Synthesis of novel acridine-sulfonamide hybrid compounds as acetylcholinesterase inhibitor for the treatment of alzheimer’s disease

Article abstract of DOI:10.1007/s00044-017-2088-2

In this study we report that amino acridine intermediates 7 and 8 were obtained from the reduction of nitro acridine derivatives 5 and 6 that were synthesized via the condensation of dimedone, p-nitrobenzaldehyde with various amine derivatives, respective

Full text of DOI:10.1007/s00044-017-2088-2

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-017-2088-2
ORIGINAL RESEARCH
Synthesis of novel acridine-sulfonamide hybrid compounds as
acetylcholinesterase inhibitor for the treatment of alzheimer’s
disease
Ramazan Ulus1 İbrahim Esirden1 Burak Aday1 Gurbet Çelik Turgut2
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Alaattin Şen2 Muharrem Kaya3
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Received: 2 November 2015 / Accepted: 25 September 2017
© Springer Science+Business Media, LLC 2017
Abstract In this study we report that amino acridine
intermediates 7 and 8 were obtained from the reduction of
nitro acridine derivatives 5 and 6 that were synthesized via
the condensation of dimedone, p-nitrobenzaldehyde with
various amine derivatives, respectively. Then acridine sul-
fonamide hybrid compounds (9–18) were synthesized by
the reaction of amino acridine 7, 8 with sulfonyl chlorides.
The new hybrid compounds were characterized by FT-IR,
1H-NMR, 13C-NMR, and HRMS analyzes. The evaluation
of in vitro anticholinesterase action of the synthesized
compounds against AChE showed that some of them are
potent inhibitors. Among them, compound 17 showed the
most potent activity against AChE with an IC50 of 0.14 µM.
Introduction
Alzheimer’s disease (AD), the most common form of
dementia among the elderly, is a progressive degenerative
disorder of the brain with loss of memory and cognition.
Inhibition of human AChE is an effective means for treating
memory loss in early stage of Alzheimer’s disease. Tacrine
molecules (Scheme 1), an acridine derivative, are hetero-
cyclic compounds and these compounds are known as anti-
Alzheimer’s agent. The first synthesis of tacrine was
reported in 1945 by Albert and Gledhill. In 1961, Heilbronn
showed that tacrine is a reversible inhibitor of both AChE
and another biologically important cholinesterase, butyr-
ylcholinesterase (BChE). Tacrine received FDA approval
for AD-related dementia in 1993. This drug may be an
effective anti-Alzheimer’s agent but these drugs tend to pose
tolerability problems in many patients because of reduced
adverse side effects. Also, tacrine has been discontinued in
the US due to safety concerns in 2013. Thus, it is necessary
to develop new compounds and new drugs with better
activity and lesser side effects (Marco-Contelles et al. 2009;
Anand and Singh 2013; Hamulakovaa et al. 2014)
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Keywords Anticholinesterase activity Tacrine Acridine
Sulfonamide
Acridine molecules are one of the principal classes of
heterocyclic compounds that contains nitrogen atom and they
are planar tricyclic aromatic molecules. These molecules
were discovered in nineteenth century and their synthesis and
application have been widely studied until today. Recently,
acridine-based compounds have been reported to have many
important biological properties such as fungicides (Srivas-
tava and Nizamuddin 2004), antibacterial (Palani et al. 2005),
anti-multidrug-resistant (Gallo et al. 2003), cytotoxic
(Antonini et al. 1999), antimicrobial (Kaya et al. 2011), β-
channel opener in cardiovascular disease (Öcal et al. 2002),
and as carbonic anhydrase inhibitor for glaucoma treatment
(Kaya et al. 2012, 2013; Yeşildağ et al. 2014).
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00044-017-2088-2) contains supplementary
material, which is available to authorized users.
* Muharrem Kaya
mhrkaya@yahoo.com
1
Chemistry Department, Faculty of Arts and Science, Dumlupınar
University, 43100 Kütahya, Turkey
2
Biology Department, Faculty of Arts & Science, Pamukkale
University, 20070 Denizli, Turkey
3
Biochemistry Department, Faculty of Arts and Science,
Dumlupınar University, 43100 Kütahya, Turkey

Med Chem Res
10-(4-Chlorophenyl)-3,3,6,6-tetramethyl-9-(4-nitrophenyl)-
3,4,6,7,9,10-hexahydro acridine-1,8(2H,5H)-dione (5)
As yellow solid, (89%), mp 310 °C (ethanol) (Tang et al.
