CCR5 antagonists as anti-HIV-1 agents. Part 2: Synthesis and biological evaluation of N-[3-(4-benzylpiperidin-1-yl)propyl]-N,N′- diphenylureas

Article abstract of DOI:10.1016/j.bmc.2004.02.004

We have previously reported the novel lead compound 1a as a CCR5 antagonist for treatment of HIV-1 infection. SAR studies on incorporating various acyl groups as a replacement for the 5-oxopyrrolidine-3-carbonyl group of the lead structure resulted in the

Full text of DOI:10.1016/j.bmc.2004.02.004

Bioorganic & Medicinal Chemistry 12 (2004) 2295–2306
CCR5 antagonists as anti-HIV-1 agents. Part 2: Synthesis and
biological evaluation of N-[3-(4-benzylpiperidin-1-yl)propyl]-N,N0-
diphenylureas
Shinichi Imamura,a,* Osamu Kurasawa,a Yoshi Nara,a Takashi Ichikawa,a
Youichi Nishikawa,a Takehiro Iida,a Shohei Hashiguchi,a Naoyuki Kanzaki,a
Yuji Iizawa,a Masanori Babab and Yoshihiro Sugiharaa
aPharmaceutical Research Division, Takeda Chemical Industries, Ltd., 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686, Japan
bDivision of Antiviral Chemotherapy, Center for Chronic Viral Diseases, Faculty of Medicine, Kagoshima University,
8-35-1, Sakuragaoka, Kagoshima 890-8520, Japan
Received 9 January 2004; revised 4 February 2004; accepted 5 February 2004
Abstract—We have previously reported the novel lead compound 1a as a CCR5 antagonist for treatment of HIV-1 infection. SAR
studies on incorporating various acyl groups as a replacement for the 5-oxopyrrolidine-3-carbonyl group of the lead structure
resulted in the discovery of N-[3-(4-benzylpiperidin-1-yl)propyl]-N,N0-diphenylurea (4a) with significantly improved CCR5 binding
affinity. Substitutions (4-Cl, 4e,f; 4-Me, 4i) on the N0-phenyl ring further increased the binding affinity. Introduction of polar
substituents on the phenyl ring of the 4-benzylpiperidine moiety enhanced the inhibitory activity of the HIV-1 envelope-mediated
membrane fusion (4v,w), suggesting that polar substituents at this position can interfere effectively with HIV-1 cell entry.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
stage of the infection, which usually persists 5–10 years.3
CCR5 is a member of the seven-transmembrane G
protein-coupled receptor superfamily, and its natural
ligands include the CC chemokines [regulated on acti-
vation, normal T cell expressed and secreted (RAN-
TES), macrophage inflammatory protein 1a (MIP-1a),
and MIP-1b], which have been reported to inhibit R5
HIV-1 infection in vitro.4 Individuals homozygous for a
defect in CCR5 expression are highly resistant to HIV-1
infection, while this defect does not represent a signifi-
cant health problem.5–7 In addition, infected individuals
heterozygous for the defective CCR5 gene appear to
have delayed disease progression.8 These observations
suggest that CCR5 antagonists functioning as HIV-1
entry inhibitors could be promising anti-HIV-1 thera-
peutic agents.
Treatment with highly active antiretroviral therapy
(HAART) has successfully suppressed viral replication,
recovered immune function, and improved quality of life
in human immunodeficiency virus type 1 (HIV-1)-
infected individuals. However, the effectiveness of cur-
rently available HAART is limited by the development
of viral resistance as well as the toxicity and complexity
of drug regimens. Therefore, there remains a need to
develop new anti-HIV-1 drugs with improved efficacy
and less toxicity.
The discovery of chemokine receptors as HIV-1 co-
receptors has provided a greater understanding of how
HIV-1 enters human cells and has led to a novel
approach for controlling HIV-1.1 HIV-1 strains that
cause the initial infection predominantly utilize CC
chemokine receptor 5 (CCR5),2 and CCR5-using (R5)
HIV-1 is isolated exclusively during the asymptomatic
Our laboratories have previously described the discov-
ery of TAK-779 as the first small-molecule CCR5
antagonist,9;10 and thereafter, several research groups
reported structurally diverse CCR5 antagonists.11–15 We
also continued the screening of our compound libraries
using a CCR5–RANTES binding assay and identified a
novel lead compound 1a (Fig. 1). Subsequent optimi-
zation of 1a resulted in compounds with improved
Keywords: CCR5 antagonist; Chemokine; HIV-1; N,N0-Diphenylurea.
* Corresponding author. Tel.: +81-6-6300-6651; fax: +81-6-6300-6306;
e-mail: imamura_shin-ichi@takeda.co.jp
0968-0896/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2004.02.004

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S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
5-Oxopyrrolidine-3-carboxamide Type
N,N'-Diphenylurea Type
R1
O
O
R3
R3
N
N
N
H
N
N
O
N
X
R2
R2
1a-c
Me
4a,e-w
CCR5
IC50 (nM)
R2
X
R3
H
H
CO
CH2
F
H
H
1900
480
57
1a
1b
1c
3,4-diCl CH2
Figure 1.
binding potency (e.g., 1c).16 As part of an effort to
identify compounds with further improved potency, we
incorporated various acyl groups as a replacement for
the 5-oxopyrrolidine-3-carbonyl group in the original
lead structure. In this paper, we describe the synthesis
and structure-activity relationships (SAR) of N-[3-(4-
benzylpiperidin-1-yl)propyl]-N,N0-diphenylureas, which
have led to a potent series of novel CCR5 antagonists.
O
a
b
N
N
N
N
N
3a
3a
Me
5
O
( )n
6a: n = 0
6b: n = 1
6c: n = 2
2. Chemistry
O
Target compounds were synthesized as outlined in
Schemes 1 and 2. Treatment of 4-benzylpiperidines 2a,b,
11, 15 with acrolein in tetrahydrofuran (THF) in the
presence of a catalytic amount of 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU) provided b-aminoaldehy-
des in situ,17 which were subjected to reductive
amination with substituted anilines using sodium tri-
acetoxyborohydride to afford anilines 3a–g (Scheme 1).
The anilines 3c,d were also prepared by coupling of
4-benzylpiperidines 11, 15 with N-(3-chloropropyl)ani-
line hydrochloride in the presence of potassium iodide
and potassium carbonate. Reaction of 3a–g with a
variety of isocyanates furnished urea derivatives
c
O
N
N
3a
7
Scheme 2. Reagents: (a) NaH, THF, then PhN(Me)COCl; (b)
Ph(CH2)nCOCl, Et3N, DCM; (c) PhCH2OCOCl, aq NaOH, THF.
4a–m,p,q,s–w. The ester group in 4m was hydrolyzed to
give carboxylic acid 4n, which was converted to car-
boxamide 4o. Methylsulfonyl derivative 4r was obtained
by oxidation of 4q with Oxone.18
O
R3
R
R3
R3
c
a
HN
N
N
H
N
N
HN
b (for 11, 15)
R2
R2
2a: R3 = H
2b: R3 = F
3a: R2 = H; R3 = H
4a-m,p,q,s-w
11: R3 = SO2Me
3b: R2 = H; R3 = F
15: R3 = SO2(morpholino)
3c: R2 = H; R3 = SO2Me
4m: R = 4-(EtOCO)-Ph
4n: R = 4-(HOCO)-Ph
4o: R = 4-(H2NCO)-Ph
d
e
3d: R2 = H; R3 = SO2(morpholino)
3e: R2 = 4-Me; R3 = H
3f: R2 = 3-Cl; R3 = H
3g: R2 = 3,4-diCl; R3 = H
4q: R = 4-(MeS)-Ph
4r: R = 4-(MeSO2)-Ph
f
Scheme 1. Reagents: (a) acrolein, cat. DBU, THF, then R2-PhNH2, NaBH(OAc)3; (b) N-(3-chloropropyl)aniline hydrochloride, KI, K2CO3, MeCN,
DMF; (c) R-NCO, Et3N, DCM; (d) aq NaOH, EtOH; (e) NH4Cl, Et3N, EDC, HOBt, DMF, (f) Oxone, aq H2SO4, MeOH.

