2-Mercaptoimidazoles, a new class of potent CCR2 antagonists

Article abstract of DOI:10.1016/j.bmcl.2004.11.064

We describe the synthesis and SAR of a new class of CCR2 antagonists based on a 2-mercaptoimidazole scaffold. The initial lead 1a was optimized to the 3,4-disubstituted analogues 1p-(S) and 1q-(S), which have IC₅₀ values in the MCP-1 induced Ca

Full text of DOI:10.1016/j.bmcl.2004.11.064

Bioorganic & Medicinal Chemistry Letters 15 (2005) 497–500
2-Mercaptoimidazoles, a new class of potent CCR2 antagonists
Guy Van Lommen,a,* Julien Doyon,a Erwin Coesemans,a Staf Boeckx,a Marina Cools,b
Mieke Buntinx,a Bart Hermansa and Jean VanWauwea
aInflammation Research, Johnson and Johnson Pharmaceutical Research and Development, Turnhoutseweg 30, B-2340 Beerse, Belgium
bBarrier Therapeutics, n.v. Cipalstraat, 3 B-2440 Geel, Belgium
Received 13 October 2004; revised 18 November 2004; accepted 25 November 2004
Available online 16 December 2004
Abstract—We describe the synthesis and SAR of a new class of CCR2 antagonists based on a 2-mercaptoimidazole scaffold. The
initial lead 1a was optimized to the 3,4-disubstituted analogues 1p-(S) and 1q-(S), which have IC50 values in the MCP-1 induced
Ca-flux below 0.01 lM.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
literature procedures, previously undescribed ketones
could be obtained by Friedel–Crafts reactions of an acyl-
chloride with the appropriate substituted benzene deriva-
tive. Enantiomers were obtained similarly using optically
pure amines synthesized as described in Scheme 2.13
Monocyte chemoattractant protein-1 (MCP-1) and its
receptor (CCR2) have been implicated in a number of
inflammatory and autoimmune diseases,1 in particular,
by affecting monocyte infiltration. So antagonists of
the CCR2 receptor are potential therapeutic agents for
various pathological conditions such as rheumatoid
arthritis,2 multiple sclerosis,3 COPD4 and athero-
sclerosis.5
4,5-Disubstituted imidazoles can be prepared following
Scheme 1 but using dimethyloxalate rather than methyl-
formiate in step f. When chloroacetonitrile is used
in step d, the corresponding 5-nitriles are obtained
although in lower yields than the esters.
Recently a number of small molecule antagonists of this
receptor have been described6–11 and a common charac-
teristic of their binding site was proposed.12
The 5-esters can be hydrolyzed by NaOH (1 N) at reflux
and the corresponding acids were reacted with SOCl2 to
give the acid chlorides. Reaction of these with amines
gave the 5-amides shown in Table 3. Also reduction of
the 5-ester 1a with superhydride in THF afforded the
alcohol 3r in good yield.
In a high throughput screening based on MCP-1 in-
duced GTPcS binding in human CCR2B-CHO cell
membranes, we identified the mercaptoimidazole 1a as
a new promising lead compound, its activity was con-
firmed in an assay based on MCP-1 induced calcium flux
in THP-1 cells14 IC50: 0.2 lM.
In the 4,5-diester series, the ester in the 4-position can be
selectively hydrolyzed to the 4-acid 5-ester under mild
conditions (1 N NaOH, rt), however, the 5-ester is much
more resistant to hydrolysis and when the temperature is
raised, decarboxylation became predominant.
Herein we describe the SAR in this new class of CCR-2
antagonists.
We could obtain low yields of diamides 3l and 3m by
heating the diester 1p in concentrated NH4OH solution
or in methanol saturated with methylamine.
2. Chemistry
The mercaptoimidazoles were synthesized as described in
Scheme 1. Starting ketones and amines were prepared by
3. Structure–activity relationship
Keywords: CCR2 antagonists; Mercaptoimidazoles.
*
Analysis of the high throughput screening data pointed
to the importance of the 3,4-dichloro substitution on the
Corresponding author. Tel.: +32 14 603656; fax: +32 14 605344;
e-mail: gvlommen@prdbe.jnj.com
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.11.064

