Practical one-pot conversion of 17β-estradiol to 10β-hydroxy- (p-quinol) and 10β-chloro-17β-hydroxyestra-1,4-dien-3-one

Article abstract of DOI:10.1016/j.steroids.2006.04.002

An efficient one-pot procedure for the preparation of 10β,17β-dihydroxyestra-1,4-dien-3-one (p-quinol, 1, 75%) is reported, involving oxidation of 17β-estradiol with potassium permanganate. Similar treatment of 17β-estradiol with sodium chlorite led to 10β-chloro-17β-hydroxyestra-1,4-dien-3-one (2) in 44% yield along with smaller amounts 4-chloro-10β,17β-dihydroxyestra-1,4-dien-3-one (3), 2,10β-dichloro-17β-hydroxyestra-1,4-dien-3-one (4), and 4,10β-dichloro-17β-hydroxyestra-1,4-dien-3-one (5).

Full text of DOI:10.1016/j.steroids.2006.04.002

steroids 7 1 ( 2 0 0 6 ) 670–673
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/steroids
Practical one-pot conversion of 17␤-estradiol to
10␤-hydroxy- (p-quinol) and
10␤-chloro-17␤-hydroxyestra-1,4-dien-3-one
Liliana Lista, Paola Manini, Alessandra Napolitano,
Alessandro Pezzella∗, Marco d’Ischia
Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Via Cintia 4, I-80126 Naples, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient one-pot procedure for the preparation of 10␤,17␤-dihydroxyestra-1,4-dien-3-one
(p-quinol, 1, 75%) is reported, involving oxidation of 17␤-estradiol with potassium per-
manganate. Similar treatment of 17␤-estradiol with sodium chlorite led to 10␤-chloro-17␤-
hydroxyestra-1,4-dien-3-one (2) in 44% yield along with smaller amounts 4-chloro-10␤,17␤-
dihydroxyestra-1,4-dien-3-one (3), 2,10␤-dichloro-17␤-hydroxyestra-1,4-dien-3-one (4), and
4,10␤-dichloro-17␤-hydroxyestra-1,4-dien-3-one (5).
Received 27 December 2005
Received in revised form 11 April
2006
Accepted 13 April 2006
Published on line 30 May 2006
© 2006 Elsevier Inc. All rights reserved.
Keywords:
10␤-Chloro-17␤-hydroxyestra-1,4-
dien-3-one
10␤,17␤-Dihydroxyestra-1,4-dien-3-
one
p-Quinol
Potassium permanganate
Sodium chlorite
Abbreviations:
NMR, nuclear magnetic resonance;
COSY, 1H,1H Correlation
spectroscopy; DQF-COSY, double
quantum filtered correlation
spectroscopy; HMQC, 1H,13
heteronuclear multiple quantum
coherence; HMBC, 1H,13
C
C
heteronuclear multiple bond
correlation; ROESY, rotating
Overhauser effect spectroscopy;
ESIMS, electrospray ionization mass
spectrometry; HRESI, high
resolution electrospray ionization;
TLC, thin layer chromatography; CD,
circular dichroism
∗
Corresponding author at: Department of Organic Chemistry and Biochemistry, University of Naples “Federico II”, Complesso Universitario
Monte S. Angelo, Via Cintia 4, I-80126 Naples, Italy. Tel.: +39 081 674130; fax: +39 081 674393.
E-mail address: alessandro.pezzella@unina.it (A. Pezzella).
0039-128X/$ – see front matter © 2006 Elsevier Inc. All rights reserved.
doi:10.1016/j.steroids.2006.04.002

