Novel bis-arylsulfonamides and aryl sulfonimides as inactivators of plasminogen activator inhibitor-1 (PAI-1)

Article abstract of DOI:10.1016/j.bmcl.2009.12.051

Inactivators of plasminogen activator inhibitor-1 (PAI-1) have been identified as possible treatments for a range of conditions, including atherosclerosis, venous thrombosis, and obesity. We describe the synthesis and inhibitory activity of a novel series

Full text of DOI:10.1016/j.bmcl.2009.12.051

Bioorganic & Medicinal Chemistry Letters 20 (2010) 966–970
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Novel bis-arylsulfonamides and aryl sulfonimides as inactivators
of plasminogen activator inhibitor-1 (PAI-1)
Nadine C. El-Ayache a, Shih-Hon Li b, Mark Warnock b, Daniel A. Lawrence b, Cory D. Emal a,
*
a Department of Chemistry, Eastern Michigan University, 225 Mark Jefferson, Ypsilanti, MI 48197, United States
b Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan Medical School, 7301 MSRB III,
1150 W. Medical Center Dr., Ann Arbor MI 48109-0644, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Inactivators of plasminogen activator inhibitor-1 (PAI-1) have been identified as possible treatments for a
range of conditions, including atherosclerosis, venous thrombosis, and obesity. We describe the synthesis
and inhibitory activity of a novel series of compounds based on bis-arylsulfonamide and aryl sulfonimide
motifs that show potent and specific activity towards PAI-1. Inhibitors containing short linking units
between the sulfonyl moieties and a 3,4-dihydroxy aryl substitution pattern showed the most potent
inhibitory activity, and retained high specificity for PAI-1 over the structurally-related serpin anti-throm-
bin III (ATIII).
Received 15 October 2009
Revised 9 December 2009
Accepted 14 December 2009
Available online 21 December 2009
Keywords:
PAI-1 inhibitors
Bis-arylsulfonamide
Aryl sulfonimide
Ó 2009 Elsevier Ltd. All rights reserved.
Plasminogen activator inhibitor-1 (PAI-1) is member of the ser-
pin superfamily of protease inhibitors and is the primary inhibitor
of urokinase type plasminogen activator (uPA) and tissue type
plasminogen activator (tPA).1 At normal physiologic levels PAI-1
plays a significant role in multiple processes, including fibrinolysis,
angiogenesis, cell migration, and wound healing.2–6 Pathologic lev-
els of PAI-1 have been connected with obesity and metabolic syn-
drome, tumor metastasis, and vascular diseases such as venous
thrombosis and atherosclerosis, making it an attractive pharmaco-
logical target.7–13 However, PAI-1 has proven to be a challenging
target for drug design as it is present in multiple conformational
forms and has a flexible reactive center loop. Despite the chal-
lenges inherent in the development of small-molecule PAI-1
inactivators, several have been reported recently, although each
has drawbacks that have impeded further progress in their devel-
opment.14–22 The most studied of these inhibitors, tiplaxti-
nin,3,19,23–26 has a reported IC50 in the low micromolar range
strategy was to synthesize compounds containing two polypheno-
lic moieties separated by linking units of various length and com-
position. Sulfonamides were chosen as a basis for the linking unit
due to the moiety’s widespread use in pharmaceutical design and
the flexible synthetic access to structural diversity it would pro-
vide. As we were also interested in the level of specificity for the
inhibition of PAI-1, we assayed the set of compounds for activity
against anti-thrombin III (ATIII), a structurally similar mammalian
serpin.
Bis-arylsulfonamides 3a–d were prepared as shown in
Scheme 1. Diamines (1a–d) were treated with 3,4-dim-
ethoxybenzenesulfonyl chloride in the presence of triethylamine
to form the bis-arylsulfonamides 2a–d. Exposure of the bis-sulfon-
amides to boron tribromide in methylene chloride achieved depro-
tection of the aryl methoxy groups, providing the fully deprotected
tetraphenols 3a–d. Bis-sulfonamide 4 was similarly produced by
this route, using piperazine as the initial diamine. Variously substi-
tuted bis-arylsulfonamides 5–7 were synthesized by analogous
routes using the appropriate sulfonyl chlorides. Unsubstituted
bis-benzenesulfonamide 8 was synthesized directly by the reaction
of benzenesulfonyl chloride and N,N0-diethylethylenediamine in
the presence of triethylamine.
although PAI-1 inhibitors with IC50 values as low as 0.2
lM have
been reported.14,20
Here we report the development of a novel class of PAI-1 inhib-
itors based on an aryl sulfonamide or aryl sulfonimide motif that
shows up to 30-fold more potent inhibitory activity toward PAI-1
than that of tiplaxtinin. Based on insights gained from a screen
for anti-PAI-1 activity of a library of structurally diverse com-
pounds,27 we developed a set of compounds designed to probe
structural requirements for PAI-1 inactivation. Our general design
The synthesis of bis-3,5-difluoro-4-hydroxybenzenesulfona-
mide 13 proceeded as shown in Scheme 2. A solution of 2,6-difluo-
rophenol in dimethylformamide was treated with iodomethane
and anhydrous potassium carbonate to provide 2,6-difluoroanisole
(10),28 which was then exposed to chlorosulfonic acid29 to provide
the aryl sulfonyl chloride 11. N,N0-Diethylethylenediamine was
added dropwise to a solution of 11 in pyridine to give the
* Corresponding author. Tel.: +1 734 487 0305; fax: +1 734 487 1496.
E-mail address: cemal@emich.edu (C.D. Emal).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.12.051

