Synthesis and antidepressant activity of a series of arylalkanol and aralkyl piperazine derivatives targeting SSRI/5-HT1A/5-HT7

Article abstract of DOI:10.1016/j.bmcl.2017.11.007

A series of arylalkanol and aralkyl piperazine derivatives have been synthesized and evaluated for 5-HT reuptake inhibitory abilities and binding affinities at the 5-HT_1A/5-HT₇ receptors. Antidepressant activities of the compounds in

Full text of DOI:10.1016/j.bmcl.2017.11.007

Accepted Manuscript
Synthesis and antidepressant activity of a series of arylalkanol and aralkyl pi-
perazine derivatives targeting SSRI/5-HT1A/5-HT7
Zheng-Song Gu, Ying Xiao, Qing-Wei Zhang, Jian-Qi Li
PII:
S0960-894X(17)31083-1
https://doi.org/10.1016/j.bmcl.2017.11.007
BMCL 25413
DOI:
Reference:
Bioorganic & Medicinal Chemistry Letters
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Revised Date:
Accepted Date:
1 July 2017
2 November 2017
5 November 2017
Please cite this article as: Gu, Z-S., Xiao, Y., Zhang, Q-W., Li, J-Q., Synthesis and antidepressant activity of a series
of arylalkanol and aralkyl piperazine derivatives targeting SSRI/5-HT1A/5-HT7, Bioorganic & Medicinal Chemistry
Letters (2017), doi: https://doi.org/10.1016/j.bmcl.2017.11.007
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Synthesis and antidepressant activity of a series of
arylalkanol and aralkyl piperazine derivatives
targeting SSRI/5-HT1A/5-HT7
Zheng-Song Gu, Ying Xiao, Qing-Wei Zhang*, Jian-Qi Li*
Novel Technology Center of Pharmaceutical Chemistry, Shanghai Institute of Pharmaceutical
Industry, China State Institute of Pharmaceutical Industry, 285 Gebaini Road, Shanghai 201203,
PR China
*Corresponding author: Tel.: +86-021-20572128. E-mail: lijianqb@126.com; sipiqingwei@163.com
Abstract
A series of arylalkanol and aralkyl piperazine derivatives have been synthesized
and evaluated for 5-HT reuptake inhibitory abilities and binding affinities at the
5-HT1A/5-HT7 receptors. Antidepressant activities of the compounds in vivo were
screened using the forced swimming test (FST). The results indicated that the
compound 8j exhibited high affinities for the 5-HT1A/5-HT7 receptors (5-HT1A, ki =
0.84 nM; 5-HT7, ki = 12 nM) coupling with moderate 5-HT reuptake inhibitory
activity (RUI, IC50 = 100 nM) and showed a marked antidepressant-like activity in
the FST model.
Key words: Antidepressant;
arylalkanol and aralkyl piperazine;
SSRI/5-HT1A/5-HT7.

Depression is a chronic, debilitating disease that can disturb thoughts, feelings,
behaviors, even sometimes leads to suicide. According to the World Health
Organization, Major depressive disorder (MDD) will become the second leading
cause of disability worldwide by the year 2020, affecting 121 million people1.
Various chemical drugs have been developed to treat patients with depression since
the late 1950s, such as the monoamine oxidase inhibitors, the tricyclic antidepressants,
the selective serotonin reuptake inhibitors, the serotonin and norepinephrine reuptake
inhibitors etc.2-3 However, there are still high unmet needs in the treatment of
depression，including therapeutics delayed onset, treatment resistance and adverse
effects such as sexual dysfunction. 4-5
To enhance drug efficacy and suppress unwanted effects, different strategies
have been developed, such as the triple reuptake inhibitors (SSRI/SNRI/SDARI) and
novel compounds with the combination of serotonin reuptake inhibition and various
5-HT receptor subtypes affinity.6-7 For example, vilazodone (Chart 1), a novel
serotonin reuptake inhibitor with 5-HT1A partial agonistic activity, displays fast
antidepressant efficacy with minimal undesirable effects, especially sexual
dysfunction. 8-9 Besides, the blockade of 5-HT7 receptors has been shown to enhance
the effects of SSRIs on serotonin levels in vivo. The combined administration of low
doses of an SSRI with selective 5-HT7 receptor antagonist (SB-269970) was found
10-11
active in behavioral models of depression.
Recently, a study showed that the
novel multimodal antidepressant vortioxetine has the potential of improving cognitive
function partly via its 5-HT7 receptor antagonism.12
To the best of our knowledge, the effect of compounds with the combination of
serotonin reuptake inhibition and 5-HT1A/5-HT7 receptors in animal models of
depression has not been studied so far. Herein we described the synthesis and
biological evaluation of novel arylalkanol and aralkyl piperazine derivatives showing
high affinities for the 5-HT1A/5-HT7 receptors coupled with 5-HT reuptake inhibitory
activity.
The compounds with dual SSRI and 5-HT1A activity have been reported. Earlier
studies by Monge et al. demonstrated that the aryl piperazine benzo[b]thiophene