S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
2297
3. Results and discussion
O
O
R
Ac
S
b (for 8)
N
N
Cl
The compounds prepared were evaluated for their
potency to inhibit binding of 125I-labeled RANTES to
Chinese hamster ovary (CHO) cells expressing human
CCR5, and the results are reported as IC50 values. Se-
lected compounds were further tested in an HIV-1
envelope-mediated membrane fusion assay to assess the
activities for inhibition of HIV-1 cell entry. The mem-
brane 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 similarly as IC50 values.
2a: R = H
8: R = Ac
9
a
O
O
R
S
c
N
d
Me
10: R = Ac
11: R = H
Scheme 3. Reagents: (a) Ac2O; (b) ClSO3H, DCM; (c) Na2SO3,
NaHCO3, H2O, then ClCH2CO2H, aq NaOH; (d) concd HCl, then aq
NaOH.
We have previously reported the identification of the
novel lead compound 1a (IC50 ¼ 1900 nM) as a CCR5
antagonist (Fig. 1). Subsequent optimization, focused
on a series of 5-oxopyrrolidine-3-carboxamides, resulted
in compounds with increased binding affinity (e.g., 1c,
IC50 ¼ 57 nM). To identify more potent compounds, our
focus was directed toward replacement of the 5-oxo-
pyrrolidine moiety in the lead structure.
N-Methyl analogue 5 was prepared from the free base of
3a by deprotonation with sodium hydride followed by
treatment with N-methyl-N-phenylcarbamoyl chloride
(Scheme 2). Coupling reaction of the aniline 3a with the
appropriate acyl chloride afforded the amide derivatives
6a–c. Carbamate derivative 7 was obtained by the
reaction of 3a with benzyl chloroformate.
We first replaced the 5-oxopyrrolidine moiety in 1b
(IC50 ¼ 480 nM) with a phenyl group to obtain com-
pound 6a, which resulted in a 5-fold reduction in bind-
ing affinity (Table 1). Extension of the phenyl as a benzyl
(6b) restored binding affinity comparable to 1b, but
further elongation did not improve the activity (6c).
More promising results were obtained with urea deriv-
atives, where replacement of the benzyl in 6b with a
phenylamino group afforded compound 4a with signifi-
cant improvement in binding affinity (IC50 ¼ 18 nM).
The marked enhancement in binding affinity of com-
pound 4a prompted us to explore the SAR of this class.
Benzylamino derivative 4b showed lower potency than
The preparation of the required piperidines 11 and 15 is
presented in Schemes 3 and 4, respectively. The amino
group of 2a was protected by acetylation affording 8,
which was treated with chlorosulfonic acid to give sul-
fonyl chloride 9 (Scheme 3). Conversion of 9 into sul-
fone 10 was accomplished by reduction of the
chlorosulfonyl group, alkylation of the intermediate
sulfinate with 2-chloroacetic acid, and decarboxyl-
ation.19 Deprotection of the acetyl group in 10 using
concentrated hydrochloric acid, followed by neutral-
ization, provided the desired piperidine 11. Sulfonamide
analogue 15 was prepared as follows (Scheme 4).
Reaction of 2a with trifluoroacetic anhydride followed
by chlorosulfonylation gave compound 13. Treatment
of 13 with morpholine provided sulfonamide 14, which
on deprotection using potassium carbonate yielded the
piperidine 15.
Table 1. Acyl modifications
O
R
N
N
Compound
R
CCR5a IC50 (nM)
O
O
O
O
R
S
1b
480
b (for 12)
N
a
F3C
N
Cl
N
Me
2a: R = H
13
4a
4b
4c
4d
5
PhNH
18
150
24
12: R = CF3CO
PhCH2NH
c-HexNH
n-PrNH
PhN(Me)
Ph
O
O
62
R
N
S
c
N
6600
2300
450
920
2000
6a
6b
6c
7
O
PhCH2
Ph(CH2)2
PhCH2O
14: R = CF3CO
15: R = H
d
Scheme 4. Reagents: (a) TFAA; (b) ClSO3H, DCM; (c) morpholine,
Et3N, THF; (d) K2CO3, H2O, MeOH.
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing
CHO cells.

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S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
4a, indicating the phenylamino substituent was optimal
for CCR5 binding. N-Methylation of 4a resulted in a
substantial loss of potency (5), suggesting that a
hydrogen donor NH group was critical for binding or
the methyl group was not sterically tolerated. It has been
reported that N-methylation of N,N0-diphenylurea cau-
ses a conformational change, in which the phenyl ring is
located trans to the urea oxygen.20 The conformational
change might affect the binding affinity. The importance
of the NH group was also confirmed by carbamate 7
showing >10-fold lower potency than the corresponding
urea 4b. Interestingly, the cyclohexyl analogue 4c also
had potent affinity comparable to 4a, while the propyl
analogue 4d had slightly lower potency than 4c. These
results suggested that the steric bulkiness of the acyl
moiety was preferable for potent binding affinity.
potent activity (IC50 ¼ 6.6 nM), but incorporation of a
bulky isopropyl group (4j) resulted in decreased binding
affinity, indicating this moiety may interact with a ste-
rically restricted pocket of the receptor. Other halogens
such as fluorine (4g) and bromine (4h) showed equiva-
lent potency to 4a, and the small polar cyano group (4l)
was also tolerated, but the bulky ethoxycarbonyl group
(4m) decreased potency. Carbamoyl (4o), methoxy (4p),
and methylsulfonyl (4r) derivatives exhibited compara-
ble affinity to 4a, suggesting that medium-size polar
groups are allowed at this position. The selectivity
profile of compound 4e for other chemokine receptors
was evaluated using a binding assay. The IC50 values for
CCR1, CCR2, CCR4, and CCR7 were all greater than
10 lM.
We next investigated substitution on the central phenyl
ring (R2). It has been demonstrated that appropriate
substitutions (e.g., 4-Me; 3-Cl; 3,4-diCl) on the central
phenyl enhanced activity in the 5-oxopyrrolidine-3-car-
boxamide series (Fig. 1, 1b vs 1c).16 In the N,N0-diphen-
ylurea series, on the contrary, the unsubstituted
derivative 4e showed more potent activity than the
4-methyl (4s), 3-chloro (4t), and 3,4-dichloro (4u)
derivatives (Table 2). The difference in SAR between the
two series might stem from their receptor binding
modes. Other substitutions (2-F, 3-F, 4-F, 2-MeO,
3-MeO, 4-MeO) on the central phenyl ring also failed to
increase the activity in the N,N0-diphenylurea derivatives
(data not shown).
Having identified the N,N0-diphenylurea group as criti-
cal for CCR5 binding affinity, we then searched for the
optimal substituent on the N0-phenyl ring (Table 2, R1).
Introduction of a chlorine atom at the 4-position of the
N0-phenyl ring of 4a resulted in about a 3-fold
improvement in the binding potency (4e, IC50 ¼ 5.9 nM).
The presence of a fluorine substituent in the 4-benz-
ylpiperidine moiety (R3 ¼ F) had little effect on CCR5
binding (4e vs 4f). Methyl analogue 4i also exhibited
Table 2. N,N0-diphenylurea derivatives
In the exploration of the 4-benzylpiperidine moiety (R3),
sulfonyl substituents were found to be effective for
increasing binding affinity. Introduction of a meth-
ylsulfonyl group at the 4-position of the benzyl showed
about a 5-fold improvement (4v, IC50 ¼ 1.2 nM) in the
CCR5 binding potency compared to the parent com-
pound 4e (IC50 ¼ 5.9 nM), and the sulfonamide analogue
4w also had potent affinity with an IC50 value of 1.0 nM.
