N-Arylalkylpiperidine urea derivatives as CC chemokine receptor-3 (CCR3) antagonists

Article abstract of DOI:10.1016/j.bmcl.2004.11.006

The synthesis and structure-activity relationships of N- arylalkylpiperidylmethyl ureas as antagonists of the CC chemokine receptor-3 (CCR3) are presented. These compounds displayed potent binding to the receptor as well as functional antagonism of eotaxin-elicited effects on eosinophils.

Full text of DOI:10.1016/j.bmcl.2004.11.006

Bioorganic & Medicinal Chemistry Letters 15 (2005) 787–791
N-Arylalkylpiperidine urea derivatives as CC chemokine
receptor-3 (CCR3) antagonists
Douglas G. Batt,* Gregory C. Houghton, John Roderick, Joseph B. Santella, III,
Dean A. Wacker, Patricia K. Welch, Yevgeniya I. Orlovsky, Eric A. Wadman,
James M. Trzaskos, Paul Davies, Carl P. Decicco and Percy H. Carter
Bristol-Myers Squibb, Pharmaceutical Research Institute, PO Box 4000, Princeton, NJ 08543-4000, USA
Received 9 August 2004; revised 29 October 2004; accepted 1 November 2004
Available online 21 November 2004
Abstract—The synthesis and structure–activity relationships of N-arylalkylpiperidylmethyl ureas as antagonists of the CC chemo-
kine receptor-3 (CCR3) are presented. These compounds displayed potent binding to the receptor as well as functional antagonism
of eotaxin-elicited effects on eosinophils.
Ó 2004 Elsevier Ltd. All rights reserved.
Many chemokines (chemotactic cytokines) are major
mediators of inflammatory responses, and antagonism
of their effects has attracted significant attention as a no-
vel approach to anti-inflammatory therapy.1,2 Eotaxin
(CC11), a CC or type 2 chemokine, appears to be a pri-
mary chemoattractant responsible for local eosinophilia
in some inflammatory conditions, including asthma,
allergic rhinitis, contact dermatitis and parasitic infec-
tions.3 The receptor for eotaxin, CCR3, which is a mem-
ber of the 7-transmembrane G-protein coupled receptor
family, is expressed by eosinophils, mast cells and Th2
lymphocytes.1,4,5 A growing body of evidence supports
the importance of eotaxin and CCR3 in the inflamma-
tory component of asthma and other diseases character-
ized by eosinophilia.4–8 Since asthma is widespread,
debilitating and often life-threatening,9 the pharmaceu-
tical research community has taken a great interest in
discovering small molecule antagonists of CCR3 as a
novel approach to an anti-inflammatory therapy for this
disease.1,2
as well as by the appropriate choice of substituents on
the urea aromatic ring.11 Further work showed that con-
formational restriction of the propyl chain by fusion
with a benzene ring, providing 2, also gave compounds
with good potency.12
An alternative rigidification of the central propylene
chain of 1 would involve breaking the piperidine ring,
to 3, and forming a new piperidine ring onto this chain,
leading to the general structure 4. We explored the
effects such a change would have on CCR3 potency.
(Examples of somewhat related CCR3 antagonists con-
taining N-benzyl piperazines and morpholines, some
linked to ureas, have been reported.)13
Ar
Ar
N
O
NH
N
O
NH
F
NH
F
NH
1a (4-substituted)
1b (3-substituted)
2
An earlier report from our group10 disclosed 4-benzylpi-
peridin-1-ylpropyureas (1a) as potent antagonists for
CCR3. Subsequent studies demonstrated that greater
potency and selectivity resulted from replacing the 4-
benzylpiperidine moiety with S-3-benzylpiperidine (1b),
Ar
NH
F
(CH2)n
HN
Ar
O
(CH2)n
O
NH
NH
N
NH
F
3
4
Keywords: CCR3; Piperidine; Eotaxin.
