Synthesis and receptor binding studies of novel 4,4-disubstituted arylalkyl/arylalkylsulfonyl piperazine and piperidine-based derivatives as a new class of σ1 ligands

Article abstract of DOI:10.1016/j.ejmech.2013.04.013

This study presents the synthesis and biological evaluation of a new series of arylalkyl/arylalkylsulfonyl piperazine and piperidine-based derivatives as sigma receptor ligands. It was found that a number of halogen substituted sulfonamides display relatively high and low affinities to σ₁ and σ₂ receptors, respectively. The σ₁ affinities and subtype selectivities of four piperidine derivatives were also found to be generally comparable to those of piperazine analogues. Compared to σ₁-Rs compounds with n = 0 and 2, those with n = 1 proved to have optimal length of carbon chain by exhibiting higher affinities. Within this series, the 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine sigma ligand was identified with 96-fold σ₁/σ₂ selectivity ratio (K_iσ₁ = 0.96 ± 0.05 nM and K _iσ₂ = 91.8 ± 8.1 nM).

Full text of DOI:10.1016/j.ejmech.2013.04.013

European Journal of Medicinal Chemistry 64 (2013) 488e497
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and receptor binding studies of novel 4,4-disubstituted
arylalkyl/arylalkylsulfonyl piperazine and piperidine-based
derivatives as a new class of s1 ligands
,
b
,
a
b
a
Masoud Sadeghzadeh a , Shahab Sheibani , Mehdi Ghandi , Fariba Johari Daha ,
*
Massoud Amanlou c, Mohammad Arjmand d, Abolfazl Hasani Bozcheloie b
a Radioisotope Research Group, Nuclear Science Research School, NSTRI, Tehran, Iran
b School of Chemistry, College of Science, University of Tehran, P.O. Box 14155 6455, Tehran, Iran
c Department of Medicinal Chemistry, Tehran University of Medical Sciences, Tehran, Iran
d Department of Biochemistry, Pasteur Institute of Iran, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
This study presents the synthesis and biological evaluation of a new series of arylalkyl/arylalkylsulfonyl
piperazine and piperidine-based derivatives as sigma receptor ligands. It was found that a number of
halogen substituted sulfonamides display relatively high and low affinities to s1 and s2 receptors,
respectively. The s1 affinities and subtype selectivities of four piperidine derivatives were also found to
be generally comparable to those of piperazine analogues. Compared to s1-Rs compounds with n ¼ 0 and
2, those with n ¼ 1 proved to have optimal length of carbon chain by exhibiting higher affinities.
Within this series, the 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine sigma ligand was identified with
Received 9 January 2013
Received in revised form
2 April 2013
Accepted 3 April 2013
Available online 12 April 2013
Keywords:
96-fold s1
/
s2 selectivity ratio (Kis1 ¼ 0.96 ꢀ 0.05 nM and Kis2 ¼ 91.8 ꢀ 8.1 nM).
Halogenated sulfonamides
Sigma receptor ligand
N-arylalkylsulfonyl piperazine
N-arylalkylsulfonyl piperidine
s1 Ligands
Ó 2013 Elsevier Masson SAS. All rights reserved.
1. Introduction
With the exception of 30% homology to the yeast enzyme sterol-
/D
D8 7 isomerase, there are no analogies between s1 receptors with
More than three decades ago, Martin and co-workers intro-
duced sigma receptors ( -Rs) as a novel subtype of opioid receptors
[1]. Nowadays, it is known that -Rs as a unique binding site with
other mammalian proteins [7,8]. High expressed s1-Rs in steroid-
producing tissues and in CNS suggest their possible roles in
neuroendocrine, central neuroactive steroid functions, involve-
ment in psychosis with modulation of synthesis and release of
neurotransmitters such as acetylcholine [13] and dopamine [14e
16], in modulation of the glutamatergic system with a neuro-
protective effect and improvement in learning and memory in
animal models of amnesia [17]. Whereas s1-Rs also plays a key role
in modulation of Ca2þ flux [18,19], both subtype receptors are
widely over-expressed in many tumor cell lines. Therefore, utili-
zation of radiolabeled sigma receptor ligands for imaging tech-
niques such as PET and SPECT for cancer diagnostic and therapeutic
applications is allowed [20e22].
s
s
distinct s1 and s2 subtypes [2,3], are widely distributed in the
central nervous system (CNS) and peripheral organs and tissues
[3e5]. Whereas the s1 subtype has recently been cloned from
numerous sources including human placental choriocarcinoma cell
lines [6e9], the elucidation of s2 receptor structure and function
has proven more difficult [2,3]. Identification of the s2 binding site
as a progesterone receptor membrane component 1 (PGRMC1) [10]
and induction of apoptotic death by putative s2 agonists by a new
mechanism involving the increase of intracellular Ca2þ level
released from endoplasmic reticulum and mitochondrial stores are
current progress in this area [11,12].
A
wide variety of unrelated chemical scaffolds such as
(þ)-pentazocine, haloperidol, N,N-di-(o-tolyl)guanidine (DTG),
alkaloid ibogaine, and 3,4-dichloro phenylmorphan derivatives
(CB64D and CB184) are known to interact selectively with s1 and s2
receptors (Fig. 1) [2,23,24]. Whereas (diphenylalkyl)piperidines,
(diphenylalkyl)piperazines and especially benzylpiperidine and
* Corresponding author. School of Chemistry, College of Science, University of
Tehran, P.O. Box 14155 6455, Tehran, Iran. Tel.: þ98 21 61112250; fax: þ98 21
66495291.
E-mail address: m.sadeghzadeh@ut.ac.ir (M. Sadeghzadeh).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.04.013

M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
489
selected as the representative models in order to design and
develop new s1 ligands [25e31].
OH
N
H3C
To achieve this goal, we decided to initially replace the directly
connected methylene group to piperazine or piperidine ring ni-
trogens by sulfonyl groups, or elongate the methylene linker (n)
thereby extending the distance between the central piperazine and
the phenyl ring and finally replace the various substituents on both
piperazine derivative phenyl rings. As such, it seemed promising if
the modified compounds could be fitted quite well into the Glen-
non’s suggested pharmacophore models [39,40]. The specificity of
this pharmacological profile prompted the evaluation of these
OCH3
N
R
R
N
H
O
Ibogaine
CB-64D, R= H
CB184, R= Cl
modifications on
s-Rs binding affinities. Herein, we report the
N
synthesis and biological evaluation of a series of 1-benzyl-4-(aryl-
sulfonyl)piperazines or piperidines, 1-benzyl-4-(arylalkylsulfonyl)
piperazines or piperidines and (E)-1-benzyl-4-(4-substituted styr-
ylsulfonyl) piperazines or piperidines as some analogues of com-
pounds _e_V (Fig. 2).
NH
N
H
N
H
HO
CH3
OH
CH3
(+)-Pentazocine
DTG
2. Results and discussion
2.1. Chemistry
O
Cl
N
Both arylalkylsulfonyl chlorides 3aef and 1-(3-substituted
benzyl)piperazines 4aeg as starting materials of compounds 5e
21, analogues of compound III, were prepared on the basis of the
previously reported methods (Scheme 1) [41e44]. Therefore, so-
dium arylalkylsulfonates were initially prepared by treatment of
the appropriate 3-substituted phenylalkyl chlorides or bromides
with Na2SO3 in 10% NaOH aqueous solution. In the case of 3-
iodobenzyl bromide, a mixture of water/acetone (2:1) was used
as solvent. The sodium arylalkylsulfonates thus obtained were then
treated with thionyl chloride in DMF to afford the arylalkylsulfonyl
chlorides 3aef. The 1-(3-substituted benzyl)piperazines 4aeg were
also prepared by reaction of N-Boc-piperazine with appropriate
substituted benzyl chlorides or benzyl bromides in two steps
(Scheme 1).
Compounds 22e27 containing SO2 functional group as the an-
alogues of compounds I and II were then prepared in moderate to
excellent yields by treatment of 4-benzylpiperidine (16) and 1-
benzylpiperazine (4a) with 2-phenylethanesulfonyl chloride (3f)
and arylsulfonyl chlorides 3geh (Scheme 2). Finally, we synthe-
sized compounds 30e33 as four analogues of _V by treatment of
arylethenesulfonyl chlorides 29aeb [45] with 16 and 4a in good
yields (Scheme 3). The structure of the synthesized compounds was
deduced from their analytical data.
F
Haloperidol
Fig. 1. Some of the putative sigma receptor ligands.
benzylpiperazine derivatives exhibit remarkable affinities to s1 and
s2 receptors, they exhibit strong selectivities to -Rs against
s
dopamine D-2 and serotonin 5-HT1A receptors (Fig. 2) [25e31].
Sulfonamides as an important class of pharmaceutical com-
pounds exhibit a broad spectrum of biological activities [32e35].
These compounds provide a key polar alternative to the frequently
used amides as a bioisosteric replacement [32]. More recently,
sulfonamides have been found to be potent cysteine protease in-
hibitors, with possible extension of their therapeutic applications
to Alzheimer’s disease, arthritis and cancer [36].
Our initial literature survey revealed that only a few reports
exist about selective sigma ligands containing sulfonamide func-
tional groups [37,38]. The present study aimed to synthesize a wide
range of suitable sulfonamide derivatives in order to explore their
s
-Rs bindings. The previously reported ([diphenylalkyl]piperidines
and [diphenylalkyl]piperazines) sigma receptor ligands were
N
X
N
N
I, Kiσ1= 5.81 nM
II, C=CH: Kiσ1= 0.4 nM, Kiσ2 = 3.3 nM
X=N: Kiσ1 = 20 nM
Kiσ
2 = 1274 nM
Cl
N
N
N
N
HO
IV
III, Kiσ1=38 nM
Kiσ2 = 177 nM
Kiσ = 0.3 nM
Fig. 2. Structure of some analogues of the synthesized compounds with good affinity for
s receptors.

490
M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
R2
R1
R3
n
X
X
O
X=Cl, Br
R1 n=1: 1a-e
n=2, R1=H: 1f
(c)
(d)
(a)
(b)
2a-g
X=Cl, Br
S
R1= H, Cl, Br, I, Me
R2= H, F,Cl, I, Me
R3= Br, OMe
O
N
N
R2
O
R3
n
S
HN
(e)
+
Cl
O
R2
R3
N
n=1: 3a-e
n=2, R1=H: 3f
R1
4a-g
5-15
Reagents and reaction conditions:
(a) Na2SO3, NaOH 10%, reflux, 4h; (b) SOCl2, DMF, r.t, 3h; (c) tert-butyl piperazine-1-
carboxylate, CH2Cl2, Et3N, r.t, overnight; (d) TFA, toluene, r.t, 80 min; (e) Et3N, CH2Cl2, r.t, 2 h.
Scheme 1. Synthesis of compounds 5e15 from 3aee and 4aeg.
