Design, synthesis and pharmacological evaluation of indolylsulfonamide amines as potent and selective 5-HT6 receptor antagonists

Article abstract of DOI:10.3109/14756366.2014.889126

A series of N′-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl ethane-1,2-diamines and N′-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl propane-1,3-diamines was designed and synthesized as 5-HT₆ receptor ligands. These compounds, when screened in a functional reporter gene-based assay, displayed potent antagonistic activity with K_b values in the range of 1.8-60 nM. The lead compound 9_y has shown good ADME surrogate properties, acceptable pharmacokinetic profile and is active in animal models of cognition like novel object recognition test and Morris water maze. It was selected for detailed profiling.

Full text of DOI:10.3109/14756366.2014.889126

http://informahealthcare.com/enz
ISSN: 1475-6366 (print), 1475-6374 (electronic)
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
2014 Informa UK Ltd. DOI: 10.3109/14756366.2014.889126
!
ORIGINAL ARTICLE
Design, synthesis and pharmacological evaluation of
indolylsulfonamide amines as potent and selective 5-HT6
receptor antagonists
Ramakrishna V. S. Nirogi1, Thrinath Reddy Bandyala1,2, Veena Reballi1, Jagadishu Babu Konda1,
Anand V. Daulatabad1, and Mukkanti Khagga2
1Discovery Research-Medicinal Chemistry, Suven Life Sciences Limited, Serene Chambers, Banjara Hills, Hyderabad, India and 2Centre for Chemical
Sciences and Technology, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Kukatpally, Hyderabad, India
Abstract
Keywords
A series of N0-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl ethane-1,2-diamines and N0-[3-(indole-
1-sulfonyl) aryl]-N,N-dimethyl propane-1,3-diamines was designed and synthesized as 5-HT6
receptor ligands. These compounds, when screened in a functional reporter gene-based assay,
displayed potent antagonistic activity with Kb values in the range of 1.8–60 nM. The lead
compound 9y has shown good ADME surrogate properties, acceptable pharmacokinetic profile
and is active in animal models of cognition like novel object recognition test and Morris water
maze. It was selected for detailed profiling.
5-Hydroxytryptamine6 receptor, central
nervous system, cognition, novel object
recognition test, structure activity
relationship, water maze
History
Received 15 July 2013
Revised 28 November 2013
Accepted 24 January 2014
Published online 25 March 2014
Introduction
The 5-HT6 receptor appears to regulate several neurotransmit-
World Health Organization recognizes the size and complexity of ter systems, including acetylcholine, glutamate, dopamine,
the dementia challenge and urges countries to view dementia as a noradrenaline or aspartate. It is unique distribution in the brain
critical public health priority. Dementia is a syndrome due to and high affinity for therapeutic antipsychotics and antidepres-
disease of the brain, usually chronic, characterized by a progres- sants7,8 suggests a possible role of the 5-HT6 receptor in central
sive, global deterioration in intellect, including memory, learning, nervous system (CNS) disorders. Along with this, several studies
orientation, language, comprehension and judgment. Alzheimer’s have been published reporting an association of 5-HT6 receptor
Disease International estimated that 36 million people worldwide variants with neuropsychological and neuropsychiatric diseases
are living with dementia in 2010 and this number is expected to such as schizophrenia9–13
,
bipolar affective disorders14,
increase in future with the increased life expectancy around the Parkinson’s disease15 or Alzheimer’s disease16–18 and the treat-
globe. There are 7.7 million new cases of dementia each year, ment of obesity and related metabolic disorders. Therefore, 5-HT6
implying that there is a new case of dementia somewhere in the receptors represent an extremely attractive target for the devel-
world every 4 s. If breakthroughs are not discovered1, the number opment of novel small molecule therapeutics for the treatment of
of people affected will be over 115.4 million by 2050.
various neurodegenerative disorders19–21
Many 5-HT6 receptor ligands have been reported and some of
.
The monoamine neurotransmitter serotonin (5-hydroxytrypta-
mine, 5-HT) mediates a wide range of physiological functions2–4 the clinically advancing molecules include SAM-760 from Pfizer,
by interacting with multiple receptors, and these receptors have SB-742457 (Figure 1) from GSK is in Phase II clinical trials for
been implicated as playing important roles in certain pathological dementia as per their product development pipeline published22,23
and psychopathological conditions. Among these receptors, in February 2013. Recently, AVN-211 (Figure 1) from Avineuro
5-hydroxytryptamine6 (5-HT6) receptor is one of the most Pharmaceuticals entered into phase IIb clinical trials for treatment
recently discovered members of serotonin receptor family of schizophrenia24–26 and Lundbeck has reported that Lu
(5-HT1–5-HT7). It is a G-protein-coupled receptor (GPCR) and AE58054 (Figure 1) met its primary endpoint in large placebo-
positively coupled to adenylate cyclase secondary messenger controlled clinical proof of concept study in people with
system5,6
.
Alzheimer’s disease27,28. Biotie therapies have completed phase
I clinical trials of the compound, SYN-12029. As part of our own
research program, we at Suven have designed and developed
selective 5-HT6 receptor antagonist compound SUVN-502 (struc-
ture not disclosed) which has completed phase I trials for
cognitive impairment in schizophrenia and Alzheimer’s disease30.
Address for correspondence: Ramakrishna Nirogi, Discovery Research-
Medicinal Chemistry, Suven Life Sciences Limited, Serene Chambers,
Banjara Hills, Hyderabad, India. Tel: +91-40-23556038/23541142. Fax:
+91-40-23541152. E-mail: nvsrk@suven.com

86 R. V. S. Nirogi et al.
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
F
Figure 1. Clinically advanced 5-HT6 receptor
ligands.
O
F
O
O
F
S
F
HN
O
S
N
O
CH
H C
N
3
N
3
S
N
N
N
F
N
H
H
CH3
SB -742457
AVN-211
Lu AE58054
CH
3
H C
3
H C
CH
3
3
CH
N
O
N
3
N
O
S
CH
3
S
O
n
H C
3
N
CH
O
3
N
H C
3
N
O
N
S
S
O
N
S
CH
3
O
O
H C
O
O
3
(i) MS-245
(iv)
K = 20 nM
(v)
K = 153 nM
(ii) n = 1, Ki = 1.5 nM
(iii) n = 2, Ki = 7.9 nM
K = 2.3 nM
i
i
i
H C
3
Cl
N
CH
3
CH
3
O
O
S
S
O
CH
N
3
N
O S
H
N
HN
NH
S
O
CH
N
3
O
N
O
N
O
CH
S
CH
O
3
N
H C
N
CH
O
3
3
(vi)
K = 58 nM
(vii)
(viii)
H C
3
3
Compound 9y
5-HT R, K = 2.1 nM
K = 94 nM
K = 40 nM
i
i
i
6
b
IC = 416 nM
50
Imax = 100 %
Figure 2. Structures of reported 5-HT6 ligands.
N,N-dimethyl-2-(5-methoxy-1-phenylsufonyl-1H-indole-3-
In vitro potencies were determined for all the synthesized
yl)ethylamine (MS-245, Figure 2) is a 5-HT6R antagonist compounds using functional reporter gene-based assay50,51. This
reported by Glennon et al.31 in early 2000. Since then a lot of assay uses a stable CHO cell line expressing recombinant human
reports have been published regarding variations in N,N-dimethyl 5-HT6 receptor and pCRE-Luc reporter system, which allows one
amino alkyl side chain on and around the indole nucleus and their to determine functional activities (agonist or antagonist) and
affinity21,32,33 (Figure 2). Numerous selective antagonists of assess potency of a compound to modulate GPCR-mediated cell
5-HT6 receptors have been disclosed during the last decade34–42 responses. By using this specific assay, the level of intracellular
and a pharmacophore model for this type of receptor antagonists cyclic AMP which is modulated by activation or inhibition of the
has been developed based on known structurally diverse 5-HT6 receptor is measured. The Kb values of N,N-dimethylamino alkyl
receptor antagonists43–49. In general, the model entails the amino aryl sulfonamides obtained from the cell-based assay of
positive ionizable atom (usually a secondary or tertiary amino 5-HT6 receptor are given in Table 1.
group), a hydrogen bond acceptor group (usually a sulfone or
sulfonamide group), a hydrophobic site (HYD) and ꢀ-electron Results and discussion
donor aromatic or heterocyclic ring (AR). Considering the
Structure activity relationship
reported 5-HT6 receptor ligands and an established pharmaco-
phore model, in an attempt to identify potent and selective 5-HT6 Several analogues of N0-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl
ligands, we have designed and synthesized
a
series of ethane-1,2-diamines
and
N0-[3-(indole-1-sulfonyl)
aryl]-
N0-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl ethane-1,2-diamines N,N-dimethyl propane-1,3-diamines were synthesized and their
and N0-[3-(indole-1-sulfonyl) aryl]-N,N-dimethyl propane-1, Kb values are given in Table 1. In the presented series, all the
3-diamines derivatives with basic amine side chain (Compounds compounds were found to have high potency, with Kb values in
9) on N-aryl sulfonyl moiety at C-30 position.
the range of 1.8–60 nM, indicating that the flexible
These compounds have high selectivity over closely related N,N-dimethylamino alkyl amine side chain on N-aryl sulfonyl
receptors and activity in the animal model of cognition. The group at C-30 position in an indolylsulfonamide amine series is
synthesis, in vitro activity, selectivity over closely related targets, well tolerated in terms of activity.
pharmacokinetics and pharmacology of these series of
compounds are discussed in this paper.
Among the compounds synthesized, 9e and 9y were the most
potent compounds with Kb values of 1.8 and 2.1 nM respectively,

