Design and synthesis of thienopyridines as novel templates for acetylcholinesterase inhibitors

Article abstract of DOI:10.1007/s00044-012-0403-5

New dual binding site acetylcholinesterase (AChE) inhibitors have been designed and synthesized as a new drug candidate for the treatment of Alzheimer's disease (AD) through the binding to both catalytic and peripheral sites of the enzyme. Therefore, a series of thienopyridine analogs of tacrine were synthesized and investigated for their ability to inhibit the activity of AChE in comparison with tacrine. All the compounds were found to inhibit AChE activity, especially compounds 7b and 11a, which were found to be more potent than tacrine.

Full text of DOI:10.1007/s00044-012-0403-5

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:4087–4095
DOI 10.1007/s00044-012-0403-5
ORIGINAL RESEARCH
Design and synthesis of thienopyridines as novel templates
for acetylcholinesterase inhibitors
•
Mohga M. Badran Maha Abdel Hakeem
•
•
Suzan M. Abuel-Maaty Afaf El-Malah
•
Rania M. Abdel Salam
Received: 15 July 2012 / Accepted: 6 December 2012 / Published online: 20 December 2012
Ó Springer Science+Business Media New York 2012
Abstract New dual binding site acetylcholinesterase
(AChE) inhibitors have been designed and synthesized as a
new drug candidate for the treatment of Alzheimer’s dis-
ease (AD) through the binding to both catalytic and
peripheral sites of the enzyme. Therefore, a series of thi-
enopyridine analogs of tacrine were synthesized and
investigated for their ability to inhibit the activity of AChE
in comparison with tacrine. All the compounds were found
to inhibit AChE activity, especially compounds 7b and
11a, which were found to be more potent than tacrine.
hydrolysis of neurotransmitter acetylcholine (ACh) at cho-
linergic synapse in the central and peripheral nervous system.
Inhibitors of AChE activity promoted an increase in the
concentration and duration of the action of synaptic ACh, thus
causing an enhancement of cholinergic transmission through
the activation of the nicotinic and muscarinic receptors.
However, the achievement of potent inhibitors of AChE cat-
alytic site will not represent a significant improvement unless
there is a concomitant inhibition of the peripheral anionic site
(PAS) of the enzyme, which is associated with the neurotoxic
cascade of AD through AChE induced Ab aggregation
(Bolognesi et al., 2005; Kwon et al., 2007). The literature
survey revealed also that new potent and selective AChE
inhibitors such as tacrine–huperzine hybrid derivative (Badia
et al., 1998; Camps et al., 1999) (a), bis-interacting galan-
thamine ligand (Mary et al., 1998) (b), and tacrine linked to
lipoicacidfragment(Rosinietal., 2005) (c) havealready been
designed and synthesized in Fig. 1.
Keywords Synthesis ꢀ Thienopyridines ꢀ
AChE inhibitors ꢀ Alzheimer’s disease
Introduction
Alzheimer’s disease (AD) is a progressive and neurodegen-
erative disorder of the central nervous system that is most
common cause of dementia among elderly people. The dis-
ease is characterized by neural loss, synaptic damage, neut-
rotic, and vascular plaques (Bartus et al., 1982; Davis and
Powchik, 1995). AChE inhibitors (Ruiz et al., 2005; Tariot
and Federoff, 2003) represent a promising approach for the
treatment of AD since AChE is the enzyme involved in the
The first analog (a) is a hybrid of two well-known AChE
inhibitors, tacrine and huperzine. Whereas, the second (b) rep-
resents an association of two pharmacophoric entities capable
of interacting with the active and peripheral site of the enzyme
(galantamine and phthalyl moiety). On the other hand, the
introduction of lipoic acid moiety (LA) to tacrine afforded
compound (c), in the third structure, combining the antioxidant
properties of LA with the ability of tacrine to interact with the
PAS. In addition, several tacrine-based compounds were also
developed, among them is a compound containing two tacrine
subunits (Butini et al., 2008; Carlier et al., 1999) (d) Fig. 2, the
amino groups of which are connected with a hepta methylene
side chain. This compound, designed taking in account the
existence of two binding sites for tacrine in AChE, is about 149
times more potent than tacrine.
M. M. Badran ꢀ M. A. Hakeem ꢀ S. M. Abuel-Maaty (&) ꢀ
A. El-Malah
Pharmaceutical Organic Chemistry Department, Faculty of
Pharmacy, Cairo University, Kaser El-Aini Street,
P.O. Box 11562, Giza, Egypt
e-mail: suzanaboelnaga@gmail.com
R. M. Abdel Salam
Pharmacology and Toxicology Department, Faculty
of Pharmacy, Cairo University, Kaser El-Aini Street,
Giza, Egypt
On the basis of this evidence, a new series of com-
pounds containing two units of thienopyridine derivatives
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Fig. 1 Tacrine based
compounds
N
NH
2
A
Tacrine-huperzine A hybrid
HO
O
N
O
N
O
B
O
Phthalyl moity
Galantamine
AchE catalytic site inhibitor
bis-interacting ligand
AchE catalytic
prepheral site ligand
O
HN
N
H
S
S
Cl
N
C
universal antioxidant, (11a–c) (Rosini et al., 2005), to get
new potent dual-binding site AChE inhibitors for
enhancement of cholinergic transmission and inhibition of
AChE-induced Ab aggregation and oxidative stress, lead-
ing to a synergic and effective treatment of AD. On the
other hand, exploratory replacement in successful drugs of
benzene ring with thiophene moiety which is widely rec-
ognized as bioisostere of benzene has become a routine
strategy in modern drug design. Encouraged by these
findings, we substituted the benzene ring in tacrine with the
thiophene ring in our study to investigate the biologic
effects of these structural modifications of tacrine.
