Benzofuran-derived benzylpyridinium bromides as potent acetylcholinesterase inhibitors

Article abstract of DOI:10.1016/j.ejmech.2015.02.009

A series of benzofuran-based N-benzylpyridinium derivatives 5a-o were designed and synthesized as novel AChE inhibitors. The synthetic pathway of the compounds involved the preparation of 4-(benzofuran-2-yl)pyridine intermediates via the reaction of different salicylaldehyde derivatives and 4-(bromomethyl)pyridine, followed by intramolecular cyclization. Subsequently, the 4-(benzofuran-2-yl)pyridines were N-benzylated by using appropriate benzyl bromide to afford the final product 5a-o. The results of in vitro AChE activity evaluation of synthesized compounds revealed that all compound had potent anti-AChE activity comparable or more potent than standard drug donepezil. The N-(3,5-dimethylbenzyl) derivative 5e with IC₅₀ value of 4.1 nM was the most active compound, being 7-fold more potent than donepezil.

Full text of DOI:10.1016/j.ejmech.2015.02.009

European Journal of Medicinal Chemistry 93 (2015) 196e201
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Benzofuran-derived benzylpyridinium bromides as potent
acetylcholinesterase inhibitors
Farzaneh Baharloo a, Mohammad Hossein Moslemin a, Hamid Nadri b, Ali Asadipour c,
Mohammad Mahdavi d, Saeed Emami e, Loghman Firoozpour f, Razieh Mohebat a,
, d, *
Abbas Shafiee d, Alireza Foroumadi c
a Department of Chemistry, Faculty of Chemistry, Islamic Azad University, Yazd, Iran
b Department of Medicinal Chemistry, Faculty of Pharmacy, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
c Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medicinal Sciences, Kerman, Iran
d Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran University of Medicinal Sciences, Tehran,
Iran
e Department of Medicinal Chemistry and Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Mazandaran University of Medical Sciences, Sari,
Iran
f Drug Design & Development Research Center, Tehran University of Medicinal Sciences, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of benzofuran-based N-benzylpyridinium derivatives 5aeo were designed and synthesized as
novel AChE inhibitors. The synthetic pathway of the compounds involved the preparation of 4-(benzo-
furan-2-yl)pyridine intermediates via the reaction of different salicylaldehyde derivatives and 4-(bro-
momethyl)pyridine, followed by intramolecular cyclization. Subsequently, the 4-(benzofuran-2-yl)
pyridines were N-benzylated by using appropriate benzyl bromide to afford the final product 5aeo. The
results of in vitro AChE activity evaluation of synthesized compounds revealed that all compound had
potent anti-AChE activity comparable or more potent than standard drug donepezil. The N-(3,5-
dimethylbenzyl) derivative 5e with IC50 value of 4.1 nM was the most active compound, being 7-fold
more potent than donepezil.
Received 29 December 2014
Received in revised form
4 February 2015
Accepted 6 February 2015
Available online 7 February 2015
Keywords:
Acetylcholinesterase
Alzheimer's disease
Benzofuran
© 2015 Elsevier Masson SAS. All rights reserved.
Docking study
Pyridinium
1. Introduction
with learning, memory, and behavioral responses, a majority of
investigations has been focused on the basal forebrain cholinergic
Alzheimer's disease (AD) is the most prevalent chronic neuro-
degenerative disorder which characterized by memory loss, lan-
guage problems, disorientation, loss of motivation, and behavioral
impairment [1]. AD is a multifactorial disease in which a complex of
proteins, enzymes, or receptors is involved [2]. The pathogenesis of
AD is not completely clear; however, the typical pathological hall-
system [4]. Accordingly, one strategy in the treatment of AD can be
the increase of synaptic levels of ACh in the brain by inhibiting the
acetylcholinesterase (AChE) enzyme, which is mainly responsible
for hydrolysis of ACh [5]. Nowadays, the symptomatic management
of patients with AD is based on utilizing acetylcholinesterase in-
hibitors (AChEIs) such as donepezil, rivastigmine, and galantamine,
as well as the NMDA-antagonist memantine [6].
marks are amyloid-b (Ab) deposits, t-protein aggregation, oxidative
stress, and decreased levels of acetylcholine (ACh) in the brain [3].