498
G. Van Lommen et al. / Bioorg. Med. Chem. Lett. 15 (2005) 497–500
R1
R2
R1
R2
R 1
R 2
b.
a.
d
R
R
R
.HCl
N
O
NH2
HO
O
c
R1
R2
R1
R2
R1
R2
R
g
f
e
O
O
R
O
R
N
O
O
O
N
O
HN
-
+
O
Na
R1
R2
R
O
HS
N
O
N
Scheme 1. Synthetic route to 2-mercaptoimidazoles. Reagents and conditions (yields for R1/R2 = Cl): (a) NH2OHÆHCl, NaOAc, MeOH [rt, 18 h]
(100%); (b) hydrogenation over RaNi/thiophene in MeOH/NH3 (85%); (c) methylglycinate/Pd/C 5% methanol, thiophene (80%); (d) methylbromo-
acetate, TEA, DMF [rt, 3 days] (80%); (e) HCOOH, xylene [reflux, 6 h] (100%); (f) HCOOMe, NaOt-Bu, THF [rt, 20 h]; (g) KSCN, HCl–H2O,
MeOH [60 ꢁC, 20 h] (70% over f+g).
O
Table 1. Substitutions on the phenyl ring
OH
X
X
H
X
X
R1
a
R2
HS
N
COOCH3
NHSO CF
2
3
3
b
N
X
NHSO CF
2
*
catalyst
Compd
R1
R2
X
pIC50
N
3
1a
1b
1c
1d
1e
1f
3-Cl
H
4-Cl
H
H
6.7
<5
<5
<5
<5
<5
<5
5.9
6.6
5.7
6
X
X
NH
2
c
H
X
X
2-Cl
3-Cl
4-Cl
4-CF3
H
H
H
H
X = Cl, F
H
H
H
H
Scheme 2. Stereospecific synthesis of 1-(3,4-dihalo-phenyl)-1-amino-
propane. Reagents and conditions (yields): (a) Zn(CH2CH3)2, Ti(i-
PropO)4, catalyst, toluene, À78 ꢁC (100%); (b) diphenylphosphoryl-
azide, DBU, toluene (75%); (c) PdC (10%), H2, methanol (75%).
1g
1h
1i
3-O-phenyl
3-F
3-Br
H
4-F
H
H
4-Br
4-CF3
4-F
H
1j
3-F
H
1k
1l
3-CF3
3-OCH3
3-CH3
3-F
H
4-OCH3
4-CH3
5-F
H
<5
<5
<5
<5
8
1m
1n
1o
1p
1q
1r
1s
1t
H
phenyl ring. Analogues with other substituents on the
phenyl (mono- or di-methyl or methoxy, and mono-halo
or phenoxy) were less active. The mercapto group
seemed essential for activity, desulfurized analogues
were devoid of activity. Also variation in the length of
the benzylic spacer led to compounds with markedly re-
duced potency.
H
3-Cl
3-Cl
5-Cl
4-Cl
4-F
H
COOCH3
COOCH3
COOCH3
COOCH3
CH3
3-F
3-F
8
4-CF3
4-F
4-Cl
7.7
7
3-CF3
3-Cl
6.6
* Standard deviation <0.24.
To get a better idea about the SAR in this series a set of
new analogues was synthesized and their biological
activity was evaluated in the MCP-1 induced calcium
flux assay in THP1-cells, results are summarized in
Tables 1–4.
Next we evaluated the role of the benzylic alkyl side
chain. Both smaller and larger groups, acyclic and cyclic,
were tolerated as shown in Table 2. An aromatic substi-
tuent at this position gave less potent compounds. With-
in the synthesized series the ethyl group seemed optimal.
The results shown in Table 1 confirm the importance of
the 3,4-dihalo (or CF3) substitution, more importantly
we also found that the introduction of a second ester
in the 4-position of the imidazole substantially enhanced
the activity and an IC50 of 10 nM or below was obtained
with a number of these di-substituted compounds, in
particular, 1p and 1q.
Table 3 summarizes the results obtained with variations
of the ester moieties, in particular nitriles and amides.
Again compounds with 4-,5-disubstitution had the high-
est activity with the exception of the monoamide 3a, that
showed a surprisingly high activity.

