Design, synthesis and biological evaluation of piperazine analogues as CB1 cannabinoid receptor ligands

Article abstract of DOI:10.1016/j.bmc.2008.01.023

After the CB1 receptor antagonist SR141716 (rimonabant) was previously reported to modulate food intake, CB1 antagonism has been considered as a new therapeutic target for the treatment of obesity. Several series of urea, carbamate, amide, sulfonamide and oxalamide derivatives based on 1-benzhydrylpiperazine scaffold were synthesized and tested for CB1 receptor binding affinity. The SAR studies to optimize the CB1 binding affinity led to the potent urea derivatives. After the additional SAR studies to optimize the substituents of diphenyl rings, the combination of 2-chlorophenyl and 4-chlorophenyl turned out to be the most potent scaffold. The CB2 binding affinity assay as well as functional assay was also conducted on these compounds. Herein we wish to introduce several novel CB1 antagonists with IC₅₀ values less than 100 nM for the CB1 receptor binding.

Full text of DOI:10.1016/j.bmc.2008.01.023

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 4035–4051
Design, synthesis and biological evaluation of piperazine
analogues as CB1 cannabinoid receptor ligands
Kwang-Seop Song,a Sung-Han Lee,a Hyun Ji Chun,b Jong Yup Kim,a Myung Eun Jung,a
Kwangwoo Ahn,a Soo-Un Kim,c Jeongmin Kima and Jinhwa Leea,*
aSmall Molecule Group, Central Research Institute, Green Cross Corporation, 341 Bojeong-dong, Giheung-gu, Yongin,
Gyunggi-do 446-799, Republic of Korea
bDepartment of Chemistry, The University of Auckland, Auckland 1142, New Zealand
cProgram in Applied Life Chemistry, School of Agricultural Biotechnology, Seoul National University,
Seoul 151-921, Republic of Korea
Received 7 December 2007; revised 14 January 2008; accepted 14 January 2008
Available online 19 January 2008
Abstract—After the CB1 receptor antagonist SR141716 (rimonabant) was previously reported to modulate food intake, CB1 antag-
onism has been considered as a new therapeutic target for the treatment of obesity. Several series of urea, carbamate, amide, sul-
fonamide and oxalamide derivatives based on 1-benzhydrylpiperazine scaffold were synthesized and tested for CB1 receptor binding
affinity. The SAR studies to optimize the CB1 binding affinity led to the potent urea derivatives. After the additional SAR studies to
optimize the substituents of diphenyl rings, the combination of 2-chlorophenyl and 4-chlorophenyl turned out to be the most potent
scaffold. The CB2 binding affinity assay as well as functional assay was also conducted on these compounds. Herein we wish to
introduce several novel CB1 antagonists with IC50 values less than 100 nM for the CB1 receptor binding.
ꢀ 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Numerous studies on causes of obesity have been made
to identify new potential targets that could be exploited
to create novel type of anti-obesity drugs. At last it was
discovered that modulation of endocannabinoid system
by specifically blocking the cannabinoid receptor 1
(CB1) in both the brain and periphery can provide a no-
vel target for the treatment of obesity.10 The endocan-
nabinoid system includes endogenous ligands (such as
anandamide and 2-AG) and two cannabinoid receptor
subtypes (CB1 and CB2). These receptors (CB1 and
CB2) belong to the G-protein coupled receptor super-
family and were first cloned in 1990 and 1993, respec-
tively.11–13 The CB1 receptors are mainly expressed in
several brain areas including the limbic system (amyg-
dala, hippocampus), hypothalamus, cerebral cortex, cer-
ebellum, and basal ganglia. It has been known that CB1
receptors, especially in the limbic system-hypothalamus
axis cannabinoids, have an important role in the control
of appetite.14,15 By contrast, CB2 receptors are almost
exclusively expressed in cells of the immune system.15,16
In recent years, obesity has become a major health prob-
lem for many postindustrial societies. The number of
deaths per year attributable to obesity is about 30,000
in the UK and nearly 400,000 in the United States,
where obesity is set to overtake smoking as the main
preventable cause of illness and premature death.1–3
The total direct and indirect costs of obesity was esti-
mated to be approximately €32,800 million per year in
the EU and $99.2 billion per year in the USA.3,4 Obesity
poses a major health risk for serious diet-related chronic
disease, including type 2 diabetes, cardiovascular dis-
ease, hypertension and stroke, and some of cancers.1
For these reasons, the World Health Organization de-
clared obesity a global epidemic5,6 and obesity is now
considered as disease that needs pharmacological treat-
ments.7–9
The physiological role of both CB receptors is not yet
completely understood, although they seem to be
involved in certain pathophysiological processes. In par-
ticular, the physiological role of CB1 receptors has been
Keywords: CB1 receptor antagonists; 1-Benzhydrylpiperazine; SAR
study; Rimonabant; Piperazine; Cannabinoid receptor; Anti-obesity.
*
Corresponding author. Tel.: +82 31 260 9892; fax: +82 31 260
9870; e-mail: jinhwalee@greencross.com
0968-0896/$ - see front matter ꢀ 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2008.01.023

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K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
of interest, since the impressive clinical results of rimo-
nabant, the first CB1 antagonist, were reported for the
treatment of obesity and metabolic disorders in 2001.
Accordingly antagonism of CB1 receptor has been pur-
sued as a highly promising strategy for the treatment of
obesity.17 Even though rimonabant (AcompliaTM) is cur-
rently launched by Sanofi–Aventis in the European Un-
ion, many research groups, including major
pharmaceutical companies, are still searching for novel
CB1 antagonists with improved physicochemical prop-
erties or reduced psychiatric adverse effects, such as
depression or anxiety.1,18,19
various derivatives with 1,1-diphenyl methylene groups
geminally coupled to the central piperazine ring, pos-
sessing good in vitro CB1 receptor binding affinity and
selectivity of CB1 over CB2 in addition to good func-
tional activity.
2. Results and discussion
2.1. Chemistry
The synthesis of compounds 13–23 commenced with the
preparation of the requisite intermediate 7 or 12a–e. The
key piperazines 7 and 12a–e were prepared as displayed
in Schemes 1 and 2, respectively. As shown in Scheme 1,
4,40-dichlorobenzophenone, the commercially available
starting material, was reduced by sodium borohydride
to prepare the symmetrical diphenylmethanol 5.23 The
compound 5 was treated with thionyl chloride to pro-
vide the corresponding chloromethylene intermediate 6
which was subsequently refluxed with piperazine in ace-
tonitrile to give 1-(bis(4-chlorophenyl)methyl)piperazine
(7).24
Most analogues, reported as novel CB1 antagonists, are
derived from the structure of rimonabant (Fig. 1A).16 In
most cases, either the central pyrazole core or the car-
bonyl moiety of rimonabant is substituted by either
other aromatic rings or other hydrogen bonding accep-
tors, respectively. However, there was an interesting
moiety distinguished by a diphenyl group geminally cou-
pled to the central core (Fig. 1B).16,17 It was identified by
Aventis Pharma and Vernalis Research that some series
of analogues with a 1,1-diphenyl methylene group,
which might mimic the 1,5-diphenyl motif of rimona-
bant, could act as CB1 antagonists.20,21 Indeed, these
derivatives were previously described for the treatment
of CNS disorders,21 such as anxiety or depression which
is a serious adverse effect of rimonabant. Compound 2
(AVE1625, Fig. 1B) is in phase II clinical trials for obes-
ity and cognitive disorder (THOMSON Pharmaꢁ). We
envisioned that some derivatives with this intriguing
moiety can divert the psychiatric adverse effect of rimo-
nabant, while retaining its good in vitro and in vivo bio-
logical activity. We thought that the central azetidine
moiety could be replaced by simple six-membered het-
erocyclic scaffolds, such as piperazine, while keeping car-
bonyl moiety to maintain the pivotal hydrogen-bonding
with backbone of the protein.22 Herein we wish to unveil
synthetic details and structure–activity studies for the
The other key intermediates 12a–e were also prepared
by the method outlined in Scheme 2. Grignard reactions
of 4-chlorophenylmagnesium bromide (8) with substi-
tuted benzaldehydes 9 in tetrahydrofuran (THF) pro-
vided the corresponding diphenylmethanols 10a–e.24
Compounds 10a–e were then treated with thionyl chlo-
ride followed by refluxing with piperazine in acetonitrile
to provide 12a–e. As shown in Scheme 3, the target com-
pounds 13–18 were prepared by the coupling reaction
between key intermediates (compounds 7 or 12a–e)
and the corresponding isocyanates in the presence of
triethylamine.25
The amide bond formations of compounds 7 or 12a–e
with required acids produced compounds 19 or 20 by
the use of dicyclohexylcarbodiimide (DCC) and 1-
hydroxybenzotriazole (HOBT) in N,N-dimethylform-
amide (DMF).26 The reaction of compounds 7 with
chloroformates in the presence of triethylamine gave
the corresponding carbamate derivatives 21.27 The com-
pounds 22, containing a sulfonamide group, were pre-
pared by the reaction of compounds 7 with required
sulfonyl chlorides.28 A piperazine intermediate 12c was
reacted with excess oxalyl chloride (more than 10 equiv-
alents) at low temperature and the resulting intermedi-
ates were successively treated with required amines to
provide a series of target compounds 23.27
A
Cl
O
N
N
HN
N
Cl
Cl
1
B
O
O S O
Cl
CF3
O
Meanwhile, a series of bromo-substituted phenyl group
such as compounds 29 was prepared by reactions of
amine compound 28 with the corresponding isocya-
nates, as described in Scheme 4. The condensation of
2-chlorobenzaldehyde (25) with 1,4-dibromobenzene
(24) in the presence of n-BuLi produced the correspond-
ing alcohol 26.29 The resulting alcohol 26 was trans-
formed into compound 28 by the treatment of thionyl
chloride followed by refluxing with piperazine in aceto-
nitrile in an analogous fashion as previously described.
The coupling reaction of intermediate 28 and the corre-
F
N
N
H
N
F
Cl
Cl
2
3
Figure 1. (A) The structure of rimonabant (1, SR141716). (B) Analogs
with benzhydryl moiety connected to the central azetidine core. These
analogs are reported by Aventis Pharma (2, AVE1625) and Vernalis
Research (3).

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4037
H
N
O
4
OH
Cl
ii
iii
i
N
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
6
5
7
Scheme 1. Reagents and conditions: (i) NaBH4, MeOH, THF, 0 ꢂC ! rt; (ii) SOCl2, DCM, rt; (iii) piperazine, MeCN, reflux.
O
R1
10a R1=R3=Cl, R2=H
10b R1=R2=Cl, R3=H
10c R1=Cl, R2=R3=H
10d R1=Me, R2=R3=H
10e R1=CF3, R2=R3=H
OH R1
MgBr
i
R2
R3
R2
R3
+
H
Cl
Cl
8
9
ii
H
N
N
Cl R1
12a R1=R3=Cl, R2=H
12b R1=R2=Cl, R3=H
12c R1=Cl, R2=R3=H
iii
R2
R3
R1
R2
R3
Cl
12d R1=Me, R2=R3=H
12e R1=CF3, R2=R3=H
Cl
11
Scheme 2. Reagents and conditions: (i) THF, rt; (ii) SOCl2, DCM, rt; (iii) piperazine, MeCN, reflux.
sponding isocyanates in the presence of triethylamine
produced the desired compounds 29.
In case of the amide derivatives, the insertion of chlorine
at the ortho position also showed the slightly improved
binding affinity (20j), with n-hexanoyl moiety as lipo-
philic pharmacophore. Except 20j, all other amide deriv-
atives demonstrated IC50 > 1 lM values, indicating the
superiority of urea functionality to amide counterpart
for CB1R binding affinity.
2.2. Structure–activity relationship studies
A symmetrical diphenylmethylene template attached to
piperazine was used to construct various target com-
pounds bearing a strong hydrogen-bonding acceptor
for the initial SAR study. As mentioned earlier, the cru-
cial receptor–ligand interaction is recognized to be a
hydrogen bond between a hydrogen-bonding acceptor
such as the carbonyl group of rimonabant and the
Lys192-Asp366 residue of the CB1 receptor. Using the
piperazine compound 7, several functional groups acting
as hydrogen-bonding acceptor were investigated. As
shown in Scheme 3, urea 13, amide 19, carbamate 21
and sulfonamide 22 derivatives were synthesized, and
subsequently biological activities of these compounds
were evaluated via a rat CB1 binding assay.30 Even
though most of the derivatives had over 2 lM of IC50
value at CB1 receptor, a urea derivative 13a, displayed
the potent CB1 receptor binding affinity while some of
amide derivatives (19a, 19c and 19h) showed slightly
weaker activities. Thus, additional urea 14 and amide
20 derivatives with chlorine at the ortho position (R1
in Scheme 3) were prepared for the further SAR study.
The chlorine substituents at both ortho and para posi-
tions were reminiscent of counterparts from rimona-
bant. The introduction of chlorine atom to the ortho
position resulted in significant improvement in binding
affinity at CB1 receptor. Especially compound 14a, in
which a chlorine was introduced to the ortho position
of compound 13a, was found to result in an approxi-
mate gain of CB1 binding affinity by one order of mag-
nitude. Among numerous ureas tested in this series,
compound 14b containing N-cycloheptyl carboxamide
moiety demonstrated the most potent binding affinity.
Further SAR study was performed on 2,4-dichloro-
phenyl moiety of urea derivatives (compound 14 series).
In order to evaluate the requirement of chlorine at the
para position, chlorine position was either switched
from R3 to R2 (Scheme 3) or completely removed. When
chlorine position was switched from the para position to
the meta position (compound 15 series), there was a
moderate loss of CB1 binding affinity. For example,
compound 14b is compared with the corresponding
compound 15b. On the other hand, removing the chlo-
rine at the para position slightly increased binding affin-
ity for the CB1 receptor as exemplified by either
compound 14a versus compound 16a or compound
14b versus compound 16b. Based on this SAR study,
it is suggested that the chlorine at the ortho position
(R1 position in Scheme 3) is essential for CB1 receptor
binding affinity.
A few of substituents at the ortho position were also ex-
plored in order to determine the optimal group at the
ortho position. The chlorine at the ortho position was
replaced by the methyl (compound 17 series) or trifluo-
romethyl (compound 18 series) group. However, these
replacements led to a mild decrease in CB1R binding
affinity. For example, methyl derivative 17b or trifluoro-
methyl derivative 18b proved to slightly lose binding
affinity compared with compound 16b. According to
this result, the chlorine was selected as the best substitu-
ent at the ortho position. In order to explore further,

