Modulators of the human CCR5 receptor. Part 1: Discovery and initial SAR of 1-(3,3-diphenylpropyl)-piperidinyl amides and ureas

Article abstract of DOI:10.1016/j.bmcl.2004.10.044

Investigation of weak screening hits led to the identification of N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-phenylacetamides and N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-N′-benzylureas as potent, selective ligands for the human CCR5 chemokine receptor. Investigation of weak screening hits led to the identification of N-alkyl-N-[1-(3,3-diphenylpropyl) piperidin-4-yl]-2-phenylacetamides and N-alkyl-N-[1-(3,3-diphenylpropyl) piperidin-4-yl]-N′-benzylureas as potent, selective ligands for the human CCR5 chemokine receptor.

Full text of DOI:10.1016/j.bmcl.2004.10.044

Bioorganic & Medicinal Chemistry Letters 15 (2005) 25–28
Modulators of the human CCR5 receptor. Part 1: Discovery
and initial SAR of 1-(3,3-diphenylpropyl)-piperidinyl
amides and ureas
Jeremy N. Burrows, John G. Cumming,* Shaun M. Fillery, Gordon A. Hamlin,
Julian A. Hudson, Ruth J. Jackson, Sharon McLaughlin and John S. Shaw
Respiratory and Inflammation Research Area, AstraZeneca, Mereside, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK
Received 7 September 2004; revised 11 October 2004; accepted 14 October 2004
Available online 6 November 2004
Abstract—Investigation of weak screening hits led to the identification of N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-2-phenyl-
acetamides and N-alkyl-N-[1-(3,3-diphenylpropyl)piperidin-4-yl]-N0-benzylureas as potent, selective ligands for the human CCR5
chemokine receptor.
Ó 2004 Elsevier Ltd. All rights reserved.
The chemokine receptor CCR5 is expressed on T-
lymphocytes, monocytes, macrophages, dendritic cells,
microglia and other cell types. These receptors detect
and respond to several chemokines, principally Ôregu-
lated on activation normal T-cell expressed and secretedÕ
(RANTES) and macrophage inflammatory proteins
(MIP) MIP-1a and MIP-1b, resulting in the recruitment
of cells of the immune system to sites of disease. CCR5
is also a co-receptor for HIV-1 and other viruses, allow-
ing these viruses to enter cells. Individuals who are
homozygous for a 32-base pair deletion in the gene
encoding CCR5, whilst otherwise healthy, are strongly
protected against HIV-1 infection.1 Other studies indi-
cate a role for CCR5 and its ligands in disorders such
as rheumatoid arthritis,2 multiple sclerosis,3 transplant
rejection4 and inflammatory bowel disease.5 These
observations suggest that molecules that modulate the
CCR5 receptor would have potential benefit in a wide
range of diseases.
their receptors.6 In particular CCR5 has generated much
interest as a drug target1 and a recent clinical trial has
provided proof of concept for this approach in the treat-
ment of HIV-1 infection.7
We began our search for small molecule CCR5 modula-
tors by screening the company compound library for
compounds which inhibited the binding of [125I]RAN-
TES to membranes prepared from Chinese hamster
ovary (CHO) cells stably expressing recombinant human
CCR5.10 1-(3,3-Diphenylpropyl)-piperidines 18 and 2a
were identified as weak ligands for CCR5 (binding
IC50s in the low micromolar range). We then set out
to investigate the effect on potency of varying the piper-
idine 4-susbstituent.9
O
R
N
1: R =
N
Me
N
N
CCR5 is a member of the seven trans-membrane G-pro-
tein coupled receptor family, many other members of
which have proved tractable targets for small molecule
drugs. Over the last few years many groups have suc-
cessfully engaged in the search for small molecules that
interfere with the interaction between chemokines and
2a: R =
O
The advanced amine intermediates 3 (Scheme 1) allowed
us to explore the SAR rapidly using multiple parallel
techniques. Intermediate 3a (R1 = Me) was prepared in
a straightforward manner from 4-Boc-amino-piperidine
by alkylation followed by reduction of the Boc group
to a methyl group. The other intermediates 3 were
Keywords: CCR5; Chemokine receptor modulators.
*
Corresponding author. Tel.: +44 1625 517755; fax: +44 1625
510823; e-mail: john.cumming@astrazeneca.com
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.10.044

