Synthesis and SAR study of novel pseudo-steroids as potent and selective progesterone receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2009.01.095

Synthesis of novel 7-pseudo-steroids 1c has been achieved from trenbolone 3 via an efficient 14 step sequence with overall yields of 10-15%. Various substitutions were incorporated at both the aromatic side chain as well as the D ring. The orientation of

Full text of DOI:10.1016/j.bmcl.2009.01.095

Bioorganic & Medicinal Chemistry Letters 19 (2009) 3977–3980
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and SAR study of novel pseudo-steroids as potent and selective
progesterone receptor antagonists
*
Nareshkumar Jain , George Allan, Olivia Linton, Pamela Tannenbaum, Xin Chen, Jun Xu, Peifang Zhu,
Joseph Gunnet, Keith Demarest, Scott Lundeen, William Murray, Zhihua Sui
Johnson and Johnson Pharmaceutical Research and Development, Medicinal Chemistry, LLC, 665 Stockton Drive, Exton, PA 19341, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of novel 7-pseudo-steroids 1c has been achieved from trenbolone 3 via an efficient 14 step
sequence with overall yields of 10–15%. Various substitutions were incorporated at both the aromatic
side chain as well as the D ring. The orientation of aromatic side chain at C10 plays a crucial role for pro-
gesterone receptor (PR) activity. Compound 2a (T47D = 1 nM) with –NMe2 para to the aromatic group
along with spirofurane groups in the D ring was the optimal substitution. All compounds were also eval-
uated for glucocorticoid receptor (GR) antagonist activities in vivo in a rat and found efficacious in uterine
complement C3 assay via the oral route of administrations.
Received 26 November 2008
Revised 26 January 2009
Accepted 27 January 2009
Available online 31 January 2009
Keywords:
Progesterone antagonists
Pseudo-steroids
Ó 2009 Elsevier Ltd. All rights reserved.
T47D
Glucocorticoid receptor (GR) antagonist
Me
N
Me
N
There exist numerous proven and potential applications for pro-
gesterone antagonists (PA) in women’s health care.
Me
Me
OH
OH
Mifepristone (RU-486),1,2 one of the most widely prescribed
PAs, is of limited clinical use due lack of selectivity5,6 for the pro-
gesterone (PR) over the glucocorticoid (GR) receptor. The resulting
undesirable side effect profile has provided the stimulus to search
for more selective PAs. These efforts have led to the discovery of a
variety of both steroidal3 and nonsteroidal4 entities in recent
years.7,8 Herein we report the synthesis and SAR of a novel series
of pseudo-steroids with an improved selectivity of PR over GR
(Fig. 1).
Me
H
Me
H
Me
R
H
H
O
O
O
mifepristone
oxa-steroids
N
OH
O
The pseudo-steroids 1c were synthesized in 14 steps starting
from commercially available trenbolone 3. Several possible ap-
proaches were evaluated starting from 3 where the strategy was
to oxidize C-ring double bond to yield the dialdehyde or equivalent
functional group. Scheme 1 represents our optimal medicinal
chemistry route which led to the common intermediate 10. The
synthesis began with Swern oxidation of the C17 hydroxyl group
of 3 to yield diketone 4 in nearly quantitative yield. The crude
product obtained from oxidation was converted selectively to ketal
5 by reacting with excess ethylene glycol in the presence of ethyl-
formate and a catalytic amount of TsOH. At lower temperature,
that is, 0–5 °C, almost no diketalization was observed even when
an excess amount of ethylene glycol was used. The next step in-
volved the dihydroxylation of 5. Several catalytic dihydroxylation
Me
H
H
O
Pseudo steroid, 1c
Figure 1. Structures of PRMs.
processes were evaluated, including number of asymmetric Sharp-
less oxidations. The dihydroxylation using catalytic amount of
OsO4 along with NMO as co-oxidant and a mixed solvent system
(t-BuOH, THF, H2O) was most efficient to yield compound 6 selec-
tively in more than 55% yield. In this reaction 44% of starting mate-
rial was recovered. The cleavage of the diol 6 to the dialdehyde 7
was efficiently carried out with lead tetracetate followed by reduc-
tion of dialdehyde using NaBH4 to triol 8 in >95% yield for two
steps. The most crucial step for the synthesis was achieving a
* Corresponding author. Tel.: +1 908 268 2336.
