added dropwise at 50 °C under N2. After being stirred at 50 °C
for 10 min, the reaction mixture was cooled at 0 °C and a sus-
pension of CuBr·Me2S (169 mg, 0.821 mmol, 1.0 eq.) in THF
(3 mL) was added and a solution of 3β-tert-butyldimethylsily-
loxy-22-tosyloxy-23,24-bisnorchola-5,7-diene (17) (492 mg,
0.821 mmol, 1.0 eq.) in THF (11 mL) was added dropwise at
0 °C under N2. After being stirred at room temperature for 1 h,
the reaction mixture was poured into saturated aqueous NH4Cl at
0 °C and the aqueous layer was extracted twice with EtOAc. The
combined organic layer was washed with saturated aqueous
NH4Cl, saturated aqueous NaHCO3 and brine, dried over
MgSO4, filtered and concentrated in vacuo. The residue
was purified by short path column chromatography on silica gel
(5% Et2O in hexane) and used for the next reaction without
further purification.
To a solution of crude silyl ether 19 in THF (16.4 mL), a sol-
ution of TBAF (1.0 M in THF, 12.3 mL, 12.3 mmol, 15 eq.) was
added at 0 °C under argon. After being stirred at room tempera-
ture for 10 h, the reaction mixture was poured into water at 0 °C
and the aqueous layer was extracted twice with EtOAc. The
combined organic layer was washed with brine, dried over
MgSO4, filtered and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (2% MeOH in
CHCl3) to give 3β,25-dihydroxycholesta-5,7-diene (8)48
(309 mg, 0.771 mmol, 94%) as a white solid. 1H NMR
(400 MHz, CDCl3): δ 5.57 (m, 1H), 5.39 (m, 1H), 3.64 (m, 1H),
1.22 (s, 6H), 0.95 (d, J = 8.8 Hz, 3H), 0.94 (s, 3H), 0.62 (s, 3H);
13C NMR (100 MHz, CDCl3): δ 141.3, 139.8, 119.6, 116.3,
71.1, 70.4, 55.8, 54.5, 46.2, 44.4, 42.9, 40.8, 39.2, 38.4, 37.0,
36.4, 36.1, 32.0, 29.4, 29.2, 28.1, 23.0, 21.1, 20.1, 18.8, 16.3,
11.8; IR (neat): 3306, 2962, 2875, 1456, 1363, 1068, 911,
829 cm−1; [α]D27 = −102.6 (c 0.47, CHCl3); mp 168–171 °C;
HRMS (ESI-TOF): calcd for [C27H44O2 + H]+ 401.3420, found
401.3418.
extracted twice with CH2Cl2. The combined organic layer was
washed with saturated aqueous NaHCO3 and brine, dried over
MgSO4, filtered and concentrated in vacuo. The residue was
used for the next reaction without further purification.
To a solution of crude tosylate 21 in MeOH (6.49 mL) and
THF (3.25 mL), potassium hydroxide (164 mg, 2.92 mmol, 4.5 eq.)
was added at 0 °C under argon. After being stirred at room temp-
erature for 12 h, the reaction mixture was poured into 1 M HCl
at 0 °C and the aqueous layer was extracted twice with EtOAc.
The combined organic layer was washed with saturated aqueous
NaHCO3 and brine, dried over MgSO4, filtered and concentrated
in vacuo. The residue was purified by column chromatography
on silica gel (3% MeOH in CHCl3) to give 1α,3β-dihydroxy-22-
tosyloxy-23,24-bisnorchola-5,7-diene
(22)
(352
mg,
0.703 mmol, quant.) as a white solid. 1H NMR (400 MHz,
CDCl3): δ 7.79 (d, J = 8.3 Hz, 2H), 7.35 (d, J = 8.3 Hz, 2H),
5.72 (m, 1H), 5.36 (m, 1H), 4.07 (m, 1H), 3.99 (dd, J = 9.3, 3.4
Hz, 1H), 3.82 (dd, J = 9.6, 6.6 Hz, 1H), 3.76 (br, 1H), 2.45 (s,
3H), 1.02 (d, J = 6.8 Hz, 3H), 0.93 (s, 3H), 0.59 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 144.6, 140.6, 136.3, 133.0, 129.8,
127.9, 121.8, 115.5, 75.5, 72.7, 65.3, 60.4, 54.2, 51.5, 43.1,
42.2, 39.9, 38.8, 38.5, 37.7, 36.5, 27.3, 22.9, 21.6, 20.7, 16.9,
16.2, 14.1, 11.8; IR (neat): 3359, 2941, 1457, 1360, 1175, 1052,
942, 845, 668, 555 cm−1; [α]D24 = −50.6 (c 1.03, CHCl3); mp
80–82 °C; HRMS (ESI-TOF): calcd for [C29H40O5S + H]+
501.2675, found 501.2657.
