Discovery of a piperidine-4-carboxamide CCR5 antagonist (TAK-220) with highly potent anti-HIV-1 activity

Article abstract of DOI:10.1021/jm051034q

We incorporated various polar groups into previously described piperidine-4-carboxamide CCR5 antagonists to improve their metabolic stability in human hepatic microsomes. Introducing a carbamoyl group into the phenyl ring of the 4-benzylpiperidine moiety

Full text of DOI:10.1021/jm051034q

2784
J. Med. Chem. 2006, 49, 2784-2793
Discovery of a Piperidine-4-carboxamide CCR5 Antagonist (TAK-220) with Highly Potent
Anti-HIV-1 Activity
Shinichi Imamura,*,† Takashi Ichikawa,† Youichi Nishikawa,† Naoyuki Kanzaki,† Katsunori Takashima,† Shinichi Niwa,†
Yuji Iizawa,† Masanori Baba,‡ and Yoshihiro Sugihara†
Pharmaceutical Research DiVision, Takeda Pharmaceutical Company Limited, 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686, Japan,
and DiVision of AntiViral Chemotherapy, Center for Chronic Viral Diseases, Graduate School of Medical and Dental Sciences,
Kagoshima UniVersity, 8-35-1, Sakuragaoka, Kagoshima 890-8544, Japan
ReceiVed October 14, 2005
We incorporated various polar groups into previously described piperidine-4-carboxamide CCR5 antagonists
to improve their metabolic stability in human hepatic microsomes. Introducing a carbamoyl group into the
phenyl ring of the 4-benzylpiperidine moiety afforded the less lipophilic compound 5f, which possessed
both high metabolic stability and good inhibitory activity of HIV-1 envelope-mediated membrane fusion
(IC50 ) 5.8 nM). Further optimization to increase potency led to the discovery of 1-acetyl-N-{3-[4-(4-
carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3-chloro-4-methylphenyl)piperidine-4-carboxamide (5m, TAK-
220), which showed high CCR5 binding affinity (IC50 ) 3.5 nM) and potent inhibition of membrane fusion
(IC50 ) 0.42 nM), as well as good metabolic stability. Compound 5m strongly inhibited the replication of
CCR5-using HIV-1 clinical isolates in human peripheral blood mononuclear cells (mean EC50 ) 1.1 nM,
EC90 ) 13 nM) and exhibited a good pharmacokinetic profile in monkeys (BA ) 29%). This compound
has been chosen as a clinical candidate for further development.
Chart 1
Introduction
Despite worldwide efforts to prevent the spread of human
immunodeficiency virus type 1 (HIV-1), the number of HIV-
1-infected people still continues to rise.1 Although highly active
antiretroviral therapy (HAART) has been successful in sup-
pressing viral replication and in reducing HIV-1-associated
mortality, there remain problems in currently available HAART
including the development of viral resistance and the toxicity
of the antiretroviral drugs.2 Thus it is strongly desired to develop
a new class of anti-HIV-1 agents with superior efficacy and
safety profiles.
Recent advances in our knowledge of chemokine receptors
functioning as HIV-1 co-receptors have provided a novel
strategy for controlling HIV-1 infection.3 HIV-1 strains that
cause the initial infection primarily utilize CC chemokine
receptor 5 (CCR5),4 and CCR5-using (R5) HIV-1 is isolated
predominantly during the asymptomatic stage of the infection,
which usually persists 5-10 years.5 CCR5 belongs to the seven-
transmembrane G protein-coupled receptor superfamily, and its
natural ligands include the CC chemokines [regulated on
activation, normal T cell expressed and secreted (RANTES),
macrophage inflammatory protein (MIP)-1R, and MIP-1â],
which have been reported to inhibit R5 HIV-1 infection in vitro.6
A 32-base pair deletion in the CCR5 gene (CCR5∆32) generates
a nonfunctional receptor, and CCR5∆32-homozygous individu-
als are highly resistant to HIV-1 infection; however, this defect
does not represent a significant health problem.7-9 In addition,
infected individuals heterozygous for the defective CCR5 gene
appear to have delayed disease progression.10 These observations
suggest that CCR5 antagonists functioning as HIV-1 entry
inhibitors could be promising anti-HIV-1 therapeutic agents, and
indeed several compounds (UK-427857,11 SCH-417690,12 GW-
87314013) are now being evaluated in clinical trials.
Our laboratories previously reported that TAK-77914,15 is an
injectable CCR5 antagonist. To develop an orally bioavailable
CCR5 antagonist, further high throughput screening was carried
out, which led to the discovery of a novel lead compound 1a16
(Chart 1, IC50 ) 1900 nM), whose chemical structure differs
from that of TAK-779. Subsequent optimization identified a
series of piperidine-4-carboxamide derivatives, exemplified by
1b, which had low nanomolar affinity for CCR5 and exhibited
good anti-HIV-1 activity.17 In vitro metabolic stability studies
in human hepatic microsomes, however, showed these com-
pounds to be rapidly metabolized. In this paper, we describe
our efforts to identify potent and metabolically stable CCR5
antagonists from the piperidine-4-carboxamide derivatives,
which eventually led to the discovery of the clinical candidate
5m.
* Corresponding author. Tel: +81-6-6300-6719. Fax: +81-6-6300-6306.
E-mail: imamura_shin-ichi@takeda.co.jp.
† Takeda Pharmaceutical Company Limited.
‡ Kagoshima University.
10.1021/jm051034q CCC: $33.50 © 2006 American Chemical Society
Published on Web 04/05/2006

Piperidine-4-carboxamide CCR5 Antagonist
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2785
Scheme 3a
Scheme 1a
a Reagents: (a) MsCl, Et3N, THF; (b) 4-F-PhSH, K2CO3, DMF; (c) 1
equiv mCPBA, DCM; (d) 2.2 equiv mCPBA, DCM; (e) HCl/EtOAc, MeOH;
(f) TFA, DCM.
Scheme 4a
a Reagents: (a) HCO2Ac; (b) Br(CH2)3Cl, Cs2CO3, acetone; (c) concd
HCl, i-PrOH; (d) Et3N, DCM; (e) NMP; (f) 4-substituted piperidine, KI,
K2CO3, MeCN or MeCN/DMF; (g) aq KOH, MeOH.
Scheme 2a
a Reagents: (a) (EtO)3P; (b) 1-Boc-4-piperidone, NaH, THF; (c) H2, Pd/
C, MeOH; (d) aq NaOH, EtOH; (e) R1R2NH‚HCl, Et3N, EDC, HOBt, DMF;
(f) HCl/EtOAc, MeOH; (g) concd H2SO4, MeOH.
Scheme 5a
a Reagents: (a) 4-piperidone hydrochloride, KI, K2CO3, MeCN; (b) 4-F-
PhNH2, NaBH(OAc)3, THF; (c) 4-(Boc-amino)piperidine, KI, K2CO3,
MeCN; (d) HCl/EtOAc, MeOH; (e) 4-F-PhSO2Cl, Et3N, DCM; (f) 4-F-
PhCOCl, Et3N, DCM.
Chemistry
Target compounds were synthesized as outlined in Schemes
1 and 2. N-Formylation of the anilines 2a and 2b using acetic
formic anhydride gave the corresponding formamides (Scheme
1). Subsequent N-alkylation with 1-bromo-3-chloropropane in
the presence of cesium carbonate followed by removal of the
formyl group under acidic conditions afforded the N-(3-
chloropropyl)anilines 3a and 3b. Acylation of 3a and 3b with
the piperidine-4-carbonyl chlorides gave the chlorides 4a-c,
which were reacted with 4-substituted piperidines in the presence
of potassium iodide and potassium carbonate to afford the target
compounds 5a-m. The ester group of compound 5e was
hydrolyzed with aqueous sodium hydroxide affording the
carboxylic acid 6.
a Reagents: (a) (EtO)3P; (b) 1-Boc-4-piperidone, NaH, THF; (c) H2, Pd/
C, MeOH; (d) H2O2, aq NaOH, EtOH; (e) HCl/EtOAc, MeOH or EtOAc;
(f) concd HCl.
Compounds 8, 11a, and 11b were accessed as shown in
Scheme 2. Chloride 4a was reacted with 4-piperidone followed
by reductive amination with 4-fluoroaniline to afford 8. N-
Alkylation of 4-(tert-butoxycarbonylamino)piperidine with the
chloride 4c gave compound 9, which on deprotection by acid
yielded the diamine 10. Compound 10 was converted to the
sulfonamide 11a and amide 11b by reaction with the corre-
sponding acid chlorides.
The required piperidines were prepared as shown in Schemes
3-5. Mesylation of the alcohol 12 followed by displacement
with 4-fluorobenzenethiol using potassium carbonate as base,
provided the sulfide 13 (Scheme 3). Mono-oxidation of 13 with
1 equiv of 3-chloroperoxybenzoic acid (mCPBA) at 0 °C
afforded the sulfoxide 14. Alternatively, use of 2.2 equiv of
mCPBA at room temperature yielded the sulfone 15. Removal
of the tert-butoxycarbonyl (Boc) group of 13 and 15 using

2786 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Imamura et al.
Table 1. Biological Activity and Metabolic Stability of Piperidine-4-carboxamide Derivatives
compd
R1
R2
X
R3
CCR5a IC50 (nM)
fusionb IC50 (nM)
stabilityc % remaining
ClogPd
1b
1c
1d
1e
5a
5b
5c
8
11a
11b
5d
5e
6
Ms
Ms
Ac
Ac
Ac
Ac
Ac
Ac
Ms
Ms
Ms
Ms
Ms
Ms
Ms
Ms
Ms
Ms
Ms
Ac
Ac
3,4-diCl
3,4-diCl
3,4-diCl
H
CH2
CH2
CH2
CH2
S
SO
SO2
NH
NHSO2
NHCO
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
4-Ms
4-F
4-F
H
4-F
4-F
4-F
4-F
4-F
4-F
4-CN
2.2
3.3
1.2
16
1.7
3.2
2.9
20
4.6
730
1.7
4.6
66
8.9
2.8
12
0.80
2.1
3.0
72
1.8
2.7
3.9
26
4.1
NTe
1.4
7.0
44
5.8
2.0
6.4
9.8
12
62
67
47
80
30
36
31
70
55
87
50
66
94
88
81
91
83
57
74
88
92
3.9
5.6
5.0
3.6
4.5
2.5
2.4
3.7
3.6
3.4
4.9
5.3
3.0
4.0
4.0
3.7
4.1
5.3
3.8
3.4
3.3
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3,4-diCl
3-Cl, 4-Me
4-CO2Me
4-CO2H
5f
4-CONH2
3-CONH2
2-CONH2
4-CONHMe
4-CONHt-Bu
4-CONMe2
4-CONH2
4-CONH2
5g
5h
5i
5j
5k
5l
5.1
11
19
3.8
3.5
8.2
2.2
0.42
5m
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing CHO cells. b Inhibition of HIV-1 envelope-mediated membrane fusion. c Metabolic
stability in human hepatic microsomes. The remaining percentage of the parent compounds was measured after incubation for 20 min. d Daylight CLOGP
4.82. e Not tested.
hydrogen chloride gave piperidines 16a and 16c, respectively.
Piperidine 16b was obtained by deprotection of 14 using
trifluoroacetic acid.
incubating compounds with human hepatic microsomes; the
percentage of parent compound remaining after incubation was
measured.
