Synthesis, vasorelaxant activity, and molecular modeling study of some new phthalazine derivatives

Article abstract of DOI:10.1016/j.ejmech.2012.02.051

New phthalazine-based vasodilators were synthesized through the chloroacylation of the starting compound 1-hydrazinophthalazine 4 to give the two key intermediates 5 and 7. These intermediates were used to alkylate various cyclic amines to furnish the final compounds 6a-h and 8a-h. Compounds were tested for their vasorelaxant activities against nor-adrenaline-induced spasm on thoracic rat aorta rings and compared to the reference drug, prazosin. Seven compounds showed higher activity than prazosin, especially compound 8d having an IC₅₀ = 0.10 mM. Molecular modeling studies, including fitting of the synthesized compounds to a 3D-pharmacophore and their docking into optimized homology model as α₁-AR antagonists showed high docking score and fit values. Most vasodilation activities of tested compounds are consistent with their molecular modeling results.

Full text of DOI:10.1016/j.ejmech.2012.02.051

European Journal of Medicinal Chemistry 52 (2012) 14e21
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, vasorelaxant activity, and molecular modeling study of some new
phthalazine derivatives
,
b
b
Fadi M. Awadallah a , Wafaa I. El-Eraky , Dalia O. Saleh
*
a Pharmaceutical Chemistry department, Faculty of Pharmacy, Cairo University, 11562 Cairo, Egypt
b Pharmacology Department, National Research centre, 12622 Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
New phthalazine-based vasodilators were synthesized through the chloroacylation of the starting
compound 1-hydrazinophthalazine 4 to give the two key intermediates 5 and 7. These intermediates
were used to alkylate various cyclic amines to furnish the final compounds 6aeh and 8aeh. Compounds
were tested for their vasorelaxant activities against nor-adrenaline-induced spasm on thoracic rat aorta
rings and compared to the reference drug, prazosin. Seven compounds showed higher activity than
prazosin, especially compound 8d having an IC50 ¼ 0.10 mM. Molecular modeling studies, including
fitting of the synthesized compounds to a 3D-pharmacophore and their docking into optimized
homology model as a1-AR antagonists showed high docking score and fit values. Most vasodilation
activities of tested compounds are consistent with their molecular modeling results.
Received 25 January 2012
Received in revised form
26 February 2012
Accepted 27 February 2012
Available online 3 March 2012
Keywords:
Phthalazine
Piperazine
a1-Adrenergic receptor
Vasorelaxant
Ó 2012 Elsevier Masson SAS. All rights reserved.
Molecular modeling
1. Introduction
efforts in the area of a1-AR antagonists have led to the discovery of
some clinically useful antihypertensive drugs such as prazosin I,
Hypertension is the most common cardiovascular disease that
represents the major risk factor for endothelial dysfunction,
metabolic syndrome, renal dysfunction, congestive heart failure,
coronary artery disease, and stroke [1]. Hypertension affects
approximately billions of people all around the world. This is
despite the great effort and progress in developing new drugs
targeting the various mechanisms of hypertension [2].
terazosin II and doxazosin III that are considered the most effective
and clinically useful class of selective a1-AR antagonists (Fig. 1)
[9e11].
In addition, 3-{2-[4-(2-methoxyphenyl)piperazin-L-yl]ethyl}-
(1H,3H)-quinazoline-2,4-dione V (SGB 1534) proved effective as
a potent a1-antagonist [12]. Furthermore, certain anthranilides e
the non-cyclic isosteres of quinazolines
e
linked to 4-
Relaxation of vascular smooth muscles is one of the strategies
for the treatment of hypertension [3]. Several agents have been
developed; however they are all associated with side effects such as
fatigue, mood change, sleep disturbances, etc [4]. Therefore, there is
a continuous need to explore, search and develop new vasorelaxant
agents with minimal side effects.
The a1-adrenergic receptors (a1-ARs), a family of G-protein
coupled seven-transmembrane helix receptors, are mainly
involved in the cardiovascular and central nervous system [5]. In
the last two decades, the search for new selective a1-AR antagonists
has been intensified, mainly due to their importance in the treat-
ment of hypertension, asthma, lower urinary tract symptoms
(LUTS) and benign prostatic hypertrophy (BPH) [6e9]. Research
arylpiperazines via propionyl spacer such as VI were reported to
exhibit a1-AR antagonist activity [13]. Recently, quinazolines linked
to arylpiperazines through an acetamido or propionamido spacers
VII have been designed and exhibited potent vasorelaxant activity
(Fig. 2) [14].
Based on these findings and on previous reports that proclaimed
that heterocyclic systems (A) linked to different arylpiperazine tails
(C) through polymethylene spacer (B) is a key element for a1-AR
affinity [5], it was aimed to design and synthesize potential vaso-
relaxant agents having arylpiperazine moieties and other related
non-classical bioisosteric groups linked to a phthalazine nucleus
(Fig. 2). The phthalazine ring is the isostere and positional isomer of
quinazoline ring and, it is also the nucleus of the well known
vasodilator, hydralazine IV (Fig. 1) [15]. In other words, a hybrid
pharmacophoric approach was adopted whereby the hydralazine
structure was hybridized with different arylpiperazines and other
related groups. Different N-(un)substituted phenylepiperazines, N-
* Corresponding author. Tel.: þ2 01223483941; fax: þ20 2 2362 8426.
E-mail address: fadi_mae@hotmail.com (F.M. Awadallah).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.02.051

F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
15
O
O
O
O
O
N
Ar
Ar=
H3CO
H3CO
N
N
N
III
Doxazosin
I
II
Prazosin
Terazosin
NH2
NH2
HN
N
N
IV Hydralazine
Fig. 1. Clinically used a1-ARs antagonists IeIII and hydralazine IV.
small groups substituted piperazines, the isosteric morpholine and
the smaller aromatic imidazole ring were employed to study the
effect of these moieties on the activity of the compounds. Moreover,
Betti et al. reported the gradual increase in affinity to a1-AR by
increasing the length of the polymethene spacer between the
arylpiperazine moiety and the pyridazinone nucleus from 2 up to 7
carbons [16]. Therefore, the second approach based on the previous
experimental finding was to subject the ethylene spacer in the lead
compound V to elongation using acetohydrazido and propionohy-
drazido linkers (Fig. 2.).
Moreover, validation of the observed pharmacological data was
performed through studying the relationship between the chem-
ical features of the synthesized compounds and their a1-binding
affinity data which were derived on the basis of a previously
reported, five features pharmacophore model for a1-AR antagonists
which consisted of positive ionizable, three hydrophobic and
a hydrogen bond acceptor pharmacophore features [17].
2. Results and discussion
2.1. Chemistry
The target compounds 6aeh and 8aeh were prepared as
depicted in Schemes 1 and 2. The key starting compound, 1-
hydrazinophthalazine 4, was prepared according to the published
procedures starting from the commercially available 2-
carboxybenzaldehyde 1 which upon reaction with hydrazine
hydrate gave phthalazin-1(2H)-one 2. Chlorination of 2 with
phosphorous oxychloride resulted in 1-chlorophthalazine 3 which
was converted to the corresponding 1-hydrazino derivative 4 upon
treatment with hydrazine hydrate (Scheme 1) [18,19].
