The reaction of azoles with 17-chloro-16-formylandrosta-5,16-dien-3β- yl-acetate: Synthesis and structural elucidation of novel 16-azolylmethylene-17- oxoandrostanes

Article abstract of DOI:10.1016/j.steroids.2011.02.009

The synthesis and structural elucidation, by 1D and 2D NMR and X-ray diffraction techniques, of novel E/Z 16-azolylmethylene-17-oxoandrostanes 2-9 prepared from the Vilsmeier-Hack reaction product 17-chloro-16-formylandrosta-5, 16-dien-3β-yl acetate 1 is reported. The reaction proceeds with pyrrole and pyrrole-alike nitrogen heterocycles such as 7-azaindole, indole, and 3-methylindole, in DMF, at 80 °C, in the presence of K₂CO ₃, and allowed the attachment of privileged heterocyclic moieties, through the nitrogen atom to the steroid core at C16 via a methine carbon bridge, which is unprecedented in the literature and of potential synthetic and biological interest. Considerations on the possible reaction mechanism are included. All the synthesized compounds are new and are currently being tested for biological activities.

Full text of DOI:10.1016/j.steroids.2011.02.009

Steroids 76 (2011) 582–587
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Steroids
journal homepage: www.elsevier.com/locate/steroids
The reaction of azoles with 17-chloro-16-formylandrosta-5,
16-dien-3␤-yl-acetate: Synthesis and structural elucidation
of novel 16-azolylmethylene-17-oxoandrostanes
Vânia M. Moreiraa,b, Jorge A.R. Salvadora,c,∗, Ana Matos Bejad, José A. Paixãod
a Centro de Química de Coimbra, Faculdade de Ciências e Tecnologia da Universidade de Coimbra, Rua Larga, 3004-535 Coimbra, Portugal
b Universidade Lusófona de Humanidades e Tecnologias, Campo Grande, 376, 1749-024 Lisboa, Portugal
c Grupo de Química Farmacêutica, Faculdade de Farmácia da Universidade de Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal
d CEMDRX, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-516 Coimbra, Portugal
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and structural elucidation, by 1D and 2D NMR and X-ray diffraction techniques, of novel
E/Z 16-azolylmethylene-17-oxoandrostanes 2–9 prepared from the Vilsmeier–Hack reaction product 17-
chloro-16-formylandrosta-5,16-dien-3␤-yl acetate 1 is reported. The reaction proceeds with pyrrole and
pyrrole-alike nitrogen heterocycles such as 7-azaindole, indole, and 3-methylindole, in DMF, at 80 ◦C, in
the presence of K2CO3, and allowed the attachment of privileged heterocyclic moieties, through the nitro-
gen atom to the steroid core at C16 via a methine carbon bridge, which is unprecedented in the literature
and of potential synthetic and biological interest. Considerations on the possible reaction mechanism are
included. All the synthesized compounds are new and are currently being tested for biological activities.
© 2011 Elsevier Inc. All rights reserved.
Received 26 November 2010
Received in revised form 29 January 2011
Accepted 16 February 2011
Available online 23 February 2011
Keywords:
16-Azolylmethylene-17-oxoandrostanes
Vilsmeier
Pyrrole
Heterocycles
1. Introduction
[6–8]. The anabolic steroid stanozolol bears a pyrazole ring attached
to ring A [9]. Other ring A pyrazole fused steroidal compounds
Heterocycles are important features of biologically active
molecules [1,2]. Pyrrole, pyrimidine, indole, quinoline and purine
are few classes of heterocycles which have served as platforms for
developing pharmaceutical agents for various applications [1,2].
