Synthesis and crystal structure of a new mestranol acetate

Article abstract of DOI:10.1007/s10870-011-0074-y

A new mestranol acetate, 17α-ethinyl-17-hydroxy-3-methoxyestra-1,3, 5(10)-triene-6-one-17-acetate, was synthesized by an efficient three-step sequence starting from norethindrone. The structure of the new steroid was characterized by ¹H NMR, ¹³C NMR, MS, IR spectrum and X-ray single crystal diffraction. It crystallizes in the triclinic system, space group P1. The molecules are arranged in a head-to-tail fashion without intra- and intermolecular hydrogen bonding.

Full text of DOI:10.1007/s10870-011-0074-y

J Chem Crystallogr (2011) 41:1208–1213
DOI 10.1007/s10870-011-0074-y
ORIGINAL PAPER
Synthesis and Crystal Structure of a New Mestranol Acetate
Hongqi Li
Shuwen Ma
•
Haichuan Qian
•
Jinxing Li
•
Received: 18 September 2008 / Accepted: 15 April 2011 / Published online: 24 April 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A new mestranol acetate, 17a-ethinyl-17-
hydroxy-3-methoxyestra-1,3,5(10)-triene-6-one-17-acetate,
was synthesized by an efficient three-step sequence starting
from norethindrone. The structure of the new steroid was
the solid state could be accelerated at elevated temperature
in the presence of air, as a result of auto-oxidation. Up until
now, little is known about the decomposition products of
mestranol. In view of providing authentic samples and ste-
roidal compounds with antitumor activity and potential
value in the radioimmunoassay [1–4], the chemical syn-
thesis and structural characterization of the decomposition
products of mestranol and related compounds is of great
importance. Recently we reported efficient synthesis and
structural characterization of a series of mestranol decom-
position products [5]. As a continuation of the study on
steroidal compounds [6], we present herein efficient syn-
thesis and crystal structure of a new mestranol acetate.
1
13
characterized by H NMR, C NMR, MS, IR spectrum and
X-ray single crystal diffraction. It crystallizes in the tri-
clinic system, space group P1. The molecules are arranged
in a head-to-tail fashion without intra- and intermolecular
hydrogen bonding.
Keywords Mestranol Á Acetate Á Synthesis Á X-ray Á
Crystal structure
Introduction
Experimental
As common components of widely used hormone regulation
and therapy medications, mestranol has been proved to be
stable in air. Nevertheless, stability samples of formulated
drug products containing mestranol stored for years under
ambient laboratory conditions were observed to contain
several oxidative transformation products of the parent
compound which were not present at the beginning of the
study. It was also found that decomposition of mestranol in
1
13
HNMRand CNMRspectrawererecordedonaBrukerAM
400 spectrometer. CDCl was used as solvent and chemical
3
shifts recorded were internally referenced to Me Si (0 ppm).
4
All chemical shifts (d) were given in ppm and coupling con-
stants (J) in Hz. IR spectra were obtained on a Thermo Elec-
tron Corporation Nicolet 380 FT-IR spectrophotometer. Mass
spectra were recorded on a Finnigan-MAT-8430 instrument
using electron ionization (EI) at 70 eV. Melting points were
determined on a WRS-2A capillary melting apparatus and the
quoted temperatures were uncorrected.
H. Li (&) Á H. Qian Á J. Li
Key Laboratory of Science & Technology of Eco-Textile,
Ministry of Education, College of Chemistry, Chemical
Engineering and Biotechnology, Donghua University,
All chemical reagents were purchased from commercial
sources and used as received unless other statements.
2999 Renmin North Road, Shanghai 201620, China
e-mail: hongqili@dhu.edu.cn
Synthesis of 3,17b-Dihydroxy-19-norpregna-1,3,5(10)-
triene-20-yne-6-one (2)
S. Ma
Faculty of Food Science, College of Life Science and
Engineering, Northwest Minorities University,
Lanzhou 730030, China
Norethindrone (17.9 g, 60 mmol) and anhydrous potas-
sium acetate (9.5 g, 96 mmol) in dry DMF (120 mL) was
1
23

