAO inhibitors.
This is the first report identifying 2-azolylchromone derivatives as potent MAO inhibitors. The biological activity of 2-azolylchrmone was only recently reported and is a potent hedgehog signaling pathway inhibitor.19)
We synthesized a series of 2-azolylchromone derivatives and evaluated their potential as potent and selective MAO-A and MAO-B inhibitors. Compounds 1b, 2b, 4a–c, 5b and 7b showed potent inhibitory activities against MAO-A, and compounds 4a, c, 5a, c, 6c and 8c showed potent inhibitory activities against MAO-B. These data suggest that 6-methoxy substitution of 2-azolylchromones favors MAO-A inhibition and that 7-methoxy substitution favors MAO-B inhibition. Compound 4b was the most potent inhibitor (IC50=0.023 µM) for MAO-A, and compound 4c was the most potent inhibitor (IC50=0.019 µM) for MAO-B. This is the first report identifying 2-azolylchromone derivatives as potent MAO inhibitors. These results suggest that the 2-triazolylchromone structure might be a useful scaffold for the design and development of novel MAO inhibitors.
All reagents and solvents were purchased from commercial sources. Analytical TLC was performed on silica-coated plates (silica gel 60 F-254, Merck) and compounds were visualized under UV light. Column chromatography was carried out using silica gel (Wakogel C-200, Wako). All melting points were determined using a Yanagimoto micro-hot stage and are uncorrected. 1H-NMR and 13C-NMR spectra were recorded on a Varian 400-MR 400 MHz spectrometer using tetramethylsilane as the internal standard. MS spectra were measured using a JEOL JMS-700 spectrometer. Elemental analyses were carried out on a Yanaco CHN MT-6 elemental analyzer.
Synthesis of 3-Iodochromone Derivatives3-Iodochromone derivatives (IIIa–c) were synthesized according to a previously reported method.18) The products (IIIa–c) were identified from their melting points and 1H-NMR spectra.
3-Iodo-4H-1-benzopyran-4-one (IIIa)Pale yellow prism. mp 97–98°C. 1H-NMR (CDCl3, 400 MHz) δ: 7.48 (1H, dd, J=8.5, 1.1 Hz, H-8), 7.46 (1H, ddd, J=8.0, 7.1, 1.1 Hz, H-6), 7.72 (1H, ddd, J=8.5, 7.1, 1.7 Hz, H-7), 7.48 (1H, dd, J=8.0, 1.7 Hz, H-5), 8.31 (1H, s, H-2). MS-electron ionization (EI) m/z: 272 [M+].
The 1H-NMR spectrum was similar to that previously reported.18)
3-Iodo-6-methoxy-4H-1-benzopyran-4-one (IIIb)White needle crystal. mp 114–115°C. 1H-NMR (CDCl3, 400 MHz) δ: 3.91 (3H, s, OMe), 7.30 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.42 (1H, d, J=9.0 Hz, H-8), 7.59 (1H, d, J=3.1 Hz, H-5), 8.29 (1H, s, H-2). MS-EI m/z: 302 [M+].
The 1H-NMR spectrum was similar to that previously reported.18)
3-Iodo-7-methoxy-4H-1-benzopyran-4-one (IIIc)Colorless prism. mp 165–166°C. 1H-NMR (CDCl3, 400 MHz) δ: 3.91 (3H, s, OMe), 6.84 (1H, d, J=2.4 Hz, H-8), 7.00 (1H, dd, J=9.0, 2.4 Hz, H-6), 8.15 (1H, d, J=9.0 Hz, H-5), 8.22 (1H, s, H-2). MS-EI m/z: 302 [M+].
The 1H-NMR spectrum was similar to that previously reported.18)
General Procedure for Preparation of 2-Azolylchromone Derivatives2-Azolylchromone derivatives were synthesized according to a previously reported method.17) A mixture of 3-iodochromone (1 mmol), azole (2 mmol) and K2CO3 (10 mmol) in N,N-dimethylformamide (DMF) (5 mL) was stirred at 80°C for 24 h. The reaction mixture was extracted with water and CHCl3. The organic layer was dried over Na2SO4 and the solvent was evaporated in vacuo. The residue was purified by silica gel column chromatography (hexane–ethyl acetate) to give 2-azolylchromone derivatives.
