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tone-d6, 400 MHz, d): 1.61 (s, 3H), 1.69 (s, 3H), 3.13 (d, 2H,
J = 7.2 Hz), 5.15 (m, 1H), 6.02 (s, 1H), 7.42 (d, 2H, J = 8.0 Hz), 7.67
(d, 2H, J = 8.0 Hz), 7.69 (d, 1H, J = 16.0 Hz), 8.19 (d, 1H,
J = 16.0 Hz), 9.16 (s, 1H, OH), 9.74 (s, 1H, OH), 14.16 (s, 1H, OH).
ESI-MS: m/z [M+H]+ 359. Anal. Calcd for C20H19ClO4: C, 66.95; H,
5.34. Found: C, 66.61; H, 5.68.
tone-d6, 400 MHz, d): 1.55 (s, 6H), 2.72 (dd, 1H, J = 3.2, 16.8 Hz),
3.12 (dd, 1H, J = 12.8, 16.8 Hz), 3.18 (d, 2H, J = 7.2 Hz), 5.16 (m,
1H), 5.45 (dd, 1H, J = 3.2, 12.8 Hz), 6.02 (s, 1H), 6.82 (dd, J = 2.0,
8.0 Hz), 6.98 (d, 1H, J = 8.0 Hz), 7.03 (d, 1H, J = 2.0 Hz), 7.22 (t, 1H,
J = 8.0 Hz), 8.46 (s, 1H, OH), 9.54 (s, 1H, OH), 12.10 (s, 1H, OH).
ESI-MS: m/z [M+H]+ 341. Anal. Calcd for C20H20O5: C, 70.57; H,
5.92. Found: C, 70.35; H, 5.79.
5.4.4. ( )Galabranin (4)
Reagent: compound 16a (200 mg, 0.49 mmol). White amor-
phous powder (102.2 mg, 65%), mp: 147–148 °C. 1H NMR (ace-
tone-d6, 400 MHz, d): 1.56 (s, 6H), 2.78 (dd, 1H, J = 3.6, 16.8 Hz),
3.09 (dd, 1H, J = 12.4, 16.8 Hz), 3.19 (d, 2H, J = 6.8 Hz), 5.15 (m,
1H), 5.53 (dd, 1H, J = 3.6, 12.4 Hz), 5.99 (s, 1H), 7.35 (m, 1H), 7.41
(t, 2H, J = 7.6 Hz), 7.54 (d, 1H, J = 7.6 Hz), 9.57 (s, 1H), 12.08 (s,
1H). ESI-MS: m/z [M+H]+ 325. Anal. Calcd for C20H20O4: C, 74.06;
H, 6.21. Found: C, 74.36; H, 6.43.
5.5. General method for synthesis of compounds 8–11
A stirred solution of corresponding prenylflavanone and iodine
in dry pyridine (4 mL) was heated to 90 °C for 6 h. The mixture was
cooled and poured into cold water. The precipitate was separated
and the mixture was extracted with ethyl acetate. The combined
organic phase was washed with saturated sodium thiosulfate and
water, successively. Then the organic layer was dried with sodium
sulfate and concentrated. The residue was purified by silica gel col-
umn chromatography using petroleum ether/ethyl acetate (2:1) to
afford 8–11.
5.4.5. ( )5,7-Dihydroxy-30,40-methylenedioxy-8-(3,3-dimethylallyl)-
flavanone (5)
Reagent: compound 16b (200 mg, 0.44 mmol). White amor-
phous powder (101.7 mg, 63%), mp: 164–165 °C. 1H NMR (ace-
tone-d6, 400 MHz, d): 1.55 (s, 3H), 1.56 (s, 3H), 2.75 (dd, 1H,
J = 2.8, 17.2 Hz), 3.10 (dd, 1H, J = 12.8, 17.2 Hz), 3.18 (d, 2H,
J = 7.2 Hz), 5.16 (m, 1H), 5.39 (dd, 1H, J = 2.8, 12.8 Hz), 6.00 (s,
1H), 6.03 (s, 2H), 6.84 (d, 1H, J = 8.0 Hz), 6.91 (dd, 1H, J = 2.0,
8.0 Hz), 7.00 (d, 1H, J = 2.0 Hz), 9.56 (s, 1H, OH), 12.08 (s, 1H,
OH). ESI-MS: m/z [M+H]+ 369. Anal. Calcd for C21H20O6: C, 68.47;
H, 5.47. Found: C, 68.31; H, 5.65.
