Further optimization of novel pyrrole 3-carboxamides for targeting serotonin 5-HT2A, 5-HT2C, and the serotonin transporter as a potential antidepressant

Article abstract of DOI:10.1016/j.bmc.2010.06.037

In the continuing search for novel compounds targeting serotonin 5-HT _2A, 5-HT_2C, and serotonin transporter, new arylpiperazine-containing pyrrole 3-carboxamide derivatives were synthesized and evaluated. Based on the lead reported previously, structural modifications regarding N-(3-(4-(2,3-dichlorophenyl)piperazin-1-yl)propyl)-1,2-dimethyl-5- phenyl-1H-pyrrole-3-carboxamide 5, were accomplished for improvements in not only binding affinity against serotonin receptors and transporter, but also in hERG channel inhibition. Along the line, both the forced swimming tests and spontaneous locomotor activity tests were performed to distinguish between antidepressant activity and false positive results. As potential antidepressant agents, both 2,4-dimethyl-5-phenyl-1H-pyrrole-3-carboxamide and 5-tert-butyl-2-methyl-1H-pyrrole-3-carboxamide derivatives exhibited favorable in vitro and in vivo activities, warranting further investigation around these scaffolds.

Full text of DOI:10.1016/j.bmc.2010.06.037

Bioorganic & Medicinal Chemistry 18 (2010) 6156–6169
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Further optimization of novel pyrrole 3-carboxamides for targeting serotonin
5-HT2A, 5-HT2C, and the serotonin transporter as a potential antidepressant
Suk Youn Kang a, Eun-Jung Park a, Woo-Kyu Park b, Hyun Jung Kim a, Gildon Choi b, Myung Eun Jung a,
Hee Jeong Seo a, Min Ju Kim a, Ae Nim Pae c, Jeongmin Kim a, Jinhwa Lee a,
*
a Research Center, Green Cross Corporation, 303 Bojeong-Dong, Giheung-Gu, Yongin 446-770, Republic of Korea
b Pharmacology Research Center, Korea Research Institute of Chemical Technology (KRICT), 100 Jang-Dong, Yuseong-Gu, Daejeon 305-343, Republic of Korea
c Biochemical Research Center, Korea Institute of Science and Technology, 39-1 Hawolgok-Dong, Seongbuk-Gu, Seoul 136-791, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
In the continuing search for novel compounds targeting serotonin 5-HT2A, 5-HT2C, and serotonin
transporter, new arylpiperazine-containing pyrrole 3-carboxamide derivatives were synthesized and
evaluated. Based on the lead reported previously, structural modifications regarding N-(3-(4-(2,3-dichlo-
rophenyl)piperazin-1-yl)propyl)-1,2-dimethyl-5-phenyl-1H-pyrrole-3-carboxamide 5, were accom-
plished for improvements in not only binding affinity against serotonin receptors and transporter, but
also in hERG channel inhibition. Along the line, both the forced swimming tests and spontaneous loco-
motor activity tests were performed to distinguish between antidepressant activity and false positive
results. As potential antidepressant agents, both 2,4-dimethyl-5-phenyl-1H-pyrrole-3-carboxamide and
5-tert-butyl-2-methyl-1H-pyrrole-3-carboxamide derivatives exhibited favorable in vitro and in vivo
activities, warranting further investigation around these scaffolds.
Received 15 April 2010
Revised 11 June 2010
Accepted 11 June 2010
Available online 25 June 2010
Keywords:
Depression
Antidepressant
Serotonin
Piperazine
Pyrrole
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
dysfunction. In addition, SSRIs are troublesome in that it is gener-
ally effective only less than two-third patients.6 Recently, there has
Depression, especially major depression, is an extremely serious
disease affecting about 121 million people and is one of the leading
causes of disability worldwide. And unipolar depression is pre-
dicted to be the second main cause of disability in 2020 by the
World Health Organization.1,2 Over the past decades, the synaptic
actions of monoamine neurotransmitters such as norepinephrine
(NE) and serotonin (SER, 5-HT) were considered as important indi-
cations to psychiatric disease,3,4 including anxiety and depression.
And individually, various psychotropic drugs were developed asso-
ciated with these neurotransmitters. After great success of a series
of selective serotonin reuptake inhibitors (SSRI), it was rationalized
the relationship between extracellular levels of serotonin and a
number of psychiatric indications, especially depressive disorder,
by inhibiting serotonin transporters and consequently elevating
synaptic serotonin levels. SSRIs such as fluoxetine, sertraline, par-
oxetine, and citalopram have been the most widely prescribed
antidepressants since 1980s.5
been achievement of important development for antidepressant,
which interacts with dual or multiple targets.7 Because numerous
side effects are associated with non-selective binding at post-syn-
aptic 5-HT receptors, addition of 5-HT receptor antagonist compo-
nent to 5-HT reuptake inhibitor has been proposed.8–10 With this
approach, it was expected to increase the level of synaptic 5-HT
and eventually achieve rapid onset time. Along the line, various
compounds have been proposed and developed as potential anti-
depressant with dual activity (Fig. 1).11–14
From the literature, common structure of antidepressants
known to have dual activities appeared to exhibit combination
of two distinct structural motifs. Thus, aryl piperazine elements
and heterocyclic motifs were connected to each other using a lin-
ker frequently to serve as SERT and 5-HT receptor inhibitors. As a
similar strategy, we recently disclosed a new class of antidepres-
sant compounds involving pyrrole 3-carboxamide compounds.15
Particularly, compound 5 showed good in vitro activity against
5-HT2A/2C receptors and serotonin reuptake inhibition, and also
demonstrated excellent oral bioavailability and brain penetrative
properties (Fig. 2). As a continuation of our investigation, we wish
to describe further exploration of the structure–activity relation-
ships (SAR) in this novel series. Evaluation of their in vitro and
in vivo profiles was conducted in terms of efficacy versus side
effects.
Despite numerous usage of SSRIs, they also have some side
effects including anxiety, sedation, headache, tremor, and sexual
* Corresponding author. Tel.: +82 31 260 9892; fax: +82 31 260 9020.
E-mail addresses: jinhwalee@greencross.com, jinhwa_2_lee@hotmail.com (J.
Lee).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.06.037

S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
6157
F
F
N
HN
O
N
S
O
N
O
HN
O
LY367265, 1
SERT = 2.3 nM, 5-HT2A = 0.81 nM
YM-35992, 2
SERT = 21 nM, 5-HT2A = 86 nM
O
H
O
N
O
N
N
N
O
N
Cl
N
N
Cl
N
Cl
Nefazodone, 3
5-HT1A = 52 nM, 5-HT2A = 7.1 nM, SERT = 220 nM
aripiprazole, 4
5-HT1A = 1.65 nM, 5-HT2 = 8.7 nM, D2 = 8.34 nM
Figure 1. Chemical structures of representative antidepressant compounds.
Hydrolysis of pyrrole ester 12 using sodium hydroxide in refluxed
ethanol afforded the corresponding acids 13.
As shown in Scheme 2, preparation of aminoalkyl arylpiper-
azine 17 started from the corresponding bromoalkyl-phthalimide
14 and arylpiperazine 15.17 Treatment of bromoalkyl-phthalimide
14 with arylpiperazine hydrochloride 15 in the presence of potas-
sium carbonate in DMF at room temperature afforded N-protected
amine 16. Compound 16 was then treated with hydrazine in etha-
nol at 80 °C to give amine 17. For the sake of convenience of han-
dling on scale, liquid amine 17 was transformed to hydrochloride
salt form 17a with 4 N HCl in dioxane.
4
Cl
N
Me1
H
N
N
Cl
N
2
Me
O
5-HT2A = 46 nM
5-HT2C = 12 nM
SERT = 62 nM
5
Figure 2. Representative compound for targeting serotonin 5-HT2A/2C, and the SERT
as a antidepressant.
As shown in Scheme 3, typical amide coupling was conducted
under conditions involving EDCI (1-[3-(dimethylamino)propyl]-3-
ethylcarbodiimide), HOBT (1-hydroxybenzotriazole) and NMM
(4-methylmorpholine) in methylene chloride or DMF to produce
amide 18. As reaction was completed, purification was performed
using preparative reverse-phase HPLC with 0.2% TFA mixture of
acetonitrile and water solution. The neutral form of product 18
was converted to HCl salt form 18a to increase the overall solubil-
ity for biological evaluation.
2. Chemistry
Based on the previous results, structural modification of lead
compound 5 was initiated as shown in Figure 3.15 The structure–
activity relationship study began with evaluation of the effect by
substitution of various arylpiperazinyl groups. Thus, novel com-
pounds can be readily prepared by typical amide coupling at the fi-
nal stage with modified acid and amine. Pyrrole 3-carboxylic acid A
and arylpiperazinyl alkyl amine B can be used as acid and amine
partners, respectively.
3. Biology
Bromoketone 9 was selected for the preparation of pyrrole
derivatives, particularly consisting of 5-substituted and 3-carbox-
ylic acid (Scheme 1).16 Substitution at nitrogen of pyrrole was fo-
cused on within proton to n-propyl based on the previous result.
For further evaluation of our lead compound 5, spontaneous
locomotor activity test was performed. Although the sensitivity
of FST (forced swimming test) to a broad range of antidepressant
drugs is one of the most important features supporting primary
Cl
O
Cl
OH
+
N
Cl
N
N
Me
H
N
H2N
N
Me
N
Cl
Me
N
6
7
Me
O
5
structural modification
R2
N
O
R2
N
OH
+
R3
R4
O
N
R4
N
N
N
R3
n
N
H
Me
H2N
R1
n
(n = 1,2,3)
(n = 1,2,3)
Me
A
B
R1
C
Figure 3. Preparation of target compounds using amide bond formation.

