Structure-activity relationships of novel piperazines as antagonists for the melanocortin-4 receptor

Article abstract of DOI:10.1016/j.bmc.2006.12.039

During the investigation of antagonists for the MC4 receptor, we found that 10ab having a naphthyl group showed almost the same binding affinity for the MC4 receptor as that of the lead compound 1 with a benzoyl group. We also developed a new type of compounds, namely, bis-piperazines, and found that the bis-piperazines 10 exhibited a high affinity for the MC4 receptor. In particular, (-)-10bg exhibited the highest affinity for the MC4 receptor with an IC₅₀ value of 8.13 nM. In this paper, we present the design, synthesis, and structure-activity relationships of the novel bis-piperazines as MC4 receptor antagonists.

Full text of DOI:10.1016/j.bmc.2006.12.039

Bioorganic & Medicinal Chemistry 15 (2007) 1989–2005
Structure–activity relationships of novel piperazines
as antagonists for the melanocortin-4 receptor
Dai Nozawa,* Taketoshi Okubo, Takaaki Ishii, Hiroyuki Kakinuma,
Shigeyuki Chaki, Shigeru Okuyama and Atsuro Nakazato
Medicinal Research Laboratories, Taisho Pharmaceutical Co., Ltd, 1-403 Yoshino-cho, Kita-ku, Saitama, Saitama 331-9530, Japan
Received 30 November 2006; revised 22 December 2006; accepted 23 December 2006
Available online 30 December 2006
Abstract—During the investigation of antagonists for the MC4 receptor, we found that 10ab having a naphthyl group showed
almost the same binding affinity for the MC4 receptor as that of the lead compound 1 with a benzoyl group. We also developed
a new type of compounds, namely, bis-piperazines, and found that the bis-piperazines 10 exhibited a high affinity for the MC4
receptor. In particular, (ꢀ)-10bg exhibited the highest affinity for the MC4 receptor with an IC50 value of 8.13 nM. In this paper,
we present the design, synthesis, and structure–activity relationships of the novel bis-piperazines as MC4 receptor antagonists.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
role in fat metabolism and energy homeostasis together
with the MC4 receptor. The MC4 receptor, which
exhibits higher affinities for a-MSH and b-MSH than
for c-MSH, is primarily expressed in the brain. The
MC5 receptor, bound by a-MSH, is expressed in various
peripheral tissues and plays a role in exocrine gland
function.
The melanocortin peptides, the natural ligands for the
melanocortin receptors, consist of the melanocyte-stim-
ulating hormones (a-MSH, b-MSH, and c-MSH) and
the adrenocorticotropic hormone (ACTH), all of which
are derived from proopiomelanocortin (POMC).1 In
addition, two endogenous antagonistic peptides, agouti
and agouti-related protein (AGRP), have also been
indentified.2,3 All the melanocortin peptides possess a
core His-Phe-Arg-Trp (HFRW) terapeptide sequence,
which has been shown to be essential for activation of
the melanocortin receptors.4,5
Numerous studies have suggested that the MC4 receptor
is involved in the regulation of feeding and metabolism.
MC4 receptor deficient-mice are severely obese and
hyperphagic. In rodents, while injection of MC4 recep-
tor agonists into the brain inhibits food intake, intracer-
ebroventricular administration of MC4 receptor
antagonists stimulates food intake.7–13 In addition, it
has also been reported that the MC4 receptor is involved
in the regulation of sexual functions,14 protection
against tumor-induced decrease of body weight,15 and
in the regulation of emotional states such as anxiety
and depression.16–22 These studies indicate that the
MC4 receptor could be a promising target for the devel-
opment of drugs for the above-mentioned conditions,
and numerous ligands of the MC4 receptor, both pep-
tidic and nonpeptidic, have been developed to date.
To date, five subtypes of melanocortin receptors (MC1–
MC5 receptors) that belong to seven-transmembrane G-
protein-coupled receptor family have been identified.6
The MC1 receptor, bound mainly by a-MSH, is promi-
nently expressed in the skin and melanoma cells and
plays a major role in regulating skin pigmentation.
The MC2 receptor, bound by only ACTH, is prominent-
ly expressed in the adrenal cortex and is involved in ste-
roidogenesis. The MC3 receptor, bound by both a- and
c-MSH with the same affinity, is widely expressed in the
central nervous system as well as placenta, and plays a
Several peptidic MC4 receptor agonists and antagonists
have been reported.23 Since peptidic compounds tend to
have properties unsuitable for an oral administration,
such as their low absorption, nonpeptidic ligands
of the MC4 receptor have been sought. Recently,
nonpeptidic agonists24 and antagonists15,25–28 have been
Keywords: Melanocortin-4 receptor; Antagonist; Bis-piperazine syn-
thesis; Anxiety and depression.
*
Corresponding author. Tel.: +81 48 663 1111; fax: +81 48 652
7254; e-mail: dai.nozawa@po.rd.taisho.co.jp
0968-0896/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.12.039

1990
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
reported (Chart 1). Compound 1, having a 1,2-bispi-
perazinylethane core, inhibited the binding of AGRP
to the MC4 receptor (IC50 = 52 nM) and also that of
NDP-MSH to the MC4 receptor (IC50 = 217 nM).25
Compound 2, having a succinamide core, exhibited a
high affinity for the MC4 receptor (IC50 = 1.4 nM) while
having no effect of activating the MC4 receptor in a
functional assay.26 Compound 3 (ML00253764) exhibit-
ed a moderate affinity (Ki = 160 nM) for the MC4 recep-
tor with antagonist activity (Ki = 103 nM), and
following subcutaneous administration in mice protect-
ed the animals against tumor-induced weight loss.15
Compound 4 was a potent MC4 receptor antagonist
(Ki = 3.2 nM) with a 240-fold selectivity for this over
the MC3 receptor. Intracerebroventricular administra-
tion of this compound potently stimulated food
intake in satiated mice.27 Thus, both MC4 receptor
agonists and antagonists are attractive targets for the
development of CNS drugs to treat obesity, erectile
dysfunction, cachexia, anxiety or depression. We report
the synthesis and structure–activity relationships of
novel bis-piperazine compounds identified as MC4
receptor antagonists.
12 with N-(Ar2-(CH2)n)-piperazine 5 in the presence of
iPr2NEt, followed by reduction of the carbonyl group
with NaBH4, yielded alcohols 14. Chlorination of the
hydroxyl group of 14 with thionyl chloride, followed
by coupling with N-Boc-piperazine 7, yielded N-protect-
ed piperazines 15. After removal of the Boc group of 15
under acidic conditions (yielded 10ak), reaction with
sodium hydride and alkyl halide yielded compounds
10al–10an (method A, Scheme 1).
Alternatively, compounds 10ao–10bd and 10bk–10bm
could be also obtained from alcohols 14 by another
pathway. Methanesulfonylation of the hydroxyl group
of 14 with MsCl in the presence of Et3N, followed by
coupling with N-R1-piperazine 6 in the presence of
Et3N, yielded 10ao–10bc and 10bk–10bm. Compound
10bd was obtained by hydrogenation of 10ba with
PtO2 as the catalyst (method B, Scheme 1).
Furthermore, compounds 10be were synthesized via
amines 20. Reaction of 12 with N-CO2Et-piperazine 8,
followed by reduction of the carbonyl group with
NaBH4, yielded alcohols 18. Chlorination of the
hydroxyl group of 18 with thionyl chloride, followed
by coupling with N-R1-piperazine 6 in the presence of
iPr2NEt, yielded N-protected piperazines 19. Removal
of the ethoxycarbonyl group using KOH yielded
deprotected amines 20. Compounds 20 were converted
to 10be by treatment with Ar2-(CH2)4-Br (9b) in the
presence of Et3N (method C, Scheme 2). Compounds
10aa–10aj, 10bf, 10bg, and 10bn–10cj were also obtained
by reduction of amides 21, which had been prepared
from 20 by condensation with Ar2-(CH2)nꢀ1CO2H
(9a), with LiAlH4. Compounds 10bi and 10bj were ob-
tained by alkylation of phenol 10bh, which had been
prepared by hydrolysis of 10bg with HBr (method D,
Scheme 2).
2. Chemistry
The syntheses of bis-piperazine compounds 10 are
shown in Schemes 1 and 2. Compounds 10aa–10cj were
prepared by four types of synthetic routes (methods A–
D) from haloacetophenone 12, which was the common
starting material for the preparation.
Compounds 10ak–10an were synthesized from com-
pounds 14 via N-protected piperazines 15. Reaction of
Cl
3. Results and discussion
F
O
O
O
N
The affinities of all the bis-piperazines for the MC4
receptor were evaluated based on their binding affinity
to membranes of COS-1 expressing the human MC4
receptor and calculated from the inhibition curve of
N
O
N
N
N
N
O
N
N
N
125I]Nle4-D-Phe7-a-MSH binding,19 and the IC50 values
S
[
O
O
are shown in Table 1. The affinities of compounds ( )-
10bo, ( )-10bs–( )-10bx, ( )-10ca, and ( )-10cb were
tested as follows; [3H]paroxetine binding to rat cortical
membranes (for SET), [3H]nisoxetine binding to rat cor-
tical membranes (for NET), [3H]prazosin binding to rat
cortical membranes (for a1),[3H]raclopride binding to
rat striatal membranes (for D2), [3H]pyrilamine binding
to rat whole brain membranes (for H1), [3H]DAMGO
binding to rat brain membranes (for l), and
[3H]DPDPE binding to rat brain membranes (for d).
1
2
Cl
Cl
F
O
Br
O
N
O
O
N
H
NH
N
N
F
O
We identified compound 1 in a high-throughput screen-
ing against our internal compounds library. Since com-
pound 1 exhibited a moderate affinity for the MC4
receptor (IC50 = 399 nM), we attempted to explore its
analogues to identify compounds with higher affinity
for the MC4 receptor.
3
4
Chart 1.

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
1991
Ar
Ar
Ar
1
Ar
d
1
1
a
b
1
Boc
N
N
O
HO
O
N
N
(CH )
Ar
2 n
Ar
N (CH )
2 n
Ar
2
N
N
N
(CH )
2 n
2
2
X
12
13
15
14
e
c
4HCl
N
Ar
Ar
1
1
f
HN
N
N
N
R
1
N
N
(CH )
N
(CH )
Ar
2 n
Ar
2
2 n
2
10
16 (10ak)
Scheme 1. Synthesis of bis-piperazine compounds 10 (methods A and B). Reagents and conditions (X = Cl or Br): (a) N-(Ar2-(CH2)n)-piperazine (5),
iPr2NEt, CHCl3, reflux; (b) NaBH4, EtOH, 50 ꢁC; (c) MeSO2Cl, Et3N, CH2Cl2, in ice-bath and then N-R1-piperazine (6), Et3N, rt; (d) SOCl2,
benzene, 50 ꢁC and then N-Boc-piperazine (7), CHCl3, 70 ꢁC; (e) 4 M HCl/AcOEt, MeOH, rt; (f) NaH, alkyl halide, DMF, rt; method A: a–f; method
B: a–c.
HCl
Ar1
Ar1
Ar1
Ar1
g
HO
N
N
R1
h
i
O
O
N
N CO2Et
N
N CO2Et
N
N CO2Et
X
12
19
18
17
j
Ar1
m
Ar1
N
N
R1
N
N
R1
N
N (CH )
2 n Ar2
N
NH
10
20
l
k
Ar1
R1
N
N
N
N C (CH2)n-1 Ar2
O
21
Scheme 2. Synthesis of bis-piperazine compounds 10 (methods C and D). Reagents and conditions (X = Cl or Br): (g) N-EtO2C-piperazine (8),
CHCl3, reflux; (h) NaBH4, EtOH, 50 ꢁC and then 4 M HCl/EtOAc; (i) SOCl2, benzene, 50 ꢁC and then N-R1-piperazine (6), iPr2NEt, benzene, 60 ꢁC;
(j) KOH, EtOH, reflux; (k) Ar2-(CH2)nꢀ1-CO2H (9a), EDC, HOBt, DMF, rt; (l) LiAlH4, THF, reflux; (m) Ar2-(CH2)4-Br (9b) NEt3, DMF, 60 ꢁC;
method C: g–j, and m; method D: g–l.
Bis-piperazine derivatives, MC4 receptor antagonists
with a benzoyl group, have been reported by Arasasing-
ham et al.25 They also showed that the carbonyl group
was essential for the binding of these bis-piperazine
derivatives to the receptor. We focused on the confor-
mational rigidity of the carbonyl group, and we adapted
a naphthyl group for the conformational rigidity as an
alternative to the benzoyl group. We prepared a com-
pound with a naphthyl part and evaluated the affinity
of the compound for the MC4 receptor. As expected,
10ab showed almost the same affinity for the MC4
receptor (IC50 = 567 nM) as 1. Then we attempted to ex-
plore the naphthyl analogues to identify compounds
with higher affinity for the MC4 receptor. To study
SAR of bis-piperazines for the MC4 receptor, syntheses
of these compounds were accomplished according to
Scheme 1 and 2.
azine ring were tested for their affinity for the MC4
receptor (10aa–10af, Table 1). The results indicated
that tetramethylene was the most favored chain length
for binding to the receptor (10ad, IC50 = 118 nM). A
similar tendency was observed for the bis-piperazine
compounds having a 2-naphthyl group (10ag–10aj).
The 2-naphthyl analogues showed
a
lower
affinity for the MC4 receptor than the 1-naphthyl
analogues.
Next, we examined bis-piperazines having various types
of Ar2. The methoxy group on the naphthalene ring at
2-position conferred a slight increase in the affinity for
the MC4 receptor (10bc: IC50 = 57.3 nM) as compared
to that of 10ad with no substitutions in the naphthalene
ring, whereas the methoxy group at 4-position conferred
a slight decrease in the affinity (10bf: IC50 = 228 nM).
These results suggest that a substitution at 2-position
probably increased the binding affinity for the MC4
receptor.
Initially, bis-piperazines with various lengths (n) of the
linking moiety between the naphthyl group and piper-

1992
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
Table 1. Binding affinity for the MC4 receptor of bis-piperazine compounds 10
Ar1
R1
N
N
N
N (CH2)n
Ar2
Compound
Method
Ar1
Ar2
R1
n
IC50 (nM)
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
)-10aa
)-10ab
)-10ac
)-10ad
)-10ae
)-10af
)-10ag
)-10ah
)-10ai
)-10aj
)-10ak
)-10al
)-10am
)-10an
)-10ao
)-10ap
)-10aq
)-10ar
)-10as
)-10at
)-10au
)-10av
)-10aw
)-10ax
)-10ay
)-10az
)-10ba
)-10bb
)-10bc
)-10bd
)-10be
)-10bf
)-10bg
D
D
D
D
D
D
D
D
D
D
A
A
A
A
B
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
Ph
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
2-Nap
2-Nap
2-Nap
2-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
1-Nap
Me
1
2
3
4
5
6
1
2
3
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
2
3
4
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
594
Me
567
Me
208
Me
118
Me
218
Me
341
Me
1250
1870
1190
336
Me
Me
Me
H
303
Et
105
n-Pr
177
iso-Pr
cyclo-Pr
cyclo-Hex
Ph
72.3
147
B
241
B
>10,000
745
B
Me
B
3-F–Ph
4-Cl–Ph
2-Br–Ph
3-Br–Ph
4-Br–Ph
Me
653
B
Me
132
B
Me
2300
565
B
Me
B
Me
159
B
4-Me–Ph
4-MeO–Ph
4-CF3–Ph
4-NO2–Ph
4-Ph–Ph
4-F–Ph
4-NH2–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
4-F–Ph
Me
296
B
Me
871
B
Me
226
B
Me
263
B
Me
756
B
2-MeO–1-Nap
1-Nap
Me
57.3
3590
36.8
228
B
Me
C
D
D
D
D
D
D
D
B
2-Br–1-Nap
iso-Pr
Me
4-MeO–1-Nap
2-MeO–1-Nap
2-MeO–1-Nap
2-MeO–1-Nap
2-HO–1-Nap
2-EtO–1-Nap
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
Et2CH
cyclo-Pen
t-Bu
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
iso-Pr
12.7
22.0
8.13
131
(+)-10bg
(ꢀ)-10bg
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
(
)-10bh
)-10bi
)-10bj
)-10bk
)-10bl
)-10bm
)-10bn
)-10bo
)-10bp
)-10bq
)-10br
)-10bs
)-10bt
)-10bu
)-10bv
)-10bw
)-10bx
)-10by
)-10bz
)-10ca
)-10cb
)-10cc
)-10cd
)-10ce
)-10cf
)-10cg
)-10ch
)-10ci
)-10cj
26.0
22.0
82.8
47.2
18.0
186
2-iso-PrO–1-Nap
2-MeO–1-Nap
2-MeO–1-Nap
2-MeO–1-Nap
2-Ph–Ph
B
B
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
2-Ph–Ph
11.2
65.1
156
2-Ph–Ph
3-Ph–Ph
4-Ph–Ph
243
2-Ph–3-F–Ph
2-Ph–4-F–Ph
2-Ph–5-F–Ph
2-Ph–6-F–Ph
2-Ph–6-Cl–Ph
2-Ph–6-Me–Ph
2-Ph–6-MeO–Ph
2-(2-F–Ph)–Ph
2-(3-F–Ph)–Ph
2-(4-F–Ph)–Ph
2-(4-Cl–Ph)–Ph
2-(4-Me–Ph)–Ph
2-(4-MeO–Ph)–Ph
2-(4-t-Bu–Ph)–Ph
2-(4-Ph–Ph)–Ph
2-(4-CF3–Ph)–Ph
2-(4-CF3O–Ph)–Ph
2-(4-Me2N–Ph)–Ph
23.0
33.0
27.1
11.7
27.1
24.3
15.2
36.8
23.6
10.5
53.2
41.8
42.6
100
228
62.8
85.9
92.5

