Chemical puzzles in the search for new, flexible derivatives of lurasidone as antipsychotic drugs

Article abstract of DOI:10.1016/j.bmc.2020.115459

In the pharmacotherapy of schizophrenia, there is a lack of effective drugs, and currently used agents cause a large number of side effects. The D₂, 5-HT_1A, 5-HT_2A receptors are among the most important receptor targets in the treatment of schizophrenia, but antagonism at 5-HT₆ and 5-HT₇ receptors may bring about additional improvement of cognitive functions. However, doubt exists regarding the importance of 5-HT₇R in the pharmacotherapy. In 2010, lurasidone (with high affinity for D₂, D₃, 5-HT_1A, 5-HT_2A, 5-HT₇ receptors) was approved for the treatment of schizophrenia. Due to the efficacy of the mentioned drug and doubts related to the role of 5-HT₇R, we decided to obtain compounds with an activity profile similar to that of lurasidone, but with the reduced affinity for 5-HT₇R and increased affinity for 5-HT₆R. For this purpose, we chose a flexible hexyl derivative of lurasidone (2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)hexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione 1a) as a hit structure. After molecular modeling, we modified it, in the area of the arylpiperazine and imide group, using the moieties found in other known CNS drugs. We received the compounds in accordance with the previously developed method of ecological synthesis in the microwave radiation field. Among the obtained compounds, N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)naphthalene-sulfonamides 1v and 1w were distinguished as multifunctional ligands showing increased affinity for 5-HT₆R, and 2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 1i – a multifunctional ligand showing moderate affinity for 5-HT₆R and threefold lower for 5-HT₇R. In the paper, we discuss some of the observed dependencies regarding 5-HT₆/5-HT₇R affinity using molecular docking methods.

Full text of DOI:10.1016/j.bmc.2020.115459

Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Chemical puzzles in the search for new, flexible derivatives of lurasidone as
antipsychotic drugs
⁎
Przemysław Zarębaa, , Anna K. Drabczyka, Jolanta Jaśkowskaa, Grzegorz Satałab
a Faculty of Chemical Engineering and Technology, Institute of Organic Chemistry and Technology, Cracow University of Technology, 24 Warszawska Street, Cracow 31-
155, Poland
b Department of Medicinal Chemistry, Maj Institute of Pharmacology of the Polish Academy of Sciences, 12 Smętna Street, Cracow 31-343, Poland
A R T I C L E I N F O
A B S T R A C T
Keywords:
In the pharmacotherapy of schizophrenia, there is a lack of effective drugs, and currently used agents cause a
large number of side effects. The D2, 5-HT1A, 5-HT2A receptors are among the most important receptor targets in
the treatment of schizophrenia, but antagonism at 5-HT6 and 5-HT7 receptors may bring about additional im-
provement of cognitive functions. However, doubt exists regarding the importance of 5-HT7R in the pharma-
cotherapy. In 2010, lurasidone (with high affinity for D2, D3, 5-HT1A, 5-HT2A, 5-HT7 receptors) was approved for
the treatment of schizophrenia. Due to the efficacy of the mentioned drug and doubts related to the role of 5-
HT7R, we decided to obtain compounds with an activity profile similar to that of lurasidone, but with the
reduced affinity for 5-HT7R and increased affinity for 5-HT6R. For this purpose, we chose a flexible hexyl de-
rivative of lurasidone (2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)hexahydro-1H-4,7-methanoi-
soindole-1,3(2H)-dione 1a) as a hit structure. After molecular modeling, we modified it, in the area of the
arylpiperazine and imide group, using the moieties found in other known CNS drugs. We received the com-
pounds in accordance with the previously developed method of ecological synthesis in the microwave radiation
field. Among the obtained compounds, N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)naphthalene-sul-
fonamides 1v and 1w were distinguished as multifunctional ligands showing increased affinity for 5-HT6R, and
Serotonin receptors
Microwave
Lurasidone
Dopamine
Schizophrenia
2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one 1i
– a multi-
functional ligand showing moderate affinity for 5-HT6R and threefold lower for 5-HT7R. In the paper, we discuss
some of the observed dependencies regarding 5-HT6/5-HT7R affinity using molecular docking methods.
1. Introduction
functions and antidepressant effect. However, the existing studies on
the role of 5-HT7 receptors are contradictory and there is no clear
Currently, there is still a lack of effective drugs in the pharma-
cotherapy of schizophrenia and the existing drugs have many side ef-
fects. The minimization of negative and cognitive symptoms seems to
be a particularly difficult problem. Therefore, new drug candidates are
still being sought, with a goal of achieving higher efficacy and mini-
mized side effects.1 The most important receptor targets in the treat-
ment of schizophrenia include the dopamine D2 receptors.2 Some re-
ports suggest that an effective antipsychotic drug should possess 5-HT2A
serotonin receptor antagonist profile in addition to the blockade of
dopamine D2R, due to the synergistic effect of the D2/5-HT2A antago-
nists.3,4 In mitigating the symptoms of schizophrenia, the effect of
partial 5-HT1AR agonism is also beneficial, resulting in the reduction of
aggressive behaviors and depressive states,5 but also antagonism at 5-
evidence of their importance and the effectiveness of their ligands in
the treatment of psychiatric conditions.8 In search of antipsychotics,
one of the leading strategies is to look for multifunctional ligands with
high affinity for several receptor targets.9 An example of a multifunc-
tional antipsychotic drug is lurasidone, long chain arylpiperazine
(LCAP) compound, introduced to the US market in 2010 (Fig.1). This
drug is characterized by high affinity for D2, D3, 5-HT1A, 5HT2A, 5-HT7
receptors.10 In current studies, it has been shown that it is highly ef-
fective in the treatment of schizophrenia and certain types of depres-
sion, including bipolar depression. In addition, this drug does not cause
a large number of side effects.11
There is no data on significant lurasidone binding with 5-HT6R in
the literature. Due to the efficacy of the lurasidone pharmacological
profile in the treatment of schizophrenia and role of 5-HT6R in relieving
HT6 and 5-HT7 receptors,7 because of improvement of cognitive
6
⁎ Corresponding author.
E-mail address: przemyslaw.zareba@doktorant.pk.edu.pl (P. Zaręba).
https://doi.org/10.1016/j.bmc.2020.115459
Received 4 October 2019; Received in revised form 17 February 2020; Accepted 16 March 2020
0968-0896/©2020TheAuthor(s).PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCCBYlicense
(http://creativecommons.org/licenses/BY/4.0/).
Pleasecitethisarticleas:PrzemysławZaręba,etal.,Bioorganic&MedicinalChemistry,https://doi.org/10.1016/j.bmc.2020.115459

P. Zaręba, et al.
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2. Results and discussion
The aim of the study was to synthesize lurasidone derivatives,
showing the increased affinity for 5-HT6R and reduced toward 5-HT7R.
The biological activity of the compounds (affinity for D2, 5-HT1A, 5-
HT2A, 5-HT6, 5-HT7 receptors) was determined in in vitro radioreceptor
assays. In the context of the interesting properties of LCAP having hexyl
carbon linker15–17 as the hit, we chose the structure 1a (3aR,4S,7R,7aS)-
3a,7a-dimethylhexahydro-1H-4,7-methano-isoindole-1,3(2H)-dione
(shown in Fig.3). As we showed in our previous publications, a change
in the length of the carbon chain can lead to a change in the activity
profile. This compound is a derivative of lurasidone with a flexible,
elongated linker. We also planned modifications of the chosen hit 1a
structure, after molecular modeling, using structural fragments from
other known drugs or drug candidates (trazodone, aripiprazole,18 fli-
banserin,19 NAN-190,20 fananserin21), and groups derived from them.
The compounds were obtained according to the previously developed,
universal method of microwave assisted synthesis, using phase transfer
catalysts (PTC).15–17,22,23
Fig. 1. The structure of lurasidone.
cognitive symptoms, it seems reasonable to search for ligands ex-
hibiting a similar receptor profile as lurasidone, while simultaneously
binding strongly with 5-HT6R. Moreover, considering the ambiguities
associated with the role of 5-HT7R in the treatment of schizophrenia, it
seems interesting to design a compound with a similar pharmacological
profile as lurasidone, which does not bind to 5-HT7R. This type of ap-
proach can help determine the role of the 5-HT7R in the treatment of
schizophrenia.
Previous research on derivatives of lurasidone described the influ-
ence of the used carbon linker on the affinity of the drug analogs for D2/
5-HT2AR. Compounds having C3-C5 carbon chains were tested. It
turned out that a butyl chain has optimal length of the alkyl chain,
while its stiffening with the cyclohexyl ring increases the selectivity
towards the D2/5-HT2A receptors. A group of amide and imide deriva-
tives of 3-(4-butylpiperazin-1-yl)-1,2-benzothiazole was also tested. The
arylpiperazine and imide fragments were chosen because of their fitting
The hit compound 1a was obtained as a result of a two-step
for the D2 receptor binding pocket and the binding inhibition (%) D2/5-
12
HT2A
.
On the basis of the reference literature and the structures of
other antipsychotic drugs perospirone and ziprasidone13 (Fig. 2), it can
be concluded that the strong binding of these compounds toward many
serotonin receptors (in particular 5-HT2AR and 5-HT7R) and the dopa-
mine D2R is influenced by the benzo[d]isothiazol-3-yl)piperazine group
(red marked, Fig. 1).
Other studies have described the pharmacological profile of a large
group of aryl sulfonamide LCAP derivatives, having a fragment of benzo
[d]isothiazol-3-ylpiperazine (red marked, Fig.1) in the structure. These
compounds were tested for binding toward the 5-HT2A, 5-HT6, 5-HT7
and D2 receptors.14 Most compounds showed high affinity for all of the
listed targets. However, none of the tested compounds showed high
binding to the 5-HT2A, 5-HT6 and D2 receptors in the absence of affinity
for 5-HT7R.15 In consideration of the previous research findings, a good
fit of the benzo[d]isothiazol-3-ylpiperazine moiety for the 5-HT6R
binding pocket was associated with high affinity to 5-HT6R, however it
was also related with strong binding toward 5-HT7R.
To build on previous research, we chose a compound with moiety’s
Fig. 3. Modification plan of the hit structure 1a.
derived from the lurasidone as
a basic structure (hit), i.e.
(3aR,4S,7R,7aS)-3a,7a-dimethylhexahydro-1H-4,7-methanoisoindole-
1,3(2H)-dione (blue marked, Fig.1) and 3-(piperazin-1-yl)-1,2-ben-
zothiazole (red marked, Fig.1). Bearing in mind the interesting prop-
erties of LCAP with a hexyl carbon chain, in particular their high affi-
nity for 5-HT1AR, as previously published,15–17 we decided to choose a
hexyl chain as a linker. In our study, we focused on the search for li-
gands with a similar binding profile to lurasidone, however, with the
increased affinity for 5-HT6R and reduced affinity toward 5-HT7R.
Fig. 2. The structure of perospirone and ziprasidone.
Scheme 1. Preparation of I group of compounds.