N
N
N
N
H
H
D
Fig. 2 Alkylene linked homodimeric tacrine
connected by methylene linkers (5a–c) is synthesized. In
addition, another series of thienopyridine analogs of tacrine
is synthesized applying a design strategy in which distinct
pharmacophores of two different drugs were combined in
the same structure leading to hybrid molecules. This is
achieved through linking the thienopyridine analog of
Tacrine by a linker of suitable length and nature to either
phthalimide moiety which could interact with PAS (7a–d)
and (9a, b) (Ishihara et al., 1991) or lipoic acid moiety, a
Results and discussion
Chemistry
The synthetic methodology employed for the preparation
of the new dual binding site heterodimers varied depending
on the bond type in the linker which was inserted in the last
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Med Chem Res (2013) 22:4087–4095
4089
Scheme 1 Reagents and
conditions: i = POCl3, reflux
3 h
O
Cl
1
O
R
C
1
R
O
i
+
2
NH
S
2
R
2
R
S
N
1 a,b
2 a,b
2a; R1 = R2 = CH
1
2
1a; R = R= = CH
=
3
3
1
2
1
2
b; R = R = (CH )
b; R R = (CH )
2 4
2 4
Scheme 2 Reagents and
NH2
NH
N
Cl
N
(CH 2
)
n
1
conditions: ii A = 1-pentanol,
reflux 72 h; ii B = ethylene
glycol, CuO/K2CO3, reflux 24 h
1
R
R
iiA or
H
N
NH
+
2
(CH
)
2
2
n
ii
B
2
2
R
S
R
S
1
3 a-c
4 a-f
2 a,b
3a; n = 3
b; n = 4
c; n = 7
1
2
2
2a; R = R = CH
3
4a; R =R = CH
,
n = 3
3
1
2
b; R
R
= (CH )
2 4
1
2
b; R = R = CH n = 4
3
1
2
c; R = R = CH
,
,
n = 7
n = 3
3
3
1
2
d; R =R = CH
1
2
e; R = R = CH n = 4
3
1
2
f; R = R = CH
, n = 7
3
NH
NH
N
Cl
N
(CH )
2 n
1
1
1
R
R
ii
A
+
H N
2
2
NH
(CH )
2 n
2
2
R
S
S
N
R
2
R
S
5 a-c
3 a,b, (o.5 mole)
2 a,b ( 1mole)
1
2
5a; R =R = CH , n = 3
3
1
2
b; R = R = CH n = 4
2a; R1 = R2 = CH3
3
3a; n = 3
b; n = 4
c; n = 7
1
2
c; R R = (CH ) , n = 4
2 n
1
2
b; R
R = (CH )
2 4
ii A= 1-pentanol, reflux 72 h
step of the synthetic pathway. The synthetic routes utilized
for the preparation of these new compounds are depicted in
Schemes 1, 2, 3, 4. The chlorothienopyridines 2a, b were
prepared in a one-step reaction by refluxing the aminothi-
ophene esters 1a, b with cyclohexanone in the presence of
phosphorous oxychloride (Scheme 1).
Cu2O (Lang et al., 2001) as a catalyst. Amination of the
chloro derivatives 2a, b with a half equivalent of the
diaminoalkanes 3a–c afforded the alkylene-linked
homodimeric derivatives 5a–c (Scheme 2).
On the other hand, preparation of the new dual heterodi-
mers containing the phthalimide moiety inserted in the ami-
nothienopyridines 4a–e was achieved through two routes. The
first one was via heating the amino derivatives 4a, b, d, e with
phthalic anhydride 6 in glacial acetic acid to afford com-
pounds 7a–d. The second route was attained through the
reaction of the appropriate aminothienopyridines 4d, e with
chloroethylphthalimide 8 in dry DMF in the presence of
anhydrous potassium carbonate to yield the corresponding
derivatives 9a, b (Scheme 3). The IR spectra of compounds
7a–d and 9a–e revealed the presence of two overlapped C=O
absorption bands at 1,705–1,720 cm-1. Besides, the 1H NMR
spectra demonstrated the aromatic protons of the phthalimide
moiety at 7.4–8 ppm. Nevertheless, the reaction of the
A search in the literature demonstrated that the synthesis
of (9-aminoalkylamino)-1,2,3,4-tetrahydroacridine could
be achieved in a good yield through the reaction of the
chloro derivative of tacrine (9-chlorotetrahydroacridine)
with the appropriate diamines in pentanol (Carlier et al.,
1999).
Applying the aforementioned method to the chloro
derivatives 2a, b afforded compounds 4a–f in a poor yield.