26
J. N. Burrows et al. / Bioorg. Med. Chem. Lett. 15 (2005) 25–28
R1
N
R2
N
N
O
O
NHBOC
a, b
e
R1
NH
HN
2
N
R1
N
H
N
a, c, d
f or g
3
R2
O
O
h
HN
R1
N
4
R2
S
O
O
N
5
Scheme 1. Reagents and conditions: (a) 3,3-diphenylpropyl bromide, K2CO3, nBu4NI (0.1equiv), MeCN, reflux, 5h; (b) (R1 = Me) LiAlH4, THF,
reflux, 5h; (c) 6M HCl, reflux, 3h; (d) R1NH2, NaBH3CN, AcOH, MeOH, rt; (e) R2CO2H, DIPCDI, HOBT (0.1equiv), DMF/DCM, rt; (f) R2NCO,
DCM, rt; (g) R2CO2H, DPPA, Et3N, THF, 0°C then toluene, 100°C then 3, EtOAc, rt; (h) R2SO2Cl, (iPr)2NEt, MeCN/pyridine.
Table 1. Binding data for selected amides
prepared by reductive amination of 1-(3,3-diphenylpro-
pyl)-4-piperidone, which was obtained from 4-piper-
idone ethylene ketal by alkylation followed by
Me
R2
N
deprotection of the ketone. The intermediates 3 were
converted to amides 2 and sulfonamides 5 by standard
methods. Ureas 4 were prepared by reaction with the
appropriate isocyanate, which was either commercially
available or prepared from a carboxylic acid by reaction
with diphenylphosphoryl azide with subsequent Curtius
rearrangement.
N
O
Compound
R2
—
IC50 (lM)a
1
4.1
6.1
7.2
5.1
8.7
7.9
7.4
3.4
5.5
0.81
2a
2b
2c
2d
2e
2f
2g
2h
2i
4-Pyridinyl
4-F-phenyl
3-NO2-phenyl
2-Thienyl
2-Furanyl
Cyclobutyl
Isobutyl
Several hundred analogues were prepared in this way;
we describe herein the results for representative exam-
ples, which illustrate the main SAR findings.
Neopentyl
Benzyl
The CCR5 binding affinity of the two initial screening
hits 1 and 2a is similar (Table 1), suggesting that there
is no potency advantage in the amide N-substituent
being cyclised onto the phenyl ring as in the 2,3-dihydro-
isoindol-1-one 1. Therefore we decided to focus on the
more synthetically accessible amides 2 and began by var-
ying the amide acyl substituent.
O
2j
5.9
6.8
Me
2k
Compounds with substituted phenyl (such as 2b and 2c),
heteroaryl (2d, 2e), cycloalkyl (2f) and alkyl (2g, 2h)
groups gave no appreciable improvement in potency.
However one particular analogue, the phenylacetyl
derivative 2i, showed sub-micromolar potency and we
decided to examine this further. Substitution of the al-
pha carbon of the phenylacetyl group with carbonyl
(2j) or small alkyl groups (2k) led to a reduction in po-
tency. We then aimed to improve the potency further by
exploring the SAR around the phenyl of the phenyl-
acetyl group (Table 2). ortho Substitution with halo is
accompanied by a reduction in potency, as shown by
2l, 2p and 2q. Halo and methoxy groups in the meta
and para positions generally have a neutral effect on po-
tency. A wide range of substituents was examined in the
para position; some led to a drop in potency such as phe-
a IC50Õs were derived from triplicate measurements whose standard
errors were normally <5% in a given assay. Assay to assay variability
was within 2-fold based on the results of a standard compound.
nyl (2ab) and benzyloxy (2aa), others gave similar poten-
cies to the unsubstituted phenyl such as acetylamino
(2ae) and methoxycarbonyl (2aj). Increases in potency
were seen with more strongly electron-withdrawing
groups such as trifluoromethyl (2ac) and trifluorometh-
oxy (2ad), and particularly with polar electron-with-
drawing groups such as nitro (2al), sulfonamido (2ag),
cyano (2af, IC50 60nM) and N,N-dimethyl-sulfonamido
(2ah, IC50 46nM).