R1
O
R3
N
H
N
N
R2
Com-
pound
R1
R2
R3
CCR5a
IC50
(nM)
Fusionb
IC50
(nM)
Selected compounds were evaluated in an HIV-1 enve-
lope-mediated membrane fusion assay (Table 2). For the
more potent CCR5 antagonists 4e and 4f, we observed a
good correlation between the inhibitory activity of
CCR5 binding and that of HIV-1 envelope-mediated
membrane fusion. Unexpected results were obtained in
the sulfone (4v) and sulfonamide (4w) derivatives, in
which the inhibitory activity of CCR5 binding did not
correlate with that of HIV-1 envelope-mediated mem-
brane fusion. As mentioned above, the IC50 values of
compounds 4v and 4w were about 5-fold lower than that
of compound 4e in the CCR5 binding assay. However,
in the HIV-1 envelope-mediated membrane fusion
assay, compound 4v showed an IC50 value of 0.59 nM,
which was about 16-fold lower than that of 4e
(IC50 ¼ 9.4 nM). Furthermore, sulfonamide analogue 4w
inhibited the membrane fusion with an IC50 value of
0.050 nM, which was about 180-fold lower than that of
4e. The discrepancy in the inhibitory activities for CCR5
binding and HIV-1 envelope-mediated membrane fusion
probably reflects the differences in the receptor binding
sites of the ligands (RANTES and effector cells
expressing HIV-1 envelope). These results suggested that
4a
4e
4f
H
Cl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
F
F
F
F
F
F
F
F
F
F
F
F
F
H
H
H
18
5.9
7.8
13
64
9.4
13
Cl
4g
4h
4i
F
Br
NT
NT
NT
NT
14
18
Me
6.6
76
4j
i-Pr
CF3
NC
EtOCO
HOCO
H2NCO
MeO
MeS
MeSO2
Cl
4k
4l
14
15
10
4m
4n
4o
4p
4q
4r
4s
4t
280
350
29
NT
NT
14
30
15
33
13
26
11
18
22
4-Me
3-Cl
3,4-diCl
H
Cl
Cl
19
62
52
61
4u
4v
4w
Cl
Cl
SO2Me
SO2(mor-
pholino)
1.2
1.0
0.59
0.050
H
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing
CHO cells.
b Inhibition of HIV-1 envelope-mediated membrane fusion.

S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
2299
polar substituents on the phenyl ring of the 4-benzyl-
piperidine moiety can interfere effectively with the HIV-
1 cell entry.
J ¼ 6:6 Hz), 2.85–3.00 (2H, m), 3.13 (2H, t, J ¼ 6:4 Hz),
6.51 (2H, d, J ¼ 8:4 Hz), 6.98 (2H, d, J ¼ 8:4 Hz), 7.10–
7.35 (5H, m). Treatment with 4 N HCl (EtOAc solution,
8 mL) in i-PrOH (20 mL) gave the HCl salt 3e (4.52 g,
1
57%) as a white solid, mp 186–192 ꢁC (dec). H NMR
(DMSO-d6) d 1.40–1.90 (5H, m), 2.00–2.25 (2H, m), 2.31
(3H, s), 2.45–2.60 (2H, m), 2.70–2.95 (2H, m), 2.95–3.55
(6H, m), 7.10–7.45 (9H, m). Anal. Calcd for
C22H30N2 Æ 2HCl Æ 0.5H2O: C, 65.34; H, 8.22; Cl,
17.53; N, 6.93. Found: C, 65.24; H, 8.38; Cl, 17.37; N,
6.98.
4. Conclusion
Replacement of the 5-oxopyrrolidine fragment in the
original structure (1b) with a phenylamino group gave
the N,N0-diphenylurea derivative 4a, which was found to
have significantly improved CCR5 binding affinity. SAR
studies of this series determined that the urea group is
essential for potent binding affinity. Substitutions on the
N0-phenyl ring revealed that small hydrophobic substit-
uents (Cl, 4e,f; Me, 4i) at the 4-position enhanced the
binding affinity. Sulfone (4v) and sulfonamide (4w)
derivatives showed more potent activity in HIV-1 enve-
lope-mediated membrane fusion assay than expected
from the activity in the CCR5 binding assay. This finding
suggests that the polar substituents play an important
role in inhibiting the HIV-1 entry process and will be
helpful in designing potent HIV-1 entry inhibitors.
The following compounds (3a,b,f,g) were prepared using
a procedure similar to that described for 3e from 2a,b
and the appropriate aniline.
5.2. N-[3-(4-Benzylpiperidin-1-yl)propyl]aniline dihydro-
chloride (3a)
1
Yield 47%, mp 215–217 ꢁC (dec). H NMR (DMSO-d6)
d 1.40–1.90 (5H, m), 2.00–2.25 (2H, m), 2.45–2.60 (2H,
m), 2.83 (2H, br t, J ¼ 11:4 Hz), 3.12 (2H, br t,
J ¼ 7:2 Hz), 3.29 (2H, br t, J ¼ 6:9 Hz), 3.41 (2H, br d,
J ¼ 12:6 Hz), 7.05–7.50 (10H, m). Anal. Calcd for
C21H28N2 Æ 2HCl Æ 0.5H2O: C, 64.61; H, 8.00; N, 7.18.
Found: C, 64.71; H, 7.92; N, 7.32.
5. Experimental
Reagents and solvents were used as obtained from
commercial suppliers without further purification. Col-
umn chromatography was carried out on silica gel (Da-
iso, IR-60-40/63-W), basic alumina (ICN Biomedicals,
activity III), or NH silica gel (Fuji Silysia, NH-DM1020).
Yields were not optimized. Melting points were deter-
mined 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 (d) are given in ppm with tetramethylsi-
lane as an internal standard, and coupling constants (J)
are given in hertz (Hz). Elemental analyses were
carried out by Takeda Analytical Research Labora-
tories, Ltd.
5.3. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}aniline
dihydrochloride (3b)
1
Yield 54%, mp 227–230 ꢁC (dec). H NMR (DMSO-d6)
d 1.35–1.90 (5H, m), 1.95–2.20 (2H, m), 2.45–2.60 (2H,
m), 2.83 (2H, br t, J ¼ 11:5 Hz), 3.11 (2H, br t,
J ¼ 7:4 Hz), 3.24 (2H, br t, J ¼ 6:8 Hz), 3.42 (2H, br d,
J ¼ 10:6 Hz), 6.90–7.20 (9H, m). Anal. Calcd for
C21H27FN2 Æ 2HClÆ 0.8 H2O: C, 60.96; H, 7.45; N, 6.77;
Cl, 17.14; F, 4.59. Found: C, 61.02; H, 7.37; N, 6.76; Cl,
17.04; F, 4.30.
5.4. N-[3-(4-Benzylpiperidin-1-yl)propyl]-3-chloroaniline
dihydrochloride (3f)
1
5.1. N-[3-(4-Benzylpiperidin-1-yl)propyl]-4-methylaniline
dihydrochloride (3e)
Yield 41%, mp 199–202 ꢁC (dec). H NMR (DMSO-d6)
d 1.53–2.01 (7H, m), 2.50–2.55 (2H, m), 2.66–2.92 (2H,
m), 3.08–3.20 (4H, m), 3.38–3.44 (2H, m), 6.61–6.69
(3H, m), 7.07–7.30 (6H, m). Anal. Calcd for
C21H27ClN2 Æ 2HCl Æ 0.1H2O: C, 60.39; H, 7.04; N, 6.71.
Found: C, 60.33; H, 6.93; N, 6.84.
To a stirred solution of 4-benzylpiperidine (2a) (3.51 g,
20 mmol) and DBU (30 lL, 0.2 mmol) in THF (40 mL)
was added dropwise a solution of acrolein (90%,
1.49 mL, 20 mmol) in THF (5 mL) at )20 ꢁC, and the
mixture was stirred at )20 to )10 ꢁC for 1 h. The mix-
ture was treated with p-toluidine (2.14 g, 20 mmol) fol-
lowed by NaBH(OAc)3 (8.48 g, 40 mmol) at )10 ꢁC, and
allowed to warm to room temperature. After 23 h, the
mixture was diluted with aqueous NaHCO3 and
extracted with EtOAc. The organic layer was dried
(MgSO4), filtered, and concentrated in vacuo. The resi-
due was purified by column chromatography on silica
gel (EtOAc/MeOH 1:0 to 4:1) to afford the free base of
3e (4.07 g) as an oil. 1H NMR (CDCl3) d 1.15–1.95 (9H,
s), 2.23 (3H, s), 2.42 (2H, t, J ¼ 6:8 Hz), 2.55 (2H, d,
5.5. N-[3-(4-Benzylpiperidin-1-yl)propyl]-3,4-dichloro-
aniline dihydrochloride (3g)
1
Yield 53%, mp 200–203 ꢁC (dec). H NMR (DMSO-d6)
d 1.49–1.76 (5H, m), 1.91–1.96 (2H, m), 2.50–2.55 (2H,
m), 2.79–3.17 (6H, m), 3.38–3.44 (2H, m), 6.68 (1H, dd,
J ¼ 2:8, 8.8 Hz), 6.75 (1H, d, J ¼ 2:6 Hz), 7.17–7.30
(6H, m). Anal. Calcd for C21H26Cl2N2 Æ 2HCl Æ 0.5H2O:
C, 54.92; H, 6.36; N, 6.10. Found: C, 55.11; H, 6.64; N,
6.37.

