Exploration of substituted arylpiperazine–tetrazoles as promising dual norepinephrine and dopamine reuptake inhibitors

Article abstract of DOI:10.1016/j.bmc.2016.09.005

In the search for potent dual norepinephrine and dopamine reuptake inhibitors, several substituted arylpiperazine–tetrazoles were designed, synthesized and evaluated for their neurotransmitter reuptake inhibitory activities. Various derivatives exhibited selective and strong neurotransmitter reuptake inhibitory activity. In particular, compounds with a three-carbon linker displayed selective and stronger potency than those with two-carbon and four-carbon linkers. Interestingly, six compounds, 9b, 9c, 9d, 9o, 9q and 9u displayed more effective activity than the standard drug, bupropion. The provided SAR data and potent biological activity can offer useful guidelines for designing dual norepinephrine and dopamine reuptake inhibitors as effective therapeutic agents for treatment of several central nervous system diseases.

Full text of DOI:10.1016/j.bmc.2016.09.005

Bioorganic & Medicinal Chemistry xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Exploration of substituted arylpiperazine–tetrazoles as promising
dual norepinephrine and dopamine reuptake inhibitors
a,
Suresh Paudel a,y, Srijan Acharya a,y, Goo Yoon b, Kyeong-Man Kim a, , Seung Hoon Cheon
⇑
⇑
a College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju 61186, Republic of Korea
b College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Jeonnam 58554, 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 search for potent dual norepinephrine and dopamine reuptake inhibitors, several substituted
arylpiperazine–tetrazoles were designed, synthesized and evaluated for their neurotransmitter reuptake
inhibitory activities. Various derivatives exhibited selective and strong neurotransmitter reuptake inhibi-
tory activity. In particular, compounds with a three-carbon linker displayed selective and stronger
potency than those with two-carbon and four-carbon linkers. Interestingly, six compounds, 9b, 9c, 9d,
9o, 9q and 9u displayed more effective activity than the standard drug, bupropion. The provided SAR data
and potent biological activity can offer useful guidelines for designing dual norepinephrine and dopamine
reuptake inhibitors as effective therapeutic agents for treatment of several central nervous system
diseases.
Received 8 August 2016
Revised 29 August 2016
Accepted 2 September 2016
Available online xxxx
Keywords:
Arylpiperazine–tetrazoles
Selective norepinephrine and dopamine
reuptake inhibitors
Norepinephrine reuptake inhibitors
Dopamine reuptake inhibitors
Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction
atomoxetine, for the treatment of ADHD, was generally considered
less efficacious compared to the stimulants.7,8
Attention deficit hyperactivity disorder (ADHD) is a neurodevel-
opmental disorder traditionally expected to affect 3–5% of children
and adults. It is characterized by age inappropriate levels of atten-
tion, impulsivity, and hyperactivity.1–3 Pathophysiologically, the
cause of ADHD is commonly associated with functional impair-
ments in the neurotransmitter system, mainly dopamine and nore-
pinephrine.4,5 A number of drugs aimed at improving prefrontal
cortex (PFC) cognitive function are being used for the treatment
of ADHD. These include dual norepinephrine (NE) and dopamine
(DA) reuptake inhibitors (psychostimulants) or selective NE reup-
take inhibitors (SNRIs).6
The abuse potential of psychostimulants generates significant
concerns about their use.7,8 Similarly, marketed dual NE and DA
reuptake inhibitor, nomifensine, was investigated for the treat-
ment of ADHD. However, it was withdrawn from the market due
to its association with immune hemolytic anemia.9–12 Bupropion,
a dual NE and DA reuptake inhibitor, has been used for the treat-
ment of ADHD.13 The limitation of this drug is an increased risk
for epileptic seizures, and it was withdrawn from the market for
some time.14 On the other hand, an approved NE inhibitor,
The limitations and side effects of established NE or dual (NE
and DA) inhibitors necessitate the development of safer and more
effective therapeutic agents for the treatment of ADHD. In addition,
there are only few dual NE and DA reuptake inhibitors.15–17 For
treatment of ADHD, it has been hypothesized that a dual NE and
DA inhibitor with a potency order of NE > DA would lead to a com-
pound with superior efficacy and safety.18 Therefore, we undertook
to develop a new dual NE and DA inhibitor which, in a single mole-
cule, could improve or balance the activity and might overcome
the limitations of existing ADHD therapies.
A common strategy to avoid a drug-related side effect is to
design molecules with different chemical scaffolds. Based on this
fact, 4-benzylpiperidine carboxamides and arylpiperazine–ben-
zylpiperidines were successfully developed as neurotransmitter
reuptake inhibitors.19,20 These derivatives have three fundamental
structures, aromatic region (A), linker (B) and heterocyclic amine
(C). Furthermore, GBR-12935 with similar structural moieties pos-
sesses dopamine reuptake inhibition.21 In addition, amine contain-
ing compounds are a rich source of reuptake inhibitors with a
variety of profiles.22 Thus, considering the basic structural compo-
nents (A, B and C), we designed substituted arylpiperazine–tetra-
zoles as possible dual reuptake inhibitors (Fig. 1). Tetrazole was
considered for the design of new dual reuptake inhibitors since it
is a bioisosteric form of carboxamide. The details of synthetic
pathways employed, the neurotransmitter reuptake inhibitory
⇑
Corresponding authors. Tel.: +82 625302936; fax: +82 625302949 (K.-M.K.);
tel.: +82 625302929; fax: +82 625302911 (S.H.C.).
E-mail addresses: kmkim@jnu.ac.kr (K.-M. Kim), shcheon@jnu.ac.kr (S.H. Cheon).
These authors contributed equally to this work.
y
http://dx.doi.org/10.1016/j.bmc.2016.09.005
0968-0896/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Paudel, S.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.09.005

2
S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
A
B
A
A
B
C
B
C
C
N
N
H
N
N
Cl
N
Ph2HC
N
Ph2HC
N
O
O
GBR-12935
4-Benzylpiperidine carboxamides
Arypiperazine-benzylpiperidines
B
A
C
N
N
N
N
( )
n
N
N
Ph2CH
Ar
Tetrazole derivatives
Figure 1. Design of substituted arylpiperazine–tetrazoles.
activities, and the structure–activity relationship (SAR) of these
compounds have been discussed in the following sections.
at 10 lM. Thus, we further synthesized tetrazole derivatives with
a three-carbon linker (9f–9w).
The structure–activity relationship (SAR) of the synthesized
compounds has been summarized in Figure 2. Norepinephrine
2. Chemistry
reuptake inhibition by all derivatives, except 9j (IC50 > 10
and 9w (IC50: 4.00 M), was greater than that by the standard drug,
bupropion. Heterocyclic derivatives (9a, 9b) were stronger inhibi-
tors (IC50 = 0.80–0.92 M) than the phenyl derivative (9f). Particu-
lM)
The arylpiperazine–tetrazoles were synthesized as illustrated in
Scheme 1. The commercially available diphenyl acetonitrile (1)
was reacted with excess sodium azide in the presence of triethy-
lamine hydrochloride to obtain 5-benzhydryl-1H-tetrazole (2).
l
l
larly, the introduction of a substituent at position 2 or 4 of the
Treatment of tetrazole
2 with 1-bromo-2-chloroethane or
phenyl ring (R) (9c, 9d, 9g, 9l, 9m, 9n, 9p, 9q), lead to improved
1-bromo-3-chloropropane or 1-bromo-4-chlorobutane afforded
corresponding haloalkyl-5-benzhydryl-1H-tetrazoles, 3 (n = 2), 4
(n = 3), and 5 (n = 4). Furthermore, the reaction of various aromatic
amines (6c–6w), with bis(2-chloroethyl)amine hydrochloride gave
N-arylpiperazine hydrochloride salts (7c–7w) (7a–7b were com-
mercially available). The haloalkyl tetrazoles 3, 4 and 5 were then
reacted with N-arylpiperazine hydrochloride salts (7a–7w) to
afford desired substituted arylpiperazine–tetrazoles 8a–8e, 9a–
9w and 10a–10e.
potency with IC50 (0.08–1.20
of the phenyl ring (R) (9i, 9m, 9p, IC50 = 1.62–2.48
l
M) than substitution at position 3
l
M). Interest-
ingly, the activity of tetrazole 9i with the CF3 substituent at
m-position of the phenyl ring was significantly greater than that
of its analog 9j with the CF3 substituent at p-position. Among the
arylpiperazine–tetrazoles, 9l (2-F) and 9n (4-F) are worth mention-
ing as 9l and 9n had the most potent neurotransmitter reuptake
inhibitory activity (IC50 = 0.34 and 0.08 lM, respectively). The
reuptake inhibitory activities of the compounds with mono-halo-
gen substitution were in the following order: 4-F > 2-F > 4-Cl > 2-
Cl > 4-Br > 3-Cl > 3-F. Majority of compounds with mono-halogens
substitution was more potent than di-halogen substitution deriva-
tives except 9s–9u.