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
1993
We then attempted chemical modifications of Ar1 to
study the effects of substituents on the benzene ring in
the binding affinity for the MC4 receptor. Substitution
of a chlorine (10at) or a bromine (10aw) at 4-position
of Ar1 resulted in a slight decrease of the affinity for
the MC4 receptor (10at: IC50 = 132 nM, 10aw:
IC50 = 159 nM) as compared to that of 10ad with a fluo-
rine atom. A halogen group at 4-position of the benzene
ring showed a favorable effect in the binding affinity to
the MC4 receptor, however, a halogen group at 2- and
3-positions proved to have an unfavorable effect (10as
vs 10ad, 10av vs 10aw, and 10au vs 10aw). Methyl, meth-
oxy, trifluoromethyl, nitro, and phenyl groups at 4-posi-
tion of Ar1 decreased a binding affinity for the MC4
receptor as compared to that of 10ad substituted with
a fluorine atom. Although methoxy group at 2-position
of the naphthyl group improved a binding affinity, a
methoxy group at 4-position of Ar1 resulted in a much
lower affinity than that of the corresponding 10ad. Com-
pound 10bd having an amino group showed almost no
affinity, whereas nonsubstituted compound 10ar showed
a 6-fold lower affinity for the receptor than 10ad substi-
tuted with a fluorine atom. These results indicate that
nonpolar substituents like halogen and alkyl groups at
4-position increase the affinity for the MC4 receptor,
while polar substituents like methoxy and amino groups
at 4-position decrease the affinity. Thus the most suit-
able group for Ar1 to increase the binding affinity for
the MC4 receptor was the 4-fluorophenyl group.
combination of each part showed a higher affinity
(IC50 = 12.7 nM) for the MC4 receptor than compounds
synthesized before.
Next, we studied the substitution effects of the methoxy
group on the naphthyl group of 10 bg with hydroxy, eth-
oxy, and iso-propoxy groups, and a bromine atom
(10bh, 10bi, 10bj, and 10be, respectively). No com-
pounds having a higher affinity for the MC4 receptor
than 10bg were found, however, compounds 10bi, 10bj,
and 10be with ethoxy and iso-propoxy groups and a bro-
mine atom, respectively, showed a higher affinity for the
receptor than the compound 10an with no substituent at
this position. These results suggest that a substitution at
2-position probably plays an important role in favoring
conformation between the naphthalene ring and alkyl-
ene part for binding to the MC4 receptor, which may
contribute to the increasing affinity.
Then, we studied the substitution effects of the methyl
group at R1 of 10bg with Et2CH (10bk), cyclopentyl
(10bl), and tert-butyl groups (10bm). None of the com-
pounds showed a higher affinity for the MC4 receptor
than 10bg. These results indicate that bulky alkyl and
cycloalkyl groups at R1 decreased the affinity for the
MC4 receptor, as described above. Since 10bg was a
racemate, optical resolution was performed to determine
the affinity of each enantiomer for the MC4 receptor.
The result showed that the (ꢀ)-enantiomer exhibited
a
higher affinity than the (+)-enantiomer (IC50;
At the next step, we examined the effects of replacement
of the methyl group at R1 of 10ad with other alkyl
groups and a phenyl group. Substitution of an iso-pro-
pyl group resulted in a slightly increased binding affinity
(10an: IC50 = 72.3 nM) as compared to that of methyl-
substituted compound 10ad, whereas that of an ethyl
group resulted in almost the same affinity (10al:
IC50 = 105 nM). Compounds 10am, 10ao, and 10ap with
n-propyl, cyclopropyl, and cyclohexyl groups, respec-
tively, showed between 1.2- and 2.0-fold lower affinity
than the corresponding 10ad, and 10aq (R1 = Ph) exhib-
ited no affinity. Removal of the methyl group resulted in
(ꢀ)-10bg:8.13 nM, (+)-10bg:22.0 nM).
As the next structural conversion, we expected that the
naphthyl group could be replaced by a biphenyl
(2-Ph–Ph) group (Chart 2). We prepared 10bp having
a 2-Ph–Ph group and evaluated the affinity of this com-
pound for the MC4 receptor. Fortunately, 10bp showed
a high affinity (IC50 = 65.1 nM) for the MC4 receptor.
This finding therefore led us to explore biphenyl ana-
logues with higher affinity for the receptor.
We investigated the effects of chemical modification of
the length (n) of the linking moiety between the 2-Ph–
Ph group and piperazine ring (10bn, 10bo, and 10bp).
The results indicated that compound 10bo
(IC50 = 11.2 nM) having a trimethylene exhibited the
highest affinity for the MC4 receptor among these com-
pounds. Interestingly, for the naphthyl compounds,
tetramethylene was the most favored chain length in
terms of binding affinity for the MC4 receptor, whereas
for the 2-Ph–Ph compounds, a trimethylene was the
most favored chain length. 3- and 4-Ph–Ph compounds
10ak with
a
slightly decreased binding affinity
(IC50 = 303 nM). These results indicate that the iso-pro-
pyl group at R1 was the most suitable for optimal bind-
ing affinity for the MC4 receptor.
From these structure–activity relationship studies, we
designed a compound having the most favorable group
at each of R1, Ar1, and Ar2, as follows; iso-propyl, 4-flu-
orophenyl, and 2-methoxy-1-naphthyl, respectively.
According to our expectation, 10 bg having favorable
A ring
F
F
F
5
6
4
3
N
O2
N
N
N
N
N
N
N
N
N
N
N
O
4
2
3
1
10bg
4
10bo
B ring
Chart 2.

1994
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
Table 2. In vitro receptor profiles of bis-piperazine compounds 10
Compound
IC50 (nM)
H1
MC4
SET
NET
a1
D2
645
Opiate l
Opiate d
( )-10bo
( )-10bs
( )-10bt
( )-10bu
( )-10bv
( )-10bw
( )-10bx
( )-10ca
( )-10cb
11.2
23.0
33.0
27.1
11.7
27.1
24.3
23.6
10.5
3130
3400
1370
1170
1460
1290
4960
2110
1340
671
2830
1850
369
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
>1000
721
206
>1000
>1000
>1000
>1000
721
1770
2400
226
290
(10bq and 10br, respectively) showed a much lower affin-
ity than the corresponding 2-Ph–Ph compound 10bo.
These results suggest that the distance between the ter-
minal benzene ring (B-ring, Chart 2) and piperazine ring
is significant in relation to the binding affinity for the
MC4 receptor, and also that the terminal benzene ring
plays an important role.
It was reported that (ꢀ)-10bg (MCL0129) exhibited a
high affinity for the MC4 receptor (IC50 = 8.13 nM),
and exhibited moderate to negligible affinities for other
stress- and anxiety/depression-related receptors and
transporters.19 The studies have shown that (ꢀ)-10bg
acts as an antagonist at the MC4 receptor, and also that
this compound exhibited anti-depressant like and anxio-
lytic-like activities in various rodent models.19 To inves-
tigate the in vitro receptor-binding profiles of the
compounds described above, several compounds with
a high affinity for the MC4 receptor were evaluated
for their affinities for the serotonin transporter (SET),
norepinephrine transporter (NET), a1-adrenoceptor
(a1), dopamine D2 receptor (D2), histamine H1 receptor
(H1), and opiate l and d receptor (Table 2). Compound
(ꢀ)-10bg did not show an affinity for the NET
(>1000 nM),19 while some biphenyl compounds exhibit-
ed a moderate affinity for this receptor (10bv and 10ca,
IC50 = 206 and 226 nM, respectively). We serendipitous-
ly obtained 10ad (MCL0042), which exhibited a relative-
ly high affinity for the MC4 receptor (IC50 = 118 nM),
showed a high affinity for the serotonin transporter
(IC50 = 42.3 nM).20 Compound 10ad, which displayed
the unique activity of both MC4 receptor antagonism
and serotonin transport inhibition, also exhibited anti-
depressant like and anxiolytic-like effects.20 None of
other tested compounds showed a significant affinity
for the receptors or transporters examined.
We then investigated the effects of chemical modification
of the substituents on the benzene ring in the biphenyl
compounds. Compounds 10bs–10bv substituted with a
fluorine atom at 3-, 4-, 5- or 6-position of the core ben-
zene ring (A-ring, Chart 2) exhibited a similar or slightly
lower affinity (IC50 = 11.7–33.0 nM) for the MC4 recep-
tor as compared to the nonsubstituted compound 10bo.
Introduction of a chlorine atom (10bw), a methyl (10bx)
or a methoxy group (10by) at 6-position of the core ben-
zene ring resulted in a slight decrease of the binding
affinity (IC50 = 15.2–27.1 nM) as compared to that of
the corresponding fluorine-substituted compound 10bv.
In the case of naphthyl compounds, introduction of a
substituent at the vicinal position (2-position, Chart 2)
resulted in an increase in the binding affinity for the
MC4 receptor as compared to that of the compound
with no substituent at this position. In contrast, for
biphenyl compounds, introduction of a substituent at
the vicinal position (6-position, Chart 2) did not increase
the binding affinity for the receptor. These results sug-
gest that the 2-Ph–Ph structure probably exhibited the
optimal conformation between the terminal benzene
ring and alkylene part without a substituent at the
vicinal position. Compound 10cb, substituted with a
fluorine atom at 4-position of terminal benzene ring
(B-ring), exhibited a similar affinity (IC50 = 10.5 nM)
to that of nonsubstituted compound 10bo, while com-
pounds 10bz or 10ca with a substituent at 2- or 3-posi-
tion exhibited a slightly lower affinity (IC50 = 36.8 and
23.6 nM, respectively) for the MC4 receptor. Com-
pounds 10cc–10cj substituted with chlorine, methyl,
methoxy, tert-butyl, phenyl, trifluoromethyl, trifluoro-
methoxy, and dimethylamino groups at 4-position of
the terminal benzene ring showed between 3.7- and 20-
fold lower affinity than nonsubstituted compound
10bo. Among these compounds, compounds which have
bulky substituents, like phenyl, at 4-position tended to
show a lower affinity for the MC4 receptor. These find-
ings suggest that the sterically acceptable space on the
benzene ring for binding to the MC4 receptor is limited.
4. Conclusion
We have reported a new series of MC4 receptor antag-
onists, namely, bis-piperazines. The lead compound
10ab was discovered by replacing of a benzoyl group
of compound 1 with a naphthyl group. Structural opti-
mization based on the SAR study led to identification
of the compound with a high affinity for the MC4
receptor, namely, (ꢀ)-10bg, which showed a 50-fold
higher affinity for the receptor than the lead com-
pound. We also identified some biphenyl compounds
which showed a high affinity for the MC4 receptor,
and in particular, compound 10bo exhibited the highest
affinity for the MC4 receptor. The various types of bis-
piperazine compounds that have been demonstrated to
show a high affinity for the MC4 receptor can be excel-
lent tools for exploring the biological and physiological
functions of the MC4 receptor, and SAR studies can