E-mail address: drnfjain@gmail.com (N. Jain).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.01.095

3978
N. Jain et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3977–3980
O
O
O
Me
Me
H
OH
H
H
ii
i
H
H
H
O
O
O
O
O
O
4
5
3
iii
OH
O
O
O
OH
Me
Me
H
Me
OH
OH
HO
O
O
HO
H
H
H
v
iv
H
H
O
O
O
O
7
O
O
6
8
vi
HO
OTBS
OTBS
Me
R1
O
OTBS
Me
OH Me
H
H
vii
H
H
viii(a-c)
H
H
O
O
O
O
11a: R1= NMe2
11b: R1=SMe
11c: R1= OMe
9
10
ix
R1
R1
O
R1
OH
OH
Me
O
MeO
O
MeO
O
H
xi
x
H
H
H
H
O
H
O
O
13a: R1= NMe2
13b: R1=SMe
13c: R1= OMe
12a: R1= NMe2
12b: R1=SMe
12c: R1= OMe
O
14a: R1= NMe2
14b: R1=SMe
14c: R1= OMe
0
Scheme 1. Reagents and conditions: (i) DMSO, (COCl)2 Et3N; (ii) ethylorthoformate, (CH2OH)2 TsOH; (iii) OsO4, NMO, t-BuOH:THF:H2O (1:1:1); (iv) lead acetate, THF, 0 °C;
(v) NaBH4, THF:H2O (10:1); (vi) TBSOTf, 2.6 lutidine, CH2Cl2, ꢀ78 °C, 44%; (vii) DMSO, (COCl)2 Et3N, CH2Cl2, ꢀ78 °C to rt, 94%; (viiia) p-Me2NPhMgBr, ꢀ78 °C, 10 h, 87% (ds
3:1); (viiib) p-MeSPhMgBr, ꢀ78 °C, 10 h, 71% (ds 2:1); (viiic) p-MeOPhMgBr, ꢀ78 °C, 10 h, 91% (ds 3:1); (ix) TBAF, THF, ꢀ0 °C; (x) TsOH (2 mol %), CH2Cl2, 0 °C to rt, 36 h, 90–
0
95% (ds >30:1); (xi) ethylorthoformate, (CH2OH)2 TsOH, 0 °C, 80–88%; (xii) MeCCMgBr, THF, 0 °C to rt, 12 h, 70–87%; (xiii) TsOH, acetone:H2O (1:1), rt, 12 h.
selective protection of primary alcohol 8. Among several reaction
conditions surveyed, the 1.5 equiv of TBSOTf and 1.4 equiv of 2,6-
lutidine in CH2Cl2 yielded desired mono TBS protected compounds
9 along with other mono or bis TBS protected alcohols (structure
not shown). The mixture of these side products were recycled by
converting back to triol 8 using n-Bu4NF in THF. The TBS-diol 9
was converted to ketoaldehyde 10 efficiently using Swern oxida-
tion conditions. The aromatic side chain was introduced during
this step using the appropriate Grignard reagent. An excess freshly
prepared Grignard reagent was added to aldehyde at ꢀ20 °C to
yield addition product in 3–4:1diastereomeric ratios. The yield of
these Grignard additions ranged from 80% to 97% depending on
quality and type of reagent prepared. Using Grignards reagents,
compound 11a (R1 = NMe2), 11b (R1 = OMe) and 11c (R1 = SMe)
were prepared. The deprotection of the diol 11a yielded diol 12a
in >90% yield. At this point, the diastereoisomers were not sepa-
rated. When the diol was treated with TsOH in acetone:water
(4:1), it gave almost exclusively ketone 13a. The stereochemistry
of 13a was determined using multiples 1D and 2D NOE experi-
ments. The A ring of diketone 13a was reprotected using ethylene
glycol and methyl orthoformate in the presence of catalytic
amount of TsOH to yield 14a. Similarly compound 14b
(R1 = OMe) and 14c (R1 = SMe) were also prepared starting from
11b and 11c, respectively, using similar sequential reactions. The
intermediates 14(a–c) were converted to compounds 1(b–k) in
two steps which included the addition of corresponding Grignard
reagent followed by hydrolysis of ketal to the yield final ketone.