4038
K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
R4
O
NH
13 R1=R2=H, R3=Cl
14 R1=R3=Cl, R2=H
15 R1=R2=Cl, R3=H
16 R1=Cl, R2=R3=H
17 R1=Me, R2=R3=H
18 R1=CF3, R2=R3=H
N
N
i
R1
R2
R3
Cl
Cl
Cl
Cl
Cl
13 ~ 18
O
R5
N
N
ii
R1
19 R1=R2=H, R3=Cl
20 R1=R3=Cl, R2=H
R2
R3
H
N
19 ~ 20
R6
N
R1
R2
R3
O
O
Cl
N
N
7 or 12
iii
Cl
21
O
O
R7
S
N
iv
N
Cl
22
O
O
R8
Cl
N
N
v
23
Scheme 3. Reagents and conditions: (i) R4-NCO, TEA, DCM, rt; (ii) R5-COOH, DCC, HOBT, DMF, rt; (iii) R6-OCOCl, TEA, DCM, 0 ꢂC ! rt;
(iv) R7-SO2Cl, TEA, DCM, rt; (v) (COCl)2, TEA, R8-NH2, DCM, 0 ꢂC ! rt.
compound 23 series was prepared by exchanging the
urea group of compound 16 series into the 2-oxoaceta-
mide group (Scheme 3). Initially, these derivatives were
hoped to improve CB1 receptor binding affinity, because
additional carbonyl group might be able to act as a sup-
plementary hydrogen-bonding acceptor. However, it
was found that 2-oxoacetamide group was about three-
fold less active than the urea counterpart in terms of
CB1R binding affinity.
para position, both 29b and 16b proved to be effective
in binding CB1 receptor.
The interesting urea compounds were further evaluated
in a functional assay using hCB1R expressed in Chinese
hamster ovary (CHO) cells in the presence of for-
skolin.35 Two compounds (29a and 29b) exhibited better
functional activities than 1 in in-house functional assay.
Binding affinities were also measured for the CB2 recep-
tor expressed in CHO cells and employing [3H]WIN-
55,212-2 as a radio-ligand.32 Almost all compounds
were devoid of activity in this CB2 binding assay, indi-
cating a great selectivity for CB1 over CB2 of the piper-
azine analogues. Selected examples of the above
derivatives are summarized in Tables 1 and 2.
Finally, 4-chlorophenyl group was replaced with 4-
bromophenyl group as shown in Scheme 4. The intro-
duction of 4-bromophenyl group provided a comparable
activity in CB1 binding affinity. Thus, it appears that de-
spite the alteration of chlorine to bromine atom at the

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
Cl
4039
OH Cl
O
Br
i
+
H
Br
Br
26
24
25
ii
R1
NH
O
H
N
N
N
Cl Cl
iv
iii
Cl
N
Cl
Br
Br
Br
27
29
28
Scheme 4. Reagents and conditions: (i) n-BuLi, THF, ꢀ78 ꢂC ! rt; (ii) SOCl2, DCM, rt; (iii) piperazine, MeCN, reflux; (iv) R1-NCO, TEA, DCM,
rt.
3. Conclusion
in CDCl3. Chemical shifts were expressed in parts per
million (ppm, d units) downfield from the signal for
TMS. Coupling constants are in units of hertz (Hz).
Splitting patterns describe apparent multiplicities and
are designated as s (singlet), d (doublet), t (triplet), q
(quartet), quint (quintet), m (multiplet), and br (broad).
Mass spectra were obtained with either a Micromass,
Quattro LC Triple Quadruple Tandem Mass Spectrom-
eter or Agilent, 1100LC/MSD system equipped with
XTerraꢁMS C18 3.5 lm 2.1 · 50 mm column with a
9 min gradient from 30% CH3CN to 90% CH3CN in
H2O.
Piperazine derivatives as CB1 receptor–ligands were de-
signed, synthesized and evaluated via in vitro cannabi-
noid CB1 and CB2 binding assays. In general, urea
derivatives linked to 1-((2-chlorophenyl)(4-chloro-
phenyl)methyl)piperazine showed the modest CB1 bind-
ing affinities and extremely weak CB2 binding affinities.
Especially, compound 16a or 16b appeared to be the
most potent among compounds tested (IC50 = 72.8 nM
and 66.5 nM, respectively) in terms of rat CB1R binding
affinity, while compound 29a or 29b showed the better
functional activities (IC50 = 62.8 nM and 49.4 nM,
respectively) than rimonabant in cell lines expressing
hCB1R. Despite slightly weaker CB1 binding affinities
compared to the affinity of rimonabant, there is no
doubt that the benzhydrylpiperazine urea derivatives
are active as cannabinoid CB1 receptor antagonists. In-
deed the benzhydryl moiety differs from the usually re-
ported moieties of CB1 receptor antagonists, which
have two phenyl pharmacophores linked to an aromatic
central core. Currently, only two companies reported
the benzhydryl moiety linked to azetidine for the CB1
receptor antagonists and while this research was being
For preparative HPLC, ca. 100 mg of a product was in-
jected in 1 mL of DMSO or MeOH onto a SunFireTM
Prep C18 OBD 5 lm 19 · 100 mm column with a
10 min gradient from 10% CH3CN to 90% CH3CN in
H2O. Flash chromatography was carried using Merck
silica gel 60 (230–400 mesh). Most of the reactions were
monitored by thin-layer chromatography on 0.25 mm E.
Merck silica gel plates (60F-254), visualized with UV
light.
4.2. Chemistry
finished,
AstraZeneca
published
a
patent
(WO2007018459), which claimed similar derivatives to
ours. However, they have not reported any detailed
CB1 and CB2 binding affinity data or functional assay
data. To the best of our knowledge, AstraZeneca has
not also published the main derivatives (14a, 14b, 16a,
16b) described in this research. Since the derivatives in
this study showed significant CB1 antagonistic charac-
ters and virtually no CB2 binding affinities, further stud-
ies should be undertaken to optimize the CB1 binding
affinity. Additional PK and in vivo efficacy studies in
addition to further SAR studies will be the subject of fu-
ture investigations.
4.2.1. 1-(Bis(4-chlorophenyl)methyl)piperazine (7). 4,40-
Dichlorobenzophenone (12.56 g, 50 mmol) was dis-
solved in a mixture of methanol (100 mL) and THF
(150 mL) and cooled to 0 ꢂC. NaBH4 (1.89 g, 50 mmol)
was added to the above solution at 0 ꢂC. After addi-
tional 10 min at 0 ꢂC, the reaction mixture was subse-
quently stirred at room temperature for 2 h. The
reaction mixture was diluted with water (200 mL), and
the product was extracted with diethyl ether (400 mL).
The organic phase was washed with 1 N HCl, followed
by a saturated NaHCO3 and finally with water. It was
dried over MgSO4 and evaporated under vacuum to
provide 4,40-dichlorobenzhydrol (5, 12.05 g, 47.6 mol,
95%). The crude product was used in the following steps
without further purification.
4. Experimental
4.1. General synthetic methods
The alcohol (5, 5.06 g, 20 mmol) was dissolved in DCM
(50 mL) and SOCl2 (1.6 mL, 22 mmol) was added to the
solution. The reaction mixture was stirred at room tem-
perature overnight and the solvent was evaporated un-
1H NMR spectra were recorded on either a Jeol ECX-
400, or a Jeol JNM-LA300 spectrometer for solution

4040
K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
Table 1. Structures and binding affinities of selected ligands to rat CB1 and human CB2 receptors, and human CB1 functional activities of the
ligands
Cl
O
N
N
Y
R1
R3 R2
Ligand
R1
R2
R3
Y
Receptor affinitya
(IC50, nM)
hCB1 functional
activitya (IC50, nM)
rCB1
hCB2
1 (rimonabant)
1.9
914
1760
—
120
—
13a
14a
14b
14c
14d
15a
15b
15c
15d
19a
19c
19h
20j
H
H
H
H
H
H
Cl
Cl
Cl
Cl
H
H
H
H
Cl
Cl
Cl
Cl
Cl
H
–NH-Cyclohexyl
–NH-Cyclohexyl
–NH-Cycloheptyl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
H
104
>10,000
>10,000
>10,000
—
367
729
1040
—
89.2
262
–NH-Cyclohexylmethyl
–NH-tert-Butyl
–NH-Cyclohexyl
–NH-Cycloheptyl
–NH-Cyclohexylmethyl
–NH-tert-Butyl
–Cyclohexyl
2000
186
>10,000
>10,000
—
441
424
—
H
158
H
2000
783
H
>10,000
—
—
316
—
Cl
Cl
Cl
Cl
1390
1070
1150
257
H
–Cyclobutyl
–Pentyl
–Pentyl
—
—
H
Cl
—
—
—
a These data were obtained by single determinations.
Table 2. Structures and binding affinities of selected ligands to rat CB1 and human CB2 receptors, and human CB1 functional activities of the
ligands
X
O
N
N
Y
R1
Ligand
X
R1
Y
Receptor affinitya (IC50
nM)
,
hCB1 functional
activitya (IC50, nM)
rCB1
hCB2
16a
16b
16c
16d
17a
17b
17c
17d
18a
18b
18c
18d
23a
23b
29a
29b
29c
29d
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Br
Br
Br
Br
Cl
Cl
–NH-Cyclohexyl
–NH-Cycloheptyl
72.8
66.5
189
122
248
151
291
680
163
141
526
2050
226
229
103
82.3
127
237
>10,000
>10,000
>10,000
4820
128
226
273
443
195
163
340
334
186
204
798
—
Cl
Cl
–NH-Cyclohexylmethyl
–NH-tert-Butyl
–NH-Cyclohexyl
Me
Me
Me
Me
CF3
CF3
CF3
CF3
Cl
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
—
–NH-Cycloheptyl
–NH-Cyclohexylmethyl
–NH-tert-butyl
–NH-Cyclohexyl
–NH-Cycloheptyl
–NH-Cyclohexylmethyl
–NH-tert-Butyl
–CO–NH-Cyclohexyl
–CO–NH-Cycloheptyl
–NH-Cyclohexyl
—
—
—
—
Cl
Cl
>10,000
>10,000
>10,000
4950
62.8
49.4
146
286
Cl
Cl
–NH-Cycloheptyl
–NH-Cyclohexylmethyl
–NH-tert-Butyl
Cl
a These data were obtained by single determinations.
der vacuum. The crude residue was dissolved in MeCN
(100 mL) and piperazine (17.23 g, 200 mmol) was added.
The mixture was refluxed at 90 ꢂC for 16 h. The solvent
was removed under vacuum. The residue was dissolved
in DCM (150 mL) and washed with water followed by
1 M HCl (100 mL). The organic phase was evaporated