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
1995
serve as a tool to explore new types of MC4 receptor
antagonists.
thyl)butyl]piperazin-1-yl}ethanol 14 (1.25 g, 2.87 mmol)
and SOCl2 (0.450 mL, 6.19 mmol) in benzene (8 mL)
was stirred at 50 ꢁC for 3 h. The mixture was partitioned
between CHCl3 and saturated aqueous NaHCO3. The
separated organic phase was dried over Na2SO4, filtered,
and concentrated in vacuo. A mixture of the residue and
tert-butyl piperazine-1-carboxylate 7 (1.12 g, 6.03 mmol)
in benzene (10 mL) was stirred at 70 ꢁC for 3 h. The mix-
ture was partitioned between EtOAc and saturated aque-
ous NaHCO3. The separated organic phase was dried over
Na2SO4, filtered, and concentrated in vacuo. The residue
was chromatographed on Silica gel C-200 (CHCl3/MeOH
20:1) to obtain ( )-tert-butyl 4-(1-(4-fluorophenyl)-2-{4-
[4-(1-naphthyl)butyl]piperazin-1-yl}ethyl)piperazine-1-
carboxylate 15 (619 mg, 38%) as an oily product: 1H
NMR (200 MHz, CDCl3) d 1.42 (9H, s), 1.60–1.82 (4H,
m), 2.20–2.70 (15H, m), 2.85 (1H, dd, J = 6.2, 13.0 Hz),
3.07 (2H, t, J = 7.5 Hz), 3.37 (4H, t, J = 5.1 Hz), 3.60
(1H, t, J = 6.7 Hz), 7.00 (2H, t, J = 8.8 Hz), 7.14–7.56
(6H, m), 7.70 (1H, d J = 7.5 Hz), 7.79–7.90 (1H, m),
8.01–8.10 (1H, m); MS (ESI, Pos) m/z 575 (M+H)+.
5. Experimental
Melting points were determined on a Yanaco MP-500D
melting point apparatus and are uncorrected. Proton
nuclear magnetic resonance (1H NMR) spectra were ob-
tained using a Varian Gemini 2000 (200 MHz) or Varian
Unity Inova 300 (300 MHz). Chemical shifts are reported
in parts per million relative to tetramethylsilane as an
internal standard. Mass spectra (MS) were obtained on
Micromass Platform LC (IonSpray). Elemental analyses
were performed by a PerkinElmer 2400 or a Yanaco
MT-6. Silica gel C-200 (100–200 mesh, Wako Pure Chem-
ical) and Chromatorex NH (100–200 mesh, Fuji Silysia
Chemical Ltd) were used for column chromatography,
using the solvent systems (volume ratios) indicated below.
5.1. General methods for the synthesis of 10ak–10an
(method A)
5.1.4. ( )-1-[2-(4-Fluorophenyl)-2-piperazin-1-ylethyl]-4-
[4-(1-naphthyl)butyl]piperazine 4 hydrochloride (16, ( )-
10ak). To a solution of ( )-tert-butyl 4-(1-(4-fluorophe-
nyl)-2-{4-[4-(1-naphthyl)butyl]piperazin-1-yl}ethyl)piper-
azine-1-carboxylate 15 (619 mg, 1.08 mmol) in a mixture
of AcOEt (3 mL) and MeOH (3 mL) was added 4 M HCl
in AcOEt (4 mL) and the mixture was stirred at room
temperature for 6 h. The resulting precipitate was
collected by filtration and washed with AcOEt to obtain
( )-1-[2-(4-fluorophenyl)-2-piperazin-1-ylethyl]-4-[4-(1-
naphthyl)butyl]piperazine 4 hydrochloride (16) (( )-
5.1.1. 1-(4-Fluorophenyl)-2-{4-[4-(1-naphthyl)butyl]pipera-
zin-1-yl} ethanone (13). A mixture of 2-chloro-1-(4-fluoro-
phenyl)ethanone 12 (486 mg, 2.87 mmol), 1-[4-(1-
naphthyl)butyl]piperazine 2 hydrochloride 5 (980 mg,
i
2.87 mmol), and Pr2NEt (2.24 g, 17.2 mmol) in CHCl3
(10 mL) was heated at reflux for 3 h. The mixture was
partitioned between CHCl3 and saturated aqueous NaH-
CO3. The separated organic phase was dried over
Na2SO4, filtered, and concentrated in vacuo. The residue
was chromatographed on Silica gel C-200 (CHCl3/MeOH
40:1) to obtain 1-(4-fluorophenyl)-2-{4-[4-(1-naphthyl)bu-
tyl]piperazin-1-yl}ethanone 13 (1.25 g, quantitative yield)
1
10ak, 425 mg, 64%) as a crystal: mp 180–182 ꢁC; H
NMR (200 MHz, DMSO-d6) d 1.60–2.03 (4H, m),
2.38–2.75 (2H, m), 2.79–2.98 (1H, m), 3.01–4.62
(21H, m), 7.21–7.62 (8H, m), 7.69–7.83 (1H, m),
7.83–7.97 (1H, m), 8.02–8.17 (1H, m), 8.88–9.13 (3H,
m) 11.6–11.8 (1H, m); MS (ESI, Pos) m/z 475
(M+H)+; Anal. (C30H39FN4Æ4HClÆ2.5H2O) C, H, N.
1
as an oily product: H NMR (200 MHz, CDCl3) d 1.53–
1.82 (4H, m), 2.42 (2H, t, J = 8.5 Hz), 2.50–2.82 (8H, m),
3.12 (2H, t, J = 7.5 Hz), 3.79 (2H, s), 7.14 (2H, t,
J = 8.9 Hz), 7.20–7.56 (4H, m), 7.71 (1H, d, J = 7.6 Hz),
7.80–7.92 (1H, m), 7.99–8.12 (3H, m); MS (ESI, Pos)
m/z 405 (M+H)+.
5.1.5. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10an). ( )-1-[2-(4-Fluorophenyl)-2-piperazin-1-ylethyl]-4-
5.1.2. ( )-1-(4-Fluorophenyl)-2-{4-[4-(1-naphthyl)butyl]pip-
erazin-1-yl}ethanol (14). 1-(4-Fluorophenyl)-2-{4-[4-(1-
naphthyl)butyl]piperazin-1-yl}ethanone 13 (1.25 g, 2.87
mmol) was dissolved in EtOH (4 mL), and to the solution
were added NaBH4 (130 mg, 3.44 mmol) and a mixture of
H2O (1 mL) and 1 drop of 10% aqueous NaOH. After
stirring at 50 ꢁC for 1 h, the reaction mixture was parti-
tioned between CHCl3 and H2O. The separated organic
phase was dried over Na2SO4, filtered, and concentrated
in vacuo to obtain ( )-1-(4-fluorophenyl)-2-{4-[4-(1-naph-
thyl)butyl]piperazin-1-yl}ethanol 14 (1.25 g, quantitative
[4-(1-naphthyl)butyl]piperazine
4
hydrochloride 16
(200 mg, 0.308 mmol) was dissolved in DMF (0.7 mL)
and the solution was cooled in ice-bath. To the cooled
solution was added 60% NaH in oil (74.0 mg, 1.85 mmol)
and the suspension was stirred at room temperature for
10 min. After addition of 2-iodopropane (203 mg,
1.19 mmol) to the mixture, the resulting mixture was stir-
red at room temperature overnight. The mixture was par-
titioned between AcOEt and water. The separated
organic phase was washed with brine, dried over Na2SO4,
filtered, and concentrated in vacuo. The residue was chro-
matographed on Chromatorex NH (hexane/EtOAc 1:1)
to obtain ( )-1-[2-(4-fluorophenyl)-2-(4-isopropylpipera-
zin-1-yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine (130 mg,
1
yield) as a powder: H NMR (200 MHz, CDCl3) d 1.60–
1.82 (4H, m), 2.26–2.62 (10H, m), 2.66–2.82 (2H, m), 3.08
(2H, t, J = 7.5 Hz), 3.90–4.15 (1H, br s), 4.70 (1H, dd,
J = 4.4, 5.3 Hz), 7.02 (2H, t, J = 8.8 Hz), 7.20–7.55 (6H,
m), 7.73 (1H, d J = 7.7 Hz), 7.79–7.92 (1H, m), 7.98–8.10
(1H, m); MS (ESI, Pos) m/z 407 (M+H)+.
1
82%) as an oily product: H NMR (200 MHz, CDCl3)
d 1.00 (6H, d, J = 6.4 Hz), 1.52–1.88 (4H, m), 2.28–2.64
(19H, m), 2.64 (1H, dd, J = 7.0, 13.0 Hz), 2.86 (1H, dd,
J = 5.7, 13.0 Hz), 3.07 (2H, dd, J = 7.0, 8.1 Hz), 3.54
(1H, t, J = 6.4 Hz), 6.93–7.02 (2H, m), 7.07 (2H, d,
5.1.3. ( )-tert-Butyl 4-(1-(4-fluorophenyl)-2-{4-[4-(1-naph-
thyl)butyl]piperazin-1-yl}ethyl)piperazine-1-carboxylate
(15). A mixture of ( )-1-(4-fluorophenyl)-2-{4-[4-(1-naph-

1996
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
J = 7.9 Hz), 7.16–7.53 (5H, m), 7.82–7.87 (1H, m), 8.02–
8.07 (1H, m); MS (ESI, Pos) m/z 517 (M+H)+. The above
free amine was dissolved in EtOH (1.5 mL) and a solu-
tion of maleic acid (88 mg, 0.76 mmol) in EtOH (1 mL)
was added. After stirred for 2 h, precipitated crystal
was collected by filtration to obtain ( )-1-[2-(4-fluorophe-
nyl)-2-(4-isopropylpiperazin-1-yl)ethyl]-4-[4-(1-naphthyl)bu-
tyl]piperazine 3 maleate ( )-10an (182 mg, 68%) as a
crystal: mp 127–129 ꢁC (EtOH); 1H NMR (200 MHz,
DMSO-d6) d 1.19 (6H, d, J = 6.6 Hz), 1.60–1.78 (4H, m),
2.58–3.53 (23H, m), 3.90–4.02 (1H, m), 6.13 (6H, s), 7.23
(2H, t, J = 7.5 Hz), 7.32–7.61 (6H, m), 7.80 (1H, d,
J = 7.5 Hz), 7.91–7.96 (1H, m), 8.06–8.10 (1H, m); MS
(ESI, Pos) m/z 517 (M+H)+; Anal. (C33H45FN4Æ3C4H4O4Æ
0.5H2O) C, H, N.
1.66 (4H, m), 2.24 (3H, s), 2.24–2.60 (18H, m), 2.62 (1H,
dd, J = 7.0, 12.9 Hz), 2.85 (1H, dd, J = 5.9, 12.9 Hz),
2.99–3.13 (2H, m), 3.55 (1H, dd, J = 5.9, 7.0 Hz), 3.90
(3H, s), 6.94–7.02 (2H, m), 7.18–7.36 (4H, m), 7.41–7.50
(1H, m), 7.69–7.80 (2H, m), 7.95 (1H, d, J = 8.4 Hz); MS
(ESI, Pos) m/z 519 (M+H)+. The above free amine
(370 mg, 0.713 mmol) was dissolved in EtOH (3.7 mL),
and to the solution was added a solution of maleic acid
(248 mg, 2.14 mmol) in EtOH (2.5 mL). After stirred at
room temperature for 1 h, the resulting precipitate was
collected by filtration to obtain ( )-1-(1-(4-fluorophenyl)-
2-{4-[4-(2-methoxy-1-naphthyl)butyl]piperazin-1-yl}ethyl)-
4-methylpiperazine 3 maleate ( )-10bc (480 mg, 78%) as a
crystal: mp 173–175 ꢁC; 1H NMR (200 MHz, DMSO-d6) d
1.48–1.76 (4H, m), 2.73 (3H, s), 2.63–3.51 (22H, m), 3.91
(3H, s), 3.87–3.95 (1H, m), 6.11 (6H, s), 7.21 (2H, t,
J = 8.9 Hz), 7.28–7.58 (4H, m), 7.85–7.89 (3H, m), 7.95
(1H, d, J = 8.6 Hz); MS (ESI, Pos) m/z 519 (M+H)+; Anal.
(C32H43FN4OÆ3C4H4O4Æ0.5H2O) C, H, N.
Compounds ( )-10al and ( )-10am were prepared by
using methods of Sections 5.1.1–5.1.5.
5.1.6. ( )-1-Ethyl-4-(1-(4-fluorophenyl)-2-{4-[4-(1-naph-
thyl)butyl]piperazin-1-yl}ethyl)piperazine 3 maleate (( )-
10al). Compound ( )-10al was obtained as a crystal. Mp
120–122 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
1.18 (3H, t, J = 7.3 Hz), 1.58–1.80 (4H, m), 2.60–3.70
(24H, m), 3.88–4.01 (1H, m), 6.11 (6H, s), 7.22 (2H, d,
J = 8.8 Hz), 7.25–7.61 (6H, m), 7.80 (1H, d,
J = 7.7 Hz), 7.88– 7.98 (1H, m), 8.01– 8.07 (1H, m);
MS (ESI, Pos) m/z 503 (M+H)+; Anal. (C32H43FN4Æ
3C4H4O4Æ1.0H2O) C, H, N.
5.2.2. ( )-1-Cyclopropyl-4-(1-(4-fluorophenyl)-2-{4-[4-(1-
naphthyl)butyl]piperazin-1-yl}ethyl)piperazine 3 maleate
(( )-10ao). Compound ( )-10ao was obtained as a crys-
tal. Mp 161–163 ꢁC (EtOH); 1H NMR (200 MHz,
DMSO-d6) d 0.55–0.72 (4H, m), 1.52–1.79 (4H, m),
2.50–3.55 (23H, m), 4.03–4.21 (1H, m), 6.13 (6H, s),
7.24 (2H, t, J = 8.8 Hz), 7.32–7.61 (6H, m), 7.79 (1H,
d, J = 7.3 Hz), 7.88–7.99 (1H, m), 8.02–8.16 (1H, m);
MS (ESI, Pos) m/z 515 (M+H)+; Anal. (C33H43FN4Æ-
3C4H4O4Æ0.1H2O) C, H, N.
1
5.1.7. ( )-1-(1-(4-Fluorophenyl)-2-{4-[4-(1-naphthyl)bu-
tyl]piperazin-1-yl}ethyl)-4-propylpiperazine 3 maleate (( )-
10am). Compound ( )-10am was obtained as a crystal.
Mp 150–152 ꢁC (EtOH); H NMR (200 MHz, DMSO-
d6) d 0.88 (3H, t, J = 7.5 Hz), 1.45–1.82 (6H, m), 2.55–
3.50 (24H, m), 3.83–4.01 (1H, m), 6.11 (6H, s), 7.22
(2H, d, J = 8.9 Hz), 7.27–7.62 (6H, m), 7.80 (1H, d,
J = 7.5 Hz), 7.91–7.99 (1H, m), 8.02–8.09 (1H, m); MS
(ESI, Pos) m/z 517 (M+H)+; Anal. (C33H45FN4Æ3C4H4-
O4Æ0.7H2O) C, H, N.
5.2.3. ( )-1-Cyclohexyl-4-(1-(4-fluorophenyl)-2-{4-[4-(1-
naphthyl)butyl]piperazin-1-yl}ethyl)piperazine 3 maleate
(( )-10ap). Compound ( )-10ap was obtained as a crys-
tal. Mp 171–173 ꢁC (EtOH); 1H NMR (200 MHz,
DMSO-d6) d 0.96–1.41 (4H, m), 1.50–1.82 (6H, m),
1.84–2.10 (4H, m), 2.55–3.50 (19H, m), 3.90–4.02 (1H,
m), 6.11 (6H, s), 7.22 (2H, d, J = 8.9 Hz), 7.28–7.61
(6H, m), 7.80 (1H, d, J = 8.1 Hz), 7.89–7.99 (1H, m),
8.03–8.13 (1H, m); MS (ESI, Pos) m/z 557 (M+H)+;
Anal. (C36H49FN4Æ3C4H4O4Æ0.5H2O) C, H, N.
1
5.2. General methods for the synthesis of 10ao–10bd and
10bk–10bm (method B)
5.2.4. ( )-1-(1-(4-Fluorophenyl)-2-{4-[4-(1-naphthyl)butyl]-
piperazin-1-yl}ethyl)-4-phenylpiperazine 2 maleate (( )-
10aq). Compound ( )-10aq was obtained as a crystal.
Mp 172–174 ꢁC (EtOH/Et2O); 1H NMR (200 MHz,
DMSO-d6) d 1.55–1.80 (4H, m), 2.55–3.60 (22H, m),
4.08–4.30 (1H, m), 6.11 (4H, s), 6.88 (1H, t, J = 7.1 Hz),
6.90 (2H, d, J = 7.9 Hz), 7.12–7.36 (3H, m), 7.38–7.63
(7H, m), 7.80 (1H, d, J = 7.7 Hz), 7.88–7.99 (1H, m),
8.02–8.16 (1H, m); MS (ESI, Pos) m/z 551 (M+H)+;
Anal. (C36H43FN4Æ2C4H4O4Æ0.5H2O) C, H, N.
5.2.1. ( )-1-(1-(4-Fluorophenyl)-2-{4-[4-(2-methoxy-1-naph-
thyl)butyl]piperazin-1-yl}ethyl)-4-methylpiperazine 3 male-
ate (( )-10bc). ( )-1-(4-Fluorophenyl)-2-{4-[4-(2-methoxy-
1-naphthyl)butyl]piperazin-1-yl}ethanol 14 (2.00 g, 4.60
mmol) was dissolved in CH2Cl2 (20 mL), and to the cooled
solution in ice-bath were added Et3N (1.28 mL, 9.20
mmol) and MsCl (0.710 mL, 9.20 mmol). After stirring
at the same temperature for 30 min, to the mixture were
added Et3N (0.640 mL, 4.60 mmol) and 1-methylpiper-
azine 6 (1.02 mL, 9.20 mmol), and the mixture was stirred
at room temperature for 3 h. The mixture was partitioned
between CH2Cl2 and saturated aqueous NaHCO3. The
separated organic phase was dried over Na2SO4, filtered,
and concentrated in vacuo. The residue was chromato-
graphed on Chromatorex NH (hexane/EtOAc 4:1) to obtain
( )-1-(1-(4-fluorophenyl)-2-{4-[4-(2-methoxy-1-naphthyl)-
butyl]piperazin-1-yl}ethyl)-4-methylpiperazine (2.30 g, 96%)
5.2.5. ( )-1-Methyl-4-(2-{4-[4-(1-naphthyl)butyl]pipera-
zin-1-yl}-1-phenylethyl)piperazine 3 maleate (( )-10ar).
Compound ( )-10ar was obtained as a crystal. Mp 167–
169 ꢁC (EtOH); 1H NMR (200 MHz, DMSO-d6) d
1.58–1.80 (4H, m), 2.60–3.80 (22H, m), 2.74 (3H, s),
3.91–3.99 (1H, m), 6.10 (6H, s), 7.22–7.60 (9H, m), 7.78
(1H, d, J = 7.7 Hz), 7.88–7.98 (1H, m), 8.02–8.11 (1H,
m); MS (ESI, Pos) m/z 471 (M+H)+; Anal. (C31H42N4Æ-
3C4H4O4) C, H, N.
1
as an oily product: H NMR (300 MHz, CDCl3) d 1.49–

