Synthesis and biological evaluation of ((4-keto)-phenoxy)methyl biphenyl-4-sulfonamides: A class of potent aggrecanase-1 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2009.03.056

The prevention of aggrecan (a key component of cartilage) cleavage via the inhibition of aggrecanase-1 may provide a unique opportunity to stop the progression of cartilage degradation in osteoarthritis. The evaluation of a series of biphenylsulfonamides

Full text of DOI:10.1016/j.bmcl.2009.03.056

Bioorganic & Medicinal Chemistry Letters 19 (2009) 2487–2491
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Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and biological evaluation of ((4-keto)-phenoxy)methyl
biphenyl-4-sulfonamides: A class of potent aggrecanase-1 inhibitors
a
a
a
b
Darrin W. Hopper a, , Matthew D. Vera , David How , Joshua Sabatini , Jason S. Xiang ,
Manus Ipek b, Jennifer Thomason b, Yonghan Hu b, Eric Feyfant b, Qin Wang c, Katy E. Georgiadis c,
Erica Reifenberg c, Richard T. Sheldon c, Cristin C. Keohan c, Manas K. Majumdar c,
Elisabeth A. Morris c, Jerauld Skotnicki a, Phaik-Eng Sum a
*
a Department of Chemical and Screening Sciences, Wyeth Research, 401 North Middletown Road, Pearl River, NY 10965, USA
b Department of Chemical and Screening Sciences, Wyeth Research, 200 CambridgePark Road, Cambridge, MA 02140, USA
c Department of Women’s Health and Musculoskeletal Biology, Wyeth Research, 200 CambridgePark Road, Cambridge, MA 02140, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
The prevention of aggrecan (a key component of cartilage) cleavage via the inhibition of aggrecanase-1
may provide a unique opportunity to stop the progression of cartilage degradation in osteoarthritis.
The evaluation of a series of biphenylsulfonamides resulted in the identification of the ((4-keto)-phen-
oxy)methyl biphenyl-4-sulfonamides analogs (19–21 and 24) with improved Agg-1 inhibition and
MMP-2, MMP-13 activity.
Received 23 January 2009
Revised 11 March 2009
Accepted 12 March 2009
Available online 18 March 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Aggrecanase-1
Agg-1
ADAMTS-4
Biphenylsulfonamides
Osteoarthritis
OA
MMP-2
MMP-13
Aggrecanase-1 (Agg-1, ADAMTS-4)3 and Aggrecanase-2 (Agg-2,
Osteoarthritis (OA) is an incapacitating joint disease resulting
from the progressive loss and breakdown of articular cartilage.
OA is characterized by pain, joint dysfunction and inflammation,
which can be debilitating and reduce quality of life. Loss of aggre-
can, a multidomain proteoglycan, via proteolysis attributable to
‘aggrecanase’ activity throughout the disease eventually results
in cartilage erosion and ultimately replacement joint surgery.1,2
ADAMTS-5) are members of the ADAMTS (a disintegrin and metal-
loprotease possessing thrombospondin domain) family of zinc-con-
taining metalloproteases and are the only known enzymes that
cleave aggrecan IGD (Interglobular domain) at Glu373–Ala374 in
osteoarthritis. In mice, ADAMTS-5 (but not ADAMTS-4) is responsi-
ble for disease progression in a surgically-induced model of OA.4,5
However, questions remain regarding the relative contribution of
ADAMTS-4 and ADAMTS-5 in human disease. In addition, ADAM-
TS-4/ADAMTS-5 double knockout mice are physiologically normal6
and also protected from developing osteoarthritis. Therefore, the
inhibition of Aggrecanases represent very attractive targets for the
development of therapeutics that could alter the progression of
OA.1,2
In our previously published research it was shown that substi-
tution beyond the biphenyl P10 group could improve activity (1–
3).7 Using this as a starting point, we decided to investigate the
SAR of a variety of substituted aromatic systems with the goal of
improving the Agg-1 inhibition potency. As part of our ongoing re-
search efforts toward Agg-1 inhibitors, we describe herein the de-
sign, synthesis and activity of a variety of analogs (4) to explore the
O
O
OH
O
O
OH
HN
S
HN
S
H
O
O O
O O
1 (Agg-1 IC50 = 3 µM)
2 (Agg-1 IC50 = 0.35 µM)
O
O
R2
OH
OH
R1O
HN
HN
S
O
O
S
O O
O O
4
3 (Agg-1 IC50 =0.7 µM)
* Corresponding author. Tel.: +1 845 602 3426; fax: +1 845 602 5561.
E-mail address: hopperd@wyeth.com (D.W. Hopper).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.03.056