DOI: 10.3109/14756366.2014.889126
Design, synthesis and pharmacological evaluation 87
Table 2. Imax and IC50 for selected potent compounds.
Table 1. 5-HT6 receptor potencies*.
4
2
R
2
5
1
3
Compound
*Kb (nM)
IC50 (nM)
Imax (%)
R
A
B
N
9d
9e
9y
3.1 0.21
1.8 0.14
2.1 0.07
613.5 12
353 8.4
416 11.3
98
100
100
6
H
1
2'
7
N
CH
O S
3
2
N
n
1'
6'
3'
C
CH
3
3
*Kb values were determined using non-radioactive cell-based assay.
IC50 and Kb values are the mean of two experiments.
R
4'
5'
(n = 1, 2)
.
(Kb ¼ 39.4 nM) and 9af (Kb ¼ 60 nM). Among the halo com-
pounds with n ¼ 1, the potencies drop down as the size of the
halogen group increases, for example, 9o (Kb ¼ 17 nM) versus 9w
(Kb ¼ 23 nM) versus 9u (Kb ¼ 43 nM). This was also true for the
compounds bearing n ¼ 2, as can be seen by comparing 9ad
(Kb ¼ 7.2 nM) versus 9ae (Kb ¼ 39.4 nM) versus 9af
(Kb ¼ 60 nM). This indicates that among the halo derivatives,
the fluoro substitution is the most tolerated and preferred
substitution at C5 position of the indole. Marginal improvement
was seen in potency when the chloro group was shifted from C4 to
C6 of indole ring as it can be seen from the Kb values of the
compounds 9t (Kb ¼ 11.9 nM) versus 9k (Kb ¼ 6.6 nM).
Increasing the chain length (n ¼ 2) in the side chain gave
compounds with almost equipotent activities, as it can be seen
from Kb values of 9e (Kb ¼ 1.8 nM) versus 9y (Kb ¼ 2.1 nM), 9g
(Kb ¼ 25 nM) versus 9z (Kb ¼ 37.7 nM), 9f (Kb ¼ 26.9 nM) versus
9aa (Kb ¼ 18 nM), 9x (Kb ¼ 40 nM) versus 9ae (Kb ¼ 39.4 nM)
and 9a (Kb ¼ 33 nM) versus 9ac (Kb ¼ 18.9 nM).
Comp. No.
R1
R2
R3
n
Kb (nM)
9a
9b
9c
9d
9e
5-OCH3
5-OCH3
H
CH3
Cl
Cl
H
CH3
CH3
H
H
CH3
H
H
H
OCH3
OCH3
OCH3
OCH3
OCH3
CH3
CH3
C2H5
C2H5
CH3
H
C2H5
C2H5
H
C2H5
H
H
C2H5
H
H
C2H5
H
C2H5
OCH3
OCH3
CH3
CH3
H
OCH3
OCH3
OCH3
OCH3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
33 0.71
23.7 0.42
4.9 0.14
3.1 0.21
1.8 0.14
26.9 0.71
25 0.42
19 0.28
29 0.28
4.6 0.14
6.6 0.16
36 0.85
40 0.71
13 0.28
17 0.21
26 0.42
27 0.28
33 0.28
33 0.71
11.9 0.42
43 0.71
47 0.35
23 0.28
40 0.80
2.1 0.07
37.7 0.42
18 0.28
23 0.21
18.9 0.28
7.2 0.14
39.4 0.60
60 0.40
H
H
9f
5-OCH3
5-OCH3
5-F
5-OCH3
6-Cl
6-Cl
5-OCH3
5-Br
4-Cl
9g
9h
9i
9j
9k
9l
9m
9n
9o
9p
9q
9r
H
CH3
CH3
CH3
H
H
H
5-F
5-OiPr
5- OiPr
5-Cl
9s
9t
5-Br
4-Cl
5-Br
5-OC2H5
5-Cl
5-Cl
The values of Imax and IC50 for most potent compounds 9d, 9e
and 9y are given in Table 2.
H
9u
9v
9w
9x
9y
9z
9aa
9ab
9ac
9ad
9ae
9af
CH3
CH3
CH3
CH3
CH3
H
CH3
CH3
CH3
CH3
CH3
CH3
All the lead compounds have shown full antagonistic activity
with Imax 100% or close to 100% (Table 2).
Selected compounds that showed an excellent potency in the
reporter gene cell-based assay were further profiled in a
radioligand binding assay for specificity on a panel of closely
related receptors. The compounds (9d, 9e and 9y) have an
excellent selectivity (Table 3) over a range of closely related
receptors like 5-HT3 and 5-HT4b, histamine H1 and H3, dopamine
D2 and D3, adrenergic a1B, and the transporters like SERT, DAT
and NET. All the tested compounds produced550% inhibition at
a concentration of 1 mM indicating high selectivity toward these
off targets. The compounds 9d, 9e and 9y showed low inhibition
of human ether-a-go-go-related gene (hERG) with the inhibition
of 32%, 12% and 23%, respectively, when tested in Astemizole
binding assay at 1 mM.
H
5-OCH3
5-OCH3
5-OCH3
5-OCH3
5-F
5-Cl
5-Br
*The compounds were tested in vitro with non-radioactive-based
approach for determination of Kb values with cell-based assay for
5-HT6 receptor. The values reported here are
a mean of two
experiments. All the compounds were characterized by 1H-NMR,
mass, IR and the purities were determined by HPLC.
Once the in vitro activity and selectivity of compounds was
achieved, our next step was to study the metabolic stability in
microsomes (Table 4). The in vitro metabolic stability of selective
compounds 9d, 9e and 9y in rat and human liver microsomes was
carried out for 30 min. Compound 9d metabolized (100% and
32%) compared with compound 9e (94% and 37%) and compound
9y (90% and 34%) in rat and human, respectively, indicating low
metabolism in human liver microsomes.
these compounds bearing n ¼ 1, R1 ¼ H, R2 ¼ CH3, R3 ¼ OCH3
and n ¼ 2, R1 ¼ H, R2 ¼ CH3, R3 ¼ OCH3, respectively. Generally,
-H, halo and smaller alkyl (namely Me) substitutions at C3 of
indole ring are well tolerated and proved to have good potency as
can be seen from the Kb values of the compounds 9c
(Kb ¼ 4.9 nM),
9d
(Kb ¼ 3.1 nM),
9e
(Kb ¼ 1.8 nM),
Since brain penetration is an important factor for molecules
targeting the CNS, we determined PK parameters (Table 5) of the
selected compounds (9d, 9e and 9y). Brain and plasma levels
were calculated in male Wistar rats after 6 h i.v. continuous
infusion of compounds 9d, 9e and 9y at 10 mg/kg/h dose. Among
these compounds 9y showed adequate brain to plasma ratio of
3.48 0.27, whereas compounds 9d and 9e exhibited higher brain
to plasma ratio of 20.16 1.84 and 13.50 4.28, respectively. The
pharmacokinetic profile of 9d, 9e and 9y was assessed in male
Wistar rats (Table 5). Following i.v. administration of 10 mg/kg,
the compounds 9d, 9e and 9y showed good mean half-life of
2.93 1.29 h, 3.37 0.29 h and 2.72 0.40 h, respectively.
9h (Kb ¼ 19 nM), 9n (Kb ¼ 13 nM), 9o (Kb ¼ 17 nM) and 9t
(Kb ¼ 11.9 nM). Compounds with electron donating and/or bulky
groups (namely OCH3, OC2H5 and OCH(CH3)3) at C5 of indole
were showing moderate potency toward 5-HT6 R, as it can be seen
from the Kb values of the compounds 9a (Kb ¼ 33 nM), 9b
(Kb ¼ 23.7 nM), 9f (Kb ¼ 26.9 nM), 9p (Kb ¼ 26 nM), 9q
(Kb ¼ 27 nM), 9v (Kb ¼ 47 nM) and 9z (Kb ¼ 37.7 nM). More or
less a very similar trend was observed in the case of electron
withdrawing and/or bulky halogen group (namely F, Cl and Br) at
C5 of indole, for example, 9h (Kb ¼ 19 nM), 9m (Kb ¼ 40 nM),
9o (Kb ¼ 17 nM), 9r (Kb ¼ 33 nM), 9s (Kb ¼ 33 nM), 9u
(Kb ¼ 43 nM), 9w (Kb ¼ 23 nM), 9ad (Kb ¼ 7.2 nM), 9ae

88 R. V. S. Nirogi et al.
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
Table 3. Compounds selectivity data*.
Comp.
5-HT6
a1B
5-HT4b
5-HT3
D2
D3
DAT
NET
SERT
H1
H3
hERG
9d
9e
9y
92.22
95.38
99.65
7.97
13.18
10.61
13.99
33.65
25.46
18.65
15.99
14.35
23.64
33.41
23.64
27.8
22.61
28.47
17.77
16.63
14.01
21.55
25.84
19.40
15.40
13.14
11.88
42.41
40.15
41.60
22.28
32.37
26.15
32.17
12.72
23.15
*Values given here are their % inhibitions at 1 mM concentration and are measured by competitive displacement of corresponding radioligand. The
reported values are mean of two experiments.
Table 4. Percentage surrogate metabolism for compounds 9d, 9e and 9y*.
Surrogate % metabolism
Compound
Wister rat
Human
9d
9e
9y
100
94
90
32
37
34
*These values are the mean of duplicate determinations. Microsomal
metabolic stability in Wistar rat and human at 0.5 h, concentration
2.5 mM.
Table 5. Pharmacokinetic profile of compounds 9d, 9e and 9y in male
Wister rats*.
Compound
9d
9e
9y
Figure 3. Novel object recognition test data for compound 9y in rats.
Compound 9y versus Vehicle (Paired t-test), n ¼ 9–10/group, p.o., dosing
drug: 60 min prior to test (p.o.). Vehicle-PEG 400 50% v/v; 1 mL/kg, p.o.
*p50.05 students t-test.
i.v. (n ¼ 3)
Dose (mg/kg)
t1/2 (h)
Vz (L/kg)
Cl (mL/min/kg)
10
2.93 1.29
10
3.37 0.29
10
2.72 0.40
22
90 18
6
17
60
2
9
11
49
1
9
p.o. (n ¼ 3)
Dose (mg/kg)
t1/2 (h)
Cmax (ng/mL)
Tmax (h)
AUC (ng h/mL)
F (%)
Cb/Cp
Materials and methods
10
1.95 0.73
41 19
0.58 0.38
88 48
10
2.27 0.20
36
1.33 0.58
158 20
10
5.06 3.28
140.2 76.8
2.33 1.53
673.5 320.3
19 7
3.48 0.27
General considerations
8
Infrared spectra were recorded in KBr disk and in solid state using
a Perkin-Elmer model 1600 FT-IR spectrophotometer (Perkin-
Elmer, Norwalk, CT). Electrospray ionization mass spectra were
recorded on API 4000 triple quadrupole instrument (MDSSCIEX,
5
2
20.16 1.84
6
1
13.50 4.28
1
Concord, Ontario, Canada). H-NMR spectra were obtained on a
*Fasted male Wistar rats, vehicle used: water for injection for both
oral and intravenous routes. Dosing volumes: 10 mL/kg p.o. and
2 mL/kg for i.v.
Bruker proton NMR spectrometer (Fallanden, Switzerland) at
400 MHz. Deuterated reagents were used as solvents and were
commercially procured. Tetramethylsilane was used as an internal
standard. Chemical shift values are expressed in parts per million
(ꢁ) and coupling constants are expressed in hertz.
Chromatography refers to column chromatography performed
using 100–200 mesh silica gel and executed under nitrogen
pressure (flash chromatography) conditions. All the reagents and
chemicals used were of ‘‘reagent grade’’.
The oral administration at 10 mg/kg showed good plasma
concentration 140.2 76.8 ng/mL for compound 9y, whereas
compounds 9d and 9e showed low plasma concentrations of
41 19 and 36 8 ng/mL, respectively. The mean oral bioavail-
ability for compound 9y was better (19 7%) as compared with
9d (5 2%) and 9e (6 1%). The low oral bioavailability of these
compounds may be because of its poor metabolic stability in rat
liver microsomes.
Determination of Kb and IC50 values for 5-HT6 receptor
antagonists
The clearance was low (49 9 mL/min/kg) for compound 9y
as compared with 9d and 9e. The compounds 9d, 9e and 9y A stable CHO cell line expressing recombinant human 5-HT6
showed volume of distributions (Vz, L/kg), i.e. 22 6, 17 2 and
11 1 at 10 mg/kg, i.v. dose.
Based on overall pharmacokinetic and brain penetration determine potency of a compound to GPCRs. In this specific
receptor and pCRE-Luc reporter system was used for cell-based
assay. The assay offers a non-radioactive-based approach to
data (Table 5), compound 9y was selected for further
assay, the level of intracellular cyclic AMP which is modulated by
profiling in pharmacological models of cognition. Oral adminis-
activation or inhibition of the receptor is measured. The
tration of compound 9y (10 mg/kg) has significantly improved recombinant cells harbor luciferase reporter gene under the
performance of rats in novel object recognition test (NORT,
Figure 3).
In Morris water maze test, the compound significantly
control of cAMP response element. The above cells were plated in
96-well clear bottom white plates at a density of 5 ꢀ 104 cells/well
using Hams F12 medium containing 10% fetal bovine serum and
reversed the scopolamine-induced memory deficit which was incubated overnight at 37 ꢁC and 5% CO2 followed by serum
apparent from lesser target latency (Figure 4).
starvation for 18–20 h. Increasing concentrations of test

