Nonsteroidal progesterone receptor antagonists based on 6-thiophenehydroquinolines

Article abstract of DOI:10.1016/S0960-894X(00)00011-1

Synthesis and biological evaluation of 6-thiophene 1,2-dihydro or 1,2,3,4-tetrahydroquinoline derivatives resulted in a number of potent nonsteroidal antiprogestins. (C) 2000 Elsevier Science Ltd. All rights reserved.

Full text of DOI:10.1016/S0960-894X(00)00011-1

Bioorganic & Medicinal Chemistry Letters 10 (2000) 415±418
Nonsteroidal Progesterone Receptor Antagonists Based on
6-Thiophenehydroquinolines
Lin Zhi,* Christopher M. Tegley,y Barbara Pio,{ Sarah J. West, Keith B. Marschke,
Dale E. Mais and Todd K. Jones{
Ligand Pharmaceuticals, 10275 Science Center Drive, San Diego, CA 92121, USA
Received 28 October 1999; accepted 13 December 1999
AbstractÐSynthesis and biological evaluation of 6-thiophene 1,2-dihydro or 1,2,3,4-tetrahydroquinoline derivatives resulted in a
number of potent nonsteroidal antiprogestins. # 2000 Elsevier Science Ltd. All rights reserved.
Chemistry
Introduction
A number of novel classes of nonsteroidal anti-
progestins1±6 have emerged during the past several years
aimed at improving the side-e€ect pro®le inherent with
steroidal antiprogestins and exploring therapeutic
opportunities other than as abortifacients, such as the
treatment of breast cancer, endometriosis and uterine
®broids or as contraceptive agents.7,8 Recently, we
reported the discovery and preliminary structure±activ-
ity relationships (SAR) of 6-phenyl 1,2-dihydroquino-
line analogues, the ®rst orally available nonsteroidal
antiprogestin pharmacophore, using cotransfection
and competitive binding assays as guides.9,10 The lead
compound LG120830 (1) demonstrated potent in vivo
antiprogestational activity which is equivalent to ona-
pristone (2, ZK98,299) in the mouse implantation
assay.9 However, the noted hepatomegaly in the tested
animals especially in the high dose groups raised some
concerns about the series.9 To continue the SAR study
of the novel pharmacophore and to address the hepa-
tomegaly issue, we explored the pendant 6-aryl group
and the dihydroquinoline ring. This report describes our
new ®ndings in using 6-thiophene as a bioisostere of the
6-phenyl group as well as preliminary SAR results on
quinoline ring modi®cation (Fig. 1).
The preparation of compounds of general structure 3 is
depicted in Scheme 1 wherein the bromothiophenes
were coupled with the dihydroquinoline boronic acid
(4)9 via a palladium catalyzed Suzuki reaction.11
Removal of the t-Boc protection group with TFA
a€orded compounds 5 and 6 in moderate to high yield.
The racemic tetrahydroquinoline analogue
7 was
obtained by palladium catalyzed hydrogenation of the
corresponding dihydroquinoline analogue 6. Scheme 2
describes the synthesis of the 3-quinolinone analogues
11 and 12 by a similar palladium catalyzed cross-cou-
pling strategy but using boronic acid 10. Hydroboration
of dihydroquinoline 8 followed by oxidation and
methylation provided the 3-quinolinone 9, which was
converted to boronic acid 10 by the standard lithiation/
borate-formation/hydrolysis procedures. The prepara-
tion of compounds 5c and 11 are illustrative.12,13
Results and Discussion
The biological activity of the new compounds on human
progesterone receptor (hPR) were evaluated in a
cotransfection assay in CV-1 cells (African green mon-
key ®broblasts) and in a competitive binding assay.14
The results are summarized in Table 1. Progesterone,
the 6-phenyl analogue LG120830 (1) and onapristone
(2) were used as standards. For the thiophene series 5,
the meta-cyano analogue 5c (R2=CN, R1=R3=H) is
the most active compound, which is consistent with the
results of LG120830 series in which a meta substituted
*Corresponding author. Tel.: +1-858-550-7663; fax: +1-858-550-
7249; e-mail: lzhi@ligand.com
yCurrent address: Amgen, One Amgen Center Dr., Thousand Oaks,
CA 91320, USA.
{Current address: The R. W. Johnson Pharmaceutical Research Insti-
tute, 3535 General Atomics Ct., San Diego, CA 92121, USA.
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00011-1

