CC chemokine receptor-3 (CCR3) antagonists: Improving the selectivity of DPC168 by reducing central ring lipophilicity

Article abstract of DOI:10.1016/j.bmcl.2007.03.065

DPC168, a benzylpiperidine-substituted aryl urea CCR3 antagonist evaluated in clinical trials, was a relatively potent inhibitor of the 2D6 isoform of cytochrome P-450 (CYP2D6). Replacement of the cyclohexyl central ring with saturated heterocycles provid

Full text of DOI:10.1016/j.bmcl.2007.03.065

Bioorganic & Medicinal Chemistry Letters 17 (2007) 2992–2997
CC chemokine receptor-3 (CCR3) antagonists: Improving
the selectivity of DPC168 by reducing central ring lipophilicity
James R. Pruitt, Douglas G. Batt,* Dean A. Wacker, Lori L. Bostrom, Shon K. Booker,
Erin McLaughlin, Gregory C. Houghton, Jeffrey G. Varnes, David D. Christ,
Maryanne Covington, Anuk M. Das, Paul Davies, Danielle Graden, Ilona Kariv,
Yevgeniya Orlovsky, Nicole C. Stowell, Krishna G. Vaddi, Eric A. Wadman,
Patricia K. Welch, Swamy Yeleswaram, Kimberly A. Solomon, Robert C. Newton,
Carl P. Decicco, Percy H. Carter and Soo S. Ko
Bristol-Myers Squibb Pharmaceutical Research Institute, PO Box 4000, Princeton, NJ 08543-4000, USA
Received 22 February 2007; revised 20 March 2007; accepted 21 March 2007
Available online 24 March 2007
Abstract—DPC168, a benzylpiperidine-substituted aryl urea CCR3 antagonist evaluated in clinical trials, was a relatively potent
inhibitor of the 2D6 isoform of cytochrome P-450 (CYP2D6). Replacement of the cyclohexyl central ring with saturated heterocy-
cles provided potent CCR3 antagonists with improved selectivity against CYP2D6. The favorable preclinical profile of DPC168 was
maintained in an acetylpiperidine derivative, BMS-570520.
ꢀ 2007 Elsevier Ltd. All rights reserved.
CC Chemokine receptor 3 (CCR3) is the dominant che-
mokine receptor on eosinophils, and is also expressed by
mast cells, basophils, and Th2 lymphocytes.1–3 A grow-
ing body of evidence supports a critical role for CCR3
and its cognate ligands (notably eotaxin) in the inflam-
matory component of diseases such as asthma, allergic
rhinitis, and contact dermatitis, all of which are charac-
terized by eosinophil migration into affected tissues.2–6
The clinical significance of these allergic diseases has
prompted research into the discovery of small molecule
antagonists of CCR3 as potential new therapeutics.1,7
against eotaxin-induced chemotaxis (double-digit
picomolar IC50).11 DPC168 was advanced into human
clinical trials based on good preclinical pharmacokinet-
ics, an acceptable toxicology profile, and robust efficacy
in rodent and monkey models of eosinophilia.
While the selectivity of DPC168 with respect to other
chemokine receptors, 7-transmembrane G protein-cou-
pled receptors, and biogenic amine transporters was
generally high (ranging from 250-fold to greater than
10,000-fold), only 15-fold selectivity was observed for
CCR3 binding relative to inhibition of the 2D6 isoform
of human cytochrome P-450 (CYP2D6). This was a
potential cause of concern, since CYP2D6 contributes
to the metabolism of about 20–25% of clinically used
drugs, and is also characterized by widespread genetic
polymorphism in the general population. Inhibition of
this enzyme raised the possibility of unpredictable inter-
actions between DPC168 and other commonly used
drugs, including antidepressants, neuroleptics, b-block-
ers, and antiarrhythmics. In particular, the antitussives
dextromethorphan and codeine, both likely to be used
by asthmatics, are metabolized by CYP2D6.15,16
Previous reports from our group detailed the discovery
of potent aryl urea antagonists of CCR3, culminating
in the identification of DPC168 (1, see Table 1).8–11
Starting with simple lead compounds,8 incorporation
of the (S)-3-(4-fluorobenzyl)piperidine moiety imparted
single-digit nanomolar CCR3 binding potency and good
selectivity,10 while rigidification of the central linker of
the molecule with the (1R,2S)-disubstituted cyclohexyl
core provided compounds with extremely potent activity
Keywords: SAR; Selectivity; CCR3; Chemokine; Cytochrome P-450;
CYP2D6.