DOI: 10.3109/14756366.2014.889126
Design, synthesis and pharmacological evaluation 89
Figure 4. Latency to target in the Morris water maze test for compound 9y in rats.
compounds were added along with 10 mM serotonin in OptiMEM protein of interest, in the presence of specific radioligands. The
to the cells. The incubation was continued at 37 ꢁC in CO2 percentage inhibition was defined as the ability of tested
incubator for 4 h. After 4 h, cells were lysed using lyses buffer and compound to inhibit binding of receptor-specific radioligands at
luciface assay buffer was added to each well and counts per tested conditions.
second were recorded using luminescence counter. From CPS
The radioligand used for the selectivity assay is mentioned in
obtained, percentage inhibition was calculated for each well by the following table:
normalizing CPS values obtained in the presence of the
Receptor
*5-HT6
a1B
5-HT4b
5-HT3
Radioligand
[3H] LSD
[3H] Prazosin
[3H] GR113808
[3H] GR65630
compounds to those with 10 mM 5-HT (0% inhibition) and with
vehicle (100% inhibition). The percentage inhibition was
determined for all concentrations of the antagonists (0.1 nM to
10 mM range, half-log increment) and plotted as a function of the
antagonist concentration. The Kb values were calculated with
Prism (GraphPad) using built-in one site competition equation, by
entering EC50 values for 5-HT obtained in the same experiments
(80–100 nM) and the 5-HT concentration 10 mM, as it was used in
all the experiments.
D2
D3
DAT
NET
SERT
H1
[3H] 7 OH – DPAT
[3H] 7 OH – DPAT
[3H] WIN 35428
[3H] Nisoxetine
[3H] Citalopram
[3H] Pyrilamine
[3H] R-a-Methylhistamine
[3H] Astemizole
H3
hERG
Competitive binding of compound 9y and Schild analysis
*Assay performed at NovaScreen Biosciences Corporation, Hanover,
Maryland, USA.
5-HT dose response curve was performed in the presence of
varying concentrations of compound 9y as shown in Figure 5. The
compound produced a rightward shift of 5-HT dose response,
with a Kb value of 5.9 nM and a slope of unity in the Schild plot
analysis proving that the compound binds to 5-HT6 receptor in a
competitive manner.
pEC50 values of 5-HT alone and in the presence of different
concentrations of compound 9y are given in Table 6, as observed
the pEC50 values of 5-HT varies with different concentrations of
compound 9y showing that compound 9y is binding competitively
to 5HT6 receptor.
Rodent pharmacokinetic study
Male Wistar rats (225 25 g) were used as experimental animals.
Three animals were housed in each cage. Two days prior to dosing
day, male Wistar rats (225–250 g) were anesthetized with
isoflurane for surgical placement of jugular vein catheter.
Animals were fasted over night before oral dosing (p.o) and
food pellets were allowed 2 h post-dosing, whereas during
intravenous dosing food and water were provided as ad libitum.
Three rats were dosed with compounds (10 mg/kg) orally and
intravenously (10 mg/kg).
Protocol for specificity profile
The specificity of the compounds for 5-HT6 receptor was tested in
10 closely related and pharmacologically relevant receptor
targets. Percentage inhibition studies were performed at single
concentration of the tested compound using membrane prepar-
ations obtained from recombinant cell lines expressing relevant
At each time point, blood was collected through jugular vein
and immediately replenish with an equivalent volume of normal
saline from freely moving rats. Collected blood was transferred
into a labeled appendorf containing 10 mL of heparin as
anticoagulant. Blood samples were collected at following time

90 R. V. S. Nirogi et al.
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
Vehicle
100
Protocol for NORT
1 µM Compound 9y
The following protocol was followed for the experiment:
For object recognition test, Male Wistar rats 10–12 weeks old
were used. Arena was 50 ꢀ 50 ꢀ 50 cm. Open field was made up
of acrylic. Twenty-four hour prior to testing, rats were habituated
to individual test arenas for 20 min in the absence of any objects.
Twenty-four hours after the habituation, during the familiarization
phase (T1), rats were placed individually in the open field for
3 min, containing two identical objects (a1 and a2). T2 trial was
carried out after 24 h after the T1 trial. Rats were allowed to
explore the open field for 3 min in the presence of one familiar
object (a3) and one novel object (b). Discriminative index was
calculated.
100 nM Compound 9y
10 nM Compound 9y
75
50
25
0
0
1
2
3
4
5
Log [5-HT] nM
Morris water maze test
Figure 5. Dose response of 5-HT and right shift in the presence of
Compound 9y.
The following protocol was followed for the experiment:
Rats were acclimatized to the laboratory environment for seven
days. Rats were housed in a group of four in a controlled
environment (temp ¼ 22 2 ꢁC; humidity ¼ 50 5%) and main-
tained 12 h light/dark cycle with lights were on at 07:00 with food
and water provided ad libitum. Water maze consisted of a 1.8-m
diameter; 0.6-m high circular water maze filled with water
24 2 ꢁC up to a platform 16-cm diameter was placed 1.0 cm
below the water surface in the center of one of the eight imaginary
quadrants, which remained constant for all the rats. Prominent
visual cues surrounding the maze were used as spatial cues around
the arena (approximate 200-lux light intensity). The experiment
consisted of five days acquisition trials and one probe trial on the
seventh day, i.e. one day after the completion of acquisition trial.
Rats were administered with vehicle or test compounds 60 min
before acquisition training and 30 min after administration of
vehicle or test compounds. Scopolamine was given at a dose of
0.6 mg/kg on the first day and the dose of scopolamine was
gradually increased at a rate of 0.05 mg/kg/day. Rat was lowered
gently, feet first into water. Rat was allowed to swim for 60 s to
find the platform. If the platform was found during the time, then
trial was stopped and rat was allowed to stay on platform for 10 s
before removed from the maze. If the platform was not found
during 60 s trials then the rat was gently guided to the platform
and allowed to stay on platform for 10 s before removed from the
maze. Each rat was received four trials in a day. The maze had
eight starting points. On the first day, the animals were started
from 1st, 3rd, 5th and 7th starting points and on the second day
the animals were started from 2nd, 4th, 6th and 8th starting points
and again on the third day the animals were started from 1st, 3rd,
5th and 7th starting points, fourth day the animals were started
from 2nd, 4th, 6th and 8th and on fifth day from 1st, 3rd, 5th and
7th. Retention of the task was assessed on 7th day in which each
animal was received a single 30 s probe test with platform
removed from the pool, and percentage of time was spent in a
target quadrant (quadrant in which platform was placed during
acquisition training) was calculated.
Table 6. pEC50 values of 5-HT in the presence of different
concentrations of compound 9y.
Compound 9y (nM)
pEC50 of 5-HT
0
10
100
1000
7.12
6.55
6.07
4.52
points: pre-dose, 0.08 (only i.v.), 0.25, 0.5, 1, 2, 4, 6, 8 and 24 h
post-dose (n ¼ 3). Blood was centrifuged at 4000 rpm for 10 min.
Plasma was prepared and stored at ꢂ20 ꢁC until analysis. The
concentrations of the compounds were quantified in plasma by
qualified the LC-MS/MS method using a suitable extraction
technique. The compounds were quantified in the calibration
range around 2–2000 ng/mL in plasma. Study samples were
analyzed using calibration samples in the batch and quality
control samples spread across the batch.
Pharmacokinetic parameters Cmax, AUC0–t, t1/2 and bioavail-
ability were calculated by the non-compartmental model using a
standard non-compartmental model by using WinNonLin 5.0.1
version Software package.
Rodent brain penetration study
Male Wistar rats (225 25 g) were used as experimental animals.
Three animals were housed in each cage. Animals were given
water and food ad libitum throughout the experiment and
maintained on a 12 h light/dark cycle.
Brain penetration was determined in discrete manner in
rats. At each time point (0.50, 1 and 2 h), n ¼ 3 animals were
used. The compounds were suitably preformulated and adminis-
tered orally at (free-base equivalent) 10 mg/kg. Blood samples
were removed via, cardiac puncture by using isoflurane anesthe-
sia. The animals were sacrificed to collect the brain tissue.
Plasma was separated and brain samples were homogenized
and stored at ꢂ20 ꢁC until analysis. The concentrations of the
compound in plasma and brain were determined using the
LC-MS/MS method.
The compounds were quantified in plasma and brain homo-
genate by the qualified LC-MS/MS method using a suitable
extraction technique. The compounds were quantified in the
calibration range of 1–2000 ng/mL in plasma and brain homo-
genate. Study samples were analyzed using calibration samples in
the batch and quality control samples spread across the batch.
Extent of brain–plasma ratio was calculated (Cb/Cp).
The general synthetic strategy used for the preparation of
N0-[3-(indole-1-sulfonyl) phenyl]-N,N-dimethyl ethane-1,2-dia-
mines and N0-[3-(indole-1-sulfonyl) phenyl]-N,N-dimethyl pro-
pane-1,3-diamines (compounds 9) is summarized in Scheme 1.
Commercially available ortho-substituted acetanilides 1 were
reacted with chlorosulfonic acid at the ambient temperature
yielding the corresponding sulfonylchlorides 2, which upon
treatment with the appropriately substituted indoles 3 in the
presence of sodium hydride as base at room temperature gave the
(3-acetylamino-4-substituted phenylsulfonyl)-1H-indole deriva-
tives 4. The latter was treated with ethanolic hydrochloric acid
under reflux to obtain (3-amino-4-substituted phenylsulfonyl)-1H-
indoles 7.

DOI: 10.3109/14756366.2014.889126
Design, synthesis and pharmacological evaluation 91
2
2
Scheme 1. Reagents and conditions:
(a) ClSO3H, RT, 10–12 h; (b) substituted
indoles, NaH, THF, RT, 20–24 h;
R
R
1
1
R
3
R
H
H
N
ClO S
N
CH
CH
N
H
2
3
3
a
N
b
(c) ethanolic HCl, reflux, 2–3 h;
H
N
O S
2
CH
3
(75-85%)
O
(90-98%)
(d) substituted indoles, Et3N, DCM, RT,
24–48 h; (e) Fe/HCl, ethanol, reflux, 2–8 h;
(f) N-chlorosuccinimide, 1,4-dioxane, reflux,
5–6 h; (g) N,N-dimethylamino ethyl or propyl
chloride, DMF, xylene, K2CO3, 10–12 h,
140 ꢁC (note: compounds bearing
O
3
3
R
R
technical yield
4
1
2
O
3
R
c
(30-50%)
R3 ¼ OCH3, C2H5 were synthesized via
intermediate 1, while rest of the compounds
wherein R3 ¼ H, CH3 were synthesized via
intermediate 5. See Table 1).
2
R
2
R
2
1
R
R
1
R
1
N
R
3
ClO S
2
NO
d
2
H
N
O S
e
N
NH
2
2
NO
O S
(75-95%)
2
(35-65%)
2
3
R
7
6
3
5
R
2
3
(R = H, CH )
R
3
f
2
(R = H)
7
g
(55-65%)
(31-63%)
2
2
R
R
1
g
1
R
R
N
2
N
2
H
N
(31-55%)
CH
NH
O S
O S
3
2
N
n
3
3
CH
R
R
3
2
(R = CI)
8
9a-af
(n = 1, 2)
Alternatively, substituted indoles 3 were reacted with com- (50 mL) under nitrogen atmosphere. A solution of 5-methoxy-
mercially available substituted 3-nitrobenzenesulfonyl chlorides 5 3-methyl indole (5.3 g, 32.9 mmol) in tetrahydrofuran (25 mL)
in the presence of triethylamine as base yielding the correspond- was added to the above mixture at 25ꢁ C and further stirred for 1 h.
ing (3-nitro-4-substituted phenylsulfonyl)-1H-indoles 6. The latter Then added a solution of 3-acetamido-4-methoxy benzenesulfonyl
was reduced with Fe-HCl under reflux to obtain (3-amino-4- chloride (13.01 g, 49.3 mmol) in tetrahydrofuran (65 mL) at 0 ꢁC.
substituted phenylsulfonyl)-1H-indoles 7.
Thereafter, it was allowed to stir for 24 h at RT while monitoring
The amine intermediate 7 was treated with N-chlorosuccini- the progress of the reaction by TLC. After completion of the
mide under reflux to afford N-substituted-3-chloro indoles 8. reaction it was quenched over ice water (100 mL) under stirring
Finally, the amines 7 and 8 were reacted with N,N-dimethylamino and the product was extracted with ethyl acetate (2 ꢀ 250 mL).
ethyl or propyl chlorides in the presence of K2CO3 as base, to The combined organic phase was washed with brine, dried over
obtain the targeted compounds 9.
anhydrous sodium sulfate and concentrated under reduced
pressure to obtain the technical product (10.2 g), which was
used as such for the next step without purification. ESI-MS (m/z):
389.4 (M + H)+.
Experimental
General (representative) procedure for the synthesis of
compound 9y
1-(30-Amino-40-methoxy benzenesulfonyl)-5-methoxy-
3-methyl-1H-indole (7a)
Experimental procedures and analytical characterization data of
compounds 2a, 4a, 7a, 7b, 8b, 6g, 7g, 9a and 9b.
To a stirred solution of 1-(30-acetamido-40-methoxy benzenesul-
fonyl)-5-methoxy-3-methyl-1H-indole (10 g, 25.7 mmol) (4a) in
ethanol (100 mL) was added aq. HCl (10 mL, 33%) and the
mixture was heated to reflux temperature and maintained under
reflux for a period of 2 h. After completion of the reaction, the
reaction mass was concentrated under vacuo. The residual mass,
thus obtained, was diluted with chilled water (100 mL) and then
pH was adjusted to 9.0–10.0 with dilute sodium hydroxide
solution. The product was extracted with dichloro methane
(2 ꢀ 100 mL). The combined organic phase was washed with
brine, dried over anhydrous sodium sulfate and concentrated the
mass under reduced pressure to obtain technical product. The
obtained technical product was purified by column chromatog-
raphy using silica gel (100–200 mesh), the eluent system being
ethyl acetate and n-hexane (2:8) to obtain 3.6 g of the title
product.
3-Acetamido-4-methoxy benzenesulfonyl chloride (2a)
A mixture of chlorosulfonic acid (43.5 g, 374 mmol) and o-
methoxy acetanilide (23) (12.25 g, 75 mmol) was stirred at 100 ꢁC
for 2 h. The reaction mixture was brought to RT and stirred for
24 h. The progress of the reaction was monitored by TLC. The
reaction mass was quenched onto ice water. The solid mass, thus
obtained, was filtered under suction and washed with water
(125 mL). The product was dried in a desiccators for 3 h. Above
impure compound was recrystallized from hot benzene.
IR (cmꢂ1): 3304, 1675, 1369, 1165; 1H-NMR (400 MHz,
CDCl3): ꢁ 2.25 (3H, s), 4.02 (3H, s), 6.99–7.01 (1H, d,
J ¼ 8.8 Hz), 7.73–7.76 (1H, dd, J ¼ 2.4, 8.8 Hz), 7.83 (1H, bs),
9.13–9.14 (1H, s).
1-(30-Acetamido-40-methoxy benzenesulfonyl)-5-meth-
oxy-3-methyl-1H-indole (4a)
HPLC (%): 98.52; IR (cmꢂ1): 3487, 3385, 1616, 1514, 1336,
1226, 1157, 624; ESI-MS (m/z): 347.1 (M + H)+; 1H-NMR
(400 MHz, CDCl3): ꢁ 2.19 (3H, s), 3.81 (3H, s), 3.82 (3H, s), 3.92
(2H, bs), 6.68–6.70 (1H, d, J ¼ 8.52 Hz), 6.85–6.86 (1H, d,
Sodium hydride (2.15 g, 49.3 mmol) was taken into a 250 mL
three-necked round bottom flask containing tetrahydrofuran