The preparation of the piperidines 22a-d was based on the
Horner-Wadsworth-Emmons reaction (Scheme 4). Arbuzov
reaction of methyl 4-(bromomethyl)benzoate (17) with triethyl
phosphite gave the corresponding phosphonate, which on
treatment with sodium hydride followed by tert-butyl 4-oxopi-
peridine-1-carboxylate formed the olefin 18. Hydrogenation of
18 followed by hydrolysis of the ester group gave the carboxylic
acid 20. Coupling of 20 with the corresponding amines using
1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride
(EDC) and 1-hydroxybenzotriazole (HOBt) afforded the amides
21a-d, which were deprotected to yield the piperidines 22a-
d. Compound 23 was prepared by heating of 22a in methanolic
sulfuric acid. Carbamoyl piperidines 27a and 27b were accessed
from the corresponding nitrile derivatives 26a and 26b, which
were prepared using the same route as above (Scheme 5).
Treatment of 26a with hydrogen peroxide in basic medium
followed by deprotection gave 27a. Alternatively, acid hydroly-
sis of the cyano group of 26b and concomitant deprotection of
the Boc group afforded 27b. The cyano piperidine 28 was
prepared by removal of the Boc group of 26c under acidic
conditions.
We have recently reported the identification of the piperidine-
4-carboxamide derivative 1b, which was found to be a potent
CCR5 antagonist with good inhibitory effect on HIV-1 entry.17
Although compound 1b showed excellent anti-HIV-1 activity
and a good pharmacokinetic profile in dogs, in vitro metabolic
studies revealed that 1b suffered from rapid oxidative metabo-
lism in human hepatic microsomes (stability ) 62%, stability
) % remaining at 20 min), and the human metabolic liability
precluded further development. We therefore investigated a
series of compounds designed for improved metabolic stability
in human hepatic microsomes. Further metabolic profiling of
1b showed that the oxidation of the left-side piperidine ring
was a major metabolic pathway. The 4-fluoro derivative 1c17
also had insufficient metabolic stability, and compound 1d,17
acetyl analogue of 1c, was metabolized more rapidly than 1c.
These compounds 1c and 1d were used as a starting point for
the development of metabolically stable compounds. It is known
that decreasing the lipophilicity of a molecule reduces the
affinity of metabolic enzymes, particularly the cytochrome P450
family, and hence improves metabolic stability.18 As shown in
Table 1, compound 1e17 (stability ) 80%), having lower
lipophilicity (ClogP19 ) 3.6), displayed improved metabolic
stability compared to the more lipophilic compound 1d (ClogP
) 5.0, stability ) 47%), suggesting that less lipophilic molecules
in this series might have higher metabolic stability. On the basis
of these data, we introduced various polar groups into a molecule
with potent activity (1c,d). Our goal was to identify compounds
that possessed both high metabolic stability and high potency,
in particular fusion inhibitory activity.
Results and Discussion
The synthesized compounds were evaluated for their potency
in the inhibition of 125I-labeled RANTES binding to Chinese
hamster ovary (CHO) cells expressing human CCR5 on their
surface; the results are reported as IC50 values (Table 1). To
assess the activities for inhibition of HIV-1 cell entry, an HIV-1
envelope-mediated membrane fusion assay was performed using
R5 HIV-1 (JR-FL strain) envelope-expressing COS-7 cells and
CCR5-expressing MOLT-4 cells, and the results are reported
as IC50 values. Metabolic stability was evaluated in vitro by
From our previous SAR studies, modification of the 4-benz-
ylpiperidine moiety was more plausible to reduce lipophilicity
without sacrificing potency than modification of the left-side

Piperidine-4-carboxamide CCR5 Antagonist
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2787
piperidine and central phenyl ring. In fact, some polar groups
turned out to be well tolerated on the right-side phenyl ring.17,20
We first derivatized the benzylic site of the 4-benzylpiperidine
moiety. Replacing the methylene group of 1d (ClogP ) 5.0,
stability ) 47%) with an amino group provided modest
improvement in metabolic stability (8, ClogP ) 3.7, stability
) 70%), while potency decreased somewhat. Sulfoxide 5b and
sulfone 5c, designed to reduce the lipophilicity (ClogP ) 2.5,
2.4), showed good activity comparable to 1d. Unfortunately,
these compounds exhibited no advantage in metabolic stability,
suggesting that lowering lipophilicity is not sufficient for
increasing stability. Indeed, amide 11b (stability ) 87%)
possessed a greater improvement in metabolic stability than
sulfonamide 11a (stability ) 55%) though both had the same
level of reduced lipophilicity (ClogP ) 3.4, 3.6). Although
compound 11b resulted in a substantial loss of CCR5 binding
affinity, it was noteworthy that the amide group could more
effectively reduce the oxidative metabolism of the 3,4-dichlo-
rinated derivative.
gp120.21 The difference in the ligands utilized in these assays
(RANTES and HIV-1 envelope gp120-expressing cells) prob-
ably causes the discrepancy in activity. The binding site of 5m
to CCR5 might be closer to the gp120-CCR5 binding site than
to the RANTES-CCR5 binding site.
On the basis of its excellent activity in the membrane fusion
assay and good stability in human hepatic microsomes, com-
pound 5m was chosen for further evaluation.22 Compound 5m
blocked RANTES-induced Ca2+ mobilization in CCR5-express-
ing HeLa cells in a dose dependent manner. Compound 5m
was also tested against a panel of other chemokine receptors
and found to be selective for CCR5. It did not inhibit ligand
binding to CHO cells expressing CCR1, CCR2b, CCR3, CCR4,
or CCR7 even at a concentration of 10 µM. These results clearly
indicate that compound 5m is a potent and specific CCR5
antagonist. Compound 5m inhibited the replication of the R5
HIV-1 strain JR-FL in human peripheral blood mononuclear
cells (PBMC) with an EC50 value of <1 nM and also inhibited
the replication of six R5 HIV-1 clinical strains isolated from
treatment-naive and -experienced Japanese patients with mean
EC50 and EC90 values of 1.1 and 13 nM, respectively. More
importantly, anti-HIV-1 activity of 5m was unaffected by
addition of high concentrations of human serum. This result
indicates low plasma protein binding of 5m (human, 53-57%).
No cytotoxicity of 5m against human PBMC was observed even
at a concentration of 10 µM, indicating that the selectivity index
of 5m is >8900. Pharmacokinetic parameters for 5m were
measured in fasted cynomolgus monkeys. After oral administra-
tion (5 mg/kg), the peak plasma concentration was 298 ng/mL
at 0.7 h with a plasma half-life of 6.0 h. The area under the
plasma concentration-time curve from 0 to 24 h was 538 ng‚
h/mL, and the oral bioavailability was 29%. These results
suggest that 5m appears to be a promising anti-HIV-1 agent
and should be further evaluated in clinical trials.
We next turned our attention to substitution of the phenyl
ring of the 4-benzylpiperidine. Replacing the fluorine atom of
1c with a cyano group yielded compound 5d, which retained
good activity, but with poor metabolic stability. Introduction
of a methoxycarbonyl group (5e), as expected from the relatively
high lipophilicity (ClogP ) 5.3), did not improve the stability.
Carboxylic acid derivative 6 was found to be metabolically
stable with 94% of the parent compound remaining, whereas
activity was unacceptably decreased.
More promising results were obtained with carboxamide
derivatives, where a reasonable balance of potency and meta-
bolic stability was achieved. Conversion of the carboxyl group
in 6 to a carbamoyl to give 5f resulted in a 7-fold improvement
in CCR5 binding affinity, while retaining good metabolic
stability (stability ) 88%). Moreover, the carbamoyl compound
5f displayed potent activity in the membrane fusion assay (IC50
) 5.8 nM). To explore the effect of the substitution position of
the carbamoyl group, compounds 5g and 5h were synthesized,
which showed good activity and stability comparable to the
4-carbamoyl derivative 5f. Attempts to modulate the steric and
hydrogen-bonding factors in this carboxamide series through
N-alkylation diminished the metabolic stability to some extent
(5i-k). In the carboxamide series, increasing lipophilicity was
found to be correlated with decreasing stability.
Conclusion
We prepared a series of the piperidine-4-carboxamide CCR5
antagonists containing various polar groups to improve their
metabolic stability in human hepatic microsomes. These efforts
led to the discovery of the carbamoyl derivative 5m, which
showed good metabolic stability as well as potent inhibition of
CCR5 binding and membrane fusion. Compound 5m exhibited
excellent antiviral efficacy against R5 HIV-1 clinical isolates
in PBMC and a good pharmacokinetic profile in monkeys.
Following further profiling, compound 5m (TAK-220) was
ultimately selected as a clinical candidate for treatment of HIV-1
infection.
With the metabolically stable and potent compound 5f in
hand, we investigated the substituents R1 and R2 to increase
potency further. Replacing the R1 methylsulfonyl group with
an acetyl group provided compound 5l, which was twice as
potent as 5f in both the binding (IC50 ) 3.8 nM) and fusion
(IC50 ) 2.2 nM) assays. Subsequent replacement of the R2
substituent with 3-chloro and 4-methyl substituents afforded 5m,
which exhibited a 5-fold potency increase in the membrane
fusion assay (IC50 ) 0.42 nM). Compound 5m was also found
to be metabolically stable in human hepatic microsomes
(stability ) 92%).
Some discrepancy was observed between activity in the CCR5
binding and activity in the HIV-1 membrane fusion assay.
Compound 5m inhibited membrane fusion with an IC50 of 0.42
nM, which was more potent than expected from the CCR5
binding potency. On the contrary, compound 1e was 4-fold less
potent in the fusion assay compared to the CCR5 binding assay.
These results indicate compound 5m can inhibit membrane
fusion more effectively than compound 1e. It has been reported
that the CCR5 binding site of CC chemokines such as RANTES
does not completely overlap with that of HIV-1 envelope
Experimental Section
All commercial reagents and solvents were used as obtained
without further purification. Column chromatography was carried
out on Daiso silica gel (IR-60-40/63-W). Yields were not opti-
mized. Melting points were determined on a Yanagimoto micro
melting point apparatus and are uncorrected. 1H NMR spectra were
recorded on a Varian Gemini 200 or Mercury 300 spectrometer.
Chemical shifts (δ) are given in ppm with tetramethylsilane as an
internal standard, and coupling constants (J) are given in hertz (Hz).
Elemental analyses were carried out at Takeda Analytical Research
Laboratories, Ltd.
3-Chloro-N-(3-chloropropyl)-4-methylaniline Hydrochloride
(3b). Step 1: N-(3-Chloro-4-methylphenyl)formamide. A mixture
of acetic anhydride (189 mL, 2.0 mol) and formic acid (91 mL,
2.4 mol) was stirred at 60 °C for 2 h, then cooled to 0 °C. To the
mixture was added 3-chloro-4-methylaniline (2b) (142 g, 1.0mol)
dropwise, and the mixture was stirred at room temperature for 18
h. After dilution with Et2O (500 mL) and EtOAc (200 mL), the

2788 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Imamura et al.
mixture was washed with water (2 × 500 mL) followed by 1 N
aqueous NaOH (4 × 250 mL) and brine (250 mL), dried (MgSO4),
filtered, and concentrated in vacuo. The residue was triturated with
EtOAc/i-Pr2O, collected by filtration, and dried in vacuo to afford
the product (121 g, 72%) as a cream-colored solid, mp 96-97 °C.
Step 2: N-(3-Chloro-4-methylphenyl)-N-(3-chloropropyl)-
formamide. To a mixture of the product from step 1 (127 g, 0.75
mol) and 1-bromo-3-chloropropane (142 g, 0.90 mol) in acetone
(750 mL) was added Cs2CO3 (293 g, 0.90 mol), and the mixture
was stirred at reflux for 8 h. After cooling to room temperature,
the mixture was filtered, and the filtrate was concentrated in vacuo.
