B.J. Compton et al. / Tetrahedron 67 (2011) 718e726
725
321.0719 [MþNa]þ (calcd for C17H14NaO5 321.0733). Compound 5
had mp 204e206 ꢀC (lit.30 206e207 ꢀC); 1H NMR (500 MHz, CDCl3)
dH 4.02 (s, 6H, 5 and 7-OCH3), 5.90 (br s, 1H, OH), 6.69 (s, 1H, H-8),
6.85 (s, 1H, H-3), 7.50 (m, 1H, H-40), 7.51 (m, 2H, H-30, 50), 7.87 (ddm,
J¼8.0, 1.5 Hz, 2H, H-20, 60); 13C NMR (125 MHz, CDCl3) dC 56.6 (q, 7-
OCH3), 62.7 (q, 5-OCH3), 96.4 (d, C-3), 108.3 (d, C-8), 112.5 (s, C-4a),
126.1 (2ꢃd, C-20, 60), 129.1 (2ꢃd, C-30, 50), 131.4 (d, C-40), 131.7 (s, C-
10),136.8 (s, C-6),144.1 (s, C-7),152.2 (s, C-8a),152.4 (s, C-5),161.5 (s,
C-2), 177.2 (s, C-4); IR (KBr) nmax 3414, 3110, 3000, 2982, 2924, 1687,
16,359, 1602, 1497, 1469, 1454, 1436, 1425, 1361, 1332, 1304, 1279,
1264,1221,1201,1157,1089,1041,1029, 994, 948, 908, 883, 843, 815,
768, 728, 706, 687, 618, 562, 510, 485 cmꢁ1; HRMS (þve ESI) m/z
321.0733 [MþNa]þ (calcd for C17H14NaO5 321.0733). Compound 7,
a yellow solid, had mp 139e141 ꢀC (from rectified spirit); 1H NMR
(500 MHz, CDCl3) dH 3.24 (s, 3H, 60-OCH3), 3.81 (s, 3H, 40-OCH3),
4.72 (d, J¼6.5 Hz, 1H, 2-OH), 5.79 (d, J¼2.0 Hz, 1H, H-50), 6.12 (d,
J¼2.0 Hz, 1H, H-30), 6.14 (d, J¼6.5 Hz, 1H, H-2), 7.53 (ddm, J¼8.0,
7.5 Hz, 2H, H-300, 500), 7.62 (dddd, J¼7.5, 7.5, 1, 1 Hz, 1H, H-400), 8.11
(ddm, J¼8, 1.5 Hz, 2H, H-200, 600), 13.05 (s, 1H, H-20-OH); 13C NMR
(125 MHz, CDCl3) dC 55.3 (q, 60-OCH3), 55.9 (q, 40-OCH3), 76.6 (d,
C-2), 91.3 (d, C-50), 94.2 (d, C-30), 103.8 (s, C-10), 128.9 (2ꢃd, C-300,
500), 129.1 (2ꢃd, C-200, 600), 133.6 (d, C-400), 135.4 (s, C-100), 162.1 (s,
C-60), 167.6 (s, C-20), 167.7 (s, C-40), 194.2 (s, C-3), 198.2 (s, C-1); IR
(KBr) nmax 3414, 3068, 3007, 2976, 2946, 2854, 1687, 1628, 1605,
1580, 1466, 1449, 1436, 1423, 1391, 1331, 1304, 1279, 1221, 1205,
1182, 1157, 1112, 1089, 1002, 992, 956, 938, 840, 814, 789, 706, 675,
618, 571, 534, 448, 433 cmꢁ1; HRMS (þve ESI) m/z 339.0850
[MþNa]þ (calcd for C17H16NaO6 339.0839). Anal. Calcd for
C17H16O6: C, 64.6; H, 5.1. Found: C, 64.4; H, 5.1%.
133.9 (d, C-4000), 134.4 (d, C-400), 138.8 (s, C-3), 144.4 (s, C-2), 150.2
(s, C-5), 154.5 (s, C-7), 156.8 (s, C-8a), 164.0 (s, PhC00OO), 165.1 (s,
PhC000OO), 171.5 (s, C-4); IR (thin film) nmax 3305, 2924, 1739, 1616,
1451, 1241, 1149, 1054, 1021, 701, 688 cmꢁ1; HRMS (þve ESI) m/z
479.1114 [MþH]þ (calcd for C29H19O7 479.1125). Anal. Calcd for
C29H18O7: C, 72.8; H, 3.8. Found: C, 72.8; H, 3.9%.