5.5.1. 5,7-Dihydroxy-30-bromo-8-(3,3-dimethylallyl)-flavone (8)
Reagents: compound 6 (40 mg, 0.10 mmol) and iodine (25.2 mg,
0.10 mmol). Light yellow solid (26.3 mg, 66%), mp: 202–203 °C. 1H
NMR (acetone-d6, 400 MHz, d): 1.61 (s, 3H), 1.76 (s, 3H), 3.50 (d,
2H, J = 7.2 Hz), 5.23 (m, 1H), 6.31 (s, 1H), 6.79 (s, 1H), 7.51 (t, 1H,
J = 8.0 Hz), 7.72 (d, 1H, J = 8.0 Hz), 7.82 (d, 1H, J = 8.0 Hz), 8.16 (s,
1H), 9.68 (s, 1H, OH), 13.05 (s, 1H, OH). ESI-MS: m/z [M+H]+ 401.
Anal. Calcd for C20H17BrO4: C, 59.87; H, 4.27. Found: C, 59.68; H,
4.39.
5.4.6. ( )5,7-Dihydroxy-30-bromo-8-(3,3-dimethylallyl)-
flavanone (6)
5.5.2. 5,7,40-Trihydroxy-30-methoxy -8-(3,3-dimethylallyl)-
flavone (9)
Reagent: compound 16c (200 mg, 0.41 mmol). White amor-
phous powder (98.5 mg, 60%), mp: 148–149 °C. 1H NMR (ace-
tone-d6, 400 MHz, d): 1.59 (s, 6H), 2.84 (dd, 1H, J = 3.6, 15.6 Hz),
3.08 (dd, 1H, J = 12.4, 15.6 Hz), 3.21 (d, 2H, J = 6.8 Hz), 5.16 (m,
1H), 5.56 (dd, 1H, J = 3.6, 12.4 Hz), 6.01 (s, 1H), 7.37 (t, 1H,
J = 7.6 Hz), 7.41 (d, 2H, J = 7.6 Hz), 7.75 (s, 1H), 9.60 (s, 1H, OH),
12.04 (s, 1H, OH). ESI-MS: m/z [M+H]+ 403. Anal. Calcd for
Reagents: compound 7 (40 mg, 0.11 mmol) and iodine (27.5 mg,
0.11 mmol). Light yellow solid (22.3 mg, 56%), mp: 196–198 °C. 1H
NMR (acetone-d6, 400 MHz, d): 1.61 (s, 3H), 1.76 (s, 3H), 3.52 (d,
2H, J = 6.8 Hz), 3.94 (s, 3H), 5.28 (m, 1H), 6.31 (s, 1H), 6.64 (s,
1H), 6.98 (dd, 1H, J = 1.6, 7.6 Hz), 7.55 (dd, 1H, J = 1.6, 7.6 Hz),
7.58 (d, 1H, J = 1.6 Hz), 8.41 (s, 1H, OH), 9.53 (s, 1H, OH), 12.92
(s, 1H, OH). ESI-MS: m/z [M+H]+ 369. Anal. Calcd for C21H20O6: C,
68.47; H, 5.47. Found: C, 68.18; H, 5.29.
C20H19BrO4: C, 59.57; H, 4.75. Found: C, 59.88; H, 4.65.
5.4.7. ( )Exiguaflavanone K (7)
Reagent: compound 16d (200 mg, 0.40 mmol); White amor-
phous powder (66.3 mg, 45%), mp: 138–139 °C. 1H NMR (ace-
tone-d6, 400 MHz, d): 1.56 (s, 6H), 2.72 (dd, 1H, J = 3.6, 17.2 Hz),
3.11 (dd, 1H, J = 12.8, 17.2 Hz), 3.18 (d, 2H, J = 7.2 Hz), 3.84 (s,
3H), 5.16 (m, 1H), 5.39 (dd, 1H, J = 3.6, 12.8 Hz), 5.98 (s, 1H), 6.83
(d, 1H, J = 8.0 Hz), 6.96 (dd, 1H, J = 1.6, 8.0 Hz), 7.16 (d, 1H,
J = 1.6 Hz), 7.69 (s, 1H, OH), 9.50 (s, 1H, OH), 12.10 (s, 1H, OH).