O
N
O
HN
N
N
N
O
V
H3CO
R
O
The intermediates 2-chloro-N0-(phthalazin-1-yl)acetohydrazide
5
and 3-chloro-N0-(phthalazin-1-yl)propanehydrazide
7 were
N
H
prepared from 1-hydrazinophthalazine 4 through acylation reac-
tion with chloroacetyl chloride and 3-chloropropionyl chloride,
respectively, in dry methylene chloride (Scheme 2). Evidence for
the reaction was drawn from the 1H NMR spectrum of 5 that
revealed the methylene protons at 5.20 ppm and that of 7 that
showed the ethylene protons as two triplets at 2.62 and 3.78 ppm.
The final compounds 6aeh and 8aeh were synthesized through
alkylation of the appropriate amine with the chloro-acetohydrazide
5 and the chloro-propanehydrazide 7, respectively, in dry acetoni-
trile in the presence of catalytic amount of triethylamine (Scheme
2). The synthesized compounds were characterized by 1H NMR
analyses that showed signals corresponding to the introduced
amine moieties. Other spectral and elemental analyses were also
performed for additional characterization of the compounds.
N
N
R'
VI
H3CO
H3CO
N
N
n
N
N
R
O
O
O
N
N
VII
N
N
H
A= heteroaromatic ring
B= spacer
N
N
n
H
2.2. Vasorelaxant activity
C= Aryl piperazine tail
R
6,8 a-d
All final compounds 6aeh and 8aeh were tested for their vas-
orelaxant activities against nor-adrenaline-induced spasm on
thoracic rat aorta rings [20e23] and compared to the reference
drug, prazosin. The results were listed in Table 1 and illustrated in
A
B
C
Fig. 2. Structure of lead compounds VeVII and strategy of the design of the target
compounds 6,8aed.

16
F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
NH2
O
Cl
HN
COOH
CHO
NH
N
N
N
a
N
N
c
b
1
3
2
4
Scheme 1. Reagents and reaction conditions. a: NH2NH2$H2O, 1 h.; b: POCl3, 2 min; c: NH2NH2$H2O, ethanol, 1 h.
Fig. 3 as IC50 values in mM. Regarding the acetohydrazide deriva-
tives, 6aeh, the compounds with arylpiperazine substituents
showed good activities comparable to prazosin, especially those
which had an electron withdrawing groups on the phenyl ring such
as compounds 6b (IC50 0.45 mM) and 6c (IC50 0.41 mM) which were
more active than 6a, 6d and were only slightly more active than
prazosin (IC50 0.48 mM). Replacement of the aryl substitution on
the piperazine ring with the small methyl group as in 6e greatly
enhanced the activity (IC50 0.16 mM). This compound is the most
active compound of this series and it is three times as potent as
prazosin. On the other hand, introduction of an N-ethoxycarbonyl
group on the piperazine ring negatively affected the activity as
compound 6f was the least active in this series (IC50 > 1.00 mM).
Substitution of the bioisosteric morpholine group for the pipera-
zine ring, in compound 6g, retained good activity (IC50 0.43 mM)
being slightly better than prazosin. Finally, decline in activity was
observed when the aromatic imidazole ring was introduced,
compound 6h (IC50 0.61 mM).
As for the propanehydrazide series 8aeh, the activity of the
arylpiperazinyl derivatives 8aed, unlike their respective analogs
6aed, showed inverse relationship with the electron withdrawing
property of the substituent on the phenyl ring where compounds
8b (IC50 0.70 mM) and 8c (IC50 0.50 mM) were less active than both
the unsubstituted derivative 8a (IC50 0.27 mM) and the 2-
methoxyphenylpiperazinyl derivative 8d (IC50 0.10 mM) (c.f.
6aed). It is worth mentioned that compound 8d is approximately 5
times more potent than prazosin and it is the most active of all
tested compounds. The N-methylpiperazinyl derivative 8e exhibi-
ted better activity (IC50 0.36 mM) than prazosin. The morpholine
derivative 8g possessed moderate activity (IC50 0.58 mM) being
slightly lower than prazosin. Finally, compound 8f with an N-
ethoxycarbonyl substituent (IC50 > 1.00 mM) and compound 8h
with the imidazolyl substituent (IC50 0.81 mM) were the least
active of this series.
With respect to the spacer between the phthalazine ring and the
amine moiety, results indicated that increasing the length of the
spacer from acetohydrazido in compounds 6b, 6c, 6e, 6g and 6h to
propanehydrazido in 8b, 8c, 8e, 8g and 8h was associated with
decrease in activity. The opposite was true for compounds 8a and
8d which were more active than their respective analogs.
In summary, the results of the in-vitro vasorelaxant activity
testing indicated that the presence of a piperazine group bearing an
aryl or a small alkyl group was befitting to good activity. Also, the
bioisosteric morpholine group is a good substitute for the pipera-
zine ring. In case of the arylpiperazine derivatives, the vasorelaxant
activity was not in a consistent relation with the nature of the
substituent on the phenyl ring. On the other hand, incorporation of
a piperazine ring substituted with an ethoxycarbonyl group
markedly decreased the activity and the same held true when the
piperazine ring was replaced by the smaller imidazole group.
However, no precise rule could be attained through the screening
results concerning the role of the length of the linker group (either
acetohydrazido or propanehydrazido) in affecting the observed
pharmacological properties.
2.3. Molecular modeling
Pharmacophore generation as well as docking of antagonists
into minimized homology model of receptor were performed using
H
H
N
N
NH2
HN
Cl
HN
HN
N
O
O
O
c
a
N
N
N
N
N
N
6a-h
5
4
b
H
N
H
N
N
Cl
c
HN
HN
O
N
N
N
N
7
8a-h
a
c
=
N
N
N
b
f
N
N
N
N
Cl
d
N
N
O
N
N
N
CF3
H3CO
N
O
g
N
e
N
CH3
h
N
OC2H5
Scheme 2. Reagents and reaction conditions. a: chloroacetyl chloride, CH2Cl2, 1 h.; b: 3-chloropropionyl chloride, CH2Cl2, 1 h.; c: appropriate amine, acetonitrile, TEA, 3 h.

F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
17
Table 1
Vasorelaxant potency (IC50), and best fit and docking conformer for each compound
in the test set (6aeh and 8aeh) mapped with the generated a1-AR antagonist
pharmacophore and active binding pocket of homology model.
H
N
HN
R
n
O
N
N
6a-h, 8a-h
Compound
R
n
1
1
IC50 (mM) Fit value E (Kcal molꢀ1
)
6a
6b
0.56
0.45
3.35
3.90
ꢀ67.35
ꢀ83.34
N
N
Fig. 3. IC50 values of the tested compounds compared to prazosin on contracture
induced by norepinephrine hydrochloride on thoracic rat aortic rings compared to
prazosin HCl.