4.5.4. 3-Hydroxy-5-acetoxy-7-methoxyflavone (3d). Crude epoxide
derived from 1d (0.305 g, 0.982 mmol), containing unchanged 1d
(ca. 10%) (method B) gave 3d (0.180 g) after recrystallisation from
chloroform. Chromatography of the mother liquors on silica gel
(10 g, CHCl3 elution) gave an additional portion of 3d (0.033 g,
overall yield 66%) along with unchanged starting material (1d)
(0.025 g, 8%). Compound 3d, yellow crystals, decomposed
170e180 ꢀC and had 1H NMR (500 MHz, CDCl3) dH 2.46 (s, 3H,
CH3COO), 3.92 (s, 3H, OCH3), 6.64 (d, J¼2.0 Hz, 1H, H-6), 6.87 (d,
J¼2.0 Hz, 1H, H-8), 7.44 (ddm, J¼7.5, 7.5 Hz, 1H, H-40), 7.51 (ddm,
J¼7.5, 7.5 Hz, 2H, H-30, 50), 8.17 (dm, J¼7.5 Hz, 2H, H-20, 60); 13C
NMR (125 MHz, CDCl3) dC 21.1 (q, CH3COO), 56.0 (q, OCH3), 98.4
(d, C-8), 108.4 (d, C-6), 108.5 (s, C-4a), 127.4 (2ꢃd, C-20, 60), 128.6
(2ꢃd, C-30, 50), 130.0 (d, C-40), 130.8 (s, C-10), 138.2 (s, C-3), 143.4
(s, C-2), 150.1 (s, C-8a), 158.0 (s, C-5), 163.7 (s, C-7), 169.6 (s,
CH3COO), 171.3 (s, C-4); IR (KBr) nmax 3301, 2975, 2846, 1769,
1623, 1603, 1573, 1559, 1497, 1454, 1417, 1374, 1288, 1259, 1229,
1207, 1160, 1120, 1088, 1070, 1040, 1010, 970, 892, 877, 839, 828,
772, 734, 722, 701, 693, 628, 620, 604, 591, 573, 552, 538, 488,
457, 419; HRMS (þve ESI) m/z 349.0690 [MþNa]þ (calcd for
C18H14NaO6 349.0683). Anal. Calcd for C18H14O6: C, 66.3; H, 4.3.
Found: C, 66.3; H, 4.3%.
(b) Crude epoxide 2a (prepared in Section 4.4.1.1 (b)) gave
a mixture, which was separated by chromatography on silica gel
(18 g). Elution with CH2Cl2/EtOAc; 17:3 gave 1h (0.002 g, 1%), 7
(0.002 g, 1%) followed by 6 (0.028 g, 30%). Elution with CH2Cl2/
EtOAc; 4:1 gave 3a (0.020 g, 13%). Elution with CH2Cl2/EtOAc; 3:7
gave 1a (0.014 g, 10%).
4.5.5. 7-Benzoyloxy-3-hydroxy-5-methoxyflavone (3e). Crude ep-
oxide derived from 1e (0.302 g, 0.811 mmol) (method B) gave 3e
(0.202 g, 64%), a white solid, after recrystallisation from isopropyl
alcohol; mp 184e185 ꢀC; 1H NMR (500 MHz, CDCl3) dH 4.04 (s, 3H,
OCH3), 6.70 (d, J¼2.0 Hz, 1H, H-6), 7.14 (d, J¼2.0 Hz, 1H, H-8), 7.38
(br s, 1H, OH), 7.45 (ddm, J¼7.5, 7.5 Hz, 1H, H-40), 7.52 (ddm, J¼7.5,
7.5 Hz, 2H, H-30, 50), 7.56 (ddm, J¼7.5, 7.5 Hz, 2H, H-300, 500), 7.68
(ddm, J¼7.5, 7.5 Hz, 1H, H-400), 8.15 (dm, J¼7.5 Hz, 4H, H-20, 60, 200,
600); 13C NMR (125 MHz, CDCl3) dC 56.8 (q, OCH3), 100.3 (d, C-6),
103.5 (d, C-8), 109.5 (s, C-4a), 127.4 (2ꢃd, C-20, 60), 128.6 (2ꢃd, C-30,
50), 128.8 (s, C-100), 128.8 (d, C-300, 500), 130.0 (d, C-40), 130.3 (d, C-200,
600), 130.8 (s, C-10), 134.2 (d, C-400), 138.7 (s, C-3), 142.8 (s, C-2), 155.3
(s, C-7),157.7 (s, C-8a),160.6 (s, C-5),164.3 (s, PhCOO), 172.3 (s, C-4);
IR (KBr) nmax 3455, 3059, 2942, 1743, 1615, 1484, 1465, 1450, 1437,
1402,1363,1322,1245,1220,1202,1148,1076.1061,1026,1008, 979,
877, 811, 803, 763, 706, 689, 622, 599, 550 cmꢁ1; HRMS (þve ESI) m/
4.5.2. 5,7-Diacetoxy-3-hydroxyflavone (3b). Epoxide 2b (0.510 g,
1.44 mmol) (method A) gave 3b (0.450 g, 88%) as a yellow solid
after recrystallisation from rectified spirit; mp 109e111 ꢀC; 1H
NMR (500 MHz, CDCl3) dH 2.36 (s, 3H, CH3COO), 2.47 (s, 3H,
CH3COO), 6.87 (d, J¼2.0 Hz, 1H, H-6), 7.06 (s, 1H, OH), 7.38 (d,
J¼2.0 Hz, 1H, H-8), 7.47 (dm, J¼7.5 Hz, 1H, H-40), 7.52 (dm, J¼7.5 Hz,
2H, H-30, 50), 8.19 (dd, J¼1.5, 7.5 Hz, 2H, H-20, 60); 13C NMR
(125 MHz, CDCl3) dC 21.1 (q, CH3COO), 21.3 (q, CH3COO), 109.1 (d, C-
8), 112.2 (s, C-4a), 113.1 (d, C-6), 127.7 (2ꢃd, C-20, 60), 128.7 (2ꢃd, C-
30, 50), 130.6 (s, C-10), 130.7 (d, C-40), 138.7 (s, C-3), 144.4 (s, C-2),
149.9 (s, C-5), 154.1 (s, C-7), 156.7 (s, C-8a), 168.1 (s, CH3COO), 169.5
(s, CH3COO), 171.5 (s, C-4); IR (Nujol) nmax 3310, 1772, 1629, 1614,
z
389.1004/411.0825 [MþH]þ/[MþNa]þ (calcd for C23H17O6/
C23H16NaO6 389.1020/411.0839). Anal. Calcd for C23H16O6: C, 71.1;
H, 4.2. Found: C, 71.0; H, 4.1%.
