Regioselective synthesis and molecular modeling study of vasorelaxant active 7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones

Article abstract of DOI:10.1016/j.ejmech.2010.06.018

Nitrilimines (PhC^-:N⁺:NR′) generated in situ from hydrazonoyl chlorides 2a,b reacted regioselectively with 5-arylidene-2,2-dimethyl[1,3]dioxane-4,6-diones 1a-f to afford 1,3,4-triaryl-8,8-dimethyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones 3a-l. In vitro vasodilation activity screening of the synthesized compounds using isolated thoracic aortic rings of male Wister rats pre-contracted with norepinephrine hydrochloride revealed considerable vasodilation activity; compounds 3f and 3j had IC₅₀ (concentration necessary for 50% reduction of maximal norepinephrine hydrochloride induced contracture) of 0.325, 0.321 mM, respectively. Molecular modeling, including fitting to a 3D-pharmacophore model using Discovery studio 2.1 programs and their docking into optimized α₁-AR homology models as α₁-AR antagonist showed high-docking score and fit values. The experimental in vitro vasodilation activity of compounds 3a-l was consistent with the molecular modeling.

Full text of DOI:10.1016/j.ejmech.2010.06.018

European Journal of Medicinal Chemistry 45 (2010) 4229e4238
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Regioselective synthesis and molecular modeling study of vasorelaxant active
7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones
,
b
a
c
c
Adel S. Girgis a , Nasser S.M. Ismail , Hanaa Farag , Wafaa I. El-Eraky , Dalia O. Saleh ,
*
Srinivasa R. Tala d, Alan R. Katritzky d
,
1
a Pesticide Chemistry Department, National Research Centre, Dokki, Cairo 12622, Egypt
b Pharmaceutical Chemistry Department, Faculty of Pharmacy, Ain Shams University, Cairo 11566, Egypt
c Pharmacology Department, National Research Centre, Dokki, Cairo 12622, Egypt
d Center for Heterocyclic Compounds, University of Florida, Department of Chemistry, Gainesville, FL 32611-7200, USA
a r t i c l e i n f o
a b s t r a c t
Nitrilimines (PhCꢀ:Nþ:NR0) generated in situ from hydrazonoyl chlorides 2a,b reacted regioselectively
with 5-arylidene-2,2-dimethyl[1,3]dioxane-4,6-diones 1a-f to afford 1,3,4-triaryl-8,8-dimethyl-7,9-
dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones 3a-l. In vitro vasodilation activity screening of the
synthesized compounds using isolated thoracic aortic rings of male Wister rats pre-contracted with
norepinephrine hydrochloride revealed considerable vasodilation activity; compounds 3f and 3j had IC50
(concentration necessary for 50% reduction of maximal norepinephrine hydrochloride induced
contracture) of 0.325, 0.321 mM, respectively. Molecular modeling, including fitting to a 3D-pharma-
cophore model using Discovery studio 2.1 programs and their docking into optimized a1-AR homology
models as a1-AR antagonist showed high-docking score and fit values. The experimental in vitro vaso-
dilation activity of compounds 3a-l was consistent with the molecular modeling.
Article history:
Received 31 March 2010
Received in revised form
31 May 2010
Accepted 10 June 2010
Available online 17 June 2010
Keywords:
5-Arylidene-2,2-dimethyl[1,3]dioxane-4,6-
diones
Hydrazonoyl halides
7,9-Dioxa-1,2-diaza-spiro[4.5]dec-2-ene-
6,10-diones
Ó 2010 Elsevier Masson SAS. All rights reserved.
Dipolar cycloaddition
Vasodilation
Molecular modeling
1. Introduction
exists without side effects, which include fatigue, mood change,
sleep disturbances, dry mouth, blurry vision or impotence. It is
Despite the significant progress in its prevention and treatment,
cardiovascular diseases remain the main cause of worldwide
mortality, with an increasing number of deaths [1]. Hypertension
and atherosclerosis are central to the pathogenesis of coronary
artery diseases (ischemia, angina, myocardial infarction), heart
failure, cerebral (stroke) and peripheral vascular disease [2]. Ther-
apeutic intervention is the most common therapy to control
hypertension and reduce hypertension-related organ damage.
Recent progress includes new antihypertensive drugs with three
main categories: (1) diuretics and adrenergic receptor blockers; (2)
calcium channel blockers and (3) inhibitors targeting the renin-
angiotensin system (RAS), namely angiotensin converting enzyme
(ACE) inhibitors and angiotensin type-1 (AT1) receptor antagonists
[3]. However, no ideal antiarrhythmic or hypotensive treatment
urgent to search for new agents with minimal side effects [4].