N
N
N
N
Cl
the Discovery Studio 2.5 software (Accelrys Inc., San Diego,
CA, USA).
6c
1
1
0.41
0.55
4.35
3.65
ꢀ92.87
ꢀ72.91
CF3
2.3.1. Studies of the pharmacophore/receptor mode of a1-AR
antagonist
N
N
6d
The simulation compare/fit study of compounds 6aeh, 8aeh
was carried out using reported common feature pharmacophore
model that encompassed five features namely; positive ionizable
(red), hydrogen bond acceptor (green) and three hydrophobic
features (blue) (Fig. 4a) [20,21]. The fitting of the tested compound
was performed using best fit during the compare/fit process.
Different mappings for all the conformers of each compound of the
test set to the pharmacophore hypothesis were visualized and the
fit values of the best fitting conformers were determined (Table 1,
see Figure 1 of supplementary meterials). Most of the fit value
derived from fitting of our compounds into the pharmacophore
hypothesis were in good agreement with the vasodilation experi-
mental data. Alignment study of compound 8d (the most promising
vasodilation active agent) and prazosin (highly selective a1-AR
antagonist) in the pharmacophore model of a1-AR antagonist
revealed that: (i) The o-methoxyphenyl residue attached to the N4-
piperazinyl function of 8d was aligned perfectly with the dime-
thoxyquinazoline moiety of prazosin exhibiting hydrophobic
interaction through both the phenyl ring and the CH3 of methoxy
group. (ii) The N1 of piperazinyl moiety of 8d is aligned with the N1
of piperazinyl residue of prazosin, mapping the same feature
(positive ionizable) on pharmacophore model. (iii) Both carbonyl
functions in 8d and prazosin have the same orientation and map-
ped into hydrogen bond acceptor feature of pharmacophore. (iv)
The phthalazine ring system was aligned with the furanyl moiety of
prazosin exhibiting hydrophobic interaction feature (Fig. 4a).
H3CO
6e
6f
1
1
0.16
3.95
2.97
ꢀ105.11
ꢀ51.12
N
N
N
N
CH3
O
>1.00
OC2H5
6g
6h
1
1
0.43
0.61
3.99
2.85
ꢀ50.24
ꢀ59.45
N
N
O
N
8a
8b
2
2
0.27
0.70
3.99
2.99
ꢀ102.10
ꢀ68.50
N
N
N
N
N
Cl
N
8c
2
0.50
3.76
ꢀ79.43
CF3
N
N
8d
8e
8f
2
2
2
0.10
0.36
4.87
3.00
2.96
ꢀ103.24
ꢀ95.32
ꢀ72.57
H3CO
2.3.2. Molecular docking studies and binding conformation
All dock runs were conducted to investigate the detailed inter-
molecular interactions between the ligand and the target protein
according to the previously reported homology modeling tech-
nique [20,24,25]. The observed binding energies and the corre-
sponding binding mode of interaction taking place between the
ligand (test compound) and the receptor (active site of the protein
N
N
N
N
CH3
O
>1.00
OC2H5
homology model) are listed in Table
1 (see Figure 2 of
8g
8h
2
2
0.58
0.81
2.79
2.75
ꢀ52.01
ꢀ52.21
N
N
O
supplementary materials). As indicated in previous reports,
Asp106 is the key amino acid involved in the interaction [20,24,25].
From the mode of interactions of the tested compounds with the
assigned active site it was noticed that the distance between the
positive ionizable center of compound 8d which is the piperazinyl
nitrogen (N1) and negative edge of Asp106, which is the carboxylate
N
Prazosin: IC50 ¼ 0.48 mM, docking E ¼ ꢀ98.2 kcal molꢀ1, and fit value ¼ 4.55.

18
F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
as a1-AR antagonists show good docking score and fit values. The
experimental vasodilation activities of tested compounds are
consistent with their molecular modeling results. Docking studies
explains the importance of the N1 of piperazine or its equivalent
nitrogen atom in the morpholine and imidazole derivatives in
interacting with Asp106.
4. Experimental
4.1. Chemistry
Melting points were determined with Stuart SMP3 version 5
apparatus and were uncorrected. FT-IR spectra were recorded on
Bruker FT-IR spectrophotometer using KBr cell. Unless otherwise
noted, 1H NMR spectra were recorded in DMSO-d6 on Varian mercury
300BB at 300 MHz. NMR of some compounds were recorded in
DMSO-d6 on JOEL (Eclipse) 400 at 400 MHz for 1H NMR and at
100 MHz for 13C NMR; using tetramethylsilane (TMS) as internal
reference. The electron impact (EI) mass spectra were recorded on
Finnigan Mat SSQ 7000 (70 ev) mass spectrometer. Elemental
microanalysis was performed at Microanalytical Center, Cairo
University and Al-Azhar University. TLC was monitored on FLUKA
silica gel TLC aluminum cards (0.2 mm thickness) with fluorescent
indicator 254 nm using chloroform/methanol (9:1) as eluent to follow
thecourseofreactionsandtocheckthepurityofproducts.Allreagents
and solvents were purified and dried by standard techniques.
Fig. 4. (a) Alignment of compound 8d (green) and prazosin (gray) on the a1-AR
antagonist pharmacophore hypothesis. (b) Alignment of compound 8d (green) and
prazosin (violet) in the binding site of a1-AR homology model. (For interpretation of
the references to colour in this figure legend, the reader is referred to the web version
of this article.)
4.1.1. General procedure for the synthesis of compounds (5) and (7)
To a solution of 1-hydrazinophthalazine 4 (1 g; 6.2 mmol) in dry
methylene chloride (25 ml), the appropriate chloroacyl chloride
(6.8 mmol) was added and the mixture was refluxed for 1 h. After
cooling, the solid formed was filtered, washed thoroughly with
methylene chloride and air dried. The crude product was crystal-
lized from ethanol.
oxygen was more or less similar to that between the nitrogen atom
of the N1-piperazinyl moiety of prazosin and the same Asp106
carboxylate oxygen (5.72 and 4.64 A, respectively) (Fig. 4b).
The involvement of N1 rather than N4 of piperazine ring in the
binding interaction with Asp106 can be explained based on the fact
that the negative charge accumulated on the N1-piperazinyl
nitrogen is greater than that on the N4-piperazinyl nitrogen prob-
ably due to the þI effect of the 3 methylene groups surrounding the
N1 compared to the -M effect of the phenyl ring on N4 which
reduces the negative charge on it. This makes N1 of piperazine ring
the most protonatable center of the molecule (positive ionizable
feature of the generated pharmacophore) and thus, can strongly
interact with the negative carboxylate of Asp106.