The dopamine reuptake inhibition by heterocyclic derivatives
(9a, 9b) was potent. The neurotransmitter reuptake inhibitory
activity of 9b (IC50 = 1.14 lM) was greater than that of the stan-
3. Results and discussion
The in vitro neurotransmitter reuptake inhibition experiments
of the synthesized compounds were conducted in human embry-
onic kidney 293 (HEK-293) cells transfected with human nore-
pinephrine transporter (hNET), human dopamine transporter
(hDAT) and human serotonin transporter (hSERT) using a neuro-
transmitter uptake assay. The IC50 values for neurotransmitter
reuptake inhibitory activity of the compounds are presented in
Tables 1 and 2.
Initially, 15 arylpiperazine–tetrazoles (8a–8e, 9a–9e and 10a–
10e) were prepared and examined for their neurotransmitter
(norepinephrine, dopamine and serotonin) reuptake inhibitory
effects. In contrast to compounds with 2 and 4 carbon linkers, com-
pounds (9a–9e) having a three carbon linker exhibited selective
and potent NE and DA reuptake inhibitory activity (IC50 = 0.46–
dard drug, bupropion. The substitution at 2 or 4 position in the
phenyl ring produced favorable results (R) (9c, 9d, 9g, 9l, 9o, 9q)
with IC50 (0.91–1.42
ring (9i, 9p, IC50 = 4.74–5.57
which contained CF3 substitution (9i, IC50 = 5.57
3 showed significantly better activity than the derivative which
contained CF3 substitution (9j, IC50 > 10 M) at position 4. The
l
M) than the substitution at C3 in the phenyl
M). Interestingly, the derivative
M) at position
l
l
l
level of inhibition of dopamine reuptake shown by derivatives,
9d and 9o, confirmed that tetrazoles with chlorine substitution
were better inhibitors than those with F-substitution. The deriva-
tive with 2-Cl substitution (9o) was more potent than bupropion.
Similarly, compound 9d with 4-Cl substitution showed potency
equal to bupropion. Among the mono-halogen substituted deriva-
1.10
reuptake inhibitory activities of derivatives with 2 and 4 carbon
linkers at 10 M were not good. Unfortunately, the serotonin reup-
take inhibitory activity of arylpiperazine–tetrazoles was not good
lM for NE and IC50 = 1.04–3.04 lM for DA). The dopamine
l
tives, the derivative with 4-bromo substitution (9q, IC50 = 0.91 lM)
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S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
3
Cl
N
N
N
NH
N
N
N
N
R
Cl
N
R NH2
6a-6w
iii
Br(CH2)nCl
ii
( )
CN
n
.
.
HN
HN
HCl
HCl
iv
Cl
i
7a-7w
3
, n = 2
1
2
4, n = 3
5, n = 4
R
N
N
N
N
N
N
( )
n
8a-8e
(n = 2),
9a-9w (n = 3) and
10a-10e (n = 4)
R=
N
Cl
N
N
MeO
Cl
Cl
a
f
c
d
e
b
CF3
CF3
i
j
g
h
F
F
Cl
OMe
F
m
CF3
l
o
t
k
n
s
F
F
Br
Cl
F
Cl
F
Cl
r
q
v
p
F
Cl
Cl
Cl
w
F
u
Scheme 1. Synthesis of substituted arylpiperazine–tetrazoles 8a–8e (n = 2), 9a–9w (n = 3) and 10a–10e (n = 4). Reagents and conditions: (i) NaN3, triethylamine
hydrochloride (NEt3ꢀHCl), toluene, 100 °C; (ii) K2CO3, acetone, room temperature (rt); (iii) diethylene glycol monomethyl ether, 150 °C; (iv) K2CO3, NaI, acetonitrile (CH3CN),
reflux.
was the most potent and had greater activity than bupropion. All
the mono-halogen substituted derivatives (IC50 = 0.91–2.48 M),
except for the derivatives with 4-F and 3-Cl substitution (9n,
IC50 = 2.48 M and 9p, IC50 = 4.74 M), were more potent than
those with di-halogen substitution (IC50 = 2.90–4.20 M). In con-
trast to di-halogen substituted compounds, 2,6-(F)2 substituted
derivative (9u, IC50 = 0.82 M) was the most potent derivative
cate that the newer arylpiperazine–tetrazoles are potent dual
norepinephrine and dopamine reuptake inhibitors, and our study
provides valuable information for the researchers who are devel-
oping therapeutic agents to treat ADHD.
l
l
l
l
l
5. Experimental section
5.1. Chemistry
among the synthesized compounds and showed even greater bio-
logical activity than bupropion.
A Thomas Hoover melting point apparatus was used for the
determination of the melting point (mp) by the capillary method,
and the values were uncorrected. Varian Unity Plus 500, 300 and
125 MHz and Bruker BioSpin GmbH spectrometers were used to
obtain 1H and 13C NMR data, which are reported in ppm downfield
from the peak of the internal standard, tetramethylsilane. The data
are reported as chemical shift, number of protons, and multiplicity
(s: singlet, d: doublet, t: triplet, q: quartet, quin: quintet, m: mul-
tiplet, dd: doublet of doublets). Merck silica gel 60 (70–230 mesh)
was used for column chromatography. Plates coated with silica gel
60 F254 (Merck) were used for thin-layer chromatography.
Reagents were purchased from Sigma–Aldrich and Alfa Aesar and
used without further purification.
4. Conclusion
In conclusion, we designed and synthesized various substituted
arylpiperazine–tetrazoles based on 4-benzylpiperidine carboxam-
ides, arylpiperazine–benzylpiperidines and GBR12935, and their
neurotransmitter reuptake inhibitory activity was examined in
the human embryonic kidney cell line (HEK). The arylpiperazine–
tetrazoles were obtained mainly through the substitution reaction.