2-(1H-Pyrrol-1-yl)-4H-1-benzopyran-4-one (1a)Yield 63%. Brown prism. mp 134–136°C. IR (KBr) cm−1: 586, 725, 779, 1056, 1388, 1419, 1566, 1635, 3070, 3116. 1H-NMR (CDCl3, 400 MHz) δ: 6.32 (1H, s, H-3), 6.45 (2H, t, J=2.3 Hz, H-3′, 4′), 7.33 (2H, t, J=2.3 Hz, H-2′, 5′), 7.46 (1H, ddd, J=7.9, 7.2, 1.0 Hz, H-6), 7.52 (1H, dd, J=8.4, 1.0 Hz, H-8), 7.72 (1H, ddd, J=8.4, 7.2, 1.7 Hz, H-7), 8.23 (1H, dd, J=7.9, 1.7 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 94.8, 113.4, 117.4, 118.2, 123.4, 125.7, 125.9, 133.7, 154.1, 155.7, 178.1. MS-EI m/z: 211 [M+].
The 1H-NMR spectrum was similar to that previously reported.17)
6-Methoxy-2-(1H-pyrrol-1-yl)-4H-1-benzopyran-4-one (1b)Yield 47%. Pale brown solid. mp 146–147°C. IR (KBr) cm−1: 555, 748, 1265, 1381, 1435, 1581, 1643, 3070, 3116. 1H-NMR (CDCl3, 400 MHz) δ: 3.90 (3H, s, OMe), 6.32 (1H, s, H-3), 6.44 (2H, t J=2.3 Hz, H-3′, 4′), 7.27 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.32 (2H, t, J=2.3 Hz, H-2′, 5′), 7.45 (1H, d, J=9.1 Hz, H-8), 7.60 (1H, d, J=3.1 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 60.0, 94.3, 105.4, 113.4, 118.2, 118.7, 123.3, 124.0, 148.8, 155.6, 157.3, 178.0. MS-EI m/z: 241 [M+]. Anal. Calcd for C14H11NO3: C, 69.70; H, 4.60; N, 5.81. Found: C, 69.42; H, 4.55; N, 5.62.
7-Methoxy-2-(1H-pyrrol-1-yl)-4H-1-benzopyran-4-one (1c)Yield 57%. Pale brown prism. mp 148–150°C. IR (KBr) cm−1: 547, 740, 856, 1172, 1280, 1388, 1604, 1651, 3070, 3132. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 6.25 (1H, s, H-3), 6.44 (2H, t, J=2.3 Hz, H-3′, 4′), 6.93 (1H, d, J=2.4 Hz, H-8), 7.02 (1H, dd, J=8.8, 2.4 Hz, H-6), 7.31 (2H, t, J=2.3 Hz H-2′, 5′), 8.13 (1H, d, J=8.8 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 55.9, 94.6, 100.4, 113.2, 114.3, 117.1, 118.2, 127.2, 155.5, 155.8, 164.1, 177.7. MS-EI m/z: 241 [M+]. Anal. Calcd for C14H11NO3: C, 69.70; H, 4.60; N, 5.81. Found: C, 69.62; H, 4.62; N, 5.71.
2-(1H-Pyrazol-1-yl)-4H-1-benzopyran-4-one (2a)Yield 70%. White solid. mp 142–143°C. IR (KBr) cm−1: 948, 1222, 1396, 1417, 1573, 1635, 3039, 3103. 1H-NMR (CDCl3, 400 MHz) δ: 6.60 (1H, dd, J=2.7, 1.6 Hz, H-4′), 6.91 (1H, s, H-3), 7.47 (1H, ddd, J=7.9, 7.1, 1.0 Hz, H-6), 7.55 (1H, dd, J=8.5, 1.0 Hz, H-8), 7.72 (1H, ddd, J=8.5, 7.1, 1.7 Hz, H-7), 7.86 (1H, d, J=1.6 Hz, H-3′), 8.24 (1H, d, J=2.7 Hz, H-5′), 8.26 (1H, dd, J=7.9, 1.7 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 96.3, 109.6, 117.4, 123.7, 125.9, 126.1, 127.7, 133.8, 144.3, 154.0, 155.2, 177.9. MS-EI m/z: 212 [M+].