The residue was diluted with EtOAc (500 mL), washed with water
(300 mL) and brine (3 × 100 mL), dried (MgSO4), filtered, and
concentrated in vacuo. The residue was purified by column
chromatography on silica gel (hexane/EtOAc 1:0 to 7:3) to afford
the product (140 g, 76%) as a pale yellow oil.
MeOH 1:0 to 9:1) to afford the free base of 5a (504 mg). The free
base (504 mg) was dissolved in MeOH (6 mL), treated with 4 N
HCl (EtOAc solution, 1.5 mL), and concentrated in vacuo. The
resulting foam was triturated with Et2O, collected by filtration, and
dried in vacuo over KOH to give 5a (445 mg, 62%) as an
amorphous solid. 1H NMR (free base, CDCl3) δ 1.45-2.10 (12H,
m), 2.05 (3H, s), 2.20-2.50 (2H, m), 2.29 (2H, t, J ) 7.1 Hz),
2.70-3.05 (4H, m), 3.65 (2H, t, J ) 7.7 Hz), 3.78 (1H, br d, J )
13.2 Hz), 4.52 (1H, br d, J ) 13.2 Hz), 6.99 (2H, m), 7.04 (1H,
dd, J ) 2.4, 8.4 Hz), 7.32 (1H, d, J ) 2.4 Hz), 7.40 (2H, m), 7.53
(1H, d, J ) 8.4 Hz). Anal. (C28H34Cl2FN3O2S‚HCl‚0.5H2O) C, H,
N.
1-Acetyl-N-(3,4-dichlorophenyl)-N-(3-{4-[(4-fluorophenyl)-
sulfinyl]piperidin-1-yl}propyl)piperidine-4-carboxamide (5b).
Compound 5b was prepared by a method similar to that described
1
for 5a from 16b. Yield 70%, amorphous solid. H NMR (CDCl3)
δ 1.40-2.10 (12H, m), 2.05 (3H, s), 2.20-2.65 (3H, m), 2.28 (2H,
t, J ) 7.2 Hz), 2.75-3.00 (3H, m), 3.63 (2H, m), 3.78 (1H, br d,
J ) 13.1 Hz), 4.53 (1H, br d, J ) 13.1 Hz), 7.02 (1H, dd, J ) 2.4,
8.6 Hz), 7.22 (2H, m), 7.29 (1H, d, J ) 2.4 Hz), 7.52 (1H, d, J )
8.6 Hz), 7.60 (2H, m). Anal. (C28H34Cl2FN3O3S‚0.75H2O) C, H,
N.
Step 3: 3-Chloro-N-(3-chloropropyl)-4-methylaniline Hy-
drochloride (3b). To a solution of the product from step 2 (139 g,
0.56 mol) in i-PrOH (500 mL) was added concentrated HCl (100
mL), and the mixture was stirred at 60 °C for 3 h, then cooled to
room temperature. The resulting precipitate was collected by
filtration, washed with i-PrOH (2 × 100 mL), and dried in vacuo
1
to give 3b (110 g, 77%) as a white solid, mp 152-154 °C. H
1-Acetyl-N-(3,4-dichlorophenyl)-N-(3-{4-[(4-fluorophenyl)sul-
fonyl]piperidin-1-yl}propyl)piperidine-4-carboxamide Hydro-
chloride (5c). Compound 5c was prepared by a method similar to
NMR (CD3OD) δ 2.22 (2H, m), 2.42 (3H, s), 3.55 (2H, m), 3.71
(2H, t, J ) 6.2 Hz), 7.39 (1H, dd, J ) 2.3, 8.3 Hz), 7.52 (1H, d,
J ) 8.3 Hz), 7.60 (1H, d, J ) 2.3 Hz). Anal. (C10H13Cl2N‚HCl) C,
H, N.
1
that described for 5a from 16c. Yield 42%, amorphous solid. H
NMR (free base, CDCl3) δ 1.50-2.10 (12H, m), 2.05 (3H, s), 2.20-
2.50 (2H, m), 2.28 (2H, t, J ) 7.2 Hz), 2.75-3.00 (4H, m), 3.62
(2H, t, J ) 7.5 Hz), 3.78 (1H, br d, J ) 13.2 Hz), 4.52 (1H, br d,
J ) 13.2 Hz), 7.02 (1H, dd, J ) 2.2, 8.4 Hz), 7.25 (2H, m), 7.29
(1H, d, J ) 2.2 Hz), 7.53 (1H, d, J ) 8.4 Hz), 7.87 (2H, m). Anal.
(C28H34Cl2FN3O4S‚HCl‚0.5H2O) C, H, N.
1-Acetyl-N-(3-chloropropyl)-N-(3,4-dichlorophenyl)-4-pipe-
ridinecarboxamide (4a). To an ice-cooled stirred suspension of
3a17 (33.8 g, 0.12 mmol) in dichloromethane (DCM) (500 mL) was
added Et3N (96 mL, 0.69 mol) followed by 1-acetylpiperidine-4-
carbonyl chloride23 (70.1 g, 0.37 mol), and the mixture was stirred
at 0 °C for 4 h. The mixture was diluted with saturated aqueous
NaHCO3 (300 mL), and the organic layer was separated. The
aqueous layer was extracted with DCM (200 mL), and the combined
organic layer was washed with saturated aqueous NaHCO3 (200
mL), 1 N aqueous HCl (2 × 300 mL), and brine (2 × 300 mL),
dried (MgSO4), filtered, and concentrated in vacuo. The residue
was purified by column chromatography on silica gel (EtOAc)
followed by trituration with i-Pr2O to afford 4a (40.4 g, 84%) as a
white solid, mp 118-120 °C. 1H NMR (CDCl3) δ 1.62-1.87 (4H,
m), 1.94-2.06 (2H, m), 2.06 (3H, s), 2.34-2.44 (2H, m), 2.81-
2.94 (1H, m), 3.54 (2H, t, J ) 6.6 Hz), 3.75-3.82 (3H, m), 4.50-
4.56 (1H, m), 7.05 (1H, dd, J ) 2.4, 8.4 Hz), 7.31 (1H, d, J ) 2.4
Hz), 7.55 (1H, d, J ) 8.4 Hz). Anal. (C17H21Cl3N2O2) C, H, N.
1-Acetyl-N-(3-chloro-4-methylphenyl)-N-(3-chloropropyl)pi-
peridine-4-carboxamide (4b). To a stirred solution of 3b (20.0 g,
78.6 mmol) in 1-methyl-2-pyrrolidone (NMP) (100 mL) was added
portionwise 1-acetylpiperidine-4-carbonyl chloride23 (44.7 g, 236
mmol), and the mixture was stirred at room temperature for 18 h.
The mixture was diluted with water (300 mL) and extracted with
EtOAc (3 × 200 mL). The organic layer was washed with saturated
aqueous NaHCO3 (2 × 100 mL) and brine (100 mL) and
concentrated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 1:0 to 9:1) followed
by recrystallization from EtOAc/Et2O to afford 4b (24.7 g, 85%)
as a white solid, mp 113-114 °C. 1H NMR (CDCl3) δ 1.50-2.10
(6H, m), 2.05 (3H, s), 2.25-2.50 (2H, m), 2.43 (3H, s), 2.75-
2.95 (1H, m), 3.53 (2H, t, J ) 6.6 Hz), 3.65-3.85 (1H, m), 3.77
(2H, t, J ) 7.1 Hz), 4.51 (1H, br d, J ) 12.8 Hz), 6.98 (1H, dd, J
) 2.2, 7.7 Hz), 7.18 (1H, d, J ) 2.2 Hz), 7.31 (1H, d, J ) 7.7 Hz).
Anal. (C18H24Cl2N2O2) C, H, N.
N-{3-[4-(4-Cyanobenzyl)piperidin-1-yl]propyl}-N-(3,4-di-
chlorophenyl)-1-(methylsulfonyl)piperidine-4-carboxamide (5d).
A mixture of 4c17 (770 mg, 1.8 mmol), 28 (355 mg, 1.5 mmol), KI
(299 mg, 1.8 mmol), and K2CO3 (829 mg, 6.0 mmol) in MeCN/
DMF (1:1, 30 mL) was stirred at 100 °C for 6 h. The mixture was
concentrated in vacuo, and the residue was partitioned between
EtOAc (40 mL) and water (10 mL). The organic layer was
separated, washed with 1 N aqueous NaOH (3 × 5 mL) followed
by brine (5 mL), and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (EtOAc/MeOH
1:0 to 9:1) to afford 5d (622 mg, 70%) as an amorphous solid. 1H
NMR (CDCl3) δ 1.10-2.05 (13H, m), 2.10-2.35 (1H, m), 2.27
(2H, t, J ) 7.4 Hz), 2.45-2.65 (2H, m), 2.57 (2H, d, J ) 6.6 Hz),
2.74 (3H, s), 2.82 (2H, br d, J ) 11.4 Hz), 3.55-3.80 (4H, m),
7.02 (1H, dd, J ) 2.5, 8.4 Hz), 7.22 (2H, d, J ) 8.4 Hz), 7.31 (1H,
d, J ) 2.5 Hz), 7.52 (1H, d, J ) 8.4 Hz), 7.56 (2H, d, J ) 8.4 Hz).
Anal. (C29H36Cl2N4O3S‚0.5H2O) C, H, N.
Methyl 4-({1-[3-((3,4-Dichlorophenyl){[1-(methylsulfonyl)-
piperidin-4-yl]carbonyl}amino)propyl]piperidin-4-yl}methyl)-
benzoate (5e). Compound 5e was prepared by a method similar to
that described for 5d from 23. Yield 62%, mp 148-151 °C (EtOAc/
i-Pr2O). 1H NMR (CDCl3) δ 1.23-1.42 (13H, m), 2.20-2.40 (3H,
m), 2.52-2.59 (4H, m), 2.74 (3H, s), 2.80-2.89 (2H, m), 3.62-
3.76 (4H, m), 3.90 (3H, s), 7.06 (1H, dd, J ) 2.6, 8.4 Hz), 7.19
(2H, d, J ) 8.4 Hz), 7.32 (1H, d, J ) 2.6 Hz), 7.52 (1H, d, J ) 8.4
Hz), 7.94 (2H, d, J ) 8.4 Hz). Anal. (C30H39Cl2N3O5S‚0.75H2O)
C, H, N.
N-{3-[4-(4-Carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3,4-
dichlorophenyl)-1-(methylsulfonyl)piperidine-4-carboxamide (5f).
Compound 5f was prepared by a method similar to that described
1
for 5d from 22a. Yield 52%, mp 196-197 °C (MeOH). H NMR
1-Acetyl-N-(3,4-dichlorophenyl)-N-(3-{4-[(4-fluorophenyl)sul-
fanyl]piperidin-1-yl}propyl)piperidine-4-carboxamide Hydro-
chloride (5a). A mixture of 4a (470 mg, 1.2 mmol), 16a (297 mg,
1.2 mmol), KI (199 mg, 1.2 mmol), and K2CO3 (498 mg, 3.6 mmol)
in MeCN (24 mL) was stirred at 80 °C for 20 h. The mixture was
concentrated in vacuo, and the residue was diluted with water (15
mL) and extracted with EtOAc (3 × 15 mL). The organic layer
was dried (Na2SO4), filtered, and concentrated in vacuo. The residue
was purified by column chromatography on silica gel (EtOAc/
(CDCl3) δ 1.21-1.34 (2H, m), 1.40-1.97 (11H, m), 2.10-2.30
(3H, m), 2.50-2.65 (2H, m), 2.57 (2H, d, J ) 5.8 Hz), 2.74 (3H,
s), 2.78-2.84 (2H, m), 3.61-3.76 (4H, m), 5.40-6.20 (2H, m),
7.02 (1H, dd, J ) 2.6, 8.4 Hz), 7.21 (2H, d, J ) 8.4 Hz), 7.31 (1H,
d, J ) 2.6 Hz), 7.52 (1H, d, J ) 8.4 Hz), 7.72 (2H, d, J ) 8.4 Hz).