The IC50 values showed that compounds having a three-carbon lin-
ker were selective and more active than those having two-carbon
and four-carbon linkers. Among them, six compounds, 9b, 9c, 9d,
9o, 9q and 9u, displayed greater neurotransmitter reuptake inhibi-
tory activity than the standard drug, bupropion. Our results indi-
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4
S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
Table 1
Norepinephrine (NE), dopamine (DA) and Serotonin (5-HT) reuptake inhibition (IC50) by substituted arylpiperazine–tetrazoles 8a–8e, 9a–9e and 10a–10e
5
6
4
Y
R1
3
N
X
1
N
N
N
N
2
N
( )
n
Compound
R1
X
Y
n
NE (lM)
DA (
lM)
5-HT (lM)
8a
8b
8c
8d
8e
9a
9b
9c
9d
9e
10a
10b
10c
10d
10e
H
H
N
N
C
C
C
N
N
C
C
C
N
N
C
C
C
C
N
C
C
C
C
N
C
C
C
C
N
C
C
C
—
—
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
—
—
>10
>10
>10
>10
>10
0.92
0.80
0.50
0.46
1.10
4.70
8.54
10
>10
>10
>10
>10
>10
1.43
1.14
1.04
1.2
3.04
>10
>10
>10
>10
>10
2.55
1.20
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
>10
0.20
—
2-OMe
4-Cl
2,3-(Cl)2
H
H
2-OMe
4-Cl
2,3-(Cl)2
H
H
2-OMe
4-Cl
2,3-(Cl)2
—
>10
8.87
—
VenlafaxineꢀHCl
—
—
Bupropion
—
3.24
Table 2
Norepinephrine (NE) and dopamine (DA) reuptake inhibition (IC50) by substituted arylpiperazine–tetrazoles 9f–9w (n = 3)
5
4
6
R1
3
N
1
2
N
N
N
N
N
Compd
R1
NE (l
M)
DA (
lM)
Compd
R1
NE (lM)
DA (lM)
9f
–H
1.45
0.87
1.72
2.48
>10
1.06
0.35
1.89
0.08
1.64
1.42
3.72
5.58
>10
3.85
1.33
1.47
2.48
9o
9p
9q
9r
9s
9t
9u
9v
9w
2-Cl
3-Cl
4-Br
2-F, 5-CF3
2-F, 4-Cl
2,4-(F)2
2,6-(F)2
2,4-(Cl)2
3,4-(Cl)2
—
0.67
1.62
1.20
1.09
1.10
2.16
0.51
2.05
4.00
3.24
1.01
4.74
0.91
2.25
2.25
2.90
0.82
3.59
4.20
1.20
9g
9h
9i
9j
9k
9l
4-Me
2,6-Me2
3-CF3
4-CF3
4-OMe
2-F
9m
9n
3-F
4-F
Bupropion
5.1.1. 5-Benzhydryl-1H-tetrazole (2)
reaction mixture was filtered after the completion of reaction
and it was concentrated. The obtained product was purified by col-
umn chromatography with n-hexane/ethyl acetate (EtOAc) = 4:1 to
obtain 3 as a clear liquid (429 mg, 48%). Retention factor Rf = 0.62
(n-hexane/EtOAc = 1:1). 1H NMR (300 MHz, CDCl3): d 7.31–7.20
(m, 11H, overlapped with CHCl3), 5.95 (s, 1H), 4.90–4.85 (m, 2H),
3.99 (t, J = 6.3 Hz, 2H).
A mixture of a diphenylacetonitrile, 1 (1.74 g, 9 mmol), sodium
azide (1.75 g, 27 mmol), and triethylamine hydrochloride (3.71 g,
27 mmol) in toluene (80 mL) was heated to 100 °C for 24 h with
stirring. After cooling, the reaction mixture was extracted with
water. Then, 36% HCl was added dropwise to the aqueous layer.
Precipitation occurred, which was filtered off and washed with
water to provide 2 (1.53 g, 72%). 1H NMR (500 MHz, CDCl3): d
7.35–7.24 (m, 10H), 5.95 (s, 1H).
5.1.3. 5-Benzhydryl-1-(3-chloropropyl)-1H-tetrazole (4)
The procedure described for the preparation of 3 was used with
compound 2 (708 mg, 3 mmol), K2CO3 (1.24 g, 9 mmol), 1-bromo-
3-chloropropane (0.44 mL, 4.5 mmol) and acetone (80 mL) to obtain
4 as a clear liquid (779 mg, 83%). Retention factor Rf = 0.29 (n-hex-
ane/EtOAc = 4:1). 1H NMR (300 MHz, CDCl3): d 7.31–7.16 (m, 10H),
5.80 (s, 1H), 4.70–4.65 (m, 2H), 3.50–3.46 (m, 2H), 2.40–2.31 (m, 2H).
5.1.2. 5-Benzhydryl-1-(2-chloroethyl)-1H-tetrazole (3)
Compound
2 (709 mg, 3 mmol) was dissolved in acetone
(80 mL), and potassium carbonate (K2CO3, 1.24 g, 9 mmol) was
added, followed by dropwise addition of 1-bromo-2-chloroethane
(0.37 mL, 4.5 mmol). The reaction mixture was stirred at rt. The
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S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
5
hydrochloride (535.5 mg, 3 mmol), and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7g as an HCl salt (562 mg, 88%).
The HCl salt was used for the next reaction without further
purification.
X
Y
R
=
,
= C,
4-Me > H > 2,6-Me2
X
Y
R
=
,
= C,
Linker n
=
3 > 4 > 2
3-CF3 > 4-CF3
5.1.10. 1-(2,6-Dimethylphenyl)piperazine hydrochloride (7h)
The procedure described for the preparation of 7c was used
with compound 6h (363.5 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol), and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7h as an HCl salt (540 mg, 79%).
The HCl salt was used for the next reaction without further
purification.
X
Y
R
= C, =
,
5
2-OMe > 4-OMe
6
4
Y
R1
3
N
X
Mono-halogen substitution
X, Y = C, R =
F > Cl > Br (NE)
Br > Cl > F (DOP)
1
N
N
N
N
2
N
( )
n
Di-halogen substitution
X, Y = C, R =
Di-F > Di-Cl
5.1.11. 1-(3-(Trifluoromethyl)phenyl)piperazine hydrochloride
(7i)
R
= H
The procedure described for the preparation of 7c was used
with compound 6i (483.3 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol), and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7i as an HCl salt (640 mg, 80%).
The HCl salt was used for the next reaction without further
purification.
2-pyrimidyl (X, Y = N) > 2-pyridyl (X = N, Y = C)
Figure 2. Structure–activity relationship (SAR) of arylpiperazine–tetrazoles.
5.1.4. 5-Benzhydryl-1-(4-chlorobutyl)-1H-tetrazole (5)
The procedure described for the preparation of 3 was used with
compound 2 (958 mg, 4.05 mmol), K2CO3 (1.68 g, 12.15 mmol), 1-
bromo-4-chlorobutane (0.69 mL, 6.075 mmol) and acetone
(80 mL) to obtain 5 as a clear liquid (1.05 g, 80%). Retention factor
Rf = 0.57 (n-hexane/EtOAc = 1:1). 1H NMR (500 MHz, CDCl3): d
7.39–7.25 (m, 10H), 5.86 (s, 1H), 4.63 (t, J = 7 Hz, 2H), 3.57–3.54
(m, 2H), 2.21–2.16 (m, 2H), 1.83–1.77 (m, 2H).
5.1.12. 1-(4-(Trifluoromethyl)phenyl)piperazine hydrochloride
(7j)
The procedure described for the preparation of 7c was used
with compound 6j (483.3 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol), and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7j as an HCl salt (520 mg, 65%).
The HCl salt was used for the next reaction without further
purification.
5.1.5. 1-(2-Methoxyphenyl)piperazine hydrochloride (7c)
A mixture of 2-methoxyaniline (369.4 mg, 3 mmol), bis(2-
chloroethyl)amine hydrochloride (535.5 mg, 3 mmol) and diethy-
lene glycol monomethyl ether (0.75 mL) was heated at 150 °C for
about 12 h. The reaction mixture was cooled to room temperature
and dissolved in methanol (4 mL), followed by the addition of
diethyl ether (150 mL). The precipitate formed was recovered by
filtration and washed with diethyl ether to obtain 7c as an HCl salt
(510 mg, 74%). The HCl salt was used for the next reaction without
further purification.
5.1.13. 1-(4-Methoxyphenyl)piperazine hydrochloride (7k)
The procedure described for the preparation of 7c was used
with compound 6k (369.4 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7k as an HCl salt (549 mg, 80%).
The HCl salt was used for the next reaction without further
purification.
5.1.14. 1-(2-Fluorophenyl)piperazine hydrochloride (7l)
The procedure described for the preparation of 7c was used
with compound 6l (333.4 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7l as an HCl salt (443 mg, 68%).
The HCl salt was used for the next reaction without further
purification.
5.1.6. 1-(4-Chlorophenyl)piperazine hydrochloride (7d)
The procedure described for the preparation of 7c was used
with compound 6d (321.4 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7d as an HCl salt (630 mg, 90%).
The HCl salt was used for the next reaction without purification.