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
1997
5.2.6. ( )-1-[2-(3-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10as). Compound ( )-10as was obtained as a crystal. Mp
173–175 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
1.60–1.78 (4H, m), 2.65–3.47 (22H, m), 2.73 (3H, s),
3.92–3.99 (1H, m), 6.11 (6H, s), 7.04–7.22 (3H, m),
7.35–7.61 (5H, m), 7.79 (1H, d, J = 8.6 Hz), 7.88–7.99
(1H, m), 8.01–8.13 (1H, m); MS (ESI, Pos) m/z 489
(M+H)+; Anal. (C31H41FN4Æ3C4H4O4) C, H, N.
5.2.12. ( )-1-[2-(4-Methoxyphenyl)-2-(4-methylpiperazin-
1-yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine maleate
3
(( )-10ay). Compound ( )-10ay was obtained as a crys-
tal. Mp 138–140 ꢁC (EtOH); 1H NMR (200 MHz,
DMSO-d6) d 1.59–1.78 (4H, m), 2.60–3.50 (22H, m),
2.72 (3H, s), 3.75 (3H, s), 3.80–3.95 (1H, m), 6.11 (6H,
s), 6.93 (2H, d, J = 8.8 Hz), 7.20 (2H, d, J = 8.6 Hz),
7.36–7.61 (4H, m), 7.79 (2H, d, J = 7.7 Hz), 7.91–7.98
(1H, m), 8.03–8.11 (1H, m); MS (ESI, Pos) m/z 501
(M+H)+; Anal. (C32H44N4OÆ3C4H4O4Æ1.0H2O) C, H, N.
1
5.2.7. ( )-1-[2-(4-Chlorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10at). Compound ( )-10at was obtained as a crystal. Mp
175–177 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
1.60–1.79 (4H, m), 2.62–3.44 (22H, m), 2.74 (3H, s),
3.91–3.97 (1H, m), 6.10 (6H, s), 7.28–7.59 (8H, m), 7.79
(1H, d, J = 7.3 Hz), 7.87–7.98 (1H, m), 8.02–8.11 (1H,
m); MS (ESI, Pos) m/z 505 (M+H)+; Anal.
(C31H41ClN4Æ3C4H4O4Æ1.0H2O) C, H, N.
5.2.13. ( )-1-Methyl-4-{2-{4-[4-(1-naphthyl)butyl]pipera-
zin-1-yl}-1-[4-(trifluoromethyl)phenyl]ethyl}piperazine
3
1
maleate (( )-10az). Compound ( )-10az was obtained
as a crystal. Mp 128–130 ꢁC (EtOH); 1H NMR
(200 MHz, DMSO-d6) d 1.60–1.80 (4H, m), 2.74 (3H, s),
2.60–3.55 (22H, m), 3.96–4.06 (1H, m), 6.12 (6H, s),
7.33–7.59 (6H, m), 7.70–7.83 (3H, m), 7.88–7.96 (1H,
m), 8.02–8.11 (1H, m); MS (ESI, Pos) m/z 539 (M+H)+;
Anal. (C32H41F3N4Æ3C4H4O4Æ1.0H2O) C, H, N.
5.2.8. ( )-1-[2-(2-Bromophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10au). Compound ( )-10au was obtained as an amor-
phous. 1H NMR (200 MHz, DMSO-d6) d 1.58–1.78
(4H, m), 2.40–3.65 (22H, m), 2.77 (3H, s), 4.05–4.24
(1H, m), 6.05 (6H, s), 7.19–7.30 (1H, m), 7.36–7.58 (6H,
m), 7.63 (1H, d, J = 8.0 Hz), 7.78 (1H, d, J = 7.5 Hz),
7.88–7.98 (1H, m), 8.02–8.12 (1H, m); MS (ESI, Pos)
m/z 549 (M+H)+, 551 (M++2+H)+; Anal. (C31H41BrN4Æ
3C4H4O4Æ1.0H2O) C, H, N.
5.2.14. ( )-1-Methyl-4-[2-{4-[4-(1-naphthyl)butyl]pipera-
zin-1-yl}-1-(4-nitrophenyl)ethyl]piperazine 3 maleate (( )-
10ba). Compound ( )-10ba was obtained as a crystal.
Mp 176–178 ꢁC (EtOH); H NMR (200 MHz, DMSO-
d6) d 1.62–1.76 (4H, m), 2.77 (3H, s), 2.60–3.65 (22H,
m), 3.97–4.07 (1H, m), 6.10 (6H, s), 7.34–7.63 (6H, m),
7.78 (1H, d, J = 7.7 Hz), 7.89–7.96 (1H, m), 8.03–8.11
(1H, m), 8.24 (2H, d, J = 8.8 Hz); MS (ESI, Pos) m/z
516 (M+H)+; Anal. (C31H41N5O2Æ3C4H4O4) C, H, N.
1
5.2.9. ( )-1-[2-(3-Bromophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10av). Compound ( )-10av was obtained as a crystal.
Mp 119–121 ꢁC (EtOH); H NMR (200 MHz, DMSO-
d6) d 1.59–1.79 (4H, m), 2.60–3.60 (22H, m), 2.74 (3H,
s), 3.93–4.00 (1H, m), 6.12 (6H, s), 7.23–7.61 (8H, m),
7.78 (1H, d, J = 7.7 Hz), 7.85–7.98 (1H, m), 8.02–8.14
(1H, m); MS (ESI, Pos) m/z 549 (M+H)+, 551
(M++2+H); Anal. (C31H41BrN4Æ3C4H4O4Æ1.0H2O) C,
H, N.
5.2.15. ( )-4-(1-(4-Methylpiperazin-1-yl)-2-{4-[4-(1-naph-
thyl)butyl]piperazin-1-yl}ethyl)aniline 3 maleate (( )-10bd).
A suspension of ( )-1-methyl-4-[2-{4-[4-(1-naphthyl)bu-
tyl]piperazin-1-yl}-1-(4-nitrophenyl)ethyl]piperazine (free
of ( )-10ba) (331 mg, 0.540 mmol) and PtO2 (10 mg) in
EtOH (20 mL) was stirred under a hydrogen atmosphere
for 2 h. The mixture was filtered through Celite and the fil-
trate was concentrated in vacuo. The residue was dissolved
in EtOH (2 mL), and to the solution was added a solution
of maleic acid (187 mg, 1.51 mmol) in EtOH (1 mL). After
stirred for at room temperature 1 h, the resulting precipi-
tate was collected by filtration to obtain ( )-4-(1-(4-meth-
ylpiperazin-1-yl)-2-{4-[4-(1-naphthyl)butyl]piperazin-1-yl}eth-
yl)aniline 3 maleate ( )-10bd (350 mg, 78% yield) as a
crystal: mp 152–154 ꢁC (EtOH); 1H NMR (200 MHz,
CDCl3) d 1.50–1.80 (4H, m), 2.30–3.20 (27H, m), 3.56–
3.63 (1H, m), 6.01 (6H, s), 6.35–6.60 (2H, m), 6.63 (1H,
s), 6.90–7.05 (1H, m), 7.25–7.60 (4H, m), 7.65–7.81 (1H,
m), 7.83–7.98 (1H, m), 8.00–8.15 (1H, m); MS (ESI, Pos)
m/z 486 (M+H)+; Anal. (C31H43N5Æ3C4H4O4Æ0.5H2O) C,
H, N.
1
5.2.10. ( )-1-[2-(4-Bromophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10aw). Compound ( )-10aw was obtained as a crystal.
1
Mp 168–170 ꢁC (EtOH); H NMR (200 MHz, DMSO-
d6) d 1.59–1.80 (4H, m), 2.55–3.70 (22H, m), 2.73 (3H,
s), 3.91–3.98 (1H, m), 6.12 (6H, s), 7.25 (2H, d,
J = 8.6 Hz), 7.36–7.63 (6H, m), 7.78 (1H, d,
J = 7.7 Hz), 7.89–7.99 (1H, m), 8.01–8.12 (1H, m); MS
(ESI, Pos) m/z 549 (M+H)+, 551 (M++2+H)+; Anal.
(C31H41BrN4Æ3C4H4O4Æ1.0H2O) C, H, N.
5.2.11. ( )-1-Methyl-4-(1-(4-methylphenyl)-2-{4-[4-(1-naph-
thyl)butyl]piperazin-1-yl}ethyl)piperazine 3 maleate (( )-
10ax). Compound ( )-10ax was obtained as a crystal.
Mp 186–188 ꢁC (EtOH); H NMR (200 MHz, DMSO-
5.2.16. ( )-1-[2-Biphenyl-4-yl-2-(4-methylpiperazin-1-yl)eth-
yl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-10bb).
Compound ( )-10bb was obtained as a crystal. Mp
123–125 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
1
1
d6) d 1.58–1.78 (4H, m), 2.30 (3H, s), 2.60–3.50 (22H,
m), 2.75 (3H, s), 3.89–3.93 (1H, m), 6.10 (6H, s), 7.10–
7.23 (4H, m), 7.36–7.60 (4H, m), 7.78 (1H, d,
J = 7.9 Hz), 7.89–7.99 (1H, m), 8.03–8.11 (1H, m); MS
(ESI, Pos) m/z 485 (M+H)+; Anal. (C32H44N4Æ3C4H4O4)
C, H, N.
1.58–1.81 (4H, m), 2.60–3.70 (22H, m), 2.73 (3H, s),
3.90–4.03 (1H, m), 6.11 (6H, s), 7.30–7.60 (8H, m),
7.61–7.77 (5H, m), 7.78 (1H, d, J = 8.4 Hz), 7.88–7.99
(1H, m), 8.01–8.13 (1H, m); MS (ESI, Pos) m/z
547 (M+H)+; Anal. (C37H46N4Æ3C4H4O4Æ1.1H2O)
C, H, N.

1998
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
5.2.17. ( )-1-(1-Ethylpropyl)-4-(1-(4-fluorophenyl)-2-{4-[4-
(2-methoxy-1-naphthyl)butyl]piperazin-1-yl}ethyl)pipera-
zine 3 maleate (( )-10bk). Compound ( )-10bk was
obtained as a crystal. Mp 141–143 ꢁC (EtOH); H NMR
(200 MHz, DMSO-d6) d 0.90 (6H, t, J = 7.3 Hz), 1.40–
1.80 (8H, m), 2.80–3.40 (23H, m), 3.92 (3H, s), 3.95–
4.05 (1H, m), 6.12 (6H, s), 7.22 (2H, d, J = 8.8 Hz),
7.29–7.54 (5H, m), 7.80–7.88 (2H, m), 7.96 (1H, d,
J = 8.6 Hz); MS (ESI, Pos) m/z 575 (M+H)+; Anal.
(C36H51FN4OÆ3C4H4O4Æ0.5H2O) C, H, N.
5.3.2. ( )-Ethyl 4-[2-(4-fluorophenyl)-2-(4-isopropylpipera-
zin-1-yl)ethyl]piperazine-1-carboxylate (19). A mixture of
( )-ethyl
4-[2-(4-fluorophenyl)-2-hydroxyethyl]pipera-
1
zine-1-carboxylate hydrochloride 18 (10.0 g, 30.1 mmol)
and SOCl2 (3.30 mL, 45.2 mmol) in benzene (30 mL)
was stirred at 50 ꢁC for 10 min and concentrated in vac-
uo. The residue was partitioned between AcOEt and 5%
aqueous NH3. The separated organic phase was washed
with brine, dried over Na2SO4, filtered, and concentrated
in vacuo to obtain crude ( )-ethyl 4-[2-chloro-2-(4-fluor-
ophenyl)ethyl]piperazine-1-carboxylate. A mixture of the
above crude product, 1-isopropylpiperazine 2 hydrochlo-
ride (12.1 g, 60.2 mmol), and iPr2NEt (21.3 mL,
120 mmol) in benzene (50 mL) was stirred at 60 ꢁC for
6 h. The mixture was partitioned between Et2O and satu-
rated aqueous NaHCO3. The separated organic phase
was washed with brine, dried over Na2SO4, filtered, and
concentrated in vacuo. The residue was chromato-
graphed on Chromatorex NH (hexane/EtOAc 4:1) to
obtain ( )-ethyl 4-[2-(4-fluorophenyl)-2-(4-isopropylpi-
perazin-1-yl)ethyl]piperazine-1-carboxylate 19 (9.60 g,
5.2.18. ( )-1-Cyclopentyl-4-(1-(4-fluorophenyl)-2-{4-[4-(2-
methoxy-1-naphthyl)butyl]piperazin-1-yl}ethyl)piperazine
3 maleate (( )-10bl). Compound ( )-10bl was obtained
as a crystal. Mp 163–164 ꢁC (EtOH); 1H NMR
(200 MHz, DMSO-d6) d 1.40–1.80 (10H, m), 1.90–2.10
(2H, m), 2.60–3.60 (23H, m), 3.92 (3H, s), 3.95–4.01
(1H, m), 6.22 (6H, s), 7.22 (2H, t, J = 8.9 Hz), 7.30–
7.54 (5H, m), 7.80–7.88 (2H, m), 7.96 (1H, d,
J = 8.4 Hz); MS (ESI, Pos) m/z 573 (M+H)+; Anal.
(C36H49FN4OÆ3C4H4O4Æ0.5H2O) C, H, N.
1
78%) as an oily product: H NMR (300 MHz, CDCl3)
5.2.19. ( )-1-tert-Butyl-4-(1-(4-fluorophenyl)-2-{4-[4-(2-
methoxy-1-naphthyl)butyl]piperazin-1-yl}ethyl)piperazine
3 maleate (( )-10bm). Compound ( )-10bm was obtained
as a crystal. Mp 116–118 ꢁC (EtOH); 1H NMR
(300 MHz, DMSO-d6) d 1.27 (9H, s), 1.49–1.62 (2H, m),
1.63–1.79 (2H, m), 2.80–3.30 (19H, m), 3.33–3.49 (3H,
m), 3.92 (3H, s), 3.98–4.06 (1H, m), 6.16 (6H, s), 7.24
(2H, t, J = 9.0 Hz), 7.31–7.56 (5H, m), 7.83 (2H, m), 7.96
(1H, d, J = 8.9 Hz); MS (ESI, Pos) m/z 547 (M+H)+; Anal.
(C35H49FN4OÆ3C4H4O4Æ1.5H2O) C, H, N.
d 1.01 (6H, d, J = 6.5 Hz), 1.22 (3H, t, J = 7.0 Hz),
2.25–2.89 (14H, m), 3.29–3.43 (5H, m), 3.50–3.58 (1H,
m), 4.02–4.13 (2H, m), 6.89–7.01 (2H, m), 7.12–7.21
(2H, m); MS (ESI, Pos) m/z 407 (M+H)+.
5.3.3. ( )-1-[1-(4-Fluorophenyl)-2-piperazin-1-ylethyl]-4-
isopropylpiperazine (20). A mixture of ( )-ethyl 4-[2-(4-
fluorophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piper-
azine-1-carboxylate 19 (2.00 g, 4.92 mmol) and KOH
(2.00 g) in EtOH (4 mL) was stirred at reflux for 1 h.
The mixture was partitioned between EtOAc and water,
and separated organic phase was washed with brine. The
organic phase was dried over Na2SO4, filtered, and
concentrated in vacuo to obtain crude ( )-1-[1-(4-fluoro-
phenyl)-2-piperazin-1-ylethyl]-4-isopropylpiperazine 20
5.3. General methods for the synthesis of 10be (method C)
5.3.1. ( )-Ethyl 4-[2-(4-fluorophenyl)-2-hydroxyethyl]pi-
perazine-1-carboxylate hydrochloride (18). A solution
of 2-chloro-1-(4-fluorophenyl)ethanone 12 (8.63 g,
50.0 mmol), ethyl piperazine-1-carboxylate 8 (16.0 g,
101 mmol) in CHCl3 (60 mL) was heated at reflux for
3 h. The mixture was concentrated in vacuo, and the res-
idue was partitioned between Et2O and 25% aqueous
NH3. The separated organic phase was dried over
Na2SO4, filtered, and concentrated in vacuo to obtain
crude ( )-ethyl 4-[2-(4-fluorophenyl)-2-oxoethyl]pipera-
zine-1-carboxylate 17. The crude 17 was dissolved in
EtOH (80 mL), and to the solution were added NaBH4
(2.00 g, 52.6 mmol) and a mixture of H2O (10 mL) and
one drop of 5% aqueous KOH. After stirring the mixture
at 50 ꢁC for 1 h, the resulting mixture was concentrated in
vacuo. The residue was partitioned between Et2O and
25% aqueous NH3. The separated organic phase was
dried over Na2SO4, filtered, and concentrated in vacuo.
To the residue was added 4 M HCl in AcOEt (30 mL),
the mixture wasconcentrated in vacuo. The resulting solid
was collected by filtration with washed with Et2O to ob-
tain crude ( )-ethyl 4-[2-(4-fluorophenyl)-2-hydroxyeth-
yl]piperazine-1-carboxylate hydrochloride 18 (18.0 g,
1
(1.39 g, 85%) as an oily product: H NMR (300 MHz,
CDCl3) d 1.01 (6H, d, J = 6.5 Hz), 1.22 (3H, t,
J = 7.0 Hz), 2.25–2.89 (14H, m), 3.29–3.43 (5H, m),
3.50–3.58 (1H, m), 4.02–4.13 (2H, m), 6.89–7.01 (2H,
m), 7.12–7.21 (2H, m); MS (ESI, Pos) m/z 335 (M+H)+.
This product was used in the next step without further
purification.
5.3.4. ( )-1-[4-(2-Bromo-1-naphthyl)butyl]-4-[2-(4-fluoro-
phenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine
3
maleate (( )-10be). A mixture of a crude ( )-1-[1-(4-flu-
orophenyl)-2-piperazin-1-ylethyl]-4-isopropylpiperazine
20 (0.39 g, 1.17 mmol), 2-bromo-1-(4-bromobutyl)naph-
thalene 9b (0.56 g, 1.64 mmol), and Et3N (0.48 mL,
3.47 mmol) in DMF (5 mL) was heated at 60 ꢁC for
5 h. The mixture was partitioned between EtOAc and
saturated aqueous NaHCO3, and separated organic
phase was washed with brine. The organic phase was
dried over Na2SO4, filtered, and concentrated in vacuo.
The residue was chromatographed on Chromatorex NH
(hexane/EtOAc 9:1) to obtain ( )-1-[4-(2-bromo-1-
naphthyl)butyl]-4-[2-(4-fluorophenyl)-2-(4-isopropylpi-
perazin-1-yl)ethyl]piperazine (0.14 g, 20%) as an oily
1
quantitative yield): H NMR (300 MHz, DMSO-d6) d
1.20 (3H, t, J = 7.0 Hz), 3.00–3.68 (8H, m), 3.90–4.11
(5H, m), 5.17–5.27 (1H, m), 7.22 (2H, t, J = 8.9 Hz),
7.42–7.51 (2H, m), 9.45–9.60 (1H, m), 10.70–10.85 (1H,
m); MS (ESI, Pos) m/z 297 (M+H)+.
1
product: H NMR (300 MHz, CDCl3) d 1.02 (6H, d,
J = 6.5 Hz), 1.60–1.73 (4H, m), 2.30–2.61 (20H, m),
2.62 (1H, dd, J = 7.0, 13.0 Hz), 2.85 (1H, dd, J = 5.7,

