Molecular modeling study and synthesis of quinazolinone-arylpiperazine derivatives as α1-adrenoreceptor antagonists

Article abstract of DOI:10.1016/j.ejmech.2010.11.045

Three series of new 2-[(4-substituted piperazin-1-yl) methyl]quinazolin- 4(3H)-ones 4a-c, Ethyl 6,7-dimethoxy-4-oxo-3-[2-(4-substituted piperazin-1-yl)acetamido/propanamido]-3,4-dihydroquinazoline-2-carboxylates 9a-f and their 2-methyl analogues 13a-l were designed and synthesized as promising α₁-adrenoceptor antagonists. The final compounds were evaluated for their in vivo hypotensive activity in normotensive cats. The most potent hypotensive quinazolinone derivatives 4b, 9e, 13i, 13j were further tested on isolated thoracic aortic rings of male Wister rats. All the tested compounds displayed α₁-blocking activity with IC₅₀ ranging from 0.2 to 0.4 mM less than prazosin. Furthermore, in the present work, molecular modeling study using Accelrys Discovery Studio 2.1 software was performed by mapping the synthesized compounds to the α₁- adrenoceptor antagonist hypothesis in order to predict their mechanism of action. Compound 13j which has the best-fitting score displayed the highest in vivo and in vitro activity among the tested compounds.

Full text of DOI:10.1016/j.ejmech.2010.11.045

European Journal of Medicinal Chemistry 46 (2011) 647e658
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Molecular modeling study and synthesis of quinazolinone-arylpiperazine
derivatives as a1-adrenoreceptor antagonists
,
b,
**
Sahar Mahmoud Abou-Seri a, Khaled Abouzid b , Dalal A. Abou El Ella
*
a Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Cairo University, Kasr El Aini street, P.O. Box 11562, Cairo, Egypt
b Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Ain Shams University, Abbassia 11566, Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Three series of new 2-[(4-substituted piperazin-1-yl) methyl]quinazolin-4(3H)-ones 4aec, Ethyl 6,7-
dimethoxy-4-oxo-3-[2-(4-substituted piperazin-1-yl)acetamido/propanamido]-3,4-dihydroquinazoline-
2-carboxylates 9aef and their 2-methyl analogues 13ael were designed and synthesized as promising
a1-adrenoceptor antagonists. The final compounds were evaluated for their in vivo hypotensive activity
in normotensive cats. The most potent hypotensive quinazolinone derivatives 4b, 9e, 13i, 13j were
further tested on isolated thoracic aortic rings of male Wister rats. All the tested compounds displayed
a1-blocking activity with IC50 ranging from 0.2 to 0.4 mM less than prazosin. Furthermore, in the present
work, molecular modeling study using Accelrys Discovery Studio 2.1 software was performed by
mapping the synthesized compounds to the a1-adrenoceptor antagonist hypothesis in order to predict
their mechanism of action. Compound 13j which has the best-fitting score displayed the highest in vivo
and in vitro activity among the tested compounds.
Received 19 June 2010
Received in revised form
23 October 2010
Accepted 30 November 2010
Available online 8 December 2010
Keywords:
Quinazolinones
Arylpiperazine derivatives
a1-Adrenoceptor antagonists
Molecular modeling
Ó 2010 Elsevier Masson SAS. All rights reserved.
1. Introduction
considered as the most effective and clinically useful class of
selective a1-ARs antagonists since they have high index of a1
/a2
Hypertension is one of the most serious health problems in the
modern world. It is estimated that there are approximately 1 billion
people worldwide that suffer from high blood pressure [1]. Since
hypertension is a leading risk factor for cardiovascular disease, such
as congestive heart failure, stroke and myocardial infarction, it is
major goal in medicinal chemistry to search for new antihyper-
tensive agents.
adrenoreceptor affinity [6].
In addition, 3-{2-[4-(2-methoxyphenyl)piperazin-l-yl]ethyl}qui-
nazoline-2,4-diones IV and V were claimed to be potent a1-antago-
nists [9,10]. Furthermore, a series of quinazolinedione bioisosteres
e.g. thieno[2,3-d]pyrimidine-2,4-dionelinkedto4-arylpiperazinevia
alkyl spacer VI was reported for their antihypertensive activity [11].
On the other hand, certain anthranilamides linked to 4-arylpiper-
azine via propionyl spacer VII were reported to exhibit a1-AR
antagonist activity [12]. Based on the previous findings, we have
recently reported the synthesis of some anthranilates and quinazo-
linones linked to 4-substituted piperazines via different spacers,
which were characterized for their hypotensive activity. Where,
compounds VIII and IX exhibited higher activity than prazosin [13]
(Fig. 2).
The a1-adrenergic receptors (a1-ARs) e a family of G-protein
coupled seven-transmembrane helix receptors
e are mainly
involved in the cardiovascular and central nervous system [2]. In the
last twodecades, the search for new selective a1-ARs antagonists has
been intensified, mainly due to their importance in treatment of
hypertension, asthma, lower urinary tract symptoms (LUTS) and
benign prostatic hypertrophy (BPH) [3e6].
Research efforts in the area of a1-ARs antagonists have led to the
discovery of some clinically useful antihypertensive drugs such as
prazosin I and related quinazoline derivatives terazosin II and
doxazosin III (Fig. 1) [7,8]. These quinazoline derivatives are
In the present work, IV, VIII and IX were chosen as lead
compounds for further optimization, aiming to enhance their
activity. A logical approach was adopted by replacing the ester
function in VIII with the more enzymatically stable amide function
(Fig. 3). But, instead of obtaining the expected amide analogues 3,
the quinazolinone derivatives 4aec were isolated as result of
intramolecular cyclization of the produced anthranilamides
(Scheme 1). The unexpected quinazolinone derivatives 4aec have
structural similarities to the lead compound IX.
* Corresponding author. Tel.: þ2012 216 5624; fax: þ202 25080728.
** Corresponding author. Tel.: þ2014 444 2542.
E-mail addresses: abouzid@yahoo.com, khaled.abouzid@pharm.asu.edu.eg
(K. Abouzid), dalal999@hotmail.com (D.A. Abou El Ella).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.11.045

648
S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
O
O
O
O
O
O
O
N
N
N
H3CO
H3CO
N
N
H3CO
H3CO
N
N
H3CO
H3CO
N
N
N
N
N
NH2
NH2
Doxazosin III
NH2
Terazosin II
Prazosin I
Fig. 1. Structures of clinically useful quinazolines of selective a1-AR antagonist activity.
H
N
H
R1
R2
O
N
O
R
T
N
N
N
OCH3
(CH2)n
N
N
O
N
O
=
S
IV
(SGB 1534, ): R1 = R2 = H
or
VI
or
T
S
V: R1 = R2 = OCH3
S
O
O
NH2
O
N
R3
N
N
H
N
H
N
N
N
N
R4
N
O
N
OC2H5
O
N
H3CO
VII
VIII
H3CO
IX
Fig. 2. Structures of some potent selective a1-AR antagonists and lead compounds.
It has been previously reported that arylpiperazine moiety linked
polymethene spacer between the arylpiperazine moiety and the pyr-
idazinone from 2 up to 7 carbons. Therefore, the second approach
basedonthepreviousexperimentalfindingswas to subject compound
IV to the following structural modification strategies (Fig. 3):
to different heterocyclic systems through polymethylene spacer is
a key element for a1-AR affinity [2]. Moreover, Betti et al. reported [14]
the gradual increase in affinity to a1-AR by increasing the length of the
O
O
N
N
N
R2
R1
N
OCH3
N
H
N
HO
OC2H5
N
H
O
H3CO
VIII
IV
(SGB 1534, ): R1 = R2 = H
O
N
O
H
N
N
R2
R1
O
N
R
N
R
N
( )
N
n
N
H
NH2
COOC2H5
9a-f
O
3
O
O
N
O
H
N
R2
R1
N
R
NH
N
N
N
( )
N
R
n
N
4a-c
13a-l
Fig. 3. Strategies for structural modifications of leads IV and VIII.

