Racemic and chiral lactams as potent, selective and functionally active CCR4 antagonists

Article abstract of DOI:10.1016/j.bmcl.2004.09.001

A series of racemic and chiral, nonracemic lactams that display high binding affinities, functional chemotaxis antagonism, and selectivity toward CCR4 are described. Compound 41, which provides reasonably high blood levels in mice when dosed intraperitoneally, was identified as a useful pharmacological tool to explore the role of CCR4 antagonism in animal models of allergic disease. A series of racemic and chiral, nonracemic lactams that display high binding affinities, functional chemotaxis antagonism, and selectivity toward CCR4 are described. Compound 41, which provides reasonably high blood levels in mice when dosed intraperitoneally, was identified as a useful pharmacological tool to explore the role of CCR4 antagonism in animal models of allergic disease.

Full text of DOI:10.1016/j.bmcl.2004.09.001

Bioorganic & Medicinal Chemistry Letters 14 (2004) 5537–5542
Racemic and chiral lactams as potent, selective and
functionally active CCR4 antagonists
Bradley Newhouse,a Shelley Allen,a Benjamin Fauber,a Aaron S. Anderson,a
C. Todd Eary,a Joshua D. Hansen,a Justin Schiro,a John J. Gaudino,a Ellen Laird,a
David Chantry,a Christine Eberhardtb and Laurence E. Burgessa,*
aArray BioPharma, 3200 Walnut Street, Boulder, Colorado 80301, USA
bIcos Corporation, 22021 20th Avenue S.E., Bothell, Washington 98021, USA
Received 6 August 2004; revised 31 August 2004; accepted 1 September 2004
Available online 25 September 2004
Abstract—A series of racemic and chiral, nonracemic lactams that display high binding affinities, functional chemotaxis antagonism,
and selectivity toward CCR4 are described. Compound 41, which provides reasonably high blood levels in mice when dosed intra-
peritoneally, was identified as a useful pharmacological tool to explore the role of CCR4 antagonism in animal models of allergic
disease.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Chemokines are a group of secreted proteins that attract
and activate a variety of cell types. To date, there appear
to be 18 chemokine receptors and over 45 chemokine
ligands known. There are two main subfamilies of
chemokines based on the position of the first two of four
conserved cysteine residues. The CC family, which con-
stitutes the largest subfamily, has its cysteine residues
adjacent to one another, while the CXC family has
one amino acid separating the cysteine residues.1 These
chemokines exert their influence through G-protein cou-
pled receptors, which bind specific ligands with high
affinity and selectivity. CCR4 was recently reported to
have two specific ligands: TARC (thymus and activation
regulated chemokine)2 and MDC (macrophage derived
chemokine).3 In vivo studies support the role of CCR4
and its ligands in Th2 mediated inflammation.4 Thus,
we undertook an effort to identify small molecule
CCR4 receptor antagonists as potential therapeutics
for allergic disease.
played good receptor affinity toward CCR4 along with
functional inhibition of chemotaxis in vitro; however,
there were concerns that the molecules lacked sufficient
drug-like properties needed for good in vivo exposure
(see Fig. 1). Indeed early pharmacokinetic analyses of
these thiazolidinones showed them to be poorly
absorbed and/or rapidly cleared upon p.o. or i.v. dosing
(data not shown). Still, the early SAR and functional
activity of these thiazolidinones was encouraging and
the demonstrated importance of stereochemistry and
enantiopurity spurred us to try and identify more potent
CCR4 antagonists that might possess suitable pharma-
cokinetic profiles for animal model studies. Accordingly,
a strategy was put in place to switch the core structure
from thiazolidinones to lactams for the following
reasons:
Cl
Cl
Cl
Cl
In a preceding report,5 a series of diastereomerically
pure, racemic thiazolidinones were identified that dis-
R
R
HN
HN
S
O
O
O
O
N
N
O
O
R
R
1
2
Keywords: Lactams; CCR4; Antagonists.
*
Figure 1. Previously explored thiazolidinones (1) and proposed analog
lactams (2).
