CCR5 antagonists as anti-HIV-1 agents. Part 3: Synthesis and biological evaluation of piperidine-4-carboxamide derivatives

Article abstract of DOI:10.1016/j.bmc.2004.10.013

Replacement of the 5-oxopyrrolidin-3-yl fragment in the previously reported lead structure with a 1-acetylpiperidin-4-yl group led to the discovery of a novel series of potent CCR5 antagonists. Introduction of small hydrophobic substituents on the central phenyl ring increased the binding affinity, providing low to sub-nanomolar CCR5 antagonists. The selected compound 11f showed excellent antiviral activity against CCR5-using HIV-1 replication in human peripheral blood mononuclear cells (EC₅₀ = 0.59 nM) and an acceptable pharmacokinetic profile in dogs.

Full text of DOI:10.1016/j.bmc.2004.10.013

Bioorganic & Medicinal Chemistry 13 (2005) 397–416
CCR5 antagonists as anti-HIV-1 agents. Part 3: Synthesis and
biological evaluation of piperidine-4-carboxamide derivatives
Shinichi Imamura,a,* Youichi Nishikawa,a Takashi Ichikawa,a Taeko Hattori,a
Yoshihiro Matsushita,a Shohei Hashiguchi,a Naoyuki Kanzaki,a Yuji Iizawa,a
Masanori Babab and Yoshihiro Sugiharaa
aPharmaceutical Research Division, Takeda Pharmaceutical Co. Ltd., 2-17-85, Jusohonmachi, Yodogawa-ku, Osaka 532-8686, Japan
bDivision 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 17 September 2004; revised 5 October 2004; accepted 6 October 2004
Abstract—Replacement of the 5-oxopyrrolidin-3-yl fragment in the previously reported lead structure with a 1-acetylpiperidin-4-yl
group led to the discovery of a novel series of potent CCR5 antagonists. Introduction of small hydrophobic substituents on the cen-
tral phenyl ring increased the binding affinity, providing low to sub-nanomolar CCR5 antagonists. The selected compound 11f
showed excellent antiviral activity against CCR5-using HIV-1 replication in human peripheral blood mononuclear cells
(EC50 = 0.59nM) and an acceptable pharmacokinetic profile in dogs.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
the asymptomatic stage of the infection, which usually
persists 5–10years.5 CCR5 belongs to the seven-trans-
membrane 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)-1a, and MIP-1b], which have been reported to
inhibit R5 HIV-1 infection in vitro.6 A 32-base pair
deletion in the CCR5 gene (CCR5D32) generates a
nonfunctional receptor, and the CCR5D32-homozygous
individuals are highly resistant to HIV-1 infection, while
this defect does not represent a significant health
problem.7–9 In addition, infected individuals hetero-
zygous 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 thera-
peutic agents.11
Despite efforts to prevent the spread of human immuno-
deficiency virus type 1 (HIV-1), the worldwide popula-
tion of HIV-1-infected patients is still increasing.1
Although highly active antiretroviral therapy (HAART)
has been successful in reducing HIV-1-associated mor-
tality and morbidity, there remain difficulties with the
currently available HAART including the development
of viral resistance as well as the toxicity and complexity
of the drug regimens.2 Thus it is strongly desired to
develop new anti-HIV-1 agents with superior efficacy
and safety profiles.
The discovery of chemokine receptors as major 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 infection.3 HIV-1
strains that cause the initial infection predominantly
utilize CC chemokine receptor 5 (CCR5),4 and the
CCR5-using (R5) HIV-1 is isolated exclusively during
We recently described the details of structure–activity
relationships (SAR) developed for newly discovered
5-oxopyrrolidine-3-carboxamide CCR5 antagonists
(1, Fig. 1).12 In an effort to further improve potency,
we introduced various acyl groups as a replacement
for the 5-oxopyrrolidine-3-carbonyl group in the
original lead structure. These efforts identified several
promising series of CCR5 antagonists including
Keywords: CCR5 antagonist; Chemokine; HIV-1; Piperidine-4-
carboxamide.
*
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.2004.10.013

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S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
5-Oxopyrrolidine-3-carboxamide Type
Piperidine-4-carboxamide Type
O
O
N
N
N
N
O
Me
N
N
Me
O
1
7a
CCR5 IC50 = 16 nM
CCR5 IC50 = 480 nM
Figure 1.
N,N0-diphenylureas13 and piperidine-4-carboxamides
(7a). In this paper, we describe the synthesis and SAR
of the piperidine-4-carboxamide derivatives, which have
led to a new class of potent CCR5 antagonists.
To explore substitution on the phenyl ring of the 4-benz-
ylpiperidine moiety, as well as to access the compound
with a four-carbon chain, we employed an alternative
route which utilized the chlorides 10a,b as key interme-
diates (Scheme 2). Treatment of 3,4-dichloroaniline (8)
with acetic formic anhydride gave N-(3,4-dichlorophen-
yl)formamide.15 Subsequent N-alkylation with bromo-
chloroalkane in the presence of cesium carbonate
followed by removal of the formyl group under acidic
conditions afforded the N-(x-chloroalkyl)anilines 9a,b.
Acylation of 9a,b with the acid chlorides 4d,c gave the
chlorides 10a,b, which were reacted with R3-substituted
4-benzylpiperidines in the presence of potassium iodide
and potassium carbonate in acetonitrile to afford the
target compounds 11a–l and 12. The nitro group in com-
pound 11b was reduced with tin(II) chloride dihydrate
affording the amine 13, which was treated with acetyl
chloride or methanesulfonyl chloride to give 14a or
14b, respectively.
2. Chemistry
Target compounds were synthesized by two different
routes as outlined in Schemes 1 and 2. The first route
(Scheme 1) was used for the investigation of the acyl
and central phenyl moiety. Treatment of 4-benzylpiper-
idines 2 and 22a 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-aminoalde-
hydes in situ,14 which were transformed into the
anilines 3a–i by reductive amination with the corre-
sponding anilines using sodium triacetoxyborohydride.
Acylation of the anilines 3a–i with the acid chlorides
4a–d furnished the target compounds 5a–l. The benzyl-
oxycarbonyl (Cbz) group of 5a,b was removed by
hydrogenolysis to give the amines 6a,b, which were con-
verted to the amides 7a–c,e or sulfonamides 7d,f by
reaction with the corresponding acyl chlorides or meth-
anesulfonyl chloride, respectively.
In order to synthesize the compound with a two-carbon
chain, 3,4-dichloroaniline (8) was reacted with chloro-
acetic anhydride to give the chloride 15 (Scheme 3). N-
Alkylation of 4-(4-fluorobenzyl)piperidine (22a) with
15 yielded compound 16. The amide group of 16 was
O
R3
R3
R3
a
b
N
N
N
HN
4
N
HN
R1
4 O
3
R2
R2
2: R3 = H
3
22a: R3 = F
N
Cl
R1
3a-i
5a-l
4a-d
R1 Position
R2
R3
3a
H
H
H
H
F
F
F
F
F
F
Cbz
3b
3c
3d
3e
3f
3,4-diCl
3-Cl, 4-Me
3-Cl
4a
4
3
4
4
Cbz
Ac
4b
4c
4d
Ms
4-Me
3,4-diCl
3-Cl, 4-Me
3g
3h 3-Cl, 4-i-Pr
3i 3-Cl, 4-MeO
O
O
R1
N
N
N
N
N
N
R1
5a: R1 = Cbz
6a: R1 = H
7a: R1 = Ac; 7b: R1 = i-PrCO
7c: R1 = Bz; 7d: R1 = Ms
5b: R1 = Cbz
6b: R1 = H
7e: R1 = Ac; 7f: R1 = Ms
c
c
d
d
Scheme 1. Reagents: (a) acrolein, cat. DBU, THF, then R2-PhNH2, NaBH(OAc)3; (b) 4a–d, Et3N, DCM; (c) H2, Pd/C, MeOH; (d) R1-Cl, Et3N,
THF.

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
399
O
NH2
a, b, c
HN (CH2)n
d
N
(CH2)n Cl
Cl
N
R1
Cl
Cl
Cl
Cl
Cl
Cl
8
9a: n = 3
9b: n = 4
10a: n = 3; R1 = Ms
10b: n = 4; R1 = Ac
O
O
R3
R3
e
N
(CH2)n
Cl
N
N
N
N
Me
N
R1
S
O
O
Cl
Cl
Cl
11a-l: n = 3; R1 = Ms
11b: R3 = NO2
13: R3 = NH2
14a: R3 = NHAc
14b: R3 = NHMs
f
12: n = 4; R1 = Ac; R3 = F
g
Scheme 2. Reagents: (a) HCO2Ac; (b) Br(CH2)nCl, Cs2CO3, acetone; (c) concd HCl, i-PrOH; (d) 4d or 4c, Et3N, DCM; (e) 4-(R3-benzyl)piperidine,
KI, K2CO3, MeCN; (f) SnCl2Æ2H2O, EtOH; (g) AcCl or MsCl, Et3N, THF.
O
O
Cl
X
N
N
NH2
a
HN
b
HN
F
F
d
N
Me
N
O
Cl
Cl
Cl
Cl
18
Cl
Cl
Cl
Cl
16: X = CO
17: X = CH2
8
15
c
Scheme 3. Reagents: (a) (ClCH2CO)2O, THF; (b) 22a, K2CO3, DMF; (c) BH3ÆMe2S, THF; (d) 4c, Et3N, DCM.
reduced with borane–methyl sulfide to give the aniline
17, and subsequent coupling reaction with 4c furnished
the target compound 18.
followed by removal of the tert-butoxycarbonyl (Boc)
group gave the 4-benzyl piperidine 22a–c.
The nitro (27a) and morpholino (27b) analogues were
prepared from compound 23, which was described in
the patent literature (Scheme 5).16 Replacement of the
trifluoroacetyl group of 23 with a Boc group followed
by reduction of the nitro group gave compound 25.
Heating of 25 with bis(2-chloroethyl) ether resulted in
the formation of a morpholine ring (26). Deprotection
of the compounds 24 and 26 afforded the 4-benzylpiper-
idines 27a and 27b, respectively.
The required 4-benzylpiperidines were synthesized as
shown in Schemes 4–7. The preparation of the 4-benz-
ylpiperidines 22a–c was based on the Wittig reaction
(Scheme 4). Arbuzov reaction of commercially available
benzyl halides 19a–c with triethyl phosphite gave the
corresponding phosphonates. Treatment of the phos-
phonates with sodium hydride followed by addition
of tert-butyl 4-oxopiperidine-1-carboxylate formed the
olefins 20a–c. Hydrogenation of compounds 20a–c
The synthesis of sulfonamide derivatives 31a,b and 35a,b
is presented in Scheme 6. The amino group of 2 was
R3
Boc
R3
a, b
N
O
X
NO2
a
HN
F3C
N
19a-c
20a-c
R3
2
23
Boc
c
N
Boc
R3
R3
b
e
R3
X
N
HN
19-22
21a-c
(for 24, 26)
F
Br
a
b
c
24: R3 = NO2
25: R3 = NH2
26: R3 = morpholino
27a: R3 = NO2
27b: R3 = morpholino
R3
c
CF3 Br
OMe Cl
d
HN
d
22a-c
Scheme 5. Reagents: (a) TFAA, then KNO3, TFA; (b) aq NaOH,
EtOH, then Boc2O; (c) NH2NH2ÆH2O, FeCl3, activated C, THF; (d)
(ClCH2CH2)2O, KI, K2CO3, DMF; (e) HCl, EtOAc.
Scheme 4. Reagents: (a) (EtO)3P; (b) 1-Boc-4-piperidone, NaH, THF;
(c) H2, Pd/C, MeOH; (d) HCl, EtOAc.

400
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
O
O
O
O
O
O
R
R
Ac
S
Ac
S
S
b
b
c
d
N
N
Cl
N
NRR'
HN
HN
NRR'
2: R = H
29
30a: NRR' = NH2
30b: NRR' = NHMe
31a: NRR' = NH2
31b: NRR' = NHMe
a
28: R = Ac
O
O
O
O
O
O
O
O
S
S
S
c
f
N
F3C
N
Cl
F3C
N
NRR'
NRR'
2: R = H
33
34a: NRR' = NMe2
34b: NRR' = morpholino
35a: NRR' = NMe2
35b: NRR' = morpholino
e
32: R = CF3CO
Scheme 6. Reagents: (a) Ac2O; (b) ClSO3H, DCM; (c) HNRR0, (Et3N), THF; (d) concd HCl; (e) TFAA; (f) K2CO3, H2O, MeOH.
O
O
O
O
O
O
Ac
S
S
Ac
S
N
R
HN
R
a
b
N
Cl
36a: R = Me
36b: R = Et
40: R = i-Pr
37a: R = Me
37b: R = Et
41: R = i-Pr
29
c
(for 39b)
e
Ac
SH
Ac
S
S
d
(for 39a)
b
N
N
R
HN
Me
38
39a: R = Me
39b: R = i-Pr
42
Scheme 7. Reagents: (a) Na2SO3, NaHCO3, H2O, then ClCH2CO2H or CH3CH(Br)CO2H, aq NaOH; (b) concd HCl, then aq NaOH; (c) Zn, H2SO4;
(d) RI, K2CO3, DMF; (e) mCPBA, DCM.
protected by acetylation affording 28, which was treated
with chlorosulfonic acid to give the sulfonyl chloride 29.
Treatment of 29 with ammonia or methylamine pro-
vided the sulfonamides 30a,b, which on deprotection
by heating in concentrated hydrochloric acid yielded
the piperidines 31a,b. In the case of N,N-disubstituted
sulfonamides 35a,b, this procedure suffered from the
concomitant cleavage of the sulfonamide bond, thus a
trifluoroacetyl group was alternatively used for amino
protection.
3. Results and discussion
The synthesized compounds were evaluated for their
potency to inhibit the binding of 125I-labeled RANTES
to Chinese hamster ovary (CHO) cells expressing human
CCR5, and the results are reported as IC50 values.
We have recently identified the 5-oxopyrrolidine-3-carb-
oxamide derivatives as novel CCR5 antagonists (1,
Fig. 1).12 Our previous study demonstrated that the 5-
oxopyrrolidine-3-carbonyl group was critical for CCR5
binding affinity, implying that the amide moiety of the
c-lactam plays an important role in interaction with
CCR5. We hypothesized that the preferred orientation
of the amide group would provide more potent CCR5
antagonists. We therefore designed and introduced a
1-acetylpiperidine group as a replacement for the 5-oxo-
pyrrolidine in the lead structure.
Reaction of 2 with trifluoroacetic anhydride followed by
chlorosulfonylation gave the sulfonyl chloride 33. Treat-
ment of 33 with dimethylamine or morpholine afforded
the sulfonamide 34a,b, which on deprotection using
potassium carbonate yielded the piperidines 35a,b.
The sulfones 37a,b, 41, and sulfide 42 were synthesized
as shown in Scheme 7. Conversion of the sulfonyl
chloride 29 into the sulfones 36a,b was accomplished
by the literature method.17 Deprotection of the acetyl
group in 36a,b using concentrated hydrochloric acid
followed by neutralization provided the desired piper-
idines 37a,b. The isopropyl sulfone analogue 41 was
prepared in a different manner as follows. Reduction
of 29 with zinc in aqueous sulfuric acid gave the thiol
38, which was S-alkylated with 2-iodopropane yielding
the sulfide 39b. Oxidation of 39b with 3-chloroperoxy-
benzoic acid (mCPBA) followed by deprotection
afforded the requisite piperidine 41. The methyl sulfide
42 was prepared by S-methylation of 38 followed by
deprotection.
Replacement of the 5-oxopyrrolidin-3-yl group in com-
pound 1 (IC50 = 480nM) with a 1-acetylpiperidin-4-yl
group afforded compound 7a (IC50 = 16nM) with signifi-
cant improvement in CCR5 binding affinity (Table 1).
The marked enhancement in the binding affinity of
compound 7a encouraged us to further explore the
SAR of this class. Removal of the acetyl group in 7a
to provide compound 6a resulted in a substantial
reduction of binding affinity, indicating that the amide
carbonyl group is critical for binding affinity. Replace-
ment of the acetyl group in 7a with an isobutyryl (7b,
IC50 = 39nM) or benzoyl (7c, IC50 = 33nM) group
resulted in a slight loss of potency relative to 7a, while