2

P. Zaręba, et al.
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synthesis (scheme 1), including N-alkylation of (3aR,4S,7R,7aS)-3a,7a-
dimethylhexahydro-1H-4,7-methanoisoindole-1,3(2H)dione (2a) by
1,6-dibromohexane (3). In the next step, the resulting intermediate (4a)
was condensed with 3-(piperazin-1-yl)-1,2-benzothiazole (5a). The re-
actions were carried out in the presence of microwave radiation, using
K2CO3 as a basic agent, tetra-n-butylammonium bromide (TBAB) as
PTC, and a small amount of dimethylformamide (DMF).
Molecular docking for D2R (pdb ID: 6CM4), and homology models
of 5-HT1A, 5-HT2A, 5-HT7 receptors (Fig. 4) and 5-HT6R (Fig. 5) were
performed to identify the binding mode of the compound 1a. For all
receptors, the presence of a salt bridge between the protonated basic
nitrogen atom in the piperazine ring and the residues Asp3.32 were
observed. The next interactions emerging in all cases were the π-π in-
teractions between the 1,2-benzothiazole group and the Phe6.51 and
Phe6.52 residues. The arrangement of this part of the ligand is very well
suited to the size of the binding pocket and consistent with the data
presented in the previous publication.24
The hit compound 1a showed a similar activity profile compared to
lurasidone (Table 1). The compound had a slightly lower affinity for 5-
HT1A, 5-HT2A and 5-HT7 receptors, with an increased affinity toward
D2R. The compound 1a showed a relatively low affinity for the 5-HT6R.
Table 1
Affinity of lurasidone10 and obtained derivatives (I group) for the tested receptors, Ki [nM]. Each compound was tested in triplicate at 8 different concentrations
(10−4 to 10−11 M).
No.
Ar
D2
5-HT1A
5-HT2A
2.03 0.46
5-HT6
5-HT7
0.5 0.09
lurasidone10
1.68
1
0.09
0.2
6.75
0.97
–
1a
27
4
4
1
486
86
9
2
1b
1c
35
4
12
18
2
4
541
81
69
5
1641
1142
213
136
198
39
29
225
370
38
41
5
1d
1e
55
32
7
4
73
6
3028
536
299
62
202
117
31
9
55
7
161
22
1f
168
41
17
5
22
4
3
189
785
23
2205
4874
251
627
53
4
1g
1
151
146
18
Fig. 4. Docking of 1a to the receptors: (a) 5-HT1A, (b) 5-HT2A, (c) 5-HT7, (d) D2. The yellow lines indicate the hydrogen bonds. Nitrogen – blue, sulfur – yellow,
oxygen – red, green – 1a.
3

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The differences appear in the bending of the alkyl chain and the
terminal imide group. In the structure of lurasidone, a straight ar-
rangement of the alkyl chain was described, where the imide group was
directed towards helix 1 and 2. In hit 1a, the bending of the imide group
towards helix 6 and 7 was observed. Ligand 1a had a slightly lower
affinity for 5-HT1AR than 5-HT2A, 5-HT7 and D2 receptors. This can be
explained by the occurrence of additional hydrogen bonds, in which
imide carboxylic groups are involved (5-HT2A, 5-HT7, D2 receptors).
In the case of the 5-HT6R, 1a binding mode was compared with
lurasidone and a phthalimide analogue. Interestingly, in the case of
compounds having no aromatic rings in the terminal part, a different
conformation of the 1,2-benzothiazole groups were observed.
Moreover, in the hit structure, there was a different bending of the
imide moiety in the terminal part of the binding pocket (similar ar-
rangement was noted for other hit analogues, without aromatic group in
the terminal part, e.g. hexyl perospirone analog). Straight binding
modes were observed for the compounds with shorter linkers, or aro-
matic imides in the terminal part. However, lurasidone (and other
compounds with short linkers), showed repulsive interactions with
Asn86 residue.
Fig. 6. The second group of compounds.
affinity for the 5-HT2AR. Interestingly, the profile of activity changed
very clearly and regularly, when the position of the substituent in the
aryl part was changed. In the presented group, two dual ligands for 5-
HT1A/D2 receptors (1b, 1g) and two dual 5-HT1A/5-HT7R ligands (1c,
1f) were distinguished. However, the compound 1a showed the highest
(albeit relatively low) affinity for 5-HT6R. Therefore, in the next part of
the work, we decided to synthesize a group of 3-(4-hexylpiperazin-1-
yl)-1,2-benzothiazole derivatives, as shown in Fig.6. The planned
compounds had aromatic moieties in the terminal part due to the high
affinity for 5-HT6R, which was previously determined in molecular
modeling.
Fig. 5. Docking of 1a (green), lurasidone (purple) and phthalimide analogue
(yellow) to the receptor 5-HT6. Nitrogen – blue, sulfur – yellow, oxygen – red.
Receptor surface – blue represents a positive charge, red – negative charge.
Based on the conducted molecular modeling, it was found that the
aromatic group in the terminal part may be used to increase the affinity
of flexible, hexyl derivatives for 5-HT6R. In the second part of the study,
we decided to investigate two groups of hexyl lurasidone analogs.
Structural modifications were performed as shown in Fig.3, using the
compound 1a as the base structure, whereas the fragments introduced
in the modifications were derived from known LCAP compounds (tra-
zodone, flibanserin, NAN-190, fananserin, aripiprazole) and from re-
lated moieties. In the first group, several analogs of the compound 1a
were obtained, with the selected arylpiperazine fragments. The
common part is marked in blue. Modifications in the arylpiperazine
moiety were introduced to assess whether the 1,2-benzothiazole group
was crucial in the context of the multifunctionality of the hexyl deri-
vatives of lurasidone.
The compounds 1h-1r were obtained as a result of a two-step
The compounds 1b-g were prepared according to the procedure
analogous to the compound 1a, including N-alkylation of
(3aR,4S,7R,7aS)-3a,7a-dimethylhexahydro-1H-4,7-methanoisoindole-
1,3(2H)-dione (2a) by 1,6-dibromohexane (3) and condensation of the
resulting intermediate (4a) with the selected arylpiperazine (5b-5 g) in
the presence of microwave radiation (Scheme 1).
In the first group, the compounds were distinguished by a markedly
higher selectivity, as compared to the hit 1a, in particular toward the 5-
HT1A receptors (Table 1). The compounds with a substituent on the aryl
group in 2nd position showed the highest affinity for the D2R (1b, 1e,
1g). The placement of the substituent at the 3rd position in the aromatic
ring resulted in an increased affinity for the 5-HT7R (1c, 1e, 1f). Sub-
stitution in the 4th (1d) or 3rd (1c) position resulted in the highest
Scheme 2. Preparation of compounds 1 h-1r from group II.
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P. Zaręba, et al.
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synthesis (scheme 2), including the N-alkylation, O-alkylation or S-
alkylation of the corresponding heterocycles (2h-2p) or sulfonamides
(2q, 2r) with 1,6-dibromohexane (3). The next step was condensation
of the resulting intermediate (4h-4r) with 3-(piperazin-1-yl)-1,2-
benzothiazole (5a). The reactions were carried out in the presence of
microwave radiation, using K2CO3 as a basic agent, TBAB as a PTC
and small additions of DMF or acetonitrile (ACN).
The compound 1s was obtained as a result of a three-step synth-
esis26 (Scheme 3), including N-alkylation of 1-(prop-1-en-2-yl)-1,3-
dihydro-2H-benzimidazol-2-one (2x) by 1,6-dibromohexane (3). The
next step was condensation of the resulting intermediate (4x) with 3-
(piperazin-1-yl)-1,2-benzothiazole (5a). In the final step, deprotec-
tion of the protected 1,3-dihydro-2H-benzimidazol-2-one derivative
(1x) by adding 4 M HCl in dioxane was performed.
The compounds numbered 1t-1w were obtained from compound
1h by a two-step reaction (scheme 4), involving the preparation of
amine 6 in the Gabriel reaction using methylamine27 followed by
condensation of the resulting amine with the corresponding ar-
ylsulfochloride (7u-7w) or arylacylchloride (7t) in the presence of
triethylamine.28
The substitution of the group (3aR,4S,7R,7aS)-3a,7a-di-
methylhexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione with an-
other imide group (1h, 1o) resulted in a decrease in 5-HT7R affinity
with a simultaneous increase of the affinity for 5-HT6R, which was
desirable in the context of this work. A much more favorable profile
was exhibited by 1h, which had a small decrease in the affinity for 5-
HT2AR and D2R as compared to 1a. The use of amide groups (1m)
caused lower affinity for all receptors, without changing the activity
profile. The compound with a benzamide moiety in the terminal part
(1t) showed the increased affinity for 5-HT6R. Very interesting
properties were exhibited by the compounds having in their structure
cyclic urea moieties (1i, 1p, 1s). The compounds 1p and 1s showed a
similar activity profile compared to 1a, with a small increase in 5-
HT6R affinity (Table 2).
Scheme 3. Preparation of compound 1 s from group II.
Scheme 4. Preparation of compounds 1 t-1w from group II.
Table 2
Affinity of obtained compounds (II group) for the tested receptors, Ki [nM]. Each compound was tested in triplicate at 8 different concentrations (10−4 to 10−11 M).
No.
R1
D2
5-HT1A
5-HT2A
5-HT6
5-HT7
1h
10
2
18
3
24
2
160
33
114
17
93
1i
1j
9
2
11
5
3
5
6
1
2
252
189
43
35
747
7
16
1
2
2
1k
1l
33
39
4
5
10
20
3
6
13
20
4
302
805
81
97
72
9
3
387
61
1m
1n
56
18
8
3
71
63
6
8
55
32
4
568
158
117
18
36
8
5
105
14
1o
1p
59
7
86
12
7
53
12
3
2
110
379
20
47
118
16
22
3
1
0.3
44
(continued on next page)
5

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Table 2 (continued)
No.
1q
R1
D2
5-HT1A
5-HT2A
5-HT6
1103
5-HT7
193
164
12
42
5
65
8
141
32
1r
1s
106
16
9
1
32
16
3
3
26
6
2
772
189
82
35
54
7
6
1
2
1t
1u
1v
14
31
31
3
7
2
22
8
4
4
3
221
317
52
42
23
7
99
37
30
8
6
4
1
15
7
39
8
63
15
9
1w
27
4
73
11
44
57
4
31
6
The compound 1i was particularly interesting, as it exhibited a very
close affinity (compared to 1a) for the 5-HT1A, D2 and 5-HT2A receptors
and an almost twofold increase in the affinity for 5-HT6R, with a very
low binding with 5-HT7R compared to 1a.
the second group, 12 compounds with an increased affinity for 5-HT6
receptors were obtained in comparison to hit 1a. In the context of high
binding for 5-HT6R, while maintaining a high affinity for other re-
ceptors, 1v and 1w had the most beneficial properties. The compound
1i appears to be particularly interesting in the context of this work,
showing a similar activity profile compared to the 1a, while at the same
time strongly reducing the affinity for 5-HT7R and moderate increase in
the affinity for 5-HT6 R.