N. C. El-Ayache et al. / Bioorg. Med. Chem. Lett. 20 (2010) 966–970
967
OMe
OH
OH
R
N
R
N
n
O O
S
O O
S
a
b
H
N
n
MeO
MeO
HO
HO
N
S
OMe
N
S
R
n
N
H
R
O O
O O
R
R
1a: n = 1, R = H
1b: n = 1, R = Et
1c: n = 3, R = H
1d: n = 5, R = H
2a: n = 1, R = H
2b: n = 1, R = Et
2c: n = 3, R = H
2d: n = 5, R = H
3a: n = 1, R = H
3b: n = 1, R = Et
3c: n = 3, R = H
3d: n = 5, R = H
O O
HO
HO
HO
S
OH
OH
5: Ar =
6: Ar =
7: Ar =
N
O O
S
OH
OH
OH
N
N
Ar
S
Ar
N
S
O O
O O
8: Ar =
4
Scheme 1. Preparation of bis-arylsulfonamides. Reagents and conditions: (a) 3,4-dimethoxybenzenesulfonyl chloride, triethylamine, ethyl acetate, 35–100%; (b) 1M BBr3 in
CH2Cl2, CH2Cl2, 0 °C to rt, 36–86%.
chloride to provide the aryl sulfonimide 16, which was then depro-
tected with BBr3 as before to provide the PAI-1 inhibitors 17a–d.
Compounds 2b, 3a–d, 4–8, 13, and 17–d were assayed in vitro
against PAI-1 and anti-thrombin III (ATIII), a related mammalian
serpin (Table 1).30 Initially we varied the length of the linking unit
in order to determine the distance between our sulfonamide units
that would lead to maximal potency against PAI-1. We found that
bis-sulfonamides containing longer linker chains (3c and 3d) were
less active than 3a, an otherwise equivalent compound containing
F
F
SO2Cl
b
RO
MeO
F
F
11
9: R = H
a
10: R = Me
c
a single ethylene linking unit (IC50 = 518 l
M, Table 1).31 Replace-
F
OR
ment of the acidic hydrogens within the sulfonamide units of 3a
with ethyl groups resulted in an increase in inhibitor potency of
O O
S
F
N
N
S
O O
F
about 55-fold (3b, IC50 = 9.32
ated version. Significantly, the anti-PAI-1 activity of 3b equaled
that of tiplaxtinin (IC50 = 9.7
M).19 Inclusion of the linking unit
lM) as compared to the non-alkyl-
RO
F
l
within a more conformationally-constrained 1,4-piperazinyl ring,
as in 4, resulted in a compound that lacked significant inhibitory
activity towards PAI-1, indicating that the relative orientation of
the aromatic rings that leads to the greatest degree of bioactivity
are not available to this molecule.
We then investigated the importance of the substitution pattern
of the aromatic ring. Given the high potency conferred by the N,N0-
ethylethylenediamine linking unit of 3b, we maintained that struc-
tural motif while varying the substitution pattern of the aromatic
rings. Hydroxyl groups at both the 3- and 4-positions are critical
for maximal activity as the compound containing this substitution,
12: R = Me
13: R = H
d
Scheme 2. Preparation of bis-3,5-difluoro-4-hydroxybenzenesulfonamide 13.
Reagents and conditions: (a) K2CO3, CH3I, DMF, 50 °C, 65%; (b) chlorosulfonic acid,
CH2Cl2, reflux, 2 h, 85%; (c) N,N0-diethylethylenediamine, Et3N, EtOAc, 40%; (d) 1M
BBr3 in CH2Cl2, CH2Cl2, 0 °C to rt, 67%.
bis-sulfonamide 12, which was demethylated using BBr3 to pro-
vide fully deprotected bis-phenol 13.
Difficulties were encountered in forming aryl sulfonimides
17a–d directly from primary amines 14a–d; instead we installed
each sulfonyl group in a stepwise fashion (Scheme 3). 3,4-Dim-
ethoxybenzenesulfonyl chloride was exposed to a solution of the
appropriate primary amine 14 and triethylamine in ethyl acetate
to provide the respective sulfonamide 15. Sulfonamide 15 was
treated with sodium hydride and 3,4-dimethoxybenzenesulfonyl
3b, was far more inactivating towards PAI-1 (IC50 = 9.32
those containing a single hydroxyl group at either the 3-position
(5, IC50 = 343 M) or 4-position (6, IC50 > 300 M). Flanking the
4-OH moiety with fluorine atoms at the 3- and 5-positions, as in
13, restored some of the activity lost with the absence of the 3-
lM) than
l
l
OH group (IC50 = 128
lM), but still resulted in an inhibitor roughly
15-fold less potent than the 3,4-dihydroxy version. Sulfonamide 7,
O O
O O O O
O O O O
a
MeO
MeO
S
b
MeO
MeO
S
S
OMe
OMe
c
HO
HO
S
S
OH
OH
NHR
N
R
N
R
NH R
2
14a: R = (CH2)2CH3
14b: R = (CH2)5CH3
14c: R = CH2Ph
15a: R = (CH2)2CH3
15b: R = (CH2)5CH3
15c: R = CH2Ph
16a: R = (CH2)2CH3
16b: R = (CH2)5CH3
16c: R = CH2Ph
17a: R = (CH2)2CH3
17b: R = (CH2)5CH3
17c: R = CH2Ph
14d: R = cyclohexyl
15d: R = cyclohexyl
16d: R = cyclohexyl
17d: R = cyclohexyl
Scheme 3. Preparation of aryl sulfonimides. Reagents and conditions: (a) 3,4-dimethoxybenzenesulfonyl chloride, Et3N, EtOAc, 63-100%; (b) NaH (60% dispersion in oil), 3,4-
dimethoxybenzenesulfonyl chloride, DMF, 25–64%; (c) 1M BBr3 in CH2Cl2, CH2Cl2, 0 °C to rt, 48–65%.