S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
649
The reaction of 2-(2-chloroacetamido)benzamide 2 with various
substituted arylpiperazines in acetonitrile in the presence of anhy-
drous K2CO3 and catalytic amount of potassium iodide produced 2-
[(4-substituted piperazin-1-yl)methyl]quinazolin-4(3H)-ones 4aec
instead of the expected compounds N-[(4-substituted piperazin-1-
yl)acetyl] anthranilamides 3 (Scheme 1). The NMR spectra of 4aec
showed an exchangeable protons of 3-NH of quinazolinone at
10.10e12.00 ppm. Moreover, the mass spectrum of 4a showed
a molecular ion peak at 320.2 instead of 338.4 for the corresponding
anthranilamide derivative 3a. The Compounds 4a [17,18] and 4b [17]
were previously reported as phosphodiesterase V (PDE5) inhibitors.
These compounds were synthesized adopting another pathway, by
the reaction of 2-(chloromethyl)-quinazolin-4(3H)-one with
substituted piperazines in DMFin the presence of triethylamine [17].
The targeted quinazolinone-2-carboxylates 9aef were synthe-
sized as shown in Scheme 2. 2-Amino-4,5-dimethoxybenzohy-
drazide 6 was obtained by the hydrazinolysis of the corresponding
methyl anthranilate 5 with hydrazine hydrate [19]. Adopting the
method of George et al. [20], the cyclized quinazolinone-2-
carboxylate derivative 7 was obtained through heating the hydra-
zide 6 with excess diethyl oxalate at 180 ꢀC. The N-acylation of 7
O
O
NH2
NH2
NH2
i
NH
Cl
2
1
O
ii
O
O
N
NH2
Ar
NH
N
O
Ar
N
N
N
H
N
4a-c
3
Ar= a=C6H5, b= 2-CH3O-C6H4, c=4-NO2-C6H4
Scheme 1. Synthesis of compounds 4aec. Reagents and condition: (i) CH3COCl, dry
toluene, Et3N, reflux. (ii) arylpiperazine, K2CO3, KI, CH3CN, reflux.
with a- or b-chloropropionyl chloride yielded the haloalkanamide
quinazolinone derivatives 8a and 8b, respectively, which alkylated
various arylpiperazines producing the final compounds 9aef.
1. Extension strategy by replacing the ethylene linker with acet-
amido or propionamido linker.
2. Substituents variation strategy through replacement of oxo
group at position 2 on quinazolinedione ring in compound IV
with an ethyl ester in analogy to VIII or methyl group aiming to
increase the lipophilicity of the molecule.
Scheme
3 outlines the synthetic pathway for 2-methyl-
quinazolinone analogues 13ael. Anthranilic acids 10a,b were
reacted with acetic anhydride and hydrazine hydrate as reported
[21e23]. Acylation of 3-amino group on quinazolinones 11a,b with
a- or b-chloropropionyl chloride afforded the corresponding halo-
Therefore, two different series of quinazolinone derivatives
9aef and 13ael were synthesized (Schemes 2 and 3).
Moreover, the relationship between chemical features of the
synthesized compounds and their a1-binding affinity data have
been derived on the basis of a previously reported, five features
pharmacophore model for a1-AR antagonists which consist of
alkanamide derivatives 12aed [22]. Finally, compounds 13ael.
were obtained through the alkylation of certain substituted piper-
azines with the corresponding haloalkanamide derivatives 12aed.
3. Results and discussion
positive ionizable, three hydrophobic and
acceptor pharmacophore features [15].
a hydrogen bond
3.1. Molecular modeling
Pharmacophore modeling method has been widely used as
a key tool of computer aided drug design in the lead discovery and
optimization [24,25]. Pharmacophore can also be used to ratio-
nalize the relationship between the structural features and phar-
macological activity [2,26]. In this study, the generated a1-AR
antagonist hypothesis was carried out adopting reported method
2. Chemistry
2-(2-Chloroacetamido)benzamide
N-acylation of anthranilamide
according to the reported methods [16].
2
was prepared through
1
with chloroacetyl chloride
Cl
O
N
Cl
H3CO
H3CO
COOCH3
H3CO
H3CO
CONHNH2
n
H3CO
H3CO
NH2
N
O
i
ii
iii
NH2
NH2
COOC2H5
6
5
7
O
N
O
N
N
N Ar
H3CO
H3CO
NH
Cl
H3CO
NH
n
HN
N Ar
n
N
O
O
N
COOC2H5
H3CO
COOC2H5
iv
8a, n=1
9 a-f
8b,
n=2
9
a
n
Ar
C6H5
1
2-CH3O-C6H4
4-NO2-C6H4
C6H5
b
c
1
1
2
d
2
2
2-CH3O-C6H4
4-NO2-C6H4
e
f
Scheme 2. Synthesis of compounds 9aef. Reagents and condition: (i) hydrazine hydrate, reflux. (ii) diethyl oxalate, reflux. (iii) dry toluene, Et3N, reflux. (iv) K2CO3, KI, CH3CN, reflux.

650
S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
O
O
N
O
H
( )
R1
R2
NH2
CH3
N
Cl
n
R1
R2
Cl
R1
R2
COOH
NH2
N
i
N
(
)
Cl
n
O
ii
N
iii
CH3
11a,b
12a-d
10a,b
10a:
11a:
R1 =R2=H
R1 =R2=H
10b: R1 =R2 = OCH3
12
R1 R2
n
11b: R1 =R2 = OCH3
H
H
H
H
1
2
a
b
c
d
O
H
OCH3 OCH3
OCH3 OCH3
1
(
)
N
n
N
2
HN
N
Ar
R1
N
N
O
Ar
iv
N
CH3
R2
13a-l
1 3
a
R1
R2
n
Ar
H
H
H
H
C6H5
1
1
1
2
2
1
1
1
2
b
c
H
2-CH3O-C6H4
H
4-NO2-C6H4
C6H5
4-NO2-C6H4
C6H5
2-CH3O-C6H4
2-furoyl
C6H5
2-CH3O-C6H4
H
H
d
e
H
H
OCH3
f
g
OCH3
OCH3
OCH3
h
i
OCH3 OCH3
OCH3
OCH3
j
OCH3 OCH3
2
2
2
k
l
OCH3
OCH3
OCH3
OCH3
4-NO2-C6H4
2-furoyl
Scheme 3. Synthesis of compounds 13ael. Reagents and condition: (i) acetic anhydride, (ii) hydrazine hydrate, reflux. (iii) dry toluene, Et3N, reflux. (iv) K2CO3, KI, CH3CN.
[15] by using Accelrys Discovery Studio 2.1 software and HipHop
modules. The ideal hypothesis encompassed five features namely;
positive ionizable (PI, red sphere), hydrogen bonding acceptor
(HBA, green sphere) and three hydrophobic features (HY1, HY2 and
HY3, blue sphere). Molecular modeling simulation studies were
then conducted by measuring the fit values, separately, between
the conformational models of prazosin (reference), 4aec, 9aef and
13ael, and the a1-AR antagonist hypothesis. The results of the best-
fitting value, as well as the relative energy of the best-fitted
conformer with this hypothesis are given in Table 1. The fitting
values may be a guide for estimating relative affinities of these
compounds to their receptor while the relative energy is a guide of
stability of the compounds. Also, the mapping of a1-AR antagonist
hypothesis with prazosin I and the most active compound 13j
illustrated that all chemical functionalities of the model are all
matched by the chemical groups of both (Figs. 4 and 5).
Fig. 5 shows the mapping of compound 13j, where the arylpi-
perazinyl moiety mapped the region where a cluster of feature
known to be crucial for interaction with the receptor. While the o-
methoxyphenyl occupied both HY1 and HY2, the piperazinyl N-1
atom was located inside the positive ionizable feature PI. The
carbonyl oxygen of quinazolinone system overlapped HBA, while
its phenyl ring mapped to YH3.
Evaluation of how well the prepared compounds were able to fit
the a1-AR pharmacophore hypothesis and the correlation of the
fitting values with the hypotensive activity highlighted that:
Table 1
Fitting and relative energy values of the best-fitted conformers of compounds 4aec,
9aef and 13ael. by mapping onto the pharmacophore model of the a1-AR antago-
nist hypothesis.
1. Compounds 4b and 13j which showed high fit values with low
relative energies exhibited the most potent hypotensive activity.
2. The substitution pattern on the arylpiperazinyl moiety is
a crucial element that accounts for the relationship between
structure properties and a1-binding affinity. The o-methoxy
substituent on the phenyl ring of the arylpiperazinyl moiety
was highly favorable to a1-AR affinity, as the o-methoxyphenyl
perfectly matched the HY1eHY2 system in the model. On the
other hand, the unsubstituted phenyl was unable to map one of
the HY1eHY2 features with consequent decrease in activity
[c.f. 13i and 13j]. On the contrary, the nitrogen in p-nitrophenyl
and the carbonyl of furoyl mapped the HBA. This arrangement
derived by reversing the orientation of the ligand might not be
favored by ligandereceptor interaction. This accounts for the
fact that, derivatives characterized by different substitution on
the piperazine ring like 13k and 13l were less active than the
corresponding o-methoxyphenyl analogue 13j.
Compound
Fitting values
Relative energy (kcal molꢁ1
)
Prazosin
4a
4b
4c
9a
9b
9c
9d
9e
3.91
2.93
3.60
No mapping
3.32
4.86
3.28
3.51
4.90
3.36
3.77
4.75
2.63
3.99
2.38
3.56
4.80
4.44
3.99
4.60
3.24
4.80
4.01
12.79
4.57
e
13.54
16.32
15.57
14.37
4.71
13.82
13.95
14.40
35.97
9.78
31.01
12.86
18.69
17.31
8.21
9f
13a
13b
13c
13d
13e
13f
13g
13h
13i
13j
13k
13l
3. The length of the amido spacer between the arylpiperazine and
the quinazolinone moiety is a key parameter affecting the
fitting efficiency of each compound to the pharmacophore.
Elongating the alkylamido chain from acetamido to prop-
anamido led to several compounds characterized by higher
4.48
13.28
9.69

S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
651
Fig. 4. Mapping of a1-AR antagonist hypothesis and prazosin. The two o-methoxy groups of quinazoline moiety occupied both HY1 and HY2 (blue sphere) and the quinazoline N-1
atom is located inside the positive ionizable feature PI (red sphere). The oxygen of the carbonyl group attached to piperazine overlapped HBA (green sphere), while the furan ring
matched YH3 (blue sphere). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
conformational flexibility, which might be responsible for
enhanced fit to the a1-AR pharmacophore model and conse-
quently more potent hypotensive activity.
4. The presence of the metabolically stable 2-methyl on the
6,7-dimethoxy-quinazolinone greatly improved the pharma-
cological activity. In fact, while changing the 2-ethyl carbox-
ylate in 9e with 2-methyl in 13j had no observable effect on the
fitting values to the pharmacophore model; it greatly improved
the hypotensive activity, probably due to better pharmacoki-
netic characters.
pressure of normotensive cats at dose of 500 mg/kg [27]. The tested
compounds were chosen in a pattern to allow verifying the effect of
three structural variations on the hypotensive activity of the
designed compounds: (1) the length of the amide spacer, (2) the
effect of substitution on the piperazine moiety, (3) the effect of
substitution at the 2-position of the quinazolinone ring. Further-
more, the molecular modeling simulation study predicted that,
these compounds would have probable affinity for the a1-AR
antagonist hypothesis.
The results of hypotensive evaluation indicated that most of the
tested compounds have the ability to reduce the blood pressure
with different degrees (Table 2).
Compound 13j showed 1.5 times more potent hypotensive
activity than prazosin, while compound 4b was comparable to
prazosin in hypotensive activity. Moreover, compounds 9e, 13i and
13l elicited moderate activity. Compound 13b had no hypotensive
effect.
3.2. Pharmacology
3.2.1. In vivo hypotensive activity
Nine selected compounds 4b, 9b, 9e, 13b, 13g, 13i, 13j, 13k and
13l were evaluated for their in vivo hypotensive activity on blood
Fig. 5. Mapping of a1-AR antagonist hypothesis and the most active compound 13j. o-Methoxyphenyl attached to piperazine moiety occupied both HY1 and HY2 (blue sphere) and
the piperazinyl N-1 atom is located inside the positive ionizable feature PI (red sphere). The carbonyl oxygen of quinazolinone system overlapped HBA (green sphere), while its
phenyl ring matched YH3 (blue sphere). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

