526 Letters in Drug Design & Discovery, 2011, Vol. 8, No. 6
Lim et al.
room temperature. The mixture was then acidified with
10% HCl and extracted with AcOEt (3 ꢀ 40 mL). The
combined organic layers were dried over Na2SO4. After
removal of the solvent under reduced pressure, purification
of the crude product using silica gel column eluted with a
mixture of hexane-ethyl acetate in increasing polarity, fol-
lowed by Sephadex LH-20 column eluted with methanol
yielded successively 2-9.
1,6,8-Trihydroxy-2,2,4,5-tetrakis(3-methylbut-2-enyl)-2H-
xanthene-3,9-dione (4)
2% (35.5 mg) as yellow crystals, mp 182-185 oC; UV ꢃmax
nm (EtOH) (log ꢄ): 204, 218, 266, 351; IR ꢅmax (KBr) cm-1
:
3415, 3035, 2972, 2914, 1672, 1614, 1550, 1455, 1413, 1293,
1
1132, 1194, 1172, 1110, 858, 784, 728; H NMR (500 MHz,
acetone-d6): 12.37 (1H, s, 1-OH), 11.49 (1H, s, 8- OH ), 6.51
(1H, s, H-7), 5.23 (1H, t, J = 6.7 Hz, H-22), 5.12 (1H, t, J =
6.5 Hz, H-17), 4.82 (2H, t, J = 7.6 Hz, H-12 & H-12’), 3.57
(2H, d, J = 6.7 Hz, H-21), 3.06 (2H, d, J = 6.5 Hz, H-16), 2.89
(2H, dd, J = 13.6, 7.6 Hz, H-11 & H-11’), 2.79 (2H, dd, J =
13.6, 7.6 Hz, H-11 & H-11’), 1.86 (3H, s, H-24), 1.74 (3H, s,
H-19), 1.74 (3H, s, H-25), 1.66 (3H, s, H-20), 1.51 (6H, s, H-
14 & H-14’), 1.48 (6H, s, H-15 & H-15’); 13C NMR (125
MHz, acetone-d6): 194.0 (C-3), 181.5 (C-9), 174.4 (C-1),
163.9 (C-6), 163.6 (C-4a), 160.1 (C-8), 154.4 (C-10a), 135.0
(C-13 & C-13’), 131.7 (C-23), 130.3 (C-18), 122.4 (C-17),
122.2 (C-22), 117.4 (C-12 & C-12’), 113.8 (C-4), 108.2 (C-
9a), 107.5 (C-5), 103.0 (C-8a), 100.0 (C-7), 57.1 (C-2), 38.7
(C-11 & C-11’), 25.0 (C-20), 24.9 (C-15, C-15' & C-25), 21.3
(C-21), 20.4 (C-16), 17.3 (C-24), 17.0 (C-14, C-14’ & C-19);
EIMS m/z (rel. int.): 532 ([M]+. 7), 463 (61), 407 (100), 393
(15), 365 (13), 353 (18), 69 (15); EIHRMS: 532.2825 ([M]+.,
C33H40O6+.; calcd 532.2825).
