A. Abad et al. / Tetrahedron 62 (2006) 3266–3283
3281
from 4:1 to 2:3, afforded atisenediol 34 (13.2 mg, 66%) as
an amorphous solid. [a]2D9 K20 (0.1, CHCl3); IR nmax/cmK1
(KBr) 3409s, 2915s, 2847m, 2353m, 2336m, 1636m,
1456m, 1112m, 1052m, 910w; 1H NMR (400 MHz) d
6.18 (1H, dd, JZ7.0, 8.0 Hz, H-13) 5.77 (1H, dd, JZ8.0,
1.0 Hz, H-14), 3.15 (1H, s, H-15), 2.37 (1H, ddd, JZ3.0,
3.0, 7.0 Hz, H-12), 2.24 (1H, ddd, JZ13.0, 3.0, 3.0 Hz, H-
7a), 2.00 (1H, ddd, JZ13.0, 9.0, 3.0 Hz, H-11b), 1.96 (1H,
m, H-7b), 1.62 (1H, m, H-6), 1.47 (1H, m, H-2), 1.43 (1H,
m, H-1) 1.39 (1H, m, 0H-3), 1.35 (1H, m, H0-2), 1.34 (1H, m,
H-9), 1.32 (1H, m, H -6), 1.26 (1H, m, H-7a), 1.14 (1H, m,
H0-3), 1.13 (3H, s, Me-C16), 0.95 (1H, ddd, JZ13.0, 7.0,
3.0 Hz, H-11a), 0.90 (1H, m, H0-1), 0.88 (3H, s, Meb-C4),
0.84 (1H, m, H-5), 0.80 (3H, s, Mea-C4), 0.61 (3H, d, JZ
0.8 Hz, Me-C10); 13C NMR (75 MHz), see Table 2; MS (EI)
m/z (%) 304 (MC, 1), 286 (MCKH2O, 7), 230 (44), 145
(28), 131 (100), 119 (67), 106 (23), 100 (20), 91 (32);
HRMS m/z calcd for C20H32O2 304.2402, found 304.2405.
m, H-3a), 1.00 (3H, s, Me-C10), 0.99 (1H, m, H-12), 0.86
(1H, m, H-1b), 0.83 (3H, s, Meb-C4), 0.785 (3H, s, Mea-
C4), 0.71 (1H, m, H-5); 13C NMR (75 MHz), see Table 2;
MS (EI) m/z (%) 332 (MC, 0.2), 314 (MCKH2O, 9), 286
(48), 257 (34), 230 (44), 137 (57), 131 (35), 131 (35), 105
(68), 100 (20), 91 (81); HRMS m/z calcd for C21H32O3
332.2351, found 332.2451.
4.4.11. 14a-Formyloxy-ent-trachyloban-15-one (38). Py-
ridine (30 mL, 0.37 mmol) was added to a solution of
alcohol 37 (39.2 mg, 0.12 mmol) in CH2Cl2 (3 mL),
followed by Dess–Martin periodinate reagent (78 mg,
0.18 mmol) in one portion. The resulting reaction mixture
was stirred at rt for 2 h before being quenched with saturated
aq NaHCO3 solution. The reaction mixture was extracted
with CH2Cl2, dried over MgSO4, and concentrated under
vacuum. The crude product was purified by chromatog-
raphy, using hexane/AcOEt 8:2 as eluent, to afford ketone
38 (33.6 mg, 86% yield) as an oil. [a]2D9 K4 (1.5, CHCl3);
IR nmax/cmK1 (NaCl) 2923m, 2858s, 1716s, 1465m, 1388m,
1164s, 984w; 1H NMR (400 MHz) d 8.19 (1H, d, JZ0.8 Hz,
OCHO), 5.19 (1H, d, JZ3.5 Hz, H-14), 2.17 (1H, m, H-7),
2.15 (1H, m, H-12), 1.94 (2H, m, H2-11), 1.91 (1H, m, H-
13), 1.54 (1H, m, H-2), 1.37 (1H, m, H0-2), 1.49 (1H, m, H-
9), 1.47 (1H, m, H-1), 1.39 (1H, m, H-7), 1.35 (1H, m, H-3),
1.26 (3H, s, Me-C13), 1.23 (1H, m, H-6), 1.12 (1H, m, H0-6),
1.10 (1H, m, H0-3), 0.98 (3H, s, Me-C10), 0.84 (3H, s, Meb-
C4), 0.79 (3H, s, Mea-C4) 0.79 (1H, m, H0-1), 0.72 (1H, dd,
JZ12.2, 2.1 Hz, H-5); 13C NMR (75 MHz), see Table 2;
MS (EI) m/z (%) 330 (MC, 2.4), 315 (2), 284 (15), 269 (7),
178 (12), 161 (7), 137 (11), 123 (13), 86 (62), 84 (100);
HRMS m/z calcd for C21H30O3 330.2194, found 330.2191.