The 1H-NMR spectrum was similar to that previously reported.17)
6-Methoxy-2-(1H-pyrazol-1-yl)-4H-1-benzopyran-4-one (2b)Yield 67%. Pale yellow needle crystal. mp 172–173°C. IR (KBr) cm−1: 555, 825, 887, 1018, 1211, 1396, 1581, 1635, 3039, 3101. 1H-NMR (CDCl3, 400 MHz) δ: 3.92 (3H, s, OMe), 6.58 (1H, m, H-4′), 6.90 (1H, s, H-3), 7.29 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.47 (1H, d, J=9.1 Hz, H-8), 7.63 (1H, d, J=3.1 Hz, H-5), 7.85 (1H, d, J=1.6 Hz, H-3′), 8.22 (1H, d, J=2.7 Hz, H-5′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 95.8, 105.6, 109.5, 118.8, 123.5, 124.4, 127.7, 144.2, 148.6, 155.2, 157.4, 177.9. MS-EI m/z: 242 [M+]. Anal. Calcd for C13H10N2O3: C, 64.46; H, 4.16; N, 11.56. Found: C 64.24; H, 4.05; N, 11.43.
7-Methoxy-2-(1H-pyrazol-1-yl)-4H-1-benzopyran-4-one (2c)Yield 89%. Pale yellow needle crystal. mp 173°C. IR (KBr) cm−1: 594, 763, 817, 1257, 1404, 1635, 3039, 3109. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 6.58 (1H, dd, J=2.7, 1.6 Hz, H-4′), 6.82 (1H, s, H-3), 6.95 (1H, d, J=2.3 Hz, H-8), 7.02 (1H, dd, J=8.8, 2.4 Hz, H-6), 7.84 (1H, d, J=1.6 Hz, H-3′), 8.15 (1H, d, J=8.8 Hz, H-5), 8.20 (1H, d, J=2.7 Hz, H-5′). 13C-NMR (CDCl3, 100 MHz) δ: 55.9, 96.2, 100.4, 109.4, 114.4, 117.4, 127.3, 127.6, 144.1, 155.0, 155.7, 164.1, 177.5. MS-EI m/z: 242 [M+]. Anal. Calcd for C13H10N2O3: C, 64.46; H, 4.16; N, 11.56. Found: C, 64.46; H, 4.12; N, 11.54.
2-(1H-Imidazol-1-yl)-4H-1-benzopyran-4-one (3a)Yield 81%. White solid. mp 197–198°C. IR (KBr) cm−1: 617, 756, 848, 887, 1056, 1265, 1303, 1427, 1635, 3062, 3116. 1H-NMR (CDCl3, 400 MHz) δ: 6.38 (1H, s, H-3), 7.27–7.28 (1H, m, H-4′), 7.46–7.48 (1H, m, H-5′), 7.49 (1H, ddd, J=7.9, 7.2, 1.0 Hz, H-6), 7.54 (1H, dd, J=8.4, 1.0 Hz, H-8), 7.75 (1H, ddd, J=8.4, 7.2, 1.7 Hz, H-7), 8.20–8.23 (1H, m, H-2′), 8.23 (1H, dd, J=7.2, 1.7 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 97.1, 115.8, 117.6, 123.4, 126.0, 126.2, 131.9, 134.3, 134.8, 153.3, 154.2, 177.7. MS-EI m/z: 212 [M+].
The 1H-NMR spectrum was similar to that previously reported.17)
2-(1H-Imidazol-1-yl)-6-methoxy-4H-1-benzopyran-4-one (3b)Yield 72%. White solid. mp 199°C. IR (KBr) cm−1: 825, 1249, 1303, 1458, 1643, 3062. 1H-NMR (CDCl3, 400 MHz) δ: 3.92 (3H, s, OMe), 6.37 (1H, s, H-3), 7.25–7.27 (1H, m, H-4′), 7.32 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.45–7.47 (1H, m, H-5′), 7.48 (1H, d, J=9.1 Hz, H-8), 7.59 (1H, d, J=3.1 Hz, H-5), 8.19–8.21 (1H, m, H-2′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 96.5, 105.5, 115.8, 119.0, 124.0, 124.1, 131.8, 134.7, 148.8, 153.2, 157.7, 177.7. MS-EI m/z: 242 [M+]. Anal. Calcd for C13H10N2O3: C, 64.46; H, 4.16; N, 11.56. Found: C, 64.21; H, 4.20; N, 11.56.