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4041
under vacuum and the crude residue was dissolved in the
mixture of 1 M HCl (100 mL) and diethyl ether
(100 mL). The diethyl ether layer was discarded and to
the remaining water layer was added 1 M NaOH
(200 mL). The aqueous solution was extracted with
DCM (200 mL). The DCM layer was washed succes-
sively with water, dried over MgSO4 and evaporated un-
der vacuum to provide the title compound (4.75 g,
14.8 mmol, 74%). [M+H]+: 321.
pound 7 (161 mg, 0.5 mmol) and cyclohexanecarboxylic
acid (70 mg, 0.55 mmol) in DMF (5 mL), were added
DCC (113 mg, 0.55 mmol) and HOBT (74 mg,
0.55 mmol). The resulting solution was stirred at room
temperature overnight. The precipitate was filtered off
and the filtrate was evaporated to remove DMF. The
residue was dissolved in DCM (40 mL), washed with
1 M HCl (20 mL) and water (20 mL). The organic phase
was dried over MgSO4, filtered and evaporated under
vacuum. The residue was further purified by prep HPLC
to provide the title compound (134 mg, 0.31 mmol, 62%)
4.2.2. 4-(Bis(4-chlorophenyl)methyl)-N-cyclohexylpiper-
azine-1-carboxamide (13a). To a solution of the com-
pound 7 (161 mg, 0.50 mmol) in DCM (5 mL) was
added cyclohexylisocyanate (63 mg, 0.50 mmol) and tri-
ethylamine (51 mg, 0.50 mmol). The reaction mixture
was subsequently stirred at room temperature overnight.
The mixture was poured into 1 M HCl solution (10 mL)
and extracted with DCM (2· 20 mL). The combined
DCM was washed successively with water, dried over
MgSO4 and evaporated under vacuum. The residue
was further purified by prep HPLC to provide the title
compound (98 mg, 0.22 mmol, 44%) as a light yellow so-
1
as a light yellow solid. H NMR (400 MHz, CDCl3): d
7.31 (d, J = 8.6 Hz, 4H), 7.26 (d, J = 8.6 Hz, 4H), 4.19
(s, 1H), 3.60 (t, J = 5.1 Hz, 2H), 3.49 (t, J = 4.4 Hz,
2H), 2.49–2.38 (m, 1H), 2.35 (m, 4H), 1.81–1.75 (m,
2H), 1.70–1.65 (m, 3H), 1.55–1.43 (m, 2H), 1.25–1.18
(m, 3H). [M+H]+: 431, HPLC: tR = 6.2 min.
4.2.8. (4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-
(cyclopentyl)methanone (19b). The procedure described
for the synthesis of 19a was applied to 7 and cyclopen-
tylcarboxylic acid providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.32 (d, J = 8.8 Hz, 4H),
7.26 (d, J = 8.8 Hz, 4H), 4.19 (s, 1H), 3.62 (t,
J = 4.8 Hz, 2H), 3.51 (t, J = 4.8 Hz, 2H), 2.88–2.78 (m,
1H), 2.33 (m, 4H), 1.87–1.64 (m, 6H), 1.60–1.49 (m,
2H). [M+H]+: 417.
1
lid. H NMR (400 MHz, CDCl3): d 7.31 (d, J = 8.7 Hz,
4H), 7.25 (d, J = 8.7 Hz, 4H), 4.22 (s, 1H), 4.20 (s, 1H),
3.62 (m, 1H), 3.32 (t, J = 5.2 Hz, 4H), 2.35 (t,
J = 4.8 Hz, 4H), 1.95–1.90 (m, 2H), 1.71–1.57 (m, 3H),
1.41–1.29 (m, 2H), 1.19–1.01 (m, 3H). [M+H]+: 446,
HPLC: tR = 5.4 min.
4.2.9. (4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-
(cyclobutyl)methanone (19c). The procedure described
for the synthesis of 19a was applied to 7 and cyclobutyl-
4.2.3. N-Benzyl-4-(bis(4-chlorophenyl)methyl)piperazine-
1-carboxamide (13b). The procedure described for the
synthesis of 13a was applied to 7 and benzylisocyanate
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.32–7.24 (m, 13H), 4.67 (t, J = 5.2 Hz, 1H),
4.41 (d, J = 5.5 Hz, 2H), 4.20 (s, 1H), 3.37 (t,
J = 5.2 Hz, 4H), 2.36 (t, J = 4.8 Hz, 4H). [M+H]+: 454.
1
carboxylic acid providing the title product. H NMR
(400 MHz, CDCl3): d 7.31 (d, J = 8.8 Hz, 4H), 7.26 (d,
J = 8.8 Hz, 4H), 4.18 (s, 1H), 3.61 (t, J = 4.8 Hz, 2H),
3.34 (t, J = 5.0 Hz, 2H), 3.26–3.14 (m, 1H), 2.38–2.25
(m, 6H), 2.15–2.04 (m, 2H), 2.00–1.78 (m, 2H).
[M+H]+: 403, HPLC: tR = 5.5 min.
4.2.4. 4-(Bis(4-chlorophenyl)methyl)-N-phenylpiperazine-
1-carboxamide (13c). The procedure described for the
synthesis of 13a was applied to 7 and phenylisocyanate
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.34–7.25 (m, 12H), 7.02 (t, J = 7.2 Hz, 1H),
6.30 (s, 1H), 4.23(s, 1H), 3.48 (t, J = 5.2 Hz, 4H), 2.41
(t, J = 4.8 Hz, 4H). [M+H]+: 440.
4.2.10. (4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-
(cyclopropyl)methanone (19d). The procedure described
for the synthesis of 19a was applied to 7 and cyclopro-
pylcarboxylic acid providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.32 (d, J = 8.6 Hz, 4H),
7.26 (d, J = 8.6 Hz, 4H), 4.21 (s, 1H), 3.65 (m, 4H),
2.37 (m, 4H), 1.72–1.65 (m, 1H), 0.99–0.90 (m, 2H),
0.76–0.70 (m, 2H). [M+H]+: 389.
4.2.5. 4-(Bis(4-chlorophenyl)methyl)-N-(4-chlorophenyl)-
piperazine-1-carboxamide (13d). The procedure de-
scribed for the synthesis of 13a was applied to 7 and
4-chlorophenylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.34–7.21 (m, 12H),
6.30 (s, 1H), 4.23(s, 1H), 3.48 (t, J = 5.2 Hz, 4H), 2.41
(t, J = 4.8 Hz, 4H). [M+H]+: 474.
4.2.11. 1-(4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-2-
ethylbutan-1-one (19e). The procedure described for the
synthesis of 19a was applied to 7 and 2-ethylbutanoic
1
acid providing the title product. H NMR (400 MHz,
CDCl3): d 7.32 (d, J = 8.6 Hz, 4H), 7.27 (d, J = 8.2 Hz,
4H), 4.18 (s, 1H), 3.67 (t, J = 5.0 Hz, 2H), 3.56 (t,
J = 4.8 Hz, 2H), 2.50–2.40 (m, 1H), 2.34 (m, 4H),
1.72–1.57 (m, 2H), 1.52–1.38 (m, 2H), 0.84 (t,
J = 7.5 Hz, 6H). [M+H]+: 419.
4.2.6. 4-(Bis(4-chlorophenyl)methyl)-N-tert-butylpiper-
azine-1-carboxamide (13e). The procedure described for
the synthesis of 13a was applied to 7 and tert-butylisocy-
1
anate providing the title product. H NMR (400 MHz,
CDCl3): d 7.31 (d, J = 8.7 Hz, 4H), 7.25 (d, J = 8.2 Hz,
4H), 4.24 (s, 1H), 4.19 (s, 1H), 3.30 (t, J = 4.8 Hz,
4H), 2.34 (t, J = 4.4 Hz, 4H), 1.33 (s, 9H). [M+H]+: 420.
4.2.12. 1-(4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)bu-
tan-1-one (19f). The procedure described for the synthesis
of 19a was applied to 7 and butanoic acid providing the
title product. H NMR (400 MHz, CDCl3): d 7.31 (d,
J = 8.4 Hz, 4H), 7.26 (d, J = 8.6 Hz, 4H), 4.20 (s, 1H),
3.61 (t, J = 4.6 Hz, 2H), 3.46 (t, J = 4.7 Hz, 2H), 2.33
1
4.2.7. (4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-
(cyclohexyl)methanone (19a). To a solution of the com-

4042
K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
(m, 4H), 2.26 (t, J = 7.3 Hz, 2H), 1.69–1.57 (m, 2H), 0.94
(t, J = 7.3 Hz, 3H). [M+H]+: 391.
4.2.19. Neopentyl 4-(bis(4-chlorophenyl)methyl)pipera-
zine-1-carboxylate (21c). The procedure described for
the synthesis of 21a was applied to 7 and neopentylchlo-
roformate providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.31 (d, J = 8.6 Hz, 4H), 7.26 (d,
J = 8.8 Hz, 4H), 4.20 (s, 1H), 3.76 (s, 2H), 3.49 (t,
J = 5.1 Hz, 4H), 2.34 (t, J = 5.1 Hz, 4H), 0.91 (s, 9H).
[M+H]+: 435.
4.2.13. 1-(4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-2-
methylpropan-1-one (19g). The procedure described for
the synthesis of 19a was applied to 7 and isobutanoic
1
acid providing the title product. H NMR (400 MHz,
CDCl3): d 7.31 (d, J = 8.4 Hz, 4H), 7.26 (d, J = 8.6 Hz,
4H), 4.20 (s, 1H), 3.62 (t, J = 4.4 Hz, 2H), 3.50 (t,
J = 4.5 Hz, 2H), 2.78–2.69 (m, 1H), 2.35 (m, 4H), 1.10
(d, J = 6.8 Hz, 6H). [M+H]+: 391.
4.2.20. tert-Butyl 4-(bis(4-chlorophenyl)methyl)pipera-
zine-1-carboxylate (21d). The procedure described for
the synthesis of 21a was applied to 7 and tert-butyl-
chloroformate providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.31 (d, J = 7.8 Hz, 4H), 7.25
(d, J = 6.9 Hz, 4H), 4.19 (s, 1H), 3.41 (t, J = 5.2 Hz,
4H), 2.31 (t, J = 4.4 Hz, 4H), 1.43 (s, 9H). [M+H]+:
421.
4.2.14. 1-(4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-
hexan-1-one (19h). The procedure described for the syn-
thesis of 19a was applied to 7 and hexanoic acid provid-
1
ing the title product. H NMR (400 MHz, CDCl3): d
7.31 (d, J = 8.4 Hz, 4H), 7.26 (d, J = 8.6 Hz, 4H), 4.20
(s, 1H), 3.61 (t, J = 4.8 Hz, 2H), 3.45 (t, J = 4.6 Hz,
2H), 2.33 (m, 4H), 2.27 (t, J = 7.3, 2H), 1.65–1.57 (m,
2H), 1.32–1.28 (m, 4H), 0.88 (t, J = 6.6 Hz, 3H).
[M+H]+: 419, HPLC: tR = 6.2 min.
4.2.21. Butyl 4-(bis(4-chlorophenyl)methyl)piperazine-1-
carboxylate (21e). The procedure described for the syn-
thesis of 21a was applied to 7 and butylchloroformate
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.31 (d, J = 8.6 Hz, 4H), 7.25 (d, J = 8.6 Hz,
4H), 4.20 (s, 1H), 4.06 (t, J = 6.6 Hz, 2H), 3.46 (t,
J = 5.0 Hz, 4H), 2.32 (t, J = 5.0 Hz, 4H), 1.63–1.54 (m,
2H), 1.42–1.25 (m, 2H), 0.91 (t, J = 7.3 Hz, 3H).
[M+H]+: 421.
4.2.15. (4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)(fur-
an-2-yl)methanone (19i). The procedure described for the
synthesis of 19a was applied to 7 and 2-furanoic acid
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.43 (m, 1H), 7.33 (d, J = 8.6 Hz, 4H), 7.27
(d, J = 8.6 Hz, 4H), 6.97 (d, J = 3.5 Hz, 1H), 6.45 (m,
1H), 4.23 (s, 1H), 3.80 (m, 4H), 2.42 (t, J = 5.0 Hz,
4H). [M+H]+: 415.
4.2.22. 1-(Bis(4-chlorophenyl)methyl)-4-(ethylsulfonyl)-
piperazine (22a). To a solution of 1-(bis(4-chloro-
phenyl)methyl)piperazine (257 mg, 0.8 mmol) and etha-
nesulfonyl chloride (103 mg, 0.8 mmol) in DCM
(5 mL) was added dropwise TEA (0.123 mL, 0.88 mmol)
at room temperature. The resulting mixture was subse-
quently stirred at room temperature overnight. 1 M
HCl (20 mL) was poured into the reaction mixture and
extracted with DCM (2· 20 mL). The combined DCM
was washed successively with water, dried over MgSO4
and evaporated under vacuum. The residue was further
purified by prep HPLC to yield the title compound
4.2.16. (4-(Bis(4-chlorophenyl)methyl)piperazin-1-yl)-
(thiophen-2-yl)methanone (19j). The procedure described
for the synthesis of 19a was applied to 7 and thiophene-
1
2-carboxylic acid providing the title product. H NMR
(400 MHz, CDCl3): d 7.42(d, J = 5.1 Hz, 1H), 7.32 (d,
J = 8.4 Hz, 4H), 7.27–7.24 (m, 5H), 7.01 (m, 1H), 4.23
(s, 1H), 3.75 (t, J = 4.8 Hz, 4H), 2.41 (t, J = 4.8 Hz,
4H). [M+H]+: 431.
1
4.2.17. Benzyl 4-(bis(4-chlorophenyl)methyl)piperazine-1-
carboxylate (21a). To a solution of the compound 7
(161 mg, 0.5 mmol) and TEA (0.077 mL, 0.55 mmol)
in DCM (4 mL) was added dropwise benzylchlorofor-
mate (94 mg, 0.55 mmol) in DCM (1 mL) at 0 ꢂC. The
resulting mixture was subsequently stirred at room tem-
perature overnight. 1 M HCl (20 mL) was poured into
the reaction mixture and extracted with DCM (2·
20 mL). The combined DCM was washed successively
with water, dried over MgSO4 and evaporated under
vacuum. The residue was further purified by prep HPLC
to yield the title compound (160 mg, 0.35 mmol, 70%) as
a light yellow solid. 1H NMR (400 MHz, CDCl3): d
7.35–7.24 (m, 13H), 5.11 (s, 2H), 4.20 (s, 1H), 3.50 (t,
J = 5.0 Hz, 4H), 2.33 (m, 4H). [M+H]+: 455.
(141 mg, 0.34 mmol, 43%) as a light yellow solid. H
NMR (400 MHz, CDCl3): d 7.30 (d, J = 8.4 Hz, 4H),
7.26 (d, J = 8.8 Hz, 4H), 4.25 (s, 1H), 3.30 (t,
J = 4.8 Hz, 4H), 2.95 (q, J = 7.5 Hz, 2H), 2.45 (t,
J = 4.8 Hz, 4H), 1.38 (t, J = 7.5 Hz, 3H). [M+H]+: 441.
4.2.23. 1-(Bis(4-chlorophenyl)methyl)-4-(isopropylsulfo-
nyl)piperazine (22b). The procedure described for the
synthesis of 22a was applied to 7 and isopropanesulfonyl
chloride providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.30 (d, J = 8.7 Hz, 4H), 7.26 (d,
J = 8.7 Hz, 4H), 4.24 (s, 1H), 3.36 (t, J = 4.8 Hz, 4H),
3.17 (m, 1H), 2.42 (t, J = 4.8 Hz, 4H), 1.34 (d,
J = 6.9 Hz, 6H). [M+H]+: 427.
4.2.24. 1-(Bis(4-chlorophenyl)methyl)-4-(butylsulfonyl)-
piperazine (22c). The procedure described for the synthe-
sis of 22a was applied to 7 and butanesulfonyl chloride
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.32–7.24 (m, 8H), 4.25 (s, 1H), 3.29 (m,
4H), 2.91 (t, J = 7.5 Hz, 2H), 2.45 (m, 4H), 1.85–1.75
(m, 2H), 1.51–1.39 (m, 2H), 0.95 (t, J = 7.2 Hz, 3H).
[M+H]+: 441.
4.2.18. Phenyl 4-(bis(4-chlorophenyl)methyl)piperazine-1-
carboxylate (21b). The procedure described for the syn-
thesis of 21a was applied to 7 and phenylchloroformate
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.37–7.26 (m, 10H), 7.20–7.16 (m, 1H),
7.10–7.06 (m, 2H), 4.26 (s, 1H), 3.62 (m, 4H), 2.42 (t,
J = 5.1 Hz, 4H). [M+H]+: 441.