J Chem Crystallogr (2011) 41:1208–1213
1209
heated to 120 °C and stirred for 20 h while oxygen or air
was bubbled through the solution. The reaction mixture
was poured onto ice water (100 mL) containing methylene
chloride (300 mL). Hydrochloric acid (1 N, 150 mL) was
added then the organic layer was separated. The aqueous
phase was extracted with methylene chloride (150 mL
1664, 1607, 1498, 1385, 1311, 1259, 1215, 1178, 1133,
-
1
1045 cm
.
Synthesis of 17a-Ethinyl-17-hydroxy-3-methoxyestra-
1,3,5(10)-triene-6-one (3)
9
3). The organic phases were combined and washed with
A mixture consisting of 2 (4.34 g, 14 mmol), anhydrous
potassium carbonate (6.36 g, 46 mmol), methyl iodide
(6 mL, 13.7 g, 97 mmol), and acetone (40 mL) was stirred
at room temperature for 36 h then refluxed for 6 h. The
reaction mixture was allowed to cool to room temperature
and poured into water (150 mL). The mixture was
extracted with ethyl acetate (80 mL 9 4) and the com-
bined organic phase was dried over Na SO . After evap-
1
50 mL each of 1 N hydrochloric acid, water, and brine
then dried over MgSO . After evaporation to remove sol-
4
vent, the crude product was purified by column chroma-
tography on silica gel with 20% ethyl acetate in petroleum
ether (bp 60–90 °C) to afford 2 (11.4 g, 61%) as pale
yellow solid. M.p.: 228.6–229.5 °C (literature [7] value:
2
29–230 °C); R = 0.25 (petroleum ether/ethyl acetate,
f
2
4
1
2
:1);
H
NMR (400 MHz, CDCl3) d = 7.53 (d,
oration to remove solvent, the crude product was purified
by column chromatography on silica gel with petroleum
ether/ethyl acetate (2:1) as eluent or by recrystallization
from methylene dichloride/hexane to give 3 (4.3 g, 95%)
as pale yellow needles. M.p.: 161.8–162.5 °C (literature [1]
J = 2.9 Hz, 1H), 7.33 (d, J = 8.5 Hz, 1H), 7.07 (dd,
J = 8.5 and 2.9 Hz, 1H), 5.24 (s, 1H), 2.74 (dd, J = 16.9
and 3.3 Hz, 1H), 2.64 (s, 1H), 2.22–2.55 (m), 1.74–2.08
(
(
m), 1.57–1.66 (m), 1.24–1.43 (m), 0.90 (s, 3H) ppm; IR
KBr) m = 3563, 3388, 3277, 2965, 2945, 2891, 2865,
value: 162–163 °C from ether); R = 0.57 (petroleum
f
Table 1 Crystal data and
experimental crystallographic
details
Empirical formula
Formula weight
Temperature
23 26 4
C H O
366.44
293(2) K
˚
Radiation, wavelength
Habit, colour
MoKa, 0.71073 A
Prism, colorless
Triclinic, P1
Crystal system, space group
Unit cell dimensions
a
˚
7.1491(19) A
˚
11.872(3) A
b
˚
12.792(3) A
c
a
109.668(5)°
98.096(5)°
94.114(5)°
b
c
3
˚
Volume
1003.9(5) A
-
3
Z, calculated density
Absorption coefficient
F(000)
2, 1.212 g cm
-
0.082 mm
1
392
Crystal size
0.507 9 0.420 9 0.327 mm
1.72–26.00°
–8 B h B 8, -14 B k B 12, -15 B l B 14
5525/3868 [R(int) = 0.1316]
Empirical
h range for data collection
Limiting indices
Reflections collected/unique
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
1.0000 and 0.8127
2
Full-matrix least-squares on F
3868/3/493
0.955
2
Goodness-of-fit on F
Final R indices [I [ 2r(I)]
R indices (all data)
R
R
1
= 0.0611, wR
= 0.0730, wR
2
2
= 0.1307
= 0.1372
1
-
3
˚
0.265 and -0.257 e A
Largest diff. peak and hole
123

