Synthesis of Novel Tacrine Analogs as Acetylcholinesterase Inhibitors

Article abstract of DOI:10.1002/jhet.2594

In this work, a wide range of novel pyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amines were synthesized as tacrine analogs. At first, reaction of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, aromatic aldehydes, and malononitrile gave 6-amino-4-aryl-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles. Then, reaction of the latter compounds with cyclohexanone led to the formation of the title compounds. Also, they were evaluated for their in vitro acetylcholinesterase and butyrylcholinesterase inhibitory activities. Interestingly, most of them showed good inhibitory activity comparing with rivastigmine as the reference drug.

Full text of DOI:10.1002/jhet.2594

Month 2016
Synthesis of Novel Tacrine Analogs as Acetylcholinesterase Inhibitors
a
b,c
a
d
c
Mohammad Mahdavi, Mina Saeedi, Laleh Gholamnia, Seyed Amir Behzad Jeddi, Reyhaneh Sabourian,
a
a
c,d
Abbas Shafiee, Alireza Foroumadi, and Tahmineh Akbarzadeh *
a
Department of Medicinal Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center,
Tehran University of Medical Sciences, Tehran, Iran
b
Medicinal Plants Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
c
Persian Medicine and Pharmacy Research Center, Tehran University of Medical Sciences, Tehran, Iran
d
Department of Medicinal Chemistry, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
E-mail: akbarzad@tums.ac.ir
*
Additional Supporting Information may be found in the online version of this article.
Received October 22, 2015
DOI 10.1002/jhet.2594
Published online 00 Month 2016 in Wiley Online Library (wileyonlinelibrary.com).
In this work, a wide range of novel pyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amines were synthesized as tacrine
analogs. At first, reaction of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, aromatic aldehydes, and malononitrile
gave 6-amino-4-aryl-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles. Then, reaction of the
latter compounds with cyclohexanone led to the formation of the title compounds. Also, they were evaluated
for their in vitro acetylcholinesterase and butyrylcholinesterase inhibitory activities. Interestingly, most of them
showed good inhibitory activity comparing with rivastigmine as the reference drug.
J. Heterocyclic Chem., 00, 00 (2016).
INTRODUCTION
anti-inflammatory [7], antibacterial, cytotoxic [8], and acetyl-
cholinesterase (AChE) inhibitory [9] activities have been
reported in the literature.
O-Heterocycles are of significant interest as they possess
versatile biological activities, and among various oxygen
containing heterocyclic compounds, pyran derivatives have
attracted lots of attention because of their important biological
activities including antimycobacterial [1], antibacterial and
antifungal [2], cytotoxic [3], quorum sensing inhibitory [4],
and antitumor activities [5]. Besides, pyrazole and its
derivatives are brilliant among N-heterocyclic compounds
as they possess outstanding biological activities and have
been widely applied in pharmaceutical industry [6]. In this
respect, synthesis and biological properties of fused pyrano–
pyrazole derivatives have attracted lots of attention because
Acetylcholine and butyrylcholine are neurotransmitters
that play significant role in various cognitive abilities, neuro-
nal and non-neuronal signaling. AChE and butyrylcholines-
terase (BChE) are enzymes that degrade choline-based
esters in numerous cholinergic pathways in the central and
peripheral nervous systems [10]. It has been revealed that loss
of cholinergic transmission is one the most important cause of
Alzheimer’s disease (AD). In this respect, much research has
been devoted to the enhancement of cholinergic system
through several ways and anticholinesterase drugs have
attracted lots of attention to reduce symptoms of AD [11].
©
2016 Wiley Periodicals, Inc.

M. Mahdavi, M. Saeedi, L. Gholamnia, S. A. B. Jeddi, R. Sabourian, A. Shafiee,
Vol 000
A. Foroumadi, and T. Akbarzadeh
4
and cyclohexanone (5) was investigated. In this
regard, reaction of 6-amino-3-methyl-1,4-diphenyl-1,4-
dihydropyrano[2,3-c]pyrazole-5-carbonitrile (4a) and
cyclohexanone (5) was conducted in the presence of
different Lewis acids such as ZnCl and AlCl as well
2
3
Figure 1. The structure of tacrine and synthesized analogs 6. [Color
figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
as different solvents like CH Cl , ClCH CH Cl (DCE),
2
2
2
2
and CHCl . It was found that the best result was obtained
3
in the presence of AlCl in DCE at reflux for 12–18 h.
3
Then, reaction of all substrates 4 and cyclohexanone (5)
was performed under the optimized conditions to give the
corresponding products 6 in good yields (Table 1). Also,
the structure of all compounds was confirmed using IR,
H-, and C-NMR spectroscopy as well as chemical
analysis.
