After 19 h the solution was evaporated under vacuum to 3/4 of its volume, treated with water (100 mL), and extracted
with CH Cl (4×50 mL). The extracts were washed with water (2×60 mL) and evaporated under vacuum. The solid was co-
2
2
evaporated under vacuum with benzene and then toluene, dried under vacuum, dissolved in ethanolic KOH (300 mL, 5%), and
stirred for 1 h. The reaction mixture was neutralized with HCl until the pH was 7, evaporated to 2/3 the volume, treated with
water (120 mL), and extracted with CH Cl (4×50 mL). The CH Cl extracts were washed with water (2×40 mL) and
2
2
2
2
evaporated under vacuum. The solid was co-evaporated with benzene, dried under vacuum, dissolved in acetone (200 mL), and
treated with stirring with chromic acid (21 mL, 8 N).
The excess of oxidant was decomposed after 0.5 h by adding isopropanol (30 mL). The reaction mixture was
evaporated under vacuum to 3/4 of the volume, diluted with water (120 mL), and extracted with ethylacetate (4×50 mL). The
combined extracts were washed with water (2×40 mL) and dried with MgSO . The solvent was evaporated under vacuum. The
4
solid was chromatographed on an Al O column with elution by petroleum ether—ethylacetate of increasing polarity (from 30:1
2
3
to 2:1). Yield of 3, 3.32 g, 44%, mp 182-183 C (ethanol—ethylacetate), lit. [10] mp 180-186oC. IR spectrum ( , cm-1): 1715
1
(C O). H NMR spectrum ( , ppm): 0.65 (18-Me, s), 0.83 (19-Me, s), 0.86 (26-Me, 27-Me, d, J = 6.5 Hz), 0.91 (21-Me, d,
J = 6 Hz), 2.70 (H-7 , t, J = 12.5 Hz), 4.21 (H-3 , m, W/2 = 21 Hz).
3 -Chloro-7 -bromo-5-hydroxy-5 -cholestan-6-one (4). A solution of 3 (7.62 g) in glacial acetic acid (250 mL) and
HBr (3 mL, 32%) at 45-50oC was stirred and treated with bromine in glacial acetic acid (10 mL, 2 M) over 40 min. It was
stirred at the same temperature for 5 h and left to cool. After 17 h the reaction mixture was evaporated under vacuum to
~60 mL volume. Successive crystallizations gave 4, 5.39 g, 60%, mp 132-135oC (ethanol). Found, %: C 63.29, H 8.50, Br +
Cl 22.38. Calc. for C27H44O2BrCl, %: C 62.85, H 8.59, Br + Cl 22.36. IR spectrum ( , cm-1): 1720 (C O). H NMR spectrum
1
( , ppm): 0.69 (18-Me, s), 0.85 (19-Me, s), 0.87 (26-Me, 27-Me, d, J = 6.5 Hz), 0.93 (21-Me, d, J = 6 Hz), 2.30 (H-4 , ddd,
J = 14 Hz, J = 4 Hz, J = 1 Hz), 2.64 (5 -OH, s), 4.22 (H-7 , d, J = 4.5 Hz), 4.24 (H-3 , m, W/2 = 29 Hz).
1
2
3
5-Hydroxy-5 -cholesta-2,7-dien-6-one (5). A solution of 4 (1.75 g) in DMF (65 mL) was treated with Li CO
2
3
(2.79 g) and LiBr (0.66 g). The mixture was heated to 135oC, stirred for 6 h, and cooled to room temperature. The precipitate
was filtered off. The filtrate was diluted with water (50 mL) and extracted with ethylacetate (4×50 mL). The extracts were dried
over MgSO and evaporated under vacuum. The solid was chromatographed on a silica-gel column with elution by
4
hexane—ethylacetate of increasing polarity (from 50:1 to 10:1). Yield of 5, 0.62 g, 41%. IR spectrum ( , cm-1): 1680 (C O),
1
1630 (C C). UV spectrum ( max, nm): 249 ( 10,000). H NMR spectrum ( , ppm): 0.61 (18-Me, s), 0.87 (26-Me, 27-Me, d,
J = 6.5 Hz), 0.88 (19-Me, s), 0.95 (21-Me, d, J = 6 Hz), 5.69 (H-2, H-3, H-7, m).