The present work describes the synthesis of dioxa-diaza-spiro
[4.5]decanes by 1,3-dipolar cycloaddition reactions of nitrilimines
to [1,3]dioxane-4,6-diones possessing an exocyclic olefinic linkage
including regioselectivity. Vasodilation is expansion of blood
vessels by relaxation of smooth muscle cells within their walls,
especially large and smaller arterioles and large veins. When
vessels dilate, the flow of blood is increased due to a decrease in
vascular resistance. Therefore, dilation of arterial blood vessels
(mainly arterioles) leads to a decrease in blood pressure. This work
is a continuation of our investigations in this area searching for
bioactive hits easily prepared from accessible starting materials and
facile synthetic approaches [5,6]. Molecular modeling is attempted
to validate the observed pharmacological properties and distin-
guish the obtained structure-activity relationships.
Adrenoceptors (AR) are classified into a-AR and b-AR [7]. a-ARs
* Corresponding author. Tel.: þ202 0120447199; fax: þ202 33370931.
E-mail addresses: girgisas10@yahoo.com (A.S. Girgis), katritzky@chem.ufl.edu
(A.R. Katritzky).
play a pivotal role in the regulation of a variety of physiological
processes, particularly within the cardiovascular system and are
divided into two main subtypes a1- and a2-ARs [2,8]. The a1- and
1
Tel.: þ1 352 392 0554; fax: þ1 352 392 9199.
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.06.018

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A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
a2-ARs are located in the vascular smooth muscle cell membrane,
and upon stimulation by an appropriate agonist, mediate vaso-
constriction. The simultaneous occurrence of both receptor
subtypes on vascular smooth muscles indicate that a1- and a2-ARs
could contribute to the maintenance of peripheral arterial tone and
may play an important role in resistance seen in hypertension.
a1-ARs modulate intercellular biochemical processes in response to
changes in extracellular concentrations of the neurotransmitter
norepinephrine and the circulating hormone epinephrine [9e11].
Compounds acting as antagonists at various post-junctional a1-ARs
are frequently used in the therapy of high blood pressure, prazosin
being the most common drug [8]. a1-AR antagonists are also used
in the treatment of benign prostatic hyperplasia, lower urinary tract
symptoms and cardiac arrhythmia [11,12].
their regio-isomers 7,9-dioxa-2,3-diaza-spiro[4.5]dec-1-ene-6,10-
diones 4, based on their spectroscopic (IR, 1H NMR, 13C NMR) and
elemental analysis data (Scheme 1).
The IR spectra of 3a-l reveal the presence of strong carbonyl
stretching vibration bands at
spectra of 3a-l show the pyrazolinyl H-4 as a sharp singlet signal
n
¼ 1791e1744 cmꢀ1
.
1H NMR
at
d
d
¼ 5.33e5.68, in addition to the methyl singlet signals at
¼ 1.72e1.88. The chemical shift values for pyrazolinyl H-4 is
evidence for the deduced regio-isomeric form; many other
similar spiro analogues such as spiro[2H-indene-2,30-[3H]pyr-
azole]-1,3-diones reveal characteristic pyrazolinyl H-40 signals at
d
¼
5.14e5.48 [13]. Additionally, pyrazolinyl H-4 of regio-
isomeric form 4 was expected to appear at
d
> 6.5 [14]. The 13C
NMR spectra of 3a-l provide a strong evidence for the structures
shown by exhibiting the characteristic HC-4 and C-5 (spiro-
carbon) at
with many similar spiro-ring systems [13e18]. The methyl
carbons ( ¼ 160.5e165.6) and
¼ 29.3e30.1), carbonyl carbons (
quaternary C-8 (
¼ 107.1e108.6) are also well recognized.
d
¼ 57.9e67.1 and 74.4e76.8, respectively in accord
2. Results and discussion
d
d
2.1. Chemistry
d
Nitrilimines (PhCꢀ:Nþ:NR0) generated in situ by dehy-
drohalogenation of the corresponding hydrazonoyl chlorides 2a,
b using triethylamine underwent 1,3-dipolar cycloadditions with
various 5-arylidene-2,2-dimethyl[1,3]dioxane-4,6-diones 1a-f
under reflux in benzene to afford single products (TLC). The isolated
products were established to be 1,3,4-triaryl-8,8-dimethyl-7,9-
dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones 3a-l rather than
2.2. Vasodilation properties
Screening of the vasodilation activity of the synthesized 7,9-
dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones 3a-f,h-l was
investigated in vitro using isolated thoracic aortic rings of male
Wister rats pre-contracted with norepinephrine hydrochloride
O
R
O
Me
O
O
Me
(1)
PhCCl=NNHR' (2)
C6H6, TEA
R
4
5
Ph
R
R'
O
O
O
N
N
2
N
O
8
O
Me
Me
N
O
Me
Me
R'
Ph
O
O
(3)
(4)
1a, R = 4-ClC6H4
1b, R = 4-FC6H4
3a, R = 4-ClC6H4, R' = Ph
3b, R = 4-ClC6H4, R' = 3-ClC6H4
3c, R = 4-FC6H4, R' = Ph
1c, R = 4-H3COC6H4
1d, R = 4-(CH3)2NC6H4
1e, R = 2-thienyl
3d, R = 4-FC6H4, R' = 3-ClC6H4
3e, R = 4-H3COC6H4, R' = Ph
1f, R = 5-methyl-2-furanyl
3f, R = 4-H3COC6H4, R' = 3-ClC6H4
3g, R = 4-(CH3)2NC6H4, R' = Ph
2a, R' = Ph
3h, R = 4-(CH3)2NC6H4, R' = 3-ClC6H4
3i, R = 2-thienyl, R' = Ph
2b, R' = 3-ClC6H4
3j, R = 2-thienyl, R' = 3-ClC6H4
3k, R = 5-methyl-2-furanyl, R' = Ph
3l, R = 5-methyl-2-furanyl, R' = 3-ClC6H4
Scheme 1.