6158
S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
O
O
O
O
OEt
R'
OEt
Me
O
O
a
b
Br
O
+
R
R'
OEt
R
R'
R
N
H
8
9
10
11
O
O
R'
R'
OEt
Me
OH
Me
R = Ph, p-Cl-Ph, m-MeO-Ph, p-MeO-Ph,
2-pyridyl, 3-pyridyl, 4-pyridyl, t-Bu
c
d
R
R
R' = H and Me
N
N
R''
R''
12
13
(R'' = H, Me, Et, nPr)
Scheme 1. Reagents and conditions: (a) NaH, THF; (b) NH4OAc, AcOH, 80 °C; (c) NaH, Alkyl iodide, DMF; (d) NaOH, EtOH, reflux.
O
O
N
N
a
b
Br
N
n
R
N
n
HN
HCl
N
O
16
O
R
14
15
2HCl
c
N
N
N
N
H2N
H2N
n
n
R
R
17a
17
Scheme 2. Reagents and conditions: (a) K2CO3, DMF, rt; (b) NH2NH2ÁH2O, EtOH, rt; (c) 4 N HCl in dioxane.
O
R'
O
2HCl
R'
N
H
N
OH
Me
13
R
n
N
N
a
N
+
N
H2N
n
Me
R
X
R''
N
X
17a
R''
18
O
R'
b
N
N
R
n
H
N
N
HCl
Me
R''
X
18a
Scheme 3. Reagents and conditions: (a) EDCI, HOBT, NMM, CH2Cl2 or DMF; (b) HCl, MeOH, 0 °C.
usage as a viable animal model, the activity in the FST is also
known to be detected by either anticholinergic or antihistamine
drugs depending on test conditions.21 The major false positives in
the FST are psychomotor stimulants, which affect immobility in
the FST. They are not anticipated to have clinical efficacy. From
these reasons, our lead compound 5 was subjected to screening
against spontaneous locomotor activity along with the FST. The re-
sults were summarized in Figure 4. Fluoxetine, a clinically estab-
lished reference, shows lower spontaneous locomotor activity
regardless of dosing amounts. And compound 5 tends to display
increasing locomotor activities with dose dependency. It means
that our compound shows antidepressant-like activity by reducing
immobility in the FST, but its efficacy was falsely produced from
hyperactivity of the compounds. That is the reason why we focused
our efforts to remove spontaneous locomotor activity, while main-
taining immobility in FST experiments.
Biological evaluations were performed upon compounds pre-
pared by the above synthetic pathway. The binding affinity of cur-
rent compounds against 5-HT2A/2C receptor and serotonin
transporter, stably expressed in CHO-K1 cells, were evaluated by
displacement binding using [3H]Ketanserin, [3H]Mesulergine and,
[3H]Imipramine, respectively, as radioligands.18
Based on our previous report,15 derivatization of arylpiperazine
was expanded to various pyrroles 13 including 1,2-dimethyl-5-
phenyl-1H-pyrrole-3-carboxylic acid and 2-methyl-5-phenyl-1-
propyl-1H-pyrrole-3-carboxylic acid. The results are summarized
in Table 1. In the case of N-methyl pyrrole, overall derivatization
showed less favorable binding affinity than that of 2,3-dichloro-
phenyl group. Particularly, 4-fluorophenyl and 8-quinolinyl group
showed more potent binding affinity at 5-HT2A and SERT, respec-
tively (24, 25, and 38). But it turned out to result in inferior activity
with consideration of other receptors. On the other hand, derivati-

S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
6159
Figure 4. Locomotor activities of the mice treated with compounds or vehicle were counted for 30 min by Activity Analyzer. Compound (10, 25, and 50 mg/Kg) or vehicle was
administered orally (po) 60 min before the test. Data were expressed as mean SEM of 6–7 mice. *P <0.05, when compared to vehicle control group.
Table 1
Competition binding assays at 5-HT2A and 5-HT2C receptor and the serotonin transporter to arylpipierazinyl pyrrole 3-carboxamide derivatives (IC50 values)
O
NH
N
N Ar
Me
N
R
unit: nM
Ar
R
Me
nPr
No.
5-HT2A
5-HT2C
SERT
No.
5-HT2A
5-HT2C
SERT
3-Chlorophenyl
19
20
5
92
57
46
160
133
12
11
12
62
23
28
29
30
191
129
324
273
225
628
93
76
420
2,3-Dimethylphenyl
2,3-Dichlorophenyl
2,4-Dichlorophenyl
3,4-Dichlorophenyl
2-Bromophenyl
21
213
349
31
54
324
284
22
221
633
225
3-Bromophenyl
32
33
34
35
221
953
153
874
633
1408
452
225
1084
322
2-Methoxyphenyl
3-Methoxyphenyl
2,3-Dimethoxyphenyl
4-Fluorophenyl
23
24
666
22
782
493
1259
183
977
1981
2,5-Difluorophenyl
3-Trifluoromethylphenyl
8-Quinolinyl
2-Methyl-8-quinolinyl
4-Pyridinyl
36
37
38
135
410
210
1006
619
420
854
381
82
25
26
27
352
832
4559
233
653
5257
22
300
>10,000
zation in N-propyl pyrrole case shows similar binding affinity with
2,3-dichlorophenyl group. It can be possibly explained that lead
2,3-dichlorophenyl compounds showed less favorable potency
than 2,3-dimethyl compounds. Nevertheless, overall binding affin-
bility, methylation at amide nitrogen was performed (Table 2). In
addition to that, methylation at C-4 position was also performed
and the results were displayed at Table 3. In the case of 2,3-dim-
ethylphenylpiperazinyl series, compound 39 showed highly im-
proved binding affinity to 5-HT2A/2C receptors, but decreased at
SERT as a trade. When compound 5 was modified into compound
40 by way of N-methylation at amide group, there appears to
slightly increase in binding affinity against serotonin receptors.
And when N-methyl at pyrrole was changed to N-propyl pyrrole
derivative 41, binding affinity against 5-HT2A/2C increased dramat-
ity displays IC50 <1 lM, implying that these compounds might hold
promises as a potential antidepressant. Thus, either 2,3-dimethyl-
phenyl or 2,3-dichlorophenyl group was adopted constantly as the
piperazinyl substituent and further SAR studies were performed.
In order to improve binding affinity against 5-HT2A/2C receptors
and the serotonin transporter as well as to improve metabolic sta-

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S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
Table 2
Table 4
Binding affinities for 5-HT2A and 5-HT2C receptor and serotonin transporter of
arylpipierazinyl pyrrole 3-carboxamide derivatives
Binding affinities against 5-HT2A and 5-HT2C receptors and inhibition against
serotonin transporter of arylpipierazinyl pyrrole 3-carboxamide derivatives
O
O
N
N
R3
N
H
N
R3
R2
R2
N
R3
N
R3
N
N
Me
Me
R1
R1
unit: nM
5-HT2C
unit: nM
No.
R1
R2
R3
5-HT2A
SERT
No.
R1
R2
R3
5-HT2A
5-HT2C
SERT
5
20
29
30
39
40
41
Me
Me
nPr
nPr
nPr
Me
nPr
H
H
H
H
Cl, Cl
46
57
129
324
17
12
13
225
628
12
62
12
76
420
163
98
Me, Me
Me, Me
Cl, Cl
Me, Me
Cl, Cl
50
51
56
52
53
54
55
57
58
59
60
61
62
63
64
65
66
67
H
Et
Et
H
Me
Et
nPr
H
Me
Et
nPr
H
Me
nPr
Me
nPr
Me
nPr
Phenyl
Phenyl
Phenyl
Me, Me
Me, Me
Cl, Cl
Me, Me
Me, Me
Me, Me
Me, Me
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
Cl, Cl
300
75
376
92
213
151
192
105
232
153
333
21
43
58
209
46
39
615
139
66
189
129
39
77
36
182
19
129
93
Me
Me
Me
4-Chlorophenyl
4-Chlorophenyl
4-Chlorophenyl
4-Chlorophenyl
4-Chlorophenyl
4-Chlorophenyl
4-Chlorophenyl
4-Chlorophenyl
2-Pyridinyl
2-Pyridinyl
2-Pyridinyl
3-Pyridinyl
3-Pyridinyl
39
33
35
21
Cl, Cl
102
26
106
39
22
41
221
267
639
92
131
56
733
629
1159
28
110
397
7
Table 3
Binding affinities against 5-HT2A and 5-HT2C receptors and inhibition against
serotonin transporter of arylpipierazinyl pyrrole 3-carboxamide derivatives
R2
O
344
175
420
133
85
78
4-Pyridinyl
4-Pyridinyl
Cl
Cl
N
R1
n
34
HN
Me
N
N
unit: nM
5-HT2C
Table 5
No.
R1
R2
n
5-HT2A
SERT
Binding affinities for 5-HT2A and 5-HT2C receptor and serotonin transporter of
arylpipierazinyl pyrrole 3-carboxamide derivatives
42
43
44
45
46
47
48
49
H
H
H
H
H
Me
Me
Me
Me
1
1
1
2
1
1
1
2
40
175
408
300
37
33
25
39
37
156
310
599
13
16
75
16
87
57
32
137
162
78
Me
nPr
H
O
R2
R2
H
N
Me
nPr
H
R1
HN
n
78
36
N
N
Me
unit: nM
No.
R1
R2
n
5-HT2A
5-HT2C
SERT
ically, thereby displaying similar level of affinity as against seroto-
nin transporter.
68
69
70
71
72
Me
Me
Me
H
Me, Me
Me, Me
Cl, Cl
Cl, Cl
Cl, Cl
1
2
1
2
2
36
386
50
107
163
2227
1145
109
1392
1021
908
252
45
860
375
As another practice, instead of N-methylation at amide group,
methylation at C-4 position of pyrrole displayed somewhat differ-
ent results (Table 3). Thus, it was observed that when 2,3-dichlor-
ophenylpiperazinyl part and pyrrole 3-carboxilic acid part was
connected with ethylene linker, and binding affinities were at level
of IC50 <80 nM for C-4 methylated analogues, except compound 46
(IC50 = 162 nM) at SERT. Favorable binding affinities against 5-HT,
5-HT, and SERT were also observed for compound 49 as shown
in Table 3.
Limited exploration of the effects of substitution on the phenyl
of pyrrole C-5 position was also undertaken (Table 4). At N-alkyl-
ated pyrrole series, 4-chlorophenyl modification tends to reduce
binding affinity against 5-HT2A and inhibition against SERT but in-
crease binding affinity against 5-HT2C receptor (51 vs 54 and 56 vs
59). On the other hand, in the case of N–H pyrrole compounds, the
exactly opposite trends are displayed (50 vs 52). With this in mind,
replacement of phenyl group with more hydrophilic pyridinyl
group was also conducted. 2-Pyridinyl substituted compound 61
is more potent than phenyl compound 50, especially against
5-HT2A and SERT. However, when N-alkylation at pyrrole N-1 posi-
tion was changed to methyl or propyl, binding affinity about
5-HT2C and SERT decreased while maintaining 5-HT2A activity
(61 vs 62 vs 63). 3-Pyridinyl and 4-pyridinyl compounds displayed
similar level of activities. Most of pyridinyl compounds exhibited
Me
more favorable activity against 5-HT2A than against 5-HT2C and
SERT.
Introduction of t-butyl group at phenyl position of pyrrole was
also studied, and the results were summarized in Table 6. Although
its Clog P value is similar to that of phenyl compound (Clog P = 6.60
at 5) and t-butyl compound (Clog P = 6.33 at 72), Compound 72
which is t-butyl version of lead compound 5, showed poor binding
affinity against 5-HT2C (IC50 = 1021 nM) and moderate activity
against 5-HT2A (IC50 = 163 nM) and SERT (IC50 = 375 nM). 2,3-
Dimethylphenyl compound 69 appeared to show similar level of
binding affinity. To date the best result of t-butyl scaffold was ob-
tained when 2,3-dichlorophenylpiperazinyl group was connected
with C2 linker (compound 70) (see Table 5).
For further evaluation of this series of compounds, several
selected compounds were subjected to hERG channel inhibition as-
say.19 Patch-clamp technique method was used for in vitro assay
for hERG blocking. And the results are summarized in Table 6. Lead
compound 5 turned out be a significant inhibitor of hERG channel