2-(1H-Imidazol-1-yl)-7-methoxy-4H-1-benzopyran-4-one (3c)Yield 89%. White solid. mp 177–179°C. IR (KBr) cm−1: 455, 648, 810, 1002, 1049, 1087, 1242, 1296, 1427, 1643, 3062. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 6.31 (1H, s, H-3), 6.94 (1H, d, J=2.4 Hz, H-8), 7.04 (1H, dd, J=8.9, 2.4 Hz, H-6), 7.25–7.26 (1H, m, H-4′), 7.43–7.44 (1H, m, H-5′), 8.12 (1H, d, J=8.9 Hz, H-5), 8.19–8.20 (1H, m, H-2′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 97.0, 100.4, 114.9, 115.8, 117.0, 127.3, 131.7, 134.7, 153.0, 155.9, 164.5, 177.2. MS-EI m/z: 242 [M+]. Anal. Calcd for C13H10N2O3: C, 64.46; H, 4.16, N; 11.56. Found: C, 63.20; H, 4.14; N, 11.56.
2-(1H-1,2,4-Triazol-1-yl)-4H-1-benzopyran-4-one (4a)Yield 73%. White solid. mp 205–207°C. IR (KBr) cm−1: 609, 655, 748, 902, 987, 1064, 1234, 1427, 1512, 1635, 3008, 3101. 1H-NMR (CDCl3, 400 MHz) δ: 6.91 (1H, s, H-3), 7.52 (1H, ddd, J=7.9, 7.2, 1.0 Hz, H-6), 7.58 (1H, dd, J=8.5, 1.0 Hz, H-8), 7.78 (1H, ddd, J=8.5, 7.2, 1.7 Hz, H-7), 8.19 (1H, s, H-3′), 8.27 (1H, dd, J=7.9, 1.7 Hz, H-5), 8.92 (1H, s, H-5′). 13C-NMR (CDCl3, 100 MHz) δ: 98.2, 117.5, 123.7, 126.3, 126.4, 134.4, 142.0, 152.9, 153.9, 154.0, 177.6. MS-EI m/z: 213 [M+].
The 1H-NMR spectrum was similar to that previously reported.17)
6-Methoxy-2-(1H-1,2,4-triazol-1-yl)-4H-1-benzopyran-4-one (4b)Yield 61%. Pale yellow solid. mp 233–235°C. IR (KBr) cm−1: 663, 825, 902, 987, 1026, 1234, 1280, 1357, 1419, 1635, 3109. 1H-NMR (CDCl3, 400 MHz) δ: 3.96 (3H, s, OMe), 6.89 (1H, s, H-3), 7.34 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.50 (1H, d, J=9.1 Hz, H-8), 7.63 (1H, d, J=3.1 Hz, H-5), 8.18 (1H, s, H-3′), 8.90 (1H, s, H-5′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 97.6, 105.7, 118.9, 124.1, 124.4, 141.9, 148.6, 152.8, 153.9, 157.6, 177.6. MS-EI m/z: 243 [M+]. Anal. Calcd for C12H9N3O3: C, 59.26; H, 3.73; N, 17.28. Found: C, 59.15; H, 3.59; N, 17.14.