*
A likely culprit contributing to the potent CYP2D6
inhibitory activity of DPC168 is the added lipophilicity
Corresponding author. Tel.: +1 609 252 4034; fax: +1 609 252
3993; e-mail: douglas.batt@bms.com
0960-894X/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2007.03.065

J. R. Pruitt et al. / Bioorg. Med. Chem. Lett. 17 (2007) 2992–2997
2993
Table 1. In vitro potency and selectivity comparison of DPC168 with two arylurea analogs
F
N
NH
NH-Ar
O
CYP2D6 IC50c (nM)
a
CCR3 IC50 (nM)
b
Chemotaxis IC50 (nM)
Compound
Ar
Ac
N
1
2.0
0.7
0.9
0.034
0.010
0.030
30
210
240
N
N
MeN
2
3
Ac
Me
S
N
a Inhibition of eotaxin binding to CCR3. See Ref. 12.
b Inhibition of eosinophil chemotaxis stimulated by eotaxin. See Ref. 13.
c Inhibition of oxidative demethylation of a model substrate by CYP2D6. See Ref. 14.
X3 COOEt
X3 COOEt
accompanying the incorporation of the cyclohexyl
group.17 Indeed, the analog of DPC168 wherein the 3-
(4-fluorobenzyl)piperidine and 3-acetylphenylurea moie-
ties are linked by a simple propylene chain displayed
similar CCR3 binding potency (IC50 2.5 nM),10 yet
was much less potent as an inhibitor of CYP2D6 (IC50
680 nM; 270-fold selective). Compounds 2 and 3 (Table
1) demonstrated the possibility of improving the selec-
tivity over CYP2D6 inhibition (300- and 370-fold,
respectively) while maintaining or even improving
CCR3 antagonism. We sought to improve the selectivity
further by replacing the cyclohexyl moiety of DPC168
with less lipophilic heterocyclic rings which would main-
tain the projection vectors of the benzylpiperidine and
arylurea groups.
b (c)
a
X4
X5
X4
X5
Ph
N
O
H
Me
11
12
X3 COOEt
F
d, e, (f)
X4
X5
O
X3
N
Ph
N
X4
H
X5
Me
Ph
Me
13
HN
14
F
X3
N
X4
X5
g, h, i
Since 2-amino-4-methyl-5-acetylthiazole (incorporated
into 3) is commercially available, we chose this aromatic
group for our SAR exploration of the central region of
the molecule. With the exception of 4 and 5,18 the com-
pounds were prepared from b-ketoesters 11, as shown in
Scheme 1).19–21 Condensation of 11 with R-(+)-a-meth-
ylbenzylamine provided the corresponding vinylogous
carbamates 12. Reduction to the b-aminoesters 13
proved to be sensitive to the structure of the starting
material, as summarized in Table 2. Standard reduction
using sodium triacetoxyborohydride (Method A) pro-
ceeded with fair to good selectivity in the piperidine
cases, providing mostly the expected22 but undesired
cis relative stereochemistry, necessitating base-catalyzed
equilibration in a subsequent step. However, unexpect-
edly, the diastereoselectivity of the reduction was much
poorer in the case of the tetrahydropyran precursor to 6.
An alternative method, using triethylsilane and trifluo-
roacetic acid (Method B), was somewhat more diaste-
reoselective and gratifyingly provided the desired trans
isomer directly. Surprisingly, in the pyrrolidine case
leading to 9, neither Method A nor a modification using
H
S
NH
PhOOCNH
S
N
Ac
Me
Ac
Me
N
O
N
15
6 - 10
Scheme 1. Reagents and conditions: (a) R-(+)-a-methylbenzylamine,
p-TsOH, benzene reflux (–H2O); (b) [see Table 2]; (c) [for 7 and 8]
K2CO3, EtOH reflux (7–22% from 11, with unepimerized material
which was separated and recycled); (d) LiOH or NaOH, H2O–THF, rt;
(e) (S)-(+)-3-(4-fluorobenzyl)piperidine, BOP, Et3N, CH2Cl2, rt (60–
100% for 2 steps); (f) [for 10] Oxone, MeOH, H2O, acetone, rt, 72%; (g)
Pd(OH)2 (20% on carbon), H2 (60 psig), EtOH, rt; (h) BH3, THF, rt,
then HOAc; (i) 15, acetonitrile, rt (12–42% for 3 steps).
chloroacetic acid in place of acetic acid (Method C) pro-
vided the desired product. However, sodium cyanoboro-
hydride in acetonitrile/acetic acid (Method D) provided
mostly the desired trans aminoester in good yield, but
unfortunately with low diastereoselectivity. Both Meth-
ods B and C provided the desired trans tetrahydrothi-
ophene analog, but with only poor to modest selectivity.