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
401
Table 1. Modification of the acyl moiety
3-position of the phenyl ring of 7a resulted in a 5-fold
improvement in the binding potency (5c, IC50 = 3.0nM).
The additional incorporation of a chlorine atom at
the 4-position of the phenyl ring of 5c afforded 5f
(IC50 = 1.2nM), which was 10-fold more potent than
7a. The 4-methyl substituted derivative 5d
(IC50 = 2.8nM) also showed enhanced activity compar-
able to the 3-chlorinated compound 5c. These observa-
tions were similar to those seen for the central phenyl
ring of the 5-oxopyrrolidine-3-carboxamide deriva-
tives.12 Combination of 3-chloro and 4-methyl substitu-
ents provided 5g and 5h, which exhibited a dramatic
improvement in CCR5 binding potency relative to 7a.
In particular, compound 5h showed binding affinity with
an IC50 of 0.29nM and was one of the most potent
CCR5 binding ligands in this study. Replacement of
the methyl group of 5h with a bulky isopropyl (5i) or
polar methoxy (5j) group resulted in a moderate loss
of binding affinity, indicating that the central phenyl
group may interact with a sterically restricted and
hydrophobic pocket of the receptor. A similar trend
was also observed for a series of methylsulfonyl ana-
logues (Table 2, R1 = Ms). The 3,4-dichloro derivative
5k had an IC50 of 3.3nM for the binding affinity, while
compound 5l, with the 3-chloro-4-methyl group, showed
a higher affinity with an IC50 of 0.50nM. The presence
of a fluorine substituent in the 4-benzylpiperidine moiety
(R3 = F) had a slightly better effect on binding affinity
(5e vs 5f, 5g vs 5h).
4 O
N
N
N
R1
3
Compound
R1
Position
CCR5a
IC50 (nM)
1
480
48
5a
6a
7a
7b
7c
7d
5b
6b
7e
7f
Cbz
H
4
4
4
4
4
4
3
3
3
3
4300
16
Ac
i-PrCO
Bz
Ms
39
33
40
Cbz
H
1200
780
680
180
Ac
Ms
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing
CHO cells.
maintaining improved affinity over the 5-oxopyrrol-
idine-3-carboxamide derivative 1. It seems that the
1-position of the piperidine ring is sterically less
restricted. Interestingly, methylsulfonyl analogue 7d
(IC50 = 40nM) also had improved potency, suggesting
that the 1-position of the piperidine ring prefers a wide
range of polar substituents. Indeed, carbamate 5a
(IC50 = 48nM) had comparable potency to the amide
analogue 7c. Compounds having a 1-acylpiperidin-3-yl
group, on the other hand, had no advantage in CCR5
binding affinity (5b, 7e,f). This indicates that the appro-
priate orientation of the polar moiety is required for
high binding potency.
With the potent compounds in hand, we examined the
alkyl linker length to confirm that it was still optimal
in the newly identified piperidine-4-carboxamide series
(Table 3). It has been demonstrated that a three-carbon
linker was optimal for CCR5 binding in the 5-oxopyrrol-
idine-3-carboxamide series.12 As shown in Table 3, a
compound with a three-carbon chain (5f) again showed
the best activity in the piperidine-4-carboxamide series.
Increasing (12) or decreasing (18) the alkyl chain length
led to decreased potency.
Having identified the 1-acylpiperidin-4-yl group as criti-
cal for potent CCR5 binding affinity, we then searched
for the optimal substituent of the central phenyl ring
(Table 2, R2). Introduction of a chlorine atom at the
Table 2. Substitution on the central phenyl ring
We next turned our attention to the substitution on the
phenyl ring of the 4-benzylpiperidine moiety. As shown
in Table 4, a variety of functional groups were allowed
at the 4-position of the phenyl ring. Introduction of a
trifluoromethyl group (11a) resulted in a 2-fold
decrease in CCR5 binding potency compared to the
O
R3
N
4
N
N
R1
R2
3
Compound R1 R2
R3 CCR5a Fusionb
IC50 (nM) IC50 (nM)
Table 3. Modification of the alkyl linker length
7a
5c
5d
5e
5f
5g
5h
5i
Ac
Ac 3-Cl
H
H
F
F
H
F
H
F
F
F
F
F
16 72
3.0 6.1
O
F
N
(CH2)n
N
Ac 4-Me
Ac 3,4-diCl
Ac 3,4-diCl
2.8
1.9
6.8
4.2
Me
N
O
1.2
3.0
Cl
Ac 3-Cl, 4-Me
Ac 3-Cl, 4-Me
Ac 3-Cl, 4-i-Pr
Ac 3-Cl, 4-MeO
Ms 3,4-diCl
0.62
0.29
0.73
0.23
Cl
Compound
n
CCR5a
IC50 (nM)
18
30
3.3
0.50
22
31
2.3
0.47
5j
5k
5l
5f
3
4
2
1.2
52
Ms 3-Cl, 4-Me
12
18
480
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing
CHO cells.
b Inhibition of HIV-1 envelope-mediated membrane fusion.
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing
CHO cells.

402
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
Table 4. Substitution on the phenyl ring of the 4-benzylpiperidine
moiety
inhibitory activity of the membrane fusion was more
potent than expected from the CCR5 binding potency
(Table 4). The methylsulfonyl derivative 11f inhibited
the membrane fusion with an IC50 of 0.80nM, which
was lower than that of the methylsulfanyl compound
11e (IC50 = 2.3nM). The methylsulfonylamino (14b),
isopropylsulfonyl (11h), and aminosulfonyl (11j–l)
derivatives also inhibited the membrane fusion at
sub-nanomolar concentrations. In particular, the
morpholinosulfonyl derivative 11l showed the inhibitory
activity with an IC50 of 0.045nM. These results suggest
that polar substituents on the phenyl ring of the 4-benz-
ylpiperidine moiety can interfere effectively with the
HIV-1 cell entry.
O
R3
N
N
Me
N
S
O
O
Cl
Cl
Compound
R3
CCR5a
IC50 (nM)
Fusionb
IC50 (nM)
5k
F
CF3
3.3
8.7
2.4
9.2
5.9
2.2
2.8
7.9
3.1
2.2
1.9
1.5
3.4
1.5
1.2
1.3
2.1
11a
11b
13
NT
NT
NT
NT
0.15
1.8
NO2
NH2
NHAc
NHMs
14a
14b
11c
11d
11e
11f
11g
11h
11i
11j
11k
11l
Finally, we selected compound 11f for further profiling.
Compound 11f was tested against a panel of other chemo-
kine receptors and found to be selective for CCR5. It
did not inhibit ligand binding to CHO cells expressing
CCR1, CCR2, CCR3, CCR4, or CCR7 even at a con-
centration of 10lM. Compound 11f inhibited the repli-
cation of R5 HIV-1 (Ba-L strain) in human peripheral
blood mononuclear cells (PBMC) with an EC50 value
of 0.59nM. No cytotoxicity of 11f against human
PBMC was observed even at a concentration of
20lM, indicating that the selectivity index of 11f is
>34,000. Preliminary pharmacokinetic parameters for
11f were measured in beagle dogs. After oral administra-
Morpholino
OMe
SMe
4.3
2.3
SO2Me
SO2Et
0.80
NT
0.60
1.4
SO2i-Pr
SO2NH2
SO2NHMe
SO2NMe2
0.33
0.25
0.045
SO2 (morpholino)
a Inhibition of 125I-labeled RANTES binding to CCR5-expressing
CHO cells.
b Inhibition of HIV-1 envelope-mediated membrane fusion.
tion (10mg/kg), the peak plasma concentration (Cmax
)
fluoro analogue 5k (IC50 = 3.3nM), while the nitro
compound 11b retained activity (IC50 = 2.4nM), sug-
gesting that polar substituents were preferable at this
position. Reduction of the nitro group in 11b provided
the amino derivative 13, which showed lower potency
was 0.57lg/mL at 4.0h. The area under the plasma con-
centration–time curve from 0 to 24h (AUC0–24 h) was
8.06lgÆh/mL.
4. Conclusion
than 11b, but the methylsulfonylamino (14b, IC50
=
2.2nM) and morpholino (11c, IC50 = 2.8nM) com-
pounds restored binding potency comparable to that
of 11b. Substitution with an electron-donating methoxy
group (11d) slightly decreased the activity, whereas a
methylsulfanyl group (11e) was found to be well toler-
ated (IC50 = 3.1nM). The alkylsulfonyl (11f–h) and ami-
nosulfonyl (11i–l) derivatives also exhibited good
activity, in which the larger groups had a better effect
on the activity (11h,k,l).
A novel series of potent CCR5 antagonists, piperidine-4-
carboxamides, was designed and synthesized. Replace-
ment of the 5-oxopyrrolidin-3-yl fragment in the
original lead structure (1) with a 1-acetylpiperidin-4-yl
group afforded the compound 7a, which had 30-fold en-
hanced activity in CCR5 binding. The acetyl group
needed to be in the appropriate position for potent bind-
ing and could be replaced with other polar groups such
as methylsulfonyl. Substitutions (3,4-diCl, 3-Cl, 4-Me)
on the central phenyl ring led to the potent CCR5 antag-
onists (5e–h,k,l) with low to sub-nanomolar activity.
Compound 11f was found to be a potent and orally bio-
available CCR5 antagonist, and inhibited the replication
of R5 HIV-1 in PBMC with an EC50 of 0.59nM. Fur-
ther development of this series will be reported in the
near future.
Selected 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
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. The results for the effect of
the central phenyl substitution are presented in Table
2, showing that the inhibitory activity of the membrane
fusion roughly correlated with the CCR5 binding
affinity. The most potent compound 5g, 5h, and 5l,
containing the 3-chloro-4-methyl substitution pattern
on the central phenyl ring, inhibited the membrane
fusion with IC50 values of 0.73, 0.23, and 0.47nM,
respectively. 3,4-Dichloro analogues 5e, 5f, and 5k also
exhibited good inhibitory activity (IC50 = 4.2, 3.0, and
2.3nM). Interesting results were obtained in the explora-
tion of the 4-benzylpiperidine moiety, where the
5. Experimental
Reagents and solvents were used as obtained from com-
mercial suppliers without further purification. Column
chromatography was carried out on silica gel (Daiso,
IR-60-40/63-W) or basic alumina (ICN Biomedicals,
activity III). Yields were not optimized. Melting points
were determined on a Yanagimoto micro melting point
1
apparatus and are uncorrected. H NMR spectra were
recorded on a Varian Gemini 200 or Mercury 300

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
403
spectrometer. Chemical shifts (d) are given in ppm with
tetramethylsilane (organic solvents) or 3-(trimethylsil-
yl)propionic-2,2,3,3-d4 acid, sodium salt (D2O) as an
internal standard, and coupling constants (J) are given
in hertz (Hz). Elemental analyses were carried out at
Takeda Analytical Research Laboratories, Ltd. Mass
spectra were obtained using a Platform II mass spec-
trometer (APCI).
J = 7.0Hz), 3.41 (2H, br d, J = 11.0Hz), 6.77 (1H, d,
J = 7.6Hz), 6.93 (1H, s), 7.10–7.40 (6H, m). Anal. Calcd
for C22H29ClN2Æ2HClÆ0.8H2O: C, 59.48; H, 7.40; N,
6.31. Found: C, 59.41; H, 7.41; N, 6.31.
5.4. 3-Chloro-N-{3-[4-(4-fluorobenzyl)piperidin-1-yl]prop-
yl}aniline dihydrochloride (3d)
Yield 59%, mp 202–208ꢁC (dec). 1H NMR (DMSO-d6):
d 1.35–2.05 (7H, m), 2.45–2.60 (2H, m), 2.60–2.95 (2H,
m), 2.95–3.30 (2H, m), 3.09 (2H, t, J = 6.6Hz), 3.41
(2H, br d, J = 12.0Hz), 6.50–6.70 (3H, m), 7.00–7.30
(5H, m). Anal. Calcd for C21H26ClFN2Æ2HClÆ0.9H2O:
C, 56.05; H, 6.67; N, 6.22. Found: C, 56.09; H, 6.62;
N, 6.27.
5.1. N-[3-(4-Benzylpiperidin-1-yl)propyl]aniline dihydro-
chloride (3a)
To a stirred solution of 4-benzylpiperidine (2) (52.6g,
0.30mol) and DBU (0.45mL, 3.0mmol) in THF
(600mL) was added dropwise a solution of acrolein
(90%, 18.7g, 0.30mol) in THF (60mL) at ꢀ20ꢁC,
and the mixture was stirred for 1h maintaining a tem-
perature of ꢀ20 to ꢀ10ꢁC. To the mixture was added
aniline (27.9g, 0.30mol) followed by NaBH(OAc)3
(127.2g, 0.60mol) at ꢀ10ꢁC, and the mixture was
stirred for 19h allowing to warm to room temperature.
The mixture was diluted with 2N NaOH (900mL)
under ice cooling, stirred for 30min, and extracted with
Et2O (400mL, 2 · 200mL). The organic layer was
dried (MgSO4), filtered, and concentrated in vacuo.
The residue dissolved in i-PrOH (400mL) was treated
with 4N HCl (EtOAc solution, 200mL) under stirring.
The resulting precipitate was collected by filtration,
washed with i-PrOH (3 · 100mL), and dried in vacuo
to afford 3a (75.7g, 66%) as a white solid, mp
215–217ꢁC (dec). 1H 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 = 11.4Hz), 3.12 (2H, br t, J = 7.2Hz),
3.29 (2H, br t, J = 6.9Hz), 3.41 (2H, br d,
J = 12.6Hz), 7.05–7.50 (10H, m). Anal. Calcd for
C21H28N2Æ2HClÆ0.5H2O: C, 64.61; H, 8.00; N, 7.18.
Found: C, 64.71; H, 7.92; N, 7.32. 1H NMR (free
base, CDCl3): d 1.05–1.85 (9H, m), 2.34 (2H, t,
J = 6.8Hz), 2.46 (2H, d, J = 6.6Hz), 2.83 (2H, br d,
J = 11.8Hz), 3.06 (2H, t, J = 6.4Hz), 6.45–6.65 (3H,
m), 7.00–7.25 (7H, m).
5.5. N-{3-[4-(4-Fluorobenzyl)piperidin-1-yl]propyl}-4-meth-
ylaniline dihydrochloride (3e)
Yield 61%, mp 206–208ꢁC (dec). 1H NMR (DMSO-d6):
d 1.40–1.90 (5H, m), 2.00–2.25 (2H, m), 2.30 (3H, s),
2.45–2.60 (2H, m), 2.83 (2H, m), 3.12 (2H, m), 3.29
(2H, m), 3.41 (2H, m), 7.05–7.40 (8H, m). Anal. Calcd
for C22H29FN2Æ2HCl: C, 63.92; H, 7.56; N, 6.78. Found:
C, 63.82; H, 7.52; N, 6.65.
5.6. 3,4-Dichloro-N-{3-[4-(4-fluorobenzyl)piperidin-1-yl]-
propyl}aniline dihydrochloride (3f)
Yield 48%, mp 203–209ꢁC (dec). 1H NMR (DMSO-
d6): d 1.35–2.05 (7H, m), 2.45–2.60 (2H, m), 2.60–
3.30 (6H, m), 3.41 (2H, br d, J = 10.6Hz), 6.57 (1H,
dd, J = 2.7, 8.8Hz), 6.75 (1H, d, J = 2.7Hz), 7.05–
7.30 (5H, m). Anal. Calcd for C21H25Cl2FN2Æ2HClÆ0.5-
H2O: C, 52.85; H, 5.91; N, 5.87. Found: C, 52.90; H,
6.12; N, 5.94.
5.7. 3-Chloro-N-{3-[4-(4-fluorobenzyl)piperidin-1-yl]prop-
yl}-4-methylaniline dihydrochloride (3g)
Yield 63%, mp 218–221ꢁC (dec). 1H NMR (DMSO-d6):
d 1.40–2.15 (7H, m), 2.22 (3H, s), 2.45–2.60 (2H, m),
2.82 (2H, m), 3.08 (2H, m), 3.16 (2H, t, J = 7.0Hz),
3.41 (2H, br d, J = 12.2Hz), 6.75–7.35 (7H, m). Anal.
Calcd for C22H28ClFN2Æ2HClÆ0.1H2O: C, 58.77; H,
6.77; N, 6.23. Found: C, 58.78; H, 6.91; N, 6.08.
The following compounds 3b–i were prepared using a
procedure similar to that described for 3a from 2, 22a
and the appropriate aniline.
5.2. N-[3-(4-Benzylpiperidin-1-yl)propyl]-3,4-dichloro-
aniline dihydrochloride (3b)
5.8. 3-Chloro-N-{3-[4-(4-fluorobenzyl)piperidin-1-yl]prop-
yl}-4-isopropylaniline dihydrochloride (3h)
Yield 53%, mp 200–203ꢁC (dec). 1H 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 = 2.8, 8.8Hz), 6.75 (1H, d, J = 2.6Hz), 7.17–7.30
(6H, m). Anal. Calcd for C21H26Cl2N2Æ2HClÆ0.5H2O:
C, 54.92; H, 6.36; N, 6.10. Found: C, 55.11; H, 6.64;
N, 6.37.
Yield 66%, mp 174–176ꢁC (dec). 1H NMR (CD3OD): d
1.25 (6H, d, J = 7.0Hz), 1.50–1.65 (2H, m), 1.86–2.02
(3H, m), 2.12–2.28 (2H, m), 2.60 (2H, d, J = 6.6Hz),
2.88–3.00 (2H, m), 3.16–3.24 (2H, m), 3.38–3.50 (3H,
m), 3.54–3.61 (2H, m), 6.97–7.05 (2H, m), 7.16–7.23
(2H, m), 7.34–7.39 (1H, m), 7.48–7.54 (2H, m). Anal.
Calcd for C24H32ClFN2Æ2HCl: C, 60.57; H, 7.20; N,
5.89. Found: C, 60.31; H, 7.23; N, 5.86.
5.3. N-[3-(4-Benzylpiperidin-1-yl)propyl]-3-chloro-4-meth-
ylaniline dihydrochloride (3c)
5.9. 3-Chloro-N-{3-[4-(4-fluorobenzyl)piperidin-1-yl]prop-
yl}-4-methoxyaniline dihydrochloride (3i)
Yield 70%, mp 195–200ꢁC (dec). 1H NMR (DMSO-d6):
d 1.40–2.15 (7H, m), 2.21 (3H, s), 2.45–2.60 (2H, m),
2.60–2.95 (2H, m), 2.95–3.30 (2H, m), 3.15 (2H, t,
Yield 65%, mp 178–184ꢁC (dec). 1H NMR (CD3OD): d
1.40–2.00 (5H, m), 2.22 (2H, m), 2.60 (2H, d,

