Identification of oxazolidinediones and thiazolidinediones as potent 17β-hydroxysteroid dehydrogenase type 3 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2011.10.095

Novel and potent inhibitors of 17β-hydroxysteroid dehydrogenase type 3 (17β-HSD3) were identified based on oxazolidinedione and thiazolidinedione derivatives, starting from a high-throughput screening hit, 5-(3-bromo-4-hydroxybenzyl)-3-(4-methoxyphenyl)-1

Full text of DOI:10.1016/j.bmcl.2011.10.095

Bioorganic & Medicinal Chemistry Letters 22 (2012) 504–507
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Identification of oxazolidinediones and thiazolidinediones as potent
17b-hydroxysteroid dehydrogenase type 3 inhibitors
Koichiro Harada a, , Hideki Kubo a, Akio Tanaka b, Kazuhiko Nishioka c
⇑
a Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd, 1-98, Kasugadenaka 3-chome, Konohana-ku, Osaka 554-8558, Japan
b Organic Synthesis Research Laboratory, Sumitomo Chemical Co., Ltd, 1-98, Kasugadenaka 3-chome, Konohana-ku, Osaka 554-8558, Japan
c Crop Protection Division-International, Sumitomo Chemical Co., Ltd, 27-1, Shinkawa 2-chome, Chuo-ku, Tokyo 104-8260, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel and potent inhibitors of 17b-hydroxysteroid dehydrogenase type 3 (17b-HSD3) were identified
based on oxazolidinedione and thiazolidinedione derivatives, starting from a high-throughput screening
hit, 5-(3-bromo-4-hydroxybenzyl)-3-(4-methoxyphenyl)-1,3-thiazol-2-one 1. 5-(3-Bromo-4-hydroxyb-
Received 12 August 2011
Revised 18 October 2011
Accepted 27 October 2011
Available online 12 November 2011
enzylidene)-3-(4-methoxyphenyl)-2-thioxo-1,3-thiazolidin-4-one 21 exhibited
a promising activity
profile and demonstrated significant selectivity over the related 17b-HSD isoenzymes and nuclear
receptors.
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
17b-Hydroxysteroid dehydrogenase type 3
inhibitors
Oxazolidinedione
Thiazolidinedione
Prostate cancer
Prostate cancer is the most frequently diagnosed cancer in men.
According to the American Cancer Society, an estimated 192,280
men were diagnosed with prostate cancer in the US during 2009.
With an estimated 27,360 deaths in 2009, prostate cancer is the
second-leading cause of cancer death in men.1 For advanced pros-
tate cancer, 10–60% of the patients experience biochemical recur-
rence associated with treatment failure, and no consensus exists
on the optimal therapy.
MeO
N
Br
S
O
OH
1
Figure 1. Structure of HTS hit compound 1.
The human prostate is a hormone-sensitive organ that depends
on androgens for growth and development. The regulation of
androgen biosynthesis or its action on the androgen receptor is
central to the management of prostate cancer.2 Production of
androgens is controlled at two levels within the central nervous
system; in addition, it is controlled locally in peripheral organs that
are targeted by the hormones. The active androgens testosterone
(T) and dihydrotestosterone (DHT) can be synthesized through
the conversion of the inactive precursor 4-androstene-3,17-dione
as a cofactor, in testis and prostate tissue.4 17b-HSD3 is expressed
at high levels in these peripheral target tissues, suggesting its po-
tential involvement in both gonadal and non-gonadal T biosynthe-
sis. In addition, the expression of 17b-HSD3 mRNA in cancerous
prostate biopsies was found to be 30-fold higher than in normal
tissue.5 Therefore, the role of 17b-HSD3 in T biosynthesis makes
this enzyme an attractive molecular target of a small-molecule
inhibitor for the treatment of prostate cancer.6
From a high-throughput screening (HTS) of a 200K-member of
small-molecule compound library in search of inhibitors of the
17b-HSD3, we identified 5-(3-bromo-4-hydroxybenzyl)-3-(4-meth
oxyphenyl)-1,3-thiazol-2-one 1 with a submicromolar IC50 value
(Fig. 1).