Criegee cis-Hydroxylation of 5-Hydroxy-5 -cholesta-2,7-dien-6-one (5). A. A solution of 5 (0.62 g) in a mixture
of THF, t-butanol, and water (50 mL, 10:10:1) was treated with N-methylmorpholine-N-oxide monohydrate (0.63 g) and OsO
4
(0.069 g) in a mixture of THF, t-butanol, and water (2 mL, 10:10:1). The mixture was stirred for 22 h at room temperature,
treated with saturated aqueous NaHSO (3 mL), stirred for 45 min, and filtered through a layer of silica gel. The filtrate was
3
treated with water (50 mL) and extracted with ethylacetate (3×40 mL). The combined extracts were washed with water
(2×30 mL), evaporated under vacuum and co-evaporated with benzene. The solid was dissolved in acetic anhydride (2 mL) and
pyridine (5 mL). The reaction mixture was stored for 48 h and co-evaporated under vacuum with toluene several times. The
solid was separated into fractions by preparative TLC on a silica-gel plate with development by a cyclohexane—ethylacetate
mixture of increasing polarity (from 3:1 to 2.8:1).
Fraction 1: 2 ,3 -Diacetoxy-5-hydroxy-5 -cholest-7-en-6-one (6). Yield 0.12 g, 15%, mp 185-188oC (ether—
petroleum ether), lit. [1] mp 192oC (methanol—water). IR spectrum ( , cm-1): 1755, 1730, 1255, 1240 (AcO), 1690 (C O),
1
1630 (C C). UV spectrum ( max, nm): 250 ( 12,000). H NMR spectrum ( , ppm): 0.58 (18-Me, s), 0.87 (26-Me, 27-Me, d,
J = 6.5 Hz), 0.98 (21-Me, d, J = 6 Hz), 1.07 (19-Me, s), 2.02 (AcO, s), 2.08 (AcO, s), 5.27 (H-3 , m, W/2 = 21 Hz), 5.31 (H-2 ,
m, W/2 = 9 Hz), 5.67 (H-7, t, J = 2 Hz).
Fraction 2: 2 ,3 -Acetoxy-5-hydroxy-5 -cholest-7-en-6-one (8). Yield 0.12 g, 15%, mp 207-209oC (ether). IR
spectrum ( , cm-1): 1750, 1255, 1240 (AcO), 1680 (C O), 1630 (C C). UV spectrum ( max, nm): 249 ( 14,000). H NMR
1
spectrum ( , ppm): 0.60 (18-Me, s), 0.87 (26-Me, 27-Me, d, J = 6.5 Hz), 0.94 (21-Me, d, J = 6 Hz), 1.00 (19-Me, s), 2.01 (2 -
AcO, s), 2.12 (3 -AcO, s), 3.26 (5 -OH, s), 5.02 (H-2 , ddd, J = 12 Hz, J = 4 Hz, J = 3 Hz), 5.60 (H-3 , m, W/2 = 7.5 Hz),
1
2
3
5.69 (H-7, t, J = 2 Hz).
Fraction 3: 3 -Acetoxy-2 ,5-dihydroxy-5 -cholest-7-en-6-one (7). Yield 0.12 g, 16%, mp 183-186oC
(cyclohexane—ethylacetate). IR spectrum ( , cm-1): 1750, 1730, 1275, 1255 (AcO), 1690 (C O), 1630 (C C). UV spectrum
1
(
max, nm): 250 ( 10,900). H NMR spectrum ( , ppm): 0.60 (18-Me, s), 0.87 (26-Me, 27-Me, d, J = 6.5 Hz), 0.95 (21-Me,
592