Many important naturally occurring steroids contain one or more
heterocyclic ring(s), fused or attached to ring D, formed by mod-
ifications of the side chain. Examples are cardanolides such as
digitoxigenin which are of particular interest due to their car-
diac activity [3], bufanolides [4], spirostans such as diosgenin and
hecogenin which are sufficiently plentiful to have become major
sources of steroidal intermediates for the synthesis of steroid hor-
mones and pharmaceutical analogues, and furostans, as well as
steroid alkaloids [5], all having received much attention in view
of their relevant biological activities. Other steroids of the preg-
nane series condensed in the 16,17␣-position with a 5-membered
heterocycle have been widely used in medical practice as anti-
inflammatory drugs (triamcinolone acetonide and budesonide)
such as cortivazol and similar arylpyrazolo derivatives have been
extensively investigated as antiinflammatory agents and have
been found to be powerful glucocorticoids rivaling dexamethasone
[10–12]. The synthesis of isoxazole, pyrazoline, and pyrimidine as
well as thiazole fused steroidal compounds with diverse biological
activities has also been reported [13].
Attachment of heterocyclic moieties at diverse positions of
the steroid core has been reported. For instance, analogues of
progesterone bearing aryl groups at C7 have been examined
as inhibitors of the P-glycoprotein reflux pump in overcom-
ing multiple drug resistance in cancer chemotherapy [14]. Both
asoprisnil and mifepristone, two steroidal progesterone recep-
tor modulators bear an 11␤-aryl-4,9-diene scaffold [15].
A
1-pyrido steroid derivative successfully inhibited the growth
of Erlich ascites carcinoma [16]. The synthesis of 16-arylidene
derivatives of estrone has been reported [17] and 16E-[3-methoxy-
4-(2-aminoethoxy)benzylidene]androstene derivatives have been
found to exhibit cytotoxic activity against several tumor cell lines
[18]. Libraries of 16-substituted estrone derivatives and further
modifications of estrone at C6, C16 and C17 have been exam-
ined in search for inhibitors of 17␤-hydroxysteroid dehydrogenase,
the enzyme which converts estrone to estradiol [19,20]. The syn-
thesis of 17-(2-oxoimidazoline) steroidal derivatives has been
reported [21]. A common approach to the synthesis of steroidal
∗
Corresponding author at: Faculdade de Farmácia da Universidade de Coimbra,
Grupo de Química Farmacêutica, Pólo das Ciências da Saúde, Azinhaga de Santa
Comba, 3000-548, Coimbra, Portugal. Tel.: +351 239 488 400;
fax: +351 239 488 503.
E-mail address: salvador@ci.uc.pt (J.A.R. Salvador).
0039-128X/$ – see front matter © 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.steroids.2011.02.009

V.M. Moreira et al. / Steroids 76 (2011) 582–587
583
factors while allowed to ride on the attached parent atoms using
SHELXL-97 defaults. Crystallographic data have been deposited at
the Cambridge Crystallographic Center Nos. 797331 (compound 2)
and 797332 (compound 3). Copy of the data can be obtained free of
charge from CCDC, 12 Union Road, Cambridge CB2 1EZ, UK. E-mail:
deposit@ccdc.cam.ac.uk.
2.1. 17-Chloro-16-formylandrosta-5,16-dien-3ˇ-yl acetate (1)
17-Chloro-16-formylandrosta-5,16-dien-3␤-yl acetate 1 was
prepared according to the previously reported procedure [24,29].
2.2. (Z)-16-(7-Aza-1H-indol-1-yl)methylen-17-oxoandrost-5-
en-3ˇ-yl acetate (2) and
Fig. 1. ꢀ16-17-Azolylandrostane derivatives.
(E)-16-(7-aza-1H-indol-1-yl)methylen-17-oxoandrost-5-en-3ˇ-
yl acetate
(3)
inhibitors of cytochrome 17␣-hydroxylase-C17,20-lyase (CYP17), a
valuable target for prostate cancer treatment, has been the design
of substrate-like molecules bearing a heterocycle at the C17 posi-
tion with privileged heteroatoms (N, S, and O) which can interact
as the sixth ligand with the heme iron of the enzyme [22]. Abi-
raterone acetate, 17-(3-pyridyl)androsta-5,16-dien-3␤-yl acetate,
is a potent CYP17 inhibitor which has successfully undergone Phase
II clinical trials [23]. In addition, the synthesis of steroidal CYP17
inhibitors in which the azole group at C17 is attached to the steroid
core through the nitrogen atom has afforded very potent inhibitors
of this enzyme (Fig. 1) [24–28].