652
S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
Table 2
3.2.2. Structure activity relationship SAR
Effects of test compounds 4b, 9b,e, 13b, g, iel on systolic (SBP) and diastolic blood
pressure (DBP) of anaesthetized normotensive cats at dose 500 g/kg.
The data in Table 2 indicates that compound 9b produced low
hypotensive effect compared to prazosin. Replacement of the
acetamido spacer in 9b by propanamido linker in 9e, led to 3 and 6
folds increase in the potency of reducing diastolic and systolic
blood pressure. Changing the 2-ethyl carboxylate on quinazolinone
ring in 9e with the more metabolically stable 2-methyl in 13j
produced the most potent hypotensive analogue. As expected,
replacing the propanamido in 13j by acetamido in 13g resulted in
sever drop in potency. Replacing the propanamido in 13j with
acetamido function in addition to removal 6,7-dimethoxy groups of
the quinazolinone ring 13b abolished the activity.
m
Compound
SBP (mmHg)
mean ꢂ SD
Mean
change %
DBP (mmHg)
mean ꢂ SD
Mean
change %
Control
Prazosin
4b
9b
9e
13b
13g
13i
13j
13k
13l
120.00 ꢂ 2.45
82.20 ꢂ 1.72a
91.58 ꢂ 1.50a
117.33 ꢂ 2.73
105.17 ꢂ 3.55a
120.00 ꢂ 2.83
116.25 ꢂ 3.68
101.33 ꢂ 1.37a
69.33 ꢂ 1.97a
114.00 ꢂ 2.10a
108.75 ꢂ 1.54a
_
110.00 ꢂ 2.37
78.10 ꢂ 2.58a
86.17 ꢂ 1.72a
105.58 ꢂ 2.25a
94.75 ꢂ 2.23a
110.00 ꢂ 4.86
107.00 ꢂ 3.79
94.67 ꢂ 2.07a
66.00 ꢂ 1.41a
102.50 ꢂ 3.21a
97.78 ꢂ 2.45a
_
29.00
23.68
2.22
12.36
0.00
3.13
15.56
42.22
5.00
9.38
29.00
21.66
4.02
13.86
0.00
2.78
13.94
40.00
6.82
11.11
With respect to substitution on the piperazine moiety,
substituting o-methoxyphenyl in 13j with phenyl 13i, p-nitro-
phenyl 13k or furoyl moiety 13l decreased the activity.
a
Significant different from control using one way analysis of variance (ANOVA) at
P < 0.05.
3.2.3. In vitro vasodilatation activity (functional bioassay)
Based on the hypotensive activity, the most potent compounds
4b, 9e, 13i and 13j were subjected to functional bioassay to eval-
uate their a1-adrenoreceptors antagonistic activity, according the
standard procedure [28,29]. The antagonistic activity was
assessed by inhibition of (ꢂ) norepinephrine-induced contraction
on isolated rat aorta tissues which predominantly express the
a1D-AR subtype [6,30]. Stimulation of a1D-AR subtype is known to
cause blood vessels contraction and control blood pressure. From
the observed data (Table 3, Fig. 6) it can has been noticed that all
the tested compounds had lower IC50 and higher potency relative
to prazosin. Furthermore, the results of the antagonistic potency
were in agreement with the in vivo hypotensive activity, where
the most potent hypotensive agent 13j revealed the lowest IC50
(0.201 mM). On the other hand, the less active quinazolinone-2-
carboxylate analogue 9e showed the highest IC50 (0.400 mM). In
summary, the consistency between the in vivo hypotensive results
and the functional bioassay data proved that the obtained hypo-
Table 3
Concentration of compounds 4b, 9e, 13i, 13j necessary to reduce the maximal
norepinephrine hydrochloride induced contracture by 50% (IC50) in thoracic rat
aortic rings.
Compound
Structure
Potency
(IC50), mM
NH
2
H CO
3
N
H CO
3
N
N
Prazosin
HCl
0.487
N
N
O
O
HCl
O
N
tensive effect is mediated through the blockage of a1
-
adrenoreceptors.
NH
4b
0.303
OCH
N
3
4. Conclusion
H CO
Some compounds belonging to a class of arylpiperazine-quina-
zolinone-2-carboxylate and their 2-methyl analogues have been
prepared through the variation of alkylamido linker between qui-
nazolinone and the arylpiperazine in addition to modification of
the substitution on the phenylpiperazine moiety. Fitting of the
proposed compounds to previously built pharmacophore model
[15] was done to prioritize the synthesized compounds and to
correlate the chemical structure of the studied compounds to their
pharmacological data. Compounds 4b, 9b, 9e, 13b, 13g, 13i, 13j, 13k
and 13l were evaluated for their in vivo hypotensive activity on
blood pressure of normotensive cats. Moreover, the most potent
hypotensive compounds 4b, 9e, 13i and 13j were tested for their
a1-adrenoceptors antagonistic activity on isolated thoracic rat
aorta. The four compounds revealed superior activity to prazosin as
reference standard.
3
N
N
O
9e
0.400
H CO
3
NH
N
O
2
H CO
3
N
COOC H
5
O
N
H
H CO
3
N
N
13i
0.303
N
O
3
H CO
N
3
CH
Some structural features have been demonstrated to markedly
affect the affinity of a1-AR antagonists and hypotensive activity. In
particular, the addition of o-methoxyphenyl on piperazine ring,
propanamido spacer and methyl at 2-position of quinazolinone led
to the best a1-affinity profile (high fitting value ¼ 4.60) and the
highest hypotensive activity (40.00 and 42.22% reduction of dia-
stolic and systolic blood pressure) as shown by compound 13j. In
addition, the results of the functional bioassay demonstrated that
13j was the most active a1-adrenoceptors antagonist among the
tested arylpiperazine-quinazolinone derivatives (IC50 ¼ 0.201 mM).
O
N
H
H CO
3
N
N
OCH
3
13j
0.201
N
O
3
H CO
3
N
CH

S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
653
Compound 9e
Compound 4b
100
90
100
90
80
70
80
70
60
50
40
60
50
40
30
20
10
0
30
20
10
0
-10
-20
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
0. 9
1
-10
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
0. 9
1
-20
-30
-40
-50
-30
-40
Concerntration (mM)
Concerntration (mM)
Compound 13i
Compound 13j
100
100
90
90
80
80
70
70
60
60
50
40
50
40
30
20
10
30
20
10
0
0
-10
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
0. 9
1
-10
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
0. 9
1
-20
-30
-20
-30
-40
-40
-50
Concerntration (mM)
Concerntration (mM)
Prazosin hydrochloride
100
90
80
70
60
50
40
30
20
10
0
-10
0
0. 1
0. 2
0. 3
0. 4
0. 5
0. 6
0. 7
0. 8
0. 9
1
-20
-30
Concerntration (mM)
Fig. 6. Effect of the tested compounds on contracture induced by norepinepherine hydrochloride (NE$HCl) on thoracic rat aortic rings.
5. Experimental
dried by standard techniques. Elemental microanalysis was per-
formed at Microanalytical Center, Vienna and Cairo Universities.
2-Amino-4,5-dimethoxybenzohydrazide 6 was prepared by modi-
fication of the reported procedure [18]. The preparation
compounds 2 [16], 11a,b [21e23] and 12a,b [22] was performed
according to reported procedures.
5.1. Chemistry
Melting points were determined with a Kofler apparatus and are
uncorrected. FT-IR spectra were recorded on a PerkineElmer
spectrophotometer and measured by y0 cmꢁ1 scale using KBr cell.
1H NMR spectra were measured in
d
scale on Brucker 200, 300 and
500 MHz spectrometers and Jeol As 500 MHz spectrometer. 13C
NMR spectra were measured in scale on Brucker 200 and
5.1.1. 2-[(4-Substituted piperazin-1-yl) methyl]quinazolin-4(3H)-
ones (4aec)
d
General procedure: A mixture of 2 (4.0 mmol), the appropriate
arylpiperazine (4.0 mmol), anhydrous potassium carbonate
(6.0 mmol), and potassium iodide (0.2 mmol) in dry acetonitrile
(10 mL) was refluxed for 6 h. The solvent was evaporated and the
residue was triturated with water. The obtained solid product 4aec
was filtered, washed with ether and recrystallized from the appro-
priate solvent.
500 MHz spectrometers Jeol As 500 MHz spectrometer. The elec-
tron impact (EI) mass spectra were recorded on Finnigan Mat SSQ
7000 (70 ev) mass spectrometer. Analytical thin layer chromatog-
raphy (TLC) on silica gel plates containing UV indicator was
employed routinely to follow the course of reactions and to check
the purity of products. All reagents and solvents were purified and