G. Van Lommen et al. / Bioorg. Med. Chem. Lett. 15 (2005) 497–500
499
Table 2. Variations of the alkyl substituent
Table 4. Stereospecificity of the activity
*
Compd
pIC50
Cl
Cl
R2
N
1a Racemic
S
6.7
6.9
5.8
8.0
8.1
8.0
8.1
5.7
7.3
7.4
5
R1
O
R
HS
O
N
1p Racemic
S
*
Compd
R1
R2
pIC50
1q Racemic
S
2a
2b
H
H
Methyl
Propyl
6.6
6.8
R
3a Racemic
S
2c
2d
H
H
5.7
6.5
R
O
* Standard deviation <0.24.
2e
2f
H
Cyclohexyl
3,4-Di-Cl-phenyl
Thienyl
5
<5
<5
<5
H
2g
2h
H
CH3
CH3
Finally we investigated the stereo specificity of the
CCR2 antagonistic activity and the S-isomers were
found to be active whereas the R-isomers showed only
weak activity as shown in Table 4. Again the mono-
amide 3a-(S) was very active, whilst the S-isomers of
the di-esters 1p-(S) and 1q-(S) were the most potent
compounds obtained within this series.
* Standard deviation <0.15.
Table 3. Variations of the ester groups
R
These three compounds were evaluated for their effects
on MCP-1 induced chemotaxis in human monocytes.15
The amide 3a-(S) has only a moderate activity (pIC50
1 lM), more in agreement with the expected activity of
monosubstituted compounds, but the two di-esters 1p-
(S) and 1q-(S) were also highly active in this test with
an IC50 value below 0.1 lM.
R
N
X
HS
N
Y
*
Compd
R
X
Y
pIC50
3a
3b
3c
3d
3e
3f
Cl
Cl
Cl
F
CONH2
CONHCH3
CN
H
H
H
H
H
H
H
H
7.3
6.5
6.2
6.5
6.5
6.3
5.7
<5
The effect of 3a-(S) and 1p-(S) on Ca-flux induced by
stimulation of other chemokine receptors was evaluated.
They showed a selectivity of >100 for the effect seen with
CCR2 stimulation versus the effects seen with stimul-
ation of CCR1, CCR3, CCR5, CXCR1, CXCR3 and
CXCR4 receptors.
COOEt
Cl
F
COOi-Prop
CONH2
CONHCH3
CONBut
3g
3h
F
F
H
3i
3j
F
F
H
H
<5
<5
N
CO
In conclusion, we have identified a new class of CCR2
receptor antagonists, structurally unrelated to other
described classes. In particular, 1p-(S) and 1q-(S) were
potent and selective antagonists and showed good func-
tional activity. Further modifications of these structures
and their in vivo activity will be the subject of future
publications.
N
CO
3k
3l
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
COOCH3
CONHCH3
CONH2
CN
COOH
CONHCH3
CONH2
CONH2
COOCH3
CH3
<5
6.4
7.2
6.9
7.4
<5
<5
<5
3m
3n
3o
3p
3q
3r
CN
CONHCH3
COOH
CH2OH
H
References and notes
H
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(3q and 3k) and the alcohol 3r were less active than
the corresponding primary-amides and esters.

500
G. Van Lommen et al. / Bioorg. Med. Chem. Lett. 15 (2005) 497–500
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10% foetal calf serum (FCS), 1% L-glutamine, penicillin
(50 U/mL) and streptomycin (50 g/mL) (all GIBCO BRL,
Gent). After centrifugation, cells were loaded for 30 min
with the Ca2+ sensitive fluorescent dye Fluo-3 AM
(Molecular Probes, Leiden, Netherlands) (2 million cells/
mL in RPMI medium containing 4 lM Fluo-3 AM,
20 mM HEPES, 0.1% bovine serum albumin (BSA) and
5 mM probenecid). Excess dye was removed by 3-fold
washing with buffer (5 mM HEPES, 140 mM NaCl, 1 mM
MgCl2, 5 mM KCl, 10 mM glucose, 2.5 mM probenecid,
1.25 mM CaCl2, 0.1% BSA; all further incubations were