Design and synthesis of novel CCR2 antagonists: Investigation of non-aryl/heteroaryl binding motifs

Article abstract of DOI:10.1016/j.bmcl.2011.01.052

This report describes the design and synthesis of a series of CCR2 antagonists incorporating novel non-aryl/heteroaryl RHS (right hand side) motifs. Previous SAR in the area has suggested an aryl/heteroaryl substituent as a necessary structural feature for binding to the CCR2 receptor. Herein we describe the SAR with regards to potency (binding to hCCR2), dofetilide activity and metabolic stability (in vitro HLM) for this series. The resulting outcome was the identification of compounds with excellent properties for the investigation of the role of CCR2 in disease.

Full text of DOI:10.1016/j.bmcl.2011.01.052

Bioorganic & Medicinal Chemistry Letters 21 (2011) 1827–1831
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis of novel CCR2 antagonists: Investigation
of non-aryl/heteroaryl binding motifs
John I. Trujillo a, , Wei Huang a, Robert O. Hughes a, D. Joseph Rogier a, Steven R. Turner a, Rajesh Devraj a,
⇑
Philip A. Morton b, Chu-Biao Xue c, Ganfeng Chao c, Maryanne B. Covington d, Robert C. Newton d,
Brian Metcalf c
a Department of Medicinal Chemistry, Pfizer Global Research and Development, Chesterfield, MO 63017, USA
b Department of Biochemical Pharmacology, Pfizer Global Research and Development, Chesterfield, MO 63017, USA
c Department of Medicinal Chemistry, Incyte Corporation, Wilmington, DE, USA
d Department of Biochemstry/Enzymology, Incyte Corporation, Wilmington, DE, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
This report describes the design and synthesis of a series of CCR2 antagonists incorporating novel
non-aryl/heteroaryl RHS (right hand side) motifs. Previous SAR in the area has suggested an aryl/
heteroaryl substituent as a necessary structural feature for binding to the CCR2 receptor. Herein we
describe the SAR with regards to potency (binding to hCCR2), dofetilide activity and metabolic stability
(in vitro HLM) for this series. The resulting outcome was the identification of compounds with excellent
properties for the investigation of the role of CCR2 in disease.
Received 11 October 2010
Revised 11 January 2011
Accepted 13 January 2011
Available online 21 January 2011
Keywords:
CCR2 antagonists
MCP-1
Ó 2011 Elsevier Ltd. All rights reserved.
hERG
Diazobicyclo[2.2.1]heptane
Central penetrance
Dofetilide
Neuropathic pain
Inflammatory diseases
Fluoropyran
The CC chemokine, Monocyte Chemotactic Protein-1 (MCP-1)
serves to recruit monocytes, dendritic cells, natural killer cells
and T-lymphocytes.1 Various chemokines and their respective
receptors have been shown to play important roles in many phys-
iological and pathological processes. Evidence exists that MCP-1 is
an important biomarker for inflammatory diseases such as rheu-
matoid arthritis2 and atherosclerosis.3 Investigations of CCR2 (ko)
and MCP-1 (ko) mice suggest that antagonism of the interaction
of MCP-1 with CCR2 may be beneficial in treating inflammatory
diseases.4
and synthesized. Initial SAR suggested that an aryl/heteroaryl
RHS (right hand side) motif is required for potency in compounds
of the general structural type (see Fig. 1)5 However, the incorpora-
tion of an aryl/heteroaryl motif brings with it some potential
deficiencies, for example reduced metabolic stability due to an in-
crease in c log D, as well as a potential anchor point for binding to
Recent literature has highlighted a range of CCR2 receptor
antagonists of varying structural types.5 In our laboratories, the
CCR2 antagonists (Fig. 1, 1) have been disclosed and served as a ba-
sis for further chemical modification.6 The compounds possess
excellent in vitro binding potency and functional activity.
In order to expand the chemical space and by extension the
modulation of the biological properties (potency, hERG binding
and metabolic stability) a series of compounds were designed
⇑
Corresponding author.
E-mail address: john.i.trujillo@pfizer.com (J.I. Trujillo).
Figure 1. General structural motif of selected CCR2 antagonists.
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.01.052