2488
D. W. Hopper et al. / Bioorg. Med. Chem. Lett. 19 (2009) 2487–2491
Table 1
SAR of substitution, particularly at the para position, of the biphe-
nyl group. Analogs 1–3 show the importance of substitution of the
biphenyl system for Agg-1 inhibition potency. In order to improve
the inhibition potency further, we investigated a variety of substi-
tutions to the biphenyl ring system as shown in Tables 1 and 2.
The substituted quinoline analogs 17 and 18 (Table 1) showed
improved Agg-1 inhibition potency8 compared to 2 and 3. In addi-
tion, the 4-phenoxybenzene analog 5 and two 4-phenoxypyridine
analogs 6 and 7 showed equivalent potency. Analogs 8–11 contain-
ing smaller non-aromatic meta substituents on the R1 phenyl
group showed diminished activity. Analogs 12 and 13, which con-
tain smaller non-aromatic substituents at the para position of the
R1 phenyl showed similarly reduced potency as Agg-1 inhibitors.
However, analog 15, containing a 2,5-substituted pyridine, showed
potency similar to that of 3. Interestingly, analogs with a larger ex-
tended aromatic R1 group (5,6,7,16–18) showed either comparable
or improved potency, However, the morpholine substituted analog
14 containing an extended bicyclic R1 group exhibited a >6-fold
loss of inhibition potency.
O
OH
R1O
HN
S
O O
Compound
R1
Agg-1 IC50
0.4
(lM)
5
O
O
6
7
0.73
0.9
N
O
N
The largest improvement in Agg-1 inhibition potency was ob-
served with the incorporation of a carbonyl group into the ex-
tended aromatic P1’ substituent (Table 2). The 4-fluorobenzoyl
(19, >4-fold), 4-cyclohexanecarbonyl (20, >3-fold) and 4-isobutyryl
(21, >3-fold) substituents all demonstrated increased Agg-1 inhib-
itor potency relative to compound 2. In addition a more modest po-
tency enhancement was observed when the carbonyl was
constrained within a fused system (24). When the carbonyl was
oriented meta to the ether linkage, inhibition potency was dimin-
ished (e.g., 22 para vs 23 meta). However, the benzophenone ana-
log 28 with the carbonyl in the meta position showed a slight
increase in activity relative to 3. If the carbonyl was incorporated
as a carbamate (29) or an amide (30, 31), potency was diminished.
Additionally, substitution of the biphenyl system ortho to the sul-
fonamide (R2, Table 2) resulted in decreased potency as the substi-
tuent increased in size (26,27). However, when R2 = F (25) potency
was retained compared to the unsubstituted analog (24).
8
1.1
OH
9
1.2
1.8
F
10
O
11
4.9
N
Recently, the crystal structure for Aggrecanase-1 (ADAMTS-4)
was described with 21 bound (Fig. 1).9 As expected, the carboxylic
functionality binds the Zn ion while the opposite end of the mole-
cule binds deeply into the S10 pocket, making extensive hydropho-
bic and some polar contacts with Agg-1 residues. Specifically, the
interaction mediated by a molecule of water between the carbonyl
group of 21 and A248 could account for the increased inhibitor po-
tency of 21 and the analogs with similar structures (19, 20 and 24).
Compounds 19–21 and 24 were also tested to determine their
ability to inhibit MMP-1, MMP-2, MMP-13, MMP-14 and Agg-2
(Table 3). These four compounds were significantly less potent
for the inhibition of MMP-1 as compared to Agg-1, and only weakly
active as inhibitors of MMP-14. Additionally, compounds 19–21
and 24 were shown to be selective for inhibition of Agg-1 over
Agg-2. All four compounds were shown to be single-digit nanomo-
lar inhibitors of MMP-2 and MMP-13. It has been shown that
MMP-13 plays an important role in cartilage degradation. Conse-
quently, inhibition of MMP-13 may likewise be beneficial in treat-
ing OA.10
12
13
14
15
1.6
1.7
6.0
0.8
O
F
O
N
N
F3C
16
17
18
0.4
0.2
0.2
N
N
Analogs 19–21 and 24 were also assessed for inhibition of pro-
teoglycan degradation in an interleukin-1 (IL-1) stimulated bovine
cartilage explant assay.11 In this very common in vitro model of
cartilage degradation exposure of bovin articular cartilage explants
to inflammatory IL-1 induces aggrecanase activity and release of
degraded extracellular matrix aggrecan. Analogs 19 (71%), 20
(69%) and 24 (53%) showed significant percent inhibition of pro-
F3C
teoglycan degradation at 10 lg/mL after a 3-day incubation
N
(Fig. 2). According to previous reports10,12 the aggrecan degrades
early in the first week of culture (days 3–7), whereas the collagen
starts to degrade rapidly only later in the culture period (days 8–
CF3