derivatives I and II (Chart 2) showed high affinity for both 5-HT1A receptor and 5-HT
transporter.13-14 The agents acting on 5-HT1A and 5-HT7 receptors have also been
reported in recent decades. Leopoldo et al. reported that 1-(2-Biphenyl)piperazine
derivatives III and IV (Chart 2) displayed high affinity for 5-HT7 and 5-HT1A
receptors.15-16
In our previous study, we evaluated the aryl piperazine
benzo[b][1,4]oxazine derivative V that exhibited potent functional activities at both
5-HT1A receptor [Ki = 1.48 nM] and serotonin transporter [IC50 = 195.02 nM] (Chart
3).17
In this study, we firstly investigated whether 5-HT reuptake inhibition could be
improved by replacing the benzo[b][1,4]oxazine moiety with 3,4-dichlorophenyl
moiety which is a preferred substituent in some SSRI antidepressants (Chart 3).18
Subsequently, we replaced the 2-methoxyphenyl moiety at the N4 position with other
aromatic substituents to explore the effect of different aromatic ring substitutions on
the affinity for dual 5-HT1A and 5-HT7 receptors(Chart 3).
Compounds were evaluated for binding affinities for 5-HT1A/5-HT7 receptors and
inhibiting 5-HT reuptake in vitro. The selected compounds were tested for
microsomal stabilities in vitro and antidepressant-like activities in vivo. Preliminary
results indicated the target compounds exhibited high potency for 5-HT1A/5-HT7
receptors and moderate 5-HT reuptake inhibitory and produced marked
antidepressant-like effects in vivo.
Chart 1. Chemical structures of representative antidepressant compounds

Chart 2. Structures of SSRI/5-HT1A agents and 5-HT1A/5-HT7 agents
Chart 3. Rational design of novel SSRI/5-HT1A/5-HT7 activity compounds
The synthesis of all target compounds was prepared as outlined in schemes 1-2.
In Scheme 1, a series of linear-chain arylalkanol piperazine derivatives (4a-4f) was
prepared. Briefly, 3-chloropropanoyl chloride or chloroacetyl chloride with
1,2-dichlorobenzene in the presence of aluminum choride and dichloromethane by the
Friedel-Crafts reaction afforded the intermediates 2. Then the compounds 2 were
reduced by sodium borohydride to provide the intermediates 3. Finally, the
compounds 3 were treated with 4-arylpiperazine derivatives via SN2 mechanism,
yielding target compounds 4a-4f. According to Scheme 2 , a series of linear-chain
aralkyl piperazine derivatives (8a-8j) were prepared. In general, compound 5 was

reduced with lithium aluminum hydride into the corresponding alcohol 6. Then the
activation of alcohol 6 with 4-toluenesulfonyl chloride in the presence of
triethylamine at room temperature provided intermediate 7. Compound 7 was then
reacted with 4-arylpiperazine derivatives to give the target compounds 8a-8j.
OH
O
Cl
Cl
O
Cl
Cl
N
c
N
b
Cl
Cl
n
Cl
Cl
n
a
N
Cl
N
n
2
2
R1
3
3
4
3
R1
3a. R1 = 2-OCH3 , n=1 3b. R1 = 2-SCH3 , n=1
1 = 2-OH , n=1 1 = 2-Ph , n=1
3f. R1 = 2-Ph , n=0
1
2
2a. n=1; 2b. n=0;
4a. R1 = 2-OCH3 , n=1 4b. R1 = 2-SCH3 , n=1
4c. R1 = 2-OH , n=1
4e. R1 = 3-Ph , n=1
4d. R1 = 2-Ph , n=1
4f. R1 = 2-Ph , n=0
R
R
3d.
3c.
3e. R1 = 3-Ph , n=1
Scheme 1. Reagents and conditions: (a) AlCl3, 3-chloropropanoyl chloride (or
o
chloroacetyl chloride), 70 C; (b) K2CO3, CH3CN, 80 C; (c) NaBH4, MeOH, room
o
temperature.
Scheme 2. Reagents and conditions: (a) LiAlH4, THF, 0-25 oC ; (b) TsCl, Et3N, DCM,
25 oC; (C) K2CO3, CH3CN, 80 oC.
All of compounds were tested for their inhibition of 5-HT reuptake and binding
affinities for the 5-HT1A and 5-HT7 receptors. The binding affinity for 5-HT1A
receptor was determined by investigating the displacement of [3H]-8-OH-DPAT to
HEK-293 cell membrane homogenates, 19 and the affinity for the 5-HT7 receptor was
determined by displacement binding to CHO cell membrane homogenates using
[3H]-LSD to previously procedures reported. 20 The inhibition of uptake of [3H]-5-HT
into rat brain synaptosomes through the serotonin transporter was also evaluated. 21
All compounds were initially screened at 10 µM concentration, and potent compounds
(inhibition >90%) were then assayed to obtain their IC50 values. The detail results
were summarized in Table 1-2. The metabolic stability of the test compounds was
measured in vitro using liver microsomes, a system widely used to evaluate the