7-Methoxy-2-(1H-1,2,4-triazol-1-yl)-4H-1-benzopyran-4-one (4c)Yield 82%. Yellow needle crystal. mp 233–235°C. IR (KBr) cm−1: 825, 902, 995, 1080, 1126, 1234, 1411, 1512, 1612, 3008, 3086. 1H-NMR (CDCl3, 100 MHz) δ: 3.96 (3H, s, OMe), 6.84 (1H, s, H-3), 6.97 (1H, d, J=2.3 Hz, H-8), 7.06 (1H, dd, J=8.9, 2.3 Hz, H-6), 8.17 (1H, d, J=8.9 Hz, H-5), 8.18 (1H, s, H-3′), 8.88 (1H, s, H-5′). 13C-NMR (CDCl3, 400 MHz) δ: 56.0, 98.1, 100.4, 115.0, 117.3, 127.5, 141.8, 152.6, 153.9, 155.7, 164.6, 177.0. MS-EI m/z: 243 [M+]. Anal. Calcd for C12H9N3O3: C, 59.26; H, 3.73; N, 17.28. Found: C, 59.27; H, 3.67; N, 17.29.
(1H-1,2,3-Triazol-1-yl)-4H-1-benzopyran-4-one (5a)Yield 47%. White needle crystal. mp 146°C. IR (KBr) cm−1: 756, 864, 948, 1273, 1465, 1658. 1H-NMR (CDCl3, 400 MHz) δ: 7.06 (1H, s, H-3), 7.51 (1H, ddd, J=8.0, 7.1, 1.1 Hz, H-6), 7.69 (1H, dd, J=8.5, 1.1 Hz, H-8), 7.77 (1H, ddd, J=8.5, 7.1, 1.7 Hz, H-7), 8.02 (2H, s, H-4′, 5′), 8.27 (1H, dd, J=8.0, 1.7 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 98.8, 118.3, 124.0, 126.2, 126.4, 134.5, 138.5 (2C), 154.5, 154.7, 178.2. MS-EI m/z: 213 [M+]. Anal. Calcd for C11H7N3O2: C, 61.97; H, 3.31; N, 19.71. Found: C, 61.95; H, 3.24; N 19.62.
6-Methoxy-2-(1H-1,2,3-triazol-1-yl)-4H-1-benzopyran-4-one (5b)Yield 16%. Pale yellow needle crystal. mp 216–217°C. IR (KBr) cm−1: 825, 948, 1273, 1458, 1651, 3086. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 7.04 (1H, s, H-3), 7.34 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.62 (1H, d, J=9.1 Hz, H-8), 7.63 (1H, d, J=3.1 Hz, H-5), 8.01 (2H, s, H-4′, 5′). 13C-NMR (CDCl3, 100 MHz) δ: 56.2, 98.1, 105.6, 119.7, 124.2, 124.7, 138.4 (2C), 149.3, 154.3, 157.8, 178.1. MS-EI m/z: 243 [M+]. Anal. Calcd for C12H9N3O3: C, 59.26; H, 3.73; N, 17.28. Found: C, 59.19; H, 3.74; N, 17.17.
7-Methoxy-2-(1H-1,2,3-triazol-1-yl)-4H-1-benzopyran-4-one (5c)Yield 37%. White solid.. mp 191°C. IR (KBr) cm−1: 833, 910, 956, 1273, 1427, 1651, 3086. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 6.99 (1H, s, H-3), 7.06 (1H, dd, J=8.8, 2.3 Hz, H-6), 7.10 (1H, dd, J=2.3 Hz, H-8), 8.00 (2H, s, H-4′, 5′), 8.16 (1H, d, J=8.8 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 55.9, 98.4, 100.4, 115.2, 117.3, 127.1, 138.0 (2C), 153.9, 156.1, 164.4, 177.3. MS-EI m/z: 243 [M+]. Anal. Calcd for C12H9N3O3: C, 59.26; H, 3.73; N, 17.28. Found: C, 59.29; H, 3.66; N, 17.29.