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
1999
13.0 Hz), 3.18–3.29 (1H, m), 3.53 (1H, t, J = 6.4 Hz),
6.99 (2H, t, J = 8.5 Hz), 7.18–7.23 (2H, m), 7.43–7.62
(4H, m), 7.80 (1H, d, J = 8.0 Hz), 8.06 (2H, d,
J = 8.9 Hz); MS (ESI, Pos) m/z 595 (M+H)+, 597
(M+2+H)+, 617 (M+Na)+, 619 (M+2+Na)+. The
above free base (0.14 g, 0.24 mmol) was dissolved in
EtOH (2.0 mL), and to the solution was added a solu-
tion of maleic acid (82 mg, 0.71 mmol) in EtOH
(1.0 mL). After stirred at room temperature for 1 h,
the resulting precipitate was collected by filtration to
obtain ( )-1-[4-(2-bromo-1-naphthyl)butyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine
3 maleate ( )-10be (0.16 g, 72%) as a crystal: mp 147–
2-(4-isopropylpiperazin-1-yl)ethyl]-4-[4-(2-methoxy-1-
naphthyl)butyl]piperazine (0.47 g, 90%) as an oily prod-
uct: 1H NMR (300 MHz, CDCl3) d 1.01 (6H, d,
J = 6.5 Hz), 1.56–1.83 (5H, m), 2.25–3.70 (17H, m),
2.62 (1H, dd, J = 7.0, 13.0 Hz), 2.83 (1H, dd, J = 5.7,
13.0 Hz), 3.01–3.13 (2H, m), 3.55 (2H, t, J = 8.0 Hz),
3.94 (3H, s), 6.98 (2H, t, J = 8.0 Hz), 7.18–7.37 (4H, m),
7.42 (1H, t, J = 8.0 Hz), 7.69–7.80 (2H, m), 7.93 (1H, d,
J = 8.0 Hz); MS (ESI, Pos) m/z 547 (M+H)+. The above
free base (0.45 g, 0.82 mmol) was dissolved in EtOH
(3 mL), and to the solution was added a solution of maleic
acid (0.29 g, 2.5 mmol) in EtOH (3 mL). After stirred at
room temperature for 1 h, the resulting precipitate was
collected by filtration to obtain ( )-1-[2-(4-fluorophe-
nyl)-2-(4-isopropylpiperazin-1-yl)ethyl]-4-[4-(2-meth-
oxy-1-naphthyl)butyl]piperazine 3 maleate ( )-10bg
(0.49 g, 67%) as a crystal: mp 154–156 ꢁC (EtOH); 1H
1
150 ꢁC; H NMR (300 MHz, DMSO-d6) d 1.20 (6H, d,
J = 6.6 Hz), 1.55–1.70 (2H, m), 1.75–1.85 (2H, m),
2.90–3.50 (23H, m), 3.98–4.06 (1H, m), 6.16 (6H, s),
7.23 (2H, d, J = 8.8 Hz), 7.28–7.42 (2H, m), 7.55–7.80
(4H, m), 7.94– 8.02 (1H, m), 8.08–8.20 (1H, m); MS
(ESI, Pos) m/z 595 (M+H)+, 597 (M+2+H)+; Anal.
(C33H46N4OBrFÆ3C4H4O4Æ2.5H2O) C, H, N.
NMR (200 MHz, DMSO-d6)
d
1.20 (6H, d,
J = 6.6 Hz), 1.50–1.80 (4H, m), 2.80–3.50 (23H, m),
3.91 (3H, s), 3.90–4.02 (1H, m), 6.10 (6H, s), 7.22
(2H, t, J = 8.9 Hz), 7.30–7.53 (5H, m), 7.79–7.98 (3H,
m); MS (ESI, Pos) m/z 547 (M+H)+; Anal. (C34H47-
FN4OÆ3C4H4O4Æ0.5H2O) C, H, N.
5.4. General methods for the synthesis of 10aa–10aj,
10bf–10bj, and 10bn–10cj (method D)
5.4.1. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-1-
yl)ethyl]-4-[4-(2-methoxy-1-naphthyl)butanoyl]piperazine
(21). To a mixture of a crude ( )-1-[1-(4-fluorophenyl)-
2-piperazin-1-ylethyl]-4-isopropylpiperazine 20 (0.74 g,
2.2 mmol), 4-(2-methoxy-1-naphthyl)butanoic acid
(0.59 g, 2.4 mmol), and HOBtÆH2O (0.51 g, 3.3 mmol)
in DMF (10 mL) was added EDCÆHCl (0.63 g,
3.3 mmol) and the mixture was stirred at room temper-
ature overnight. The mixture was partitioned between
EtOAc and saturated aqueous NaHCO3, and separated
organic phase was washed with brine. The organic
phase was dried over Na2SO4, filtered, and concentrated
in vacuo. The residue was chromatographed on Silica
gel C-200 (CHCl3/MeOH 10:1) to obtain ( )-1-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]-4-[4-(2-
methoxy-1-naphthyl)butanoyl]piperazine 21 (0.61 g,
49%) as an oily product: 1H NMR (300 MHz,
CDCl3) d 1.02 (6H, d, J = 6.5 Hz), 1.65–1.99 (6H, m),
2.22–2.59 (11H, m), 2.62 (1H, dd, J = 7.0, 13.0 Hz),
2.82 (1H, dd, J = 5.7, 13.0 Hz), 3.12 (2H, t,
J = 8.0 Hz), 3.21–3.27 (2H, m), 3.41–3.58 (3H, m),
3.92 (3H, s), 6.89–7.01 (2H, m), 7.10–7.21 (2H, m),
7.24–7.35 (2H, m), 7.40–7.49 (1H, m), 7.70–7.79 (2H,
m), 8.01 (1H, d, J = 9.0 Hz); MS (ESI, Pos) m/z 361
(M+H)+.
Each enantiomer was obtained from free base of ( )-
10bg by using HPLC for optical resolution [Chiralpak
AD (Daicel Chemical Industries, Ltd), 2.0 · 25 cm, mo-
bile phase: hexane/2-propanol/diethylamine = 98:2:0.1,
flow rate: 5.0 mL/min]. Compound 10bg detected at a
shorter retention time (0.21 g, 0.38 mmol) was dis-
solved in EtOH (4 mL), treated with 4 M HCl in
AcOEt (1 mL) at room temperature, and the mixture
was concentrated in vacuo. The residue was crystallized
in EtOAc, and the precipitate was collected by filtra-
tion to obtain (ꢀ)-1-[2-(4-fluorophenyl)-2-(4-isopro-
pylpiperazin-1-yl)ethyl]-4-[4-(2-methoxy-1-naphthyl)bu-
tyl]piperazine 4 hydrochloride (ꢀ)-10bg (0.15 g, 60%)
26
D
as
a
crystal: ½aꢁ
ꢀ13.1 (c 0.24, MeOH), mp
1
183–185 ꢁC (EtOAc); H NMR (200 MHz, DMSO-d6)
d 1.23 (6H, d, J = 6.6 Hz), 1.48–1.70 (2H, m), 1.76–
2.00 (2H, m), 2.10–2.28 (1H, m), 2.53–2.77 (1H, m),
2.90–3.81 (23H, m), 3.94 (3H, s), 3.98–4.62 (8H, m),
7.20–7.55 (7H, m), 7.77–8.02 (3H, m); MS (ESI, Pos)
m/z 547 (M+H)+; Anal. (C34H47FN4OÆ4HClÆ1.0H2O)
C, H, N. Compound 10bg detected at a longer reten-
26
D
tion time gave (+)-10bg as a crystal. ½aꢁ +12.1 (c
0.20, MeOH), mp 183–185 ꢁC (EtOAc); m/z 547
(M+H)+; Anal. (C34H47FN4OÆ4HClÆ1.0H2O) C, H, N.
1H NMR was corresponding to that of (ꢀ)-10bg.
5.4.2. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-[4-(2-methoxy-1-naphthyl)butyl]piperazine 3
maleate (( )-10bg). A mixture of ( )-1-[2-(4-fluorophe-
nyl)-2-(4-isopropylpiperazin-1-yl)ethyl]-4-[4- (2-methoxy-
1-naphthyl)butanoyl]piperazine 21 (0.53 g, 0.95 mmol)
and LiAlH4 (72 mg, 1.9 mmol) in THF (10 mL) was stir-
red at reflux for 1 h. To the mixture were added drop-
wise H2O (2.0 mL) and 1 M NaOH aqueous (8.0 mL)
at room temperature, and the mixture was extracted
with Et2O. The organic phase was washed with brine,
dried over Na2SO4, filtered, and concentrated in vacuo.
The residue was chromatographed on Chromatorex NH
(hexane/EtOAc 1:2) to obtain ( )-1-[2-(4-fluorophenyl)-
Compounds 10aa–10aj, 10bf, 10bh–10bj, and 10bn–10cj
were prepared by using methods of Sections 5.4.1 and
5.4.2.
5.4.3. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-(1-naphthylmethyl)piperazine 3.5 maleate
(( )-10aa). Compound ( )-10aa was obtained as a crys-
tal. Mp 173–175 ꢁC (Et2O); 1H NMR (200 MHz,
DMSO-d6) d 2.60–3.63 (20H, m), 2.71 (3H, s), 3.98–
4.31 (1H, m), 6.17 (6H, s), 7.21–7.38 (4H, m), 7.43–
7.62 (4H, m), 7.89–8.01 (2H, m), 8.28–8.37 (1H, m);
MS (ESI, Pos) m/z 447 (M+H)+; Anal. (C28H35FN4Æ3.5-
C4H4O4) C, H, N.