9
-Amino-1,2,3,4-tetrahydroacridine known as tacrine (Fig. 1)
[12] was found to be an efficient drug inhibiting both AChE
and BChE [13]. However, extensive use of tacrine was
limited as it showed various side effects [14]. Hence, recent
reports have been attributed to the design and synthesis of
novel and efficient tacrine-based AChE inhibitors.
Herein, in continuation of our research on the synthesis
of novel heterocycles [15] and bioactive heterocyclic com-
pounds [16], we focused on the synthesis of novel pyrazolo
1
13
Biological investigation.
The in vitro anti-AChE
activity of the all compounds 6 was evaluated using
Ellman’s method [17] and compared with rivastigmine as
the reference drug (Table 1). Our results depicted that
compound 6a having phenyl substituent at the 4-position
of the compound possessed the best inhibitory activity
[
4′,3′:5,6]pyrano[2,3-b]quinolin-5-amines 6 as anti-AChE
and BChE agents (Fig. 1).
(
IC = 2.77μM) in comparison to rivastigmine as the
50
reference drug (IC =11.07 μM). Compound 6b having
50
RESULTS AND DISCUSSION
The preparation of pyrazolo[4′,3′:5,6]
pyrano[2,3-b]quinolin-5-amines 6 is shown in Scheme 1.
For this purpose, various 6-amino-4-aryl-3-methyl-1-
phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles 4
were prepared through the reaction of 3-methyl-1-phenyl-
4
-MeO-phenyl group at the 4-position showed activity
with IC = 2.84 μM slightly different from compound 6a.
50
Chemistry.
However, increasing the number of methoxy groups on
the phenyl ring at different positions (compounds 6c and
6
d) led to the lack of activity (IC >100). Replacing the
50
4
-MeO-phenyl group by 4-Me-phenyl (compound 6e)
reduced the activity (IC = 13.04 μM). It should be noted
50
1
H-pyrazol-5(4H)-one (1), aromatic aldehydes 2, and
that changing the position of methyl group did not
malononitrile (3). To obtain the best reaction conditions,
reaction of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one (1),
benzaldehyde (2a), and malononitrile (3) was conducted as
a model reaction under various conditions. Accordingly,
the model reaction was achieved in the presence of
improve the inhibitory activity (IC = 26.01 and >100
50
for compounds 6f and 6g, respectively). However, the
presence of methyl group at ortho position deleted the anti-
AChE activity (compound 6g). Compound 6j having 3-F-
phenyl group at the 4-position showed IC =4.04μM.
50
different basic reagents such as DABCO, NEt , K CO ,
3
2
3
Changing the position of fluorine on the phenyl ring gave
lower activity because compounds 6i and 6k exhibited
IC = 9.00 and 15.71 μM, respectively. It was found that
and piperidine. Also, solvent screening was performed in
EtOH, MeOH, CH CN, PhCH , and CH Cl . It was found
3
3
2
2
50
that using DABCO in EtOH led to the formation of the
corresponding product 4a in good yield (85%). It should
be noted that the previously mentioned reaction was
successfully performed at room temperature for 12 h, and
increasing temperature did not lead to higher yield. The
scope of the reaction was investigated by varying aromatic
aldehydes 2. It was clear that all aldehydes possessing
different electronic substituents participated in the reaction
to afford product 4. In the next step, reaction of compounds
introduction of chlorine at different positions reduced AChE
inhibitory activity. Compounds 6l and 6m possessing 4-Cl-
phenyl and 2-Cl-phenyl, respectively, at the 4-position of the
synthesized compounds showed IC =24.24 and 29.57μM,
50
respectively. Also, increasing the number of chlorine at 2,3-,
2,4-, 3,4- (compounds 6n–p) deleted the inhibitory activity.
Nevertheless, 2,6-diCl showed moderate activity with
IC = 16.78 μM. Introduction of electron-withdrawing NO
2
50
group into the discussing position (compound 6h) led to
Scheme 1. Synthesis of pyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amines 6.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2016
Synthesis of Novel Tacrine Analogs as Acetylcholinesterase Inhibitors
Table 1
The IC50 values of the compounds 6 against AChE and BChE.