2010).
Scheme 1 Tacrine
10-(4-Bromophenyl)-3,3,6,6-tetramethyl-9-(4-nitrophenyl)-
3,4,6,7,9,10-hexahydro acridine-1,8(2H,5H)-dione (6)
Acetylcholinesterase (AChE) belongs to the serine
hydrolase family that handles acetylcholine breakdown in
the body. Although the primary role of AChE is hydrolysis
of ACh, it also plays an important part in the expression of
amyloid precursor protein, promotion of amyloid assembly,
phosphorylation of tau protein, inflammation, cell pro-
liferation, and apoptosis (Soreq and Seidman 2001; Silman
and Sussman 2005). Design and synthesis of compounds
that can inhibit AChE activities have recently gained higher
interest since AChE inhibitors are the key compounds used
to treat Alzheimer’s disease (AD) and myasthenia gravis.
Sulfonamides are another important compounds family
for the medicinal industry and they are now extensively
used drugs for the treatment or conservation of different
illnesses (Supuran and Scozzafava 2001). In clinical medi-
cine, they have been used as anticancer (Monti et al. 2013),
antimicrobial (Kaya et al. 2013), antiobesity (Scozzafava
et al. 2013), carbonic anhydrase inhibitors (Zolnowska et al.
2014; Slawinski et al. 2014a, b), and acetylcholinesterase
inhibitor agents for Alzheimer’s disease (Bag et al. 2015).
For this reason, novel acridine-sulfonamide hybrid
compounds were synthesized and characterized by Fourier
Yield 91%; m.p. 315–316 oC; IR (ATR) νmax 3047, 2956,
1631, 1575 cm−1; 1H NMR (300 MHz, dimethyl sulphoxide
(DMSO)-d6): δ 0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-CH3),
1.80 (d, 2H, J = 17.46Hz, –CH2), 2.00 (d, 2H, J = 15.93
Hz, –CH2), 2.18–2.24 (m, 4H, 2x-CH2), 5.10 (s, 1H, –CH)
7.48 (d, 2H, J = 8.4 Hz, Ar–H), 7.58 (d, 2H, J = 8.7 Hz,
Ar–H), 7.83 (d, 2H, J = 8.4 Hz, Ar–H), 8.14 (d, 2H, J =
8.7 Hz, Ar–H); 13C-NMR (75 MHz, DMSO-d6): δ 26.57,
29.60, 32.47, 33.35, 41.38, 49.86, 112.50, 123.21, 123.75,
129.42, 132.46, 133.50, 137.98, 146.16, 151.25, 154.00,
195.51; HRMS (QTOF-ESI): m/z calcd. for C29H29BrN2O4:
548.1311; found: 571.1209 [M + Na]+.
General procedure for preparation of reduced acridine
compounds (7 and 8)
The acridine compounds (5) were dissolved in 10 ml etha-
nol. This solution of sodium poly-sulfur was then added
drop wise to a stirred and warm solution of compound 5 (1
mmol) in 50 ml ethanol–water. The progress of the reaction
was monitored by TLC. Once the reaction is completed, the
mixture was cooled to room temperature and solid filtered
off and washed with H2O. The sulfonamide product was
purified and recrystallized from the ethanol (84–87%)
(Kaya et al. 2013).
1
transform infrared, H-nuclear magnetic resonance (NMR),
13C-NMR, and high-resolution mass spectral (HRMS)
analyzes. The inhibitory effects of newly synthesized
compounds on acetylcholinesterase enzyme were investi-
gated under in vitro conditions using SH-SY5Y cell lines
AChE activity.
9-(4-Aminophenyl)-10-(4-chlorophenyl)-3,3,6,6-
tetramethyl-3,4,6,7,9,10-hexahydro acridine-1,8(2H,5H)-
dione (7)
Methods
Yield 84%; m.p. 254–255 °C; IR (ATR) νmax 3408, 3047,
2956, 1631, 1575 cm−1; 1H NMR (300 MHz, DMSO-d6): δ
0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-CH3), 1.74 (d, 2H,
J = 17.40 Hz, –CH2), 1.99 (d, 2H, J = 16.03 Hz, –CH2),
2.14–2.20 (m, 4H, 2x-CH2), 4.79 (s, 2H, –NH2), 4.86 (s,
1H, –CH) 6.42 (d, 2H, J = 8.3 Hz, Ar–H), 6.93 (d, 2H, J =
8.3 Hz, Ar–H), 7.42 (s, 2H, Ar–H), 7.67 (d, 2H, J = 8.8 Hz,
Ar–H); 13C-NMR (75 MHz, DMSO-d6): δ 26.53, 29.80,
30.94, 32.43, 41.34, 50.17, 114.11, 114.24, 128.37, 130.52,
132.08, 134.26, 134.53, 137.99, 146.81, 149.88, 195.58;
HRMS (QTOF-ESI): m/z calcd. for C29H31ClN2O2:
474.2074; found: 473.2000 [M − H]−.
