A. Gioiello et al. / Steroids 77 (2012) 250–254
251
dropwise and reacted at 60 °C for 18 h. The reaction mixture was
cooled at room temperature, diluted with H O (30 mL) and ex-
tracted with Et
O (3 ꢀ 25 mL). The collected organic layers were
washed with brine (20 mL), dried over anhydrous Na SO and con-
2
2
O
O
2
4
centrated under reduced pressure. The crude was dissolved in THF
(50 mL) and treated with HCl 37% (1 mL) at room temperature for
O
O
2
h. The mixture was diluted with EtOAc (30 mL), washed with 10%
E-4,17(20)-pregnadiene-3,16-dione Z-4,17(20)-pregnadiene-3,16-dione
E-Guggulsterone (1)
Z-Guggulsterone (2)
NaHCO SO
and concentrated under reduced pressure. The residue was puri-
3
(2 ꢀ 20 mL), brine (20 mL), dried over anhydrous Na
2
4
fied by flash chromatography with petroleum ether/EtOAc to give
1
8
0
2
in 95% yield (0.98 g, 16.73 mmol). H NMR (CDCl
3
, 200 MHz) d:
O
O
O
.91 (s, 3H, 18-CH
1-CH ), 5.07–5.18 (m, 1H, 20-CH), 5.72 (s, 1H, 4-CH). C NMR
, 100.6 MHz) d: 13.0, 16.7, 17.3, 20.9, 24.1, 31.2, 31.8, 32.8,
3.9, 35.1, 35.6, 36.8, 38.6, 44.0, 53.7, 55.5, 113.6, 123.7, 149.5,
171.4, 199.5.
3
), 1.18 (s, 3H, 19-CH
3
), 1.63 (d, 3H, J = 7.1 Hz,
13
3
(
CDCl
3
3
AcO
HO
16,17-epoxy-pregnenolone (4)
1
6-dehydropregnenolone
2
.2.3. (17E)-16
t-Butylhydroperoxide (TBHP) (0.16 mL, 0.88 mmol) was added
to a stirred suspension of SeO (0.041 g, 0.37 mmol) in distilled
CH Cl (3 mL) under N atmosphere at 0 °C. The resulting mixture
was reacted for 30 min. A solution of 8 (0.022 g, 0.74 mmol) in
CH Cl (3 mL) was then added dropwise, warmed to room temper-
ature and reacted at this temperature overnight. The reaction was
quenched with NaHCO 10% (5 mL) and extracted with CH Cl
3 ꢀ 5 mL). The collected organic layers were washed with brine
5 mL), dried over anhydrous Na SO and concentrated under re-
a-hydroxy-pregna-4,17-dien-3-one (9)
acetate (16-DIPA) (3)
Fig. 1. Structure of E- and Z-guggulsterone, and related synthetic precursors.
2
2
2
2
2
. Experimental
2
2
2
.1. Materials
3
2
2
(
(
All reagents were commercially available unless otherwise
2
4
noted. The final products were purified by chromatography on sil-
ica-gel (70–230 mesh). TLC was performed on aluminum backed
silica plates (silica gel 60 F254). Spots on TLC were visualized by
using UV and by staining and warming with phosphomolybdate re-
agent (5% solution in EtOH). All the reactions were performed
duced pressure. The residue was purified by flash chromatography
with petroleum ether/EtOAc to give 0.208 g (0.66 mmol, 90%) of 9.
mp: 132–134 °C. C21
H
30
O
2
: Calcd. C, 80.21; H, 9.62. Found. C,
0.30; H, 9.30. H NMR (CDCl , 400 MHz) d: 0.89 (s, 3H, 18-CH ),
.16 (s, 3H, 19-CH ), 1.71 (d, 3H, J = 7.2 Hz, 21-CH ), 4.42 (br d,
H, J = 4.0 Hz, 16-CH), 5.57 (q, 1H, J = 7.2 Hz, 20-CH), 5.71 (s, 1H,
1
8
1
1
4
3
1
3
3
3
3
1
using distilled solvents. H NMR spectra were recorded at 200
1
3
and 400 MHz, C NMR spectra were recorded at 100.6 MHz, using
the solvents indicated below. Chemical shifts are reported in parts
per million (ppm). The abbreviations used are as follows: s, singlet;
d, doublet; t, triplet; q, quartet; psd, pseudo singlet. Melting points
were determined with an electrothermal apparatus and are uncor-
rected. Optical rotations were measured with a Jasco Dip-1000
13
3
-CH). C NMR (CDCl , 100.6 MHz) d: 13.2, 17.2, 17.3, 21.0, 31.7,
2.7, 33.9, 34.4, 34.9, 35.5, 36.9, 38.5, 44.1, 51.8, 53.7, 74.1,
19.8, 123.8, 154.6, 171.1, 199.5.