AChE inhibition
BChE inhibition
Entry
Compound 6
Ar
[IC50 (μM)]
[IC50 (μM)]
1
2
3
4
5
6
7
8
9
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
C
6
H
5
2.77 ± 0.25
2.84 ± 0.42
>100
2.21 ± 0.02
1.02 ± 0.03
0.06 ± 0.01
>100
>100
5.92 ± 0.09
>100
>100
1.57 ± 0.05
>100
10.00 ± 0.06
3.84 ± 0.50
>100
>100
>100
>100
>100
4.16 ± 1.01
7.72 ± 0.02
4-MeOC
2,4-diMeOC
2,3,4-triMeOC
6 4
H
6
H
3
6
H
2
>100
4-MeC
3-MeC
2-MeC
6
6
6
H
H
H
4
4
4
13.04 ± 0.34
26.01 ± 0.76
>100
6.24 ± 1.18
15.71 ± 1.04
4.04 ± 0.14
9.00 ± 0.17
24.24 ± 0.59
29.57 ± 0.085
>100
>100
>100
16.78 ± 1.29
>100
11.07 ± 0.01
3-NO
2
C
6
H
4
4-FC
3-FC
2-FC
4-ClC
2-ClC H
6 4
2,3-diClC
2,4-diClC
3,4-diClC
2,6-diClC
6
6
6
H
H
H
4
4
4
10
11
12
13
14
15
16
17
18
21
6 4
H
6
6
6
6
H
H
H
H
3
3
3
3
6q
6r
2-Thiophenyl
Rivastigmine
Data are expressed as mean ± SE (three independent experiments).
IC =6.24μM. Clearly, the efficacy of nitro group is higher
50
CONCLUSIONS
than chlorine and methyl groups. Another instructive result
is related to the introduction of heterocyclic substitution,
In conclusion, novel pyrazolo[4′,3′:5,6]pyrano[2,3-b]
quinolin-5-amines were synthesized as tacrine analogs.
It was found that the prepared compounds possessed
anticholinesterase activity. In this respect, 3-methyl-1,4-
diphenyl-1,4,6,7,8,9-hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]
quinolin-5-amine and 4-(2,4-dimethoxyphenyl)-3-methyl-1-
phenyl-1,4,6,7,8,9-hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]
quinolin-5-amine were the most potent anti-AChE and anti-
BChE compounds.
2-thiophenyl at the 4-position of compound 6r that led to
the lack of activity.
Results related to the anti-BChE activity revealed that
compounds 6a–c, 6f, 6i, 6k, 6l, and 6r showed good to high
activity (IC =0.06–10.00μM) toward BChE comparing
50
with rivastigmine (IC =7.72μM). Other compounds
50
exhibited no anti-BChE activity (IC > 100). The best
50
activity was related to compound 6c having 2,4-diMeO-
phenyl group, which showed no anti-AChE activity
(
IC =0.06μM), 128 times more potent than the reference
50
drug. Compounds 6b, 6i, and 6a depicted good activity with
IC s=1.02, 1.57, and 2.21μM. Also, compound 6l having
EXPERIMENTAL
50
4
-Cl-phenyl group at the 4-position showed good activity
Chemistry. Melting points were taken on a Kofler hot
stage apparatus (England) and are uncorrected. H- and
C-NMR spectra were recorded on Bruker FT-500
1
(IC =3.48μM), and the introduction of heterocyclic
50
13
substituent, 2-thiophenyl at the 4-position of compound 6r
gave IC =4.16μM. Compound 6f possessing 3-Me-phenyl
group inhibited BChE with IC =5.92μM. These findings
(Germany), using TMS as an internal standard. The IR
spectra were obtained on a Nicolet Magna FTIR 550
spectrometer (KBr disks) (USA). The elemental analysis
was performed with an Elementar Analysensystem GmbH
VarioEL CHNS mode (Germany).
Procedure for the synthesis of 6-amino-3-methyl-1-phenyl-
4-aryl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile 4.
A mixture of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one 1
50
50
indicated that compounds 6a–c, 6f, 6i, 6l, and 6r were
1
.8–128 times more potent than rivastigmine. It should be
noted that compound 6k showed moderate anti-BChE
activity (IC =10.00μM). According to our results, both
compounds 6a and 6b showed high anti-AChE and
50
anti-BChE activity.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

M. Mahdavi, M. Saeedi, L. Gholamnia, S. A. B. Jeddi, R. Sabourian, A. Shafiee,
Vol 000
A. Foroumadi, and T. Akbarzadeh
1
3
(1mmol), appropriate aldehyde 2 (1mmol), malononitrile 3
2H, Ph); C-NMR (DMSO-d , 125 MHz) δ (ppm):
6
(
1mmol), and DABCO (20mol%) in EtOH (10mL) was
12.7, 21.9, 22.2, 22.8, 31.8, 35.2, 55.9, 59.8, 97.7,
99.8, 105.3, 113.1, 119.9, 125.7, 129.2, 137.9, 139.8,
145.2, 146.1, 150.9, 151.1, 152.6, 152.8, 154.5. Anal.