J. N. Burrows et al. / Bioorg. Med. Chem. Lett. 15 (2005) 25–28
27
Table 2. Binding data for selected phenylacetamides
Table 3. Binding data for selected ureas
R1
N
R1
N
H
N
R2
N
N
O
O
X
Compound
R1
R2
Cyclohexyl
IC50 (lM)a
Compound
R1
X
H
IC50 (lM)a
4a
4b
4c
4d
4e
4f
Me
Me
Me
Allyl
Me
Me
Et
1.8
4.9
2i
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Et
0.77
3.6
3-CN–phenyl
3-Me–phenyl
Phenyl
2l
2-Cl
3-Cl
5.9
2.1
2m
2n
2.2
4-Cl
0.80
0.78
2.6
3,4-di-Cl–phenyl
4-F–phenyl
4-Me–phenyl
Benzyl
0.37
0.19
0.32
0.10
0.062
2o
2p
3,4-di-Cl
2,4-di-Cl
2-F
4g
4h
4i
2q
2r
1.9
1.4
Me
Et
3-F
4-F
Benzyl
2s
0.66
0.69
0.68
0.58
0.65
2.7
Me
2t
2u
3,4-di-F
3-OMe
4-OMe
4j
Et
5.4
2v
2w
2x
3,4-di-OMe
3,5-di-OMe
2,4,5-tri-OMe
4-Br
4k
4l
Allyl
Allyl
Et
3-Me–benzyl
4-OMe–benzyl
3-Me–benzyl
0.24
0.11
2y
2z
1.1
4m
4n
4o
0.035
0.042
0.049
0.58
3.5
Et
Et
4-OMe–benzyl
4-SO2Me–benzyl
2aa
2ab
2ac
2ad
2ae
2af
2ag
2ah
2ai
2aj
2ak
2al
2am
2an
2ao
2ap
2aq
2ar
2as
2at
2au
2av
2aw
2ax
4-Benzyloxy
4-Phenyl
4-CF3
2.3
a See footnote a of Table 1.
0.37
0.29
0.68
0.060
0.091
0.046
0.56
0.63
0.47
0.15
0.31
0.066
0.038
<0.010
0.076
0.11
0.033
0.051
0.31
0.35
0.037
0.18
4-OCF3
4-NHCOMe
4-CN
and benzyl. The SAR reflected to some extent that
found in the phenylacetamide series, for example the
alpha methyl benzyl 4j had reduced potency compared
to its benzyl analogue 4i. However, the substitution pat-
tern on the phenylmethyl group required to achieve
binding potency less than 100nM appeared less
restricted than in the phenylacetamide series: groups
such as 3-methyl (4m) and 4-methoxy (4n) were as
potent as 4-methanesulfonyl (4o). Also in this series
the compounds with the proximal nitrogen substituted
with allyl tended to show lower potency compared to
ethyl and methyl, as illustrated by comparing 4k with
4m and 4l with 4n. In the sulfonamide series it did not
prove possible to achieve potency below 1lM (data
not shown), so further work in this area was abandoned.
4-SO2NH2
4-SO2N(Me)2
4-SMe
4-CO2Me
4-OH
4-NO2
4-OCF3
4-CN
Et
Et
4-SO2NH2
4-SO2N(Me)2
4-SO2Me
4-NO2
Et
Et
Et
Cyclopropyl
Cyclopropyl
Cyclopropyl
Allyl
4-SO2NH2
4-SO2Me
4-NO2
4-OCF3
4-SO2Me
4-NO2
Allyl
Allyl
The observed differences in structure–activity require-
ments for the group R2 between the amides 2, ureas 4
and sulfonamides 5 is not surprising since the orienta-
tion of that group relative to the rest of the molecule will
be different due to the differing geometries of the linker
groups. However it is interesting to note the higher
activity for compounds having R2 as benzyl in both
the amide and the urea series.
a See footnote a of Table 1.
We selected some of these preferred groups in a survey
of the substitution on the nitrogen of the amide group
(compounds 2am–2ax, Table 2). Replacing the methyl
with ethyl, cyclopropyl or allyl had little effect on the
binding potency when compounds with the same phenyl
substituent were compared (e.g., the 4-nitrophenyl com-
pounds 2al, 2ar, 2au and 2ax all have IC50 values be-
tween 0.1 and 0.3lM).
Compounds in both the amide and the urea series are
highly selective for the human CCR5 receptor over
other chemokine receptors. Amides 2ah, 2ap, 2aw and
urea 4h (which all have CCR5 binding IC50 values of
100nM or lower) were screened at 10lM for binding
to human CCR1, CCR2b, CCR3, CXCR1 and CXCR2
using assays analogous to the CCR5-[125I]RANTES
binding assay (data not shown). All four compounds
showed less than 50% inhibition in all five assays, imply-
ing that their selectivity for CCR5 versus these other
We also synthesised a large number of compounds in the
urea (4) and sulfonamide (5) series. Binding results for
selected compounds are shown in Table 3. In the ureas
the preferred substituents on the nitrogen distal to the
piperidine were found to be para-substituted phenyl