However, the synthesis of these compounds which could be
considered adaptable key intermediates in our study, were
accomplished in a satisfactory yield through their heating
with the appropriate diamine in ethylene glycol, using
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O
N
O
NH
NH2
NH
(CH )
2 n
1
R
1
(CH2)n
R
iii
O
O
2
R
S
N
+
2
R
S
N
O
7a-d
6
4
7a; R1 =R2 = CH3, n = 3
b; R1 = R2 = CH3 n = 4
c; R1R2 = (CH2)4, n = 3
d; R1R2 = (CH2)4, n = 4
a,b,d,e
+
O
H
N
NH
N
O
(CH )
N
NH2
1
2 n
NH
N
R
1
(CH2)n
Cl
R
N
O
2
R
S
+
2
O
R
S
9a,b
8
1
2
4
d.e
9a ;R R = (CH ) , n = 3
2 4
1
2
b ;R R = (CH ) ,n = 4
2 4
Scheme 3 Reagents and conditions: iii = glacial acetic acid, reflux 20 h; iv = K2CO3/DMF, reflux 24 h
O
NH2
NH
N
NH
(CH2)n
1
O
NH
N
(CH )
R
2 n
1
1
R
S
S
v
HO
+
S S
S
2
R
R
S
10
11a-c
4
b,d,e
11a ; R1= R2 = CH3, n = 4
b ; R1R2 = (CH2) ,n = 3
C ; R1R2 = (CH2)4 , n =4
Scheme 4 Reagents and conditions V = N2/DMF, rt, 24 h
aminothienopyridines4b, d, e with lipoic acid 10 was fulfilled
via stirring under nitrogen in the presence of 1-(3-dimethyl-
aminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI) as
dehydrating agent in dry DMF and at room temperature to
furnish the corresponding thienopyridine-lipoic acid hetero-
dimers 11a–c (Scheme 4). The IR spectra of compounds
11a–c showed C=O absorption bands at 1,647, 1,685, and
1,699 cm, respectively.
Conclusion
We reported here the synthesis of various thienopyridines
as tacrine heterodimer analogs. The synthesized com-
pounds were tested for their antiacetylcholinesterase
activity. Results showed that all the compounds demon-
strated significant activity in comparison with tacrine; they
are more or less similar to each other and showed good to
moderate inhibitory activity. The higher activity of com-
pound 11b might be attributed to the lipoic acid moiety
which was reported to possess antioxidant effect (Rosini
et al., 2005). Whereas, the higher activity of 7b might be
referred to the phthalimide (Ishihara et al., 1991) moiety
that has two carbonyl groups which may contribute to the
enzyme inhibition by hydrogen bonding with the enzyme.
It is worth mentioning that all attempts to react com-
pound 4f which contains seven methylene groups with
phthalic anhydride, chloroethylphthalimide, or lipoic acid
were fruitless. This may be attributed to the nature of this
compound, as it has rubber-like property and it is nearly
insoluble in all solvents. All the new compounds have been
fully characterized through their spectral data.
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Med Chem Res (2013) 22:4087–4095
4091
chloride. The extract was concentrated in vacuum. Triturating
of the residue with diethyl ether and crystallization from
benzene yielded the title compounds 2a, b.
Table 1 Inhibition of AChE activity of tacrine and synthesized
thienopyridines
Compound
Cholinesterase content (U/gm Inhibition
(%)
net weight)
4-Chloro-2,3-dimethyl-5,6,7,8-tetrahydrothieno[2,3-b]quin-
Normal control (saline) 334.31 26.49
0
oline (2a) Yield 70 %; mp 138–140 °C; IR (KBr) cm-1
:
Tacrine (10 mg/kg)
5a (10 mg/kg)
5b (10 mg/kg)
5c (10 mg/kg)
7a (10 mg/kg)
7b (10 mg/kg)
7c (10 mg/kg)
7d (10 mg/kg)
9a (10 mg/kg)
9b (10 mg/kg)
11a (10 mg/kg)
11b (10 mg/kg)
11c (10 mg/kg)
153,56 12.38*
250.24 28.19*
195.49 11.59*
215.05 14.09*
179.86 7.82*
148.58 7.82*
191.59 18.59*
234.59 33.18*
187.68 20.98*
183.76 11.19*
191.03 20.75*
144.67 16.49*
262.75 27.16@
54.91
25.15
41.53
35.67
46.20
55.56
42.69
29.83
43.86
45.03
42.86
56.73
21.41
2,927, 2,856 (CH aliphatic), 1,683 (C=N); 1H NMR
(CDCl3)d: 1.66–1.74(m, 4H, 2CH2), 2.40(s, 3H, CH3),
2.45(s, 3H, CH3), 2.80–3.20(m, 4H, 2CH2); MS: m/z (%
abundance) 251(M?) (27.86); Anal. Calcd for C13H14Cl NS:
C, 62.01; H, 5.60; N, 5.56. Found: C,61.98, H, 5.60; N, 5.56.
11-Chloro-1,2,3,4,7,8,9,10-octahydro[1]benzothieno[2,3-
quinoline (2b) Yield 80 %; mp 160–162 °C; IR (KBr)
cm-1: 2,931, 2,858 (CH aliphatic), 1,682 (C=N); 1H
NMR(CDCl3)d : 1.75–2.00(m, 8H, 4CH2), 2.75–2.89(m,
4H, 2CH2), 2.95–3.10(2 m, 4H, 2CH2); MS: m/z
(% abundance) 277(M?) (100); Anal. Calcd for C15H16Cl
NS: C, 64.85; H, 5.81; N, 5.04. Found: C, 64.82, H, 5.80;
N, 5.04.