Corresponding author. Tel.: +1 303 381 6686; fax: +1 303 381
6652; e-mail: lburgess@arraybiopharma.com
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.09.001

5538
B.Newhouse et al./ Bioorg.Med.Chem.Lett.14 (2004) 5537–5542
R1
R1
R1
R1
R1
R1
R1
R2
R3
R2
R2
OH
R2
R2
HN
HO
R2
O
ii
iii
iv
viii
ix
x
R2
NH2
O
O
TBSO
N
TBSO
N
R
TBSO
N
O
HO
N
TBSO
N
R = H
N
O
xi
O
HO
3
R
O
O
O
12
O
i
R
O
4
9
10
11
6
R = H, Ph
5
vii
v, R = Ph
R2
R1
R1
R1
R1
R2
R3
R2
R3
R1
HN
R2
HN
xii
X
O
O
R1 = R2 = Cl
R1 = R2 = F
vi
O
N
O
N
N
O
HN
R2
O
O
HO
R
R
O
8
7
13
14
N
N
H
= A
= B
When
When
R =
R =
O
N
N
H
Scheme 1. (i) (a) Aluminum chloride, 3-carbomethoxypropionyl chloride, 0ꢁC then 80ꢁC, 80%; (b) aq LiOH, H2O, THF, 90%; (ii) toluene, reflux,
Dean–Stark, 16h, 100%; (iii) TiCl4, DCM, Et3SiH, À78ꢁC to rt, 16h, 80%; (iv) TBDMSCl, imidazole, DMF, 95%; (v) (a) SOCl2, THF, 0ꢁC to rt,
95%, (b) NaOEt, EtOH, 45ꢁC, 80%; (vi) 1N HCl (aq), THF, reflux, 85%; (vii) KH, DMF, (2-bromoethoxy)-tert-butyldimethylsilane, rt, 1h, 75%;
(viii) LDA, THF, À78ꢁC then allyl bromide, 70%; (ix) (a) ozone, CH2Cl2, À78ꢁC, then PS–PPh3, 90%; (b) KMnO4, NaH2PO4, t-BuOH, 90%; (x)
EDCI, HOBt, H2O, amine, 65%; (xi) Jones rgt., acetone, 80%; (xii) CDI, CH2Cl2, amine, 20%.
• Replacing a sulfur atom with a carbon atom removes
a potential oxidative metabolic liability from the
compounds.6
• A simple carbon-for-sulfur substitution may have a
minimal effect on the binding conformation of the
antagonists and thereby allow us to build upon the
SAR already established for the thiazolidinones.7
• The facile preparation and characterization of enan-
tiopure lactams is well established in the synthetic
organic literature.8
of the chiral auxiliary in the former series.10 Bicyclic lac-
tam 5 was readily prepared from precursors 3 and 4 with
subsequent reductive opening to substituted lactam 6 in
overall yields approaching 80%. Compound 6 could be
readily chlorinated and eliminated to enamide 7, fol-
lowed by hydrolysis to provide the free pyrroldinone 8
in 65% overall yield. This procedure was compatible
with other functionality. Additionally, it is worthy to
note the excellent diastereoselectivity in the lactam allyl-
ation (9 to 10) that provided the requisite trans disposi-
tion (the other diastereomer in this alkylation was not
observed). It appears from calculations and experi-
ments11 that the diastereoselectivity is due to the lone
pair of the lactam nitrogen imparting a strong stereo-
electronic effect. Subsequent manipulation of the olefin
and amide formation took place without event to pro-
vide the desired series of analogs.
• The pyrrolidine scaffold is very well represented in the
pharmaceutical literature and certain pyrrolidinones
possess excellent in vivo properties.9
As shown previously in the thiazolidinone series, the
trans diastereomer proved to be more potent than its
cis counterpart so it became necessary to develop a syn-
thetic route to the trans lactam diastereomer in both
racemic and enantiopure forms (Scheme 1). Ultimately,
the chosen synthetic route was based upon a series of lit-
erature reports.8 The method of preparation for the
enantiopure and racemic analogs were almost identical
except for a three-step modified sequence for removal
In an effort to verify that the SAR of the lactam series
was congruent to the earlier reported thiazolidinone ser-
ies, a relatively small number of lactam analogs were
prepared for comparison in receptor binding12 and
microsomal stability assays (see Table 1). In general,
Table 1. Comparison of previously reported thiazolidinone-based with lactam-based CCR4 antagonists
Compda
R
X
R1
R2
R3
MDC IC50 (lM)
HLM t1/2 (min)
14
15
16
17
18
19
20
21
22
23
A
A
A
A
A
A
A
A
A
A
CH2
S
Cl
Cl
F
Cl
Cl
F
1-Methylnaphthalene
1-Methylnaphthalene
1-Methylnaphthalene
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
2,3-Dimethyl benzyl
2,3-Dimethyl benzyl
2,3-Dimethyl benzyl
2
3.3
8.2
2.5
4.8
11
0.69
2.2
0.88
0.40
0.24b
3
CH2
CH2
S
Cl
Cl
Cl
F
Cl
Cl
Cl
F
CH2
CH2
CH2
S
3.0
2.3
4.3
3.1
2.3
Cl
Cl
F
Cl
Cl
F
1.3
0.44
3
CH2
a All compounds are racemic trans diastereomer unless otherwise noted.