Among the naphthyl sulfonamide derivatives 1n, 1v, 1w, some
decrease in the affinity for the D2, 5-HT1A, 5-HT2A and 5-HT7 receptors
can be observed. The compounds remain active in the said region, but
also showed a much higher affinity for the 5-HT6R compared to the 1a.
Interestingly, the use of a stiffened naphthalene sulfonamide moiety
(1n) caused a threefold decrease in 5-HT6R affinity in comparison with
other naphthalenesulfonamide derivatives (1v, 1w). Phenyl sulfona-
mide derivatives (1q, 1u, 1r) are characterized by a decrease in the
binding towards D2 and 5HT7 receptors, as well as a significant de-
crease in the affinity for 5-HT6R (except for 1u). 1j shows an increase in
5-HT1AR, 5-HT6R and 5-HT7R affinity compared to 1a, with a decrease
in binding toward D2R. The compound 1l showed a high affinity for 5-
HT1AR, 5-HT2AR and D2R with a low affinity for 5-HT6R and 5-HT7R. In
In the context of binding for 5-HT6R, the best results were obtained
for naphthalenesulfonamide compounds 1v and 1w. Interestingly, 1n,
with the stiffened naphthalene sulfonamide fragment showed a sig-
nificant decrease in the affinity for the 5-HT6R. Its imide analog, 1o,
showed a slightly higher affinity for 5-HT6R. We decided to investigate
this with molecular docking methods (Fig.7). We performed docking
using the homology 5-HT6 receptor model (template 5-HT2A, pdb ID:
6A94).
Fig. 7. Docking of a) 1v, b) 1n, for 5-HT6R and a comparison of binding modes and the possibility of occurrence of intramolecular hydrogen bonds in 1v and 1n. The
yellow lines indicate the hydrogen bonds. Nitrogen – blue, sulfur – yellow, oxygen – red, turquoise – 1v, violet – 1n.
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For the naphthalenesulfonamide 1v (Fig.7a) and the stiffened 1n
3. Conclusion
(Fig.7b), a similar arrangement of the arylpiperazine moiety in the 5-
HT6R binding pocket was observed. In both cases, the ligands showed
the ability to form a salt bridge between the nitrogen atom in the pi-
perazine structure and the residue Asp106. Interestingly, both com-
pounds were involved in the formation of π-π interactions in the 3-
(piperazin-1-yl)-1,2-benzothiazole part with the residues Phe284 and
Phe285. The differences between the ligands were found in the bending
of the naphthalenesulfonamide group. In the case of the compound 1v,
this group was arranged in the direction of helices 1 and 2, while in 1n
it bent towards the helix 6. Both ligands demonstrated the ability to
form a hydrogen bond of the sulphonyl group with Arg181. In 1v, an
additional hydrogen bond was observed between the NH group in the
sulfonamide structure and Asp303. The ability to form intramolecular
hydrogen bonds in the arylsulfonamide fragment may also affect the
affinity of 5-HT6R.25 In 1v, the probability of occurrence of this type of
binding was much greater than in the case of 1n, which was confirmed
by the geometry of the hypothetical hydrogen bond (Fig.7c.). These
observations are consistent with the theory presented previously.25
Most of the compounds in group II showed a high or moderate af-
finity for 5-HT7R. The exception here was the compound 1i, which was
particularly interesting in the context of this work. The molecular
In summary, the hit compound, which was a flexible, hexyl analog
of lurasidone, had a similar binding profile to the mentioned drug. In
1a, high binding for D2 and 5-HT2A receptors was maintained with a
small decrease in the affinity for 5-HT1A and 5-HT7 receptors. The
studies focused on the search for lurasidone analogs with the increased
affinity for 5-HT6R and reduced to 5-HT7R. Unfortunately, no com-
pound was obtained that showed complete reversal of 5-HT6/5-HT7R
activity. However, compounds with partial reversal of activity were
obtained, and the relation between this effect and the structural mod-
ifications create a field for further studies.
In the context of the binding toward 5-HT6R, the hit showed rela-
tively low affinity. The presence of the 1,2-benzothiazole moiety proved
to be crucial for the binding toward this receptor. In the group of de-
rivatives of the aforementioned arylpiperazine, the most active com-
pounds turned out to be the ones with a naphthalenesulfonamide
fragment (1v and 1w) in their structure, while the use of a stiffened
naphthalenesulfonamide fragment (sultam; 1n) caused a three-fold
decrease in affinity. High binding with this type of compounds may
result from the good alignment of the said arylpiperazine for the 5-
HT6R binding pocket, hydrogen bonds stabilizing the receptor-ligand
complex, but also the possibility of intramolecular hydrogen bonds in
the naphthalenesulfonamide fragment. The latter fact may explain the
higher affinity of 1v and 1w compounds compared to 1n, and also
remains in accordance with previously published reports.25 Interest-
ingly, the 1,2-benzothiazole group was also of key importance in the
context of the binding toward 5-HT7R. Among the tested compounds,
one (1i) was found which, despite the presence of the said moiety,
showed a low affinity for 5-HT7R, with moderate affinity for 5-HT6R. In
this compound, the affinities for the D2, 5-HT1A and 5-HT2A receptors
remained at a very high level. Low binding with the 5-HT7R was dis-
cussed, emphasizing the different bending of the triazolopyridinone
group, as compared to the conformations of the active compounds. All
compounds were obtained using the previously developed ecological
method of the synthesis in the microwave radiation field, which con-
firmed its versatility in obtaining differentiated LCAP libraries. The
development of the new analogs of currently used drugs with an altered
activity profile may help to assess the actual importance of some re-
ceptor targets in the treatment of CNS disorders.
docking to the 5-HT7 receptor (homology modeling, template 5-HT1B
;
pdb ID: 6G79) was performed to compare the binding mode of active
compounds (1a – bright green, 1m – blue, 1p – pink, 1s – brown) and
inactive (1i – dark green) (Fig.8).
In the arylpiperazine fragment, all compounds exhibited similar
alignment as previously described for the compound 1a. In the com-
pound 1i, the piperazine nitrogen atom was the furthest away from
Asp162, which could reduce the possibility of hydrogen bonding. The
biggest differences were observed in the bending of the terminal
groups. For the active compounds, the arrangement of the terminally
located groups were identical. Polar interactions (hydrogen bonds) with
Trp148 were observed. The inactive compound strongly bent towards
helices 2 and 3, which may explain its low binding with 5-HT7R.
4. Experimental section
4.1. Chemistry
The microwave-assisted reactions were carried out in the CEM
Discover microwave reactor (100 W). All chemicals were purchased
from Sigma Aldrich and all solvents used in the synthesis were from
POCH. Thin-layer chromatography (TLC) was preformed using chlor-
oform:methanol as an eluent, in the ratio of 9:1, on Sigma Aldrich
sheets (silica gel on aluminium, with fluorescent indicator 254 nm,
200 µm layer thickness, 60 Å pore diameter, 8.0–12.0 µm particle size)
and UV light with a wavelength of 254 nm was used for the analysis.
High-performance liquid chromatography (HPLC) was performed on
a Perkin Elmer Series 200 HPLC (XTerra RP C-18, 3.5 µm seed size,
4.6 × 150 mm) column and MeOH:H2O 1:1 eluent acidified with 0.1%
formic acid. The melting points were measured using a Boëtius appa-
ratus. IR spectra were taken on an FTS-165 spectrometer. 1H NMR
Fig. 8. Docking of selected ligands, for 5-HT7R. The yellow lines indicate the
hydrogen bonds. Nitrogen – blue, sulfur – yellow, oxygen – red, 1a – bright
green, 1 m – blue, 1p – pink, 1 s – brown, 1i – dark green.
7

P. Zaręba, et al.
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spectra were recorded on Bruker Avance 400 MHz spectrometer, using
TMS as an internal reference. The LC-MS system consisted of a Waters
Acquity UPLC system coupled to a Waters TQD mass spectrometer
(electrospray ionization mode ESI-tandem quadrupole). The analyses
were carried out using an Acquity UPLC BEH C18, 1.7, 2.1 × 100 mm
column.
J = 8.4, 6.7 Hz, 2H, CHAliph), 2.01–1.40 (m, 8H, CHAliph), FT-IR: 3176
(NeH Amine, Str), 3030 (CeH Ar, Str), 2969; 2936; 2858 (CeC Aliph, Str),
1747 (C]O, Str), 1502; 1485 (C]C Ar, Str), 1366 (CeN, Str), UPLC-MS:
329.17 (M + 1, 20) 328.17 (M, 100), 327.17 (M−1, 23), 326.17 (M−2,
97), HPLC: Rt = 12.18 min, P = 100%, TLC: Rf = 0.90, mp = 115 °C,
Y = 90%.
4.1.1. Synthesis of intermediates 4a, 4h-4r
4.1.1.7. 1-(6-bromohexyl)benzo[cd]indol-2(1H)-one 4m. Molecular formula:
A mixture of heterocycle 2a, 2h-2p, 2x or sulfonamide 2q, 2r
(0.001 mol) with 0.414 g of K2CO3 (0.003 mol) and 0.032 g of TBAB
(0.0001 mol) were triturated in a mortar. The triturated mixture was
transferred to a round bottom flask, after which 0.46 cm3 (0.003 mol)
of 1,6-dibromohexane (3) and 0.2 cm3 of ACN or DMF was added. The
reactions were carried out for 30 s in a CEM Discover microwave re-
actor at 100 W output power. After the reaction had been completed,
40 cm3 of water was added to the mixture and extracted with methy-
lene chloride. After the distillation of methylene chloride, the product
was macerated in 20 cm3 of hexane to get rid of the excess 1,6-di-
bromohexane (3). The reaction yields for each product were calculated
on the basis of the weight of the obtained product.
C
17H18BrNO, 1H NMR (400 MHz, CDCl3) δ 8.09 (d, J = 7.0 Hz, 1H, ArH),
8.07–8.01 (m, 1H, ArH), 7.76–7.72 (m, 1H, ArH), 7.56 (d, J = 8.4 Hz, 1H,
ArH), 7.52–7.46 (m, 1H, ArH), 6.94 (d, J = 6.9 Hz, 1H, ArH), 3.99–3.93
(m, 2H, CONCH), 3.44–3.40 (m, 2H, BrCHAliph), 1.89–1.80 (m, 4H, CHAliph),
1.50–1.41 (m, 4H, CHAliph), FT-IR: 3055 (CeH Ar Str), 2932; 2857 (CeH
Aliph, Str), 1694 (C]O, Str), 1602; 1495 (C]C Ar, Str), 1373 (CeN, Str),
773 (C-Br, Str), HPLC: Rt = 4.05 min, P = 88%, TLC: Rf = 0.90, mp = oil,
Y = 78%.