ESI-MS: m/z [M+H]+ 371. Anal. Calcd for C21H22O6: C, 68.10; H,
5.99. Found: C, 68.18; H, 5.88.
5.5.3. 5,7-Dihydroxy-30,40,50-trimethoxy-8-(3,3-dimethylallyl)-
flavone (10)
Reagents: compound 17e (40 mg, 0.10 mmol) and iodine
(25.2 mg, 0.10 mmol). Light yellow solid (27.9 mg, 70%), mp:
229–230 °C. 1H NMR (acetone-d6, 400 MHz, d): 1.61 (s, 3H), 1.75
(s, 3H), 3.54 (d, 2H, J = 7.2 Hz), 3.79 (s, 3H), 3.92 (s, 6H), 5.32 (m,
1H), 6.31 (s, 1H), 6.76 (s, 1H), 7.34 (s, 2H), 9.56 (s, 1H, OH), 12.81
(s, 1H, OH). ESI-MS: m/z [M+H]+ 413. Anal. Calcd for C23H24O7: C,
66.98; H, 5.87. Found: C, 67.09; H, 5.69.
5.4.8. ( )5,7-Dihydroxy-30,40,50-trimethoxy-8-(3,3-dimethylallyl)-
flavanone (17e)
5.5.4. 5,7-Dihydroxy-30-hydroxy-8-(3,3-dimethylallyl)-flavone (11)
Reagents: compound 17f (40 mg, 0.12 mmol), iodine (29.9 mg,
0.12 mmol). Light yellow solid (25.4 mg, 64%), mp: 228–229 °C.
1H NMR (acetone-d6, 400 MHz, d): 1H NMR (acetone-d6,
400 MHz, d): 1.61 (s, 3H), 1.77 (s, 3H), 3.51 (d, 2H, J = 6.8 Hz),
5.25 (m, 1H), 6.30 (s, 1H), 6.66 (s, 1H), 7.04 (dd, 1H, J = 1.6,
8.0 Hz), 7.38 (t, 1H, J = 8.0 Hz), 7.48 (d, 1H, J = 1.6 Hz), 7.49 (d,
1H, J = 8.0 Hz), 8.82 (s, 1H, OH), 9.60 (s, 1H, OH), 12.80 (s, 1H,
OH). ESI-MS: m/z [M+H]+ 339. Anal. Calcd for C20H18O5: C, 70.99;
H, 5.36. Found: C, 70.18; H, 5.49.
Reagent: compound 16e (200 mg, 0.40 mmol); White amor-
phous powder (85.8 mg, 52%), mp: 215–216 °C. 1H NMR (ace-
tone-d6, 400 MHz, d): 1.57 (s, 3H), 1.59 (s, 3H), 2.77 (dd, 1H,
J = 2.8, 17.2 Hz), 3.10 (dd, 1H, J = 12.8, 17.2 Hz), 3.20 (d, 2H,
J = 7.2 Hz), 3.70 (s, 3H), 3.82 (s, 6H), 5.21 (m, 1H), 5.44 (dd, 1H,
J = 2.8, 12.8 Hz), 6.00 (s, 1H), 6.87 (s, 2H), 9.54 (s, 1H, OH), 12.07
(s, 1H, OH). ESI-MS: m/z [M+H]+ 415. Anal. Calcd for C23H26O7: C,
66.65; H, 6.32. Found: C, 66.81; H, 6.23.
5.4.9. ( )5,7-Dihydroxy-30-hydroxy-8-(3,3-dimethylallyl)-flavanone
(17f)
5.6. Vasodilator effect assay
Reagent: compound 16f (200 mg, 0.43 mmol). White amor-
Vascular rings were prepared from the aorta of male Sprague–
Dawley rats (4 to 6 months old and weighing on average 250 g),
phous powder (69.2 mg, 48%), mp: 175–176 °C. 1H NMR (ace-