2994
J. R. Pruitt et al. / Bioorg. Med. Chem. Lett. 17 (2007) 2992–2997
Table 2. Reduction of vinylogous carbamates
X3 COOEt
X3 COOEt
X3 COOEt
X4
X5
X4
X5
X4
X5
+
Ph
Me
Ph
N
Ph
N
N
H
H
H
Me
Me
Target Compound
X3
X4
X5
Methoda
Yieldb
cis:trans
dec (%)
6
6
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
O
A
B
79%
76%
81%
47%
(nr)
>9:1
1:3
20
46
67
50
O
CH2
7
NBoc
CH2
NBoc
NBoc
S
A
A
C
D
A
B
>9:1
>9:1
8
NBoc
Bond
Bond
Bond
Bond
Bond
9
9
71%
(nr)
1:9
26
10
10
10
S
67%
60%
1:4
1:3
36
56
S
C
a Method A: NaBH(OAc)3, HOAc, acetonitrile, 0 ꢁC. Method B: CF3COOH, Et3SiH, rt. Method C: NaBH(OAc)3, ClCH2COOH, acetonitrile, rt.
Method D: NaBH3CN, HOAc, acetonitrile, rt.
b Overall yield of all isomers; (nr), no reaction.
c Diastereomeric excess of major isomer (cis or trans), based on reverse phase HPLC.
Saponification of the esters and coupling with (S)-(+)-
3-(4-fluorobenzyl)piperidine provided the amide inter-
mediates 14. Reductive removal of the benzylic chiral
auxiliary was followed by amide reduction with
borane, and urea formation by reaction with the phen-
oxycarbonylaminothiazole 15. (In the case of the tetra-
hydrothiophene derivative, oxidation to the sulfone
was performed prior to the reductive debenzylation.)
Finally, Boc removal from 7a, 8a, 9a, and 9c, followed
by standard nitrogen derivatization reactions (alkyl-
ation, reductive alkylation, acylation), provided the
analogs 7c–x, 8c–x, 9b, and 9d.
CCR3 binding and CYP2D6 inhibition results for an
initial set of different heterocyclic replacements for the
cyclohexyl group are shown in Table 3, along with the
carbocyclic parent 3. Calculated logD values at pH 7.4
(clogD7.4) were determined for the core heterocyclic
linkers (lacking the two appendages) and are listed in
the table in order to facilitate comparing the relative
lipophilicity of the different analogs.23
The potencies of the six-membered ring heterocycles (4–
8) varied within a 10-fold range and were similar to that
of 3. The Boc-piperidine analogs (7a, 8a) showed slightly
Table 3. In vitro binding and selectivity data for an initial set of heterocyclic DPC168 analogs
F
X3
N
X4
X5
H
NH
S
N
Ac
Me
O
N
a
CCR3 IC50 (nM)
b
CYP2D6 IC50 (nM)
c
Compound
X3
X4
X5
linker clogD7.4
3
CH2
O
CH2
CH2
O
CH2
CH2
CH2
O
0.9
1.7
240
100
3.39
0.89
4
5
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
2.0
1.0
490
440
0.89
0.89
6
CH2
NBoc
NH
7a
7b
8a
8b
9a
9b
9cd
9dd
10
CH2
CH2
NBoc
NH
6.0
570
20,000
160
2.61
À2.10
2.61
1.9e
9.2
CH2
CH2
NBoc
NH
2.1f
2.6
56,000
800
À2.10
1.39
Bond
Bond
Bond
Bond
Bond
7.6
28,000
1400
À2.66
1.39
NBoc
NH
SO2
16.0
44.0
1.2g
>100,000
2100
À2.66
À0.75
a See Ref. 12.
b See Ref. 14.
c See Ref. 23.
d 3,4-cis-Disubstituted pyrrolidine.
e Chemotaxis IC50 0.10 nM.
f Chemotaxis IC50 0.075 nM.
g Chemotaxis IC50 0.90 nM.