1α,3β-Dihydroxycholesta-5,7-diene {1α-hydroxyprovitamin D3
(9)}
To stirred magnesium turnings (90.7 mg, 3.73 mmol, 10 eq.),
two drops of 1-bromo-3-methylbutane were added and a solution
of 1-bromo-3-methylbutane (563 mg, 3.73 mmol, 10 eq.) in
THF (5.2 mL) was added dropwise at 50 °C under N2. After
being stirred at the same temperature for 10 min, the reaction
mixture was cooled at 0 °C and a suspension of CuBr·Me2S
(76.7 mg, 0.373 mmol, 1.0 eq.) in THF (2 mL) was added and a
solution of 1α,3β-dihydroxy-22-tosyloxy-23,24-bisnorchola-5,7-
diene (22) (187 mg, 0.373 mmol, 1.0 eq.) in THF (3.2 mL) was
added dropwise at 0 °C under N2. After being stirred at room
temperature for 30 min, the reaction mixture was poured into
saturated aqueous NH4Cl at 0 °C and the aqueous layer was
extracted twice with EtOAc. The combined organic layer was
washed with saturated aqueous NH4Cl, saturated aqueous
NaHCO3 and brine, and dried over MgSO4. The obtained
mixture was filtered and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (40% EtOAc in
hexane) to give 1α,3β-dihydroxycholesta-5,7-diene (9)49
(95.0 mg, 0.237 mmol, 64%) as a white solid. 1H NMR
(400 MHz, CDCl3): δ 5.73 (m, 1H), 5.38 (m, 1H), 4.06 (m, 1H),
3.77 (br, 1H), 0.94 (s, 3H), 0.94 (d, J = 4.9 Hz, 3H), 0.87 (d,
J = 6.4 Hz, 3H), 0.87 (d, J = 6.8 Hz, 3H), 0.63 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 141.8, 135.8, 122.1, 115.2, 72.9,
65.5, 55.9, 54.7, 43.1, 42.3, 40.0, 39.5, 39.2, 38.5, 38.0. 36.1,
36.1, 28.1, 28.0, 23.9, 23.0, 22.8, 22.5, 20.9, 18.8, 16.3, 11.9;
IR (neat): 3381, 2954, 2872, 1464, 1377, 1366, 1052, 826,
690 cm−1; [α]D27 = −50.2 (c 1.14, CHCl3); mp 114–117 °C;
1α,3β-Bis(methoxycarbonyloxy)-22-hydroxy-23,24-bisnorchola-
5,7-diene (20)
1H NMR (400 MHz, CDCl3): δ 5.67 (m, 1H), 5.37 (m, 1H),
4.89 (m, 1H), 4.83 (br, 1H), 3.78 (s 3H), 3.77 (s, 3H), 3.64 (dd,
J = 10.6, 3.2 Hz, 1H), 3.38 (dd, J = 10.7, 6.8 Hz, 1H), 1.06 (d,
J = 6.8 Hz, 3H), 1.00 (s, 3H), 0.63 (s, 3H); 13C NMR
(100 MHz, CDCl3): δ 155.0, 155.0, 140.9, 133.8, 122.1, 115.5,
78.4, 72.2, 67.8, 54.8, 54.6, 54.2, 52.1, 42.9, 41.2, 39.0, 38.7,
37.7, 35.5, 31.8, 27.5, 23.0, 20.3, 16.8, 16.0, 12.0; IR (neat):
3545, 2959, 2875, 1747, 1444, 1281, 1255, 984, 755 cm−1
;
[α]2D8 = −40.6 (c 1.22, CHCl3); mp 83–86 °C; HRMS
(ESI-TOF): calcd for [C26H38O7 + NH4]+ 480.2961, found
480.2966.
1α,3β-Dihydroxy-22-tosyloxy-23,24-bisnorchola-5,7-diene (22)
To a solution of 1α,3β-bis(methoxycarbonyloxy)-22-hydroxy-
23,24-bisnorchola-5,7-diene (20) (300 mg, 0.649 mmol, 1.0 eq.)
in CH2Cl2 (3.25 mL), tosyl chloride (247 mg, 1.30 mmol, 2.0
eq.) and DMAP (238 mg, 1.95 mmol, 3.0 eq.) were added at
0 °C under argon. After being stirred at 0 °C for 4 h, the reaction
mixture was poured into water at 0 °C and the aqueous layer was
This journal is © The Royal Society of Chemistry 2012
Org. Biomol. Chem., 2012, 10, 5205–5211 | 5209