* Significantly different from normal control group at P \ 0.05
@
Significantly different from tacrine group at P \ 0.05
General methods for alkylation reaction
Experimental
Method A. A mixture chlorothienopyridines 2a or 2b
(4.61 mmol), certain diaminoalkane 3a–c (13.8 mmol),
and 1-pentanol (5 ml) was heated under reflux for 72 h.
After cooling to room temperature, the mixture was diluted
with methylene chloride (50 ml) and then washed with
10 % NaOH (19 50 ml) and water (29 40 ml). The
organic layer was concentrated in vacuum and crystallized
from acetic acid to give the desired product.
Chemistry
Melting points are obtained on griffin apparatus and the
values given are uncorrected. IR spectra were recorded on
a Shimadzu 435 spectrometer, using KBr disks. 1H NMR
spectra were recorded on a Mercury-300BB 300 MHZ and
a Varian GEMINI-200 MHZ spectrometer using TMS as
an internal standard. Mass spectra were recorded on a
JEON JMS-AX 500 Mass Spectrometer. Elemental analy-
ses for C, H, and N were within 0.4 % of the theoretic
values and were performed at the Micro Analytical Center,
Cairo University. Progress of the reaction was monitored
by TLC using pre-coated silica gel aluminum sheets
MERCK 60 F 254 and was visualized by UV lamp.
Compounds 1a and b were prepared adopting Gewaled
conditions (Gewald et al., 1966). All the chemicals were
purchased from Aldrich and Sigma Companies.
Method B. To a solution of the appropriate chloro
derivatives 2a or 2b (0.01 mol) in ethylene glycol l(10 ml),
the selected diamine 3a–c (0.03 mol) was added in the
presence of catalytic amounts of cuprous oxide and
potassium carbonate. The mixture was heated under reflux
for 24 h, filtered, and the filtrate was left aside to cool and
poured on ice-cooled water. The separated solid was fil-
tered, dried, and crystallized from ethanol.
4-(3-Aminopropyl)amino-2,3-dimethyl-5,6,7,8-tetrahydrothieno
[2,3-b]quinoline (4a) The title compound was prepared
from the reaction of 2a and 1,3-diamino propane (3a)
adopting Method A or B to give 4a. Yield 35 % (Method A),
General procedures for the synthesis of compounds
2a and b
64 % (Method B); mp 120–122 °C; IR (KBr) cm-1
:
3,383–3,273 (NH2, NH), 2,927, 2,854 (CH aliphatic), 1,635
(C=N); 1H NMR(DMSO-d6)d: 1.20–1.32(m, 2H, CH2),
1.49–1.76(2 m, 4H, 2CH2), 2.46(s, 3H, CH3), 2.51(s, 3H,
CH3), 2.73–2.79(m, 4H, 2CH2), 3.65–3.70(m, 4H, 2CH2));
MS: m/z (% abundance) 289(M?) (11.94); Anal. Calcd for
C16H23N3S: C, 66.39; H, 8.01; N, 14.52. Found: C, 66.89, H,
8.02; N, 14.53.
Cyclohexanone (0.1 mol) was added portion wise to a slurry
of 2-amino-3-ethoxycarbonylthiophenes 1a, b (0.1 mol) and
phosphorus oxychloride (75 ml). The reaction mixture was
stirred under reflux for 3 h and concentrated under reduced
pressure. The residue was dissolved in chloroform and poured
carefully into a mixture of ice and ammonium hydroxide. The
aqueous phase was separated and extracted with methylene
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mp [300 °C; IR (KBr) cm-1: 3,404–3,300 (NH2, NH),
2,929, 2,856 (CH aliphatic), 1,622 (C=N); 1H NMR(DMSO-
d6, TFAA-H)d: 1.12–1.28(m, 6H, 3CH2), 1.55–1.76(2m,
12H, 6CH2), 2.72–2.92(m, 8H, 4CH2), 3.38–3.39 (m, 2H,
CH2), 3.49–3.50(m, 2H, CH2); MS: m/z (% abundance)
371(M?) (5.15); Anal. Calcd for C22H33N3S: C, 71.11; H,
8.95; N, 11.31. Found: C, 17.17; H, 8.96; N, 11.32.
4-(4-Aminobutyl)amino-2,3-dimethyl-5,6,7,8-tetrahydrothie-
no[2,3-b]quinoline (4b) The title compound was prepared
from the reactionof 2a and 1,4-diamino butane (3b) adopting
Method A or B to give 4b. Yield 21 % (Method A), 45 %
(Method B); mp [300 °C; IR (KBr) cm-1: 3,354–3,255
1
(NH2, NH), 2,927, 2,856 (CH aliphatic), 1,635 (C=N); H
NMR(DMSO-d6)d: 1.22–1.75(m, 8H, 4CH2), 2.36(s, 3H,
CH3), 2.44(s, 3H, CH3), 2.65–2.97(m, 4H, 2CH2),
3.20–3.40(m, 4H, 2CH2); MS: m/z (% abundance) 303(M?)