susceptibility to first-pass oxidative metabolism (Table 3).22
We first focused on the R1 substituent in the 2- or 3- position of phenylpiperazine
ring in 4 (Scheme 1). Compounds 4a-4c showed more than 90% inhibition for dual
5-HT1A and 5-HT7 receptors but expressed less than 90% inhibition for 5-HT reuptake
even at a concentration of 10 µM. Interestingly, the 1-(2-biphenyl)piperazine
derivative 4d exhibited moderate inhibitory for 5-HT reuptake (IC50 = 590 nM) and
showed more than 90% inhibition for 5-HT1A/5-HT7 receptors, whereas the
1-(3-biphenyl)piperazine counterpart 4e remained selectively inhibitory for 5-HT
reuptake and 5-HT1A receptor (inhibition ratio >90%). These results showed that
2-phenyl was essential as 5-HT1A /5-HT7 pharmacophore moiety.
The influence of the length of the linker on 5-HT reuptake inhibition in relation
to 5-HT1A and 5-HT7 receptor affinity was also explored. The two-carbon chain
analog 4f displayed outstanding affinity for 5-HT1A/5-HT7 receptors (5-HT1A, ki = 2.4
nM; 5-HT7, ki = 3.2 nM) and better 5-HT reuptake inhibitory activity (IC50 = 340 nM).
In our next series, we investigated the effects of removing the hydroxyl group at
the C1 position in arylalkanol-piperazine derivatives (Scheme 2). As shown in Table
1-2, compound 8a showed potent inhibition for 5-HT1A/5-HT7 receptors (5-HT1A, ki
= 6.3 nM; 5-HT7, ki = 0.75 nM) and lower inhibition for 5-HT reuptake (IC50 = 840
nM). Meanwhile, the role of various substituted phenyl groups was also explored. We
first introduced a methyl into the ortho-, meta- and pair- position of the phenyl group.
Compounds 8b, 8c and 8e showed selectively inhibition for 5-HT1A/5-HT7 receptors
(inhibition ratio > 90%) . The 2,4-dimethyl and 3,4-dimethyl substituted derivatives
8h and 8i were also weak inhibitors of 5-HT reuptake. The replacement of methyl
group with methoxy group did not improve the activity of 5-HT reuptake inhibition
(compare 8f with 8e). Besides, the 3-fluorophenyl 8d (RUI, IC50 = 880 nM) and
4-fluorophenyl 8g (RUI, IC50 = 950 nM) analogs showed lower inhibition for 5-HT
reuptake. Those results indicated that the introduction of various substitutions on the
phenyl ring led to reduce 5-HT reuptake inhibition activity. To explore the effect of
aromatic heterocycle at the N4 position on 5-HT reuptake inhibitory activity, the
biphenyl moiety was replaced by benzo[d]isothiazole to produce compound 8j.

