Sulfonamido-aryl ethers as bradykinin B1 receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2008.11.005

The synthesis and identification of sulfonamido-aryl ethers as potent bradykinin B1 receptor antagonists from a ～60,000 member encoded combinatorial library are reported. Two distinct series of compounds exhibiting different structure-activity relationshi

Full text of DOI:10.1016/j.bmcl.2008.11.005

Bioorganic & Medicinal Chemistry Letters 19 (2009) 119–122
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Sulfonamido-aryl ethers as bradykinin B1 receptor antagonists
a
a
a
a
Andrew G. Cole a, , Axel Metzger , Marc-Raleigh Brescia , Lan-Ying Qin , Kenneth C. Appell ,
Christopher T. Brain b, Allan Hallett c, Pam Ganju c, Alastair A. Denholm d, James R. Wareing b,
Timothy J. Ritchie c, Gillian M. Drake c, Stuart J. Bevan c, Aisling MacGloinn c, Andrew McBryde c, Viral Patel c,
Paul J. Oakley c, Ximena Nunez c, Hubert Gstach e, Peter Schneider f, John J. Baldwin a, Roland E. Dolle a,
Edward McDonald a, Ian Henderson a
*
a Pharmacopeia Inc., PO Box 5350, Princeton, NJ 08543, USA
b Novartis Institutes of Biomedical Research, 100 Technology Square, Cambridge, MA 02139, USA
c Novartis Institutes of Biomedical Research, 5 Gower Place, London WC1E 6BS, UK
d Novartis Institutes of Biomedical Research, Wimblehurst Road, Horsham, West Sussex, RH12 5AB, UK
e Novartis Institutes of Biomedical Research, Vienna, Austria
f Novartis Institutes of Biomedical Research, Basel, Switzerland
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and identification of sulfonamido-aryl ethers as potent bradykinin B1 receptor antagonists
from a ꢀ60,000 member encoded combinatorial library are reported. Two distinct series of compounds
exhibiting different structure–activity relationships were identified in a bradykinin B1 whole-cell recep-
tor-binding assay. Specific examples exhibit Ki values of ꢀ10 nM.
Received 9 September 2008
Revised 28 October 2008
Accepted 3 November 2008
Available online 6 November 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Bradykinin
Sulfonamide
Combinatorial chemistry
ECLiPSTM
Bradykinin B1 and B2 receptors are G-protein coupled receptors
that play a role in pain and inflammation pathways. The peptides,
bradykinin and kallidin, are released following tissue injury and
serve as physiological agonists for the constitutively expressed
B2 receptor.1,2 Further metabolism of bradykinin and kallidin
result in the formation of [des-Arg9]-bradykinin and [des-Arg10]-
kallidin, the natural agonists for the B1 receptor. While this recep-
tor is not widely expressed in non-disease states, it is induced
during conditions of inflammation and tissue trauma.3 Subsequent
activation of the B1 receptor is believed to contribute to chronic
inflammatory diseases and inflammatory and neuropathic pain.4
As such there is considerable interest in the identification of small
molecule antagonists of the B1 receptor with therapeutic interest
against chronic inflammation and pain.
in the identification of novel, potent B1 receptor antagonists from
high-throughput screening of a ꢀ60,000 member sulfonamido-aryl
ether combinatorial ECLiPSTM (Encoded Combinatorial Libraries on
Polymeric Support)12 library. The general structures of the com-
pounds present within the library are consistent with a proposed
B1 antagonist pharmacophore of an aryl sulfonamide incorporating
a spacer and either a carboxamide or other hydrogen-bond accep-
tor13 that has been observed in a number of B1 antagonists. This
proposed common pharmacophore is exemplified by the reported
non-peptide bradykinin B1 antagonists SSR-2406124 and I14 (Fig. 1).
The sulfonamido-aryl ether library was constructed on solid-
phase in four combinatorial steps. The library was designed to pro-
vide two distinct spurs as defined by the synthetic strategy used to
generate the sulfonamide-based aryl ether framework.