2.2. Receptor binding studies
compounds 24 and 25 were synthesized and pharmacological
profiles were evaluated. Interestingly, replacement of the para-H
substituent of N-benzenesulfonyl residue with Cl atom revealed
similar binding affinity patterns.
Competitive inhibition experiments were carried out to mea-
sure the s1 and s2 binding affinities (Ki) of newly synthesized
compounds using the well-established assay conditions [46,47].
The s1 binding sites were assayed with the s1 selective radioligand,
[3H](þ)-pentazocine using the guinea pig brain homogenates. On
the other hand, the s2 binding sites were assayed on rat liver ho-
mogenates in the presence of an excess of the (þ)-pentazocine as a
sigma-1 receptor blocker using non-selective [3H]di-o-tolylguani-
dine radioligand ([3H]-DTG). Nonspecific binding was determined
In the next step, we focused on the synthesis of some derivatives
of 1-benzyl-4-(phenylmethanesulfonyl)piperazine or 1-(phenyl-
methanesulfonyl)-4-(3-substituted benzyl)piperazine derivatives
5e15 and those of 4-benzyl-1-(phenylmethanesulfonyl)piperidines
17e21 containing longer spaced chain length (Table 1). Signifi-
cantly, 4-benzyl-1-(arylmethanesulfonyl)piperidines displayed
high s1 binding affinities (Ki) varying from 0.96 to 40.0 nM, with the
most and the least potent for the 3-iodo compound 20 and the 3-
chloro compound 18, respectively. A wider range of affinities was
also observed in 1-benzyl-4-(arylmethanesulfonyl)piperazine se-
ries, ranging from 1.8 to 68.7 nM. In the case of 4-methoxy
substituted 15, the rather lower binding affinities of 192 and
2128 nM for s1- and s2-Rs were obtained, respectively. Compared
to the para-bromosubstituted 14 containing a weaker electron-
donating group, lower sigma-1 and sigma-2 affinities were
observed for compound 15 containing the stronger electron-
donating methoxy group at the para-position. Notably, higher s1
binding affinities observed within the substituted piperazines
having direct connection between nitrogen atom and benzylic
moiety is consistent with Glennon’s suggested pharmacophore
models [39,40].
In order to assess the sigma affinities in those analogues con-
taining longer carbon chain lengths, compounds 26, 27 and 30e33
were synthesized. Inspection of the results revealed that either
enlargement of the linker length or replacement of the eCH2CH2e
spacer with eCH]CHe moiety reduces the ligand affinities by 6e
20 fold in both receptor subtypes in comparison to those of the
corresponding N-phenylmethanesulfonyl derivatives 5 and 17.
Within the piperazine derivatives, the lead compound 5 and
those containing methyl or iodo-substituents (8, 9 and 12) exclu-
sively displayed moderate sigma-2 affinities. Moreover, all piperi-
dine derivatives excluding the 3-chloro analogue, showed
moderate to good s2 binding affinities. With the exception of
compounds 12 and 20, none of these compounds exhibited high
selectivities for sigma-1 receptor. Such results lead to rather high
selectivity ratios of 65.0 and 95.5 for 12 and 20, respectively. In
contrast to highly selective 12 and 20 which contain iodine-
in the presence of haloperidol (10 mM). Recall that ten concentra-
tions of each sigma compound (0.1e10,000 nM) were used in the
assays. Haloperidol, DTG and (þ)-pentazocine as reference com-
pounds were also evaluated and gave Ki values near those reported
previously (Table 2) [2,23,24]. The chemical structures, sigma
binding affinities and selectivity ratios of the new compounds are
summarized in Tables 1 and 2.
In general, all the parent compounds (Table 2) with different
spacer length (n ¼ 0e2) exhibit moderate to good affinities ranging
from 9.9 to 78.4 nM and 38.9e191.0 nM for s1 and s2 subtypes,
respectively. Compared to the corresponding piperazine analogues,
piperidine derivatives showed higher affinities in agreement to that
reported previously [48,49]. Comparison of 23 (Kis1 ¼ 28.4 nM and
K
is2 ¼ 87.1 nM) with _ (Kis1 ¼ 5.8 nM and Kis2 ¼ 1274.0 nM) reveals
that replacement of methylene with sulfonyl group demonstrated
5-fold lower affinity at sigma-1 sites and 15-fold greater affinity at
sigma-2 (Table 1 and Fig. 2). To explore the effect of a halogenated
phenyl group on sigma-1 and sigma-2 binding affinities,
SO2Cl
n
O
Et3N, CH2Cl2
n
S
r.t, 2 h
N
O
X
R2
R1
R1
R2
17-27
X
NH
X= CH, N; n=0-2
R1= H, Cl, Br, I, Me
R2= H, Cl
n=0: 3g-h
n=1: 3a-e
n=2: 3f
16: (X=CH), 4a
substituted phenyl rings, observation of s1/s2 selectivity ratios of
Scheme 2. Synthesis of compounds 17e27 from 3aeh and 16, 4a.

M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
491
O
Cl
O
S
R
S
(b)
(a)
X
N
O
O
R
R
X
R=H, Br
NH
16: (X=CH), 4a
X= CH, N
28a-b
29a-b
30-33
Reagents and reaction conditions: (a) DMF, SO2Cl2, 5 °C-r.t, 30 min and then 90 °C , 4h; (b) Et3N, CH2Cl2, r.t, 5h.
Scheme 3. Synthesis of compounds 30e33 from 29aeb and 16, 4a.
ꢀ
ꢀ
21.5 and 16.2 for compounds 14 and 19 bearing bromo-substituent
seems interesting.
basic N-atom (4.084 A in compound 23 versus 3.772 A in compound
_). A similar relationship between the s1 affinity and structure of
the N-residues was observed in the piperazine derivatives 5e15,
although the level of s1 affinity was considerably higher. In
particular, compounds bearing iodo-substituent (8 and 12) repre-
sent very potent s1 receptor ligands interacting in the low nano-
molar range. Overall, compounds containing piperidine ring with a
Overall, the increasing sigma-1 affinity trend n ¼ 1 > 0 > 2 of
these compounds correlates nicely with the distance present be-
tween the basic amino moiety and the phenyl-A ring as is proposed
in Glennon’s pharmacophore model [39,40]. This rationalization
could be obtained by the values determined using standard MM2
energy minimization calculations and different binding modes of
linear piperazine and piperidine derivatives suggested by Ablor-
deppey et al. [48] (Fig. 3). Compared to compound _, the lower
sigma-1 affinities of compounds 22e25 may be explained by the
larger distance present between the phenyl-A ring center and the
ꢀ
shorter distance ranging from 3.984 to 4.407 A show a higher s1
affinity. On the other hand, compound 17 with a shorter distance
exhibited more s1 receptor affinity than that of compound 5.
Finally, compounds 26, 27 and 30e33 seem not to be fitted exactly
within this model because of an enormous distance present be-
tween hydrophobic regions and basic N-atom (Fig. 3).
Table 1
3. Conclusion
Binding affinities of the prepared compounds towards s1 and s2 receptors.
In conclusion, an expedient, mild and efficient method for the
synthesis of novel 4,4-disubstituted arylalkyl/arylalkylsulfonyl
piperazine and piperidine-based derivatives was described in this
presentation. Evaluation of these ligands as s1 and s2 receptors by
means of radioligand binding assays revealed that compounds
containing iodo-substituent (8, 12 and 20) demonstrated greater
Table 2
Comparison of binding affinities of lead compounds as well as compounds 30e33 for
s1 and receptors.
Compd R1 R2 R3 R4
X
n
K
is1 (nM)a
K
is2 (nM)b
Selectivity
s1 s2
(
/
)
5
6
7
8
H
Cl
Br
I
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
CI
CI
H
H
H
H
H
H
H
F
H
H
H
H
H
H
H
H
N
N
N
N
N
N
N
N
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
2
2
11.2 ꢀ 1.4c
68.1 ꢀ 2.4
29.9 ꢀ 1.0
2.7 ꢀ 0.6
48.4 ꢀ 4.7
134 ꢀ 8.7
148 ꢀ 11
4.3
2.0
4.9
88.8 ꢀ 1.9 32.9
9
Me
H
H
H
H
H
H
H
CI
Br
I
Me
H
H
H
H
H
H
35.9 ꢀ 2.6
68.7 ꢀ 8.4
51.8 ꢀ 5.7
1.8 ꢀ 0.3
89.4 ꢀ 3.4
181 ꢀ 12
174 ꢀ 19
117 ꢀ 10
151 ꢀ 14
288 ꢀ 17
2.5
2.6
3.4
10
11
12
13
14
15
17
18
19
20
21
22
23
24
25
26
27
Cl
I
65
10.1
21.5
Me
H
H
e
e
e
e
e
e
e
e
e
e
e
H
N
N
N
15.0 ꢀ 1.2
13.4 ꢀ 1.8
192 ꢀ 21
9.9 ꢀ 1.6
Compd
Y
X
K
is1 (nM)a
K
is2 (nM)b
Br
OMe
e
e
e
e
e
e
e
e
e
e
e
2128 ꢀ 205 11.1
22
23
17
5
26
27
30
31
Ph
Ph
PhCH2
PhCH2
Ph(CH2)2
Ph(CH2)2
PhCH]CH
PhCH]CH
4-BrPhCH]CH
4-BrPhCH]CH
CH
N
CH
N
CH
N
CH
N
24.3 ꢀ 1.6c
28.4 ꢀ 2.3
9.9 ꢀ 1.6
11.2 ꢀ 1.4
59.9 ꢀ 3.6
78.4 ꢀ 4.1
138 ꢀ 12
201 ꢀ 18
843 ꢀ 48
1075 ꢀ 62
2.8 ꢀ 0.4
4.6 ꢀ 0.9
38.4 ꢀ 2.0
56.7 ꢀ 4.9
87.1 ꢀ 9.6
38.9 ꢀ 3.8
48.4 ꢀ 4.7
187 ꢀ 13
CH
CH
CH
CH
CH
CH
N
CH
N
CH
N
38.9 ꢀ 3.8
199 ꢀ 14
3.9
5.0
40.0 ꢀ 0.9
1.6 ꢀ 0.08 25.9 ꢀ 1.8 16.2
0.96 ꢀ 0.05 91.8 ꢀ 8.1 95.6
4.7 ꢀ 0.09 48.9 ꢀ 2.0 10.4
191 ꢀ 15
24.3 ꢀ 1.6
28.4 ꢀ 2.3
551 ꢀ 31
969 ꢀ 67
59.9 ꢀ 3.6
78.4 ꢀ 4.1
56.7 ꢀ 4.9
87.1 ꢀ 9.6
778 ꢀ 52
1547 ꢀ 107
187 ꢀ 13
191 ꢀ 15
2.3
3.1
1.4
1.6
3.1
2.4
1965 ꢀ 37
8136 ꢀ 164
248 ꢀ 23
32
33
CH
N
485 ꢀ 38
Haloperidol
(þ)-Pentazocine
DTG
43.5 ꢀ 1.3
1871 ꢀ 164
58.4 ꢀ 3.2
Nonspecific binding was determined in the presence of 10
m
M haloperidol.
a
s1 Affinities were determined in rat liver homogenates using [3H](þ)-
Nonspecific binding was determined in the presence of 10 mM haloperidol.
a
pentazocine.