Anal. (C29H38Cl2N4O4S) C, H, N.
N-{3-[4-(3-Carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3,4-
dichlorophenyl)-1-(methylsulfonyl)piperidine-4-carboxamide (5g).

Piperidine-4-carboxamide CCR5 Antagonist
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2789
Compound 5g was prepared by a method similar to that described
for 5d from 27b. Yield 59%, mp 184-186 °C (EtOAc). 1H NMR
(CDCl3) δ 1.10-2.00 (13H, m), 2.10-2.35 (3H, m), 2.45-2.70
(2H, m), 2.57 (2H, d, J ) 6.2 Hz), 2.74 (3H, s), 2.82 (2H, br d, J
) 11.0 Hz), 3.55-3.80 (4H, m), 5.50-6.20 (2H, m), 7.03 (1H,
dd, J ) 2.2, 8.4 Hz), 7.25-7.40 (3H, m), 7.52 (1H, d, J ) 8.4
Hz), 7.55-7.65 (2H, m). Anal. (C29H38Cl2N4O4S) C, H, N.
N-{3-[4-(2-Carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3,4-
dichlorophenyl)-1-(methylsulfonyl)piperidine-4-carboxamide (5h).
Compound 5h was prepared by a method similar to that described
added 4b (20.0 g, 54 mmol) followed by KI (8.94 g, 54 mmol)
and MeCN (200 mL), and the mixture was stirred at 80 °C for 14
h. The mixture was concentrated in vacuo, and the residue was
partitioned between DCM (500 mL) and water (100 mL). The
organic layer was separated, washed with 1 N aqueous NaOH (3
× 100 mL) and brine (100 mL), dried (Na2SO4), filtered, and
concentrated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 1:0 to 7:3) to afford
5m (21.4 g, 72%) as an amorphous solid. Recrystallization from
EtOAc/EtOH (4:1) gave 5m as a white crystalline solid, mp 166-
167 °C. 1H NMR (CDCl3) δ 1.15-1.35 (2H, m), 1.42-1.90 (11H,
m), 2.04 (3H, s), 2.20-2.46 (2H, m), 2.26 (2H, t, J ) 7.5 Hz),
2.42 (3H, s), 2.57 (2H, d, J ) 6.6 Hz), 2.73-2.92 (3H, m), 3.64
(2H, t, J ) 7.7 Hz), 3.76 (1H, br d, J ) 13.5 Hz), 4.50 (1H, br d,
J ) 13.5 Hz), 5.25-6.35 (2H, m), 6.95 (1H, dd, J ) 2.1, 8.1 Hz),
7.17 (1H, d, J ) 2.1 Hz), 7.20 (2H, d, J ) 8.3 Hz), 7.28 (1H, d,
J ) 8.1 Hz), 7.72 (2H, d, J ) 8.3 Hz). Anal. (C31H41ClN4O3) C,
H, N.
4-({1-[3-((3,4-Dichlorophenyl){[1-(methylsulfonyl)piperidin-
4-yl]carbonyl}amino)propyl]piperidin-4-yl}methyl)benzoic Acid
(6). To a solution of 5e (113 mg, 0.18 mmol) in MeOH (3 mL)
was added 1 N aqueous NaOH (0.72 mL), and the mixture was
stirred at 60 °C for 3 h. The mixture was treated with 1 N aqueous
HCl (0.72 mL) and concentrated in vacuo. The residue was diluted
with water and extracted with DCM. The organic layer was dried
(Na2SO4), filtered, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (DCM/MeOH 1:0
to 4:1) to afford 6 (103 mg, 93%) as an amorphous solid. 1H NMR
(CD3OD) δ 1.51-1.95 (11H, m), 2.20-2.40 (1H, m), 2.40-2.60
(2H, m), 2.67 (2H, d, J ) 6.6 Hz), 2.73 (3H, s), 2.80-3.10 (4H,
m), 3.46-4.89 (6H, m), 7.23 (2H, d, J ) 8.0 Hz), 7.36 (1H, dd, J
) 2.2, 8.4 Hz), 7.68 (1H, d, J ) 8.4 Hz), 7.70 (1H, d, J ) 2.2 Hz),
7.91 (2H, d, J ) 8.0 Hz). Anal. (C29H37Cl2N3O5S‚2H2O) C, H, N.
1-Acetyl-N-(3,4-dichlorophenyl)-N-[3-(4-oxopiperidin-1-yl)-
propyl]piperidine-4-carboxamide (7). Compound 7 was prepared
by a method similar to that described for 5a from 4-piperidone
monohydrate hydrochloride. Yield 54%, mp 107-110 °C (i-Pr2O).
1H NMR (CDCl3) δ 1.62-1.82 (6H, m), 2.06 (3H, s), 2.30-2.49
(8H, m), 2.71 (4H, q, J ) 5.8 Hz), 2.81-2.94 (1H, m), 3.69-3.82
(3H, m), 4.51-4.57 (1H, m), 7.06 (1H, dd, J ) 2.6, 8.4 Hz), 7.33
(1H, d, J ) 2.6 Hz), 7.55 (1H, d, J ) 8.4 Hz). Anal. (C22H29-
Cl2N3O3‚H2O) C, H, N.
1
for 5d from 27a. Yield 73%, amorphous solid. H NMR (CDCl3)
δ 1.10-2.05 (13H, m), 2.10-2.35 (3H, m), 2.45-2.65 (2H, m),
2.65-2.90 (2H, m), 2.74 (3H, s), 2.77 (2H, d, J ) 6.6 Hz), 3.55-
3.80 (4H, m), 5.60-5.85 (2H, m), 7.04 (1H, dd, J ) 2.4, 8.4 Hz),
7.10-7.50 (5H, m), 7.52 (1H, d, J ) 8.4 Hz). Anal. (C29H38-
Cl2N4O4S‚H2O) C, H, N.
N-(3,4-Dichlorophenyl)-N-(3-{4-[4-(methylcarbamoyl)benzyl]-
piperidin-1-yl}propyl)-1-(methylsulfonyl)piperidine-4-carboxa-
mide Hydrochloride (5i). Compound 5i was prepared by a method
similar to that described for 5d from 22b. Yield 55%, amorphous
1
solid. H NMR (free base, CDCl3) δ 1.20-1.40 (2H, m), 1.40-
2.00 (11H, m), 2.10-2.40 (3H, m), 2.54-2.62 (2H, m), 2.55 (2H,
d, J ) 6.4 Hz), 2.74 (3H, s), 2.80-2.85 (2H, m), 3.01 (3H, d, J )
4.8 Hz), 3.61-3.76 (4H, m), 6.12 (1H, br q, J ) 4.8 Hz), 7.03
(1H, dd, J ) 2.2, 8.0 Hz), 7.18 (2H, d, J ) 8.4 Hz), 7.31 (1H, d,
J ) 2.2 Hz), 7.53 (1H, d, J ) 8.4 Hz), 7.66 (2H, d, J ) 8.0 Hz).
Anal. (C30H40Cl2N4O4S‚HCl‚2H2O) C, H, N.
N-(3-{4-[4-(tert-Butylcarbamoyl)benzyl]piperidin-1-yl}propyl)-
N-(3,4-dichlorophenyl)-1-(methylsulfonyl)piperidine-4-carboxa-
mide (5j). Compound 5j was prepared by a method similar to that
described for 5d from 22c. Yield 67%, mp 121-122 °C (EtOAc/
1
i-Pr2O). H NMR (CDCl3) δ 1.20-1.40 (2H, m), 1.47 (9H, s),
1.55-2.00 (11H, m), 2.20-2.30 (3H, m), 2.50-2.70 (2H, m), 2.55
(2H, d, J ) 6.2 Hz), 2.74 (3H, s), 2.75-2.84 (2H, m), 3.59-3.76
(4H, m), 5.91 (1H, br s), 7.03 (1H, dd, J ) 2.6, 8.4 Hz), 7.16 (2H,
d, J ) 8.0 Hz), 7.31 (1H, d, J ) 2.6 Hz), 7.53 (1H, d, J ) 8.4 Hz),
7.63 (2H, d, J ) 8.0 Hz). Anal. (C33H46Cl2N4O4S‚0.5H2O) C, H,
N.
N-(3,4-Dichlorophenyl)-N-(3-{4-[4-(dimethylcarbamoyl)benz-
yl]piperidin-1-yl}propyl)-1-(methylsulfonyl)piperidine-4-carbox-
amide Hydrochloride (5k). Compound 5k was prepared by a
method similar to that described for 5d from 22d. Yield 43%,
1
amorphous solid. H NMR (free base, CDCl3) δ 1.12-1.40 (2H,
1-Acetyl-N-(3,4-dichlorophenyl)-N-{3-[4-(4-fluoroanilino)pi-
peridin-1-yl]propyl}piperidine-4-carboxamide Dihydrochloride
(8). To an ice-cooled stirred solution of 7 (1000 mg, 2.2 mmol)
and 4-fluoroaniline (269 mg, 2.4 mmol) in THF (3 mL) was added
AcOH (126 µL, 2.2 mmol) followed by NaBH(OAc)3 (699 mg,
3.3 mmol), and the mixture was stirred at room temperature for 20
h. The mixture was diluted with saturated aqueous NaHCO3 (100
mL), stirred for 2 h, and extracted with EtOAc (2 × 100 mL). The
organic layer was washed with brine (100 mL), dried (Na2SO4),
filtered, and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc/MeOH 1:0 to 4:1)
to afford the free base of 8 (695 mg). The free base (208 mg) was
converted to the hydrochloride salt using 4 N HCl (EtOAc solution)
to give the dihydrochloride 8 (187 mg, 46%) as a pale purple
m), 1.40-2.00 (11H, m), 2.10-2.40 (3H, m), 2.40-2.63 (2H, m),
2.53 (2H, d, J ) 6.6 Hz), 2.74 (3H, s), 2.74-2.90 (2H, m), 3.00
(3H, br s), 3.10 (3H, br s), 3.62 (4H, m), 7.02-7.06 (1H, m), 7.15
(2H, d, J ) 6.2 Hz), 7.32 (1H, d, J ) 2.0 Hz), 7.34 (2H, d, J ) 6.2
Hz), 7.52 (1H, d, J ) 8.4 Hz). Anal. (C31H42Cl2N4O4S‚HCl‚2H2O)
C, H, N.