Recent literature reports have detailed the discovery of non-pep-
tide B1 receptor antagonists incorporating sulfamoylbenzamide,5
benzodiazepine,6 arylsulfone,7 benzimidazole8 and diaminopyri-
dine9 core structures, and multiple classes of non-peptide B2 antag-
onists.10,11 We herein describe the results of our research resulting
Aminomethyl-terminated TentagelÒ resin (1) was used as the
polymeric support together with a 2-nitrobenzylic photo-cleavable
linker.15 Solid-phase synthesis was initiated by acylating 1 with
N-a-N-e-bis-Fmoc-lysine followed by Fmoc deprotection to gener-
ate 2 (Scheme 1). This increases the loading capacity of the resin by
doubling the number of amino groups for further functionalization.
This was followed by diisopropyl carbodiimide (DIC)-mediated
acylation with 4-(bromomethyl)-3-nitrobenzoic to provide 3. This
* Corresponding author. Tel.: +1 609 452 3653; fax: +1 609 655 4187.
E-mail addresses: acole@pcop.com, acole4@verizon.net (A.G. Cole).
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.11.005

120
A. G. Cole et al. / Bioorg. Med. Chem. Lett. 19 (2009) 119–122
Combinatorial components R1 and R3 are common to both
library spurs, whereas R2 and R4 differ in nature between the library
spurs. Amino substituents included at the R1 position incorporate
aliphatic, aromatic, acidic and basic functionalities. Sulfonamide
formation to install R3 utilizes primarily aromatic and heteroaro-
matic sulfonyl chlorides, incorporating electron-withdrawing, elec-
tron-donating and basic functionalities. In library spur 1, R2 is based
on a series of substituted and unsubstituted anilino-, benzylic- and
phenethyl-based fragments, whereas the R2 component of library
spur 2 is based on unsubstituted alkyl chains of varying length. In
each spur, R2 provides varying separation of the sulfonamide func-
tionality and what may be a key hydrogen-bond acceptor in the
form of the ether oxygen atom.13 The alcohols employed in the final
synthetic step of spur 1 install aliphatic, benzylic and basic func-
tionalities and the phenolic components present within spur 2 pro-
vide varying substitutions of the aromatic system.
O
N
O
O
O
O
N
S
N
HN
N
H
H
O
O
O
S
O
N
HN
I
SSR-240612
CF3
OMe
Figure 1. Reported non-peptide bradykinin B1 antagonists.4,14
linker allows photo-mediated cleavage of the final compounds
from solid-phase, and is compatible with the chemistry required
to conduct the solid-phase synthesis. Generation of resin-bound
secondary amines 4 was achieved by alkylation of a series of
primary amines (R1-NH2) with 3 in THF. DIC-mediated bromoacet-
ylation of 4 with bromoacetic acid provided the common interme-
diate 5, which was used in the construction of the two library
spurs.
The generation of library spur 1 involved alkylation of a series of
O-TBS protected amino-, methylamino- and ethylaminophenols
with 5 to provide 6 (Scheme 2). Sulfonylation of 6 with a diverse
selection of sulfonyl chlorides followed by acid-mediated silyl
deprotection provided the resin-bound phenols 8. Mitsunobu reac-
tion of 8 with a solution-phase alcoholic component mediated by
diisopropylazodicarboxylate (DIAD) and triphenyl phosphine
generated aryl ethers 10. The generation of library spur 2 was con-
ducted via alkylation of a series of O-TBS-protected aminoalcohols
with 5 to provide 7 (Scheme 3). Sulfonylation of 7 with a diverse
selection followed by silyl deprotection provided 9. DIAD/triphenyl-
phosphine-mediated Mitsunobu reaction of 9 employing a solution-
phase phenolic component generated aryl ethers 11.