Displacement of 3 nM [3H](þ)-pentazocine.
b
b
s2 Affinities were determined in guinea pig brain using [3H]-DTG in the pres-
Displacement of 2 nM [3H]-DTG in the presence of (þ)-pentazocine to block s1
ence of (þ)-pentazocine to block s1 receptors.
receptors.
c
c
The values are means ꢀ SEM of three experiments performed in duplicate.
Values are means ꢀ SEM of three experiments performed in duplicate.

492
M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
O
X
S
O
N
N
O
S
X
O
6.418 Å in 17
6.252 Å in 5
3.984 Å in 17
4.030 Å in 5
6.365 Å in 22
6.268 Å in 23
4.077 Å in 22
4.084 Å in 23
X
O
S
X
N
O
N
S
O
O
6.484 Å in 30
6.215 Å in 31
6.080 Å in 30 and 31
6.399 Å in 26
6.306 Å in 27
4.407 Å in 26
4.455 Å in 27
Fig. 3. Comparison of the calculated distances between two aromatic rings and basic amino moiety of N-arylalkylsulfonyl derivatives.
sigma-1 affinities (Ki ¼ 2.7 nM, Ki ¼ 1.8 nM and Ki ¼ 0.96 nM) and
good s1 s2 selectivity ratios (33e96-fold). The s1 affinities and
purified by recrystallization from CH3OH (95%). These in-
termediates (4.81 mmol) were then treated with thionyl chloride
(11.8 mmol) in DMF (5 mL) for 3 h at room temperature. The residue
was subsequently poured into the ice-water mixture (20 g) and the
solid was then extracted with diethyl ether (3 ꢂ 20 mL). After
removing the solvent under reduced pressure, compounds 3aee
were obtained in 63e82% yields. Compound 3f was also prepared
in 78% yield using the previously reported methods [43].
/
subtype selectivities of piperidines 17e21 are generally comparable
to those of the piperazine analogues. Generally, s1 receptor affin-
ities of disubstituted arylalkyl/arylalkylsulfonyl piperazine and
piperidine-based derivatives increase in the order of n ¼ 1 > 0 > 2.
This trend correlates nicely with the distance present between the
basic amino moiety and the phenyl-A ring proposed in Glennon’s
pharmacophore model. Compared to the N-arylmethanesulfonyl
derivatives 5e21, the N-arylsulfonyl and N-arylethanesulfonyl an-
alogues 22e27 are considerably less active to sigma-1 receptors.
These halogen substituted sulfonamides are anticipated to be
useful targets as tumor imaging agents. Further studies on these
newly found halogenated sulfonamides are currently under
investigation in our laboratory.
4.1.2. General procedure for the synthesis of 1-(3-substituted
benzyl)piperazines 4aeg
These compounds were prepared by means of the previously
reported methods [44]. To a solution of tert-butyl piperazine-1-
carboxylate (0.559 g, 3.0 mmol) and triethylamine (0.63 mL,
3.3 mmol) in CH2Cl2 (15 mL) appropriate substituted benzyl chlo-
rides or benzyl bromides 2aeg (3.6 mmol) were added. After stir-
ring the mixture at room temperature overnight, it was then
diluted with H2O and the organics extracted with CH2Cl2
(2 ꢂ 20 mL), dried over MgSO4, and concentrated under reduced
pressure. Purification of the crude material by flash column chro-
matography (SiO2, PE/AcOEt, 60/40) gave the corresponding in-
termediates. These intermediates (2.49 mmol) were then treated
with TFA (5.75 mL, 76.8 mmol) in toluene (15 mL) and stirred for
80 min at room temperature. After the removal of the solvent under
reduced pressure, the residue was diluted with aqueous NaOH (1N)
and the organics extracted with CH2Cl2 (2 ꢂ 20 mL), dried over
MgSO4, and concentrated under reduced pressure to give the
desired compounds 4aeg (72e89%).
4. Experimental
4.1. Chemistry
All commercially available chemicals and reagents were used
without further purification. Melting points were determined with
an Electrothermal model 9100 apparatus and are uncorrected. IR
spectra were recorded on a Shimadzu 4300 spectrophotometer, in
cmꢁ1. 1H and 13C NMR spectra were recorded on a Bruker DRX-500-
AVANCE spectrometer at 500 (1H) and 125 MHz (13C) using CDCl3 as
solvent and with the residual solvent signal as an internal reference
(CDCl3, 7.24 and 77.0 ppm). Mass spectra of the products were
obtained with an HP (Agilent technologies) 5937 Mass Selective
Detector. Elemental analyses were carried out by a CHN-Rapid
Heraeus elemental analyzer (Wellesley, MA).
4.1.3. General procedure for the preparation of 1-benzyl-4-(3-
substituted benzylsulfonyl)piperazines 5e9 and 1-(benzylsulfonyl)-
4-(3-substituted benzyl)piperazines 10e15
4.1.1. General procedure for the synthesis of arylmethanesulfonyl
chlorides 3aee
The method adopted for the synthesis of 1-benzyl-4-(benzyl-
sulfonyl)piperazine (5) is described. To a solution of phenyl-
methanesulfonyl chloride (3a) (1.0 mmol) in dry CH2Cl2 (5 mL) was
added 4-benzylpiperazine (4a) (1.0 mmol, 0.179 mL) followed by
triethylamine (1.0 mmol, 0.14 mL) and the mixture was stirred for
2 h at room temperature. It was then diluted with CH2Cl2, washed
with H2O and then with saturated NaHCO3. The organic phase was
separated and dried over anhydrous Na2SO4. The solvent was then
removed under reduced pressure and the residue was purified
using chromatography on silica gel (a short column). Elution with
Arylmethanesulfonyl chlorides 3aee were prepared using the
previously reported procedure [41,42]. Appropriate 3-substituted
benzyl chlorides (or benzyl bromides) (1aee, 50 mmol) were
added dropwise to a solution of sodium sulfite (50 mmol) in
aqueous NaOH (10%, 25 mL) and the reaction mixture was heated at
reflux for 4 h (in the case of 3-iodobenzyl bromide, a 2:1 water/
acetone mixture was used as solvent). After cooling the solution in
an ice bath, the corresponding sodium arylmethanesulfonates were

M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
493
40:60 ethyl acetate in hexane furnished 304 mg (92%) of compound
d
(ppm) ¼ 7.43e7.41 (m, 5H, Ar), 7.31e7.28 (m, 1H, Ar), 7.06 (bs, 2H,
5 as a white crystal. m.p. 142e144 ꢃC; IR (nmax/cmꢁ1) ¼ 2905 (CeH),
Ar), 6.98 (t, J ¼ 8.2 Hz, 1H, Ar), 4.24 (s, 2H, PhCH2SO2e), 3.51 (s, 2H,
1340 (SO2), 1153 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.44e7.39 (m,
ArCH2Ne), 3.20 (bs, 4H, e(CH2)2NeSO2Bn), 2.44 (bs, 4H, e(CH2)2Ne
6H, Ar), 7.36e7.28 (m, 4H, Ar), 4.23 (s, 2H, ArCH2SO2e), 3.53 (s, 2H,
PhCH2Ne), 3.19 (t, J ¼ 4.6 Hz, 4H, e(CH2)2NeSO2Bn), 2.45 (t,
CH2Ar); 13C NMR (CDCl3):
d
(ppm) ¼ 131.2, 130.2, 130.1, 129.2, 129.1,
124.9, 116.1, 115.9, 114.7, 114.5, 62.5, 57.2, 53.2, 46.4; Anal. calcd. for
J ¼ 4.6 Hz, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
d
(ppm) ¼ 130.2,
C18H21FN2O2S: C 62.05 H 6.07 N 8.04 found C 62.36 H 6.28 N 8.01;
129.6, 129.2, 129.1, 128.8, 127.8, 63.1, 57.2, 53.1, 46.4; Anal. calcd. for
MS (EI, 70 eV) m/z ¼ 349 [Mþ þ 1], 348 [Mþ], 193 [Mþ ꢁ SO2Bn,
C
18H22N2O2S: C 65.42 H 6.71 N 8.48 found C 65.58 H 6.68 N 8.52;
100], 109 [FPhCHþ2 ], 91 [PhCH2þ].
MS (EI, 70 eV) m/z ¼ 330 [Mþ], 175 [Mþ ꢁ SO2CH2Ph, 100], 91
[PhCHþ2 ].
4.1.9. 1-(Benzylsulfonyl)-4-(3-chlorobenzyl)piperazine 11
This compound was prepared from 3a and 4c as described for 5.
4.1.4. 1-Benzyl-4-(3-chlorobenzylsulfonyl)piperazine 6
White crystal, yield 310 mg (85%). m.p. 147e149 ꢃC; IR (nmax
/
This compound was prepared from 3b and 4a as described for 5.
cmꢁ1) ¼ 2915 (CeH), 1343 (SO2), 1156 (SO2); 1H NMR (CDCl3):
White crystal, yield 262 mg (72%). m.p. 124e126 ꢃC; IR (nmax
/
d
(ppm) ¼ 7.43 (m, 5H, Ar), 7.33 (s, 1H, Ar), 7.26 (s, 2H, Ar), 7.18 (s,
cmꢁ1) ¼ 2942 (CeH), 1324 (SO2), 1158 (SO2); 1H NMR (CDCl3):
1H, Ar), 4.24 (s, 2H, PhCH2SO2e), 3.49 (s, 2H, ArCH2Ne), 3.20 (bs,
d
(ppm) ¼ 7.44 (s, 1H, Ar), 7.39-7.30 (m, 8H, Ar), 4.17 (s, 2H,
4H, e(CH2)2NeSO2Bn), 2.43 (bs, 4H, e(CH2)2NeCH2Ar); 13C NMR
ArCH2SO2e), 3.54 (s, 2H, PhCH2Ne), 3.22 (s, 4H, e(CH2)2Ne
(CDCl3):
d
(ppm) ¼ 140.8, 134.7, 131.2, 130.1, 129.4, 129.2, 129.1,
SO2CH2Ar), 2.47 (s, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
127.9, 127.5, 125.9, 62.5, 57.2, 53.2, 46.4; Anal. calcd. for
d
(ppm) ¼ 137.8, 135.0, 131.2, 131.1, 130.4, 129.5, 129.4, 128.8, 127.8,
C18H21ClN2O2S: C 59.25 H 5.80 N 7.68 found C 60.03 H 6.02 N 7.73;
63.1, 56.4, 53.1, 46.5; Anal. calcd. for C18H21ClN2O2S: C 59.25 H 7.68
N 5.80 found C 60.03 H 7.73 N 6.02; MS (EI, 70 eV) m/z ¼ 366
[Mþ þ 2], 364 [Mþ], 175 [Mþ ꢁ SO2CH2Ar, 100], 91 [PhCHþ2 ].