404
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
J = 6.6Hz), 2.95 (2H, dt, J = 2.2, 12.7Hz), 3.21 (2H, m),
3.47 (2H, m), 3.58 (2H, br d, J = 12.2Hz), 3.93 (3H, s),
7.01 (2H, m), 7.20 (2H, m), 7.25 (1H, d, J = 8.9Hz), 7.49
(1H, dd, J = 2.7, 8.9Hz), 7.63 (1H, d, J = 2.7Hz). Anal.
Calcd for C22H28ClFN2OÆ2HCl: C, 56.97; H, 6.52; N,
6.04. Found: C, 56.70; H, 6.47; N, 6.11.
5.11. Benzyl 3-{[[3-(4-benzylpiperidin-1-yl)propyl](phen-
yl)amino]carbonyl}piperidine-1-carboxylate hydrochlo-
ride (5b)
5.11.1. Step 1: 1-[(Benzyloxy)carbonyl]piperidine-3-carb-
oxylic acid. The product was prepared using a procedure
similar to that described for 1-[(benzyloxy)carbonyl]pip-
eridine-4-carboxylic acid from nipecotic acid. Yield
89%, mp 96–98ꢁC. 1H NMR (CDCl3): d 1.35–1.85
(3H, m), 2.00–2.20 (1H, m), 2.40–2.65 (1H, m), 2.85–
3.25 (2H, m), 3.90–4.05 (1H, m), 4.05–4.35 (1H, m),
5.12 and 5.15 (2H, ABq, J = 12.4Hz), 7.20–7.40 (5H,
m). Anal. Calcd for C14H17NO4: C, 63.87; H, 6.51; N,
5.32. Found: C, 63.83; H, 6.44; N, 5.33.
5.10. Benzyl 4-{[[3-(4-benzylpiperidin-1-yl)propyl](phen-
yl)amino]carbonyl}piperidine-1-carboxylate fumarate
(5a)
5.10.1. Step 1: 1-[(Benzyloxy)carbonyl]piperidine-4-carb-
oxylic acid. To an ice-cooled stirred solution of isonipe-
cotic acid (64.6g, 0.50mol) and NaOH (44.0g, 1.1mol)
in water (250mL) was added dropwise benzyl chlorofor-
mate (93.8g, 0.55mol). After stirring at room tempera-
ture for 4h, the mixture was washed with Et2O
(3 · 150mL), acidified with 6N HCl (140mL), and
extracted with EtOAc (3 · 200mL). The organic layer
was dried (MgSO4), filtered, and concentrated in vacuo.
The residue was recrystallized from toluene/hexane to
give the product (121.5g, 92%) as a white solid, mp 71–
5.11.2. Step 2: Benzyl 3-{[[3-(4-benzylpiperidin-1-yl)prop-
yl](phenyl)amino]carbonyl}piperidine-1-carboxylate hyd-
rochloride (5b). Compound 5b was prepared using a
procedure similar to that described for 5a from
1-[(benzyloxy)carbonyl]piperidine-3-carboxylic
acid.
Yield 71%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.00–1.90 (13H, m), 2.15–2.35 (1H, m), 2.26
(2H, t, J = 7.7Hz), 2.50 (2H, d, J = 6.6Hz), 2.55–
3.05 (2H, m), 2.81 (2H, br d, J = 11.8Hz), 3.55–3.80
(2H, m), 3.95–4.20 (2H, m), 5.03 (2H, br s), 7.00–7.50
(15H, m). Anal. Calcd for C35H43N3O3ÆHClÆ0.9H2O:
C, 69.32; H, 7.61; N, 6.93. Found: C, 69.26; H, 7.69;
N, 7.05.
1
73ꢁC. H NMR (CDCl3): d 1.55–1.80 (2H, m), 1.80–
2.05 (2H, m), 2.53 (1H, tt, J = 4.0, 10.7Hz), 2.85–3.05
(2H, m), 4.10 (2H, br d, J = 13.0Hz), 5.13 (2H, s),
7.30–7.40 (5H, m). Anal. Calcd for C14H17NO4: C,
63.87; H, 6.51; N, 5.32. Found: C, 63.85; H, 6.45; N, 5.26.
5.10.2. Step 2: Benzyl 4-{[[3-(4-benzylpiperidin-1-yl)prop-
yl](phenyl)amino]carbonyl}piperidine-1-carboxylate fuma-
rate (5a). To a stirred solution of the product from
step 1 (2.37g, 9.0mmol) and N,N-dimethylformamide
(DMF) (7lL) in dichloromethane (DCM) (15mL) was
added oxalyl chloride (1.00mL, 12mmol), and the mix-
ture was stirred at room temperature for 1h. The mix-
ture was concentrated in vacuo followed by addition
of toluene (10mL) and evaporation to remove traces
of oxalyl chloride, affording 1-[(benzyloxy)carbonyl]pip-
eridine-4-carbonyl chloride (4a). The residue was dis-
solved in DCM (5mL), and the solution was added
dropwise to a stirred solution of 3a (1.91g, 5.0mmol)
and Et3N (3.97mL, 28mmol) in DCM (45mL) at
ꢀ20ꢁC. The mixture was stirred for 1h allowing to
warm to room temperature. The mixture was treated
with saturated aqueous NaHCO3 (45mL), and the
organic solvent was removed in vacuo. The aqueous
layer was extracted with EtOAc (40mL, 2 · 20mL).
The organic layer was washed with saturated aqueous
NaHCO3 (3 · 10mL) and brine (10mL), dried (MgSO4),
and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc/MeOH
1/0–9/1) to afford the free base of 5a (2.54g) as a color-
less oil. The free base (206mg) was treated with fumaric
acid (1equiv) and recrystallized from EtOAc/EtOH to
give the fumarate 5a (224mg, 83%) as a white solid,
5.12. 1-Acetyl-N-[3-(4-benzylpiperidin-1-yl)propyl]-N-(3,4-
dichlorophenyl)piperidine-4-carboxamide hydrochloride
(5e)
To an ice-cooled stirred solution of 3b (450mg,
1.0mmol) and Et3N (836lL, 6.0mmol) in DCM
(10mL) was added 1-acetylpiperidine-4-carbonyl
chloride (4c)18 (569mg, 3.0mmol), and the mixture
was stirred at 0ꢁC for 1h. The mixture was diluted with
saturated aqueous NaHCO3 (15mL), and the organic
solvent was removed in vacuo. The residue was
extracted with EtOAc (3 · 15mL), and the organic layer
was washed with saturated aqueous NaHCO3 (3 · 5mL)
and brine (5mL), dried (Na2SO4), filtered, and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 1/0–9/1)
to afford the free base of 5e (522mg) as a colorless oil.
The free base (522mg) was converted to the hydrochlo-
ride salt using 4N HCl (EtOAc solution) to afford 5e
(477mg, 84%) as an amorphous solid. 1H NMR
(free base, CDCl3): d 1.10–1.90 (13H, m), 2.04 (3H,
s), 2.20–2.55 (2H, m), 2.27 (2H, t, J =
7.4Hz), 2.51 (2H, d, J = 6.2Hz), 2.75–2.95 (1H, m),
2.82 (2H, br d, J = 11.2Hz), 3.65 (2H, t, J = 7.5Hz),
3.77 (1H, br d, J = 13.4Hz), 4.52 (1H, br d,
J = 13.4Hz), 7.00–7.35 (5H, m), 7.04 (1H, dd, J = 2.4,
8.4Hz), 7.32 (1H, d, J = 2.4Hz), 7.52 (1H, d,
J = 8.4Hz). Anal. Calcd for C29H37Cl2N3O2ÆHClÆ0.9-
H2O: C, 59.72; H, 6.88; N, 7.21. Found: C, 59.76; H,
6.81; N, 7.19.
1
mp 165–168ꢁC. H NMR (free base, CDCl3): d 1.10–
1.90 (13H, m), 2.15–2.35 (1H, m), 2.27 (2H,
t, J = 7.3Hz), 2.40–2.65 (2H, m), 2.50 (2H, d, J =
6.6Hz), 2.82 (2H, br d, J = 11.8Hz), 3.67 (2H, t,
J = 7.7Hz), 4.00–4.20 (2H, m), 5.09 (2H, s), 7.05–
7.50 (15H, m). Anal. Calcd for C35H43N3O3ÆC4H4O4:
C, 69.93; H, 7.07; N, 6.27. Found: C, 69.70; H, 7.05;
N, 6.25.
The following compounds 5c,d,f–j were prepared using
a procedure similar to that described for 5e from the
anilines 3c–i.

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
405
5.13. 1-Acetyl-N-(3-chlorophenyl)-N-{3-[4-(4-fluorobenz-
yl)piperidin-1-yl]propyl}piperidine-4-carboxamide hydro-
chloride (5c)
(2H, d, J = 6.6Hz), 2.70–2.95 (1H, m), 2.83 (2H, br d,
J = 11.0Hz), 3.65 (2H, t, J = 7.7Hz), 3.76 (1H, br d,
J = 12.8Hz), 4.51 (1H, br d, J = 12.8Hz), 6.85–7.15
(5H, m), 7.19 (1H, d, J = 2.2Hz), 7.29 (1H, d,
J = 8.0Hz). Anal. Calcd for C30H39ClFN3O2ÆHClÆ0.5-
H2O: C, 62.82; H, 7.20; N, 7.33. Found: C, 62.77; H,
7.20; N, 7.21.
Yield 77%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–1.90 (13H, m), 2.05 (3H, s), 2.20–2.55
(2H, m), 2.27 (2H, t, J = 7.5Hz), 2.48 (2H, d,
J = 6.6Hz), 2.70–2.95 (1H, m), 2.82 (2H, br d, J =
11.6Hz), 3.67 (2H, t, J = 7.7Hz), 3.77 (1H, br d,
J = 13.1Hz), 4.52 (1H, br d, J = 13.1Hz), 6.94 (2H, t,
J = 8.8Hz), 7.00–7.15 (3H, m), 7.20 (1H, s), 7.38 (2H,
d, J = 5.0Hz). Anal. Calcd for C29H37ClFN3O2ÆHClÆ0.5-
H2O: C, 62.25; H, 7.03; N, 7.51. Found: C, 62.34; H,
7.06; N, 7.64.
5.18. 1-Acetyl-N-(3-chloro-4-isopropylphenyl)-N-{3-[4-
(4-fluorobenzyl)piperidin-1-yl]propyl}piperidine-4-carbox-
amide hydrochloride (5i)
Yield81%,amorphoussolid.1HNMR(freebase,CDCl3):
d 1.10–1.40 (2H, m), 1.28 (6H, d, J = 7.0Hz), 1.50–1.97
(11H, m), 2.05 (3H, s), 2.23–2.42 (4H, m), 2.48 (2H, d,
J = 6.6Hz), 2.80–2.93 (3H, m), 3.42 (1H, septet,
J = 7.0Hz), 3.60–3.80 (3H, m), 4.47–4.54 (1H, m), 6.70–
7.10 (5H, m), 7.16 (1H, d, J = 2.2Hz), 7.33 (1H, d,
J = 8.4Hz). Anal. Calcd for C32H43ClFN3O2ÆHClÆ4H2O:
C,57.82;H,7.89;N,6.32.Found:C,57.95;H,7.89;N,6.34.
5.14. 1-Acetyl-N-{3-[4-(4-fluorobenzyl)piperidin-1-yl]prop-
yl}-N-(4-methylphenyl)piperidine-4-carboxamide hydro-
chloride (5d)
Yield 87%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–1.90 (13H, m), 2.03 (3H, s), 2.20–2.55
(2H, m), 2.29 (2H, t, J = 7.7Hz), 2.40 (3H, s), 2.48
(2H, d, J = 6.6Hz), 2.70–2.95 (1H, m), 2.84 (2H, br d,
J = 11.2Hz), 3.65 (2H, t, J = 7.6Hz), 3.74 (1H, br d,
J = 13.2Hz), 4.50 (1H, br d, J = 13.2Hz), 6.85–7.15
(6H, m), 7.22 (2H, d, J = 7.6Hz). Anal. Calcd for
C30H40FN3O2ÆHClÆ0.5H2O: C, 66.83; H, 7.85; N, 7.79.
Found: C, 66.87; H, 8.08; N, 7.75.
5.19. 1-Acetyl-N-(3-chloro-4-methoxyphenyl)-N-{3-[4-(4-
fluorobenzyl)piperidin-1-yl]propyl}piperidine-4-carbox-
amide hydrochloride (5j)
Yield 80%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–1.95 (13H, m), 2.04 (3H, s), 2.20–2.55
(2H, m), 2.29 (2H, t, J = 7.5Hz), 2.48 (2H, d,
J = 6.6Hz), 2.75–2.95 (3H, m), 3.63 (2H, t, J = 7.5Hz),
3.76 (1H, br d, J = 13.4Hz), 3.95 (3H, s), 4.52 (1H, br
d, J = 13.4Hz), 6.85–7.15 (6H, m), 7.21 (1H, d,
J = 2.6Hz). Anal. Calcd for C30H39ClFN3O3ÆHClÆ0.6-
H2O: C, 60.93; H, 7.02; N, 7.11. Found: C, 60.94; H,
7.06; N, 7.25.
5.15. 1-Acetyl-N-(3,4-dichlorophenyl)-N-{3-[4-(4-fluoro-
benzyl)piperidin-1-yl]propyl}piperidine-4-carboxamide
hydrochloride (5f)
Yield 91%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–1.90 (13H, m), 2.05 (3H, s), 2.20–2.55
(2H, m), 2.27 (2H, t, J = 7.5Hz), 2.48 (2H, d,
J = 6.6Hz), 2.70–3.00 (1H, m), 2.81 (2H, br d, J =
11.8Hz), 3.65 (2H, t, J = 7.5Hz), 3.78 (1H, br d,
J = 13.0Hz), 4.52 (1H, br d, J = 13.0Hz), 6.94 (2H, t,
J = 8.6Hz), 6.95–7.15 (3H, m), 7.32 (1H, d, J =
2.2Hz), 7.52 (1H, d, J = 8.4Hz). Anal. Calcd for
C29H36Cl2FN3O2ÆHClÆ0.5H2O: C, 58.64; H, 6.45; N,
7.07. Found: C, 58.61; H, 6.56; N, 7.03.
5.20. N-(3,4-Dichlorophenyl)-N-{3-[4-(4-fluorobenzyl)-
piperidin-1-yl]propyl}-1-(methylsulfonyl)piperidine-
4-carboxamide (5k)
5.20.1. Step 1: Ethyl-1-(methylsulfonyl)piperidine-4-carb-
oxylate. To an ice-cooled stirred solution of ethyl isoni-
pecotate (157g, 1.0mol) and Et3N (153mL, 1.1mol) in
EtOAc (800mL) was added dropwise methanesulfonyl
chloride (85mL, 1.1mol). After stirring at room temper-
ature for 2.5h, the mixture was diluted with water
(800mL), and the organic layer was separated. The aque-
ous layer was extracted with EtOAc (2 · 200mL), and
the combined organic layer was washed with 1N HCl
(2 · 100mL) and brine (100mL), dried (MgSO4), filtered,
and concentrated in vacuo. The residue was triturated
with i-Pr2O (300mL), collected by filtration, washed with
i-Pr2O (3 · 200mL), and dried in vacuo to afford the
5.16. 1-Acetyl-N-[3-(4-benzylpiperidin-1-yl)propyl]-N-(3-
chloro-4-methylphenyl)piperidine-4-carboxamide (5g)
Yield 54%, mp 96–99ꢁC. 1H NMR (CDCl3): d 1.10–1.90
(13H, m), 2.04 (3H, s), 2.20–2.45 (2H, m), 2.27 (2H, t,
J = 7.5Hz), 2.42 (3H, s), 2.51 (2H, d, J = 6.6Hz), 2.70–
2.95 (1H, m), 2.82 (2H, br d, J = 11.4Hz), 3.64 (2H, t,
J = 7.7Hz), 3.76 (1H, br d, J = 13.9Hz), 4.51 (1H, br d,
J = 13.9Hz), 6.96 (1H, dd, J = 2.2, 8.0Hz), 7.05–7.35
(7H, m). Anal. Calcd for C30H40ClN3O2: C, 70.64; H,
7.90; N, 8.24. Found: C, 70.40; H, 8.01; N, 8.18.
1
product (210g, 89%) as a white solid, mp 91–92ꢁC. H
NMR (CDCl3): d 1.27 (3H, t, J = 7.2Hz), 1.75–2.10
(4H, m), 2.35–2.55 (1H, m), 2.78 (3H, s), 2.80–2.95
(2H, m), 3.60–3.75 (2H, m), 4.16 (2H, q, J = 7.2Hz).
Anal. Calcd for C9H17NO4S: C, 45.94; H, 7.28; N,
5.95. Found: C, 45.87; H, 7.19; N, 5.80.
5.17. 1-Acetyl-N-(3-chloro-4-methylphenyl)-N-{3-[4-(4-
fluorobenzyl)piperidin-1-yl]propyl}piperidine-4-carbox-
amide hydrochloride (5h)
5.20.2. Step 2: 1-(Methylsulfonyl)piperidine-4-carboxylic
acid. To a stirred solution of NaOH (42.9g, 1.1mol) in
water (525mL) was added portionwise the product from
step 1 (210g, 0.89mol), and the mixture was stirred for
Yield 84%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–1.90 (13H, m), 2.04 (3H, s), 2.20–2.55
(2H, m), 2.28 (2H, t, J = 7.5Hz), 2.42 (3H, s), 2.48