4.1.1.1. 2-Chloro-N0-(phthalazin-1-yl)acetohydrazide
(5). Mp
187e189 ꢁC; yield 97%. IR nmax/cmꢀ1: 3425, 3217 (NHs), 3074
(aromatic CH), 2947 (aliphatic CH), 1674 (C]O), 1635 (NHs). 1H
NMR:
d
5.20 (s, 2H, CH2), 7.88 (t, 1H, J ¼ 8 Hz, CH-6), 7.93 (t, 1H,
J ¼ 8 Hz, CH-7), 8.20 (d, 1H, J ¼ 8 Hz, CH-5), 8.45 (d, 1H, J ¼ 8 Hz, CH-
8), 9.07 (s, 1H, CH-4), 10.20 (br s, 2H, NHs, exchanged with D2O).
Anal. Calcd. for C10H9ClN4O (236.66): C, 50.75; H, 3.83; N, 23.67.
Found: C, 50.74; H, 379; N, 24.05.
4.1.1.2. 3-Chloro-N0-(phthalazin-1-yl)propanehydrazide
(7). Mp
Also, by observing the binding mode of the rest of the
compounds, it can be assumed that the N1 of piperazine or its
equivalent nitrogen atom in the morpholine and imidazole deriv-
atives is crucial for interacting with Asp106.
141e143 ꢁC; yield 90%. IR nmax/cmꢀ1: 3425, 3194 (NHs), 3074 (CH
aromatic), 2966 (CH aliphatic), 1682 (C]O), 1635 (NHs). 1H NMR:
d
2.62 (t, 2H, J ¼ 6.3 Hz, CH2Cl), 3.78 (t, 2H, J ¼ 6.3 Hz, COCH2), 7.93
(t, 1H, J ¼ 8 Hz, CH-6), 8.08 (t, 1H, J ¼ 8 Hz, CH-7), 8.26 (d, 1H,
J ¼ 8 Hz, CH-5), 8.52 (d, 1H, J ¼ 8 Hz, CH-8), 9.11 (s, 1H, CH-4), 10.23
(br s, 2H, NHs, exchanged with D2O). Anal. Calcd. for
C11H11ClN4O.H2O (268.70): C, 49.17; H, 4.88; N, 20.85. Found: C,
48.88; H, 4.85; N, 21.31.
3. Conclusion
Two series of phthalazine derivatives hybridized to a variety of
N-substituted piperazines, morpholine and imidazole moieties
through either an acetohydrazido linker, compounds 6aeh, or
a propanehydrazido spacer, compounds 8aeh, were synthesized.
The synthesized compounds were tested in vitro for their vaso-
relaxant activities against nor-adrenaline-induced spasm on
thoracic rat aorta rings and compared to the reference drug, pra-
zosin. Seven out of the sixteen tested compounds showed vaso-
relaxant activity higher than that of prazosin viz. 6b, 6c, 6e, 6g, 8a,
8d and 8e. Compound 8d is the most active among all derivatives
being 5 times more potent than prazosin. Molecular modeling
studies, including fitting of the synthesized compounds to a 3D-
pharmacophore and their docking into optimized homology model
4.1.2. General procedure for the synthesis of compounds (6aeh)
and (8aeh)
A mixture of the corresponding chloro derivative 5 or 7
(4.2 mmol), the appropriate amine (4.2 mmol) and triethylamine
(1.16 ml, 8.4 mmol) in dry acetonitrile was heated under reflux for
3 h. The mixture was cooled, poured on iceewater and filtered. The
residue was washed with cold water and dried. The crude product
was crystallized from the appropriate solvent.
4.1.2.1. 2-(4-Phenylpiperazin-1-yl)-N0-(phthalzin-1-yl)acetohydrazide
(6a). Mp 222e224 ꢁC (ethanol); yield 90%. IR nmax/cmꢀ1: 3350

F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
19
(NHs), 3059 (CH aromatic), 2954, 2843 (CH aliphatic), 1680 (C]O),
1597 (NHs). 1H NMR:
2.69 (br s, 4H, CH2-2 and CH2-6 piperazine),
4.1.2.6. 2-(4-Ethoxycarbonylpiperazin-1-yl)-N0-(phthalzin-1-yl)ace-
d
tohydrazide (6f). Mp 142e143 ꢁC (methanol); yield 58%. IR nmax
/
3.11 (br s, 4H, CH2-3 and CH2-5 piperazine), 4.14 (s, 2H, CH2),
6.75e7.15 (m, 5H, phenyl H), 7.94 (t, 1H, J ¼ 8 Hz, CH-6), 8.04 (t, 1H,
J ¼ 8 Hz, CH-7), 8.21 (d, 1H, J ¼ 8 Hz, CH-5), 8.50 (d, 1H, J ¼ 8 Hz,
CH-8), 9.11 (s, 1H, CH-4), 11.60 (br s, 2H, NHs, exchanged with D2O).
Anal. Calcd. for C20H22N6O (362.43): C, 66.28; H, 6.12; N, 23.19.
Found: C, 66.50; H, 5.89; N, 23.42.
cmꢀ1: 3421 (NHs), 3020 (CH aromatic), 2978, 2900, 2866 (CH
aliphatic), 1712 (C]O), 1685 (C]O), 1627 (NHs).
1H NMR:
d
1.15 (t, 3H, J ¼ 7.5 Hz, CH2CH3), 2.50 (br s, 4H, CH2-2
and CH2-6 piperazine), 3.37 (br s, 4H, CH2-3 and CH2-5 piperazine),
3.96 (q, 2H, J ¼ 7.5 Hz, CH2CH3), 4.11 (s, 2H, CH2), 7.91 (t,1H, J ¼ 8 Hz,
CH-6), 8.03 (t, 1H, J ¼ 8 Hz, CH-7), 8.12 (d, 1H, J ¼ 8 Hz, CH-5), 8.48
(d, 1H, J ¼ 8 Hz, CH-8), 9.09 (s, 1H, CH-4), 9.89 (br s, 2H, NHs,
exchanged with D2O). Anal. Calcd. for C17H22N6O3 (358.39): C,
56.97; H, 6.19; N, 23.45. Found: C, 57.26; H, 6.29; N, 23.79.