4.1.1.8. 2-(6-bromohexyl)–2H-naphtho[1,8-cd]isothiazole1,1-dioxide
4m. Molecular formula: C16H18BrNOS, 1H NMR (400 MHz, CDCl3) δ
8.08–8.00 (m, 1H, ArH), 7.98–7.91 (m, 1H, ArH), 7.77–7.72 (m, 1H,
ArH), 7.62–7.51 (m, 1H, ArH), 7.46 (t, J = 9.4 Hz, 1H, ArH), 6.75–6.68
(m, 1H, ArH), 3.86 (t, J = 7.3 Hz, 2H, SONCH), 3.44 (t, J = 6.7 Hz, 2H,
BrCHAliph), 1.95–1.86 (m, 4H, CHAliph), 1.61–1.53 (m, 4H, CHAliph), FT-
IR: 3060 (CeH Ar, Str), 2933; 2856 (CeH, Aliph, Str), 1591; 1492
(C]C Ar, Str), 1371 (CeN, Str), 1348 (S]O, Str), 851 (NeS, Str), 756
(C-Br, Str), HPLC: Rt = 4.12 min, P = 95%, TLC: Rf = 0.90, Y = 67%.
4.1.1.1. (3aR,4S,7R,7aS)-2-(6-bromohexyl)-3a,7a-dimethylhexahydro-
1H-4,7-methanoisoindole-1,3(2H)-dione
4a. Molecular
formula:
C
15H22BrNO2, 1H NMR (400 MHz, DMSO) δ 3.51 (t, J = 6.7 Hz, 2H,
CONCH), 3.40 (s, 2H, BrCHAliph), 3.32 (t, J = 7.3 Hz, 2H, CHAliph),
2.65–2.57 (m, 2H, CHAliph), 2.53–2.46 (m, 4H, CHAliph), 1.81–1.71 (m,
2H, CHAliph), 1.65–1.49 (m, 2H, CHAliph), 1.48–1.11 (m, 5H, CHAliph),
1.00–0.90 (m, 1H, CHAliph), FT-IR: 3034 (CeH, Ar, Str), 2934; 2857
(CeH Aliph, Str), 1692 (C]O, Str), 1491; 1436 (C]C Ar, Str), 1342
(CeN, Str), HPLC: Rt = 5.41 min, P = 99%, TLC: Rf = 0.91, mp = oil,
Y = 79%.
4.1.1.9. 2-(6-bromohexyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione
4o. Molecular formula: C18H18BrNO2, 1H NMR (400 MHz, DMSO) δ
8.48–8.40 (m, 4H, ArH), 7.91–7.79 (m, 2H, ArH), 4.07–4.01 (m, 2H,
CONCH), 3.53 (t, J = 6.7 Hz, 2H, BrCHAliph), 1.87–1.75 (m, 2H,
CHAliph), 1.64 (dd, J = 14.7, 7.3 Hz, 2H, CHAliph), 1.40–1.33 (m, 4H,
CHAliph), FT-IR: 3061 (CeH Ar Str), 2933; 2855 (CeH Aliph, Str), 1692
(C]O, Str), 1587; 1461 (C]C Ar, Str), 1361 (CeN, Str), 779 (C-Br, Str),
HPLC: Rt = 3.85 min, P = 99%, TLC: Rf = 0.90, Y = 87%.
4.1.1.2. 2-(6-bromohexyl)isoindoline-1,3-dione 4h. Molecular formula:
C
14H16BrNO2, mp = 55–57 °C, HPLC: Rt = 7.14 min, P = 99%, TLC:
Rf = 0.90, Y = 79%.
4.1.1.3. 2-(6-bromohexyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one
4i. Molecular formula: C12H16BrN3O, 1H NMR (400 MHz, CDCl3) δ 7.78
(ddd, J = 5.5, 3.3, 2.2 Hz, 1H, ArH), 7.15–7.07 (m, 2H, ArH), 6.51
(ddd, J = 7.2, 4.4, 3.0 Hz, 1H, ArH), 4.02 (t, J = 7.1 Hz, 2H, CONCH),
3.42–3.96 (dd, J = 8.0, 5.6 Hz, 2H, BrCHAliph), 1.89 (ddd, J = 10.3,
7.3, 3.4 Hz, 4H, CHAliph), 1.55–1.48 (m, 2H, CHAliph), 1.46–1.39 (m, 2H,
CHAliph), FT-IR: 3066 (CeH Ar, Str), 2942; 2854 (CeH Aliph, Str), 1703
(C]O, Str), 1641 (C]N, Str), 1593; 1491 (C]C, Str), 1376 (CeN, Str),
HPLC: Rt = 7.31 min, P = 91%, TLC: Rf = 0.96, mp = oil, Y = 79%.
4.1.1.10. 1-(6-bromohexyl)-5,6-dihydro-1H-imidazo[4,5,1-ij]quinolin-
2(4H)-one 4p. Molecular formula: C16H21BrN2O, 1H NMR (400 MHz,
CDCl3) δ 7.00–6.91 (m, 2H, ArH), 6.85–6.77 (m, 1H, ArH), 4.39 (d,
J = 12.4 Hz, 2H, CONCH), 3.44–3.40 (m, 2H, BrCHAliph), 3.15 (s, 2H,
CHAliph), 2.84 (t, J = 6.0 Hz, 2H, CHAliph), 2.12–2.05 (m, 2H, CHAliph),
1.90– 1.85 (m, 2H, CHAliph), 1.84–1.74 (m, 2H, CHAliph), 1.40– 1.38 (m,
4H, CHAliph), FT-IR: 3059 (CeH Ar Str), 2928; 2852 (CeH Aliph, Str),
1703 (C]O, Str), 1599; 1486 (C]C Ar, Str), 1373 (CeN, Str), 780 (C-
Br, Str), HPLC: Rt = 4.17 min, P = 96%, TLC: Rf = 0.90, mp = oil,
Y = 79%.
4.1.1.4. 3-(6-bromohexyl)benzo[d]oxazol-2(3H)-one
4j. Molecular
formula: C13H16BrNO2, 1H NMR (400 MHz, CDCl3) δ 7.44–6.84 (m,
4H, ArH), 3.83 (dt, J = 17.0, 8.5 Hz, 2H, CONCH), 3.42 (t, J = 6.7 Hz,
2H, BrCHAliph), 1.97–0.96 (m, 8H, CHAliph), FT-IR: 2969; 2931; 2860
(CeC Aliph, Str), 1743 (C]O, Str), 1615 (NeH, Str), 1484 (C]C, Str),
1371 (CeN,Str), 750 (C-Br, Str), HPLC: Rt = 3.20 min, P = 90%, TLC:
Rf = 0.89, mp = 55 °C, Y = 71%.
4.1.1.11. N-(6-bromohexyl)-N-(3-(trifluoromethyl)phenyl)
benzenesulfonamide 4q. Molecular formula: C19H21BrF3NO2S, 1H NMR
(400 MHz, DMSO) δ 7.72–7.66 (m, 2H, ArH), 7.62–7.53 (m, 5H, ArH),
7.40 (d, J = 8.2 Hz, 1H, ArH), 7.34 (s, 1H, ArH), 3.66–3.57 (m, 2H,
SONCH), 3.47 (t, J = 6.7 Hz, 2H, BrCHAliph), 1.71 (dd, J = 13.5,
6.9 Hz, 2H, CHAliph), 1.31–1.25 (m, 5H, CHAliph), 1.20 (s, 1H, CHAliph),
FT-IR: 3063 (CeH Ar, Str), 2937; 2855 (CeH Aliph, Str), 1491 (C]C
Ar, Str), 1370 (CeN, Str), 1326 (S]O, Str), 1232 (C-F, Str), 786 (C-Br,
Str), 690 (SeN, Str), 651 (CeS, Str), HPLC: Rt = 7.15 min, P = 99%,
TLC: Rf = 0.95, mp = 57–58 °C, Y = 81%.
4.1.1.5. 2-((6-bromohexyl)thio)benzo[d]oxazole 4 k. Molecular formula:
C
14H16BrNOS, 1H NMR (400 MHz, DMSO) δ 7.74–7.50 (m, 2H, ArH),
7.40–7.19 (m, 2H, ArH), 3.65–3.20 (m, 2H, SCHAliph), 2.67–2.39 (m,
2H, BrCHAliph), 1.96–0.84 (m, 8H, CHAliph), FT-IR: 3090 (CeH Ar, Str),
2970; 2934; 2856 (CeC Aliph), 1738 (C]O, Str), 1589; 1491 (C]C Ar,
Str), 1380 (CeN, Str), HPLC: Rt = 3.83 min, P = 99%, mp = 76 °C,
Y = 67%.
4.1.1.12. N-(6-bromohexyl)-4-methyl-N-phenylbenzenesulfonamide
4r. Molecular formula: C19H24BrNO2S, 1H NMR (400 MHz, DMSO) δ
7.43 (dd, J = 8.2, 6.2 Hz, 2H, ArH), 7.40–7.35 (m, 3H, ArH), 7.35–7.31
(m, 2H, ArH), 7.08–6.98 (m, 2H, ArH), 3.51 (d, J = 6.2 Hz, 2H,
SONCH), 3.47 (t, J = 6.7 Hz, 2H, BrCHAliph), 1.71 (dd, J = 13.6,
6.8 Hz, 2H, CHAliph), 1.51–1.44 (m, 3H, CHAliph) 1.29–1.20 (m, 5H,
CHAliph), 1.18 (s, 1H, CHAliph), FT-IR: 3030 (CeH Ar, Str), 2926; 2863
(CeH Aliph, Str), 1489 (C]C Ar, Str), 1384 (CeN, Str), 1342 (S]O,
4.1.1.6. 6-((6-bromohexyl)oxy)-3,4-dihydroquinolin-2(1H)-one
4l. Molecular formula: C15H20BrNO2, 1H NMR (400 MHz, CDCl3) δ 9.11 (s,
1H, NH), 6.89–6.60 (m, 3H, ArH), 3.93 (t, J = 6.4 Hz, 2H, OCHAliph), 3.44
(t, J = 6.8 Hz, 2H, BrCHAliph), 3.02–2.88 (m, 2H, CONCH), 2.63 (dd,
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Str), 744 (C-Br, Str), 695 (SeN, Str), 655 (CeS, Str), HPLC:
Str), HPLC: Rt = 2.63 min, P = 94%, TLC: Rf = 0.65, mp = 184–186 °C,
Rt = 7.80 min, P = 91%, TLC: Rf = 0.95, mp = 54–55 °C, Y = 72%.
Y = 71%.
4.1.1.13. 1-(6-bromohexyl)-3-(prop-1-en-2-yl)-1H-benzo[d]imidazol-
2(3H)-one 4x. Molecular formula: C16H21BrN2O, 1H NMR (400 MHz,
CDCl3) δ 7.17–6.96 (m, 4H, ArH), 5.41–5.15 (m, 2H, isopropenyl-CH2),
3.96–3.81 (m, 2H, CONCH), 3.40 (dt, J = 13.5, 6.8 Hz, 2H, BrCHAliph),
2.28–2.18 (s, 3H, isopropenyl-CH3), 1.93–1.73 (m, 4H, CHAliph),
1.57–1.34 (m, 4H, CHAliph), FT-IR: 3062 (CeH Ar, Str), 2956; 2935;
2854 (CeC Aliph, Str), 1624; 1485 (C]C, Str), 1402; 1377; 1363 (CeN,
Str), P = 95%, TLC: Rf = 0.85, mp = 75 °C, Y = 40%.