Compounds were photo-released from the polymeric support
under previously optimized photolysis conditions16 prior to high-
throughput screening in a whole-cell binding assay. Structural
assignment of the active compounds was performed by electron-
capture gas-chromatographic analysis of the binary encoding
sequence of electrophoric molecular tags incorporated during
ECLiPSTM library synthesis.12,17
Screening of library spur 1 in a whole-cell binding assay using
WI-38 cells18 yielded a set of potent B1 binding ligands exhibiting
distinct structural features. A strong preference was observed for
the 2-chlorobenzyl functionality at the secondary carboxamide
position in conjunction with a 4-functionalized aminomethyl ben-
zenesulfonamide. This highlights the possible importance of a ba-
sic center at this position within this series. In addition, a
benzylic spacer separating the sulfonamide from the aryl ether
oxygen atom was exclusively selected. The isobutyl-substituted
phenyl ether incorporated via the final Mitsunobu reaction was
also shown to be desirable. Specific examples were resynthesized
in multi-milligram quantities for accurate Ki determinations in
the B1 receptor-binding assay18 (Table 1). These Ki’s revealed supe-
rior affinity for incorporation of the 4-(4-methylpiperazin-1-yl)-
O
Br
NO2
O
4
H
c
a, b
N
L
Br
N
NH2
=
N
H
NH2
H
O
NH2
2
1
HN
4
3
NO2
Br
O
3
O
d
e
Br
L
NH
R1
L
N
R1
4
5
Scheme 1. Reagents and conditions: (a) N-a-N-e-bis-Fmoc-Lys, HOBt monohydrate, DIC, CH2Cl2, DMF, 25 °C; (b) piperidine, DMF, 25 °C; (c) 4-(bromomethyl)-3-nitrobenzoic
acid, HOBt monohydrate, DIC, CH2Cl2, DMF, 25 °C; (d) R1-NH2, THF, 25 °C; (e) bromoacetic acid DIC, CH2Cl2, DMF, 25 °C.
Library Spur 1 (15R1 x 7R2 x 15R3 x 21Ar4).
R2
N
R2
R2
R4
O
OTBS
OH
b,c
a
d
O
O
O
m
m
m
X
5
X
X
O
O
NH
N
L
N
R1
S
L
N
R1
L
N
R1
S
R3
R3
O
O
6 (m = 0, 1, 2)
8
10
Scheme 2. Library spur 1. Reagents and conditions: (a) R2-NH2, DMSO, 25 °C; (b) R3SO2Cl, 2,6-lutidine, CH2Cl2, 25 °C; (c) HCl, MeOH, 25 °C; (d) R4-OH, DIAD, PPh3, Et3N,
CH2Cl2, THF, 25 °C.

A. G. Cole et al. / Bioorg. Med. Chem. Lett. 19 (2009) 119–122
121
Library Spur 2 (15R1 x 5R2 x 22R3 x 21Ar4).
Ar4
R2
R2
R2
OH
O
OTBS
n
O
n
O
n
O
O
O
a
b, c
d
5
N
N
NH
L
N
R1
S
L
N
R1
S
L
N
R1
R3
R3
O
O
9
11
7 (n = 1-4)
Scheme 3. Library spur 2. Reagents and conditions: (a) R2-NH2, DMSO, 25 °C; (b) R3SO2Cl, 2,6-lutidine, CH2Cl2, 25 °C; (c) HCl, MeOH, 25 °C; (d) Ar4-OH, DIAD, PPh3, Et3N,
CH2Cl2, 25 °C.
methyl substitution of the benzene sulfonamide (10a) in compari-
son to the corresponding 4-piperidinylmethyl (10c), 4-(dimethyl-
amino)methyl (10d) and 4-morpholinomethyl substitutions (10f).
Methoxylation (10a) or chlorination (10b) of the central aromatic
ring was also shown to provide a 5- to 10-fold increase in affinity
in comparison to the phenyl analog (10e), suggesting the potential
contribution of a steric effect to increased binding.