S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
6161
Table 6
was administered orally 30 min before the test in mice at 50 or
100 mg/kg. And the results were displayed in Figure 5. Compared
with reference compound Prozac, ten compounds show similar
or even better antidepressant-like efficacy. Modification of arylpip-
erazinyl group did not lead to good efficacy. N-Methylated amide
compounds 39 and 40 appeared to enhance efficacy, even with
dimethylphenyl analogue 39. C-4 Methyl compounds displayed
nice structure–activity correlation (46, 47, 48, and 49) in that anti-
depressant-like effects increase for ethylene carbon linker when N-
alkyls are elongated from proton to propyl (H 46 vs Me 47 vs nPr
48). Thus, while compound 46 do not show good in vivo efficacy
on FST, significant enhancement was demonstrated for its propyl-
ene version 49.
Compound 58, 4-chlorophenyl group at pyrrole, appears to re-
duce efficacy than lead compound 5. And this result was well-corre-
lated with in vitro data (compound 5: 5-HT2A IC50 = 46 nM, 5-HT2C
IC50 = 12 nM, SERT IC50 = 62 nM and compound 58: 5-HT2A
IC50 = 232 nM, 5-HT2C IC50 = 39, SERT IC50 = 733 nM). 2-Pyridinyl
compound 62 shows better antidepressant-like activity than that
of the corresponding 3-pyridinyl or 4-pyridinyl compound. 5-t-Bu-
tyl pyrrole analogues 70, 71, and 72 produce more favorable activity
compared to fluoxetine (Prozac). The best result was obtained when
5-t-butylpyrrole moiety was connected to 2,3-dichlorophenylpyrid-
inyl via C3-carbon linker 72 (immobility = 12.5 4.8%).
The hERG channel blocking data assayed for selected compounds
No.
hERG
No.
hERG
No.
hERG
5
30
39
40
0.14
0.54
0.70
0.50
45
61
62
63
0.10
0.90
1.70
1.00
64
68
70
Prozac
6.80
11.8
6.90
3.10a
a
See Ref. 23.
(IC50 = 0.14
compound 45 (IC50 = 0.10
fourfold when N-methyl was replaced with N-n-propyl (IC50
0.54 M, 5 vs 30).
lM). Similar result was also obtained for N–H pyrrole
l
M). hERG inhibition decreased by about
=
l
N-methylation at amide group resulted in reduced hERG inhibi-
tion in approximately 3.5-fold (5 vs 40), suggesting that hERG inhi-
bition profiles can be altered when compound is structurally
modified by removing a hydrogen bond donor in amide functional
group.
Pyridinyl groups were not able to improve hERG channel block-
ing except compound 64 (IC50 = 6.8 lM). However, 5-t-butylpyr-
role compounds 68, 70 indeed showed significant improvement
toward hERG channel inhibition compared to other scaffolds. For
the reference, IC50 value for fluoxetine was reported to be
3.1 l
M.23 Therefore, the compounds near this value for hERG chan-
The second in vivo test involves spontaneous locomotor activity
test. Compounds 64, 68, and 70 which show moderate safety in
hERG blocking experiment were selected. And the results were
summarized in Table 7.
Although various pyrrole derivatives were changed, most com-
pounds showed hyperactivity. At this point, we also observed that
when arylpiperazine was altered from dichlorophenyl into dimeth-
ylphenyl, a degree of locomotor activity was also decreased. Thus,
nel inhibition appear to be promising for current stage of research.
The representative compounds were tested in vivo models in
mice to further confirm its ability to inhibit the monoamine
transport and produce antidepressant-like effects. As the first
experiment, the potential antidepressant-like effect of current
compounds was evaluated in the forced swimming test (FST),
which is sensitive to known antidepressant drugs.20 The compound
Figure 5. Effects of drugs on immobility in forced swimming test on mice. Drugs (100 and 50 mg/kg) were injected orally (po) 60 min before the testing, and total duration of
immobility was recorded during the last 5 min of the 6-min testing period. Values are means S.E.M and vehicle = 100%.

6162
S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
Table 7
4. Conclusion
Locomotor activities of the mice treated with compounds (25 mg/kg) or vehicle were
counted for 30 min by Activity Analyzer
In summary, we investigated new arylpiperazine-containing
pyrrole 3-carboxamide series of compounds as our continuing ef-
fort to identify novel compounds targeting 5-HT2A/2C and SERT
for the treatment of depressive disorders. Based on the lead com-
pound 5, a number of structural modifications are presented
including modification of arylpiperazinyl group, N-alkylation of
amide group, C-4 methylation at pyrrole, and replacement of phe-
nyl group of pyrrole with p-chlorophenyl, pyridinyl, or t-butyl. All
the prepared compounds were evaluated by competition binding
assays against 5-HT2A/2C and SERT. Structure–activity relationships
(SARs) were established. hERG blocking assay was conducted for
further evaluation of this series. A few of selected compounds were
tested in vivo FST animal models. More than ten compounds in this
series produced similar or better antidepressant-like activity com-
pared with fluoxetine, well-established reference antidepressant.
Spontaneous locomotor activity test was conducted to distinguish
the false positive effects in the FST. In order to overcome hyperac-
tivity issue, 3-chloro-2-methylphenyl group was introduced into
the series. Through a series of lead optimization efforts, compound
74 was identified to possess good binding affinity (5-HT2A
IC50 = 54 nM, 5-HT2C IC50 = 210 nM, SERT IC50 = 315 nM) in addi-
No.
Locomotor activity
Hyperactivity sign
64a
68
70
72
—
Hyperactivea
Mid-hyperactive
Hyperactive
Hyperactive
Mid-hyperactive
Normal
7302 2414
14860 1531
15804 5162
7158 484
5931 1979
À5000
Effexorb
Prozacb
Vehicle
Normal
Data were expressed as mean S.E.M of 6–7 mice.
a
See Ref. 22.
In-house data.
b
in order to reduce hyperactivity with maintaining antidepressant
activity, 3-chloro-2-methylphenyl piperazine was introduced as a
novel arylpepierazine moiety, and with consideration of hERG
blocking issue, t-butylpyrrole analogues were selected. Derivatives
of compound 68 or 70 were evaluated and the in vitro and in vivo
results are shown in Table 8.
Comparing with 2,3-dichlorophenyl compound 43, 2-methyl-3-
chlorophenyl compound 73 showed similar profiles to 5-HT2A and
SERT and mild decrease to 5-HT2C (compound 43: 5-HT2A
IC50 = 175 nM, 5-HT2C IC50 = 156 nM, SERT IC50 = 57 nM and com-
pound 73: 5-HT2A IC50 = 152 nM, 5-HT2C = 233 nM, SERT = 64 nM).
In a series of t-butylpyrrole, when 2-methyl-3-chlorophenyl com-
pound 74 was compared with 2,3-dimethyl analogue 68, compound
74 was observed to show slight decrease against 5-HT2A and out-
standing activity improvement against 5-HT2C and SERT (compound
68: 5-HT2A IC50 = 36 nM, 5-HT2C IC50 = 2227 nM, SERT IC50 = 908 nM
and compound 74: 5-HT2A IC50 = 54 nM, 5-HT2C = 210 nM,
SERT = 315 nM). On the contrary to 2,3-dimethylphenyl, when com-
pound 74 is compared with 2,3-dichlorophenyl compound 70, they
showed similar binding affinity against 5-HT2A, and 2 and sevenfold
reduction against 5-HT2C and SERT, respectively (compound 70:
5-HT2A IC50 = 50 nM, 5-HT2C IC50 = 109 nM, SERT IC50 = 45 nM and
compound 74: 5-HT2A IC50 = 54 nM, 5-HT2C = 210 nM, SERT =
tion to relatively safe hERG inhibition (IC50 = 3.6 lM). By in vivo
efficacy study, compound 74 also showed reasonable antidepres-
sant activity without exhibiting hyperactivity. Thus, novel pyrrole
3-carboxamides targeting serotonin 5-HT2A, 5-HT2C, and the sero-
tonin transporter may have potential as a pharmacotherapy for
the treatment of depressive disorders.
5. Experimental
5.1. General methods
All reactions are conducted under an inert atmosphere at room
temperature, unless otherwise noted. All reagents were purchased
at the highest commercial quality and used without further purifi-
cation, unless otherwise indicated. Microwave reaction was con-
ducted with a Biotage Initiator microwave reactor. NMR spectra
were obtained on a Varian 400-MR (400 MHz 1H, 100 MHz 13C)
spectrometer. NMR spectra were recorded in ppm (d) relative to
tetramethylsilane (d = 0.00) as an internal standard unless stated
otherwise and are reported as follows: chemical shift, multiplicity
(s = singlet, d = doublet, t = triplet, q = quartet, quint = quintet,
sext = sextet, m = multiplet, and br = broad), coupling constant,
and integration. 13C NMR spectra were referenced to the residual
CDCl3 (d = 77.0) or DMSO-d6 (d = 39.7). Mass spectra were obtained
with an Agilent 6110 quadruple LC-MSD (ESI+). Preparative HPLC
purifications were performed on a Gilson purification system. For
preparative HPLC, ca. 100 mg of a product was injected in 1 ml of
315 nM). Additionally, compound 74 showed 3.6 lM about hERG
channel inhibition assay. With compounds 73 and 74, forced swim-
ming test (FST) and spontaneous locomotor activity test (SLA) were
also performed. Compound 73 showed moderate hyperactivity and
showed less antidepressant-like activity. However, in the case of t-
butyl version, compound 74 displayed good antidepressant activity
with normal behavior.
Although compound 5 in our prior work15 demonstrated good
in vitro and in vivo antidepressant-like activity, 5 also suffered
from negative aspects including strong hERG inhibition and false
positive effects. Current research successfully identified compound
74 bearing t-butyl group at pyrrole C-5, overcoming the inherent
problems of compound 5.
methanol onto a SunFire Prep C18 OBD 5
l
m 30 Â 100 mm Column
Table 8
Binding affinities against 5-HT2A and 5-HT2C receptors and inhibition against serotonin transporter of compound 73 and 74 and effects on immobility in forced swimming test on
mice and locomotor activities
R
O
HN
Me
Cl
N
Me
N
N
Me
R
No.
5-HT2A (nM)
5-HT2C(nM)
SERT (nM)
FST (%)
SLA (cm)
Phenyl
t-Butyl
73
74
152
54
233
210
64
315
86.15 10.89
49.12 14.50
7096 1926
6217 2903
For FST, drugs (25 mg/kg) were injected orally (po) 60 min before the testing, and total duration of immobility was recorded during the last 5-min of the 6-min testing period.
For locomotor activities, locomotion of mice treated with compounds or vehicle were counted for 30 min by Activity Analyzer. Data were expressed as mean S.E.M.

