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G. Zhou et al. / Tetrahedron: Asymmetry 11 (2000) 1819±1826
(72), 121 (69), 107 (50), 95 (24), 43(100); IR: 3410, 2940, 1595, 1458, 1375, 1105, 1046 cm^1. Anal.
calcd for C15H26O3: C, 70.87; H, 10.24. Found: C, 70.40; H, 10.50.
16
D
1
Compound 12 (30% de): ꢀ +4.2 (c 2.4, CHCl3); H NMR (400 MHz, CDCl3): ꢁ (ppm) 1.02
(s, 3H, 10-Me), 1.09 (s, 3H, 11-Me), 1.28 (s, 3H, 4-Me), 3.43 and 3.53 (dd, 2H, J=11.06 Hz, 12-H);
EIMS m/z (%): 254 (M+, 1), 239 (2), 223 (10), 205 (29), 187 (35), 178 (17), 161 (67), 147 (42), 121
(29), 43 (100); IR: 3385, 2934, 1594, 1460, 1377, 1107, 1030 cm^1. Anal. calcd for C15H26O3: C,
70.87; H, 10.24. Found: C, 70.39; H, 10.34.
3.5. (^)-[11S]-4b,5b-Epoxyeudesm-11S,12-isopropylidene ketal 13
The diol 10 (80 mg) in acetone (3 mL) was treated with p-toluenesulfonic acid (cat.) for 10 min
at room temperature. The reaction mixture was diluted with ethyl acetate (20 mL), and the
organic layer was washed successively with aq. Na2CO3 (2Â10 mL), water (2Â10 mL), brine
(2Â10 mL), and dried over MgSO4. Evaporation of the solvent and separation on silica gel gave
the acetonide 13 of 10 as colorless oil (54 mg, 58%) and acetonide of 12 (20 mg, 21%). Com-
pound 13: 1H NMR (400 MHz, CDCl3): ꢁ (ppm) 1.05 (s, 3H, 10-Me), 1.25 (s, 3H, 11-Me), 1.34 (s,
3H, 4-Me), 1.38 (s, 3H, acetonide), 1.42 (s, 3H, acetonide), 3.67 and 3.82 (dd, 2H, J=8.5 Hz, 12-H);
EIMS m/z (%): 294 (M+, 2), 279 (10), 261 (3), 236 (45), 219 (13), 201 (54), 187 (6), 115 (100), 95
(10), 55 (48), 43 (25); IR: 2990, 2929, 2880, 1467, 1376, 887 cm^1.
3.6. (^)-[11S]-5b-Hydroxyeudesm-4(14)-en-11S,12-isopropylidene ketal 14
To a freshly prepared solution of LDA (0.17 M in THF, 5 mL) was added a solution of 13 (50
mg) in dry THF (4 mL) under argon. The reaction mixture was stirred at room temperature for
24 h. Then some water was added to the reaction mixture at 0ꢀC, and stirring was continued for
additional 10 min. The organic layer was separated and aqueous layer was extracted with ether
(2Â20 mL). The combined organic fractions were washed with H2O (2Â10 mL), brine (2Â10
mL), and dried (MgSO4). After removal of the solvents, the crude products were chromato-
graphed on silica gel eluting with petroleum ether:ether (6:1) to yield 14 (42 mg, 84%) as colorless
20
oil. Compound 14: ꢀ ^27.3 (c 0.55, CHCl3); 1H NMR (400 MHz, CDCl3): ꢁ (ppm) 1.06 (s, 3H,
D
10-Me), 1.30 (s, 3H, 11-Me), 1.40 (s, 3H, acetonide), 1.44 (s, 3H, acetonide), 3.70 and 3.95 (dd, 2H,
J=8.3 Hz, 12-H), 4.96 (br s, 2H, 14-H); EIMS m/z (%): 294 (M+, 7), 279 (23), 276 (14), 236 (20),
201 (55), 187 (60), 137 (20), 115 (100), 43 (35); IR: 3485, 3085, 2982, 2928, 2871, 1637, 1377, 1209,
1067, 1039, 895 cm^1. Anal. calcd for C18H30O3: C, 73.47; H, 10.20. Found: C, 73.22; H, 10.79.
3.7. (^)-[11S]-Eudesm-4(14)-en-5b,11S,12-triol 3b
Some drops of aqueous HCl (1N, 0.5 mL) were added dropwise to a solution of 14 (20 mg) in
THF (5 mL), and the mixture was re¯uxed for 3 h. After cooling, the reaction mixture was diluted
with ethyl acetate (20 mL). The organic layer was washed with 10% aq. Na2CO3 (2Â10 mL),
H2O (2Â10 mL), brine (2Â10 mL), and dried over MgSO4. Evaporation of the solvents aorded
the crude products which were chromatographed on silica gel to yield 3b (15 mg, 90%) as color-
11
1
less oil: ꢀ ^42.3 (c 0.36, CHCl3); H NMR (400 MHz, CDCl3): ꢁ (ppm) 1.02 (s, 3H, 10-Me),
D
1.13 (s, 3H, 11-Me), 3.44 and 3.63 (dd, 2H, AB, J=10.8 Hz, 12-H), 4.94 (brs, 1H, 14-H), 5.07
(brs, 1H, 14-H); EIMS m/z (%): 254 (M+, 3), 239 (3), 236 (5), 222 (2), 205 (15), 187 (12), 161 (56),
147 (27), 43 (100); IR: 3400, 2932, 2869, 1641, 1449, 1378, 1281, 1028 cm^1.