Compound 1 represented an attractive starting point for medic-
inal chemistry in consideration of its biochemical potency.
We focused on the central ring system of biaryl-substituted het-
erocycle series. The biaryl analogs were prepared following the
synthetic procedure outlined in Scheme 1. Commercially available
p-anisidine 2 was treated with Boc2O, followed by addition of
(D
4-dione) by 17b-hydroxysteroid dehydrogenases (17b-HSDs),
which mediate the activation and deactivation of sex steroids
involving redox reactions centered about the C17 area of the ste-
roid backbone.3
17b-Hydroxysteroid dehydrogenase type 3 (17b-HSD3) cata-
lyzes the final step in the steroidogenesis of the potent androgen
T by selectively reducing the C17 ketone of
D
4-dione with NADPH
⇑
Corresponding author.
E-mail address: haradak@sc.sumitomo-chem.co.jp (K. Harada).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.10.095

K. Harada et al. / Bioorg. Med. Chem. Lett. 22 (2012) 504–507
505
MeO
MeO
MeO
O
f,g
NH2
N
N
H
NH2
NCO
H
2
6
9
a,b
h
j
MeO
MeO
MeO
O
N
N
NH
O
NH
N
OEt
O
O
c
t-Bu
O
k
O
3
7
10
11
i
MeO
MeO
MeO
O
O
Br
N
N
N
N
OTBS
N
O
O
O
t-Bu
Br
OH
O
8
4
d,e
m
l
MeO
MeO
MeO
O
O
O
O
N
N
N
O
Br
OH
Br
Br
OH
O
O
O
5
12
13
OH
Scheme 1. Reagents and conditions: (a) Boc2O, THF, rt, 5 h, 82%; (b) propargyl bromide, NaH, DMF, rt, 1 h, 71%; (c) 2-bromo-4-iodo-1-(t-butyldimethylsilyloxy)benzene,
Pd(OAc)2, CuI, PPh3, TEA, toluene, rt, 5 h, 68%; (d) AuPPh3Cl, AgSbF6, CH2Cl2, rt, 1.5 h, 43%; (e) TBAF, THF, rt, 0.5 h, 72%; (f) PhOCOCl, pyridine, AcOEt, rt, 1 h, 100%; (g)
hydrazine, DMF, rt, 3 h, 79%; (h) formamidine acetate, DMF, 80 °C, 5 h, 59%; (i) 3-bromo-4-acetoxybenzyl chloride, K2CO3, DMF, 80 °C, 5 h, then water, 50 °C, 1 h, 47%; (j)
HOCH2CO2Me, DMF, rt, 3 h, 91%; (k) NaOMe, toluene, 100 °C, 1 h, 85%; (l) 3-bromo-4-(t-butyldimethylsilyloxy)benzyl chloride, MeOMgOCO2Me, DMF, 85 °C, 3 h, 42%; and (m)
3-bromo-4-hydroxybenzaldehyde, b-alanine, AcOH, 120 °C, 4 h, 54%.
propargyl bromide, giving carbamate 3. The phenol moiety was
incorporated by Sonogashira cross-coupling with 2-bromo-4-
iodo-1-(t-butyldimethylsilyloxy)benzene to afford an intermediate
4 in a moderate yield. Intramolecular cyclization of 4 to benzyli-
dene oxazolidinone 5 was achieved by treatment with Au catalyst
and tetrafluoroantimonide.7 Conversion of aniline 2 to phenylcar-
bamate, followed by addition of hydrazine, provided (4-methoxy-
phenyl)semicarbazide 6. Then, addition of formamidine acetate
in DMF afforded (4-methoxyphenyl)triazolone 7. Alkylation of 7
with benzylchloride, followed by deprotection of the acetyl group,
gave the corresponding target compound 8. 4-Methoxyphenyliso-
cyanate 9 was treated with glycolate ester to give carbamate 10.