S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
6163
with a 30 min gradient from 5% to 90% acetonitrile in water and a
5.2.2. 2-(4-(2,3-dichlorophenyl)piperazin-1-yl)ethanamine
dihydrochloride (7)
45 ml/min flow rate. Biotage SP1 and Isolera purification systems
were used for normal phase column chromatography with ethyl
acetate and hexane. Flash chromatography was performed using
E. Merck 230–400 mesh silica gel according to the procedure of
Still et al. Reactions were monitored by either thin-layer chroma-
tography (TLC) on 0.25 mm E. Merck silica gel plates (60F-254)
using UV light and p-anisaldehyde solution as visualizing agents
or HPLC analysis on an Agilent 1200 series system.
5.2.2.1. Step 1: 2-(3-(4-(2,3-dichlorophenyl)piperazin-1-yl)pro-
pyl)isoindoline-1,3-dione. 1-(2,3-Dichlorophenyl)piperazine
hydrochloride (3.16 g, 11.8 mmol) and potassium carbonate
(4.08 g, 29.5 mmol) were added to the solution of 2-(3-bromopro-
pyl)isoindoline-1,3-dione (3.16 g, 11.8 mmol) in DMF (20 ml). The
reaction mixture was stirred for overnight at room temperature.
After reaction was completed, water (40 ml) was added and then
normal work-up was conducted. The residue was purified with
normal phase preparative column chromatography to afford the ti-
tle compound (4 g, 81% yield) as white solid. MH+ 418.
5.2. Chemistry
5.2.1. 1,2-Dimethyl-5-phenyl-1H-pyrrole-3-carboxylic acid (6)
5.2.1.1. Step 1: Ethyl 2-acetyl-4-oxo-4-phenylbutanoate. To a
solution of ethyl acetoacetate (10 g, 76.8 mmol) in tetrahydrofuran
(50 ml) at 0 °C was added sodium hydride (4 g, 60% in mineral oil,
100 mmol) portionwise. The reaction mixture was stirred for
30 min, and 2-bromoacetophenone (16.8 g, 84.5 mmol) in tetrahy-
drofuran (20 ml) was added dropwisely. After warming the mix-
ture to room temperature, it was stirred for 4 h. The resulting
solution was quenched with water and normal work-up was con-
ducted with diethyl ether. The organic layer was dried with MgSO4,
and purified by silica gel column chromatography (EtOAc/
Hex = 1:5) to produce the desired compound (19 g, 98%) as light
yellow color oil. MH+ 249.
5.2.2.2. Step 2: 3-(4-(2,3-dichlorophenyl)piperazin-1-yl)propan-
1-amine dihydrochloride. To a stirred solution of 2-(3-(4-(2,3-
dichlorophenyl)piperazin-1-yl)propyl)isoindoline-1,3-dione (4 g,
9.57 mmol) in ethanol (50 ml) was added hydrazine (3 ml) at room
temperature. The reaction mixture was heated to 80 °C and stirred
for 1 day at that temperature. The resulting solution was cooled
down to room temperature, and the volatiles were evaporated un-
der reduced pressure. The residue was work-up with EtOAc and
saturated sodium bicarbonate solution. After evaporation of organ-
ic layer under reduced pressure, it was poured into 1 N HCl solu-
tion. The aqueous solution was washed with ethyl ether, and
then basified with aqueous ammonia. CH2Cl2 was used for work-
up organic layer, dried with MgSO4. After solvent was removed un-
der reduced pressure, 4 N HCl in dioxane (5 ml) was added at 0 °C
and stirred 10 min to produce HCl salt form. Light yellow solid title
compound (3.1 g, 89%) was obtained by evaporation and drying in
vacuo volatile compounds. MH+ 274 (–2HCl).
5.2.1.2. Step 2: Ethyl 2-methyl-5-phenyl-1H-pyrrole-3-carboxyl-
ate. Ethyl 2-acetyl-4-oxo-4-phenylbutanoate (19 g, 76.8 mmol)
was treated with NH4OAc (29.4 g, 384 mmol) in acetic acid
(100 ml) at room temperature. After stirring 10 min, the reaction
mixture was heated to 80 °C for overnight. After cooling to room
temperature, acetic acid was evaporated under reduced pressure
and subsequently water (50 ml) was added. The organic layer
was separated and the aqueous layer was extracted with diethyl
ether. Purification by normal phase preparative LC provided the
desired compound (13.3 g, 76%) as yellow solid. 1H NMR
(400 MHz, CDCl3) d 8.45 (br s, 1H), 7.45 (dd, J = 8.4, 1.6 Hz, 2H),
7.36 (t, J = 7.6 Hz, 2H), 7.20 (dd, J = 7.2, 1.1 Hz, 1H), 6.84 (d,
J = 2.8 Hz, 1H), 4.29 q, J = 7.2 Hz, 2H), 2.59 (s, 3H), 1.36 (t,
J = 6.8 Hz, 3H). MH+ 230.
5.2.3. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide (5)
To the mixture of 1,2-dimethyl-5-phenyl-1H-pyrrole-3-carbox-
ylic acid (100 mg, 0.46 mmol) and 3-(4-(2,3-dichlorophenyl)pipera-
zin-1-yl)propan-1-amine dihydrochloride (166 mg, 0.46 mmol) in
CH2Cl2 (5 ml) were added EDCI (178 mg, 0.92 mmol), HOBT
(130 mg, 0.9 mmol) and NMM (0.3 ml, 1.8 mmol). After stirring for
1 day at room temperature, MeOH was added to the resulting solu-
tion, and filter off. After evaporation under reduced pressure, the
residue was purified by reverse-phase preparative HPLC to provide
the title compound (149 mg, 71%) as white solid. 1H NMR
(400 MHz, CDCl3) d 7.46 (br s, 1H), 7.24–7.13 (m, 6H), 6.87–6.73
(m, 4H), 6.27 (s, 1H), 3.54 (dd, J = 11.2, 5.2 Hz, 2H), 3.48 (s, 3H),
3.25–3.19 (m, 5H), 2.64 (s, 3H), 2.60–2.44 (m, 6H), 1.80 (m, 2H).
MH+ 451.
5.2.1.3. Step 3: Ethyl 1,2-dimethyl-5-phenyl-1H-pyrrole-3-car-
boxylate. To ethyl 2-methyl-5-phenyl-1H-pyrrole-3-carboxylate
(3 g, 13 mmol) in THF (50 ml) was added iodomethane (4 ml,
65 mmol) and sodium hydride (630 mg, 60% in mineral oil,
15.6 mmol) at 0 °C. After warming the reaction mixture to room
temperature, it was stirred for 1 day. Water (20 ml) was added
and extracted the resulting mixture with diethyl ether. With nor-
mal phase preparative LC, purification was conducted to gave the
title compound (3 g, 94%) as yellow solid. 1H NMR (400 MHz,
CDCl3) d 7.42–7.31 (m, 5H), 6.58 (s, 1H), 4.28 (q, J = 7.2 Hz, 2H),
3.50 (s, 3H), 2.60 (s, 3H), 1.34 (t, J = 7.2 Hz, 3H). MH+ 244.
5.2.4. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide hydrochloride
(5a)
HCl solution (4 N in dioxane, 0.5 ml) was added to the solution
of N-(3-(4-(2,3-dichlorophenyl)piperazin-1-yl)propyl)-1,2-dimeth-
yl-5-phenyl-1H-pyrrole-3-carboxamide (100 mg) in methanol
(5 ml). After stirring for 10 min, the volatiles were evaporated un-
der reduced pressure and dried in vacuo to produce HCl salt form
as light yellow solid.
5.2.1.4. Step 4: 1,2-Dimethyl-5-phenyl-1H-pyrrole-3-carboxylic
acid (6). To the solution of ethyl 1,2-dimethyl-5-phenyl-1H-pyr-
role-3-carboxylic acid (3 g, 13 mmol) in EtOH (50 ml) was added
NaOH (1.6 g, 39 mmol) at room temperature. The reaction mixture
was refluxed for 1 day with LC–MS monitoring. After the reaction
was completed, EtOH was evaporated under reduced pressure.
Water (50 ml) was added and extracted the aqueous layer with
diethyl ether twice. 1 N HCl solution was added to the aqueous
layer until the solution became acidic (pH <3). And extraction
was accomplished with EtOAc. The organic layer was dried with
MgSO4 and the filtered organic volatiles were evaporated in vacuo
to provide the title compound (2.6 g, 95%) as yellow solid. Without
further purification, the acid was used for the next amide coupling.
5.2.5. N-(3-(4-(3-Chlorophenyl)piperazin-1-yl)propyl)-1,2-dimeth-
yl-5-phenyl-1H-pyrrole-3-carboxamide (19)
Compound 19 was obtained by repeating the procedure of
compound 5. 1H NMR (400 MHz, CDCl3) d 7.46 (br s, 1H), 7.24–
7.13 (m, 6H), 6.87–6.73 (m, 4H), 6.27 (s, 1H), 3.54 (dd, J = 11.2,
5.2 Hz, 2H), 3.48 (s, 3H), 3.25–3.19 (m, 5H), 2.64 (s, 3H), 2.60–
2.44 (m, 6H), 1.80 (m, 2H). MH+ 451.