A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
4231
according to the standard reported procedure [5,6,19,20]. The data
(Table 1, Figs. 1 and 2) reveal that, all the tested compounds show
significant vasodilation and in particular, compounds 3f and 3j
exhibit remarkable vasodilation activities among all the tested
analogues with IC50 (potency, concentration necessary for 50%
reduction of maximal norepinephrine hydrochloride induced
contracture) ¼ 0.325, 0.321 mM, respectively.
appropriate (Fig. 3). This is because the simulated fitting values of
such hypothesis with the training hypotensive test set
a
compounds (3a-l) were more consistent with the experimental
results than the other hypotheses. The hypothesis encompassed
five features namely; positive ionizable (PI), hydrogen bonding
acceptor (HBA) and three hydrophobic features (HY1, HY2 and
HY3). Barbora et al. [24] reported a Hypogen a1-ARs antagonist
hypothesis, which contains the same kind and number of features
as our hypothesis. Nevertheless, the difference between them was
in the constraint distances between the five feature pharmaco-
phore centers (Table 2). However, Barbora et al. [24] did not report
the constraint angles between the pharmacophore centers. These
constraint angles are now reported (Table 2, Fig. 3).
The structures of the test set of 7,9-dioxa-1,2-diaza-spiro[4.5]
dec-2-ene-6,10-diones 3a-l were built using the Discovery studio
software, and their conformational models were generated in the
energy range of 20 kcal/mol above the estimated global energy
minima. The fitting of each 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 hypothesis
were visualized and the fit values of the best-fitting conformers
were found (Table 3).
Structure-activity relationships based on the observed results
indicated that the type of substituent attached at either 1- or
4-position is a controlling factor governing the total observed
pharmacological properties. In most cases, the presence of a meta-
chlorine in the 1-phenyl group of a tested compound enhanced
significantly the observed vasodilation activity as exhibited in pairs
3a,3b (IC50 ¼ 0.590, 0.448 mM, respectively), 3c,3d (IC50 ¼ 1.469,
0.643 mM, respectively), 3e,3f (IC50 ¼ 0.500, 0.325 mM, respec-
tively) and 3i,3j (IC50 ¼ 0.585, 0.321 mM, respectively). Addition-
ally, attachment of the 4-phenyl group with an electron-donating
function at the 4-position (e.g. methoxy or dimethylamino func-
tions) enhanced the observed pharmacological properties
compared with the case, where an electron withdrawing group was
included (e.g. chloro- or fluoro-substituent) as shown in
compounds 3a,3c,3e (IC50 ¼ 0.590, 1.469, 0.500 mM, respectively)
and 3b,3d,3f,3h (IC50 ¼ 0.448, 0.643, 0.325, 0.430 mM, respec-
tively). Furthermore, attachment of a thienyl function at the 4-
position of the tested analogues gave enhanced vasodilation
activity compared to a furanyl moiety as exhibited in pairs 3i,3k
(IC50 ¼ 0.585, 0.719 mM, respectively) and 3j,3l (IC50 ¼ 0.321, 0.729
mM, respectively).
2.3.2. Generation of homology models
This technique used for building a protein structure, where
homology models of a1-ARs were based on a crystal structure of
(2BQ0) obtained from the Protein Data Bank (http://www.rcsb.org/
pdb), after identifying a homologous structure using the BLAST
search and analyzing the BLAST results [22]. This template (2BQ0)
was chosen as it gave the best resultant homology models in terms
of secondary and tertiary structure validation. The model sequence
was aligned with the template sequence using the aligned multiple
sequences protocol. 3D model of original protein sequence was
built using the created alignment and the 2BQ0 structure as the
template. Evaluation of the generated model was carried out by
comparing the model structure with the template, where the
a1-ARs have approximately 24% identity and 52% similarity with
the template sequence.
2.3. Molecular modeling
Pharmacophore was produced using the Discovery Studio 2.1
(Accelrys Inc., San Diego, CA, USA). Docking of antagonists into
minimized homology models of receptors was performed using the
Molsoft ICM-pro software.
2.3.1. Generation of a1-AR antagonist hypothesis
The pharmacophore modeling method has been widely used in
lead discovery and optimization as a key tool of computer aided
2.3.3. Molecular docking studies and binding conformation
drug design.