4.1.2.4. (3aR,4S,7R,7aS)-2-(6-(4-(4-chlorophenyl)piperazin-1-yl)hexyl)
qhexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione 1d. Molecular formula:
C
25H34ClN3O2, 1H NMR (400 MHz, DMSO) δ 7.29 (d, J = 9.0 Hz, 2H, ArH),
7.02 (d, J = 9.1 Hz, 2H, ArH), 3.80 (d, J = 10.2 Hz, 2H, CONCH),
3.59–3.48 (m, 2H, CHPip), 3.34 (t, J = 7.2 Hz, 2H, CHPip), 3.23–2.99 (m,
6H, CHPip, CHAliph), 2.71–2.63 (m, 2H, CHAliph), 2.38–2.29 (m, 1H, CHAliph),
2.09 (s, 1H, CHAliph), 1.70 (s, 2H, CHAliph), 1.57 (d, J = 7.8 Hz, 2H, CHAliph),
1.47 (dd, J = 14.3, 7.2 Hz, 2H, CHAliph), 1.41–1.19 (m, 6H, CHAliph), 1.16
(d, J = 10.7 Hz, 1H, CHAliph), 0.97 (d, J = 10.9 Hz, 1H, CHAliph), FT-IR:
3057 (CeH Ar, Str), 2944; 2874 (CeH Aliph, Str), 1693 (C]O Str), 1491;
1455 (C]C Ar, Str), 1364 (CeN, Str), 711 (C-Cl, Str), HPLC: Rt = 3.39 min,
P = 96%, TLC: Rf = 0.64, mp = 146–149 °C, Y = 70%.
4.1.2. Synthesis of compounds (1a-1r)
A mixture of 6-bromohexylated derivative 4a/4r-4h (0.001 mol), ar-
ylpiperazine 4a-g (0.00095 mol), 0.414 g of K2CO3 (0.003 mol) and 0.032 g
of TBAB (0.0001 mol) were triturated in a mortar. The triturated mixture
was transferred to a round bottom flask, and 0.2 cm3 of ACN, or DMF was
added. The reactions were carried out for 60 s in a CEM Discover micro-
wave reactor at 100 W output power. The progress of the reaction was
monitored by TLC. After the reaction had been completed, 40 cm3 of water
was added to the mixture and placed in the refrigerator overnight. After
cooling, the crude product was filtered off. In the absence of the required
purity, the crude product was crystallized from methanol or methanol–-
water. After obtaining a minimum of 95% purity, the compounds were
dissolved in acetone, then converted to hydrochlorides by 4 M HCl in di-
oxane. The reaction yields for individual compounds were calculated on the
basis of the weight of the obtained hydrochloride.
4.1.2.5. (3aR,4S,7R,7aS)-2-(6-(4-(2,3-dichlorophenyl)piperazin-1-yl)
hexyl)hexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione 1e. Molecular
formula: C25H33Cl2N3O2, 1H NMR (400 MHz, DMSO) δ 7.42–7.33 (m,
2H, ArH), 7.23 (dd, J = 7.4, 2.1 Hz, 1H, ArH), 3.61 (t, J = 6.6 Hz, 2H,
CONCH), 3.57–3.49 (m, 2H, CHPip), 3.45 (d, J = 12.1 Hz, 2H, CHPip),
3.21–3.14 (m, 4H, CHPip), 1.74–1.70 (m, 2H, CHPip), 1.68–1.64 (m, 2H,
CHAliph, 1.56–1.50 (m, 4H, CHAliph), 1.46–1.41 (m, 2H, CHAliph),
1.40–1.35 (m, 2H, CHAliph), 1.31–1.28 (m, 4H, CHAliph), 1.24 (d,
J = 7.0 Hz, 2H, CHAliph), 1.15 (d, J = 10.7 Hz, 1H, CHAliph),
1.00–0.95 (m, 1H, CHAliph), FT-IR: 3049 (CeH Ar, Str), 2937; 2873
(CeH Aliph, Str), 1693 (C]O Str), 1486; 1452 (C]C Ar, Str), 1373
(CeN, Str), 776 (C-Cl, Str), HPLC: Rt = 3.55 min, P = 95%, TLC:
Rf = 0.63 mp = oil, Y = 66%.
4.1.2.1. (3aR,4S,7R,7aS)-2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-
yl)hexyl)hexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione
1a. Molecular formula: C26H34N4O2S, 1H NMR (400 MHz, DMSO) δ
7.42–7.35 (m, 2H, ArH), 7.15–7.11 (m, 2H, ArH), 4.24 (d, J = 12.9 Hz,
2H, CONCH), 3.68–3.52 (m, 4H, CHPip), 3.33–3.24 (m, 2H, CHPip),
3.12–3.06 (m, 4H, CHPip), 2.65 (s, 2H, CHAliph), 1.52–1.44 (m, 8H,
CHAliph), 1.31–1.26 (m, 6H, CHAliph), 1.16 (d, J = 9.7 Hz, 1H, CHAiph),
0.96 (d, J = 9.9 Hz, 1H, CHAliph), FT-IR: 3034 (CeH Ar, Str), 2941;
2870 (CeH Aliph, Str), 1686 (C]O Str), 1630 (C]N, Str), 1477; 1430
(C]C Ar, Str), 1371 (CeN, Str), 693 (SeN, Str), 624 (CeS, Str), UPLC-
MS: 468.32 (M + 2, 5), 467.39 (M + 1, 35), 466.24 (M, 100), HPLC:
Rt = 5.80 min, P = 96%, TLC: Rf = 0.73, mp = 169–172 °C, Y = 67%.
4.1.2.6. (3aR,4S,7R,7aS)-2-(6-(4-(3-trifluoromethylphenyl)piperazin-1-
yl)hexyl)hexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione
1f. Molecular formula: C26H34F3N3O2, 1H NMR (400 MHz, DMSO) δ
7.48 (t, J = 8.0 Hz, 1H, ArH), 7.30 (d, J = 13.2 Hz, 2H, ArH), 7.17 (d,
J = 7.7 Hz, 1H, ArH), 3.97 (d, J = 10.2 Hz, 2H, CONCH), 3.60–3.49
(m, 4H, CHPip), 3.34 (t, J = 7.2 Hz, 2H, CHPip), 3.15–3.07 (m, 6H,
CHPip, , CHAliph), 2.70–2.64 (m, 2H, CHAliph), 2.39–2.30 (m, 1H,
CHAliph), 1.72 (d, J = 27.7 Hz, 2H, CHAliph), 1.57 (d, J = 7.6 Hz, 2H,
CHAliph), 1.53–1.41 (m, 2H, CHAliph), 1.41–1.24 (m, 5H, CHAliph), 1.16
(d, J = 10.9 Hz, 1H, CHAliph), 0.97 (d, J = 10.9 Hz, 1H, CHAliph), FT-IR:
3045 (CeH Ar, Str), 2933; 2871 (CeH Aliph, Str), 1695 (C]O Str),
1471; 1455 (C]C Ar, Str), 1372 (CeN, Str), 1170 (C-F, Str), HPLC:
Rt = 3.01 min, P = 95%, TLC: Rf = 077, mp = 190–191 °C, Y = 65%.
4.1.2.2. (3aR,4S,7R,7aS)-2-(6-(4-(2-chlorophenyl)piperazin-1-yl)hexyl)hexa
hydro-1H-4,7-methanoisoindole-1,3(2H)-dione 1b. Molecular formula: C25
H34ClN3O2, 1H NMR (400 MHz, DMSO) δ 7.46–7.40 (m, 1H, ArH),
7.37–7.31 (m, 1H, ArH), 7.21–7.18 (m, 1H, ArH), 7.12–7.08 (m, 1H,
ArH), 3.57 (d, J = 5.8 Hz, 2H, CONCH), 3.41 (d, J = 9.1 Hz, 2H, CHPip),
3.34 (t, J = 7.2 Hz, 2H, CHPip), 3.22–3.06 (m, 6H, CHPip, CHAliph),
2.69–2.64 (m, 2H, CHAliph), 2.50 (s, 2H, CHAliph), 1.74–1.69 (m, 2H,
CHAliph), 1.57 (d, J = 8.0 Hz, 2H, CHAliph), 1.48 (dd, J = 14.4, 7.2 Hz, 2H,
CHAliph), 1.38–1.21 (m, 6H, CHAliph), 1.16 (d, J = 10.7 Hz, 1H, CHAliph),
0.97 (d, J = 10.8 Hz, 1H, CHAliph), FT-IR: 3036 (CeH Ar, Str), 2936; 2875
(CeH Aliph, Str), 1692 (C]O Str), 1470; 1455 (C]C Ar, Str), 1362 (CeN,
Str), 764 (C-Cl, Str), HPLC: Rt = 2.73 min, P = 95%, TLC: Rf = 0.76,
mp = 189–191 °C, Y = 63%.
4.1.2.7. (3aR,4S,7R,7aS)-2-(6-(4-(2-methoxyphenyl)piperazin-1-yl)
hexyl)hexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione 1g. Molecular
formula: C26H37N3O3, 1H NMR (400 MHz, DMSO) δ 7.04–6.97 (m,
2H, ArH), 6.93–6.88 (m, 2H, ArH), 3.80 (s, 3H, OCH), 3.51–3.47 (m,
4H, CHPip), 3.34 (t, J = 7.2 Hz, 2H, CONCH), 3.28–2.93 (m, 8H, CHPip,
CHAliph), 2.71–2.62 (m, 2H, CHAliph), 1.72 (d, J = 18.5 Hz, 2H,
CHAliph), 1.57 (d, J = 7.8 Hz, 2H, CHAliph), 1.47–1.44 (m, 2H,
CHAliph), 1.30–1.21 (m, 6H, CHAliph), 1.16 (d, J = 10.8 Hz, 1H,
CHAliph), 0.97 (d, J = 10.8 Hz, 1H, CHAliph), FT-IR: 3054 (CeH Ar,
Str), 2940; 2867(CeH Aliph, Str), 1696 (C]O Str), 1453 (C]C Ar, Str),
1375(CeN, Str), 1261; 1029 (CeO, Str), UPLC-MS: 442.28 (M + 3, 5),
441.35 (M + 2, 40), 440.46 (M+, 100), HPLC: Rt = 1.92 min,
P = 97%, TLC: Rf = 0.73, mp = 147–150 °C, Y = 54%.