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J. I. Trujillo et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1827–1831
various ion channels.7 Therefore, an exploration of non-aryl con-
taining CCR2 antagonists was of interest to avoid these potential
pitfalls and expand the chemistry space.
From previous work, compound 2 (see Fig. 2) was identified as a
potent CCR2 antagonist (hCCR2 binding IC50 = 3.0 nM, human
whole blood assay = 3.9 nM, human liver microsome stability
t1/2 = 93 min), with modest activity on hERG (IC50 = 1.7 l
M).8 Initial
analog work investigating the removal of the N-linked aryl group
and replacement with an isosteric t-butoxycarbonyl group disap-
pointingly resulted in a significant loss of binding affinity (see
Fig. 3). Further expansion of the SAR led us to the incorporation
of the bridged 2.2.1 piperazine ring system for the piperazine ring
leading to compound 5. Compound 5 gratifyingly possessed equiv-
alent activity to 2, but without an aryl/heteroaryl ring system on
the RHS. An overlay of compound 6 onto 4 suggested that
perhaps alternate hydrophobic pocket was being accessed (see
Fig. 4). Alternatively, the conformational restriction introduced
by the methylene bridge may be locking the RHS into the more
active conformation. In order to explore the SAR for this compound
a series of analogs were prepared wherein the t-butoxycarbonyl
was replaced with other carbamates, amides and ureas. The syn-
theses of these compounds are described in Schemes 1 and 2.
The activities for these compounds are depicted in Tables 1–3.
The initial investigations of the SAR were done wherein the LHS
(left hand side) pyran was unsubstituted. Thus the key intermedi-
ate 7 was prepared as previously described.8 To the acid 7 was
coupled the boc-2.2.1 piperazine, followed by removal of the
2,5-dimethylpyrrole protecting group and reduction to give 10.
Reductive amination with 4-pyranone provided 6, which was then
protected with trifluoroacetic anhydride. The Boc group was
Figure 4. Overlay of compound 4 and 6.
removed to give the free amine to which a series of carbamates,
amides and ureas were prepared. The methoxy pyran and F-pyran
series were prepared in a similar manner (see Scheme 2).
In order to gauge the steric requirements of the RHS region of
the binding site a series of amides were prepared with gradual in-
i
t
creases in steric bulk (CH3, CH3CH2, Pr, Bu, cPr, cBu, cPen, cHex,
compounds 14–21). From the activity displayed it was clear that
the receptor required a minimal degree of steric bulk, with the
cyclo-pentyl and cyclo-hexyl possessing activity most similar to
the parent N-Boc compound. The isosteric 3,3-trimethylbutana-
mide displayed a slight reduction in potency (37 nM vs 5 nM) for
the parent. Interestingly, when the c-hexyl group 21 was replaced
with a pyran to give 22, a significant decrease in activity was ob-
served suggesting a very lipophilic pocket intolerate of polarity.
From previous studies in the aryl series8, incorporation of a CF3-
group enhanced potency, thus a group of CF3 containing amides
were synthesized. The activities of these compounds (23–25) were
equivalent with compound 6, exhibiting a slight reduction in met-
abolic stability, due to the increased lipophilicity.
With the SAR of the pyran series showing a clear requirement
for a minimal degree of steric bulk for activity, a subset of com-
pounds wherein the pyran was replaced with the methoxy pyran
was prepared. Previous work had shown the methoxy pyran to
bring activity on the mouse homolog of CCR29 allowing target val-
idation in in vivo murine models. Very similar SAR was observed
with regards to 3,3-trimethylbutanamide 30 (17 nM) and t-butyl
amide 31 (40% at 300 nM). Interestingly, in the methoxy pyran
Figure 2. Structure of lead compound 2 and biological data.
Figure 3. Structure of lead compound 2–6 and binding data.

J. I. Trujillo et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1827–1831
1829
Scheme 1. Preparation of compounds 6 and 13–25. Reagents and conditions: (a) (1S,4S)-tert-butyl 2,5-diazabicyclo[2.2.1]heptane-2-carboxylate, TBTU, Et3N, DMF, 0 °C, 95%;
(b) H2NOH, THF/H2O, 90%; (c) H2, Pt/C, HOAc, 40 psi; (d) dihydro-2H-pyran-4(3H)-one, Et3N, NaBH(OAc)3, 95%; (e) TFAA, Et3N, CH2Cl2, 0 °C, 95%; (f) 30% TFA, CH2Cl2, rt, 90%
yield; (g) (i) RCOCl, Et3N, CH2Cl2, 0 °C, 90% or (ii) RCO2H, TBTU, Et3N, DMF, 91%; (h) K2CO3, MeOH, rt, 80–94%.
Scheme 2. Preparation of compounds 30–34 and 38–50. Reagents and conditions: (a) pyranone, Et3N, NaBH(OAc)3, 95%; (b) TFAA, Et3N, CH2Cl2, 0 °C, 95%; (c) 30% TFA, CH2Cl2,
rt, 90% yield; (d) (i) RCOCl, Et3N, CH2Cl2, 0 °C, 90% or (ii) RCO2H, TBTU, Et3N, DMF, 91% or (iii) RNCO, Et3N, CH2Cl2, 0 °C; (e) K2CO3, MeOH, rt, 80–94%.
series a slight enhancement in potency was observed with the c-
butyl amide (19 vs 32, threefold). Finally, analogs 33 (c-pentyl)
and 34 (benzamide) showed good activity and metabolic stability.
Recent work in the CCR2 field has suggested penetrance into the
CNS as a possible requisite for activity in certain disease states (e.g.,
neuropathic pain).10 As a strategy to enhance the permeability for
the chemical series the pyran was fluorinated beta to the second-
ary amine resulting in a reduction of basicity (ꢀ1.7 pKa units).
Compound 35 exhibited very good potency (4.2 nM), however with
a reduction in metabolic stability, likely due to the increased
c log D (ꢀ1.1 units). A similar reduction in metabolic stability
was observed for the F-pyran series across the various substitu-
tions (amide and carbamate), again likely due to the increased
c log D. On the other hand, compounds 42 and 43 retained their
metabolic stability along with good affinity to CCR2 despite the
fluorination of the pyran. Further evaluation of these compounds