Since the AD is associated with a loss of cholinergic neuro-
transmission with decreased levels of ACh in the brain areas dealing
The crystal structure of AChE indicates that the catalytic triad is
located at the bottom of a narrow gorge [7]. The entrance of the
gorge is termed the peripheral anionic site (PAS) in which the ar-
omatic residues of amino acids interact with cationic ligands. At the
bottom of the gorge, there is the catalytic active site (CAS) [8]. The
AChE inhibition by AChE inhibitors maybe occurs via a competitive
interaction with CAS, via a non-competitive binding with PAS, or
via both interactions. It was demonstrated that AChE also interacts
* Corresponding author. Department of Medicinal Chemistry, Faculty of Phar-
macy and Pharmaceutical Sciences Research Center, Tehran University of Medicinal
Sciences, Tehran, Iran
with Ab by a hydrophobic environment close to the PAS. The latter
E-mail address: aforoumadi@yahoo.com (A. Foroumadi).
http://dx.doi.org/10.1016/j.ejmech.2015.02.009
0223-5234/© 2015 Elsevier Masson SAS. All rights reserved.

F. Baharloo et al. / European Journal of Medicinal Chemistry 93 (2015) 196e201
197
interaction can promote the deposition and aggregation of A
brain [9].
b
in the
pyridinium bromide salts 5.
Accordingly, the AChE inhibitors with dual action on PAS and
CAS could be more effective agents for the management of AD [10].
Despite the purely symptomatic mode of action of AChE inhibitors,
they still represent the first-line treatment of AD [11]. Considering
this information and looking at the high prevalence of AD, dis-
covery and development of a highly effective AChE inhibitor is ur-
gently needed.
Among the various compounds developed as AChE inhibitors,
donepezil analogs are studied more extensively. The X-ray crys-
tallography and docking studies demonstrated that donepezil has
dual-binding mode of action. It was found that the presence of
benzyl piperidine contributes its inhibitory activity by interacting
with the CAS, while the indanone moiety of the molecule as a hy-
drophobic aromatic part binds to the PAS [12,13].
3. Results and discussion
3.1. AChE inhibitory activity
The anti-AChE activity of compounds 5aeo was assessed in vitro
by using reported method [14]. The obtained IC50 values of com-
pounds are presented in Table 1, in comparison with reference drug
donepezil. All compounds showed very potent inhibitory activity
against AChE at nano-molar level. A survey on IC50 values of com-
pounds revealed that all compounds with exception of 5i were
more potent than donepezil. However, compound 5i with IC50
value of 31.5 nM was as potent as donepezil. Among the tested
compounds, 3,5-dimethylbenzyl derivative 5e with IC50 value of
4.1 nM was the most potent compound. Its inhibitory activity was
7-times more than that of donepezil.
The limited structure-activity relationships study on the
benzofuran ring indicated that the introduction of 5-bromo group
diminished the activity (compare compounds 5i and 5c or 5j and
5d). Moreover, by comparing the IC50 values of 7-methoxy com-
pounds 5n and 5o with those of corresponding congeners 5c and
5d, it could be concluded that the insertion of methoxy group on C-
7 position decreased the anti-AChE activity. Compounds 5g, 5h, and
5l containing fluorobenzyl moiety were more potent than related
benzyl derivatives 5f and 5k, respectively. Therefore, the presence
of fluorine atom on benzyl pendent group had positive effect on
inhibitory activity. In contrast, 4-bromobenzyl derivatives 5i and 5n
showed less activity when compared to their corresponding benzyl
analogs 5f and 5k. Thus, the 4-bromo substitution on benzyl group
diminished the activity. Also, the introduction of 4-nitro on the
benzyl group of compounds 5f and 5k resulted in more active
compounds 5j and 5o.
In the search for finding new AChE inhibitors, we have recently
reported benzofuranone-based compounds containing benzylpyr-
idinium moiety as dual-binding inhibitors (Fig. 1) [14]. It was
postulated that the presence of N-benzylpyridinium moiety con-
tributes to inhibitor activity by interacting with the catalytic site,
and the aromatic part of benzofuranone ring engages in
pep
stacking with the PAS of AChE. In continue of the work, we
simplified the primary lead structure by replacing benzofuranone
moiety with benzofuran ring which directly connected to the N-
benzylpyridinium moiety. Thus we described here, the synthesis
and anti-AChE activity of new benzofuran-derived compounds
5aeo bearing N-benzylpyridinium scaffold (Fig. 1). It is interesting
to highlight that a series of 2-arylbenzofurans [15] and pyridinium-
type [16] AChE inhibitors have received much attention as multi-
potent AD modifying agents.
2. Chemistry
The synthesis of compounds 5 was illustrated in Scheme 1. The
reaction of salicylaldehyde derivatives 1 with 4-(bromomethyl)
pyridine 2 in the presence of K2CO3 produced O-substituted sali-
cylaldehydes 3. Cyclization of compounds 3 by using t-BuOK as base
in DMF afforded 4-(benzofuran-2-yl)pyridine derivatives 4 [17].