5.1.15. 1-(3-Fluorophenyl)piperazine hydrochloride (7m)
The procedure described for the preparation of 7c was used
with compound 6m (333.4 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7m as an HCl salt (488 mg,
75%). The HCl salt was used for the next reaction without further
purification.
5.1.7. 1-(2,3-Dichlorophenyl)piperazine hydrochloride (7e)
The procedure described for the preparation of 7c was used
with compound 6e (486.1 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7e as an HCl salt (643 mg, 80%).
The HCl salt was used for the next reaction without purification.
5.1.8. 1-Phenylpiperazine hydrochloride (7f)
5.1.16. 1-(4-Fluorophenyl)piperazine hydrochloride (7n)
The procedure described for the preparation of 7c was used
with compound 6n (333.4 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7n as an HCl salt (550 mg, 85%).
The HCl salt was used for the next reaction without further
purification.
The procedure described for the preparation of 7c was used
with compound 6f (279.4 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7f as an HCl salt (530 mg, 89%).
The HCl salt was used for the next reaction without further
purification.
5.1.9. 1-(4-Methylphenyl)piperazine hydrochloride (7g)
The procedure described for the preparation of 7c was used
with compound 6g (321.2 mg, 3 mmol), bis(2-chloroethyl)amine
5.1.17. 1-(2-Chlorophenyl)piperazine hydrochloride (7o)
The procedure described for the preparation of 7c was used
with compound 6o (321.5 mg, 3 mmol), bis(2-chloroethyl)amine
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6
S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7o as an HCl salt (595 mg, 85%).
The HCl salt was used for the next reaction without further
purification.
5.1.26. 1-(2-(5-Benzhydryl-1H-tetrazol-1-yl)ethyl)-4-(pyridin-2-
yl)piperazine (8a)
The compound 7a (0.23 mL, 1.5 mmol), was dissolved in ace-
tonitrile (CH3CN, 15 mL). K2CO3 (276.4 mg, 2 mmol) was added fol-
lowed by compound 3 (300 mg, 1 mmol) and sodium iodide (NaI,
catalyst). The reaction mixture was heated overnight at 100 °C.
After completion, the reaction mixture was cooled, filtered and
concentrated. The obtained product was purified by column chro-
matography on silica gel with n-hexane/EtOAc/MeOH (10:1.5:0.5)
to obtain 8a (59 mg, 13%) as a white solid. Rf = 0.75 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 166–170 °C. 1H NMR (500 MHz,
CDCl3): d 8.20–8.19 (m, 1H), 7.51–7.47 (m, 1H), 7.36–7.22 (m,
11H, overlapped with CHCl3), 6.66–6.62 (m, 2H), 5.83 (s, 1H),
4.30–4.28 (m, 2H), 3.49 (t, J = 3 Hz, 4H), 2.75–2.73 (m, 2H), 2.50
(t, J = 5 Hz, 4H); 13C NMR (125 MHz, CDCl3): d 159.2, 156.6,
147.9, 138.4, 137.6, 129, 128.6, 127.8, 113.6, 107.1, 57.3, 53.1,
46.4, 45.1, 45.
5.1.18. 1-(2-Chlorophenyl)piperazine hydrochloride (7p)
The procedure described for the preparation of 7c was used
with compound 6p (321.5 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7p as an HCl salt (490 mg, 70%).
The HCl salt was used for the next reaction without further
purification.
5.1.19. 1-(2-Bromophenyl)piperazine hydrochloride (7q)
The procedure described for the preparation of 7c was used
with compound 6q (537.3 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7q as an HCl salt (598 mg, 70%).
The HCl salt was used for the next reaction without purification.
5.1.27. 2-(4-(2-(5-Benzhydryl-1H-tetrazol-1-yl)ethyl)piperazin-
1-yl)pyrimidine (8b)
5.1.20. 1-(2-Fluoro-5-(trifluoromethyl)phenyl)piperazine
hydrochloride (7r)
The procedure described for the preparation of 8a was used
with compound 3 (300 mg, 1 mmol), 7b (0.21 mL, 1.5 mmol),
K2CO3 (276.4 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 8b (72 mg, 23%) as a white solid. Rf = 0.18 (n-hexane/
EtOAc = 1:1). Mp = 166–170 °C. 1H NMR (500 MHz, CDCl3): d 8.31
(d, J = 4.5 Hz, 2H), 7.37–7.28 (m, 6H), 7.24–7.22 (m, 4H), 6.52–
6.50 (m, 1H), 5.83 (s, 1H), 4.30–4.28 (m, 2H), 3.77 (t, J = 5 Hz, 4H)
2.74 (t, J = 6 Hz, 2H), 2.45–2.43 (m, 4H); 13C NMR (125 MHz,
CDCl3): d 161.5, 157.7, 156.5, 138.4, 129.1, 128.6, 127.9, 110.1,
57.3, 53.2, 46.4, 45, 43.5.
The procedure described for the preparation of 7c was used
with compound 6r (516.1 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7r as an HCl salt (540 mg, 65%).
The HCl salt was used for the next reaction without purification.
5.1.21. 1-(4-Chloro-2-fluorophenyl)piperazine hydrochloride
(7s)
The procedure described for the preparation of 7c was used
with compound 6s (436.7 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7s as an HCl salt (362 mg, 48%).
The HCl salt was used for the next reaction without purification.
5.1.28. 1-(2-(5-Benzhydryl-1H-tetrazol-1-yl)ethyl)-4-(2-metho-
xyphenyl)piperazine (8c)
The procedure described for the preparation of 8a was used
with compound 3 (300 mg, 1 mmol), 7c (288 mg, 1.5 mmol),
K2CO3 (276.4 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 8c (59 mg, 13%) as a sticky white solid. Rf = 0.5 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.36–7.24
(m, 11H, overlapped with CHCl3), 7.04–6.86 (m, 4H), 5.86 (s, 1H),
4.29 (t, J = 6 Hz, 2H), 3.87 (s, 3H), 3.04 (s, 4H), 2.77 (t, J = 6 Hz,
2H), 2.63–2.62 (m, 2H); 13C NMR (125 MHz, CDCl3): d 156.6,
152.2, 140.9, 138.5, 129, 128.6, 127.8, 123.2, 121, 118.2, 111.15,
57.4, 55.4, 53.9, 50.5, 46.3, 45.0.
5.1.22. 1-(2,4-Difluorophenyl)piperazine hydrochloride (7t)
The procedure described for the preparation of 7c was used
with compound 6t (387.3 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7t as an HCl salt (317 mg, 45%).
The HCl salt was used for the next reaction without purification.
5.1.23. 1-(2,6-Difluorophenyl)piperazine hydrochloride (7u)
The procedure described for the preparation of 7c was used
with compound 6u (387.3 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7u as an HCl salt (353 mg,
50%). The HCl salt was used for the next reaction without
purification.
5.1.29. 1-(2-(5-Benzhydryl-1H-tetrazol-1-yl)ethyl)-4-(4-chloro-
phenyl)piperazine (8d)
The procedure described for the preparation of 8a was used
with compound 3 (300 mg, 1 mmol), 7d (349.7 mg, 1.5 mmol),
K2CO3 (276.4 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 8d (70 mg, 15%) as a sticky white solid. Rf = 0.75 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.36–
7.19 (m, 13H, overlapped with CHCl3), 6.82–6.79 (m, 2H), 5.78 (s,
1H), 4.31–4.28 (m, 2H), 3.08–3.06 (m, 4H), 2.76–2.73 (m, 2H),
2.54–2.52 (m, 4H); 13C NMR (125 MHz, CDCl3): d 156.5, 149.6,
138.4, 129, 128.99, 128.6, 127.9, 117.4, 57, 53, 49.0, 46.4, 45.
5.1.24. 1-(2,4-Dichlorophenyl)piperazine hydrochloride (7v)
The procedure described for the preparation of 7c was used
with compound 6v (486.1 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7v as an HCl salt (640 mg,
80%). The HCl salt was used for the next reaction without
purification.