General procedure for preparation of acridine
derivatives (5 and 6)
A mixture of dimedone 1 (2 mmol), p-nitrobenzaldehyde 2
(1 mmol), 4-chloroaniline 3 (1 mmol), and dodecylbenze-
nesulphonic acid (DBSA) catalyst (10% mmol) in 10 mL
H2O was heated to reflux continuously for 6 h. The reaction
progress was monitored by thin layer chromatography
(TLC). The solid product was filtered, washed with 500 mL
water, and recrystallized from ethanol (88–91%) (Kaya
et al. 2012).

Med Chem Res
9-(4-Aminophenyl)-10-(4-bromophenyl)-3,3,6,6-
tetramethyl-3,4,6,7,9,10-hexahydro acridine-1,8(2H,5H)-
dione (8)
–CH3), 4.90 (s, 1H, –CH), 6.93 (d, 2H, J = 8.4 Hz, Ar–H),
7.13 (d, 2H, J = 8.4 Hz, Ar–H), 7.27 (d, 2H, J = 8.1 Hz,
Ar–H), 7.45 (d, 2H, J = 8.1 Hz, Ar–H), 7.57 (d, 2H, J =
8.2 Hz, Ar–H), 7.66 (d, 2H, J = 8.8 Hz, Ar–H), 10.05 (s,
1H, –NH); 13C-NMR (75 MHz, DMSO-d6): δ 21.41, 26.40,
29.69, 31.64, 32.42, 41.33, 49.99, 113.40, 120.32, 127.02,
128.54, 130.00, 130.50, 132.16, 134.35, 135.85, 137.34,
137.74, 142.44, 143.51, 150.48, 195.51; HRMS (QTOF-
ESI): m/z calcd. for C36H37ClN2O4S: 628.2163; found:
651.2057 [M + Na]+.
Yield 87%; m.p. 268–269 °C; IR (ATR) νmax 3404, 3063,
2947, 1630, 1578 cm−1; 1H NMR (300 MHz, DMSO-d6): δ
0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-CH3), 1.75 (d, 2H, J
= 17.32 Hz, –CH2), 1.99 (d, 2H, J = 16.04 Hz, –CH2),
2.14–2.20 (m, 4H, 2x-CH2), 4.80 (s, 2H, –NH2), 4.90 (s,
1H, –CH) 6.42 (d, 2H, J = 8.3 Hz, Ar–H), 6.94 (d, 2H, J =
8.3 Hz, Ar–H), 7.43 (s, 2H, Ar–H), 7.67 (d, 2H, J = 8.8 Hz,
Ar–H); 13C-NMR (75 MHz, DMSO-d6): 26.53, 29.79,
30.92, 32.44, 41.33, 50.17, 114.07, 114.23, 122.88, 128.35,
132.46, 133.49, 134.46, 138.42, 146.87, 149.81, 195.57;
HRMS (QTOF-ESI): m/z calcd. for C29H31BrN2O2:
518.1569; found: 519.1469 [M + H]+.
N-(4-(10-(4-Chlorophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)-4-
methoxybenzenesulfonamide (11)
Yield 82%; m.p. 300–302 °C; IR (ATR) νmax 3242, 3051,
1
2959, 1637, 1580, 1500, 1362, 1151 cm−1; H NMR (300
General procedure for preparation of acridine-
sulfonamide hybrid compounds (9–18)
MHz, DMSO-d6): δ 0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.41 Hz, –CH2), 1.97 (d, 2H, J =
16.14 Hz, –CH2), 2.12–2.18 (m, 4H, 2x-CH2), 3.80 (s, 3H,
–OCH3), 4.90 (s, 1H, –CH), 6.92–7.00 (m, 4H, Ar–H), 7.13
(d, 2H, J = 8.4 Hz, Ar–H), 7.45 (d, 2H, J = 7.9 Hz, Ar–H),
7.60–7.68 (m, 4H, Ar–H), 9.95 (s, 1H, –NH); 13C-NMR
(75 MHz, DMSO-d6): δ 26.40, 29.69, 31.62, 32.42, 41.32,
49.99, 56.00, 113.41, 114.67, 120.26, 128.51, 129.19,
130.51, 131.80, 132.15, 134.35, 135.98, 137.74, 142.34,
150.48, 162.74, 195.51; HRMS (QTOF-ESI): m/z calcd. for
C36H37ClN2O5S: 644.2112; found: 667.2024 [M + Na]+.