654
S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
5.1.1.1. 2-[(4-Phenylpiperazin-1-yl)methyl]quinazolin-4(3H)-one (4a).
Recrystallization from methanol (yield 84%), m.p. 147e149 ꢀC. IR
(KBr, cmꢁ1): 3111 (NH), 2930, 2884 and 2837 (CH2), 1692 (C]O),
5.1.4. Ethyl 3-(2-chloroacetamido/3-chloropropanamido)-6,
7-dimethoxy-4-oxo-3,4-dihydroquinazoline-2-carboxylate (8a, 8b)
General procedure: Chloroacetyl chloride or chlorpropionyl chlo-
ride (36 mmol) was added gradually to a stirred solution of 7
(30mmol)indrytoluene(20mL). Thereactionmixturewasallowedto
reflux for 2 h. The solvent was evaporated and the residue was tritu-
rated with petroleum ether. The obtained solid product was filtered,
washedwithpetroleumetherandrecrystallizedfromsuitablesolvent.
1616 (C]C). 1H NMR, 300 MHz (CDCl3):
d
2.85 (t, 4H, J ¼ 4.80 Hz,
2CH2 of piperazine), 3.28 (s, 2H, CH2), 3.38 (t, 4H, J ¼ 4.80 Hz, 2CH2
of piperazine), 6.89 (t, 1H, J ¼ 7.20 Hz, H-40 of C6H5), 6.96 (m, 2H,
H-20 and H-60 of C6H5), 7.15 (t, 2H, J ¼ 7.30 Hz, H-30 and H-50 of
C6H5), 7.20 (t, 1H, J ¼ 8.10 Hz, H-7), 7.63 (m, 2H, H-6 and H-8), 8.54
(d, 1H, J ¼ 8.40 Hz. H-5), 10.17 (s, br, 1H, NH, D2O exchangeable). MS
(m/z, %): 320.2 (Mþ, 34.17), 175.2 (100.0).
5.1.4.1. Ethyl 3-(2-chloroacetamido)-6,7-dimethoxy-4-oxo-3,4-dihy-
droquinazoline-2-carboxylate (8a). Recrystallized from methanol
(yield 86%); m.p. 222e224 ꢀC. IR (KBr, cmꢁ1): 3514 (NH), 2974 and
2939 (CH2, CH3), 1747 (C]O ester),1678 (C]O), 1607 (C]C). 1H
5.1.1.2. 2-{[4-(2-Methoxyphenyl)piperazin-1-yl]methyl}quinazolin-4
(3H)-one (4b). Recrystallization from acetone (yield 84%), m.p.
203e205 ꢀC. IR (KBr, cmꢁ1): 3163 (NH), 2936, 2881 and 2825 (CH2),
NMR, 500 MHz (DMSO-d6):
d
1.27 (t, 3H, J ¼ 6.90 Hz, COOCH2CH3),
1666 (C]O), 1607 (C]C). 1H NMR, 300 MHz (CDCl3):
d
2.81 (t, 4H,
3.89 and 3.91 (s,s, 2ꢃ 3H, 2CH3O), 4.32e4.35 (m, 4H, COOCH2CH3
and COCH2Cl), 7.27 (s, 1H, H-8), 7.47 (s, 1H, H-5), 11.66 (s, 1H, CONH,
D2O exchangeable). 13C NMR, 500 MHz (DMSO-d6): 14.29
(COOCH2CH3), 40.22 (COCH2Cl), 56.52 (OCH3), 56.83 (OCH3), 63.28
(COOCH2CH3), 106.24 (C-5), 109.44 (C-8), 115.49 (C-4a), 142.09 (C-
8a), 146.63 (C-6), 150.51 (C-7), 155.84 (C-2), 157.61 (COOCH2CH3),
160.15 (C-4), 166.76 (CONH). MS (m/z, %): 369.2 (Mþ, 75.0) (M þ 2,
25.26), 296.1 (100.0). Anal. Calc. for C15H16ClN3O6$0.5H2O: C, 47.65;
H, 4.49; N, 11.10, Found: C, 47.52; H, 4.69; N, 10.86.
J ¼ 4.80 Hz, 2CH2 of piperazine), 3.17 (br, 4H, 2CH2 of piperazine),
3.67 (s, 2H, CH2), 3.88 (s, 3H, OCH3), 6.88e7.04 (m, 4H, H30-60 of
C6H4), 7.48 (t,1H, J ¼ 7.80 Hz, H-6), 7.69 (d,1H, J ¼ 7.80 Hz, H-8), 7.74
(t, 1H, J ¼ 7.80 Hz, H-7), 8.29 (d, 1H, J ¼ 7.80 Hz, H-5), 10.10 (s, br, 1H,
NH, D2O exchangeable).
5.1.1.3. 2-{[4-(4-Nitrophenyl)piperazin-1-yl]methyl}quinazolin-4(3H)-
one (4c). Recrystallization from DMF (yield 92%), m.p. 251e253 ꢀC.
IR (KBr, cmꢁ1): 3174 (NH), 2939 and 2854 (CH2), 1658 (C]O), 1612
(C]C). 1H NMR, 300 MHz (DMSO-d6):
d
2.64 (t, 4H, J ¼ 4.6 Hz, 2CH2
5.1.4.2. Ethyl
3-(3-chloropropanamido)-6,7-dimethoxy-4-oxo-3,4-
of piperazine), 3.45e3.52 (m, 6H, 2CH2 of piperazine and CH2), 6.70
(d, 2H, J ¼ 9.60 Hz, H-20 and H-60 of 40-NO2eC6H5), 7.48 (t, 1H,
J ¼ 8.40 Hz, H-7), 7.63 (d,1H, J ¼ 8.40 Hz, H-8), 7.77 (t,1H, J ¼ 8.40 Hz,
H-6), 8.03 (d, 2H, J ¼ 9.60 Hz, H-30 and H-50 of 40-NO2eC6H5), 8.10 (d,
dihydroquinazoline-2-carboxylate (8b). Recrystallized from acetone
(yield92%); m.p. 216e8 ꢀC. IR (KBr, cmꢁ1): 3297 (NH), 3001 and 2944
(CH2, CH3), 1735 (C]O ester), 1697 (C]O), 1607 (C]C). 1H NMR,
500 MHz (CDCl3):
d
1.39 (t, 3H, J ¼ 6.90 Hz, COOCH2CH3), 2.92 (t, 2H,
1H, J ¼ 8.40 Hz, H-5), 12.00 (s, br, 1H, NH, D2O exchangeable). 13
C
J ¼ 6.10 Hz, COCH2CH2Cl), 3.85 (t, 2H, J ¼ 6.10 Hz, COCH2CH2Cl), 3.99
(s, 6H, 2CH3O), 4.44 (q, 2H, J ¼ 6.90 Hz, COOCH2CH3), 7.15 (s,1H, H-8),
7.52 (s, 1H, H-5), 8.82 (s, br, 1H, CONH, D2O exchangeable). 13C NMR,
500 MHz (CDCl3): 14.03 (COOCH2CH3), 37.36 (COCH2CH2Cl), 38.89
(COCH2CH2Cl), 56.47 (OCH3), 63.46 (COOCH2CH3), 106.13 (C-5),
109.04 (C-8), 115.65 (C-4a), 142.05 (C-8a), 145.56 (C-6), 150.51 (C-7),
155.64 (C-2), 158.50 (COOCH2CH3), 160.02(C-4), 169.25 (CONH).
Anal. Calc. for C16H18ClN3O6: C, 50.07; H, 4.73; N, 10.95, Found: C,
50.12; H, 4.52; N, 10.93.
NMR, 500 MHz (DMSO-d6):
d 46.48 (2CH2 of piperazine), 54.05
(2CH2 of piperazine), 60.84 (CH2), 113.17 (C-20 and C-60), 121.91 (C-
4a),122.94 (C-30 and C-50), 126.23,127.01 and 129.05 (C-5, C-6 and C-
8), 134.87 (C-7), 137.45 (C-40), 154.48 and 155.21 (C-8a and C-10),
162.13 (C-4), 169.5 (C-2), Anal. Calc. for C19H19N5O: C, 62.46; H, 5.24;
N, 19.17. Found: C, 62.00; H, 5.34; N, 19.34.
5.1.2. 2-Amino-4,5-dimethoxybenzohydrazide (6)
A mixture of 5 (2.5 mmol) and hydrazine hydrate (10 mL) was
heated under reflux for 6 h, and then concentrated under reduced
pressure. After cooling the separated solid was filtered, washed
with water and dried; yield (68%). The product was recrystallized
from methanol (yield 68%), m.p. 182e184 ꢀC (reported 178e179 ꢀC)
[19]. IR (KBr, cmꢁ1): 3412, 3303 and 3256 (NH and NHeNH2), 3014
(CH aromatic), 2948 and 2840 (CH2)s, 1630 (C]O), 1592 (C]C).
5.1.5. Ethyl 6,7-dimethoxy-4-oxo-3-[2-(4-subistituted piperazin-1-
yl)acetamido]-3,4-dihydroquinazoline-2-carboxylates (9aec)
General procedure: A mixture 8a (4.0 mmol), the appropriate
arylpiperazine (4.0 mmol), anhydrous potassium carbonate
(6.0 mmol), and potassium iodide (0.2 mmol) in dry acetonitrile
(10 mL) was refluxed for 4 h. The solvent was evaporated under
vacuum. The residue was dissolved in water and neutralized with
acetic acid. The solution was extracted with chloroform. The
chloroformic layer was dried over anhydrous sodium sulfate, and
then evaporated to dryness. The obtained solid product was
recrystallized from the appropriate solvent.
5.1.3. Ethyl3-amino-6,7-dimethoxy-4-oxo-3,4-dihydroquinazoline-2-
carboxylate (7)
A mixture of the 2-amino-4,5-dimethoxybenzohydrazide 6
(2.5 mmol) in diethyl oxalate (8 ml) was stirred at 180 ꢀC in an oil
bath for 6 h. The excess diethyl oxalate was removed under
vacuum. The resulting semi solidified mass was treated with
ethanol to afford a white precipitate. The precipitate was filtered,
washed with aqueous ethanol and dried; yield (40%), then
recrystallized from acetone, m.p. 191e193 ꢀC. IR (KBr, cmꢁ1): 3325
and 3248 (NH2), 2977 and 2941 (CH, CH3), 1750 (C]O ester), 1667
5.1.5.1. Ethyl 6,7-dimethoxy-4-oxo-3-[2-(4-phenylpiperazin-1-yl)acet-
amido]-3,4-dihydroquinazoline-2-carboxylate
(9a). Recrystallized
from acetone (yield 80%); m.p. 253e255 ꢀC. IR (KBr, cmꢁ1): 3387
(NH), 2830 (CH2, CH3), 1658, 1650 and 1641 (3C]O), 1598(C]C). 1H
NMR, 500 MHz (DMSO-d6):
d
1.24 (t, 3H, J ¼ 6.10 Hz, COOCH2CH3),
(C]O). 1H NMR, 500 MHz (CDCl3):
d
1.42 (t, 3H, J ¼ 5.35 Hz,
2.56 (br, 4H, 2CH2 of piperazine), 2.83 (s, 2H, COCH2), 3.11 (br, 4H,
2CH2 of piperazine), 3.85 (s, 6H, 2CH3O), 4.23 (q, 4H, J ¼ 6.10 Hz,
COOCH2CH3), 6.75 (t, 1H, J ¼ 6.85, H-40 of C6H5), 6.92 (t, 2H, J ¼ 6.85,
H-20 and H-60 of C6H5), 7.07 (s, 1H, H-8), 7.18 (t, 2H, J ¼ 6.85, H-30 and
H-50 of C6H5), 7.39 (s, 1H, H-5). 13C NMR, 500 MHz (DMSO-d6): 14.45
(COOCH2CH3), 48.59 (2CH2 of piperazine), 53.36 (2CH2 of pipera-
zine), 56.18 (OCH3), 56.37 (OCH3), 61.50 (COCH2N), 63.12
(COOCH2CH3), 105.54 (C-5), 107.96 (C-8), 109.50 (C-4a), 115.71 (C-20
and C-60), 118.99 (C-40), 129.39 (C-30 and C-50), 143.07 (C-8a), 148.01
COOCH2CH3), 3.94 and 3.97 (s,s, 2ꢃ 3H, 2OCH3), 4.48 (q, 2H,
J ¼ 5.35 Hz, COOCH2CH3), 5.22 (s, br, 1H, NH2, D2O exchangeable),
7.09 (s, 1H, H-8), 7.48 (s, 1H, H-5). 13C NMR, 500 MHz (CDCl3):
14.07 (COOCH2CH3), 56.38 (OCH3), 56.42 (OCH3), 63.05
(COOCH2CH3), 105.39 (C-5), 108.47 (C-8), 114.98 (C-4a), 142.49 (C-
8a), 145.66 (C-6), 150.19 (C-7), 155.17 (C-2), 159.70 (COOCH2CH3),
161.14 (C-4). Anal. Calc. for C13H15N3O5: C, 53.24; H, 5.16; N, 14.33,
Found: C, 52.81; H, 4.87; N, 14.43.