The N-benzylation of the latter compounds with appropriate
benzyl bromide in acetonitrile gave final compounds as benzyl
3.2. Docking study
To get insight into whether and how the binding and inhibition
profile of synthesized compounds are influenced by the structure,
the docking simulation was performed. Therefore, all the com-
pounds 5aeo were investigated computationally to define their
binding profile. For instance, the most active compound 5e was
Fig. 1. Structures of donepezil hydrochloride as a well-known inhibitor of AChE, benzofuranone-based compounds reported as anti-AChE agents [14] and benzofuran-derived
benzylpyrininium analogs as newly designed AChE inhibitors.

198
F. Baharloo et al. / European Journal of Medicinal Chemistry 93 (2015) 196e201
Scheme 1. Synthesis of N-benzyl-4-(benzofuran-2-yl)pyridinium bromide derivatives 5.
Table 1
The IC50 values (nM) of compounds 5aeo against AChE.
R'
N
R
O
Br
Compounds
R
R0
IC50 (nM)
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
H
H
H
H
2-Me
2-NO2
4-Br
4-NO2
3,5-(Me)2
H
3-F
4-F
4-Br
4-NO2
H
6.8 1.2
4.9 1.1
16.0 3.8
5.8 2.4
4.1 1.5
13.5 2.8
9.6 1.8
8.7 2.1
31.5 5.3
8.1 2.5
26.5 4.2
18.9 3.7
22.4 4.6
29.5 4.6
10.6 3.9
31.0 5.2
H
5-Br
5-Br
5-Br
5-Br
5-Br
7-MeO
7-MeO
7-MeO
7-MeO
7-MeO
3-F
3-Br
4-Br
4-NO2
Donepezil
Fig. 2. Illustrative interaction of compound 5e with AChE active site. The key residues
are showed by yellow color. (For interpretation of the references to colour in this figure
legend, the reader is referred to the web version of this article.)
subjected for further analysis. The detailed picture and key inter-
action table of the docking pose of compound 5e is displayed in
Fig. 2 and Table 2, respectively. From the results, it is demonstrated
that the inhibitor is well-fitted in the active site. As expected, the
aromatic interactions are involved in the binding of inhibitor to the
active site. The benzyl pyridinium part of the molecule locates
around Trp84 in the vicinity of catalytic site. The positively charged
Table 2
The ligand-protein contacts on the basis of distance at 5 Å.
Residue
Type of contact
Distance (Å)
Angle (degree)
Asp72
Trp84
Ionic
4.65
4.01
3.85
3.9
4.40
4.30
4.52
e
nitrogen contributes in forming
residues (Phe330 and Tyr334) at mid-gorge recognition site.
Moreover, pyridinium ring is engaged in T-shape stacking
with Tyr121. Another stacking stabilizes the inhibitor conformation
p-cation interaction with aromatic
Parallel stacking
T-shape stacking
Parallel stacking
12
63
17
e
Tyr121
Trp279
Phe330
Phe331
Tyr334
pep
p
-cation
Lipophilic
-cation
e
through making a
Trp279 in the PAS.
pep interaction of benzofuran moiety with
p
e
4. Conclusion
initial preparation of 4-(benzofuran-2-yl)pyridine precursors via a
reaction between different salicylaldehyde derivatives with 4-
(bromomethyl)pyridine followed by intramolecular cyclization in
the presence of potassium tert-butoxide. The 4-(benzofuran-2-yl)
We have designed and synthesized a novel series of benzofuran-
based N-benzylpyridinium derivatives as AChE inhibitors. The
multistep sequence for synthesis of the compounds involved the

F. Baharloo et al. / European Journal of Medicinal Chemistry 93 (2015) 196e201
199
pyridines were subsequently subjected to an N-benzylation reac-
tion by using appropriate benzyl bromide, providing the final
product. The results of in vitro AChE activity evaluation of synthe-
sized compounds revealed that all compound had potent anti-AChE
activity comparable or more potent than standard drug donepezil.
Compound 5e containing N-(3,5-dimethylbenzyl) moiety was the
most active compound, being 7-fold more potent than donepezil.
The synthetic feasibility and highly potent activity of compound 5e
prototypes make them as promising lead compounds for further
investigation in the field of AD management and therapy.
hexane (15 ml) was added to the residue, the precipitated crystals
were separated by filtration and washed with n-hexane to give
compounds 5.