A
mixture of 17-chloro-16-formylandrosta-5,16-dien-3␤-yl
acetate 1 (300 mg, 0.8 mmol), 7-azaindole (142 mg, 1.2 mmol), and
K2CO3 (331 mg, 2.4 mmol) in dry DMF (6 ml) was heated at 80 ◦C
under N2 atmosphere for 8 h. The mixture was then concen-
trated under reduced pressure. Water (30 ml) and ethyl acetate
(100 ml) were added and the aqueous and organic layers separated.
The aqueous phase was extracted twice with the ethyl acetate
(2 × 25 ml). The organic phase was then washed with 5% aqueous
HCl (30 ml), 10% aqueous NaHCO3 (30 ml), 10% aqueous Na2SO3
(30 ml), water (30 ml), brine (30 ml), dried with anhydrous Na2SO4,
filtered, and concentrated under reduced pressure to give a yel-
lowish oil (270 mg; 74%). 1H NMR analysis of the reaction crude
revealed a 50:50 ratio of the two reaction products 2 and 3. The
products were separated by flash column chromatography (FCC)
using ethyl acetate/petroleum ether 40–60 ◦C (1:8).
We herein report that the reaction of 17-chloro-16-
formylandrosta-5,16-dien-3␤-yl acetate
1 with pyrrole-alike
nitrogen heterocycles can be exploited in order to prepare new
E/Z 16-azolylmethylene-17-oxoandrostanes. This provides a novel
strategy to attach privileged heterocyclic structures to the steroid
core at C16 via a methine carbon bridge, examples of which, to
the best of our knowledge, are non-existent in the literature. In
addition, the presence of the carbonyl group at C17 may allow
further modifications of the molecules, which is of high synthetic
interest. The reaction is most likely to proceed via Michael sub-
stitution at C17 with subsequent uptake of a second heterocyclic
moiety by the reaction intermediate, which in turn affords the
final 16-azolylmethylene-17-oxoandrostanes by hydrolysis. All
the synthesized compounds are new and are currently being tested
for their potential biological activities. Structural elucidation by
1D and 2D NMR techniques and X-ray analysis have been used in
order to unequivocally identify the isomeric compound pairs.
Compound
2
(90 mg; 33%): Mp (ethyl acetate/n-hexane)
244–247 ◦C; IR 1245, 1426, 1698, 1730 cm−1
.
1H NMR (CDCl3,
400 MHz) ı 1.00 (s, 3H, 18-CH3), 1.06 (s, 3H, 19-CH3), 2.03 (s, 3H,
3␤-OAc), 4.61 (m, 1H, 3␣-H), 5.41 (m, 1H, 6-H), 6.55 (m, J = 3.88,
Hz 1H, 2ꢀ-H), 7.16 (m, J1 = 4.64 and J2 = 7.71 Hz, 1H, 4ꢀ-H), 7.88 (m,
2H, 3ꢀ-H, and methine-H), 8.30 (m, J1 = 1.05 and J2 = 4.64 Hz, 1H, 5ꢀ-
H), 8.90 (m, J = 3.88 Hz, 1H, 1ꢀ-H); 13C NMR (CDCl3, 100 MHz) ı 73.7
(C3), 103.3, 117.6, 118.2, 121.3, 121.8, 125.9, 129.0, 130.3, 139.9,
143.0, 147.7, 170.4 (CH3CO), 207.3 (C17). EI-MS m/z (%): 459 (100)
M + 1, 336 (55), 331 (84), 312 (69), 292 (60), 269 (69), 155 (72), 79
(63).
2. Experimental
Compound
3
(80 mg; 30%): Mp (ethyl acetate/n-hexane)
286–287 ◦C; IR 1243, 1430, 1633, 1727 cm−1
;
1H NMR (CDCl3,
All reagents were obtained from Sigma–Aldrich Co. All solvents
used were previously dried and purified according to standard pro-
cedures. For thin layer chromatography (TLC) analysis, Kieselgel
60HF254/Kieselgel 60G was used. Melting points were determined
using a BUCHI Melting Point B-540 apparatus and are uncorrected.