Compound 1a was prepared using LAH reduction of ketone 14a fol-
lowed by hydrolysis of the ketal using 1 N HCl. Details of these
steps are in Table 1.
The spirofuranes 2a and 2b were prepared in three steps from
14a and 14b as shown in Scheme 2. The iodide 16 (t-butyl-(3-
iodo-but-3-enyloxy)-dimethyl-silane was prepared according to
the procedure described by Piers and Karunaratne.9 The halogen
metal exchange was carried out at ꢀ100 °C in THF using 1.1 equiv
of n-BuLi. The ketones 14a or 14b were added to this reaction mix-
ture to yield addition products 17a (77%) and 17b (80%), respec-
tively. The TBS group was exchanged in situ first by treating
compound 17a or 17b with TBAF (1 M, in THF) followed by reac-
tion with MsCl and pyridine to yield the spirofuranes 18a and
18b. Compound 18a and 18b were converted to corresponding ke-
tones by hydrolysis using catalytic amount of TsOH in acetone/
water to yield spirofuranes 2a and 2b, respectively.
Compounds 1(a–k) and 2(a–b) were evaluated for PR antago-
nist activity based on their ability to block progesterone induction
of alkaline phosphatase activity in the human breast cancer cell
line T47D. They were also tested for GR antagonist activity based
on their ability to inhibit corticoid-induced transcription from a
glucocorticoid response element (GRE)-linked luciferase reporter
gene in the human lung carcinoma cell line A549. The IC50 values

N. Jain et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3977–3980
3979
Table 1
SAR study of Pseudo-steroids
R1
O
R1
R1
MeO
O
O
Me
O
MeOH
R2
O
H
v
H
H
CH2
H
H
H
O
O
O
2
14
1
.
Compound
R1
R2
–H
–CCH
–CCMe
–CCPh
–CF2CF3
–C(Me)CH2
–CF2CF3
–C(Me)CH2
–C(Me)CH2
CCH
CCMe
CCPh
CCPhpCF3
—
—
Reagent (v)
Yield (%)
T47D (PR) IC50 (nM)
A549 (GR) IC50 (nM)
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
2a
2b
NMe2
NMe2
NMe2
NMe2
NMe2
NMe2
SMe
SMe
SO2Me
OMe
OMe
OMe
OMe
NMe2
OMe
LiAlH4
77
65
51
81
41
81
30
61
—
55
54
61
41
—
930
33
34
60
36
1400
68
17
102
20
150
7
HCCMgBr
MeCCMgBr
PhCCMgBr
LiCF2CF3
BrMgC(Me)CH2
LiCF2CF3
BrMgC(Me)CH2
NA
HCCMgBr
MeCCMgBr
BrMgCCPh
BrMgCCPhpCF3
—
0.3
56
3.3
>1000
>1000
>1000
280
82
1
7
1.4
58
>3000
110
41
21
26
62
132
1.6
—
—
Mifepristone
of the compounds from the T47D and A549 assays are listed in Ta-
ble 1. The ratio of their IC50 values was calculated as a measure of
the separation of PR and GR antagonist activities. Mifepristone was
tested as a control.
The PR and GR activities of pseudo-steroids 1(a–l) with various
substitutions at the C17-ethynyl position and various modifica-
tions at C10 are listed in Table 1. Compound 1a ? 1f have a similar
aromatic side chain as that of mifepristone. Compound 1a (R2 = H)
showed poor PR antagonist activity in T47D cell-based functional
assay. Similarly, poor activity was also observed in GR antagonist
activity in A549 cell-based functional assay. Moderate gain in PR
activity (IC50 33–60 nM) was observed when H was replaced by
various substituted alkynes (1a vs 1b–1c). Similar modest gain in
activity was observed for compound 1e (R2 = CF2CF3). These com-
pounds also showed modest gain in GR antagonist activity (IC50
20–102 nM) with very little signs of separation between PR and
GR antagonist activity. When R2 = H was replaced by an isopropyl-
ene group R2 = –C(Me)@CH2 (1a vs 1f) significant increase in PR
R1
R1
Li
OTBS
MeO
O
MeOH
CH2
O
OTBS
H
H
O
-78 ºC
(i)
O
H
H
17a-b
O
O
14a: R1= NMe2
14c: R1= OMe
(ii)
R1
O
R1
OMs
MeOH
CH2
O
MeO
O
H
H
H
CH2
O
H
O
O
18a-b
(iii)
R1
MeO
O
H
2a; R1=NMe2
2b; R1=OMe
CH2
H
O
Scheme 2. Reagents and conditions: (i) CH2@C(I)CH2CH2OTBS, n-BuLi, ꢀ78 °C, 78–91%; (ii) n-Bu4NF (5 equiv), THF, 3 h followed by pyridine (excess); MsCl, rt, 24 h, 61–77%;
(iii) TsOH, acetone/H2O; 93–95%.