5.1.4.1. N-(2-Methylbenzyl)-4-(benzofuran-2-yl)pyridinium bromide
(5a). Quantitative yield, mp 317e320 ꢀC, IR nmax/cmꢁ1 (KBr): 1633
(C]N), 1574 (C]C), 2930 (CH3), 1H NMR (DMSO-d6, 500 MHz), 9.1
(d, 2H, Ha, J ¼ 6.8 Hz), 8.7 (d, 2H, Hb, J ¼ 6.8 Hz), 8.35 (s, 1H, H3), 7.87
(d, 1H, H5, J ¼ 7.8 Hz), 7.77 (d, 1H, H8, J ¼ 8.4 Hz), 7.55 (t, 1H, H7,
0
0
0
0
J ¼ 7.8 Hz), 7.22e7.41 (m, 5H, H6,2 ,3 ,4 ,5 ), 5.94 (s, 2H, CH2N), 2.4 (s,
3H, CH3). 13C NMR (125 MHz, DMSO-d6): dC (ppm) 18.8 (CH3), 60.7
(CH2N), 111.9, 113.2, 118, 121.9, 123.1, 124.4, 126.7, 128.4, 129.0, 129.3,
130.9, 132.4, 136.9, 143.7, 145.2, 149.4, 155.8. MS, m/z (%): 301 (Mþ1,
<1), 105 (96), 139 (35), 166 (21), 195 (100).
5. Experimental
5.1. Chemistry
5.1.4.2. N-(2-Nitrobenzyl)-4-(benzofuran-2-yl)pyridinium bromide
(5b). Quantitative yield, mp 322e225 ꢀC, IR nmax/cmꢁ1 (KBr): 1636
(C]N), 1577 (C]C), 1342,1525 (NO2), 1H NMR (DMSO-d6,
500 MHz), 9.17 (d, 2H, Ha, J ¼ 5.7 Hz), 8.63 (d, 2H, Hb, J ¼ 5.7 Hz),
5.1.1. General information
The melting points of synthesized compounds were taken on a
Kofler hot-stage apparatus and are uncorrected. 1H and 13C NMR
spectra were recorded on Bruker FT-500 using TMS as an internal
standard. Fig. 3 presenting the atom numbering of the general
formula of compounds 5aeo was used for easy interpretation of
NMR data. The IR spectra were obtained on a Nicolet Magna FTIR
550 spectrometer (KBr disks). Mass spectra were recorded with an
Agilent Technology (HP) mass spectrometer operating at an ioni-
zation potential of 70 eV.
0
8.39 (s, 1H, H3), 8.27 (d, 1H, H5 , J ¼ 8.2 Hz), 7.88 (d, 1H, H5,
0
0
J ¼ 8.0 Hz), 7.82 (t, 1H, H3 , J ¼ 7.6 Hz), 7.73e7.78 (m, 2H, H8,4 ), 7.56
0
(t, 1H, H7, J ¼ 8.0 Hz), 7.4 (t, 1H, H6, J ¼ 7.8 Hz), 7.31 (d, 1H, H2 ,
J ¼ 7.6 Hz) 6.27 (s, 2H, CH2N). 13C NMR (125 MHz, DMSO-d6): dC
(ppm) 59.8 (CH2N), 111.9, 113.5, 122, 123.2, 124.4, 125.6, 127.8, 128.5,
129.4, 130.3, 130.4, 134.9, 144, 145.8, 147.5, 149.5, 155.8.
5.1.4.3. N-(4-Bromobenzyl)-4-(benzofuran-2-yl)pyridinium bromide
(5c). Quantitative yield, mp 311e315 ꢀC, IR nmax/cmꢁ1 (KBr): 1635
(C]N), 1578 (C]C), 1H NMR (DMSO-d6, 500 MHz), 9.25 (d, 2H, Ha,
J ¼ 6.6 Hz), 8.55 (d, 2H, Hb, J ¼ 6.6 Hz), 8.33 (s, 1H, H3), 7.86 (d, 1H,
5.1.2. General procedure for the preparation of 2-((pyridin-4-yl)
methoxy)benzaldehydes 3
A mixture of appropriate salicylaldehyde 1 (5.0 mmol), 4-(bro-
momethylpyridine (2, 850 mg, 5.0 mmol) and K2CO3 (691 mg,
5.0 mmol) in DMF (5 ml) was stirred at 50 ꢀC for 3 h. The reaction
mixture was cooled down to room temperature and poured into
ice-cold water, and the white precipitates were filtered off and
recrystallized from EtOH to give pure 2-((pyridin-4-yl)methoxy)
benzaldehyde derivative 3.
0
0
,
H5, J ¼ 7.8 Hz), 7.78 (d, 1H, H8, J ¼ 8.0 Hz),7.68 (d, 2H, H3 ,5
0
0
J ¼ 8.3 Hz), 7.57 (d, 2H, H2 ,6 , J ¼ 8.3 Hz), 7.55 (t, 1H, H7, J ¼ 7.8 Hz),
7.39 (t, 1H, H6, J ¼ 7.5 Hz),5.85 (s, 2H, CH2N). 13C NMR (125 MHz,
DMSO-d6): dC (ppm) 61.6 (CH2N), 111.9, 113.3, 122.1, 122.8, 123.2,
124.4, 127.8, 128.4, 131.1, 132.1, 133.7, 143.7, 145.1, 149.4, 155.8.