IR spectra were obtained using a JASCO FT/IR-420 spectropho-
tometer (FTIR-ATR). NMR spectra were obtained using a Brucker
Digital NMR—Avance 300 or a Brucker Digital NMR—Avance 400
spectrometer, in CDCl3 with Me4Si as the internal standard.
Mass spectra were recorded on a Finnigan PolarisQGC/MS Bench-
top Ion Trap mass spectrometer. Elemental analysis was carried
out on a Fisons Instruments EA 1108 CHNS-O elemental anal-
yser. Single-crystal X-ray diffractometry analysis was made on a
Bruker–Nonius Kappa Apex II CCD diffractometer using graphite
400 MHz) ı 0.98 (s, 3H, 18-CH3), 1.08 (s, 3H, 19-CH3), 2.03 (s, 3H,
3␤-OAc), 4.60 (m, 1H, 3␣-H), 5.43 (m, 1H, 6-H), 6.68 (m, J1 = 0.54
and J2 = 3.88 Hz, 1H, 2ꢀ-H), 7.18 (m, J1 = 4.74 and J2 = 7.79 Hz, 1H, 4ꢀ-
H), 7.68 (m, J = 3.88 Hz, 1H, 1ꢀ-H), 7.91 (m, J1 = 1.58 and J2 = 7.79 Hz,
1H, 3ꢀ-H), 8.38 (m, J1 = 1.58 and J2 = 4.74 Hz, 1H, 5ꢀ-H), 8.66 (m, 1H,
methine-H); 13C NMR (CDCl3, 100 MHz) ı 73.6 (C3), 105.3, 118.3,
118.6, 120.9, 121.6, 125.1, 126.3, 129.1, 140.1, 144.1, 148.2, 170.4
(CH3CO), 208.9 (C17). EI-MS m/z (%): 459 (39) M+1, 432 (34), 395
(28), 322 (43), 293 (29), 166 (40), 89 (61), 75 (100).
2.3. (Z)-16-(1H-Indol-1-yl)methylen-17-oxoandrost-5-en-3ˇ-yl
acetate (4) and
(E)-16-(1H-indol-1-yl)methylen-17-oxoandrost-5-en-3ˇ-yl
acetate (5)
˚
monochromated Mo K␣ radiation (ꢁ = 0.71073 A). The structures
were solved by direct methods and conventional Fourier synthe-
sis (SHELXS-97). The refinement of the structures was made by
full matrix least-squares on F2 (SHELXL-97). All non-H-atoms were
refined anisotropically. The H atoms positions were initially placed
at idealized calculated positions and refined with isotropic thermal
The method followed that described for compounds 2 and
3 using 17-chloro-16-formylandrosta-5,16-dien-3␤-yl acetate 1
(300 mg, 0.8 mmol), indole (140 mg; 1.2 mmol), andK2CO3 (220 mg,
1.6 mmol) in dry DMF (6 ml), at 80 ◦C under N2 atmosphere, for
22 h. After this time additional K2CO3 (80 mg, 0.6 mmol) was added

584
V.M. Moreira et al. / Steroids 76 (2011) 582–587
and after 5 h the reaction was complete. The work up procedure
afforded a yellowish oil (310 mg; 85%). 1H NMR analysis of the
reaction crude revealed a 34:66 ratio of the two reaction prod-
ucts 4 and 5. The products were separated by FCC using ethyl
acetate/petroleum ether 40–60 ◦C (1:8).
(42 ␮l; 0.6 mmol) in dry DMF (3 ml) was added and the mixture
was heated at 80 ◦C, under N2 atmosphere, for 8 h to afford the
two reaction products 8 and 9 (140 mg, 86%). 1H NMR analysis of
the reaction crude revealed a 70:30 ratio of compounds 8 and 9.
The products were separated by FCC using ethyl acetate/petroleum
ether 40–60 ◦C (1:10).
