J. Poza et al. / Bioorg. Med. Chem. 15 (2007) 4722–4740
4733
(25a, 0.059 g, 0.136 mmol) in dichloromethane (1 mL)
was added in a dropwise fashion. The clear colorless
solution was stirred at ꢀ60 ꢁC for 1.5 h. After the drop-
wise addition of triethylamine (0.130 mL, 0.928 mmol),
the pale yellow reaction mixture was stirred for a further
1.5 h at ꢀ60 ꢁC, warmed to rt, diluted with dichloro-
methane (4 mL), poured into aqueous 1 M HCl
was stirred at ꢀ78 ꢁC for 1 h. The residue was diluted
with water (20 mL) and extracted with CH2Cl2
(50 mL). The organic phase was washed (10% HCl,
10% NaHCO3, brine), dried with anhydrous Na2SO4,
and evaporated under reduced pressure. The residue
was subjected to chromatography (silica gel, hexanes/
ethyl acetate, 8:2) to give 3b,7a-dihydroxycholest-5-ene
(28, 1.82 g, 95%): white solid; [a]D ꢀ130.2 (CH2Cl2,
c = 1.0); 1H NMR (200 MHz, CDCl3) dH: 5.59 (H6,
1H, d, J = 4.9 Hz); 3.84 (H7b, 1H, m); 3.58 (H3a, 1H,
m); 0.99 (H19, 3H, s); 0.92 (H21, 3H, d, J = 6.2 Hz);
0.85 (H26, H27, 6H, d, J = 6.6 Hz); 0.68 (H18, 3H, s).
13C NMR (50 MHz, CDCl3) dC: 146.2 (C5, s); 123.8
(C6, d); 71.3 (C3, d); 65.3 (C7, d); 56.2; 48.6; 42.3;
39.4; 39.2; 37.2; 36.0; 35.8; 35.6; 34.7; 33.3; 31.2; 30.7;
28.0; 27.9; 24.5; 23.7; 22.7; 22.5; 21.4; 20.6; 18.2 (C19,
q); 11.6 (C18, q). LREIMS (70 eV, m/z %): 402 (M+,
4); 385 (M+ꢀOH, 30); 384 (M+ꢀH2O, 13); 368 (M+ꢀ2
OH, 4); 237 (100).
(5 mL),
and
extracted
with
dichloromethane
(2 · 5 mL). The combined organic extracts were washed
with saturated NaHCO3 (20 mL), dried (MgSO4), fil-
tered, and concentrated in vacuo. The residue was puri-
fied by flash chromatography (silica gel, CH2Cl2/MeOH,
from 100:0 to 9:1) to give 6E-hydroximino-4-hydroxy-
cholest-4-en-3-one (26, 12 mg, 20%): white solid; [a]D
1
ꢀ46.9 (CHCl3, c = 0.1); H NMR (500 MHz, CDCl3)
dH: 3.08 (H7b, 1H, dd, J = 18.1, 6.3 Hz); 2.89 (H2,
1H, m); 2.66 (H20, 1H, br d, J = 18.1 Hz); 2.29 (H7a,
1H, dd, J = 18.1, 10.6 Hz); 2.18 (H1, 1H, br d,
J = 13.5 Hz); 1.84 (H10, 1H, td, J = 13.5, 4.5 Hz); 1.32
(H19, 3H, s); 0.96 (H21, 3H, d, J = 6.5 Hz); 0.89 (H26,
H27, 6H, d, J = 6.6 Hz); 0.77 (H18, 3H, s). 13C NMR
(125 MHz, CDCl3) dC: 185.6 (C3, s); 159.9 (C6, s);
156.5 (C4, s); 138.6 (C5, s); 56.8; 56.0; 48.7; 42.8; 39.6;
39.0; 38.3 (C1, t); 36.8 (C2, t); 36.2; 35.8; 33.4; 32.5;
28.1; 28.0; 26.1 (C7, t); 24.5; 23.9; 22.8 (C26, C27, q);
20.8; 19.2 (C19, q); 18.8 (C21, q); 12.1 (C18, q). (+)-
LRFABMS, m/z (%): 452 ([M+Na]+, 3); 434
([MꢀH2O+Na]+, 8), 412 ([MꢀH2O+H]+, 100). (+)-
HRESIMS: m/z 412.3218 [MꢀH2O+H]+ (calcd for
C27H42NO2, 412.3216), m/z 434.3048 [MꢀH2O+Na]+
(calcd for C27H41NO2Na, 434.3035).
4.25. 3b,7a-Diacetoxycholest-5-ene (29)
3b,7a-Dihydroxycholest-5-ene (28, 3 g, 7.4 mmol) was
acetylated in a similar way as compound 15 to give
3b,7a-diacetoxycholest-5-ene (29, 3 g, 99%): white solid;
[a]D ꢀ407.9 (CH2Cl2, c = 0.2); 1H NMR (200 MHz,
CDCl3) dH: 5.58 (H6, 1H, d, J = 4.6 Hz); 4.96 (H7b,
1H, dd, J = 8.7, 4.6 Hz); 4.64 (H3a, 1H, m); 2.35 (H4,
2H, d, J = 7.8 Hz); 2.04 (OAc, 3H, s); 2.02 (OAc, 3H,
s); 1.01 (H19, 3H, s); 0.91 (H21, 3H, d, J = 6.7 Hz);
0.85 (H26, H27, 6H, d, J = 6.2 Hz); 0.66 (H18, 3H, s).