Screening of library spur 2 also yielded compounds with affinity
for the B1 receptor. Similarly, specific examples were resynthe-
sized in multi-milligram quantities for accurate Ki determinations
in the B1 receptor-binding assay18 (Table 2). Although compounds
from this library spur exhibited weaker activity, distinct structural
features were still observed. A different SAR to spur 1 was evident
for both the secondary carboxamide and sulfonamide substitu-
tions. In contrast to the hydrophobic 2-chlorobenzyl amide present
in all of the B1 binding ligands from spur 1, a distinct preference
was observed for a more hydrophilic amide in spur 2. Notably,
compounds 11b, 11c and 11e, incorporate an amido-substituent
derived from b-alanine. Comparison of 11a and 11e reveals
increased activity for the 2-methoxyphenethyl-based secondary
carboxamide compared with the carboxylic acid-containing com-
pound. However, the b-alanine-derived compound (11b) does
show superior affinity to the corresponding methoxypropyl (11d)
and methyl (11f) analogs. The R2 component present within the
active compounds consistently displayed a two carbon spacer
between the sulfonamide nitrogen and the ether oxygen-acceptor
atom. The 2,4-dichlorosubstituted benzene sulfonamide was also
a common structural feature, being exclusively selected from the
diverse set of sulfonamides in the active compounds identified
from spur 2. A number of fragments could be incorporated in the
final combinatorial variant (R4), with library members based on
sesamol (11a and 11e), 2,3-dihydro-1H-inden-5-ol (11b, 11d and
11f) and 3-chlorophenol (11c) all demonstrating activity.
For comparison, the compound exhibiting R4 as unsubstituted
phenyl (11g) was synthesized and exhibited considerably weaker
activity than the bicyclic or chlorinated examples.
The more potent compounds from library spur 1 were also eval-
uated in a functional assay to confirm their role as antagonists.
Functional antagonism was demonstrated by evaluation in a cal-
cium mobilization assay against cloned hBK1 expressed in Cos-7
cells also expressing aequorian.19 Active compounds displayed
Ki’s of 37–500 nM in the functional assay (Table 3).
Table 2
B1 antagonists from library spur 2
R4
O
Table 1
O
B1 antagonists from library spur 1
O
S
R1
N
N
O
H
O
Cl
Cl
O
Y
O
S
R1
R4
Kia
(lM)
R
N
Compound
N
H
O
O
X
O
O
11a
0.21 0.19
Compound
R
X
Y
Kia
(lM)
O
O
O
Cl
O
O
H
11b
11c
11d
11e
11f
0.41 0.30
1.09 0.31
1.21 0.29
1.57 0.72
2.20 1.10
13.01 11.30
10a
0.011 0.002
0.021 0.003
0.034 0.008
0.093 0.022
0.113 0.024
0.149 0.05
N
N
N
N
HO
Cl
Cl
Cl
Cl
Cl
Cl
Cl
10b
10c
10d
10e
HO
O
N
N
N
O
O
O
HO
N
O
O
O
11g
10f
N
HO
a
a
Binding Ki SEM based on 4 independent determinations.
Binding Ki SEM based on P2 independent determinations.

122
A. G. Cole et al. / Bioorg. Med. Chem. Lett. 19 (2009) 119–122
Hussain, Z.; Simhadri, S.; Brescia, M.-R.; Waksmunski, F. S.; Strohl, B.; Tellew, J.
Table 3
Binding18 and functional19 activities of B1 antagonists from library spur 1
E.; Williams, J. P.; Saunders, J.; Appell, K. C.; Henderson, I.; Webb, M. L. Bioorg.
Med. Chem. Lett. 2008, 18, 5420.
Compound
Ki bindinga
(l
M)
Ki functionala
(lM)
16. Compounds were photoreleased from the polymeric support by irradiation of
individual polymeric beads in 100 lL of 2% TFA/i-PrOH at 365 nm over 1 h
(intensity of lamp is equal to 4.5 mW measured at 365 nm using a 365 nm
bandpass filter with a bandwidth of 10 nm)