Compound 4 (16 mg; 5%): Mp (acetone) 249–251 ◦C; IR 1242,
1457, 1605, 1697, 1730 cm−1
;
1H NMR (C6D6, 400 MHz) ı 0.79 (s,
Compound
8
(59 mg; 42%): Mp (ethyl acetate/n-hexane)
3H, 18-CH3), 0.84 (s, 3H, 19-CH3), 1.76 (s, 3H, 3␤-OAc), 4.85 (m, 1H,
3␣-H), 5.34 (m, 1H, 6-H), 6.51 (d, J = 3.57 Hz, 1H, 2ꢀ-H), 6.78 (brs,
1H, methine-H), 7.48 (m, 1H, aromatic-H); 9.24 (d, J = 3.57 Hz, 1H,
1ꢀ-H); 13C NMR (C6D6, 100 MHz) ı 73.7 (C3), 106.6, 109.8, 116.7,
121.6, 122.0, 122.5, 123.1, 127.0, 130.0, 130.6, 137.2, 140.3, 169.6
(CH3CO), 205.4 (C17). EI-MS m/z (%): 457 (34) M+, 397 (67), 281
(34), 184 (36), 139 (52), 117 (100), 91 (54), 81 (38).
223–225 ◦C; IR 1244, 1618, 1705, 1733 cm−1
;
1H NMR (CDCl3,
400 MHz) ı 0.97 (s, 3H, 18-CH3), 1.06 (s, 3H, 19-CH3), 2.03 (s,
3H, 3␤-OAc), 4.60 (m, 1H, 3␣-H), 5.40 (m, 1H, 6-H), 6.24 (m, 2H,
aromatic-H), 6.78 (methine-H), 7.55 (m, 2H, aromatic-H); 13C NMR
(CDCl3, 100 MHz) ı 73.7 (C3), 111.32, 117.5, 121.7 (C6), 123.9, 131.4,
140.0 (C5), 170.4 (CH3CO), 206.2 (C17). EI-MS m/z (%): 407 (24) M+,
401 (47), 396 (33), 340 (47), 248 (37), 175 (43), 162 (40), 76 (100).
Compound 5 (74 mg; 24%): Mp (acetone) 284–286 ◦C; IR 1240,
Compound
9
(45 mg; 32%): Mp (ethyl acetate/n-hexane)
1458, 1630, 1722 cm−1
;
1H NMR (CDCl3, 400 MHz) ı 0.99 (s, 3H, 18-
220–224 ◦C; IR 1247, 1638, 1729 cm−1
;
1H NMR (CDCl3, 400 MHz) ı
CH3), 1.08 (s, 3H, 19-CH3), 2.04 (s, 3H, 3␤-OAc), 4.61 (m, 1H, 3␣-H),
5.43 (m, 1H, 6-H), 6.74 (m, J = 3.44 Hz; 1H, 2ꢀ-H), 7.27 and 7.32 (m,
1H and m, 1H, 4ꢀ- and 5ꢀ-H); 7.60 (m, 3H, 1ꢀ-, 3ꢀ- and 6ꢀ-H), 8.14
(brs, 1H, methine-H); 13C NMR (CDCl3, 100 MHz) ı 73.6 (C3), 108.0,
110.2, 117.7, 121.2, 121.6, 122.3, 123.5, 124.9, 127.5, 128.8, 136.9,
140.0, 170.5 (CH3CO), 209.4 (C17). EI-MS m/z (%): 457 (10) M+, 397
(20), 281 (25), 184 (36), 154 (60), 117 (100), 91 (52), 79 (48).
0.95 (s, 3H, 18-CH3), 1.07 (s, 3H, 19-CH3), 2.03 (s, 3H, 3␤-OAc), 4.60
(m, 1H, 3␣-H), 5.41 (m, 1H, 6-H), 6.33 (m, 2H, aromatic-H), 7.03 (m,
2H, aromatic-H), 7.66 (methine-H); 13C NMR (CDCl3, 100 MHz) ı
73.6 (C3), 112.1, 118.9, 121.6 (C6), 121.9, 131.3, 140.1 (C5), 170.4
(CH3CO), 209.5 (C17). EI-MS m/z (%): 407 (32) M+, 318 (18), 296
(29), 287 (100), 205 (24), 180 (13), 115 (28), 60 (15).