A hypothesis was formulated using generation
All Dock runs were conducted using Molsoft ICM-pro software.
An automated docking study was carried out using the 3D structure
of the generated homology model. The regularized protein was
used in determination of the important amino acids in ligand-
binding pocket (LBP) (Asp 106) [22], which is mentioned in the
literature. Interactive docking using mol table ligand was carried
out for all the conformers of each compound of the test set (3ael) to
the selected active site. Each docked compound was assigned
a score according to its fit in the LBP [25]. The predicted binding
energies of the compounds and the corresponding experimental
values are also listed in the Table 3.
common feature pharmacophore model in Discovery studio 2.1. The
lead compounds, which were reported to have selective a1-ARs
antagonistic activity (Scheme 2), were used to generate common
feature hypotheses for the a1-ARs antagonists [21,22]. The set of
conformational models of each structure of the lead compounds
was performed and used to generate the common feature
hypotheses, where ten hypotheses were generated [23]. The
assessment of the preferred hypothesis among the generated ones
indicated that hypothesis ranked number
3 was the most
Table 1
The archetypal a1-AR antagonist prazosin was docked into
optimized homology models of a1-AR. The best docking energy of
prazosin was ꢀ82 kcal/mol. It was found that prazosin and
compound 3j exhibit interaction with the PI feature in the a1-AR
antagonist pharmacophore and their docking showed the distance
between the carbonyl oxygens of Asp 106 and the closest nitrogen
Concentration of compounds necessary to reduce maximal norepinephrine-induced
contracture by 50% (IC50) in rat thoracic aortic rings.
Entry
Compound
R
R0
Potency (IC50),
mM
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3f
3h
3i
3j
4-ClC6H4
4-ClC6H4
4-FC6H4
4-FC6H4
4-H3COC6H4
4-H3COC6H4
4-(CH3)2NC6H4
2-thienyl
2-thienyl
5-methyl-2-furanyl
5-methyl-2-furanyl
Ph
3-ClC6H4
Ph
3-ClC6H4
Ph
3-ClC6H4
3-ClC6H4
Ph
0.590
0.448
1.469
0.643
0.500
0.325
0.430
0.585
0.321
0.719
0.729
ꢀ
of piperazinyl prazosin and pyrazolinyl nucleus of 3j were 5.6 A and
ꢀ
6.2 A, respectively (Fig. 4A and B). Alignment study of docked
compound 3j and prazosin with the binding pocket of homology
model protein (Fig. 4C) revealed that (i) pyrazolinyl residue of 3j
was perfectly aligned with the piperazinyl nucleus of prazosin (ii)
aryl group oriented at 4-position of 3j superimposing with the
furanyl moiety of prazosin (iii) additionally, both the prazosin and
compound 3j make positive ionizable interaction with carbonyl
9
10
11
3-ClC6H4
Ph
3-ClC6H4
3k
3l

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A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
Fig. 1. Effect of tested compounds on contracture induced by norepinephrine hydrochloride (NE.HCl) in rat thoracic aortic rings.
oxygens of Asp 106. In other words, through docking studies it
could be concluded that the pyrazolinyl ring system is responsible
for fitting the tested structures (3a-l) in an appropriate position
occupied by the piperazinyl nucleus of prazosin (potent a1-AR
antagonist). However, the aryl group attached to the 4-position of
the tested heterocyles 3a-l plays an important role in optimizing
the docking process. These attained observations seem similar to
the mentioned ones due to SAR controlling factors. Docking results
provide useful information in understanding the structural features
of the target and chemical features of the ligands. This was
extended to the successful designing of highly active analogs of
7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione derivatives as
a1-AR antagonist.
3. Conclusion
In conclusion, 1,3-dipolar cycloaddition reaction of nitrili-
mines with 5-arylidene[1,3]dioxane-4,6-diones 1 proceeds highly
regioselectively affording 7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-
ene-6,10-diones 3 in good yields (60e79% yield). The constructed
heterocycles possess good vasorelaxant properties as exhibited
during in vitro activity screening using thoracic aortic rings of

A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
Compound 3i
4233
Compound 3h
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
-10
-20
-30
-40
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
10
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Concentration (mM)
Compound 3j
Concentration (mM)
Compound 3k
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
0
0.1
0.2
0.3
0.4
0.5
0.6
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Concentration (mM)
Concentration (mM)
Compound 3l
100
90
80
70
60
50
40
30
20
10
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Concentration (mM)
Fig. 1. (continued).
male Wister rats pre-contracted with norepinephrine hydro-
chloride according to the standard reported procedure.
Compounds 3f and 3j are the most active vasodilation derivatives
among all the tested analogues. Molecular modeling study was
undertaken based on a pharmacophore generation due to potent
a1-adrenoceptor antagonists possessing five features (positive
ionizable, hydrogen bonding acceptor and three hydrophobics).