steroids 7 1 ( 2 0 0 6 ) 670–673
671
1.
Introduction
10␤-Substituted-17␤-hydroxyestra-1,4-dien-3-ones are an
interesting class of estradiol-related compounds that have
found application in estrogen replacement therapy, preven-
tion, and treatment of osteoporosis [1], in the detection and
treatment of hormone dependent tumors [2], or for the pre-
vention and therapy of ophthalmic diseases [3]. In addition,
the identification of the 10-hydroxy derivative (p-quinol, 1)
in the redox cycling mechanisms underlying the putative
antioxidant and cytoprotective properties of 17␤-estradiol
[4], suggested its employment as prodrug of antioxidants [5],
while the halogenated derivatives have been shown to be
valuable tools for probing interactions at estrogen receptors
[6].
A number of synthetic approaches to 10␤-substituted-
17␤-hydroxyestra-1,4-dien-3-ones have been reported [7–10],
but they often require manipulation of estrone and estradiol
derivatives, lengthy protection/deprotection steps or func-
tional group modifications, resulting in complex mixtures
of products. The best procedure for preparation of p-quinol
derivatives involves oxidation of 17␤-estradiol monoacetate
with m-chloroperbenzoic acid and a catalytic amount of (BzO)2
for 1.5 h under irradiation with a 60 W tungsten lamp leading
to the product in 52% yield, along with an epoxy-derivative
[11]. Other procedures are also available that afford the desired
product, but in lower yields.
Access routes to 10␤-halo derivatives of 17␤-estradiol
have also been reported [12–14], though expensive organic
chlorinating agents are employed and complex mixtures
of products are usually obtained requiring separation and
purification steps. For example, access to the 10␤-chloro
derivative 2 is based on the reaction of 17␤-estradiol with
2,3,4,5,6,6-hexachloro-2,4-cyclohexadienone in DMF which
affords the desired compound in ca 75% yield together
with 25% of other chlorinated derivatives [13] (Schemes 1
and 2).
As part of our studies [15–17] toward the prepara-
tion of functionalized steroidal scaffolds of potential inves-
tigative value and/or to be evaluated as pharmaceutical
agents, we report herein operationally simple and conve-
nient procedures for the one-pot conversion of 17␤-estradiol
to 10␤,17␤-dihydroxyestra-1,4-dien-3-one (1) and 10␤-chloro-
17␤-hydroxyestra-1,4-dien-3-one (2).
Scheme 2
2.
Experimental
Materials and methods
2.1.
17␤-Estradiol, potassium permanganate, sodium chlorite,
were from Aldrich Chemie. Melting points were obtained with
a Gallenkamp apparatus. Elemental analyses were performed
with a Perkin-Elmer CHN analyzer mod. 2400. Ultraviolet spec-
tra were performed using a diode array Hewlett Packard spec-
trophotometer model 8453E. CD spectra were taken on Spec-
tropolarimeter Jasco J-715 at 25 ◦C using solutions of the prod-
ucts in ethanol exhibiting absorbance values in the range
0.1–0.2 at 220 nm. 1H (13C) NMR spectra were recorded at 400.1
(100.6) MHz using a Bruker DRX–400 MHz instrument fitted
with a 5 mm 1H broadband gradient probe with inverse geom-
etry. 1H,1H Correlation spectroscopy (COSY), 1H,13C heteronu-
clear multiple quantum coherence (HMQC), 1H,13C heteronu-
clear multiple bond correlation (HMBC), rotating Overhauser
effect spectroscopy (ROESY) and double-quantum-filtered cor-
relation spectroscopy (DQF-COSY) experiments were run at
400.1 MHz using standard pulse programs from the Bruker
library. Electrospray ionization mass spectrometry (ESIMS)
spectra were recorded in negative or positive ion mode with
a Waters ZQ quadrupole mass spectrometer on samples dis-
solved in methanol. High resolution electrospray ionization
(HRESI) mass spectra were obtained with a Finnegan MAT 90
instrument. Analytical and preparative thin layer chromatog-
raphy (TLC) analyses were performed on F254 0.25 and 0.5 mm
silica gel plates using cyclohexane/ethyl acetate 40:60 (v/v) as
the eluant. HPLC was carried out on an Agilent mod. 1100
apparatus equipped with a UV detector set at 280 nm using a
Sphereclone ODS(2) (5 ␮m, 4.6 mm × 250 mm) using 1% acetic
acid/acetonitrile 50:50 (v/v) as the eluant, at a flow rate of
1 mL/min.
2.2.
10ˇ,17ˇ-dihydroxyestra-1,4-dien-3-one (1)
A solution of 17␤-estradiol (100 mg, 0.37 mmol) in ethyl acetate
(16 mL) was added under vigorous stirring to a solution of
potassium permanganate (116 mg, 0.74 mmol) in 0.05 M aque-
ous HCl (16 mL). After 30 s, when substrate consumption was
complete (TLC evidence), the mixture was extracted with ethyl
acetate (3 × 75 mL), the organic layers were collected, and
taken to dryness to afford pure 1 (80 mg, 75% yield, Rf = 0.30)
as crystals from ethyl acetate, m.p. 217–219 ◦C; UV (MeOH):
ꢀmax 243 nm; 1H and 13C NMR (see Table 1); ESI(−)MS m/z: 287
Scheme 1