J. R. Pruitt et al. / Bioorg. Med. Chem. Lett. 17 (2007) 2992–2997
2995
decreased potency, while both N-unsubstituted piperi-
dines (7b, 8b) showed excellent binding potency as well
as good activity as antagonists of eosinophil chemotaxis.
The trans-substituted pyrrolidine analogs (9a,b) showed
similar potency, whereas the corresponding cis analogs
(9c, d) showed a slightly greater loss in potency. The
trans compounds in particular can readily adopt a con-
formation in which the projection of the two substitu-
ents approximates that achieved in the six-membered
ring cases, although with less rigidity. Interestingly, in
the case of 9, the Boc derivatives were a bit more potent
than the unsubstituted analogs, unlike the piperidines 7
and 8, where the opposite was true. The tetrahydrothi-
ophene sulfone 10, expected to mimic the six-membered
ring more closely due to the larger size of the sulfur
atom, was equivalent in binding potency to 3. However,
its potency as an antagonist of chemotaxis was signifi-
cantly reduced (900 pM vs 30 pM for 3).24
fairly lipophilic Boc derivatives of the nitrogen heterocy-
cles. However, the unsubstituted piperidine and pyrroli-
dine analogs (7b, 8b, 9b, 9d) showed greatly enhanced
selectivity for binding over CYP2D6 inhibition. The
polar sulfone moiety of 10 also increased the selectivity,
although to a lesser extent.
Because both piperidines 7b and 8b showed good bind-
ing potency and chemotaxis inhibition, as well as a great
improvement in selectivity against CYP2D6, a variety of
N-substituted analogs were evaluated for binding and
selectivity. Results of these efforts are shown in Table
4. Interestingly, the potency for CCR3 antagonism of
all the analogs shown fell within a 10-fold range, sup-
porting the contention that this region of the molecule
has little direct interaction with the receptor. In contrast,
dramatic effects were seen on the selectivity toward
CYP2D6, where the inhibitory potencies covered a
10,000-fold range.
In contrast to the effects on CCR3 binding, the structure
of the core ring could have a dramatic effect on CYP2D6
inhibition. Although the three isomeric tetrahydropyran
derivatives 4–6 would be expected to display greater
polarity based on clogD7.4, the CYP2D6 inhibition
was only slightly impacted. This was also true of the
The compounds in which the piperidine nitrogen was
rendered non-basic through acylation or carbamyla-
tion tended to display greater selectivity in the ‘3-
aza’ series (8a,c–n) than in the ‘4-aza’ series (7a,c–n).
The Boc derivatives (7/8a) were outliers from this gen-
Table 4. In vitro binding and selectivity results for piperidine core analogs
F
F
N
N
RN
H
H
N
RN
8a-x
NH
NH
S
S
N
Ac
Me
Ac
Me
O
O
7a-x
N
N
a
Linker clogD7.4 (nM)
R
Compound
CCR3
b
IC50 (nM)
CYP2D6
c
IC50 (nM)
Compound
CCR3
b
IC50 (nM)
CYP2D6
c
IC50 (nM)
Boc
2.61
2.23
7a
7c
7d
7e
7f
6.0
2.9
1.2
2.0
2.3
3.3
3.2
1.3
0.9
1.5
0.7
1.6
1.3
0.9
1.3
0.9
1.8
4.0
2.2
2.0
2.3
2.0
1.9
570
340
8a
8c
8d
8e
8f
9.2
3.6
1.5
2.1
4.9
2.1
2.5
1.9
1.3
1.1
0.6
1.6
1.2
2.6
6.9
1.2
2.0
2.7
2.0
1.4
2.8
1.2
2.1
160
910
C(@O)cyclopentyl
C(@O)-4-THPd
C(@O)iPr
C(@O)OMe
C(@O)Et
C(@O)cyclopropyl
C(@O)Me
C(@O)CH2OMe
C(@O)NHEt
C(@O)NHMe
C(@O)CH2NMe2
CH2CN
2.23
1.61
1200
50
1800
810
1.38
1.26
10
140
80
7g
7h
7i
8g
8h
8i
1500
80
1.10
0.73
60
1400
1200
170
1300
1200
1100
1200
500
0.57
0.35
7j
8j
7k
7m
7n
7o
7p
7q
7r
7s
7t
8k
8m
8n
8o
8p
8q
8r
8s
8t
À0.18
À0.18
0.80
550
5100
2000
780
410
170
CH2-2-furyl
CH2C(@O)Me
CH2CH2F
0.73
0.72
28,000
4300
2800
920
3900
3300
740
0.58
0.03
CH2C(@O)NMe2
CH2-cyclopropyl
1-Ac-4-piperidinyl
1-Me-4-piperidinyl
CH2CH2OH
Me
À0.12
À0.35
À0.52
À0.58
À1.09
À2.10
2200
1100
12,000
12,000
7400
56,000
7u
7v
7w
7x
7b
36,000
>100,000
23,000
2200
20,000
8u
8v
8w
8x
8b
H
a See Ref. 23.