S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
655
(C-6), 149.29 (C-10), 153.00 (C-7), 156.5 (C-2), 158.50 (COOCH2CH3),
166.50 (C-4), 171.45 (CONH). MS (m/z, %): 495.4 (Mþ, 7.75), 175.2
(100.0). Anal. Calc. for C25H29N5O6$2H2O: C, 56.49; H, 6.26; N, 13.18,
Found: C, 56.79; H, 5.67; N, 13.37.
5.1.6.2. Ethyl 6,7-dimethoxy-3-{3-[4-(2-methoxyphenyl)piperazin-1-
yl]-propanamido}-4-oxo-3,4-dihydroquinazoline-2-carboxylate (9e).
Recrystallized from methanol/ethyl acetate (yield 64%); m.p.
212e214 ꢀC. IR (KBr, cmꢁ1): 3424 (NH), 2944 and 2833 (CH2, CH3),
1620 broad (3C]O). 1H NMR, 500 MHz (DMSO-d6):
d 1.54 (t, 3H,
5.1.5.2. Ethyl 6,7-dimethoxy-3-{2-[4-(2-methoxyphenyl)piperazin-1-
yl]-acetamido}-4-oxo-3,4-dihydroquinazoline-2-carboxylate (9b). Rec-
rystallized from acetone/ethyl acetate (yield 65%); m.p.180e182 ꢀC. IR
(KBr, cmꢁ1): 3517 (NH), 2936 and 2823 (CH2, CH3), 1731 (C]O ester),
J ¼ 6.90 Hz, COOCH2CH3), 2.32 (m, 2H, COCH2CH2N), 2.51e2.58 (m,
6H, 2CH2 of piperazine and COCH2CH2N), 2.92 (br, 4H, 2CH2 of
piperazine), 3.74 (s, 3H, CH3O of C6H4), 3.83 and 3.87 (s,s, 2ꢃ 3H,
2CH3O of quinazoline), 3.90 (overlapped, 2H, COOCH2CH3),
6.83e6.89 (m, 4H, H30-60 of C6H4), 6.96 (s, 1H, H-8), 7.32 (s, 1H, H-5).
1664 (2C]O),1611 (C]C).1HNMR, 300MHz(DMSO-d6):
d1.14 (br, 3H,
COOCH2CH3), 2.49 (br, 4H, 2CH2 of piperazine), 3.54 (overlapped, 2CH2
of piperazine), 3.79 (s, 3H, CH3O of C6H4), 3.82 and 3.92 (s,s, 2ꢃ 3H,
2CH3O of quinazoline), 4.21 (br, 2H, COCH2), 4.69 (br, 2H, COOCH2CH3),
6.89e7.07 (m, 4H, H30-60 of C6H4), 7.26 (s, 1H, H-8), 7.52 (s, 1H, H-5).
Anal. Calc. for C26H31N5O7: C, 59.42; H, 5.95; N, 13.18, Found: C, 59.60;
H, 5.63; N, 13.28.
13C NMR, 500 MHz (DMSO-d6):
d 13.00 (COOCH2CH3), 32.13
(COCH2CH2N), 50.55 (2CH2 of piperazine), 53.22 (2CH2 of pipera-
zine), 54.26 (COCH2CH2N), 55.88 (OCH3), 56.14 (OCH3), 56.41
(OCH3), 67.35 (COOCH2CH3),105.86 (C-5),108.32 (C-8),112.53 (C-30),
114.58 (C-4a), 118.45 (C-50), 121.39 (C-40), 122.83 (C-60), 141.86 (C-
8a), 144.29 (C-20), 148.30 (C-6), 152.53 (C-7), 154.87 (C-2), 156.50
(COOCH2CH3), 158.73 (C-4), 164.00 (C-10), 171.63 (CONH). Anal. Calc.
for C27H33N5O7: C, 60.10; H, 6.16; N, 12.98, Found: C, 59.93; H, 6.20;
N, 12.78.
5.1.5.3. Ethyl 6,7-dimethoxy-3-{2-[4-(4-nitrophenyl)piperazin-1-yl]
acetamido}-4-oxo-3,4-dihydroquinazoline-2-carboxylate (9c). Recry
stallized from benzene (yield 56%); m.p. 168e170 ꢀC. IR (KBr, cmꢁ1):
3535 (NH), 2925 and 2832 (CH2, CH3), 1738 (C]O ester), 1690 and
5.1.6.3. Ethyl
6,7-dimethoxy-3-{3-[4-(4-nitrophenyl)piperazin-1-yl]-
1679 (2C]O), 1594 (C]C). 1H NMR, 500 MHz (CDCl3):
d
1.39 (t, 3H,
propanamido}-4-oxo-3,4-dihydroquinazoline-2-carboxylate (9f). Recr-
ystallized from acetone/ethyl acetate (yield 69%); m.p. 230e232 ꢀC. IR
(KBr, cmꢁ1):3446(NH), 2937and2834(CH2,CH3),1688broad(3C]O),
J¼6.90Hz,COOCH2CH3), 2.86(br, 4H,2CH2 ofpiperazine), 3.31(s, 2H,
COCH2), 3.46 (br, 4H, 2CH2 of piperazine), 3.94 and 3.69 (s,s, 2ꢃ 3H,
2CH3O), 4.42 (q, 2H, J ¼ 6.90 Hz, COOCH2CH3), 6.79 (d, 2H, J ¼ 9.20 Hz,
H-20 and H-60 of 4-NO2eC6H5), 7.20 (s,1H, H-8), 7.54 (s,1H, H-5), 8.08
(d, 2H, J ¼ 9.20 Hz, H-30 and H-50 of 4-NO2eC6H5), 9.55 (s,1H, NHCO).
1598 (C]C). 1H NMR, 500 MHz (DMSO-d6):
d
1.19 (t, 3H, J ¼ 7.20 Hz,
COOCH2CH3), 2.62e2.79 (m, 6H, 2CH2 of piperazine and COCH2CH2N),
3.64 (br, 6H, 2CH2 of piperazine and COCH2CH2N), 3.87 and 3.9 (s,s, 2ꢃ
3H, 2CH3O), 4.32 (m, 2H, COOCH2CH3), 6.94(d, 2H, J¼ 8.40Hz, H-20 and
H-60 of 4-NO2eC6H5), 7.01 (s, 1H, H-8), 7.44 (s, 1H, H-5), 8.02 (d, 2H,
J ¼ 8.40 Hz, H-30 and H-50 of 4-NO2eC6H5), 11.38 (s, 1H, NHCO). 13C
13C NMR, 500 MHz (CDCl3):
d 14.09 (COOCH2CH3), 47.24 (2CH2 of
piperazine), 53.10 (2CH2 of piperazine), 56.49 (OCH3), 56.54 (OCH3),
60.77 (COCH2N), 63.26 (COOCH2CH3), 106.08 (C-5), 109.21 (C-8),
113.04 (C-20 andC-60),116.00 (C-4a),125.94 (C-30 andC-50),138.95 (C-
40), 141.18 (C-8a), 145.50 (C-6), 150.67 (C-7), 154.75 (C-10), 155.69 (C-
2), 158.50 (COOCH2CH3), 160.05 (C-4), 169.36 (CONH). Anal. Calc. for
C25H28N6O8$1.5H2O: C, 52.91; H, 5.51; N, 14.81, Found: C, 53.12; H,
5.36; N, 15.16.
NMR, 500 MHz (DMSO-d6): d 14.38 (COOCH2CH3), 31.11 (COCH2CH2N),
46.28 (2CH2 of piperazine), 52.16 (2CH2 of piperazine), 53.50
(COCH2CH2N), 56.50 (OCH3), 56.80 (OCH3), 63.13 (COOCH2CH3),106.19
(C-5), 109.33 (C-8), 113.34 (C-20 and C-60), 115.56 (C-4a), 126.17 (C-30
and C-50), 137.72 (C-40), 142.20 (C-8a), 150.39 (C-6), 154.61, 155.05 and
155.74 (C-7, C-10 and C-2), 157.87 (COOCH2CH3), 160.38 (C-4), 171.45
(CONH). Anal. Calc. for C26H30N6O8: C, 56.31; H, 5.45; N,15.15, Found: C,
56.23; H, 5.46; N, 15.40.
5.1.6. Ethyl 6,7-dimethoxy-4-oxo-3-[3-(4-substituted piperazin-1-yl)
propanamido]-3,4-dihydroquinazoline-2-carboxylate (9def)
General procedure: A mixture of 8b (4.0 mmol), the appropriate
arylpiperazine (4.0 mmol), anhydrous potassium carbonate
(6.0 mmol), and potassium iodide (0.2 mmol) in dry acetonitrile
(10 mL) was refluxed for 6 h. The solvent was evaporated and the
residue was triturated with water. The obtained solid product was
filtered, washed with ether and recrystallized from the appropriate
solvent.
5.1.7. 2-Chloro-N-(6,7-dimethoxy-2-methyl-4-oxoquinazolin-3
(4H)-yl)acetamide (12c) and 3-chloro-N-(6,7-dimethoxy-2-methyl-
4-oxoquinazolin-3(4H)-yl)-propanamide (12d)
General procedure: Chloroacetyl chloride or chloropropionyl chlo-
ride (36 mmol) was added gradually to a stirred solution of 3-amino-
6,7-dimethoxy-2-methylquinazolin-4(3H)-one 11b (30 mmol) in dry
toluene (20 mL). The reaction mixture was allowed to reflux for 4 h.
After cooling, the formed precipitate was filtered to produce 12c and
12d.
5.1.6.1. Ethyl 6,7-dimethoxy-4-oxo-3-[3-(4-phenylpiperazin-1-yl)prop-
anamido]-3,4-dihydroquinazoline-2-carboxylate (9d). Recrystallized
from acetone (yield 76%); m.p.175e177 ꢀC. IR (KBr, cmꢁ1): 3442 (NH),
2946 and 2831 (CH2, CH3), 1645 and 1616 broad (3C]O),1616 (C]C).
5.1.7.1. Compound 12c. Yield ¼ 96%; m.p. ¼ 122e125 ꢀC. IR (KBr,
cmꢁ1): 3251 (NH), 2951 and 2889 (CH2), 1696 and 1669 (2C]O). 1H
1H NMR, 500 MHz (DMSO-d6):
d
1.03 (t, 3H, J ¼ 7.65 Hz, COOCH2CH3),
2.57 (br, 2H, COCH2CH2N), 2.72 (t, 4H, 2CH2, J ¼ 4.80 of piperazine),
3.13 (br, 2H, COCH2CH2N), 3.34 (overlapped, 2CH2 of piperazine), 3.85
and 3.89 (s,s, 2ꢃ 3H, 2CH3O), 4.33 (br, 2H, COOCH2CH3), 6.74 (t, 1H,
J ¼ 7.65 Hz, H-40 of C6H5), 6.91 (d, 2H, J ¼ 6.90 Hz, H-20 and H-60 of
C6H5), 7.18 (t, 2H, J ¼ 7.65, H-30 and H-50 of C6H5), 7.45 (s, 1H, H-8),
8.06 (s, 1H, H-5), 11.25 (s, br, 1H, NHCO, D2O exchangeable). 13C NMR,
NMR, 200 MHz (CDCl3):
3H, 2CH3O), 3.31 (d, 2H, J ¼ 3.2 Hz, COCH2Cl), 7.06 (s, 1H, H-8), 7.47
(s, 1H, H-5), 9.17 (s, 1H, NHCO). 13C NMR, 200 MHz (CDCl3):
21.43
d
2.52 (s, 3H, CH3), 3.97 and 3.99 (s,s, 2ꢃ
d
(CH3), 41.52 (COCH2N), 56.65 (OCH3), 56.73 (OCH3), 106.08, 108.06,
143.63, 149.39, 153.85, 155.94, 159.45, 166.89.
500 MHz (DMSO-d6):
d
14.09 (COOCH2CH3), 32.50 (COCH2CH2N),
5.1.7.2. Compound 12d. Yield ¼ 96%; m.p. ¼ 133e135 ꢀC. IR (KBr,
cmꢁ1): 3251 (NH), 2951 and 2889 (CH2), 1696 and 1669 (2C]O). 1H
48.67 (2CH2 of piperazine), 52.88 (2CH2 of piperazine), 53.74
(COCH2CH2N), 56.39 (OCH3), 56.62 (OCH3), 63.26 (COOCH2CH3),
105.98 (C-5),108.90 (C-8),115.58 (C-4a),115.90 (C-20 and C-60), 119.33
(C-40), 129.43 (C-30 and C-50), 144.00 (C-8a), 147.84 (C-6), 149.52 (C-
10), 151.53 (C-7), 155.37, 158.35 (C-2, C-4 and COOCH2CH3), 172.10
(CONH). Anal. Calc. for C26H31N5O6$1.5H2O: C, 58.20; H, 6.39; N,13.05,
Found: C, 57.79; H, 5.69; N, 13.05.
NMR, 200 MHz (DMSO-d6):
d 2.42 (s, 3H, CH3), 2.92 (t, 2H,
J ¼ 6.8 Hz, COCH2CH2Cl), 3.87 and 3.91 (s,s, 2ꢃ 3H, 2CH3O), 4.65 (br,
2H, COCH2CH2Cl), 7.18 (s, 1H, H-8), 7.40 (s, 1H, H-5), 11.46 (s, 1H,
NHCO).13C NMR, 200 MHz (DMSO-d6):
d 20.76 (CH3), 36.75
(COCH2CH2Cl), 41.09 (COCH2CH2Cl), 56.22 (OCH3), 56.49 (OCH3),
105.95, 107.01, 141.74, 149.05, 155.43, 155.78, 158.99, 169.48