672
steroids 7 1 ( 2 0 0 6 ) 670–673
([M − H]−). Anal. calcd. for C18H24O3: C, 74.97; H, 8.39. Found:
5: UV (CH3OH): ꢀmax 247, 289 nm; 1H NMR [14]; ESI(+)MS m/z:
341 ([M + H]+, 100), 343 ([M + 2 + H]+, 63), 345 ([M + 4 + H]+, 15).
C, 75.00; H, 8.42.
2.3.
10ˇ-Chloro-17ˇ-hydroxyestra-1,4-dien-3-one (2),
4-chloro-10ˇ, 17ˇ-dihydroxyestra-1,4-dien-3-one (3),
2,10ˇ-dichloro-17ˇ-hydroxyestra-1,4-dien-3-one (4),
4,10ˇ-dichloro-17ˇ-hydroxyestra-1,4-dien-3-one (5)
3.
Results and discussion
Several oxidants, such as potassium permanganate, lead
tetraacetate, diacetoxyiodobenzene, sodium periodate, potas-
sium persulfate were tested for their ability to bring about
direct conversion of 17␤-estradiol to the quinol 1. Of these,
potassium permanganate proved to be the most efficient in
producing the desired quinol in good yield. The reaction was
investigated under different experimental conditions, and
an optimized procedure was eventually developed, using an
acidic water/ethyl acetate 1:1 as solvent and 2 molar equiv-
alents of the oxidant. By this method, complete substrate
consumption was observed in less than 1 min, and the desired
quinol 1 was obtained in 75% isolated yield in pure form in the
organic phase. Product identity was determined by spectral
analysis and comparison with literature data; the stereochem-
istry of the C-10 centre was confirmed from the CD spectrum
[18] showing a negative Cotton effect similar to that reported
for 10␤-substituted compounds [14,18–20]. To the best of our
knowledge, this is the first method for preparing 1 by direct
oxidation of 17␤-estradiol without functional group protection
and chromatographic separation.
10␤-Chloro-17␤-hydroxyestra-1,4-dien-3-one (2) was pre-
pared in 44% isolated yield (48% formation yield as determined
by HPLC) by treating 17␤-estradiol with 2 molar equivalents
of NaClO2. After 30 min, substrate consumption was com-
plete, and compound 2 was obtained by extraction of the mix-
ture with ethyl acetate, followed by chromatographic purifi-
cation. Configuration at C-10 was determined by CD analysis
[14]. Under these reaction conditions no formation of 1 was
observed.
17␤-Estradiol (100 mg, 0.37 mmol) in methanol (7 mL) was
added under vigorous stirring to 0.01 M aqueous HCl (20 mL)
containing NaClO2 (66 mg, 0.74 mmol). After 30 min reac-
tion time, when substrate consumption was complete (HPLC
evidence), the mixture was extracted with ethyl acetate
(3 × 75 mL), the organic layers were collected, taken to dryness,
and the residue fractionated on silica plates to afford pure 2
(50 mg, 44% yield, Rf = 0.49, RT = 12.7 min) as colourless crystals
from ethyl acetate, 3 (2 mg, 2% yield, Rf = 0.17, RT = 5.5 min),
4 (7 mg, 6% yield, Rf = 0.55, RT = 19.3 min), 5 (12 mg, 9% yield,
Rf = 0.52, RT = 21.2 min).
2: m.p. 158–160 ◦C [14]; UV (CH3OH): ␭
241, 280 (sh) nm;
max
1H and 13C NMR [14] (see Table 1); ESI(+)MS m/z: 307 ([M + H]+,
100), 309 ([M + 2 + H]+, 35). Anal. calcd. for C18H23O2Cl: C, 70.46;
H, 7.56. Found C, 70.89; H, 7.45.
3: UV (CH3OH): ꢀmax 249, 289 nm; 1H NMR (CDCl3), ı (ppm)
0.85 (3H, s), 1.03 (1H, m), 1.07 (2H, m), 1.09 (1H, m), 1.34 (1H,
m), 1.45 (1H, m), 1.50 (1H, m), 1.64 (1H, m), 1.65 (1H, m), 1.86
(1H, m), 2.00 (2H, m), 2.09 (1H, m), 2.60 (1H, m), 3.17 (1H, m),
3.64 (1H, m), 6.31 (1H, d, J = 10.4 Hz), 7.12 (1H, d, J = 10.4 Hz); 13
C
NMR (CDCl3), ı (ppm) 11.0 (CH3), 22.8 (CH2), 23.6 (CH2), 28.7
(CH2), 30.4 (CH2), 31.9 (CH2), 35.0 (CH), 36.1 (CH2), 43.0 (C), 49.7
(CH), 55.3 (CH), 72.8 (C), 81.5 (CH), 126.9 (CH), 127.0 (C), 150.6
(CH), 160.6 (C), 178.7 (C); ESI(−)MS m/z: 321 ([M − H]−, 100), 323
([M + 2−H]−, 35).
4: UV (CH3OH): ꢀmax 253, 288 (sh) nm; 1H NMR [14]; ESI(+)MS
m/z: 341 ([M + H]+, 100), 343 ([M + 2 + H]+, 63), 345 ([M + 4 + H]+,
12).
For both products 1 and 2 complete resonances assignment
(Table 1) was obtained by 2D (COSY, HMQC, HMBC, and ROESY)
NMR analysis. Coupling constants (Table 2) were obtained by
DQF-COSY experiments.
Table 1 – Selected NMR data for compounds 1–2a
Careful analysis of the reaction mixture of 17␤-estradiol
with NaClO2 revealed the presence of minor components
which were purified by preparative TLC and subjected to com-
plete spectral analysis. The most polar compound was char-
acterized as the novel 4-chloro-10␤, 17␤-dihydroxyestra-1,4-
dien-3-one (3). The CD spectrum supporting the assignment
of configuration at C-10 is shown in Fig. 1. The other two prod-
ucts were identified as 2,10␤-dichloro-17␤-hydroxyestra-1,4-
1
2
ıC
ıH
ıC
ıH
C-1
C-2
C-3
C-4
C-5
C-6
C-7
C-8
151.1
131.3
186.0
126.1
165.2
32.3
33.4
35.1
55.6
76.3
22.7
36.3
43.2
49.9
23.6
30.4
81.6
11.0
6.98
6.34
–
6.17
–
2.45 (␤), 2.33
1.95 (␤), 1.06
1.97
1.20
–
1.83 (␤), 1.68
1.99 (␤), 1.05
–
147.9
126.6
185.0
123.8
161.1
32.3
32.3
35.8
53.4
67.7
22.9
35.9
43.0
49.4
23.5
30.4
81.4
11.0
7.13
6.18
–
6.06
–
2.85 (␤), 2.41
1.96 (␤), 1.03
1.96
C-9
1.34
C-10
C-11
C-12
C-13
C-14
C-15
C-16
C-17
C-18
–
1.89 (␤), 1.80
1.91 (␤), 1.12
–
0.92
1.02
1.33 (␤),1.62
1.45 (␤), 2.04
3.65
1.38 (␤), 1.61
1.50 (␤), 2.09
3.65
0.83
0.85
a
Spectra were taken in CDCl3.
Fig. 1 – CD spectrum of compound 3 taken in methanol.