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J. I. Trujillo et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1827–1831
Table 1
Table 2
Binding affinities, dofetilide and hlm stability of unsubstituted pyran series
Binding affinities, dofetilide and hlm stability of methoxy pyran series
No.
R
CCR2 HWCB (nM)
5.0b
Dof (%inh)
4.8
HLM (t1/2)
No.
R
CCR2 HWCB (nM)
2.9b
Dof (%inh)
0
HLM (t1/2)
O
O
6
>120
5
>120
O
O
17.0b
24.2a
13
36.9b
5.7
>120
30
31
0
6
>120
>120
O
O
O
O
O
O
14
15
1% at 0.30a
0
6
>120
>120
40% at 0.3b
11.7b
28% at 0.30a
32
33
4
>120
>120
16
17
18
19
40% at 0.30a
23% at 0.30a
130a
3.7
2
>120
>120
>120
>120
O
8.5b
6.7
11.1a
O
O
O
O
6.5b
34
7.8
94.2
12.0a
2.3
6
O
Abbreviations: HWCB = human whole cell binding assay (a = 30 min preincubation,
b = 1 h preincubation); Dof = hERG dofetilide assay, %inh at 10 M; HLM = human
liver microsome-half life, 1 lM dose.
l
32b
20
21
12.2b
11.6a
2
4
>120
93.2
O
O
O
Table 3
Binding affinities, dofetilide and hlm stability of fluropyran series
O
22
46% at 0.30a
0
>120
No.
R
CCR2 HWCB (nM)
4.2b
Dof (%inh)
6
HLM (t1/2)
CF3
O
O
3.5a
13a
2
5
1
78
>120
>120
35
37.2
23
24
25
O
O
O
O
CF3
CF3
36
37
39.5a
38.4a
0
76
21
O
O
14.6a
17
Abbreviations: HWCB = human whole cell binding assay (a = 30 min preincubation,
b = 1 h preincubation); Dof = hERG dofetilide assay, %inh at 10 M; HLM = human
liver microsome-half life, 1 M dose.
13.9a
3
>120
l
38
l
O
CF3
CF3
CF3
in an efflux assay showed low levels of efflux suggesting that they
would be reasonable substrates for passage across the blood–brain
barrier (BBB), compound 40 (MDCK A/B = 11.8 ⁄ 10À6 cm/s; B/A
10.2 ⁄ 10À6 cm/s; BA/AB = 0.8), compound 41 (MDCK A/B = 8.35 ⁄
10À6 cm/s; B/A = 5.3 ⁄ 10À6 cm/s; BA/AB = 0.6).
O
39
40
41
3.2a
12.8a
17.3a
3
0
5
26
>120
>120
O
O
O
In conclusion, we have identified a series of CCR2 antagonists
bearing non-aryl/heteroaryl RHS motifs with excellent potency in
human whole cell binding.11 The compounds displayed good
in vitro human metabolic stability and low affinity for the hERG

J. I. Trujillo et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1827–1831
1831
Table 3 (continued)
References and notes
No.
R
CCR2 HWCB (nM)
14.7a
Dof (%inh)
3
HLM (t1/2)
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75.9a
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Abbreviations: HWCB = human whole cell binding assay (a = 30 min preincubation,
b = 1 h preincubation); Dof = hERG dofetilide assay, %inh at 10 M; HLM = human
liver microsome-half life, 1 M dose.
l
l
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Acknowledgements
We thank Jim Doom and Shen Yang for expert assistance with
LC/MS instrumentation and NMR instrumentation, respectively.