1-Acetyl-N-{3-[4-(4-carbamoylbenzyl)piperidin-1-yl]propyl}-
N-(3,4-dichlorophenyl)piperidine-4-carboxamide (5l). A mixture
of 4a (392 mg, 1.0 mmol), 22a (280 mg, 1.1 mmol), KI (183 mg,
1.1 mmol), and K2CO3 (415 mg, 3.0 mmol) in MeCN/DMF (1:1,
6 mL) was stirred at 80 °C for 20 h. The mixture was concentrated
in vacuo, and the residue was diluted with EtOAc (20 mL) and
washed with water (2 × 20 mL), 1 N aqueous NaOH (2 × 20
mL), and brine (20 mL). The organic layer was dried (Na2SO4),
filtered, and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc/MeOH 1:0 to 3:2)
followed by trituration with Et2O to afford 5l (320 mg, 56%) as a
white solid, mp 126-127 °C. 1H NMR (CDCl3) δ 1.19-1.34 (2H,
m), 1.40-1.87 (11H, m), 2.05 (3H, s), 2.23-2.42 (4H, m), 2.57
(2H, d, J ) 6.2 Hz), 2.79-2.92 (3H, m), 3.61-3.81 (3H, m), 4.49-
4.55 (1H, m), 5.60-6.20 (2H, m), 7.03 (1H, dd, J ) 2.6, 8.4 Hz),
7.20 (2H, d, J ) 8.0 Hz), 7.31 (1H, d, J ) 2.6 Hz), 7.52 (1H, d,
J ) 8.4 Hz), 7.73 (2H, d, J ) 8.0 Hz). Anal. (C30H38Cl2N4O3‚
0.5H2O) C, H, N.
1
amorphous solid. H NMR (free base, CDCl3) δ 1.30-1.50 (2H,
m), 1.50-1.87 (6H, m), 2.00-2.13 (4H, m), 2.06 (3H, s), 2.30-
2.37 (4H, m), 2.78-2.93 (3H, m), 3.10-3.30 (1H, m), 3.63-3.81
(4H, m), 4.50-4.57 (1H, m), 6.52 (2H, dd, J ) 4.4, 8.8 Hz), 6.87
(2H, t, J ) 8.8 Hz), 7.09 (1H, dd, J ) 2.2, 8.4 Hz), 7.32 (1H, d,
J ) 2.2 Hz), 7.53 (1H, d, J ) 8.4 Hz). Anal. (C28H35Cl2FN4O2‚
2HCl‚1.5H2O) C, H, N.
N-(3-{4-[(tert-Butoxycarbonyl)amino]piperidin-1-yl}propyl)-
N-(3,4-dichlorophenyl)-1-(methylsulfonyl)piperidine-4-carboxa-
mide (9). A mixture of 4c17 (2.99 g, 7.0 mmol), 4-[(tert-
butoxycarbonyl)amino]piperidine (1.40 g, 7.0 mmol), KI (1.16 g,
7.0 mmol), and K2CO3 (0.97 g, 7.0 mmol) in MeCN (35 mL) was
stirred at 80 °C for 18 h. The mixture was concentrated in vacuo,
and the residue was partitioned between EtOAc/THF (2:1, 120 mL)
and water (20 mL). The organic layer was separated, washed with
1-Acetyl-N-{3-[4-(4-carbamoylbenzyl)piperidin-1-yl]propyl}-
N-(3-chloro-4-methylphenyl)piperidine-4-carboxamide (5m). A
mixture of 22a (16.5 g, 65 mmol) and K2CO3 (22.3 g, 161 mmol)
in DMF (200 mL) was stirred at 80 °C for 1 h. To the mixture was

2790 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Imamura et al.
water (2 × 20 mL) and brine (20 mL), dried (MgSO4), filtered,
and concentrated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 1:0 to 9:1) followed
by trituration with i-Pr2O to afford 9 (3.21 g, 78%) as a white solid,
15.0 mmol), 4-fluorobenzenethiol (2.08 mL, 19.5 mmol), and
potassium carbonate (2.70 g, 19.5 mmol) in DMF (150 mL) was
stirred at 70 °C for 7 h. The mixture was concentrated in vacuo,
and the residue was diluted with EtOAc (80 mL) and washed with
water (20 mL), 0.5 N aqueous NaOH (3 × 10 mL), and brine (10
mL). The organic layer was dried (MgSO4), filtered, and concen-
trated in vacuo. The residue was purified by column chromatog-
raphy on silica gel (hexane/EtOAc 19:1 to 9:1) to give 13 (4.04 g,
1
mp 100-103 °C. H NMR (CDCl3) δ 1.20-2.10 (12H, m), 1.44
(9H, s), 2.10-2.35 (1H, m), 2.29 (2H, t, J ) 7.3 Hz), 2.45-2.85
(4H, m), 2.74 (3H, s), 3.30-3.55 (1H, m), 3.60-3.80 (4H, m),
4.25-4.50 (1H, m), 7.02 (1H, dd, J ) 2.4, 8.4 Hz), 7.31 (1H, d, J
) 2.4 Hz), 7.52 (1H, d, J ) 8.4 Hz). Anal. (C26H40Cl2N4O5S) C,
H, N.
1
86%) as a colorless oil. H NMR (CDCl3) δ 1.44 (9H, s), 1.49
(2H, m), 1.88 (2H, m), 2.88 (2H, ddd, J ) 3.0, 10.6, 13.6 Hz),
3.09 (1H, tt, J ) 4.0, 10.3 Hz), 3.97 (2H, m), 7.01 (2H, m), 7.43
(2H, m).
N-[3-(4-Aminopiperidin-1-yl)propyl]-N-(3,4-dichlorophenyl)-
1-(methylsulfonyl)piperidine-4-carboxamide Dihydrochloride
(10). To a stirred suspension of 9 (2.99 g, 5.1 mmol) in MeOH (20
mL) was added 4 N HCl (EtOAc solution, 40 mL), and the mixture
was stirred at room temperature for 6 h. The mixture was
concentrated in vacuo, and the residue was triturated with EtOAc,
collected by filtration, and dried in vacuo to give 10 (2.70 g, 95%)
tert-Butyl 4-[(4-Fluorophenyl)sulfinyl]piperidine-1-carboxy-
late (14). To an ice-cooled stirred solution of 13 (1.87 g, 6.0 mmol)
in DCM (30 mL) was added a solution of mCPBA (70%, 1.48 g,
6.0 mmol) in DCM (30 mL) dropwise over 30 min, and the mixture
was stirred at 0 °C for 1 h. The mixture was filtered, and the filtrate
was washed with saturated aqueous NaHCO3 (3 × 30 mL). The
organic layer was dried (MgSO4), filtered, and concentrated in
vacuo. The residue was purified by column chromatography on
silica gel (hexane/EtOAc 3:1 to 1:2) to give 14 (1.39 g, 71%) as a
1
as a white solid, mp 250-254 °C. H NMR (CD3OD) δ 1.60-
2.65 (13H, m), 2.73 (3H, s), 3.00-3.30 (4H, m), 3.40-3.85 (5H,
m), 3.80 (2H, t, J ) 6.8 Hz), 7.41 (1H, dd, J ) 2.3, 8.5 Hz), 7.70
(1H, d, J ) 8.5 Hz), 7.73 (1H, d, J ) 2.3 Hz). Anal. (C21H32-
Cl2N4O3S‚2HCl‚0.5H2O) C, H, N.
1
colorless oil, which solidified on standing, mp 112-114 °C. H
NMR (CDCl3) δ 1.40-1.85 (4H, m), 1.44 (9H, s), 2.55-2.80 (3H,
N-(3,4-Dichlorophenyl)-N-[3-(4-{[(4-fluorophenyl)sulfonyl]-
amino}piperidin-1-yl)propyl]-1-(methylsulfonyl)piperidine-4-
carboxamide Hydrochloride (11a). To a stirred suspension of 10
(564 mg, 1.0 mmol) in DCM (10 mL) was added Et3N (502 µL,
3.6 mmol) followed by 4-fluorobenzenesulfonyl chloride (234 mg,
1.2 mmol), and the mixture was stirred at room temperature for 18
h. The mixture was concentrated in vacuo, and the residue was
partitioned between EtOAc (40 mL) and saturated aqueous NaHCO3
(15 mL). The organic layer was separated, washed with saturated
aqueous NaHCO3 (3 × 5 mL) and brine (5 mL), dried (MgSO4),
filtered, and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc/MeOH 1/0 to 9/1)
to afford the free base of 11a (613 mg). The free base (613 mg)
was converted to the hydrochloride salt using 4 N HCl (EtOAc
m), 4.20 (2H, m), 7.24 (2H, m), 7.60 (2H, m).
tert-Butyl 4-[(4-Fluorophenyl)sulfonyl]piperidine-1-carboxy-
late (15). To an ice-cooled stirred solution of 13 (1.87 g, 6.0 mmol)
in DCM (30 mL) was added mCPBA (70%, 3.25 g, 13 mmol), and
the mixture was stirred at 0 °C for 1 h and at room temperature for
1 h. The mixture was filtered, and the filtrate was washed with 5%
aqueous sodium thiosulfate (2 × 10 mL) and saturated aqueous
NaHCO3 (3 × 10 mL). The organic layer was dried (MgSO4),
filtered, and concentrated in vacuo. The residue was triturated with
Et2O, collected by filtration, and dried in vacuo to give 15 (1.85 g,
90%) as a white solid, mp 167-169 °C. 1H NMR (CDCl3) δ 1.43
(9H, s), 1.59 (2H, m), 1.98 (2H, br d, J ) 11.8 Hz), 2.66 (2H, br
t, J ) 12.6 Hz), 3.03 (1H, tt, J ) 3.8, 12.0 Hz), 4.23 (2H, br d, J
) 13.2 Hz), 7.26 (2H, m), 7.89 (2H, m).
1
solution) to give 11a (614 mg, 90%) as an amorphous solid. H
NMR (free base, CDCl3) δ 1.25-2.05 (12H, m), 2.10-2.35 (1H,
m), 2.25 (2H, t, J ) 7.4 Hz), 2.45-2.80 (4H, m), 2.74 (3H, s),
3.14 (1H, m), 3.63 (2H, t, J ) 7.7 Hz), 3.73 (2H, m), 4.62 (1H, br
d, J ) 8.0 Hz), 7.01 (1H, dd, J ) 2.4, 8.5 Hz), 7.19 (2H, m), 7.29
(1H, d, J ) 2.4 Hz), 7.52 (1H, d, J ) 8.5 Hz), 7.89 (2H, m). Anal.
(C27H35Cl2FN4O5S2‚HCl‚0.5H2O) C, H, N.
4-[(4-Fluorophenyl)sulfanyl]piperidine Hydrochloride (16a).
To a solution of 13 (1.87 g, 6.0 mmol) in MeOH (10 mL) was
added 4 N HCl (EtOAc solution, 20 mL), and the mixture was
stirred at room temperature for 18 h. The mixture was concentrated
in vacuo, and the residue was triturated with EtOAc, collected by
filtration, washed with EtOAc, and dried in vacuo to give 16a (1.35
g, 91%) as a white solid, mp 169-172 °C. H NMR (CD3OD) δ
1.73 (2H, dtd, J ) 4.0, 10.6, 14.5 Hz), 2.16 (2H, m), 3.05 (2H, m),
3.25-3.50 (3H, m), 7.11 (2H, m), 7.53 (2H, m).
1
N-(3,4-Dichlorophenyl)-N-(3-{4-[(4-fluorobenzoyl)amino]-
piperidin-1-yl}propyl)-1-(methylsulfonyl)piperidine-4-carbox-
amide (11b). Compound 11b was prepared by a method similar to
that described for 11a from 4-fluorobenzoyl chloride. Yield 91%,
4-[(4-Fluorophenyl)sulfinyl]piperidine Trifluoroacetate (16b).