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4043
4.2.25. 1-(Bis(4-chlorophenyl)methyl)-4-(octylsulfonyl)piper-
azine (22d). The procedure described for the synthesis of
22a was applied to 7 and octanesulfonyl chloride provid-
ing the title product. 1H NMR (400 MHz, CDCl3): d
7.30 (d, J = 8.8 Hz, 4H), 7.26 (d, J = 8.8 Hz, 4H), 4.24
(s, 1H), 3.28 (t, J = 4.4 Hz, 4H), 2.89 (t, J = 8.1 Hz, 2H),
2.45 (t, J = 4.4 Hz, 4H), 1.86–1.76 (m, 2H), 1.45–1.35
(m, 2H), 1.35–1.20 (m, 8H), 0.89 (t, J = 0.66 Hz, 3H).
[M+H]+: 497.
J = 5.0 Hz, 4H), 2.38–2.34 (m, 4H), 1.95–1.90 (m, 2H),
1.71–1.57 (m, 3H), 1.41–1.29 (m, 2H), 1.19–1.00 (m,
3H). [M+H]+: 480, HPLC: tR = 6.8 min.
4.2.32. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-cycloheptylpiperazine-1-carboxamide (14b). The pro-
cedure described for the synthesis of 13a was applied
to 12a and cycloheptylisocyanate providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.70 (d,
J = 8.4 Hz, 1H), 7.35–7.24 (m, 6H), 4.74 (s, 1H), 4.28
(d, J = 7.4 Hz, 1H), 3.88–3.78 (m, 1H), 3.31 (t,
J = 5.1 Hz, 4H), 2.41–2.32 (m, 4H), 1.94–1.85 (m, 2H),
1.61–1.36 (m, 10H). [M+H]+: 494, HPLC: tR = 7.0 min.
4.2.26. 1-(Bis(4-chlorophenyl)methyl)-4-tosylpiperazine
(22e). The procedure described for the synthesis of 22a
was applied to 7 and tosyl chloride providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.64 (d,
J = 8.7 Hz, 2H), 7.35 (d, J = 8.2 Hz, 2H), 7.22 (s, 8H),
4.19 (s, 1H), 3.00 (t, J = 4.0 Hz, 4H), 2.47 (s, 3H), 2.44
(t, J = 4.4 Hz, 4H). [M+H]+: 475.
4.2.33. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-(cyclohexylmethyl)piperazine-1-carboxamide
(14c).
The procedure described for the synthesis of 13a was ap-
plied to 12a and cyclohexanemethylisocyanate providing
1
4.2.27. 1-(Bis(4-chlorophenyl)methyl)-4-(4-chlorophenyl-
sulfonyl)piperazine (22f). The procedure described for
the synthesis of 22a was applied to 7 and 4-chloro-
the title product. H NMR (400 MHz, CDCl3): d 7.70
(d, J = 8.4 Hz, 1H), 7.35–7.24 (m, 6H), 4.74 (s, 1H),
4.43 (m, 1H), 3.34 (t, J = 5.0 Hz, 4H), 3.06 (t,
J = 6.6 Hz, 2H), 2.39–2.32 (m, 4H), 1.72–1.60 (m, 5H),
1.46–1.38 (m, 1H), 1.28–1.10 (m, 3H), 0.94–0.83 (m,
2H). [M+H]+: 494, HPLC: tR = 7.1 min.
1
phenylsulfonyl chloride providing the title product. H
NMR (400 MHz, CDCl3): d 7.69 (d, J = 8.8 Hz, 2H),
7.54 (d, J = 8.8 Hz, 2H), 7.23 (s, 8H), 4.20 (s, 1H),
3.01 (t, J = 4.0 Hz, 4H), 2.44 (t, J = 4.4 Hz, 4H).
[M+H]+: 495.
4.2.34. N-tert-Butyl-4-((4-chlorophenyl)(2,4-dichlorophenyl)-
methyl)piperazine-1-carboxamide (14d). The procedure
described for the synthesis of 13a was applied to 12a
and tert-butylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.70 (d, J = 8.4 Hz,
1H), 7.36–7.24 (m, 6H), 4.73 (s, 1H), 4.26 (s, 1H), 3.29
(t, J = 5.1 Hz, 4H), 2.42–2.30 (m, 4H), 1.33 (s, 9H).
[M+H]+: 454, HPLC: tR = 6.4 min.
4.2.28. 1-(Bis(4-chlorophenyl)methyl)-4-(thiophen-2-yls-
ulfonyl)piperazine (22g). The procedure described for
the synthesis of 22a was applied to 7 and thiophen-2-yls-
1
ulfonyl chloride providing the title product. H NMR
(400 MHz, CDCl3): d 7.66 (d, J = 5.2 Hz, 1H), 7.54 (d,
J = 4.0 Hz, 1H), 7.24 (s, 8H), 7.18 (t, J = 4.0 Hz, 1H),
4.21 (s, 1H), 3.08 (t, J = 4.8 Hz, 4H), 2.47 (t,
J = 4.8 Hz, 4H). [M+H]+: 467.
4.2.35. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-isopropylpiperazine-1-carboxamide (14e). The proce-
dure described for the synthesis of 13a was applied
to 12a and isopropylisocyanate providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.70 (d,
J = 8.4 Hz, 1H), 7.35–7.24 (m, 6H), 4.74 (s, 1H),
4.15 (d, J = 7.1 Hz, 1H), 4.01–3.90 (m, 1H), 3.32 (t,
J = 5.0 Hz, 4H), 2.41–2.31 (m, 4H), 1.14 (d,
J = 6.4 Hz, 6H). [M+H]+: 440.
4.2.29. (4-Chlorophenyl)(2,4-dichlorophenyl)methanol (10a).
To the solution of 2,4-dichlorobenzaldehyde (17.5 g,
0.10 mol) in THF (400 mL) was added dropwise 4-chlor-
ophenylmagnesium bromide (110 mL, 1.0 M solution in
THF) at room temperature. After additional stirring for
5 h, NH4Cl aqueous solution (1 M, 300 mL) and diethyl
ether (300 mL) were added to the reaction mixture. The or-
ganic phase was removed under vacuum. The crude resi-
due was dissolved in hexane/EtOAc (1:1, 500 mL),
washed successively with brine (200 mL), dried over
MgSO4 and evaporated under vacuum. The further purifi-
cation by flash chromatography (silica gel 60) afforded the
title compound (11.2 g, 0.039 mol, 39%). [MꢀH2O+H]+:
266.
4.2.36. N-Butyl-4-((4-chlorophenyl)(2,4-dichlorophenyl)-
methyl)piperazine-1-carboxamide (14f). The procedure
described for the synthesis of 13a was applied to 12a
and butylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.70 (d, J = 8.4 Hz, 1H),
7.35–7.24 (m, 6H), 4.74 (s, 1H), 4.34 (t, J = 5.1 Hz,
1H), 3.33 (t, J = 5.0 Hz, 4H), 3.21 (q, J = 6.5 Hz, 2H),
2.42–2.31 (m, 4H), 1.52–1.43 (m, 2H), 1.39–1.27 (m,
2H), 0.91 (t, J = 7.1 Hz, 3H). [M+H]+: 454.
4.2.30. 1-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazine (12a). The procedure described for the syn-
thesis of 7 was applied to 10a instead of 5 providing
the title product. [M+H]+: 355.
4.2.37. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-hexylpiperazine-1-carboxamide (14g). The procedure
described for the synthesis of 13a was applied to 12a
and hexylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.70 (d, J = 8.4 Hz, 1H),
7.35–7.24 (m, 6H), 4.74 (s, 1H), 4.36 (m, 1H), 3.33 (t,
J = 5.0 Hz, 4H), 3.24–3.17 (m, 2H), 2.41–2.34 (m, 4H),
1.55–1.40 (m, 2H), 1.39–1.20 (m, 6H), 0.88 (t,
J = 6.6 Hz, 3H). [M+H]+: 482.
4.2.31. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-cyclohexylpiperazine-1-carboxamide (14a). The proce-
dure described for the synthesis of 13a was applied to
12a and cyclohexylisocyanate providing the title prod-
uct. 1H NMR (400 MHz, CDCl3):
d
7.70 (d,
J = 8.4 Hz, 1H), 7.35–7.24 (m, 6H), 4.74 (s, 1H),
4.21(d, J = 7.7 Hz, 1H), 3.67–3.58 (m, 1H), 3.32 (t,