416
L. Zhi et al. / Bioorg. Med. Chem. Lett. 10 (2000) 415±418
Figure 1. LG120830 (1), onapristone (2), and general structure of 6-
thiophene analogues (3).
Scheme 2. (a) BH3-THF, H2O2, THF, rt; (b) PCC, CH2Cl2, rt; (c)
NaH, MeI, Toluene, rt; (d) n-BuLi, THF, 78 ꢀC; (e) B(OMe)3; (f)
H3O+; (g) Pd(PPh3)4, K2CO3, DME, 80 ꢀC; (h) TFA, CH2Cl2, rt.
the T47D assay. Most of the potent new compounds in
CV-1 cells are much less active and some of them
behaved as partial agonists in T47D cells.18
The cross-reactivity of a number of representative ana-
logues (5c, 6g, 6h, 6k, 7, 11 and 12) with other steroid
receptors was assessed using human androgen (hAR),
glucocorticoid (hGR), estrogen (hER), and miner-
alocortocoid (hMR) cotransfection assays (Table 2). No
agonist activity was observed for any of the tested
compounds, but antagonist activity was detected, most
notably on the AR and GR. Compound 7 is much less
selective than compound 6k in terms of hPR/hAR and
hPR/hGR ratios, which suggests that the 3,4-ole®n is
important for the receptor selectivity. The 30-methyl of
the 2-thiophene series also has a signi®cant impact on
the selectivity (compare compounds 6k and 12 with
compounds 6h and 11) (Table 3).
Scheme 1. (a) Pd(PPh3)4, K2CO3, DME, 80 ꢀC; (b) TFA, CH2Cl2, rt;
(c) 5% Pd/C, H2, EtOAc.
electron-withdrawing group on the pendent 6-aryl
group enhanced the antiprogestational activity. In the
thiophene series 6, the meta-nitro and meta-cyano ana-
logues (6g and 6h) are the best compounds. An addi-
tional methyl group at the ortho position has no e€ect
on biological activity (compare 6h with 6k). The SAR
around the dihydroquinoline ring was also explored and
it was noted that removal of the 3,4-ole®n and/or
introduction of a 3-ketone group did not have sig-
ni®cant impact on the hPR antagonist activity (com-
pounds 7, 11 and 12). It is worthy of mention that in a
related hPR agonist series the 3,4-ole®n or 3-ketone was
essential for progestational activity.15 All of the 6-thio-
phene 1,2-dihydroquinoline analogues showed good
ecacy as hPR antagonists regardless their potency. It
is interesting that the analogues without the 3,4-ole®n
(compounds 7, 11 and 12) exhibited excellent hPR
antagonist activity at low concentration but behaved as
agonists at higher concentration with good ecacy.
The lead compound 5c (LG121046) demonstrated
potent oral antiprogestational activity in rodent models
such as the mouse implantation9 and decidualization
assays. No hepatomegaly was observed at the pharma-
cological doses.19
Conclusion
The SAR study around the pendent 6-phenyl group of
LG120830 series generated 6-thiophene analogue series
(3), which served as bioisostere of 6-phenyl analogues
but without having the hepatomegaly e€ect in rodents.
The preliminary SAR at the 1,2-dihydroquinoline moi-
ety revealed the sensitivity of the new structure towards
the steroid hormone receptor selectivity. The unique
biological activity and the chemistry simplicity of the
orally available pharmacophore o€er great opportu-
nities for developing clinically attractive selective non-
steroidal antiprogestins.
The new antiprogestins were also evaluated in the T47D
human breast cancer cell line16,17 and the assay results
are summarized in Table 2. Steroidal antiprogestin
onapristone showed similar activity in both the
cotransfection and T47D assays while the 6-thiophene
1,2-dihydroquinoline analogues behaved quite poorly in