2.2.4. E-guggulsterone (1)
Oxalyl chloride (0.064 mL, 0.74 mmol) was added to a stirred
3
polarimeter in CHCl .
solution of DMSO (0.11 mL, 1.49 mmol) in distilled CH
under N
atmosphere at ꢁ50 °C. After 10 min a solution of 9
(195 mg, 0.62 mmol) in CH Cl (3 mL) was added dropwise and
2 2
Cl (3 mL)
2
2
2
.2. Synthesis
2
2
the mixture was reacted at ꢁ50 °C for 40 min. Then Et
3
N
.2.1. 3-Ethoxyandrosta-3,5-dien-17-one (6)
(0.43 mL, 3.10 mmol) was added, and the resulting reaction was
stirred at ꢁ50 °C for 40 min, at ꢁ20 °C for additional 2 h, and finally
warmed at room temperature. The mixture was diluted with
CH Cl (10 mL) and treated with HCl 3 N (10 mL) for 10 min. The
Triethyl orthoformate (2.60 mL, 15.63 mmol) and p-toluensulf-
onic acid (0.027 g, 0.14 mmol) were added to a stirred solution of
androsten-3,17-dione (5) (2.00 g, 6.98 mmol) in freshly distilled
2
2
THF (20 mL) and absolute EtOH (0.64 mL) under N
The resulting mixture was heated at 45 °C for 2 h. The reaction
was quenched with 10% NaHCO (5 mL) and extracted with Et
3 ꢀ 15 mL). The collected organic layers were washed with brine
10 mL), dried over anhydrous Na SO and concentrated under re-
2
atmosphere.
organic phase was separated, washed with H O (5 mL), NaHCO3
2
10% (5 mL), brine (5 mL), dried over anhydrous Na SO4 and con-
2
3
2
O
centrated under reduced pressure. The residue was purified by
flash chromatography with petroleum ether/EtOAc to give the de-
(
(
2
4
sired E-guggulsterone (1) (0.165 g, 0.52 mmol, 85%). R (petroleum
f
duced pressure, to give 6 in almost quantitative yield (2.19 g,
ether/EtOAc-7:3, v/v) 0.18. mp: 169–171 °C. C21H28O : Calcd. C,
2
1
20
D
6
0
2
.97 mmol). H NMR (CDCl
.99 (s, 3H, 19-CH ), 1.24–1.31 (m, 3H, OCH
H, OCH CH ), 5.11 (s, 1H, 4-CH), 5.21 (s, 1H, 6-CH). C NMR
, 100.6 MHz) d: 13.6, 14.6, 18.9, 20.4, 21.8, 25.4, 30.7, 31.4,
3
, 400 MHz) d: 0.90 (s, 3H, 18-CH
3
),
80.73; H, 9.03. Found. C, 79.89; H, 8.88. ½
a
ꢂ
ꢁ27.4° (c = 0.016,
1
3
2
CH ), 3.73–3.81 (m,
3
3 3 3
CHCl ). H NMR (CDCl , 400 MHz) d: 1.08 (s, 3H, 18-CH ), 1.25 (s,
1
3
2
3
3 3
3H, 19-CH ), 1.86 (d, 3H, J = 7.3 Hz, 21-CH ), 5.75 (s, 1H, 4-CH),
1
3
(
CDCl
3
6.52 (q, 1H, J = 7.5 Hz, 20-CH). C NMR (CDCl , 100.6 MHz) d:
3
3
1
1.5, 33.7, 35.2, 35.8, 47.6, 48.4, 51.91, 62.1, 98.8, 117.0, 141.21,
54.6, 221.0.
13.1, 17.3, 17.5, 20.6, 31.8, 32.5, 33.8, 34.2, 35.4, 35.9, 37.7, 38.6,
43.0, 49.5, 53.3, 124.1, 129.5, 147.4, 170.1, 199.2, 205.6.
2
.2.2. (17Z)-pregna-4,17-dien-3-one (8)
Potassium t-butoxide (3.02 g, 26.90 mmol) was added to a stir-
2.2.5. General procedure for the synthesis of Z-guggulsterone (2)
E-guggulsterone (1) (0.16 mmol) was dissolved in the appropri-
ate solvent (10 mL) and treated with the catalyst (0.3 equivalents).
The mixture was stirred at room temperature for 7 h. The reaction
red solution of ethyl-triphenylphosphonium bromide (6.56 g,
7.62 mmol) in distilled THF (50 mL) and under N atmosphere.
1
2
The resulting suspension was reacted at 60 °C for 90 min. A solu-
tion of 6 (1.09 g, 3.49 mmol) in THF (25 mL) was then added
mixture was filtered (when needed), washed with 10% NaHCO
and brine, dried over anhydrous Na SO and concentrated under
3
2
4