5.1.30. 1-(2-(5-Benzhydryl-1H-tetrazol-1-yl)ethyl)-4-(2,3-dichl-
orophenyl)piperazine (8e)
The procedure described for the preparation of 8a was used
with compound 3 (300 mg, 1 mmol), 7e (401 mg, 1.5 mmol),
K2CO3 (276.4 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 8e (80 mg, 16%) as a sticky white solid. Rf = 0.2 (n-hexane/
EtOAc = 1:1). 1H NMR (500 MHz, CDCl3): d 7.37–7.24 (m, 11H,
overlapped with CHCl3), 7.19–7.13 (m, 2H), 6.88 (dd, J = 7.5 Hz,
2 Hz, 1H), 5.79 (s, 1H), 4.32–4.29 (m, 2H), 2.96 (s, 4H), 2.79–2.77
(m, 2H), 2.58 (s, 4H); 13C NMR (125 MHz, CDCl3): d.156.5, 150.8,
5.1.25. 1-(3,4-Dichlorophenyl)piperazine hydrochloride (7w)
The procedure described for the preparation of 7c was used
with compound 6w (486.1 mg, 3 mmol), bis(2-chloroethyl)amine
hydrochloride (535.5 mg, 3 mmol) and diethylene glycol mono-
methyl ether (0.75 mL) to obtain 7w as an HCl salt (627 mg,
78%). The HCl salt was used for the next reaction without
purification.
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S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
7
138.5, 134.1, 129, 128.6, 127.8, 127.5, 124.8, 118.6, 57, 53.3, 51.1,
46.4, 45.0.
2H); 13C NMR (125 MHz, CDCl3): d.167.8, 151.2, 140.8, 134.0,
128.7, 128.6, 127.5, 127.4, 127.0, 118.6, 54.8, 53.2, 51.2, 48.6, 26.5.
5.1.31. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(pyridin-
2-yl)piperazine (9a)
5.1.36. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-phenyl-
piperazine (9f)
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 1 mmol), 7a (0.22 mL, 1.44 mmol),
K2CO3 (265 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9a as a white solid (261 mg, 62%). Rf = 0.44 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 73–76 °C. 1H NMR (500 MHz,
CDCl3): d 8.20–8.19 (m, 8H), 7.50–7.46 (m, 1H), 7.35–7.29 (m,
8H), 7.25–7.22 (m, 2H), 6.64–6.61 (m, 2H), 5.82 (s, 1H), 4.71 (t,
J = 7 Hz, 2H), 3.49 (t, J = 5 Hz, 4H), 2.51 (t, J = 5 Hz, 4H), 2.44–2.42
(m, 2H), 2.24–2.19 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8,
159.5, 147.9, 140.8, 137.4, 128.7, 128.6, 128.4, 127, 113.3, 107,
54.9, 52.9, 51.3, 48.6, 45.2, 26.6.
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 1 mmol), 7f (286 mg, 1.44 mmol),
K2CO3 (265 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9f as a light brown liquid (229 mg, 55%). Rf = 0.6 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.37–
7.23 (m, 13H), 6.94–6.86 (m, 3H), 5.83 (s, 1H), 4.71 (t, J = 7 Hz,
2H), 3.16 (t, J = 5 Hz, 4H), 2.57 (t, J = 5 Hz, 4H), 2.47–2.44 (m, 2H),
2.25–2.20 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8, 151.2,
140.8, 129.1, 128.7, 128.6, 128.58, 127.0, 119.7, 116.1, 54.9, 53.1,
51.4, 49.1, 48.7, 26.6.
5.1.37. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
methylphenyl)piperazine (9g)
5.1.32. 2-(4-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)pipera-
zin-1-yl)pyrimidine (9b)
The procedure described for the preparation of 8a was used
with compound 4 (310 mg, 0.99 mmol), 7g (315.9 mg, 1.48 mmol),
K2CO3 (273 mg, 1.98 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9g as a light brown liquid (296 mg, 66%). Rf = 0.58 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.36–
7.23 (m, 10H), 7.10–7.08 (m, 2H), 6.86–6.83 (m, 2H), 5.83 (s, 1H),
4.70 (t, J = 7 Hz, 2H), 3.13–3.11 (m, 4H), 2.57 (t, J = 5 Hz, 4H), 2.45
(t, J = 5 Hz, 2H), 2.29 (s, 3H), 2.26–2.20 (m, 2H); 13C NMR
(125 MHz, CDCl3): d 167.8, 149.2, 140.8, 129.6, 129.2, 128.7,
128.6, 127.0, 116.4, 54.9, 53.2, 51.4, 49.7, 48.6, 26.6, 20.4.
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 1 mmol), 7b (0.20 mL, 1.44 mmol),
K2CO3 (265 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9b as a white solid (220 mg, 52%). Rf = 0.6 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 100–105 °C. 1H NMR (500 MHz,
CDCl3): d 8.30 (d, J = 5 Hz, 2H), 7.36–7.29 (m, 10H), 7.25–7.21 (m,
2H), 5.82 (s, 1H), 6.48–6.46 (m, 2H), 4.10 (t, J = 7 Hz, 2H), 3.78 (t,
J = 5 Hz, 4H), 2.46–2.18 (m, 6H), 2.23–2.18 (2H); 13C NMR
(125 MHz, CDCl3): d 167.7, 161.6, 157.7, 140.8, 128.7, 128.6, 127,
109.8, 54.9, 53, 51.3, 48.6, 43.5, 26.5.
5.1.38. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2,6-
dimethylphenyl)piperazine (9h)
5.1.33. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2-meth-
oxyphenyl)piperazine (9c)
The procedure described for the preparation of 8a was used
with compound 4 (313 mg, 1 mmol), 7h (340.1 mg, 1.5 mmol),
K2CO3 (276 mg, 2.04 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9h as a light brown liquid (294 mg, 63%). Rf = 0.64 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.42–
7.34 (m, 10H), 7.30–7.27 (m, 3H), 5.89 (s, 1H), 4.76–4.73 (m, 2H),
3.13–3.16 (m, 4H), 2.57–2.55 (m, 4H), 2.49 (t, J = 7 Hz, 2H), 2.38
(s, 6H), 2.27 (p, J = 4.2 Hz, 2H); 13C NMR (125 MHz, CDCl3): d
167.8, 148.3, 140.9, 137.0, 129.0, 128.8, 128.6, 127.1, 125.1, 55.3,
54.5, 51.4, 49.7, 48.7, 26.7, 19.7.
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 1 mmol), 7c (276.8 mg, 1.44 mmol),
K2CO3 (265 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9c as a light brown liquid (180 mg, 38%). Rf = 0.56 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.34–
7.21 (m, 11H), 7.02–6.84 (m, 4H), 5.81 (s, 1H), 4.70–4.67 (m, 2H),
3.85 (s, 3H), 3.04 (s, 4H), 2.61 (s, 4H), 2.45 (t, J = 8.5 Hz, 2H),
2.24–2.17 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8, 152.3,
141.3, 140.8, 128.7, 128.6, 127, 122.9, 121, 118.2, 111.2, 55.4, 55,
53.3, 50.6, 48.6, 26.6.
5.1.39. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(3-
(trifluoromethyl)phenyl)piperazine (9i)
5.1.34. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
chlorophenyl)piperazine (9d)
The procedure described for the preparation of 8a was used
with compound 4 (315 mg, 1 mmol), 7i (402.8 mg, 1.5 mmol),
K2CO3 (278 mg, 2.04 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9i as a light brown liquid (294 mg, 58%). Rf = 0.67 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.37–
7.23 (m, 11H), 7.10–7.03 (m, 3H), 5.83 (s, 1H), 4.71 (t, J = 7 Hz,
2H), 3.16 (t, J = 5 Hz, 4H), 2.55 (t, J = 5 Hz, 4H), 2.47–2.44 (m, 2H),
2.25–2.20 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8, 151.3,
140.8, 129.5, 128.7, 128.6, 127.0, 118.6, 115.8, 115.78, 115.75,
115.7, 112.1, 112.1, 112.1, 122.0, 54.9, 51.4, 48.7, 48.5.