Calcd for C H N O : C, 69.86; H, 6.06; N, 11.24.
stirred at room temperature for 12h. After completion of
the reaction, the mixture was filtered off, washed with cold
EtOH, and dried at 50°C to give pure compounds 4.
2
9
30
4
4
Procedure for the synthesis of 4-aryl-3-methyl-1-
Found: C, 69.71; H, 6.24; N, 11.14.
phenyl-1,4,6,7,8,9-hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-
3-Methyl-1-phenyl-4-(p-tolyl)-1,4,6,7,8,9-hexahydropyrazolo
c]quinolin-5-amine 6.
(
A mixture of compound 4
1mmol) and cyclohexanone 5 (2mmol) was added to
the suspension of AlCl3 in dry DCE (2mmol in
0mL) and heated at reflux for 12–18h. After
completion of the reaction (checked by TLC),
[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine (6e).
Yield 78%;
mp >250°C; IR (KBr): 3455, 3370, 3082, 2924, 2801,
À1
1
1614, 1557, 1404cm ; H-NMR (CDCl , 500MHz) δ
3
3
(ppm): 1.83–1.87 (m, 4H, 2CH ), 2.05 (s, 3H, CH ), 2.27–
2
3
a
2.30 (m, 2H, CH ), 2.32 (s, 3H, CH ), 2.80–2.81 (m, 2H,
2
3
mixture of H O/THF (1:1, 100mL) was added to the
2
CH ), 4.14 (s, 2H, NH ), 4.95 (s, 1H, CH), 7.14
2 2
mixture, and it was basicified with NaOH (10%). The
mixture was stirred at room temperature for 30min,
(
d, J=7.8Hz, 1H, H3′, H5′), 7.21–7.26 (m, 3H, H2′, H6′,
Ph), 7.44 (t, J=8.5Hz, 2H, Ph), 7.53 (dd, J= 8.5, 1.0 Hz,
2H, Ph); C-NMR (CDCl , 125MHz) δ (ppm): 13.2,
3
13
2
and the crude product was extracted with CH Cl2
(2×50) and washed with brine (2×50). The organic
2
1.0, 22.3, 22.5, 22.87, 32.5, 37.4, 99.03, 99.2, 113.7,
121.0, 125.8, 127.9, 129.1, 129.8, 137.1, 138.2, 140.3,
45.8, 146.0, 152.2, 154.2, 155.1. Anal. Calcd for
C H N O: C, 76.75; H, 6.20; N, 13.26. Found: C,
phase was dried over Na SO , and the solvent was
2
4
evaporated under vacuum. All compounds were
recrystallized from EtOH to afford pure products 6.
1
27 26 4
3-Methyl-1,4-diphenyl-1,4,6,7,8,9-hexahydropyrazolo[4′,3′:5,6]
7
6.58; H, 6.34; N, 13.18.
3
pyrano[2,3-c]quinolin-5-amine (6a).
Yield 85%; mp 217–
19°C; IR (KBr): 3490, 3375, 2909, 2850, 2195, 1634,
-Methyl-1-phenyl-4-(m-tolyl)-1,4,6,7,8,9-hexahydropyrazolo
4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine (6f). Yield 70%; mp
>250°C; IR (KBr): 3517, 3422, 2924, 2850, 1632, 1588,
2
1
1
2
[
À1
1
597, 1517cm ; H-NMR (DMSO-d , 500MHz) δ (ppm):
6
.70–1.72 (m, 4H, 2CH ), 2.00 (s, 3H, CH ), 2.18–2.35 (m,
À1
1
2
3
1515 cm ; H-NMR (DMSO-d , 500 MHz) δ (ppm):
1.72–1.74 (m, 4H, 2CH ), 1.99 (s, 3H, CH ), 2.23 (s, 3H,
CH ), 2.24–2.35 (m, 2H, CH ), 2.62–2.64 (m, 2H, CH ),
3 2 2
6
H, CH ), 2.60–2.62 (m, 2H, CH ), 5.29 (s, 1H, CH), 5.55
2
2
2
3
(
s, 2H, NH ), 7.17 (t, J= 7.2Hz, 1H, Ph), 7.26–7.36 (m, 5H,
2
Ph), 7.53 (t, J= 8.2Hz, 2H, Ph), 7.80 (d, J= 8.2Hz, 2H, Ph);
5
.21 (s, 1H, CH), 5.45 (s, 2H, NH ), 6.98 (t, J=7.5Hz, 1H,
2
13
C-NMR (DMSO-d , 125 MHz) δ (ppm): 12.7, 22.0, 22.2,
H5′), 7.12 (s, 1H, H2′), 7.16–7.17 (m, 2H, H4′, H6′),
7.31 (t, J=8.0Hz, 1H, Ph), 7.52 (t, J=8.0Hz, 2H,
Ph), 7.80 (d, J=8.0 Hz, 2H, Ph); C-NMR (DMSO-
d6, 125 MHz) δ (ppm): 12.6, 21.0, 21.9, 22.2, 22.8,
31.8, 34.8, 99.0, 100.0, 113.2, 119.7, 124.9, 125.7, 127.3,
128.2, 128.4, 129.2, 137.5, 137.9, 144.0, 145.1, 145.8, 152.4,
6
2
1
1
5
3.0, 31.9, 34.7, 98.0, 100.2, 113.3, 119.9, 125.9, 126.5,
27.8, 128.5, 129.4, 137.9, 144.2, 145.2, 145.9, 152.5,
52.7, 154.5. Anal. Calcd for C H N O: C, 76.45; H,
13
26 24 4
.92; N, 13.72. Found: C, 76.31; H, 6.14; N, 13.58.