A mixture of the amino acridine compound (0.5 mmol) and
the sulphonyl chlorides (0.5 mmol) in dry THF (5 ml) was
refluxed for 12 h. After the solvent was removed in vacuo,
the crude product was purified by recrystallization from
ethanol (72–90%) (Supuran and Scozzafava 2001).
N-(4-(10-(4-Chlorophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)
benzenesulfonamide (9)
4-Bromo-N-(4-(10-(4-chlorophenyl)-3,3,6,6-tetramethyl-
1,8-dioxo-1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)
phenyl)benzenesulfonamide (12)
Yield 80%; m.p. 290–291 °C; IR (ATR) νmax 3203, 3060,
1
2958, 1632, 1572, 1507, 1363, 1160 cm−1; H NMR (300
MHz, DMSO-d6): δ 0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.37 Hz, –CH2), 1.97 (d, 2H, J =
16.01 Hz, –CH2), 2.12–2.18 (m, 4H, 2x-CH2), 4.90 (s, 1H,
–CH), 6.94 (d, 2H, J = 8.4 Hz, Ar–H), 7.13 (d, 2H, J = 8.4
Hz, Ar–H), 7.43–7.69 (m, 9 H, Ar–H), 10.10 (s, 1H, –NH);
13C-NMR (75 MHz, DMSO-d6): δ 26.40, 29.69, 31.64,
32.42, 41.33, 49.98, 113.37, 120.59, 126.96, 128.55,
129.54, 130.49, 132.13, 133.20, 134.35, 135.70, 137.73,
140.12, 142.62, 150.49, 195.50; HRMS (QTOF-ESI): m/z
calcd. for C35H35ClN2O4S: 614.2006; found: 637.1940 [M
+ Na]+.
Yield 85%; m.p. 324–326 °C; IR (ATR) νmax 3191, 3064,
1
2959, 1638, 1570, 1509, 1362, 1165 cm−1; H NMR (300
MHz, DMSO-d6): δ 0.65 (s, 6H, 2x-CH3), 0.85 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.43 Hz, –CH2), 1.97 (d, 2H, J =
16.03 Hz, –CH2), 2.16 (d, 4H, J = 16.63 Hz, 2x-CH2), 4.90
(s, 1H, –CH), 6.94 (d, 2H, J = 8.4 Hz, Ar–H), 7.15 (d, 2H,
J = 8.4 Hz, Ar–H), 7.45 (d, 2H, J = 7.9 Hz, Ar–H),
7.57–7.71 (m, 6H, Ar–H), 10.20 (s, 1H, –NH); 13C-NMR
(75 MHz, DMSO-d6): δ 26.37, 29.71, 31.69, 32.42, 41.33,
49.98, 113.35, 120.84, 127.08, 128.65, 129.03, 130.50,
132.13, 132.65, 134.36, 135.37, 137.72, 139.30, 142.92,
150.50, 195.48; HRMS (QTOF-ESI): m/z calcd. for
C35H34BrClN2O4S: 692.1111; found: 717.0994 [M + Na]+.