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S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
5.2.6. N-(3-(4-(2,3-Dimethylphenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide (20)
Compound 20 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.43 (br s, 1H), 7.39–7.31 (m,
5H), 6.94 (t, J = 7.6 Hz, 1H), 6.88 (d, J = 7.2 Hz, 1H), 6.40 (s, 1H), 3.54
(dd, J = 11.2, 5.6 Hz, 2H), 3.49 (s, 3H), 2.92 (t, J = 4.0 Hz, 4H), 2.65 (s,
3H), 2.60 (t, J = 5.2 Hz, 2H), 2.26 (s, 3H), 2.19 (s, 3H), 1.83–1.79 (m,
2H). MH+ 445.
7.92–7.87 (m, 1H), 7.43–7.35 (m, 4H), 7.32–7.28 (m, 1H), 7.25 (d,
J = 7.6 Hz, 2H), 6.58 (s, 1H), 3.44 (s, 3H), 4.21–3.88 (m, 4H), 3.34–
3.22 (m, 6H), 3.08–3.04 (m, 2H), 2.50 (s, 3H), 1.94–1.92 (m, 2H).
MH+ 418 (–2HCl).
5.2.14. N-(3-(4-(3-Chlorophenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (28)
Compound 28 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.40–7.28 (m, 2H), 7.24–7.20
(m, 1H), 7.18–7.13 (m, 5H), 6.87–6.71 (m, 4H), 6.23 (s, 1H), 3.80(t,
J = 7.6 Hz, 2H), 3.53 (dd, J = 11.6, 5.6 Hz, 2H), 3.22–3.18 (m, 4H),
2.64 (s, 3H), 2.64–2.56 (m, 5H), 1.80 (t, J = 4.0 Hz, 2H), 1.61–1.51
(m, 2H), 0.73 (t, J = 7.2 Hz, 3H). MH+ 479.
5.2.7. N-(3-(4-(2,4-Dichlorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide hydrochloride (21)
Compound 21 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, DMSO-d6) d 10.95 (br s, 1H), 7.91 (br
s, 1H), 7.57 (d, J = 2.0 Hz, 1H), 7.43–7.28 (m, 6H), 7.19 (d, J = 8.4 Hz,
1H), 6.58 (s, 1H), 4.38–4.28 (m, 4H), 3.54–3.52 (m, 2H), 3.44 (s, 3H),
3.38–3.35 (m, 2H), 3.25–3.13 (m, 4H), 2.51 (s, 3H), 1.94–1.91 (m,
2H). MH+ 485 (–HCl).
5.2.15. N-(3-(4-(2,3-Dimethylphenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (29)
Compound 29 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.38–7.26 (m, 6H), 6.96–6.87
(m, 3H), 6.63 (d, J = 7.6 Hz, 1H), 6.36 (s, 1H), 3.84–3.80 (m, 3H),
3.53 (t, J = 6.0 Hz, 2H), 2.91–2.88 (m, 6H), 2.65 (s, 3H), 2.61–2.57
(m, 5H), 2.25 (s, 3H), 2.19 (s, 3H), 1.79–1.77 (m, 2H), 1.55–1.54
(m, 2H), 0.74 (t, J = 7.6 Hz, 3H). MH+ 473.
5.2.8. N-(3-(4-(2-Bromophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide (22)
Compound 22 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CD3OD) d 7.61–7.59 (m, 1H), 7.43–
7.32 (m, 6H), 7.23–7.21 (m, 1H), 7.05–7.02 (m, 1H), 3.63 (s, 3H),
3.54–3.45 (m, 4H), 3.33–3.15 (m, 8H), 2.59 (s, 3H), 2.07 (m, 2H).
MH+ 495.
5.2.16. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (30)
Compound 30 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.41–7.27 (m, 6H), 7.14 (dd,
J = 8.4, 1.6 Hz, 1H), 7.00 (t, J = 8.0 Hz, 1H), 6.65 (dd, J = 8.4, 1.6 Hz,
1H), 6.34 (s, 1H), 3.82 (t, J = 8.0 Hz, 2H), 3.56–4.51 (m, 2H), 3.20
(m, 4H), 2.66 (s, 3H), 2.59 (t, J = 6.4 Hz, 3H), 1.83–1.74 (m, 3H),
1.60–1.51 (m, 5H), 0.81–0.73 (m, 4H). MH+ 513.
5.2.9. N-(3-(4-(2,3-Dimethoxyphenyl)piperazin-1-yl)propyl)-
1,2-dimethyl-5-phenyl-1H-pyrrole-3-carboxamide (23)
Compound 23 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.43–7.37 (m, 1H), 7.31–7.25
(m, 5H), 6.90 (t, J = 8.4 Hz, 1H), 6.61 (dd, J = 8.4, 1.2 Hz, 1H), 6.41
(dd, J = 8.4, 1.2 Hz, 1H), 6.35 (s, 1H), 3.85 (s, 3H), 3.82 (s, 3H),
3.53 (quartet, J = 6.0 Hz, 2H), 3.45 (s, 3H), 3.17 (br s, 4H), 2.70–
2.62 (m, 7H), 2.58 (t, J = 6.0 Hz, 2H), 1.80 (quartet, J = 6.0 Hz, 2H).
MH+ 477.
5.2.17. N-(3-(4-(3,4-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide hydro-
chloride (31)
Compound 31 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, DMSO-d6) d 10.98 (br s, 1H), 7.90 (br,
1H), 7.43–7.30 (m, 6H), 7.21 (d, J = 2.8 Hz, 1H), 6.97 (dd, J = 8.8,
2.8 Hz, 1H), 6.53 (s, 1H), 3.87–3.79 (m, 4H), 3.53–3.47 (m, 2H),
3.22–3.13 (m, 4H), 3.10–3.02 (m, 4H), 2.52 (s, 3H), 1.93–1.90 (m,
2H), 1.46–1.37 (m, 2H), 0.63 (t, J = 7.2 Hz, 3H). MH+ 513 (–HCl).
5.2.10. N-(3-(4-(4-Fluorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide (24)
Compound 24 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, DMSO-d6) d 7.70 (br s, 1H), 7.36–7.25
(m, 5H), 7.00 (t, J = 8.8 Hz, 2H), 6.91–6.88 (m, 2H), 6.49 (s, 1H), 3.43
(s, 3H), 3.20 (q, J = 6.0 Hz, 2H), 3.08–3.01 (m, 4H), 2.49 (s, 3H),
2.54–2.46 (m, 4H), 2.39–2.32 (m, 2H), 1.68–1.62 (m, 2H). MH+ 435.
5.2.18. N-(3-(4-(2-Bromophenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (32)
Compound 32 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.53 (dd, J = 8.0, 1.2 Hz, 1H),
7.34 (m, 5H), 7.12 (td, J = 8.0, 1.2 Hz, 1H), 6.89 (td, J = 7.6, 1.2 Hz,
1H), 6.74 (dd, J = 8.0, 1.6 Hz, 1H), 3.82 (t, J = 7.6 Hz, 2H), 3.55–
3.51 (m, 2H), 3.05 (m, 4H), 2.65 (s, 3H), 2.60 (t, J = 6.0 Hz, 3H),
1.82–1.76 (m, 2H), 1.63–1.50(m, 5H), 0.74 (t, J = 7.6 Hz, 3H). MH+
523.
5.2.11. 1,2-Dimethyl-5-phenyl-N-(3-(4-(quinolin-8-yl)piperazin-
1-yl)propyl)-1H-pyrrole-3-carboxamide (25)
Compound 25 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.88 (dd, J = 1.6, 4.0 Hz, 1H),
8.10 (dd, J = 1.6, 8.0 Hz, 1H), 7.45–7.31 (m, 8H), 7.13 (dd, J = 3.6,
5.2 Hz, 1H), 6.46 (br s, 1H), 6.30 (s, 1H), 3.58 (q, J = 6.0 Hz, 2H),
3.50 (s, 3H), 3.46 (br s, 3H), 2.87 (br s, 3H), 2.72 (t, J = 6.0 Hz,
2H), 2.64 (s, 3H), 1.58–1.52 (m, 2H). MH+ 467.
5.2.19. N-(3-(4-(2-Methoxyphenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (33)
Compound 33 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, DMSO-d6) d 7.72 (br s, 1H), 7.39–7.28
(m, 5H), 6.92–6.86 (m, 2H), 6.83–6.78 (m, 2H), 6.46 (s, 1H), 3.80 (d,
J = 8.0 Hz, 2H), 3.72 (s, 3H), 3.18 (q, J = 6.8 Hz, 2H), 2.95–2.87 (m,
4H), 2.50 (s, 3H), 2.52–2.42 (m, 4H), 2.36–2.32 (m, 2H), 1.64–1.60
(m, 2H), 1.43–1.37 (m, 2H), 0.62 (t, J = 7.2 Hz, 3H). MH+ 475.
5.2.12. 1,2-Dimethyl-N-(3-(4-(2-methylquinolin-8-yl)piperazin-
1-yl)propyl)-5-phenyl-1H-pyrrole-3-carboxamide (26)
Compound 26 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.12 (dd, J = 1.6, 8.0 Hz, 1H),
7.44–7.32 (m, 8H), 7.15 (dd, J = 3.6, 5.2 Hz, 1H), 6.46 (br s, 1H), 6.31
(s, 1H), 3.57 (q, J = 6.0 Hz, 2H), 3.52 (s, 3H), 3.46 (br s, 3H), 2.87 (br
s, 3H), 2.72 (t, J = 6.0 Hz, 2H), 2.64 (s, 3H), 2.53 (s, 3H), 1.58–1.52
(m, 2H). MH+ 481.
5.2.20. N-(3-(4-(3-Methoxyphenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (34)
Compound 34 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, DMSO-d6) d 7.73 (br s, 1H), 7.36–7.29
(m, 5H), 7.08 (t, J = 8.0 Hz, 1H), 6.50 (d, J = 7.6 Hz, 1H), 6.46 (s, 1H),
5.2.13. 1,2-Dimethyl-5-phenyl-N-(3-(4-(pyridin-4-yl)piperazin-
1-yl)propyl)-1H-pyrrole-3-carboxamide dihydrochloride (27)
Compound 27 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, DMSO-d6) d 8.32 (d, J = 7.6 Hz, 2H),