2.4. (Z)-16-(3-Methyl-1H-indol-1-yl)methylen-17-oxoandrost-
3. Results and discussion
5-en-3ˇ-yl acetate (6) and
(E)-16-(3-methyl-1H-indol-1-yl)methylen-17-oxoandrost-5-en-
3ˇ-yl acetate
(7)
3.1. Synthesis and structural assignment of the E/Z
16-azolylmethylene-17-oxoandrostanes
The reaction of the Vilsmeier Hack product 17-chloro-16-
The method followed that described for compounds
and 3 using 17-chloro-16-formylandrosta-5,16-dien-3␤-yl acetate
(300 mg, 0.8 mmol), K2CO3 (220 mg, 1.6 mmol), and 3-
methylindole (157 mg; 1.2 mmol), in dry DMF (6 ml), at 80 ◦C under
N2 atmosphere for 21 h, to afford a yellowish oil (232 mg; 62%). 1
NMR analysis of the reaction crude revealed a 70:30 ratio of the
two reaction products 6 and 7. The products were separated by
FCC using ethyl acetate/petroleum ether 40–60 ◦C (1:7).
2
formylandrosta-5,16-dien-3␤-yl acetate
1 with 7-azaindole,
indole, 3-methylindole, and pyrrole, in DMF, at 80 ◦C, in
the presence of K2CO3, afforded the corresponding E/Z 16-
azolylmethylene-17-oxoandrostanes 2–9 (Scheme 1). Thus,
integration of the aromatic 2ꢀ-H signals on the 1H NMR spectrum
of the reaction crude revealed a 50:50 ratio of the E/Z isomers
for the reaction with 7-azaindole, which were obtained in 74%
yield and separated by FCC on silica gel. The 1H NMR signal of
the methine-H was found downfield at 8.66 ppm for the E-isomer
3 as expected due to deshielding caused by proximity to the
carbonyl group, as opposed to the same proton on the Z-isomer 2
which was seen at 7.88 ppm. Accordingly, the aromatic 1ꢀ-H signal
of the Z-isomer 2 appeared downfield at 8.90 ppm whereas for
compound 3 the same signal was found at 7.68 ppm. Unequivocal
assignment of the isomeric pair was performed by X-ray analysis
(Figs. 2 and 3). Bond lengths and angles from the X-ray analysis
are within the normal range of values. The conformations of
the androstane nuclei of both isomers are rather similar, with
rings A and C close to chair conformations and ring B adopting
a conformation close to half-chair, while the D ring has a C-14
envelope conformation in the Z-isomer and a more slightly dis-
torted conformation, twisted around C13–C14, in the E-isomer, as
1
H
Compound 6 (93 mg; 40%): Mp (ethanol) 212–214 ◦C; IR 1245,
1460, 1603, 1703, 1729 cm−1; 1H NMR (CD3COCD3, 400 MHz) ı 1.00
(s, 3H, 18-CH3), 1.11 (s, 3H, 19-CH3), 1.97 (s, 3H, 3␤-OAc), 2.31 (s,
3H, aromatic-CH3), 4.53 (m, 1H, 3␣-H), 5.44 (m, 1H, 6-H), 7.21 (m,
1H, 3ꢀ-H), 7.25 (m, 1H, 4ꢀ-H), 7.49 (brs, 1H, methine-H); 7.54 (m, 1H,
2ꢀ-H); 7.70 (m, 1H, 5ꢀ-H); 8.59 (brs, 1H, 1ꢀ-H); 13C NMR (CD3COCD3,
100 MHz) ı 75.1 (C3), 111.9, 116.8, 117.7, 120.7, 123.6, 123.7, 124.9,
128.9, 129.2, 131.1, 139.2, 142.0, 171.3 (CH3CO), 207.6 (C17). EI-MS
m/z (%): 471 (47) M+, 411 (43), 281 (46), 197 (38), 168 (89), 131
(100), 91 (67), 81 (41).