(18.13); Anal. Calcd for C17H25N3S: C, 67.28; H, 8.30; N,
13.85. Found: C, 67.36, H, 8.31; N, 13.86.
General procedure for synthesis of alkylene-linked
dimers of thienopyridines 5a–c
The title compound was prepared adopting Method A using
chlorothienopyridines 2a or 2b (23.1 mmol), suitable dia-
mine 3a or 3b (11.5 mmol), and 1-pentanol (30 ml).
4-(7-Aminoheptyl)amino-2,3-dimethyl-5,6,7,8-tetrahydrothi-
eno[2,3-b]quinoline (4c) The title compound was prepared
from the reaction of 2a and 1,7-diamino heptane (3c)
adopting Methods A or B to give 4c. Yield 45 % (Method A),
Propane-1,3-diamino-N,N0-diyl-4,40-bis(2,3-dimethyl-5,6,7,8-
tetrahydro thieno[2,3-b]quinoline) (5a) Yield 80 %; mp
[300 °C;); IR (KBr) cm-1: 3,440–3,400 (2NH), 2,927,
2,854 (CH aliphatic), 1,620 (C=N); 1H NMR(DMSO-d6)d:
1.18–1.44(m, 2H, CH2), 1.49–1.61(m, 4H, 2CH2),
1.77–2.04(m, 4H, 2CH2), 2.45 (s, 6H, 2CH3), 2.47(s, 6H,
2CH3), 2.75–2.79(m, 8H, 4CH2), 2.85–2.92(m, 4H, 2CH2);
MS: m/z (%abundance) 504(M?) (1.06); Anal. Calcd for
C29H36N4S2: C, 69.01; H, 7.19; N, 11.10. Found: C, 69.02;
H, 7.19; N, 11.12.
50 % (Method B); mp [300 °C; IR (KBr) cm-1
:
3,450–3,300 (NH2, NH), 2,924, 2,850 (CH aliphatic), 1,650
1
(C=N); H NMR(DMSO-d6)d: 1.15–1.29(m, 6H, 3CH2),
1.38–1.52 (2m, 4H, 2CH2), 1.82–1.85(m, 4H, 2CH2), 2.49(s,
3H, CH3), 2.51(s, 3H, CH3), 2.68–2.73(m, 4H, 2CH2),
3.25–3.43(m, 4H, 2CH2); MS: m/z (% abundance) 345(M ?)
(2.12); Anal. Calcd for C20H31N3S: C, 69.52; H, 9.04; N,
12.16. Found: C, 69.48; H, 9.04; N, 12.15
11-(3-Aminopropyl)amino-1,2,3,4,7,8,9,10-octahydro[1] ben-
zothieno [2,3-b]quinoline (4d) The title compound was
prepared from the reaction of 2b and 3a adopting Method A
or B to give 4d. Yield 45 % (Method A), 53 % (Method B);
mp [300 °C; IR (KBr) cm-1: 3,400–3,300 (NH2, NH),
2,941, 2,858 (CH aliphatic), 1,633 (C=N); 1H NMR
(DMSOd6)d: 1.18–2.08(m, 10H, 5CH2), 2.63–2.91(m, 8H,
4CH2), 3.29–3.49(m, 4H, 2CH2), 4.40, 7.36(2s, 3H, NH,
NH2 D2O exchangeable); MS: m/z (% abundance) 315(M ?)
(4.70); Anal. Calcd for C18H25N3S: C, 68.53; H, 7.99; N,
13.32. Found: C,68.52; H, 7.99; N,13.32.
Butane-1,4-diamino-N,N0-diyl-4,40-bis(2,3-dimethyl-5,6,7,8-
tetrahydro thieno[2,3-b]quinoline (5b) Yield 83 %; mp
[300 °C; IR (KBr) cm-1: 3,425–3,375(2NH), 2,927,
2,858 (CH aliphatic), 1,625 (C=N); 1H NMR(DMSO-d6)d:
1.23–1.52(m, 4H, 2CH2), 1.72–1.82(m, 8H, 4CH2), 2.38(s,
6H, 2CH3), 2.44(s, 6H, 2CH3), 2.80–2.90(2m, 12H, 6CH2),
4.90, 5.90(2s, 2H, 2NH D2O exchangeable); MS: m/z (%
abundance) 516(M-2) (3.10); Anal. Calcd for C30H38N4
S2: C, 69.46; H, 7.38; N, 10.80. Found: C, 69.51; H, 7.39;
N, 10.85
11-(4-Aminobutyl)amino-1,2,3,4,7,8,9,10 octahydro[1] benzo-
thieno [2,3-b]quinoline (4e) The title compound was
prepared from the reaction of 2b and 3b adopting Methods
A or B to give 4e. Yield 55 % (Method A), 66 % (Method
B); mp[300 °C; IR (KBr) cm-1: 3,390–3,273 (NH2, NH),
2,926, 2,854 (CH aliphatic), 1,624 (C=N); 1H NMR
(DMSO) d6)d: 1.42–1.75(m, 12H, 6CH2), 2.70–3.15(m,
8H, 4CH2), 3.40–3.70(m, 4H, 2CH2), 5.97, 7.80 (2s, 3H,
NH, NH2 D2O exchangeable); MS: m/z (% abundance)
330(M?1) (0.43); Anal. Calcd for C19H27N3S: C, 69.25; H,
8.26; N, 12.75. Found: C, 69.36; H, 8.27; N, 12.77.