10a
10b
10c
10d
10f
0.011 0.002
0.021 0.003
0.034 0.008
0.093 0.022
0.149 0.05
0.037 0.009
0.188 0.057
0.267 0.050
0.497 0.196
0.463 0.080
17. Dolle, R. E.; Guo, J.; Li, W.; Zhoa, N.; Connelley, J. A. Mol. Divers. 2000, 5, 35.
18. WI-38 cells are grown in Dulbecco’s Modified Eagle Medium supplemented
with 1% non-essential amino acids, 2 mM L-Glutamine, 100 IU/mL penicillin,
100 mg/mL streptomycin and 10% fetal calf serum. The cells were grown in
175 cm2 tissue culture flasks and split approximately 1–2 times a week at a
ratio of 1:2 using trypsin to detach the cells. WI-38 cells were plated onto
24-well plates at approximately 50,000 cells/well and grown overnight. To
upregulate expression of the receptor the cells are treated with100 units/mL
of IL-1b for 3 h prior to the assay. The binding buffer is 10 nM HEPES in
Hank’s Balanced Salt Solution (HBSS) at pH 7.4 plus 1 mM phenanthrinone
and 0.14 mg/mL bacitracin. The cells were incubated for 1 h at 4 °C in
binding buffer containing the radioligand [3H]-desArg10kallidin in a volume
a
Ki SEM based on P3 independent determinations.
In summary, evaluation of a ꢀ60,000-member sulfonamide-aryl
ether combinatorial library in a high-throughput whole-cell bind-
ing screen vs bradykinin B1 has resulted in the successful discovery
of two series of antagonists with differing SAR. Although all library
compounds are consistent with the proposed common pharmaco-
phore of an aryl sulfonamide incorporating a spacer and either a
carboxamide or other hydrogen-bond acceptor,13 specific combi-
natorial components were selected at the diversity positions in
each of the active series. The selection of key fragments highlights
the benefits of screening large compound collections to obtain
valuable SAR information that extends beyond the core structure.
of 500 lL. Non-specific binding is determined with 3 l
M desArg10kallidin. At
the end of the incubation, the cells were washed three times with 50 mM
Tris–HCl, pH 7.4, containing 300 mM sucrose. The cells were solubilized with
0.2% SDS and the amount of radioactivity in the samples determined by
liquid scintillation counting. The affinity constant (Kd) was obtained by
incubating the cells with a range of [3H]-desArg10kallidin concentrations. For
displacement experiments, the cells are incubated with approximately 1 nM
[3H]-desArg10kallidin and various concentrations of test compound. Com-
pounds were made up in DMSO and diluted into binding buffer to give a
final DMSO concentration of 0.5%. Results are calculated by subtracting the
value for non-specific binding from all values and calculating the amount of
binding for each concentration of compound as a percentage of the specific
binding with no compound. The IC50 values were calculated in ORIGIN using
References and notes
a
logistical fit. Ki values were calculated from the IC50 values using the
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infection confluent cells were split by
a factor of 1 in 3 giving 75–85%
confluency by time of transfection. The cells were detached by trypsination,
washed twice by resuspension in phosphate buffered saline and finally
resuspended at 5 Â 106 cells/mL in the same buffer.
4 Million cells in a
volume of 0.8 mL were added to a 0.4 cm gap Biorad electroporation cuvette
containing the 16 lg human B1 cDNA plus 50 lg aequorian cDNA. The cells
and cDNA were mixed several times with a 1 mL pipette and left to stand for 5–
10 min at room temperature. The cells were electroporated using a Biorad
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replaced with 50
lL of 20 lM coelenterzine made up in growth medium
containing 30 M glutathione for at least 2 h. Compounds were dissolved in
l
DMSO to give a 2 mM solution and transferred to 1 mL Eppendorf tubes. A
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preplates and to plates of Cos-7 cells. The 2 mM stocks were serially diluted
with DMSO in half log steps. Six concentrations of diluted test compound were
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l
Hanks Balanced Salts Solution pH 7.4). In addition 200 mL of the standards
used as controls were also transferred to the preplate. The standards were:
assay buffer + 3% DMSO to give the control response; assay buffer + 3%
DMSO + 80 nM desArg10HOE140, to give a partly inhibited response; assay
buffer + 3% DMSO + 2 l
M desArg10HOE140, to give the basal value. At this
stage the concentrations of the compounds and standards in the preplates
were twice the final concentration. The coelenterzine solution was removed
from the cells and replaced with 50 lL assay buffer. Fifty microliters from each
well of the preplate was then transferred to the cells to give the final
concentration. A cover was placed on the base of the plate, which was then
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placed in
desArg10kallidin was injected onto each well, thus giving
concentration of 30 nM and the luminescence signal was integrated over 20 s.
a
Luminoskan luminometer.
A
20
lL
aliquot of 180 nM
a
final