5.1.4.4. N-(4-Nitrobenzyl)-4-(benzofuran-2-yl)pyridinium bromide
(5d). Quantitative yield, mp 310e314 ꢀC, IR nmax/cmꢁ1 (KBr): 1636
(C]N), 1575 (C]C), 1H NMR (DMSO-d6, 500 MHz), 9.29 (d, 2H, Ha,
J ¼ 5.7 Hz), 8.6 (d, 2H, Hb, J ¼ 5.7 Hz), 8.36 (s, 1H, H3), 8.3 (d, 2H,
5.1.3. General procedure for the preparation of 4-(benzofuran-2-yl)
pyridine derivatives 4
A mixture of compound 3 (639 mg, 3.0 mmol) and potassium
tert-butoxide (561 mg, 5.0 mmol) in DMF (5 ml) was stirred at 80 ꢀC
for 3 h. The reaction mixture was cooled down to room tempera-
ture and poured into ice-cold water, and the white precipitates
were filtered off and recrystallized from EtOH to give 4-(benzo-
furan-2-yl)pyridine derivative 4.
0
0
0
0
,
H
3 ,5 , J ¼ 7.55 Hz), 7.87 (d, 1H, H5, J ¼ 7.6 Hz), 7.83 (d, 2H, H2 ,6
J ¼ 7.8 Hz), 7.77 (d, 1H, H8, J ¼ 7.8 Hz), 7.56 (t, 1H, H7, J ¼ 7.5 Hz), 7.4
(t, 1H, H6, J ¼ 7.2 Hz), 6.04 (s, 2H, CH2N). 13C NMR (125 MHz, DMSO-
d6): dC (ppm) 61.3 (CH2N), 112, 113.5, 122.2, 123.2, 124.1, 124.5, 127.8,
130, 141.4, 143.9, 145.5, 147.9, 149.4, 155.8.
5.1.4. General procedure for the preparation of N-benzyl-4-
(benzofuran-2-yl)pyridinium bromides 5aeo
5.1.4.5. N-(3,5-dimethylbenzyl)-4-(benzofuran-2-yl)pyridinium bro-
mide (5e). Quantitative yield, mp 216e219 ꢀC, IR nmax/cmꢁ1 (KBr):
1634 (C]N), 1576 (C]C), 2906 (CH3), 1H NMR (DMSO-d6,
500 MHz), 9.21 (d, 2H, Ha, J ¼ 6.6 Hz), 8.54 (d, 2H, Hb, J ¼ 6.6 Hz),
8.32 (s,1H, H3), 7.87 (d,1H, H5, J ¼ 7.8 Hz), 7.77 (d,1H, H8, J ¼ 8.3 Hz),
Dry acetonitrile (7 ml) was added to 4-(benzofuran-2-yl)pyri-
dine 4 (1 equiv), and the mixture was dissolved by heating under
reflux. Then the appropriate benzyl bromide derivative (1.2 equiv)
was added thereto. After heating under reflux condition for 2e3 h,
the solvent was evaporated under reduced pressure. Then n-
0
0
7.55 (t, 1H, H7, J ¼ 7.6 Hz), 7.4 (t, 1H, H6, J ¼ 7.8 Hz), 7.18 (s, 2H, H2 ,6 ),
7.06 (s, 1H, H4 ), 5.75 (s, 2H, CH2N), 2.3 (s, 6H, CH3). 13C NMR
0
(125 MHz, DMSO-d6): dC (ppm) 20.8 (CH3), 62.6 (CH2N), 111.9, 113.1,
122, 123.1, 124.4, 126.3, 127.8, 128.4, 130.6, 134.2, 138.4, 143.6, 145,
149.5, 155.8. MS, m/z (%): 314 (Mþ, 15), 264 (96), 239 (48), 195 (75),
119 (58), 83(74), 69 (87), 57 (100).
5.1.4.6. N-Benzyl-4-(5-bromobenzofuran-2-yl)pyridinium bromide
(5f). Quantitative yield, mp 307e310 ꢀC, IR nmax/cmꢁ1 (KBr): 1634
(C]N), 1577 (C]C), 1H NMR (DMSO-d6, 500 MHz), 9.44 (bs, 2H,
Ha), 8.32 (bs, 2H, Hb), 7.81 (s, 1H, H5), 7.78 (s, 1H, H3), 7.66 (d, 2H,
0
0
H
2 ,6 , J ¼ 6.4 Hz), 7.51 (d, 1H, H8, J ¼ 8.6 Hz), 7.36e7.37 (m, 4H,
7,3 ,4 ,5 ), 6.24 (s, 2H, CH2N). 13C NMR (125 MHz, DMSO-d6): dC
0
0
0
H
Fig. 3. Atom numbering of compounds 5aeo, only used for NMR spectra
interpretation.