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S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
5.6. N-(3-{4-[4-(Morpholin-4-ylsulfonyl)benzyl]piperidin-
1-yl}propyl)aniline (3d)
90 mmol). After being stirred at room temperature for
12 h, the mixture was washed with saturated aqueous
NaHCO3 (2 · 400 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 recrystallization from Et2O to
afford 4e (13.8 g, 50%) as a white solid, mp 101–103 ꢁC.
1H NMR (CDCl3) d 1.23–1.46 (2H, m), 1.46–1.90 (7H,
m), 2.36 (2H, t, J ¼ 7:3 Hz), 2.51 (2H, d, J ¼ 6:6 Hz),
2.82–2.90 (2H, m), 3.77 (2H, t, J ¼ 7:3 Hz), 6.66 (1H,
br), 7.10–7.52 (14H, m). Anal. Calcd for C28H32ClN3O:
C, 72.79; H, 6.98; Cl, 7.67; N, 9.09. Found: C, 72.41; H,
6.97; Cl, 7.72; N, 8.98.
5.6.1. Step 1: N-(3-chloropropyl)aniline hydrochloride. To
a mixture of formanilide (100 g, 0.83 mol) and 1-bromo-
3-chloropropane (156 g, 0.99 mol) in acetone (500 mL)
was added Cs2CO3 (323 g, 0.99 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
(2 · 100 mL), and concentrated in vacuo. The residue
was purified by column chromatography on silica gel
(hexane/EtOAc 1:0 to 7:3) to afford (3-chloroprop-
yl)phenylformamide (145 g, 89%) as a pale yellow oil.
This oil (144 g, 0.73 mol) was dissolved in i-PrOH
(500 mL) and treated with concentrated HCl (120 mL).
The mixture was stirred at 60 ꢁC for 5 h, then cooled
with an ice bath. The resulting precipitate was collected
by filtration, washed with i-PrOH (2 · 100 mL), and
dried in vacuo to give N-(3-chloropropyl)aniline
hydrochloride (109 g, 72%) as a white solid.
The following compounds (4a–d,f–m,p,q,s–w) were pre-
pared using a procedure similar to that described for 4e
from 3a–g and the appropriate isocyanate.
5.9. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N,N0-diphenyl-
urea hydrochloride (4a)
1
Yield 82%, amorphous solid. H NMR (DMSO-d6) d
1.30–1.95 (7H, m), 2.54–2.57 (2H, m), 2.80–2.93 (2H,
m), 3.00–3.12 (2H, m), 3.42–3.80 (2H, m), 3.62–3.78
(2H, m), 6.95–7.55 (15H, m), 7.85 (1H, s). Anal. Calcd
for C28H33N3O Æ HCl Æ 0.75H2O: C, 70.42; H, 7.71; N,
8.80. Found: C, 70.43; H, 7.31; N, 8.74.
5.6.2. Step 2: N-(3-{4-[4-(morpholin-4-ylsulfonyl)ben-
zyl]piperidin-1-yl}propyl)aniline (3d).
N-(3-chloropropyl)aniline hydrochloride
A
mixture of
(1.63 g,
7.9 mmol), 15 (2.33 g, 7.2 mmol), KI (1.31 g, 7.9 mmol),
and K2CO3 (3.97 g, 29 mmol) in MeCN/DMF (1:1,
28 mL) was stirred at 100 ꢁC for 6 h. The mixture was
concentrated in vacuo, and the residue was partitioned
between EtOAc (50 mL) and water (50 mL). The organic
layer was separated, and the aqueous layer was ex-
tracted with EtOAc (2 · 50 mL). The combined organic
layer was washed with brine (30 mL) and concentrated
in vacuo. The residue was purified by column chroma-
tography on silica gel (EtOAc/MeOH 1:0 to 4:1) to give
3d (2.89 g, 88%) as a pale yellow oil. 1H NMR (CDCl3) d
1.20–2.00 (9H, m), 2.45 (2H, t, J ¼ 6:8 Hz), 2.64 (2H, d,
J ¼ 6:4 Hz), 2.85–3.05 (6H, m), 3.17 (2H, t, J ¼ 6:4 Hz),
3.70–3.80 (4H, m), 6.50–6.75 (3H, m), 7.10–7.25 (2H,
m), 7.33 (2H, d, J ¼ 8:4 Hz), 7.67 (2H, d, J ¼ 8:4 Hz).
5.10. N0-Benzyl-N-[3-(4-benzylpiperidin-1-yl)propyl]-N-
phenylurea hydrochloride (4b)
1
Yield 67%, amorphous solid. H NMR (DMSO-d6) d
1.40–1.81 (7H, m), 2.53–2.56 (2H, m), 2.77–2.89 (2H,
m), 2.98–3.18 (2H, m), 3.35–3.40 (2H, m), 3.65–3.70
(2H, m), 4.20 (2H, s), 7.18–7.54 (15H, m). Anal. Calcd
for C29H35N3O Æ HCl Æ 0.5H2O: C, 71.51; H, 7.66; N,
8.63. Found: C, 71.60; H, 7.74; N, 8.46.
5.11. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N0-cyclohexyl-
N-phenylurea (4c)
1
5.7. N-(3-{4-[4-(Methylsulfonyl)benzyl]piperidin-1-yl}-
propyl)aniline (3c)
Yield 72%, mp 106–108 ꢁC (Et2O). H NMR (CDCl3) d
0.80–1.95 (19H, m), 2.30 (2H, t, J ¼ 7:6 Hz), 2.50 (2H,
d, J ¼ 6:6 Hz), 2.83 (2H, br d, J ¼ 11:8 Hz), 3.40–3.75
(1H, m), 3.68 (2H, t, J ¼ 7:3 Hz), 4.15 (1H, d,
J ¼ 8:0 Hz), 7.05–7.50 (10H, m). Anal. Calcd for
C28H39N3O: C, 77.55; H, 9.07; N, 9.69. Found: C, 77.65;
H, 8.96; N, 9.75.
Compound 3c was prepared using a procedure similar to
that described for 3d from 11 in 98% yield, oil. 1H NMR
(CDCl3) d 1.26–1.91 (9H, m), 2.45 (2H, t, J ¼ 6:8 Hz),
2.66 (2H, d, J ¼ 6:6 Hz), 2.95 (2H, d, J ¼ 11:4 Hz), 3.05
(3H, s), 3.17 (2H, t, J ¼ 6:3 Hz), 4.65 (1H, br s), 6.58
(2H, d, J ¼ 7:2 Hz), 6.68 (1H, t, J ¼ 7:2 Hz), 7.17 (2H, t,
J ¼ 8:0 Hz), 7.35 (2H, d, J ¼ 8:4 Hz), 7.86 (2H, d,
J ¼ 8:0 Hz).
5.12. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N-phenyl-N0-
propylurea (4d)
Yield 92%, oil. 1H NMR (CDCl3) d 0.84 (3H, t,
J ¼ 7:3 Hz), 1.10–1.95 (11H, m), 2.33 (2H, t,
J ¼ 7:6 Hz), 2.53 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, br d,
J ¼ 11:6 Hz), 3.05–3.20 (2H, m), 3.71 (2H, t,
J ¼ 7:3 Hz), 4.55–4.70 (1H, m), 7.10–7.50 (10H, m).
Anal. Calcd for C25H35N3O Æ 0.5H2O: C, 74.59; H, 9.01;
N, 10.44. Found: C, 74.78; H, 9.19; N, 10.43.