92 R. V. S. Nirogi et al.
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
J ¼ 2.44 Hz), 6.88–6.91 (1H, dd, J ¼ 8.92, 2.52 Hz), 7.05–7.06 HCl (33%) and stirring the mass at 80 ꢁC for 45 min. A solution of
(1H, d, J ¼ 2.32 Hz), 7.23–7.26 (2H, m), 7.83–7.85 (1H, d, compound 6g (2.5 g, in 100 mL of ethanol) was added to the
J ¼ 8.92 Hz).
activated iron suspension at reflux temperature. Then, the mass
was further stirred for a period of 8–10 h under reflux, while
monitoring the progress of the reaction by thin layer chromatog-
raphy. After completion of the reaction, the reaction mass was
concentrated under reduced pressure, the residual mass was
quenched onto chilled water and the pH adjusted to 9.0–10.0 with
40% aqueous sodium hydroxide solution. The product was
extracted with dichloromethane (3 ꢀ 100 mL). The combined
organic layer was washed with brine solution (100 mL), dried over
anhydrous sodium sulfate and concentrated under reduced
pressure to obtain the technical product (2.2 g). The technical
product was purified by column chromatography, the eluent being
ethyl acetate and n-hexane (1:3), to obtain 1.9 g of the title
compound.
1-(30-Amino-40-methoxy benzenesulfonyl)-5-methoxy-
1H-indole (7b)
This compound was prepared by using the method described for
the preparation of 7a.
HPLC (%): 98.48; IR (cmꢂ1): 3481, 3385, 1616, 1510, 1365,
1342, 1224, 1168, 1147, 677; ESI-MS (m/z): 333.2 (M + H)+;
1H-NMR (400 MHz, CDCl3): ꢁ 3.80 (3H, s), 3.82 (3H, s), 3.94
(2H, bs), 6.55–6.56 (1H, d, J ¼ 3.6 Hz), 6.70–6.72 (1H, d,
J ¼ 8.54 Hz), 6.89–6.92 (1H, dd, J ¼ 8.98, 2.48 Hz), 6.96–6.97
(1H, d, J ¼ 2.41 Hz), 7.07–7.08 (1H, d, J ¼ 2.31 Hz), 7.26–7.28
(1H, dd, 8.57, 2.31 Hz), 7.490–7.499 (1H, d, J ¼ 3.6 Hz), 7.84–
7.87 (1H, d, J ¼ 9.0 Hz).
HPLC (%): 95.27; IR (cmꢂ1): 3479, 3387, 1620, 1467, 1365,
1342, 1224, 1145, 1028, 680; ESI-MS (m/z): 317.2 (M + H)+;
1H-NMR (400 MHz, CDCl3): ꢁ 2.09 (3H, s), 3.77 (2H, bs), 3.80
(3H, s), 6.56–6.57 (1H, d, J ¼ 3.56 Hz), 6.89–6.92 (1H, dd,
1-(30-Amino-40-methoxy benzenesulfonyl)-5-methoxy-
3-chloro-1H-indole (8b)
A stirred solution of 1-(30-Amino-40-methoxy benzenesulfonyl)-5- J ¼ 9.01, 2.48 Hz), 6.96–6.98 (1H, d, 2.44 Hz), 7.03–7.05 (1H, d,
methoxy-1H-indole (1.85 g, 5.57 mmol) (7a) in 20 mL of 7.92 Hz), 7.07 (1H, d, J ¼ 1.83 Hz), 7.13–7.15 (1H, dd, J ¼ 7.88,
1,4-dioxane was treated with N-chloro succinimide (0.818 g, 1.86 Hz), 7.47–7.49 (1H, d, J ¼ 7.96 Hz), 7.85–7.87 (1H, d,
6.12 mmol) at 100 ꢁC for a period of 8–10 h. After completion of J ¼ 9.02 Hz).
the reaction, the reaction mass was cooled to room temperature,
quenched over chilled water (30 mL) and the pH was adjusted to N0-[2-methoxy-5-(5-methoxy-3-methyl indole-1-sulfonyl)
9.0–10.0 with saturated aq.sodium carbonate. The solid com- phenyl]-N,N-dimethyl ethane-1,2-diamine (9ae)
pound that separated was filtered through buchner funnel and
To a stirred solution of 1-(30-amino-40-methoxy benzenesulfonyl)-
washed with 50 mL ice cold water. The wet material was dried
5-methoxy-3-methyl-1H-indole (0.6 g, 1.7 mmol) (7a) in a mix-
under reduced pressure and then purified by column chromatog-
ture of DMF (3 mL) and m-xylene (3 mL) was added
raphy, eluent being ethyl acetate and n-hexane (1:5) to obtain
2-dimethylaminoethyl chloride hydrochloride (0.49 g, 3.4 mmol)
1.31 g of the title product.
and potassium carbonate (0.7 g, 5.1 mmol) at room temperature.
HPLC (%): 98.09; IR (cmꢂ1): 3487, 3387, 1618, 1512, 1365,
Then, the reaction mass was heated to 135–138 ꢁC and maintained
1350, 1213, 1168, 1024, 680; ESI-MS (m/z): 367.1, 369.1
at this temperature for a period of 10 h. After completion of the
(M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ 3.83 (3H, s), 3.84
reaction, the mass was cooled to room temperature and quenched
(3H, s), 3.97 (2H, bs), 6.71–6.73 (1H, d, J ¼ 8.55 Hz), 6.93–6.94
onto chilled water (25 mL). The pH of the reaction mass was
(1H, d, J ¼ 2.37 Hz), 6.95–6.98 (1H, dd, J ¼ 8.94, 2.52 Hz), 7.06–
adjusted to 9.0–10.0 with lye solution and the product was
7.07 (1H, d, J ¼ 2.35 Hz), 7.26–7.28 (1H, dd, J ¼ 8.62, 2.35 Hz),
extracted with dichloromethane (2 ꢀ 50 mL). The combined
7.48 (1H, s), 7.85–7.87 (1H, d, J ¼ 8.99 Hz).
organic layer was washed with brine, dried over anhydrous
sodium sulfate and concentrated under reduced vacuum to obtain
1-(30-Nitro-40-methyl benzenesulfonyl)-5-methoxy-
the technical product. The latter was purified by column
1H-indole (6g)
chromatography, eluent being ethyl acetate and triethylamine
To a stirred mixture of 5-methoxy-1H-indole (3.0 g, 20.4 mmol) (99:1) to obtain 0.24 g of the title product.
and triethylamine (5.15 g, 51.02 mmol) in dichloromethane
HPLC (%): 97.67; IR (cmꢂ1): 3404, 1597, 1359, 1166;
(40 mL) was added a solution of 3-nitro-4-methyl benzenesulfonyl ESI-MS (m/z): 418.5 (M + H)+; H-NMR (400 MHz, CDCl3): ꢁ
chloride (5.76 g, 24.48 mmol) in dichloromethane (65 mL) at 0 ꢁC 2.2 (3H, s), 2.29 (6H, s), 2.58–2.61 (2H, t, J ¼ 5.92 Hz), 3.14–3.16
over a period of 10 min. Then, it was allowed to stir at room (2H, t, J ¼ 5.96 Hz), 3.80 (3H, s), 3.82 (3H, s), 4.8 (1H, bs), 6.62–
temperature for 48 h. After completion of the reaction, the organic 6.64 (1H, d, J ¼ 8.45 Hz), 6.84–6.85 (1H, d, J ¼ 2.42 Hz), 6.86
reaction mass was washed with brine, dried over anhydrous (1H, d, J ¼ 2.27 Hz), 6.88–6.90 (1H, dd, J ¼ 8.93, 2.49 Hz), 7.15–
sodium sulfate and concentrated under reduced pressure to obtain 7.17 (1H, dd, J ¼ 8.39, 2.27 Hz), 7.24 (1H, s), 7.86–7.88 (1H, d,
technical product (7.06 g). The technical product was purified by J ¼ 8.93 Hz); HRMS: [M + H]+ C21H28N3O4S calc. 418.1801,
column chromatography, eluent being ethyl acetate and n-hexane found. 418.1804.
1
(1:10) to obtain 2.60 g of the title product.
IR (cmꢂ1): 3130, 2997, 2970 1608, 1531, 1375, 1348, 1224,
1182, 1026, 596; ESI-MS (m/z): 345 (M ꢂ H+); 1H-NMR N0-[5-(3-chloro-5-methoxy indole-1-sulfonyl)-2-methoxy
(400 MHz, CDCl3): ꢁ 2.59 (3H, s), 3.81 (3H, s), 6.63–6.64 (1H, phenyl]-N, N-dimethyl ethane-1,2-diamine (9b)
d, J ¼ 3.64 Hz), 6.94 (1H, d, J ¼ 2.51 Hz), 6.96–6.98 (1H, dd,
This compound was prepared by using the method described for
J ¼ 3.5, 1.99 Hz), 7.40–7.42 (1H, d, J ¼ 8.15 Hz), 7.49–7.50 (1H,
the preparation of 9a.
d, 3.65 Hz), 7.86–7.88 (1H, d, J ¼ 8.78 Hz), 7.90–7.92 (1H, dd,
J ¼ 8.14, 1.98 Hz), 8.43 (1H, d, 1.93 Hz).
HPLC (%): 98.09; IR (cmꢂ1): 3415, 1597, 1367, 1166; ESI-
1
MS (m/z): 438.3 (M + H)+; H-NMR (400 MHz, CDCl3): ꢁ 2.29
(6H, s), 2.59–2.62 (2H, t, J ¼ 5.92 Hz), 3.15–3.18 (2H,
t, J ¼ 5.96 Hz), 3.82 (3H, s), 3.83 (3H, s), 4.91 (1H, bs), 6.66–
6.68 (1H, d, J ¼ 8.45 Hz), 6.84 (1H, d, J ¼ 2.14 Hz), 6.92–6.93
1-(30-Amino-40-methyl benzenesulfonyl)-5-methoxy-
1H-indole (7g)
Iron powder (4.2 g, 73.57 mmol) was taken in a RBF along with (1H, d, J ¼ 2.29 Hz), 6.94–6.97 (1H, dd, J ¼ 8.98, 2.44 Hz), 7.19–
40 mL of water and then activated it by adding 5 mL of conc. 7.22 (1H, dd, J ¼ 8.4, 2.2 Hz), 7.51 (1H, s), 7.88–7.9 (1H, d,