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K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4.2.38. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-octylpiperazine-1-carboxamide (14h). The procedure
described for the synthesis of 13a was applied to 12a
and octylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.70 (d, J = 8.4 Hz, 1H),
7.35–7.24 (m, 6H), 4.74 (s, 1H), 4.36 (t, J = 5.3 Hz,
1H), 3.33 (t, J = 5.1 Hz, 4H), 3.20 (q, J = 5.7 Hz, 2H),
2.39–2.32 (m, 4H), 1.48 (m, 2H), 1.39–1.20 (m, 10H),
0.88 (t, J = 6.4 Hz, 3H). [M+H]+: 510.
J = 8.4 Hz, 1H), 7.36–7.24 (m, 6H), 4.74 (s, 1H), 3.65–
3.50 (m, 2H), 3.54–3.47 (m, 2H), 2.89–2.78 (m, 1H),
2.49–2.30 (m, 4H), 1.83–1.65 (m, 6H), 1.60–1.50 (m,
2H). [M+H]+: 451.
4.2.45. (4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)(cyclobutyl)methanone (20c). The proce-
dure described for the synthesis of 19a was applied to
12a and cyclobutanecarboxylic acid providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.70 (d,
J = 8.4 Hz, 1H), 7.35–7.24 (m, 6H), 4.73 (s, 1H), 3.59
(q, J = 5.1 Hz, 2H), 3.34–3.31 (m, 2H), 3.26–3.15 (m,
1H), 2.41–2.27 (m, 6H), 2.16–2.05 (m, 2H), 2.00–1.79
(m, 2H). [M+H]+: 437.
4.2.39.
N-Adamantyl-4-((4-chlorophenyl)(2,4-dichloro-
phenyl)methyl)piperazine-1-carboxamide (14i). The pro-
cedure described for the synthesis of 13a was applied
to 12a and adamantylisocyanate providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.70 (d,
J = 8.4 Hz, 1H), 7.35–7.24 (m, 6H), 4.73 (s, 1H), 4.14
(s, 1H), 3.29 (t, J = 5.0 Hz, 4H), 2.40–2.31 (m, 4H),
2.06 (m, 3H), 1.97–1.95 (m, 6H), 1.66 (m, 6H).
[M+H]+: 532.
4.2.46. (4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)(cyclopropyl)methanone (20d). The proce-
dure described for the synthesis of 19a was applied to
12a and cyclopropanecarboxylic acid providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.72 (d,
J = 8.4 Hz, 1H), 7.37–7.24 (m, 6H), 4.76 (s, 1H),
3.66–3.59 (m, 4H), 2.43–2.32 (m, 4H), 1.72–1.64 (m,
1H), 1.00–0.90 (m, 2H), 0.82–0.70 (m, 2H). [M+H]+:
423.
4.2.40. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-phenylpiperazine-1-carboxamide (14j). The procedure
described for the synthesis of 13a was applied to 12a
and phenylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.71 (d, J = 8.6 Hz, 1H),
7.37–7.24 (m, 10H), 7.06–6.99 (m, 1H), 6.31 (s, 1H),
4.77 (s, 1H), 3.47 (t, J = 4.9 Hz, 4H), 2.48–2.36 (m,
4H). [M+H]+: 474.
4.2.47. 1-(4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)-2-cyclopentylethanone (20e). The proce-
dure described for the synthesis of 19a was applied to
12a and cyclopentylacetic acid providing the title prod-
4.2.41. N-Benzyl-4-((4-chlorophenyl)(2,4-dichlorophenyl)-
methyl)piperazine-1-carboxamide (14k). The procedure
described for the synthesis of 13a was applied to 12a
and benzylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.69 (d, J = 8.4 Hz, 1H),
7.35–7.24 (m, 11H), 4.74 (s, 1H), 4.68 (t, J = 5.3 Hz,
1H), 4.42 (d, J = 5.3 Hz, 2H), 3.36 (t, J = 5.0 Hz, 4H),
2.39–2.34 (m, 4H). [M+H]+: 488.
uct. 1H NMR (400 MHz, CDCl3):
d
7.71 (d,
J = 8.4 Hz, 1H), 7.36–7.24 (m, 6H), 4.74 (s, 1H), 3.63–
3.57 (m, 2H), 3.50–3.43 (m, 2H), 2.41–2.30 (m, 6H),
2.28–2.15 (m, 1H), 1.87–1.77 (m, 2H), 1.64–1.49 (m,
6H), 1.20–1.06 (m, 2H). [M+H]+: 465.
4.2.48. 1-(4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)-2-cyclopropylethanone (20f). The proce-
dure described for the synthesis of 19a was applied to
12a and cyclopropylacetic acid providing the title prod-
uct. 1H NMR (400 MHz, CDCl3): d 7.70 (d, J = 8.4 Hz,
1H), 7.37–7.24 (m, 6H), 4.74 (s, 1H), 3.65–3.59 (m, 2H),
3.47–3.42 (m, 2H), 2.42–2.25 (m, 4H), 2.24 (d,
J = 6.8 Hz, 2H), 1.25–0.94 (m, 1H), 0.59–0.47 (m, 2H),
0.23–0.12 (m, 2H). [M+H]+: 437.
4.2.42. 4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
N-(furan-2-yl)piperazine-1-carboxamide (14l). The proce-
dure described for the synthesis of 13a was applied
to 12a and 2-furanylisocyanate providing the title prod-
uct. 1H NMR (400 MHz, CDCl3): d 7.69 (d, J = 8.4 Hz,
1H), 7.35–7.24 (m, 7H), 6.32–6.30 (m, 1H), 6.21 (d,
J = 3.1 Hz, 1H), 4.74 (s, 1H), 4.70 (t, J = 5.5 Hz, 1H),
4.40 (d, J = 5.3 Hz, 2H), 3.35 (t, J = 4.9 Hz, 4H), 2.41–
2.31 (m, 4H). [M+H]+: 464.
4.2.49. 1-(4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)-2-methylpropan-1-one (20g). The proce-
dure described for the synthesis of 19a was applied to
12a and isobutanoic acid providing the title product.
1H NMR (400 MHz, CDCl3): d 7.71 (d, J = 8.4 Hz,
1H), 7.37–7.24 (m, 6H), 4.74 (s, 1H), 3.65–3.57 (m,
2H), 3.53–3.47 (m, 2H), 2.78–2.69 (m, 1H), 2.41–2.32
(m, 4H), 1.10 (t, J = 6.8 Hz, 6H). [M+H]+: 425.
4.2.43. (4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)(cyclohexyl)methanone (20a). The proce-
dure described for the synthesis of 19a was applied to
12a and cyclohexanecarboxylic acid providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.71 (d,
J = 8.4 Hz, 1H), 7.36–7.24 (m, 6H), 4.74 (s, 1H), 3.65–
3.55 (m, 2H), 3.53–3.44 (m, 2H), 2.44–2.30 (m, 5H),
1.82–1.65 (m, 5H), 1.59–1.43 (m, 2H), 1.28–1.16 (m,
3H). [M+H]+: 465.
4.2.50. 1-(4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)-2-ethylbutan-1-one (20h). The procedure
described for the synthesis of 19a was applied to 12a
and 2-ethylbutanoic acid providing the title product.
1H NMR (400 MHz, CDCl3): d 7.72 (d, J = 8.4 Hz,
1H), 7.36–7.24 (m, 6H), 4.73 (s, 1H), 3.70–3.62 (m,
2H), 3.59–3.51 (m, 2H), 2.50–2.29 (m, 5H), 1.72–1.57
(m, 2H), 1.52–1.38 (m, 2H), 0.85 (t, J = 7.3 Hz, 6H).
[M+H]+: 453.
4.2.44. (4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)(cyclopentyl)methanone (20b). The proce-
dure described for the synthesis of 19a was applied to
12a and cyclopentanecarboxylic acid providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.71 (d,

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4045
4.2.51. 1-(4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)butan-1-one (20i). The procedure de-
scribed for the synthesis of 19a was applied to 12a and
butanoic acid providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.70 (d, J = 8.6 Hz, 1H), 7.36–
7.25 (m, 6H), 4.74 (s, 1H), 3.64–3.56 (m, 2H), 3.48–
3.42 (m, 2H), 2.39–2.31 (m, 4H), 2.27 (t, J = 7.3 Hz,
2H), 1.70–1.57 (m, 2H), 0.95 (t, J = 7.3 Hz, 3H).
[M+H]+: 425.
cedure described for the synthesis of 13a was applied to
12b and cycloheptylisocyanate providing the title prod-
uct. 1H NMR (400 MHz, CDCl3): d 7.73 (d, J = 7.9 Hz,
1H), 7.37–7.32 (m, 3H), 7.27–7.20 (m, 3H), 4.81 (s, 1H),
4.30 (d, J = 7.1 Hz, 1H), 3.86–3.78 (m, 1H), 3.32 (t,
J = 5.1 Hz, 4H), 2.43–2.30 (m, 4H), 1.96–1.86 (m, 2H),
1.64–1.33 (m, 10H). [M+H]+: 494, HPLC: tR = 6.9 min.
4.2.59. 4-((4-Chlorophenyl)(2,3-dichlorophenyl)methyl)-
N-(cyclohexylmethyl)piperazine-1-carboxamide
(15c).
The procedure described for the synthesis of 13a was ap-
plied to 12b and cyclohexylmethylisocyanate providing
4.2.52. 1-(4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)hexan-1-one (20j). The procedure de-
scribed for the synthesis of 19a was applied to 12a and
hexanoic acid providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.70 (d, J = 8.4 Hz, 1H), 7.36–
7.24 (m, 6H), 4.74 (s, 1H), 3.65–3.54 (m, 2H), 3.46–
3.42 (m, 2H), 2.42–2.31 (m, 4H), 2.28 (t, J = 7.5 Hz,
2H), 1.65–1.55 (m, 2H), 1.36–1.25 (m, 4H), 0.89 (t,
J = 6.8 Hz, 3H). [M+H]+: 453, HPLC: tR = 7.6 min.
1
the title product. H NMR (400 MHz, CDCl3): d 7.73
(d, J = 7.9 Hz, 1H), 7.37–7.32 (m, 3H), 7.27–7.20 (m,
3H), 4.81 (s, 1H), 4.46 (t, J = 5.9 Hz, 1H), 3.34 (t,
J = 5.0 Hz, 4H), 3.06 (t, J = 6.0 Hz, 2H), 2.44–2.30 (m,
4H), 1.75–1.63 (m, 5H), 1.51–1.37 (m, 1H), 1.28–1.11
(m, 3H), 0.95–0.83 (m, 2H). [M+H]+: 494, HPLC:
tR = 7.0 min.
4.2.53. (4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)(furan-2-yl)methanone (20k). The proce-
dure described for the synthesis of 19a was applied to
12a and 2-furanylcarboxylic acid providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.73 (d,
J = 8.4 Hz, 1H), 7.44–7.43 (m, 1H), 7.38–7.24 (m, 6H),
6.98 (d, J = 7.3 Hz, 1H), 6.46 (q, J = 1.7 Hz, 1H), 4.78
(s, 1H), 3.85–3.74 (m, 4H), 2.49–2.38 (m, 4H).
[M+H]+: 449.
4.2.60. N-tert-Butyl-4-((4-chlorophenyl)(2,3-dichlorophenyl)-
methyl)piperazine-1-carboxamide (15d). The procedure
described for the synthesis of 13a was applied to 12b
and tert-butylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.73 (d, J = 7.9 Hz,
1H), 7.38–7.32 (m, 3H), 7.27–7.20 (m, 3H), 4.81 (s,
1H), 4.26 (s, 1H), 3.30 (t, J = 5.1 Hz, 4H), 2.43–2.30
(m, 4H), 1.33 (s, 9H). [M+H]+: 454, HPLC:
tR = 6.3 min.
4.2.54. (4-((4-Chlorophenyl)(2,4-dichlorophenyl)methyl)-
piperazin-1-yl)(thiophen-2-yl)methanone (20l). The pro-
cedure described for the synthesis of 19a was applied
to 12a and thiophene-2-carboxylic acid providing the ti-
tle product. 1H NMR (400 MHz, CDCl3): d 7.72 (d,
J = 8.4 Hz, 1H), 7.43–7.41 (m, 1H), 7.37–7.24 (m, 7H),
7.03–6.99 (m, 1H), 4.78 (s, 1H), 3.74 (t, J = 4.9 Hz,
4H), 2.45–2.38 (m, 4H). [M+H]+: 465.
4.2.61. 4-((4-Chlorophenyl)(2,3-dichlorophenyl)methyl)-
N-isopropylpiperazine-1-carboxamide (15e). The proce-
dure described for the synthesis of 13a was applied
to 12b and isopropylisocyanate providing the title prod-
uct. 1H NMR (400 MHz, CDCl3): d 7.73 (d, J = 7.7 Hz,
1H), 7.38–7.32 (m, 3H), 7.27–7.21 (m, 3H), 4.81 (s, 1H),
4.16 (d, J = 7.1 Hz, 1H), 4.01–3.90 (m, 1H), 3.32 (t,
J = 5.1 Hz, 4H), 2.44–2.30 (m, 4H), 1.14 (d,
J = 6.4 Hz, 6H). [M+H]+: 440.
4.2.55.
(4-Chlorophenyl)(2,3-dichlorophenyl)methanol
(10b). The procedure described for the synthesis of 10a
was applied to 2,3-dichlorobenzaldehyde instead of
2,4-dichlorobenzaldehyde providing the title product.
[MꢀH2O+H]+: 269.
4.2.62. N-Butyl-4-((4-chlorophenyl)(2,3-dichlorophenyl)-
methyl)piperazine-1-carboxamide (15f). The procedure
described for the synthesis of 13a was applied to 12b
and butylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.73 (d, J = 7.7 Hz, 1H),
7.38–7.32 (m, 3H), 7.27–7.21 (m, 3H), 4.81 (s, 1H), 4.38
(t, J = 5.1 Hz, 1H), 3.33 (t, J = 5.0 Hz, 4H), 3.21 (q,
J = 7.0 Hz, 2H), 2.44–2.30 (m, 4H), 1.52–1.43 (m, 2H),
1.39–1.27 (m, 2H), 0.91 (t, J = 7.1 Hz, 3H). [M+H]+: 454.
4.2.56. 1-((4-Chlorophenyl)(2,3-dichlorophenyl)methyl)-
piperazine (12b). The procedure described for the syn-
thesis of 7 was applied to 10b instead of 5 providing
the title product. [M+H]+: 355.
4.2.57. 4-((4-Chlorophenyl)(2,3-dichlorophenyl)methyl)-
N-cyclohexylpiperazine-1-carboxamide (15a). The proce-
dure described for the synthesis of 13a was applied to
12b and cyclohexylisocyanate providing the title prod-
4.2.63. (2-Chlorophenyl)(4-chlorophenyl)methanol (10c).
The procedure described for the synthesis of 10a was ap-
plied to 2-chlorobenzaldehyde instead of 2,4-dichloro-
benzaldehyde
providing
the
title
product.
uct. 1H NMR (400 MHz, CDCl3):
d
7.73 (d,
[MꢀH2O+H]+: 235.
J = 7.8 Hz, 1H), 7.37–7.32 (m, 3H), 7.27–7.20 (m, 3H),
4.81 (s, 1H), 4.22 (d, J = 7.5 Hz, 1H), 3.71–3.58 (m,
1H), 3.32 (t, J = 5.0 Hz, 4H), 2.44–2.30 (m, 4H), 1.98–
1.87 (m, 2H), 1.75–1.52 (m, 3H), 1.45–1.24 (m, 2H),
1.20–1.00 (m, 3H). [M+H]+: 480, HPLC: tR = 6.6 min.
4.2.64. 1-((2-Chlorophenyl)(4-chlorophenyl)methyl)piper-
azine (12c). The procedure described for the synthesis of
7 was applied to 10c instead of 5 providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.71 (d,
J = 8.0 Hz, 1H), 7.37 (d, J = 8.8 Hz, 2H), 7.29–7.21
(m, 4H), 7.12 (t, J = 7.2 Hz, 1H), 4.82 (s, 1H), 2.98 (t,
J = 5.2 Hz, 4H), 2.51–2.42 (m, 4H). [M+H]+: 321.
4.2.58. 4-((4-Chlorophenyl)(2,3-dichlorophenyl)methyl)-
N-cycloheptylpiperazine-1-carboxamide (15b). The pro-