MS (EI, 70 eV) m/z ¼ 366 [Mþ þ 2], 364 [Mþ], 209 [Mþ ꢁ SO2Bn],125
[ClPhCHþ2 ], 91 [PhCHþ2 , 100].
4.1.10. 1-(Benzylsulfonyl)-4-(3-methylbenzyl)piperazine 12
4.1.5. 1-Benzyl-4-(3-bromobenzylsulfonyl)piperazine 7
This compound was prepared from 3a and 4d as described for 5.
This compound was prepared from 3c and 4a as described for 5.
White crystal, yield 303 mg (88%). m.p. 121e123 ꢃC; IR (nmax
/
White crystal, yield 368 mg (90%). m.p. 128e130 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2911 (CeH), 1344 (SO2), 1156 (SO2); 1H NMR (CDCl3):
cmꢁ1) ¼ 2936 (CeH), 1324 (SO2), 1158 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.43e7.41 (m, 5H, Ar), 7.24 (t, J ¼ 7.3 Hz, 1H, Ar), 7.12 (bs,
d
(ppm) ¼ 7.59 (bs, 1H, Ar), 7.53 (dd, J ¼ 6.7, 1.6 Hz, 1H, Ar), 7.38e
3H, Ar), 4.23 (s, 2H, PhCH2SO2e), 3.50 (s, 2H, ArCH2Ne), 3.20 (bs,
4H, e(CH2)2NeSO2Bn), 2.44 (bs, 4H, e(CH2)2NeCH2Ar), 2.38 (s, 3H,
7.32 (m, 4H, Ar), 7.32e7.27 (m, 3H, Ar), 4.17 (s, 2H, ArCH2SO2e), 3.55
(s, 2H, PhCH2Ne), 3.22 (t, J ¼ 4.6 Hz, 4H, e(CH2)2NeSO2CH2Ar), 2.47
eCH3); 13C NMR (CDCl3):
129.0, 128.6, 128.5, 126.6, 63.2, 57.1, 53.2, 46.5, 21.8; Anal. calcd. for
d
(ppm) ¼ 138.4, 131.2, 130.3, 129.2, 129.1,
(t, J ¼ 4.6 Hz, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
(ppm) ¼ 134.1,
d
132.3, 131.5, 130.7, 129.8, 129.5, 128.8, 127.8, 123.1, 63.1, 56.4, 53.1,
46.5; Anal. calcd. for C18H21BrN2O2S: C 52.81 H 5.17 N 6.84 found C
53.01 H 5.21 N 6.88; MS (EI, 70 eV) m/z ¼ 409 [Mþ], 175
[Mþ ꢁ SO2CH2Ar, 100], 91 [PhCHþ2 ].
C19H24N2O2S: C 66.25 H 7.02 N 8.13 found C 66.62 H 7.17 N 8.13; MS
(EI, 70 eV) m/z ¼ 344 [Mþ], 189 [Mþ ꢁ SO2Bn, 100], 105 [MePhCHþ2 ],
91 [PhCHþ2 ].
4.1.11. 1-(Benzylsulfonyl)-4-(3-iodobenzyl)piperazine 13
4.1.6. 1-Benzyl-4-(3-iodobenzylsulfonyl)piperazine 8
This compound was prepared from 3a and 4e as described for 5.
This compound was prepared from 3d and 4a as described for 5.
White crystal, yield 410 mg (90%). m.p. 151e153 ꢃC; IR (nmax
/
White crystal, yield 319 mg (70%). m.p. 114e115 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2938 (CeH), 1343 (SO2), 1156 (SO2); 1H NMR (CDCl3):
cmꢁ1) ¼ 2916 (CeH), 1324 (SO2), 1158 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.69 (s, 1H, Ar), 7.62 (d, J ¼ 7.8 Hz, 1H, Ar), 7.43e7.41 (m,
d
(ppm) ¼ 7.77 (s, 1H, Ar), 7.73 (d, J ¼ 7.9 Hz, 1H, Ar), 7.41 (d,
5H, Ar), 7.24 (d, J ¼ 7.4 Hz, 1H, Ar), 7.08 (t, J ¼ 7.7 Hz, 1H, Ar), 4.24 (s,
2H, PhCH2SO2e), 3.45 (s, 2H, ArCH2Ne), 3.18 (s, 4H, e(CH2)2Ne
SO2Bn), 2.42 (s, 4H, e(CH2)2NeCH2Ar); 13C NMR (CDCl3):
J ¼ 7.6 Hz, 1H, Ar), 7.37e7.30 (m, 5H, Ar), 7.15 (t, J ¼ 7.9 Hz, 1H, Ar),
4.14 (s, 2H, ArCH2SO2e), 3.55 (s, 2H, PhCH2Ne), 3.22 (bs, 4H, e
(CH2)2NeSO2CH2Ar), 2.47 (bs, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
d
(ppm) ¼ 140.5, 138.3, 136.8, 131.2, 130.5, 129.2, 129.1, 128.7, 94.8,
d
(ppm) ¼ 140.0, 138.2, 131.5, 130.8, 130.4, 129.5, 128.8, 94.7, 63.1,
62.3, 57.2, 53.1, 46.4; Anal. calcd. for C18H21IN2O2S: C 47.38 H 4.64 N
6.14 found C 47.98 H 4.92 N 6.02; MS (EI, 70 eV) m/z ¼ 457 [Mþ þ 1],
456 [Mþ], 301 [Mþ ꢁ SO2Bn, 100], 217 [IPhCH2þ], 91 [PhCHþ2 ].
56.3, 53.1, 46.5; Anal. calcd. for C18H21IN2O2S: C 47.38 H 4.64 N 6.14
found C 48.03 H 4.97 N 5.98; MS (EI, 70 eV) m/z ¼ 456 [Mþ], 217
[IPhCHþ2 ], 175 [Mþ ꢁ SO2CH2Ar], 91 [PhCHþ2 , 100].
4.1.12. 1-(Benzylsulfonyl)-4-(4-bromobenzyl)piperazine 14
4.1.7. 1-Benzyl-4-(3-methylbenzylsulfonyl)piperazine 9
This compound was prepared from 3a and 4f as described for 5.
This compound was prepared from 3e and 4a as described for 5.
White crystal, yield 389 mg (95%). m.p. 180e183 ꢃC; IR (nmax
/
White crystal, yield 220 mg (64%). m.p. 90e91 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2932 (CeH), 1348 (SO2), 1159 (SO2); 1H NMR (CDCl3):
cmꢁ1) ¼ 2944 (CeH), 1322 (SO2), 1156 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.46 (d, J ¼ 8.2 Hz, 2H, Ar), 7.45e7.40 (m, 5H, Ar), 7.18 (d,
d
(ppm) ¼ 7.34e7.22 (m, 9H, Ar), 4.20 (s, 2H, ArCH2SO2e), 3.53 (s,
J ¼ 8.2 Hz, 2H, Ar), 4.24 (s, 2H, PhCH2SO2e), 3.46 (s, 2H, ArCH2Ne),
3.17 (bs, 4H, e(CH2)2NeSO2Bn), 2.42 (t, J ¼ 4.5 Hz, 4H, e(CH2)2Ne
2H, PhCH2Ne), 3.20 (bs, 4H, e(CH2)2NeSO2CH2Ar), 2.45 (bs, 4H, e
(CH2)2NeBn), 2.41 (s, 3H, eCH3); 13C NMR (CDCl3):
d
(ppm) ¼ 138.9,
CH2Ar); 13C NMR (CDCl3):
d
(ppm) ¼ 137.1, 131.9, 131.2, 131.1, 129.2,
131.9, 129.9, 129.5, 129.0, 128.8, 128.2, 127.7, 63.1, 57.0, 53.1, 46.5,
21.8; Anal. calcd. for C19H24N2O2S: C 66.25 H 7.02 N 8.13 found C
66.53 H 7.12 N 8.13; MS (EI, 70 eV) m/z ¼ 344 [Mþ], 175
[Mþ ꢁ SO2CH2Ar, 100], 105 [MePhCH2þ], 91 [PhCH2þ].
129.1, 121.5, 62.4, 57.2, 53.1, 46.4; Anal. calcd. for C18H21BrN2O2S: C
52.81 H 5.17 N 6.84 found C 53.01 H 5.24 N 6.91; MS (EI, 70 eV) m/
z ¼ 410 [Mþ], 255 [Mþ ꢁ SO2Bn, 100], 171 [BrPhCH2þ], 91 [PhCHþ2 ].
4.1.13. 1-(Benzylsulfonyl)-4-(4-methoxybenzyl)piperazine 15
This compound was prepared from 3a and 4g as described for 5.
4.1.8. 1-(Benzylsulfonyl)-4-(3-fluorobenzyl)piperazine 10
This compound was prepared from 3a and 4b as described for 5.
White crystal, yield 306 mg (85%). m.p. 132e134 ꢃC; IR (nmax
/
White crystal, yield 292 mg (84%). m.p. 138e139 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2953 (CeH), 1320 (SO2), 1245,1158 (SO2); 1H NMR (CDCl3):
cmꢁ1) ¼ 2937 (CeH), 1342 (SO2), 1153 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.44e7.40 (m, 5H, Ar), 7.21 (d, J ¼ 8.5 Hz, 2H, Ar), 6.88 (d,

494
M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
J ¼ 8.6 Hz, 2H, Ar), 4.23 (s, 2H, PhCH2SO2e), 3.83 (s, 3H, eOCH3),
3.46 (s, 2H, ArCH2Ne), 3.18 (t, J ¼ 4.5 Hz, 4H, e(CH2)2NeSO2Bn),
2.42 (t, J ¼ 4.6 Hz, 4H, e(CH2)2NeCH2Ar); 13C NMR (CDCl3):
PhCH2CHe), 1.66 (d, J ¼ 13.0 Hz, 2H, eCH2CHCH2e), 1.63e1.58 (m,
1H, eCH2CHCH2e), 1.30e1.19 (m, 2H, eCH2CHCH2e); 13C NMR
(CDCl3):
d
(ppm) ¼ 140.2, 139.9, 138.0, 131.8, 130.8, 130.3, 129.5,
d
(ppm) ¼ 159.3, 131.2, 130.7, 129.8, 129.3, 129.2, 129.1, 114.1, 62.5,
128.8, 126.6, 94.6, 56.7, 46.8, 43.2, 37.9, 32.3; Anal. calcd. for
57.1, 55.7, 53.1, 46.5; Anal. calcd. for C19H24N2O3S: C 63.31 H 6.71 N
7.77 found C 63.57 H 6.72 N 7.82; MS (EI, 70 eV) m/z ¼ 360 [Mþ], 205
[Mþ ꢁ SO2Bn], 121 [MeOPhCH2þ, 100], 91 [PhCHþ2 ].