*
A series of 1-(4-fluorophenylalkyl)piperidines attached
through a methylene linker to an arylurea moiety served
Corresponding author. Tel.: +1 609 252 4034; fax: +1 609 252
6601; e-mail: douglas.batt@bms.com
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.11.006

788
D. G. Batt et al. / Bioorg. Med. Chem. Lett. 15 (2005) 787–791
Table 1. Effect of chain length, urea position and absolute configu-
ration on binding and eotaxin-induced Ca2+ release
mer in the ethylene series was 3-fold more potent than
the optical antipode (12 vs 13), yet the (R) isomer was
more potent with a propylene chain (14 vs 15). This
may reflect the degree of flexibility inherent in these mole-
cules, allowing the critical binding moieties (presumably
the basic nitrogen, the fluorophenyl and the urea) to
reach similar conformations in all cases. This suggests
that the piperidine ring does not interact significantly
with the receptor, serving only as a spacer.
N
N
(CH2)n
H
N
H
N
N
N
N
F
CH3
O
R
n
Isomer
R
CCR3
IC50 (nM)a
Ca2+
IC50 (nM)b
5
6
7
1
2
3
4(RS)
4(RS)
4(RS)
H
H
H
54
1200
ca. 10,000c
2500
The addition of a second meta-substituent on the phenyl
ring of the urea (examples 16 through 19 in Table 1) in-
creased potency still further, in agreement with prior re-
sults.11 In this case, the differences in binding potency
between (R) and (S), and between chain lengths of 2
or 3 carbons, were minimal. However, the Ca2+ mobili-
zation assay still favoured the ethylene analogue by 10-
fold in the (S) series (17 vs 19).
350
230
8
1
2
3
4
3(RS)
3(RS)
3(RS)
3(RS)
H
H
H
H
3500
6
>10,000d
180
1500
9
10
11
36
29
12
13
14
15
2
2
3
3
3(R)
3(S)
3(R)
3(S)
H
H
H
H
13
5
870
260
15
100e
1500
ca. 10,000f
The substitution on the phenethyl ring was varied in the
(S) series, as shown in Table 2. In agreement with previ-
ous reports for 1a and 1b,10,11 halogens (17 and 20
through 26) were preferable to alkyl (28), or to larger
or more polar substituents (29 through 31). The unsub-
stituted case (27) was nearly as potent. Interestingly, in
the fluorine-substituted compounds, para-substitution
was somewhat favoured (17 vs 20), while a meta-chloro
substituent seemed preferable to the para-isomer (25 vs
24), ortho-substitution was slightly disfavoured (21 and
22 vs 17, 26 vs 24 and 25).
16
17
18
19
2
2
3
3
3(R)
3(S)
3(R)
3(S)
Et
Et
Et
Et
1.6
0.7
2.2
1.9
27
290
a See Ref. 14.
b See Ref. 15.
c 57% at 10,000nM.
d 0% at 10,000nM.
e 45% at 100nM.
f 67% at 10,000nM.
The ethylene series possesses five rotatable bonds be-
tween the phenyl ring and the urea moiety, which can
dramatically effect the overall shape of the molecules.
This flexibility may contribute to the similar potency
of compounds having different absolute stereochemistry
and chain length (e.g., 12 through 14). Seeking to limit
this flexibility, we prepared three compounds (Table 3,
32 through 34) lacking the methylene spacer between
to evaluate the optimal chain length and substitution
position, as shown by compounds 5 through 11 in Table
1. The 4-fluorophenyl and 3-(1-methyltetrazol-5-yl)-phen-
yl substituents were chosen for their known potency-
enhancing effects in 1a and 1b.10,11
Substitution at the 3-position of the piperidine ring en-
hanced potency significantly relative to the 4-substituted
analogues. This change, allowing a more pronounced
bend in the overall shape of the molecule, is consistent
with the enhanced potency displayed by the ortho-disub-
stituted phenyl series 3 over the corresponding para-iso-
mers.12 The effect of chain length on potency differed
dramatically between the 3- and 4-substituted series.
Maximal binding potency in the 4-substituted series
was provided by the N-benzyl analogue (5), yet this
compound was by far the least potent of the 3-substi-
tuted compounds examined. In the 4-substituted series,
ethylene and propylene linkers were very similar (6
and 7), while in the 3-substituted series the ethylene ana-
logue 9 was significantly more potent than either propyl-
ene (10) or butylene (11). In general, inhibition of
eotaxin-induced Ca2+ mobilization in eosinophils dem-
onstrated that these compounds were receptor antago-
nists, with the rank-order potency of this effect similar
to that of receptor binding.