5.8. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N0-(4-chloro-
phenyl)-N-phenylurea (4e)
To a stirred solution of 3a (22.9 g, 60 mmol) and Et3N
(18.5 mL, 132 mmol) in dichloromethane (DCM)
(500 mL) was added 4-chlorophenyl isocyanate (13.8 g,

S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
2301
5.13. N0-(4-Chlorophenyl)-N-{3-[4-(4-fluorobenzyl)piperi-
din-1-yl]propyl}-N-phenylurea hydrochloride (4f)
2.48 (2H, d, J ¼ 6:9 Hz), 2.86 (2H, d, J ¼ 11:7 Hz), 3.78
(2H, t, J ¼ 7:1 Hz), 6.79 (1H, br s), 6.95 (2H, t,
J ¼ 8:7 Hz), 7.04–7.09 (2H, m), 7.29–7.52 (9H, m).
Anal. Calcd for C29H31F4N3O Æ HCl Æ 0.5H2O: C, 62.31;
H, 5.95; N, 7.52. Found: C, 62.23; H, 6.13; N, 7.48.
Yield 94%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.10–2.00 (9H, m), 2.36 (2H, br t, J ¼ 7:3 Hz),
2.48 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, br d, J ¼ 11:6 Hz),
3.77 (2H, t, J ¼ 7:1 Hz), 6.60 (1H, br s), 6.85–7.55 (13H,
m). Anal. Calcd for C28H31ClFN3O Æ HCl Æ 0.5H2O: C,
64.00; H, 6.33; N, 8.00. Found: C, 64.12; H, 6.39; N, 8.00.
5.19. N0-(4-Cyanophenyl)-N-{3-[4-(4-fluorobenzyl)piperi-
din-1-yl]propyl}-N-phenylurea hydrochloride (4l)
Yield 94%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.15–1.91 (9H, m), 2.36 (2H, t, J ¼ 7:3 Hz),
2.49 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, d, J ¼ 11:8 Hz), 3.78
(2H, t, J ¼ 7:3 Hz), 6.87–7.11 (5H, m), 7.29 (2H, d,
J ¼ 8:4 Hz), 7.37–7.54 (7H, m). Anal. Calcd for
C29H31FN4O Æ HCl Æ 0.6H2O: C, 67.26; H, 6.46; N, 10.82.
Found: C, 67.38; H, 6.72; N, 10.54.
5.14. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N0-
(4-fluorophenyl)-N-phenylurea hydrochloride (4g)
Yield 91%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.13–1.89 (9H, m), 2.36 (2H, t, J ¼ 7:3 Hz),
2.47 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, d, J ¼ 11:8 Hz), 3.77
(2H, t, J ¼ 7:1 Hz), 6.60 (1H, s), 6.87–7.10 (6H, m),
7.19–7.51
(7H,
m).
Anal.
Calcd
for
C28H31F2N3O Æ HCl Æ 0.7H2O: C, 65.60; H, 6.57; N, 8.20.
Found: C, 65.63; H, 6.78; N, 8.04.
5.20. Ethyl 4-({[3-[4-(4-fluorobenzyl)piperidin-1-yl]prop-
yl(phenyl)amino]carbonyl}amino)benzoate (4m)
Yield 97%, mp 89–90 ꢁC (EtOAc/hexane). 1H NMR
(CDCl3) d 1.15–1.90 (12H, m), 2.37 (2H, t, J ¼ 7:5 Hz),
2.49 (2H, d, J ¼ 6:6 Hz), 2.87 (2H, d, J ¼ 11:6 Hz), 3.78
(2H, t, J ¼ 7:4 Hz), 4.33 (2H, q, J ¼ 7:2 Hz), 6.80 (1H,
br s), 6.91–7.11 (4H, m), 7.28–7.53 (7H, m), 7.92 (2H, d,
J ¼ 8:8 Hz). Anal. Calcd for C31H36FN3O3: C, 71.93; H,
7.01; N, 8.12. Found: C, 71.95; H, 6.85; N, 8.18.
5.15. N0-(4-Bromophenyl)-N-{3-[4-(4-fluorobenzyl)piperi-
din-1-yl]propyl}-N-phenylurea (4h)
1
Yield 88%, mp 84–85 ꢁC (i-Pr2O). H NMR (CDCl3) d
1.13–1.89 (9H, m), 2.36 (2H, t, J ¼ 7:5 Hz), 2.48 (2H, d,
J ¼ 6:6 Hz), 2.86 (2H, d, J ¼ 11:8 Hz), 3.76 (2H, t,
J ¼ 7:3 Hz), 6.62 (1H, br s), 6.90–7.10 (4H, m), 7.18–
7.51 (9H, m). Anal. Calcd for C28H31BrFN3O: C, 64.12;
H, 5.96; N, 8.01. Found: C, 63.88; H, 5.95; N, 8.02.
5.21. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N0-
(4-methoxyphenyl)-N-phenylurea hydrochloride (4p)
5.16. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N0-
(4-methylphenyl)-N-phenylurea hydrochloride (4i)
Yield 97%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.12–1.89 (9H, m), 2.36 (2H, t, J ¼ 7:5 Hz),
2.47 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, d, J ¼ 11:8 Hz),
3.73–3.81 (5H, m), 6.47 (1H, s), 6.79 (2H, d, J ¼ 8:8 Hz),
6.90–7.10 (4H, m), 7.19 (2H, d, J ¼ 8:8 Hz), 7.28–7.50
(5H, m). Anal. Calcd for C29H34FN3O2 Æ HCl Æ 0.5H2O:
C, 66.85; H, 6.96; N, 8.06. Found: C, 67.05; H, 7.11; N,
7.76.
Yield 88%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.21–1.86 (9H, m), 2.27 (3H, s), 2.35 (2H, t,
J ¼ 7:5 Hz), 2.47 (2H, d, J ¼ 6:9 Hz), 2.85 (2H, d,
J ¼ 12:0 Hz), 3.77 (2H, t, J ¼ 7:4 Hz), 6.45 (1H, s), 6.94
(2H, t, J ¼ 8:9 Hz), 7.02–7.09 (4H, m), 7.17 (2H, d,
J ¼ 8:7 Hz), 7.28–7.49 (5H, m). Anal. Calcd for
C29H34FN3O Æ HCl Æ H2O: C, 67.75; H, 7.25; N, 8.17.
Found: C, 67.82; H, 7.39; N, 7.92.
5.22. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N0-
[4-(methylsulfanyl)phenyl]-N-phenylurea hydrochloride
(4q)
5.17. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N0-
(4-isopropylphenyl)-N-phenylurea hydrochloride (4j)
Yield 100%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.15–1.89 (9H, m), 2.36 (2H, t, J ¼ 7:5 Hz),
2.43 (3H, s), 2.48 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, d,
J ¼ 11:8 Hz), 3.77 (2H, t, J ¼ 7:1 Hz), 6.55 (1H, br s),
Yield 99%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.18–1.88 (15H, m), 2.35 (2H, t, J ¼ 7:5 Hz),
2.47 (2H, d, J ¼ 6:6 Hz), 2.76–2.90 (2H, m), 3.77 (2H, t,
J ¼ 7:3 Hz), 6.45 (1H, s), 6.94–7.49 (13H, m). Anal.
Calcd for C31H38FN3O Æ HCl Æ 0.5H2O: C, 69.84; H, 7.56;
N, 7.88. Found: C, 69.77; H, 7.51; N, 7.67.
6.90–7.50
(13H,
m).
Anal.
Calcd
for
C29H34FN3OS Æ HCl Æ 0.7H2O: C, 64.41; H, 6.79; N, 7.77.
Found: C, 64.47; H, 6.67; N, 7.59.
5.23. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N0-(4-chloro-
phenyl)-N-(4-methylphenyl)urea hydrochloride (4s)
5.18. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N-phen-
yl-N0-[4-(trifluoromethyl)phenyl]urea hydrochloride (4k)
1
Yield 87%, amorphous solid. H NMR (DMSO-d6) d
1.20–1.95 (7H, m), 2.34 (3H, s), 2.45–2.60 (2H, m), 2.60–
Yield 81%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.22–1.89 (9H, m), 2.37 (2H, t, J ¼ 7:4 Hz),
3.50 (6H, m), 3.68 (2H, t, J ¼ 6:8 Hz), 7.10–7.35 (11H,

2302
S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
m), 7.44 (2H, d, J ¼ 9:2 Hz), 7.93 (1H, s). Anal. Calcd
for C29H34ClN3O Æ HCl Æ 0.5H2O: C, 66.79; H, 6.96; N,
8.06. Found: C, 66.84; H, 6.99; N, 7.95.
DCM and water. The organic layer was separated, and
the aqueous layer was extracted with DCM. The com-
bined organic layer was washed with brine and con-
centrated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 10:1 to
1
4:1) to give 4n (0.58 g, 32%) as an amorphous solid. H
5.24. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N-(3-chloro-
phenyl)-N0-(4-chlorophenyl)urea hydrochloride (4t)
NMR (CDCl3) d 1.47–1.78 (5H, m), 1.96–2.35 (4H, m),
2.52 (2H, br s), 2.85 (2H, br s), 3.44 (2H, d,
J ¼ 10:4 Hz), 3.75 (2H, br s), 4.35 (1H, br s), 6.35 (1H,
s), 6.89–7.13 (6H, m), 7.26–7.37 (5H, m), 7.82 (2H, d,
J ¼ 8:8 Hz). Anal. Calcd for C29H32FN3O3 Æ H2O: C,
68.62; H, 6.75; N, 8.28. Found: C, 68.78; H, 6.56; N,
8.05.