28
J. N. Burrows et al. / Bioorg. Med. Chem. Lett. 15 (2005) 25–28
chemokine receptors is of the order of 100-fold or better.
In order to survey the selectivity profile of the series rep-
resentative compounds were tested in a panel of assays
for binding to a range of GPCRs and ion channels (data
not shown).11 Binding to muscarinic and serotoninergic
receptors was seen at 1–10lM. On the basis of these re-
sults we established radioligand binding assays to meas-
ure activity at human M1 and 5-HT2A receptors,
compound 2ap showed IC50 values of 0.4 and 0.8lM,
respectively. In addition, compound 2aw showed micro-
molar activity at the hERG ion channel. These results
indicated to us that further optimisation was required
to increase the selectivity with respect to these other
activities.
the biological assays and Tom McInally for helpful ad-
vice on multiple parallel techniques.
References and notes
1. For a review of CCR5 as a target for HIV-1 and small
molecule CCR5 ligands, see: Kazmierski, W.; Bifulco, N.;
Yang, H.; Boone, L.; DeAnda, F.; Watson, C.; Kenakin,
T. Bioorg. Med. Chem. 2003, 11, 2663–2676.
2. Pipitone, N.; Pitzalis, C. Curr. Opin. Anti-inflammat.
Immunomodulat. Investigat. Drugs 2000, 2, 9.
3. Sellebjerg, F.; Madsen, H. O.; Jensen, C. V.; Jensen, J.;
Garred, P. J. Neuroimmunol. 2000, 102, 98–106.
4. Fischereder, M.; Luckow, B.; Wuthrich, R. P.; Rothenpi-
¨
eler, U.; Schneeberger, H.; Panzer, U.; Stahl, R. A. K.;
Hauser, I. A.; Budde, K.; Neumayer, H.-H.; Kra¨mer, B.
K.; Land, W.; Schlo¨ndorff, D. Lancet 2001, 357, 1758–
1761.
We then studied the effects of a representative com-
pound, 2aw, in functional systems. Compound 2aw
was tested for its ability to inhibit MIP-1b-stimulated
calcium transients in CHO cells stably expressing rec-
ombinant human CCR5 and was found to have an
IC50 of 78nM. Also 2aw was shown to have an IC50
of 38nM in an assay measuring the inhibition of the
chemotaxis of human AlloT cells in response to MIP-
1b. In the same system 2aw had no effect on the response
to MIP-1c at concentrations up to 10lM indicating that
the inhibition of chemotaxis is mediated through CCR5.
The similar potencies seen in these assays, in which
MIP-1b is used, to those previously observed in the
RANTES binding assay is evidence that the compound
is acting as an antagonist at the receptor since it is able
to block different CCR5 ligands.
5. Andres, P. G.; Beck, P. L.; Mizoguchi, E.; Mizoguchi, A.;
Bhan, A. K.; Dawson, T.; Kuziel, W. A.; Maeda, N.;
MacDermott, R. P.; Podolsky, D. K.; Reinecker, H. C. J.
Immunol. 2000, 164, 6303–6312.
6. For reviews, see: (a) Gao, Z.; Metz, W. A. Chem. Rev.
2003, 103, 3733; (b) Onuffer, J. J.; Horuk, R. Trends
Pharmacol. Sci. 2002, 23, 459–467.
7. Palani, A.; Shapiro, S.; Clader, J. W.; Greenlee, W. J.;
Blythin, D.; Cox, K.; Wagner, N. E.; Strizki, J.; Baroudy,
B. M.; Dan, N. Bioorg. Med. Chem. Lett. 2003, 13, 705–
708.
8. Compound 1 is an inhibitor of microsomal triglyceride
transfer protein, see: Jamil, H.; Gordon, D. A.; Eustice, D.
C.; Brooks, C. M.; Dickson, J. K., Jr.; Chen, Y.; Ricci, B.;
Chu, C.-H.; Harrity, T. W., et al. Proc. Natl. Acad. Sci.
U.S.A. 1996, 93, 11991–11995.
In summary SAR studies around two weak screening
hits have led to the identification of a series of potent
and selective CCR5 functional antagonists (exemplified
by 2aw), which provide good leads for further optimisa-
tion. Our further development of this series to give po-
tent, orally bioavailable CCR5 antagonists will be the
subject of future publications.
9. Burrows, J.; Cooper, A.; Cumming, J.; McInally, T.;
Tucker, H. WO 01/087839, 2001; Chem. Abstr. 2002, 135,
371644.
10. SPA binding assays were conducted in 96-well Optiplates
[
125I]RANTES
(Packard 6005190). Displacement of
(Amersham IM-288) by compounds was measured using
membranes prepared from a h-CCR5 transfected CHO
cell line. Compounds were incubated overnight with
0.1nM
[
125I]RANTES, SPA beads (Amersham
RPNQ0001) and membranes expressing the human
CCR5 receptor. The signal was read on a Packard
Topcount.
Acknowledgements
The authors thank our colleagues Susan Mellor and
Lorraine D. Newboult for developing and carrying out
11. Work carried out on behalf of AstraZeneca by MDS
Pharma Services, Taipei, Taiwan.