To an ice-cooled stirred solution of 14 (1.08 g, 3.3 mmol) in DCM
(21 mL) was added trifluoroacetic acid (7 mL), and the mixture
was stirred at 0 °C for 1 h. The mixture was concentrated in vacuo,
and the residue was triturated with i-Pr2O, collected by filtration,
dried in vacuo to give 16b (1.11 g, 99%) as a white solid, mp 177-
1
mp 184-187 °C (i-Pr2O/EtOAc). H NMR (CDCl3) δ 1.40-2.40
(15H, m), 2.48-2.67 (2H, m), 2.74 (3H, s), 2.77-2.90 (2H, m),
3.62-3.80 (4H, m), 3.85-4.07 (1H, m), 5.82-5.93 (1H, m), 7.01-
7.16 (3H, m), 7.32 (1H, d, J ) 2.2 Hz), 7.54 (1H, d, J ) 8.4 Hz),
7.70-7.80 (2H, m). Anal. (C28H35Cl2FN4O4S‚0.75H2O) C, H, N.
tert-Butyl 4-[(4-Fluorophenyl)sulfanyl]piperidine-1-carboxy-
late (13). Step 1: tert-Butyl 4-[(Methylsulfonyl)oxy]piperidine-
1-carboxylate. To an ice-cooled stirred solution of tert-butyl
4-hydroxypiperidine-1-carboxylate (12) (20.13 g, 100 mmol) and
Et3N (16.7 mL, 120 mmol) in THF (200 mL) was added meth-
anesulfonyl chloride (9.3 mL, 120 mmol) dropwise, and the mixture
was stirred at 0 °C for 3 h. The mixture was diluted with water
(200 mL) and extracted with EtOAc (200 mL, 2 × 100 mL). The
organic layer was washed with 1 N aqueous HCl (2 × 50 mL)
followed by saturated aqueous NaHCO3 (2 × 50 mL) and brine
(50 mL), dried (MgSO4), filtered, and concentrated in vacuo. The
residue was triturated with i-Pr2O/hexane (1:1, 200 mL), collected
by filtration, and dried in vacuo to give the product (25.65 g, 92%)
as a white solid, mp 89-91 °C. 1H NMR (CDCl3) δ 1.46 (9H, s),
1.70-2.10 (4H, m), 3.04 (3H, s), 3.30 (2H, ddd, J ) 4.2, 7.9, 13.7
Hz), 3.71 (2H, ddd, J ) 4.1, 6.7, 13.7 Hz), 4.89 (1H, tt, J ) 3.8,
7.7 Hz).
1
178 °C. H NMR (CD3OD) δ 1.65-2.05 (3H, m), 2.19 (1H, m),
2.90-3.20 (3H, m), 3.50 (2H, m), 7.40 (2H, m), 7.73 (2H, m).
4-[(4-Fluorophenyl)sulfonyl]piperidine Hydrochloride (16c).
Compound 16c was prepared by a method similar to that described
1
for 16a from 15. Yield 97%, mp 250-255 °C (EtOAc). H NMR
(CD3OD) δ 1.90 (2H, m), 2.20 (2H, m), 3.01 (2H, dt, J ) 3.3,
12.9 Hz), 3.40-3.65 (3H, m), 7.43 (2H, m), 7.99 (2H, m).
4-{[1-(tert-Butoxycarbonyl)piperidin-4-yl]methyl}benzoic Acid
(20). Step 1: Methyl 4-[(Diethoxyphosphoryl)methyl]benzoate.
A mixture of methyl 4-(bromomethyl)benzoate (17) (25.0 g, 109
mmol) and triethyl phosphite (24.3 mL, 142 mmol) was stirred at
150 °C for 24 h. The mixture was purified by vacuum distillation
to give the product (21.5 g, 69%) as a colorless oil, bp 165-172
°C/1 Torr. 1H NMR (CDCl3) δ 1.24 (6H, t, J ) 7.0 Hz), 3.21 (2H,
d, J ) 22.4 Hz), 3.91 (3H, s), 4.02 (4H, qd, J ) 7.0, 8.1 Hz), 7.38
(2H, dd, J ) 2.4, 8.4 Hz), 7.99 (2H, d, J ) 8.4 Hz).
Step 2: tert-Butyl 4-[4-(Methoxycarbonyl)benzylidene]pip-
eridine-1-carboxylate (18). To an ice-cooled stirred solution of
compound from step 1 (40.0 g, 140 mmol) and 15-crown-5 (2.3
Step 2: tert-Butyl 4-[(4-Fluorophenyl)sulfanyl]piperidine-1-
carboxylate (13). A mixture of the product from step 1 (4.19 g,

Piperidine-4-carboxamide CCR5 Antagonist
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2791
mL, 12 mmol) in THF (240 mL) was added NaH (60% in oil, 5.60
g, 140 mmol), and the mixture was stirred at 0 °C for 30 min. To
the mixture was added a solution of tert-butyl 4-oxopiperidine-1-
carboxylate (23.3 g, 117 mmol) in THF (100 mL) dropwise over
20 min at 0 °C, and the mixture was stirred at room temperature
for 4 h. The mixture was poured into ice water (200 mL) and
extracted with EtOAc (2 × 200 mL). The organic layer was washed
with saturated aqueous NaHCO3 (2 × 100 mL) and brine (100 mL),
dried (MgSO4), filtered, and concentrated in vacuo. The residue
was purified by column chromatography on silica gel (hexane/
EtOAc 1:0 to 4:1) to give a mixture of 18 and tert-butyl 4-[4-
(ethoxycarbonyl)benzylidene]piperidine-1-carboxylate (18′) (37.9
171 °C. 1H NMR (CDCl3) δ 1.05-1.26 (2H, m), 1.45 (9H, s), 1.47
(9H, s), 1.55-1.80 (3H, m), 2.57 (2H, d, J ) 7.0 Hz), 2.62-2.69
(2H, m), 4.04-4.11 (2H, m), 5.91 (1H, br s), 7.18 (2H, d, J ) 8.0
Hz), 7.64 (2H, d, J ) 8.0 Hz).
tert-Butyl 4-[4-(Dimethylcarbamoyl)benzyl]piperidine-1-car-
boxylate (21d). Compound 21d was prepared by a method similar
to that described for 21a from dimethylamine hydrochloride. Yield
1
98%, oil. H NMR (CDCl3) δ 1.10-1.30 (2H, m), 1.45 (9H, s),
1.58-1.70 (3H, m), 2.55 (2H, d, J ) 7.0 Hz), 2.63-2.69 (2H, m),
3.00 (3H, br s), 3.10 (3H, br s), 4.04-4.18 (2H, m), 7.16 (2H, d,
J ) 8.2 Hz), 7.35 (2H, d, J ) 8.2 Hz).
4-(Piperidin-4-ylmethyl)benzamide Hydrochloride (22a). To
a stirred solution of 21a (30.5 g, 96 mmol) in MeOH (100 mL)
was added 4 N HCl (EtOAc solution, 200 mL), and the mixture
was stirred at room temperature for 3 h. The mixture was
concentrated in vacuo, and the residue was triturated with EtOAc,
collected by filtration, washed with EtOAc, and dried in vacuo to
1
g, 98%, 18:18′ ) ca. 2:1 by H NMR) as a semisolid, which was
used for the next step without further purification. Compound 18
could be isolated in pure form by recrystallization from hexane.
1H NMR (CDCl3) δ 1.48 (9H, s), 2.35 (2H, t, J ) 5.8 Hz), 2.47
(2H, t, J ) 5.8 Hz), 3.42 (2H, t, J ) 5.8 Hz), 3.52 (2H, t, J ) 5.8
Hz), 3.91 (3H, s), 6.38 (1H, s), 7.25 (2H, d, J ) 8.4 Hz), 7.99 (2H,
d, J ) 8.4 Hz).
1
give 22a (27.3 g, quant.) as a white solid, mp 235-238 °C. H
NMR (CD3OD) δ 1.25-1.56 (2H, m), 1.82-2.01 (3H, m), 2.68
(2H, d, J ) 6.8 Hz), 2.88-3.01 (2H, m), 3.30-3.40 (2H, m), 7.31
(2H, d, J ) 8.4 Hz), 7.82 (2H, d, J ) 8.4 Hz).
Step 3: tert-Butyl 4-[4-(Methoxycarbonyl)benzyl]piperidine-
1-carboxylate (19). A mixture of 18 and 18′ (37.8 g) was dissolved
in MeOH/THF (1:1, 200 mL) and hydrogenated over 10% Pd/C
(water ∼50%, 7.56 g) at room temperature for 18 h. The catalyst
was removed by filtration, and the filtrate was concentrated in
vacuo. The residue was purified by column chromatography on
silica gel (hexane/EtOAc 1:0 to 4:1) to give a mixture of 19 and
tert-butyl 4-[4-(ethoxycarbonyl)benzyl]piperidine-1-carboxylate (19′)
N-Methyl-4-(piperidin-4-ylmethyl)benzamide Hydrochloride
(22b). Compound 22b was prepared by a method similar to that
1
described for 22a from 21b. Yield quant., mp 218-221 °C. H
NMR (CD3OD) δ 1.30-1.60 (2H, m), 1.82-2.00 (3H, m), 2.68
(2H, d, J ) 7.0 Hz), 2.88-2.99 (2H, m), 2.91 (3H, s), 3.29-3.39
(2H, m), 7.30 (2H, d, J ) 8.4 Hz), 7.76 (2H, d, J ) 8.4 Hz).
N-(tert-Butyl)-4-(piperidin-4-ylmethyl)benzamide Hydrochlo-
ride (22c). Compound 22c was prepared by a method similar to
that described for 22a from 21c. Yield quant., mp 220-224 °C.
1H NMR (CD3OD) δ 1.32-1.45 (2H, m), 1.45 (9H, s), 1.82-2.00
(3H, m), 2.67 (2H, d, J ) 7.0 Hz), 2.86-3.00 (2H, m), 3.29-3.39
(2H, m), 7.27 (2H, d, J ) 8.0 Hz), 7.69 (2H, d, J ) 8.0 Hz).
N,N-Dimethyl-4-(piperidin-4-ylmethyl)benzamide (22d). To
a stirred solution of 21d (367 mg, 1.06 mmol) in MeOH (10 mL)
was added 4 N HCl (EtOAc solution, 20 mL), and the mixture
was stirred at room temperature for 3 h. The mixture was
concentrated in vacuo, and the residue was diluted with water (20
mL) and basified with 1 N aqueous NaOH (5 mL) at 0 °C. The
aqueous layer was treated with brine (20 mL) and extracted with
DCM (3 × 20 mL). The organic layer was dried (K2CO3), filtered,
and concentrated in vacuo to give 22d (88 mg, 34%) as an
1
(39.0 g, quant.) as a colorless oil. H NMR (CDCl3) δ 1.05-1.42
(2H, m), 1.45 (9H, s), 1.55-1.77 (3H, m), 2.59 (2H, d, J ) 7.0
Hz), 2.57-2.69 (2H, m), 3.91 (3H, s), 4.04-4.18 (2H, m), 7.21
(2H, d, J ) 8.0 Hz), 7.96 (2H, d, J ) 8.0 Hz).
Step 4: 4-{[1-(tert-Butoxycarbonyl)piperidin-4-yl]methyl}-
benzoic Acid (20). To a solution of a mixture of 19 and 19′ (38.9
g) in EtOH (175 mL) was added 1 N aqueous NaOH (175 mL),
and the mixture was stirred at 80 °C for 8 h. The mixture was
concentrated in vacuo, and the residue was diluted with DCM (300
mL) and acidified with 1 N aqueous HCl (210 mL) at 0 °C. The
organic layer was separated, and the aqueous layer was extracted
with DCM (100 mL). The combined organic layer was dried
(MgSO4), filtered, and concentrated in vacuo. The residue was
triturated with i-Pr2O/hexane, collected by filtration, and dried in
vacuo to give 20 (33.8 g, 91%) as a white solid, mp 165-167 °C.