1
210
J Chem Crystallogr (2011) 41:1208–1213
4
Table 2 Atomic coordinates (910 ) and equivalent isotropic dis-
Table 2 continued
´
2
placement parameters (A 9 10 ) for 4
3
˚
Atom
x
y
z
Ueq
51(1)
Atom
x
y
z
Ueq
84(1)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
3339(6)
2688(8)
4389(6)
5123(7)
4344(6)
5473(9)
-209(10)
-1602(4)
-1857(5)
-854(4)
-271(5)
-3468(4)
-4440(6)
4225(8)
7249(3)
9028(4)
6757(3)
6321(4)
6121(4)
6199(5)
O(1)
-692(5)
5030(5)
285(4)
5480(4)
3461(4)
-2199(3)
-2248(3)
4506(2)
5025(3)
10695(3)
14740(3)
7158(2)
5282(3)
550(4)
69(1)
56(1)
72(1)
57(1)
90(2)
116(2)
O(2)
87(1)
60(1)
81(1)
87(1)
93(1)
61(1)
69(1)
54(1)
61(1)
58(1)
60(1)
52(1)
56(1)
55(1)
43(1)
47(1)
47(1)
56(1)
53(1)
45(1)
44(1)
62(1)
60(1)
48(1)
63(1)
55(1)
68(1)
63(1)
86(2)
84(2)
65(1)
74(1)
69(1)
67(1)
56(1)
61(1)
60(1)
49(1)
49(1)
53(1)
56(1)
55(1)
47(1)
48(1)
65(1)
60(1)
O(3)
10009(3)
11001(3)
2938(4)
3658(4)
-2666(3)
-3372(3)
4710(4)
4086(4)
4019(4)
4499(4)
5110(4)
5608(4)
6323(4)
6931(4)
5953(4)
5227(3)
6482(4)
7345(4)
8311(4)
7700(4)
8728(5)
9615(4)
9109(4)
9156(4)
8394(4)
7804(5)
10888(4)
11683(5)
2863(5)
2088(4)
2650(5)
3136(5)
3075(4)
2482(4)
2411(4)
1624(4)
677(4)
O(4)
-2168(6)
-1565(5)
1454(6)
4294(4)
3563(5)
3636(6)
4664(6)
4106(6)
2538(7)
1504(6)
-169(6)
-1208(6)
103(5)
O(5)
O(6)
14855(6)
O(7)
U(eq) is defined as one-third of the trace of the orthogonalized
ij
U tensor
O(8)
C(1)
C(2)
-272(4)
-1359(4)
-1663(4)
-840(3)
-1222(3)
-327(3)
805(3)
1
ether/ethyl acetate, 2:1); H NMR (400 MHz, CDCl3)
C(3)
d = 7.57 (d, J = 2.9 Hz, 1H), 7.36 (d, J = 8.6 Hz, 1H),
C(4)
7
.12 (dd, J = 8.6 and 2.9 Hz, 1H), 3.85 (s, 3H), 2.75 (dd,
J = 16.9 and 3.3 Hz, 1H), 2.63 (s, 1H), 2.23–2.57 (m),
.72–2.05 (m), 1.56–1.66 (m), 1.26–1.49 (m), 0.90 (s, 3H)
C(5)
C(6)
1
C(7)
13
ppm; C NMR (100 MHz, CDCl ) d = 197.8 (C=O),
3
C(8)
1
58.2 (3-C), 139.5 (10-C), 133.4 (5-C), 126.6 (1-C), 121.6
2-C), 109.7 (4-C), 87.2 (21-C), 79.6 (17-C), 74.4 (22-C),
5.5 (OCH ), 49.3 (13-C), 46.9 (14-C), 44.0 (9-C), 42.6
C(9)
993(5)
1194(3)
302(3)
(
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
2072(5)
2196(6)
1204(6)
472(5)
5
3
2363(3)
3245(3)
2827(3)
1705(3)
1499(4)
2676(4)
3516(3)
2751(4)
3899(3)
4173(4)
5191(4)
6153(4)
-2019(5)
12570(4)
13612(4)
13672(4)
12721(4)
11648(4)
10644(4)
9526(4)
9601(3)
10422(3)
11575(4)
10432(3)
9252(3)
8538(3)
8456(3)
7559(4)
6748(4)
(7-C), 40.7 (8-C), 38.9 (16-C), 32.4 (12-C), 25.7 (11-C), 22.5
(
15-C), 12.5 (CH ) ppm; IR (KBr) m = 3523, 3275, 2946,
3
-
674, 1605, 1493, 1327, 1286, 1246, 1224, 1038 cm ; MS
1
1
?
-881(5)
-1877(7)
-1927(6)
-893(5)
2138(6)
-2213(6)
-3287(7)
-498(8)
938(9)
(EI, 70 eV): m/z (%) 324 (M , 77), 256 (50), 241 (68), 227
(12), 214 (15), 200 (60), 188 (100), 174 (19), 161 (23), 145
(10), 128 (12), 115 (18), 103 (11), 91 (11), 77 (13).
Synthesis of 17a-Ethinyl-17-hydroxy-3-methoxyestra-
1,3,5(10)-triene-6-one-17-acetate (4)
A mixture consisting of 3 (2.79 g, 8.6 mmol), pyridine
(3 mL, 2.93 g, 37.1 mmol), and acetic anhydride (7 mL,
7.56 g, 74.1 mmol) was heated to 80 °C and stirred for 5 h.
The reaction mixture was allowed to cool to room tem-
perature and poured into water (30 mL). The mixture was
extracted with ethyl acetate (40 mL 9 3) and the com-
6552(8)
4036(7)
3534(8)
1834(7)
668(7)
bined organic phase was dried over Na SO . After evap-
2
4
oration the crude product was purified by column
chromatography on silica gel with petroleum ether/ethyl
acetate (4:1) as eluent to give 4 (2.56 g, 81%) in addition to
the starting material 3 (0.28 g, 10%) as colorless prismatic
1175(6)
-166(6)
216(6)
1507(5)
3355(5)
2865(6)
4932(6)
5233(6)
3386(5)
1916(5)
280(6)
crystals. M.p.: 167.5–168.5 °C; R = 0.71 (petroleum
f
1336(4)
1980(4)
532(4)
1
ether/ethyl acetate, 2:1); H NMR (400 MHz, CDCl3)
d = 7.60 (d, J = 2.9 Hz, 1H, 4-H), 7.39 (d, J = 8.6 Hz,
1H, 1-H), 7.15 (dd, J = 8.6 and 2.9 Hz, 1H, 2-H), 3.88 (s,
-198(4)
-924(4)
-75(4)
3
H, OCH ), 2.76 (m, 2H), 2.69 (s, 1H, C:CH), 2.12–2.54
3
(m, 3H), 2.10 (s, 3H, COCH ), 1.92–2.08 (m, 4H),
3
1
.60–1.69 (m, 2H), 1.29–1.48 (m, 2H), 0.89 (s, 3H, CH )
3
-881(5)
-1859(4)
1
3
ppm; C NMR (100 MHz, CDCl ) d = 200.0 (C=O),
3
1227(6)
171.8 (O–C=O), 160.6 (3-C), 141.7 (10-C), 135.7 (5-C),
1
23