N-(4-(10-(4-Chlorophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)-4-
methylbenzenesulfonamide (10)
N-(4-(10-(4-Chlorophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)-2,4,6-
trimethylbenzenesulfonamide (13)
Yield 81%; m.p. 294–295 °C; IR (ATR) νmax 3200, 3054,
1
2959, 1631, 1571, 1508, 1363, 1162 cm−1; H NMR (300
MHz, DMSO-d6): δ 0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.36Hz, –CH2), 1.97 (d, 2H, J =
16.07 Hz, –CH2), 2.12–2.18 (m, 4H, 2x-CH2), 2.31 (s, 3 H,
Yield 72%; m.p. 308–309 °C; IR (ATR) νmax 3196), 3049,
1
2957, 1636, 1573, 1507, 1363, 1152 cm−1; H NMR (300

Med Chem Res
MHz, DMSO-d6): δ 0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.45 Hz, –CH2), 1.96 (d, 2H, J =
15.99 Hz, –CH2), 2.12–2.20 (m, 7H, 2x-CH2 and –CH3),
2.47 (s, 6H, 2x-CH3), 4.90 (s, 1H, –CH), 6.84 (d, 2H, J =
7.8 Hz, Ar–H), 6.95 (s, 2H, Ar–H), 7.12 (d, 2H, J = 7.9 Hz,
Ar–H), 7.45, (d, 2H, J = 7.8 Hz, Ar–H), 7.66 (d, 2H, J =
7.9 Hz, Ar–H), 9.90 (s, 1H, –NH); 13C-NMR (75 MHz,
DMSO-d6): δ 20.83, 22.90, 26.44, 29.69, 31.72, 32.41,
41.33, 49.98, 113.40, 120.63, 128.55, 130.50, 132.15,
134.35, 134.58, 135.46, 137.74, 138.99, 142.24, 142.51,
150.47, 195.50; HRMS (QTOF-ESI): m/z calcd.
for C38H41ClN2O4S: 656.2476; found: 679.2368 [M +
Na]+.
4-Bromo-N-(4-(10-(4-bromophenyl)-3,3,6,6-tetramethyl-
1,8-dioxo-1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)
phenyl)benzenesulfonamide (16)
Yield 88%; m.p. 330–332 °C; IR (ATR) νmax 3158, 3063,
1
2955, 1638, 1626, 1571, 1362, 1165 cm−1; H NMR (300
MHz, DMSO-d6): δ 0.65 (s, 6H, 2x-CH3), 0.85 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.41 Hz, –CH2), 1.98 (d, 2H, J =
16.05 Hz, –CH2), 2.13–2.18 (m, 4H, 2x-CH2), 4.90 (s, 1H,
–CH), 6.94 (d, 2H, J = 8.5 Hz, Ar–H), 7.15 (d, 2H, J = 8.5
Hz, Ar–H), 7.38 (d, 2H, J = 8.1 Hz, Ar–H), 7.59 (d, 2H, J
= 8.6Hz, Ar–H), 7.70 (d, 2H, J = 8.6Hz, Ar–H), 7.80 (d,
2H, J = 8.7 Hz, Ar–H), 10.20 (s, 1H, –NH); 13C-NMR (75
MHz, DMSO-d6): δ 26.36, 29.70, 31.69, 32.43, 41.33,
49.98, 113.34, 120.84, 123.01, 127.08, 128.65, 129.03,
132.65, 133.45, 135.37, 138.15, 139.29, 142.92, 150.45,
N-(4-(10-(4-Bromophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)
benzenesulfonamide (14)
195.49;
HRMS
(QTOF-ESI):
m/z
calcd.
for
C35H34Br2N2O4S: 736.0606; found: 739.0653 [M + H]+.
Yield 83%; m.p. 295–296 °C; IR (ATR) νmax 3190, 3059,
1
2956, 1634, 1572, 1507, 1363, 1160 cm−1; H NMR (300
N-(4-(10-(4-Bromophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)-2,4,6-
trimethylbenzenesulfonamide (17)
MHz, DMSO-d6): δ 0.65 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-
CH3), 1.74 (d, 2H, J = 17.37 Hz, –CH2), 1.97 (d, 2H, J =
16.05 Hz, –CH2), 2.12–2.18 (m, 4H, 2x-CH2), 4.90 (s, 1H,
–CH), 6.94 (d, 2H, J = 8.5 Hz, Ar–H), 7.13 (d, 2H, J = 8.5
Hz, Ar–H), 7.38 (d, 2H, J = 8.1 Hz, Ar–H), 7.45–7.60 (m,
3H, Ar–H), 7.67 (d, 2H, J = 8.5 Hz, Ar–H), 7.79 (d, 2H, J
= 8.8 Hz, Ar–H), 10.10 (s, 1H, –NH); 13C-NMR (75 MHz,
DMSO-d6): δ 26.40, 29.69, 31.65, 32.43, 41.33, 49.98,
113.37, 120.59, 123.00, 126.96, 128.55, 129.54, 132.45,
133.21, 133,45, 135.70, 138.16, 140.12, 142.62, 150.43,
Yield 78%; m.p. 312 °C; IR (ATR) νmax 3357, 3052, 2958,
1
1640, 1578, 1506, 1363, 1158 cm−1; H NMR (300 MHz,
DMSO-d6): 0.70 (s, 6H, 2x-CH3), 0.90 (s, 6H, 2x-CH3),
1.74 (d, 2H, J = 17.40 Hz, –CH2), 1.97 (d, 2H, J = 15.97
Hz, –CH2), 2.12–2.20 (m, 7 H, 2x-CH2 and –CH3), 2.45 (s,
6H, 2x-CH3) 4.90 (s, 1H, –CH), 6.83 (d, 2H, J = 8.4 Hz,
Ar–H), 6.95 (s, 2H, Ar–H), 7.12 (d, 2H, J = 8.4 Hz, Ar–H),
7.38 (d, 2H, J = 8.1 Hz, Ar–H), 7.79 (d, 2H, J = 8.7 Hz,
Ar–H), 9.90 (s, 1H, –NH); 13C-NMR (75 MHz, DMSO-d6):
δ 20.84, 22.91, 26.45, 29.69, 31.72, 32.43, 41.33, 49.99,
113.41, 120.64, 123.00, 128.55, 132.15, 132.44, 133.44
134.59, 135.46, 138.18, 139.00, 142.24, 142.51, 150.41,
195.50;
HRMS
(QTOF-ESI):
m/z
calcd.