L. Zhi et al. / Bioorg. Med. Chem. Lett. 10 (2000) 415±418
417
Table 1. Cotransfection and binding data for the new compoundsa,b
hPR Cotransfection assay in CV-1 cells
Agonist Antagonist
Ecacy (%)
hPR
Binding
No.
R1
R2
R3
Ecacy (%)
EC50 (nM)
IC50 (nM)
Ki (nM)
Progesterone
LG120830
Onapristone
100
Ð
Ð
Ð
2.9‹0.9
Ð
Ð
Ð
30‹4
2.2‹0.4
318‹169
245‹22
24‹9
3.5‹0.2
10‹1
18‹3
1
2
82‹3
95‹1
88‹3
83‹11
84‹8
78‹7
74‹6
85‹11
76‹10
91‹4
75‹5
78‹12
71‹10
77‹3
77‹11
86‹4
95‹4
89‹6
80‹7
79‹1
73‹6
Ð
Ð
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
6f
6g
6h
6i
CN
H
H
Me
Me
H
H
H
Cl
H
CHO
CN
CN
CN
H
H
Br
H
H
H
H
H
H
H
H
H
Me
H
Me
H
H
H
H
H
H
Br
H
Me
>100
Ð
Ð
1800‹700
37‹16
3.5‹0.6
31‹10
36‹5
237‹80
25‹5
32‹12
12‹3
31‹7
34‹10
Ð
Ð
Ð
Ð
29
Ð
Ð
Ð
Ð
35
Ð
Ð
Ð
Ð
Ð
Ð
2700
Ð
Ð
Ð
Ð
2900
Ð
Ð
109‹32
124‹31
416‹98
232‹48
105‹31
43‹18
65‹31
729‹204
31‹20
27‹9
52‹15
242‹80
33‹13
31‹14
14‹5
Br
CHO
NO2
CN
CN
CN
CN
80‹8
2.6‹1.0
55‹16
433‹93
249‹58
26‹2
6.2‹2.2
12.4‹5.7
3.9‹1.87
H
Br
H
6j
6k
7
11
12
Ð
Ð
88‹2
73‹5
95‹13
2290‹290
1190‹440
350‹200
10‹1
aEcacy for agonist assays is de®ned in % versus progesterone=100. Ecacy for antagonist assays is % inhibition of transscriptional activity
observed at an EC50 concentration of progesterone.
bValues are in nM, mean ‹SEM, N>2. If no SEM is noted, value is from a single determination. ``Ð''=not active (<20% ecacy and/or >10 mM
potency).
Table 2. T47D Assay data for reference compounds and the new analoguesa
hPR T47D Assay
Agonist
Antagonist
Ecacy (%)
No.
R1
R2
R3
Ecacy (%)
EC50 (nM)
IC50 (nM)
Progesterone
LG120830
Onapristone
100
40
Ð
Ð
1.8‹0.3
2200
Ð
Ð
Ð
245‹47
1400
580
Ð
Ð
3500
2650
Ð
Ð
59‹5
83‹8
90
Ð
37‹22
3.3‹2.2
278
1
2
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
6f
6g
6h
6i
CN
H
H
Me
Me
H
H
H
Cl
H
CHO
CN
CN
CN
H
H
Br
H
H
H
H
H
H
H
H
H
Me
H
Me
H
H
H
H
H
H
Br
H
Me
Ð
95
102
37‹2
43
58
Ð
Ð
35
33
Ð
Ð
35
41
60
Ð
63‹3
67‹3
39‹2
95
75‹5
84‹4
69
80
95
60
55
106‹11
120‹26
150‹21
700
105‹35
190‹20
151
Br
71
78
70
80
CHO
NO2
CN
CN
CN
CN
Ð
1024
1800
700
Ð
500
H
Br
H
40
100
56‹2
120
250
123‹22
6j
6k
45
aSee Table 1 for legend.