2000
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
5.4.4. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-yl)-
ethyl]-4-[2-(1-naphthyl)ethyl]piperazine 3 maleate (( )-
10ab). Compound ( )-10ab was obtained as a crystal.
Mp 174–176 ꢁC (EtOH); H NMR (200 MHz, CDCl3)
7.06 (2H, t, J = 8.6 Hz), 7.11–7.28 (2H, m), 7.30–7.38
(1H, m), 7.43–7.53 (2H, m), 7.70 (1H, s), 7.79–7.88
(3H, m); MS (ESI, Pos) m/z 461 (M+H)+; Anal.
(C29H37FN4Æ3C4H4O4Æ0.7H2O) C, H, N.
1
d 2.60–3.58 (25H, m), 3.69–3.79 (1H, m), 6.30 (6H, s),
6.99–7.12 (2H, m), 7.15–7.29 (2H, m), 7.31–7.62 (4H,
m), 7.78–7.92 (2H, m), 7.93–8.02 (1H, m); MS (ESI,
Pos) m/z 461 (M+H)+; Anal. (C29H37FN4Æ3C4H4O4Æ0.7-
H2O) C, H, N.
5.4.11. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[3-(2-naphthyl)propyl]piperazine
3
maleate
(( )-10ai). Compound ( )-10ai was obtained as a crys-
tal. Mp 180–182 ꢁC (EtOH); 1H NMR (200 MHz,
DMSO-d6) d 1.93–2.08 (2H, m), 2.65–3.62 (22H, m),
2.71 (3H, s), 3.89–4.02 (1H, m), 6.12 (6H, s), 7.08–7.53
(8H, m), 7.71 (1H, s), 7.80–7.92 (2H, m); MS (ESI,
Pos) m/z 475 (M+H)+; Anal. (C30H39FN4Æ3C4H4O4) C,
H, N.
5.4.5. 1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-yl)eth-
yl]-4-[3-(1-naphthyl)propyl]piperazine 3 maleate (( )-10ac).
Compound ( )-10ac was obtained as a crystal. Mp 175–
177 ꢁC; NMR (200 MHz, DMSO-d6) d 1.95–2.05 (2H,
m), 2.61–3.58 (22H, m), 2.73 (3H, s), 3.85–3.95 (1H, m),
6.11 (6H, s), 7.18–7.63 (8H, m), 7.81 (1H, d, J = 7.9 Hz),
7.90–7.99 (1H, m), 8.03–8.12 (1H, m); MS (ESI) m/z 475
(M+H)+; Anal. (C30H39FN4Æ3C4H4O4) C, H, N.
5.4.12. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(2-naphthyl)butyl]piperazine 3 maleate (( )-
10aj). Compound ( )-10aj was obtained as a crystal. Mp
1
185–187 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
5.4.6. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[4-(1-naphthyl)butyl]piperazine 3 maleate (( )-
10ad). Compound ( )-10ad was obtained as a crystal. Mp
1.50–1.78 (4H, m), 2.30–3.80 (22H, m), 2.70 (3H, s),
3.91–3.98 (1H, m), 6.11 (6H, s), 7.18–7.57 (8H, m),
7.73 (1H, s), 7.78–7.92 (2H, m); MS (ESI, Pos) m/z
489 (M+H)+; Anal. (C31H41FN4Æ3C4H4O4Æ0.1H2O) C,
H, N.
1
174–176 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
1.58–1.80 (4H, m), 2.80–3.55 (22H, m), 2.71 (3H, s),
3.89–4.02 (1H, m), 6.12 (6H, s), 7.18–7.58 (8H, m), 7.79
(1H, d, J = 7.9 Hz), 7.88–7.97 (1H, m), 8.02–8.11 (1H,
m); MS (ESI, Pos) m/z 489 (M+H)+; Anal. (C31H41FN4Æ
3C4H4O4) C, H, N.
5.4.13. ( )-1-(1-(4-Fluorophenyl)-2-{4-[4-(4-methoxy-1-
naphthyl)butyl]piperazin-1-yl}ethyl)-4-methylpiperazine 3
maleate (( )-10bf). Compound ( )-10bf was obtained as a
1
crystal. Mp 178–181 ꢁC (EtOH); H NMR (300 MHz,
5.4.7. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[5-(1-naphthyl)pentyl]piperazine 3 maleate (( )-
10ae). Compound ( )-10ae was obtained as a crystal. Mp
DMSO-d6) d 1.58–1.73 (4H, m), 2.73 (3H, s), 2.79–3.31
(22 H, m), 3.88–3.94 (1H, m), 3.94 (3H, s), 6.11 (6H, s),
6.88 (1H, d, J = 7.9 Hz), 7.18–7.36 (5H, m), 7.48–7.60
(2H, m), 8.00 (1H, d, J = 7.6 Hz), 8.17– 8.21 (1H, m);
MS (ESI, Pos) m/z 519 (M+H)+; Anal. (C32H43FN4OÆ-
3C4H4O4) C, H, N.
1
170–172 ꢁC (EtOH); H NMR (200 MHz, DMSO-d6) d
1.30–1.49 (2H, m), 1.50–1.79 (4H, m), 2.74 (3H, s),
2.80–3.43 (22H, m), 3.93–3.97 (1H, m), 6.11 (6H, s),
7.19–7.58 (8H, m), 7.79 (1H, d, J = 8.0 Hz), 7.86–7.97
(1H, m), 8.01–8.07 (1H, m); MS (ESI, Pos) m/z 503
(M+H)+; Anal. (C32H43FN4Æ3C4H4O4) C, H, N.
5.4.14. ( )-1-(2-Biphenyl-2-ylethyl)-4-[2-(4-fluorophenyl)-
2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 3.5 hydro-
chloride (( )-10bn). Compound ( )-10bn was obtained
as a crystal. Mp 233–237 ꢁC (AcOEt–MeOH); 1H NMR
(300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.7 Hz), 2.40–
2.70 (1H, m), 2.93–3.05 (2H, m), 3.10–3.80 (19H, m),
3.99–4.18 (1H, m), 4.38–4.56 (1H, m), 7.21–7.78 (13H,
m); MS (ESI, Pos) m/z 515 (M+H)+; Anal.
(C33H43FN4Æ3.3HCl) C, H, N.
5.4.8. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[6-(1-naphthyl)hexyl]piperazine 3 maleate (( )-
10af). Compound ( )-10af was obtained as a crystal.
1
Mp 182–184 ꢁC (EtOH); H NMR (200 MHz, DMSO-
d6) d 1.21–1.79 (8H, m), 2.60–3.75 (22H, m), 2.76 (3H,
s), 3.92–3.98 (1H, m), 6.11 (6H, s), 7.18–7.60 (8H, m),
7.78 (1H, d, J = 8.0 Hz), 7.86–7.97 (1H, m), 8.01–8.07
(1H, m); MS (ESI, Pos) m/z 517 (M+H)+; Anal.
(C33H45FN4Æ3C4H4O4) C, H, N.
5.4.15. ( )-1-(3-Biphenyl-2-ylpropyl)-4-[2-(4-fluorophe-
nyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4 hydro-
chloride (( )-10bo). Compound ( )-10bo was obtained as
1
5.4.9. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-(2-naphthylmethyl)piperazine 3 maleate (( )-
10ag). Compound ( )-10ag was obtained as a crystal. Mp
a crystal. Mp 190–193 ꢁC (AcOEt–MeOH); H NMR
(300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.7 Hz), 1.82–
2.01 (2H, m), 2.10–2.22 (1H, m), 2.50–2.70 (1H, m),
2.92–3.03 (2H, m), 3.08–3.77 (14H, m), 3.98–4.56 (6H,
m), 7.19 (1H, d, J = 7.3 Hz), 7.21–7.48 (12H, m); MS
(ESI, Pos) m/z 529 (M+H)+; Anal. (C34H45FN4Æ4HClÆ1.5-
H2O) C, H, N.
1
189–191 ꢁC (EtOH/Et2O); H NMR (200 MHz, DMSO-
d6) d 2.60–3.82 (20H, m), 2.72 (3H, s), 3.88–4.12 (1H, m),
6.17 (6H, s), 7.20–7.39 (4H, m), 7.50–7.63 (3H, m), 7.86–
8.02 (4H, m); MS (ESI, Pos) m/z 447 (M+H)+; Anal.
(C28H35FN4Æ3C4H4O4Æ0.3H2O) C, H, N.
5.4.16. ( )-1-(4-Biphenyl-2-ylbutyl)-4-[2-(4-fluorophenyl)-
2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4 hydrochlo-
ride (( )-10bp). Compound ( )-10bp was obtained as a
crystal. Mp 193–196 ꢁC (AcOEt–MeOH); 1H NMR
(300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.5 Hz), 1.42–
1.71 (4H, m), 2.04–2.12 (1H, m), 2.52–2.67 (1H, m),
5.4.10. ( )-1-[2-(4-Fluorophenyl)-2-(4-methylpiperazin-1-
yl)ethyl]-4-[2-(2-naphthyl)ethyl]piperazine 3 maleate (( )-
10ah). Compound ( )-10ah was obtained as a crystal.
Mp 187–189 ꢁC (EtOH); H NMR (200 MHz, CDCl3)
d 2.62–3.60 (25H, m), 3.68–3.80 (1H, m), 6.31 (6H, s),
1

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
2001
2.93–3.03 (2H, m), 3.06–3.76 (14H, m), 4.02–4.21 (1H, m),
4.40–4.81 (5H, m), 7.17 (1H, d, J = 7.2 Hz), 7.20–7.49
(12H, m); MS (ESI, Pos) m/z 543 (M+H)+; Anal.
(C35H47FN4Æ4HClÆ2.1H2O) C, H, N.
J = 6.5 Hz), 1.81–2.00 (2H, m), 2.06–2.20 (1H, m), 2.51–
2.68 (1H, m), 2.94–3.03 (2H, m), 3.08–3.76 (18H, m),
4.01–4.20 (1H, m), 4.42–4.58 (1H, m), 7.06 (1H, d,
J = 6.7 Hz), 7.19–7.55 (11H, m); MS (ESI, Pos) m/z 547
(M+H)+; Anal. (C34H44F2N4Æ3.9HCl) C, H, N.
5.4.17. ( )-1-(3-Biphenyl-3-ylpropyl)-4-[2-(4-fluorophenyl)-
2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4 hydrochlo-
ride (( )-10bq). Compound ( )-10bq was obtained as a
crystal. Mp 173–176 ꢁC (AcOEt–MeOH); 1H NMR
(300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.5 Hz), 2.03–
2.13 (3H, m), 2.51–2.77 (1H, m), 3.09–3.93 (16H, m),
4.07–4.80 (6H, m), 7.21–7.59 (11H, m), 7.63–7.69 (2H,
m); HRMS 529.3707 (M+1).
5.4.23. ( )-1-[3-(3-Chlorobiphenyl-2-yl)propyl]-4-[2-(4-
fluorophenyl)-2-4-isopropylpiperazin-1-yl)ethyl]piperazine
4 hydrochloride (( )-10bw). Compound ( )-10bw was
obtained as a crystal. Mp 185–187 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6) d 1.23 (6H, d,
J = 6.4 Hz), 1.81–2.01 (2H, m), 2.14–2.23 (1H, m), 2.58–
2.78 (1H, m), 2.93–3.02 (2H, m), 3.08–3.75 (14H, m),
4.06–4.21 (1H, m), 4.22–4.79 (5H, m), 7.17 (1H, dd,
J = 1.2, 6.4 Hz), 7.23–7.51 (11H, m); MS (ESI, Pos)
m/z 563 (M+H)+; Anal. (C34H44ClFN4Æ4HClÆ3.5H2O) C,
H, N.
5.4.18. ( )-1-(3-Biphenyl-4-ylpropyl)-4-[2-(4-fluorophenyl)-
2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4 hydrochlo-
ride (( )-10br). Compound ( )-10br was obtained as a
crystal. Mp 182–185 ꢁC (AcOEt–MeOH); 1H NMR
(300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.5 Hz), 2.01–
2.21 (2H, m), 2.50–2.78 (2H, m), 3.05–3.43 (8H, m),
3.45–3.92 (8H, m), 3.95–4.40 (5H, m), 4.51–4.60 (1H,
m), 7.22–7.49 (9H, m), 7.58–7.65 (4H, m); MS (ESI,
Pos) m/z 529 (M+H)+; Anal. (C34H45FN4Æ4HClÆ1.0H2O)
C, H, N.
5.4.24. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-[3-(3-methylbiphenyl-2-yl)propyl]piperazine
4 hydrochloride (( )-10bx). Compound ( )-10bx was ob-
tained as a crystal. Mp 178–180 ꢁC (AcOEt–MeOH); 1H
NMR (300 MHz, DMSO-d6) d 1.23 (6H, d, J = 6.5 Hz),
1.77–1.92 (2H, m), 2.14–2.23 (1H, m), 2.40 (3H, s), 2.61–
2.78 (1H, m), 2.92–3.00 (2H, m), 3.07–3.74 (14H, m),
4.07–4.21 (1H, m), 4.40–4.90 (5H, m), 6.98 (1H, dd,
J = 1.6, 6.6 Hz), 7.17–7.50 (11H, m); MS (ESI, Pos)
m/z 543 (M+H)+; Anal. (C35H47FN4Æ4HClÆ4H2O) C,
H, N.
5.4.19. ( )-1-[3-(6-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-4-isopropylpiperazin-1-yl)ethyl]piperazine
4
hydrochloride (( )-10bs). Compound ( )-10bs was ob-
tained as a crystal. Mp 196–199 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6) d 1.22 (6H, d,
J = 6.4 Hz), 1.79–2.01 (2H, m), 2.04–2.31 (2H, m),
2.50–2.77 (2H, m), 3.15–3.93 (18H, m), 3.98–4.22 (1H,
m), 4.41–4.60 (1H, m), 7.09–7.58 (12H, m); MS (ESI,
Pos) m/z 547 (M+H)+; Anal. (C34H44F2N4Æ4HClÆ0.4H2O)
C, H, N.
5.4.25. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-[3-(3-methoxybiphenyl-2-yl)propyl]piperazine
4 hydrochloride (( )-10by). Compound ( )-10by was ob-
tained as a crystal. Mp 175–177 ꢁC (AcOEt–MeOH); 1H
NMR (300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.4 Hz),
1.81–1.98 (2H, m), 2.07–2.22 (1H, m), 2.60–2.77 (1H, m),
2.87–3.01 (2H, m), 3.09–3.75 (18H, m), 2.92 (3H, s),
4.05–4.21 (1H, m), 4.43–4.58 (1H, m), 6.79 (1H, d,
J = 7.7 Hz), 7.04 (1H, d, J = 8.4 Hz), 7.19–7.50 (10H,
m); MS (ESI, Pos) m/z 559 (M+H)+; Anal. (C35H47
FN4OÆ4HClÆ2.0H2O) C, H, N.
5.4.20. ( )-1-[3-(5-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-
fluorophenyl)-2-4-isopropylpiperazin-1-yl)ethyl]piperazine
3.8 hydrochloride (( )-10bt). Compound ( )-10bt was ob-
tained as a crystal. Mp 205–208 ꢁC (AcOEt–MeOH); 1H
NMR (300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.7 Hz),
1.81–1.99 (2H, m), 2.03–2.20 (1H, m), 2.53–2.72 (1H,
m), 2.95–3.03 (2H, m), 3.08–3.77 (18H, m), 4.01–4.20
(1H, m), 4.44–4.56 (1H, m), 7.02 (1H, dd, J = 2.8,
6.8 Hz), 7.19–7.49 (11H, m); MS (ESI, Pos) m/z 547
(M+H)+; Anal. (C34H44F2N4Æ3.8HCl) C, H, N.
5.4.26. ( )-1-[3-(20-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4
hydrochloride (( )-10bz). Compound ( )-10bz was ob-
tained as a crystal. Mp 171–173 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6)
d 1.22 (6H, d,
5.4.21. ( )-1-[3-(4-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-4-isopropylpiperazin-1-yl)ethyl]piperazine 4
hydrochloride (( )-10bu). Compound ( )-10bu was ob-
tained as a crystal. Mp 197–199 ꢁC (AcOEt–MeOH); 1H
NMR (300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.5 Hz),
1.88–2.02 (2H, m), 2.07–2.22 (1H, m), 2.53–2.70 (1H,
m), 2.96–3.04 (2H, m), 3.09–3.78 (18H, m), 4.03–4.21
(1H, m), 4.43–4.58 (1H, m), 7.12 (1H, dt, J = 2.6,
5.9 Hz), 7.19–7.48 (11H, m); MS (ESI, Pos) m/z 547
(M+H)+; Anal. (C34H44F2N4Æ4HCl) C, H, N.
J = 6.5 Hz), 1.83–1.99 (2H, m), 2.08–2.21 (1H, m),
2.58–2.71 (1H, m), 2.89–3.03 (2H, m), 3.07–3.78 (18H,
m), 4.04–4.21 (1H, m), 4.42–4.56 (1H, m), 7.15–7.50
(12H, m); MS (ESI, Pos) m/z 547 (M+H)+; Anal.
(C34H44F2N4Æ4HClÆ0.5H2O) C, H, N.
5.4.27. ( )-1-[3-(30-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4
hydrochloride (( )-10ca). Compound ( )-10ca was ob-
tained as a crystal. Mp 171–173 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6)
d 1.22 (6H, d,
5.4.22. ( )-1-[3-(3-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine
3.9 hydrochloride (( )-10bv). Compound ( )-10bv was
obtained as a crystal. Mp 178–181 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6) d 1.22 (6H, d,
J = 6.6 Hz), 1.83–2.01 (2H, m), 2.07–2.23 (1H, m),
2.56–2.70 (1H, m), 2.93–3.05 (2H, m), 3.09–3.77 (18H,
m), 4.06–4.21 (1H, m), 4.44–4.58 (1H, m), 7.16–7.52
(12H, m); MS (ESI, Pos) m/z 547 (M+H)+; Anal.
(C34H44F2N4Æ4HClÆ0.5H2O) C, H, N.