for
C35H35BrN2O4S: 658.1501; found: 683.1387 [M + Na]+.
N-(4-(10-(4-Bromophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)-4-
methoxybenzenesulfonamide (15)
195.49;
HRMS
(QTOF-ESI):
m/z
calcd.
for
C38H41BrN2O4S: 700.1970; found: 725.1843 [M + Na]+.
Yield 84%; m.p. 304 °C; IR (ATR) νmax 3243, 3047, 2959,
1636, 1578, 1360, 1149 cm−1
;
1H NMR (300 MHz,
N-(4-(10-(4-Bromophenyl)-3,3,6,6-tetramethyl-1,8-dioxo-
1,2,3,4,5,6,7,8,9,10-decahydro acridin-9-yl)phenyl)
naphthalene-2-sulfonamide (18)
DMSO-d6): δ 0.65 (s, 6H, 2x-CH3), 0.85 (s, 6H, 2x-CH3),
1.74 (d, 2H, J = 17.32 Hz, –CH2), 1.97 (d, 2H, J = 16.05
Hz, –CH2), 2.12–2.18 (m, 4H, 2x-CH2), 3.75 (s, 3H,
–OCH3), 4.90 (s, 1H, –CH), 6.91–6.99 (m, 4H, Ar–H), 7.12
(d, 2H, J = 8.5 Hz, Ar–H), 7.38 (d, 2H, J = 7.8 Hz, Ar–H),
7.59–7.63 (m, 2H, Ar–H), 7.79 (d, 2H, J = 8.7 Hz, Ar–H),
9.95 (s, 1H, –NH); 13C-NMR (75 MHz, DMSO-d6): δ
26.41, 29.69, 31.61, 32.43, 41.32, 50.00, 56.00, 113.40,
114.67, 120.26, 122.99, 128.51, 129.19, 131.80, 132.44,
133.45, 135.98, 138.17, 142.34, 150.42, 162.74, 195.51;
HRMS (QTOF-ESI): m/z calcd. for C36H37BrN2O5S:
688.1607; found: 713.1487 [M + Na]+.
Yield 90%; m.p. 320–321 °C; IR (ATR) νmax 3188, 3055,
1
2956, 1634, 1577, 1506, 1363, 1157 cm−1; H NMR (300
MHz, DMSO-d6): δ 0.60 (s, 6H, 2x-CH3), 0.80 (s, 6H, 2x-
CH3), 1.70 (d, 2H, J = 17.33 Hz, –CH2), 1.92 (d, 2H, J =
15.98 Hz, –CH2), 2.10–2.15 (m, 4H, 2x-CH2), 4.90 (s, 1H,
–CH), 6.98 (d, 2H, J = 8.5 Hz, Ar–H), 7.12 (d, 2H, J = 8.5
Hz, Ar–H), 7.35 (d, 2H, J = 7.6Hz, Ar–H), 7.59–7.71 (m, 3
H, Ar–H), 7.77 (d, 2H, J = 8.7 Hz, Ar–H), 7.96–8.07 (m,
3H, Ar–H), 8.35 (s, 1H, Ar–H), 10.20 (s, 1H, –NH); 13C-

Med Chem Res
NMR (75 MHz, DMSO-d6): δ 26.32, 29.64, 31.68, 32.38,
41.29, 49.94, 113.35, 120.66, 122.42, 122.97, 128.02,
128.20, 128.27, 128.59, 129.28, 129.61, 129.72, 131.96,
132.44, 133.41, 134.63, 135.68, 137.17, 138.14, 142.65,
150.36, 195.45; HRMS (QTOF-ESI): m/z calcd. for
C39H37BrN2O4S: 708.1657; found: 733.1545 [M + Na]+.