Molecular modeling simulation studies including fit values due to
the generated pharmacophore and docking energy values into
optimized a1-AR homology models of the tested compounds 3a-l
are in good accord with the experimentally observed vaso-
relaxant properties. Additionally, comparing prazosin (potent

4234
A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
MERCURY 300 (1H: 300; 13C: 75 MHz) spectrometer. The starting
compounds 1a-f [26e30] and 2a,b [31,32] were prepared according
to the previously reported procedures.
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
4.1. Reaction of 1a-f with hydrazonoyl chlorides 2a,b (general
procedure)
A mixture of equimolar amounts of 1a-f (5 mmol) and the cor-
responding 2a,b in dry benzene (25 ml) containing triethylamine
(7.5 mmol) was heated under reflux for the appropriate time. The
reaction mixture was filtered while hot to remove triethylamine
hydrochloride then, was stored at room temperature (20e25 ꢁC)
overnight. Separated solid was collected and recrystallized from
a suitable solvent affording the corresponding 3a,e,g,i. In the case
of 3b-d,f,h,j-l the reaction mixture was evaporated till dryness
under reduced pressure and the remaining residue was triturated
with methanol (5 ml). Separated solid material was collected and
crystallized from a suitable solvent.
3a
3b
3c
3d
3e
3f
3h
3i
3j
3k
3l
Tested Compounds
Fig. 2. Potency (IC50, mM) of the tested compounds on contracture induced by
norepinephrine hydrochloride in rat thoracic aortic rings.
a1-AR) docking behavior with that of our constructed analogues,
exhibited that the pyrazolinyl moiety was perfectly aligned with
the piperazinyl nucleus of prazosin while, the aryl group oriented
at the 4-position of the constructed heterocycles superimposed
with the furanyl moiety of prazosin. These observed features
support the attained SAR assumptions due to vasodilation
activity screening data of the prepared compounds 3, which
could be considered promising hits for developing good effective
leads.
4.1.1. 4-(4-Chlorophenyl)-8,8-dimethyl-1,3-diphenyl-7,9-dioxa-1,2-
diaza-spiro[4.5]dec-2-ene-6,10-dione (3a)
Reaction time 12 h, colorless microcrystals from n-butanol, mp
201e203 ꢁC, yield 70%. IR: nmax/cmꢀ1 1788, 1747 (C]O), 1596, 1495
(C]N, C]C). 1H NMR (CDCl3):
d
1.74 (s, 3H, CH3), 1.78 (s, 3H, CH3),
5.35 (s, 1H, H-4), 7.00e7.53 (m, 14H, arom. H). 13C NMR (DMSO- d6):
d 29.3, 30.0 (CH3), 62.0 (HC-4), 74.7 (C-5 “spiro-carbon”), 108.4 (C-
4. Experimental
8), 113.9, 114.5, 121.7, 127.4, 129.1, 129.3, 130.1, 130.3, 132.3, 132.7,
134.5, 142.7, 148.8 (arom. C), 161.2, 164.2 (C]O). Anal. Calcd. for
C26H21ClN2O4 (460.92): C, 67.75; H, 4.59; N, 6.08. Found: C, 67.88; H,
4.58; N, 5.93.
Melting points were recorded on a Stuart SMP3 digital melting
point apparatus. IR spectra (KBr) were recorded on a JASCO 6100
FT-IR spectrophotometer. NMR spectra were recorded on a Varian
NH2
O
N
N
H
O
N
N
O
O
N
N
O
N
N
N
O
O
I (Prazosin)
II (5-Methylurapidil)
O
N
O
N
N
O
N
O
N
H
N
O
OH
N
O
N
O
III (BMY-7378)
IV (B8805-033)
O
H
N
O
O
O
O
O
N
N
O
O
N
O
N
VI (WB 4101)
V
Scheme 2. Structure of potent a1-adrenoceptor antagonists.

A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
4235
Fig. 3. (A) Constraint distances of a1-AR antagonist hypothesis. (B) Constraint angles of a1-AR antagonist hypothesis. (C) and (D) Mapping of a1-AR antagonist pharmacophore with
compounds BMY-7378 and 3j, respectively.

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A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
Table 2
Comparison of the constraint distances and angles between the features of the reported Barbaro’s a1-AR antagonist hypothesis and the features of our hypothesis.