1
Yield 27%, amorphous solid. H NMR (DMSO-d6) d
1.40–1.91 (7H, m), 2.51–2.54 (2H, m), 2.78–2.90 (2H,
m), 3.00–3.17 (2H, m), 3.37–3.43 (2H, m), 3.71–3.78
(2H, m), 7.15–7.50 (13H, m), 8.34 (1H, s). Anal. Calcd
for C28H31Cl2N3O Æ HCl Æ H2O: C, 61.04; H, 6.22; N,
7.63. Found: C, 60.80; H, 6.20; N, 7.73.
5.29. 4-({[{3-[4-(4-Fluorobenzyl)piperidin-1-yl]prop-
yl}(phenyl)amino]carbonyl}amino)benzamide (4o)
5.25. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N0-(4-chloro-
phenyl)-N-(3,4-dichlorophenyl)urea (4u)
To a mixture of 4n (300 mg, 0.61 mmol), HOBt (83 mg,
0.61 mmol) and NH4Cl (43 mg, 0.80 mmol) in DMF
(5 mL) were added Et3N (0.11 mL, 0.80 mmol), and
EDC (153 mg, 0.80 mmol). The mixture was stirred at
room temperature for 3 h and concentrated in vacuo.
The residue was diluted with saturated aqueous
NaHCO3 (60 mL) and extracted with EtOAc
(3 · 60 mL). The organic layer was dried (MgSO4), fil-
tered, and concentrated in vacuo. The residue was
purified by column chromatography on NH silica gel
(EtOAc/MeOH 100:1) followed by trituration with
hexane/EtOAc to give 4o (200 mg, 77%) as a white solid,
mp 198–200 ꢁC. 1H NMR (CDCl3) d 1.22–1.91 (9H, m),
2.37 (2H, t, J ¼ 7:5 Hz), 2.49 (2H, d, J ¼ 6:2 Hz), 2.87
(2H, d, J ¼ 11:2 Hz), 3.78 (2H, t, J ¼ 7:4 Hz), 5.50 (1H,
br s), 5.92 (1H, br s), 6.87–7.11 (4H, m), 7.26–7.53 (7H,
m), 7.72 (2H, d, J ¼ 8:4 Hz). Anal. Calcd for
C29H33FN4O2: C, 71.29; H, 6.81; N, 11.47. Found: C,
71.17; H, 6.77; N, 11.30.
1
Yield 78%, mp 128–131 ꢁC. H NMR (CDCl3) d 1.10–
2.00 (9H, m), 2.39 (2H, t, J ¼ 6:8 Hz), 2.51 (2H, d,
J ¼ 6:2 Hz), 2.88 (2H, br d, J ¼ 11:8 Hz), 3.78 (2H, t,
J ¼ 6:6 Hz), 7.05–7.40 (10H, m), 7.41 (1H, d,
J ¼ 2:6 Hz), 7.49 (1H, d, J ¼ 8:4 Hz), 7.90 (1H, br s).
Anal. Calcd for C28H30Cl3N3O: C, 63.34; H, 5.70; N,
7.91. Found: C, 63.25; H, 5.58; N, 7.93.
5.26. N0-(4-Chlorophenyl)-N-(3-{4-[4-(methylsulfon-
yl)benzyl]piperidin-1-yl}propyl)-N-phenylurea hydrochlo-
ride (4v)
Yield 68%, amorphous solid. 1H NMR (free base,
CDCl3) d 1.10–1.95 (9H, m), 2.35 (2H, t, J ¼ 7:5 Hz),
2.60 (2H, d, J ¼ 6:6 Hz), 2.86 (2H, br d, J ¼ 11:0 Hz),
3.04 (3H, s), 3.76 (2H, t, J ¼ 7:3 Hz), 6.48 (1H, br s),
7.10–7.55 (11H, m), 7.84 (2H, d, J ¼ 8:0 Hz). Anal.
Calcd for C29 H34ClN3O3S Æ HCl Æ H2O: C, 58.58; H,
6.27; N, 7.07. Found: C, 58.52; H, 6.25; N, 7.02.
5.30. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-N0-
[4-(methylsulfonyl)phenyl]-N-phenylurea hydrochloride
(4r)
5.27. N0-(4-Chlorophenyl)-N-(3-{4-[4-(morpholin-4-yl-
sulfonyl)benzyl]piperidin-1-yl}propyl)-N-phenylurea
hydrochloride (4w)
To an ice-cooled solution of 4q (498 mg, 1.01 mmol) in
MeOH (5 mL) was added 1 N H2SO4 (1.01 mL) followed
by a solution of Oxone (2KHSO5 Æ KHSO4 Æ K2SO4)
(938 mg, 1.53 mmol) in water (5 mL). After being stirred
at room temperature for 1 h, the mixture was partitioned
between EtOAc and saturated aqueous NaHCO3. The
organic layer was separated, and the aqueous layer was
extracted with EtOAc. The combined organic layer was
dried (MgSO4), filtered, and concentrated in vacuo. The
residue was purified by column chromatography on NH
silica gel (hexane/EtOAc 1:1) to give an oil (400 mg).
Treatment with 4 N HCl (EtOAc solution) gave 4r
Yield 54%, amorphous solid. 1H NMR (CD3OD) d
1.40–2.10 (7H, m), 2.75 (2H, d, J ¼ 6:6 Hz), 2.80–3.10
(6H, m), 3.18 (2H, t, J ¼ 7:3 Hz), 3.45–3.75
(6H, m), 3.86 (2H, t, J ¼ 6:6 Hz), 7.15–7.65 (11H, m),
7.71 (2H, d, J ¼ 8:6 Hz). Anal. Calcd for
C32H39ClN4O4S Æ HCl Æ 1.4H2O: C, 57.12; H, 6.41; N,
8.33. Found: C, 57.18; H, 6.57; N, 8.02.
1
5.28. 4-({[{3-[4-(4-Fluorobenzyl)piperidin-1-yl]prop-
yl}(phenyl)amino]carbonyl}amino)benzoic acid (4n)
(389 mg, 69%) as an amorphous solid. H NMR (free
base, CDCl3) d 1.23–1.91 (9H, m), 2.37 (2H, t,
J ¼ 7:3 Hz), 2.49 (2H, d, J ¼ 6:4 Hz), 2.87 (2H, d,
J ¼ 11:4 Hz), 3.01 (3H, s), 3.78 (2H, t, J ¼ 7:2 Hz),
6.91–7.11 (5H, m), 7.27–7.55 (7H, m), 7.79 (2H, d,
To a stirred solution of 4m (1.90 g, 3.67 mmol) in EtOH
(20 mL) was added 1 N aqueous NaOH (5.50 mL), and
the mixture was stirred at 80 ꢁC for 5 h. The mixture was
treated with 1 N aqueous HCl (5.50 mL) and concen-
trated in vacuo. The residue was partitioned between
J ¼ 8:8 Hz).
Anal.
Calcd
for
C29H34FN3O3
S Æ HCl Æ 0.8H2O: C, 60.62; H, 6.42; N, 7.31. Found: C,
60.82; H, 6.55; N, 7.14.

S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
2303
5.31. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N0-methyl-
N,N0-diphenylurea hydrochloride (5)
(2H, t, J ¼ 6:9 Hz), 7.05–7.40 (15H, m). Anal. Calcd for
C28H32N2O Æ HCl Æ H2O: C, 72.01; H, 7.55; N, 6.00.