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N. C. El-Ayache et al. / Bioorg. Med. Chem. Lett. 20 (2010) 966–970
Table 1
Inhibitory activity of bis-arylsulfonamides and aryl sulfonimides against PAI-1 and ATIII
a
a
Compd
Structure
PAI-1 Inhibition IC50
(l
M)
ATIII Inhibition IC50
>300
(lM)
OMe
OMe
O
O
MeO
MeO
S
N
2b
>300
N
S
O
O
OH
O
O
H
HO
HO
S
N
3a
518 ( 64)
>3000b
N
S
OH
H
O
O
OH
OH
O
O
O
HO
HO
S
S
N
3b
3c
3d
9.32 ( 0.36)
>1000b
>3000
>3000
N
S
O
O
OH
OH
O
H
N
HO
HO
>3000
N
H
S
O
O
OH
OH
O
O
O
H
HO
S
S
N
1384 ( 112)
N
H
S
O
O
HO
HO
O
OH
OH
N
4
5
6
>300c
>300
>1000
>300
N
HO
HO
S
O
O
O
O
O
S
S
N
343 ( 14)
>300
N
S
OH
O
O
OH
OH
O
N
N
S
O
O
O
HO
HO
HO
O
O
N
S
N
7
8
>300c
>300
>300
>300
S
O
OH
O
O
S
N
N
S
O
O
F
OH
F
O
O
F
S
N
13
128 ( 18)
>3000
>1000
>300b
N
S
O
O
HO
F
O
O O
N
O
HO
HO
S
S
OH
17a
17b
2.67 ( 0.27)
OH
O
O O
N
O
HO
HO
S
S
OH
OH
0.284 ( 0.016)