Butane-1,4-diamino-N,N0-diyl-11,110-bis(1,2,3,4,7,8,9,
10-octahydro [1] benzothieno[2,3-b]quinoline (5c) Yield
88 %; mp [300 °C; IR (KBr) cm-1: 3,444–3,383 (2NH),
2,929, 2,856 (CH aliphatic), 1,645 (C=N); 1H NMR(DMSO-
d6)d: 1.78–1.82(m, 20H, 10CH2), 2.75–2.85(m, 16H,
8CH2), 2.90–3.04(2m, 4H, 2CH2); MS:m/z (% abundance)
568(M-2) (2.13); Anal. Calcd for C34H42N4S2: C, 71.53; H,
7.42;N, 9.82. Found: C, 71.55; H, 7.45; N, 9.82.
General procedure for synthesis of of compounds 7a–d
To a solution of the desired aminothienopyridines 4a, b, d,
e (0.01 mol) in glacial acetic acid (10 ml) phthalic anhy-
dride was added (6) (0.01 mol) and the mixture was heated
under reflux for 20 h. The separated solid was filtered,
11-(7-Aminoheptyl)amino-1,2,3,4,7,8,9,10 octahydro[1] ben-
zothieno[2,3-b]quinoline (4f) The title compound was pre-
pared from the reaction of 2b and 3c adopting Methods A
or B to give 4f. Yield 57 % (Method A), 66 % (Method B);
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Med Chem Res (2013) 22:4087–4095
4093
General procedure for synthesis of compounds 9a, b
washed with water, dried, and crystallized from ethanol to
afford the respective thienopyridine derivatives.
The selected aminothienopyridines 4d, e (0.01 mol), N-(2-
chloroethyl) phthalimide (8) (0.01 mol), catalytic amount
of potassium carbonate, and dimethylformamide (10 ml)
were heated under reflux for 24 h. After cooling to room
temperature, the separated solid was filtered, washed with
water, and crystallized from 1,4-dioxane
4-[3-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)propyl]amino-
2,3-dimethyl-5,6,7,8-tetrahydrothieno[2,3-b]quinoline (7a)
Yield 69 %; mp 190–192 °C; IR(KBr) cm-1: 3,398(NH),
3,062(CH aromatic), 2,927, 2,858(CH aliphatic), 1,712(C=O),
1,654 (C=N); 1H NMR(DMSO-d6)d: 1.87–2.02(m, 6H, 3CH2),
2.49(s, 3H, CH3), 2.51(s, 3H, CH3), 2.72–2.73(m, 4H, 2CH2),
3.43–3.64(m, 4H, 2CH2), 7.56–7.68(2m, 4H, aromatic H); MS:
m/z (% abundance) 419(M?) (0.15); Anal. Calcd for C24H25
N3O2S: C, 68.71; H, 6.01; N, 10.02. Found: C, 68.75; H, 6.10;
N, 10.22.
11-{3-[2-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)ethylamino]
propyl} amino-1,2,3,4,7,8,9,10-octahydro[1] benzothieno
[2,3-b]quinoline (9a) Yield 68 %; mp 100–102 °C; IR
(KBr) cm-1: 3,381, 3,244(2NH), 3,088, 3,062(CH aro-
matic), 2,931, 2,858(CH aliphatic),1,734(2C=O), 1,618(C=N);
1H NMR(DMSO-d6, TFAA-H)d: 1.62–1.78(m, 10H,
5CH2), 2.46–2.51(m, 4H, 2CH2), 2.62–2.70(m, 4H, 2CH2),
2.88–2.98(m, 4H, 2CH2), 3.60(t, 2H, CH2, J = 6 Hz),
3.77(t, 2H, CH2, J = 6 Hz), 7.57–7.62(m, 4H, aromatic
H); MS: m/z (% abundance) 488(M?) (2.21); Anal. Calcd
for C28H32N4O2S: C, 68.82; H, 6.60; N, 11.47. Found: C,
68.80; H, 6.65; N, 11.20.
4-[4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)butyl]amino-
2,3-dimethyl-5,6,7,8-tetrahydrothieno[2,3-b]quinoline (7b)
Yield 83 %; mp [300 °C;); IR (KBr)cm-1: 3,433(NH),
3,093, 3,062(CH aromatic), 2,927, 2,858(CH aliphatic),
1
1,716(C=O),1.612(C=N); H NMR(DMSO-d6, TFAA-H)d:
1.22–1.23(m, 8H, 4CH2), 2.38 (s, 3H,CH3), 2.44(s, 3H, CH3),
3.13–3.39(m, 4H, 2CH2), 3.41–3.75(m,4H,2CH2), 7.44–7.63
(2m, 4H, aromaticH), 7.90(s, 1H, NH D2O exchangeable); MS:
m/z (% abundance) 433(M?) (1.07); Anal. Calcd for
C25H27N3O2S: C, 69.25; H, 6.28; N, 9.96. Found: C,69.18; H,
6.27; N, 9.68.