Compound 7 (53 mg; 23%): Mp (ethanol) 227–229 ◦C; IR 1238,
1461, 1624, 1730 cm−1 1H NMR (CD3COCD3, 400 MHz) ı 0.98 (s,
;
3H, 18-CH3), 1.12 (s, 3H, 19-CH3), 1.97 (s, 3H, 3␤-OAc), 2.33 (s,
3H, aromatic-CH3), 4.53 (m, 1H, 3␣-H), 5.45 (m, 1H, 6-H), 7.24 (m,
J1 = J2 = 7.24 Hz, 3ꢀ-H); 7.34 (m, 1H, 4ꢀ-H); 7.59 (m, 1H, 2ꢀ-H); 7.64
(brs, 1H, 1ꢀ-H); 7.71 (m, 1H, 5ꢀ-H), 8.03 (brs, 1H, methine-H); 13C
NMR (CD3COCD3, 100 MHz) ı 75.1 (C3), 111.8, 111.9, 119.2, 121.0,
123.6, 123.7, 124.6, 125.4, 128.1, 131.6, 139.3, 142.0, 171.3 (CH3CO),
209.6 (C17). EI-MS m/z (%): 471 (30) M+, 411 (50), 281 (48), 197 (38),
168 (87), 131 (100), 91 (66), 81 (36).
˚
shown by the Cremer and Pople parameters [2: A: Q = 0.542(5) A,
◦
◦
˚
ꢂ = 6.2(4) , ϕ = 83(4); B: Q = 0.457(4) A, ꢂ = 51.3(5) , ϕ = 208.5(6) ;
C: Q = 0.566(4) A, ꢂ = 6.2(4)◦, ϕ = 283(3); D: Q2 = 0.414(4) A,
˚
˚
ϕ2 = 209.0(6); 3: A: Q = 0.548(2) A, ꢂ = 4.9(2)◦, ϕ = 88(3); B:
˚
Q = 0.472(2) A, ꢂ = 49.6(2)◦, ϕ = 203.4(3)◦; C: Q = 0.565(2) A,
˚
˚
ꢂ = 6.3(2)◦, ϕ = 265(2); D: Q2 = 0.413(2) A, ϕ2 = 200.7(2)]. The
˚
pseudo-torsion angle C19–C10–C13–C18 is close to 15◦ in both
isomers, showing some torsion of the androstane nucleus.
2.5. (Z)-16-(1H-Pyrrol-1-yl)methylen-17-oxoandrost-5-en-3ˇ-yl
acetate (8) and
(E)-16-(1H-pyrrol-1-yl)methylen-17-oxoandrost-5-en-3ˇ-yl
acetate (9)
The reaction with indole afforded the expected Z/E isomers 4
and 5, in 85% yield. The ratio of the two isomers 4:5 was found to
be 34:66. The same pattern was observed on the 1H NMR spectra for
the methine- and 1ꢀ-H signals which appeared at 6.78 and 9.24 ppm,
respectively, for compound 4, and at 8.14 and 7.60 ppm for com-
pound 5. The Z/E isomers 6 and 7 were obtained in the reaction of 1
The method followed that described for compounds 2 and
3 using 17-chloro-16-formylandrosta-5,16-dien-3␤-yl acetate 1
(150 mg, 0.4 mmol) and K2CO3 (165.5 mg, 1.2 mmol). Pyrrole

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585
Scheme 1. Novel E/Z 16-azolylmethylene-17-oxoandrostanes 2–9 prepared from compound 1.
Fig. 2. Ortep diagram of compound 2.

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V.M. Moreira et al. / Steroids 76 (2011) 582–587
Fig. 3. Ortep diagram of compound 3.