3980
N. Jain et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3977–3980
progesterone derived compounds such as mifepristone. In this
compound (1a), the oxygen in the C-ring available for the hydrogen
bonding with water molecule bridges with amino acid ANS710.
There is wider open space available around D ring and this finding
is consistent with our SAR study. The presence of phenylalanine
amino acid 797 could possibly induce the
p–p interaction and
hence provide better potency for compounds with isopropene
and spirofurane in D ring system. The A ring system as well as side
chain of the pseudo-steroids have a similar binding pocket as
mifepristone.
In summary, several novel pseudo-steroid analogs were pre-
pared in 14–16 steps. Modifications of the C10 side chain as well
as D ring system lead to changes in both PR as well as GR antag-
onist activity in cell-based functional assays. Molecular modeling
using known X-ray crystal structure revealed that these com-
pounds have different mode of binding. The oxygen atom in C-
ring played a similar role as the C17 hydroxy group in D ring
of the mifeprestone. The SAR study executed on the C17 as well
as C10 positions resulted in several potent and novel PR antag-
onists. Analog 1c showed in vivo efficacy in the C3 model via
oral route.
Figure 2. Molecular modeling of compound 1 and mifepristone bound to PR based
on the X-ray crystal structures of hPR-norenthindrone and hGR-mifepristone
complexes.
antagonist activity was observed (IC50 = 0.3 nM) with only modest
gain in GR antagonist activity (IC50 = 150 nM).
Acknowledgement
In compounds 1g and 1h –NMe2 was replaced by SMe in the
aromatic side chain at C10 of pseudo-steroid scaffold. As observed
previously for compound with an isopropene group 1h (1g vs 1h),
when the R1 = SMe attached to the aromatic group was replaced by
–SO2Me, complete loss of PR as well as GR activity was observed.
In compounds 14j–14m, the R1 = NMe2 group was replaced by
OMe in the aromatic side chain at C10 of pseudo-steroid scaffold.
Interestingly complete loss of the PR antagonist activity was ob-
served in small alkyne substituted compounds (1j: R2 = CCH and
1k: R2 = CCMe) while GR antagonist activity was unchanged in
these compounds. In bulky alkyne group, a moderate gain in PR
antagonist activity was observed.
Compounds 2a and 2b, with spirofurane at C17 position and
with two different substitution groups at C10 aromatic side chain
were potent in the PR antagonist T47D cell-based functional assay
(IC50 = 1–7 nM) while modest activity in GR antagonist A549 cell-
based functional assay (IC50 = 62–132 nM) was observed as shown
in Table 1.
We thanks Dr. James Lanter for his valuable suggestions during
preparation of this manuscripts.
References and notes
1. (a) Murphy, A. A.; Kettel, L. M.; Morales, A. J.; Roberts, V. J.; Yen, S. S. J. Clin.
Endocrinol. Metab. 1993, 76, 513; (b) Murphy, A. A.; Morales, A. J.; Kettel, L. M.;
Yen, S. S. Fertil. Steril. 1995, 64, 187; (c) Kettel, L. M.; Murphy, A. A.; Morales, A.
J.; Yen, S. S. Am. J. Obstet. Gynecol. 1998, 178, 1151; (d) Kettel, L. M.; Murphy, A.
A.; Morales, A. J.; Yen, S. S. Hum. Reprod. 1994, 9, 116.