406
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
3h. The mixture was neutralized with concentrated HCl
(98mL, 1.2mol) at 0ꢁC and stirred for 1h. The resulting
precipitate was collected by filtration, washed with
water, and dried (P2O5) in vacuo to afford the product
(170g, 92%) as a white solid, mp 161–163ꢁC. 1H
NMR (D2O): d 1.60–1.85 (2H, m), 1.95–2.15 (2H, m),
2.45–2.65 (1H, m), 2.80–3.00 (2H, m), 2.98 (3H, s),
3.55–3.75 (2H, m). Anal. Calcd for C7H13NO4S: C,
40.57; H, 6.32; N, 6.76. Found: C, 40.73; H, 6.24; N,
6.79.
MeOH (30mL) was stirred under a hydrogen atmos-
phere at room temperature for 16h. The catalyst was fil-
tered off, and the filtrate was concentrated in vacuo to
give 6a (1.70g, 97%) as a colorless oil. 1H NMR
(CDCl3): d 1.10–1.95 (13H, m), 2.05–2.45 (5H, m),
2.51 (2H, d, J = 6.6Hz), 2.84 (2H, br d, J = 11.8Hz),
3.01 (2H, br d, J = 12.8Hz), 3.67 (2H, t, J = 7.7Hz),
7.05–7.50 (10H, m).
5.23. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N-phenylpiper-
idine-3-carboxamide (6b)
5.20.3. Step 3: 1-(Methylsulfonyl)piperidine-4-carbonyl
chloride (4d). To a stirred mixture of the product from
step 2 (51.8g, 0.25mol) and DMF (194lL, 2.5mmol)
in DCM (250mL) was added dropwise oxalyl chloride
(32mL, 0.37mmol), and the mixture was stirred at room
temperature for 3h followed by concentration in vacuo.
The residue was triturated with petroleum ether, col-
lected by filtration, and dried in vacuo to afford 4d
(54.5g, 97%) as a white solid.
Compound 6b was prepared using a procedure similar
to that described for 6a from 5b. Yield 95%, oil. H
NMR (CDCl3): d 1.00–2.05 (13H, m), 2.15–2.40 (1H,
m), 2.26 (2H, t, J = 7.5Hz), 2.45–2.70 (1H, m), 2.51
(2H, d, J = 6.6Hz), 2.70–3.00 (5H, m), 3.66 (2H, t,
J = 7.5Hz), 7.05–7.50 (10H, m).
1
5.24. 1-Acetyl-N-[3-(4-benzylpiperidin-1-yl)propyl]-N-
phenylpiperidine-4-carboxamide hydrochloride (7a)
5.20.4. Step 4: N-(3,4-Dichlorophenyl)-N-{3-[4-(4-fluoro-
benzyl)piperidin-1-yl]propyl}-1-(methylsulfonyl)piperidine-
4-carboxamide (5k). To an ice-cooled stirred solution of
3f (468mg, 1.0mmol) and Et3N (836lL, 6.0mmol) in
DCM (10mL) was added 4d (564mg, 2.5mmol), and
the mixture was stirred at 0ꢁC for 3h. The mixture
was diluted with saturated aqueous NaHCO3 (15mL)
and extracted with DCM. The organic layer was washed
with saturated aqueous NaHCO3 and brine, dried
(Na2SO4), filtered, and concentrated in vacuo. The resi-
due was purified by column chromatography on silica
gel (EtOAc/MeOH 1/0–9/1) followed by trituration with
Et2O to afford 5k (485mg, 83%) as a white solid, mp
To an ice-cooled stirred solution of 6a (252mg,
0.60mmol) and Et3N (201lL, 1.4mmol) in THF
(5mL) was added acetyl chloride (85lL, 1.2mmol),
and the mixture was stirred at 0ꢁC for 30min. The
mixture was diluted with saturated aqueous NaHCO3
(15mL) and extracted with EtOAc (3 · 15mL). The
organic layer was dried (MgSO4), filtered, and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 1/0–
4/1) to give the free base of 7a (237mg) as a colorless
oil. The free base (237mg) in MeOH was treated with
an excess of HCl in Et2O followed by evaporation of
the solvent. The resulting foam was triturated with
Et2O, collected by filtration, and dried in vacuo to
give the hydrochloride 7a (216mg, 72%) as an amor-
phous solid. 1H NMR (free base, CDCl3): d 1.10–
1.90 (13H, m), 2.03 (3H, s), 2.20–2.45 (2H, m), 2.28
(2H, t, J = 7.5Hz), 2.50 (2H, d, J = 6.6Hz), 2.70–
2.90 (1H, m), 2.83 (2H, br d, J = 11.6Hz), 3.68 (2H,
t, J = 7.7Hz), 3.74 (1H, br d, J = 12.8Hz), 4.50 (1H,
br d, J = 12.8Hz), 7.05–7.50 (10H, m). Anal. Calcd
for C29H39N3O2ÆHClÆ0.9H2O: C, 67.72; H, 8.19; Cl,
6.89; N, 8.17. Found: C, 67.80; H, 8.02; Cl, 7.18; N,
8.03.
1
148–150ꢁC. H NMR (CDCl3): d 1.05–2.05 (13H, m),
2.10–2.35 (1H, m), 2.27 (2H, t, J = 7.5Hz), 2.40–2.70
(2H, m), 2.48 (2H, d, J = 6.6Hz), 2.74 (3H, s), 2.81
(2H, br d, J = 11.8Hz), 3.55–3.80 (4H, m), 6.85–7.15
(5H, m), 7.31 (1H, d, J = 2.6Hz), 7.52 (1H, d,
J = 8.4Hz). Anal. Calcd for C28H36Cl2FN3O3SÆ0.5H2O:
C, 56.66; H, 6.28; N, 7.08. Found: C, 56.88; H, 6.10; N,
7.01.
5.21. N-(3-Chloro-4-methylphenyl)-N-{3-[4-(4-fluorobenz-
yl)piperidin-1-yl]propyl}-1-(methylsulfonyl)piperidine-
4-carboxamide hydrochloride (5l)
Compound 5l was prepared using a procedure similar to
that described for 5k from 3g. Yield 67%, amorphous
solid. H NMR (free base, CDCl3): d 1.10–2.00 (13H,
The following compounds 7b–f were prepared using a
procedure similar to that described for 7a from the
appropriate acyl chloride and 6a,b.
1
m), 2.15–2.40 (1H, m), 2.28 (2H, t, J = 7.6Hz), 2.41
(3H, s), 2.48 (2H, d, J = 6.4Hz), 2.55 (2H, dt, J = 2.8,
11.4Hz), 2.72 (3H, s), 2.84 (2H, br d, J = 11.6Hz),
3.64 (2H, t, J = 7.5Hz), 3.71 (2H, m), 6.85–7.15 (5H,
m), 7.18 (1H, d, J = 2.2Hz), 7.28 (1H, d, J = 8.0Hz).
Anal. Calcd for C29H39ClFN3O3SÆ0.6H2O: C, 56.97;
H, 6.79; N, 6.87. Found: C, 56.99; H, 7.07; N, 6.80.
5.25. N-[3-(4-Benzylpiperidin-1-yl)propyl]-1-isobutyryl-
N-phenylpiperidine-4-carboxamide hydrochloride (7b)
Yield 62%, amorphous solid. 1H NMR (free base,
CDCl3): d 0.95–2.00 (19H, m), 2.15–2.60 (2H, m),
2.32 (2H, t, J = 7.7Hz), 2.51 (2H, d, J = 6.6Hz),
2.60–2.95 (2H, m), 2.87 (2H, br d, J = 11.8Hz),
3.68 (2H, t, J = 7.5Hz), 3.87 (1H, br d, J =
14.1Hz), 4.54 (1H, br d, J = 14.1Hz), 7.05–7.50
(10H, m). Anal. Calcd for C31H43N3O2ÆHClÆ0.6H2O:
C, 69.34; H, 8.48; N, 7.83. Found: C, 69.42; H,
8.36; N, 7.68.
5.22. N-[3-(4-Benzylpiperidin-1-yl)propyl]-N-phenylpiper-
idine-4-carboxamide (6a)
A mixture of the free base of 5a (2.32g, 4.2mmol) and
10% palladium on carbon (water ꢁ50%, 0.93g) in

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
407
5.26. 1-Benzoyl-N-[3-(4-benzylpiperidin-1-yl)propyl]-N-
phenylpiperidine-4-carboxamide hydrochloride (7c)
step 1 (133g, 0.70mol) and 1-bromo-3-chloropropane
(132g, 0.84mol) in acetone (700mL) was added Cs2CO3
(274g, 0.84mol). After stirring at reflux for 5h, the mix-
ture was concentrated in vacuo, diluted with EtOAc
(500mL), and filtered. The filtrate was washed with
water (300mL) and brine (3 · 100mL), dried (MgSO4),
and concentrated in vacuo. The residue was purified
by column chromatography on silica gel (hexane/EtOAc
1/0–7/3) to give the product (144g, 77%) as a pale yellow
Yield 88%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–1.95 (13H, m), 2.20–2.90 (3H, m), 2.29
(2H, t, J = 7.7Hz), 2.50 (2H, d, J = 6.2Hz), 2.83 (2H,
br d, J = 11.8Hz), 3.45–3.90 (1H, m), 3.69 (2H, t,
J = 7.7Hz), 4.40–4.85 (1H, m), 7.05–7.50 (15H, m).
Anal. Calcd for C34H41N3O2ÆHClÆ0.8H2O: C, 71.07; H,
7.65; N, 7.31. Found: C, 71.00; H, 7.61; N, 7.23.
1
oil. H NMR (CDCl3): d 1.9–2.2 (2H, m), 3.5–3.6 (2H,
m), 3.85–4.0 (2H, m), 7.06 (7/8 · 1H, dd, J = 2.7,
8.7Hz), 7.22 (1/8 · 1H, dd, J = 2.4, 8.7Hz), 7.31 (7/
8 · 1H, d, J = 2.7Hz), 7.50 (1/8 · 1H, d, J = 2.4Hz),
7.50 (1/8 · 1H, d, J = 8.7Hz), 7.51 (7/8 · 1H, d,
J = 8.7Hz), 8.37 (1/8 · 1H, s), 8.40 (7/8 · 1H, s).
5.27. N-[3-(4-Benzylpiperidin-1-yl)propyl]-1-(methyl-
sulfonyl)-N-phenylpiperidine-4-carboxamide (7d)
1
Yield 37%, mp 116–118ꢁC (i-Pr2O). H NMR (CDCl3):
d 1.10–2.00 (13H, m), 2.15–2.40 (3H, m), 2.40–2.60 (2H,
m), 2.51 (2H, d, J = 6.2Hz), 2.72 (3H, s), 2.75–2.95 (2H,
m), 3.60–3.80 (4H, m), 7.05–7.50 (10H, m). Anal. Calcd
for C28H39N3O3SÆ0.2H2O: C, 67.09; H, 7.92; N, 8.38.
Found: C, 67.10; H, 8.06; N, 8.34.
5.30.3. Step 3: 3,4-Dichloro-N-(3-chloropropyl)aniline
hydrochloride (9a). To a stirred solution of the product
from step 2 (142g, 0.53mol) in i-PrOH (500mL) was
added concentrated HCl (100mL). After stirring at
60ꢁC for 3h, the mixture was cooled to room tempera-
ture, and the resulting precipitate was collected by filtra-
tion. The precipitate was washed with i-PrOH
(3 · 100mL) and dried in vacuo to give 9a (133g,
91%) as a white solid, mp 173–174ꢁC. 1H NMR
(CD3OD): d 2.20 (2H, m), 3.51 (2H, m), 3.71 (2H, t,
J = 6.2Hz), 7.33 (1H, dd, J = 2.9, 8.7Hz), 7.59 (1H, d,
J = 2.9Hz), 7.66 (1H, d, J = 8.7Hz). Anal. Calcd for
C9H10Cl3NÆHCl: C, 39.31; H, 4.03; N, 5.09. Found: C,
39.47; H, 4.18; N, 5.07.
5.28. 1-Acetyl-N-[3-(4-benzylpiperidin-1-yl)propyl]-N-
phenylpiperidine-3-carboxamide hydrochloride (7e)
Yield 85%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.00–2.00 (16H, m), 2.10–2.55 (1H, m), 2.29
(2H, t, J = 7.5Hz), 2.51 (2H, d, J = 6.6Hz), 2.65–3.40
(2H, m), 2.83 (2H, br d, J = 11.0Hz), 3.50–3.85 (3H,
m), 4.40–4.65 (1H, m), 7.05–7.50 (10H, m). Anal. Calcd
for C29H39N3O2ÆHClÆ0.8H2O: C, 67.96; H, 8.18; N, 8.20.
Found: C, 67.86; H, 8.17; N, 8.18.
5.31. 3,4-Dichloro-N-(4-chlorobutyl)aniline hydrochloride
(9b)
5.29. N-[3-(4-Benzylpiperidin-1-yl)propyl]-1-(methyl-
sulfonyl)-N-phenylpiperidine-3-carboxamide hydrochlo-
ride (7f)
Compound 9b was prepared using a procedure similar to
that described for 9a from 1-bromo-4-chlorobutane. Mp
1
Yield 41%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–2.00 (13H, m), 2.20–2.65 (2H, m), 2.28
(2H, t, J = 7.5Hz), 2.51 (2H, d, J = 6.6Hz), 2.68 (3H, s),
2.75–2.95 (3H, m), 3.50–3.85 (4H, m), 7.05–7.50 (10H,
m). Anal. Calcd for C28H39N3O3SÆHClÆ0.6H2O: C,
61.71; H, 7.62; N, 7.71. Found: C, 61.79; H, 7.46; N, 7.76.
134–136ꢁC. H NMR (CD3OD): d 1.75–2.05 (4H, m),
3.43 (2H, m), 3.64 (2H, m), 7.44 (1H, dd, J = 2.8,
8.8Hz), 7.72 (1H, d, J = 2.8Hz), 7.72 (1H, d,
J = 8.8Hz). Anal. Calcd for C10H12Cl3NÆHCl: C, 41.56;
H, 4.53; N, 4.85. Found: C, 41.52; H, 4.43; N, 4.95.
5.32. N-(3-Chloropropyl)-N-(3,4-dichlorophenyl)-1-(meth-
ylsulfonyl)piperidine-4-carboxamide (10a)
5.30. 3,4-Dichloro-N-(3-chloropropyl)aniline hydrochlo-
ride (9a)
To an ice-cooled stirred suspension of 9a (35.0g,
0.13mmol) in DCM (500mL) was added Et3N (71mL,
0.51mol) followed by 4d (86.2g, 0.38mol), and the mix-
ture was stirred at room temperature for 12h. The mix-
ture was diluted with water (300mL), and the organic
solvent was removed in vacuo. The residue was diluted
with EtOAc (300mL)/THF (300mL), and the insoluble
material was removed by filtration. The organic layer
was separated, washed with 1N NaOH (3 · 100mL)
and brine (100mL), dried (MgSO4), filtered, and concen-
trated in vacuo. The residue was purified by column
chromatography on silica gel (DCM/EtOAc 1/2) fol-
lowed by recrystallization from DCM/EtOAc/i-Pr2O to
afford 10a (42.2g, 78%) as a white solid, mp 167–
5.30.1. Step 1: N-(3,4-Dichlorophenyl)formamide. A mix-
ture of acetic anhydride (189mL, 2.0mol) and formic
acid (91mL, 2.4mol) was stirred at 60ꢁC for 2h, then
cooled to 0ꢁC. To the mixture was added 3,4-dichloro-
aniline (8) (162g, 1.0mol) portionwise, and the mixture
was stirred at room temperature for 20h. After dilution
with Et2O (500mL), the mixture was washed with water
(2 · 500mL), 1N NaOH (3 · 200mL), and brine
(100mL), dried (MgSO4), filtered, and concentrated in
vacuo. The residue was triturated with i-Pr2O, collected
by filtration, and dried in vacuo to give the product
(145g, 76%) as a white solid, mp 107–108 ꢁC. Anal.
Calcd for C7H5Cl2NO: C, 44.24; H, 2.65; N, 7.37.
Found: C, 44.23; H, 2.82; N, 7.40.
1
168ꢁC. H NMR (CDCl3): d 1.60–2.01 (6H, m), 2.05–
2.37 (1H, m), 2.39–2.68 (2H, m), 2.74 (3H, s), 3.55
(2H, t, J = 6.4Hz), 3.65–3.83 (4H, m), 7.05 (1H, dd,
J = 2.2, 8.4Hz), 7.31 (1H, d, J = 2.2Hz), 7.55 (1H, d,
5.30.2. Step 2: N-(3-Chloropropyl)-N-(3,4-dichlorophen-
yl)formamide. To a stirred mixture of the product from