Table 2. Phenyl substitution effects on CCR3 binding
CH3
O
CH3
X
H
N
N
N
H
N
H
N
N
N
X
CCR3, IC50 (nM)a
17
20
21
22
23
24
25b
26
27
28
29
30
31
4-F
3-F
0.7
12
2-F
5.5
1.8
3.2
3.6
0.6
5.5
3.7
9.7
82
2,4-F2
3,4-F2
4-Cl
3-Cl
2,4-Cl2
H
Me
CF3
OMe
NMe2
120
380
Since shifting the piperidine substituent from the 4- to
the 3-position introduced chirality into the molecules,
the individual enantiomers were prepared and evalu-
ated. Although both isomers were active, the (S) enantio-
a See Ref. 14.
b Ca2+ IC50 15nM; see Ref. 15.

D. G. Batt et al. / Bioorg. Med. Chem. Lett. 15 (2005) 787–791
789
Table 3. Effect of attempted conformational restraint on binding and
Ca2+ release
O
Boc
Boc
a
(CH2)m
N
(CH2)m
N
NH2
N
H
NHAr
CH3
42
44 (R = Boc)
b, c
O
CH3
(CH2)n
46 (R = Ar'(CH2)n)
(CH2)m
N
N
H
N
H
N
N
N
Scheme 1. Reagents and conditions: (a) ArNHCOOPh (43), DMF,
Et3N, rt, 70–80%; (b) HCl(g), EtOAc, rt, quant.; (c) Ar0(CH2)nOTs
(45), K2CO3, acetone or acetonitrile, reflux, 50–70%.
R
R'
N
F
(+/-)
n
m
R
R0
CCR3
IC50 (nM)a
Ca2+
IC50 (nM)b
32
33
34
35c
36
37
38
39
40
41
2
3
4
2
2
2
2
2
2
2
0
0
0
1
1
1
1
1
1
1
H
H
H
H
H
H
H
H
Me
H
H
14
unlike the observations for previously-reported com-
pounds. The explanation for this might lie in differences
in the kinetics of receptor binding between the two ser-
ies. Perhaps the greater flexibility of the phenethylamine
moiety of the present series relative to the benzypiper-
idine moiety of 1b results in faster dissociation from
the receptor. This could translate to reduced functional
effects for the same degree of receptor occupancy.
H
1.2
7.9
3.4
1.3
2.2
1.6
0.63
3.0
3.0
H
H
46
17
Me
Et
i-Pr
Me
CF3
Ph
10
27
a See Ref. 14.
b See Ref. 15.
The compounds described were prepared from readily-
available building blocks. As shown in Scheme 1, 1-
Boc-protected 4-aminomethyl-,17 3-aminomethyl-18 or
3-amino-piperidine19 42 was acylated with a substituted
phenylcarbamate 43 (prepared according to published
procedures).20 The enantiomeric 3-aminomethyl-piper-
idine derivatives 42 (m = 1) were prepared from the
corresponding alcohols, separated by enzymatic kinetic
resolution.18,21 (The S isomers had 97% ee, and the R
isomers had 92% ee.) Deprotection of the ring nitrogen
of 44 was followed by alkylation with the appropriate x-
tosyloxyalkylbenzene derivative 45 under standard
conditions in good yields. (The alternative of reductive
alkyl- ations with the corresponding aldehydes produced
variable yields of products, and the purities of the crude
products were generally worse.) Those alcohol precur-
sors to the tosylates not commercially available were
prepared by borane reduction of the corresponding
acids, which were either purchased or readily prepared
by Horner–Emmons reactions from the substituted
benzaldehydes.
c This compound is the racemate of 17.
the piperidine ring and the urea. Comparing compounds
with the same atom count between the two aromatic
rings (33 vs 9 and 34 vs 10), potency was increased about
5-fold by this change. The change was much more dra-
matic for the shortest analogues (32 vs 8), where a
250-fold improvement resulted.
Incorporation of a 4-substituent on the piperidine ring
offered another possibility for altering the conforma-
tional preference of the urea-containing chain via a but-
tressing effect. However, several analogues with such a
substituent trans to the ureidomethyl group (36 through
41) showed marginal to no improvement in binding po-
tency relative to 35. Some slight improvements in antag-
onism of Ca2+ mobilization by the three analogues
examined were probably not significant relative to that
shown by 35.