2. Brogden, R. N.; Goa, K. L.; Faulds, D. Drugs 1993, 45, 384.
3. (a) Teutsch, G.; Philibert, D. Hum. Reprod. 1994, 9, 12; (b) Chwalisz, K.; Perez, M.
C.; DeManno, D.; Winkel, C.; Schubert, G.; Elger, W. Endocr. Rev. 2005, 26, 423;
(c) Chabbert-Buffet, N.; Meduri, G.; Bouchaard, P.; Spitz, I. M. Hum. Reprod.
Update 2005, 11, 293.
4. (a) Allan, G. F.; Sui, Z. Mini-Rev. Med. Chem. 2005, 5, 701; (b) Zhang, P.; Fensome,
A.; Wrobel, J.; Winneker, R.; Zhang, Z. Expert Opin. 2003, 13, 1839; (c) Zhang, P.;
Kern, J. C.; Terefenko, E. A.; Fensome, A.; Unwalla, R.; Zhang, Z.; Cohen, J.;
Berrodin, T. J.; Yudt, M. R.; Winneker, R. C.; Wrobel, J. Bioorg. Med. Chem. 2008,
16, 6589.
5. Lazar, G.; Lazar, G., Jr.; Husztik, E.; Duda, E.; Agarwal, K. K. Ann. N. Y. Acad. Sci.
1995, 277, 248.
Compound 1c was tested orally in ovariectomized Sprague–
Dawley rats in a rat uterine complement C3 assay.10 In this assay,
ethinyl estradiol (EE) was used to stimulate C3 expression. Proges-
tins inhibited EE-induced expression. In turn, antiprogestins coun-
teracted progestin-dependent inhibition. When compound 1c was
administered via the oral route along with EE and progesterone, it
was found to be efficacious. An ID50 = 16 mg/kg was calculated for
this compound 1c. The ID50 for the mifepristone was 4.6 mg/kg.
The possible binding modes of compounds 1 and 2 in the li-
gand-binding domain of PR suggested by molecular modeling are
shown in Figure 2. The model was built based on the X-ray crystal
structures of hPR-norenthindrone and hGR-mifepristone com-
plexes.7 The molecular modeling suggests that these novel pseu-
do-steroids have different mode of binding compared to normal
6. (a) Kang, F.; Guan, J.; Jain, N.; Allan, G.; Linton, O.; Tannenbaum, P.; Chen, X.;
Xu, Jun; Peifang, Z.; Joseph, G.; Keith, D.; Lundeen, S.; Sui, Z. Bioorg. Med. Chem.
Lett. 2007, 17, 2531; (b) Kang, F.; Allan, G.; Guan, J.; Jain, N.; Linton, O.;
Tannenbaum, P.; Xu, J.; Zhu, P.; Gunnet, J.; Chen, X.; Demarest, K.; Lundeen, S.;
Sui, Z. Bioorg. Med. Chem. Lett. 2007, 17, 907; (c) Kang, F.; Jain, N.; Sui, Z.
Tetrahedron Lett. 2006, 48, 193; (d) Kang, F.; Jain, N.; Sui, Z. Tetrahedron Lett.
2006, 47, 9021; (e) Michna, H.; Parczyk, K.; Schneider, M. R.; Nishino, Y. Ann. N.
Y. Acad. Sci. 1995, 761, 224.
7. (a) Poole, A. J.; Li, Y.; Kim, Y.; Lin, S.-C. J.; Lee, W.-H.; Lee, E. Y.-H. P. Science 2006,
314, 1467; (b) Marx, J. Science 2006, 314, 1370.
8. (a) Kang, F.-A.; Allan, G.; Guan, J.; Jain, N.; Linton, O.; Tannenbaum, P.; Xu, J.;
Zhu, P.; Gunnet, J.; Chen, X.; Demarest, K.; Lundeen, S.; Sui, Z. Bioorg. Med. Chem.
Lett. 2007, 17, 907; (b) Kang, F.-A.; Jain, N.; Sui, Z. Tetrahedron Lett. 2007, 48,
193.
9. Piers, E.; Karunaratne, V. J. Org. Chem. 1983, 48, 1774.
10. Lundeen, S. G.; Zhang, Z.; Zhu, Y.; Carver, J. M.; Winneker, R. C. J. Steroid
Biochem. Mol. Biol. 2001, 78, 137.