C19H22INO2S: C 50.12 H 4.87 N 3.08 found C 50.89 H 5.09 N 3.06; MS
(EI, 70 eV) m/z ¼ 455 [Mþ], 390 [Mþ ꢁ SO2], 217 [IPhCHþ2 ], 174
[Mþ ꢁ SO2CH2Ar, 100], 91 [PhCHþ2 ].
4.1.14. 4-Benzyl-1-(benzylsulfonyl)piperidine 17
4.1.18. 4-Benzyl-1-(3-methylbenzylsulfonyl)piperidine 21
This compound was prepared from 3a and 16 as described for 5.
In the case of compounds 17e21 containing piperidine ring, the
reaction mixture was diluted with CH2Cl2, washed with H2O and
then with 2 N HCl. White crystal, yield 257 mg (78%). m.p. 132e
134 ꢃC; IR (nmax/cmꢁ1) ¼ 2927 (CeH), 1331 (SO2), 1147 (SO2); 1H
This compound was prepared from 3e and 16 as described for 17.
White crystal, yield 261 mg (76%). m.p. 98e100 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2927 (CeH), 1331 (SO2), 1147 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.33e7.27 (m, 3H, Ar), 7.25e7.20 (m, 4H, Ar), 7.14 (d,
J ¼ 7.1 Hz, 2H, Ar), 4.19 (s, 2H, ArCH2SO2e), 3.68 (d, J ¼ 12.4 Hz, 2H,
eCH2NCH2e), 2.58e2.54 (m, 4H, eCH2NCH2e and PhCH2CHe), 2.40
(s, 3H, eCH3), 1.64 (d, J ¼ 13.7 Hz, 2H, eCH2CHCH2e), 1.62e1.55 (m,
1H, eCH2CHCH2e), 1.26e1.22 (m, 2H, eCH2CHCH2e); 13C NMR
NMR (CDCl3):
d
(ppm) ¼ 7.42e7.39 (m, 5H, Ar), 7.32e7.31 (m, 2H,
Ar), 7.23 (t, J ¼ 7.3 Hz, 1H, Ar), 7.13 (d, J ¼ 7.2 Hz, 2H, Ar), 4.22 (s, 2H,
PhCH2SO2e), 3.66 (d, J ¼ 12.4 Hz, 2H, eCH2NCH2e), 2.56e2.51 (m,
4H, eCH2NCH2e and PhCH2CHe), 1.64 (d, J ¼ 13.6 Hz, 2H, e
CH2CHCH2e), 1.59e1.55 (m, 1H, eCH2CHCH2e), 1.27e1.20 (m, 2H, e
(CDCl3):
d
(ppm) ¼ 140.2, 139.9, 138.0, 131.8, 130.8, 130.3, 129.5,
128.8, 126.6, 94.6, 56.7, 46.8, 43.2, 37.9, 32.3; Anal. calcd. for
CH2CHCH2e); 13C NMR (CDCl3):
d
(ppm) ¼ 140.2, 131.1, 129.5, 129.4,
C20H25NO2S: C 50.12 H 4.87 N 3.08 found C 50.39 H 5.09 N 3.06; MS
129.1, 129.0, 128.7, 126.5 (Ar), 57.4, 46.8, 43.2, 38.0, 32.4; Anal. calcd.
for C19H23NO2S: C 69.27 H 7.04 N 4.25 found C 69.48 H 7.09 N 4.33;
MS (EI, 70 eV) m/z ¼ 329 [Mþ], 264 [Mþ ꢁ SO2], 174 [PhCHþNC5H10],
91 [PhCHþ2 , 100].
(EI, 70 eV) m/z ¼ 343 [Mþ], 278 [Mþ ꢁ SO2], 174 [Mþ ꢁ SO2CH2Ar],
105 [MePhCHþ2 , 100], 91 [PhCHþ2 ].
4.1.19. 4-Benzyl-1-(phenylsulfonyl)piperidine 22
This compound was prepared from 3g and 16 as described for 17.
4.1.15. 4-Benzyl-1-(3-chlorobenzylsulfonyl)piperidine 18
White solid, yield 268 mg (85%). m.p. 130e133 ꢃC; IR (nmax
/
This compound was prepared from 3b and 16 as described for
cmꢁ1) ¼ 2947 (CeH), 1330 (SO2), 1152 (SO2); 1H NMR (CDCl3):
17. White crystal, yield 287 mg (79%). mp 154e155 ꢃC; IR (nmax
/
d
(ppm) ¼ 7.79e7.77 (m, 2H, Ar), 7.61e7.53 (m, 3H, Ar), 7.27 (d,
cmꢁ1) ¼ 2927 (CeH), 1326 (SO2), 1147 (SO2); 1H NMR (CDCl3):
J ¼ 7.6 Hz, 1H, Ar), 7.22 (t, J ¼ 7.4 Hz, 1H, Ar), 7.11 (d, J ¼ 7.0 Hz, 2H,
Ar), 3.81 (d, J ¼ 11.8 Hz, 2H, eCH2NCH2e), 2.54 (d, J ¼ 6.9 Hz, 2H,
PhCH2CHe), 2.22 (td, J ¼ 11.9, 2.3 Hz, 2H, eCH2NCH2e), 1.73e1.70
(m, 2H, eCH2CHCH2e), 1.50e1.45 (m, 1H, eCH2CHCH2e), 1.40e1.37
d
(ppm) ¼ 7.42 (s, 1H, Ar), 7.37 (dt, J ¼ 7.3, 1.9 Hz, 1H, Ar), 7.35e7.29
(m, 4H, Ar), 7.25e7.22 (m, 1H, Ar), 7.14 (d, J ¼ 7.1 Hz, 2H, Ar), 4.16 (s,
2H, ArCH2SO2e), 3.68 (d, J ¼ 12.4 Hz, 2H, eCH2NCH2e), 2.59 (td,
J ¼ 12.4, 2.2 Hz, 2H, eCH2NCH2e), 2.55 (d, J ¼ 7.0 Hz, 2H, PhCH2CHe
), 1.66 (d, J ¼ 13.4 Hz, 2H, eCH2CHCH2e), 1.63e1.58 (m, 1H, e
CH2CHCH2e), 1.28e1.20 (m, 2H, eCH2CHCH2e); 13C NMR (CDCl3):
(m, 2H, eCH2CHCH2e); 13C NMR (CDCl3):
d
(ppm) ¼ 140.2, 136.7,
133.0,129.4,129.3,128.7,128.1,126.5 (Ar), 46.9, 43.1, 37.8, 31.7; Anal.
calcd. for C18H21NO2S: C 68.54 H 6.71 N 4.44 found C 68.48 H 6.79 N
4.33; MS (EI, 70 eV) m/z ¼ 315 [Mþ], 174 [Mþ ꢁ SO2Ph, 100], 132, 91
[PhCHþ2 ].
d
(ppm) ¼ 140.1, 134.9, 131.5, 131.2, 130.4, 129.5, 129.3, 128.8, 126.5,
56.7, 46.8, 43.2, 37.9, 32.3; Anal. calcd. for C19H22ClNO2S: C 62.71 H
6.09 N 3.85 found C 63.01 H 6.29 N 3.76; MS (EI, 70 eV) m/z ¼ 365
[Mþ þ 2], 363 [Mþ], 298 [Mþ ꢁ SO2], 174 [Mþ ꢁ SO2CH2Ar, 100], 125
[ClPhCHþ2 ], 91 [PhCHþ2 ].
4.1.20. 1-Benzyl-4-(phenylsulfonyl)piperazine 23
This compound was prepared from 3g and 4a as described for 5.
White solid, yield 262 mg (83%). m.p. 139e141 ꢃC; IR (nmax
/
4.1.16. 4-Benzyl-1-(3-bromobenzylsulfonyl)piperidine 19
cmꢁ1) ¼ 2928 (CeH), 1354 (SO2), 1156 (SO2); 1H NMR (CDCl3):
This compound was prepared from 3c and 16 as described for 17.
d
(ppm) ¼ 7.78e7.53 (m, 5H, Ar), 7.33e7.21 (m, 3H, Ar), 7.15e7.13
White crystal, yield 282 mg (69%). m.p. 146e149 ꢃC; IR (nmax
/
(m, 2H, Ar), 3.52 (s, 2H, PhCH2Ne), 3.22 (bs, 4H, e(CH2)2NeSO2Ph),
2.50 (bs, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
(ppm) ¼ 138.4,
133.5, 129.9, 129.2, 128.9, 127.5, 61.7, 51.9, 46.3; Anal. calcd. for
cmꢁ1) ¼ 2922 (CeH), 1326 (SO2), 1147 (SO2); 1H NMR (CDCl3):
d
d
(ppm) ¼ 7.57 (s, 1H, Ar), 7.53 (d, J ¼ 8.0 Hz, 1H, Ar), 7.37 (d,
J ¼ 7.7 Hz, 1H, Ar), 7.33e7.22 (m, 4H, Ar), 7.14 (d, J ¼ 7.1 Hz, 2H, Ar),
4.15 (s, 2H, ArCH2SO2e), 3.68 (d, J ¼ 12.4 Hz, 2H, eCH2NCH2e), 2.60
(td, J ¼ 12.4, 2.1 Hz, 2H, eCH2NCH2e), 2.56 (d, J ¼ 7.0 Hz, 2H,
PhCH2CHe), 1.66 (d, J ¼ 13.2 Hz, 2H, eCH2CHCH2e), 1.63e1.59 (m,
1H, eCH2CHCH2e), 1.30e1.20 (m, 2H, eCH2CHCH2e); 13C NMR
C17H20N2O2S: C 64.53 H 6.37 N 8.85 found C 64.64 H 6.48 N 8.79;
MS (EI, 70 eV) m/z ¼ 316 [Mþ], 175 [Mþ ꢁ SO2Ph], 132, 91 [PhCHþ2 ,
100].
4.1.21. 4-Benzyl-1-(4-chlorophenylsulfonyl)piperidine 24
(CDCl3):
128.8, 126.6, 123.0, 56.7, 46.8, 43.2, 37.9, 32.3; Anal. calcd. for
19H22BrNO2S: C 55.88 H 5.43 N 3.43 found C 56.20 H 5.74 N 3.24;
d
(ppm) ¼ 140.1, 134.1, 132.2, 131.8, 130.6, 129.8, 129.5,
This compound was prepared from 3h and 16 as described for
17. White solid, yield 234 mg (67%). m.p. 150e153 ꢃC; IR (nmax
/
C
cmꢁ1) ¼ 2942 (CeH), 1350 (SO2), 1168 (SO2); 1H NMR (CDCl3):
MS (EI, 70 eV) m/z
¼
409 [Mþ], 344 [Mþ
ꢁ
SO2], 174
d
(ppm) ¼ 7.70 (d, J ¼ 8.6 Hz, 2H, Ar), 7.51 (d, J ¼ 8.6 Hz, 2H, Ar),
[Mþ ꢁ SO2CH2Ar, 100], 91 [PhCHþ2 ].