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 1 mmol), 7d (335.7 mg, 1.44 mmol),
K2CO3 (265 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9d as a light brown liquid (230 mg, 51%). Rf = 0.5 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.35–
7.19 (m, 13H, overlapped with CHCl3), 6.83–6.80 (m, 2H), 5.81 (s,
1H), 4.70 (t, J = 7 Hz, 2H), 3.10 (t, J = 5 Hz, 4H), 2.54 (t, J = 5 Hz,
4H), 2.45–2.43 (m, 2H), 2.24–2.18 (m, 2H); 13C NMR (125 MHz,
CDCl3): d 167.8, 149.9, 140.8, 128.9, 128.7, 128.6, 127, 124.5,
117.2, 54.8, 51.1, 49.1, 48.7, 26.5.
5.1.40. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
(trifluoromethyl)phenyl)piperazine (9j)
5.1.35. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2,3-
dichlorophenyl)piperazine (9e)
The procedure described for the preparation of 8a was used
with compound 4 (315 mg, 1 mmol), 7j (402.8 mg, 1.5 mmol),
K2CO3 (278 mg, 2.04 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9j as a light brown liquid (291 mg, 57%). Rf = 0.67 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.50
(d, J = 5.1 Hz, 2H), 7.39–7.24 (m, 10H), 6.91 (d, J = 8.5 Hz, 2H),
5.89 (s, 1H), 4.73–4.70 (m, 2H), 3.22 (t, J = 5 Hz, 4H), 2.54 (t,
J = 5 Hz, 4H), 2.47–2.44 (m, 2H), 2.25–2.20 (m, 2H); 13C NMR
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 1 mmol), 7e (385 mg, 1.44 mmol),
K2CO3 (265 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9e as a light brown liquid (234 mg, 48%). Rf = 0.48 (n-hex-
ane/EtOAc = 1:1). 1H NMR (500 MHz, CDCl3): d 7.36–7.13 (m,
12H), 6.93 (dd, J = 7.5, 2.5 Hz, 1H), 5.82 (s, 1H), 4.71 (t, J = 7 Hz,
2H), 3.01 (s, 4H), 2.59 (s, 4H), 2.48–2.45 (m, 2H), 2.25–2.19 (m,
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S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
(125 MHz, CDCl3): d 167.8, 153.2, 140.8, 128.7, 128.6, 127.0,
126.41, 126.4, 126.35, 126.3, 54.9, 51.3, 48.7, 47.9, 26.5.
MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.38–7.21 (m,
15H), 7.03–6.96 (m, 3H), 5.82 (s, 1H), 4.72–4.69 (m, 2H), 3.04 (s,
4H), 2.61 (s, 4H), 2.49–2.47 (m, 2H), 2.26–2.20 (m, 2H); 13C NMR
(125 MHz, CDCl3): d 167.8, 149.2, 140.8, 130.6, 129.1, 128.7, 128.6,
127.6, 127.0, 123.7, 120.4, 54.9, 53.3, 51.3, 51.2, 48.7, 26.6.
5.1.41. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
methoxyphenyl)piperazine (9k)
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 0.96 mmol), 7k (329 mg, 1.44 mmol),
K2CO3 (265 mg, 1.92 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9k as a white solid (184 mg, 41%). Rf = 0.61 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 80–83 °C. 1H NMR (500 MHz,
CDCl3): d 7.35–7.30 (m, 8H), 7.27–7.23 (m, 2H), 6.91–6.84 (m,
4H), 5.83 (s, 1H), 4.70 (t, J = 7 Hz, 2H), 3.78 (s, 3H), 3.07–3.05 (m,
4H), 2.57 (t, J = 5 Hz, 4H), 2.46–2.44 (m, 2H), 2.24–2.19 (m, 2H);
13C NMR (125 MHz, CDCl3): d 167.8, 153.8, 145.7, 140.8, 128.7,
128.6, 127.0, 118.2, 114.4, 55.6, 54.9, 53.2, 50.6, 48.6, 26.6.
5.1.46. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(3-
chlorophenyl)piperazine (9p)
The procedure described for the preparation of 8a was used
with compound 4 (310 mg, 0.99 mmol), 7p (346 mg, 1.48 mmol),
K2CO3 (273.5 mg, 1.98 mmol), NaI (catalyst) and CH3CN (15 mL)
to obtain 9p as a white solid (314 mg, 67%). Rf = 0.67 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 100–103 °C. 1H NMR (500 MHz,
CDCl3): d 7.35–7.22 (m, 12H, overlapped with CHCl3), 7.18–7.15
(m, 3H), 5.82 (s, 1H), 4.70 (t, J = 7 Hz, 2H), 3.12 (t, J = 5 Hz, 4H),
2.53 (t, J = 5 Hz, 4H), 2.46–2.43 (m, 2H), 2.24–2.19 (m, 2H); 13C
NMR (125 MHz, CDCl3): d 167.8, 152.3, 140.9, 134.9, 130.1, 128.7,
128.6, 127.1, 119.2, 115.7, 113.9, 54.9, 52.9, 51.4, 48.7, 48.56, 26.5.
5.1.42. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2-
flurophenyl)piperazine (9l)
The procedure described for the preparation of 8a was used
with compound 4 (315 mg, 1.01 mmol), 7l (327.3 mg, 1.57 mmol),
K2CO3 (278 mg, 2.1 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9l as a light brown liquid (279 mg, 61%). Rf = 0.67 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.41–
7.39 (m, 4H), 7.36–7.32 (m, 4H), 7.28–7.25 (m, 2H), 7.10–7.03
(m, 2H), 6.97–6.93 (m, 2H), 5.83 (s, 1H), 4.71 (t, J = 7 Hz, 2H),
3.09 (t, J = 4.5 Hz, 4H), 2.60 (t, J = 4.5 Hz, 4H), 2.46 (t, J = 7 Hz,
2H), 2.25–2.19 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8,
156.7, 154.8, 140.9, 140.2, 140.1, 128.8, 128.6, 127.1, 124.5,
124.4, 122.4, 119.0, 118.96, 116.2, 116.0, 54.9, 53.2, 50.5, 48.7,
26.6.
5.1.47. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
bromophenyl)piperazine (9q)
The procedure described for the preparation of 8a was used
with compound 4 (312 mg, 1 mmol), 7q (416.4 mg, 1.5 mmol),
K2CO3 (276.4 mg, 2 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9q as a light brown liquid (315 mg, 61%). Rf = 0.61 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.37–
7.23 (m, 12H), 6.94–6.86 (m, 3H), 5.83 (s, 1H), 4.71 (t, J = 7 Hz,
2H), 3.16 (t, J = 5 Hz, 4H), 2.57 (t, J = 5 Hz, 4H), 2.45 (t, J = 7 Hz,
2H), 2.25 (p, J = 7 HZ, 2H); 13C NMR (125 MHz, CDCl3): d 167.8,
151.2, 140.8, 129.1, 128.7, 128.6, 127.0, 119.7, 116.1, 54.9, 53.1,
51.4, 49.1, 48.7, 26.6.
5.1.43. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(3-
flurophenyl)piperazine (9m)
5.1.48. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2-fluro-
5-(trifluromethyl)phenyl)piperazine (9r)
The procedure described for the preparation of 8a was used
with compound
1.53 mmol), K2CO3 (282 mg, 2.04 mmol), NaI (catalyst) and CH3CN
(15 mL) to obtain 9m as a white solid (275 mg, 59%). Rf = 0.68 (n-
hexane/EtOAc/MeOH = 2.5:1.5:1).