2-(1H-Indol-1-yl)-4H-1-benzopyran-4-one (6a)Yield 44%. Pale yellow needle crystal. mp 157–158°C. IR (KBr) cm−1: 732, 1419, 1543, 1635, 3062, 3116. 1H-NMR (CDCl3, 400 MHz) δ: 6.47 (1H, s, H-3), 6.81 (1H, d, J=3.6 Hz, H-3′), 7.30 (1H, ddd, J=7.8, 7.2, 1.0 Hz, H-5′), 7.39 (1H, ddd, J=8.4, 7.2, 1.2 Hz, H-6′), 7.48 (1H, ddd, J=7.9, 7.2, 1.0 Hz, H-6), 7.56 (1H, d, J=3.6 Hz, H-2′), 7.59 (1H, dd, J=8.4, 1.0 Hz, H-8), 7.67 (1H, br d, J=7.8 Hz, H-4′), 7.74 (1H, ddd, J=8.4, 7.2, 1.7 Hz, H-7), 8.01 (1H, br d, J=8.4 Hz, H-7′), 8.26 (1H, dd, J=7.9, 1.7 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 97.4, 108.9, 113.4, 117.4, 121.8, 123.0, 123.5, 124.5, 124.6, 125.8, 126.0, 130.7, 133.8, 134.6, 154.5, 156.6, 178.1. MS-EI m/z: 261 [M+].
The 1H-NMR spectrum was similar to that previously reported.17)
2-(1H-Indol-1-yl)-6-methoxy-4H-1-benzopyran-4-one (6b)Yield 9%. Pale brown solid. mp 166°C. IR (KBr) cm−1: 817, 1342, 1450, 1566, 1635. 1H-NMR (CDCl3, 400 MHz) δ: 3.93 (3H, s, OMe), 6.46 (1H, s, H-3), 6.81 (1H, d, J=3.6 Hz, H-3′), 7.23–7.33 (2H, m, H-7, 5′), 7.39 (1H, ddd, J=8.4, 7.2, 1.7 Hz, H-6′), 7.52 (1H, d, J=9.1 Hz, H-8), 7.55 (1H, d, J=3.6 Hz, H-2′), 7.64 (1H, d, J=3.1 Hz, H-5), 7.67 (1H, br d, J=7.8 Hz, H-4′), 8.00 (1H, br d, J=8.4 Hz H-7′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 96.9, 105.5, 108.8, 113.3, 118.7, 121.8, 122.9, 123.4, 124.1, 124.4, 124.5, 130.7, 134.6, 149.0, 156.5, 157.4, 178.0. MS-EI m/z: 291 [M+]. Anal. Calcd for C18H13NO3: C, 74.22; H, 4.50; N, 4.81. Found: C, 73.94; H, 4.41; N, 4.70.
2-(1H-Indol-1-yl)-7-methoxy-4H-1-benzopyran-4-one (6c)Yield 17%. Pale brown solid. mp 172–174°C. IR (KBr) cm−1: 732, 833, 1342, 1419, 1627, 3070, 3116. 1H-NMR (CDCl3, 400 MHz) δ: 3.97 (3H, s, OMe), 6.41 (1H, s, H-3), 6.81 (1H, d, J=3.6 Hz, H-3′), 6.99 (1H, d, J=2.3 Hz, H-8), 7.05 (1H, dd, J=8.8, 2.3 Hz, H-6), 7.30 (1H, ddd, J=7.8, 7.2, 1.0 Hz, H-5′), 7.40 (1H, ddd, J=8.4, 7.2, 1.2 Hz, H-6′), 7.56 (1H, d, J=3.6 Hz, H-2′), 7.68 (1H, br d, J=7.8 Hz, H-4′), 7.98 (1H, br d, J=8.4 Hz H-7′), 8.18 (1H, d, J=8.8 Hz, H-5). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 97.5, 100.4, 108.6, 113.2, 114.4, 117.1, 121.8, 122.9, 124.4, 124.6, 127.3, 130.6, 134.6, 156.1, 156.3, 164.2, 177.7. MS-EI m/z: 291 [M+]. Anal. Calcd for C18H13NO3: C, 74.22; H, 4.50; N, 4.81. Found: C, 73.97; H, 4.47; N, 4.81.