7.31e7.28 (m, 2H, Ar), 7.22 (t, J ¼ 7.3 Hz, 1H, Ar), 7.11 (d, J ¼ 7.1 Hz,
2H, Ar), 3.79 (d, J ¼ 11.7 Hz, 2H, eCH2NCH2e), 2.55 (d, J ¼ 7.0 Hz, 2H,
PhCH2CHe), 2.22 (td, J ¼ 11.9, 2.3 Hz, 2H, eCH2NCH2e), 1.72 (d,
J ¼ 12.9 Hz, 2H, eCH2CHCH2e), 1.51e1.46 (m, 1H, eCH2CHCH2e),
1.42e1.34 (m, 2H, eCH2CHCH2e); 13C NMR (CDCl3):
4.1.17. 4-Benzyl-1-(3-iodobenzylsulfonyl)piperidine 20
This compound was prepared from 3d and 16 as described for
17. White crystal, yield 328 mg (72%). m.p. 136e137 ꢃC; IR (KBr)
(
d
nmax/cmꢁ1) ¼ 2909 (CeH), 1329 (SO2), 1148 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 139.2, 135.1, 132.3, 129.2, 128.9, 128.4, 128.1, 126.0 (Ar),
(ppm) ¼ 7.76 (s, 1H, Ar), 7.73 (d, J ¼ 8.0 Hz, 1H, Ar), 7.41 (d,
45.9, 41.9, 37.7, 32.1; Anal. calcd. for C18H20ClNO2S: C 61.79 H 5.76 N
4.00 found C 61.88 H 5.79 N 4.03; MS (EI, 70 eV) m/z ¼ 351 [Mþ þ 2],
349 [Mþ], 243, 174 [Mþ ꢁ SO2Ar, 100], 132, 111 [C6H4Clþ], 91
[PhCHþ2 ].
J ¼ 7.7 Hz, 1H, Ar), 7.23 (t, J ¼ 7.3 Hz, 1H, Ar), 7.33e7.12 (m, 5H, Ar),
4.13 (s, 2H, ArCH2SO2e), 3.66 (d, J ¼ 12.5 Hz, 2H, eCH2NCH2e), 2.60
(td, J ¼ 12.4, 2.1 Hz, 2H, eCH2NCH2e), 2.57 (d, J ¼ 6.9 Hz, 2H,

M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
495
4.1.22. 1-Benzyl-4-(4-chlorophenylsulfonyl)piperazine 25
4.1.27. (E)-4-benzyl-1-(4-bromostyrylsulfonyl)piperidine 32
This compound was prepared from 29b and 16 as described for
This compound was prepared from 3h and 4a as described for 5.
White solid, yield 249 mg (71%). m.p. 131e133 ꢃC; IR (nmax
/
17. Yellow solid, yield 315 mg (75%). m.p. 136e138 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2942 (CeH), 1350 (SO2), 1168 (SO2); 1H NMR (CDCl3):
cmꢁ1) ¼ 2923 (CeH), 1337 (SO2), 1144 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.71 (ABq, J ¼ 8.6 Hz, 2H, Ar), 7.54 (ABq, J ¼ 8.6 Hz, 2H,
d
(ppm) ¼ 7.57 (d, J ¼ 8.4 Hz, 2H, Ar), 7.40 (d, J ¼ 15.5 Hz, 1H, ArCH]
Ar), 7.33e7.28 (m, 5H, Ar), 3.53 (s, 2H, PhCH2Ne), 3.06 (bs, 4H, e
CHe), 7.37 (d, J ¼ 8.4 Hz, 2H, Ar), 7.31 (m, 2H, Ar), 7.23 (t, J ¼ 7.3 Hz,
1H, Ar), 7.15 (d, J ¼ 7.1 Hz, 2H, Ar), 6.69 (d, 1H, J ¼ 15.5 Hz, SO2CH]
Ce), 3.80 (d, J ¼ 11.9 Hz, 2H, eCH2CHCH2e), 2.65e2.59 (m, 4H, e
CH2NCH2e and PhCH2CHe), 1.77 (d, J ¼ 12.8 Hz, 2H, eCH2CHCH2e),
1.66e1.61 (m, 1H, eCH2CHCH2e), 1.44e1.35 (m, 2H, eCH2CHCH2e);
(CH2)2NeSO2Ar), 2.56 (bs, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
d
(ppm) ¼ 139.8, 138.4, 134.6, 129.9, 129.2, 129.0, 128.9, 127.1, 60.7,
51.7, 46.2; Anal. calcd. for C17H19ClN2O2S: C 58.19 H 5.46 N 7.98
found C 58.34 H 5.48 N 7.79; MS (EI, 70 eV) m/z ¼ 352 [Mþ þ 2], 350
[Mþ], 175 [Mþ ꢁ SO2Ar, 100], 145, 132, 111 [C6H4Clþ], 91 [PhCHþ2 ].
13C NMR (CDCl3):
d
(ppm) ¼ 141.9, 140.2, 132.8, 132.0, 130.0, 129.5,
128.8, 126.6, 125.6, 123.1, 46.5, 43.1, 37.9, 31.9; Anal. calcd. for
4.1.23. 4-Benzyl-1-(phenethylsulfonyl)piperidine 26
C20H22BrNO2S: C 57.14 H 5.28 N 3.33 found C 57.37 H 5.43 N 3.44;
This compound was prepared from 3f and 16 as described for
MS (EI, 70 eV) m/z ¼ 420 [Mþ], 355 [Mþ ꢁ SO2], 174 [Mþ ꢁ SO2CH]
17. White crystal, yield 287 mg (81%). m.p. 140e143 ꢃC; IR (nmax
/
CHAr, 100], 102, 91 [PhCHþ2 ].
cmꢁ1) ¼ 2921 (CeH), 1340 (SO2), 1145 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.45e7.40 (m, 5H, Ar), 7.36e7.32 (m, 2H, Ar), 7.25 (t,
4.1.28. (E)-1-benzyl-4-(4-bromostyrylsulfonyl)piperazine 33
This compound was prepared from 29b and 4a as described for
J ¼ 7.4 Hz, 1H, Ar), 7.11 (d, J ¼ 7.3 Hz, 2H, Ar), 4.08e4.07 (m, 2H,
PhCH2CH2SO2e), 3.65 (d, J ¼ 12.5 Hz, 2H, eCH2NCH2e), 3.12e3.11
(m, 2H, PhCH2CH2SO2e), 2.55e2.51 (m, 4H, eCH2NCH2e and
PhCH2CHe), 1.63 (d, J ¼ 13.6 Hz, 2H, eCH2CHCH2e), 1.58e1.52 (m,
1H, eCH2CHCH2e), 1.26e1.19 (m, 2H, eCH2CHCH2e); 13C NMR
5. White solid, yield 271 mg (79%). m.p. 155e167 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2942 (CeH), 1328 (SO2), 1150 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.58 (d, J ¼ 8.4 Hz, 2H, Ar), 7.41 (d, J ¼ 15.5 Hz,1H, ArCH]
CHe), 7.37 (d, J ¼ 8.4 Hz, 2H, Ar), 7.35e7.31 (m, 5H, Ar), 6.71 (d,
J ¼ 15.5 Hz, 1H, SO2CH]Ce), 3.58 (s, 2H, PhCH2Ne), 3.27 (bs, 4H, e
(CH2)2NeSO2), 2.60 (bs, 4H, e(CH2)2NeBn); 13C NMR (CDCl3):
(CDCl3):
d
(ppm) ¼ 138.2, 131.1, 129.5, 129.4, 129.1, 129.0, 128.7,
126.5 (Ar), 55.3, 46.8, 43.2, 38.0, 32.4, 30.3; Anal. calcd. for
C
20H25NO2S: C 69.93 H 7.34 N 4.08 found C 70.28 H 7.49 N 4.11; MS
d
(ppm) ¼ 141.7, 140.1, 132.9, 131.9, 130.3, 129.2, 129.0, 126.8, 125.5,
(EI, 70 eV) m/z ¼ 343 [Mþ], 278 [Mþ ꢁ SO2], 174 [PhCHþNC5H10
,
123.1, 61.7, 52.0, 46.6; Anal. calcd. for C19H21BrN2O2S: C 54.16 H 5.02
N 6.65 found C 54.43 H 5.10 N 6.50; MS (EI, 70 eV) m/z ¼ 421 [Mþ],
175 [Mþ ꢁ SO2CH]CHAr, 100], 132, 102, 91 [PhCHþ2 ].
100], 91 [PhCHþ2 ].
4.1.24. 1-Benzyl-4-(phenethylsulfonyl)piperazine 27
This compound was prepared from 3f and 4a as described for 5.
4.2. Receptor binding studies
White crystal, yield 261 mg (76%). m.p. 149e151 ꢃC; IR (nmax
/
cmꢁ1) ¼ 2918 (CeH), 1337 (SO2), 1148 (SO2); 1H NMR (CDCl3):
Sigma-1 and sigma-2 receptor binding assays were carried out
as previously described [46,47] using homogenates prepared from
male Dunkin Hartley guinea pig brain membrane and male Spra-
gue-Dawley rat liver membrane by a Bandelin SONOPULS HD 2070
homogenizer. [3H](þ)-Pentazocine (specific activity ¼ 34.8 Ci/
mmol, Perkin-Elmer) was used as a sigma-1 radiotracer and [3H]-
DTG (specific activity ¼ 53.3 Ci/mmol, Perkin-Elmer) in the pres-
ence of (þ)-pentazocine was used as sigma-2 radiotracer. Filtration
was carried out with appropriate glass fiber filters (Whatman GF/
B), presoaked in 0.5% aqueous polyethylenimine for 2 h at 4 ꢃC
before use. The scintillation analysis was performed using a Wallac
1410 Liquid Scintillation Counter. The counting efficiency was 56%.
Data from binding assays were analyzed with the non-linear curve-
fitting computer programs GrapgPad PrismÒ 5.0 (GraphPad Soft-
ware). Statistical analyses were carried out with Prism program.
Each experiment was repeated three times, and data points
repeated in duplicates, yielding means and standard errors.
Apparent binding affinities (Ki) were calculated by the Cheng and
Prusoff equation [50] using IC50 values, the radioligand concen-
tration, and the radioligand experimentally determined Kd of the
radioligand.
d
(ppm) ¼ 7.42e7.35 (m, 5H, Ar), 7.33e7.28 (m, 5H, Ar), 4.12e4.11
(m, 2H, PhCH2CH2SO2e), 3.55 (s, 2H, PhCH2Ne), 3.18e3.11 (m, 6H, e
(CH2)2NeSO2Bn and PhCH2CH2SO2e), 2.45 (t, J ¼ 4.5 Hz, 4H, e
(CH2)2NeBn); 13C NMR (CDCl3):
129.3, 129.0, 128.7, 127.8, 62.9, 57.5, 53.2, 46.5, 30.8; Anal. calcd. for
d
(ppm) ¼ 138.9, 131.4, 130.0, 129.7,
C
19H24N2O2S: C 66.25 H 7.02 N 8.13 found C 66.50 H 7.10 N 8.22; MS
(EI, 70 eV) m/z ¼ 344 [Mþ], 175 [Mþ ꢁ SO2CH2Ph, 100], 91 [PhCHþ2 ].