steroids 7 1 ( 2 0 0 6 ) 670–673
673
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1, 2
2, 4
4, 6␤
6␣, 6␤
6␣, 7␣
6␣, 7␤
6␤, 7␣
6␤, 7␤
7␣, 7␤
7␣, 8␤
7␤, 8␤
8␤, 9␣
8␤, 14␣
9, 11␣
9, 11␤
11␣, 11␤
11␣, 12␣
11␣, 12␤
11␤, 12␣
11␤, 12␤
12␣, 12␤
14␣, 15␣
14␣, 15␤
15␣, 15␤
15␣, 16␣
15␣, 16␤
15␤, 16␣
15␤, 16␤
16␣, 16␤
17␣, 16␣
17␣, 16␤
10.4
2.0
1.7
13.2
4.4
2.6
10.4
2.0
1.6
13.2
4.4
2.4
13.4
4.4
13.6
4.8
13.0
11.2
n.d.
12.9
10.8
4.0
11.6
13.2
4.5
12.0
11.2
n.d.
12.0
11.0
4.8
n.d.
13.2
4.5
2.0
12.0
4.4
11.2
6.8
11.6
11.6
8.8
2.2
12.0
n.d.
13.4
7.4
12.5
11.8
10.2
3.4
3.6
5.6
12.0
9.2
7.6
5.4
11.4
12.9
8.6
8.3
8.0
n.d.: not determined.
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The procedures here disclosed for the preparation of the
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Acknowledgements
This work was supported in part by a grant from MIUR, and ST-
Microelectronics. We thank the “Centro Interdipartimentale
di Metodologie Chimico-fisiche” (CIMCF, University of Naples
Federico II) for NMR and MS facilities. The technical assistance
of Miss Silvana Corsani is acknowledged.
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