N. C. El-Ayache et al. / Bioorg. Med. Chem. Lett. 20 (2010) 966–970
969
Table 1 (continued)
a
a
Compd
Structure
PAI-1 Inhibition IC50
(l
M)
ATIII Inhibition IC50 (lM)
O
O
O O
N
O
HO
HO
S
S
OH
17c
4.82 ( 0.32)
>300
OH
O O
N
O
HO
HO
S
S
OH
17d
0.594 ( 0.086)
>300
OH
a
Each value is the average of at least three determinations; standard error is given in parentheses.
<30% of ATIII was inhibited at the highest compound concentration used.
<30% of PAI-1 was inhibited at the highest compound concentration used.
b
c
containing a hydroxyl group at each of the 2- and 5-positions,
tent and selective inhibitory activity towards PAI-1. We have
determined the minimal structural requirements for inhibition of
PAI-1 by these classes of compounds, as shorter linking units and
3,4-dihydroxy substitution of flanking aromatic rings are essential
for maximal inhibitor potency. We will report further work based
on this molecular scaffold in the near future.
lacked significant potency towards PAI-1, supporting the impor-
tance of the 3,4-substitution pattern. Additionally, compounds that
lacked hydroxyl groups entirely, such as 2b and 8, displayed no
inhibitory activity against PAI-1 at the tested range of concentra-
tions (>300 lM).
In order to confirm that two aryl sulfonyl groups are indeed re-
quired for anti-PAI-1 activity, three compounds containing a single
such group (18–20, Fig. 1) were synthesized by routes analogous to
those described in Scheme 1. These compounds showed a complete
lack of activity towards PAI-1 at the range of concentrations tested
Acknowledgments
The authors wish to thank Robert Cody for his assistance with
analysis by Direct Analysis in Real Time (DART) mass spectroscopy.
This work was supported by NIH Grants HL55374, HL54710, and
HL089407 to DAL.
(>3000 lM), confirming that both arylsulfonamide groups are re-
quired for inhibitory activity.
Interested in exploring the inhibitory activity of bisarylsulfonyl
compounds with even shorter linking units, we synthesized a set of
N-substituted aryl sulfonimides, 17a–d. The sulfonimides showed
improved potency towards PAI-1, performing 2–30-fold better
in vitro compared to the best of the bis-sulfonamides (cf. Table
Supplementary data
Supplementary data (containing synthetic details, spectroscopic
characterization of novel compounds, and assay conditions)
associated with this article can be found, in the online version,
at doi:10.1016/j.bmcl.2009.12.051.
1). Inhibitors containing n-hexyl (17b, IC50 = 0.284
cyclohexyl (17d, IC50 = 0.594 M) substituents displayed some-
what better activity against PAI-1 compared to n-propyl (17a,
IC50 = 2.67 M) and benzyl (17c, IC50 = 4.82 M) moieties. In addi-
tion, the most potent of the sulfonimides (17b and 17d) proved to
be 15–34-fold more potent than tiplaxtinin (IC50 = 9.7 M).
lM) and
l
l
l
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l
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Figure 1. Tested compounds containing a single sulfonamide unit.

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