b Pure enantiomer.

B.Newhouse et al./ Bioorg.Med.Chem.Lett.14 (2004) 5537–5542
5539
the trans racemic lactam analogs were 2–4 fold less
potent than the corresponding trans racemic thiazolidi-
nones (14 vs 15; 17 vs 18; 21 vs 22), but trends within
each series remained the same and we still felt that cer-
tain advantages were inherent in the lactams. Fluorine
substitution on the central aromatic ring failed to im-
prove potency (16, 20, and 23), although we were
encouraged by enantiopure compound 19, which pro-
vided a threefold enhancement in binding affinity over
its corresponding racemate, compound 17. Unfortu-
nately, these lactams showed poor in vitro stability in
pooled human liver microsomes preparations (HLM)
as evidenced by their relatively short half-lives (most
t1/2 < 5min).13 Subsequent metabolic profiling revealed
the morpholine moiety as a site of hydroxylation. Fur-
thermore, in vivo pharmacokinetic data indicated that
poor absorption and rapid clearance were still issues
with these compounds (data not shown).
In an effort to engender more metabolic stability, en-
hance the physiochemical properties (clogP, molecular
weight,14 rotatable bonds15), and improve the binding
affinity of these compounds, we next focused on morpho-
line replacements and other left side modifications in
addition to enantiopurity (see Table 2).16 Initially com-
pounds were prepared that incorporated 4-monosubsti-
tution on the central aromatic ring (R2 = H;
compounds 24–31) because, while it has been shown
that 2,4-disubstitution (R2 = Cl) results in a slight in-
crease in binding affinity, it also adds to the overall lipo-
philicity of the molecule as well as molecular weight.
Although the right hand side aromatic ring seemed to
favor a 3-chloro-2-methyl substitution pattern for opti-
mal receptor binding affinity as evidenced by a
concurrent SAR study (see Table 3), the 3-chloro substi-
tution pattern was chosen here because it resulted in
lower molecular weight, lower clogPÕs, and did not
Table 2. Modifications of the left side chain in the enantiopure series of lactams (see compound 14 X = CH2)
Compounda
R
R1
R2
R3
MDC IC50 (lM)b
HLM t1/2 (min)
H
N
24
Cl
H
3-Cl benzyl
1
N
N
25
Cl
H
3-Cl benzyl
1.3
3.4
N
H
H
N
26
27
Cl
Cl
H
H
3-Cl benzyl
3-Cl benzyl
3
3
8
N
N
5.8
N
H
N
N
28
29
30
Cl
Cl
Cl
H
H
H
3-Cl benzyl
3-Cl benzyl
3-Cl benzyl
5.5
1
2.6
N
N
N
H
N
0.98
4
N
N
N
31
32
Cl
Cl
H
3-Cl benzyl
3-Cl benzyl
3.3
N
H
N
N
H
N
Cl
0.82
N
N
33
34
Cl
Cl
Cl
Cl
3-Cl benzyl
1.3
N
H
N
N
H
N
3-Cl, 2-Me benzyl
0.340 (0.630)
3.8
2.3
N
N
35
Cl
Cl
3-Cl, 2-Me benzyl
0.400 (1.0)
N
H
a All compounds are single enantiomers unless otherwise noted.
b Figures in parentheses represent IC50Õs for the corresponding racemic compounds.