4.1.2.3. (3aR,4S,7R,7aS)-2-(6-(4-(3-chlorophenyl)piperazin-1-yl)hexyl)
hexahydro-1H-4,7-methanoisoindole-1,3(2H)-dione 1c. Molecular formula:
C
25H34ClN3O2, 1H NMR (400 MHz, DMSO) δ 7.27–7.19 (m, 1H, ArH),
7.09–7.03 (m, 1H, ArH), 6.97 (d, J = 8.1 Hz, 1H, ArH), 6.88 (d, J = 7.8 Hz,
1H, ArH), 3.88 (d, J = 12.6 Hz, 2H, CONCH), 3.74–3.61 (m, 8H, CHPip),
3.54 (d, J = 10.2 Hz, 2H, CHPip), 3.34 (t, J = 7.2 Hz, 1H, CHAliph),
3.22–3.05 (m, 6H, CHAliph), 2.66 (s, 1H, CHAliph), 1.72–1.69 (m, 2H,
CHAliph), 1.57 (d, J = 7.7 Hz, 1H, CHAliph), 1.49–1.44 (m, 1H, CHAliph),
1.37–1.25 (m, 4H, CHAliph), 1.16 (d, J = 10.8 Hz, 1H, CHAliph), 1.04–0.83
(m, 1H, CHAliph), FT-IR: 3051 (CeH Ar, Str), 2939; 2870 (CeH Aliph, Str),
1689 (C]O Str), 1475; 1455 (C]C Ar, Str), 1375 (CeN, Str), 787 (C-Cl,
4.1.2.8. 2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)isoindoline-
1,3-dione 1h. Molecular formula: C25H28N4O2S, 1H NMR (300 MHz,
CDCl3) δ 7.83 (dt, J = 10.2, 3.8 Hz, 4H, ArH), 7.75–7.66 (m, 2H, ArH),
7.51 (td, J = 8.2, 7.0, 1.1 Hz, 1H, ArH), 7.40 (td, J = 8.0, 7.0, 1.1 Hz,
1H, ArH), 4.24–4.03 (m, 4H, CHPip), 3.67 (t, J = 7.1 Hz, 2H, CONCH),
3.50 (d, J = 11.2 Hz, 2H, CHPip), 3.13 (dd, J = 20.2, 8.1 Hz, 2H,
CHPip), 3.03–2.91 (m, 2H CHPip), 1.95 (m, 2H, CHAliph), 1.76–1.65 (m,
2H, CHAliph), 1.61–1.35 (m, 4H, CHAliph), FT-IR: 3037 (CeH Ar, Str),
9

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2936; 2861 (CeH Aliph, Str), 1770, 1709 (C]O Str), 1612, 1591; 1560
(C]C Ar, Str), 1397, 1366 (CeN, Str), 796, 776, 743 (SeN, Str), 717,
710, 675 (CeS, Str), HPLC: Rt = 5.06 min, P = 98%, TLC: Rf = 0.56,
mp = 179–185 °C, Y = 44%.
1.73–1.63 (m, 4H, CHAliph), 1.39–1.29 (m, 4H, CHAliph), FT-IR: 3037
(CeH Ar, Str), 2945; 2842 (CeH Aliph, Str), 1708 (C]O, Str), 1642
(C]N, Str), 1540; 1471 (C]C, Str), 1371 (CeN, Str), 692 (SeN, Str),
660 (CeS, Str), UPLC-MS: 473.19 (M + 3, 10), 472.26 (M + 2, 50),
471.20 (M+, 100), HPLC: Rt = 11.16 min, P = 95%, TLC: Rf = 0.82,
mp = 193–194 °C, Y = 36%.
4.1.2.9. 2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-[1,2,4]
triazolo[4,3-a]pyridin-3(2H)-one 1i. Molecular formula: C23H28N6OS,
1H NMR (300 MHz, DMSO) δ 8.12 (t, J = 7.5 Hz, 2H, ArH), 7.84 (d,
J = 7.1 Hz, 1H, ArH), 7.63–7.55 (m, 2H, ArH), 7.47 (t, J = 7.6 Hz, 1H,
ArH), 7.22 (d, J = 3.2 Hz, 1H, ArH), 6.61 (t, J = 7.2 Hz, 1H, ArH), 4.06
(d, J = 13.7 Hz, 2H, CONCH), 3.90 (t, J = 6.8 Hz, 2H, CHPip),
3.58–3.51 (m, 2H, CHPip), 3.26––3.14 (m, 4H, CHPip), 3.12–3.08 (m,
2H, CHPip), 1.77–1.63 (m, 4H, CHAliph), 1.34–1.28 (s, 4H, CHAliph), FT-
IR: 3037 (CeH Ar, Str), 2940; 284 (CeH Aliph, Str), 1708 (C]O, Str),
1640 (C]N, Str), 1539; 1476 (C]C, Str), 1371 (CeN, Str), 692 (SeN,
Str), 665 (CeS, Str), HPLC: Rt = 8.12 min, P = 97%, TLC: Rf = 0.63,
mp = 62–64 °C (oiled), Y = 51%.
4.1.2.14. 2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)–2H-naphtho
[1,8-cd]isothiazole 1,1-dioxide 1n. Molecular formula: C27H30N4O2S2 1H
NMR (400 MHz, DMSO) δ 8.31 (d, J = 8.1 Hz, 1H, ArH), 8.25 (d,
J = 7.2 Hz, 1H, ArH), 8.17–8.10 (m, 2H, ArH), 7.93–7.88 (m, 1H, ArH),
7.64–7.57 (m, 3H, ArH), 7.48 (t, J = 7.2 Hz, 1H, ArH), 7.11 (d, J = 6.6 Hz,
1H, ArH), 4.09 (d, J = 12.8 Hz, 2H, SONCH), 3.87 (t, J = 7.3 Hz, 2H,
CHPip), 3.61–3.53 (m, 2H, CHPip), 3.39–3.30 (m, 2H, CHPip), 3.27–3.20 (m,
2H, CHPip), 3.19–3.09 (m, 2H, CHPip), 1.90–1.85 (m, 2H, CHAliph),
1.73–1.66 (m, 2H, CHAliph), 1.55–1.47 (m, 2H, CHAliph), 1.43 (d,
J = 7.3 Hz, 2H, CHAliph), FT-IR: 2978 (CeH Ar, Str), 2939, 2884 (CeH,
Aliph, Str), 1639 (C]N, Str), 1594, 1476 (C]C Ar, Str), 1376 (CeN, Str),
1298 (S]O, Str), 687 (SeN, Str), HPLC: Rt = 8.97 min, P = 100%, TLC:
Rf = 0.87, mp = 117–121 °C, Y = 45%.
4.1.2.10. 3-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)benzo[d]
oxazol-2(3H)-one 1j. Molecular formula:
C
24H28N4O2S, 1H NMR
(400 MHz, DMSO) δ 8.12 (t, J = 8.4 Hz, 2H, ArH), 7.60 (dd, J = 11.5,
4.4 Hz, 1H, ArH), 7.48 (t, J = 7.6 Hz, 1H, ArH), 7.35 (d, J = 7.9 Hz, 2H,
ArH), 7.24 (td, J = 7.8, 1.0 Hz, 1H, ArH), 7.14 (td, J = 7.8, 1.2 Hz, 1H,
ArH), 4.05 (d, J = 13.4 Hz, 2H, CONCH), 3.83 (dd, J = 13.6, 6.6 Hz, 2H,
CHPip), 3.60–3.55 (m, 2H, CHPip), 3.50 (t, J = 13.0 Hz, 2H, CHPip), 3.24
(dd, J = 21.2, 9.3 Hz, 2H, CHPip), 3.12 (dt, J = 10.6, 5.3 Hz, 2H, CHPip),
1.74 (d, J = 6.6 Hz, 4H, CHAliph), 1.37 (s, 4H, CHAliph), FT-IR: 3030 (CeH
Ar, Str), 2970; 2929; 2857 (CeH Aliph, Str), 1591 (C]C Ar, Str), 1365
(CeN, Str), 752 (SeN, Str), 677 (CeS, Str), HPLC: Rt = 5.21 min, P = 96%,
TLC: Rf = 0.71, mp = 170–172 °C, Y = 47%.
4.1.2.15. 2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-1H-benzo[de]
isoquinoline-1,3(2H)-dione 1o. Molecular formula: C29H30N4O2S 1H NMR
(400 MHz, DMSO) δ 8.50–8.41 (m, 4H, ArH), 8.16–8.08 (m, 2H, ArH), 7.88
(d, J = 7.7 Hz, 2H, ArH), 7.60 (t, J = 7.6 Hz, 1H, ArH), 7.47 (t, J = 7.4 Hz,
1H, ArH), 3.64 (t, J = 19.2 Hz, 2H, CONCH), 3.59 (t, J = 12.1 Hz, 2H,
CHPip), 3.47 (t, J = 12.3 Hz, 2H, CHPip), 3.37–3.20 (m, 4H, CHPip),
3.16–3.10 (s, 2H, CHPip), 1.73 (d, J = 19.2 Hz, 2H, CHAliph), 1.69–1.53 (m,
2H, CHAliph), 1.41–1.33 (m, 4H, CHAliph), FT-IR: 3062 (CeH Ar, Str), 2942,
2874 (CeH, Aliph, Str), 1693 (C]O, Str), 1656 (C]N, Str), 1589, 1493
(C]C Ar, Str), 1354 (CeN, Str), 697 (SeN, Str), UPLC-MS: 501.11 (M + 3,
15), 500.24 (M + 2, 40), 499.25 (M+, 100), 158.24 (5) HPLC:
Rt = 5.83 min, P = 100%, TLC: Rf = 0.47, mp = 201–203 °C, Y = 47%.
4.1.2.11. 2-((6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)thio)
benzo[d]oxazole 1k. Molecular formula: C24H28N4OS2 1H NMR
(400 MHz, DMSO) δ 8.13 (t, J = 8.5 Hz, 1H, ArH), 7.68–7.64 (m,
1H, ArH), 7.60 (t, J = 7.5 Hz, 1H, ArH), 7.48 (t, J = 7.6 Hz, 1H, ArH),
7.34–7.31 (m, 1H, ArH), 7.28 (d, J = 7.4 Hz, 1H, ArH), 7.18–7.01 (m,
1H, ArH), 6.85 (m, 1H, ArH), 4.06 (d, J = 13.5 Hz, 2H, CONCH),
3.70–3.45 (m, 4H, CHPip), 3.39–3.23 (m, 2H, CHPip), 3.14 (m, 2H,
CHPip), 3.04–2.76 (m, 2H, CHPip), 1.88–1.27 (m, 8H, CHAliph), FT-IR:
3290 (NeH amine, Str), 3024 (CeH Ar, Str), 2994, 2969; 2938; 2856
(CeH Aliph, Str), 1591 (C]C Ar, Str), 1379 (CeN, Str), 742 (SeN, Str),
677 (CeS, Str), UPLC-MS: 455.18 (M + 3, 15), 454.25 (M + 2, 40),
453.25 (M + 1, 100), HPLC: Rt = 6.06 min, P = 97%, TLC: Rf = 0.82,
mp = 164 °C, Y = 40%.