1,8-Dihydroxy-2,2,4,5,7,7-hexakis(3-methylbut-2-enyl)-
2H-xanthene-3,6,9 (7H)-trione (2)
2% (43.2 mg) as a yellow liquid, UV ꢃmax nm (EtOH)
(log ꢄ): 209, 235, 245, 274; IR ꢅmax (KBr) cm-1 : 3436,
2973, 2927, 2856, 1638, 1438, 1381, 1278, 1174, 818, 776;
1H NMR (400 MHz, CDCl3): 11.73 (2H, s, 1- OH & 8- OH
), 5.01 (2H, t, J = 6.7 Hz, H-17 & H-22), 4.72 (4H, t, J =
7.3 Hz, H-12, H-12’, H-27 & H-27’), 3.01 (4H, d, J = 6.7
Hz, H-16 & H-21), 2.94 (4H, dd, J = 14.0, 7.3 Hz, H-11,
H-11’, H-26 & H-26’), 2.68 (4H, dd, J = 14.0, 7.3 Hz, H-
11, H-11’, H-26 & H-26’), 1.69 (6H, s, C-19 & C-24), 1.60
(6H, s, H-20 & H-25), 1.50 (12H, s, H-14, H-14’, H-29 &
H-29’), 1.49 (12H, s, H-15, H-15’, H-30 & H-30’); 13C
NMR (100 MHz, CDCl3): 193.8 (C-3 & C-6), 179.7 (C-9),
173.8 (C-1 & C-8), 161.5 (C-4a & C-10a), 135.7 (C-13, C-
13’, C-28 & C-28’), 130.9 (C-18 & C-23), 121.8 (C-17 &
C-22), 116.9 (C-12, C-12’, C-27 & C-27’), 115.7 (C-4 &
C-5), 114.1 (C-8a & C-9a), 55.6 (C-2 & C-7), 38.5 (C-11,
C11’, C-26 & C-26’), 25.2 (C-20 & C-25), 25.0 (C-15, C-
15’, C-30 & C-30’), 20.6 (C-16 & C-21), 17.3 (C-14, C-
14’, C-29 & C-29’), 17.1 (C-19 & C-24); EIMS m/z (rel.
int.): 668 ([M]+. 5), 599 (31), 531 (85), 475 (88), 419 (82),
363 (33), 149 (35), 69 (100); EIHRMS: 668.4054 ([M]+.,
C43H56O6+.; calcd 668.4077).
1,3,6,8-Tetrahydroxy-2,4,7-tris(3-methylbut-2-enyl)-9H-
xanthen-9-one (5)
3% (50.9 mg) as yellow crystals, mp 179-181 oC; UV ꢃmax
nm (EtOH) (log ꢄ): 216, 237, 261, 297, 341; IR ꢅmax (KBr) cm-
1
: 3474, 3414, 2966, 2913, 1618, 1437, 1317, 1275, 1236,
1176, 1120, 1099, 812, 787; 1H NMR (500 MHz, acetone-d6):
12.34 (1H, s, 1-OH), 12.33 (1H, s, 8- OH ), 6.54 (1H, s, H-5),
5.28 (1H, t, J = 7.2 Hz, H-22), 5.22 (1H, t, J = 7.1 Hz, H-12),
5.21 (1H, t, J = 7.3 Hz, H-17), 3.53 (2H, d, J = 7.2 Hz, H-21),
3.43 (2H, d, J = 7.3 Hz, H-16), 3.36 (2H, d, J = 7.1 Hz, H-11),
1.86 (3H, s, H-24), 1.79 (6H, s, H-14 & H-19), 1.66 (3H, s, H-
20), 1.65 (6H, s, H-15 & H-25); 13C NMR (125 MHz, acetone-
d6 ): 183.5 (C-9), 163.2 (C-6), 160.4 (C-3), 159.8 (C-8), 157.7
(C-1), 155.6 (C-10a), 152.7 (C-4a), 131.7 (C-13), 131.5 (C-
18), 130.8 (C-23), 122.3 (C-22), 122.0 (C-12 & C-17), 110.8
(C-7), 110.5 (C-2), 106.3 (C-4), 101.3 (C-8a), 100.9 (C-9a),
93.5 (C-5), 25.0 (C-15, C-20 & C-25), 21.6 (C-21), 21.2 (C-
11), 21.0 (C-16), 17.2 (C-24), 17.1 (C-14), 17.0 (C-19); EIMS
m/z (rel. int.): 464 ([M]+. 100), 421 (28), 409 (91), 393 (73),
365 (62), 353 (71), 337 (41), 309 (57), 297 (72), 69 (16), 43
(24); EIHRMS: 464.2200 ([M]+., C28H32O6+.; calcd 464.2199).