(ppm) 63.9 (CH2N), 112.4, 113.4, 117.6, 122.1, 125.5, 129.6, 129.7, 130,

200
F. Baharloo et al. / European Journal of Medicinal Chemistry 93 (2015) 196e201
3
0
0
131.5, 132.8, 144, 145.1, 149.8, 155.
129.3, 131.3 (d, 3JCF ¼ 7.73 Hz, C3 ), 136.8 (d, JCF ¼ 7.3 Hz, C1 ), 143.7,
145.1, 149.4, 162.2 (d, 1JCF ¼ 243.52 Hz, C5 ).
0
5.1.4.7. N-(3-Fluorobenzyl)-4-(5-bromobenzofuran-2-yl)pyridinium
bromide (5g). Quantitative yield, mp 311e316 ꢀC, IR nmax/cmꢁ1
(KBr): 1640 (C]N), 1574 (C]C), 1H NMR (DMSO-d6, 500 MHz), 9.33
(d, 2H, Ha, J ¼ 6.4 Hz), 8.57 (d, 2H, Hb, J ¼ 6.4 Hz), 8.26 (s, 1H, H3),
8.08 (s,1H, H5), 7.73 (d,1H, H8, J ¼ 8.8 Hz), 7.63 (d,1H, H7, J ¼ 8.8 Hz),
5.1.4.13. N-(3-Bromobenzyl)-4-(7-methoxybenzofuran-2-yl)pyr-
idinium bromide (5m). Quantitative yield, mp 319e324 ꢀC, IR nmax
/
cmꢁ1 (KBr): 1635 (C]N), 1579 (C]C), 1H NMR (DMSO-d6,
500 MHz), 9.27 (d, 2H, Ha, J ¼ 6.7 Hz), 8.52 (d, 2H, Hb, J ¼ 6.7 Hz),
0
0
0
0
7.46e7.56 (m, 3H, H2 ,3 ,6 ), 7.26e7.29 (m, 1H, H4 ), 5.9 (s, 2H, CH2N).
0
0
0
8.29 (s, 1H, H3), 7.91 (s, 1H, H6 ), 7.63e7.64 (m, 2H, H2 ,4 ), 7.43 (t, 1H,
13C NMR (125 MHz, DMSO-d6): dC (ppm) 61.7 (CH2N), 112.2, 113.9,
0
H3 , J ¼ 7.9 Hz), 7.36 (d, 1H, H5, J ¼ 7.9 Hz), 7.27 (t, 1H, H6, J ¼ 7.9 Hz),
2
2
7.11 (d, 1H, H7, J ¼ 7.9 Hz), 5.88 (s, 2H, CH2N), 4.0 (s, 3H, OMe). 13
C
0
0
115.9 (d, JCF ¼ 22.36 Hz, C4 ), 116.2 (d, JCF ¼ 20.68 Hz, C6 ), 116.6,
122.1, 125, 125.4, 129.9, 130.8, 131.3 (d, 3JCF ¼ 7.72 Hz, C3 ), 136.7 (d,
0
NMR (125 MHz, DMSO-d6): dC (ppm) 55.9 (OCH3), 61.4 (CH2N),
110.1, 113.5, 114.6, 122.1, 122.2, 125.2, 128, 129.1, 129.3, 131.3, 131.7,
132.2, 136.8, 143.6, 145.1, 145.2, 149.4.
3JCF
¼
6.85 Hz, C1 ), 143.3, 145.2, 150.6, 154.5, 162.1 (d,
0
1
0
JCF ¼ 243.68 Hz, C5 ).