Results and discussion
Chemistry
The general synthetic method shown in Scheme 2 was used
to prepare the novel acridine sulfonamide hybrid com-
pounds 9–18.
In the first step, acridine compounds were synthesized in
water in a single process through three successive reactions
(Aldol condensation, Michael addition, and cyclization) and
p-DBSA. Dimedone (1) were condensed with 4-nitro ben-
zaldehyde (2) and various amine derivatives (3 and 4), in
the molar range of 2:1:1.
In the second step, synthesized acridine compounds
(5, 6) are reduced in the presence of sodium poly-sulfur in
ethanol-water mixture. As a result of reduction, com-
pounds 9-(4-aminophenyl)-10-(4-chlorophenyl)-3,3,6,6-
tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H, 5H)-
dione (7) and 9-(4-aminophenyl)-10-(4-bromophenyl)-
3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro acridine-1,8
(2H, 5H)-dione (8) are obtained.
Cell culture
The human neuroblastoma cell line (SH-SY5Y) was
obtained from ATCC. The cells were cultured in DMEM:
F12 supplemented with 10% FBS and 1% penicillin/
streptomycin mixture in a humidified atmosphere of 95%
air with 5% CO2 at 37 °C and were sub-cultured twice a
week.
Preparation of cell homogenate
SH-SY5Y cells (1 × 106 cells per 75 cm2 flask) were
washed twice with PBS and scraped from culture dishes in
lysis buffer (0.1 M phosphate buffer, pH 7.8, 0.2% Triton
X-100, 2 mM EDTA, 0.5 mM PMFS, 0.3 mM EACA, and
1 mM DTT) and homogenized mechanically by sonication.
Total cellular protein concentration was determined by
Bradford assay using BSA as the standard (Bradford
1976).
In the last step, novel acridine sulfonamide hybrid com-
pounds (9–18) were obtained by interacting various sulfonyl
chlorides with the compounds 7 and 8, which are obtained as
a result of the reduction reaction in dry THF refluxed for 12 h.
The infrared (IR) spectra of all the acridine compounds
showed sharp peaks for the carbonyl groups in the region
between 1640–1626 cm−l. Besides, in the IR spectra of the
compounds, aliphatic C–H stretching bands were observed
between 2962–2947 cm−1 and aromatic C–H stretching
Cholinesterase assay
bands were observed between 3064–3034 cm−1
.
1
The H-NMR spectra of the acridine compounds (5–18)
belonging to protons of the methyl groups showed singlet
peaks in position 3 and 6 between 0.60 and 0.90 ppm. The
–CH2 group protons of the cyclohexene rings of the com-
pounds 5–18 showed doublet peaks in the 1.69–2.24 ppm.
Signals for the methoxy group of protons for compounds 12
and 16 were shown in the range of 3.75–3.80 ppm. The signals
for the –CH protons were observed at 4.86–5.10 ppm and the
signals for the aromatic protons were observed in the range of
6.42–8.14 ppm. All compounds found in sulfonamide groups
–NH protons were observed between 9.90 and 10.20 ppm.
The 13C-NMR (APT) spectra of all the compounds 5–18
showed carbonyl carbons peaks at 195.45–195.58 ppm
(Ulus et al. 2015; Pamuk et al. 2015). Also, when their
high-resolution mass spectra (HRMS) are examined, the
observed molecule ion peaks are in compliance with the
recommended structures.
SH-SY5Y cell lysate AChE activity was characterized using
acetylthiocholine iodide (ATCh-I) substrate by following
the appearance of thiocholine-DTNB conjugate at 412 nm
according to the method of Ellman (Ellman et al. 1961). The
test compounds were dissolved in a mixture of DMSO and
0.1 M Tris–HCl buffer pH 8.5 (the final concentration of
DMSO is 0.02%. For each compound, at least five different
concentrations were tested to obtain the range of 10–90%
enzyme inhibition. AChE activities were assayed in a
medium containing 0.6 DTNB in 80 mM Tris–HCl buffer
pH 8.5, 1 mg protein, and test compound. After incubation
for 5 min at 25 °C, reaction was initiated by adding 2.5 mM
ATCh-I and the reaction rate was monitored spectro-
photometrically on an Analytik Jena Specord 200 UV-1601
double-beam spectrophotometer at 412 nm for 150 s at 25 °C.