4046
K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4.2.65.
4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-N-
3.22 (q, J = 6.9 Hz, 2H), 2.43–2.32 (m, 4H), 1.51–1.43
(m, 2H), 1.38–1.28 (m, 2H), 0.91 (t, J = 7.3 Hz, 3H).
[M+H]+: 420.
cyclohexylpiperazine-1-carboxamide (16a). The proce-
dure described for the synthesis of 13a was applied to
12c and cyclohexylisocyanate providing the title prod-
uct. 1H NMR (400 MHz, CDCl3):
d
7.74 (d,
4.2.71.
4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-N-
J = 7.8 Hz, 1H), 7.38 (d, J = 8.7 Hz, 2H), 7.31–7.23
(m, 4H), 7.13 (t, J = 7.8 Hz, 1H), 4.80 (s, 1H), 4.22 (d,
J = 7.8 Hz, 1H), 3.68–3.58 (m, 1H), 3.32 (t, J = 5.5 Hz,
4H), 2.43–2.32 (m, 4H), 1.97–1.89 (m, 2H), 1.72–1.56
(m, 3H), 1.43–1.29 (m, 2H), 1.19–1.01 (m, 3H).
[M+H]+: 446, HPLC: tR = 5.7 min.
hexylpiperazine-1-carboxamide (16g). The procedure de-
scribed for the synthesis of 13a was applied to 12c and
hexylisocyanate providing the title product. H NMR
(400 MHz, CDCl3): d 7.74 (d, J = 7.8 Hz, 1H), 7.38 (d,
J = 8.7 Hz, 2H), 7.31–7.23 (m, 4H), 7.14 (t, J = 7.8 Hz,
1H), 4.80 (s, 1H), 4.37 (t, J = 5.0 Hz, 1H), 3.33 (t,
J = 5.0 Hz, 4H), 3.21 (q, J = 6.4 Hz, 2H), 2.43–2.32
(m, 4H), 1.51–1.44 (m, 2H), 1.34–1.25 (m, 6H), 0.88 (t,
J = 7.4 Hz, 3H). [M+H]+: 448.
1
4.2.66.
4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-N-
cycloheptylpiperazine-1-carboxamide (16b). The proce-
dure described for the synthesis of 13a was applied to
12c and cycloheptylisocyanate providing the title prod-
4.2.72. (4-Chlorophenyl)(o-tolyl)methanol (10d). The pro-
cedure described for the synthesis of 10a was applied to
o-tolualdehyde instead of 2,4-dichlorobenzaldehyde
providing the title product. [MꢀH2O+H]+: 215.
uct. 1H NMR (400 MHz, CDCl3):
d 7.74 (d,
J = 8.2 Hz, 1H), 7.38 (d, J = 8.2 Hz, 2H), 7.31–7.23
(m, 4H), 7.14 (t, J = 7.8 Hz, 1H), 4.80 (s, 1H), 4.29 (d,
J = 7.3 Hz, 1H), 3.87–3.78 (m, 1H), 3.32 (t, J = 5.0 Hz,
4H), 2.43–2.32 (m, 4H), 1.96–1.88 (m, 2H), 1.64–1.33
(m, 10H). [M+H]+: 460, HPLC: tR = 6.0 min.
4.2.73. 1-((4-Chlorophenyl)(o-tolyl)methyl)piperazine (12d).
The procedure described for the synthesis of 7 was applied
to 10d instead of 5 providing the title product. H NMR
1
4.2.67.
4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-N-
(400 MHz, CDCl3): d 7.68 (d, J = 7.6 Hz, 1H), 7.30 (d,
J = 9.2 Hz, 2H), 7.24–7.16 (m, 3H), 7.12–7.03 (m, 2H),
4.46 (s, 1H), 3.05–2.99 (m, 2H), 2.57–2.54 (m, 2H),
2.47–2.40 (m, 4H), 2.29 (s, 3H). [M+H]+: 301.
(cyclohexylmethyl)piperazine-1-carboxamide (16c). The
procedure described for the synthesis of 13a was applied
to 12c and cyclohexylmethylisocyanate providing the ti-
tle product. 1H NMR (400 MHz, CDCl3): d 7.74 (d,
J = 7.8 Hz, 1H), 7.39 (d, J = 8.7 Hz, 2H), 7.31–7.23
(m, 4H), 7.14 (t, J = 7.4 Hz, 1H), 4.81 (s, 1H), 4.46 (t,
J = 5.5 Hz, 1H), 3.34 (t, J = 5.0 Hz, 4H), 3.06 (t,
J = 6.0 Hz, 2H), 2.44–2.33 (m, 4H), 1.74–1.65 (m, 5H),
1.49–1.38 (m, 1H), 1.27–1.11 (m, 3H), 0.95–0.83 (m,
2H). [M+H]+: 460, HPLC: tR = 6.1 min.
4.2.74. 4-((4-Chlorophenyl)(o-tolyl)methyl)-N-cyclohexyl-
piperazine-1-carboxamide (17a). The procedure described
for the synthesis of 13a was applied to 12d and cyclohexy-
lisocyanate providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.71 (d, J = 7.3 Hz, 1H), 7.31 (d,
J = 8.7 Hz, 2H), 7.26–7.20 (m, 3H), 7.13–7.05 (m, 2H),
4.41 (s, 1H), 4.20 (d, J = 7.3 Hz, 1H), 3.68–3.58 (m,
1H), 3.36–3.28 (m, 4H), 2.47–2.38 (m, 2H), 2.31–2.25
(m, 5H), 1.97–1.90 (m, 2H), 1.73–1.56 (m, 3H), 1.42–
1.30 (m, 2H), 1.19–1.01 (m, 3H). [M+H]+: 426, HPLC:
tR = 4.3 min.
4.2.68. N-tert-Butyl-4-((2-chlorophenyl)(4-chlorophenyl)-
methyl)piperazine-1-carboxamide (16d). The procedure
described for the synthesis of 13a was applied to 12c
and tert-butylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.74 (d, J = 7.8 Hz,
1H), 7.38 (d, J = 8.2 Hz, 2H), 7.31–7.23 (m, 4H), 7.13
(t, J = 7.8 Hz, 1H), 4.80 (s, 1H), 4.25 (s, 1H), 3.29 (t,
J = 5.5 Hz, 4H), 2.43–2.32 (m, 4H), 1.33 (s, 9H).
[M+H]+: 420, HPLC: tR = 5.2 min.
4.2.75. 4-((4-Chlorophenyl)(o-tolyl)methyl)-N-cyclohep-
tylpiperazine-1-carboxamide (17b). The procedure de-
scribed for the synthesis of 13a was applied to 12d
and cycloheptylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.71 (d, J = 7.8 Hz,
1H), 7.31 (d, J = 8.2 Hz, 2H), 7.26–7.20 (m, 3H),
7.14–7.05 (m, 2H), 4.41 (s, 1H), 4.28 (d, J = 7.8 Hz,
1H), 3.87–3.78 (m, 1H), 3.35–3.28 (m, 4H), 2.45–2.38
(m, 2H), 2.31–2.24 (m, 5H), 1.96–1.88 (m, 2H),
1.64–1.33 (m, 10H). [M+H]+: 440, HPLC:
tR = 5.1 min.
4.2.69.
4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-N-
isopropylpiperazine-1-carboxamide (16e). The procedure
described for the synthesis of 13a was applied to 12c
and isopropylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.74 (d, J = 8.0 Hz,
1H), 7.38 (d, J = 8.2 Hz, 2H), 7.31–7.23 (m, 4H), 7.14
(t, J = 7.8 Hz, 1H), 4.80 (s, 1H), 4.16 (d, J = 7.3 Hz,
1H), 4.0–3.91 (m, 1H), 3.32 (t, J = 5.5 Hz, 4H),
2.43–2.32 (m, 4H), 1.14 (d, J = 6.4 Hz, 6H). [M+H]+:
406.
4.2.76. 4-((4-Chlorophenyl)(o-tolyl)methyl)-N-(cyclohexylm-
ethyl)piperazine-1-carboxamide (17c). The procedure
described for the synthesis of 13a was applied to 12d and
cyclohexylmethylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.71 (d, J = 7.8 Hz,
1H), 7.32 (d, J = 8.7 Hz, 2H), 7.26–7.18 (m, 3H), 7.13–
7.04 (m, 2H), 4.45–4.40 (m, 2H), 3.38–3.29 (m, 4H), 3.06
(t, J = 6.4 Hz, 2H), 2.47–2.38 (m, 2H), 2.33–2.26 (m,
5H), 1.74–1.62 (m, 5H), 1.49–1.38 (m, 1H), 1.27–1.11 (m,
3H), 0.95–0.83 (m, 2H). [M+H]+: 440, HPLC:
tR = 5.2 min.
4.2.70. N-Butyl-4-((2-chlorophenyl)(4-chlorophenyl)methyl)-
piperazine-1-carboxamide (16f). The procedure described
for the synthesis of 13a was applied to 12c and butylisocy-
1
anate providing the title product. H NMR (400 MHz,
CDCl3): d 7.74 (d, J = 8.4 Hz, 1H), 7.39 (d, J = 8.2 Hz,
2H), 7.31–7.24 (m, 4H), 7.14 (t, J = 7.8 Hz, 1H), 4.80 (s,
1H), 4.38 (t, J = 5.0 Hz, 1H), 3.33 (t, J = 5.0 Hz, 4H),