1H NMR (CDCl3) δ 1.08-1.26 (2H, m), 1.45 (9H, s), 1.57-1.77
(3H, m), 1.26-2.70 (2H, m), 2.61 (2H, d, J ) 7.4 Hz), 4.05-4.11
(2H, m), 7.24 (2H, d, J ) 8.0 Hz), 8.03 (2H, d, J ) 8.0 Hz).
tert-Butyl 4-(4-Carbamoylbenzyl)piperidine-1-carboxylate (21a).
To an ice-cooled stirred mixture of 20 (33.73 g, 106 mmol), HOBt‚
H2O (16.17 g, 106 mmol), and ammonium chloride (7.34 g, 137
mmol) in DMF (200 mL) was added Et3N (19.1 mL, 137 mmol)
followed by EDC (26.32 g, 137 mmol), and the mixture was stirred
at room temperature for 20 h. The mixture was diluted with water
(800 mL) and extracted with EtOAc (3 × 200 mL). The organic
layer was washed with 1 N aqueous HCl (2 × 100 mL) followed
by saturated aqueous NaHCO3 (3 × 100 mL) and brine (100 mL),
dried (MgSO4), filtered, and concentrated in vacuo. The residue
was purified by column chromatography on silica gel (hexane/
EtOAc 1:1 to 0:1) followed by trituration with i-Pr2O to give 21a
(30.52 g, 91%) as a white solid, mp 144-145 °C. 1H NMR (CDCl3)
δ 1.05-1.25 (2H, m), 1.45 (9H, s), 1.56-1.76 (3H, m), 2.59 (2H,
d, J ) 2.0 Hz), 2.57-2.69 (2H, m), 4.04-4.10 (2H, m), 5.50-
6.20 (2H, m), 7.22 (2H, d, J ) 8.4 Hz), 7.74 (2H, d, J ) 8.4 Hz).
tert-Butyl 4-[4-(Methylcarbamoyl)benzyl]piperidine-1-car-
boxylate (21b). Compound 21b was prepared by a method similar
to that described for 21a from methylamine hydrochloride. Yield
1
amorphous solid. H NMR (CDCl3) δ 1.09-1.26 (2H, m), 1.59-
1.65 (3H, m), 1.80-2.00 (1H, m), 2.49-2.60 (4H, m), 3.01-3.09
(8H, m), 7.16 (2H, d, J ) 8.0 Hz), 7.34 (2H, d, J ) 8.0 Hz).
Methyl 4-(Piperidin-4-ylmethyl)benzoate (23). A mixture of
the free base of 22a (2.18 g, 10 mmol) and concentrated sulfuric
acid (1.1 mL) in MeOH (20 mL) was stirred at reflux for 20 h.
The mixture was concentrated in vacuo, and the residue was diluted
with saturated aqueous NaHCO3 (100 mL) and extracted with DCM
(40 mL, 4 × 20 mL). The organic layer was dried (Na2SO4), filtered,
and concentrated in vacuo to give 23 (2.28 g, 98%) as a colorless
1
oil. H NMR (CDCl3) δ 1.10-1.35 (2H, m), 1.55-1.80 (3H, m),
2.45-2.70 (4H, m), 2.95-3.20 (2H, m), 3.90 (3H, s), 7.21 (2H, d,
J ) 8.5 Hz), 7.95 (2H, d, J ) 8.5 Hz).
tert-Butyl 4-(2-Cyanobenzylidene)piperidine-1-carboxylate
(25a). Step 1: Diethyl (2-Cyanobenzyl)phosphonate. A mixture
of 2-(bromomethyl)benzonitrile (24a) (24.0 g, 122 mmol) and
triethyl phosphite (25.1 mL, 146 mmol) was stirred at 150 °C for
20 h. The mixture was purified by vacuum distillation to give the
product (29.4 g, 95%) as a colorless oil, bp 160-170 °C/1.4 Torr.
1H NMR (CDCl3) δ 1.28 (6H, t, J ) 7.0 Hz), 3.41 (2H, d, J )
22.2 Hz), 4.10 (4H, qd, J ) 7.0, 8.0 Hz), 7.30-7.45 (1H, m), 7.50-
7.60 (2H, m), 7.66 (1H, d, J ) 7.6 Hz).
Step 2: tert-Butyl 4-(2-Cyanobenzylidene)piperidine-1-car-
boxylate (25a). To an ice-cooled stirred solution of compound from
step 1 (27.4 g, 108 mmol) and 15-crown-5 (0.54 mL, 2.7 mmol) in
THF (180 mL) was added NaH (60% in oil, 4.32 g, 108 mmol),
and the mixture was stirred at room temperature for 30 min. To
the mixture was added a solution of tert-butyl 4-oxopiperidine-1-
carboxylate (17.9 g, 90 mmol) in THF (90 mL) dropwise over 10
1
86%, mp 148-150 °C. H NMR (CDCl3) δ 1.04-1.25 (2H, m),
1.45 (9H, s), 1.56-1.79 (3H, m), 2.57 (2H, d, J ) 6.6 Hz), 2.63-
2.69 (2H, m), 3.01 (3H, d, J ) 4.8 Hz), 4.04-4.10 (2H, m), 6.14
(1H, br s), 7.19 (2H, d, J ) 8.0 Hz), 7.68 (2H, d, J ) 8.0 Hz).
tert-Butyl 4-[4-(tert-Butylcarbamoyl)benzyl]piperidine-1-car-
boxylate (21c). Compound 21c was prepared by a method similar
to that described for 21a from tert-butylamine. Yield 89%, mp 168-

2792 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9
Imamura et al.
1
min at 0 °C, and the mixture was stirred at room temperature for
5 h. The mixture was diluted with water (180 mL) at 0 °C and
extracted with EtOAc (2 × 180 mL). The organic layer was washed
with 1 N aqueous NaOH (3 × 30 mL) followed by brine (30 mL),
dried (MgSO4), filtered, and concentrated in vacuo. The residue
was triturated with i-Pr2O, collected by filtration, and dried in vacuo
27b (472 mg, 56%) as a white solid, mp 222-225 °C. H NMR
(CD3OD) δ 1.30-1.60 (2H, m), 1.75-2.10 (3H, m), 2.69 (2H, d,
J ) 7.0 Hz), 2.94 (2H, dt, J ) 2.9, 12.9 Hz), 3.25-3.45 (2H, m),
7.35-7.45 (2H, m), 7.65-7.80 (2H, m).
4-(Piperidin-4-ylmethyl)benzonitrile Hydrochloride (28). To
a stirred solution of 26c (32.0 g, 107 mmol) in EtOAc (50 mL)
was added 4 N HCl (EtOAc solution, 50 mL), and the mixture
was stirred at room temperature for 2 h. The mixture was
concentrated in vacuo, and the residue was triturated with EtOAc,
collected by filtration, washed with EtOAc, and dried in vacuo to
give 28 (20.4 g, 81%) as a white solid, mp 196-198 °C. 1H NMR
(CD3OD) δ 1.35-1.55 (2H, m), 1.75-2.05 (3H, m), 2.71 (2H, d,
J ) 7.1 Hz), 2.93 (2H, dt, J ) 3.0, 13.1 Hz), 3.30-3.40 (2H, m),
7.40 (2H, d, J ) 8.1 Hz), 7.67 (2H, d, J ) 8.1 Hz).
Receptor Binding Assays. CHO-K1 and CCR5-expressing CHO
cells14 were incubated with various concentrations of test com-
pounds in binding buffer (Ham’s F-12 medium containing 20 mM
HEPES and 0.5% bovine serum albumin, pH 7.2) containing 200
pM 125I-labeled RANTES. Binding reactions were performed at
room temperature for 40 min. The binding reactions were terminated
by washing out the free ligand with cold phosphate-buffered saline,
and the cell-associated radioactivity was counted by a TopCount
scintillation counter (Packard). Binding assays for other chemokine
receptors were carried out in a similar manner using the following
ligands: RANTES for CCR1, monocyte chemoattractant protein 1
for CCR2b, eotaxin for CCR3, thymus- and activation-regulated
chemokine for CCR4, and MIP-3â for CCR7.
HIV-1 Envelope-mediated Membrane Fusion Assay. COS-7
cells were maintained in Dulbecco’s modified Eagle medium
(D-MEM) supplemented with 10% fetal bovine serum (FBS), 100
U/mL penicillin G, and 100 µg/mL streptomycin. MOLT-4/CCR5/
Luc+ cells, a lymphoblastoid cell line that expresses human CCR5
and that has an integrated copy of the HIV-1 long terminal repeat-
driven luciferase reporter gene, were maintained in RPMI 1640
medium supplemented with 10% FBS, 100 U/mL penicillin G, 100
µg/mL streptomycin, and 500 µg/mL Geneticin. Tat, Rev, and
envelope cDNA were amplified from total RNA of R5 HIV-1 (JR-
FL)-infected cells and cloned into an expression vector for
mammalian cells. Those expression vectors were mixed at a ratio
of 5:1:3 and cotransfected into COS-7 cells using Lipofectamine
2000 (Invitrogen). After a 2-day incubation, transfected COS-7 cells
and MOLT-4/CCR5/Luc+ cells were seeded in a 96-well plate at
104 cells in each well, and various concentrations of test compounds
were added to the wells. The cell suspension was incubated at 37
°C. The mixture of D-MEM and RPMI 1640 medium supplemented
with 10% FBS, 100 U/mL penicillin G, and 100 µg/mL strepto-
mycin was used as a medium for the membrane fusion. After an
overnight incubation, Luc-Screen (Tropix) was added to each well,
and the mixtures were incubated at room temperature for 10 min.
The luciferase activity was measured with a luminometer (Wallac
1420 ARVOsx).
Metabolic Stability Assay. Human hepatic microsomes were
purchased from Xenotech, LLC (Lenexa, KS). An incubation
mixture with a final volume of 0.1 mL consisted of microsomal
protein in 50 mmol/L KH2PO4-K2HPO4 phosphate buffer (pH 7.4)
and 0.5 µmol/L test compound. The concentration of hepatic
microsomal protein was 0.4 mg/mL. An NADPH-generating system
containing 50 mmol/L MgCl2, 50 mmol/L glucose-6-phosphate, 5
mmol/L beta-NADP+ and 15 unit/mL glucose-6-phosphate dehy-
drogenase was prepared and added to the incubation mixture with
a 10% volume of the reaction mixture. After the addition of the
NADPH-generating system, the mixture was incubated at 37 °C
for 0 and 20 min. The reaction was terminated by the addition of
acetonitrile equivalent to the volume of the reaction mixture. All
incubations were made in triplicate.