DOI: 10.3109/14756366.2014.889126
Design, synthesis and pharmacological evaluation 93
J ¼ 8.96 Hz); HRMS: [M + H]+ C20H25ClN3O4S calc. 438.1254, 7.51–7.52 (1H, d, J ¼ 3.62 Hz), 7.88–7.90 (1H, d, J ¼ 9.0 Hz);
found. 438.1251.
HRMS: [M + H]+ C20H26N3O3S calc. 388.1695, found. 388.1693.
Examples 9c–9af
N0-[2-ethyl-5-(5-fluoro indole-1-sulfonyl) phenyl]-N,
N-dimethyl ethane-1,2-diamine (9h)
The compounds 9c–9af were prepared by using the method
described in example 9a and 9b with some non-critical variations. HPLC (%): 99.50; MR (ꢁC): 81.21; IR (cmꢂ1): 3412, 1595, 1367,
The analytical data are presented below.
1168; ESI-MS (m/z): 390.2 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 1.16–1.20 (3H, t, J ¼ 7.45 Hz), 2.22 (6H, s), 2.39–
2.45 (2H, q, J ¼ 7.48 Hz), 2.54–2.57 (2H, t, J ¼ 5.67 Hz), 3.06–
3.10 (2H, q, J ¼ 5.08 Hz), 4.66 (1H, bs), 6.58–6.59 (1H, d,
J ¼ 3.6 Hz), 6.91–6.92 (1H, d, J ¼ 1.90 Hz), 6.99–7.04 (1H, dt,
J ¼ 9.0, 2.54 Hz), 7.05–7.07 (1H, d, J ¼ 7.92 Hz), 7.12–7.18 (2H,
m), 7.59–7.60 (1H, d, J ¼ 3.64 Hz), 7.93–7.96 (1H, d,
J ¼ 4.40 Hz); HRMS: [M + H]+ C20H25FN3O2S calc. 390.1651,
found. 390.1653.
N0-[5-(3-chloro indole-1-sulfonyl)-2-methoxy phenyl]-N,
N-dimethyl ethane-1,2-diamine (9c)
HPLC (%): 97.38; MR (ꢁC): 96.88; IR (cmꢂ1): 3388, 1597, 1367,
1168; ESI-MS (m/z): 408.2 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 2.35 (6H, s), 2.66–2.69 (2H, t, J ¼ 5.96 Hz), 3.21–
3.24 (2H, t, J ¼ 6.02 Hz), 3.82 (3H, s), 4.98 (1H, bs), 6.67–6.69
(1H, d, J ¼ 8.47 Hz), 6.86 (1H, d, J ¼ 2.26 Hz), 7.23–7.25 (1H, dd,
J ¼ 6.24, 2.29 Hz), 7.27–7.31 (1H, dd, J ¼ 8.05, 0.87 Hz), 7.34–
7.38 (1H, dt, J ¼ 8.28, 1.1 Hz), 7.53–7.55 (1H, d, J ¼ 7.87 Hz),
7.56 (1H, s), 8.0–8.02 (1H, d, J ¼ 7.62 Hz); HRMS: [M + H]+
C19H23ClN3O3S calc. 408.1149, found. 408.1145.
N0-[2-ethyl-5-(5-methoxy-3-methyl indole-1-sulfonyl)
phenyl]-N, N-dimethyl ethane-1,2-diamine (9i)
HPLC (%): 98.89; IR (cmꢂ1): 2964, 1597, 1363, 1168; ESI-MS
1
(m/z): 416.4 (M + H)+; H-NMR (400 MHz, CDCl3): ꢁ 1.15–1.19
N0-[5-(indole-1-sulfonyl)-2-methoxy phenyl]-N, N-dimethyl
ethane-1,2-diamine (9d)
(3H, t, J ¼ 7.48 Hz), 2.2 (3H, s), 2.22 (6H, s), 2.37–2.43 (2H, q,
J ¼ 7.48 Hz), 2.53–2.56 (2H, t, J ¼ 5.68 Hz), 3.06–3.10 (2H,
q, J ¼ 5.08 Hz), 3.82 (3H, s), 4.60 (1H, bs), 6.86 (1H, d,
J ¼ 2.38 Hz), 6.89–6.92 (1H, dd, J ¼ 2.47, 8.94 Hz), 6.92–6.93
(1H, d, J ¼ 1.72 Hz), 7.02–7.03 (1H, d, J ¼ 7.94 Hz), 7.09–7.11
(1H, dd, J ¼ 7.84, 1.80 Hz), 7.27 (1H, s), 7.88–7.90 (1H, d,
J ¼ 8.9 Hz); HRMS: [M + H]+ C22H30N3O3S calc. 416.2008,
found. 416.2005.
HPLC (%): 98.93; MR (ꢁC): 127.73; IR (cmꢂ1): 3392, 1597,
1361, 1168; ESI-MS (m/z): 374.1 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 2.37 (6H, s), 2.68–2.71 (2H, t, J ¼ 5.96 Hz), 3.21–3.24
(2H, t, J ¼ 6.04 Hz), 3.81 (3H, s), 5.05 (1H, bs), 6.62–6.63 (1H, d,
J ¼ 3.6 Hz), 6.66–6.68 (1H, d, J ¼ 8.44 Hz), 6.89–6.9 (1H, d,
J ¼ 2.25 Hz), 7.18–7.25 (2H, m), 7.29–7.31 (1H, dd, J ¼ 8.19,
0.96 Hz), 7.51–7.53 (1H, d, J ¼ 7.76 Hz), 7.56–7.57 (1H, d,
J ¼ 3.64 Hz), 7.99–8.01 (1H, d, J ¼ 8.16 Hz); HRMS: [M + H]+
C19H24N3O3S calc. 374.1538, found. 374.1534.
N0-[5-(6-chloro indole-1-sulfonyl)-2-methyl phenyl]-N,
N-dimethyl ethane-1,2-diamine (9j)
HPLC (%): 99.48; MR (ꢁC): 84.8–87.5; IR (cmꢂ1): 3412, 1598,
1365, 1134; ESI-MS (m/z): 392.3 (M + H)+;. 1H-NMR (400 MHz,
CDCl3): ꢁ 2.1 (3H, s), 2.25 (6H, s), 2.59–2.62 (2H, t, J ¼ 5.92 Hz),
3.12–3.16 (2H, t, J ¼ 5.88 Hz), 4.59 (1H, bs), 6.58–6.60 (1H, d,
J ¼ 3.64 Hz), 6.96 (1H, d, J ¼ 1.8 Hz), 7.05–7.10 (2H, m), 7.16–
7.19 (1H, dd, J ¼ 8.4, 1.84 Hz), 7.41–7.43 (1H, d, J ¼ 8.36 Hz),
7.54–7.55 (1H, d, J ¼ 3.68 Hz), 8.03–8.04 (1H, d, J ¼ 1.84 Hz);
HRMS: [M + H]+ C19H23ClN3O2S calc. 392.1199, found.
392.1202.
N0-[2-methoxy-5-(3-methyl-indole-1-sulfonyl) phenyl]-N,
N-dimethyl ethane-1,2-diamine (9e)
HPLC (%): 99.04; MR (ꢁC): 110.42; IR (cmꢂ1): 3396, 1597,
1361, 1166; ESI-MS (m/z): 388.2 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 2.2 (3H, s), 2.29 (6H, s), 2.59–2.62 (2H, t, J ¼ 5.92 Hz),
3.15–3.18 (2H, t, J ¼ 5.96 Hz), 3.80 (3H, s), 4.86 (1H, bs), 6.65–
6.67 (1H, d, J ¼ 8.44 Hz), 6.90 (1H, d, J ¼ 2.26 Hz), 7.20 (1H, d,
J ¼ 2.24 Hz), 7.22–7.23 (1H, m), 7.27–7.31 (2H, m), 7.43–7.45
(1H, d, J ¼ 7.61 Hz), 7.98–8.0 (1H, d, J ¼ 8.24 Hz); HRMS:
[M + H]+ C20H26N3O3S calc. 388.1695, found. 388.1692.
N0-[3-(6-chloro indole-1-sulfonyl) phenyl]-N, N-dimethyl
ethane-1,2-diamine (9k)
HPLC (%): 97.69; IR (cmꢂ1): 2933, 1602, 1369, 1170; ESI-MS
(m/z): 378.7, 380.7(M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ 2.28
(6H, s), 2.60–2.63 (2H, t, J ¼ 5.63 Hz), 3.13–3.16 (2H,
t, J ¼ 5.55 Hz), 5.0 (1H, bs), 6.60–6.61 (1H, d, J ¼ 3.70 Hz),
6.72–6.75 (1H, m), 7.00–7.01 (1H, dt, J ¼ 2.1 Hz), 7.10–7.12
(1H, m), 7.17–7.21 (2H, m), 7.42–7.44 (1H, d, J ¼ 8.36 Hz), 7.53–
7.54 (1H, d, J ¼ 3.68 Hz), 8.02 (1H, d, J ¼ 1.0 Hz); HRMS:
[M + H]+ C18H21ClN3O2S calc. 378.1043, found. 378.1046.
N0-[5-(5-methoxy-3-methyl indole-1-sulfonyl)-2-methyl
phenyl]-N,N-dimethyl ethane-1,2-diamine (9f)
HPLC (%): 97.19; IR (cmꢂ1): 3390, 1598, 1363, 1168; ESI-MS
(m/z): 402.4 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ 2.07
(3H, s), 2.19–2.20 (3H, s), 2.23 (6H, s), 2.55–2.58 (2H,
t, J ¼ 6.0 Hz), 3.10 (2H, t), 3.82 (3H, s), 4.48 (1H, bs), 6.85–
6.86 (1H, d, J ¼ 2.43 Hz), 6.88–6.91 (2H, m), 6.99–7.01 (1H, d,
J ¼ 7.98 Hz), 7.05–7.07 (1H, dd, J ¼ 7.78, 1.84 Hz), 7.26 (1H, s),
7.87–7.89 (1H, d, J ¼ 8.94 Hz); HRMS: [M + H]+ C21H28N3O3S
calc. 402.1851, found. 402.1855.
N0-[2-ethyl-5-(5-methoxy indole-1-sulfonyl) phenyl]-N,
N-dimethyl ethane-1,2-diamine (9l)
HPLC (%): 98.06; IR (cmꢂ1): 3377, 2966, 1597, 1365, 1147;
ESI-MS (m/z): 402.6 (M+H)+; 1H-NMR (400 MHz, CDCl3):
ꢁ 1.15–1.19 (3H, t, J ¼ 7.48 Hz), 2.31 (6H, s), 2.39–2.44 (2H, q,
J ¼ 7.48 Hz), 2.65–2.68 (2H, t, J ¼ 5.96 Hz), 3.15–3.18 (2H,
t, J ¼ 5.6 Hz), 3.80 (3H, s), 5.3 (1H, bs), 6.55–6.56 (1H, d,
J ¼ 3.56 Hz), 6.89–6.90 (1H, d, J ¼ 2.23 Hz), 6.91–6.92 (1H,
d, J ¼ 2.51 Hz), 6.96–6.97 (1H, d, J ¼ 2.44 Hz), 7.04–7.06 (1H, d,
J ¼ 7.91 Hz), 7.12–7.15 (1H, dd, J ¼ 7.90, 1.89 Hz), 7.51–7.52
(1H, d, J ¼ 3.61 Hz), 7.89–7.91 (1H, d, J ¼ 9.0 Hz); HRMS:
[M + H]+ C21H28N3O3S calc. 402.1851, found. 402.1854.
N0-[5-(5-methoxy indole-1-sulfonyl)-2-methyl phenyl]-
N,N-dimethyl ethane -1,2-diamine (9g)
HPLC (%): 98.21; MR (ꢁC): 99.7–101.2; IR (cmꢂ1): 3336, 1604,
1350, 1138; ESI-MS (m/z): 388.4 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 2.08 (3H, s), 2.25 (6H, s), 2.57–2.60 (2H, t, J ¼ 6.0 Hz),
3.10–3.13 (2H, t, J ¼ 5.72 Hz), 3.80 (3H, s), 4.53 (1H, bs), 6.55–
6.56 (1H, d, J ¼ 3.55 Hz), 6.89 (1H, d, J ¼ 2.52 Hz), 6.90–6.92
(1H, d, J ¼ 2.74 Hz), 6.95–6.96 (1H, d, J ¼ 2.45 Hz), 7.01–7.03
(1H, d, J ¼ 7.89 Hz), 7.07–7.10 (1H, dd, J ¼ 7.78, 1.87 Hz),