Dimensions
Barbaro’s hypothesis
Our hypothesis
ꢀ
Constraint distances (A) between features of Barbaro’s
and our hypothesis
PI-HBA, 5.62; PI-HY1, 6.69; PI-HY2, 6.17;
PI-HY3, 9.78
Not reported
PI-HBA, 6.18; PI-HY1, 7.35; PI-HY2, 6.11; PI-HY3, 8.54
Constraint angles (ꢁ) between features of Barbaro’s and
our hypothesis
PI-HY3-HBA, 31.13; PI-HY2-HBA, 26.89; PI-HY2-HY3,
90.74; PI-HBA vector, 101.43
4.1.2. 1-(3-Chlorophenyl)-4-(4-chlorophenyl)-8,8-dimethyl-3-
phenyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3b)
Reaction time 15 h, colorless microcrystals from n-butanol, mp
200e202 ꢁC, yield 61%. IR: nmax/cmꢀ1 1779, 1745 (C]O), 1592, 1483
(C]N, C]C). 1H NMR (CDCl3):
3.77 (s, 3H, OCH3), 5.36 (s,1H, H-4), 6.84e7.56 (m,14H, arom. H). 13
NMR (CDCl3): 29.6, 30.1 (CH3), 55.4 (OCH3), 66.5 (HC-4), 76.8 (C-5
“spiro-carbon”), 107.1 (C-8), 114.7, 115.8, 122.3, 124.1, 127.0, 128.6,
129.2, 129.5, 130.6, 131.8, 143.2, 147.1, 160.5 (arom. C), 161.4, 165.6
(C]O). Anal. Calcd. for C27H24N2O5 (456.50): C, 71.04; H, 5.30; N,
6.14. Found: C, 71.51; H, 5.32; N, 6.10.
d 1.72 (s, 3H, CH3), 1.78 (s, 3H, CH3),
C
d
(C]N,C]C).1H NMR (CDCl3):
d
1.75(s, 3H, CH3),1.82(s, 3H, CH3), 5.34
(s,1H, H-4), 6.90e7.51 (m,13H, arom. H).13C NMR (CDCl3):
d
29.7, 29.9
(CH3), 65.8 (HC-4), 76.4 (C-5 “spiro-carbon”), 107.5 (C-8), 113.2, 116.1,
122.3, 127.1, 128.8, 129.2, 129.8, 130.5, 131.8, 135.5, 136.0, 144.0, 147.4
(arom. C),161.0,164.9 (C]O). Anal. Calcd. for C26H20Cl2N2O4 (495.37):
C, 63.04; H, 4.07; N, 5.66. Found: C, 63.08; H, 3.89; N, 5.55.
4.1.6. 1-(3-Chlorophenyl)-8,8-dimethyl-4-(4-methoxyphenyl)-3-
phenyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3f)
Reaction time 16 h, pale yellow microcrystals from n-butanol,
mp 197e199 ꢁC, yield 65%. IR: nmax/cmꢀ1 1781, 1744 (C]O), 1593,
4.1.3. 8,8-Dimethyl-1,3-diphenyl-4-(4-fluorophenyl)-7,9-dioxa-1,2-
diaza-spiro[4.5]dec-2-ene-6,10-dione (3c)
1512 (C]N, C]C). 1H NMR (CDCl3):
d
1.73 (s, 3H, CH3), 1.82 (s, 3H,
CH3), 3.78 (s, 3H, OCH3), 5.36 (s, 1H, H-4), 6.84e7.53 (m, 13H, arom.
H). 13C NMR (CDCl3):
29.7, 30.1 (CH3), 55.4 (OCH3), 66.5 (HC-4),
Reaction time 14 h, colorless microcrystals from n-butanol, mp
213e215 ꢁC, yield 77%. IR: nmax/cmꢀ1 1791, 1750 (C]O), 1600, 1500
d
(C]N, C]C). 1H NMR (CDCl3):
d
1.72 (s, 3H, CH3), 1.77 (s, 3H, CH3),
5.38 (s, 1H, H-4), 7.02e7.51 (m, 14H, arom. H). 13C NMR (DMSO- d6):
29.4, 30.0 (CH3), 62.1 (HC-4), 74.7 (C-5 “spiro-carbon”), 108.4
76.8 (C-5 “spiro-carbon”), 107.4 (C-8), 113.0, 114.7, 115.9, 122.0,
123.8, 127.1, 128.6, 129.5, 130.3, 130.4, 131.8, 135.4, 144.2, 147.8
(arom. C), 160.6, 161.1 (C]O). Anal. Calcd. for C27H23ClN2O5
(490.95): C, 66.06; H, 4.72; N, 5.71. Found: C, 66.53; H, 4.71; N, 5.67.
d
(C-8), 114.5, 116.1, 116.4, 121.7, 127.4, 129.3, 129.6, 130.1, 130.4, 133.2,
142.8, 149.0 (arom. C), 161.3, 164.3 (C]O). Anal. Calcd. for
C26H21FN2O4 (444.47): C, 70.26; H, 4.76; N, 6.30. Found: C, 70.25; H,
4.74; N, 6.20.