4
-(2,4-Dimethoxyphenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
152.6, 154.4. Anal. Calcd for C27H N O: C, 76.75; H, 6.20;
26 4
(
2
5
(
6c). Yield 75%; mp >250°C; IR (KBr): 3463, 3376,
N, 13.26. Found: C, 76.91; H, 6.11; N, 13.35.
À1
1
929, 2835, 1632, 1597, 1515cm ; H-NMR (DMSO-d ,
3-Methyl-4-(3-nitrophenyl)-1-phenyl-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(6h). Yield 75%; mp >250°C; IR (KBr): 3525, 3437,
6
00MHz) δ (ppm): 1.70–1.72 (m, 4H, 2CH ), 2.02
2
s, 3H, CH ), 2.30–2.81 (m, 4H, CH ), 3.67 (s, 3H,
3 2
À1
1
OCH ), 3.71 (s, 3H, OCH ), 5.17 (s, 1H, CH), 5.50
(
3017, 2946, 2859, 1634, 1599, 1519, 1373 cm ; H-
NMR (DMSO-d , 500MHz) δ (ppm): 1.74–1.75 (m, 4H,
2CH ), 2.11 (s, 3H, CH ), 2.25–2.39 (m, 2H, CH ), 2.61–
2.63 (m, 2H, CH ), 5.73 (s, 1H, CH), 5.78 (s, 2H, NH ),
3
3
s, 2H, NH ), 6.67 (d, J= 8.5Hz, 1H, H6′), 6.83 (dd,
6
2
J= 8.5, 2.0 Hz, 1H, H5′), 7.14 (s, 1H, H3′), 7.31
t, J=7.5Hz, 1H, Ph), 7.53 (t, J=7.5Hz, 2H, Ph), 7.79
2
3
2
(
2
2
(
7
d, J=7.5Hz, 2H, Ph). Anal. Calcd for C H N O : C,
1.78; H, 6.02; N, 11.96. Found: C, 71.89; H, 6.18; N, 12.14.