D. W. Hopper et al. / Bioorg. Med. Chem. Lett. 19 (2009) 2487–2491
2489
Table 2
Table 3
O
R2
Compound
IC50 (nM)
OH
R1O
HN
MMP-1
MMP-2
MMP-13
MMP-14
Agg-2
S
O O
19
20
21
24
>100,000
>100,000
>100,000
>100,000
3.6
5.3
1.3
6.3
6.3
15
1.1
2.2
220
1641
915
55% inhib. @ 2.5
2600
8400
lM
Compound
R1
R2
H
Agg-1 IC50
0.08
(lM)
1305
6600
F
19
O
20
21
22
H
H
H
0.09
0.1
O
O
O
0.43
O
23
H
1.0
Figure 1. Crystal structure of Agg-1 with 21 (green) bound.9 H-bonds are
represented as yellow dash lines and coordination bonds are represented as blue
dash lines.
24
25
26
27
28
29
30
H
0.23
0.18
3.2
O
O
O
O
90
F
1 ug/mL
10 ug/mL
80
70
60
50
40
30
20
10
0
CF3
OCF3
20
19
20
21
24
H
0.23
0.59
1.9
Figure 2. Proteoglycan (PG) inhibition of compounds 19–21, 24.
O
O
In addition, the pharmacokinetics of compound 20 were exam-
ined using intravenous (iv) and oral (po) modes of administration
to male Sprague–Dawley rats. Animals received a single iv bolus
of 2 mpk and a po dose of 25 mpk. Compound 20 exhibited low
clearance (6.9 mL/min/kg) and the oral bioavailability was 13%
(T1/2 = 184 min, Cmax = 694 ng/mL). The low bioavailability is most
likely attributable to the high molecular weight and high clogP
(e.g., 20, MW = 549, clogP = 7.27) for this series of compounds.
The synthesis of compounds 5–31 and their intermediates is
shown in Schemes 1–5. As shown in Scheme 1 the aryl bromide
intermediates 34–39 are formed through the sulfonylation of the
appropriate amino ester or acid. Aryl bromide 40 was formed
through the protection of 34 as the 2-(trimethylsilyl)ethyl ester.
Compounds 6–8 were synthesized by Suzuki coupling of 34 as
shown in Scheme 2. In addition, compounds 5, 9–14, 22, 23, 28–
31 were also synthesized through a Suzuki coupling of 35 or 40
H
O
N
N
H
H
O
O
31
H
5.2
N
O
14). Consequently, the activity in this 3-day assay is most likely
attributable to aggrecanase inhibition.