4.1.7. 8,8-Dimethyl-4-(4-dimethylaminophenyl)-1,3-diphenyl-7,9-
dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3g)
Reaction time 12 h, colorless microcrystals from benzene, mp
4.1.4. 1-(3-Chlorophenyl)-8,8-dimethyl-4-(4-fluorophenyl)-3-
phenyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3d)
Reaction time 15 h, colorless microcrystals from n-butanol, mp
170e172 ꢁC, yield 67%. IR: nmax/cmꢀ1 1781, 1744 (C]O), 1594, 1509
229e231 ꢁC, yield 68%. IR: nmax/cmꢀ1 1787, 1750 (C]O), 1604, 1522
(C]N, C]C). 1H NMR (CDCl3):
d
1.76 (s, 3H, CH3), 1.79 (s, 3H, CH3),
2.94 (s, 6H, NMe2), 5.33 (s,1H, H-4), 6.71e7.59 (m,14H, arom. H). 13
NMR (DMSO- d6): 29.5, 30.0 (CH3), 40.3 (NCH3), 63.3 (HC-4), 74.9
C
d
(C]N, C]C). 1H NMR (CDCl3):
d
1.73 (s, 3H, CH3), 1.81 (s, 3H, CH3),
5.39 (s, 1H, H-4), 6.90e7.55 (m, 13H, arom. H). 13C NMR (CDCl3):
29.6, 29.9 (CH3), 65.9 (HC-4), 76.5 (C-5 “spiro-carbon”), 107.5
(C-5 “spiro-carbon”), 107.9 (C-8), 112.2, 114.3, 119.5, 121.2, 127.4,
129.1, 129.7, 130.0, 130.9, 131.7, 143.0, 149.2, 150.7 (arom. C), 161.2,
164.6 (C]O). Anal. Calcd. for C28H27N3O4 (469.55): C, 71.63; H,
5.80; N, 8.95. Found: C, 71.71; H, 5.92; N, 8.94.
d
(C-8), 113.2, 116.1, 122.2, 126.5, 127.1, 128.0, 128.7, 129.2, 129.7, 129.9,
130.5, 132.4, 135.4, 144.1, 147.6, 161.0 (arom. C), 161.7, 165.0 (C]O).
Anal. Calcd. for C26H20ClFN2O4 (478.91): C, 65.21; H, 4.21; N, 5.85.
Found: C, 65.30; H, 4.15; N, 5.74.
4.1.8. 1-(3-Chlorophenyl)-8,8-dimethyl-4-(4-
dimethylaminophenyl)-3-phenyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-
2-ene-6,10-dione (3h)
4.1.5. 8,8-Dimethyl-1,3-diphenyl-4-(4-methoxyphenyl)-7,9-dioxa-
1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3e)
Reaction time 15 h, colorless microcrystals from n-butanol,
mp 214e216 ꢁC, yield 64%. IR: nmax/cmꢀ1 1747 (C]O), 1594, 1524
Reaction time 10 h, colorless microcrystals from n-butanol, mp
(C]N, C]C). 1H NMR (CDCl3):
d
1.77 (s, 3H, CH3), 1.82 (s, 3H,
CH3), 2.96 (s, 6H, NMe2), 5.34 (s, 1H, H-4), 6.80e7.58 (m, 13H,
arom. H). 13C NMR (CDCl3):
29.7, 30.1 (CH3), 40.3 (NCH3), 67.1
210e212 ꢁC, yield 70%. IR: nmax/cmꢀ1 1779, 1745 (C]O), 1598, 1503
d
Table 3
(HC-4), 76.5 (C-5 “spiro-carbon”), 107.3 (C-8), 112.3, 112.8, 115.7,
118.3, 121.7, 127.2, 128.6, 129.3, 130.4, 130.6, 131.4, 135.4, 144.3,
148.1, 151.0 (arom. C), 161.2, 165.4 (C]O). Anal. Calcd. for
C28H26ClN3O4 (503.99): C, 66.73; H, 5.20; N, 8.34. Found: C,
66.81; H, 5.04; N, 8.25.
Best fit and docking conformer for each compound in the test set (3ael) mapped
with generated a1-AR antagonist pharmacophore and binding pocket of homology
model.
Entry
Compound
R
R0
Fit
value
Docking
value
(kcal/mol)
4.1.9. 8,8-Dimethyl-1,3-diphenyl-4-(2-thienyl)-7,9-dioxa-1,2-
diaza-spiro[4.5]dec-2-ene-6,10-dione (3i)
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3f
3g
3h
3i
4-ClC6H4
4-ClC6H4
4-FC6H4
4-FC6H4
4-H3COC6H4
4-H3COC6H4
4-(CH3)2NC6H4
4-(CH3)2NC6H4
2-thienyl
2-thienyl
5-methyl-2-furanyl
5-methyl-2-furanyl
Ph
3-ClC6H4
Ph
3-ClC6H4
Ph
3-ClC6H4
Ph
3-ClC6H4
Ph
3-ClC6H4
Ph
2.89
3.77
1.93
2.79
2.95
3.91
2.92
3.85
3.30
3.95
2.91
2.65
ꢀ66.21
ꢀ71.87
ꢀ58.99
ꢀ64.72
ꢀ66.53
ꢀ75.25
ꢀ66.54
ꢀ70.56
ꢀ69.44
ꢀ77.45
ꢀ65.86
ꢀ61.72
Reaction time 15 h, colorless microcrystals from n-butanol, mp
219e221 ꢁC, yield 69%. IR: nmax/cmꢀ1 1782, 1747 (C]O), 1597, 1497
(C]N, C]C). 1H NMR (CDCl3):
d
1.78 (s, 3H, CH3), 1.81 (s, 3H, CH3),
5.68 (s, 1H, H-4), 6.99e7.61 (m, 13H, arom. H). 13C NMR (CDCl3):
29.9 (CH3), 60.7 (HC-4), 76.8 (C-5 “spiro-carbon”), 107.2 (C-8),
d
116.1, 122.6, 126.9, 127.9, 128.2, 128.7, 129.4, 129.5, 130.5, 130.9,
133.4, 143.2, 146.2 (arom. C), 161.1, 165.2 (C]O). Anal. Calcd. for
C24H20N2O4S (432.50): C, 66.65; H, 4.66; N, 6.48. Found: C, 66.67; H,
4.55; N, 6.40.