408
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
J = 8.4Hz). Anal. Calcd for C16H21Cl3N2O3S: C, 44.92;
H, 4.95; N, 6.55. Found: C, 44.75; H, 5.00; N, 6.34.
J = 6.9Hz), 2.73 (3H, s), 2.90–3.05 (2H, m), 3.12
(4H, t, J = 4.7Hz), 3.60–3.80 (4H, m), 3.85 (4H,
t, J = 4.7Hz), 6.83 (2H, d, J = 8.3Hz), 7.00–
7.15 (1H, m), 7.03 (2H, d, J = 8.3Hz), 7.33 (1H, d,
J = 2.4Hz), 7.53 (1H, d, J = 8.4Hz). MS m/z: 651
(MH+).
5.33. 1-Acetyl-N-(4-chlorobutyl)-N-(3,4-dichlorophenyl)-
piperidine-4-carboxamide (10b)
Compound 10b was prepared using a procedure similar
to that described for 10a from 9b and 4c. Yield 79%, mp
99–101ꢁC (i-Pr2O). 1H NMR (CDCl3): d 1.45–1.90 (8H,
m), 2.06 (3H, s), 2.20–2.50 (2H, m), 2.87 (1H, m), 3.55
(2H, t, J = 6.0Hz), 3.68 (2H, t, J = 7.0Hz), 3.78 (1H,
br d, J = 12.8Hz), 4.54 (1H, br d, J = 12.8Hz), 7.05
(1H, dd, J = 2.6, 8.4Hz), 7.31 (1H, d, J = 2.6Hz), 7.55
(1H, d, J = 8.4Hz). Anal. Calcd for C18H23Cl3N2O2:
C, 53.28; H, 5.71; N, 6.90. Found: C, 53.25; H, 5.69;
N, 6.94.
5.37. N-(3,4-Dichlorophenyl)-N-{3-[4-(4-methoxybenzyl)-
piperidin-1-yl]propyl}-1-(methylsulfonyl)piperidine-
4-carboxamide (11d)
Yield 73%, amorphous solid. 1H NMR (CDCl3): d 1.10–
2.05 (13H, m), 2.10–2.35 (3H, m), 2.45 (2H, d,
J = 6.6Hz), 2.45–2.65 (2H, m), 2.70–2.90 (2H, m),
2.74 (3H, s), 3.55–3.80 (4H, m), 3.79 (3H, s), 6.81
(2H, d, J = 8.4Hz), 6.95–7.10 (1H, m), 7.04 (2H, d,
J = 8.4Hz), 7.31 (1H, d, J = 2.6Hz), 7.52 (1H, d,
J = 8.6Hz). Anal. Calcd for C29H39Cl2N3O4SÆ0.6H2O:
C, 57.34; H, 6.67; N, 6.92. Found: C, 57.33; H, 6.75;
N, 6.79.
5.34. N-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-N-(3-{4-
[4-(trifluoromethyl)benzyl]piperidin-1-yl}propyl)piper-
idine-4-carboxamide (11a)
A mixture of 10a (428mg, 1.0mmol), 22b (336mg,
1.2mmol), KI (199mg, 1.2mmol), K2CO3 (498mg,
3.6mmol) in MeCN (24mL) was stirred at 80ꢁC for
13h. The mixture was concentrated in vacuo, and the
residue was partitioned between EtOAc (40mL) and
water (10mL). The organic layer was separated, washed
with 1N NaOH (2 · 5mL) and brine (5mL), dried
(Na2SO4), filtered, and concentrated in vacuo. The resi-
due was purified by column chromatography on silica
gel (EtOAc) followed by recrystallization from EtOAc/
i-Pr2O to afford 11a (393mg, 62%) as a white solid,
5.38. N-(3,4-Dichlorophenyl)-N-(3-{4-[4-(methylsulfanyl)-
benzyl]piperidin-1-yl}propyl)-1-(methylsulfonyl)piperi-
dine-4-carboxamide hydrochloride (11e)
Yield 92%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–2.05 (13H, m), 2.10–2.35 (3H, m),
2.40–2.70 (4H, m), 2.47 (3H, s), 2.70–2.90 (2H, m),
2.74 (3H, s), 3.55–3.80 (4H, m), 6.95–7.10 (1H, m),
7.05 (2H, d, J = 8.4Hz), 7.18 (2H, d, J = 8.4Hz), 7.31
(1H, d, J = 2.6Hz), 7.52 (1H, d, J = 8.6Hz). Anal. Calcd
for C29H39Cl2N3O3S2ÆHClÆ0.8H2O: C, 52.49; H, 6.32; N,
6.33. Found: C, 52.51; H, 6.40; N, 6.46.
1
mp 120–124ꢁC. H NMR (CDCl3): d 1.10–2.05 (13H,
m), 2.10–2.35 (3H, m), 2.45–2.90 (4H, m), 2.57 (2H, d,
J = 6.2Hz), 2.74 (3H, s), 3.55–3.85 (4H, m), 7.02 (1H,
dd, J = 2.4, 8.4Hz), 7.23 (2H, d, J = 8.4Hz), 7.31 (1H,
d, J = 2.4Hz), 7.52 (1H, d, J = 8.4Hz), 7.52 (2H, d,
J = 8.4Hz). Anal. Calcd for C29H36Cl2F3N3O3S: C,
54.89; H, 5.72; N, 6.62. Found: C, 54.64; H, 5.54; N,
6.52.
5.39. N-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-N-(3-{4-
[4-(methylsulfonyl)benzyl]piperidin-1-yl}propyl)piperidine-
4-carboxamide hydrochloride (11f)
Yield 66%, mp 172–176ꢁC (DCM/EtOH). 1H NMR
(free base, CDCl3): d 1.10–2.05 (13H, m), 2.10–2.35
(3H, m), 2.45–2.70 (2H, m), 2.61 (2H, d, J = 6.6Hz),
2.70–2.90 (2H, m), 2.74 (3H, s), 3.05 (3H, s), 3.55–3.80
(4H, m), 7.02 (1H, dd, J = 2.2, 8.5Hz), 7.31 (1H, d,
J = 2.2Hz), 7.32 (2H, d, J = 8.6Hz), 7.52 (1H, d,
J = 8.5Hz), 7.85 (2H, d, J = 8.6Hz). Anal. Calcd for
C29H39Cl2N3O5S2ÆHClÆH2O: C, 49.82; H, 6.05; Cl,
15.21; N, 6.01; S, 9.17. Found: C, 49.87; H, 5.98; Cl,
15.22; N, 6.05; S, 9.19.
The following compounds 11b–l were prepared using a
procedure similar to that described for 11a from the cor-
responding piperidines.
5.35. N-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-N-{3-[4-
(4-nitrobenzyl)piperidin-1-yl]propyl}piperidine-4-carbox-
amide (11b)
Yield 47%, oil. 1H NMR (CDCl3): d 1.10–2.10 (13H, m),
2.10–2.40 (3H, m), 2.45–2.70 (2H, m), 2.63 (2H, d,
J = 5.8Hz), 2.70–2.95 (2H, m), 2.74 (3H, s), 3.60–3.85
(4H, m), 7.03 (1H, dd, J = 2.5, 8.5Hz), 7.29 (2H, d,
J = 8.8Hz), 7.31 (1H, d, J = 2.5Hz), 7.52 (1H, d,
J = 8.5Hz), 8.14 (2H, d, J = 8.8Hz). MS m/z: 611
(MH+).
5.40. N-(3,4-Dichlorophenyl)-N-(3-{4-[4-(ethylsulfonyl)-
benzyl]piperidin-1-yl}propyl)-1-(methylsulfonyl)piper-
idine-4-carboxamide hydrochloride (11g)
Yield 84%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–2.05 (13H, m), 1.28 (3H, t, J = 7.4Hz),
2.10–2.35 (3H, m), 2.45–2.70 (2H, m), 2.61 (2H, d,
J = 6.4Hz), 2.74 (3H, s), 2.75–2.90 (2H, m), 3.11 (2H,
q, J = 7.4Hz), 3.55–3.80 (4H, m), 7.03 (1H, dd,
J = 2.6, 8.4Hz), 7.31 (1H, d, J = 2.6Hz), 7.32 (2H, d,
J = 8.0Hz), 7.52 (1H, d, J = 8.4Hz), 7.80 (2H, d,
J = 8.0Hz). Anal. Calcd for C30H41Cl2N3O5S2ÆHClÆ0.5-
H2O: C, 51.17; H, 6.15; N, 5.97. Found: C, 51.14; H,
6.31; N, 5.74.
5.36. N-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-N-{3-[4-
(4-morpholin-4-ylbenzyl)piperidin-1-yl]propyl}piperidine-
4-carboxamide (11c)
Yield 37%, amorphous solid. 1H NMR (CDCl3): d 1.20–
2.10 (13H, m), 2.10–2.65 (5H, m), 2.46 (2H, d,