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4047
4.2.77. N-tert-Butyl-4-((4-chlorophenyl)(o-tolyl)methyl)piper-
azine-1-carboxamide (17d). The procedure described for
the synthesis of 13a was applied to 12d and tert-butylis-
ocyanate providing the title product. 1H NMR
(400 MHz, CDCl3): d 7.71 (d, J = 7.8 Hz, 1H), 7.31 (d,
J = 8.7 Hz, 2H), 7.26–7.20 (m, 3H), 7.13–7.05 (m, 2H),
4.41 (s, 1H), 4.24 (s, 1H), 3.32–3.27 (m, 4H), 2.46–2.38
(m, 2H), 2.31–2.25 (m,5H), 1.33 (s, 9H). [M+H]+: 400,
HPLC: tR = 3.0 min.
J = 8.0 Hz, 1H), 7.60 (d, J = 8.0 Hz, 1H), 7.54 (t,
J = 7.6 Hz, 1H), 7.44 (d, J = 8.4 Hz, 2H), 7.34–7.22
(m, 3H), 4.67 (s, 1H), 4.22 (d, J = 7.6 Hz, 1H), 3.65–
3.54 (m, 1H), 3.36–3.27 (m, 4H), 2.45–2.35 (m, 2H),
2.33–2.24 (m, 2H), 1.97–1.88 (m, 2H), 1.73–1.55 (m,
3H), 1.42–1.29 (m, 2H), 1.19–1.01 (m, 3H). [M+H]+:
480, HPLC: tR = 6.4 min.
4.2.84. 4-((4-Chlorophenyl)(2-(trifluoromethyl)phenyl)-
methyl)-N-cycloheptylpiperazine-1-carboxamide (18b).
The procedure described for the synthesis of 13a was ap-
plied to 12e and cycloheptylisocyanate providing the ti-
tle product. 1H NMR (400 MHz, CDCl3): d 7.98 (d,
J = 8.0 Hz, 1H), 7.60 (d, J = 7.6 Hz, 1H), 7.55 (t,
J = 8.0 Hz, 1H), 7.43 (d, J = 8.4 Hz, 2H), 7.34–7.23
(m, 3H), 4.67 (s, 1H), 4.29 (d, J = 7.6 Hz, 1H), 3.87–
3.76 (m, 1H), 3.35–3.25 (m, 4H), 2.45–2.37 (m, 2H),
2.33–2.23 (m, 2H), 1.95–1.85 (m, 2H), 1.66–1.33 (m,
10H). [M+H]+: 494, HPLC: tR = 6.7 min.
4.2.78. 4-((4-Chlorophenyl)(o-tolyl)methyl)-N-isopropyl-
piperazine-1-carboxamide (17e). The procedure de-
scribed for the synthesis of 13a was applied to 12d and
isopropylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.71 (d, J = 8.0 Hz, 1H),
7.31 (d, J = 8.2 Hz, 2H), 7.27–7.20 (m, 3H), 7.14–7.06
(m, 2H), 4.41 (s, 1H), 4.14 (d, J = 7.3 Hz, 1H), 4.01–
3.91 (m, 1H), 3.35–3.26 (m, 4H), 2.46–2.37 (m, 2H),
2.31–2.25 (m, 5H), 1.14 (d, J = 6.4 Hz, 6H). [M+H]+:
386.
4.2.85. 4-((4-Chlorophenyl)(2-(trifluoromethyl)phenyl)-
methyl)-N-(cyclohexylmethyl)piperazine-1-carboxamide
(18c). The procedure described for the synthesis of 13a
was applied to 12e and cyclohexylmethylisocyanate pro-
viding the title product. 1H NMR (400 MHz, CDCl3): d
7.98 (d, J = 8.4 Hz, 1H), 7.60 (d, J = 8.0 Hz, 1H), 7.55 (t,
J = 7.6 Hz, 1H), 7.43 (d, J = 8.4 Hz, 2H), 7.34–7.23 (m,
3H), 4.67 (s, 1H), 4.45 (t, J = 5.2 Hz, 1H), 3.31 (t,
J = 5.2 Hz, 4H), 3.05 (t, J = 6.4 Hz, 2H), 2.44–2.37 (m,
2H), 2.32–2.25 (m, 2H), 1.74–1.61 (m, 5H), 1.49–1.37
(m, 1H), 1.27–1.10 (m, 3H), 0.95–0.82 (m, 2H).
[M+H]+: 494, HPLC: tR = 6.8 min.
4.2.79. N-Butyl-4-((4-chlorophenyl)(o-tolyl)methyl)piper-
azine-1-carboxamide (17f). The procedure described for
the synthesis of 13a was applied to 12d and butylisocy-
1
anate providing the title product. H NMR (400 MHz,
CDCl3): d 7.71 (d, J = 7.8 Hz, 1H), 7.32 (d, J = 8.7 Hz,
2H), 7.26–7.20 (m, 3H), 7.14–06 (m, 2H), 4.41 (s, 1H),
4.34 (t, J = 5.5 Hz, 1H), 3.36–3.29 (m, 4H), 3.22 (q,
J = 6.8 Hz, 2H), 2.46–2.38 (m, 2H), 2.31–2.26 (m, 5H),
1.53–1.42 (m, 2H), 1.38–1.28 (m, 2H), 0.91 (t,
J = 7.3 Hz, 3H). [M+H]+: 400.
4.2.80. 4-((4-Chlorophenyl)(o-tolyl)methyl)-N-hexylpiper-
azine-1-carboxamide (17g). The procedure described for
the synthesis of 13a was applied to 12d and hexylisocy-
4.2.86. N-tert-Butyl-4-((4-chlorophenyl)(2-(trifluoromethyl)-
phenyl)methyl)piperazine-1-carboxamide (18d). The proce-
dure described for the synthesis of 13a was applied to
12e and tert-butylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.99 (d, J = 8.0 Hz, 1H),
7.60 (d, J = 8.0 Hz, 1H), 7.54 (t, J = 7.6 Hz, 1H), 7.44
(d, J = 8.0 Hz, 2H), 7.34–7.24 (m, 3H), 4.67 (s, 1H), 4.25
(s, 1H), 3.27 (t, J = 4.8 Hz, 4H), 2.43–2.36 (m, 2H),
2.31–2.25 (m,2H), 1.33 (s, 9H). [M+H]+: 454, HPLC:
tR = 6.1 min.
1
anate providing the title product. H NMR (400 MHz,
CDCl3): d 7.71 (d, J = 7.8 Hz, 1H), 7.32 (d, J = 8.7 Hz,
2H), 7.26–7.18 (m, 3H), 7.14–7.05 (m, 2H), 4.41 (s,
1H), 4.34 (t, J = 5.0 Hz, 1H), 3.38–3.28 (m, 4H), 3.21
(q, J = 6.4 Hz, 2H), 2.47–2.39 (m, 2H), 2.31–2.25 (m,
5H), 1.51–1.43 (m, 2H), 1.35–1.24 (m, 6H), 0.88 (t,
J = 7.4 Hz, 3H). [M+H]+: 428.
4.2.81. (4-Chlorophenyl)(2-(trifluoromethyl)phenyl)meth-
anol (10e). The procedure described for the synthesis of
10a was applied to 2-(trifluoromethyl)benzaldehyde in-
stead of 2,4-dichlorobenzaldehyde providing the title
product. [MꢀH2O+H]+: 269.
4.2.87. 4-((4-Chlorophenyl)(2-(trifluoromethyl)phenyl)-
methyl)-N-isopropylpiperazine-1-carboxamide (18e). The
procedure described for the synthesis of 13a was applied
to 12e and isopropylisocyanate providing the title prod-
uct. 1H NMR (400 MHz, CDCl3): d 7.98 (d, J = 8.0 Hz,
1H), 7.61 (d, J = 8.0 Hz, 1H), 7.54 (t, J = 7.2 Hz, 1H),
7.44 (d, J = 8.4 Hz, 2H), 7.35–7.24 (m, 3H), 4.68 (s,
1H), 4.16 (d, J = 6.8 Hz, 1H), 4.0–3.91 (m, 1H), 3.35–
3.26 (m, 4H), 2.45–2.36 (m, 2H), 2.32–2.25 (m, 5H),
1.13 (d, J = 6.4 Hz, 6H). [M+H]+: 440.
4.2.82. 1-((4-Chlorophenyl)(2-(trifluoromethyl)phenyl)-
methyl)piperazine (12e). The procedure described for
the synthesis of 7 was applied to 10e instead of 5 provid-
1
ing the title product. H NMR (400 MHz, CDCl3): d
7.98 (d, J = 8.0 Hz, 1H), 7.58 (d, J = 7.6 Hz, 1H), 7.52
(t, J = 7.6 Hz, 1H), 7.41 (d, J = 8.4 Hz, 2H), 7.31–7.22
(m, 3H), 4.69 (s, 1H), 2.91 (t, J = 4.8 Hz, 4H), 2.44–
2.31 (m, 4H). [M+H]+: 355.
4.2.88. N-Butyl-4-((4-chlorophenyl)(2-(trifluoromethyl)-
phenyl)methyl)piperazine-1-carboxamide (18f). The pro-
cedure described for the synthesis of 13a was applied
to 12e and butylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.98 (d, J = 8.0 Hz,
1H), 7.60 (d, J = 8.0 Hz, 1H), 7.54 (t, J = 7.6 Hz, 1H),
7.44 (d, J = 8.4 Hz, 2H), 7.34–7.25 (m, 3H), 4.67 (s,
1H), 4.37 (t, J = 5.5 Hz, 1H), 3.31 (t, J = 4.8 Hz, 4H),
4.2.83. 4-((4-Chlorophenyl)(2-(trifluoromethyl)phenyl)-
methyl)-N-cyclohexylpiperazine-1-carboxamide
(18a).
The procedure described for the synthesis of 13a was ap-
plied to 12e and cyclohexylisocyanate providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.98 (d,

4048
K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
3.21 (q, J = 7.2 Hz, 2H), 2.44–2.37 (m, 2H), 2.31–2.26
(m, 2H), 1.50–1.43 (m, 2H), 1.38–1.28 (m, 2H), 0.91 (t,
J = 7.2 Hz, 3H). [M+H]+: 454.
4.2.93. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-N-cyclopentyl-2-oxoacetamide (23d). The
procedure described for the synthesis of 23a was applied
to cyclopentylamine instead of cyclohexylamine provid-
1
4.2.89. 4-((4-Chlorophenyl)(2-(trifluoromethyl)phenyl)-
methyl)-N-hexylpiperazine-1-carboxamide (18g). The
procedure described for the synthesis of 13a was applied
to 12e and hexylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.98 (d, J = 8.0 Hz,
1H), 7.61 (d, J = 8.0 Hz, 1H), 7.55 (t, J = 7.6 Hz, 1H),
7.44 (d, J = 8.4 Hz, 2H), 7.34–7.24 (m, 3H), 4.67 (s,
1H), 4.38 (t, J = 5.0 Hz, 1H), 3.31 (t, J = 5.2 Hz, 4H),
3.20 (q, J = 6.8 Hz, 2H), 2.44–2.37 (m, 2H), 2.32–2.27
(m, 2H), 1.51–1.43 (m, 2H), 1.35–1.23 (m, 6H), 0.88 (t,
J = 6.8 Hz, 3H). [M+H]+: 482.
ing the title product. H NMR (400 MHz, CDCl3): d
7.74 (d, J = 7.9 Hz, 1H), 7.39 (d, J = 8.4 Hz, 2H),
7.32–7.23 (m, 4H), 7.20–7.11 (m, 2H), 4.83 (s, 1H),
4.18–4.09 (m, 3H), 3.65 (t, J = 5.0 Hz, 2H), 2.53–2.38
(m, 4H), 2.05–1.92 (m, 2H), 1.78–1.53 (m, 4H), 1.51–
1.39 (m, 2H). [M+H]+: 460.
4.2.94. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-N-cyclobutyl-2-oxoacetamide (23e). The
procedure described for the synthesis of 23a was applied
to cyclobutylamine instead of cyclohexylamine provid-
1
ing the title product. H NMR (400 MHz, CDCl3): d
4.2.90. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-N-cyclohexyl-2-oxoacetamide (23a). Oxa-
lyl chloride (857 mg, 6.8 mmol) was added to DCM
(10 mL) with TEA (0.17 mL, 1.25 mmol) at 0 ꢂC under
nitrogen. After stirring for 10 min at 0 ꢂC, 1-((2-chloro-
phenyl)(4-chlorophenyl)methyl)piperazine (12c, 0.2 g,
0.62 mmol) in DCM (2 mL) was added to the solution.
The resulting solution was allowed to warm to room
temperature, stirred overnight and evaporated under
vacuum. The residue was dissolved in DCM (5 mL)
and cyclohexylamine (185 mg, 1.87 mmol) in DCM
(1 mL) was added to the above solution. After stirring
at room temperature overnight, the reaction mixture
was poured into 1 M HCl (20 mL) and extracted with
DCM (2· 20 mL). The combined organic extracts were
washed with water, dried over MgSO4, filtered and
evaporated under vacuum. The residue was further puri-
fied by prep HPLC to provide the title compound
7.73 (d, J = 7.9 Hz, 1H), 7.38 (d, J = 8.4 Hz, 3H),
7.31–7.24 (m, 4H), 7.15 (t, J = 7.7 Hz, 1H), 4.82 (s,
1H), 4.40–4.20 (m, 1H), 4.14 (t, J = 5.0 Hz, 2H), 3.65
(t, J = 4.8 Hz, 2H), 2.51–2.40 (m, 4H), 2.39–2.20 (m,
2H), 2.10–1.86 (m, 2H), 1.81–1.67 (m, 2H). [M+H]+:
446.
4.2.95. N-tert-Butyl-2-(4-((2-chlorophenyl)(4-chlorophenyl)-
methyl)piperazin-1-yl)-2-oxoacetamide (23f). The proce-
dure described for the synthesis of 23a was applied to
tert-butylamine instead of cyclohexylamine providing the
1
title product. H NMR (400 MHz, CDCl3): d 7.73 (d,
J = 7.7 Hz, 1H), 7.38 (d, J = 7.6 Hz, 2H), 7.31–7.24 (m,
4H), 7.14 (t, J = 7.7 Hz, 1H), 7.02 (s, 1H), 4.83 (s, 1H),
4.09 (t, J = 5.1 Hz, 2H), 3.63 (t, J = 5.1 Hz, 2H), 2.51–
2.42 (m, 4H), 1.36 (s, 9H). [M+H]+: 448.
4.2.96. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-2-oxo-N-(pentan-3-yl)acetamide
1
(100 mg, 0.21 mmol, 34%) as a light yellow solid. H
(23g).
NMR (400 MHz, CDCl3): d 7.74 (d, J = 7.7 Hz, 1H),
7.39 (d, J = 8.6 Hz, 2H), 7.31–7.24 (m, 4H), 7.17–7.11
(m, 2H), 4.83 (s, 1H), 4.15 (t, J = 5.0 Hz, 2H), 3.85–
3.62 (m, 3H), 2.53–2.39 (m, 4H), 1.95–1.85 (m, 2H),
1.79–1.57 (m, 3H), 1.42–1.05 (m, 5H). [M+H]+: 474,
HPLC: tR = 6.7 min.
The procedure described for the synthesis of 23a was ap-
plied to pentan-3-amine instead of cyclohexylamine pro-
viding the title product. 1H NMR (400 MHz, CDCl3): d
7.74 (d, J = 7.9 Hz, 1H), 7.39 (d, J = 8.4 Hz, 2H), 7.31–
7.24 (m, 4H), 7.15 (t, J = 7.7 Hz, 1H), 6.96 (d,
J = 9.0 Hz, 1H), 4.83 (s, 1H), 4.15 (t, J = 5.1 Hz, 2H),
3.78–3.62 (m, 3H), 2.45 (q, J = 5.0 Hz, 4H), 2.52–2.38
(m, 4H), 1.63–1.51 (m, 2H), 1.48–1.33 (m, 2H), 0.89 (t,
J = 7.3 Hz, 6H). [M+H]+: 462.
4.2.91. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-N-cycloheptyl-2-oxoacetamide (23b). The
procedure described for the synthesis of 23a was applied
to cycloheptylamine instead of cyclohexylamine provid-
4.2.97. N-Butyl-2-(4-((2-chlorophenyl)(4-chlorophenyl)-
methyl)piperazin-1-yl)-2-oxoacetamide (23h). The proce-
dure described for the synthesis of 23a was applied to
butylamine instead of cyclohexylamine providing the ti-
tle product. 1H NMR (400 MHz, CDCl3): d 7.74 (d,
J = 7.9 Hz, 1H), 7.39 (d, J = 8.4 Hz, 2H), 7.31–7.24
(m, 4H), 7.15 (t, J = 7.7 Hz, 1H), 4.83 (s, 1H), 4.15 (t,
J = 5.0 Hz, 2H), 3.65 (t, J = 5.0 Hz, 2H), 3.26 (q,
J = 6.2 Hz, 2H), 2.50–2.39 (m, 4H), 1.57–1.46 (m, 2H),
1.41–1.29 (m, 2H), 0.92 (t, J = 7.4 Hz, 3H). [M+H]+:
448.
1
ing the title product. H NMR (400 MHz, CDCl3): d
7.74 (d, J = 7.0 Hz, 1H), 7.38 (d, J = 8.4 Hz, 2H),
7.31–7.24 (m, 4H), 7.20–7.11 (m, 2H), 4.83 (s, 1H),
4.15 (t, J = 5.1 Hz, 2H), 3.95–3.82 (m, 1H), 3.65 (t,
J = 5.0 Hz, 2H), 2.50–2.37 (m, 4H), 1.96–1.87 (m, 2H),
1.70–1.40 (m, 10H). [M+H]+: 488, HPLC: tR = 6.9 min.
4.2.92. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-2-oxo-N-(piperidin-1-yl)acetamide (23c).
The procedure described for the synthesis of 23a was ap-
plied to aminopiperidine instead of cyclohexylamine
providing the title product. 1H NMR (400 MHz,
CDCl3): d 7.81 (s, 1H), 7.74 (d, J = 7.7 Hz, 1H), 7.39
(d, J = 8.6 Hz, 2H), 7.31–7.24 (m, 4H), 7.14 (t,
J = 7.7 Hz, 1H), 4.82 (s, 1H), 4.10 (t, J = 5.0 Hz, 2H),
3.63 (m, 2H), 2.82–2.62 (m, 4H), 2.51–2.38 (m, 4H),
1.76–1.59 (m, 4H), 1.50–46 (m, 2H). [M+H]+: 475.
4.2.98. 2-(4-((2-Chlorophenyl)(4-chlorophenyl)methyl)-
piperazin-1-yl)-N-hexyl-2-oxoacetamide (23i). The proce-
dure described for the synthesis of 23a was applied to
hexylamine instead of cyclohexylamine providing the ti-
tle product. 1H NMR (400 MHz, CDCl3): d 7.74 (d,
J = 7.7 Hz, 1H), 7.39 (d, J = 7.5 Hz, 2H), 7.32–7.24