94 R. V. S. Nirogi et al.
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
N0-[5-(5-bromo indole-1-sulfonyl)-2-ethyl phenyl]-N,
N-dimethyl ethane-1,2-diamine (9m)
CDCl3): ꢁ 1.16–1.20 (3H, t, J ¼ 7.45 Hz), 2.22 (6H, s), 2.39–
2.45 (2H, q, J ¼ 7.49 Hz), 2.55–2.57 (2H, t, J ¼ 5.67 Hz), 3.06–
3.10 (2H, q, J ¼ 5.08 Hz), 4.67 (1H, bs), 6.56–6.57 (1H, d,
J ¼ 3.69 Hz), 6.91 (1H, d, J ¼ 1.89 Hz), 7.05–7.07 (1H, d,
J ¼ 7.90 Hz), 7.12–7.15 (1H, dd, J ¼ 7.9, 1.96 Hz), 7.23–7.24
(1H, d, J ¼ 2.04 Hz), 7.49–7.52 (1H, dd, J ¼ 9.89, 1.99 Hz), 7.58–
7.59 (1H, d, J ¼ 3.66 Hz), 7.92–7.94 (1H, d, J ¼ 8.8 Hz); HRMS:
[M + H]+ C20H25ClN3O2S calc. 406.1356, found. 406.1354.
HPLC (%): 98.66; IR (cmꢂ1): 3388, 1571, 1369, 1170; ESI-MS
(m/z): 450.6, 452.6 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ
1.15–1.18 (3H, t, J ¼ 7.48 Hz), 2.23 (6H, s), 2.39–2.45 (2H, q,
J ¼ 7.48 Hz), 2.55–2.58 (2H, t, J ¼ 5.64 Hz), 3.07–3.11 (2H, q,
t ¼ 5.16 Hz), 4.69 (1H, bs), 6.56–6.57 (1H, d, J ¼ 3.69 Hz), 6.90–
6.91 (1H, d, J ¼ 1.9 Hz), 7.05–7.07 (1H, d, J ¼ 7.91 Hz), 7.12–
7.15 (1H, dd, J ¼ 7.88, 1.92 Hz), 7.37–7.39 (1H, dd, J ¼ 8.80,
1.92 Hz), 7.56–7.57 (1H, d, J ¼ 3.36 Hz), 7.65 (1H, d,
J ¼ 1.83 Hz), 7.87–7.89 (1H, d, J ¼ 8.82 Hz); HRMS: [M + H]+
C20H25BrN3O2S calc. 450.0851, found. 450.0849.
N0-[3-(5-bromo indole-1-sulfonyl) phenyl]-N, N-dimethyl
ethane-1,2-diamine (9s)
HPLC (%): 97.54; IR (cmꢂ1): 3311, 1600, 1369, 1172; ESI-MS
(m/z): 422.5, 424.5 (M + H)+; 1H-NMR (400 MHz, CDCl3):
ꢁ 2.28 (6H, s), 2.58–2.61 (2H, t, J ¼ 5.87 Hz), 3.10–3.13 (2H,
t, J ¼ 5.57 Hz), 4.96 (1H, bs), 6.58–6.59 (1H, d, J ¼ 3.60 Hz),
6.70–6.73 (1H, m), 6.96–6.97 (1H, t, J ¼ 2.08 Hz), 7.08–7.11 (1H,
m), 7.15–7.19 (1H, dt, J ¼ 7.88 Hz), 7.38–7.40 (1H, dd, J ¼ 8.81,
1.9 Hz), 7.55 (1H, d, J ¼ 3.64 Hz), 7.66 (1H, d, J ¼ 1.8 Hz), 7.85–
7.87 (1H, d, J ¼ 8.81 Hz); HRMS: [M + H]+ C18H21BrN3O2S
calc. 422.0538, found. 422.0536.
N0-[3-(4-chloro-3-methyl indole-1-sulfonyl) phenyl]-N,
N-dimethyl ethane-1,2-diamine (9n)
HPLC (%): 95.06; IR (cmꢂ1): 3390, 1600, 1367, 1174; ESI-MS
(m/z): 392.3, 394.3 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ
2.24 (6H, s), 2.46 (3H, s), 2.53–2.55 (2H, t, J ¼ 5.64 Hz), 3.06–
3.10 (2H, t, J ¼ 5.63 Hz), 4.71 (1H, bs), 6.72 (1H, m), 6.97–6.98
(1H, dt, J ¼ 2.1 Hz), 7.08–7.11 (1H, m), 7.13–7.19 (3H, m), 7.30
(1H, d, J ¼ 1.22 Hz), 7.86–7.89 (1H, dd, J ¼ 9.17, 2.53 Hz);
HRMS: [M + H]+ C19H23ClN3O2S calc. 392.1199, found.
392.1202.
N0-[3-(4-chloro indole-1-sulfonyl) phenyl]-N, N-dimethyl
ethane-1,2-diamine (9t)
HPLC (%): 96.30; IR (cmꢂ1): 3371, 1600, 1371, 1166; ESI-MS
(m/z): 378.5, 380.5 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ
2.29 (6H, s), 2.60–2.63 (2H, t, J ¼ 5.64 Hz), 3.11–3.14 (2H,
t, J ¼ 5.56 Hz), 5.29 (1H, bs), 6.69–6.72 (1H, m), 6.75–6.76
(1H, d, J ¼ 3.72 Hz), 6.95–6.96 (1H, t, J ¼ 2.09 Hz), 7.10–7.12
(1H, m), 7.15–7.19 (1H, t, J ¼ 7.84 Hz), 7.20–7.22 (2H, m), 7.58–
7.59 (1H, d, J ¼ 3.7 Hz), 7.86–7.90 (1H, m); HRMS: [M + H]+
C18H21ClN3O2S calc. 378.1043, found. 378.1045.
N0-[2-ethyl-5-(5-fluoro-3-methyl indole-1-sulfonyl)
phenyl]-N, N-dimethyl ethane-1,2-diamine (9o)
HPLC (%): 98.52; MR (ꢁC): 105.4–108.2; IR (cmꢂ1): 3404, 1595,
1359, 1178; ESI-MS (m/z): 404.4 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 1.16–1.19 (3H, t, J ¼ 7.45 Hz), 2.19–2.20 (3H, s), 2.22
(6H, s), 2.39–2.44 (2H, q, J ¼ 7.49 Hz), 2.54–2.57 (2H, t,
J ¼ 5.67 Hz), 3.06–3.10 (2H, q, J ¼ 4.89 Hz), 4.64 (1H, bs), 6.92
(1H, d, J ¼ 1.85 Hz), 7.01–7.12 (4H, m), 7.33 (1H, d,
J ¼ 0.92 Hz), 7.92–7.95 (1H, dd, J ¼ 4.38 Hz); HRMS: [M + H]+
C21H27FN3O2S calc. 404.1808, found. 404.1806.
N0-[5-(5-bromo-3-methyl indole-1-sulfonyl)-2-ethyl
phenyl]-N, N-dimethyl ethane-1,2-diamine (9u)
N0-[3-(5-isopropoxy-3-methyl indole-1-sulfonyl) phenyl]-
N, N-dimethyl ethane-1,2-diamine (9p)
HPLC (%): 99.25; MR (ꢁC): 105.4–108.2; IR (cmꢂ1): 3373, 1597,
1367, 1166; ESI-MS (m/z): 464.7, 466.7 (M + H)+; 1H-NMR
(400 MHz, CDCl3): ꢁ 1.15–1.19 (3H, t, J ¼ 7.44 Hz), 2.20 (3H, s),
2.28 (6H, s), 2.61–2.64 (2H, t, J ¼ 5.97 Hz), 2.96–3.02 (2H, q,
J ¼ 7.3 Hz), 3.13–3.16 (2H, t, J ¼ 5.65 Hz), 4.75 (1H, bs), 6.89–
6.90 (1H, d, J ¼ 1.85 Hz), 7.04–7.06 (1H, d, J ¼ 7.93 Hz), 7.10–
7.12 (1H, dd, J ¼ 7.88, 1.89 Hz), 7.37–7.39 (1H, dd, J ¼ 8.78,
1.91 Hz), 7.57 (1H, s), 7.76–7.78 (1H, d, J ¼ 8.3 Hz), 7.87–7.89
(1H, d, J ¼ 8.82 Hz); HRMS: [M + H]+ C21H27BrN3O2S calc.
464.1007, found. 464.1009.
HPLC (%): 96.13; MR (ꢁC): 86.24; IR (cmꢂ1): 3387, 2978, 1602,
1359, 1176; ESI-MS (m/z): 416.3 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 1.32–1.33 (6H, d, J ¼ 6.0 Hz), 2.18 (3H, s), 2.23 (6H,
s), 2.51–2.54 (2H, t, J ¼ 5.65 Hz), 3.05–3.07 (2H, q, J ¼ 4.98 Hz),
4.50–4.56 (1H, sept, J ¼ 6.0Hz), 4.64 (1H, bs), 6.66–6.69 (1H, m),
6.88–6.90 (2H, m), 6.98–6.99 (1H, t, J ¼ 3.04 Hz), 7.07–7.09 (1H,
m), 7.12–7.16 (1H, t, J ¼ 7.84 Hz), 7.23 (1H, s), 7.84–7.86 (1H,
dd, J ¼ 7.8, 1.8 Hz); HRMS: [M + H]+ C22H30N3O3S calc.
416.2008, found. 416.2010.
N0-[3-(5-ethoxy-3-methyl indole-1-sulfonyl) phenyl]-
N,N-dimethyl ethane-1,2-diamine (9v)
N0-[3-(5-isopropoxy indole-1-sulfonyl) phenyl]-N,
N-dimethyl ethane-1,2-diamine (9q)
HPLC (%): 97.12; IR (cmꢂ1): 3390, 1602, 1363, 1172; ESI-MS
1
(m/z): 402.5 (M + H)+; H-NMR (400 MHz, CDCl3): ꢁ 1.40–1.43
HPLC (%): 97.46; IR (cmꢂ1): 3387, 2974, 1600, 1367, 1174; ESI-
MS (m/z): 402.3 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ 1.31–
1.33 (6H, d, J ¼ 6.0 Hz), 2.22 (6H, s), 2.50–2.53 (2H, t,
J ¼ 5.64 Hz), 3.03–3.07 (2H, t, J ¼ 5.04 Hz), 4.47–4.53 (1H, m),
4.61(1H, bs), 6.54–6.55 (1H, d, J ¼ 3.6 Hz), 6.70 (1H, m), 6.88–
6.91 (1H, dd, J ¼ 8.96, 2.44 Hz), 6.97 (1H, d, J ¼ 2.36 Hz), 6.98–
6.99 (1H, t, J ¼ 1.96 Hz), 7.11 (1H, m), 7.14–7.16 (1H, dt,
J ¼ 7.92 Hz), 7.48–7.49 (1H, d, J ¼ 3.64 Hz), 7.85–7.87 (1H, d,
J ¼ 9.0 Hz); HRMS: [M + H]+ C21H28N3O3S calc. 402.1851,
found. 402.1849.
(3H, t, J ¼ 6.99 Hz), 2.19 (3H, s), 2.22 (6H, s), 2.49–2.52 (2H, t,
J ¼ 5.98 Hz), 3.03–3.07 (2H, q, J ¼ 5.01 Hz), 4.02–4.07 (2H, q,
J ¼ 6.98 Hz), 4.56–4.58 (1H, bs), 6.66–6.68 (1H, m), 6.86 (1H, d,
J ¼ 2.38 Hz), 6.89–6.92 (1H, dd, J ¼ 8.92, 2.46 Hz), 6.98–6.99
(1H, t, J ¼ 2.07 Hz), 7.06–7.09 (1H, m), 7.12–7.16 (1H, dt,
J ¼ 7.84 Hz), 7.24 (1H, s), 7.85–7.87 (1H, d, J ¼ 8.95 Hz); HRMS:
[M + H]+ C21H28N3O3S calc. 402.1851, found. 402.1848.
N0-[3-(5-chloro-3-methyl indole-1-sulfonyl)-2-ethyl
phenyl]-N, N-dimethyl ethane-1,2-diamine (9w)
N0-[2-ethyl-5-(5-chloro indole-1-sulfonyl) phenyl]-
N,N-dimethyl ethane-1,2-diamine (9r)
HPLC (%): 98.28; IR (cmꢂ1): 3390, 1597, 1367, 1168; ESI-MS
(m/z): 420.2, 422.2 (M + H)+; 1H-NMR (400 MHz, CDCl3):
ꢁ 1.16–1.19 (3H, t, J ¼ 7.48 Hz), 2.20 (3H, s), 2.23 (6H, s),
2.39–2.44 (2H, q, J ¼ 7.48 Hz), 2.55–2.57 (2H, t, J ¼ 5.66 Hz),
HPLC (%): 99.34; IR (cmꢂ1): 3390, 1597, 1369, 1168;
ESI-MS (m/z): 406.3, 408.3 (M + H)+; 1H-NMR (400 MHz,