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
409
5.41. N-(3,4-Dichlorophenyl)-N-(3-{4-[4-(isopropylsulfon-
yl)benzyl]piperidin-1-yl}propyl)-1-(methylsulfonyl)piper-
idine-4-carboxamide hydrochloride (11h)
2.45–2.65 (2H, m), 2.60 (2H, d, J = 6.6Hz), 2.74 (3H,
s), 2.75–2.90 (2H, m), 2.90–3.10 (4H, m), 3.55–3.85
(8H, m), 7.02 (1H, dd, J = 2.2, 8.4Hz), 7.30 (2H, d,
J = 8.0Hz), 7.31 (1H, d, J = 2.2Hz), 7.52 (1H, d,
J = 8.4Hz), 7.65 (2H, d, J = 8.0Hz). Anal. Calcd for
C32H44Cl2N4O6S2ÆHClÆ1.7H2O: C, 49.10; H, 6.23; N,
7.16. Found: C, 49.06; H, 6.34; N, 7.09.
Yield 77%, amorphous solid. 1H NMR (free base,
CDCl3):
d
1.10–2.05 (13H, m), 1.29 (6H, d,
J = 6.9Hz), 2.10–2.35 (3H, m), 2.45–2.70 (2H, m), 2.61
(2H, d, J = 6.2Hz), 2.74 (3H, s), 2.75–2.90 (2H, m),
3.18 (1H, septet, J = 6.9Hz), 3.55–3.80 (4H, m), 7.03
(1H, dd, J = 2.4, 8.5Hz), 7.31 (1H, d, J = 2.4Hz), 7.31
(2H, d, J = 8.4Hz), 7.52 (1H, d, J = 8.5Hz), 7.78 (2H,
d, J = 8.4Hz). Anal. Calcd for C31H43Cl2N3O5S2Æ
HClÆ0.8H2O: C, 51.46; H, 6.35; N, 5.81. Found: C,
51.43; H, 6.64; N, 5.84.
5.46. 1-Acetyl-N-(3,4-dichlorophenyl)-N-{4-[4-(4-fluoro-
benzyl)piperidin-1-yl]butyl}piperidine-4-carboxamide (12)
Compound 12 was prepared using a procedure similar
to that described for 11a from 10b and 22a. Yield
58%, oil. 1H NMR (CDCl3): d 1.10–1.90 (15H, m),
2.06 (3H, s), 2.20–2.55 (4H, m), 2.49 (2H, d, J =
6.6Hz), 2.75–3.00 (1H, m), 2.85 (2H, br d,
J = 11.6Hz), 3.64 (2H, m), 3.78 (1H, br d, J =
13.7Hz), 4.53 (1H, br d, J = 13.7Hz), 6.95 (2H, m),
7.03 (1H, dd, J = 2.6, 8.5Hz), 7.08 (2H, m), 7.30 (1H,
d, J = 2.6Hz), 7.53 (1H, d, J = 8.5Hz). Anal. Calcd
for C30H38Cl2FN3O2Æ1.3H2O: C, 61.49; H, 6.98; N,
7.17. Found: C, 61.50; H, 6.62; N, 7.06.
5.42. N-(3-{4-[4-(Aminosulfonyl)benzyl]piperidin-1-yl}-
propyl)-N-(3,4-dichlorophenyl)-1-(methylsulfonyl)piper-
idine-4-carboxamide (11i)
1
Yield 66%, mp 179–181ꢁC (DCM/EtOAc). H NMR
(CDCl3): d 1.10–2.00 (13H, m), 2.10–2.35 (3H, m),
2.45–2.65 (2H, m), 2.59 (2H, d, J = 6.2Hz), 2.70–2.90
(2H, m), 2.74 (3H, s), 3.55–3.80 (4H, m), 4.93 (2H, br
s), 7.03 (1H, dd, J = 2.4, 8.6Hz), 7.27 (2H, d,
J = 8.3Hz), 7.31 (1H, d, J = 2.4Hz), 7.52 (1H, d,
J = 8.6Hz), 7.83 (2H, d, J = 8.3Hz). Anal. Calcd for
C28H38Cl2N4O5S2Æ0.3H2O: C, 51.65; H, 5.98; N, 8.61.
Found: C, 51.67; H, 6.10; N, 8.39.
5.47. N-{3-[4-(4-Aminobenzyl)piperidin-1-yl]propyl}-N-
(3,4-dichlorophenyl)-1-(methylsulfonyl)piperidine-4-carb-
oxamide (13)
A mixture of 11b (85mg, 0.14mmol) and SnCl2Æ2H2O
(156mg, 0.70mmol) in EtOH (0.4mL) was stirred at re-
flux for 30min. The mixture was diluted with 1N NaOH
(10mL) and EtOAc (10mL), and the insoluble material
was removed by filtration (Celite). 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 basic alumina
(hexane/EtOAc 1/2) to give 13 (72mg, 89%) as a foam.
1H NMR (CDCl3): d 1.10–2.00 (13H, m), 2.15–2.35
(1H, m), 2.27 (2H, t, J = 7.3Hz), 2.40 (2H, d,
J = 6.9Hz), 2.57 (2H, br t, J = 11.3Hz), 2.74 (3H, s),
2.81 (2H, br d, J = 11.7Hz), 3.35–3.85 (2H, br), 3.65
(2H, t, J = 7.5Hz), 3.72 (2H, br d, J = 12.6Hz), 6.61
(2H, d, J = 8.4Hz), 6.91 (2H, d, J = 8.4Hz), 7.03 (1H,
dd, J = 2.3, 8.6Hz), 7.31 (1H, d, J = 2.3Hz), 7.51 (1H,
d, J = 8.6Hz). MS m/z: 581 (MH+).
5.43. N-(3,4-Dichlorophenyl)-N-[3-(4-{4-[(methylamino)-
sulfonyl]benzyl}piperidin-1-yl)propyl]-1-(methylsulfonyl)-
piperidine-4-carboxamide (11j)
Yield 60%, amorphous solid. 1H NMR (CDCl3): d 1.10–
2.05 (13H, m), 2.10–2.35 (3H, m), 2.45–2.95 (4H, m),
2.59 (2H, d, J = 6.2Hz), 2.67 (3H, d, J = 5.4Hz), 2.74
(3H, s), 3.55–3.80 (4H, m), 4.20–4.40 (1H, m), 7.03
(1H, dd, J = 2.2, 8.4Hz), 7.28 (2H, d, J = 8.4Hz), 7.31
(1H, d, J = 2.2Hz), 7.52 (1H, d, J = 8.4Hz), 7.76 (2H,
d, J = 8.4Hz). Anal. Calcd for C29H40Cl2N4O5S2Æ0.5-
H2O: C, 52.09; H, 6.18; N, 8.38. Found: C, 52.14; H,
5.95; N, 8.37.
5.44. N-(3,4-Dichlorophenyl)-N-[3-(4-{4-[(dimethylamino)-
sulfonyl]benzyl}piperidin-1-yl)propyl]-1-(methylsulfonyl)-
piperidine-4-carboxamide hydrochloride (11k)
5.48. N-(3-{4-[4-(Acetylamino)benzyl]piperidin-1-yl}prop-
yl)-N-(3,4-dichlorophenyl)-1-(methylsulfonyl)piperidine-
4-carboxamide (14a)
Yield 64%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–2.05 (13H, m), 2.10–2.40 (3H, m),
2.45–2.65 (2H, m), 2.60 (2H, d, J = 6.2Hz), 2.70 (6H,
s), 2.73 (3H, s), 2.80–2.95 (2H, m), 3.60–3.80 (4H, m),
7.06 (1H, dd, J = 2.4, 8.7Hz), 7.29 (2H, d, J = 8.2Hz),
7.32 (1H, d, J = 2.4Hz), 7.53 (1H, d, J = 8.7Hz), 7.68
(2H, d, J = 8.2Hz). Anal. Calcd for C30H42Cl2N4O5-
S2ÆHClÆ1.3H2O: C, 49.12; H, 6.27; N, 7.64. Found: C,
49.17; H, 6.32; N, 7.71.
To an ice-cooled stirred solution of 13 (24mg,
0.041mmol) and Et3N (6.3mg, 0.062mmol) in THF
(0.3mL) was added AcCl (3.8lL, 0.053mmol). After
stirring at room temperature for 10min, the mixture
was diluted with 1N NaOH and extracted with EtOAc.
The organic layer was dried (MgSO4), filtered, and con-
centrated in vacuo. The residue was purified by column
chromatography on basic alumina to give 14a (25mg,
5.45. N-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-N-(3-{4-
[4-(morpholin-4-ylsulfonyl)benzyl]piperidin-1-yl}propyl)-
piperidine-4-carboxamide hydrochloride (11l)
1
97%) as a foam. H NMR (CDCl3): d 1.10–2.00 (13H,
m), 2.10–2.35 (3H, m), 2.16 (3H, s), 2.45–2.65 (2H, m),
2.47 (2H, d, J = 6.9Hz), 2.74 (3H, s), 2.83 (2H, br d,
J = 12.0Hz), 3.65 (2H, t, J = 7.5Hz), 3.72 (2H, br
d, J = 12.6Hz), 7.00–7.10 (1H, m), 7.07 (2H, d,
Yield 83%, amorphous solid. 1H NMR (free base,
CDCl3): d 1.10–2.05 (13H, m), 2.10–2.35 (3H, m),

410
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
J = 8.4Hz), 7.31 (1H, d, J = 2.4Hz), 7.39 (2H, d,
J = 8.4Hz), 7.52 (1H, d, J = 8.4Hz). MS m/z: 623
(MH+).
water (20mL, 2 10mL) and brine (10mL), dried
(MgSO4), filtered, and concentrated in vacuo. The resi-
due was triturated with i-Pr2O/Et2O (2/1) and collected
by filtration to give 16 (5.90g) as a white solid, mp
98–99ꢁC. A second crop (1.20g) was obtained from
the mother liquor. The combined yield was 7.10g
5.49. N-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-N-[3-(4-
{4-[(methylsulfonyl)amino]benzyl}piperidin-1-yl)propyl]-
piperidine-4-carboxamide (14b)
1
(90%). H NMR (CDCl3): d 1.20–1.80 (5H, m), 2.21
(2H, dt, J = 2.1, 11.6Hz), 2.55 (2H, d, J = 7.0Hz), 2.86
(2H, br d, J = 11.8Hz), 3.08 (2H, s), 6.97 (2H, m),
7.10 (2H, m), 7.37 (1H, d, J = 8.5Hz), 7.45 (1H, dd,
J = 2.5, 8.5Hz), 7.77 (1H, d, J = 2.5Hz), 9.26 (1H, br
s). Anal. Calcd for C20H21Cl2FN2O: C, 60.77; H, 5.35;
N, 7.09. Found: C, 60.76; H, 5.35; N, 7.20.
To an ice-cooled stirred solution of 13 (30mg,
0.052mmol) and Et3N (21mg, 0.21mmol) in THF
(0.3mL) was added MsCl (12lL, 0.16mmol). After stir-
ring at room temperature for 1h, the mixture was di-
luted with 1N NaOH (7mL) and extracted with
EtOAc (2 · 10mL). The organic layer was dried
(MgSO4), filtered, and concentrated in vacuo. The resi-
due was subjected to column chromatography on basic
alumina (EtOAc) to give two fractions. The first fraction
contained N-[3-(4-{4-[bis(methylsulfonyl)amino]benz-
yl}piperidin-1-yl)propyl]-N-(3,4-dichlorophenyl)-1-(meth-
ylsulfonyl)piperidine-4-carboxamide (12mg, 32%). 1H
5.52. 3,4-Dichloro-N-{2-[4-(4-fluorobenzyl)piperidin-1-yl]-
ethyl}aniline dihydrochloride (17)
To a stirred solution of 16 (3.95g, 10mmol) in THF
(30mL) was added dropwise borane–methyl sulfide
complex (3.0mL) at room temperature, and the mixture
was stirred at reflux for 3h. MeOH (10mL) was added
dropwise to the mixture at room temperature. After
being stirred for 18h, the mixture was treated with a
1N HCl (Et2O solution, 30mL) and concentrated
in vacuo. The residue was diluted with MeOH
(30mL) and concentrated in vacuo. The residue was
triturated with EtOAc and collected by filtration to give
NMR (CDCl3):
d 1.10–1.40 (2H, m), 1.40–2.00
(11H, m), 2.10–2.40 (3H, m), 2.50–2.70 (2H, m), 2.55
(2H, d, J = 5.8Hz), 2.74 (3H, s), 2.83 (2H, br d,
J = 10.4Hz), 3.40 (6H, s), 3.60–3.80 (4H, m), 7.02 (1H,
dd, J = 2.6, 8.4Hz), 7.17–7.40 (5H, m), 7.52 (1H, d,
J = 8.4Hz). The second fraction gave 14b (13mg, 38%)
1
as a foam. H NMR (CDCl3): d 1.10–2.00 (13H, m),
1
2.10–2.35 (3H, m), 2.40–2.70 (2H, m), 2.50 (2H, d,
J = 6.2Hz), 2.74 (3H, s), 2.83 (2H, br d, J = 10.8Hz),
2.99 (3H, s), 3.60–3.80 (4H, m), 7.03 (1H, dd, J = 2.6,
8.4Hz), 7.12 (4H, s), 7.31 (1H, d, J = 2.6Hz), 7.52
(1H, d, J = 8.4Hz).
17 (4.07g, 90%) as a white solid, mp 143–146ꢁC. H
NMR (CD3OD): d 1.40–2.00 (5H, m), 2.60 (2H, d,
J = 6.2Hz), 2.98 (2H, m), 3.28 (2H, t, J = 6.4Hz),
3.53 (2H, t, J = 6.4Hz), 3.61 (2H, br d, J = 12.4Hz),
6.64 (1H, dd, J = 2.6, 8.8Hz), 6.85 (1H, d, J =
2.8Hz), 7.01 (2H, m), 7.20 (2H, m), 7.24 (1H, d,
J = 8.8Hz). Anal. Calcd for C20H23Cl2FN2Æ2HCl: C,
52.88; H, 5.55; N, 6.17. Found: C, 52.73; H, 5.56; N,
6.26.
5.50. 2-Chloro-N-(3,4-dichlorophenyl)acetamide (15)
To a stirred solution of 3,4-dichloroaniline (8) (8.10g,
50mmol) in THF (50mL) was added chloroacetic anhy-
dride (9.40g, 55mmol), and the mixture was stirred at
room temperature for 3h. The mixture was concentrated
in vacuo, and the residue was diluted with EtOAc
(100mL). The organic layer was washed with saturated
aqueous NaHCO3 (50mL, 2 · 20mL) and brine
(20mL), dried (MgSO4), filtered, and concentrated in
vacuo. The residue was triturated with i-Pr2O (30mL)
and collected by filtration to yield 15 (8.08 g) as a white
solid, mp 105–106ꢁC. The mother liquor was concen-
trated in vacuo, triturated with i-Pr2O/hexane (1/1) to
give a second crop (3.01g). The combined yield was
5.53. 1-Acetyl-N-(3,4-dichlorophenyl)-N-{2-[4-(4-fluoro-
benzyl)piperidin-1-yl]ethyl}piperidine-4-carboxamide (18)
Compound 18 was prepared using a procedure similar
to that described for 5e from 17. Yield 99%, oil. H
1
NMR (CDCl3): d 1.05–2.00 (11H, m), 2.06 (3H, s),
2.25–2.55 (2H, m), 2.40 (2H, t, J = 6.4Hz), 2.49 (2H,
d, J = 7.0Hz), 2.70–3.00 (3H, m), 3.60–3.90 (3H, m),
4.53 (1H, br d, J = 13.2Hz), 6.95 (2H, m), 7.08 (2H,
m), 7.10 (1H, dd, J = 2.9, 8.5Hz), 7.50 (1H, d,
J = 8.5Hz), 7.51 (1H, d, J = 2.9Hz). Anal. Calcd for
C28H34Cl2FN3O2Æ0.7H2O: C, 61.47; H, 6.52; N, 7.68.
Found: C, 61.53; H, 6.43; N, 7.62.
1
11.09g (93%). H NMR (CDCl3): d 4.20 (2H, s), 7.38
(1H, dd, J = 1.9, 8.8Hz), 7.43 (1H, dd, J = 0.8,
8.8Hz), 7.80 (1H, dd, J = 0.8, 1.9Hz), 8.22 (1H, br s).
Anal. Calcd for C8H6Cl3NO: C, 40.29; H, 2.54; N,
5.87. Found: C, 40.28; H, 2.51; N, 5.92.
5.54. tert-Butyl-4-(4-fluorobenzylidene)piperidine-1-
carboxylate (20a)
5.51. N-(3,4-Dichlorophenyl)-2-[4-(4-fluorobenzyl)piper-
idin-1-yl]acetamide (16)
5.54.1. Step 1: Diethyl (4-fluorobenzyl)phosphonate. A
mixture of 4-fluorobenzyl bromide (19a) (100g,
0.53mol) and triethyl phosphite (120mL, 0.70mol) was
stirred at 150ꢁC for 22h. The mixture was purified
by vacuum distillation to give the product (125g, 96%)
as a colorless oil, bp 115–120ꢁC/0.15Torr. 1H NMR
(CDCl3): d 1.25 (6H, t, J = 7.3Hz), 3.12 (2H, d,
J = 21.4Hz), 4.02 (4H, dq, J = 7.3, 7.3Hz), 6.90–7.10
(2H, m), 7.20–7.35 (2H, m).
To a stirred solution of the free base of 22a (4.25g,
22mmol) in DMF (50mL) were added 15 (4.77g,
20mmol) and K2CO3 (3.04g, 22mmol), and the mixture
was stirred at room temperature for 12 h. The mixture
was concentrated in vacuo, and the residue was diluted
with EtOAc (70mL). The organic layer was washed with