11-{4-[2-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl) ethyl amino]
butyl} amino-1,2,3,4,7,8,9,10-octahydro[1] benzothieno
[2,3-b]quinoline (9b) Yield 90 %; mp 210–212 °C; IR
(KBr) cm-1: 3,400, 3,398(2NH), 3,050(CH aromatic),
1
2,927, 2,854(CH,aliphatic), C=O), 1,662(C=N); H NMR
11-[3-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)propyl]amino-
1,2,3,4,7,8, 9,10-octahydro[1] benzothieno[2,3-b]quinoline
(DMSO-d6)d: 1.70–1.90(m, 12H, 6CH2), 2.79–2.90
(2m, 8H, 4CH2), 3.03–3.31(m, 4H, 2CH2), 3.85(t, 2H, CH2,
J = 6 Hz), 3.91(t, 1,716(22H, CH2, J = 6 Hz), 7.80–7.90
(m, 4H, aromatic H); MS: m/z (% abundance) 502(M?)
(0.14); Anal. Calcd for C29H34N4O2S: C, 69.29; H, 6.82; N,
11.15. Found: C, 69.33; H, 6.90; N,11.25.
(7c) Yield 85 %; mp 220–222 °C; IR (KBr)cm-1
:
3,433(NH), 3,066, 3,032(CH aromatic), 2,939, 2,862(CH
aliphatic), 1,705(C=O), 1,627(C=N); 1H NMR(DMSO-
d6)d: 1.16–1.31(m, 6H, 3CH2), 1.65–1.83(m, 4H, 2CH2),
1.96–2.03(m, 4H, 2CH2), 2.64–2.89(m, 4H, 2CH2),
3.60–3.64(m, 4H, 2CH2), 4.10(m, 1H, NH,D2O exchange-
able), 7.42–8.03(m, 4H, aromatic H); MS: m/z (% abun-
dance) 445(M?) (0.92); Anal. Calcd for C26H27N3O2S: C,
70.08; H, 6.11; N, 9.43. Found: C,70.03; H, 6.10; N, 9.52.
General procedure for synthesis of compounds 11a–c
A mixture of the appropriate aminothienopyridines 4b, d, e
(0.1 mol), lipoic acid (10) (0.15 mol), and 1-(3-dimethyl-
aminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI)
(0.12 mol) in dry DMF (15 ml) was stirred at room temper-
ature under nitrogen for 24 h. The mixture was poured into
ice/water. The separated solid was filtered and crystallized
from ethanol.
11-[4-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)butyl]amino-
2,3,4,7,8,9,10-octahydro[1]
benzothieno[2,3-b]quinoline
(7d) Yield 85 %; mp [300 °C; IR (KBr) cm-1:3,466
(NH), 3,095, 3,064(CH aromatic), 2,935, 2,868(CH ali-
phatic),1,720(2C=O), 1,647(C=N); 1H NMR(DMSO-d6,
TFAA-H)d: 1.16–1.20(m, 4H, 2CH2), 1.56–1.62(m, 8H,
4CH2), 1.83–1.84(m, 2H, CH2), 2.49–2.51(m, 8H, 4CH2),
3.52–3.60(m, 2H, CH2), 7.70–7.78(m, 4H, aromatic H); MS:
m/z (% abundance) 458(M-1) (8.10); Anal. Calcd for
C27H29N3O2S: C, 70.56; H, 6.36; N, 9.14. Found: C, 70.49; H,
6.35; N, 9.15.
4-{4-[(5-{1,2-Dithiolan-3-yl}-1-oxopentyl)amino]butyl}
amino-2,3-dimethyl-5,6,7,8-tetrahydrothieno[2,3-b]quin
oline(11a) Yield 25 %; mp 180–182 °C; IR (KBr)cm-1
3,446, 3,419(2NH), 2,924, 2,852 (CH aliphatic),1,647(C=O),
:
123

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Med Chem Res (2013) 22:4087–4095
1,608(C=N); 1H NMR(DMSO-d6)d: 1.30–1.37(m, 6H,
3CH2), 1.47–1.54(m, 8H, 4CH2), 1.80–1.86(m, 2H, CH2),
2.02–2.07(m, 4H, 2CH2), 2.38–2.40(m, 2H, CH2), 2.66(s, 3H,
CH3), 2.87(s, 3H, CH3), 3.01–3.14(m, 6H, 3CH2), 3.55–3.60(m,
1H, CH), 7.90(m, 1H, NH D2O exchangeable); MS: m/z (%
abundance) 491(M?) (3.70); Anal. Calcd for C25H37N3OS3: C,
61.06; H, 7.59; N, 8.54. Found: C, 16.13; H, 7.55; N, 8.50
tacrine as a reference compound. AChE was obtained from
homogenates of rat brain. Results of anti-acetylcholine
esterase activity of the tested compounds as well as tacrine
are shown in (Table 1). The screening results showed that all
the compounds exhibited significant inhibitory activity
(p \ 0.05) against AChE in comparison with tacrine. From
the biologic activity studies, we could conclude that com-
pounds 7b and 11b are the most active compounds; they
demonstrated inhibitory activity higher than tacrine (55.56
and 56.73 %, respectively), while compounds 5b and c, 7a
and c, 9a and b, and 11a showed moderate activity. In
addition, compounds 5a, 7d, and 11c showed the lowest
activity (Table 1).