DOI: 10.3109/14756366.2014.889126
Design, synthesis and pharmacological evaluation 95
3.07–3.11 (2H, q, J ¼ 5.14 Hz), 5.3 (1H, bs), 6.91–6.92 (1H, d, t, 7.96 Hz), 7.25 (1H, m), 7.86–7.88 (1H, d, J ¼ 8.88 Hz); HRMS:
J ¼ 1.86 Hz), 7.04–7.06 (1H, d, J ¼ 7.91 Hz), 7.09–7.12 (1H, [M + H]+ C21H28N3O3S calc. 402.1851, found. 402.1848.
dd, J ¼ 7.9, 1.9 Hz), 7.23–7.24 (1H, d, J ¼ 2.06 Hz), 7.32 (1H, d,
J ¼ 1.14 Hz), 7.40–7.41 (1H, d, J ¼ 1.98 Hz), 7.91–7.93 (1H, d, N0-[2-methoxy-5-(5-methoxy-3-methyl indole-1-sulfonyl)
J ¼ 8.82 Hz); HRMS: [M + H]+ C21H27ClN3O2S calc. 420.1512, phenyl]-N,N-dimethyl propane-1,3-diamine (9ac)
found. 420.1515.
HPLC (%): 97.33; IR (cmꢂ1): 3418, 2941, 1597, 1519, 1359,
1166; ESI-MS (m/z): 432.4 (M + H)+; 1H-NMR (400 MHz,
CDCl3): ꢁ 1.75–1.80 (2H, m), 2.19 (3H, s), 2.27 (6H, s), 2.4–
N0-[2-methoxy-5-(5-chloro-3-methyl indole-1-sulfonyl)
phenyl]-N, N-dimethyl ethane-1,2-diamine (9x)
2.44 (2H, t, J ¼ 6.96 Hz), 3.10–3.13 (2H, t, J ¼ 6.72 Hz), 3.80 (3H,
HPLC (%): 98.90; IR (cmꢂ1): 3408, 2941, 1596, 1361, 1167; s), 3.82 (3H, s), 4.8 (1H, bs), 6.63–6.65 (1H, d, J ¼ 8.44 Hz),
ESI-MS (m/z): 422.2, 424.2 (M + H)+; 1H-NMR (400 MHz, 6.85–6.91 (3H, m), 7.14–7.16 (1H, dd, J ¼ 8.40, 2.28 Hz), 7.26
CDCl3): ꢁ 2.2 (3H, s), 2.24 (6H, s), 2.53–2.56 (2H, t), 3.09– (1H, s), 7.87–7.89 (1H, d, J ¼ 8.92 Hz); HRMS: [M + H]+
3.10 (2H, t), 3.82 (3H, s), 4.85 (1H, bs), 6.65–6.69 (1H, d, C22H30N3O4S calc. 432.1957, found. 432.1954.
J ¼ 8.44 Hz), 6.85–6.86 (1H, d, J ¼ 2.28 Hz), 7.17–7.19 (1H, dd,
J ¼ 8.4, 2.28 Hz), 7.23–7.25 (1H, dd, J ¼ 8.8, 2.08 Hz), 7.31 (1H, N0-[2-methoxy-5-(5-fluoro-3-methyl indole-1-sulfonyl)
d, J ¼ 1.08 Hz), 7.40 (1H, d, J ¼ 2.0 Hz), 7.90–7.92 (1H, d, phenyl]-N,N-dimethyl propane-1,3-diamine (9ad)
J ¼ 8.76); HRMS: [M + H]+ C20H25ClN3O3S calc. 422.1305,
HPLC (%): 98.69; IR (cmꢂ1): 3426, 2942, 1596, 1363, 1166;
found. 422.1303.
1
ESI-MS (m/z): 420.3 (M + H)+; H-NMR (400 MHz, CDCl3): ꢁ
1.76–1.79 (2H, m), 2.19 (3H, s), 2.27 (6H, s), 2.41–2.44 (2H,
N0-[2-methoxy-5-(3-methyl indole-1-sulfonyl) phenyl]-N,
N-dimethyl propane-1,3-diamine (9y)
t, 6.92 Hz), 3.10–3.13 (2H, t, 6.72 Hz), 3.82 (3H, s), 4.8 (1H, bs),
6.65–6.67 (1H, d, J ¼ 8.48 Hz), 6.86–6.87 (1H, d, J ¼ 2.28 Hz),
HPLC (%): 98.20; IR (cmꢂ1): 3407, 2962, 1595, 1361, 1166; ESI- 7.0–7.01 (1H, m), 7.06–7.09 (1H, dd, J ¼ 8.76, 2.48 Hz), 7.15–
MS (m/z): 402.4 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ 1.74– 7.17 (1H, dd, J ¼ 8.44, 2.32 Hz), 7.32 (1H, s), 7.91–7.94 (1H, m);
1.81 (2H, m), 2.23 (3H, s), 2.28 (6H, s), 2.41–2.44 (2H, t, HRMS: [M + H]+ C21H27FN3O3S calc. 420.1757, found.
6.88 Hz), 3.11–3.14 (2H, t, 6.72 Hz), 3.81 (3H, s), 4.8 (1H, bs), 420.1755.
6.64–6.66 (1H, d, J ¼ 8.44 Hz), 6.90–6.91 (1H, d, J ¼ 2.28 Hz),
N0-[2-methoxy-5-(5-chloro-3-methyl indole-1-sulfonyl)
phenyl]-N,N-dimethyl propane-1,3-diamine (9ae)
7.17–7.23 (2H, m), 7.27–7.31 (2H, m), 7.43–7.45 (1H, d,
J ¼ 7.76 Hz), 7.98–8.0 (1H, d, J ¼ 8.16 Hz); HRMS: [M + H]+
C21H28N3O3S calc. 402.1851, found. 402.1854.
HPLC (%): 98.20; IR (cmꢂ1): 3425, 2942, 1596, 1364, 1167; ESI-
1
MS (m/z): 436.3, 438.3 (M + H)+; H-NMR (400 MHz, CDCl3):
N0-[5-(5-methoxy indole-1-sulfonyl)-2-methyl phenyl]-N,
ꢁ 1.74–1.80 (2H, m), 2.19 (3H, s), 2.27 (6H, s), 2.40–2.44 (2H, t),
N-dimethyl propane-1,3-diamine (9z).
3.10–3.13 (2H, t), 3.82 (3H, s), 4.85 (1H, bs), 6.64–6.67 (1H, d,
HPLC (%): 98.21; MR (ꢁC): 139.5–141; IR (cmꢂ1): 3226, 1602, J ¼ 8.84 Hz), 6.86–6.87 (1H, d, J ¼ 2.28 Hz), 7.14–7.17 (1H, dd,
1355, 1139; ESI-MS (m/z): 402.4 (M + H)+; 1H-NMR (400 MHz, J ¼ 8.4, 2.28 Hz), 7.22–7.25 (1H, dd, J ¼ 8.8, 2.04 Hz), 7.31 (1H,
CDCl3): ꢁ 1.77–1.83 (2H, m), 2.02 (3H, s), 2.25 (6H, s), 2.43– d, J ¼ 1.12 Hz), 7.40 (1H, d, J ¼ 2.0 Hz), 7.90–7.92 (1H, d,
2.46 (2H, t, J ¼ 6.0 Hz), 3.14–3.17 (2H, t, J ¼ 6.0 Hz), 3.80 (3H, J ¼ 8.56 Hz); HRMS: [M + H]+ C21H27ClN3O3S calc. 436.1462,
s), 5.80 (1H, bs), 6.54–6.55 (1H, d, J ¼ 3.54 Hz), 6.86–6.87 (1H, found. 436.1465.
d, J ¼ 1.8 Hz), 6.88–6.91 (1H, dd, J ¼ 9.0, 2.52 Hz), 6.95–6.96
N0-[2-methoxy-5-(5-bromo-3-methyl indole-1-sulfonyl)
phenyl]-N,N-dimethyl propane-1,3-diamine (9af)
(1H, d, J ¼ 2.46 Hz), 6.99–7.01 (1H, d, J ¼ 7.88 Hz), 7.04–7.06
(1H, dd, J ¼ 7.77, 1.86 Hz), 7.51–7.52 (1H, d, J ¼ 3.62 Hz), 7.87–
7.90 (1H, d, J ¼ 8.98 Hz); HRMS: [M + H]+ C21H28N3O3S calc.
HPLC (%): 96.08; IR (cmꢂ1): 3411, 2924, 1596, 1364, 1167; ESI-
402.1851, found. 402.1854.
MS (m/z): 480.2, 482.2 (M + H)+; 1H-NMR (400 MHz, CDCl3): ꢁ
1.73–1.82 (2H, m), 2.19 (3H, s), 2.33 (6H, s), 2.49–2.53 (2H, t,
N0-[5-(5-methoxy-3-methyl indole-1-sulfonyl)-2-methyl
phenyl]-N, N-dimethyl propane-1,3-diamine (9aa)
7.08 Hz), 3.11–3.14 (2H, t, 6.72 Hz), 3.82 (3H, s), 4.8 (1H, bs),
6.65–6.67 (1H, d, J ¼ 8.48 Hz), 6.85 (1H, d, J ¼ 2.4 Hz), 7.15–
HPLC (%): 98.64; MR (ꢁC): 122.3–125.3; IR (cmꢂ1): 3221, 1595, 7.18 (1H, dd, J ¼ 8.4, 2.28 Hz), 7.29 (1H, dd, J ¼ 1.2 Hz),
1355, 1166; ESI-MS (m/z): 416.6 (M + H)+; 1H-NMR (400 MHz, 7.36–7.39 (1H, dd, J ¼ 8.76, 1.92 Hz), 7.56 (1H, d, J ¼ 2.0 Hz),
CDCl3): ꢁ 1.77–1.83 (2H, m), 2.02 (3H, s), 2.19 (3H, s), 2.25 (6H, 7.88–7.85
s), 2.44–2.47 (2H, t, J ¼ 6.0 Hz), 3.14–3.17 (2H, t, J ¼ 6.0 Hz), C21H27BrN3O3S calc. 480.0956, found. 480.0959.
(1H,
d,
J ¼ 8.76 Hz);
HRMS:
[M + H]+
3.82 (3H, s), 5.29 (1H, bs), 6.85 (1H, d, J ¼ 2.44 Hz), 6.87–6.89
(1H, dd, J ¼ 6.98, 2.51 Hz), 6.90–6.91 (1H, d, J ¼ 2.51 Hz), 6.97–
Conclusion
6.99 (1H, d, J ¼ 7.85 Hz), 7.01–7.04 (1H, dd, J ¼ 7.78, 1.81 Hz),
7.26 (1H, s), 7.87–7.89 (1H, d, J ¼ 8.92 Hz); HRMS: [M + H]+
In summary, more flexible N,N-dimethylamino alkyl amino group
was well tolerated on N-benzene sulfonyl ring at C-30 position in
an indolylsulfonamide amines series in terms of 5-HT6 receptor
activity. The compounds have shown selectivity over other closely
related receptors.
C22H30N3O3S calc. 416.2008, found. 416.2010.
N0-[3-(5-methoxy-3-methyl indole-1-sulfonyl) phenyl]-N,
N-dimethyl propane-1,3-diamine (9ab)
The lead compound 9y has shown adequate steady-state
HPLC (%): 97.62; IR (cmꢂ1): 3402, 1601, 1364, 1174; ESI-MS brain penetration (Cb/Cp), and active in cognition models like
1
(m/z): 402.3 (M + H)+; H-NMR (400 MHz, CDCl3): ꢁ 1.73–1.76 NORT and Water maze. Metabolic instability of these compounds
(2H, m), 2.04 (3H, s), 2.26 (6H, s), 2.41–2.44 (2H, t, 6.6 Hz), could be the reason for suboptimal pharmacokinetic profile.
3.10–3.13 (2H, t, 6.4 Hz), 3.83 (3H, s), 4.8 (1H, bs), 6.65 (1H, m), Efforts are underway toward identifying the metabolic profile, so
6.86–6.89 (1H, d, J ¼ 2.44 Hz), 6.89–6.92 (1H, dd, J ¼ 8.92, that it can be further optimized by a suitable choice of
2.52 Hz), 6.94–6.95 (1H, t, 2.08 Hz), 7.05 (1H, m), 7.10–7.12 (1H, substitutions while maintaining the desired 5-HT6 potency.