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D. W. Hopper et al. / Bioorg. Med. Chem. Lett. 19 (2009) 2487–2491
O
OR1
O
OtBu
O
OtBu
R2 Cl
R2 HN
R2 HN
O
OR1
(a)
S
O
(a)
R2 HN
O
+
S
O
S
O
O
O
H2N
S
O
Br
O
Br
44
32
33
34 - R1 = H, R2 = H
Br
35 - R1 = Me, R2 = H
36-39 R2 = H, F, CF3, OCF3
(b)
O
36-39 - R1 = tBu, R2 = H, F, CF3, OCF3
OtBu
O
OtBu
O
OH
O
O
R2 HN
R2 HN
Si
S
O
(c)
O
(b)
S
O
O
R2 HN
HN
S
O
S
O
O
O
45
46
Br
40
R1O
34
Br
Br
(d)
Scheme 1. Reagents and conditions: (a) R1 = Me or tBu, DIEA, CH2Cl2 (87–98%);
1 = H, H2O, THF, TEA (80%); (b) HOCH2CH2Si(CH3)3, EDCI, TEA, DMAP, CH2Cl2
(100%).
O
OH
R
R2 HN
S
O
O
R1O
O
B
O
B
16,18-21, 24-27
O
O
(a)
R1O
Br
41
42
Scheme 4. Reagents and conditions: (a) Pd(PPh3)4, p-tolylboronic acid, K2CO3, DME,
H2O, 80 °C (58–81%); (b) CCl4 NBS, AIBN, 70 °C (69–98%); (c) R1OH, acetone, K2CO3,
reflux (11–88%); (d) TFA, CH2Cl2 (47–100%).
(b)
O
OH
HN
S
O
O
O
B
O
B
R1O
O
O
O
(a),(b)
6-8
O
RO
47
48
Scheme 2. Reagents and conditions: (a) R1OH, THF, nBuNOH (37–73%) or acetone,
K2CO3, 50 °C (25–64%); (b) 34, Pd(PPh3)4, K2CO3, DME, H2O, 80 °C (9–19%).
(c)
35
O
O
OH
HN
S
O
HN
S
O
(d)
O
O
O
B
O
B
O
O
O
(a)
RO
RO
R =
49
R1O
Br
41
42
35 or 40
(b)
N
OR2
N
F3C
O
OH
15
17
HN
S
O
HN
S
O
Scheme 5. Reagents and conditions: (a) NaBH4, MeOH (74%); (b) RCl, NaH, DMF
(80–85%); (c) Pd(PPh3)4, K2CO3, DME, H2O, 80 °C (50–66%); (d) NaOH, MeOH (70–
93%).
(c)
O
O
R1O
R1O
43
(36–39) and p-tolylboronic acid to form 44, which was converted
to the benzyl bromide 45 using NBS. Displacement of the benzylic
bromide 45 with the desired phenol derivative furnished 46. Cleav-
5,9-14,22,23,28-31
Scheme 3. Reagents and conditions: (a) ROH, THF, nBuNQH (37–73%) or acetone,
K2CO3, 50 °C (25–64%); (b) Pd(PPh3)4, K2CO3, DME, H2O, 80 °C (51–66%); (c) R2 = Me
5, 11, 29, LiOH, MeOH, THF (70–93%). R2 = CH2CH2Si(CH3)3 9, 10, 12–14, 22, 23, 28,
30, 31, CH2Cl2, MgBr2–Et2O (73–100%). For compounds 5, 22, 23, 28, PdCl2(dppf)
(22–67%) was used in the Suzuki coupling rather than Pd(PPh3)4.
t
age of the butyl ester gave the desired analogs 16, 18–21, 24–27.
Compounds 15 and 17 were synthesized (Scheme 5) by the
reduction of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benz-
aldehyde and alkylation of the resulting alcohol followed by a Su-
zuki coupling with the appropriate aryl bromide. Deprotection of
the ester formed the desired carboxylic acids 15 and 17.
In conclusion, we have described the synthesis and biological
evaluation of a series of biphenylsulfonamide Agg-1 inhibitors.
In so doing, we identified a series of ((4-keto)-phenoxy)methyl
biphenyl-4-sulfonamide analogs with improved Agg-1 inhibition
potency, however, this series retained significant activity for MMP-
2 and MMP-13. The enhancement of inhibition potency for Agg-1
and the desired aryl boronic ester followed by the deprotection of
the ester to the carboxylic acid (Scheme 3). The aryl boronic esters
used in Scheme 2 and 3 were synthesized using the commercially
available 2-(4-(bromomethyl)phenyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane and the desired phenol derivative.
Compounds 16, 18–21, 24–27 were synthesized (Scheme 4)
starting with the Suzuki coupling of the appropriate aryl bromide

D. W. Hopper et al. / Bioorg. Med. Chem. Lett. 19 (2009) 2487–2491
2491
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is likely attributable to the interaction of the ligand’s ketone car-
bonyl with residue A248, which was observed in the recently re-
ported crystal structure of Agg-1 with compound 21 bound.9 In
addition, this series of analogs showed significant inhibition of pro-
teoglycan degradation at 10 lg/mL in a cell based assay. Additional
analogs will be designed using the crystals structure of compound
21 bound in aggrecanase-1 and these results will be reported in
due course.
Acknowledgments
8. Assay details for the inhibition of aggrecan cleavage is described in Ref. 7.
9. Mosyak, L.; Georgiadis, K.; Shane, T.; Svenson, K.; Hebert, T.; McDonagh,
T.; Mackie, S.; Olland, S.; Lin, L.; Zhong, X.; Kriz, R.; Reifengerg, E. L.;
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2008, 17, 16.
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Magolda, R.; Newton, R. C.; Trzaskos, J. M.; Arner, R. C. J. Biol. Chem. 2003, 278,
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11. Assay details for the inhibition of proteoglycan inhibition is described in Ref. 7.
12. Little, C.; Hughes, C.; Curtis, C.; Janusz, M.; Bohme, R.; Wang-Weigand, S.;
Taiwo, Y.; Mitchell, P.; Otterness, E.; Flannery, C.; Caterson, B. Matrix Biol. 2002,
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The authors acknowledge the Wyeth Discovery Analytical
Chemistry Department for providing the spectral data. Addition-
ally, we thank Dr. Tarek Mansour for his support.
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