11-{3-[(5-{1,2-Dithiolan-3-yl}-1-oxopentyl)amino]propyl}
amino-1,2,3,4,7,8,9,10- octahydro[1] benzothieno[2,3-
b]quinoline (11b) Yield 40 %; mp 155–157 °C; IR (KBr)
cm-1: 3,425, 3,350(2NH), 2,931, 2,866 (CH aliphatic),
1
1,685(C=O), 1,624(C=N); H NMR(DMSO-d6)d: 1.17–1.37
O
O
NH
NH
N
NH
1
R
S
S
O
2
N
S
R
N
S
7b
11b
(m, 8H, 4CH2), 1.52–1.83(m, 8H, 4CH2), 1.85–1.87(m, 2H,
CH2), 2.21–2.27(m, 2H, CH2), 2.66–2.89(2m, 8H, 4CH2),
3.13–3.31(m, 6H, 3CH2), 3.58–3.65(m, 1H, CH), 7.95(s, 1H,
NH D2O exchangeable; MS: m/z (% abundance) 503(M?)
(10.79); Anal. Calcd for C26H37N3OS3: C, 61.98; H, 7.40; N,
8.34. Found: C, 61.70; H, 7.45; N, 8.55.
Based on the just-mentioned results, it was speculated
that compounds 7b and 11b, which are linked to phthal-
imide and lipoic acid moieties, respectively, were the
most active among the tested compounds. Moreover,
other compounds that are bound to phthalimide moiety
(7a and c) and (9a and b) showed moderate inhibitory
activity. Only compound 7d revealed low inhibitory
activity. Once more, compound 11a, where the thieno-
pyridine is linked to lipoic acid, showed moderate activ-
ity, while compound 11c of the same series showed the
lowest activity. Regarding the bis-thienopyridins 5a–c,
compounds 5b and c showed moderate activity, while
compounds 5a had low activity. It is worth mentioning
that we could not observe adaptable correlation between
structures and biologic activities.
11-{4-[(5-{1,2-Dithiolan-3-yl}-1-oxopentyl)amino]butyl}
amino-1,2,3,4,7,8,9,10-octahydro[1] benzothieno [2,3-b]
quinoline (11c) Yield 67 %; mp 138–140 °C; IR (KBr)
cm-1: 3,400, 3,388(2NH), 2,926, 2,854 (CH aliphatic),
1,699(C=O), 1,610(C=N); 1H NMR(DMSO-d6, TFAA-H)d:
1.17–1.25(m, 4H, 2CH2), 1.27–1.33(m, 4H, 2CH2),1.46–
1.63(m, 6H, 3CH2), 1.78–1.84(m, 6H, 3CH2), 2.13–2.18
(m, 2H, CH2), 2.33–2.39(m, 2H, CH2), 2.69–2.84(m, 4H,
2CH2), 2.82–2.98(m, 2H, CH2), 3.02–3.14(m, 6H,3CH2),
3.41–3.54(m, 1H, CH); MS: m/z (% abundance) 517(M?)
(3.53); Anal. Calcd for C27H39N3OS3: C, 62.63; H, 7.59; N,
8.12. Found: C, 62.69; H, 7.60; N, 8.15.
Materials and methods
Adult male albino Wister rats weighing 180–200 g were
used in the present study. Rats were purchased from the
animal house of El-Nile Company (Cairo, Egypt). Rats
were kept under constant laboratory conditions and were
allowed free access to food and water throughout the per-
iod of investigation. The tested compounds were orally
administered once. 30 min later, rats were killed, decapi-
tated, and the brains were carefully removed and homog-
enized in normal saline (pH 7.4).
Results
Biologic evaluation
The preliminary anti-acetylcholine esterase activity for the
synthesized thienopyridines derivatives was assessed
according to Ellman’s method (Ellman et al., 1961) using
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Med Chem Res (2013) 22:4087–4095
AChE inhibition assay in vitro
4095
acetylcholinesterase and acetylcholinesterase-induced amyloid-b
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The final concentration containing test compound of the
assay solution consisted of 0.1 M sodium phosphate buffer
(pH 8.0), 0.3 mM 5,5-dithiobis-2-nitobenzoic acid (DTNB,
Ellman’s reagent), 0.02 U of AChE from electrophorus
lectricus, and 0.5 mM acetylthiocholine iodide as substrate
of the enzymatic reaction. The assay solutions except
substrate were pre-incubated with enzyme for 10 min at
37 °C. Following pre-incubation, the substrate was added.
The absorbance changes at 405 nm were recorded for
5 min, using a microplate reader GENios FI29004 (Tecan
Ltd, Austria). The AChE inhibition was determined for
each compound. Each assay was run in triplicate and each
reaction was repeated at least three independent times. The
study was carried out according to international guidelines
and approved by the ethical committee of animal experi-
mentation at the Faculty of pharmacy, Cairo University.
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Statistical analysis was carried out by one-way ANOVA
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Acknowledgments The authors are very grateful to the staff
members of the Department of Pharmacology, Faculty of Pharmacy,
Cairo University, for carrying out the pharmacological screening of
the newly synthesized compounds.
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