5540
B.Newhouse et al./ Bioorg.Med.Chem.Lett.14 (2004) 5537–5542
Table 3. Modifications of the right side amide in the racemic series of lactams (see compound 14 X = CH2)
Compd
R
R1
R2
R3
MDC IC50 (lM)
HLM t1/2 (min)
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
B
Cl
F
Cl
F
1-Methylnaphthalene
1-Methylnaphthalene
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
3-Cl, 2-Me benzyl
2,3-Di-Cl benzyl
3-Cl benzyl
0.50
0.52
0.50
0.09a
0.50
0.13a
12.0b
0.60
0.61
0.16
1.2c
2.2c
1.0
29.1
Cl
Cl
F
Cl
Cl
F
16.6
11.6
5.5
F
F
17.4
10.0
4.2
F
F
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
9.4
4.1
4-Cl benzyl
(S)-a-Me benzyl
(R)-a-Me benzyl
Benzyl
35.3
19.4
57.4
34.8
11.3
19.4
15.6
10.1
10.1
17.9
5.6
4-F benzyl
3-F benzyl
1.0
2.0
3,4-Di-Cl benzyl
4-OMe benzyl
0.57
3.0
3-Cl-2-F benzyl
3-CF3-2-F benzyl
2,3,4-Tri-fluoro benzyl
2-Cl-6-F-3-Me benzyl
2-CF3 benzyl
0.42
0.50
0.50
4.0
1.8
3.3
4.5
3.2
2,3-Di-OMe benzyl
3-Chloro-2-CF3 benzyl
0.89
3.9
a R,R-enantiomer.
b S,S-enantiomer.
c Mixture of diastereomers.
incorporate a potential site of metabolism (i.e., an ortho-
methyl group). Changes in chain length to the basic
amine, conformational restriction, and the addition of
a second basic amine were studied on the left side of
the molecule. All compounds were enantiomerically
pure and prepared as outlined in Scheme 1. Compound
24 compared to 25 shows the lack of an effect when
removing a single methylene group from the left side
tether. To remove molecular weight from the molecule,
the dimethylamine was used at the basic amine moiety
and, again, no change in potency was observed between
26 and 27, but compared to 24 and 25, the piperidine is
preferred. Compound 28 illustrates a hybrid of 26 and
27 that incorporates a homopiperazine group. In this
molecule, rotatable bonds are removed at the expense
of molecular weight, but binding affinity suffers. Com-
pound 29 is a conformationally restricted version of 26
and showed slightly improved binding. We next looked
at the addition of a second basic site on the left side by
using an N-methyl piperazine group as a way to optim-
ize physiochemical properties (log D and log P calcula-
tions on these piperazine analogs suggested that they are
in the desired range for gut permeability). While no
improvement in potency was observed over the piperi-
dine containing compounds (compare 30 with 24), chain
shortening proved to be detrimental as potency dropped
when going from three to two methylenes (compare 30
to 31), counter to what was observed in compounds 24
and 25. Although we improved clogP values, molecular
weights, and, in some cases, reduced the number of
rotatable bonds, potencies were not acceptable. To re-
gain binding affinity, we reintroduced preferred groups
at the R2 and R3 positions on the molecule. Accord-
ingly, compounds 32–35 have R2 as chlorine and
improvements in binding potency were observed in com-
pounds 32 and 33 over 30 and 31. Replacing R4 with a
methyl group (compounds 34 and 35) results in a two- to
threefold boost in potency over 32 and 33. Unfortu-
nately, these changes failed to improve the metabolic
stability (HLM t1/2 < 5min) of the molecules and poor
absorption and rapid clearance were still issues in phar-
macokinetic experiments.
Concurrent with the exploration of the left side analogs,
a series of right side analogs were generated in the lac-
tam series (see Table 3). As in the thiazolidinone series,
when the piperidine group was incorporated into the
lactam series, the resulting compounds showed greater
potency and metabolic stability. All compounds are
trans racemic diastereomers unless otherwise noted. As
before, efforts were directed at replacing the naphthalene
group due to issues with its metabolism and toxicity17
and the 2,3-disubstituted phenyls emerged as excellent
mimics. Where R1 and R2 are fluorine, no significant
improvement in potency or chemotaxis was observed,
although these analogs have more optimal physiochem-
ical properties in terms of molecular weight and clogP.
A 90-fold difference in potency was observed between
enantiomers 41 and 42, again demonstrating the impor-
tance of stereochemistry within this series. Various sub-
stitution around the right side aromatic ring (36, 37, 41–
45, 48–59) or methyl group substitution on the benzyl
position (46 and 47) maintained or detracted from bind-
ing potency. Numerous analogs were also prepared
where substitution on the central aromatic ring was
varied. As in the thiazolidinone series, this resulted in

B.Newhouse et al./ Bioorg.Med.Chem.Lett.14 (2004) 5537–5542
5541
2. Imai, T.; Baba, M.; Nishimura, M.; Kakizaki, M.; Takagi,
S.; Yoshie, O. J.Biol.Chem. 1997, 272, 15036–15042.