S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
6165
6.42 (s, 1H), 6.35 (d, J = 6.0 Hz, 1H), 3.80 (d, J = 7.6 Hz, 2H), 3.68 (s,
3H), 3.21–3.19 (m, 2H), 3.14–3.02 (m, 4H), 2.51 (s, 3H), 2.52–2.35
(m, 6H), 1.72–1.65 (m, 2H), 1.46–1.36 (m, 2H), 0.63 (t, J = 7.2 Hz,
3H). MH+ 475.
(t, J = 7.5 Hz, 1H), 7.01 (m, 2H), 4.26 (t, J = 6.9 Hz, 2H), 4.13 (s, 3H),
3.70–3.64 (m, 2H), 3.58 (s, 3H), 3.48–3.23 (m, 8H), 2.09–2.06 (m,
4H), 1.10 (t, J = 6.8 Hz, 3H). MH+ 527 (–HCl).
5.2.28. N-(2-(4-(2,3-Dichlorophenyl)piperazin-1-yl)ethyl)-2-
methyl-5-phenyl-1H-pyrrole-3-carboxamide (42)
5.2.21. N-(3-(4-(2,3-Dimethoxyphenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (35)
Compound 35 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.35–7.25 (m, 6H), 6.90
(t, J = 8.0 Hz, 1H), 6.61 (dd, J = 8.4, 1.2 Hz, 1H), 6.38 (dd, J = 8.4,
1.2 Hz, 1H), 6.31 (s, 1H), 3.87–3.78 (m, 8H), 3.53 (quartet,
J = 5.6 Hz, 2H), 3.17 (br s, 4H), 2.69–2.55 (m, 9H), 1.78 (quartet,
J = 6.0 Hz, 2H), 1.62–1.49 (m, 2H), 0.74 (t, J = 7.2 Hz, 3H). MH+ 505.
Compound 42 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.57–7.55 (m, 2H), 7.35–7.27
(m, 4H), 7.20–7.16 (m, 2H), 3.83 (d, J = 12.0 Hz, 2H), 3.76 (t,
J = 5.2 Hz, 2H), 3.56 (t, J = 13.6 Hz, 2H), 3.45 (t, J = 5.6 Hz, 2H),
3.36 (t, J = 9.6 Hz, 2H), 3.20 (t, J = 9.6 Hz, 2H), 2.56 (s, 3H). MH+ 457.
5.2.29. N-(2-(4-(2,3-Dichlorophenyl)piperazin-1-yl)ethyl)-1-
ethyl-2-methyl-5-phenyl-1H-pyrrole-3-carboxamide hydro-
chloride (43)
Compound 43 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.43–7.26 (m, 7H), 7.17
(dd, J = 6.4, 2.8 Hz, 1H), 3.96 (q, J = 6.8 Hz, 2H), 3.82 (d, J = 12.4 Hz,
2H), 3.73 (t, J = 5.2 Hz, 2H), 3.55 (d, J = 13.2 Hz, 2H), 3.43 (t,
J = 5.6 Hz, 3.38–3.15 (m, 4H), 2.61 (s, 3H), 1.12 (t, J = 7.2 Hz, 3H).
MH+ 485 (–HCl).
5.2.22. N-(3-(4-(2,4-Difluorophenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide hydro-
chloride (36)
Compound 36 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, DMSO-d6) d 11.02 (br s, 1H), 7.91 (br,
1H), 7.43–7.40 (m, 2H), 7.34–7.30 (m, 3H), 7.25–7.19 (m, 1H),
7.14–7.09 (m, 1H), 6.53 (s, 1H), 3.81 (t, J = 7.6 Hz, 2H), 3.53–3.46
(m, 2H), 3.37–3.32 (m, 2H), 3.23–3.10 (m, 8H), 2.52 (s, 3H), 1.96–
1.90 (m, 2H), 1.46–1.37 (m, 2H), 0.63 (t, J = 7.6 Hz, 3H). MH+ 481
(–HCl).
5.2.30. N-(2-(4-(2,3-Dichlorophenyl)piperazin-1-yl)ethyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (44)
Compound 44 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.43–7.40 (m, 2H), 7.35–7.31
(m, 3H), 7.28–7.26 (m, 2H), 7.19–7.16 (m, 1H), 6.45 (br s, 1H), 3.90
(t, J = 7.2 Hz, 2H), 3.82 (d, J = 11.6 Hz, 2H), 3.72 (t, J = 5.6 Hz, 2H),
3.55 (d, J = 13.2 Hz, 2H), 3.50–3.11 (m, 8H), 1.53–1.44 (m, 2H),
0.70 (t, J = 7.6 Hz, 3H). MH+ 499.
5.2.23. 2-Methyl-5-phenyl-1-propyl-N-(3-(4-(3-(trifluoromethyl)-
phenyl)piperazin-1-yl)propyl)-1H-pyrrole-3-carboxamide hydro-
chloride (37)
Compound 37 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, CD3OD) d 7.48–7.39 (m, 3H), 7.35–
7.33 (m, 3H), 7.28–7.27 (m, 2H), 7.19–7.18 (m, 1H), 3.96–3.88
(m, 4H), 3.73–3.64 (m, 3H), 3.50–3.47 (m, 2H), 3.26–3.17 (m,
4H), 2.57 (s, 3H), 2.11–2.08 (m, 2H), 1.53–1.44 (m, 2H), 0.69 (t,
J = 7.6 Hz, 3H). MH+ 513 (–HCl).
5.2.31. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1H-pyrrole-3-carboxamide (45)
Compound 45 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.46 (br s, 1H), 7.53 (m, 1H),
7.39 (d, J = 7.6 Hz, 2H), 7.21–7.13 (m, 2H), 6.98 (t, J = 8.0 Hz, 1H),
6.81 (d, J = 8.0 Hz, 1H), 6.62 (d, J = 2.4 Hz, 1H), 3.57–3.53 (m, 2H),
3.13 (br s, 4H), 2.71 (br s, 5H), 2.63 (s, 3H), 1.84–1.79 (m, 2H).
MH+ 471.
5.2.24. 2-Methyl-5-phenyl-1-propyl-N-(3-(4-(quinolin-8-yl)pipe-
razin-1-yl)propyl)-1H-pyrrole-3-carboxamide (38)
Compound 38 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.90 (dd, J = 1.6, 4.0 Hz, 1H),
8.12 (dd, J = 1.6, 8.0 Hz, 1H), 7.46–7.30 (m, 8H), 7.14 (dd, J = 4.0,
5.2 Hz, 1H), 6.50 (br s, 1H), 6.31 (s, 1H), 3.86 (t, J = 7.2 Hz, 2H),
3.55 (q, J = 5.6 Hz, 2H), 3.08 (br s, 4H), 2.69 (br s, 4H), 2.61 (t,
J = 6.0 Hz, 2H), 1.83–1.77 (m, 2H), 1.71–1.61 (m, 3H), 0.79 (t,
J = 7.6 Hz, 3H). MH+ 467.
5.2.32. N-(2-(4-(2,3-Dichlorophenyl)piperazin-1-yl)ethyl)-2,4-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide hydrochloride
(46)
Compound 46 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.40–7.31 (m, 4H), 7.30–
7.28 (m, 2H), 7.26–7.18 (m, 1H), 7.16–7.15 (m, 1H), 3.84–3.80 (m,
4H), 3.56 (d, J = 12.8 Hz, 2H), 3.49–3.43 (m, 2H), 3.38 (d, J = 11.2 Hz,
2H), 3.21 (t, J = 11.2 Hz, 2H), 2.45 (s, 3H), 2.30 (s, 3H). MH+ 471
(–HCl).
5.2.25. N-(2-(4-(2,3-Dichlorophenyl)piperazin-1-yl)ethyl)-2-
methyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide (39)
Compound 39 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.43–7.40 (m, 2H), 7.35–7.31
(m, 3H), 7.28–7.26 (m, 2H), 7.19–7.16 (m, 1H), 6.45 (br s, 1H), 3.90
(t, J = 7.2 Hz, 2H), 3.82 (d, J = 11.6 Hz, 2H), 3.72 (t, J = 5.6 Hz, 2H),
3.55 (d, J = 13.2 Hz, 2H), 3.50–3.11 (m, 8H), 1.53–1.44 (m, 2H),
0.70 (t, J = 7.6 Hz, 3H). MH+ 499.
5.2.33. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1,2,4-
trimethyl-5-phenyl-1H-pyrrole-3-carboxamide hydrochloride (47)
Compound 47 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.46–7.42 (m, 2H), 7.38–
7.31 (m, 1H), 7.30–7.23 (m, 4H), 7.20–7.15 (m, 1H), 3.70 (d,
J = 11.6 Hz, 2H), 3.58–3.53 (m, 4H), 3.37–3.10 (m, 6H), 3.35 (s,
3H), 2.42 (s, 3H), 2.19–2.12 (m, 2H), 2.06 (s, 3H). MH+ 499 (–HCl).
5.2.26. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-
N,1,2-trimethyl-5-phenyl-1H-pyrrole-3-carboxamide (40)
Compound 40 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.43–7.26 (m, 6H), 7.19–7.04
(m, 2H), 3.68–3.64 (m, 2H), 3.52 (s, 3H), 3.33 (s, 3H), 3.30–3.22 (m,
8H), 2.38 (s, 3H). MH+ 499.
5.2.34. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2,4-
dimethyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide hydro-
chloride (48)
5.2.27. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-N,2-
dimethyl-5-phenyl-1-propyl-1H-pyrrole-3-carboxamide hydro-
chloride (41)
Compound 48 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.45–7.42 (m, 2H), 7.39–
7.37 (m, 1H), 7.35–7.18 (m, 4H), 7.17–7.18 (m, 1H), 3.76–3.68 (m,
4H), 3.57–3.53 (m, 4H), 3.36–3.18 (m, 4H), 2.44 (s, 3H), 2.18–2.11
Compound 41 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.46–7.37 (m, 5H), 7.06
(m, 2H), 2.02 (s, 3H), 1.47–1.40 (m, 2H), 0.66 (t, J = 7.2 Hz, 3H). 13
C