418
L. Zhi et al. / Bioorg. Med. Chem. Lett. 10 (2000) 415±418
Table 3. Cross-reactivity data in cotransfection assays for selected analoguesa,b
No.
hAR Ecacy
(%)
hAR IC50
(nM)
hGR Ecacy
(%)
hGR IC50
(nM)
hER Ecacy
(%)
hER IC50
(nM)
hMR Ecacy
(%)
hMR IC50 (nM)
1
2
88
210
Ð
100‹0
83‹10
Ð
Ð
27‹4
2600‹200
Ð
3200
780‹230
113‹18
900‹170
35‹8
Ð
27‹4
Ð
Ð
Ð
Ð
Ð
Ð
Ð
Ð
>1000
Ð
Ð
Ð
Ð
Ð
Ð
Ð
80‹2
34‹9
88‹2
Ð
>1000
>1000
2050‹800
Ð
Ð
2000‹600
1000‹500
2700‹300
2100‹800
93‹4
91‹7
89
79
99
87‹3
90‹1
91‹5
269‹57
494‹145
1460
1110
200
45‹10
1100‹490
150‹70
5c
6g
6h
6k
7
61
Ð
99‹1
98‹1
98‹1
99‹2
97‹2
89‹12
56‹15
83‹3
11
12
aEcacy is % inhibition of transcriptional activity observed at an EC50 concentration of DHT for AR, dexamethasone for GR, estradiol for ER and
aldosterone for MR.
bSee Table 1 for legend.
13. Preparation of 11: To a solution of compound 8 (6.5 g, 18
mmol) in THF (20 mL) at 0 ꢀC was added BH3-THF (1 M, 29
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mmol) portion-wise and stirred at room temperature for 2 h.
The mixture was ®ltered through a plug of Florisil to remove
chromium and was concentrated to a€ord the crude 3-ketone
compound (4.3 g, 81%). To a solution of the 3-ketone (3.0 g,
8.1 mmol) in toluene (70 mL) at 78 ꢀC was added lithium
bis(trimethylsilyl)amide (1 M in THF, 24 mL) slowly and
warmed to 0 ꢀC. Excess iodomethane (2.5 mL) was added to
the reaction mixture and was allowed to stir at rt till the
starting material was consumed. Standard work up followed
by chromatography provided compound 9 as yellow oil (1.8 g,
58%). To a solution of compound 9 (0.10 g, 0.26 mmol) in
ether (3 mL) at 78 ꢀC was treated with nBuLi (1.6 M in hex-
ane, 0.19 mL) and stirred for 5 min before the addition of
B(OMe)3 (0.09 mL, 0.78 mmol). The reaction was warmed to
room temperature and quenched with aqueous HCl (0.5 M) to
adjust the PH <2. Extraction with EtOAc followed by chro-
matography a€orded compound 10 in 60% yield. The cross-
coupling reaction between compound 10 and 4-bromo-2-cya-
nothiophene was performed by a similar procedure as descri-
bed above to give compound 11 as colorless oil; 1H NMR (400
MHz, CDCl3) 7.83 (d, J=1.4 Hz, 1H), 7.54 (d, J=1.4 Hz,
1H), 7.31 (d, J=2.0 Hz, 1H), 7.30 (dd, J=8.0 and 2.0 Hz, 1H),
6.73 (d, J=8.0 Hz, 1H), 3.78 (bs, 1H), 1.49 (s, 6H) and 1.36 (s,
6H); 13C NMR (100 MHz, CDCl3) 214.5, 143.6, 143.0, 136.3,
130.3, 126.2, 126.1, 125.2, 123.8, 116.5, 114.5, 110.6, 60.1, 47.0,
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acid (2.4 g, 21 mmol) in CH3CN/H2O (995%, 20 mL) was
stired at 65 ꢀC for 8 h and quenched with aqueous NaOH
(10%, 10 mL). The mixture was extracted with EtOAc and
concentrated. Chromotography a€orded 4-bromo-2-cyanthio-
phene as a white solid (0.50 g, 51%); 1H NMR (400 MHz,
CDCl3 7.54 (d, J=1.3 Hz, 1H), 7.50 (d, J=1.3 Hz, 1H). A mix-
ture of the bromothiophene (0.50 g, 2.7 mmol), Pd(PPh3)4 (22
mg, 0.02 mmol), compound 4 (0.30 g, 0.63 mmol) and aqueous
K2CO3 (1 M, 1 mL) in toluene (50 mL) and EtOH (10 mL)
was heated at 80 ꢀC for 2 h and was diluted with EtOAc. The
mixture was washed with brine, concentrated and then treated
with TFA (2 mL) in CH2Cl2 (20 mL) for 2 h at rt. Chroma-
tography of the crude mixture a€orded compound 5c as a
white solid (0.16 g, 91%); mp 66±67 ꢀC; 1H NMR (400 NMz),
CDCl3) 7.79 (d, J=1.3 Hz, 1H), 7.46 (d, J=1.3 Hz, 1H), 7.20
(d, J=1.9 Hz, 1H), 7.16 (dd, J=8.0 and 1.9 Hz, 1H), 6.46 (d,
J=8.0 Hz, 1H), 5.37 (s, 1H), 3.84 (bs, 1H), 2.03 (s, 3H) and
1.30 (s, 6H).
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18. See activity di€erences of related nonsteroidal progestin
series in CV-1 and T47D cell lines (ref 15).
19. Results of these experiments will be reported in due course.