Found: C, 72.23; H, 7.66; N, 5.96.
5.31.1. Step 1: N-[3-(4-benzylpiperidin-1-yl)propyl]ani-
line. Hydrochloride salt 3a (3.81 g, 10 mmol) was basi-
fied with 1 N aqueous NaOH (30 mL) and extracted with
Et2O. The organic layer was dried (Na2SO4), filtered,
and concentrated in vacuo to give the corresponding
free base (2.96 g, 96%).
5.34. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N,3-diphenyl-
propanamide (6c)
1
Yield 95%, oil. H NMR (CDCl3) d 1.10–1.90 (9H, m),
2.20–2.35 (4H, m), 2.51 (2H, d, J ¼ 6:6 Hz), 2.82 (2H, br
d, J ¼ 11:4 Hz), 2.89 (2H, t, J ¼ 7:9 Hz), 3.68 (2H, t,
J ¼ 7:5 Hz), 6.90–7.40 (15H, m). Anal. Calcd for
C30H36N2O Æ 0.2H2O: C, 81.11; H, 8.26; N, 6.31. Found:
C, 80.99; H, 8.35; N, 6.33.
5.31.2. Step 2: N-[3-(4-benzylpiperidin-1-yl)propyl]-N0-
methyl-N,N0-diphenylurea hydrochloride (5). To a stirred
solution of the product from step 1 (308 mg, 1.0 mmol)
was added NaH (60% in oil, 120 mg, 3.0 mmol) at 0 ꢁC,
and the mixture was stirred at room temperature for 1 h.
The mixture was treated with N-methyl-N-phenylcar-
bamoyl chloride (509 mg, 3.0 mmol) and stirred at 80 ꢁC
for 17 h. The mixture was diluted with water (15 mL) at
0 ꢁC and extracted with Et2O (3 · 15 mL). The organic
layer was dried (MgSO4), filtered, and concentrated in
vacuo. The residue was purified by column chromato-
graphy on alumina (hexane/EtOAc 5:1 to 2:1) followed
by column chromatography on silica gel (hexane/EtOAc
1:1 to 0:1) to give an oil (393 mg). The oil was dissolved
in MeOH, treated with 1 N HCl (Et2O solution, 2 mL),
and concentrated in vacuo. The residue was triturated
with hexane to give 5 (351 mg, 74%) as a hygroscopic
5.35. Benzyl [3-(4-benzylpiperidin-1-yl)propyl]phenylcar-
bamate (7)
To a stirred suspension of 3a (381 mg, 1.0 mmol) in THF
(7 mL) was added 1 N aqueous NaOH (7 mL) followed
by benzyl chloroformate (571 lL, 4.0 mmol), and the
mixture was stirred at room temperature for 3 h. The
mixture was diluted with water (15 mL) and extracted
with Et2O (3 · 15 mL). The organic layer was dried
(MgSO4), filtered, and concentrated in vacuo. The resi-
due was purified by column chromatography on silica
gel (hexane/EtOAc 1:1 to 1:3) to give 7 (422 mg, 95%) as
1
amorphous solid. H NMR (free base, CDCl3) d 1.10–
1
a colorless oil. H NMR (CDCl3) d 1.10–1.90 (9H, m),
1.90 (9H, m), 2.29 (2H, t, J ¼ 7:5 Hz), 2.50 (2H, d,
J ¼ 6:6 Hz), 2.83 (2H, br d, J ¼ 11:8 Hz), 3.15 (3H, s),
3.59 (2H, t, J ¼ 7:6 Hz), 6.65–7.35 (15H, m). Anal.
Calcd for C29H35N3O Æ HCl Æ 0.5H2O: C, 71.51; H, 7.66;
N, 8.63. Found: C, 71.46; H, 7.69; N, 8.64.
2.27 (2H, t, J ¼ 7:5 Hz), 2.50 (2H, d, J ¼ 6:2 Hz), 2.78
(2H, br d, J ¼ 11:2 Hz), 3.70 (2H, t, J ¼ 7:3 Hz), 5.13
(2H, s), 7.05–7.40 (15H, m). Anal. Calcd for
C29H34N2O2 Æ 0.2H2O: C, 78.06; H, 7.77; N, 6.28. Found:
C, 77.98; H, 7.80; N, 6.13.
5.32. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N,2-diphenyl-
acetamide (6b)
5.36. 1-Acetyl-4-benzylpiperidine (8)
Acetic anhydride (110 mL, 1.17 mol) was added drop-
wise to 4-benzylpiperidine (2a) (100 g, 0.57 mol) at 0 ꢁC
under stirring, and the mixture was stirred at room
temperature for 1 h and concentrated in vacuo. The
residue was partitioned between EtOAc (500 mL) and
saturated aqueous NaHCO3 (1 L). The organic layer
was separated, and the aqueous layer was extracted with
EtOAc (200 mL). The combined organic layer was wa-
shed with water (500 mL) and brine (500 mL), dried
(MgSO4), filtered, and concentrated in vacuo to give 8
To a stirred mixture of 3a (381 mg, 1.0 mmol) and
phenylacetyl chloride (198 lL, 1.5 mmol) in DCM
(10 mL) was added Et3N (558 lL, 4.0 mmol) at 0 ꢁC.
After being stirred at room temperature for 15 h, the
mixture was treated with 1 N aqueous NaOH (6 mL)
and extracted with DCM. The organic layer was washed
with brine and concentrated in vacuo. The residue was
purified by column chromatography (NH silica gel,
hexane/EtOAc 4:1 to 2:1) to give 6b (404 mg, 95%) as an
1
oil. H NMR (CDCl3) d 1.10–1.90 (9H, m), 2.20–2.40
1
(129 g, quant.) as a pale yellow oil. H NMR (CDCl3) d
(2H, m), 2.52 (2H, d, J ¼ 6:6 Hz), 2.83 (2H, br d, J ¼
11:4 Hz), 3.42 (2H, s), 3.73 (2H, t, J ¼ 7:6 Hz), 6.95–7.50
(15H, m). Anal. Calcd for C29 H34N2O Æ 0.3H2O: C,
80.63; H, 8.07; N, 6.48. Found: C, 80.72; H, 8.05; N, 6.49.
1.00–1.30 (2H, m), 1.60–1.90 (3H, m), 2.07 (3H, s), 2.35–
2.60 (3H, m), 2.85–3.05 (1H, m), 3.65–3.85 (1H, m),
4.50–4.70 (1H, m), 7.05–7.35 (5H, m).
The following compounds (6a,c) were prepared using a
procedure similar to that described for 6b from the
appropriate acid chloride.
5.37. 4-[(1-Acetylpiperidin-4-yl)methyl]benzenesulfonyl
chloride (9)
A solution of 8 (60.0 g, 0.28 mol) in DCM (100 mL) was
added dropwise to chlorosulfonic acid (92 mL, 1.4 mol)
at 0 ꢁC under stirring, and the mixture was stirred at
0 ꢁC for 30 min and at room temperature for 1.5 h. The
mixture was poured into ice water (1 L) and extracted
with DCM (500, 250 mL). The organic layer was washed
5.33. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N-phenylbenz-
amide hydrochloride (6a)
1
Yield 65%, amorphous. H NMR (DMSO-d6) d 1.30–
2.05 (7H, m), 2.45–2.60 (2H, m), 2.60–3.50 (6H, m), 3.89

2304
S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
with 5% aqueous NaHCO3 (2 · 500 mL) and brine
(250 mL). The organic layer was dried (MgSO4), filtered,
and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc) to give 9
anhydride (159 mL, 1.13 mol) at 0 ꢁC. The mixture was
stirred at room temperature for 3 h and concentrated in
vacuo. The residue was partitioned between EtOAc
(500 mL) and saturated aqueous NaHCO3 (1 L). The
organic layer was separated, washed with saturated
aqueous NaHCO3 (2 · 200 mL), 1 N aqueous HCl
(2 · 200 mL), and brine (200 mL), dried (MgSO4), fil-
tered, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (hex-
ane/EtOAc 1:0 to 9:1) to give 12 (149 g, 97%) as a col-
1
(54.2 g, 62%) as a white solid, mp 72–75 ꢁC. H NMR
(CDCl3) d 1.05–1.35 (2H, m), 1.60–1.95 (3H, m), 2.09
(3H, s), 2.35–2.65 (1H, m), 2.68 (2H, d, J ¼ 6:6 Hz),
2.85–3.15 (1H, m), 3.70–3.90 (1H, m), 4.50–4.75 (1H,
m), 7.39 (2H, d, J ¼ 8:4 Hz), 7.97 (2H, d, J ¼ 8:4 Hz).