4.1.2.2. 2-(4-(4-Chlorophenyl)piperazin-1-yl)-N0-(phthalzin-1-yl)aceto-
hydrazide (6b). Mp 234-235 ꢁC (isopropanol); yield 86%. IR
nmax/cmꢀ1: 3441 (NHs), 3050 (CH aromatic), 2958, 2920 (CH
aliphatic), 1690 (C]O), 1630 (NHs). 1H NMR:
d
2.71 (br s, 4H, CH2-2
4.1.2.7. 2-(1-Morpholinyl)-N0-(phthalzin-1-yl)acetohydrazide (6g). Mp
192e193 ꢁC (isopropanol); yield 60%. IR nmax/cmꢀ1: 3387, 3332
(NHs), 3059 (CH aromatic), 2954, 2924 (CH aliphatic), 1690 (C]O),
and CH2-6 piperazine), 3.12 (br s, 4H, CH2-3 and CH2-5 piperazine),
4.15 (s, 2H, CH2), 6.88 (d, 2H, J ¼ 9 Hz, CH-20 and CH-60 phenyl), 7.17
(d, 2H, J ¼ 9 Hz, CH-30 and CH-50 phenyl), 7.90 (t, 1H, J ¼ 8 Hz, CH-6),
8.07 (t, 1H, J ¼ 8 Hz, CH-7), 8.21 (d, 1H, J ¼ 8 Hz, CH-5), 8.50 (d, 1H,
J ¼ 8 Hz, CH-8), 9.10 (s, 1H, CH-4), 10.35 (br s, 2H, NHs, exchanged
1608 (NHs). 1H NMR:
d 2.44 (br s, 4H, CH2-2 and CH2-6 morpholine),
3.54 (br s, 4H, CH2-3 and CH2-5 morpholine), 4.15 (s, 2H, CH2), 7.85
(t, 1H, J ¼ 8 Hz, CH-6), 7.97 (t, 1H, J ¼ 8 Hz, CH-7), 8.13 (d, 1H,
J ¼ 8 Hz, CH-5), 8.47 (d, 1H, J ¼ 8 Hz, CH-8), 9.09 (s, 1H, CH-4), 11.57
(br s, 2H, NHs, exchanged with D2O). Anal. Calcd. for C14H17N5O2
(287.32): C, 58.52; H, 5.96; N, 24.37. Found: C, 58.80; H, 5.72;
N, 24.73.
with D2O). 13C NMR (100 MHz):
d
47.8 (C3 þ C5 piperazine), 49.6
(C2 þ C6 piperazine), 52.1 (COCH2), 116.8e134.3 (C aromatic), 142.1
(C4-phthalazine), 146.9 (C1-phenyl), 149.6 (C1-phthalazine), 165.4
(CO). MS, m/z: 396.10 [Mþ], 398.40 [Mþþ2]. Anal. Calcd. for
C20H21ClN6O (396.87): C, 60.53; H, 5.33; N,21.18. Found: C, 60.29; H,
5.47; N, 21.56.
4.1.2.8. 2-(1-Imidazolyl)-N0-(phthalzin-1-yl)acetohydrazide (6h). Mp
251e254 ꢁC (methanol); yield 52%. IR nmax/cmꢀ1: 3394, 3332 (NHs),
3059 (CH aromatic), 2974, 2924 (CH aliphatic), 1612 (C]O), 1570
4.1.2.3. 2-(4-(3-Trifluoromethylphenyl)piperazin-1-yl)-N0-(phthalzin-
1-yl)acetohydrazide (6c). Mp 164e166 ꢁC (ethanol); yield 85%. IR
nmax/cmꢀ1: 3425 (NHs), 3062 (CH aromatic), 2958, 2927 (CH
(NHs). 1H NMR (400 MHz):
d
3.48 (s, 2H, CH2-N), 7.57 (m, 2H, CH-40
and CH-50 imidazole), 7.98 (s, 1H, CH-20 imidazole), 8.10 (t, 1H,
J ¼ 7.6 Hz, CH-6), 8.26 (t, 1H, J ¼ 7.8 Hz, CH-7), 8.28 (d, 1H, J ¼ 8 Hz,
CH-5), 8.42 (d, 1H, J ¼ 8 Hz, CH-8), 8.83 (s, 1H, CH-4), 9.22 (br s, 2H,
aliphatic), 1670 (C]O), 1608 (NHs). 1H NMR:
d 2.71 (br s, 4H, CH2-
2 and CH2-6 piperazine), 3.22 (br s, 4H, CH2-3 and CH2-5 pipera-
zine), 4.15 (s, 2H, CH2), 7.03e7.41 (m, 4H, phenyl), 7.94 (t, 1H,
J ¼ 8 Hz, CH-6), 8.04 (t, 1H, J ¼ 8 Hz, CH-7), 8.21 (d, 1H, J ¼ 8 Hz,
CH-5), 8.50 (d, 1H, J ¼ 8 Hz, CH-8), 9.11 (s, 1H, CH-4), 10.24 (br s,
NHs, exchanged with D2O). 13C NMR (100 MHz):
d
35.3 (COCH2),
119.1e131.2
(C
aromatic), 138.5
(C20eimidazole), 143.2
(C4ephthalazine),151.9 (C4ephthalazine),162.2 (CO). Anal. Calcd. for
C13H12N6O (268.27): C, 58.20; H, 4.51; N,31.33. Found: C, 57.64; H,
4.43; N, 31.65.
2H, NHs, exchanged with D2O). 13C NMR (100 MHz):
d 47.4
(C3 þ C5 piperazine), 49.6 (C2 þ C6 piperazine), 52.1 (COCH2),
118.7e134.3 (C aromatic), 142.1 (C4ephthalazine), 146.9
(C1ephenyl), 148.3 (C1ephthalazine), 167.0 (CO).Anal. Calcd. for
C21H21F3N6O (430.43): C, 58.60; H, 4.92; N, 19.52. Found: C, 59.02;
H, 5.11; N, 19.80.
4.1.2.9. 3-(4-Phenylpiperazin-1-yl)-N0-(phthalazin-1-yl)propane-
hydrazide (8a). Mp 211e212 ꢁC (isopropanol); yield 84%. IR
nmax/cmꢀ1: 3217 (NHs), 3035 (CH aromatic), 2947, 2823 (CH
aliphatic), 1610 (C]O), 1579 (NHs). 1H NMR:
d
2.34 (t, 2H, J ¼ 6 Hz,
4.1.2.4. 2-(4-(2-Methoxyphenyl)piperazin-1-yl)-N0-(phthalzin-1-yl)
COCH2), 2.62 (br s, 4H, CH2-2 and CH2-6 piperazine), 3.10 (br s, 4H,
CH2-3 and CH2-5 piperazine), 3.34 (t, 2H, J ¼ 6 Hz, CH2-N), 6.74e7.17
(m, 5H, phenyl), 7.61 (t, 1H, J ¼ 7.6 Hz, CH-6), 7.98 (t, 1H, J ¼ 7.8 Hz,
CH-7), 8.02 (d, 1H, J ¼ 8 Hz, CH-5), 8.50 (d, 1H, J ¼ 8 Hz, CH-8), 9.00
(s, 1H, CH-4), 11.60 (br s, 2H, NHs, exchanged with D2O). 13C NMR
acetohydrazide (6d). Mp 178e180 ꢁC (ethanol); yield 87%. IR nmax
/
cmꢀ1: 3444 (NHs), 3059 (CH aromatic), 2939, 2938, 2831 (CH
aliphatic), 1680 (C]O),1589 (NHs). 1H NMR (400 MHz):
d
2.68 (br s,
4H, CH2-2 and CH2-6 piperazine), 2.92 (br s, 4H, CH2-3 and CH2-5
piperazine), 3.72 (s, 3H, OCH3), 4.14 (s, 2H, CH2), 6.83e6.89 (m, 4H,
phenyl), 7.93 (t, 1H, J ¼ 8 Hz, CH-6), 8.05 (t, 1H, J ¼ 8 Hz, CH-7), 8.20
(d, 1H, J ¼ 8 Hz, CH-5), 8.51 (d, 1H, J ¼ 8 Hz, CH-8), 9.10 (s, 1H, CH-4),
10.25 (br s, 2H, NHs, exchanged with D2O). 13C NMR (100 MHz):
(100 MHz):
(eCOCH2CH2eN), 54.5 (C2
aromatic), 143.6 (C4ephthalazine), 147.8 (C1ephenyl), 150.1
(C1ephthalazine), 168.3 (CO). Anal. Calcd. for C21H24N6O (376.45):
C, 67.00; H, 6.43; N, 22.32. Found: C, 66.82; H, 6.70; N, 22.78.