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S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
NMR (100 MHz, MeOH-d4) d 170.2, 149.3, 133.7, 132.0, 131.9,
130.6, 128.2, 128.0, 127.6, 127.2, 125.6, 119.2, 114.9, 112.8, 54.0,
52.0, 48.2, 45.3, 37.1, 23.8, 23.5, 10.4, 9.8, 9.6. MH+ 527 (–HCl).
J = 7.6 Hz, 2H), 3.64 (d, J = 10.8 Hz, 2H), 3.48 (t, J = 6.4 Hz, 2H),
3.36–3.17 (m, 6H), 2.59 (s, 3H), 2.25 (s, 6H), 2.12–2.05 (m, 2H),
1.52–1.46 (m, 2H), 0.71 (t, J = 7.2 Hz, 3H). MH+ 507 (–HCl).
5.2.35. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2,4-
dimethyl-5-phenyl-1H-pyrrole-3-carboxamide hydrochloride (49)
Compound 49 was obtained by repeating the procedure of
compound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.41–7.35 (m, 4H),
7.31–7.28 (m, 2H), 7.26–7.20 (m, 1H), 7.18–7.16 (m, 1H), 3.70 (d,
J = 11.6 Hz, 2H), 3.58–3.53 (m, 4H), 3.36–3.19 (m, 6H), 2.43 (s,
3H), 2.28 (s, 3H), 2.20–2.12 (m, 2H). MH+ 485 (–HCl).
5.2.42. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1-
ethyl-2-methyl-5-phenyl-1H-pyrrole-3-carboxamide (56)
Compound 56 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.38–7.32 (m, 5H), 7.14 (dd,
J = 8.4, 1.6 Hz, 1H), 7.01 (t, J = 7.6 Hz, 1H), 6.66 (dd, J = 8.0, 1.6 Hz,
1H), 6.34 (s, 1H), 3.91 (q, J = 7.2 Hz, 2H), 3.53 (dd, J = 11.2, 5.6 Hz,
2H), 3.06 (m, 4H), 2.67 (s, 3H), 2.61 (t, J = 6.0 Hz, 2H), 1.83–1.73
(m, 3H), 1.37–1.25 (m, 2H), 1.19 (t, J = 7.6 Hz, 3H). MH+ 499.
5.2.36. N-(3-(4-(2,3-Dimethylphenyl)piperazin-1-yl)propyl)-2-
methyl-5-phenyl-1H-pyrrole-3-carboxamide (50)
5.2.43. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dichlorophenyl)pipera-
zin-1-yl)propyl)-2-methyl-1H-pyrrole-3-carboxamide hydroch-
loride (57)
Compound 57 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.53 (d, J = 8.4 Hz, 2H),
7.35–7.28 (m, 3H), 7.18 (dd, J = 6.4, 3.2 Hz, 2H), 3.68 (d,
J = 12.0 Hz, 2H), 3.37 (d, J = 13.2 Hz, 2H), 3.50 (t, J = 6.0 Hz, 2H),
3.36–3.18 (m, 5H), 2.26 (s, 3H), 2.13–2.07 (m, 2H). MH+ 505 (–HCl).
Compound 50 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.41 (br s, 1H), 7.58 (m, 1H),
7.44–7.42 (m, 2H), 7.32–7.26 (m, 2H), 7.23–7.19 (m, 1H), 6.96–6.81
(m, 3H), 6.67 (d, J = 2.4 Hz, 1H), 3.55 (dd, J = 11.6, 5.6 Hz, 2H), 2.98
(t, J = 4.8 Hz, 4H), 2.64 (s, 3H), 2.62–2.57 (m, 2H), 2.26 (s, 3H), 2.21
(S, 3H), 1.84–1.78 (m, 2H), 1.63–1.60 (m, 2H). MH+ 431.
5.2.37. N-(3-(4-(2,3-Dimethylphenyl)piperazin-1-yl)propyl)-1-
ethyl-2-methyl-5-phenyl-1H-pyrrole-3-carboxamide (51)
Compound 51 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.03–7.35 (m, 7H), 6.96–6.87
(m, 2H), 6.64 (d, J = 7.6 Hz, 1H), 6.37 (s, 1H), 3.91 (q, J = 7.2 Hz, 2H),
3.54 (dd, J = 11.6, 5.6 Hz, 2H), 2.92–2.89 (m, 3H), 2.67 (s, 3H), 2.60
(t, J = 6.0 Hz, 3H), 2.56 (s, 3H), 2.19 (s, 3H), 1.81–1.77 (m, 2H), 1.19
(t, J = 7.2 Hz, 3H). MH+ 459.
5.2.44. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dichlorophenyl)pipera-
zin-1-yl)propyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide (58)
Compound 58 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 11.46 (br s, 1H), 7.32–7.21
(m, 5H), 7.13 (t, J = 8.0 Hz, 1H), 6.93 (d, J = 7.6 Hz, 1H), 6.82 (s,
1H), 6.55 (br s, 1H), 3.67–6.64 (m, 3H), 3.50–3.43 (m, 1H), 3.44
(s, 3H), 3.33–3.31 (m, 4H), 3.14 (br s, 2H), 2.56 (s, 3H), 2.31 (br s,
2H). 13C NMR (100 MHz, CDCl3) d 167.3, 148.8, 137.2, 134.1,
133.4, 133.2, 130.7, 130.2, 128.7, 127.8, 127.5, 126.0, 119.2,
108.1, 54.6, 52.5, 48.0, 37.5, 32.0, 23.9, 12.2. MH+ 519.
5.2.38. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dimethylphenyl)pipera-
zin-1-yl)propyl)-2-methyl-1H-pyrrole-3-carboxamide hydrochlo-
ride (52)
Compound 52 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.52 (d, J = 8.8 Hz, 2H),
7.32 (d, J = 8.4 Hz, 2H), 7.06 (t, J = 8.0 Hz, 1H), 6.96 (t, J = 8.4 Hz,
2H), 3.63 (d, J = 11.2 Hz, 2H), 3.49 (t, J = 6.4 Hz, 2H), 3.30–3.11
(m, 8H), 2.54 (s, 3H), 2.25 (s, 3H), 2.24 (s, 3H), 2.12–2.06 (m, 2H).
MH+ 465 (–HCl).
5.2.45. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dichlorophenyl)pipera-
zin-1-yl)propyl)-1-ethyl-2-methyl-1H-pyrrole-3-carboxamide
hydrochloride (59)
Compound 59 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.43–7.41 (m, 2H), 7.36–
7.34 (m, 2H), 7.30–7.29 (m, 2H), 7.18–7.16 (m, 2H), 3.95 (q,
J = 6.8 Hz, 2H), 3.67 (d, J = 12.0 Hz, 2H), 3.54 (d, J = 12.4 Hz, 2H),
3.47 (t, J = 6.4 Hz, 2H), 3.34–3.17 (m, 6H), 2.60 (s, 3H), 2.10–2.06
(m, 2H), 1.13 (t, J = 7.2 Hz, 3H). 13C NMR (100 MHz, MeOH-d4) d
170.0, 150.8, 136.6, 135.2, 134.8, 133.6, 133.0, 131.9, 129.9,
129.5, 128.7, 127.2, 120.7, 114.4, 55.5, 53.5, 40.0, 37.4, 25.7, 16.4,
11.9. MH+ 534 (–HCl).
5.2.39. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dimethylphenyl)pipera-
zin-1-yl)propyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide hydro-
chloride (53)
Compound 53 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.38 (dd, J = 8.0, 20.8 Hz,
4H), 7.07 (d, J = 7.6 Hz, 1H), 7.03–6.97 (m, 2H), 3.66 (br s, 1H),
3.51–3.48 (m, 5H), 3.38–3.37 (br s, 1H), 3.33–3.32 (m, 1H), 2.26
(d, J = 1.6 Hz, 3H), 2.26 (d, 2.4 Hz, 6H), 2.13–2.10 (m, 2H). MH+
479 (–HCl).
5.2.46. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dichlorophenyl)pipera-
zin-1-yl)propyl)-2-methyl-1-propyl-1H-pyrrole-3-carboxamide
hydrochloride (60)
Compound 60 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.43–7.41 (m, 2H), 7.34–
7.32 (m, 2H), 7.30–7.26 (m, 2H), 7.20–7.16 (m, 1H), 3.89 (t,
J = 7.6 Hz, 2H), 3.67 (d, J = 11.6 Hz, 2H), 3.54 (d, J = 12.4 Hz, 2H),
3.47 (t, J = 6.0 Hz, 2H), 3.34–3.17 (m, 4H), 2.59 (s, 3H), 2.11–2.07
(m, 2H), 1.54–1.44 (m, 2H), 0.71 (t, J = 7.2 Hz, 3H). MH+ 547 (–HCl).
5.2.40. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dimethylphenyl)pipera-
zin-1-yl)propyl)-1-ethyl-2-methyl-1H-pyrrole-3-carboxamide
hydrochloride (54)
Compound 54 was obtained by repeating the procedure of
compound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.43–7.41 (m, 2H),
7.36–7.34 (m, 2H), 7.07 (t, J = 7.6 Hz, 1H), 6.99–6.95 (m, 2H), 3.95
(q, J = 6.8 Hz, 2H), 3.64 (d, J = 10.0 Hz, 2H), 3.48 (t, J = 6.0 Hz, 2H),
3.33–3.28 (m, 2H), 3.26–3.16 (m, 6H), 2.59 (d, J = 2.0 Hz, 3H), 2.25
(s, 6H), 2.10–2.07 (m, 2H), 1.13 (t, J = 7.2 Hz, 3H). MH+ 493 (–HCl).
5.2.47. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-5-(pyridin-2-yl)-1H-pyrrole-3-carboxamide dihydrochlo-
ride (61)
Compound 61 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 8.55 (dd, J = 8.0, 6.0 Hz,
1H), 8.45 (dt, J = 1.6, 8.8 Hz, 1H), 8.13 (d, J = 8.4 Hz, 1H), 7.68 (dt,
J = 1.2, 7.2 Hz, 1H), 7.59–7.56 (m, 1H), 7.31–7.28 (m, 2H), 7.15–
7.10 (m, 1H), 3.70 (d, J = 12.0 Hz, 2H), 3.54 (d, J = 13.6 Hz, 2H),
3.50 (t, J = 6.8 Hz, 2H), 3.37–3.31 (m, 4H), 3.21 (d, J = 12.4 Hz,
2H), 2.46 (s, 3H), 2.14–2.11 (m, 2H). MH+ 472 (–2HCl).
5.2.41. 5-(4-Chlorophenyl)-N-(3-(4-(2,3-dimethylphenyl)pipera-
zin-1-yl)propyl)-2-methyl-1-propyl-1H-pyrrole-3-carboxamide
hydrochloride (55)
Compound 55 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.43–7.41 (m, 2H), 7.35–
7.32 (m, 2H), 7.10–7.05 (m, 1H), 6.99–6.95 (m, 2H), 3.89 (t,