The 3,4-disubstituted aminomethylpiperidine derivative
precursors to compounds 36 through 41 were obtained
as shown in Scheme 2. Substituted acrylamides 47 were
obtained in high recrystallized yields (70–98%) from the
corresponding substituted acryloyl chloride or acrylic
acid and 4-fluorophenethylamine. Base-catalyzed addi-
tion of diethyl malonate provided the piperidine-2,6-
diones 48. (Only the trans isomers were isolated when
one of R and R0 was H.) Reduction with LiAlH4 pro-
vided moderate yields of the hydroxymethyl compounds
49, which were converted to the aminomethyl com-
pounds using reported methods.18 Alternatively, addi-
tion of ethyl cyanoacetate22 to 47 followed by
reduction of the cyanoimides 50 provided the amino-
methyl derivatives directly, although the yields of the
reduction step were modest (30–60%). Acylation with
phenyl carbamates 43 as in Scheme 1 provided the de-
sired products 36–38, 40 and 41 in 60–80% yields.
Four of the compounds described were shown to inhibit
chemotaxis of human eosinophils in response to eotaxin
(Table 4). However, these were clearly weaker than close-
ly related 3-benzylpiperidine analogues of structure 1b,
which had chemotaxis IC50 values below 5nM.11 Simi-
larly, the calcium mobilization potencies were
significantly reduced relative to the binding potencies,
Table 4. Antagonism of eotaxin-induced chemotaxis compared to
binding and Ca2+ release
CCR3,
IC50 (nM)a
Ca2+
,
Chemotaxis,
% inhib. @ 30nMc
EC50 (nM)b
17
25
35
36
0.7
0.6
3.4
1.3
27
15
46
17
51
24
51
42
a See Ref. 14.
b See Ref. 15.
c See Ref. 16.
In the case of the 4,4-dimethyl analogue 39, no reaction
of either malonate or cyanoacetate esters with the

790
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Today 2000, 6, 20.
R2-NH
R
[R2 = 4-F-Ph-(CH2)2-]
O
R'
47
4. Ma, W.; Bryce, P. J.; Humbles, A. A.; Laouini, D.;
Yalcindag, A.; Alenius, H.; Friend, D. S.; Oettgen, H. C.;
Gerard, C.; Geha, R. S. J. Clin. Invest. 2002, 109, 621.
5. Humbles, A. A.; Lu, B.; Friend, D. S.; Okinaga, S.; Lora,
J.; Al-garawi, A.; Martin, T. R.; Gerard, N. P.; Gerard, C.
Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 1479.
6. Lilly, C. M.; Woodruff, P. G.; Camargo, C. A., Jr.;
Nakamura, H.; Drazen, J. M.; Nadel, E. S.; Hanrahan, J.
P. J. Allergy Clin. Immunol. 1999, 104, 786.
a or b
Y
O
R2
N
X
R2
N
c or d
R
R
O
R'
R'
7. Ying, S.; Meng, Q.; Zeibecoglou, K.; Robinson, D. S.;
Macfarlane, A.; Humbert, M.; Kay, A. B. J. Immunol.
1999, 163, 6321.
48 (X = COOEt)
50 (X = CN)
49 (Y = OH)
51 (Y = NH2)
8. Justice, J. P.; Borchers, M. T.; Crosby, J. R.; Hines, E. M.;
Shen, H. H.; Ochkur, S. I.; McGarry, M. P.; Lee, N. A.;
Lee, J. J. Am. J. Physiol. Lung Cell Mol. Physiol. 2003,
284, L169.
9. Elias, J. A.; Lee, C. G.; Zheng, T.; Ma, B.; Homer, R. J.;
Zhu, Z. J. Clin. Invest. 2003, 111, 291.
f
O
e
R2-NH2
CN
R2-NH
10. Wacker, D. A.; Santella, J. B., III; Gardner, D. S.; Varnes,
J. G.; Estrella, M.; DeLucca, G. V.; Ko, S. S.; Tanabe, K.;
Watson, P. S.; Welch, P. K.; Covington, M. B.; Stowell,
N. C.; Wadman, E. A.; Davies, P.; Solomon, K. A.;
Newton, R. C.; Trainor, G. L.; Friedman, S. M.; Decicco,
C. P.; Duncia, J. V. Bioorg. Med. Chem. Lett. 2002, 12,
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11. Varnes, J. G.; Gardner, D. S.; Santella, J. B., III; Duncia,
J. V.; Estrella, M.; Watson, P. S.; Clark, C. M.; Ko, S. S.;
Welch, P.; Covington, M.; Stowell, N.; Wadman, E.;
Davies, P.; Solomon, K.; Newton, R. C.; Trainor, G. L.;
Decicco, C. P.; Wacker, D. A. Bioorg. Med. Chem. Lett.