K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
4049
(m, 5H), 7.15 (t, J = 7.5 Hz, 1H), 4.83 (s, 1H), 4.15 (t,
J = 5.0 Hz, 2H), 3.66 (t, J = 4.8 Hz, 2H), 3.25 (q,
J = 6.8 Hz, 2H), 2.52–2.38 (m, 4H), 1.60–1.48 (m, 2H),
1.40–1.21 (m, 6H), 0.88 (t, J = 7.0 Hz, 3H). [M+H]+:
476.
4.2.104. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
tert-butylpiperazine-1-carboxamide (29d). The procedure
described for the synthesis of 13a was applied to 28 and
tert-butylisocyanate providing the title product. 1H
NMR (400 MHz, CDCl3): d 7.74 (d, J = 7.8 Hz, 1H),
7.40 (d, J = 8.7 Hz, 2H), 7.34–7.24 (m, 4H), 7.14 (t,
J = 7.8 Hz, 1H), 4.79 (s, 1H), 4.25 (s, 1H), 3.29 (t,
J = 5.0 Hz, 4H), 2.40–2.32 (m, 4H), 1.33 (s, 9H).
[M+H]+: 466, HPLC: tR = 5.4 min.
4.2.99. (4-Bromophenyl)(2-chlorophenyl)methanol (26).
1,4-Dibromobenzene (11.8 g, 50 mmol) in THF
(60 mL) was treated with n-BuLi (20 mL, 2.5 M solution
in hexane) at ꢀ78 ꢂC under nitrogen. After the mixture
was stirred for 10 min, 2-chlorobenzaldehyde (7.03 g,
70 mmol) in THF (5 mL) was added dropwise and stir-
red at ꢀ78 ꢂC for additional 1 h. The reaction mixture
was allowed to warm to room temperature and stirred
overnight. It was poured into water (200 mL) and ex-
tracted twice with MTBE (200 mL). The combined or-
ganic phases were dried over anhydrous Na2SO4,
filtered and evaporated to dryness (13.6 g, 45.8 mmol,
92%). The expected alcohol was used without further
purification in the next step. [MꢀH2O+H]+: 281.
4.2.105. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
isopropylpiperazine-1-carboxamide (29e). The procedure
described for the synthesis of 13a was applied to 28
and isopropylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.73 (d, J = 7.8 Hz,
1H), 7.40 (d, J = 8.3 Hz, 2H), 7.34–7.24 (m, 4H),
7.14 (t, J = 7.8 Hz, 1H), 4.79 (s, 1H), 4.16 (d,
J = 7.4 Hz, 1H), 4.05–3.91 (m, 1H), 3.32 (t,
J = 5.0 Hz, 4H), 2.43–2.32 (m, 4H), 1.14 (d,
J = 6.4 Hz, 6H). [M+H]+: 452.
4.2.100. 1-((4-Bromophenyl)(2-chlorophenyl)methyl)pipera-
zine (28). The procedure described for the synthesis of 7
was applied to 26 instead of 5 providing the title product.
1H NMR (400 MHz, CDCl3): d 7.69 (d, J = 8.0 Hz, 1H),
7.41–7.35(m, 2H), 7.33–7.21 (m, 4H), 7.15–7.08 (m, 1H),
4.86 (s, 1H), 3.07 (t, J = 4.8 Hz, 2H), 2.63–2.55 (m, 4H),
2.48–2.34 (m, 2H). [M+H]+: 367.
4.2.106. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
butylpiperazine-1-carboxamide (29f). The procedure de-
scribed for the synthesis of 13a was applied to 28 and
1
butylisocyanate providing the title product. H NMR
(400 MHz, CDCl3): d 7.73 (d, J = 7.8 Hz, 1H), 7.40 (d,
J = 8.3 Hz, 2H), 7.35–7.24 (m, 4H), 7.14 (t, J = 7.8 Hz,
1H), 4.79 (s, 1H), 4.37 (t, J = 5.5 Hz, 1H), 3.33 (t,
J = 5.0 Hz, 4H), 3.22 (q, J = 7.3 Hz, 2H), 2.43–2.32
(m, 4H), 1.51–1.43 (m, 2H), 1.38–1.28 (m, 2H), 0.91 (t,
J = 7.3 Hz, 3H). [M+H]+: 466.
4.2.101. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
cyclohexylpiperazine-1-carboxamide (29a). The proce-
dure described for the synthesis of 13a was applied to 28
and cyclohexylisocyanate providing the title product.
1H NMR (400 MHz, CDCl3): d 7.73 (d, J = 7.8 Hz,
1H), 7.41 (d, J = 8.7 Hz, 2H), 7.34–7.24 (m, 4H), 7.14 (t,
J = 7.8 Hz, 1H), 4.79 (s, 1H), 4.22 (d, J = 7.4 Hz, 1H),
3.68–3.58 (m, 1H), 3.32 (t, J = 5.0 Hz, 4H), 2.43–2.32
(m, 4H), 1.97–1.89 (m, 2H), 1.72–1.56 (m, 3H), 1.43–
1.29 (m, 2H), 1.19–1.01 (m, 3H). [M+H]+: 492, HPLC:
tR = 5.9 min.
4.2.107. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
hexylpiperazine-1-carboxamide (29g). The procedure de-
scribed for the synthesis of 13a was applied to 28 and
1
hexylisocyanate providing the title product. H NMR
(400 MHz, CDCl3): d 7.74 (d, J = 7.8 Hz, 1H), 7.41 (d,
J = 8.3 Hz, 2H), 7.35–7.24 (m, 4H), 7.14 (t, J = 7.8 Hz,
1H), 4.79 (s, 1H), 4.37 (t, J = 5.0 Hz, 1H), 3.33 (t,
J = 5.5 Hz, 4H), 3.21 (q, J = 6.9 Hz, 2H), 2.44–2.33
(m, 4H), 1.52–1.44 (m, 2H), 1.34–1.24 (m, 6H), 0.88 (t,
J = 6.9 Hz, 3H). [M+H]+: 494.
4.2.102. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
cycloheptylpiperazine-1-carboxamide (29b). The proce-
dure described for the synthesis of 13a was applied to
28 and cycloheptylisocyanate providing the title prod-
4.3. CB1 and CB2 receptor binding assay
uct. 1H NMR (400 MHz, CDCl3):
d
7.73 (d,
For CB1 receptor binding studies, rat cerebellar mem-
branes were prepared as previously described by the
methods of Kuster et al.30 Male Sprague–Dawley rats
(200–300 g) were sacrificed by decapitation and the
cerebella rapidly removed. The tissue was homoge-
nized in 30 volumes of TME buffer (50 mM Tris–
HCl, 1 mM EDTA, 3 mM MgCl2, pH 7.4) using a
Dounce homogenizer. The crude homogenates were
immediately centrifuged (48,000g) for 30 min at 4 ꢂC.
The resultant pellets were resuspended in 30 volumes
of TME buffer and protein concentration was deter-
mined by the method of Bradford and stored at
ꢀ70 ꢂC until use.31
J = 7.8 Hz, 1H), 7.41 (d, J = 8.7 Hz, 2H), 7.34–7.24
(m, 4H), 7.14 (t, J = 7.3 Hz, 1H), 4.79 (s, 1H), 4.28 (d,
J = 7.3 Hz, 1H), 3.87–3.78 (m, 1H), 3.32 (t, J = 5.0 Hz,
4H), 2.43–2.32 (m, 4H), 1.96–1.88 (m, 2H), 1.63–1.33
(m, 10H). [M+H]+: 506, HPLC: tR = 6.2 min.
4.2.103. 4-((4-Bromophenyl)(2-chlorophenyl)methyl)-N-
(cyclohexylmethyl)piperazine-1-carboxamide (29c). The
procedure described for the synthesis of 13a was applied
to 28 and cyclohexylmethylisocyanate providing the title
product. 1H NMR (400 MHz, CDCl3): d 7.74 (d,
J = 7.8 Hz, 1H), 7.41 (d, J = 8.7 Hz, 2H), 7.35–7.24
(m, 4H), 7.14 (t, J = 7.8 Hz, 1H), 4.80 (s, 1H), 4.45 (t,
J = 5.5 Hz, 1H), 3.34 (t, J = 5.0 Hz, 4H), 3.06 (t,
J = 6.4 Hz, 2H), 2.44–2.33 (m, 4H), 1.74–1.62 (m, 5H),
1.48–1.38 (m, 1H), 1.27–1.11 (m, 3H), 0.95–0.83 (m,
2H). [M+H]+: 506, HPLC: tR = 6.3 min.
For CB2 receptor binding studies, CHO K-1 cells were
transfected with human CB2 receptor as previously de-
scribed, and cell membranes were prepared as described
above.32

4050
K.-S. Song et al. / Bioorg. Med. Chem. 16 (2008) 4035–4051
Competitive binding assays were performed as de-
scribed.33 Briefly, approximately 10 lg of rat cerebella
membranes (containing CB1 receptor) or cell mem-
branes (containing CB2 receptor) were incubated in
96-well plate with TME buffer containing 0.5% essen-
tially fatty acid-free bovine serum albumin (BSA),
3 nM [3H]CP55,940 (for CB1 receptor, NEN; specific
activity 120–190 Ci/mmol) or 3 nM [3H]WIN55,212-2
(for CB2 receptor, NEN; specific activity 50–80 Ci/
mmol) and various concentrations of the synthesized
cannabinoid ligands in a final volume of 200 lL. The as-
says were incubated for 1 h at 30 ꢂC and then immedi-
ately filtered over GF/B glass fibre filter (PerkinElmer
Life and Analytical Sciences, Boston, MA) that had
been soaked in 0.1% PEI for 1 h by a cell harvester
(PerkinElmer Life and Analytical Sciences, Boston,
MA). Filters were washed five times with ice-cold TBE
buffer containing 0.1% essentially fatty acid free BSA,
followed by oven-drying for 60 min and then placed in
5 mL of scintillation fluid (Ultima Gold XR; PerkinEl-
mer Life and Analytical Sciences, Boston, MA), and
radioactivity was quantitated by liquid scintillation
spectrometry. In CB1 and CB2 receptor competitive
binding assay, nonspecific binding was assessed using
1 lM SR141716A and 1 lM WIN 55,212-2, respec-
tively. Specific binding was defined as the difference be-
tween the binding that occurred in the presence and
absence of 1 lM concentrations of SR 141716 A or
WIN55,212-2 and was 70–80% of the total binding.
IC50 was determined by nonlinear regression analysis
using GraphPad PRISM.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.bmc.2008.01.023.
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