(500 MHz, CDCl3): d 7.44–7.19 (11H), 6.70–6.57 (m, 3H), 5.91 (s,
1H), 4.70 (t, J = 7 Hz, 2H), 3.15 (t, J = 4.5 Hz, 4H), 2.53 (t, J = 5 Hz,
4H), 2.45–2.42 (m, 2H), 2.24–2.19 (m, 2H); 13C NMR (125 MHz,
CDCl3): d 167.8, 164.9, 162.9, 153.0, 152.9, 141.0, 130.2, 130.16,
128.8, 127.1, 111.13, 111.1, 105.8, 105.6, 102.7, 102.5, 54.9, 51.4,
48.8, 48.5, 26.5.
4
(320 mg, 1.02 mmol), 7m (331.5 mg,
The procedure described for the preparation of 8a was used
with compound 4 (320 mg, 1.02 mmol), 7r (435.5 mg, 1.53 mmol),
K2CO3 (276 mg, 2.04 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9r as a light brown liquid (290 mg, 54.2%). Rf = 0.75 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.40–
7.38 (m, 4H), 7.34–7.31 (m, 4H), 7.25–7.20 (m, 3H), 7.16–7.08
(m, 2H), 5.85 (s, 1H), 4.72–4.70 (m, 2H), 3.08–3.06 (m, 4H), 2.58–
2.56 (m, 4H), 2.47–2.45 (m, 2H), 2.24–2.19 (m, 2H); 13C NMR
(125 MHz, CDCl3): d 168.7, 158.2, 156.2, 140.9, 140.6, 140.5,
128.7, 128.6, 127.0, 125.0, 122.9, 119.33, 119.3, 119.26, 119.2,
116.5, 116.4, 116.1, 116.03, 116.0, 54.8, 52.9, 51.3, 50.14, 50.1,
48.7, 26.5.
Mp = 90–92 °C.
1H
NMR
5.1.44. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
flurophenyl)piperazine (9n)
The procedure described for the preparation of 8a was used
with compound 4 (330 mg, 1.05 mmol), 7n (341.2 mg, 1.57 mmol),
K2CO3 (290 mg, 2.1 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9n as a white solid (312 mg, 65%). Rf = 0.65 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 93–96 °C. 1H NMR (500 MHz,
CDCl3): d 7.38–7.23 (m, 10H), 7.09–6.95 (m, 2H), 6.88–6.85 (m,
2H), 5.84 (s, 1H), 4.70 (t, J = 7 Hz, 2H), 3.07 (t, J = 5 Hz, 4H), 2.56
(t, J = 5 Hz, 4H), 2.45 (t, J = 7 Hz, 2H), 2.25–2.19 (m, 2H); 13C NMR
(125 MHz, CDCl3): d 167.8, 158.1, 156.2, 147.94, 147.9, 140.8,
128.7, 128.6, 127.0, 117.8, 117.76, 115.6, 115.4, 54.8, 53.1, 51.3,
50.1, 48.7, 26.6.
5.1.49. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(4-
chloro-2-fluorophenyl)piperazine (9s)
The procedure described for the preparation of 8a was used
with compound 4 (310 mg, 0.99 mmol), 7s (373 mg, 1.48 mmol),
K2CO3 (274 mg, 1.98 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9s as a white solid (291 mg, 60%). Rf = 0.65 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 83–85 °C. 1H NMR (500 MHz,
CDCl3): d 7.37–7.29 (m, 10H), 7.26–7.22 (m, 2H), 7.07–7.03 (m,
1H), 5.83 (s, 1H), 4.70 (t, J = 7 Hz, 2H), 3.02–3.00 (m, 4H), 2.57–
2.55 (m, 4H), 2.46–2.44 (m, 2H), 2.23–2.18 (m, 2H); 13C NMR
(125 MHz, CDCl3): d 167.8, 156.3, 154.3, 140.8, 139.0, 138.9,
128.7, 128.6, 127.0, 126.74, 126.7, 124.5, 124.46, 119.6, 119.5,
116.9, 116.7, 60.39, 54.84, 53.0, 51.3, 50.43, 50.4, 48.7, 26.5.
5.1.45. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2-
chlorophenyl)piperazine (9o)
The procedure described for the preparation of 8a was used with
compound 4 (330 mg, 1.05 mmol), 7o (367.2 mg, 1.57 mmol), K2CO3
(290 mg, 2.1 mmol), NaI (catalyst) and CH3CN (15 mL) to obtain 9o
as a light brown liquid (293 mg, 59%). Rf = 0.64 (n-hexane/EtOAc/
5.1.50. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2,4-
diflurophenyl)piperazine (9t)
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 0.96 mmol), 7t (338 mg, 1.44 mmol),
Please cite this article in press as: Paudel, S.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.09.005

S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
9
K2CO3 (265 mg, 1.92 mmol), NaI (catalyst) and CH3CN (15 mL) to
5.1.55. 2-(4-(4-(5-Benzhydryl-1H-tetrazol-1-yl)butyl)piperazin-
1-yl)pyrimidine (10b)
obtain 9t as a white solid (287 mg, 63%). Rf = 0.68 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 75–78 °C. 1H NMR (500 MHz,
CDCl3): d 7.39–7.23 (m, 10H), 6.90–6.78 (m, 3H), 5.85 (s, 1H),
4.70 (t, J = 7 Hz, 2H), 3.01–2.99 (m, 4H), 2.58 (s, 4H), 2.47–2.44
(m, 2H), 2.24–2.18 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8,
158.9, 158.8, 156.9, 156.8, 156.6, 156.5, 154.6, 140.9, 136.7,
128.7, 128.6, 127.0, 119.5, 119.4, 110.8, 110.7, 110.6, 104.9,
104.7, 104.5, 54.8, 53.1, 51.3, 50.9, 48.7, 26.5.
The procedure described for the preparation of 8a was used
with compound 5 (300 mg, 0.91 mmol), 7b (0.19 mL, 1.36 mmol),
K2CO3 (251.5 mg, 1.82 mmol), NaI (catalyst) and CH3CN (15 mL)
to obtain 10b as a light brown liquid (199 mg, 48%). Rf = 0.32 (n-
hexane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d
8.30 (d, J = 4.5 Hz, 2H), 7.34–7.29 (m, 8H), 7.25–7.22 (m, 2H),
6.48–6.46 (m, 1H), 4.63 (t, J = 7 Hz, 2H), 3.81–3.79 (m, 2H), 2.44–
2.42 (m, 4H), 2.39–2.37 (m, 2H), 2.09–2.02 (m, 2H), 1.57–1.51
(m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8, 161.6, 157.7, 140.8,
128.7, 128.6, 127, 109.8, 57.6, 53, 52.9, 48.6, 43.6, 27.3, 23.5.
5.1.51. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2,6-
diflurophenyl)piperazine (9u)
The procedure described for the preparation of 8a was used
with compound 4 (300 mg, 0.96 mmol), 7u (352 mg, 1.44 mmol),
K2CO3 (265 mg, 1.92 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9u as a light brown liquid (282 mg, 62%). Rf = 0.75 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.37–
7.30 (m, 8H), 7.26–7.23 (m, 2H), 6.96–6.90 (m, 1H), 6.87–6.81
(m, 2H), 5.83 (s, 1H), 4.71 (t, J = 7 Hz, 2H), 3.21–3.19 (m, 4H),
2.55–2.53 (m, 4H), 2.46–2.43 (m, 2H), 2.24–2.18 (m, 2H); 13C
NMR (125 MHz, CDCl3): d 167.8, 159.6, 159.57, 157.7, 157.6,
140.8, 128.7, 128.6, 127.0, 123.3, 123.2, 123.1, 112.2, 112.1,
112.05, 112.0, 55.0, 53.8, 51.3, 51.1, 51.05, 51.0, 48.7, 26.6.