1
orless oil. H NMR (CDCl3) d 1.10–1.40 (2H, m), 1.65–
5.38. 1-Acetyl-4-[4-(methylsulfonyl)benzyl]piperidine (10)
1.95 (3H, m), 2.57 (2H, d, J ¼ 7:0 Hz), 2.60–2.80 (1H,
m), 2.95–3.15 (1H, m), 3.90–4.10 (1H, m), 4.45–4.60
(1H, m), 7.05–7.40 (5H, m).
To a solution of Na2SO3 (4.57 g, 36 mmol) and
NaHCO3 (6.10 g, 73 mmol) in water (40 mL) was added
portionwise 9 (11.46 g, 36 mmol) at 75 ꢁC. After being
stirred at 75 ꢁC for 1 h, the mixture was treated with
chloroacetic acid (5.14 g, 54 mmol) followed by a solu-
tion of NaOH (2.18 g, 55 mmol) in water (4.4 mL) and
stirred at reflux for 20 h. The mixture was treated with
1 N aqueous HCl (20 mL) at 0 ꢁC and extracted with
EtOAc (60, 30 mL). The organic layer was washed
with brine (2 · 10 mL), dried (MgSO4), filtered, and
concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc/MeOH
5.41. 4-{[1-(Trifluoroacetyl)piperidin-4-yl]methyl}benz-
enesulfonyl chloride (13)
A solution of 12 (54.3 g, 0.20 mol) in DCM (100 mL)
was added dropwise to chlorosulfonic acid (117 g,
1.0 mol) at 0 ꢁC under stirring, and the mixture was
stirred at room temperature for 5 h. The mixture was
poured into ice water (500 g) and extracted with DCM
(400, 2 · 200 mL). The combined organic layer was wa-
shed with saturated aqueous NaHCO3 (200 mL) and
brine (200 mL), and concentrated in vacuo. The residue
was purified by column chromatography on silica gel
(hexane/EtOAc 1:0 to 1:1) to give 13 (47.8 g, 65%) as a
colorless oil, which solidified on standing in a refriger-
1
1:0 to 9:1) to give 10 (8.76 g, 82%) as a colorless oil. H
NMR (CDCl3) d 1.05–1.35 (2H, m), 1.55–1.95 (3H, m),
2.08 (3H, s), 2.40–2.60 (1H, m), 2.66 (2H, d, J ¼ 7:4 Hz),
2.90–3.10 (1H, m), 3.06 (3H, s), 3.70–3.90 (1H, m), 4.55–
4.70 (1H, m), 7.34 (2H, d, J ¼ 8:4 Hz), 7.87 (2H, d,
J ¼ 8:4 Hz).
1
ator, mp 65–68 ꢁC. H NMR (CDCl3) d 1.26–1.39 (2H,
m), 1.75–2.05 (3H, m), 2.66–2.78 (1H, m), 2.48 (2H, d,
J ¼ 7:0 Hz), 3.01–3.15 (1H, m), 3.98–4.10 (1H, m), 4.50–
4.61 (1H, m), 7.40 (2H, d, J ¼ 8:4 Hz), 7.98 (2H, d,
J ¼ 8:4 Hz).
5.39. 4-[4-(Methylsulfonyl)benzyl]piperidine (11)
A mixture of 10 (8.76 g, 30 mmol) and concentrated HCl
(100 mL) was stirred at reflux for 4 h, and concentrated
in vacuo. The residue was suspended in i-PrOH
(100 mL) and concentrated in vacuo. The residue was
suspended in i-PrOH (50 mL), stirred at reflux for
30 min, and cooled to room temperature. The precipitate
was collected by filtration, washed with i-PrOH, and
dried in vacuo to give the hydrochloride salt of 11
(7.51 g) as a white solid. 1H NMR (CD3OD) d 1.30–1.60
(2H, m), 1.75–2.10 (3H, m), 2.75 (2H, d, J ¼ 7:0 Hz),
2.80–3.05 (2H, m), 3.10 (3H, s), 3.25–3.45 (2H, m), 7.49
(2H, d, J ¼ 8:1 Hz), 7.89 (2H, d, J ¼ 8:1 Hz). A solution
of the hydrochloride salt (7.51 g) in water was basified
with 1 N aqueous NaOH (40 mL) and extracted with
DCM (3 · 30 mL). The organic layer was washed with
brine (10 mL), dried (Na2SO4), filtered, and concen-
trated in vacuo. The residue was triturated with i-Pr2O
to give the free base 11 (6.16 g, 82%) as a white solid, mp
5.42. 4-[(4-{[1-(Trifluoroacetyl)piperidin-4-yl]methyl}-
phenyl)sulfonyl]morpholine (14)
To a stirred solution of morpholine (1.05 g, 12 mmol)
and Et3N (2.09 mL, 15 mmol) in THF (10 mL) was ad-
ded a solution of 13 (3.70 g, 10 mmol) in THF (20 mL),
and the mixture was stirred at room temperature for 2 h.
The mixture was diluted with EtOAc (50 mL), washed
with water (10 mL), 1 N aqueous HCl (10 mL), and brine
(3 · 10 mL), and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (hex-
ane/EtOAc 4:1 to 1:1) to give 14 (3.99 g, 95%) as a
1
colorless oil. H NMR (CDCl3) d 1.17–1.38 (2H, m),
1.73–1.94 (3H, m), 2.66 (2H, d, J ¼ 7:0 Hz), 2.68–2.78
(1H, m), 3.00 (4H, t, J ¼ 4:8 Hz), 3.01–3.15 (1H, m),
3.76 (4H, t, J ¼ 4:8 Hz), 3.98–4.10 (1H, m), 4.53–4.60
(1H, m), 7.33 (2H, d, J ¼ 8:4 Hz), 7.69 (2H, d, J ¼
8:4 Hz).
1
97–99 ꢁC. H NMR (CDCl3) d 1.07–1.27 (2H, m), 1.50–
1.73 (3H, m), 2.48–2.61 (2H, m), 2.62 (2H, d,
J ¼ 6:6 Hz), 3.03–3.08 (2H, m), 3.05 (3H, s), 7.34 (2H, d,
J ¼ 8:4 Hz), 7.85 (2H, d, J ¼ 8:4 Hz).
5.43. 4-{[4-(Piperidin-4-ylmethyl)phenyl]sulfonyl}mor-
pholine (15)
5.40. 4-Benzyl-1-(trifluoroacetyl)piperidine (12)
To a stirred solution of 4-benzylpiperidine (2a) (98.8 g,
0.56 mol) in EtOAc (500 mL) was added trifluoroacetic
To a stirred solution of 14 (3.93 g, 9.3 mmol) in MeOH
(40 mL) was added a solution of K2CO3 (3.88 g,

S. Imamura et al. / Bioorg. Med. Chem. 12 (2004) 2295–2306
2305
28 mmol) in water (20 mL), and the mixture was stirred
Acknowledgements
at room temperature for 12 h. The organic solvent was
removed in vacuo, and the residue was extracted with
DCM (40, 2 · 20 mL). The organic layer was dried
(Na2SO4), filtered, and concentrated in vacuo to give 15
(3.08 g, quant.) as a white solid, mp 98–101 ꢁC. 1H NMR
(CDCl3) d 1.21–1.82 (5H, m), 2.60–2.71 (4H, m), 3.00
(4H, t, J ¼ 4:8 Hz), 3.19–3.26 (2H, m), 3.75 (4H, t,
J ¼ 4:8 Hz), 5.08 (1H, br s), 7.32 (2H, d, J ¼ 8:4 Hz),
7.67 (2H, d, J ¼ 8:4 Hz).
We would like to thank Mr. Kenichi Kuroshima for
CCR5 binding assay. We would also like to thank Mr.
Katsunori Takashima, Dr. Hiroshi Miyake, and Ms.
Shikiko Shiki for membrane fusion assay.
References and notes
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