d
37.4 (COCH2CH2eN), 48.0 (C3 þ C5 piperazine), 52.3
þ
C6 piperazine), 118.7e128.8 (C
d
49.7 (C3 þ C5 piperazine), 50.9 (C2 þ C6 piperazine), 52.5 (OCH3),
55.3 (COCH2), 117.8e134.3 (C aromatic), 141.1 (C4ephthalazine),
146.9 (C1ephenyl), 148.5 (C2ephenyl), 152.0 (C1ephthalazine),
165.2 (CO).Anal. Calcd. for C21H24N6O2 (392.45): C, 64.27; H, 6.16;
N, 21.41. Found: C, 64.54; H, 6.03; N, 21.67.
4.1.2.10. 3-(4-(4-Chlorophenyl)piperazin-1-yl)-N0-(phthalazin-1-yl)
propanehydrazide (8b). Mp 132e134 ꢁC (isopropanol); yield 78%. IR
nmax/cmꢀ1: 3394, 3329 (NHs), 3035 (CH aromatic), 2924, 2823 (CH
aliphatic), 1610 (C]O), 1589 (NHs). 1H NMR (400 MHz):
d 2.35 (t,
4.1.2.5. 2-(4-Methylpiperazin-1-yl)-N0-(phthalzin-1-yl)acetohydrazide
(6e). Mp 235e237 ꢁC (isopropanol); yield 65%. IR nmax/cmꢀ1: 3441,
3329 (NHs), 3059 (CH aromatic), 2966, 2920, 2850 (CH aliphatic),
2H, J ¼ 6 Hz, COCH2), 2.70 (br s, 4H, CH2-2 and CH2-6 piperazine),
3.07 (br s, 4H, CH2-3 and CH2-5 piperazine), 3.33 (t, 2H, J ¼ 6 Hz,
CH2eN), 6.92 (d, 2H, J ¼ 9 Hz, CH-20 and CH-60 phenyl), 7.18 (, 2H,
J ¼ 9 Hz, CH-30 and CH-50 phenyl), 7.61 (t,1H, J ¼ 8 Hz, CH-6), 7.93 (t,
1H, J ¼ 8 Hz, CH-7), 8.20 (d, 1H, J ¼ 8 Hz, CH-5), 8.47 (d, 1H, J ¼ 8 Hz,
CH-8), 9.05 (s, 1H, CH-4), 11.50 (br s, 2H, NHs, exchanged with D2O).
1608 (C]O), 1585 (NHs). 1H NMR:
d 2.48 (s, 3H, CH3), 3.29 (br s, 4H,
CH2-3 and CH2-5 piperazine), 3.40 (br s, 4H, CH2-2 and CH2-6
piperazine), 4.35 (s, 2H, CH2), 7.56 (t, 1H, J ¼ 8 Hz, CH-6), 8.06 (t, 1H,
J ¼ 8 Hz, CH-7), 8.26 (d, 1H, J ¼ 8 Hz, CH-5), 8.64 (d,1H, J ¼ 8 Hz, CH-
8), 9.22 (s, 1H, CH-4), 11.58 (br s, 2H, NHs, exchanged with D2O). MS,
m/z: 300.30 [Mþ]. Anal. Calcd. for C15H20N6O (300.36): C, 59.98; H,
6.71; N, 27.98. Found: C, 59.42; H, 6.08; N, 28.37.
13C NMR (100 MHz):
zine), 52.3 (eCOCH2CH2eN), 54.7 (C2 þ C6 piperazine), 116.7e131.1
(C aromatic), 143.9 (C4ephthalazine), 148.1 (C1ephenyl), 149.8
(C1ephthalazine), 169.9 (CO). Anal. Calcd. for C21H23ClN6O
d
37.5 (COCH2CH2eN), 48.0 (C3 þ C5 pipera-

20
F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
(410.90): C, 61.38; H, 5.64; N, 20.45. Found: C, 61.47; H, 5.58; N,
20.59.
4.1.2.16. 3-(1-Imidazolyl)-N0-(phthalzin-1-yl)acetohydrazide (8h). Mp
225e227 ꢁC (ethanol); yield 62%. IR nmax/cmꢀ1: 3402, 3332 (NHs),
3062 (CH aromatic), 2924, 2850 (CH aliphatic), 1615 (C]O), 1589
4.1.2.11. 3-(4-(3-Trifluoromethylphenyl)piperazin-1-yl)-N0-(phthalzin-
1-yl)propanehydrazide (8c). Mp 267e269 ꢁC (isopropanol); yield
68%. IR nmax/cmꢀ1: 3390, 3329 (NHs), 3035 (CH aromatic), 2920,
2850 (CH aliphatic), 1608 (C]O), 1581 (NHs). 1H NMR (400 MHz):
(NHs). 1H NMR:
d
2.64 (t, 2H, J ¼ 6 Hz, COCH2), 3.82 (t, 2H, J ¼ 6 Hz,
CH2eN), 7.59 (m, 2H, CH-40 and CH-50 imidazole), 7.87 (s, 1H, CH-20
imidazole), 7.98 (t, 1H, J ¼ 7.6 Hz, CH-6), 8.15 (t, 1H, J ¼ 7.8 Hz, CH-7),
8.28 (d, 1H, J ¼ 8 Hz, CH-5), 8.64 (d, 1H, J ¼ 8 Hz, CH-8), 9.15 (s, 1H,
CH-4), 10.18 (br s, 2H, NHs, exchanged with D2O). 13C NMR
d
2.51 (t, 2H, J ¼ 6 Hz, COCH2), 2.75 (br s, 4H, CH2-2 and CH2-6
piperazine), 3.27 (br s, 4H, CH2-3 and CH2-5 piperazine), 3.43 (t, 2H,
J ¼ 6 Hz, CH2eN), 7.10e7.45 (m, 4H, phenyl), 7.57 (t,1H, J ¼ 8 Hz, CH-
6), 7.77 (t, 1H, J ¼ 8 Hz, CH-7), 8.20 (d, 1H, J ¼ 8 Hz, CH-5), 8.64 (d,
1H, J ¼ 8 Hz, CH-8), 9.15 (s, 1H, CH-4), 11.57 (br s, 2H, NHs,
(100 MHz):
(eCOCH2CH2eN), 55.0 (C2
d
38.1 (COCH2CH2eN), 48.1 (C3 þ C5 piperazine), 51.8
þ
C6 piperazine), 119.8e130.8 (C
aromatic), 135.6 (C20’eimidazole), 143.3 (C4ephthalazine), 146.9
(C1ephenyl), 149.2 (C1ephthalazine), 167.0 (CO). MS, m/z: 282.00
[Mþ]. Anal. Calcd. for C14H14N6O (282.30): C, 59.56; H, 5.00; N, 29.77.