3. Imai, T.; Chantry, D.; Raport, C.; Wood, C.; Nishimura,
M.; Godiska, R.; Yoshie, O.; Gray, P. J.Biol.Chem. 1998,
273, 1764–1768.
4. (a) Gonzalo, J. A.; Pan, Y.; Lloyd, C. M.; Jia, G.-Q.; Yu,
G.; Dussault, B.; Powers, C. A.; Proudfoot, A. E.; Coyle,
A. J.; Gearing, D.; Gutierrez-Ramos, J.-C. J.Immunol.
1999, 163, 403–411; (b) Vestergaard, C.; Yoneyama, H.;
Murai, M.; Nakamura, K.; Tamaki, K.; Terashima, Y.;
Imai, T.; Yoshie, O.; Irimura, T.; Mizutani, H.; Matsu-
shima, K. J.Clin.Invest. 1999, 104, 1097–1105; (c) Lloyd,
C. M.; Delaney, T.; Nguyan, T.; Tian, J.; Martinez, A. C.;
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191, 265–273.
a rigid SAR wherein R1 and R2 were optimal as dichloro
or difluoro substitution. Compound 38 was prepared in
racemic form and displayed an IC50 of 0.5lM. Subse-
quent preparation in enantiopure form (compound 39;
R,R stereochemistry) provided a 5–6 fold increase in po-
tency to 0.09lM, the most potent CCR4 binder we had
identified so far. It is important to note that chiral
HPLC analysis on intermediate 9 (R1 = R2 = Cl; see
Scheme 1) revealed that the enantiomeric excess was
>95% and no epimerization or diastereomer formation
was observed by NMR during subsequent chemistry
leading to 39. This compound showed excellent chemo-
taxis inhibition in both MDC and TARC driven cell
migration assays (EC50 = 0.3 and 0.1lM, respectively).
In general, the IC50/EC50 ratio was closer to unity with
the lactams series as compared to the thiazolidinone
series. Compound 39 also displayed excellent selecti-
vity for CCR4 versus CCR3, CCR5, CCR6, CCR8,
and CX3CR1, as <20% inhibition of chemotaxis was
observed at 10lM concentrations of 39 against these
chemokine receptors.
5. Allen, S.; Newhouse, B.; Anderson, A. S.; Fauber, B.;
Allen, A.; Chantry, D.; Eberhardt, C.; Odingo, J.;
Burgess, L. E. Bioorg.Med.Chem.Lett. 2004, 14, 1619–
1624.
6. Mutlib, A. E.; Jurcak, J.; Hrib, N. Drug Metab.Dispos.
1996, 24, 1139–1150.
7. The results of ab initio calculations demonstrated that two
envelope conformations were energetically accessible for
both the thiazolidinone and the lactam scaffold, allowing
comparable orientations for the substituents. Optimiza-
tions were performed using the 6-31G(d) basis set; Gaus-
sian 98, Revision A.11 Frisch, M. J.; Trucks, G. W.;
Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman,
J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.; Strat-
mann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.;
Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.; Mennucci,
B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.;
Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.;
Salvador, P.; Dannenberg, J. J.; Malick, D. K.; Rabuck, A.
D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.;
Ortiz, J. V.; Baboul, A. G.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P.
M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Andres, J.
L.; Gonzalez, C.; Head-Gordon, M.; Replogle, E. S.;
Pople, J. A.; Gaussian Inc.: Pittsburgh, PA, 2001.
8. (a) Meyers, A. I.; Brengel, G. P. Chem.Commun. 1997, 1–
8; (b) Stewart, J. D.; Fields, S. C.; Kochhar, K. S.;
Pinnick, H. W. J.Org.Chem. 1987, 52, 2110–2113; (c)
Zhuang, Z.-P.; Kung, M.-P.; Mu, M.; Kung, H. F. J.Med.
Chem. 1998, 41, 157–166.
Ultimately, we proceeded to obtain mouse pharmacoki-
netic data on compound 41.18 This lactam showed
promising blood levels when administered intraperiton-
eally (Cmax = 2445ng/ml; t1/2 = 1.4h; AUC = 3473ngh/
ml at 10mg/kg in the mouse) and provided an excellent
pharmacological tool to study the validity of CCR4
antagonism in vivo. Results of these studies will be re-
ported in due course.