2002
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
5.4.28. ( )-1-[3-(40-Fluorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4
hydrochloride (( )-10cb). Compound ( )-10cb was ob-
tained as a crystal. Mp 197–199 ꢁC (AcOEt–MeOH);
3.12 (2H, m), 3.18–4.21 (17H, m), 4.37–4.52 (1H, m),
7.21–7.56 (13H, m), 7.72–7.81 (4H, m); MS (ESI, Pos)
m/z 605 (M+H)+; Anal. (C40H49FN4Æ3.8HClÆ0.5H2O) C,
H, N.
1H NMR (300 MHz, DMSO-d6)
d 1.21 (6H, d,
J = 6.6 Hz), 1.82–2.01 (2H, m), 2.06–2.25 (1H, m),
2.51–2.79 (3H, m), 2.95–3.05 (2H, m), 3.08–3.78 (16H,
m), 4.08–4.21 (1H, m), 4.49–4.61 (1H, m), 7.16–7.52
(12H, m); MS (ESI, Pos) m/z 547 (M+H)+; Anal.
(C34H44F2N4Æ4HClÆ0.5H2O) C, H, N.
5.4.34. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-{3-[40-(trifluoromethyl)biphenyl-2-yl]propyl}-
piperazine
4
hydrochloride (( )-10ch). Compound
( )-10ch was obtained as a crystal. Mp 183–186 ꢁC
(AcOEt–MeOH); 1H NMR (300 MHz, DMSO-d6) d
1.21 (6H, d, J = 6.6 Hz), 1.91–2.06 (2H, m), 2.13–2.29
(1H, m), 2.53–2.68 (3H, m), 2.97–3.09 (2H, m), 3.18–
3.81 (16H, m), 4.09–4.25 (1H, m), 4.49–4.62 (1H, m),
7.20–7.49 (8H, m), 7.69 (2H, d, J = 7.5 Hz), 7.81 (2H,
d, J = 7.5 Hz); MS (ESI, Pos) m/z 597 (M+H)+; Anal.
(C35H44F4N4Æ4HClÆ3H2O) C, H, N.
5.4.29. ( )-1-[3-(40-Chlorobiphenyl-2-yl)propyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine 4
hydrochloride (( )-10cc). Compound ( )-10cc was ob-
tained as a crystal. Mp 175–177 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6)
d 1.21 (6H, d,
J = 6.6 Hz), 1.82–2.01 (2H, m), 2.06–2.25 (1H, m),
2.51–2.79 (3H, m), 2.95–3.05 (2H, m), 3.08–3.78 (16H,
m), 4.08–4.21 (1H, m), 4.49–4.61 (1H, m), 7.16–7.52
(12H, m); MS (ESI, Pos) m/z 563 (M+H)+; Anal.
(C34H44ClFN4Æ4HClÆ2.5H2O) C, H, N.
5.4.35. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-{3-[40-(trifluoromethoxy)biphenyl-2-yl]propyl}-
piperazine 4 hydrochloride (( )-10ci). Compound ( )-10ci
was obtained as a crystal. Mp 172–174 ꢁC (AcOEt–
1
MeOH); H NMR (300 MHz, DMSO-d6) d 1.22 (6H, d,
5.4.30. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-[3-(40-methylbiphenyl-2-yl)propyl]piperazine
4 hydrochloride (( )-10cd). Compound ( )-10cd was ob-
tained as a crystal. Mp 172–174 ꢁC (AcOEt–MeOH); 1H
NMR (300 MHz, DMSO-d6) d 1.22 (6H, d, J = 6.6 Hz),
1.84–2.01 (2H, m), 2.11–2.30 (1H, m), 2.38 (3H, s), 2.53–
2.78 (3H, m), 2.93–3.03 (2H, m), 3.07–3.74 (16H, m),
4.06–4.22 (1H, m), 4.40–4.62 (1H, m), 7.09–7.42 (12H,
m); MS (ESI, Pos) m/z 543 (M+H)+; Anal.
(C35H47FN4Æ4HClÆ1.6H2O) C, H, N.
J = 6.6 Hz), 1.91–2.03 (2H, m), 2.15–2.29 (1H, m), 2.53–
2.78 (3H, m), 2.97–3.11 (2H, m), 3.18–3.78 (16H, m),
4.09–4.22 (1H, m), 4.48–4.62 (1H, m), 7.19–7.52 (12H,
m); MS (ESI, Pos) m/z 613 (M+H)+; Anal.
(C35H44F4N4OÆ4HClÆ2H2O) C, H, N.
5.4.36. ( )-20-(3-{4-[2-(4-Fluorophenyl)-2-(4-isopropylpi-
perazin-1-yl)ethyl]piperazin-1-yl}propyl)-N,N-dimethylbi-
phenyl-4-amine 5 hydrochloride (( )-10cj). Compound
( )-10cj was obtained as a crystal. Mp 194–197 ꢁC
(AcOEt–MeOH); 1H NMR (300 MHz, DMSO-d6) d
1.22 (6H, d, J = 6.6 Hz), 1.90–2.01 (2H, m), 2.11–2.22
(1H, m), 2.59–2.68 (3H, m), 2.98–3.03 (2H, m), 3.09
(6H, s), 3.19–3.74 (16H, m), 4.08–4.21 (1H, m), 4.50–
4.59 (1H, m), 7.18 (2H, d, J = 7.3 Hz), 7.19–7.52 (10H,
m); MS (ESI, Pos) m/z 572 (M+H)+; Anal.
(C36H50FN5Æ5HClÆ2H2O) C, H, N.
5.4.31. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-[3-(40-methoxybiphenyl-2-yl)propyl]piperazine
4 hydrochloride (( )-10ce). Compound ( )-10ce was ob-
tained as a crystal. Mp 168–170 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6)
d 1.21 (6H, d,
J = 6.6 Hz), 1.88–2.01 (2H, m), 2.05–2.30 (1H, m),
2.57–2.78 (3H, m), 2.95–3.04 (2H, m), 3.08–3.77 (16H,
m), 3.91 (3H, s), 4.05–4.23 (1H, m), 4.42–4.57 (1H, m),
7.00 (2H, d, J = 7.5 Hz), 7.14–7.43 (10H, m); MS (ESI,
Pos) m/z 559 (M+H)+; Anal. (C35H47FN4OÆ4HClÆ2H2O)
C, H, N.
5.4.37. ( )-1-(4-{4-[2-(4-Fluorophenyl)-2-(4-isopropylpipe-
razin-1-yl)ethyl]piperazin-1-yl}butyl)-2-naphthol 3 maleate
(( )-10bh). A mixture of ( )-1-[2-(4-fluorophenyl)-2-(4-
isopropylpiperazin-1-yl)ethyl]-4-[4- (2-methoxy-1-naph-
thyl)butyl]piperazine ( )-10bg (61 mg, 0.11 mmol)
in 48% HBr aqueous (10 mL) was stirred at 105 ꢁC for
3 h and concentrated in vacuo. The residue was parti-
tioned between 1 M NaOH aqueous and Et2O. The sep-
arated organic phase was washed with brine, dried over
Na2SO4, filtered, and concentrated in vacuo to obtain
crude ( )-1-(4-{4-[2-(4-fluorophenyl)-2-(4-isopropylpipera-
zin-1-yl)ethyl]piperazin-1-yl}butyl)-2-naphthol (50 mg, 85%)
5.4.32. ( )-1-[3-(40-tert-Butylbiphenyl-2-yl)propyl]-4-[2-(4-
fluorophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine
4 hydrochloride (( )-10cf). Compound ( )-10cf was ob-
tained as a crystal. Mp 177–179 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6) d 1.22 (6H, d,
J = 6.7 Hz), 1.33 (9H, s), 1.89–2.03 (2H, m), 2.08–2.22
(1H, m), 2.58–2.68 (3H, m), 2.97–3.04 (2H, m), 3.09–
3.79 (16H, m), 4.07–4.21 (1H, m), 4.47–4.57 (1H, m),
7.19 (2H, dd, J = 1.6, 5.9 Hz), 7.21–7.49 (10H, m); MS
(ESI, Pos) m/z 585 (M+H)+; Anal. (C38H53FN4Æ4-
HClÆ2.5H2O) C, H, N.
1
as an oily product. H NMR (300 MHz, CDCl3) d 1.00
(6H, d, J = 6.5 Hz), 1.50–1.62 (2H, m), 1.65–1.79 (2H,
m), 2.30–2.76 (21H, m), 2.88–3.02 (3H, m), 3.57 (1H, t,
J = 6.2 Hz), 6.99 (2H, t, J = 8.8 Hz), 7.14–7.29 (4H, m),
7.42 (1H, t, J = 7.4 Hz), 7.60 (1H, d, J = 7.8 Hz), 7.75
(1H, d, J = 7.7 Hz), 7.85 (1H, d, J = 7.9 Hz). The above
free base (50 mg, 0.094 mmol) was dissolved in EtOH
(2 mL), and to the solution was added a solution of male-
ic acid (38 mg, 0.31 mmol) in EtOH (1 mL). After stirred
at room temperature for 1 h, the resulting precipitate was
collected by filtration to obtain ( )-1-(4-{4-[2-(4-fluoro-
5.4.33. ( )-1-[2-(4-Fluorophenyl)-2-(4-isopropylpiperazin-
1-yl)ethyl]-4-[3-(1,10:40,100-terphenyl-2-yl)propyl]piperazine
3.8 hydrochloride (( )-10cg). Compound ( )-10cg was
obtained as a crystal. Mp 192–195 ꢁC (AcOEt–MeOH);
1H NMR (300 MHz, DMSO-d6) d 1.21 (6H, d, J =
6.7 Hz), 1.90–2.18 (3H, m), 2.59–2.73 (3H, m), 2.97–

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
2003
phenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazin-1-
yl}butyl)-2-naphthol 3 maleate ( )-10bh (61 mg, 74%)
as an amorphous: H NMR (300 MHz, CDCl3) d 1.22
(6H, d, J = 6.5 Hz), 1.58–1.82 (4H, m), 2.50–3.31
(21H, m), 3.53–3.62 (1H, m), 6.25 (6H, s), 3.57 (1H,
t, J = 6.2 Hz), 6.98 (2H, t, J = 8.9 Hz), 7.10–7.30
(4H, m), 7.42 (1H, t, J = 7.6 Hz), 7.59 (1H, d,
J = 7.9 Hz), 7.74 (1H, d, J = 7.7 Hz), 7.85 (1H, d,
J = 7.9 Hz); HRMS 533.3656 (M+1).
International (Buckinghamshire, England). COS-1 cells
were purchased from American Type Culture Collection
(Rocksville, MD, USA). [Nle4,D-Phe7]a-MSH was pur-
chased from Peninsula Laboratories (Belmont, CA,
USA). All other chemicals used in this study were ob-
tained commercially, and all were of the highest purity
available.
1
5.5.2. [125I][Nle4,D-Phe7]a-MSH binding to recombinant
MC4 receptor. COS-1 cells expressing the MC4 recep-
tor, prepared according to the method reported previ-
ously,19 were washed with phosphate buffered saline,
scraped, and pelleted by centrifugation. Cell pellets
were homogenized with 50 mM Tris–HCl buffer (pH
7.4) containing 2 mM EDTA, 10 mM CaCl2, and
100 lM phenylmethylsulfonyl fluoride, and centrifuged
at 48,000g for 20 min at 4 ꢁC. The pellet was washed
twice with the buffer, and the final pellet was suspend-
ed in an assay buffer (50 mM Tris–HCl buffer (pH 7.4)
containing 2 mM EDTA, 10 mM CaCl2, 100 lM phen-
ylmethylsulfonyl fluoride, and 0.1% bovine serum albu-
min (BSA)), and served as crude membrane
preparation for binding studies. Binding assays of
5.4.38. ( )-1-[4-(2-Ethoxy-1-naphthyl)butyl]-4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazine
3.5 maleate (( )-10bi). A mixture of ( )-1-(4-{4-[2-(4-flu-
orophenyl)-2-(4-isopropylpiperazin-1-yl)ethyl]piperazin-
1-yl}butyl)-2-naphthol (free base of ( )-10bh) (0.10 g,
0.19 mmol), iodoethane (15 lL, 0.19 mmol), and K2CO3
(26 mg, 0.19 mmol) in DMF (5 mL) was stirred at 80 ꢁC
for 6 h. The mixture was partitioned between EtOAc
and H2O, and separated organic phase was washed with
saturated aqueous NaHCO3 and brine. The organic phase
was dried over Na2SO4, filtered, and concentrated in vac-
uo. The residue was chromatographed on Chromatorex
NH (hexane/EtOAc 2:1) to obtain ( )-1-[4-(2-ethoxy-1-
naphthyl)butyl]-4-[2-(4-fluorophenyl)-2-(4-isopropylpi-
perazin-1-yl)ethyl]piperazine (20 mg, 19%) as an oily
[
125I][Nle4,D-Phe7]a-MSH were performed according
to Chaki et al.19 Membranes were incubated with
125I][Nle4,D-Phe7]a-MSH (0.2 nM) for 120 min at
1
product. H NMR (300 MHz, CDCl3) d 1.00 (6H, d,
[
J = 6.5 Hz), 1.42 (3H, d, J = 7.0 Hz), 1.50–1.72 (4H, m),
2.25–2.71 (21H, m), 2.88–2.92 (1H, m), 3.00–3.12 (2H,
m), 3.58 (1H, t, J = 6.4 Hz), 3.58 (1H, q, J = 7.0 Hz),
6.97 (2H, t, J = 8.0 Hz), 7.16–7.31 (4H, m), 7.42 (1H, t,
J = 7.0 Hz), 7.67 (1H, d, J = 8.0 Hz), 7.78 (1H, d,
J = 7.5 Hz), 7.95 (1H, d, J = 8.0 Hz). The above free base
(20 mg, 0.036 mmol) was dissolved in EtOH (1 mL), and
to the solution was added a solution of maleic acid
(13 mg, 0.11 mmol) in EtOH (1 mL). After stirred at room
temperature for 1 h, the resulting precipitate was collected
by filtration to obtain ( )-1-[4-(2-ethoxy-1-naphthyl)bu-
tyl]-4-[2-(4-fluorophenyl)-2-(4-isopropylpiperazin-1-yl)-
ethyl]piperazine 3 maleate ( )-10bi (10 mg, 31%) as an
amorphous: 1H NMR (200 MHz, DMSO-d6) d 1.20
(6H, d, J = 6.6 Hz), 1.37 (3H, t, J = 6.9 Hz), 1.45–1.79
(4H, m), 2.20–3.60 (23H, m), 3.88–4.03 (1H, m), 4.18
(2H, q, J = 6.8 Hz), 6.12 (6H, s), 7.15–7.22 (2H, t,
J = 8.8 Hz), 7.55 (5H, m), 7.82 (2H, t, J = 9.0 Hz), 7.94
(1H, d, J = 8.4 Hz); MS (ESI, Pos.) m/z 561 (M+H)+;
Anal. (C35H49FN4OÆ3.5C4H4O4Æ1.0H2O) C, H, N.
25 ꢁC, and the reaction was terminated by rapid filtra-
tion over a GF/C filter presoaked with 0.5% BSA, after
which the filters were washed three times with the buff-
er. Radioactivity was quantified in a c-counter. Non-
specific binding was determined in the presence of
1 lM [Nle4,D-Phe7]a-MSH. Specific binding was deter-
mined by subtracting nonspecific from total binding. In
the competition assay, concentration of the test
compound that caused 50% inhibition of the specific
binding (IC50 value) was determined from each concen-
tration–response curve.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.bmc.2006.12.039.
References and notes
5.4.39. 1-(1-(4-Fluorophenyl)-2-{4-[4-(2-isopropoxy-1-naph-
thyl)butyl]piperazin-1-yl}ethyl)-4-isopropylpiperazine
maleate (( )-10bj). Compound ( )-10bj was obtained by
3
1. Irani, B. G.; Holder, J. R.; Todorovic, A.; Wilczynski, A.
M.; Joseph, C. G.; Wilson, K. R.; Haskell-Luevano, C.
Curr. Pharm. Des. 2004, 10, 3443.
2. Lu, D.; Willard, D.; Patel, I. R.; Kadwell, S.;
Overton, L.; Kost, T.; Luther, M.; Chen, W.; Yowc-
hik, R. P.; Wilkinson, W. O.; Cone, R. D. Nature
1994, 371, 799.
3. Ollmann, M. M.; Wilson, B. D.; Yang, Y.-K.; Kerns, J.
A.; Chen, Y.; Gantz, I.; Barsh, G. S. Science 1997, 278,
135.
using the method of Section 5.4.38 as a crystal. Mp 167–
1
169 ꢁC; H NMR (200 MHz, DMSO-d6) d 1.20 (6H, d,
J = 6.6 Hz), 1.30 (6H, d, J = 6.0 Hz), 1.50–1.80 (4H, m),
2.70–3.50 (23H, m), 3.94–4.02 (1H, m), 4.54 (1H, m),
6.10 (6H, s), 7.22 (2H, t, J = 8.8 Hz), 7.30–7.53 (5H, m),
7.78–7.97 (3H, m); MS (ESI, Pos.) m/z 575 (M+H)+; Anal.
(C36H51FN4OÆ3C4H4O4) C, H, N.
4. Holder, J. R.; Haskell-Luevano, C. Med. Res. Rev. 2004,
24, 325.
5.5. Binding test
5. Hruby, V. J.; Wilkes, B. C.; Hadley, M. E.; Al-Obeidi, F.;
Sawyer, T. K.; Staples, D. J.; DeVaux, A.; Dym, O.;
Castrucci, A. M.; Hintz, M. F.; Riehm, J. P.; Rao, K. R.
J. Med. Chem. 1987, 30, 2126.
5.5.1. Material. [125I][Nle4,D-Phe7]a-Melanocyte-stimu-
lating hormone ([Nle4,D-Phe7]a-MSH) (specific radioactiv-
ity: 81.4 TBq/mmol) was purchased from Amersham