Found: C, 59.68; H, 5.16; N, 30.12.
exchanged with D2O). 13C NMR (100 MHz):
d 37.9 (COCH2CH2eN),
46.5 (C3 þ C5 piperazine), 52.5 (eCOCH2CH2eN), 53.2 (C2 þ C6
piperazine), 124.4e136.4 (C aromatic CF3), 143.8
þ
(C4ephthalazine), 148.2 (C1ephenyl), 153.4 (C1ephthalazine),
168.1 (CO). Anal. Calcd. for C22H23F3N6O (444.45): C, 59.45; H,
5.22; N, 18.91. Found: C, 59.63; H, 5.29; N, 19.20.
4.2. Vasorelaxant activity
The vasodilation activity screening procedures were carried out
according to the standard reported techniques [20e23] by testing
the effects of the synthesized compounds 6aeh, 8aeh on isolated
thoracic aortic rings of male Wister rats (250e350 g). After light
ether anesthesia, the rats were sacrificed by cervical dislocation.
The aorta were immediately excised, freed of extraneous tissues
and prepared for isometric tension recording. Aorta was cut into
(3e5 mm width) rings and each ring was placed in a vertical
chamber “10 ml jacketed automatic multi-chamber organ bath
system (Model no. ML870B6/C, Panlab, Spain)” filled with Krebs
solution composed of (in mM): NaCl, 118.0; KCl, 4.7; NaHCO3, 25.0;
CaCl2, 1.8; NaH2PO4, 1.2; MgSO4, 1.2; glucose, 11.0 and oxygenated
with carbogen gas (95% O2/5% CO2) at 37 ꢂ 0.5 ꢁC. Each aortic ring
was mounted between two stainless steel hooks passed through its
lumen. The lower hook was fixed between two plates, while the
upper one was attached to a force displacement transducer (Model
no. MLT0201, Panlab, Spain) connected to an amplifier (PowerLab,
AD Instruments Pty. Ltd.) which is connected to a computer. The
Chart for windows (v 3.4) software was used to record and elabo-
rate data.
Preparations were stabilized under 2 g resting tension during
2 h and then the contracture response to norepinephrine hydro-
chloride (10ꢀ6 M) was measured before and after exposure to
increasing concentrations of the tested synthesized compounds.
The tested compounds 6aeh, 8aeh 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
4.1.2.12. 3-(4-(2-Methoxyphenyl)piperazin-1-yl)-N0-(phthalzin-1-yl)
propanehydrazide (8d). Mp 150e153 ꢁC (ethanol); yield 62%. IR nmax
/
cmꢀ1: 3387, 3332 (NHs), 3059 (CH aromatic), 2920, 2831 (CH
aliphatic), 1612 (C]O), 1589 (NHs). 1H NMR:
2.64 (t, 2H, J ¼ 6 Hz,
d
COCH2), 2.80 (br s, 4H, CH2-2 and CH2-6 piperazine), 3.57 (br s, 4H,
CH2-3and CH2-5 piperazine), 3.76 (t, 2H, J ¼ 6 Hz, CH2eN), 3.81 (s, 3H,
OCH3),6.78e6.97 (m, 4H, phenyl), 7.58 (t,1H, J ¼ 7.6 Hz, CH-6), 8.04 (t,
1H, J ¼ 7.8 Hz, CH-7), 8.22 (d,1H, J ¼ 8 Hz, CH-5), 8.64 (d,1H, J ¼ 8 Hz,
CH-8), 9.31 (s, 1H, CH-4), 11.60 (br s, 2H, NHs, exchanged with D2O).
MS, m/z: 406.55 [Mþ]. Anal. Calcd. for C22H26N6O2 (406.48): C, 65.01;
H, 6.45; N, 20.68. Found: C, 65.14; H, 6.52; N, 21.07.
4.1.2.13. 3-(4-Methylpiperazin-1-yl)-N0-(phthalzin-1-yl)propane-
hydrazide (8e). Mp 252e254 ꢁC (ethanol); yield 55%. IR nmax/cmꢀ1
:
3398, 3329 (NHs), 3055 (CH aromatic), 2924, 2850 (CH aliphatic),
1620 (C]O), 1589 (NHs). 1H NMR:
d
2.49 (s, 3H, CH3), 2.50 (t, 2H,
J ¼ 6 Hz, COCH2), 3.35 (br s, 4H, CH2-2 and CH2-6 piperazine), 3.41 (br
s, 4H, CH2-3 and CH2-5 piperazine), 3.56 (t, 2H, J ¼ 6 Hz, CH2eN), 7.56
(t, 1H, J ¼ 7.6 Hz, CH-6), 7.82 (t, 1H, J ¼ 7.8 Hz, CH-7), 8.23 (d, 1H,
J ¼ 8 Hz, CH-5), 8.67 (d, 1H, J ¼ 8 Hz, CH-8), 9.09 (s, 1H, CH-4), 11.60
(br s, 2H, NHs, exchanged with D2O). Anal. Calcd. for C16H22N6O
(314.39): C, 61.13; H, 7.05; N, 26.73. Found: C, 61.43; H, 6.77; N, 27.15.
4.1.2.14. 3-(4-Ethoxycarbonylpiperazin-1-yl)-N0-(phthalzin-1-yl)pro-
panehydrazide (8f). Mp 177e179 ꢁC (methanol); yield 50%. IR
nmax/cmꢀ1: 3441, 3329 (NHs), 3051 (CH aromatic), 2920, 2850 (CH
aliphatic), 1630 (C]O), 1612 (C]O), 1589 (NHs). 1H NMR:
d 1.21 (t,
3H, J ¼ 7.8 Hz, CH2CH3), 2.46 (t, 2H, J ¼ 6 Hz, COCH2), 2.62 (br s, 4H,
CH2-2 and CH2-6 piperazine), 3.07 (br s, 4H, CH2-3 and CH2-5
piperazine), 3.36 (t, 2H, J ¼ 6 Hz, CH2eN), 4.22 (q, 2H, J ¼ 7.8,
CH2CH3), 7.61 (t, 1H, J ¼ 7.6 Hz, CH-6), 7.95 (t, 1H, J ¼ 7.8 Hz, CH-7),
8.02 (d, 1H, J ¼ 8 Hz, CH-5), 8.68 (d, 1H, J ¼ 8 Hz, CH-8), 9.21 (s, 1H,
CH-4), 11.82 (br s, 2H, NHs, exchanged with D2O). Anal. Calcd. for
C18H24N6O3 (372.42): C, 58.05; H, 6.50; N, 22.57. Found: C, 58.30; H,
6.38; N, 22.93.
screening data are reported (Table 1, Fig. 3) and the potency (IC50
,
concentration necessary for 50% reduction of maximal norepi-
nephrine hydrochloride induced contracture) was determined by
the best-fit line technique.