4.1.25. (E)-4-benzyl-1-(styrylsulfonyl)piperidine 30
This compound was prepared from 29a and 16 as described for
17. Milky oil, yield 273 mg (80%); IR (nmax/cmꢁ1) ¼ 2931 (CeH),1335
(SO2), 1140 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.57e7.54 (m, 2H, Ar),
7.50e7.30 (m, 6H, Ar), 7.25 (t, J ¼ 7.3 Hz, 1H, Ar), 7.21 (d, J ¼ 7.1 Hz,
2H, Ar), 6.91 (d, J ¼ 15.5 Hz,1H, SO2CH]Ce), 3.74 (d, J ¼ 11.8 Hz, 2H,
eCH2NCH2e), 2.60e2.51 (m, 4H, eCH2NCH2e and PhCH2CHe), 1.74
(d, J ¼ 12.8 Hz, 2H, eCH2CHCH2e), 1.61e1.59 (m, 1H, eCH2CHCH2e),
1.41e1.37 (m, 2H, eCH2CHCH2e); 13C NMR (CDCl3):
d
(ppm) ¼ 141.5,
140.8, 133.5, 130.9, 130.4, 129.3, 128.6, 126.2, 125.1; 47.0, 43.6, 37.4,
32.2; Anal. calcd. for C20H23NO2S: C 70.35 H 6.79 N 4.10 found C
70.57 H 6.73 N 4.10; MS (EI, 70 eV) m/z ¼ 341 [Mþ], 276 [Mþ ꢁ SO2],
174 [Mþ ꢁ SO2CH]CHPh, 100], 132, 91 [PhCHþ2 ].
4.2.1. Preparation of the tissue for the s1 assay
4.1.26. (E)-1-benzyl-4-(styrylsulfonyl)piperazine 31
Tissue preparation for s1 assay was performed by previously
reported method [47]. Briefly, three guinea pig brains were ho-
mogenized in a 10-fold volume of cold 0.32 M sucrose. The sus-
pension was centrifuged at 3000 rpm for 10 min at 4 ꢃC. The
supernatant was separated and centrifuged at 30,000 rpm for
20 min at 4 ꢃC. The pellet was separated and was resuspended in ca.
10 volumes of buffer (50 mM TriseHCl; pH 7.4) and after incubation
at 37 ꢃC for 30 min, centrifuged again at 30,000 rpm (20 min, 4 ꢃC).
This procedure was repeated twice. The final pellet was resus-
pended in buffer, and the protein concentration was determined
according to Bradford method [51] using bovine serum albumin as
This compound was prepared from 29a and 4a as described for
5. Yellow oil, yield 264 mg (77%); IR (nmax/cmꢁ1) ¼ 2943 (CeH),
1358 (SO2), 1149 (SO2); 1H NMR (CDCl3):
d
(ppm) ¼ 7.59e7.57 (m,
2H, Ar), 7.43e7.30 (m, 9H, Ar), 6.75 (d, J ¼ 15.5 Hz, 1H, SO2CH]C),
3.61 (s, 2H, PhCH2Ne), 3.22 (bs, 4H, e(CH2)2NeSO2), 2.58 (bs, 4H, e
(CH2)2NeBn); 13C NMR (CDCl3):
129.5, 128.8, 126.5, 125.9, 125.1, 61.0, 51.9, 47.2; Anal. calcd. for
d
(ppm) ¼ 141.7, 136.2, 133.3, 131.0,
C
19H22N2O2S: C66.64 H 6.48 N 8.18 found C 66.96 H 6.56 N 8.14; MS
(EI, 70 eV) m/z ¼ 342 [Mþ], 277 [Mþ ꢁ SO2], 175 [Mþ ꢁ SO2CH]
CHPh, 100], 91 [PhCHþ2 ].

496
M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
standard. Subsequently, the preparation was frozen (ꢁ70 ꢃC) in
013. These data include MOL files and InChiKeys of the most
important compounds described in this article.
5 mL portions containing about 1 mg protein/mL.
4.2.2. Preparation of the tissue for the s2 assay
References
Tissue preparation for s2 assay was performed by previously
reported method [23]. Briefly, two rat livers were cut into small
pieces and homogenized in a 10-fold volume of appropriate cold
buffer (mixture of 10 mM TriseHCl with pH 7.4 and 0.32 M sucrose
solutions). The suspension was centrifuged at 3000 rpm for 10 min
at 4 ꢃC. The supernatant was separated and centrifuged at
42,000 rpm for 20 min at 4 ꢃC. The pellet was separated, resus-
pended in ca. 10 volumes of buffer (10 mM TriseHCl; pH 7.4), and
incubated at 25 ꢃC for 15 min. After the incubation, the suspension
was centrifuged again at 42,000 rpm for 20 min at 4 ꢃC. The final
pellet was resuspended in buffer, and the protein concentration
was determined according to Bradford method [51] using bovine
serum albumin as standard. Subsequently, the preparation was
frozen (ꢁ70 ꢃC) in 10 mL portions containing about 1e2 mg pro-
tein/mL.
[1] P.E. Gilbert, W.R. Martin, The effects of morphine- and nalorphine-like drugs
in the nondependent, morphine-dependent and cyclazocine-dependent
chronic spinal dog, J. Pharmacol. Exp. Ther. 198 (1976) 66e82.
[2] R. Quirion, W.D. Bowen, Y. Itzhak, J.L. Junien, J.M. Musacchio, R.B. Rothman,
T.P. Su, S.W. Tam, D.P. Taylor, A proposal for the classification of sigma binding
sites, Trends Pharmacol. Sci. 13 (1992) 85e86.
[3] J.M. Walker, W.D. Bowen, F.O. Walker, R.R. Matsumoto, B. De Costa, K.C. Rice,
Sigma receptors: biology and function, Pharmacol. Rev. 42 (1990) 355e402.
[4] T.-P. Su, J.-L. Junien, Sigma receptors in the central nervous system and the
periphery, in: Y. Itzhak (Ed.), Sigma Receptors, Academic Press, London, 1994,
pp. 21e44.
[5] S.A. Wolfe Jr., E.B. De Souza, Sigma and phencyclidine receptors in the braine
endocrineeimmune axis, NIDA Res. Monogr. 133 (1993) 95e123.
[6] M. Hanner, F.F. Moebius, A. Flandorfer, H.G. Knaus, J. Striessnig, E. Kempner,
H. Glossmann, Purification, molecular cloning, and expression of the
mammalian sigma1-binding site, Proc. Natl. Acad. Sci. U.S.A. 93 (1996) 8072e
8077.
[7] P. Seth, Y.-J. Fei, H.W. Li, W. Huang, F.H. Leibach, V. Ganapathy, Cloning and
functional characterization of a
s receptor from rat brain, J. Neurochem. 70
(1998) 922e931.
4.2.3. Sigma-1 binding assays
[8] Y.-X. Pan, J. Mei, J. Xu, B.-L. Wan, A. Zuckerman, G.W. Pasternak, Cloning and
characterization of a mouse s1 receptor, J. Neurochem. 70 (1998) 2279e2285.
[9] R. Kekuda, P.D. Prasad, Y.-J. Fei, F.H. Leibach, V. Ganapathy, Cloning and
functional expression of the human type 1 sigma receptor (hSigmaR1), Bio-
chem. Biophys. Res. Commun. 229 (1996) 553e558.
[10] J. Xu, C. Zeng, W. Chu, F. Pan, J.M. Rothfuss, F. Zhang, Z. Tu, D. Zhou, D. Zeng,
S. Vangveravong, F. Johnston, D. Spitzer, K.C. Chang, R.S. Hotchkiss,
W.G. Hawkins, K.T. Wheeler, R.H. Mach, Identification of the PGRMC1 protein
complex as the putative sigma-2 receptor binding site, Nat. Commun. 2 (2011)
380.
Binding assays were performed as described by McKinney et al.
[46]. Sigma-1 binding assays were carried out on guinea pig brain
membranes prepared by the procedure of DeHaven-Hudkins and
Ford-Rice [47]. Each tube contained 200 mg of membrane protein,
and was incubated with 3 nM [3H](þ)-pentazocine in 50 mM Trise
HCl (pH 7.4). Test compounds were dissolved in dimethylsulfoxide
and then diluted in buffer for a total volume of 1 mL. Test com-
pounds were added in concentration ranging from 10ꢁ5 to 10ꢁ10 M.
[11] W.D. Bowen, Sigma receptors: recent advances and new clinical potentials,
Pharm. Acta Helv. 74 (2000) 211e218.
[12] B.J. Vilner, W.D. Bowen, Sigma receptors: recent advances and new clinical
potentials, J. Pharmacol. Exp. Ther. 292 (2000) 900e911.
Nonspecific binding was assessed by the addition of 10
mM of
haloperidol. The reaction was performed for 120 min at 25 ꢃC and
terminated by filtering the solution through glass fiber filters (GF/B)
that were presoaked for 2 h at 4 ꢃC in a 0.5% polyethylenimine
solution before use. Filters were washed twice with 4 mL of ice-cold
buffer. Scintillation counting was carried out in 5 mL of HiSafe 2
cocktail (Perkin-Elmer) after an overnight extraction of counts by a
liquid scintillation counter.
[13] K. Matsuno, K. Matsunaga, T. Senda, S. Mita, Increase in extracellular acetyl-
choline level by sigma ligands in rat frontal cortex, J. Pharmacol. Exp. Ther.
265 (1993) 851e859.
[14] G.M. Gonzalez-Alvear, L.L. Werling, Regulation of [3H]-dopamine release from
rat striatal slices by sigma receptor ligands, J. Pharmacol. Exp. Ther. 271
(1994) 212e219.
[15] G.A. Gudelsky, Biphasic effect of sigma receptor ligands on the extracellular
concentration of dopamine in the striatum of the rat, J. Neural Transm. 106
(1999) 849e856.
[16] S. Chaki, S. Okuyama, S. Ogawa, K. Tomisawa, Regulation of NMDA-induced
[3H]-dopamine release from rat hippocampal slices through sigma-1 bind-
ing sites, Neurochem. Int. 33 (1998) 29e34.
[17] J.E. Bermack, G. Debonnel, Distinct modulatory roles of sigma receptor sub-
types on glutamatergic responses in the dorsal hippocampus, Synapse 55
(2005) 37e44.
[18] T. Hayashi, T.-P. Su, Sigma-1 receptor chaperones at the ER-mitochondrion
interface regulate Ca2þ signaling and cell survival, Cell 131 (2007) 596e
610.