656
S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
5.1.8. N-(2-Methyl-4-oxoquinazolin-3(4H)-yl)-2-(4-substituted
piperazin-1-yl) acetamide (13aec), N-(2-methyl-4-oxoquinazolin-3
(4H)-yl)-3-(4-substituted piperazin-1-yl)propanamide (13d,e),
N-(6,7-dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-2-(4-
substituted piperazin-1-yl)acetamide (13feh) and N-(6,7-
dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-3-(4-substituted
piperazin-1-yl)propanamide (13iel)
General procedure: A mixture of 12a/b/c/d (4.0 mmol), the
appropriate arylpiperazine (4.0 mmol), anhydrous potassium
carbonate (6.0 mmol), and potassium iodide (0.2 mmol) in dry
acetonitrile (10 mL) was refluxed for 6 h. The solvent was evapo-
rated and the residue was triturated with water. The obtained solid
product 13ael was filtered, washed with ether and recrystallized
from the appropriate solvent.
5.1.8.4. N-(2-Methyl-4-oxoquinazolin-3(4H)-yl)-3-(4-phenylpiperazin-
1-yl)-propanamide (13d). Recrystallized from ethanol/water (yield
73%); m.p. 79e81 ꢀC. IR (KBr, cmꢁ1): 3480 (NH), 2933 and 2829
(CH2), 1705 and 1674 (2C]O), 1603 (C]C). 1H NMR, 500 MHz
(CDCl3): d 2.53 (s, 3H, CH3), 2.68 (m, 2H, COCH2CH2N), 2.94 (m, 4H,
2CH2 of piperazine), 3.02 (m, 2H, COCH2CH2N), 3.25 (br, 4H, 2CH2 of
piperazine), 6.85 (t, 1H, J ¼ 7.50, H-40 of C6H5), 6.91 (d, 2H, J ¼ 7.50,
H-20 and H-60 of C6H5), 7.24 (t, 2H, J ¼ 7.50, H-30 and H-50 of C6H5),
7.42 (t, 1H, J ¼ 8.5 Hz, H-6), 7.64 (d, 1H, J ¼ 8.5 Hz, H-8), 7.72 (t, 1H,
J ¼ 8.5 Hz, H-7), 8.18 (d, 1H, J ¼ 8.5 Hz, H-5), 9.98 (s, 1H, NH). 13C
NMR, 500 MHz (CDCl3):
d 21.41 (CH3), 31.20 (COCH2CH2N), 49.18
(2CH2 of piperazine), 52.19 (2CH2 of piperazine), 52.76
(COCH2CH2N), 116.12 (C-20 and C-60), 120.03 (C-40), 120.72 (C-4a),
126.39 (C-5), 126.71 (C-6), 126.96 (C-8), 129.02 (C-30 and C-50),
134.59 (C-7), 146.94 (C-8a), 150.77 (C-10), 155.42 (C-2), 159.62 (C-4),
173.21 (CONH). MS (m/z, %): 391.4 (Mþ, 7.16), 54.95 (100.0). Anal.
Calc. for C22H25N5O2$0.25H2O: C, 66.73; H, 6.49; N, 17.69, Found: C,
66.55; H, 6.51; N, 17.55.
5.1.8.1. N-(2-Methyl-4-oxoquinazolin-3(4H)-yl)-2-(4-phenylpiperazin-
1-yl)-acetamide (13a). Recrystallized from ethanol (yield 38%); m.p.
89e91 ꢀC. IR (KBr, cmꢁ1): 3541 (NH), 2933 and 2819 (CH2), 1700 and
1669 (2C]O), 1603 (C]C). 1H NMR, 200 MHz (CDCl3):
d 2.56 (s, 3H,
CH3), 2.81 (br, 2H, CH2 of piperazine), 3.11 (t, 2H, CH2 of piperazine),
3.32 (t, 4H, CH2 of piperazine, J ¼ 5.3 Hz, 2), 3.38 (s, 2H, COCH2),
6.86e6.98 (m, 3H, H-20, H-40 and H-60 of C6H5), 7.29 (m, 2H, H-30 and
H-50 of C6H5), 7.47 (t, 1H, J ¼ 7.60 Hz, H-6), 7.69 (d, 1H, J ¼ 7.60 Hz, H-
8), 7.78 (t,1H, J ¼ 7.60 Hz, H-7), 8.22 (d,1H, J ¼ 7.60 Hz, H-5). 13C NMR,
5.1.8.5. N-(2-Methyl-4-oxoquinazolin-3(4H)-yl)-3-[4-(4-nitrophenyl)
piperazin-1-yl]propanamide (13e). Recrystallized from methanol
(yield 30%); m.p. 183e186 ꢀC. IR (KBr, cmꢁ1): 3277 (NH), 2925 and
2828 (CH2), 1697 and 1661 (2C]O), 1594 (C]C). 1H NMR, 200 MHz
(CDCl3):
d 2.53 (s, 3H, CH3), 2.70 (m, 2H, COCH2CH2N), 2.86 (m, 4H,
200 MHz (CDCl3):
d
21.43 (CH3), 49.28 (2CH2 of piperazine), 53.74
2CH2 of piperazine), 2.91 (m, 2H, COCH2CH2N), 3.48 (br, 4H, 2CH2 of
piperazine), 6.81 (d, 2H, J ¼ 9.45 Hz, H-20 and H-60 of 40-NO2eC6H5),
7.43 (t, 1H, J ¼ 7.62 Hz, H-7), 7.61 (d, 1H, J ¼ 7.62 Hz, H-8), 7.73 (t, 1H,
J ¼ 7.62 Hz, H-6), 8.08 (d, 2H, J ¼ 9.45 Hz, H-30 and H-50 of 40-
NO2eC6H5), 8.17 (d, 1H, J ¼ 7.62 Hz, H-5). 13C NMR, 200 MHz (CDCl3):
(2CH2 of piperazine), 60.94 (COCH2N), 116.19, 120.06, 126.73, 126.83,
127.18,129.51,134.92,140.80,146.94,150.91,158.70,170.94. Anal. Calc.
for C21H23N5O2: C, 66.83; H, 6.14; N,18.55, Found: C, 66.64; H, 6.07; N,
18.30.
d
21.79 (CH3), 31.66 (COCH2CH2N), 47.36 (2CH2 of piperazine), 52.15
5.1.8.2. N-(2-Methyl-4-oxoquinazolin-3(4H)-yl)-2-(4-(2-methoxyphe-
nyl)-piperazin-1-yl)-acetamide (13b). Recrystallized from ethanol
(yield 53%); m.p. 183e185 ꢀC. IR (KBr, cmꢁ1): 3145 (NH), 2951 and
2828 (CH2), 1713 and 1696 (2C]O), 1603 (C]C). 1H NMR,
(2CH2 of piperazine), 53.12 (COCH2CH2N), 113.82, 121.04, 126.16,
126.86, 127.06, 127.48, 135.08, 139.13, 147.39, 154.94, 155.65, 160.13,
173.51. Anal. Calc. forC22H24N6O4: C, 60.54; H, 5.54; N,19.25, Found: C,
60.09; H, 5.48; N, 19.00.
500 MHz (CDCl3):
d 2.54 (s, 3H, CH3), 2.82 (br, 2H, CH2 of piper-
azine), 3.18 (br, 6H, 3CH2 of piperazine), 3.34 and 3.45 (d,d, 2H,
5.1.8.6. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-2-(4-
phenylpiperazin-1-yl)acetamide (13f). Recrystallized from ethanol/
water (yield 29%); m.p. 90e92 ꢀC. IR (KBr, cmꢁ1): 3506 (NH), 2916
and 2819 (CH2), 1705 and 1678 (2C]O), 1599 (C]C). 1H NMR,
J ¼ 13.39 Hz, COCH2), 3.87 (s, 3H, CH3O), 6.86 (d, 1H, J ¼ 8.19 Hz, H-
30 of C6H4), 6.92 (t, 1H, J5 ,6 ¼ 8.19 Hz, H-50 of C6H4), 6.98 (dd, 1H,
0
0
J6 ,5 ¼ 8.19 Hz, J6 ,4 ¼ 1.5 Hz, H-60 of C6H4), 6.98 (td, 1H,
0
0
0
0
J4 ,5 ¼ J4 ,3 ¼ 8.19 Hz, J4 ,6 ¼ 1.5 Hz, H-40 of C6H4), 7.45 (t, 1H,
J6,5 ¼ J6,7 ¼ 8.69 Hz, H-6), 7.65 (d, 1H, J8,7 ¼ 8.69 Hz, H-8), 7.78 (td,
1H, J7,6 ¼ J7,8 ¼ 8.69 Hz, J7,5 ¼ 1.5 Hz, H-7), 8.20 (dd, 1H,
J5,6 ¼ 8.69 Hz, J5,7 ¼ 1.50 Hz, H-5). 13C NMR, 500 MHz (CDCl3):
500 MHz (DMSO-d6):
d 2.37 (s, 3H, CH3), 2.73 (m, 2H, CH2 of
0
0
0
0
0
0
piperazine moiety), 2.89 (m, 2H, CH2 of piperazine), 3.15 (d, 1H,
J ¼ 15.95 Hz, COCH2), 3.23 (br, 4H, 2CH2 of piperazine), 3.45 (d,
1H, J ¼ 15.95 Hz, COCH2), 3.86 and 3.90 (s,s, 2ꢃ 3H, 2OCH3), 6.77 (t,
1H, J ¼ 7.41 Hz, H-40 of C6H5), 6.96 (d, 2H, J ¼ 7.41 Hz, H-20 and H-60 of
C6H5), 7.12 (s,1H, H-8), 7.22 (t, 2H, J ¼ 7.41 Hz, H-30 and H-50 of C6H5),
7.41 (s,1H, H-5),10.73 (br,1H, NHCO). 13C NMR, 500 MHz (DMSO-d6):
d
21.46 (CH3), 50.64 (2CH2 of piperazine), 54.00 (2CH2 of pipera-
zine), 55.34 (OCH3), 60.99 (COCH2N), 111.19 (C-30), 118.18 (C-60),
120.69 (C-4a), 120.94 (C-50), 123.15 (C-40), 126.67, 126.82 and
127.16 (C-5, C-6, C-8), 134.55 (C-7), 140.80 (C-10), 146.95 (C-8a),
152.19 (C-20), 155.27 (C-2), 159.86 (C-4), 171.08 (CONH). MS (m/z,
%): 335.15 (Mþ, 4.9), 145.0 (100.0). Anal. Calc. for C22H25N5O3: C,
64.85; H, 6.18; N, 17.19, Found: C, 64.76; H, 6.14; N, 16.97.
d
20.98 (CH3), 47.97 (2CH2 of piperazine), 52.79 (2CH2 of piperazine),
55.75 and 56.03 (2OCH3), 60.07 (COCH2N), 105 (C-5), 107.78 (C-8),
113.49 (C-4a), 115.35 (C-20 and C-60), 118.79 (C-40), 128.95 (C-30 and
C-50), 142.82 (C-8a), 148.40 (C-6), 150.97 (C-10), 154.47 (C-2), 154.87
(C-7), 158.24 (C-4), 169.22 (NHCOCH2). MS (m/z, %): 437.5 (Mþ,
20.29), 42.05 (100.0). Anal. Calc. for C23H27N5O4$0.5H2O: C, 61.87; H,
6.30; N, 15.69, Found: C, 61.97; H, 6.69; N, 15.77.
5.1.8.3. N-(2-Methyl-4-oxoquinazolin-3(4H)-yl)-2-[4-(4-nitrophenyl)
piperazin-1-yl]acetamide (13c). Recrystallized from methanol (yield
85%); m.p. 208e211 ꢀC. IR (KBr, cmꢁ1): 3295 (NH), 2950 and 2828
(CH2), 1710 and 1687 (2C]O), 1599 (C]C). 1H NMR, 200 MHz
5.1.8.7. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-3-[4-
(DMSO-d6):
d
2.42 (s, 3H, CH3), 2.81 (br, 4H, 2CH2 of piperazine), 327
(2-methoxyphenyl)piperazin-1-yl]acetamide
(13g). Recrystallized
(br, 4H, 2CH2 of piperazine), 3.45 (s, 2H, COCH2), 7.07 (d, 2H,
J ¼ 8.6 Hz, H-20 and H-60 of 40-NO2eC6H5), 7.55 (t, 1H, J ¼ 7.51 Hz, H-
7), 7.66 (d, 1H, J ¼ 7.51 Hz, H-8), 7.86 (t, 1H, J ¼ 7.51 Hz, H-6), 8.06 (m,
from methanol/water (yield 67%); m.p. 104e106 ꢀC. IR (KBr, cmꢁ1):
3506 (NH), 2933 and 2819 (CH2), 1705 and 1678 (2C]O), 1608 (C]
C). 1H NMR, 200 MHz (DMSO-d6):
d 2.36 (s, 3H, CH3), 2.71 (br, 2H,
3H, H-5, H-30 and H-50). 13C NMR, 200 MHz (DMSO-d6):
d
22.24
CH2 of piperazine), 2.83 (br, 2H, CH2 of piperazine), 3.21(m, 4H,
2CH2 of piperazine), 3.44 (s, 2H, COCH2), 3.78 (s, 3H, 20-CH3O of
C6H4), 3.86 and 3.90 (s,s, 2ꢃ 3H, 2CH3O of quinazoline), 6.90e6.93
(m, 4H, H-30-60 of C6H4), 7.13 (s, 1H, H-8), 7.41 (s, 1H, H-5). 13C NMR,
(CH3), 47.31 (2CH2 of piperazine), 53.39 (2CH2 of piperazine), 60.79
(COCH2N), 113.42, 113.77, 121.66, 127.49, 127.90, 128.00, 136.13,
137.97, 147.67, 155.80, 157.30, 159.95, 170.32. Anal. Calc. for
C21H22N6O4: C, 59.71; H, 5.25; N, 19.89, Found: C, 59.33; H, 5.21; N,
19.73.
200 MHz (DMSO-d6):
d 22.22 (CH3), 51.07 (2CH2 of piperazine),
54.38 (2CH2 of piperazine), 56.55, 57.00 and 57.27 (3OCH3), 61.42