Then, addition of catalytic sodium methoxide in toluene, followed
by azeotropic removal of the generated alcohol under reflux, pro-
vided the cyclized product 11. A direct alkylation of 11 with 3-bro-
mo-4-(t-butyldimethyl silyloxy)benzyl chloride using magnesium
methyl carbonate (MMC) and subsequent deprotection of TBDMS
in situ gave benzyloxazolidinedione 12.8 Knoevenagel condensa-
tion of 11 with benzaldehyde in the presence of b-alanine in acetic
acid afforded the corresponding benzylidene derivative 13.9
Biological activities of the synthesized compounds were evalu-
ated in a human cellular assay, which measured the ability of the
compounds to inhibit 17b-HSD3. The IC50 values were calculated
dinedion 12 maintained a potent inhibitory activity. Based on this
result, introduction of a polar functional group at the 4-position of
5-benzylideneoxazolidinone 5 was expected to provide a substan-
tial boost in potency. On combining the oxazolidinone 12 with struc-
tural rigidity by an exo-olefin, the resultant 5-benzylideneoxazolid
inedione 13 exhibited a potent inhibitory activity with IC50 value
of 23 nM. On the other hand, the activity of compound 8 was much
weaker than that of the others.
Molecular modeling overlay indicated the differences in shape
between 1 and 13, based on the structures: in compound 1, the
benzyl group was bent at the sp3 carbon of the methylene; on
the other hand, the benzylidene oxazolidinedione part of com-
pound 13 was nearly planar. In both, it was found that the
methoxyphenyl group was practically located on the same plane
as the five-membered heterocyclic ring (Fig. 2).
With the identification of the benzylidene oxazolidine-dione as
a new active scaffold, we explored the replacement of oxygen on
the heterocyclic ring system to study further modification. The
methodology used to synthesize compounds 14–18 has been previ-
ously descried.10 Compounds 19–23 were prepared in an analogous
fashion as that is described for its close analog 13. Condensation of
oxazolidinediones and thiazolidinediones with 4-hydroxybenzal-
dehyde was achieved by Knoevenagel reaction (Scheme 2).
As a result, benzylidene oxazolidinedione and thiazolidinedione
derivatives showed good inhibitory activity; in particular, 2-thi-
oxo-1,3-oxazolidin-4-one 19 and rhodanine 21 improved in vitro
activity, with IC50 values of 13 and 14 nM, respectively.
for the inhibition at each concentration (1, 10, 100 nM, and 1 lM)
of each compound, by measured concentration of T converted from
D
4-dione with human 17b-HSD3 expressing HeLa cells.
As revealed by a comparison of biological activities between 1
and 5, replacement of the benzylthiazolone with benzylideneoxazo-
lidinone resulted in a similar potency (Table 1). 5-Benzyloxazoli-
Compound 20 substituted with sulfur at the 1-position of the
oxazolidinedione reduced the activity to one-fourth of the original

506
K. Harada et al. / Bioorg. Med. Chem. Lett. 22 (2012) 504–507
Table 1
MeO
MeO
SAR on the thiazolone ring of compound 1
O
O
N
N
a
MeO
X
Y
X
Y
Br
Heterocycles
Br
14 (X=O,Y=S)
19 (X=O,Y=S)
20 (X=S,Y=O)
21 (X=S,Y=S)
22 (X=NH,Y=O)
23 (X=NMe,Y=O)
OH
OH
15 (X=S,Y=O)
16 (X=S,Y=S)
17 (X=NH,Y=O)
18 (X=NMe,Y=O)
a
Compound
Heterocyclic ring
HSD IC50
0.57
(lM)
*
N
*
1
S
Scheme 2. Synthesis of oxazolidinedione and thiazolidinedione derivatives.
Reagents and conditions: (a) 3-bromo-4-hydroxybenzaldehyde, ammonium acetate
or b-alanine, AcOH, 120 °C, 2–6 h, 50–90%.