b See Ref. 12.
c See Ref. 14.
d THP, tetrahydropyranyl.

2996
J. R. Pruitt et al. / Bioorg. Med. Chem. Lett. 17 (2007) 2992–2997
Table 5. Comparison of potency, selectivity, pharmacokinetic, and
in vivo efficacy results for DPC168 (1) and BMS-570520 (8i)a
eralization, as were the dimethylaminoacetyl deriva-
tives (7/8n). However, 7n and 8n bear a basic nitrogen
on the substituent, and so are more properly consid-
ered with other charged analogs (see below). Only
some variants provided improved selectivity over the
cyclohexyl analog 3. In neither isomeric series was
the correlation between selectivity and the clogD7.4
strong, but among structurally similar compounds
there was a tendency for more lipophilic analogs to
display reduced selectivity (compare 7i, 7g, and 7e).
As the substituent became larger (7d) the trend was
reversed, suggesting a steric clash with the active site.
The lack of selectivity of the methyl carbamates (7/8f)
relative to 3 was quite unexpected. Clearly bulk lipo-
philicity is unable to completely explain the results ob-
served, suggesting some contribution from specific
interactions between the active site of the cytochrome
and the substituent on the inhibitor.
Assay or PK parameter
Compound 1 Compound 8i
CCR3 IC50 (nM)
2.0
1.9
0.068
2.6
Chemotaxis IC50 (nM)
Ca2+ mobilization IC50 (nM)
CYP2D6 IC50 (nM)
5HT2A IC50 (nM)
0.034
8.0
30
1300
5300
640
920
1000
2900
D2 IC50 (nM)
Serotonin transporter Ki (nM)
29,000
6500
7700
Dopamine transporter Ki (nM) 490
Norepinephrine transporter
Ki (nM)
hERG IC50 (nM)
950
400
6000
Mouse F (%)
Mouse t1/2 (h)
20
2.0
25
1.2
Mouse CL (L/h/kg)
Cyno F (%)
Cyno t1/2 (h)
1.8
2.5
18
8
4.0
5.5
Cyno CL (L/h/kg)
Chimp F (%)
Chimp t1/2 (h)
2.1
22
0.87
7
In contrast to the results seen with non-basic piperidine
derivatives, the alkylated derivatives 7/8o–x were almost
all significantly more selective than 3 for CCR3 over
CYP2D6, indicating that the second positive charge
present at physiological pH is poorly tolerated by the
CYP2D6 active site. The unsubstituted analogs 7/8b
and the dimethylaminoacetamides 7/8n should be con-
sidered with this group as well, since they also bear a
second positive change. Unlike the acylated derivatives
discussed above, the ‘4-aza’ charged analogs (7) usually
but not always showed greater selectivity than the ‘3-
aza’ series (8). As was the case for the acylated com-
pounds, there was little correlation of selectivity with
calculated polarity for the doubly charged compounds
(compare, for example, 7/8w, 7/8s, and 7/8q). Interest-
ingly, these trends were the same in both isomeric series
(7 and 8).
5.0
1.2
4.5
1.3
Chimp CL (L/h/kg)
Protein binding (human, %)
Caco-2, Papp (cm/s)
Intrinsic clearance (L/h/kg)
96.3
11 · 10À6
0.97
93.1
2.8 · 10À6
0.96
Mouse CCR3 IC50 (nM)
Mouse chemotaxis IC50 (nM)
Mouse eotaxin challenge
EC50 (mg/kg)
54
41
20
3.6
7.0
1.5
Mouse OVA challenge
(% inhibition at 100 mg/kg bid)
86%
82%
a See Refs. 11,25 for descriptions of the assays and tests, the results for
compound 1, and the in vivo results for compound 8i.