S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
657
(COCH2N), 106.99, 109.03, 113.16, 114.76, 119.12, 122.10, 123.63,
142.43, 144.07, 149.64, 153.22, 155.75, 156.11, 159.48, 170.54. Anal.
Calc. for C24H29N5O5$H2O: C, 59.37; H, 6.44; N, 14.42, Found: C,
58.89; H, 6.34; N, 13.97.
170.64. Anal. Calc. for C24H29N5O5$1.5H2O: C, 55.06; H, 5.97; N,16.05,
Found: C, 55.10; H, 5.84; N, 15.93.
5.1.8.12. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-3-[4-
(furan-2-carbonyl)piperazin-1-yl]propanamide (13l). Recrystallized
from ethanol/acetonitrile (yield 62%); m.p. 94e96 ꢀC. IR (KBr, cmꢁ1):
3462 (NH), 2933 and 2819 (CH2), 1678 (br, 2C]O), 1608 (C]C). 1H
5.1.8.8. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-2-[4-
(furan-2-carbonyl)piperazin-1-yl]acetamide
(13h). Recrystallized
from ethanol (yield 33%); m.p. 120e122 ꢀC. IR (KBr, cmꢁ1): 3506
NMR, 200 MHz (CDCl3): d 2.51 (s, 3H, CH3), 2.65e2.94 (m, 10H,
(NH), 2925 and 2845 (CH2), 1705 and 1683 (2C]O), 1612 (C]C). 1H
COCH2CH2N and 4H, 2CH2 of piperazine), 3.75 (t,br, 2H, COCH2CH2N),
3.95 and 3.97 (s,s, 2ꢃ 3H, 2OCH3), 6.47 (m,1H, H-40 of furoyl), 7.00 (d,
1H, J ¼ 3.28 Hz, H-50 of furoyl), 7.05 (s, 1H, H-8), 7.46 (m, 1H, H-30 of
NMR, 200 MHz (CDCl3):
d 2.71 (s, 3H, CH3), 2.73 (br, 4H, CH2 of
piperazine), 3.13 (m, 4H, 2CH2 of piperazine), 3.48 and 3.61 (br, 2ꢃ
1H, COCH2), 4.15 and 4.18 (s,s, 2ꢃ 3H, 2OCH3), 6.67 (m, 1H, H-40 of
furoyl), 7.23 (m, 2H, H-30 and H-50 of furoyl), 7.44 (s,1H, H-8), 8.67 (s,
furoyl), 7.48 (s, 1H, H-5). 13C NMR, 200 MHz (CDCl3):
d 21.89 (CH3),
31.81 (COCH2CH2N), 52.97 (4CH2 of piperazine), 53.36 (COCH2CH2N),
56.75 and 56.86 (2OCH3),106.15,108.18,109.65,111.90,114.39,117.29,
144.03, 144.33, 148.20, 149.32, 154.58, 155.78, 159.57, 173.77. Anal.
Calc. for C23H27N5O6: C, 58.84; H, 5.80; N, 14.92, Found: C, 58.43; H,
6.20; N, 14.74.
1H, H-5). 13C NMR, 200 MHz (CDCl3):
d 21.46 (CH3), 53.88 (4CH2 of
piperazine), 56.45 and 56.49 (2OCH3), 61.06 (COCH2N), 102.17,
105.75, 107.90, 111.54, 113.86, 116.99, 143.58, 143.95, 147.86, 149.11,
154.00, 155.59, 159.24, 170.89. Anal. Calc. for C22H25N5O6: C, 58.01;
H, 5.53; N, 15.38, Found: C, 58.04; H, 5.55; N, 15.59.
5.2. Computational study
5.1.8.9. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-3-(4-
phenylpiperazin-1-yl)propanamide (13i). Recrystallized from ethanol
(yield 63%); m.p. 143e145 ꢀC. IR (KBr, cmꢁ1): 3506 (NH), 2916 and
2819 (CH2), 1705 and 1678 (2C]O), 1599 (C]C). 1H NMR, 200 MHz
In this work, we utilized pharmacophore model for a set of
potent a1-AR antagonists developed in a previous publication to
prioritize the designed compounds by mapping them to the
generated pharmacophore model [15].
(DMSO-d6):
d 2.37 (s, 3H, CH3), 2.50e288 (m, 8H, COCH2CH2N and
2CH2 of piperazine), 3.12 (br, 4H, 2CH2 of piperazine), 3.86 and 3.90
(s,s, 2ꢃ 3H, 2OCH3), 6.76 (t, 1H, J ¼ 7.41 Hz, H-40 of C6H5), 6.93 (d, 2H,
J ¼ 7.41 Hz, H-20 and H-60 of C6H5), 7.12 (s, 1H, H-8), 7.20 (t, 2H,
J ¼ 7.41 Hz, H-30 and H-50 of C6H5), 7.39 (s, 1H, H-5), 11.01 (br, 1H,
The pharmacophore hypothesis was produced using Accelrys
Discovery Studio 2.1 (Accelrys Inc., San Diego, CA, USA). HipHop
algorithm, which identifies common chemical features from a set of
ligands without the use of affinity data, was used to develop the
pharmacophore model. The set of conformational models of each
structure of the lead compounds was performed and was used to
generate the common feature hypotheses. The ideal hypothesis
encompassed five features; positive ionizable nitrogen, three
hydrophobic pockets and a hydrogen bond acceptor group.
The calculation of fitting and relative energy values of the best-
fitted conformers of the target compounds preceded as follows:
NHCO). 13C NMR, 200 MHz (DMSO-d6):
d 22.33 (CH3), 32.66
(COCH2CH2N), 49.40 (2CH2 of piperazine), 53.69 (2CH2 of pipera-
zine), 54.84 (COCH2CH2N), 57.01 and 57.27 (2OCH3), 106.63, 109.05,
114.76, 116.57, 120.03, 130.16, 144.11, 149.61, 152.23, 155.81, 156.10,
159.61, 172.30. MS (m/z, %): 451.1 (Mþ, 0.60), 55.00 (100.0). Anal. Calc.
for C24H29N5O4$H2O: C, 61.39; H, 6.65; N, 14.92, Found: C, 61.81; H,
6.58; N, 14.93.
5.1.8.10. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-3-[4-
(2-methoxyphenyl)piperazin-1-yl]propanamide (13j). Recrystallized
from ethanol/water (yield 45%); m.p. 83e85 ꢀC. IR (KBr, cmꢁ1): 3463
(NH), 2933 and 2819 (CH2), 1678 (br, 2C]O), 1608 (C]C). 1H NMR,
1. The structures of the test set of the target quinazolinones were
built using the Discovery studio software.
2. Their conformational models were generated in the energy
range of 20 kcal/mol above the estimated global energy
minimum to ensure conformational diversity.
200 MHz (DMSO-d6):
d 2.39 (s, 3H, CH3), 2.64 (m, 2H, COCH2CH2N),
2.85e2.99 (m, 6H, 2CH2 of piperazine and COCH2CH2N), 3.13 (br, 4H,
2CH2 of piperazine), 3.85 (s, 3H, 20-CH3O of C6H4), 3.94 and 3.96 (s,s,
2ꢃ 3H, 2CH3O of quinazoline), 6.82e6.95 (m, 4H, H-30-60 of C6H4),
7.12 (s, 1H, H-8), 7.49 (s, 1H, H-5). 13C NMR, 200 MHz (DMSO-d6):
3. The fitting of the tested compounds was performed using
ligand pharmacophore mapping protocol. The best fit option
has been selected which manipulate conformers of each
compound to find, when possible, different mapping modes of
the ligand within the model. Different mappings for all the
conformers of each compound of the test set to the hypothesis
were visualized and the fit values of the best-fitting conformers
were found and are listed in Table 1.
d
21.65 (CH3), 31.47 (COCH2CH2N), 50.92, (2CH2 of piperazine), 52.70
(2CH2 of piperazine), 53.14 (COCH2CH2N), 55.61, 56.52 and 56.89 (3
OCH3), 105.97, 107.82, 111.42, 114.25, 118.45, 121.16, 123.47, 140.94,
143.70, 148.93, 152.38, 154.49, 155.36, 159.34, 173.67. Anal. Calc. for
C24H31N5O5$H2O: C, 60.11; H, 6.66; N, 14.02, Found: C, 60.38; H, 6.60;
N, 13.91.
5.3. Pharmacology
5.1.8.11. N-(6,7-Dimethoxy-2-methyl-4-oxoquinazolin-3(4H)-yl)-3-[4-
(4-nitrophenyl)piperazin-1-yl]propanamide
(13k). Recrystallized
5.3.1. In vivo biological evaluation
from methanol/acetone (yield 58%); m.p. 147e149 ꢀC. IR (KBr, cmꢁ1):
In vivo biological evaluation of the hypotensive effect of the
tested compounds on the arterial blood pressure of normotensive
adult cats was conducted adopting the reported method [27].
Male cats weighing 2e3 kg were housed in the animal facility
for 7 days prior to the experiment. Animals were kept at 22 ꢂ 2 ꢀC
and 12 h light/12 h dark cycle. Stressful condition or manipulation
was avoided. Experiments were performed between 8 and 10 a.m.
Cats were divided into groups, each of six animals. Cats were
anaesthetized with phenobarbitone sodium (30 mg/kg ip). The
right femoral artery of the leg was exposed, cleared from connec-
tive tissue for a distance of about 2 cm and was used for blood
3480 (NH), 2949 and 2828 (CH2), 1674 (br, 2C]O), 1599 (C]C). 1H
NMR, 200 MHz (CDCl3):
d 1.97 (s, 3H, CH3), 2.10e2.35 (m, 6H,
COCH2CH2N and 2CH2 of piperazine), 3.01 (br, 2H, COCH2CH2N), 3.13
(br, 4H, 2CH2 of piperazine), 3.46 and 3.48 (s,s, 2ꢃ 3H, 2CH3O of
quinazoline), 6.83 (d, 2H, J ¼ 7.40 Hz, H-20 and H-60 of 40-NO2eC6H5),
6.93 (s,1H, H-8), 7.32 (s,1H, H-5), 7.95 (d, 2H, J ¼ 7.40 Hz, H-30 and H-
50). 13C NMR, 200 MHz (CDCl3):
d 20.27 (CH3), 30.88 (COCH2CH2N),
45.47, (2CH2 of piperazine), 51.04 (2CH2 of piperazine), 52.79
(COCH2CH2N), 54.75 and 54.86 (2OCH3), 104.40, 106.35, 111.42,
112.91, 124.55, 127.26, 142.03, 147.10, 153.51, 153.64, 153.73, 157.62,