J Chem Crystallogr (2011) 41:1208–1213
1211
1
8
29.0 (1-C), 123.9 (2-C), 112.0 (4-C), 86.5 (17-C or 19-C),
5.4 (19-C or 17-C), 77.6 (:CH), 57.8 (OCH ), 50.1 (14-
3
C), 46.3 (13-C), 44.8 (9-C), 42.7 (7-C), 39.6 (8-C), 35.2
(
(
16-C), 33.2 (12-C), 27.9 (11-C), 25.3 (22-C or 15-C), 23.7
15-C or 22-C), 15.6 (18-C) ppm; IR (KBr) m = 3266,
2
1
7
940, 2872, 2125, 1742, 1730, 1686, 1675, 1606, 1492,
445, 1422, 1369, 1319, 1290, 1262, 1248, 1028,
-
14 cm ; MS (EI, 70 eV): m/z (%) 366 (M , 91), 351
1
?
?
M –CH , 37), 324 (29), 306 (15), 291 (12), 264 (12), 256
(
(
(
(
3
21), 254 (21), 241 (49), 213 (11), 200 (18), 188 (60), 187
62), 174 (19), 161 (22), 131 (10), 115 (13), 91 (15), 77
12), 53 (10), 43 (100).
Measurement of Crystal Structure
Fig. 1 A view of the molecule of compound 4. Displacement
ellipsoids are drawn at the 30% probability level and H atoms are
shown as small spheres of arbitrary radii
The X-ray diffraction experiment for compound 4 was car-
ried out on a Bruker Smart CCD diffractometer with
graphite monochromated Mo-Ka radiation (k = 0.710
˚
3 A) at 293(2) K. Data collection, cell refinement, data
7
reduction and correction for absorption were all performed
using Bruker programs [8]. The structure was solved by
direct methods and refined anisotropically by full-matrix
2
least-squares calculations on F with SHELXTL for the non-
hydrogen atoms [9]. The hydrogen atoms were assigned
based on the expected bonding geometry and were refined
isotropically in the final least-squares cycles. The crystal
data and experimental details for compound 4 were sum-
marized in Table 1. Atomic coordinates and equivalent
isotropic displacement parameters were provided in Table 2.
Results and Discussion
The target compound, 17a-ethinyl-17-hydroxy-3-methoxyes-
tra-1,3,5(10)-triene-6-one-17-acetate (4), was synthesized
Fig. 2 Unit cell packing of compound 4, viewed along a axis
Scheme 1 Synthetic route of
the mestranol acetate 4
OH
OH
air, AcOK
DMF, 120 o
C
MeI, K CO3
2
61%
95%
HO
O
O
1
2
O
OH
O
Ac O/Py
2
81%
MeO
MeO
O
O
3
4
123