2-(1H-Indazol-1-yl)-4H-1-benzopyran-4-one (7a)Yield 89%. White needle crystal. mp 239–240°C. IR (KBr) cm−1: 748, 1180, 1419, 1566, 1627, 3055. 1H-NMR (CDCl3, 400 MHz) δ: 6.95 (1H, s, H-3), 7.39 (1H, ddd, J=8.0, 7.0, 0.9 Hz, H-5′), 7.50 (1H, ddd, J=8.0, 7.0, 1.1 Hz, H-6), 7.63 (1H, ddd, J=8.6, 7.0, 1.1 Hz, H-6′), 7.67 (1H, dd, J=8.5, 1.1 Hz, H-8), 7.76 (1H, ddd, J=8.5, 7.1, 1.7 Hz, H-7), 7.84 (1H, dt, J=8.0, 1.0 Hz, H-4′), 8.27 (1H, br d, J=8.6 Hz, H-7′), 8.30 (1H, dd, J=8.0, 1.7 Hz, H-5), 8.32 (1H, d, J=0.9 Hz, H-3′). 13C-NMR (CDCl3, 100 MHz) δ: 96.5, 113.5, 117.2, 121.8, 123.8, 123.9, 125.9, 126.2, 126.5, 129.2, 133.6, 138.6, 140.3, 154.0, 158.0, 177.8. MS-EI m/z: 262 [M+].
The 1H-NMR spectrum was similar to that previously reported.17)
2-(1H-Indazol-1-yl)-6-methoxy-4H-1-benzopyran-4-one (7b)Yield 75%. White solid. mp 206–208°C. IR (KBr) cm−1: 756, 1018, 1573, 3078. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 6.94 (1H, s, H-3), 7.32 (1H, dd, J=9.0, 3.1 Hz, H-7), 7.39 (1H, ddd, J=8.0, 7.0, 0.9 Hz, H-5′), 6.59 (1H, d, J=9.0 Hz, H-8), 7.62 (1H, ddd, J=8.6, 7.0, 1.1 Hz, H-6′), 7.68 (1H, d, J=3.1 Hz, H-5), 7.83 (1H, dt, J=8.0, 1.0 Hz, H-4′), 8.25 (1H, br d, J=8.6 Hz, H-7′), 8.31 (1H, d, J=0.9 Hz, H-3′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 95.9, 105.7, 113.4, 118.6, 121.8, 123.2, 123.8, 124.6, 126.4, 129.1, 138.6, 140.2, 148.6, 157.9, 157.8, 177.7. MS-EI m/z: 292 [M+]. Anal. Calcd for C17H12N2O3: C, 69.86; H, 4.14; N, 9.58. Found: C, 69.85; H, 4.01; N, 9.48.
2-(1H-Indazol-1-yl)-7-methoxy-4H-1-benzopyran-4-one (7c)Yield 75%. White solid. mp 219–222°C. IR (KBr) cm−1: 740, 1010, 1165, 1419, 1566, 3070. 1H-NMR (CDCl3, 400 MHz) δ: 3.99 (3H, s, OMe), 6.86 (1H, s, H-3), 7.03–7.07 (2H, m, H-6, 8), 7.39 (1H, ddd, J=8.0, 7.0, 0.8 Hz, H-5′), 7.63 (1H, ddd, J=8.6, 7.0, 1.1 Hz, H-6′), 7.83 (1H, dt, J=8.0, 1.0 Hz, H-4′), 8.19 (1H, d, J=8.6 Hz, H-5), 8.21 (1H, br d, J=8.6 Hz, H-7′), 8.31 (1H, d, J=0.9 Hz, H-3′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 96.5, 100.4, 113.3, 114.3, 117.6, 121.8, 123.8, 126.4, 127.4, 129.1, 138.5, 140.0, 155.7, 157.6, 164.0, 177.4. MS-EI m/z: 292 [M+]. Anal. Calcd for C17H12N2O3: C, 69.86; H, 4.14; N, 9.58. Found: C, 69.57; H, 4.00; N, 9.41.
2-(1H-Benzimidazol-1-yl)-4H-1-benzopyran-4-one (8a)Yield 48%. White crystal. mp 232–234°C. IR (KBr) cm−1: 617, 748, 1118, 1180, 1311, 1411, 1651, 3070, 3109. 1H-NMR (CDCl3, 400 MHz) δ: 6.60 (1H, s, H-3), 7.43–7.53 (2H, m, H-5′, 6′), 7.53 (1H, ddd, J=7.9, 7.1, 1.0 Hz, H-6), 7.62 (1H, dd, J=8.4, 1.0 Hz, H-8), 7.79 (1H, ddd, J=8.4, 7.1, 1.7 Hz, H-7), 7.87–7.94 (2H, m, H-4′, 7′), 8.29 (1H, dd, J=7.9, 1.7 Hz, H-5), 8.48 (1H, s, H-2′). 13C-NMR (CDCl3, 100 MHz) δ: 98.9, 112.4, 117.6, 121.5, 123.5, 124.7, 125.5, 126.1, 126.3, 131.0, 134.3, 139.8, 144.4, 153.9, 154.5, 177.8. MS-EI m/z: 262 (M+).