Acknowledgments
The authors are grateful to Dr. Adel S. Girgis, Professor of
Pesticide Chemistry, National Research Centre for his kind help in
performing the calculations of the pharmacological screening. The
authors are also thankful to Dr. Nasser S. M. Ismail, associate
professor of Pharmaceutical Chemistry, faculty of Pharmacy, Ain-
Shams university for performing the molecular modeling study.
4.1.2.15. 3-(1-Morpholinyl)-N0-(phthalzin-1-yl)acetohydrazide (8g). Mp
265e266 ꢁC (isopropanol); yield 62%. IR nmax/cmꢀ1: 3398, 3332 (NHs),
3059 (CH aromatic), 2920, 2840 (CH aliphatic), 1608 (C]O), 1589
(NHs). 1H NMR:
d
2.50 (t, 2H, J ¼ 6 Hz, COCH2), 2.85 (br s, 4H, CH2-2 and
CH2-6 morpholine), 3.31 (br s, 4H, CH2-3 and CH2-5 morpholine), 3.42
(t, 2H, J ¼ 6 Hz, CH2eN), 7.55 (t, 1H, J ¼ 7.6 Hz, CH-6), 7.85 (t, 1H,
J ¼ 7.8 Hz, CH-7), 8.25 (d, 1H, J ¼ 8 Hz, CH-5), 8.67 (d, 1H, J ¼ 8 Hz, CH-
8), 9.12 (s, 1H, CH-4), 11.60 (br s, 2H, NHs, exchanged with D2O). Anal.
Calcd. for C15H19N5O2 (301.34): C, 59.79; H, 6.36; N, 23.24. Found: C,
59.54; H, 6.09; N, 23.61.
Appendix. Supplementary material
Supplementary data related to this article can be found online at
doi:10.1016/j.ejmech.2012.02.051.

F.M. Awadallah et al. / European Journal of Medicinal Chemistry 52 (2012) 14e21
21
[12] H. Nagano, M. Takagi, N. Kubodera, I. Matsunaga, H. Nabata, Y. Ohba, K. Sakai,
S. Hata, Y. Uchida, Eur. Pat. 89065, 1983, Chugai Pharmaceutical Co., Ltd.,
Japan; Chem. Abstr. 100 (1983) p. 6547.
[13] T. Elworthy, A. Ford, G. Bantle, D. Morgans, et al., J. Med. Chem. 40 (1997)
2674e2687.
[14] S.M. Abou-Seri, K. Abouzid, D.A. Abou El Ella, Eur. J. Med. Chem. 46 (2011)
647e658.
[15] Hydralazine, through: http://www.drugs.com/pro/hydralazine.html.
[16] L. Betti, M. Botta, F. Corelli, M. Floridi, P. Fossa, G. Giannaccini,
F. Manetti, G. Strappaghetti, S. Corasno, Bioorg. Med. Chem. Lett. 12
(2002) 437e440.
[17] M.A. Ismail, M.N. Aboul-Enein, K.A. Abouzid, R.A. Serya, Bioorg. Med. Chem. 14
(2006) 898e910.
[18] Y. Chen, W. Hua, Spectrochimica Acta 56 (2000) 1045e1049.
[19] D. J. Nelson, US 7,220,858 B2 (2007).
[20] A.S. Girgis, N.S.M. Ismail, H. Farag, Eur. J. Med. Chem. 46 (2011) 2397e2407.
[21] A.S. Girgis, N.S.M. Ismail, H. Farag, W.I. El-Eraky, D.O. Saleh, S.R. Tala,
A.R. Katritzky, Eur. J. Med. Chem. 45 (2010) 4229e4238.
[22] A.S. Girgis, N. Mishriky, A.M. Farag, W.I. El-Eraky, H. Farag, Eur. J. Med. Chem.
43 (2008) 1818e1827.
References
[1] A.E. Kümmerle, J.M. Raimundo, C.M. Leal, G.S. daSilva, T.L. Balliano,
M.A. Pereira, C.A. de Simone, R.T. Sudo, G. Zapata-Sudo, C.A. M. Fraga,
E.J. Barreiro, Eur. J. Med. Chem. 44 (2009) 4004e4009.
[2] A.D. Lopez, C.D. Mathers, M. Ezzati, D.T. Jamison, C.J. Murray, Lancet 367
(2006) 1747e1757.
[3] G.S. Stokes, J. Clin. Hypertens. 6 (2004) 192e197.
[4] H. Marona, N. Szkaradek, A. Rapacz, B. Filipek, M. Dybata, A. Siwek, M. Cegta,
E. Szneler, Bioorg. Med. Chem. 17 (2009) 1345e1352.
[5] R. Barbaro, L. Betti, M. Botta, F. Corelli, G. Giannaccini, L. Maccari, F. Manetti,
G. Strappaghetti, F. Corsano, J. Med. Chem. 44 (2001) 2118e2132.
[6] D. Bylund, D. Eikenberg, J. Heieble, S. Langer, R. Lefkowiskitz,
K. Minneman, P. Molinoff, R. Rufolo, U. Trendelenburg, Pharmacol. Rev. 46
(1994) 121e136.
[7] C. Forray, J. Bard, J. Wetzel, G. Chiu, E. Shapiro, R. Tang, H. Lepor, P. Hartig,
R. Weinshbank, T. Brancheck, Mol. Pharmacol. 45 (1994) 703e708.
[8] M.A. Patane, A.L. Scott, T.P. Broten, R.S.L. Chang, R.W. Ransom, J. DiSalvo,
C. Forray, M.G. Bock, J. Med. Chem. 41 (1998) 1206e1210.
[9] J. Handzlik, D. Maciag, M. Kubacka, S. Mogliski, B. Filipek, K. Stadnicka, K. Kiec-
Kononowicz, Bioorg. Med. Chem. 16 (2008) 5982e5998.
[23] A.S. Girgis, A. Kalmouch, M. Ellithey, Bioorg. Med. Chem. 14 (2006)
8488e8494.
[24] I.J. MacDougall, R. Griffith, J. Mol. Graph. Model. 25 (2006) 146e157.
[25] R. Barbaro, L. Betti, M. Botta, F. Corelli, G. Giannaccini, L. Maccari, F. Manetti,
G. Strappaghetti, S. Corsano, Bioorg. Med. Chem. 10 (2002) 361e369.
[10] V. Alabaster, S. Campbell, J. Danilewicz, C. Greengrass, R.M. Plews, J. Med.
Chem. 30 (1987) 999e1003.
[11] H. Lepor, Prostate (1990) 75e84 Suppl. 3.