4.1.2.16. 1-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-5,6-
dihydro-1H-imidazo[4,5,1-ij]quinolin-2(4H)-one 1p. Molecular formula:
C
27H33N5OS 1H NMR (400 MHz, DMSO) δ 8.12 (t, J = 8.6 Hz, 2H,
ArH), 7.60 (t, J = 7.6 Hz, 1H, ArH), 7.48 (t, J = 7.2 Hz, 1H, ArH), 7.00
(d, J = 7.6 Hz, 1H, ArH), 6.93 (dd, J = 9.5, 5.8 Hz, 1H, ArH), 6.83 (d,
J = 7.4 Hz, 1H, ArH), 4.05 (d, J = 13.7 Hz, 2H, CONCH), 3.78–3.65
(m, 4H, CHPip), 3.58–3.44 (m, 4H, CHPip), 3.31–3.21 (m, 2H, CHPip),
3.11–3.03 (m, 2H, CHPip), 2.79 (t, J = 5.8 Hz, 2H, CHAliph), 2.02–1.98
(m, 2H, CHAliph), 1.69–1.60 (m, 4H, CHAliph), 1.35 (d, J = 3.6 Hz, 4H,
CHAliph), FT-IR: 3067 (CeH Ar, Str), 2935; 2859 (CeH Aliph, Str), 1672
(C]O Str), 1642 (C]N, Str), 1589; 1498 (C]C Ar, Str), 1379 (CeN,
Str), 677 (SeN, Str), 656 (CeS, Str), HPLC: Rt = 4.54 min, P = 97%,
TLC: Rf = 0.80, mp = 55–58 °C, (oiled), Y = 67%.
4.1.2.12. 6-((6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)oxy)-
3,4-dihydroquinolin-2(1H)-one 1l. Molecular formula: C26H32N4O2S 1H
NMR (400 MHz, CDCl3) δ 8.08 (d, J = 22.1 Hz, 1H, ArH), 7.86 (dd,
J = 10.9, 6.1 Hz, 1H, ArH), 7.53 (dd, J = 14.5, 7.1 Hz, 1H, ArH), 7.42
(dd, J = 14.4, 7.4 Hz, 1H, ArH), 6.78–6.67 (m, 4H, ArH), 4.15 (m, 2H,
CONCH), 3.93 (dd, J = 13.2, 6.7 Hz, 2H, CHPip), 3.57 (t, J = 6.7 Hz,
2H, CHPip), 3.10 (dd, J = 50.5, 10.1 Hz, 2H, CHPip), 2.98–2.89 (m, 2H,
CHPip), 2.67–2.57 (m, 2H, CHPip), 2.13–1.43 (m, 12H, CHAliph), FT-IR:
3343 (NeH, Str), 3056 (CeH Ar, Str), 2926; 2855, 2812 (CeH Aliph,
Str), 1700 (C]O Str), 1655 (C]N, Str), 1591; 1559 (C]C Ar, Str),
1391, 1379 (CeN, Str), 771, 771, 734 (SeN, Str), 679 (CeS, Str), HPLC:
Rt = 4.86 min, P = 96%, TLC: Rf = 0.69, mp = 159–161 °C, Y = 53%.
4.1.2.17. N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-N-(3-
(trifluoromethyl)phenyl)benzenesulfonamide 1q. Molecular formula:
C
30H33F3N4O2S2 1H NMR (400 MHz, DMSO) δ 8.12–8.08 (m, 2H,
ArH), 7.73 (d, J = 7.2 Hz, 2H, ArH), 7.66–7.52 (m, 6H, ArH),
7.48–7.45 (m, 1H, ArH), 7.42 (d, J = 7.5 Hz, 1H, ArH), 7.34 (s, 1H,
ArH), 3.67–3.61 (m, 2H, SONCH), 3.21–3.14 (m, 8H, CHPip), 1.74–1.69
(m, 2H, CHPip), 1.56–1.40 (m, 4H, CHAliph), 1.33–1.21 (vm, 4H,
CHAliph), FT-IR: 3063 (CeH Ar, Str), 2937; 2854 (CeH Aliph, Str),
1490 (C]C Ar, Str), 1370 (CeN, Str), 1326 (S]O, Str), 1233 (C-F, Str),
690 (SeN, Str), 654 (CeS, Str), HPLC: Rt = 7.82 min, P = 92%, TLC:
Rf = 0.88, mp = 217–220 °C, Y = 54%.
4.1.2.13. 1-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)benzo[cd]
indol-2(1H)-one
1
m. Molecular formula:
C
28H30N4OS 1H NMR
(400 MHz, DMSO) δ 8.20 (d, J = 8.1 Hz, 1H, ArH), 8.13 (d,
J = 8.2 Hz, 2H, ArH), 8.07 (d, J = 6.9 Hz, 1H, ArH), 7.82–7.77 (m,
1H, ArH), 7.66 (d, J = 8.4 Hz, 1H, ArH), 7.59–7.51 (m, 2H, ArH), 7.49
(d, J = 8.0 Hz, 1H ArH), 7.24 (d, J = 7.0 Hz, 1H ArH), 4.05 (s, 2H,
CONCH), 3.93 (t, J = 6.9 Hz, 2H, CHPip), 3.58–3.50 (d, J = 10.9 Hz,
2H, CHPip), 3.45–3.36 (m, 4H, CHPip), 3.16–3.03 (m, 2H, CHPip),
4.1.2.18. N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-4-
methyl-N-phenylbenzenesulfonamide 1r. Molecular formula:
C30H36N4
O2S2 1H NMR (400 MHz, DMSO) δ 8.17–8.09 (m, 3H, ArH), 7.61 (t,
J = 7.5 Hz, 2H, ArH), 7.51–7.44 (m, 3H, ArH), 7.42 (s, 1H, ArH),
7.41–7.32 (m, 3H, ArH), 7.08–7.05 (m, 1H, ArH), 4.08 (d, J = 13.5 Hz,
2H, SONCH), 3.44 (d, J = 14.5 Hz, 2H, CHPip), 3.36–3.24 (m, 4H,
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CHPip), 3.21–3.14 (m, 2H, CHPip), 1.80–1.71 (m, 2H, CHPip), 1.62 (d,
J = 39.1 Hz, 2H, CHAliph), 1.55–1.44 (m, 3H, CHAliph), 1.38 (d,
J = 19.4 Hz, 2H, CHAliph), 1.36–1.28 (m, 4H, CHAliph), FT-IR: 3067
(CeH Ar, Str), 2932; 2833 (CeH Aliph, Str), 1590, 1484 (C]C Ar, Str),
1380 (CeN, Str), 1361 (S]O, Str), 691 (SeN, Str), 653(CeS, Str),
HPLC: Rt = 6.29 min, P = 91%, TLC: Rf = 0.88, mp = 128–130 °C,
Y = 63%.
4.1.5. Synthesis of compounds 1 t-w
A mixture of 1.91 g of 6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)
hexan-1-amine 6 (0.006 mol), 30 cm3 of methylene chloride and
0.63 cm3 of triethylamine was stirred in a round bottom flask. After
complete dissolution of substrate (6),
a benzoyl chloride 7 t
(0.0006 mol) or corresponding arylsulphonyl chloride 7u/v/w
(0.0006 mol) was added. The reaction mixture was stirred upon dis-
solution of chloride and left at room temperature for 3 h. After that
time, the remaining solvent was evaporated under reduced pressure and
the precipitate was dissolved in 20 cm3 methylene chloride and washed
with 20 cm3 of 5% NaHCO3 and 20 cm3 of water. Then, the organic
layer was dried over anhydrous magnesium sulphate and the solvent
was evaporated. Crude benzamide (1t) and sulphonamides (1u/1v/1w)
were purified by column chromatography using chloroform:methanol
9:1 eluent as mobile phase, and after obtaining min. 95%, the com-
pounds (1t/1u/1v/1w) were dissolved in acetone and converted to
hydrochloride by 4 M HCl in dioxane. The reaction yields were calcu-
lated on the basis of the weight of the obtained hydrochlorides.
4.1.3. Synthesis of compound 1s
A mixture of 6-bromohexylated derivative 4x (0.002 mol), ar-
ylpiperazine 5a (0.002 mol), 0.76 g of K2CO3 (0.006 mol) and 0.06 g of
TBAB (0.0002 mol) were triturated in a mortar. The triturated mixture
was transferred to a round bottom flask, and 0.5 cm3 of DMF was
added. The reactions were carried out for 60 s in a CEM Discover mi-
crowave reactor at 100 W output power. The progress of the reaction
was monitored by TLC. After completion of the reaction, 50 cm3 of
water was added to the mixture and placed in the refrigerator over-
night. After cooling, the crude product (1x) was filtered off. In the
absence of the required purity, the crude product was purified by
column chromatography using chloroform:methanol 9:1 eluent as mo-
bile phase. After obtaining a minimum of 95% purity, the product (1x)
was dissolved in acetone, then converted to hydrochloride by 4 M HCl
in dioxane resulting in the desired compound (1s). The reaction yield
for 1-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-1H-benzo[d]
imidazol-2(3H)-one (1s) was calculated on the basis of the weight of the
obtained hydrochloride.
4.1.5.1. N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)benzamide
1t. Molecular formula: C24H30N4OS 1H NMR (400 MHz, CDCl3) δ
7.92–7.79 (m, 3H, ArH), 7.58–7.39 (m, 5H, ArH), 6.57 (m, 1H, ArH),
4.25–4.06 (m, 4H, CHPip, CONCH), 3.75 (q, J = 7.0 Hz, 1H, NH), 3.50
(d, J = 6.3 Hz, 4H, CHPip), 3.24–3.07 (m, 2H, CHPip), 3.04–2.94 (m, 2H,
CHPip), 2.00 (m, 2H, CHAliph), 1.76–1.67 (m, 2H, CHAliph), 1.51 (d,
J = 3.5 Hz, 2H, CHAliph), 1.27 (dd, J = 8.6, 5.5 Hz, 2H, CHAliph), FT-IR:
3288 (NeH amine,Str), 3055 (CeH Ar, Str), 2939, 2856 (CeH Aliph,
Str), 1642, 1576 (C]C Ar, Str), 1487 (CeN, Str), 773, 742 (SeN, Str),
677, 669 (CeS, Str), HPLC: Rt = 1.70 min, P = 95%, TLC: Rf = 0.54,
mp = 210 °C, Y = 28%.