O
*
N
*
5
8
0.67
5.7
O
O
O
Table 2
*
N
N
Inhibition of 17b-HSD3 by oxazolidinedione and thiazolidinedione derivatives in
human cellular assay
N
*
O
*
O
N
12
13
0.30
MeO
*
O
N
O
Br
X
O
Y
OH
*
N
0.023
*
O
a
Compound
X
Y
HSD IC50 (nM)
O
13
19
20
21
22
23
O
O
S
S
NH
NMe
O
S
O
S
O
O
23
13
90
14
na
na
a
Inhibition of 17b-HSD3 in human cellular assay. Data shown were obtained by
performing the tests in duplicate. The deviations were within 5%.
a
Human cell-based assay. Data shown were obtained by performing the tests in
duplicate. The deviations were within 5%. na = not active.
Table 3
The specificity of 5-(3-bromo-4-hydroxybenzylidene)-3-(4-methoxyphenyl)-2-thi-
oxo-1,3-thiazolidin-4-one 21
a
Human cell-based assay IC50
17b-HSD isoenzyme
Type 1
Type 2
Type 3
na
na
14 nM
Figure 2. Overlay of a low energy conformer of compound 13 (red) onto HTS hit
compound 1 (green).
Reporter gene assay agonist/antagonistb
Nuclear receptor
AR
ER
a
GR
na/na
na/na
na/na
13. On the other hand, hydantoins (22 and 23) led to lack of cellular
activity (Table 2). When the rhodanine derivative 21 was evaluated
against testes homogenate 17b-HSD3, it was found to possess IC50
values of 6.0 (human), 40 (mouse), and 0.6 nM (marmoset).
In an effort to determine specificity, compound 21 was evalu-
ated against the oxidative isoenzyme 17b-HSD2 or 17b-HSD1
which convert estrone (E1) into estradiol (E2). This compound
did not show any undesired inhibition of estrogen-biosynthesis.
In selectivity over nuclear receptors such as androgen receptor
a
Data shown were obtained by performing the tests in duplicate. The deviations
were within 5%. na = not active.
b
na = not active.
group and the polar group on the heterocyclic ring of inhibitor 21,
respectively. The phenyl group of the phenol moiety overlaps onto
C and D-ring of the steroid backbone; in addition, the bridge part is
located on B-ring. In a brief structure–activity relationship (SAR)
surrounding compound 21, the methoxyphenyl group which is
nearly perpendicular to the rhodanine ring is important to exhibit
a potent inhibitory activity, and deletion of the methoxyphenyl
group resulted in a dramatic loss in potency (inhibition of 23% at
(AR), estrogen receptor alpha (ERa), and glucocorticoid receptor
(GR), this inhibitor did not possess the transcriptional activity
against any of these nuclear receptors. Compound 21 showed
excellent selectivity over 17b-HSD isoenzymes and nuclear recep-
tors (Table 3).
10 lM). The corresponding hydrophobic binding pocket of the en-
Superimposition of the rhodanine derivative 21 with
D
4-dione,
zyme was observed to affect a key interaction with this chemotype.
Starting from an HTS hit, benzylthiazolone 1, the SAR studies on
replacement of the central ring-system culminated in the discov-
ery of benzylidene oxazolidinedione and thiazolidinedione deriva-
tives, highly potent and selective inhibitors of 17b-HSD3. Although
compound 21 exhibited a promising activity profile, the compound
which is an endogenous substrate, was performed by a molecular
structure alignment method using Hopfield neural network.11
Figure 3 shows that 21 overlaps well with
phobic regions and hydrogen-bonding functional groups: the C-3
and C-17 carbonyl groups of
4-dione correspond to the hydroxyl
D
4-dione in the hydro-
D

K. Harada et al. / Bioorg. Med. Chem. Lett. 22 (2012) 504–507
507
Acknowledgment
The authors are grateful to Sumika Technoservice Corporation
for compound synthesis, characterization, and helpful discussions.
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