4.2.4. Sigma-2 binding assays
Sigma-2 binding assays were carried out on rat liver membranes
prepared as described by Mach et al. [23]. The membranes were
incubated with 2 nM [3H]-DTG [1,3-di-(2-tolyl)-guanidine] in the
presence of 200 nM (þ)-pentazocine to block s1 sites. Incubation
was carried out in 50 mM TriseHCl (pH 7.4) for 150 min at 37 ꢃC,
and assays were terminated by the addition of ice-cold 10 mM
TriseHCl pH 7.4, followed by filtration through glass fiber filters
(GF/B) that were presoaked for 2 h at 4 ꢃC in a 0.5% poly-
ethylenimine solution before use. Filters were washed twice with
4 mL of ice-cold buffer. Nonspecific binding was evaluated in the
[19] S.-Y. Tsai, T. Hayashi, T. Mori, T.-P. Su, Sigma-1 receptor chaperones and
diseases, Cent. Nerv. Syst. Agents Med. Chem. 9 (2009) 184e189.
[20] N. Akhter, K. Shiba, K. Ogawa, S. Tsuji, S. Kinuya, K. Nakajima, H. Mori,
A change of in vivo characteristics depending on specific activity of radio-
iodinated (þ)-2-[4-(4-iodophenyl)piperidino]cyclohexanol [(þ)-pIV] as
a
ligand for sigma receptor imaging, Nucl. Med. Biol. 35 (2008) 29e34.
presence of 10 mM haloperidol. Scintillation counting was carried
out in 5 mL of the HiSafe 2 cocktail (Perkin-Elmer) after an over-
night extraction of counts by a liquid scintillation counter.
[21] Z. Tu, J. Xu, L.A. Jones, S. Li, C. Dumstorff, S. Vangveravong, D.L. Chen,
K.T. Wheeler, M.J. Welch, R.H. Mach, Fluorine-18-labeled benzamide ana-
logues for imaging the s2 receptor status of solid tumors with positron
emission tomography, J. Med. Chem. 50 (2007) 3194e3204.
[22] B. Vilner, C.S. John, W.D. Bowen, Sigma-1 and sigma-2 receptors are expressed
in a wide variety of human and rodent tumor cell lines, Cancer Res. 55 (1995)
408e413.
Acknowledgments
[23] R.H. Mach, C.R. Smith, S.R. Childers, Ibogaine possesses a selective affinity for
sigma-2 receptors, Life Sci. 57 (1995) 57e62.
[24] W.D. Bowen, C.M. Bertha, B.J. Vilner, K.C. Rice, CB-64D and CB-184: ligands
with high sigma 2 receptor affinity and subtype selectivity, Eur. J. Pharmacol.
278 (1995) 257e260.
[25] R.A. Glennon, A.M. Ismail, S. Ablordeppey, M. El-Ashmawy, J.B. Fisher, Thio-
xanthene-derived analogs as s1 receptor ligands, Bioorg. Med. Chem. Lett. 14
(2004) 2217e2220.
The authors acknowledge the University of Tehran and NSTRI for
financial support of this research. They also acknowledged from Ms.
Zahra Heydari for her cooperation in performing the standard MM2
energy minimization calculations.
[26] L. Costantino, F. Gandolfi, C. Sorbi, S. Franchini, O. Prezzavento, F. Vittori,
G. Ronsisvalle, A. Leonardo, E. Poggesi, L. Brasili, Synthesis and structuree
activity relationships of 1-aralkyl-4-benzylpiperidine and 1-aralkyl-4-
Appendix A. Supplementary data
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.ejmech.2013.04.
benzylpiperazine derivatives as potent
s ligands, J. Med. Chem. 48 (2005)
266e273.

M. Sadeghzadeh et al. / European Journal of Medicinal Chemistry 64 (2013) 488e497
497
[27] S. Beduerftig, B. Wuensch, Chiral, nonracemic (piperazin-2-yl)methanol de-
rivatives with -receptor affinity, Bioorg. Med. Chem. 12 (2004) 3299e3311.
[40] R.A. Glennon, Pharmacophore identification for sigma-1 receptor binding,
Minirev. Med. Chem. 5 (2005) 927e940.
s
[28] J. Charton, A.C. Gassiot, S. Girault-Mizzi, M.-A. Debreu-Fontaine, P. Melnyk,
C. Sergheraert, Synthesis and pharmacological evaluation of Tic-hydantoin de-
rivatives as selective s1 ligands, Bioorg. Med. Chem. Lett. 15 (2005) 4833e4837.
[29] S. Younes, Y. Labssita, G. Baziard-Mouysset, M. Payard, M.-C. Rettori,
P. Renard, B. Pfeiffer, D.-H. Caignard, Synthesis and structureeactivity re-
[41] M. Hamer, O.F. Batzer, M.J. Moats, C.C. Wu, E.P. Lira, Synthesis of 2-pyridyl-a-
toluenesulfonates as antimalarials, J. Pharm. Sci. 64 (1975) 1961e1964.
[42] P.A. Procopiou, V.J. Barrett, N.J. Bevan, K. Biggadike, P.R. Butchers, D.M. Coe,
R. Conroy, D.D. Edney, R.N. Field, A.J. Ford, S.B. Guntrip, B.E. Looker, I.M. McLay,
M.J. Monteith, V.S. Morrison, P.J. Mutch, S.A. Richards, R. Sasse, C.E. Smith,
Synthesis and structureeactivity relationships of long-acting beta2 adrenergic
receptor agonists incorporating arylsulfonamide groups, J. Med. Chem. 52
(2009) 2280e2288.
lationships of novel arylalkyl 4-benzyl piperazine derivatives as
s site selec-
tive ligands, Eur. J. Med. Chem. 35 (2000) 107e121.
[30] S.Y. Ablordeppey, J.B. Fischer, H. Law, R.A. Glennon, Probing the proposed phenyl-
A region of the sigma-1 receptor, Bioorg. Med. Chem. 10 (2002) 2759e2765.
[31] C. Mésangeau, E. Amata, W. Alsharif, M.J. Seminerio, M.J. Robson,
R.R. Matsumoto, J.H. Poupaert, C.R. McCurdy, Synthesis and pharmacological
evaluation of indole-based sigma receptor ligands, Eur. J. Med. Chem. 46
(2011) 5154e5161.
[32] R.-J. Liu, J.A. Tucker, T. Zinevitch, O. Kirichenko, V. Konoplev, S. Kuznetsova,
S. Sviridov, J. Pickens, S. Tandel, E. Brahmachary, Y. Yang, Design and synthesis
of human immunodeficiency virus entry inhibitors: sulfonamide as an iso-
stere for the alpha-ketoamide group, J. Med. Chem. 50 (2007) 6535e6544.
[33] W.G. Harter, H. Albrect, K. Brady, B. Caprathe, J. Dunbar, J. Gilmore, S. Hays,
C.R. Kostlan, B. Lunney, N. Walker, The design and synthesis of sulfonamides
as caspase-1 inhibitors, Bioorg. Med. Chem. Lett. 14 (2004) 809e812.
[34] N.S. Reddy, M.R. Mallireddigari, K.G. Cosenza, S.C. Bell, E.P. Reddy,
M.V.R. Reddy, Synthesis of new coumarin 3-(N-aryl) sulfonamides and their
anticancer activity, Bioorg. Med. Chem. Lett. 14 (2004) 4093e4097.
[43] R.A. Abramovitch, W.D. Holcomb, W.M. Thompson, S. Wake, Solution and
flash vacuum pyrolyses of b-(3,5-disubstituted-phenyl)ethanesulfonyl azides,
sultam, pyrindine, and azepine formation, J. Org. Chem. 49 (1984) 5124e5131.
[44] M. Perez, M. Lamothe, C. Maraval, E. Mirabel, C. Loubat, B. Planty, C. Horn,
J. Michaux, S. Marrot, R. Letienne, C. Pignier, A. Bocquet, F. Nadal-Wollbold,
D. Cussac, L. De Vries, B.L. Grand, Discovery of novel protease activated re-
ceptors 1 antagonists with potent antithrombotic activity in vivo, J. Med.
Chem. 52 (2009) 5826e5836.
[45] B.M. Culbertson, S. Dietz, Some aromatic vinyl sulphonyl chlorides, J. Chem.
Soc. (C) (1968) 992e993.
[46] M. McKinney, R. Raddatz, Curr. Protoc. Pharmacol. (Suppl. 33) (2006) 1.3.1e
1.3.42.
[47] D.L. DeHaven-Hudkins, Y. Ford-Rice, Characterization of the binding of
[3H](þ)-pentazocine to sigma recognition sites in guinea pig brain, Eur. J.
Pharmacol. 227 (1992) 371e378.
[35] B.R. Stranix, J.F. Lavallee, G. Sevigny, J. Yelle, V. Perron, N. Leberre, D. Herbart,
J.J. Wu, Lysine sulfonamides as novel HIV-protease inhibitors: N3-acyl aro-
[48] S.Y. Ablordeppey, B. Fischer, R.A. Glennon, Is a nitrogen atom an important
pharmacophoric element in sigma ligand binding? Bioorg. Med. Chem. 8
(2000) 2105e2111.
matic a-amino acids, Bioorg. Med. Chem. Lett. 16 (2006) 3459e3462.
[36] A. Shaabani, E. Soleimani, A.H. Rezayan, A novel approach for the synthesis of
alkyl and aryl sulfonamides, Tetrahedron. Lett. 48 (2007) 2185e2188.
[37] C.S. John, B.B. Lim, B.J. Vilner, B.C. Geyer, W.D. Bowen, Substituted halogenated
arylsulfonamides: a new class of sigma receptor binding tumor imaging
agents, J. Med. Chem. 41 (1998) 2445e2450.
[38] H. Radeke, P.E. Persons, J.R. Hauske, Spirocyclic Ligands for Sigma Receptors,
and Libraries and Methods of Use Thereof, US 2006/0194785 A1.
[39] R.A. Glennon, S.Y. Ablordeppey, A.M. Ismaiel, M.B. El-Ashmawy, J.B. Fischer,
K.B. Howie, Structural features important for s1 receptor binding, J. Med.
Chem. 37 (1994) 1214e1219.
[49] G. Baziard-Mouysset, S. Younes, Y. Labssita, M. Payard, D.-H. Caignard, M.-
C. Rettori, P. Renard, B. Pfeiffer, B. Guardiola-Lemaitre, Synthesis and struc-
tureeactivity relationships of novel 2-amino alkyl chromones and related
derivatives as a site-selective ligands, Eur. J. Med. Chem. 33 (1998) 339e347.
[50] Y.-C. Cheng, W.H. Prusoff, Relationship between the inhibition constant (Ki)
and the concentration of inhibitor which causes 50 per cent inhibition (I50) of
an enzymatic reaction, Biochem. Pharmacol. 22 (1973) 3099e3108.
[51] M.M. Bradford, A. Rapid, Sensitive, Method for the quantitation of microgram
quantities of protein utilizing the principle of protein-dye binding, Anal.
Biochem. 72 (1976) 248e254.