4.1.3.1. 1-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)-1H-benzo
[d]imidazol-2(3H)-one 1s. Molecular formula: C24H28N5OS 1H NMR
(400 MHz, CDCl3) δ 9.50 (s, 1H, NH), 7.85 (t, J = 8.8 Hz, 2H, ArH),
7.53 (t, J = 7.4 Hz, 1H, ArH), 7.41 (t, J = 7.5 Hz, 1H, ArH), 7.09 (dt,
J = 21.7, 7.5 Hz, 3H, ArH), 6.99 (d, J = 7.8 Hz, 1H, ArH), 4.14 (d,
J = 28.7 Hz, 4H, CHPip), 3.89 (t, J = 6.7 Hz, 2H, CONCH), 3.54 (dd,
J = 7.9, 4.5 Hz, 2H, CHPip), 3.12 (s, 2H, CHPip), 3.01 (d, J = 4.3 Hz,
2H, CHPip), 1.99 (m, 4H, CHAliph), 1.43 (m, 3H, CHAliph), FT-IR: 3398
(NeH amine, Str), 3030 (CeH Ar, Str), 2931; 2856 (CeH Aliph, Str),
1758; 1708 (C]O, Str), 1612; 1590 (C]C Ar, Str), 1364 (CeN, Str),
742 (SeN, Str), 650 (CeS, Str), UPLC-MS: 439,43 (M + 4, 5), 438,36
(M + 3, 10), 437,43 (M + 2, 32), 436,37 (M + 1, 100), 177,18 (5);
HPLC: Rt = 4.86 min, P = 96%, TLC: Rf = 0.58, mp = 134–135 °C,
Y = 20%.
4.1.5.2. N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)
benzenesulfonamide 1u. Molecular formula: C23H30N4O2S2 1H NMR
(400 MHz, CDCl3) δ 7.96–7.91 (m, 2H, ArH), 7.86 (t, J = 8.2 Hz,
2H, ArH), 7.61–7.49 (m, 4H, ArH), 7.42 (t, J = 7.9 Hz, 1H, ArH), 5.79
(s, 1H, NH), 4.26–4.05 (m, 4H, CHPip, CONCH), 3.65 (d, J = 10.6 Hz,
2H, CHPip), 3.24–3.04 (m, 4H, CHPip), 2.99–2.93 (m, 2H, CHPip),
2.17–1.18 (m, 8H, CHAliph), FT-IR: 3268 (NeH amine, Str), 3054
(CeH Ar, Str), 2941; 2855 (CeH Aliph, Str), 1589 (C]C Ar, Str),
1380 (CeN, Str), 1317 (S]O, Str), 751 (SeN, Str), 659 (CeS, Str),
HPLC: Rt = 1.705 min, P = 96%, TLC: Rf = 0.6, mp = 164–166 °C,
Y = 41%.
4.1.4. Synthesis of amine 6
4.1.5.3. N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)
naphthalene-1-sulfonamide 1v. Molecular formula: C27H32N4O2S2 1H
NMR (400 MHz, CDCl3) δ 8.77 (d, J = 8.7 Hz, 1H, ArH), 8.29–8.24
(m, 1H, ArH), 8.07 (d, J = 8.3 Hz, 1H, ArH), 7.96 (d, J = 8.1 Hz, 1H,
ArH), 7.87 (t, J = 7.4 Hz, 2H, ArH), 7.72 (m, 1H, ArH), 7.64–7.59 (m,
1H, ArH), 7.58–7.52 (m, 2H, ArH), 7.42 (t, J = 7.6 Hz, 1H, ArH), 5.85
(s, 1H, NH), 4.26–4.04 (m, 4H, CHPip), 3.60 (d, J = 12.2 Hz, 2H,
SONCH), 3.17–3.11 (m, 2H, CHPip), 3.05–2.97 (m, 2H, CHPip), 2.93 (t,
J = 6.4 Hz, 2H, CHPip), 1.97–1.33 (m, 8H, CHAliph). FT-IR: 3268 (NeH
amine,Str), 3055 (CeH Ar, Str), 2969; 2940; 2855 (CeH Aliph, Str),
1589 (C]C Ar, Str), 1380 (CeN, Str), 1316 (S]O, Str), 751 (SeN, Str),
659 (CeS, Str), HPLC: Rt = 1.91 min, P = 97%, TLC: Rf = 0.67,
mp = 156 °C, Y = 75%.
A mixture of 0.35 g of 2-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-
yl)hexyl)isoindoline-1,3-dione 1h (0.003 mol) and 15 ml of 40% aqu-
eous solution of methylamine was stirred at room temperature for 48 h.
After this time, 15 ml 20% aqueous solution of NaOH was added to the
mixture and the mixture was stirred for another 24 h. Then, the re-
sulting solution was mixed with 10 cm3 of brine and extracted with
2 × 30 cm3 methylene chloride. Organic layer was washed with water
and dried over anhydrous magnesium sulphate. After the evaporation
of methylene chloride under reduced pressure, the desired product (6)
was obtained. The reaction yield for 6-(4-(benzo[d]isothiazol-3-yl)pi-
perazin-1-yl)hexan-1-amine (6) was calculated on the basis of the
weight of the obtained product (6).
4.1.4.1. 6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexan-1-amine
4.1.5.4. N-(6-(4-(benzo[d]isothiazol-3-yl)piperazin-1-yl)hexyl)
6. Molecular formula:
C
17H26N4S 1H NMR (400 MHz, CDCl3)
δ
naphthalene-2-sulfonamide 1w. Molecular formula: C27H32N4O2S2 1H
NMR (400 MHz, CDCl3) δ 8.02 (m, J = 14.1, 8.7 Hz, 3H, ArH), 7.93
(m, J = 6.4 Hz, 1H, ArH), 7.87 (m, J = 7.0 Hz, 1H, ArH), 7.79 (m,
J = 11.6, 8.1 Hz, 1H, ArH), 7.65 (m, J = 13.7, 7.7 Hz, 3H, ArH), 7.54
(t, J = 7.4 Hz, 1H, ArH), 7.48–7.42 (m, 1H, ArH), 4.16 (s, 1H, NH),
3.70–3.64 (m, 2H, CONCH), 3.39–3.33 (m, 2H, CHPip), 3.13 (m,
J = 7.3, 4.9 Hz, 4H, CHPip), 1.84–1.39 (m, 12H, CHPip, CHAliph), FT-
IR: 3293 (NeH amine,Str), 3092 (CeH Ar, Str), 2942, 2919, 2879, 2862
8.01–7.66 (m, 2H, ArH), 7.57–7.19 (m, 2H, ArH), 3.79–3.35 (m, 4H,
CHPip), 3.11 (dd, J = 13.5, 8.7 Hz, 2H, CHAliph), 2.83–2.60 (m, 4H,
CHPip 2.55–2.31 (m, 2H, amine-NH2), 1.79–1.14 (m, 10H, CHAliph), FT-
IR: 3342 (NeH amine,Str), 3054 (CeH Ar, Str), 2926, 2846, 2812,
27,69 (CeH Aliph, Str), 1633, 1590, 1559 (C]C Ar, Str), 1258, 1147,
1130, (CeN, Str), 773, 734 (SeN, Str), 679 (CeS, Str); HPLC:
Rt = 1.39 min, P = 99%, TLC: Rf = 0.07, mp = 72–75 °C, Y = 100%.
11

P. Zaręba, et al.
Bioorganic&MedicinalChemistryxxx(xxxx)xxxx
(CeH Aliph, Str), 1585 (C]C Ar, Str), 1426 (CeN, Str), 1316 (S]O,
Str), 773 (SeN, Str), 657 (CeS, Str), HPLC: Rt = 1.91 min, P = 98%,
TLC: Rf = 0.65, mp = 112 °C, Y = 74%.
used, from gpcrdb36, as well as the crystal structure of the D2 (pdb ID:
6CM437) receptor in the complex with Risperidone. The homology
model of the 5-HT6R and 5-HT7R were generated in SWISS-MODEL
automated protein structure homology-modelling server,38 using tem-
plates: 5-HT6 (template 5-HT2A; pdb ID: 6A9439) 5-HT7 (template 5-
HT1B; pdb ID: 6G7940). Amino acid sequences were taken from Uni-
prot.41 For the graphic presentation of selected the structures, PyMOL
3.742 software was used. The models were validated using SWISS-
MODEL server38, by QMEAN43 parameters determination. The percent
of residues in favored regions of the Ramachandran plot was also de-
termined.44 Molecular docking was carried out for a set of ligands with
known affinity. The sets of ligands with known activities (Ki < 50 nM)
and inactivities (Ki > 500 nM) were retrieved from the ChEMBL da-
tabase.45 The selected set contained mainly ligands from the group of
long-chain arylpiperazines and arylpiperidines due to the similarity of
the binding mode. 25 active and 25 inactive ligands were selected.
4.2. In vitro evaluation
4.2.1. Cell culture and preparation of cell membranes for radioligand
binding assays
HEK293 cells with stable expression of human 5-HT1A, 5-HT6, 5-
HT7b and D2L receptors were prepared with the use of Lipofectamine
2000. CHO-K1 cells, with plasmid containing the sequence coding for
the human serotonin 5-HT2A receptor were prepared using
PerkinElmer. The cells were maintained at 37 °C in a humidified at-
mosphere, with 5% CO2 and grown in Dulbecco’s Modifier Eagle
Medium (10% dialyzed fetal bovine serum, 500 µg/ml G418 sulfate).
For membrane preparation, the cells were subcultured in 150 cm2
flasks, grown to 90% confluence and then washed twice with pre-
warmed to 37 °C phosphate buffered saline (PBS) and pelleted by
centrifugation (using ×200g) in PBS containing 0.1 mM EDTA and
1 mM dithiothreitol. The pellets were stored at −80 °C.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
4.2.2. Radioligand binding assays
The thawed cell pellets were homogenized in 20 volumes of assay
buffer in tissue homogenizer (Ultra Turrax) and then centrifuged twice
at 35g for 20 min (4 °C), with incubation for 15 min (37 °C) in between
rounds of centrifugation. The composition of the assay buffers:
5-HT1A − 50 mM Tris–HCl, 0.1 mM EDTA, 4 mM MgCl2, 10 μM
pargyline and 0.1% ascorbate; 5-HT2A − 50 mM Tris–HCl, 0.1 mM
EDTA, 4 mM MgCl2, and 0.1% ascorbate; 5-HT6 − 50 mM Tris–HCl,
0.5 mM EDTA and 4 mM MgCl2; 5-HT7 − 50 mM Tris–HCl, 4 mM
MgCl2, 10 μM pargyline and 0.1% ascorbate; D2 − 50 mM Tris HCl,
1 mM EDTA, 4 mM MgCl2, 120 mM NaCl, 5 mM KCl, 1.5 mM CaCl2 and
0.1% ascorbate.
Acknowledgements
The research was supported by the National Centre for Research and
Development, LIDER VI project (LIDER/015/L-6/14/NCBR/2015).
The computing resources from Academic Computer Centre
CYFRONET AGH (member of PL-Grid Infrastructure, grant lcaps2019)
are gratefully acknowledged.
The authors acknowledge the support of the PROM programme
no.PPI/PRO/2018/1/00013/U/001, which is co-financed by the
European Social Fund under the Knowledge Education Development
Operational Programme.
The assays were incubated in a total volume of 200 μl in 96-well
microtiter plates for 1 h (37 °C, except for 5-HT1A and 5-HT2A, which
were incubated at room temperature). The process of equilibration was
terminated by rapid filtration through Unifilter plates (96-well cell
harvester, PerkinElmer), and the radioactivity retained on the filters
was quantified on a Microbeta plate reader (PerkinElmer).
For displacement studies, the assay samples contained the following
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