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12. De Lucca, G. V.; Kim, U. T.; Johnson, C.; Vargo, B. J.;
Welch, P. K.; Covington, M.; Davies, P.; Solomon, K. A.;
Newton, R. C.; Trainor, G. L.; Decicco, C. P.; Ko, S. S. J.
Med. Chem. 2002, 45, 3794.
13. (a) Gong, L.; Hogg, J. H.; Collier, J.; Wilhelm, R. S.;
Soderberg, C. Bioorg. Med. Chem. Lett. 2003, 13, 3597; (b)
Gong, L.; Kertezs, D. J.; Smith, D. B.; Talamas, F. X.;
Wilhelm, R. S. Eur. Patent Appl. EP 903349, 1999; (c)
Ancliff, R. A.; Cook, C. M.; Eldred, C. D.; Gore, P. M.;
Harrison, L. A.; Hodgson, S. T.; Judd, D. B.; Keeling, S.
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Intl. Pat. Appl. WO 02/26723, 2002.
52
Scheme 2. Reagents and conditions: (a) diethyl malonate, NaOEt,
toluene, reflux, 75%; (b) ethyl cyanoacetate, NaH, THF, reflux (45–
75%); or KOBut, t-BuOH, THF, reflux (75–96%); (c) LiAlH4, THF,
reflux (40%); (d) BH3, THF, reflux, then HOAc (30–60%); (e) ethyl
cyanoacetate, neat, 100°C, 52%; (f) ethyl b-methylpropenoate, KOBut,
t-BuOH, THF, reflux, 85%.
dimethyl acrylamide 47 (R = R0 = Me) was observed
under a variety of conditions. In order to take advantage
of the increased electrophilicity of esters over amides,
the order of assembly was reversed. Thus, the cyano-
acetamide 52 was prepared from ethyl cyanoacetate
and 4-fluorophenethylamine, followed by base-catalyzed
addition to ethyl b-methylpropenoate, to provide the de-
sired imide 50 (R = R0 = Me) in excellent yield. Borane
reduction provided 51 (R = R0 = Me).
In conclusion, compounds of general structure 4, con-
ceptually derived from 1 and 2, bound to CCR3 with
good potency and also displayed functional antagonism
of the eotaxin-induced effects on human eosinophils.
Broad features of the SAR were similar to the previ-
ously-reported series. The greater conformational free-
dom of 4 relative to 1 and 2 seemed to be reflected in
a relatively high tolerance for changes in chain length
and absolute stereochemistry, and may also be the cause
of the relatively weaker inhibition of eotaxin-induced
chemotaxis than was reported for the earlier com-
pounds. Further work addressing these issues will be re-
ported in due course.
14. The binding assay was carried out using 125I-labelled
human eotaxin and CHO cells stably transfected with a
gene encoding human CCR3 as described in Ref. 12. In
some cases cells stably transfected with a chimeric recep-
tor, consisting of the intracellular domain of human CCR2
with the extracellular and transmembrane domains of
human CCR3, were used. This variation was found to give
results nearly identical to those obtained using the native
CCR3 receptor; details will be published in due course.
The value reported represents the average of three
determinations with a standard deviation of 20–50% of
the mean value.
15. The Ca2+ mobilization assay was carried out using eotaxin
and human eosinophils preloaded with a calcium-depend-
ent fluorescent dye, as described in Ref. 12.
16. The chemotaxis assay was carried out using eotaxin and
human eosinophils in 96-well chemotaxis chambers, as
described in Ref. 12.
Acknowledgements
We gratefully acknowledge the assistance of A. J. Mical
and K. A. Rathgeb for determination of the enantio-
meric purity of 12 and 13 by chiral HPLC.
17. Carceller, E.; Merlos, M.; Giral, M.; Balsa, D.; Garcia-
Rafanell, J.; Forn, J. J. Med. Chem. 1996, 39, 487.
18. Hilpert, K.; Ackermann, J.; Banner, D. W.; Gast, A.;
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