In summary, we have prepared a series of lactams that
show good binding potency, excellent chemotaxis inhib-
itory activity and selectivity over other chemokine recep-
tors. The (R,R) enantiopure lactams were prepared in
>95% ee and have about a two- to fivefold advantage
in binding over their racemic counterparts. The lactams,
although in general less potent than the original thiazo-
lidinones, tracked well with the previously reported
SAR and displayed enhanced chemotaxic antagonism.
Preliminary in vitro and in vivo pharmacokinetic prop-
erties continues to be optimized and will be reported in
due course along with pharmacodynamic results in ani-
mal models of allergic disease.
9. (a) Kraus, W.; Kuehne, G.; Sauerbrey, N. Eur.J.Clin.
Pharm. 1990, 38, 71–75; (b) Krause, W.; Kuehne, G.;
Matthes, H. Xenobiotica 1989, 19, 683–692.
10. (a) Nyzam, V.; Belaud, C.; Zammattio, F.; Villieras, J.
Tetrahedron: Asymmetry 1996, 7, 1835–1843; (b) Ennis,
M. D.; Hoffman, R. L.; Ghazal, N. B.; Old, D. W.;
Mooney, P. A. J.Org.Chem. 1996, 61, 5813–5817; (c)
Fains, O.; Vernon, J. M. Tetrahedron Lett. 1997, 38, 8265–
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Acknowledgements
The authors wish to thank Dr. Andrew Allen for his
assistance in NMR acquisition and interpretation.
Supplementary data
11. Meyers, A. I.; Seefield, M. A.; Lefker, B. A.; Blake, J. F. J.
Am.Chem.Soc. 1997, 119, 4565–4566.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.bmcl.2004.09.001.
12. Assay measures inhibition of binding of 125I-MDC to
murine pre-B cell line L1.2 cells over-expressing CCR4.
IC50 values are shown as the mean of duplicate determi-
nations and possess a standard error of <20%. See: Imai,
T.; Chantry, D.; Raport, C. J.; Wood, C. L.; Nishimura,
M.; Godiska, R.; Yoshie, O.; Gray, P. W. J.Biol.Chem.
1998, 273, 1764–1768.
References and notes
1. (a) Carter, P. H. Curr.Opin.Chem.Biol. 2002, 6, 510–525;
(b) Luster, A. D. N.Eng.J.Med. 1998, 338, 436–445.
13. In general, the human liver microsome stabilities of the
compounds in Table 1 correlated well with the mouse liver

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microsome (MLM) stabilities. For example, compounds
14, 16, 19, and 20 gave MLM half-lives of 2.2, 2.0, 4.4, and
1.8min, respectively.
1735. Unfortunately, bioisosteric replacement or removal
of these linkages resulted in compounds devoid of affinity
for the CCR4 receptor (data not shown).
14. (a) Lipinski, C. A.; Lombado, F.; Dominy, B. W.; Feeney,
P. J. Adv.Drug Del.Rev. 1997, 23, 3–25; (b) Blake, J. F.
BioTechniques 2003, 34, 516–520.
15. Veber, D. F.; Johnson, S. R.; Cheng, H.-Y.; Smith, B. R.;
Ward, K. W.; Kopple, K. D. J.Med.Chem. 2002, 45,
2615–2623.
16. Another less than desirable feature of these antagonists, as
pointed out by a reviewer, is the presence of two amide
bonds which might limit permeability for a similar
example, see: Boyd, S. A. et al. J.Med.Chem. 1992, 35,
17. (a) Shultz, M. A.; Choudary, P. V.; Buckpitt, A. R. J.
Pharm.Exp.Ther. 1999, 290, 281–288; (b) Chichester, C.
H.; Buckpitt, A. R.; Chang, A.; Plopper, C. G. Mol.
Pharm. 1993, 45, 664–672; (c) Buckpitt, A. R.; Franklin,
R. B. Pharmac.Ther. 1989, 41, 393–410.
18. In general, the human and mouse liver microsome
stabilities for compounds in Table 3 provided acceptable
correlation but there were several anomalies. For example,
compounds 36, 41, and 48 provided MLM half-lives of
9.9, 47.5, and 12.2min, respectively.