proved or maintained against not only CYP2D6, but
also against other 7-transmembrane G protein-coupled
receptors, biogenic amine transporters, and the hERG
potassium channel. Pharmacokinetic parameters were
similar in the mouse and improved in the Cynomolgus
monkey, despite the reduced absorption predicted by
the smaller Caco-2 permeability. Poorer absorption
was, however, consistent with the reduced bioavail-
ability of 8i in the chimpanzee. Both 1 and 8i showed
good activity in two murine models of CCR3 antago-
nism. The greater in vitro potency of compound 8i
against mouse CCR3 was reflected in vivo in the
mouse intranasal eotaxin challenge model.25
While the doubly changed analogs tended, as a group, to
demonstrate better selectivity, this advantage was
accompanied by a liability not wholly unexpected. Al-
most without exception, these compounds showed very
poor potential for absorption as estimated using the
Caco-2 model system (data not shown). The apparent
permeability generally fell below 2.5 · 10À6 cm/s, and
was in many cases unmeasurable.
The more selective acylated derivatives were expected
to be somewhat better absorbed, although the Caco-
2 apparent permeability values (2.5 · 10À6–5.5 · 10À6
cm/s) were still significantly lower than that observed
for DPC168, which was well-absorbed (see Table 5).
Considering these results, as well as the measured de-
gree of protein binding in human serum and the ex-
pected metabolic liability (estimated by incubation
with hepatocyte microsomes, data not shown), com-
pound 8i (BMS-570520) emerged as the analog with
the best overall balance of selectivity and predicted
pharmacokinetic characteristics. BMS-570520 was
compared with DPC168 in a variety of in vitro and
in vivo models, with the results shown in Table 5.
Very similar CCR3 potency and in vitro efficacy in
chemotaxis and calcium mobilization assays were ob-
served for the two compounds. Selectivity was im-
In summary, heterocyclic replacement of the cyclohexyl
linker ring of the potent, efficacious CCR3 antagonist
DPC168 led to significant improvement in selectivity
with respect to CYP2D6 inhibition. Incorporation of a
nitrogen in the ring allowed the preparation of analogs
which showed dramatic improvement while retaining
binding and chemotaxis potency, leading to the discov-
ery of BMS-570520, a more selective compound with a
very similar activity profile. Increasing the polarity of
the central portion of molecule, while retaining the pro-
jection vectors of the 3-benzylpiperidine and arylurea
moieties, is a viable approach for improvement of the
preclinical profile of this series of antiinflammatory
compounds.

J. R. Pruitt et al. / Bioorg. Med. Chem. Lett. 17 (2007) 2992–2997
2997
generating system. The model substrate 3-[2-(N,N-diethyl-
N-methylamino)-ethyl]-7-methoxy-4-methylcoumarin was
used at a single concentration (approximately the appar-
ent Km), with production of 3-[2-(N,N-diethylami-
no)ethyl]-7-hydroxy-4-methylcoumarin monitored by
fluorescence detection. Multiple concentrations of inhib-
itor, separated by half-log units, were evaluated in
duplicate and the IC50 was determined. Quinidine served
as a positive control.
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16. Ingelman-Sundberg, M. Pharmacogenomics J. 2005, 5, 6.
17. Lipophilic alkaloids such as quinidine are well-known
inhibitors of CYP2D6. See, for example, Ref. 18, and
McLaughlin, L. A.; Paine, M. J. I.; Kemp, Carol A.;
4. Lilly, C. M.; Woodruff, P. G.; Camargo, C. A., Jr.;
Nakamura, H.; Drazen, J. M.; Nadel, E. S.; Hanrahan, J.
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5. Ying, S.; Meng, Q.; Zeibecoglou, K.; Robinson, D. S.;
Macfarlane, A.; Humbert, M.; Kay, A. B. J. Immunol.
1999, 163, 6321.
´
Marechal, J.; Flanagan, J. U.; Ward, C. J.; Sutcliffe, M. J.;
6. 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. Am. J. Physiol. Lung Cell. Mol. Physiol. 2003, 284,
L169.
7. De Lucca, G. V. Curr. Opin. Drug Discov. Devel. 2006, 9,
516.
Roberts, G. C. K.; Wolf, C. R. J. Biol. Chem. 2005, 280,
38617.