13C NMR (50 MHz, CDCl3) dC: 170.7 (OAc, s); 170.4
(OAc, s); 146.4 (C5, s); 120.8 (C6, d); 73.1 (C3, d);
68.2 (C7, d); 56.2; 55.2; 48.9; 45.5; 42.3; 39.5; 37.4;
36.0; 35.5; 34.3; 33.3; 31.6; 29.7; 29.0; 28.0; 27.9; 24.4;
24.0; 23.7; 22.7; 22.5; 21.4; 20.4; 18.1 (C19, q); 11.4
(C18, q). (+)-LRFABMS, m/z (%): 509 ([M+Na]+, 16);
367 (100).
4.23. 3b-Acetoxycholest-5-en-7-one (27)
tert-Butylhydroperoxide (15.4 mL) was added dropwise
to
a
solution of 3b-acetoxy-5-cholestene (5.5 g,
12.8 mmol) and CuI (0.1 g, 0.5 mmol) in dry benzene
(50 mL). The mixture was heated under reflux for 24 h
and then cooled. The reaction mixture was dropped into
a solution of Na2SO3 (30 mL). The resulting precipitate
was extracted with ether and the organic phase was
washed (10% HCl, 10% NaHCO3, and brine), dried with
anhydrous Na2SO4, and evaporated under reduced pres-
sure. The residue was subjected to chromatography (sil-
ica gel, hexanes/ethyl acetate, 9:1), to give 3b-
acetoxycholest-5-en-7-one (27, 2.1 g, 40%): white solid;
[a]D ꢀ78.1 (CH2Cl2, c = 1.0); 1H NMR (200 MHz,
CDCl3) dH: 5.70 (H6, 1H, s); 4.72 (H3a, 1H, m); 2.53
(H8, 1H, m); 2.06 (OAc, 3H, s); 1.02 (H19, 3H, s);
0.93 (H21, 3H, d, J = 6.3 Hz); 0.87 (H26, H27, 6H, d,
J = 6.6 Hz); 0.67 (H18, 3H, s). 13C NMR (50 MHz,
CDCl3) dC: 210.8 (C7, s); 170.2 (OAc, s); 163.8 (C5, s);
126.6 (C6, d); 72.1 (C3, d); 56.8; 56.0; 50.2; 42.2; 39.6;
39.4; 36.8; 36.2; 35.9; 35.7; 32.0; 31.6; 27.9; 27.7; 25.8;
24.2; 22.7; 22.5; 21.7; 21.3; 20.6; 20.3; 17.2 (C19, q);
11.9 (C18, q). (+)-LRFABMS, m/z (%): 465
([M+Na]+, 5); 399 (100).
4.26. 3b,7a-Diacetoxy-5a,6a-epoxycholestane (30a) and
3b,7a-diacetoxy-5b,6b-epoxycholestane (30b)
3b,7a-Diacetoxycholest-5-ene (29, 2.8 g, 5.7 mmol) was
epoxidized in a similar way as compound 7 to give a res-
idue which was subjected to chromatography (silica gel
hexanes/ethyl acetate, from 9:1 to 8:2) to afford 3b,7a-
diacetoxy-5a,6a-epoxycholestane (30a, 1.65 g) and
3b,7a-diacetoxy-5b,6b-epoxycholestane (30b, 0.82 g) in
a 2:1 ratio with a yield of 85%. Compound 30a: white
solid; [a]D ꢀ109.1 (CH2Cl2, c = 1.0); 1H NMR
(200 MHz, CDCl3) dH: 4.98 (H7b, 1H, d, J = 4.5,
1.8 Hz); 4.89 (H3a, 1H, m); 3.29 (H6b, 1H, d,
J = 4.5 Hz); 2.12 (OAc, 3H, s); 1.98 (OAc, 3H, s); 1.04
(H19, 3H, s); 0.92 (H21, 3H, d, J = 6.9 Hz); 0.86 (H26,
H27, 6H, d, J = 6.4 Hz); 0.59 (H18, 3H, s). 13C NMR
(50 MHz, CDCl3) dC: 170.6 (OAc, s); 170.5 (OAc, s);
71.4 (C7, d); 70.1. (C3, d); 63.3 (C5, s); 62.0 (C6, d);
56.0; 43.4; 42.4; 39.8; 37.8; 37.0; 36.5; 35.4; 34.8; 33.2;
32.5; 32.1; 30.7; 29.4; 28.0; 27.6; 25.4; 23.2; 22.7; 22.3;
21.0; 20.7; 20.5; 18.1 (C19, q); 11.8 (C18, q). LREIMS
(70 eV, m/z %): 502 (M+, 3); 442 (M+ꢀ2 CH3COOH,
10); 382 (100). Compound 30b: white solid; [a]D ꢀ19.2
(CH2Cl2, c = 1.0); 1H NMR (200 MHz, CDCl3) dH:
4.24. 3b,7a-Dihydroxycholest-5-ene (28)
To a solution of 3b-acetoxycholest-5-en-7-one (27, 1.9 g,
4.4 mmol) in dry THF (50 mL) was added L-selectride
(14 mL) dropwise over 15 min. The reaction mixture