4.4.9. 14a-Hydroxy-ent-beyeran-15-one (36). A solution
of cyclopropyl-ketone 26a (29.0 mg, 0.095 mmol) in THF
(1 mL) was added dropwise to a solution of lithium (5 mg,
0.83 mmol) in liquid ammonia (1 mL) and THF (0.5 mL) at
K78 8C. After stirring for 10–15 min, isoprene was added
dropwise until disappearance of the blue colour. The
ammonia was allowed to evaporate, saturated aq NH4Cl
solution was added and the mixture was extracted with
EtOAc. The combined organic layers were washed with
water and brine and dried over Na2SO4. Evaporation of the
solvent and chromatography of the residue, using hexane/
AcOEt 8:2 as eluent, afforded hydroxy-beyeranone 36
(24.9 mg, 85%) as a solid. Mp 165–166 8C (from pentane);
[a]2D9 C42 (1.6, CHCl3); IR nmax/cmK1 (KBr) 3440m,
1
2949s, 2864m, 1713s, 1460m, 1150m, 1108m, 1038m; H
4.4.12. 14a-Hydroxy-ent-trachyloban-15-one (39). A
solution of formate ester 38 (35 mg, 0.11 mmol) and
Na2CO3 (50 mg, 0.46 mmol) in MeOH (1 mL) was stirred
at rt for 1 h. After addition of H2O, the solution was
extracted with AcOEt. The organic layers were washed with
H2O, then brine and dried. Evaporation of the solvent and
purification by chromatography, using hexane/AcOEt 7:3 as
eluent, gave alcohol 39 (29 mg, 90%) as a white foam solid.
[a]2D9 K19 (1.5, CHCl3); IR nmax/cmK1 (KBr) 3420m,
2912s, 2874m, 1694s, 1448m, 1388m, 1099s; 1H NMR
(400 MHz) d 4.09 (1H, m, H-14), 2.15 (1H, ddd, JZ14.3,
14.3, 5.9 Hz, H-7b), 2.02 (1H, dd, JZ7.2, 3.8 Hz, H-13),
1.93 (3H, m, H-12 and H2-11), 1.51 (2H, m, H-6 and H-2),
1.42 (2H, m, H-1 and H-9), 1.32 (3H, m, H0-7, H0-6 and
H0-2), 1.30 (1H, m, H-3), 1.24 (3H, s, Me-C16), 1.12 (1H, m,
H0-3), 1.04 (3H, s, Me-C10), 0.84 (3H, s, Meb-C4), 0.80 (1H,
m, H0-1), 0.69 (1H, dd, JZ12.1, 1.3 Hz, H-5), 0.80 (3H, s,
Mea-C4); 13C NMR (75 MHz), see Table 2; MS (EI) m/z
(%) 302 (MC, 65), 287 (25), 269 (16), 165 (50), 137 (10),
123 (68), 105 (40), 84 (100), 69 (82); HRMS m/z calcd for
C20H30O2 302.2246, found 302.2232.
NMR (400 MHz) d 3.17 (1H, s, H-14), 2.20 5 (1H, d, JZ
19.0 Hz, H-16), 1.85 (1H, d, JZ19.0 Hz, H -16), 1.55 (1H,
br s, OH), 1.07 (3H, s, Me-C13), 0.86 (3H, s, Meb-C4), 0.83
(3H, s, Mea-C4), 0.80 (3H, s, Me-C10); 13C NMR (75 MHz),
see Table 2; MS (EI) m/z (%) 305 (MCC1, 25), 304 (MC,
100), 289 (46), 286 (62), 245 (40), 244 (56), 229 (47), 138
(39), 123 (91), 95 (34); HRMS m/z calcd for C20H32O2
304.2402, found 304.2397. Anal. Calcd for C20H32O2: C
78.90, H 10.59; found: C 78.79, H 10.66.
4.4.10. 14a-Formyloxy-ent-trachyloban-15b-ol (37). A
solution of diol 33 (48.1 mg, 0.15 mmol) in buffered formic
acid (4.5 mL of a solution of 50 mg of anhydrous Na2CO3 in
10 mL of formic acid) and THF (1.5 mL) was stirred at 5 8C
for 14 h. The mixture was diluted with cold ether and
washed with saturated aq NaHCO3 solution until basic, then
with water until neutral and then with brine. The organic
layer was dried over MgSO4 and concentrated under
reduced pressure to yield an oily residue, which was
purified by chromatography, using hexane/Et2O 1:1 as
eluent, to afford formate 37 (41.3 mg, 80%) as a colourless
oil. [a]2D9 K12 (0.5, CHCl3); IR nmax/cmK1 (film) 3414m,
2923s, 2859m, 1716s, 1463m, 1439m, 1166s, 1092m, 983w,
745m; 1H NMR (400 MHz) d 8.17 (1H, d, JZ0.8 Hz,
OCHO), 4.92 (1H, d, JZ3.5 Hz, H-14), 3.44 (1H, s, H-15),
1.76–1.95 (2H, m, H2-11), 1.72 (1H, m, H-9), 1.56 (1H, m,
H-2a), 1.53 (1H, m, H-1a), 1.44 (1H, m, H-6b), 1.38 (1H,
m, H-2b), 1.37 (1H, m, H-3b), 1.30 (1H, dd, JZ3.5, 7.5 Hz,
H-13), 1.20 (3H, s, Me-C16), 1.20 (1H, m, H-6a), 1.14 (1H,
4.4.13. 14a-Hydroxy-ent-kauran-15-one (40). A solution
of cyclopropyl-ketone 39 (22.8 mg, 0.075 mmol) in THF
(0.5 mL) was added dropwise to a solution of lithium (5 mg,
0.71 mmol) in liquid ammonia (1 mL) and THF (0.5 mL) at
K78 8C. After stirring for 15–20 min, the reaction mixture
was worked-up as described above for the preparation of 36.
The crude product was purified by chromatography, using
hexane/AcOEt 9:1 as eluent, to obtain kauranone 40 (19.6 mg,