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
411
5.54.2. Step 2: tert-Butyl-4-(4-fluorobenzylidene)piperi-
dine-1-carboxylate (20a). To an ice-cooled stirred solu-
tion of the product from step 1 (60.8g, 0.25mol) and
15-crown-5 (4.0mL, 0.02mol) in THF (400mL) was
added NaH (60% in oil, 9.75g, 0.24mol), and the mix-
ture was stirred at 0ꢁC for 30min. A solution of tert-
butyl-4-oxopiperidine-1-carboxylate (42.0g, 0.21mol)
in THF (150mL) was added dropwise to the mixture
at 0ꢁC. After stirring at room temperature for 22h,
the mixture was diluted with water at 0ꢁC and extracted
with EtOAc. The organic layer was washed with satu-
rated aqueous NaHCO3 and brine, dried (MgSO4), fil-
tered, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (hex-
ane/EtOAc 30/1–10/1) to give 20a (47.0g, 77%) as a col-
orless oil. 1H NMR (CDCl3): d 1.48 (9H, s), 2.32 (2H, t,
J = 5.8Hz), 2.42 (2H, t, J = 5.8Hz), 3.40 (2H, t,
J = 5.8Hz), 3.50 (2H, t, J = 5.8Hz), 6.31 (1H, s), 6.95–
7.20 (4H, m).
3.95–4.20 (2H, m), 7.24 (2H, d, J = 8.0Hz), 7.54 (2H,
d, J = 8.0Hz).
5.59. tert-Butyl-4-(4-methoxybenzyl)piperidine-1-carb-
oxylate (21c)
Yield 97%. 1H NMR (CDCl3): d 1.00–1.25 (2H, m), 1.45
(9H, s), 1.50–1.70 (3H, m), 2.47 (2H, d, J = 7.0Hz),
2.50–2.75 (2H, m), 3.79 (3H, s), 3.95–4.20 (2H, m),
6.82 (2H, d, J = 8.7Hz), 7.05 (2H, d, J = 8.7Hz).
5.60. 4-(4-Fluorobenzyl)piperidine hydrochloride (22a)
To a stirred solution of 21a (39.9g, 0.14mol) in EtOAc
(30mL) was added 4N HCl (EtOAc solution, 100mL).
After stirring at room temperature for 1h, the mixture
was concentrated in vacuo. The residue was triturated
with Et2O, collected by filtration, washed with Et2O,
and dried in vacuo to give 22a (30.1g, 96%) as a white
1
solid, mp 164–166ꢁC. H NMR (CD3OD): d 1.30–1.50
5.55. tert-Butyl-4-[4-(trifluoromethyl)benzylidene]piper-
idine-1-carboxylate (20b)
(2H, m), 1.75–2.00 (3H, m), 2.60 (2H, d, J = 6.3Hz),
2.93 (2H, dt, J = 2.9, 12.8Hz), 3.30–3.40 (2H, m),
6.95–7.10 (2H, m), 7.15–7.25 (2H, m).
Compound 20b was prepared using a procedure similar
to that described for 20a from 4-(trifluoromethyl)benzyl
bromide. H NMR (CDCl3): d 1.47 (9H, s), 2.35 (2H, t,
The following compounds 22b,c were prepared using a
procedure similar to that described for 22a from 21b,c.
1
J = 6.2Hz), 2.43 (2H, t, J = 6.2Hz), 3.41 (2H, t,
J = 6.2Hz), 3.52 (2H, t, J = 6.2Hz), 6.37 (1H, s), 7.28
(2H, d, J = 8.0Hz), 7.56 (2H, d, J = 8.0Hz).
5.61. 4-[4-(Trifluoromethyl)benzyl]piperidine hydrochlo-
ride (22b)
5.56. tert-Butyl-4-(4-methoxybenzylidene)piperidine-1-
carboxylate (20c)
Yield 97%, mp 222–224ꢁC. 1H NMR (CD3OD): d 1.35–
1.55 (2H, m), 1.80–2.05 (3H, m), 2.71 (2H, d,
J = 7.2Hz), 2.93 (2H, dt, J = 3.0, 13.1Hz), 3.30–3.40
(2H, m), 7.40 (2H, d, J = 7.8Hz), 7.60 (2H, d,
J = 7.8Hz).
Compound 20c was prepared using a procedure similar
to that described for 20a from 4-methoxybenzyl
1
chloride. H NMR (CDCl3): d 1.48 (9H, s), 2.31 (2H,
t, J = 5.9Hz), 2.45 (2H, t, J = 5.9Hz), 3.40 (2H, t,
J = 5.9Hz), 3.49 (2H, t, J = 5.9Hz), 3.81 (3H, s),
6.30 (1H, s), 6.86 (2H, d, J = 8.8Hz), 7.13 (2H, d,
J = 8.8Hz).
5.62. 4-(4-Methoxybenzyl)piperidine hydrochloride (22c)
Yield 76%, mp 175–177ꢁC. 1H NMR (CD3OD): d 1.28–
1.55 (2H, m), 1.73–1.95 (3H, m), 2.55 (2H, d,
J = 6.8Hz), 2.92 (2H, dt, J = 3.0, 13.0Hz), 3.29–3.43
(2H, m), 3.75 (3H, s), 6.84 (2H, d, J = 8.4Hz), 7.09
(2H, d, J = 8.4Hz).
5.57. tert-Butyl-4-(4-fluorobenzyl)piperidine-1-carboxy-
late (21a)
Compound 20a (47.0g, 0.16mol) was dissolved in
MeOH (450mL) and hydrogenated over 10% Pd/C
(water ꢁ50%, 4.70g) at room temperature for 5h. The
catalyst was removed by filtration, and the filtrate was
concentrated in vacuo. The residue was purified by col-
umn chromatography on silica gel (hexane/EtOAc 10/1)
5.63. tert-Butyl-4-(4-nitrobenzyl)piperidine-1-carboxylate
(24)
To a stirred solution of 2316 (19.0g, 60mmol) in EtOH
(200mL) was added a solution of NaOH (9.6g,
0.24mol) in water (80mL). After stirring at room tem-
perature for 1h, the mixture was treated with di-tert-
butyl-dicarbonate (26.2g, 0.12mol), stirred for an
additional 1h, and concentrated in vacuo. The residue
was partitioned between EtOAc and water, and the or-
ganic layer was separated, dried (MgSO4), filtered, and
concentrated in vacuo. The residue was purified by col-
umn chromatography on silica gel (hexane/EtOAc 4/1)
to give 24 (19.9g, quant.) as a pale yellow oil, which
solidified on standing, mp 97–100ꢁC. 1H NMR
(CDCl3): d 1.05–1.30 (2H, m), 1.45 (9H, s), 1.53–1.80
(3H, m), 2.55–2.72 (2H, m), 2.65 (2H, d, J = 7.2Hz),
4.01–4.15 (2H, m), 7.30 (2H, d, J = 8.8Hz), 8.16 (2H,
d, J = 8.8Hz).
1
to give 21a (39.9g, 84%) as a colorless oil. H NMR
(CDCl3): d 1.00–1.80 (5H, m), 1.45 (9H, s), 2.50 (2H,
d, J = 6.8Hz), 2.50–2.75 (2H, m), 3.95–4.20 (2H, m),
6.90–7.15 (4H, m).
The following compounds 21b,c were prepared using a
procedure similar to that described for 21a form 20b,c.
5.58. tert-Butyl-4-[4-(trifluoromethyl)benzyl]piperidine-1-
carboxylate (21b)
Yield 90%. 1H NMR (CDCl3): d 1.00–1.80 (5H, m), 1.45
(9H, s), 2.50–2.75 (2H, m), 2.59 (2H, d, J = 7.0Hz),

412
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
5.64. tert-Butyl-4-(4-aminobenzyl)piperidine-1-carboxy-
late (25)
water (500mL) and brine (500mL), dried (MgSO4), fil-
tered, and concentrated in vacuo to give 28 (129g,
quant.) as a pale yellow oil. 1H NMR (CDCl3): d
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).
A mixture of 24 (10.00g, 31mmol), FeCl3Æ6H2O (0.81g,
3mmol), activated carbon (2.00g), and NH2NH2ÆH2O
(6.08mL, 125mmol) in THF (100mL) was stirred at re-
flux for 18h. The mixture was cooled to room tempera-
ture and filtered, and the filtrate was concentrated in
vacuo. The residue was purified by column chromato-
graphy on silica gel (hexane/EtOAc 3/1–1/1) to give 25
(8.51g, 94%) as a colorless oil, which solidified on stand-
5.69. 4-[(1-Acetylpiperidin-4-yl)methyl]benzenesulfonyl
chloride (29)
A solution of 28 (60.0g, 0.28mol) in DCM (100mL) was
added dropwise to chlorosulfonic acid (92mL, 1.4mol)
at 0ꢁC under stirring, and the mixture was stirred at
0ꢁC for 30min and at room temperature for 1.5h. The
mixture was poured into ice water (1L) and extracted
with DCM (500mL, 250mL). The organic layer was
washed with 5% aqueous NaHCO3 (2 · 500mL) and
brine (250mL). The organic layer was dried (MgSO4),
filtered, and concentrated in vacuo. The residue was
purified by column chromatography on silica gel
(EtOAc) to give 29 (54.2g, 62%) as a white solid, mp
72–75ꢁC. 1H 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 = 6.6Hz), 2.85–3.15 (1H, m), 3.70–3.90
(1H, m), 4.50–4.75 (1H, m), 7.39 (2H, d, J = 8.4Hz),
7.97 (2H, d, J = 8.4Hz).
1
ing, mp 68–71ꢁC. H NMR (CDCl3): d 0.95–1.25 (2H,
m), 1.45 (9H, s), 1.50–1.70 (3H, m), 2.42 (2H, d,
J = 6.6Hz), 2.50–2.75 (2H, m), 3.57 (2H, br s), 3.95–
4.15 (2H, m), 6.62 (2H, d, J = 8.5Hz), 6.92 (2H, d,
J = 8.5Hz).
5.65. tert-Butyl-4-(4-morpholin-4-ylbenzyl)piperidine-1-
carboxylate (26)
A mixture of 25 (970mg, 3.3mmol), bis(2-chloroethyl)
ether (715mg, 5.0mmol), KI (1.66g, 10mmol), and
K2CO3 (1.38g, 10mmol) in DMF (15mL) was stirred
at 80ꢁC for 18h. The mixture was diluted with water
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 (hexane/EtOAc 3/1) followed by recrystallization
from hexane/EtOAc to give 26 (880mg, 73%) as a pale
yellow solid, mp 126–127ꢁC. 1H NMR (CDCl3): d
1.00–1.25 (2H, m), 1.45 (9H, s), 1.50–1.70 (3H, m),
2.46 (2H, d, J = 6.6Hz), 2.50–2.75 (2H, m), 3.13 (4H,
m), 3.86 (4H, m), 3.95–4.20 (2H, m), 6.84 (2H, d,
J = 8.6Hz), 7.05 (2H, d, J = 8.6Hz).
5.70. 4-[(1-Acetylpiperidin-4-yl)methyl]benzenesulfon-
amide (30a)
A solution of 29 (6.32g, 20mmol) in THF (50mL) was
added dropwise to 25% aqueous ammonia (30mL)
under stirring, and the mixture was stirred at room
temperature for 2h. The organic solvent was removed
in vacuo, and the residue was treated with 1N HCl
(10mL) and extracted with EtOAc (80mL, 2 · 20mL).
The organic layer was dried (MgSO4), filtered, and con-
centrated in vacuo. The residue was purified by column
chromatography on silica gel (EtOAc/MeOH 1/0–9/1) to
5.66. 4-(4-Nitrobenzyl)piperidine hydrochloride (27a)
Compound 27a was prepared using a procedure similar
to that described for 22a from 24. Yield 91%, mp 205–
207ꢁC. 1H NMR (CD3OD): d 1.33–1.58 (2H, m),
1.79–2.10 (3H, m), 2.76 (2H, d, J = 7.0Hz), 2.95 (2H,
dt, J = 2.9, 13.0Hz), 3.30–3.44 (2H, m), 7.46 (2H, d,
J = 8.8Hz), 8.18 (2H, d, J = 8.8Hz).
1
give 30a (5.58g, 94%) as a colorless foam. H NMR
(CDCl3): d 1.03–1.32 (2H, m), 1.58–1.90 (3H, m), 2.08
(3H, s), 2.48 (1H, dt, J = 2.8, 13.2Hz), 2.63 (2H, d,
J = 6.8Hz), 2.98 (1H, dt, J = 2.2, 12.4Hz), 3.70–
3.87(1H, m), 4.53–4.67 (1H, m), 4.90–5.05 (2H, m),
7.29 (2H, d, J = 8.4Hz), 7.86 (2H, d, J = 8.4Hz).
5.67. 4-[4-(Piperidin-4-ylmethyl)phenyl]morpholine
dihydrochloride (27b)
5.71. 4-[(1-Acetylpiperidin-4-yl)methyl]-N-methylbenzene-
sulfonamide (30b)
Compound 27b was prepared using a procedure similar to
that described for 22a from 26. Yield 79%. H NMR
1
(DMSO-d6): d 1.36–1.88 (5H, m), 2.52–2.80 (4H, m),
3.17–3.22 (2H, m), 3.42 (4H, m), 4.00 (4H, m), 7.25–7.30
(2H, m), 7.53–7.60 (2H, m), 8.89 (1H, m), 9.12 (1H, m).
Compound 30b was prepared using a procedure similar
to that described for 30a from 40% aqueous methyl-
amine. Yield 46%, oil. H NMR (CDCl3): d 1.05–1.30
1
(2H, m), 1.60–1.91 (3H, m), 2.08 (3H, s), 2.49 (1H, dt,
J = 2.6, 12.8Hz), 2.63 (2H, d, J = 8.4Hz), 2.67 (3H, d,
J = 6.2Hz), 2.99 (1H, dt, J = 2.6, 12.8Hz), 3.73–3.86
(1H, m), 4.53–4.80 (2H, m), 7.29 (2H, d, J = 8.4Hz),
7.79 (2H, d, J = 8.4Hz).
5.68. 1-Acetyl-4-benzylpiperidine (28)
Acetic anhydride (110mL, 1.17mol) was added drop-
wise to 4-benzylpiperidine (2) (100g, 0.57mol) at 0ꢁC
under stirring, and the mixture was stirred at room tem-
perature for 1h and concentrated in vacuo. The residue
was partitioned between EtOAc (500mL) and saturated
aqueous NaHCO3 (1L). The organic layer was sepa-
rated, and the aqueous layer was extracted with EtOAc
(200mL). The combined organic layer was washed with
5.72. 4-(Piperidin-4-ylmethyl)benzenesulfonamide
hydrochloride (31a)
A solution of 30a (5.53g, 19mmol) in concentrated HCl
(50mL) was stirred at reflux for 6h. The mixture was

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
413
concentrated in vacuo, and the residue was recrystallized
from MeOH/i-PrOH to give 31a (4.53g, 83%) as a white
solid, mp 218–220ꢁC. H NMR (CD3OD): d 1.32–1.58
(2H, m), 1.78–2.05 (3H, m), 2.71 (2H, d, J = 6.8Hz),
2.83–3.02 (2H, m), 3.28–3.43 (2H, m), 7.38 (2H, d,
J = 8.4Hz), 7.83 (2H, d, J = 8.4Hz).
(80mL) and extracted with EtOAc (2 · 100mL). The or-
ganic layer was washed with water (100mL) and brine
(50mL), dried (MgSO4), filtered, and concentrated in
vacuo. The residue was purified by column chromato-
graphy on silica gel (hexane/EtOAc 3/1–3/2) to give
1
1
34a (5.25g, 82%) as a colorless oil. H NMR (CDCl3):
d 1.15–1.40 (2H, m), 1.68–2.00 (3H, m), 2.65–2.80 (1H,
m), 2.66 (2H, d, J = 7.0Hz), 2.72 (6H, s), 2.98–3.17
(1H, m), 3.93–4.07 (1H, m), 4.47–4.62 (1H, m), 7.32
(2H, d, J = 8.4Hz), 7.72 (2H, d, J = 8.4Hz).
5.73. N-Methyl-4-(piperidin-4-ylmethyl)benzenesulfon-
amide hydrochloride (31b)
Compound 31b was prepared using a procedure similar
to that described for 31a from 30b. Yield 90%. 1H NMR
(CD3OD): d 1.30–1.60 (2H, m), 1.78–2.05 (3H, m), 2.50
(3H, s), 2.71 (2H, d, J = 7.0Hz), 2.83–3.04 (2H, m),
3.30–3.45 (2H, m), 7.42 (2H, d, J = 8.4Hz), 7.77 (2H,
d, J = 8.4Hz).
5.77. 4-[(4-{[1-(Trifluoroacetyl)piperidin-4-yl]methyl}phen-
yl)sulfonyl]morpholine (34b)
To a stirred solution of morpholine (1.05g, 12mmol)
and Et3N (2.09mL, 15mmol) in THF (10mL) was
added a solution of 33 (3.70g, 10mmol) in THF
(20mL), and the mixture was stirred at room tempera-
ture for 2h. The mixture was diluted with EtOAc
(50mL), washed with water (10mL), 1N HCl (10mL),
and brine (3 · 10mL), and concentrated in vacuo. The
residue was purified by column chromatography on sil-
ica gel (hexane/EtOAc 4/1–1/1) to give 34b (3.99g, 95%)
5.74. 4-Benzyl-1-(trifluoroacetyl)piperidine (32)
To a stirred solution of 4-benzylpiperidine (2) (98.8g,
0.56mol) in EtOAc (500mL) was added trifluoroacetic
anhydride (TFAA) (159mL, 1.13mol) at 0ꢁC. The mix-
ture was stirred at room temperature for 3h and concen-
trated in vacuo. The residue was partitioned between
EtOAc (500mL) and saturated aqueous NaHCO3
(1L). The organic layer was separated, washed with sat-
urated aqueous NaHCO3 (2 · 200mL), 1N HCl
(2 · 200mL), and brine (200mL), dried (MgSO4), fil-
tered, and concentrated in vacuo. The residue was puri-
fied by column chromatography on silica gel (hexane/
EtOAc 1/0–9/1) to give 32 (149g, 97%) as a colorless
1
as a colorless oil. H NMR (CDCl3): d 1.17–1.38 (2H,
m), 1.73–1.94 (3H, m), 2.66 (2H, d, J = 7.0Hz), 2.68–
2.78 (1H, m), 3.00 (4H, t, J = 4.8Hz), 3.01–3.15 (1H,
m), 3.76 (4H, t, J = 4.8Hz), 3.98–4.10 (1H, m), 4.53–
4.60 (1H, m), 7.33 (2H, d, J = 8.4Hz), 7.69 (2H, d,
J = 8.4Hz).
5.78. 4-{[4-(Piperidin-4-ylmethyl)phenyl]sulfonyl}morpho-
line (35b)
1
oil. H NMR (CDCl3): d 1.10–1.40 (2H, m), 1.65–1.95
(3H, m), 2.57 (2H, d, J = 7.0Hz), 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 stirred solution of 34b (3.93g, 9.3mmol) in MeOH
(40mL) was added a solution of K2CO3 (3.88g,
28mmol) in water (20mL), and the mixture was stirred
at room temperature for 12h. The organic solvent was
removed in vacuo, and the residue was extracted with
DCM (40mL, 2 · 20mL). The organic layer was dried
(Na2SO4), filtered, and concentrated in vacuo to give
5.75. 4-{[1-(Trifluoroacetyl)piperidin-4-yl]methyl}benz-
enesulfonyl chloride (33)
A solution of 32 (54.3g, 0.20mol) in DCM (100mL) was
added dropwise to chlorosulfonic acid (117g, 1.0mol) at
0ꢁC under stirring, and the mixture was stirred at room
temperature for 5h. The mixture was poured into ice
water (500g) and extracted with DCM (400mL,
2 · 200mL). The combined organic layer was washed
with saturated aqueous NaHCO3 (200mL) and brine
(200mL) and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (hex-
ane/EtOAc 1/0–1/1) to give 33 (47.8g, 65%) as a color-
less oil, which solidified on standing in a refrigerator,
1
34b (3.08g, quant.) as a white solid, mp 98–101ꢁC. H
NMR (CDCl3): d 1.21–1.82 (5H, m), 2.60–2.71 (4H,
m), 3.00 (4H, t, J = 4.8Hz), 3.19–3.26 (2H, m), 3.75
(4H, t, J = 4.8Hz), 5.08 (1H, br s), 7.32 (2H, d,
J = 8.4Hz), 7.67 (2H, d, J = 8.4Hz).
5.79. N,N-Dimethyl-4-(piperidin-4-ylmethyl)benzenesulf-
onamide (35a)
Compound 35a was prepared using a procedure similar
to that described for 35b from 34a. Yield 89%, mp 66–
1
mp 65–68ꢁC. H NMR (CDCl3): d 1.26–1.39 (2H, m),
1
1.75–2.05 (3H, m), 2.66–2.78 (1H, m), 2.71 (2H, d,
J = 7.0Hz), 3.01–3.15 (1H, m), 3.98–4.10 (1H, m),
4.50–4.61 (1H, m), 7.40 (2H, d, J = 8.4Hz), 7.98 (2H,
d, J = 8.4Hz).
70ꢁC. H NMR (CDCl3): d 1.05–1.30 (2H, m), 1.50–
1.80 (3H, m), 2.45–2.65 (2H, m), 2.61 (2H, d,
J = 7.0Hz), 2.71 (6H, s), 3.00–3.15 (2H, m), 7.31 (2H,
d, J = 8.3Hz), 7.69 (2H, d, J = 8.3Hz).
5.76. N,N-Dimethyl-4-{[1-(trifluoroacetyl)piperidin-4-yl]-
methyl}benzenesulfonamide (34a)
5.80. 1-Acetyl-4-[4-(methylsulfonyl)benzyl]piperidine
(36a)
To an ice-cooled stirred solution of 33 (6.24g, 17mmol)
in THF (40mL) was added 50% aqueous dimethylamine
(4.4mL, 42mmol). After stirring at room temperature
for 0.5h, the mixture was diluted with 1N HCl
To a solution of Na2SO3 (4.57g, 36mmol) and NaHCO3
(6.10g, 73mmol) in water (40mL) was added portion-
wise 29 (11.46g, 36mmol) at 75ꢁC. After being stirred
at 75ꢁC for 1h, the mixture was treated with chloroacetic