1
to give 25a (21.7 g, 81%) as a white solid, mp 109-111 °C. H
NMR (CDCl3) δ 1.48 (9H, s), 2.25-2.50 (4H, m), 3.44 (2H, t, J
) 5.8 Hz), 3.55 (2H, t, J ) 5.8 Hz), 6.50 (1H, s), 7.20-7.40 (2H,
m), 7.45-7.60 (1H, m), 7.60-7.70 (1H, m).
tert-Butyl 4-(3-Cyanobenzylidene)piperidine-1-carboxylate
(25b). Compound 25b was prepared by a method similar to that
described for 25a from 3-(bromomethyl)benzonitrile (24b). Mp 87-
88 °C. 1H NMR (CDCl3) δ 1.48 (9H, s), 2.25-2.50 (4H, m), 3.42
(2H, t, J ) 5.8 Hz), 3.52 (2H, t, J ) 5.8 Hz), 6.32 (1H, s), 7.35-
7.55 (4H, m).
tert-Butyl 4-(4-Cyanobenzylidene)piperidine-1-carboxylate
(25c). Compound 25c was prepared by a method similar to that
described for 25a from 4-(bromomethyl)benzonitrile (24c). 1H NMR
(CDCl3) δ 1.48 (9H, s), 2.36 (2H, t, J ) 5.8 Hz), 2.44 (2H, t, J )
5.8 Hz), 3.42 (2H, t, J ) 5.8 Hz), 3.53 (2H, t, J ) 5.8 Hz), 6.36
(1H, s), 7.28 (2H, d, J ) 8.3 Hz), 7.61 (2H, d, J ) 8.3 Hz).
tert-Butyl 4-(2-Cyanobenzyl)piperidine-1-carboxylate (26a).
Compound 25a (2.98 g, 10 mmol) was dissolved in MeOH/THF
(1:1, 20 mL), and hydrogenated over 10% Pd/C (water ∼50%, 596
mg) at room temperature for 1 h. The catalyst was removed by
filtration, and the filtrate was concentrated in vacuo. The residue
was purified by column chromatography on silica gel (hexane/
EtOAc 9:1 to 2:1) followed by trituration with hexane to give 26a
1
(2.50 g, 83%) as a white solid, mp 71-73 °C. H NMR (CDCl3)
δ 1.05-1.42 (2H, m), 1.45 (9H, s), 1.55-1.77 (3H, m), 2.59 (2H,
d, J ) 7.0 Hz), 2.57-2.69 (2H, m), 3.91 (3H, s), 4.04-4.18 (2H,
m), 7.21 (2H, d, J ) 8.0 Hz), 7.96 (2H, d, J ) 8.0 Hz).
tert-Butyl 4-(3-Cyanobenzyl)piperidine-1-carboxylate (26b).
Compound 26b was prepared by a method similar to that described
1
for 26a from 25b. Yield 35%, mp 95-97 °C (i-Pr2O/hexane). H
NMR (CDCl3) δ 1.00-1.30 (2H, m), 1.40-1.80 (3H, m), 1.45 (9H,
s), 2.50-2.75 (2H, m), 2.58 (2H, d, J ) 6.8 Hz), 3.95-4.20 (2H,
m), 7.30-7.60 (4H, m).
tert-Butyl 4-(4-Cyanobenzyl)piperidine-1-carboxylate (26c).
Compound 26c was prepared by a method similar to that described
for 26a from 25c. Yield 70%. 1H NMR (CDCl3) δ 1.00-1.85 (5H,
m), 1.45 (9H, s), 2.50-2.80 (2H, m), 2.60 (2H, d, J ) 7.2 Hz),
3.95-4.25 (2H, m), 7.24 (2H, d, J ) 7.8 Hz), 7.58 (2H, d, J ) 7.8
Hz).
2-(Piperidin-4-ylmethyl)benzamide Hydrochloride (27a). Step
1: tert-Butyl 4-(2-Carbamoylbenzyl)piperidine-1-carboxylate.
To a mixture of 26a (984 mg, 3.3 mmol) and 8 N aqueous NaOH
(412 µL, 3.3 mmol) in EtOH (5 mL) was added 30% H2O2 (2 mL),
and the mixture was stirred at 50 °C for 6 h. To the mixture was
added 30% H2O2 (10 mL), and the mixture was stirred at 50 °C
for an additional 6 h. The mixture was concentrated in vacuo,
diluted with water, and extracted with DCM. The organic layer
was dried (Na2SO4), filtered, and concentrated in vacuo. The residue
was purified by column chromatography on silica gel (hexane/
EtOAc 1:1 to 0:1) followed by recrystallization from i-Pr2O to give
1
the product (571 mg, 55%) as a white solid, mp 125-127 °C. H
NMR (CDCl3) δ 1.00-1.30 (2H, m), 1.43 (9H, s), 1.50-1.90 (3H,
m), 2.45-2.70 (2H, m), 2.77 (2H, d, J ) 7.0 Hz), 3.90-4.15 (2H,
m), 6.13 (1H, br s), 6.30 (1H, br s), 7.10-7.50 (4H, m).
Step 2: 2-(Piperidin-4-ylmethyl)benzamide Hydrochloride
(27a). Compound 27a was prepared by a method similar to that
described for 22a using the product from step 1. Yield quant.,
amorphous solid. 1H NMR (CD3OD) δ 1.30-1.60 (2H, m), 1.75-
2.10 (3H, m), 2.75-3.00 (2H, m), 2.82 (2H, d, J ) 7.0 Hz), 3.25-
3.45 (2H, m), 7.20-7.50 (4H, m).
Test compound in the reaction mixture was measured by LC/
MS. The HPLC system consisted of an Agilent 1100 series (Agilent
Technologies, Inc.) equipped with a degasser, a high-pressure binary
gradient pump, an autosampler, and a thermostated column
compartment. The column was Cadenza CD-C18 (30 × 2 mm I.D.;
Imtakt Co. Ltd., Kyoto, Japan). The column temperature and the
3-(Piperidin-4-ylmethyl)benzamide Hydrochloride (27b). A
mixture of 26b (1000 mg, 3.3 mmol) and concentrated hydrochloric
acid (5 mL) was stirred at 70 °C for 3 h. The mixture was
concentrated in vacuo, treated with MeOH (10 mL), and concen-
trated again. The residue was recrystallized from i-PrOH to give

Piperidine-4-carboxamide CCR5 Antagonist
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 9 2793
T.; Rana, S.; Yi, Y.; Smyth, R. J.; Collman, R. G.; Doms, R. W.;
Vassart, G.; Parmentier, M. Resistance to HIV-1 infection in
Caucasian individuals bearing mutant alleles of the CCR-5 chemokine
receptor gene. Nature 1996, 382, 722-725.
flow-rate were 40 °C and 0.2 mL/min, respectively. The mobile
phase consisted of 0.01 mol/L ammonium formate-formic acid
(1000:2, v/v) and acetonitrile. The time program for the gradient
elution was as follows: the concentration of acetonitrile was 10%
for 0.1 min, followed by a linear increase from 10% to 90% over
0.1 min, held at 90% until 3 min, and then the column was
equilibrated at 10% for 4 min. The column effluent was analyzed
using a LCQdeca mass spectrometer (Thermo Electron Corporation)
equipped with an electrospray ionization source. The ion source
was operated at 350 °C with the capillary voltage at 11 V. Nitrogen
was used as sheath gas (flow rate ) 80) and auxiliary gas (flow
rate ) 20). The protonated parent ion was monitored to produce
mass-extracted chromatogram, which was then integrated to
measure analyte response.
For metabolic stability determinations, chromatograms were
analyzed for parent compound disappearance from the reaction
mixtures. The parent compound peak area in the 0-min incubation
sample was considered to be the 100% value and parent compound
levels were expressed as percent (%) parent remaining.
Antiviral Assay, Cytotoxicity Assay, and Pharmacokinetic
Analysis in Monkeys. Procedures for these studies have been
reported previously.22
(10) Michael, N. L.; Chang, G.; Louie, L. G.; Mascola, J. R.; Dondero,
D.; Birx, D. L.; Sheppard, H. W. The role of viral phenotype and
CCR-5 gene defects in HIV-1 transmission and disease progression.
Nat. Med. 1997, 3, 338-340.
(11) Wood, A.; Armour, D. The Discovery of the CCR5 Receptor
Antagonist, UK-427,857, A New Agent for the Treatment of HIV
Infection and AIDS. Prog. Med. Chem. 2005, 43, 239-271.
(12) Tagat, J. R.; McCombie, S. W.; Nazareno, D.; Labroli, M. A.; Xiao,
Y.; Steensma, R. W.; Strizki, J. M.; Baroudy, B. M.; Cox, K.;
Lachowicz, J.; Varty, G.; Watkins, R. Piperazine-Based CCR5
Antagonists as HIV-1 Inhibitors. IV. Discovery of 1-[(4,6-Dimethyl-
5-pyrimidinyl)carbonyl]-4-[4-[2-methoxy-1(R)-4-(trifluoromethyl)-
phenyl]ethyl-3(S)-methyl-1-piperazinyl]-4-methylpiperidine (Sch-
417690/Sch-D), a Potent, Highly Selective, and Orally Bioavailable
CCR5 Antagonist. J. Med. Chem. 2004, 47, 2405-2408.
(13) Maeda, K.; Nakata, H.; Koh, Y.; Miyakawa, T.; Ogata, H.; Takaoka,
Y.; Shibayama, S.; Sagawa, K.; Fukushima, D.; Moravek, J.;
Koyanagi, Y.; Mitsuya, H. Spirodiketopiperazine-Based CCR5
Inhibitor Which Preserves CC-Chemokine/CCR5 Interactions and
Exerts Potent Activity against R5 Human Immunodeficiency Virus
Type 1 In Vitro. J. Virol. 2004, 78, 8654-8662.
(14) Baba, M.; Nishimura, O.; Kanzaki, N.; Okamoto, M.; Sawada, H.;
Iizawa, Y.; Shiraishi, M.; Aramaki, Y.; Okonogi, K.; Ogawa, Y.;
Meguro, K.; Fujino, M. A small-molecule, nonpeptide CCR5
antagonist with highly potent and selective anti-HIV-1 activity. Proc.
Natl. Acad. Sci. U.S.A. 1999, 96, 5698-5703.
(15) Shiraishi, M.; Aramaki, Y.; Seto, M.; Imoto, H.; Nishikawa, Y.;
Kanzaki, N.; Okamoto, M.; Sawada, H.; Nishimura, O.; Baba, M.;
Fujino, M. Discovery of Novel, Potent, and Selective Small-Molecule
CCR5 Antagonists as Anti-HIV-1 Agents: Synthesis and Biological
Evaluation of Anilide Derivatives with a Quaternary Ammonium
Moiety. J. Med. Chem. 2000, 43, 2049-2063.
(16) Imamura, S.; Ishihara, Y.; Hattori, T.; Kurasawa, O.; Matsushita,
Y.; Sugihara, Y.; Kanzaki, N.; Iizawa, Y.; Baba, M.; Hashiguchi, S.
CCR5 Antagonists as Anti-HIV-1 Agents. 1. Synthesis and Biological
Evaluation of 5-Oxopyrrolidine-3-carboxamide Derivatives. Chem.
Pharm. Bull. 2004, 52, 63-73.
(17) Imamura, S.; Nishikawa, Y.; Ichikawa, T.; Hattori, T.; Matsushita,
Y.; Hashiguchi, S.; Kanzaki, N.; Iizawa, Y.; Baba, M.; Sugihara, Y.
CCR5 antagonists as anti-HIV-1 agents. Part 3: Synthesis and
biological evaluation of piperidine-4-carboxamide derivatives. Bioorg.
Med. Chem. 2005, 13, 397-416.
Acknowledgment. We would like to thank Ms. Yoshi Nara
for synthetic assistance, Mr. Kenichi Kuroshima for the receptor
binding assay, Dr. Hiroshi Miyake and Ms. Shikiko Shiki for
the membrane fusion assay, Mr. Masashi Yamaguchi, Mr.
Shinichi Matsumoto, and Dr. Yoshihiko Tagawa for pharma-
cokinetic analysis.
Supporting Information Available: Elemental analysis data.
This material is available free of charge via the Internet at http://
pubs.acs.org.
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