Finally, the IC50 values were determined graphically from
inhibition curves (log inhibitor concentration vs. percent of
inhibition). One unit activity was defined to be the amount
of enzyme that catalyzed the hydrolysis of 1 mmol of
substrate/min at saturating substrate concentration (Talesa
et al. 1993).
Anticholinesterase activity
All compounds (5–18) reported here and the standard
drug tacrine were assayed as inhibitors of human

Med Chem Res
Scheme 2 The synthesis of
novel acridine-sulfonamide
hybrid compounds
a
b
c
d
e
f
R
C6H5-
p-CH3C6H4-
p-BrC6H4-
p-CH3OC6H4-
2,4,6-(CH3)3C6H2-
2-Naphthyl-
acetylcholinesterase (AChE) (Table 1). As seen from data of
Table 1, IC50 analysis values of the compounds revealed that
some compounds had potent in vitro anticholinesterase
activity. The following structure–activity relationship (SAR)
could be observed: The hAChE was inhibited with inhibition
constants in the micromolar range by most of the newly
synthesized amino-acridine compounds (7 and 8) and
acridine-sulfonamides 7–18, which showed IC50 of
0.14–1.46 μM (Table 1). The compound 14 was less effective
as hAChE inhibitors with IC50 of 1.41 0.045 μM. The novel
synthesized compounds 9–18 showed better inhibition effects
than tacrine molecule. In addition, the compound 13 (IC50
0.15 0.012), compound 17 (IC50 0.14 0.011 μM),
possessing 2-mesitylene sulfonamide substituent as the part of
the molecule that is originally present in the amino compo-
nent, were the best AChE inhibitor.
Conclusions
A series of novel acridine sulfonamide hybrid compounds
showed selective AChE inhibitor effects. In order to
determine the in vitro anti-acetylcholinesterase activity, SH-
SY5Y human neuroblastoma cells were used as AChE
source since it is human? and the expression, activity and
localization of the AChE are well documented (Thullbery

Med Chem Res
Table 1 The acetylcholinesterase inhibition activities of novel
acridine-sulfonamide hybrid compounds
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Entry
−R
IC50 (μM)
5
–
0.48 0.021
0.56 0.015
0.46 0.023
0.39 0.018
0.19 0.018
0.32 0.022
0.33 0.012
0.20 0.014
0.15 0.012
1.41 0.045
0.34 0.021
0.22 0.018
0.14 0.011
0.22 0.018
0.50 0.020
6
–
7
–
8
–
9
–C6H5
10
11
12
13
14
15
16
17
18
Tacrinea
a
p-CH3C6H4
p-CH3OC6H4
p-BrC6H4
2,4,6-(CH3)3C6H2
–C6H5
p-CH3OC6H4
p-BrC6H4
2,4,6-(CH3)3C6H2
2-Naphthyl
–
Tacrine was used as a standard inhibitor for all acetylcholinesterase
investigated here
et al. 2005). Therefore, it yields much more precise result
for inhibition studies since it is known that small amino acid
substitutions may strongly affect the stereoselectivity of
inhibitors (Bosak et al. 2008). Analysis of IC50 values of the
synthesized compounds demonstrated that some of them
can be potently drug since they are selective inhibitors of
AChE. Among them, 17 with IC50 value of 0.14 µM was the
most potent compound. Further studies such as toxicity and
safety evaluations should be carried out to determine its
effectiveness as model compounds for potential drugs.
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channel openers in isolated rabbit thoracic arteries. Eur J Med
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Ramakrishnan VT (2005) Synthesis and characterization of 9-(4-
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(2H,5H) acridinedione and its methoxyphenyl derivative. J Chem
Crystallogr 35:751–760
Compliance with ethical standards
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efficient and reusable catalyst for one-pot synthesis of acridine-
dione derivatives. RSC Adv 5:49295–49300
Conflict of interest The authors declare that they have no competing
Scozzafava A, Supuran CT, Carta F (2013) Antiobesity carbonic
anhydrase inhibitors: a literature and patent review. Expert Opin
Ther Patents 23:725–735
interests.
Silman I, Sussman JL (2005) Acetylcholinesterase: ‘classical’ and
‘non-classical’ functions and pharmacology. Curr Opin Pharmacol
5:293–302
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