1,6,8-Trihydroxy-2,2,4,5,7-pentakis(3-methylbut-2-enyl)-
2H-xanthene-3,9-dione (3)
1% (18.8 mg) as a yellow liquid, UV ꢃmax nm (EtOH)
(log ꢄ): 209, 229, 262, 353; IR ꢅmax (KBr) cm-1 : 3608,
3524, 3412, 3004, 2967, 2924, 1722, 1421, 1367, 1220,
1
1092, 902, 785; H NMR (400 MHz, acetone-d6): 12.35
(1H, s, 1-OH), 11.80 (1H, s, 8-OH ), 5.19 (1H, t, J = 7.0
Hz, H-27), 5.11 (1H, t, J = 6.2 Hz, H-22), 5.07 (1H, t, J =
7.0 Hz, H-17), 4.76 (2H, t, J = 7.4 Hz, H-12 & H-12’),
3.61 (2H, d, J = 6.2 Hz, H-21), 3.44 (2H, d, J = 7.0 Hz, H-
26), 3.01 (2H, d, J = 7.0 Hz, H-16), 2.82 (2H, dd, J = 13.6,
7.4 Hz, H-11 & H-11’), 2.72 (2H, dd, J = 13.6, 7.4 Hz, H-
11 & H-11’), 1.82 (3H, s, H-24), 1.76 (3H, s, H-29), 1.70
(3H, s, H-19), 1.64 (6H, s, H-25 & H-30), 1.61 (3H, s, H-
20), 1.45 (6H, s, H-14 & H-14’), 1.42 (6H, s, H-15 & H-
15’); 13C NMR (100 MHz, acetone-d6): 194.2 (C-3), 181.7
(C-9), 174.4 (C-1), 163.7 (C-4a), 161.0 (C-6), 157.0 (C-8),
152.5 (C-10a), 135.1 (C-13 & C-13’), 132.4 (C-23), 132.3
(C-28), 130.5 (C-18), 122.4 (C-17), 122.2 (C-22), 121.3
(C-27), 117.5 (C-12 & C-12’), 113.8 (C-4), 113.3 (C-7),
108.3 (C-9a), 107.3 (C-5), 101.9 (C-8a), 57.1 (C-2), 38.8
(C-11 & C11’), 25.1 (C-25 & 30), 25.0 (C-15 & C-15’),
24.9 (C-20), 21.7 (C-26), 21.5 (C-21), 20.5 (C-16), 15.5
(C-29), 17.2 (C-24), 17.1 (C-19), 17.0 (C-14 & C-14’);
EIMS m/z (rel. int.): 600 ([M]+. 15), 531 (100), 475 (72),
419 (76), 363 (29), 309 (23), 69 (38), 43 (21); EIHRMS:
600.3440 ([M]+., C38H48O6+.; calcd 600.3451).
1,3,6,8-Tetrahydroxy-2,4,5-tris(3-methylbut-2-enyl)-9H-
xanthen-9-one (6)
4% (65.5 mg) as yellow crystals, mp 179-181 oC; UV ꢃmax
nm (EtOH) (log ꢄ): 216, 237, 261, 341; IR ꢅmax (KBr) cm-1
:
3420, 2966, 2921, 1618, 1466, 1313, 1232, 1170, 1085, 815,
1
753; H NMR (500 MHz, acetone-d6): 12.34 (1H, s, 1-OH),
12.01 (1H, s, 8- OH ), 6.32 (1H, s, H-7), 5.28 (1H, t, J = 7.2
Hz, H-22), 5.22 (2H, t, J = 7.1 Hz, H-12 & H-17), 3.59 (2H, d,
J = 6.7 Hz, H-21), 3.49 (2H, d, J = 6.9 Hz, H-16), 3.43 (2H, d,
J = 6.9 Hz, H-11), 1.79 (9H, s, H-14, H-19 & H-24), 1.68 (3H,
s, H-20), 1.66 (6H, s, H-15 & H-25); 13C NMR (125 MHz,
acetone-d6): 183.7 (C-9), 163.0 (C-8), 160.7 (C-6), 160.6 (C-
3), 157.7 (C-1), 154.8 (C-10a), 152.8 (C-4a), 131.9 (C-13),
131.7 (C-18), 131.1 (C-23), 122.6 (C-12 & C-17), 122.0 (C-