1
212
J Chem Crystallogr (2011) 41:1208–1213
starting from norethindrone (1). It was first reported by
Wiechert and co-workers [10] that norethidrone could be
oxidized to 6-keto ethinyl estradiol (2) by oxygen in DMF
containing potassium acetate at 120 °C. This procedure was
followed and the yield of compound 2 was about 40% [7, 11].
We found that the yield of 2 could be improved up to 61% by
prolonging the reaction time. Moreover, the oxidation pro-
cedure could be simplified by replacing oxygen with air
without substantial decrease in yields (Scheme 1). Methyl-
ation of compound 2 with methyl iodide in the presence of
potassium carbonate afforded 3, the minor degradation
product of mestranol, in high yield (95%). Acetylation of 3
with acetic anhydride and pyridine gave 4 in good yield
(81%). Thus, the efficient three-step sequence starting from
norethindrone produced compound 4 in an overall yield of
47%.
Single crystals of compound 4 suitable for X-ray dif-
fraction were obtained by slow evaporation of a solution in
petroleum ether and ethyl acetate (2:1). The crystal struc-
ture and the packing of the molecules in the unit cell of 4
were showed in Figs. 1, 2, respectively. The selected bond
lengths and angles were listed in Table 3. Compound 4
crystallizes in the triclinic system with unusual space group
P1. There are two molecules in the asymmetric unit and it
appears that the two unique molecules only differ by a small
change in their configurations. P1 is a chiral space group
and the molecules are chiral. But the absolute configuration
for the structure is not determined and the structure pre-
sented represents a postulated absolute configuration.
Although there are no hydrogen bonds, there are numerous
short contacts. For example, the attraction of H43–O4 and
H20–O8 make a close pair of the two molecules. The ste-
roid skeleton does not significantly differ from mestranol as
observed in the crystal structure [12]. The molecules are
arranged in a head-to-tail fashion, similar to that in
˚
Table 3 Selected bond lengths (A) and angles (°)
˚
Bond lengths (A)
O(1)–C(6)
1.207(5)
1.392(5)
1.334(6)
1.454(5)
1.363(6)
1.402(6)
0.9300
O(2)–C(3)
O(3)–C(21)
O(3)–C(17)
C(1)–C(10)
C(1)–C(2)
17a-ethinyl-3-methoxyestra-1,3,5(10),9(11)-tetraene-17-ol
C(1)–H(1)
[
13] but different from the head-to-head fashion as observed
C(5)–C(10)
1.416(5)
1.466(6)
1.502(6)
1.521(5)
0.9700
in mestranol [12] without intra- and intermolecular hydro-
gen bonding. In the molecular structure, rings B, C and D
adopt distorted chair, approximately planar, and envelope
conformation, respectively.
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(7)–H(7A)
In conclusion, 17a-ethinyl-17-hydroxy-3-methoxyestra-
1,3,5(10)-triene-6-one-17- acetate was synthesized by an
efficient three-step sequence starting from norethindrone.
X-Ray crystal structure of the new mestranol acetate
revealed the head-to-tail molecular arrangement fashion
and ring conformation.
C(11)–C(12)
1.542(6)
1.562(5)
1.169(6)
0.9300
C(13)–C(17)
C(19)–C(20)
C(20)–H(20)
C(21)–C(22)
1.478(7)
Bond angles (°)
C(23)–O(2)–C(3)
C(10)–C(1)–C(2)
C(3)–C(2)–H(2)
C(2)–C(3)–O(2)
O(1)–C(6)–C(5)
C(5)–C(6)–C(7)
C(14)–C(8)–C(9)
C(10)–C(9)–C(8)
C(9)–C(11)–H(11A)
C(13)–C(14)–C(15)
C(16)–C(15)–C(14)
C(15)–C(16)–H(16A)
C(16)–C(17)–C(13)
C(20)–C(19)–C(17)
C(19)–C(20)–H(20)
C(21)–C(22)–H(22A)
O(2)–C(23)–H(23C)
117.1(4)
122.6(4)
120.6
Supplementary Material
124.7(4)
122.8(4)
116.7(3)
109.8(3)
109.1(3)
108.8
CCDC-699083 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/data_request/cif, by
e-mailing data_request@ccdc.cam.ac.uk, or by contacting
The Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: ?44(0)1223-336033.
104.1(3)
104.7(3)
110.4
Acknowledgments Financial support of the project by Shanghai
Natural Science Foundation (No. 06ZR14001) was acknowledged.
103.2(3)
178.0(4)
180.0
References
109.5
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1
23

J Chem Crystallogr (2011) 41:1208–1213
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