658
S.M. Abou-Seri et al. / European Journal of Medicinal Chemistry 46 (2011) 647e658
pressure determination. The left femoral vein was exposed and
then connected to saline infusion through a cannula. Tested drugs
were all dissolved in 1 mL DMSO and then diluted with water to the
Acknowledgment
Our deep appreciation for Prof. Dr. Ernst Urban, Institute of
Pharmacy, Vienna University for his tremendous help in measuring
the 2D, 500 MHz NMR spectra.
The authors are also thankful to Prof. Dr. Adel Girgis, National
research centre, Egypt for his help in carrying out the pharmaco-
logical screening.
final volume. Tested compounds were injected in 500 mg/kg dose
through the femoral vein and washed with 1 mL saline. Blood
pressure was recorded using Washington 400 MD2C mercury
manometers on smoked kymograph. The effects of prazosin
(reference drug) and saline/DMSO (control) were compared to
those of the tested compounds. The results are given in Table 2.
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Preparations were stabilized under 2 g resting tension during
2 h. The lack of endothelium was confirmed by the absence of
acetylcholine (1
mM) vasorelaxent action in aortic rings preco-
tracted by noradrenaline (0.1
mM). The contractile response to
norepinephrine hydrochloride (10ꢁ6 M) was measured before and
after exposure to increasing concentrations of the tested
compounds. The compounds 4b, 9e, 13i, 13j as well as prazosin
hydrochloride (as reference standard) were dissolved in dime-
thylsulfoxide (DMSO) as stock solution (10 mL of 0.01 M). Control
experiments were performed in the presence of DMSO alone, at the
same concentrations as those used with the derivatives tested,
which demonstrated that the solvent did not affect the contractile
response of isolated aorta. The observed vasodilatation activity data
are reported (Table 3, Fig. 6) and the potency (IC50, concentration
necessary for 50% reduction of maximal norepinephrine hydro-
chloride induced contracture) was determined by the best fit line
technique.