5.1.4.8. N-(4-Fluorobenzyl)-4-(5-bromobenzofuran-2-yl)pyridinium
bromide (5h). Quantitative yield, mp 305e310 ꢀC, IR nmax/cmꢁ1
(KBr): 1634 (C]N), 1579 (C]C), 1H NMR (DMSO-d6, 500 MHz), 9.35
(bs, 2H, Ha), 8.58 (bs, 2H, Hb), 8.28 (s, 1H, H3), 8.10 (s, 1H, H5),
5.1.4.14. N-(4-Bromobenzyl)-4-(7-methoxybenzofuran-2-yl)pyr-
idinium bromide (5n). Quantitative yield, mp 314e320 ꢀC, IR nmax
/
cmꢁ1 (KBr): 1638 (C]N), 1583 (C]C), 2955 (CH3) 1H NMR (DMSO-
d6, 500 MHz), 9.19 (d, 2H, Ha, J ¼ 6.7 Hz), 8.54 (d, 2H, Hb, J ¼ 6.7 Hz),
0
0
7.7e7.74 (m, 3H, H 8,3 ,5 ), 7.66 (d, 1H, H7, J ¼ 8.4 Hz), 7.31 (m, 2H,
0
0
0
0
,
8.3 (s, 1H, H3), 7.68 (d, 2H, H3 ,5 , J ¼ 8.4 Hz), 7.54 (d, 2H, H2 ,6
3 ,5 ), 6.05 (s, 2H, CH2N). 13C NMR (125 MHz, DMSO-d6): dC (ppm)
0 0
H
J ¼ 8.4 Hz), 7.4 (d, 1H, H5, J ¼ 7.9 Hz), 7.32 (t, 1H, H6, J ¼ 7.9 Hz), 7.17
(d, 1H, H7, J ¼ 7.9 Hz), 5.82 (s, 2H, CH2N), 4.0 (s, 3H, OMe). 13C NMR
(125 MHz, DMSO-d6): dC (ppm) 56 (OCH3), 63.9 (CH2N), 110.15,
113.5, 114.7, 122.1, 122.8, 125.3, 129.3, 131, 132.1, 133.6, 143.7, 145.1,
145.3, 149.4. MS, m/z (%): 394 (Mþ, <1), 250 (8), 225 (63), 169 (61),
69 (100), 41 (94).
61.6 (CH2N), 112.2, 114, 116.1 (d, 2JCF ¼ 21.75 Hz, C3 ,5 ), 116.6, 122.4,
0
0
125.4, 129.9, 130.7, 130.8, 131.5 (d, 3JCF ¼ 8.02 Hz, C2 ,6 ), 143.2, 145.2,
0
0
150.7, 154.5, 162 (d, 1JCF ¼ 243 Hz, C4 ).
0
5.1.4.9. N-(4-Bromobenzyl)-4-(5-bromobenzofuran-2-yl)pyridinium
bromide (5i). Quantitative yield, mp 308e312 ꢀC, IR nmax/cmꢁ1
(KBr): 1633 (C]N), 1574 (C]C), 1H NMR (DMSO-d6, 500 MHz), 9.22
(d, 2H, Ha, J ¼ 6.7 Hz), 8.56 (d, 2H, Hb, J ¼ 6.7 Hz), 8.33 (s, 1H, H3),
7.87 (d, 1H, H8, J ¼ 7.7 Hz), 7.77 (d, 1H, H5, J ¼ 8.5 Hz), 7.68 (d, 2H,
5.1.4.15. N-(4-Nitrobenzyl)-4-(7-methoxybenzofuran-2-yl)pyr-
idinium bromide (5o). Quantitative yield, mp 312e316 ꢀC, IR nmax
/
cmꢁ1 (KBr): 1636 (C]N), 1584 (C]C), 1348, 1520 (NO2), 1H NMR
(DMSO-d6, 500 MHz), 9.26 (d, 2H, Ha, J ¼ 6.8 Hz), 8.58 (d, 2H, Hb,
0
0
0
0
H
3 ,5 , J ¼ 8.4 Hz), 7.55 (d, 2H, H2 ,6 , J ¼ 8.4 Hz),7.41 (t, 1H, H6,
J ¼ 7.6 Hz), 5.82 (s, 2H, CH2N). 13C NMR (125 MHz, DMSO-d6): dC
(ppm) 61.7 (CH2N), 112, 122.1, 122.8, 123.2, 124.4, 127.8, 128.4, 131.1,
132.1, 133.6, 143.7, 145.1, 149.4, 155.8.
0
0
J ¼ 6.8 Hz), 8.33 (s, 1H, H3), 8.3 (d, 2H, H3 ,5 , J ¼ 8.7 Hz), 7.82 (d, 2H,
0
0
H
2 ,6 , J ¼ 8.7 Hz), 7.4 (d,1H, H5, J ¼ 7.8 Hz), 7.31 (t,1H, H6, J ¼ 7.9 Hz),
7.16 (d, 1H, H7, J ¼ 7.9 Hz), 6.04 (s, 2H, CH2N), 3.95 (s, 3H, OMe). 13
C
NMR (125 MHz, DMSO-d6): dC (ppm) 55.9 (OCH3), 61.3 (CH2N),
110.2, 113.7, 114.7, 122.2, 124.1, 125.3, 129.3, 130, 141.4, 143.8, 145.2,
145.3, 145.5, 147.8, 149.4. MS, m/z (%): 361 (Mþ, <1), 339 (11), 313
(20), 225 (68), 195 (28), 154 (32), 136 (36), 83 (52), 69 (74), 55 (94),
43 (100).