5.1.56. 1-(4-(5-Benzhydryl-1H-tetrazol-1-yl)butyl)-4-(2-
methoxyphenyl)piperazine (10c)
The procedure described for the preparation of 8a was used
with compound 5 (300 mg, 0.91 mmol), 7c (261.5 mg, 1.36 mmol),
K2CO3 (251.5 mg, 1.82 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 10c as a light brown liquid (218 mg, 45%). Rf = 0.58 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.34–
7.19 (m, 11H), 7.01–6.83 (m, 4H), 5.81 (s, 1H), 4.63–4.60 (m, 2H),
3.84 (s, 3H), 3.06 (s, 4H), 2.58 (s, 4H), 2.43–2.39 (m, 2H), 1.57–
1.50 (m, 2H), 1.24 (t, J = 9 Hz, 2H). 13C NMR (125 MHz, CDCl3): d
167.8, 152.3, 141.3, 140.8, 128.7, 128.6, 127, 122.9, 121, 118.2,
111.2, 57.6, 55.4, 53, 50.6, 48.6, 27.4, 23.6.
5.1.52. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(2,4-
dichlorophenyl)piperazine (9v)
5.1.57. 1-(4-(5-Benzhydryl-1H-tetrazol-1-yl)butyl)-4-(2-
chlorophenyl)piperazine (10d)
The procedure described for the preparation of 8a was used
with compound 4 (320 mg, 1.02 mmol), 7v (409.4 mg, 1.53 mmol),
K2CO3 (282 mg, 2.04 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9v as a light brown liquid (321 mg, 61%). Rf = 0.65 (n-hex-
ane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d 7.36–
7.29 (m, 13H), 6.92 (d, J = 5.1 Hz, 1H), 5.82 (s, 1H), 4.70 (t,
J = 4.2 Hz, 2H), 2.98 (s, 4H), 2.58 (s, 4H), 2.48–2.45 (m, 2H), 2.24–
2.19 (m, 2H); 13C NMR (125 MHz, CDCl3): d 168.8, 148.0, 140.8,
130.3, 129.4.6, 128.7, 128.6, 128.1, 127.6, 127.0, 121.1, 54.8, 53.1,
51.3, 51.1, 48.6, 26.5.
The procedure described for the preparation of 8a was used
with compound 5 (300 mg, 0.91 mmol), 7d (318 mg, 1.36 mmol),
K2CO3 (251.5 mg, 1.82 mmol), NaI (catalyst) and CH3CN (15 mL)
to obtain 10d as a light brown liquid (208 mg, 47%). Rf = 0.46 (n-
hexane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d
7.36–7.13 (m, 13H), 6.96–6.94 (m, 2H), 5.84 (s, 1H), 4.65 (t,
J = 7 Hz, 2H), 3.04 (s, 4H), 2.58 (s, 4H), 2.45–2.42 (m, 2H), 2.11–
2.06 (m, 2H), 1.58–1.52 (m, 2H); 13C NMR (125 MHz, CDCl3): d
167.8, 151.3, 140.8, 134, 128.7, 127.5, 127, 124.5, 118.6, 57.5,
53.2, 53, 51.3, 48.6, 27.2, 23.5.
5.1.53. 1-(3-(5-Benzhydryl-1H-tetrazol-1-yl)propyl)-4-(3,4-
dichlorophenyl)piperazine (9w)
5.1.58. 1-(4-(5-Benzhydryl-1H-tetrazol-1-yl)butyl)-4-(2,3-
dichlorophenyl)piperazine (10e)
The procedure described for the preparation of 8a was used
with compound 5 (300 mg, 0.91 mmol), 7e (363.9 mg, 1.36 mmol),
K2CO3 (251.5 mg, 1.82 mmol), NaI (catalyst) and CH3CN (15 mL) to
The procedure described for the preparation of 8a was used
with compound 4 (320 mg, 1.02 mmol), 7w (409.4 mg, 1.53 mmol),
K2CO3 (282 mg, 2.04 mmol), NaI (catalyst) and CH3CN (15 mL) to
obtain 9w as a white solid (290 mg, 56%). Rf = 0.64 (n-hexane/
EtOAc/MeOH = 2.5:1.5:1). Mp = 103–105 °C. 1H NMR (500 MHz,
CDCl3): d 7.36–7.22 (m, 12H), 6.92 (d, J = 3 Hz, 1H), 6.70 (dd,
J = 9, 3, 1H) 5.81 (s, 1H), 4.70 (t, J = 7 Hz, 2H), 3.08–3.06 (m, 4H),
2.51 (t, J = 5 Hz, 4H), 2.45–2.42 (m, 2H), 2.23–2.18 (m, 2H); 13C
NMR (125 MHz, CDCl3): d 168.8, 150.6.0, 140.7, 132.7, 130.4,
128.7, 128.6, 127.0, 122.1, 117.2, 115.2, 54.8, 51.3, 48.7, 48.5, 26.5.
obtain 10e as
a light brown liquid (204 mg, 43%). Rf = 0.46
(n-hexane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d
7.35–7.19 (m, 12H), 6.84–6.81 (m, 2H), 5.82 (s, 1H), 4.65 (t,
J = 7 Hz, 2H), 3.12 (t, J = 5 Hz, 4H), 2.53–2.51 (m, 4H), 2.42–2.39
(m, 2H), 2.10–2.04 (m, 2H), 1.58–1.52 (m, 2H); 13C NMR
(125 MHz, CDCl3): d 167.8, 149.9, 140.8, 128.9, 128.7, 128.6, 127,
124.5, 117.2, 57.4, 53, 52.9, 49.1, 48.6, 27.2, 23.5.
5.1.54. 1-(4-(5-Benzhydryl-1H-tetrazol-1-yl)butyl)-4-(pyridin-2-
yl)piperazine (10a)
6. Neurotransmitter uptake assay
The procedure described for the preparation of 8a was used
with compound 5 (300 mg, 0.91 mmol), 7a (0.20 mL, 1.36 mmol),
K2CO3 (251.5 mg, 1.82 mmol), NaI (catalyst) and CH3CN (15 mL)
to obtain 10a as a light brown liquid (110 mg, 50%). Rf = 0.37 (n-
hexane/EtOAc/MeOH = 2.5:1.5:1). 1H NMR (500 MHz, CDCl3): d
8.24–8.19 (m, 1H), 7.49–7.46 (m, 1H), 7.36–7.23 (m, 10H), 6.65–
6.62 (m, 2H), 5.83 (s, 1H), 4.64 (t, J = 7 Hz, 2H), 3.52 (t, J = 5 Hz,
4H), 2.50–2.48 (m, 4H), 2.41–2.04 (m, 2H), 2.10–2.04 (m, 2H),
1.58–1.52 (m, 2H); 13C NMR (125 MHz, CDCl3): d 167.8, 159.5,
148, 140.8, 137.4, 128.7, 128.6, 127, 113.3, 107, 57.6, 53, 52.9,
48.6, 45.2, 27.3, 23.5.
The assay was performed following the method described in the
literature with slight modification.19 HEK-293 cells were cultured
in
a medium supplemented with fetal bovine serum and
transfected with hSERT, hNET and hDAT. Radiolabeled [3H]-5-HT
(PerkinElmer, Waltham, MA, USA), [3H]-5-NE (PerkinElmer,
Waltham, MA, USA) and [3H]-DA (PerkinElmer) were used at a con-
centration of 20 nM in the assay. Radioactivity was measured using
a Wallac 1450 MicroBetaÒ TriLux liquid scintillation counter
(PerkinElmer). Bupropion and venlafaxine hydrochloride were
used as standard neurotransmitter reuptake inhibitors.
Please cite this article in press as: Paudel, S.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.09.005

10
S. Paudel et al. / Bioorg. Med. Chem. xxx (2016) xxx–xxx
6. Schmeichel, B. E.; Zemlan, F. P.; Berridge, C. W. Neuropharmacology 2013, 64,
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This research was supported by Basic Science Research Program
through the National Research Foundation of Korea (NRF) funded
by the Ministry of Education (grant No. 2012R1A1A2006613) and
K.M. Kim was funded by KRF-2014R1A2A2A01002547. The authors
would like to thank the Korea Basic Science Institute Gwangju cen-
ter for performing the 1H NMR and 13C NMR.
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A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2016.09.005.
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Please cite this article in press as: Paudel, S.; et al. Bioorg. Med. Chem. (2016), http://dx.doi.org/10.1016/j.bmc.2016.09.005