2004
D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
6. (a) Wikberg, J. E. S. Eur. J. Pharmacol. 1999, 375, 295; (b)
Hruby, V. J. J. Med. Chem. 2003, 46, 4965; (g) Grieco, P.;
Lavecchia, A.; Cai, M.; Trivedi, D.; Weinberg, D.;
MacNeil, T.; Van der Ploeg, L. H.; Hruby, V. J. J. Med.
Chem. 2002, 45, 5287; (h) Holder, J. R.; Bauzo, R. M.;
Xiang, Z.; Haskell-Luevano, C. J. Med. Chem. 2002, 45,
3073; (i) Holder, J. R.; Bauzo, R. M.; Xiang, Z.; Haskell-
Luevano, C. J. Med. Chem. 2002, 45, 2801; (j) Kavarana,
M. J.; Trivedi, D.; Cai, M.; Ying, J.; Hammer, M.;
Cabello, C.; Grieco, P.; Han, G.; Hruby, V. J. J. Med.
Chem. 2002, 45, 2644; (k) Bednarek, M. A.; MacNeil, T.;
Kalyani, R. N.; Tang, R.; Van der Ploeg, L. H.; Weinberg,
D. H. J. Med. Chem. 2001, 45, 3665; (l) Fotsch, C.; Smith,
D. M.; Adams, J. A.; Cheetham, J.; Croghan, M.;
Doherty, E. M.; Hale, C.; Jarosinski, M. A.; Kelly, M.
G.; Norman, M. H.; Tomayo, N. A.; Xi, N.; Baumgart-
ner, J. W. Bioorg. Med. Chem. Lett. 2003, 13, 2337; (m)
Haskell-Luevano, C.; Hendrata, S.; North, C.; Sawyer, T.
K.; Hadley, M. E.; Hruby, V. J.; Dickinson, C.; Gantz, I.
J. Med. Chem. 1997, 40, 2133; (n) Cheung, A. W.-H.;
Gore, L. Q. V.; Chu, X.-J.; Bartkovitz, D.; Kurylko, G.;
Swistok, J.; Danho, W.; Chen, L.; Yagaloff, K. Bioorg.
Med. Chem. Lett. 2005, 15, 5504; (o) Yan, L. Z.; Flora, D.;
Edwards, P.; Smiley, D. L.; Emmerson, P. J.; Hsiung, H.
M.; Gadski, R.; Hertel, J.-A.; Heiman, M. L.; Husain, S.;
O’Brien, T. P.; Kahl, S. D.; Zhang, L.; DiMarchi, R. D.;
Mayer, J. P. Bioorg. Med. Chem. Lett. 2005, 15, 4611; (p)
Odagami, T.; Tsuda, Y.; Kogami, Y.; Kouji, H.; Okada,
Y. Bioorg. Med. Chem. Lett. 2006, 16, 3723.
Chaki, S.; Nakazato, A. Drugs future 2004, 29(10), 1065;
(c) Chaki, S.; Okuyama, S. Peptides 2005, 26, 1952.
7. Fan, W.; Boston, B. A.; Kesterson, R. A.; Hruby, V. J.;
Cone, R. D. Nature 1997, 385, 165.
8. Forbes, S.; Bui, S.; Robinson, B. R.; Hochgeschwendr, U.;
Brenna, M. B. Proc. Natl. Acad. Sci. U.S.A. 2001, 98,
4233.
9. Huszar, D.; Lynch, C. A.; Fairchild-Huntress, V.; Dun-
more, J. H.; Fang, Q.; Berkemeier, L. R.; Gu, W.;
Kesterson, R. A.; Boston, B. A.; Cone, R. D.; Smith, F. J.;
Campfield, L. A.; Burn, P.; Lee, F. Cell 1997, 88, 131.
10. Kask, A.; Rago, L.; Wikberg, J. E. S.; Schiotch, H. B. Eur.
J. Pharmacol. 1998, 360, 15.
11. Murphy, B.; Nunes, C. N.; Ronan, J. J.; Harper, C. M.;
Beall, M. J.; Hanaway, M.; Fairhurst, A. M.; Van der
Ploeg, L. H. T.; MacIntyre, D. E.; Mellin, T. N.
Neuropeptides 1998, 32, 491.
12. Giraudo, S. Q.; Billington, C. J.; Levine, A. S. Brain Res.
1998, 809, 302.
13. Kask, A.; Rago, L.; Mutulis, F.; Pahkla, R.; Wikberg, J.
E. S.; Schiotch, H. B. Biochem. Biophys. Res. Commun.
1998, 245, 90.
14. van der Ploeg, L. H. T.; Martin, W. J.; Howard, A. D.;
Nargund, R. P.; Austin, C. P.; Guan, X.; Drisko, J.;
Cashen, D.; Sebhat, I.; Patchett, A. A.; Figueroa, D. J.;
DiLella, A. G.; Connolly, B. M.; Weinberg, D. H.; Tan, C.
T.; Palyha, O. C.; Pong, S.; MacNeil, T.; Rosenblum, C.;
Vongs, A.; Tang, R.; Yu, H.; Sailer, A. W.; Fong, T. M.;
Huang, C.; Tota, M.; Chang, R. S.; Stearns, R.; Tamvak-
opoulos, C.; Christ, G.; Drazen, D. L.; Spar, B. D.;
Nelson, R. J.; MacIntyre, D. E. Proc. Natl. Acad. Sci.
U.S.A. 2002, 99, 11381.
15. Vos, T. J.; Caracoti, A.; Che, J. L.; Dai, M.; Farrer, C. A.;
Forsyth, N. E.; Drabic, S. V.; Horlick, R. A.; Lamppu, D.;
Yowe, D. L.; Balani, S.; Li, P.; Zeng, H.; Joseph, I. B. J.
K.; Rodriguez, L. E.; Maguire, M. P.; Patane, M. A.;
Claiborne, C. F. J. Med. Chem. 2004, 47, 1602.
16. Adan, R. A.; Szklarczyk, A. W.; Oosterom, J.; Brakkee, J.
H.; Nijenhuis, W. A.; Schaaper, W. M.; Meloen, R. H.;
Gispen, W. H. Eur. J. Pharmacol. 1999, 378, 249.
17. Gonzalez, M. I.; Vaziri, S.; Wilson, C. A. Peptides 1996,
17, 171.
18. Vergoni, A. V.; Bertolini, A.; Wikberg, J. E.; Schioth, H.
B. Eur. J. Pharmacol. 1999, 369, 11.
19. Chaki, S.; Hirota, S.; Funakoshi, T.; Suzuki, Y.; Suetake,
S.; Okubo, T.; Ishii, T.; Nakazato, A.; Okuyama, S.
J. Pharmcol. Exp. Ther. 2003, 304, 818.
20. Chaki, S.; Oshida, Y.; Ogawa, S.; Funakoshi, T.; Shima-
zaki, T.; Okubo, T.; Nakazato, A.; Okuyama, S. Phar-
macol. Biochem. Behav. 2005, 82, 621.
21. Chaki, S.; Ogawa, S.; Toda, Y.; Funakoshi, T.; Okuyama,
S. Eur. J. Pharmacol. 2003, 474, 95.
24. (a) Sebhat, I. K.; Martin, W. J.; Ye, Z.; Barakat, K.;
Mosley, R. T.; Johnston, D. B. R.; Bakshi, R.; Palucki, B.;
Weinberg, D. H.; MacNeil, T.; Kalyani, R. N.; Tang, R.;
Stearns, R. A.; Miller, R. R.; Tamvakopoulos, C.; Strack,
A. M.; McGowan, E.; Cashen, D. E.; Drisko, J. E.; Hom,
G. J.; Howard, A. D.; MacIntyre, D. E.; van der Ploeg, L.
H. T.; Patchett, A. A.; Nargund, R. P. J. Med. Chem.
2002, 45, 4589; (b) Palucki, B. L.; Park, M. K.; Nargund,
R. P.; Ye, Z.; Sebhat, I. K.; Pollard, P. G.; Kalyani, R. N.;
Tang, R.; MacNeil, T.; Weinberg, D. H.; Vongs, A.;
Rosenblum, C. I.; Doss, G. A.; Miller, R. R.; Stearns, R.
A.; Peng, Q.; Tamvakopoulos, C.; McGowan, E.; Martin,
W. J.; Metzger, J. M.; Shepherd, C. A.; Strack, A. M.;
MacIntyre, D. E.; van der Ploeg, L. H. T.; Patchett, A. A.
Bioorg. Med. Chem. Lett. 2005, 15, 171; (c) Ye, Z.; Guo,
L.; Barakat, K. J.; Pollard, P. G.; Palucki, B. L.; Sebhat, I.
K.; Bakshi, R. K.; Tang, R.; Kalyani, R. N.; Vongs, A.;
Chen, A. S.; Chen, H. Y.; Rosenblum, C. I.; MacNeil, T.;
Weinberg, D. H.; Peng, Q.; Tamvakopoulos, C.; Miller, R.
R.; Stearns, R. A.; Cashen, D. E.; Martin, W. J.; Metzger,
J. M.; Strack, A. M.; MacIntyre, D. E.; van der Ploeg, L.
H. T.; Patchett, A. A.; Wyvratt, M. J.; Nargund, R. P.
Bioorg. Med. Chem. Lett. 2005, 15, 3501; (d) Dyck, B.;
Parker, J.; Phillips, T.; Carter, L.; Murphy, B.; Summers,
R.; Hermann, J.; Baker, T.; Cismowski, M.; Saunders, J.;
Goodfellow, Val. Bioorg. Med. Chem. Lett. 2003, 13, 3793;
(e) Pontillo, J.; Tran, J. A.; Arellano, M.; Fleck, B. A.;
Huntley, R.; Marinkovic, D.; Lanier, M.; Nelson, J.;
Parker, J.; Saunders, J.; Tucci, F. C.; Jiang, W.; Chen, C.
W.; White, N. S.; Foster, A. C.; Chen, C. Bioorg. Med.
Chem. Lett. 2004, 14, 4417; (f) Chen, C.; Pontillo, J.;
Fleck, B. A.; Gao, Y.; Wen, J.; Tran, J. A.; Tucci, F. C.;
Marinkovic, D.; Foster, A. C.; Saunders, J. J. Med. Chem.
2004, 47, 6821; (g) Richardson, T. I.; Ornstein, P. L.;
Briner, K.; Fisher, M. J.; Backer, R. T.; Biggers, C. K.;
Clay, M. P.; Emmerson, P. J.; Hertel, L. W.; Hsiung, H.
M.; Husain, S.; Kahl, S. D.; Lee, J. A.; Lindstrom, T. D.;
Martinelli, M. J.; Mayer, J. P.; Mullaney, J. T.; O’Brien,
T. P.; Pawlak, J. M.; Revell, K. D.; Shah, J.; Zgombick, J.
M.; Herr, R. J.; Melekhov, A.; Sampson, P. B.; King,
C.-H. R. J. Med. Chem. 2004, 47, 744; (h) Fisher, M. J.;
22. Shimazaki, T.; Chaki, S. Pharmacol. Biochem. Behav.
2005, 80, 395.
23. (a) Todorovic, A.; Holder, J. R.; Bauzo, R. M.; Scott, J.
W.; Kavanagh, A.; Abdel-Malek, Z.; Haskell-Luevano, C.
J. Med. Chem. 2005, 48, 3328; (b) Wilczynski, A.; Wilson,
K. R.; Scott, J. W.; Edison, A. S.; Haskell-Luevano, C.
J. Med. Chem. 2005, 48, 3060; (c) Joseph, C. G.; Wang, X.
S.; Scott, J. W.; Bauzo, R. M.; Xiang, Z.; Richards, N. G.;
Haskell-Luevano, C. J. Med. Chem. 2004, 47, 6702; (d)
Wilczynski, A.; Wang, X. S.; Joseph, C. G.; Xiang, Z.;
Bauzo, R. M.; Scott, J. W.; Sorensen, N. B.; Shaw, A. M.;
Millard, W. J.; Richards, N. G.; Haskell-Luevano, C.
J. Med. Chem. 2004, 47, 2194; (e) Han, G.; Haskell-
Luevano, C.; Kendall, L.; Bonner, G.; Hadley, M. E.;
Cone, R. D.; Hruby, V. J. J. Med. Chem. 2004, 47, 1514;
(f) Balse-Srinivasan, P.; Grieco, P.; Cai, M.; Trivedi, D.;

D. Nozawa et al. / Bioorg. Med. Chem. 15 (2007) 1989–2005
2005
Backer, R. T.; Husain, S.; Hsiung, H. M.; Mullaney, J. T.;
O’Brien, T. P.; Ornstein, P. L.; Rothhaar, R. R.; Zgom-
bick, J. M.; Briner, K. Bioorg. Med. Chem. Lett. 2005, 15,
4459; (i) Pan, K.; Scott, M. K.; Lee, D. H. S.; Fitzpatrick,
L. J.; Crooke, J. J.; Rivero, R. A.; Rosenthal, D. I.;
Vaidya, A. H.; Zhao, B.; Reitz, A. B. Bioorg. Med. Chem.
2003, 11, 185; (j) Fotsch, C.; Han, N.; Arasasingham, P.;
Bo, Y.; Carmouche, M.; Chen, N.; Davis, J.; Goldberg,
M. H.; Hale, C.; Hsieh, F.-Y.; Kelly, M. G.; Liu, Q.;
Norman, M. H.; Smith, D. M.; Stec, M.; Tamayo, N.; Xi,
N.; Xu, S.; Bannon, A. W.; Baumgartner, J. W. Bioorg.
Med. Chem. Lett. 2005, 15, 1623.
Foster, A. C.; Chen, C. Bioorg. Med. Chem. Lett. 2005,
14, 2541.
28. (a) Pontillo, J.; Marinkovic, D.; Tran, J. A.; Arellano, M.;
Fleck, B. A.; Wen, J.; Tucci, F. C.; Nelson, J.; Saunders, J.;
Foster, A. C.; Chen, C. Bioorg. Med. Chem. Lett. 2005, 14,
4615; (b) Tucci, F. C.; White, N. S.; Markison, S.; Joppa,
M.; Tran, J. A.; Fleck, B. A.; Madan, A.; Dyck, B. P.;
Parker, J.; Pontillo, J.; Arellano, L. M.; Marinkovic, D.;
Jiang, W.; Chen, C. W.; Gogas, K. R.; Goodfellow, V. S.;
Saunders, J.; Foster, A. C.; Chen, C. Bioorg. Med. Chem.
Lett. 2005, 14, 4389; (c) Pontillo, J.; Tran, J. A.; Fleck, B. A.;
Marinkovic, D.; Arellano, M.; Tucci, F. C.; Lanier, M.;
Nelson, J.; Parker, J.; Saunders, J.; Murphy, B.; Foster, A.
C.; Chen, C. Bioorg. Med. Chem. Lett. 2004, 14, 5605; (d)
Tran, J. A.; Pontillo, J.; Arellano, M.; White, N. S.; Fleck,
B. A.; Marinkovic, D.; Tucci, F. C.; Lanier, M.; Nelson, J.;
Saunders, J.; Foster, A. C.; Chen, C. Bioorg. Med. Chem.
Lett. 2005, 14, 833; (e) Marsilje, T. H.; Roses, J. B.;
Calderwood, E. F.; Stroud, S. G.; Forsyth, N. E.; Black-
burn, C.; Yowe, D. L.; Miao, W.; Drabic, S. V.; Bohane, M.
D.; Daniels, J. S.; Li, P.; Wu, L.; Patane, M. A.; Claiborne,
C. F. Bioorg. Med. Chem. Lett. 2004, 14, 3721.
25. Arasasingham, P. N.; Fotsch, C.; Ouyang, X.; Norman,
M. H.; Kelly, M. G.; Stark, K. L.; Karbon, B.; Hale, C.;
Baumgartner, J. W.; Zambrano, M.; Cheettham, J.;
Tomayo, N. J. Med. Chem. 2003, 46, 9.
26. Xi, N.; Hale, C.; Kelly, M. G.; Norman, M. H.; Stec, M.;
Xu, S.; Baumgartner, J. W.; Fotsch, C. Bioorg. Med.
Chem. Lett. 2004, 14, 377.
27. Pontillo, J.; Tran, J. A.; Markison, S.; Joppa, M.; Fleck,
B. A.; Marinkovic, D.; Arellano, M.; Tucci, F. C.;
Lanier, M.; Nelson, J.; Saunders, J.; Hoare, S. R. J.;