The 1H-NMR spectrum was similar to that previously reported.17)
2-(1H-Benzimidazol-1-yl)-6-methoxy-4H-1-benzopyran-4-one (8b)Yield 54%. White crystal. mp 221°C. IR (KBr) cm−1: 894, 1018, 1404, 1573, 1620, 3001, 3078. 1H-NMR (CDCl3, 400 MHz) δ: 3.94 (3H, s, OMe), 6.59 (1H, s, H-3), 7.36 (1H, dd, J=9.1, 3.1 Hz, H-7), 7.43–7.52 (2H, m, H-5′, 6′), 7.55 (1H, d, J=9.0 Hz, H-8), 7.65 (1H, d, J=3.1 Hz, H-5), 7.87–7.94 (2H, m, H-4′, 7′), 8.46 (1H, s, H-2′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 98.3, 105.6, 112.4, 118.9, 121.4, 124.0, 124.2, 124.7, 125.5, 131.0, 139.8, 144.4, 149.1, 153.7, 157.7, 177.8. MS-EI m/z: 292 [M+]. Anal. Calcd for C17H12N2O3: C, 69.86; H, 4.14; N, 9.58. Found: C, 69.76; H, 4.04; N, 9.47.
2-(1H-Benzimidazol-1-yl)-7-methoxy-4H-1-benzopyran-4-one (8c)Yield 54%. White solid. mp 200°C. IR (KBr) cm−1: 624, 740, 1080, 1165, 1404, 1627, 3078. 1H-NMR (CDCl3, 400 MHz) δ: 3.97 (3H, s, OMe), 6.53 (1H, s, H-3), 6.99 (1H, d, J=2.3 Hz, H-8), 7.07 (1H, dd, J=8.9, 2.3 Hz, H-6), 7.42–7.51 (2H, m, H-5′, 6′), 7.84–7.93 (2H, m, H-4′, 7′), 8.17 (1H, d, J=8.9 Hz, H-5), 8.45 (1H, s, H-2′). 13C-NMR (CDCl3, 100 MHz) δ: 56.0, 99.0, 100.4, 112.3, 115.0, 117.1, 121.4, 124.6, 125.4, 127.4, 131.0, 139.8, 144.4, 153.5, 156.2, 164.6, 177.3. MS-EI m/z: 292 [M+]. Anal. Calcd for C17H12N2O3: C; 69.86, H; 4.14, N, 9.58. Found: C, 69.66; H, 3.99; N, 9.44.
Biological AssayRecombinant human monoamine oxidase A (MAO-A), MAO-B, pargyline and kynuramine were purchased from Sigma-Aldrich Japan.
MAO Inhibitory AssayMAO inhibitory activity was assayed using the method of Novaroli et al.20) with minor modifications. Briefly, 140 µL of 0.1 M potassium phosphate buffer (pH 7.4), 8 µL of 0.75 mM kynuramine, and 2 µL of a dimethyl sulfoxide (DMSO) inhibitor solution (final DMSO concentration of 1% (v/v)), were preincubated at 37°C for 10 min. Diluted human recombinant enzyme (50 µL) was then added to obtain a final protein concentration of 0.0075 mg/mL (MAO-A) or 0.015 mg/mL (MAO-B) in the assay mixture. Further incubation was carried out at 37°C and the reaction was stopped after 20 min by addition of 75 µL of 2 M NaOH. The product generated by MAO, 4-quinolinol, is fluorescent and was measured at Ex 310 nm/Em 400 nm using a micro-plate reader (Molecular Devices SPECTRA MAX M2). The sample solution was replaced with DMSO to provide a negative control and pargyline was used as a positive control.
The authors declare no conflict of interest.