6.91 (t, J=8.0Hz, 1H, Ph), 7.23 (d, J=3.4Hz, 1H, H2′),
7.23–7.34 (m, 3H, H4′, H5′, H6′), 7.44 (t, J=8.0Hz, 2H,
28 28 4 3
13
3
-Methyl-1-phenyl-4-(2,4,6-trimethoxyphenyl)-1,4,6,7,8,9-
Ph), 7.53 (dd, J=8.0, 1.0Hz, 2H, Ph); C-NMR (DMSO-
, 125MHz) δ (ppm): 12.7, 22.0, 22.2, 23.0, 31.9, 34.0,
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
d
6
(
2
6d). Yield 70%; mp >250°C; IR (KBr): 3499, 3412,
940, 2850, 1639, 1592, 1518 cm ; H-NMR (DMSO-
97.3, 99.4, 113.6, 120.0, 121.8, 122.2, 126.1, 129.4, 130.3,
134.6, 137.9, 145.1, 146.1, 146.5, 147.6, 152.6, 153.2,
À1
1
d , 500 MHz) δ (ppm): 1.72–1.74 (m, 4H, 2CH ), 2.05
154.4. Anal. Calcd for C26H N O : C, 68.86; H, 5.11; N,
23 5 3
6
2
(
s, 3H, CH ), 2.26–2.61 (m, 4H, 2CH ), 3.60 (s, 3H,
15.44. Found: C, 68.69; H, 5.27; N, 15.31.
3
2
OCH ), 3.77 (s, 2H, 2OCH ), 5.19 (s, 1H, CH), 5.49
4-(4-Fluorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(6i). Yield 72%; mp >250°C; IR (KBr): 3514, 3415,
3
3
(
s, 2H, NH ), 6.67 (s, 2H, H3′, H5′), 7.30 (t, J = 7.5 Hz,
2
1
H, Ph), 7.51 (t, J = 7.5 Hz, 2H, Ph), 7.80 (d, J = 7.5 Hz,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2016
Synthesis of Novel Tacrine Analogs as Acetylcholinesterase Inhibitors
À1
1
3
(
018, 2924, 2850, 1639, 1592, 1518 cm ; H-NMR
(td, J = 8.5, 1.5 Hz, 2H, Ph), 7.71 (d, J = 8.5 Hz, 2H, Ph);
1
3
CDCl , 500 MHz) δ (ppm): 1.83–1.84 (m, 4H, 2CH ),
C-NMR (DMSO-d , 125 MHz) δ (ppm): 12.7, 22.0,
3
2
6
2
.05 (s, 3H, CH ), 2.28–2.36 (m, 2H, CH ), 2.80–2.82
22.2, 23.0, 31.9, 33.9, 97.7, 99.8, 113.4, 119.9, 126.0,
128.4, 129.4, 129.6, 131.1, 137.9, 143.3, 145.2, 145.9,
152.5, 152.8, 154.4. Anal. Calcd for C H ClN O: C,
70.50; H, 5.23; N, 12.65. Found: C, 70.38; H, 5.41; N,
12.51.
3
2
(
m, 2H, CH ), 4.10 (s, 2H, NH ), 4.99 (s, 1H, CH),
2 2
7
1
.03 (t, J = 8.5 Hz, 2H, H3′, H5′), 7.25 (t, J = 7.5 Hz,
H, Ph), 7.31 (t, J = 8.5, 5.2 Hz, 2H, H2′, H6′), 7.44 (t,
2
6
23
4
J = 7.5 Hz, 2H, Ph), 7.87 (dd, J = 7.5, 1.1 Hz, 2H, Ph);
1
3
C-NMR (CDCl , 125 MHz) δ (ppm): 13.2, 22.3,
4-(2,3-Dichlorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(6n). Yield 70%; mp >250°C; IR (KBr): 3483, 3406,
3
2
2.5, 22.9, 32.5, 37.1, 98.7, 98.8, 113.9, 116.1 (d, JC-
=
21.6 Hz), 121.0, 125.9, 129.1, 129.4, 129.5, 138.1,
39.2, 145.8, 152.0, 154.5, 155.0, 161.8 (d, JC-
245.0 Hz). Anal. Calcd for C H FN O: C, 73.22;
F
À1
1
1
3054, 2939, 2856, 1633, 1598, 1517 cm ; H-NMR
=
(DMSO-d , 500 MHz) δ (ppm): 1.71–1.72 (m, 4H,
F
26 23
4
6
H, 5.44; N, 13.14. Found: C, 73.11; H, 5.52; N, 13.31.
2CH ), 1.93 (s, 3H, CH ), 2.22–2.32 (m, 2H, CH ),
2
3
2
4
-(3-Fluorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
2.55–2.61 (m, 2H, CH ), 5.26 (s, 2H, NH ), 5.65 (s, 1H,
2 2
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
CH), 7.32–7.33 (m, 3H, H5′, H6′, Ph), 7.53–7.54
1
3
(
3
5
6j). Yield 70%; mp >250°C; IR (KBr): 3502, 3412,
015, 2949, 2850, 1639, 1521 cm ; H-NMR (CDCl ,
3
(
m, 3H, H4′, Ph), 7.80 (d, J = 7.3 Hz, 2H, Ph); C-
À1
1
NMR (DMSO-d , 125 MHz) δ (ppm): 12.7, 21.9, 22.2,
6
00 MHz) δ (ppm): 1.84–1.85 (m, 4H, 2CH ), 2.08
2
22.9, 31.9, 39.0, 96.1, 98.9, 113.7, 120.1, 126.1, 128.2,
128.8, 129.4, 130.3, 131.1, 131.8, 132.3, 137.8, 145.2,
147.1, 152.5, 153.2, 154.5. Anal. Calcd for
C H Cl N O: C, 65.41; H, 4.65; N, 11.74. Found: C,
(
s, 3H, CH ), 2.26–2.37 (m, 2H, CH ), 2.81–2.82
3 2
(
m, 2H, CH ), 4.12 (s, 2H, NH ), 5.01 (s, 1H, CH),
2 2
6
.94–7.00 (m, 2H, H2′, H4′), 7.18 (d, J = 7.6 Hz, 1H,
2
6
22
2 4
H6′), 7.26 (t, J = 8.0 Hz, 1H, Ph), 7.32 (td, J = 7.6,
.0 Hz, 1H, H5′), 7.45 (t, J = 8.0 Hz, 2H, Ph), 7.87 (dd,
6
5.28; H, 4.80; N, 11.58.