96 R. V. S. Nirogi et al.
J Enzyme Inhib Med Chem, 2015; 30(1): 85–97
´
20. Holenz J, Pauwels PJ, Dıaz JL, et al. Medicinal chemistry strategies
to 5-HT(6) receptor ligands as potential cognitive enhancers and
antiobesity agents. Drug Discov Today 2006;1:283–99.
21. Liu KG, Robichaud AJ. 5-HT6 antagonists as potential
treatment for cognitive dysfunction. Drug Develop Res 2009;
70:145–68.
The results of these studies will be reported in due course in a
future publication.
Acknowledgements
The support received from Discovery Analytical, DMPK, In vitro, In vivo
departments and Mr Venkateswarlu Jasti, CEO, Suven Life Sciences Ltd.,
Hyderabad, India is gratefully acknowledged.
22. Available from: http://www.pfizer.com/sites/default/files/product-
pipeline/pipeline_2013_0509.pdf/Neuroscience
accessed 21 Jun 2013].
&
pain [last
23. Available from: http://www.gsk.com/research/our-product-pipeline.
html [last accessed 21 Jun 2013].
24. Available from: http://www.biocentury.com/products/avn-211 [last
accessed 21 Jun 2013].
Declaration of interest
The authors report no conflicts of interest. The authors alone are
responsible for the content and writing of this article.
25. Ivachtchenko AV, Savchuk NP, Ivachtchenko AA. Substituted 4-
sulphonyl-pyrazoles and 3-sulphonyl-pyrazolo[1,5-a]pyrimidines-
antagonists of serotonin 5-HT6 receptors, active component,
pharmaceutical composition, medicinal agent and method of
obtaining them. RU Patent 2369600; 2009.
References
1. ADI/WHO. World Health Organization and Alzheimer’s Disease
International say dementia must be a global health priority, Geneva.
News Release/11-Apr-2012. Available from: http://www.alz.co.uk
[last accessed 21 Jun 2013].
26. Ivachtchenko AV, Savchuk NP, Ivachtchenko AA. 3-Sulfonyl-
pyrazolo[1,5-a] pyrimidines/antagonists of serotonin 5-ht6 receptors,
methods for the production and the use thereof. WO Patent 093206;
2009.
2. Roth BL, Lopez E, Patel S, Kroeze WK. Neuronal signal transduc-
tion pathways. Neuroscientist 2000;6:252–62.
3. Hoyer D, Hannon JP. Molecular, pharmacological and functional
diversity of 5-HT receptors. Pharmacol Biochem Behav 2002;71:
533–54.
27. Lundbeck. Lundbeck’s Lu AE58054 meets primary endpoint in
large placebo-controlled clinical proof of concept study in people
with Alzheimer’s disease. Corporate Releases/29-May-2012.
Available from: http://www.lundbeck.com/global [last accessed 02
Apr 2013].
4. Jones BJ, Blackburn TP. The medical benefit of 5-HT research.
Pharmacol Biochem Behav 2002;71:555–68.
28. Jorn A, Benny B, Ben G, et al. Lu AE58054, a 5-HT6 antagonist,
reverses cognitive impairment induced by subchronic phencyclidine
5. Bikker JA, Trump-Kallmeyer S, Humblet S. G-protein coupled
receptors: models, mutagenesis, and drug design. J Med Chem 1998;
41:2911–27.
6. Sebben M, Ansanay H, Bockaert J, Dumuis A. 5-HT6 receptors
positively coupled to adenylyl cyclase in striatal neurones in culture.
Neuroreport 1994;5:2553–7.
7. Arnt J, Olsen CK. 5-HT6 receptor ligands and their antipsychotic
potential. Int Rev Neurobiol 2011;96:141–61.
8. Roth BL, Craigo SC, Choudhary MS, et al. Binding of typical
and atypical antipsychotic agents to 5-hydroxytryptamine-6 and
5-hydroxytryptamine-7 receptors. J Pharmacol Exp Ther 1994;268:
1403–10.
in
Neuropsychopharmacol 2010;13:1021–33.
29. Available from: http://www.biotie.com/en/product_and_develop-
ment/development_pipeline/syn120 [last accessed 21 Jun 2013].
30. Nirogi R, Kambhampati R, Shinde A, et al. 12th International
Conference on Alzheimer’s disease; 2009; Vienna.
31. Glennon RA, Lee M, Rangisetty JB, et al. 2-Substituted tryptamines:
agents with selectivity for 5-HT(6) serotonin receptors. J Med Chem
2000;43:1011–18.
32. Kambhampati R, Konda J, Reballi V, et al. Design, synthesis and
preliminary screening of novel 3-(2-N,N-dimethylaminoethylthio)
indole derivatives as potential 5-HT6 receptor ligands. J Enz Inhib
Med Chem 2008;23:302–12.
33. Nirogi RVS, Kambhampati R, Daulatabad AV, et al. Design,
synthesis and pharmacological evaluation of conformationally
restricted N-arylsulfonyl-3-aminoalkoxy indoles as a potential 5-
HT6 receptor ligands. J Enz Inhib Med Chem 2011;26:341–9.
34. Davies SL, Silvestre JS, Guitart X. Drug discovery targets: 5-HT6
receptor. Drugs of the Future 2005;30:479–95.
35. Kim HJ, Doddareddy MR, Choo H, et al. New serotonin 5-HT6
ligands from common feature pharmacophore. Hypotheses. J Chem
Inf Model 2008;48:197–206.
36. Nirogi RVS, Kambhampati R, Kothmirkar P, et al. Synthesis and
structure–activity relationship of novel conformationally restricted
analogues of serotonin as 5-HT6 receptor ligands. J Enz Inhib Med
Chem 2012;27:443–50.
37. Ivachtchenko A, Golovina E, Kadieva M, et al. Synthesis of
substituted diphenyl sulfones and their structure–activity relation-
ship with the antagonism of 5-HT6 receptors. Bioorg Med Chem
2013;21:4614–27.
a
novel object recognition test in rats. Int
J
9. Shinkai T, Ohmori O, Kojima H, et al. Association study of the
5-HT6 receptor gene in schizophrenia. Am J Med Genet 1999;88:
120–2.
10. Tsai SJ, Chiu HJ, Wang YC, Hong CJ. Association study of
serotonin-6 receptor variant (C267T) with schizophrenia and
aggressive behavior. Neurosci Lett 1999;271:135–7.
11. Vogt IR, Shimron-Abarbanell D, Neidt H, et al. Investigation of the
human serotonin 6 [5-HT6] receptor gene in bipolar affective
disorder and schizophrenia. Am J Med Genet 2000;96:217–21.
12. Ohmori O, Shinkai T, Hori H, Nakamura J. Novel polymorphism in
the 50-upstream region of the human 5-HT6 receptor gene and
schizophrenia. Neurosci Lett 2001;310:17–20.
13. East SZ, Burnet PW, Leslie RA, et al. 5-HT6 receptor binding sites
in schizophrenia and following antipsychotic drug administration:
autoradiographic studies with [125I]SB-258585. Synapse 2002;45:
191–9.
14. Wu WH, Huo SJ, Cheng CY, et al. Association study of the 5-HT6
receptor polymorphism (C267T) and symptomatology and anti-
depressant
Neuropsychobiology 2001;44:172–5.
response
in
major
depressive
disorders.
38. Ivachtchenko AV, Golovina ES, Kadieva MG, et al. Synthesis and
structure–activity relationship (SAR) of (5,7-disubstituted 3-phenyl-
sulfonyl-pyrazolo[1,5-a]pyrimidin-2-yl)-methylamines as potent
serotonin 5-HT6 receptor (5-HT6R) antagonists. J Med Chem
2011;54:8161–73.
39. Ivachtchenko AV, Dmitriev DE, Golovina ES, et al.
(3-Phenylsulfonylcycloalkano[e and d]pyrazolo[1,5-a]pyrimidin-2-
yl)amines: potent and selective antagonists of the serotonin 5-HT6
receptor. J Med Chem 2010;53:5186–96.
15. Messina D, Annesi G, Serra P, et al. Association of the 5-HT6
receptor gene polymorphism C267T with Parkinson’s disease.
Neurology 2002;58:828–9.
16. Thome J, Retz W, Baader M, et al. Association analysis of HTR6 and
HTR2A polymorphisms in sporadic Alzheimer’s disease. J Neural
Transm 2001;108:1175–80.
17. Liu HC, Hong CJ, Liu CY, et al. Association analysis of the 5-HT6
receptor polymorphism C267T with depression in patients with
Alzheimer’s disease. Psychiatry Clin Neurosci 2001;55:427–9.
18. Garcia-Alloza M, Hirst WD, Chen CP, et al. Differential
involvement of 5-HT1B/1D and 5-HT6 receptors in cognitive and
40. Ivachtchenko AV, Golovina ES, Kadieva MG, et al. Antagonists of
5-HT6 receptors. Substituted 3-(phenylsulfonyl) pyrazolo[1,5-
a]pyrido[3,4-e]pyrimidines and 3-(phenylsulfonyl) pyrazolo[1,5-
a]pyrido[4,3-d]pyrimidines – synthesis and ‘structure–activity’
relationship. Bioorg Med Chem Lett 2012;22:4273–80.
non-cognitive
Neuropsychopharmacology 2004;29:410–16.
symptoms
in
Alzheimer’s
disease.
41. Ivachtchenko AV, Golovina ES, Kadieva MG, et al. Synthesis and
SAR of 3-arylsulfonyl-pyrazolo[1,5-a]pyrimidines as potent
19. Glennon RA. Higher-end serotonin receptors: 5-HT(5), 5-HT(6),
and 5-HT(7). J Med Chem 2003;46:2795–812.

DOI: 10.3109/14756366.2014.889126
Design, synthesis and pharmacological evaluation 97
serotonin 5-HT6 receptor antagonists. Bioorg Med Chem 2011;19: 47. Dukat M, Mosier PD, Kolanos R, et al. Binding of serotonin and
1482–91.
42. Ivachtchenko AV, Golovina ES, Kadieva MG, et al. 2-Substituted
N1-benzenesulfonyltryptamine-related analogs at human 5-HT6
serotonin receptors: receptor modeling studies. J Med Chem 2008;
51:603–11.
5,6-dimethyl-3-phenylsulfonyl-pyrazolo[1,5-a]pyrimidines:
new
series of highly potent and specific serotonin 5-HT6 receptor 48. Sikazwe D, Bondarev ML, Dukat M, et al. Binding of sulfonyl-
antagonists. Eur J Med Chem 2011;46:1189–97.
containing arylalkylamines at human 5-HT6 serotonin receptors.
J Med Chem 2006;49:5217–25.
dimensional pharmacophore model for 5-hydroxytryptamine6 49. Heal DJ, Smith SL, Fisas A, et al. Selective 5-HT6 receptor ligands:
43. Lopez-Rodriguez ML, Benhamu B, Fuente T, et al. A three-
(5-HT6) receptor antagonists. J Med Chem 2005;48:4216–19.
44. Bromidge SM. Potent and selective 5-HT6 receptor antagonists.
Spec Publ – R Soc Chem 2001;264:101–19.
progress in the development of a novel pharmacological approach to
the treatment of obesity and related metabolic disorders. Pharmacol
Therapeutics 2008;17:207–31.
45. Hirst WD, Minton JA, Bromidge SM, et al. Characterization of 50. Kohen R, Fashingbauer LA, Heidmann DE, et al. Cloning of the
[125I]-SB-258585 binding to human recombinant and native 5-HT6
receptors in rat, pig and human brain tissue. Br J Pharmacol 2000;
130:1597–605.
mouse 5-HT6 serotonin receptor and mutagenesis studies of the third
cytoplasmic loop. Brain Res Mol Brain Res 2001;90:110–17.
51. Gonzalo R, Elisabeth S, Marta P, et al. Efficacy of selective
5-HT6 receptor ligands determined by monitoring 5-HT6 receptor-
mediated cAMP signaling pathways. Br J Pharmacol 2006;148:
1133–43.
46. Pullagurla MR, Westkaemper RB, Glennon RA. Possible differ-
ences in modes of binding of agonist and antagonist binding at
human 5-HT6 receptors. Bioorg Med Chem Lett 2004;14:4569–73.