1410, 1226, 1214, 1186, 1148, 1123, 1073, 1022, 774, 693 cmꢁ1
;
HRMS (þve ESI) m/z 355.0807 [MþH]þ (calcd for C19H15O7
355.0812).Anal. Calcd for C19H14O7: C, 64.4; H, 4.0. Found: C, 64.2;
H, 4.0%.
4.5.6. 3-Hydroxy-7-acetoxy-5-methoxyflavone (3f). Crude epoxide
derived from (1f) (0.305 g, 0.982 mmol) (method B) gave 3f
(0.201 g) as pale yellow crystals, after recrystallisation from iso-
propyl alcohol. Chromatography of the mother liquors on silica gel
(10 g, CHCl3 elution) gave a further portion (0.029 g, overall yield
72%); mp 165e167 ꢀC; 1H NMR (500 MHz, CDCl3) dH 2.35 (s, 3H,
CH3COO), 4.00 (s, 3H, OCH3), 6.55 (d, 1H, J¼2.0 Hz, H-6), 7.00
(d, J¼2.0 Hz, 1H, H-8), 8.20 (dm, J¼7.5 Hz, 2H, H-20, 60), 7.51 (ddm,
J¼7.5, 7.5 Hz, 2H, H-30, 50), 7.45 (ddm, J¼7.5, 7.5 Hz, 1H, H-40); 13C
NMR (125 MHz, CDCl3) dC 21.3 (q, CH3CO), 56.7 (q, OCH3), 100.2
(d, C-6), 103.3 (d, C-8), 109.5 (s, C-4a), 127.4 (2ꢃd, C-20, 60), 128.6
(2ꢃd, C-30, 50), 130.0 (d, C-40), 130.8 (s, C-10), 138.7 (s, C-3), 142.8 (s,
C-2), 155.0 (s, C-7), 157.6 (s, C-8a), 160.6 (s, C-5), 168.4 (s, CH3COO),
172.3 (s, C-4); IR (KBr) nmax 3195, 2944, 1760, 1649, 1626, 1574, 1481,
1460,1442,1405,1366,1225,1146,1130,1099,1075,1033,1005, 983,
899, 878, 825, 771, 707, 689 cmꢁ1; HRMS (þve ESI) m/z 349.0673
4.5.3. 5,7-Dibenzoyloxy-3-hydroxyflavone
(3c). Epoxide
2c
(0.060 g, 0.125 mmol) (method A) gave 3c (0.055 g, 89%) as
a yellow solid after recrystallisation from rectified spirit; mp
212e213 ꢀC; 1H NMR (500 MHz, CDCl3) dH 7.03 (br s, 1H, OH), 7.16
(d, J¼2.0 Hz, 1H, H-6), 7.48 (dd, J¼7.0, 7.0 Hz, 1H, H-40), 7.53 (dd,
J¼7.0, 7.0 Hz, 2H, H-30, 50), 7.56 (m, 2H, H-300, 500), 7.58 (d, J¼2.0 Hz,
1H, H-8), 7.58 (m, 2H, H-3000, 5000), 7.67 (dd, J¼7.5, 7.5 Hz, 1H, H-4000),
7.69 (dd, J¼7.5, 7.5 Hz, 1H, H-400), 8.21 (d, J¼7.0 Hz, 2H, H-20, 60),
8.22 (d, J¼7.5 Hz, 2H, H-200, 600), 8.30 (d, J¼7.5 Hz, 1H, H-2000, 6000);
13C NMR (125 MHz, CDCl3) dC 109.4 (d, C-8), 112.5 (s, C-4a), 113.6
(d, C-6), 127.7 (2ꢃd, C-20, 60), 128.6 (s, C-100), 128.7 (2ꢃd, C-30, 50),
128.8 (d, C-300, 500), 128.9 (2ꢃd, C-3000, 5000), 129.4 (s, C-1000), 130.4 (d,
C-40), 130.5 (2ꢃd, C-200, 600), 130.5 (d, C-2000, 6000), 130.6 (s, C-10),