Fig. 4. Proposed mechanism for the formation of the Z/E isomers 8 and 9.
with 3-methylindole, in 62% yield. Integration of the aromatic 2ꢀ-H
signals on the reaction crude 1H NMR spectrum revealed a 70:30
ratio of compounds 6:7. The methine-H signal of the E-isomer 7 was
found downfield at 8.03 ppm whereas the same signal was seen at
7.49 ppm for the Z-isomer 6. Further evidence to support the assign-
ment of the isomeric pair lies on the NOESY correlation between the
aromatic 1ꢀ-H signal at 8.59 ppm and the signal at 1.10 ppm belong-
ing to the 18-methyl group in compound 6 which is non-existent
for compound 7. Furthermore, a NOESY correlation between the
signal at 2.33 ppm belonging to the aromatic methyl protons and
the signal at 5.45 ppm belonging to the 6-H was found for com-
pound 7. Compounds 8 (Z-isomer) and 9 (E-isomer) were obtained
in the reaction of 1 with pyrrole. Integration of the methine-H sig-
nals on the reaction crude 1H NMR spectrum, at 6.78 and 7.66 ppm,
respectively, showed a 70:30 ratio of the two isomers.
Conversion of the least stable Z-isomer into the E-isomer was
found to occur for all isomeric pairs, in CDCl3, during NMR analy-
sis, however at different rates, most likely due to the presence of
residual HCl. Thus, when a 1:1 mixture of compounds 4 and 5 was
placed in chloroform acidified with HCl to pH 3–4, full conversion of
4 into 5 was found to occur in 15 min. The same effect was observed
for a 1:1 mixture of compounds 8 and 9, with full conversion of 8
into 9 occurring within 3 h. In CDCl3, isomerization of the indolyl
derivatives 4 and 5 was immediate and no 1H NMR spectrum of
the Z-isomer 4 could be recorded in this solvent. The NMR analy-
sis of compound 4 was ultimately performed in C6D6. Conversion
of the 7-azaindolyl compound 2 into 3 was somewhat slower. Thus
after 5 days in CDCl3 the 2:3 ratio changed from 97:3 to 65:35. Con-
version of the Z-isomers 6 and 8 into the corresponding E-isomers
7 and 9 was complete after 6 h in CDCl3. This phenomenon sug-
gests that the ratio of the E/Z isomers formed during the reaction is
under kinetic control and that the E-isomer is favored by thermo-
dynamics. Although a thorough study of the isomerization of these
compounds is not the aim of this work, the isolation of only one
isomer could prove advantageous from the synthetic point of view.
3.2. Mechanistic considerations
The reaction of 17-chloro-16-formylandrosta-5,16-dien-3␤-yl
acetate 1 with nitrogen heterocycles in DMF, at 80 ◦C, in the pres-
ence of K2CO3, had previously been exploited in order to prepare
several CYP17 inhibitors in which the azole bound the steroid core
via the nitrogen atom at C17 (Fig. 1) [24–27]. The reaction was
described as a nucleophilic vinylic “addition–elimination” Michael
substitution on the steroidal substrate by nitrogen heterocyclic
nucleophiles such as imidazole, to afford the corresponding ꢀ16
-
formyl-17-azolylsteroids. Thus, examples of azoles which have
been reported to successfully replace the 17-chlorine atom of 17-
chloro-16-formylandrosta-5,16-dien-3␤-yl acetate 1 are 1,3- and
1,2-azoles, and tri- and tetrazoles [24–27]. The difference in the
products obtained under the same reaction conditions with other
azoles suggests that the nature of the heterocycle used is respon-
sible for a different course in the reaction path. We reason that
␲-excessive heterocycles such as pyrrole, indole, 3-methylindole
and 7-azaindole can promote a second attack on the aldehyde
function of the Michael substitution product (i) to form a salt

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587
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In conclusion, the synthesis of novel E/Z 16-azolylmethylene-
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uct 17-chloro-16-formylandrosta-5,16-dien-3␤-yl acetate
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Acknowledgements
Vânia M Moreira wishes to thank Fundac¸ ão para a Ciência
e a Tecnologia for financial support (SFRH/BD/12508/2003 and
SFRH/BPD/45037/2008). Jorge A R Salvador wishes to thank Uni-
versidade de Coimbra for financial support. We thank Professor
Teresa Pinho e Melo (Centro de Química de Coimbra, Universidade
de Coimbra) for the kind discussions with which she has privileged
us.
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Appendix A. Supplementary data
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Synthesis 2001:1941–8.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.steroids.2011.02.009.