414
S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
acid (5.14g, 54mmol) followed by a solution of NaOH
(2.18g, 55mmol) in water (4.4mL) and stirred at reflux
for 20h. The mixture was treated with 1N HCl (20mL)
at 0ꢁC and extracted with EtOAc (60mL, 30mL). The
organic layer was washed with brine (2 · 10mL), dried
(MgSO4), filtered, and concentrated in vacuo. The resi-
due was purified by column chromatography on silica
gel (EtOAc/MeOH 1/0–9/1) to give 36a (8.76g, 82%) as
9.5mmol) followed by Zn powder (6.33g, 97mmol),
and the mixture was stirred at 60ꢁC for 6h. After cool-
ing to room temperature, the mixture was diluted with
water (40mL) and filtered (Celite). The filtrate was ex-
tracted with DCM (80, 50mL), and the organic layer
was dried (MgSO4), filtered, and concentrated in vacuo
to give 38 (2.22g, 94%) as a colorless oil. 1H NMR
(CDCl3): d 1.00–1.25 (2H, m), 1.60–2.00 (3H, m), 2.07
(3H, s), 2.38–2.57 (3H, m), 2.88–3.03 (1H, m), 3.41
(1H, s), 3.72–3.83 (1H, m), 4.55–4.65 (1H, m), 7.01
(2H, d, J = 8.5Hz), 7.21 (2H, d, J = 8.5Hz).
1
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 = 7.4Hz), 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 = 8.4Hz), 7.87 (2H, d, J = 8.4Hz).
5.85. 1-Acetyl-4-[4-(methylsulfanyl)benzyl]piperidine
(39a)
5.81. 1-Acetyl-4-[4-(ethylsulfonyl)benzyl]piperidine (36b)
To a stirred solution of 38 (2.22g, 8.9mmol) in DMF
(50mL) was added iodomethane (0.72mL, 12mmol) fol-
lowed by K2CO3 (2.40g, 17mmol). After stirring at
room temperature for 15h, the mixture was diluted with
water and extracted with EtOAc. The organic layer was
washed with water and brine, dried (MgSO4), filtered,
and concentrated in vacuo. The residue was purified
by column chromatography on silica gel (EtOAc) to give
39a (2.03g, 87%) as a colorless oil. 1H NMR (CDCl3): d
1.00–1.25 (2H, m), 1.60–1.75 (3H, m), 2.07 (3H, s), 2.40–
2.57 (3H, m), 2.47 (3H, s), 2.88–3.03 (1H, m), 3.71–3.84
(1H, m), 4.54–4.65 (1H, m), 7.06 (2H, d, J = 8.4Hz),
7.21 (2H, d, J = 8.4Hz).
Compound 36b was prepared using a procedure similar
to that described for 36a from 2-bromopropionic acid.
Yield 61%, oil. 1H NMR (CDCl3): d 1.05–1.30 (2H,
m), 1.29 (3H, t, J = 7.2Hz), 1.60–1.92 (3H, m), 2.09
(3H, s), 2.40–2.60 (1H, m), 2.65 (2H, dd, J = 2.0,
7.4Hz), 2.90–3.05 (1H, m), 3.12 (2H, q, J = 7.2Hz),
3.72–3.88 (1H, m), 4.55–4.70 (1H, m), 7.34 (2H, d,
J = 8.4Hz), 7.83 (2H, d, J = 8.4Hz).
5.82. 4-[4-(Methylsulfonyl)benzyl]piperidine (37a)
A mixture of 36a (8.76g, 30mmol) and concentrated
HCl (100mL) was stirred at reflux for 4h and concen-
trated in vacuo. The residue was suspended in i-PrOH
(100mL) and concentrated in vacuo. The residue was
suspended in i-PrOH (50mL), stirred at reflux for
30min, 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 37a
5.86. 1-Acetyl-4-[4-(isopropylsulfanyl)benzyl]piperidine
(39b)
Compound 39b was prepared using a procedure similar
to that described for 39a from 2-iodopropane. Yield
1
80%, oil. H NMR (CDCl3): d 1.02–1.30 (2H, m), 1.29
(6H, d, J = 6.6Hz), 1.60–1.82 (3H, m), 2.07 (3H, s),
2.40–2.58 (3H, m), 2.90–3.05 (1H, m), 3.25–3.42 (1H,
m), 3.70–3.85 (1H, m), 4.55–4.65 (1H, m), 7.06 (2H, d,
J = 8.0Hz), 7.33 (2H, d, J = 8.0Hz).
1
(7.51g) as a white solid. H NMR (CD3OD): d 1.30–
1.60 (2H, m), 1.75–2.10 (3H, m), 2.75 (2H, d,
J = 7.0Hz), 2.80–3.05 (2H, m), 3.10 (3H, s), 3.25–3.45
(2H, m), 7.49 (2H, d, J = 8.1Hz), 7.89 (2H, d,
J = 8.1Hz). A solution of the hydrochloride salt
(7.51g) in water was basified with 1N NaOH (40mL)
and extracted with DCM (3 · 30mL). The organic layer
was washed with brine (10mL), dried (Na2SO4), filtered,
and concentrated in vacuo. The residue was triturated
with i-Pr2O to give the free base 37a (6.16g, 82%) as a
5.87. 1-Acetyl-4-[4-(isopropylsulfonyl)benzyl]piperidine
(40)
To an ice-cooled stirred solution of 39b (1.06g,
3.6mmol) in DCM (30mL) was added mCPBA (70%,
1.89g, 7.7mmol). After stirring at room temperature
for 3h, the mixture was diluted with DCM (30mL),
washed with 5% aqueous Na2S2O3 (20mL), saturated
aqueous NaHCO3 (3 · 20mL), and brine (20mL), dried
(MgSO4), filtered, and concentrated in vacuo. The resi-
due was purified by column chromatography on silica
gel (EtOAc/MeOH 10/1) to give 40 (1.12g, 95%) as a
1
white solid, mp 97–99ꢁC. 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 = 6.6Hz), 3.03–3.08 (2H, m), 3.05 (3H,
s), 7.34 (2H, d, J = 8.4Hz), 7.85 (2H, d, J = 8.4Hz).
5.83. 4-[4-(Ethylsulfonyl)benzyl]piperidine (37b)
1
colorless oil. H NMR (CDCl3): d 1.03–1.40 (2H, m),
Compound 37b was prepared using a procedure similar
to that described for 37a from 36b. Yield 69%, oil. H
1.29 (6H, d, J = 6.8Hz), 1.53–2.00 (3H, m), 2.07 (3H,
s), 2.40–2.70 (3H, m), 2.82–3.05 (1H, m), 3.10–3.25
(1H, m), 3.70–3.85 (1H, m), 4.55–4.70 (1H, m), 7.32
(2H, d, J = 8.2Hz), 7.80 (2H, d, J = 8.2Hz).
1
NMR (CDCl3): d 1.05–1.30 (2H, m), 1.28 (3H, t,
J = 7.5Hz), 1.55–1.78 (3H, m), 2.45–2.65 (4H, m),
3.00–3.15 (2H, m), 3.11 (2H, q, J = 7.5Hz), 7.34 (2H,
d, J = 8.4Hz), 7.81 (2H, d, J = 8.4Hz).
5.88. 4-[4-(Isopropylsulfonyl)benzyl]piperidine (41)
5.84. 4-[(1-Acetylpiperidin-4-yl)methyl]benzenethiol (38)
Compound 41 was prepared using a procedure similar
to that described for 37a from 40. Yield 86%. 1H
NMR (CDCl3): d 1.07–1.25 (2H, m), 1.30 (6H, d,
J = 7.0Hz), 1.55–1.78 (3H, m), 2.55 (2H, dt, J = 2.6,
To an ice-cooled stirred solution of concentrated H2SO4
(6.6mL) in water (36mL) was added 29 (3.00g,

S. Imamura et al. / Bioorg. Med. Chem. 13 (2005) 397–416
415
12.0Hz), 2.62 (2H, d, J = 6.8Hz), 3.00–3.30 (3H, m),
7.33 (2H, d, J = 8.4Hz), 7.78 (2H, d, J = 8.4Hz).
que gradient density centrifugation and cultured in
RPMI 1640 medium supplemented with 20% FBS,
5lg/mL phytohemagglutinin-P (PHA), 100U/mL
recombinant human interleukin 2, 100U/mL penicillin
G, and 100lg/mL streptomycin for 3days. The
above medium without PHA was used in the following
assay. The PHA-stimulated PBMC were inoculated with
10ng of p24 of R5 HIV-1 (Ba-L strain) per 4 · 106 cells
and incubated for 2h. The cells were washed with media
to remove unadsorbed viral particles and then seeded
into 96-well plates (2 · 105 cells/well) with media
containing various concentrations of test compounds.
On day 4 after infection, two-thirds of the culture
supernatant was removed and replaced with media
containing the same concentration of the test
compounds. On day 7 after infection, the culture
supernatants were collected, and their p24 antigen levels
were determined using an HIV-1 p24 antigen ELISA kit
(ZeptoMetrix).
5.89. 4-[4-(Methylsulfanyl)benzyl]piperidine (42)
Compound 42 was prepared using a procedure similar
to that described for 37a from 39a. Yield 73%. 1H
NMR (CDCl3): d 1.08–1.34 (2H, m), 1.52–1.72 (3H,
m), 2.47 (3H, s), 2.47–2.67 (4H, m), 3.02–3.15 (2H, m),
7.06 (2H, d, J = 8.5Hz), 7.19 (2H, d, J = 8.5Hz).
5.90. Receptor binding assays
CHO-K1 and CCR5-expressing CHO cells19 were incu-
bated with various concentrations of test compounds in
binding buffer (Hamꢀs F-12 medium containing 20mM
HEPES and 0.5% bovine serum albumin, pH7.2) con-
taining 200pM 125I-labeled RANTES. Binding reactions
were performed at room temperature for 40min. 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 Top-
Count scintillation counter (Packard). Binding assays
for other chemokine receptors were carried out in a simi-
lar manner using the following ligands: RANTES
for CCR1, monocyte chemoattractant protein 1 for
CCR2, eotaxin for CCR3, thymus- and activation-regu-
lated chemokine for CCR4, and MIP-3b for CCR7.
5.93. Pharmacokinetic analysis in dogs
Test compounds (10mg/2mL/kg) suspended in 0.5%
methylcellulose were administered to male beagle dogs
(n = 3) by oral gavage. Blood samples were collected at
different time points (pre, 15, 30min, 1, 2, 4, 8, 24h)
from the jugular vein. Each blood sample was taken into
a heparinized tube, and plasma was separated by centri-
fugation (3000rpm, 15min, 4ꢁC). The plasma sample
(100lL) was deproteinized with acetonitrile (100lL),
and the resulting protein precipitate was removed by
centrifugation (15,000rpm, 10min). The compound con-
centrations in the supernatant were measured by LC/
MS/MS. The LC/MS/MS analyses were performed on
an API 3000 triple quadruple mass spectrometer (Per-
kin–Elmer Sciex) interfaced with an LC-10Avp HPLC
system (Shimadzu). The mass spectrometer was
equipped with a turbo ionspray source and operated in
positive ion mode. The HPLC conditions were as fol-
lows: column, L-column ODS (2.1 · 150mm); mobile
phase, 0.01M HCO2NH4 (adjusted to pH3.0 with
HCO2H)/MeCN = 1/1; flow rate, 0.2mL/min; column
temperature, 40ꢁC.
5.91. HIV-1 Envelope-mediated membrane fusion assay
COS-7 cells were maintained in Dulbeccoꢀs modified
Eagle medium (D-MEM) supplemented with 10% fetal
bovine serum (FBS), 100U/mL penicillin G, and
100lg/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 termi-
nal repeat-driven luciferase reporter gene, were main-
tained in RPMI 1640 medium supplemented with 10%
FBS, 100U/mL penicillin G, 100lg/mL streptomycin,
and 500lg/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 co-transfected into COS-7 cells
using Lipofectamine 2000 (Invitrogen). After a 2day
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 37ꢁC. The mixture of D-MEM and
RPMI 1640 medium supplemented with 10% FBS,
100U/mL penicillin G, and 100lg/mL streptomycin
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 10min. The luciferase activity
was measured with a luminometer (Wallac 1420
ARVOsx).
Acknowledgements
We would like to thank Mr. Kenichi Kuroshima for the
receptor binding assays; Mr. Katsunori Takashima, Dr.
Hiroshi Miyake, and Ms. Shikiko Shiki for the mem-
brane fusion and antiviral assays; and Mr. Masashi
Yamaguchi and Mr. Shinichi Matsumoto for pharmaco-
kinetic analysis.
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