5.1.4.10. N-(4-Nitrobenzyl)-4-(5-bromobenzofuran-2-yl)pyridinium
bromide (5j). Quantitative yield, mp 318e322 ꢀC, IR nmax/cmꢁ1
(KBr): 1633 (C]N), 1575 (C]C), 1349, 1534 (NO2), 1H NMR (DMSO-
d6, 500 MHz), 9.33 (d, 2H, Ha, J ¼ 6.2 Hz), 8.61 (d, 2H, Hb, J ¼ 6.3 Hz),
0
0
8.29e8.31 (m, 3H, H3,3 ,5 ), 8.13 (d, 1H, H5, J ¼ 1.4 Hz), 7.83 (d, 2H,
0
0
H
2 ,6 , J ¼ 8.5 Hz), 7.76 (d, 1H, H8, J ¼ 8.9 Hz), 7.69 (dd, 1H, H7, J ¼ 8.9,
5.2. AChE inhibition test
1.4 Hz), 6.05 (s, 2H, CH2N). 13C NMR (125 MHz, DMSO-d6): dC (ppm)
61.5 (CH2N), 112.4, 114, 116.6, 122.5, 124.1, 125.5, 129.9, 130, 130.9,
141.3, 143.5, 145.6, 147.8, 150.6, 154.6.
AChE (E.C.3.1.1.7, Type VeS, from Electric eel), Ellman's reagent
(DTNB), and acetylthiocholine (ATC) were purchased from Sigma-
eAldrich. Donepezil (Sigma) was used as reference drug for AChE
inhibition. The AChE inhibitory activities of compounds 5aeo were
determined by using previously reported method [14].
5.1.4.11. N-Benzyl-4-(7-methoxybenzofuran-2-yl)pyridinium
bro-
mide (5k). Quantitative yield, mp 316e320 ꢀC, IR nmax/cmꢁ1 (KBr):
1640 (C]N), 1582 (C]C), 1351, 1513 (NO2), 2982 (CH3), 1H NMR
(DMSO-d6, 500 MHz), 9.24 (d, 2H, Ha, J ¼ 6.3 Hz), 8.52 (d, 2H, Hb,
5.3. Molecular modeling
0
0
J ¼ 6.3 Hz), 8.29 (s, 1H, H3), 7.59 (d, 2H, H 2 ,6 , J ¼ 7.0 Hz), 7.43e7.47
0
0
0
(m, 3H, H3 ,4 ,5 ), 7.38 (d,1H, H5, J ¼ 7.8 Hz), 7.29 (t,1H, H6, J ¼ 7.8 Hz),
The structure of AChE containing co-crystalized ligand E2020
(PDB code: 1EVE) was retrieved from RCSB Protein Data Bank (PDB,
http://www.rcsb.org/pdb/home/home.do) and docking studies
were performed by Autodock Vina (1.1.1) as previously described
method [18].
7.13 (d, 1H, H7, J ¼ 7.8 Hz), 5.87 (s, 2H, CH2N), 3.9 (s, 3H, OMe). 13
C
NMR (125 MHz, DMSO-d6): dC (ppm) 55.9 (OCH3), 62.5 (CH2N),
110.1, 113.4, 114.7, 122, 125.2, 128.7, 129.2, 129.3, 134.4, 143.5, 145.1,
145.2, 149.4. MS, m/z (%): 316 (Mþ, <1), 225(100), 195 (20), 182 (28),
154 (36), 91(95).
Appendix A. Supplementary data
5.1.4.12. N-(3-Fluorobenzyl)-4-(7-methoxybenzofuran-2-yl)pyr-
idinium bromide (5l). Quantitative yield, mp 317e322 ꢀC, IR nmax
/
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2015.02.009.
cmꢁ1 (KBr): 1634 (C]N), 1585 (C]C), 2971 (CH3), 1H NMR (DMSO-
d6, 500 MHz), 9.25 (d, 2H, Ha, J ¼ 6.5 Hz), 8.54 (d, 2H, Hb, J ¼ 6.5 Hz),
0
0
0
8.31 (s, 1H, H3), 7.43e7.54 (m, 3H, H2 ,3 ,6 ), 7.39 (d, 1H, H5,
References
0
J ¼ 7.8 Hz), 7.31 (m, 2H, H6,4 ), 7.15 (d, 1H, H7, J ¼ 7.8 Hz), 5.88 (s, 2H,
CH2N), 4.00 (s, 3H, OMe). 13C NMR (125 MHz, DMSO-d6): dC (ppm)
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55.96 (OCH3), 61.7 (CH2N), 110.1, 113.5, 114.7, 115.8 (d,
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2
0
0
JCF ¼ 22.38 Hz, C4 ),116.2 (d, JCF ¼ 20.72 Hz, C6 ),122.1,124.9,125.2,

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