4-(2,4-Dichlorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
3
1
3
J = 8.0, 1.0 Hz, 2H, Ph); C-NMR (CDCl , 125 MHz) δ
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(6o). Yield 75%; mp >250°C; IR (KBr): 3490, 3412,
2937, 2850, 1639, 1590 cm
500 MHz) δ (ppm): 1.80–1.82 (m, 4H, 2CH ), 2.06
(s, 3H, CH ), 2.23–2.35 (m, 2H, CH ), 2.78–2.79
3
(
ppm): 13.2, 22.2, 22.5, 22.9, 32.5, 37.6, 98.3, 113.8,
À1
1
114.5 (d, JC-F = 20.9 Hz), 115.0 (d, JC-F = 21.5 Hz),
121.0, 123.5, 126.0, 129.1, 130.6, 130.7, 138.1, 145.8,
145.9, 146.1, 152.1, 154.6, 155.0, 163.4 (d, JC-F =246.5Hz).
;
H-NMR (CDCl3,
2
3
2
Anal. Calcd for C H FN O: C, 73.22; H, 5.44; N, 13.14.
(m, 2H, CH
2
), 4.22 (s, 2H, NH
2
), 5.49 (s, 1H, CH), 7.07
26
23
4
Found: C, 73.50; H, 5.28; N, 13.04.
(d, J = 8.0 Hz, 1H, H6′), 7.15 (dd, J = 8.0, 1.5 Hz, 1H,
H5′), 7.25 (t, J = 7.5 Hz, 1H, Ph), 7.39 (d, J = 1.5 Hz,
1H, H3′), 7.44 (t, J = 7.5 Hz, 2H, Ph), 7.87 (d, J = 7.5 Hz,
4
-(2-Fluorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
1
3
(
2
5
6k). Yield 65%; mp >250°C; IR (KBr): 3440, 3323,
950, 2850, 1630, 1588 cm
00 MHz) δ (ppm): 1.83–1.84 (m, 4H, 2CH ), 2.05
2H, Ph); C-NMR (CDCl , 125 MHz) δ (ppm): 12.9,
3
À1
1
;
H-NMR (CDCl3,
22.3, 22.5, 22.9, 32.5, 36.5, 94.1, 98.5, 113.7, 121.0,
126.0, 128.5, 128.9, 129.2, 130.2, 132.4, 133.5, 138.2,
139.6, 145.8, 146.4, 151.7, 154.6, 155.0. Anal. Calcd for
2
(
s, 3H, CH ), 2.25–2.37 (m, 2H, CH ), 2.79–2.81
3 2
(
m, 2H, CH ), 4.24 (s, 2H, NH ), 5.37 (s, 1H, CH),
C H22Cl N O: C, 65.41; H, 4.65; N, 11.74. Found: C,
26 2 4
2
2
7
.06–7.14 (m, 3H, H5′, H6′, Ph), 7.21–7.25 (m, 2H,
65.31; H, 4.51; N, 11.86.
H3′, H4′), 7.44 (t, J = 7.5 Hz, 2H, Ph), 7.88 (dd, J = 7.5,
4-(3,4-Dichlorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(6p). Yield 70%; mp >250°C; IR (KBr): 3485, 3375,
13
1
.1Hz, 2H, Ph); C-NMR (DMSO-d , 125MHz) δ (ppm):
6
12.1, 21.8, 22.1, 22.8, 29.9, 31.7, 96.8, 98.1, 113.3, 115.8
À1
1
(d, JC-F = 21.2 Hz), 119.8 (d, JC-F =11.2Hz), 124.4, 125.8,
2950, 2850, 1640, 1588, 1525 cm
(DMSO-d , 500 MHz) δ (ppm): 1.71–1.72 (m, 4H,
2CH ), 1.94 (s, 3H, CH ), 2.19–2.36 (m, 2H, CH ),
2.59–2.61 (m, 2H, CH ), 5.29 (s, 2H, NH ), 5.55
;
H-NMR
1
1
28.8 (d, JC-F =8.7Hz), 129.2, 129.8, 129.9, 130.4, 137.8,
45.0, 152.2, 152.6, 154.4, 159.5 (d, JC-F =245.0Hz). Anal.