18. Compounds 4 and 5 were prepared from the correspond-
ing Boc-protected aminoaldehydes, using the route
described in Ref. 11. Briefly, synthesis of the aldehydes
involved establishment of the chirality via stereospecific
aldol condensations, with ring closure achieved by intra-
molecular alkylation of the resulting alcohols. See Ref. 19
for details.
19. Details of the synthetic steps described may be found in
Ko, S. S.; Pruitt, J. R.; Wacker, D. A.; Batt, D. G. PCT
Int. Appl. 2002/002525, 2002 U.S. Patent 6,627,629, 2003;
Chem. Abstr. 2002, 136, 102384.
20. Known b-ketoester starting materials: (a) methyl Boc-4-
piperidone-3-carboxylate Christoffers, J.; Scharl, H. Eur.
J. Org. Chem. 2002, 1505; Methyl Boc-3-piperidone-4-
carboxylate (b) Knight, D. W.; Lewis, N.; Share, A. C.;
Haigh, D. J. Chem. Soc., Perkin Trans. 1 1998, 3673;
Pyrrolidine (c) Wang, X.; Espinosa, J. F.; Gellman, S. H.
J. Amer. Chem. Soc. 2000, 122, 4821; Tetrahydrothioph-
ene (d) Hromatka, O.; Binder, D.; Eichinger, K. Monatsh.
Chem. 1973, 104, 1520.
21. The ketoester precursor to 6 was prepared in three steps
from c-butyrolactone: ethanolysis, rhodium-catalyzed
alkylation of the alcohol with ethyl diazoacetate, and
Dieckmann cyclization. See Ref. 19 for details.
22. Cimarelli, C.; Palmieri, G. J. Org. Chem. 1996, 61, 5557.
23. The clogD7.4 values were calculated using the ACD/logD
Suite, version 9.0, Advanced Chemistry Development,
Inc., Torontoc, ON, Canada, www.acdlabs.com, 2006.
24. The lack of correlation between receptor antagonism and
chemotaxis inhibition has been seen previously. It has
been hypothesized that increased flexibility (expected from
the five-membered ring of 10, relative to 7 and 8) can
contribute to this disparity. See Batt, D. G.; Houghton, G.
C.; Roderick, J.; Santella, J. B., III; Wacker, D. A.; Welch,
P. K.; Orlovsky, Y. I.; Wadman, E. A.; Trzaskos, J. M.;
Davies, P.; Decicco, C. P.; Carter, P. H. Bioorg. Med.
Chem. Lett. 2005, 15, 787.
8. Wacker, D. A.; Santella, J. B., III; Gardner, D. S.; Varnes,
J. G.; Estrella, M.; De Lucca, G. V.; Ko, S. S.; Tanabe, K.;
Watson, P. S.; Welch, P. K.; Covington, M.; 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, 1785.
9. 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.
10. 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.
2004, 14, 1645.
11. De Lucca, G. V.; Kim, U. T.; Vargo, B. J.; Duncia, J. V.;
Santella, J. B., III; Gardner, D. S.; Zheng, C.; Liauw, A.;
Wang, Z.; Emmett, G.; Wacker, D. A.; Welch, P. K.;
Covington, M.; Stowell, N. C.; Wadman, E. A.; Das, A.
M.; Davies, P.; Yeleswaram, S.; Graden, D. M.; Solomon,
K. A.; Newton, R. C.; Trainor, G. L.; Decicco, C. P.; Ko,
S. S. J. Med. Chem. 2005, 48, 2194.
12. The CCR3 binding assay was carried out using 125I-
labeled human eotaxin and CHO cells stably transfected
with a gene encoding human CCR3 as described in Ref. 9.
In some cases cells stably transfected with a chimeric
receptor, 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
duplicate determinations.
25. Das, A. M.; Vaddi, K. G.; Solomon, K. A.; Krauthauser,
C.; Jiang, X.; McIntyre, K. W.; Yang, X. X.; Wadman, E.;
Welch, P.; Covington, M.; Graden, D.; Yeleswaram, K.;
Trzaskos, J. M.; Newton, R. C.; Mandlekar, S.; Ko, S. S.;
Carter, P. H.; Davies, P. J. Pharmacol. Exp. Ther. 2006,
318, 411.
13. The chemotaxis assay was carried out using eotaxin and
human eosinophils in 96-well chemotaxis chambers, as
described in Ref. 9.
14. Inhibition of CYP2D6 was evaluated using recombinant
human enzyme (prepared from baculovirus-infected insect
cells) in 96-well plates in the presence of an NADPH