Surprisingly, compound 8j exhibited higher inhibition for 5-HT reuptake than the
other biphenyl substituted compounds (RUI, IC50 = 100 nM), and also displayed
excellent affinity for 5-HT1A/5-HT7 receptors (5-HT1A, ki = 0.84 nM; 5-HT7, ki = 12
nM).
The metabolic stability of potent compounds 4f and 8j was tested herein. The
data indicated that the two compounds displayed short half-life (t1/2 values were 6.1
min and 5.3 min, respectively), which was a little faster than vortioxetine (t1/2 = 9
min).
Compounds 4f and 8j was selected for further profiling in the mouse forced
swim test (FST). The compounds were administered orally once daily for 7 days at
doses of 10, 20 and 40 mg/kg/day (PO), respectively. For comparative purposes,
vortioxetine was acted as a positive control (20 mg/kg/day, PO). The results are
shown in Figure 1. Compared with vehicle, the selected compounds 4f and 8j reduced
immobility times in the FST in a dose-dependent manner that was statistically
significant at 20 and 40 mg/kg (PO). The positive control, vortioxetine, also produced
a statistically significant reduction of immobility time at 20 mg/kg dose.
In summary, a novel series of arylalkanol-piperazine derivatives 4a-4f and
aralkyl piperazine derivatives 8a-8j were designed and synthesized. Several
compounds showed potent binding affinities at the 5-HT1A/5-HT7 receptors and
moderate inhibition of 5-HT reuptake, and exhibited marked antidepressant-like
activity in the FST. Especially, compound 8j showed more potent efficacy in the
animal test, and could act as a potential candidate for a promising antidepressant. The
preliminary results lay a foundation for future development of novel derivatives
targeting SSRI/5-HT1A/5-HT7 as potent multi-model antidepressant agents. The
analogs possessing an improved pharmacokinetic property will be the focus of future
disclosures.

Table 1
5-HT1A and 5-HT7 Receptor Binding and 5-HT Reuptake Inhibition of target compounds a
Compd. RUI (Inhibition ratio)
5-HT1A (Inhibition ratio)
99.3%
5-HT7 (Inhibition ratio)
100.9%
101.1%
102.4%
101.5%
69.8%
88.8%
89.04%
84.9%
98.9%
105.3%
112.0%
103.7%
61.6%
72.3%
97.2%
65.8%
66.1%
92.1%
31.5%
17.6%
101.6%
4a
4b
4c
4d
4e
4f
99.9%
99.4%
98.9%
91.5%
98.5%
99.8 %
97.8%
101.1%
97.3%
8a
8b
8c
8d
8e
8f
93.9%
98.4%
94.7%
99.7%
96.4%
99.5%
98.1%
98.7%
97.5%
98.8%
96.7%
8g
8h
8i
83.2%
93.5%
96.8%
93.2%
98.7%
96.0%
8j
a Percent inhibition measured at a concentration of 10 µM.
Table 2
5-HT1A and 5-HT7 Receptor Binding and 5-HT Reuptake Inhibition of selected compounds a
Compd.
RUI (IC50, nM)
5-HT1A(Ki, nM)
5-HT7 (Ki, nM)
590
340
840
880
950
100
2.9
-
2.4
6.3
-
-
3.2
0.75
-
4d
4f
8a
8d
-
-
8g
8j
0.84
12
9.5
26
Vortioxetine
a IC50 and Ki values were obtained from 8 concentrations of the compound, each in duplicate.
(Binding assays were conducted by Eurofins Cerep SA, Celle L'Evescault, France).
Table 3
Rat Liver Microsomal Metabolic Stability Assay
Compd.
4f
t1/2 (min)
CL (µL/min/mg)
225.6
6.1
5.3
9
261.7
8j
153.2
Vortioxetine
Omeprazole
8.5
162.6

compound 4f (mg/kg, PO)
compound 8j (mg/kg, PO)
Figure 1. Effect of treatment of mice with compounds 4f and 8j at graded doses on the immobility
time in the forced swim test. Results are represented as mean SEM. with n = 10 in each group.
Values are significant at *P < 0.05, **P < 0.01 when compared with vehicle group.
Acknowledgements
The authors gratefully acknowledge the financial support from the National
Science and Technology Major Project (Grant No. 2017ZX09101004-002-009), the
National Natural Science Foundation of China (Grant No. 81703358), Shanghai
S&T Innovation Action Plan (Grant No. 16431903400,14431901500, 17431903900 ) .
We thank M.S. Feng-hua Gu (Department of pharmacology, Shanghai Institute of

Pharmaceutical Industry, China) for in vivo studies.
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Synthesis and antidepressant activity of a series of
arylalkanol and aralkyl piperazine derivatives
targeting SSRI/5-HT1A/5-HT7
Zheng-Song Gu, Ying Xiao, Qing-Wei Zhang*, Jian-Qi Li*
Novel Technology Center of Pharmaceutical Chemistry, Shanghai Institute of Pharmaceutical
Industry, China State Institute of Pharmaceutical Industry, 285 Gebaini Road, Shanghai 201203,
PR China
*Corresponding author: Tel.: +86-021-20572128. E-mail: lijianqb@126.com; sipiqingwei@163.com
Graphical abstract