S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
6167
5.2.48. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-(pyridin-2-yl)-1H-pyrrole-3-carboxamide dihydro-
chloride (62)
(dd, J = 1.2, 8.0 Hz, 1H), 6.40 (s, 1H), 3.81 (t, J = 8.0 Hz, 2H), 3.53
(t, J = 6.0 Hz, 2H), 3.03 (br s, 4H), 2.67 (br s, 4H), 2.66 (s, 3H),
2.60 (t, J = 6.0 Hz, 2H), 1.81–1.78 (m, 2H), 1.58–1.52 (m, 2H), 0.76
(t, J = 7.2 Hz, 3H). MH+ 514.
Compound 62 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 8.74 (d, J = 6.0 Hz, 1H),
8.58 (dt, J = 1.6, 8.0 Hz, 1H), 8.13 (d, J = 8.4 Hz, 1H), 7.90 (t,
J = 6.4 Hz, 1H), 7.31–7.28 (m, 2H), 7.26–7.25 (m, 1H), 7.18–7.15
(m, 1H), 3.73 (s, 3H), 3.68 (d, J = 12.0 Hz, 2H), 3.53 (d, J = 12.4 Hz,
2H), 3.48 (t, J = 6.4 Hz, 2H), 3.33–3.28 (m, 2H), 3.23–3.19 (m, 2H),
2.65 (s, 3H), 2.13–2.09 (m, 2H). 13C NMR (100 MHz, CDCl3) d
167.7, 152.2, 151.0, 148.8, 137.2, 136.5, 134.0, 131.3, 127.3,
124.5, 121.8, 120.7, 118.4, 115.2, 108.5, 58.4, 53.5, 51.3, 39.7,
32.5, 25.0, 11.3. MH+ 486 (–2HCl).
5.2.54. 5-tert-Butyl-N-(2-(4-(2,3-dimethylphenyl)piperazin-1-
yl)ethyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide (68)
Compound 68 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.08 (t, J = 7.6 Hz, 1H), 6.93–
6.89 (m, 2H), 6.31 (br s, 1H), 6.01 (s, 1H), 3.59(s, 3H), 3.51 (q,
J = 5.2 Hz, 2H), 2.92 (br s, 4H), 2.65 (br s, 4H), 2.63 (q, J = 6.0 Hz,
2H), 2.54 (s, 3H), 2.27 (s, 3H), 2.23 (s, 3H), 1.37 (s, 9H). MH+ 410.
5.2.55. 5-tert-Butyl-N-(3-(4-(2,3-dimethylphenyl)piperazin-1-
yl)propyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide (69)
Compound 69 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.05 (t, J = 7.6 Hz, 1H), 6.93–
6.87 (m, 2H), 6.02 (s, 1H), 3.58 (s, 3H), 3.50–3.42 (m, 2H), 2.94(br s,
4H), 2.64 (br s, 4H), 2.57 (t, J = 6.0 Hz, 2H), 2.55 (s, 3H), 2.26 (s, 2H),
2.21(s, 3H) 1.80–1.77 (m, 2H), 1.35 (s, 9H). MH+ 424.
5.2.49. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-1-propyl-5-(pyridin-2-yl)-1H-pyrrole-3-carboxamide
dihydrochloride (63)
Compound 63 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 8.77 (dd, J = 1.2, 6.0 Hz,
1H), 8.61 (dt, J = 1.6, 8.4 Hz, 1H), 8.12 (d, J = 8.0 Hz, 1H), 7.94 (dt,
J = 1.2, 7.2 Hz, 1H), 7.31–7.28 (m, 2H), 7.26–7.25 (m, 1H), 7.18–
7.15 (m, 1H), 4.14 (t, J = 7.2 Hz, 2H), 3.79 (d, J = 12.4 Hz, 2H), 3.54
(d, J = 13.6 Hz, 2H), 3.48 (t, J = 6.4 Hz, 2H), 3.33–3.28 (m, 2H),
3.21 (d, J = 12.0 Hz, 2H), 2.45 (s, 3H), 2.12–2.10 (m, 2H), 1.59–
1.56 (m, 2H), 0.76 (t, J = 7.2 Hz, 3H). MH+ 514 (–2HCl).
5.2.56. 5-tert-Butyl-N-(2-(4-(2,3-dichlorophenyl)piperazin-1-
yl)ethyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide hydrochlo-
ride (70)
Compound 70 was obtained by repeating the procedure of com-
pound 5a. 1H NMR (400 MHz, MeOH-d4) d 7.28–7.26 (m, 2H), 7.17–
7.14 (m, 1H), 3.80 (d, J = 12.4 Hz, 2H), 3.72 (t, J = 5.2 Hz, 2H), 3.56
(d, J = 13.6 Hz, 2H), 3.42 (t, J = 5.6 Hz, 2H), 3.39–3.18 (m, 3H),
2.48 (s, 3H), 1.35 (s, 9H). 13C NMR (100 MHz, MeOH-d4) d 169.1,
149.3, 140.7, 135.8, 133.7, 128.0, 127.2, 125.6, 119.2, 110.8, 57.4,
52.4, 52.4, 31.9, 31.3, 29.1, 10.3. MH+ 450 (–HCl).
5.2.50. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-(pyridin-3-yl)-1H-pyrrole-3-carboxamide (64)
Compound 64 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.64 (d, J = 1.6 Hz, 1H), 8.55
(dd, J = 1.2, 4.8 Hz, 1H), 7.62 (td, J = 2.0, 8.0 Hz, 1H), 7.26–7.24
(m, 1H), 7.16–7.13 (m, 1H), 7.02 (t, J = 8.0 Hz, 1H), 6.65 (dd,
J = 1.2, 8.0 Hz, 1H), 6.44 (s, 1H), 3.55–3.52 (m, 3H), 3.51 (s, 3H),
3.04 (br s, 4H), 2.67 (br s, 2H), 2.65 (s, 3H), 2.61 (t, J = 5.6 HZ,
2H), 1.83–1.77 (m, 2H). 13C NMR (100 MHz, CDCl3) d 165.46
150.9, 149.5, 148.2, 135.9, 135.8, 133.9, 129.5, 128.8, 127.5,
124.6, 123.3, 118.3, 115.4, 107.5, 77.3, 58.1, 53.5, 51.3, 39.4, 31.7,
25.1, 11.4. MH+ 486.
5.2.57. 5-tert-Butyl-N-(3-(4-(2,3-dichlorophenyl)piperazin-1-yl)-
propyl)-2-methyl-1H-pyrrole-3-carboxamide hydrochloride (71)
Compound 71 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.78 (br s, 1H), 7.19–7.10 (m,
2H), 6.99 (br s, 1H), 6.93 (dd, J = 2.4, 2.0 Hz, 1H), 5.98 (d, J = 2.8 Hz,
1H), 3.50 (q, J = 6.0 Hz, 2H), 3.13 (br s, 4H), 2.69 (br s, 4H), 2.59
(t, J = 6.4 Hz, 2H), 2.54 (s, 3H), 1.82–1.76 (m, 2H), 1.23 (s, 9H).
MH+ 451 (–HCl).
5.2.51. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-1-propyl-5-(pyridin-3-yl)-1H-pyrrole-3-carboxamide (65)
Compound 65 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.63 (d, J = 2.0 Hz, 1H), 8.57
(dd, J = 1.6, 4.8 Hz, 1H), 7.60 (td, J = 2.0, 8.0 Hz, 1H), 7.26–7.22 (m,
1H), 7.14 (dd, J = 1.2, 8.0 Hz, 1H), 7.03 (t, J = 8.0 Hz, 1H), 6.64 (dd,
J = 1.2, 8.0 Hz, 1H), 6.40 (s, 1H), 3.81 (t, J = 8.0 Hz, 2H), 3.53 (t,
J = 6.0 Hz, 2H), 3.03 (br s, 4H), 2.67 (br s, 3H), 2.66 (s, 3H), 2.60
(t, J = 6.0 Hz, 2H), 1.83–1.77 (m, 2H), 1.60–1.50 (m, 2H), 0.76 (t,
J = 7.2 Hz, 3H). MH+ 514.
5.2.58. 5-tert-Butyl-N-(3-(4-(2,3-dichlorophenyl)piperazin-1-
yl)propyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide (72)
Compound 72 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.17–7.10 (m, 2H), 6.92 (dd,
J = 2.0, 2.4 Hz, 1H), 6.87 (br s, 1H), 5.99 (s 1H), 3.58 (s, 3H), 3.49 (q,
J = 5.6 Hz, 2H), 3.11 (br s, 4H), 2.68 (br s, 4H), 2.58 (t, J = 6.8 Hz, 2H),
2.55 (s, 3H), 1.80–1.77 (m, 2H), 1.33 (s, 9H). 13C NMR (100 MHz,
CDCl3) d 166.1 151.0, 140.2 134.8, 134.0, 127.3, 127.3, 124.5,
118.5, 112.9, 102.1, 58.1, 53.5, 51.3, 39.2, 32.6, 31.7, 30.3, 25.6,
11.2. MH+ 465.
5.2.52. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-1,2-
dimethyl-5-(pyridin-4-yl)-1H-pyrrole-3-carboxamide (66)
Compound 66 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.64 (d, J = 1.2 Hz, 1H), 8.55
(dd, J = 1.6, 4.8 Hz, 1H), 7.61 (td, J = 2.0, 8.0 Hz, 1H), 7.26–7.24
(m, 1H), 7.14 (dd, J = 2.8, 6.8 Hz, 1H), 7.02 (t, J = 8.4 Hz, 1H), 6.65
(dd, J = 1.2, 8.0 Hz, 1H), 6.43 (s, 1H), 3.55–3.51 (m, 2H), 3.51 (s,
3H), 3.04 (br s, 4H), 2.67 (br s, 2H), 2.65 (s, 3H), 2.61 (t,
J = 6.4 Hz, 2H), 1.83–1.77 (m, 2H). MH+ 486.
5.2.59. 5-tert-Butyl-N-(2-(4-(3-chloro-2-methylphenyl)pipera-
zin-1-yl)ethyl)-1,2-dimethyl-1H-pyrrole-3-carboxamide (74)
Compound 74 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 7.10–7.06 (m, 2H), 6.95–6.92
(m, 1H), 6.25 (br s, 1H), 6.00 (s, 1H), 3.59 (s, 3H), 3.51 (q, J = 6.4 Hz,
2H), 2.92 (t, J = 4.4 Hz, 4H), 2.67–2.62 (m, 6H), 2.54 (s, 3H), 2.34 (s,
3H), 1.36 (s, 9H). MH+ 431.
5.2.53. N-(3-(4-(2,3-Dichlorophenyl)piperazin-1-yl)propyl)-2-
methyl-1-propyl-5-(pyridin-4-yl)-1H-pyrrole-3-carboxamide (67)
Compound 67 was obtained by repeating the procedure of com-
pound 5. 1H NMR (400 MHz, CDCl3) d 8.62 (d, J = 1.2 Hz, 1H), 8.56
(dd, J = 1.6, 4.8 Hz, 1H), 7.60 (td, J = 2.0, 7.6 Hz, 1H), 7.26–7.24
(m, 1H), 7.14 (dd, J = 1.2, 8.0 Hz, 1H), 7.03 (t, J = 8.0 Hz, 1H), 6.64
5.3. Biology
5.3.1. Measurement of binding affinity for serotonin 5-HT2A and
5-HT2C receptors
Receptor binding affinities of the compounds for serotonin
receptors were measured by the method described in the litera-

6168
S. Y. Kang et al. / Bioorg. Med. Chem. 18 (2010) 6156–6169
ture.18 For serotonin 5-HT2A binding, an aliquot of human recombi-
nant serotonin 5-HT2A receptor (PerkinElmer Life and Analytical
Test drugs were suspended in 3% Tween 80 solution, and adminis-
tered orally (po) 60 min before the testing.
Sciences, USA) expressed in CHO-K1 cells (5
[3H]Ketanserin (PerkinElmer) were used in the presence of mian-
serin (20 M) as nonspecific. The reaction mixture was incubated
lg/well) and 1 nM
5.3.5. Measurement of locomotor activity (for Figure 4)
One day before the test, mice were placed in transparent poly-
carbonate cages located in activity chambers and were allowed to
habituate for 20 min. For locomotor activity test, compound was
suspended in 3% tween80 solution, and administered orally
60 min before the test. Spontaneous locomotor activity was re-
corded every 10 min for 30 min using Activity Analyzer (AM1052
Activity Monitor, Benwick, UK). Unit is count/30 min.
l
for 60 min at 27 °C using 50 mM Tris–HCl (pH 7.4) buffer contain-
ing 4 mM CaCl2 and 0.1% ascorbic acid, and harvested through fil-
termate A glass fiber filter (Wallac, Finland) presoaked in 0.5%
polyethyleneimine (PEI) by microbeta filtermate-96 harvester
(PerkinElmer) to terminate the reaction, and then washed with
ice cold 50 mM Tris–HCl buffer solution (pH 7.4). The filter was
then covered with MeltiLex, sealed in a sample bag, dried in an
oven. The radioactivity retained in the filter was finally counted
using MicroBeta Plus (Wallac). The binding affinity (IC50) of a com-
pound for the receptor was calculated by computerized nonlinear
regression analysis (GraphPad Prism Program, San Diego, USA)
using 7–8 varied concentrations of the compound run in duplicate
tubes.
5.3.6. Measurement of locomotor activity (for Tables 7 and 8)
We measured using an automated video tracking system (Nol-
dus Information Technology, Wagenin, the Netherlands) to exam-
ine locomotor patterns. Mice was treated with test compounds
(25 mg/kg B.W., po) and acclimated to the test chamber for
10 min before starting the experiment. Locomotor activity was
then measured for 30 min. The distance travelled in centimeters
by the animals in horizontal locomotor activity was analyzed. Data
were collected and analyzed between 09:00 and 17:00 h.
For serotonin 5-HT2C binding, frozen membranes from stable
CHO-K1 cell line expressing the human recombinant 5-HT2C recep-
tor (PerkinElmer, 4 l
g/well), [3H]Mesulergine (Amersham, 1.3 nM)
and test compounds were added into 50 mM Tris–HCl (pH 7.4) buf-
fer containing 0.1% ascorbic acid and 4 mM CaCl2. Nonspecific
Acknowledgments
binding was determined using 100 lM mianserin. The incubations
were performed for 60 min at 27 °C, and these were terminated by
rapid filtration through filtermate. A glass fiber filter presoaked in
0.5% PEI.
We are grateful to Dr. Eun Chul Huh for his leadership at R&D
operation, Green Cross Corporation (GCC). This work is in part sup-
ported by Korea Ministry of Knowledge Economy.
5.3.2. Measurement of binding affinity for serotonin transporter
For serotonin transporter binding assays, a reaction mixture
with a final volume of 0.25 ml was prepared by mixing a test com-
pound, human serotonin transporter membrane expressed in HEK-
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22. Although spontaneous locomotor activity of compound 64 was not measured
by Activity Analyzer, hyperactivity was observed by its behavior such as
climbing strongly, etc. during forced swimming test.
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