6
2
3
2
Calcd for C H FN O: C, 73.22; H, 5.44; N, 13.14. Found:
2
2
26
23
4
C, 73.38; H, 5.31; N, 13.29.
(s, 1H, CH), 7.33 (t, J = 8.0 Hz, 1H, Ph), 7.38–7.40
(m, 2H, H5′, H6′), 7.54 (t, J = 8.0 Hz, 2H, Ph), 7.59
4
-(4-Chlorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
1
3
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(s, 1H, H2′), 7.79 (d, J = 8.0 Hz, 2H, Ph); C-NMR
(DMSO-d , 125 MHz) δ (ppm): 12.6, 21.9, 22.2, 22.9,
(
6l). Yield 80%; mp >250°C; IR (KBr): 3505, 3409,
6
À1
1
3
035, 2921, 2859, 1629, 1596, 15717 cm ; H-NMR
31.7, 32.8, 96.9, 97.7, 113.7, 120.1, 126.1, 128.2,
129.2, 129.4, 132.4, 132.5, 132.9, 137.8, 139.3, 145.2,
146.3, 152.5, 153.1, 154.4. Anal. Calcd for
(
DMSO-d , 500 MHz) δ (ppm): 1.63–1.64 (m, 4H,
6
2
2
CH ), 2.10 (s, 3H, CH ), 2.25–2.28 (m, 2H, CH ),
2 3 2
.42–2.44 (m, 2H, CH ), 5.25 (s, 1H, CH), 5.52 (s, 2H,
C
26
H
22Cl
2
N
4
O: C, 65.41; H, 4.65; N, 11.74. Found: C,
2
NH ), 7.24–7.29 (m, 5H, H2′, H3′, H5′, H6′, Ph), 7.45
65.31; H, 4.74; N, 11.62.
2
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

M. Mahdavi, M. Saeedi, L. Gholamnia, S. A. B. Jeddi, R. Sabourian, A. Shafiee,
Vol 000
A. Foroumadi, and T. Akbarzadeh
4
-(2,6-Dichlorophenyl)-3-methyl-1-phenyl-1,4,6,7,8,9-
at 405nm followed by the addition of substrate (ATCI
3mM in water). The change in absorbance was measured at
405nm after 15 min. The IC50 values were determined
graphically from inhibition curves (log inhibitor concentration
vs percent of inhibition). A control experiment was
performed under the same conditions without inhibitor
and the blank contained buffer, water, DTNB, and
substrate. The described method was also used for BChE
inhibition assay.
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
6q). Yield 70%; mp >250°C; IR (KBr): 3471, 3385,
937, 2850, 1642, 1592 cm
00 MHz) δ (ppm): 1.80–1.82 (m, 4H, 2CH ), 2.00
s, 3H, CH ), 2.25–2.31 (m, 2H, CH ), 2.75–2.77
3 2
m, 2H, CH ), 4.19 (s, 2H, NH ), 6.00 (s, 1H, CH), 7.16
t, J=8.0Hz, 1H, H4′), 7.23 (t, J=8.0Hz, 1H, Ph), 7.41–
.45 (m, 4H, Ph, H3′, H5′), 7.86 (d, J=8.0Hz, 2H, Ph);
(
2
5
(
(
(
À1
1
;
H-NMR (CDCl3,
2
2
2
7
1
3
C-NMR (CDCl , 125MHz) δ (ppm): 12.8, 22.3, 22.5,
3
2
1
1
4
2.9, 32.4, 33.6, 95.1, 96.8, 113.5, 121.2, 126.0, 128.0,
29.1, 131.7, 134.3, 135.5, 137.1, 138.2, 145.6, 151.5,
54.2, 156.0. Anal. Calcd for C H Cl N O: C, 65.41; H,
Acknowledgments. This research was supported by a grant from
the research council of Tehran University of Medical Sciences on
the project number 92-03-33-24363.
26
22
2 4
.65; N, 11.74. Found: C, 65.29; H, 4.80; N, 11.55.
3
-Methyl-1-phenyl-4-(thiophen-2-yl)-1,4,6,7,8,9-
hexahydropyrazolo[4′,3′:5,6]pyrano[2,3-b]quinolin-5-amine
(
3
5
6r). Yield 65%; mp >250°C; IR (KBr): 3459, 3323,
072, 2915,, 1660, 1592, 1514 cm ; H-NMR (DMSO-d ,
6
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(
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concentrations. All tests were conducted at 25°C, and four
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9
5
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Month 2016
Synthesis of Novel Tacrine Analogs as Acetylcholinesterase Inhibitors
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