9
10
11
12
3j
3k
3l
3-ClC6H4

A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
4237
ꢀ
Fig. 4. (A) and (B) docking of prazosin and compound 3j into a1-AR with distance between Asp 106 carbonyl O, piperazinyl N of prazosin and pyrazolinyl N of compound 3j are 5.6 A
and 6.2 A, respectively. (C) Alignment of docked compound 3j and prazosin with the binding pocket.
ꢀ
4.1.10. 1-(3-Chlorophenyl)-8,8-dimethyl-3-phenyl-4-(2-thienyl)-
7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3j)
(C]N, C]C). 1H NMR (CDCl3):
furanyl CH3), 5.54 (s,1H, H-4), 5.93e7.61 (m,12H, arom. H). 13C NMR
(CDCl3): 13.8 (furanyl CH3), 29.4, 29.6 (CH3), 59.2 (HC-4), 74.8 (C-5
“spiro-carbon”), 107.2 (C-8), 108.2, 114.5, 115.0, 122.1, 126.7, 128.7,
129.1, 129.4, 129.5, 130.6, 142.7, 143.6, 144.1, 153.4 (arom. C), 161.3,
165.2 (C]O). Anal. Calcd. for C25H22N2O5 (430.46): C, 69.76; H, 5.15;
N, 6.51. Found: C, 69.64; H, 5.12; N, 6.35.
d 1.86 (s, 6H, 2CH3), 2.28 (s, 3H,
Reaction time 16 h, colorless microcrystals from n-butanol, mp
d
219e221 ꢁC,yield60%. IR:nmax/cmꢀ11778,1746 (C]O),1591,1480 (C]
N, C]C). 1H NMR (CDCl3):
d
1.79 (s, 3H, CH3), 1.85 (s, 3H, CH3), 5.68 (s,
1H, H-4), 6.81e7.79 (m,12H, arom. H).13C NMR (DMSO- d6):
d
29.3, 30.1
(CH3), 57.9 (HC-4), 74.7 (C-5 “spiro-carbon”), 108.6 (C-8), 112.0, 114.8,
121.3, 127.6, 127.8, 129.3, 129.6, 130.2, 130.4, 131.1, 131.9, 134.8, 144.0,
149.4 (arom. C), 160.5, 163.7 (C]O). Anal. Calcd. for C24H19ClN2O4S
(466.95): C, 61.73; H, 4.10; N, 6.00. Found: C, 61.92; H, 4.04; N, 5.81.
4.1.12. 1-(3-Chlorophenyl)-8,8-dimethyl-4-(5-methyl-2-furanyl)-3-
phenyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione
(3l).
Reaction time 16 h, yellow microcrystals from n-butanol, mp
4.1.11. 8,8-Dimethyl-1,3-diphenyl-4-(5-methyl-2-furanyl)-7,9-
dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-dione (3k)
199e201 ꢁC, yield 60%. IR: nmax/cmꢀ1 1786, 1750 (C]O), 1591, 1480
(C]N, C]C). 1H NMR (CDCl3):
d
1.88 (s, 6H, 2CH3), 2.28 (s, 3H,
furanyl CH3), 5.54 (s,1H, H-4), 5.90e7.61 (m,11H, arom. H). 13C NMR
(CDCl3): 13.8 (furanyl CH3), 29.4, 29.6 (CH3), 59.3 (HC-4), 74.4 (C-5
Reaction time 15 h, colorless microcrystals from n-butanol, mp
207e209 ꢁC, yield 79%. IR: nmax/cm-1 1779, 1748 (C]O), 1596, 1498
d

4238
A.S. Girgis et al. / European Journal of Medicinal Chemistry 45 (2010) 4229e4238
“spiro-carbon”), 107.5 (C-8), 108.2, 112.3, 114.7, 115.4, 121.8, 126.9,
128.7, 129.7, 130.2, 130.5, 135.5, 143.3, 143.7, 144.9, 153.6 (arom. C),
161.0, 164.9 (C]O). Anal. Calcd. for C25H21ClN2O5 (464.91): C,
64.59; H, 4.55; N, 6.03. Found: C, 64.68; H, 4.47; N, 5.91.
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This work is sponsored by the U.S. e Egypt Science and Tech-
nology Joint Fund under project No. MAN10-007-002.