Novel 4(3H)-quinazolinone analogs: Synthesis and anticonvulsant activity

Article abstract of DOI:10.1007/s00044-012-0280-y

A new series of quinazoline analogs was designed, synthesized, and evaluated for their anticonvulsant activity. Compounds 6, 12, 21, 36, 37, and 38 showed 70-100 % protection against PTZ-induced seizures acting as GABA _A receptor agonists. Compound N-(3,4,5,6-tetrachloro-phthalimido)-2- [(3-phenyl-4-oxo-6-methyl-3H-quinazolin-2-yl)-thio]acetamide (12) representing the moderate active compounds and 2-[6-iodo-4-oxo-2-(thiophen-2-yl)-quinazolin- 3(4H)-yl]-isoindoline-1,3-dione (38) representing the remarkably active compounds in this stud, showed ED₅₀ values of 457 and 251 mg/kg; TD₅₀ values of 562 and 447 mg/kg; PI values of 1.22 and 1.78, LD ₅₀ values of 1,288 and 1,380 mg/kg, and TI values of 2.82 and 5.50, respectively. Compound 38 proved to be almost twofold more active than the standard drug sodium valproate.

Full text of DOI:10.1007/s00044-012-0280-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:2815–2827
DOI 10.1007/s00044-012-0280-y
ORIGINAL RESEARCH
Novel 4(3H)-quinazolinone analogs: synthesis and anticonvulsant
activity
•
Adel S. El-Azab Sami G. Abdel-Hamide Mohamed M. Sayed-Ahmed
•
•
•
Ghada S. Hassan Tariq M. El-Hadiyah Othman A. Al-Shabanah
•
•
•
Omar A. Al-Deeb Hussein I. El-Subbagh
Received: 25 June 2012 / Accepted: 15 October 2012 / Published online: 26 October 2012
Ó Springer Science+Business Media New York 2012
Abstract A new series of quinazoline analogs was
designed, synthesized, and evaluated for their anticonvulsant
activity. Compounds 6, 12, 21, 36, 37, and 38 showed
70–100 % protection against PTZ-induced seizures acting as
GABAA receptoragonists. Compound N-(3,4,5,6-tetrachloro-
phthalimido)-2-[(3-phenyl-4-oxo-6-methyl-3H-quinazolin-
2-yl)-thio]acetamide (12) representing the moderate active
compounds and 2-[6-iodo-4-oxo-2-(thiophen-2-yl)-quinaz-
olin-3(4H)-yl]-isoindoline-1,3-dione (38) representing the
remarkably active compounds in this stud, showed ED50
values of 457 and 251 mg/kg; TD50 values of 562 and
447 mg/kg; PI values of 1.22 and 1.78, LD50 values of 1,288
and 1,380 mg/kg, and TI values of 2.82 and 5.50,
respectively. Compound 38 proved to be almost twofold
more active than the standard drug sodium valproate.
Keywords Synthesis Á 4(3H)-Quinazolinones Á
Anticonvulsant activity
Introduction
Methaqualone (1) as a quinazoline analog is an important
landmark in the field of synthetic anticonvulsants; its
6-chloro analog (2) found to possess marked anticonvulsant
potency, which is 1.5 times more potent than phenytoin
sodium against electroshock-induced convulsions and 10
times more active than troxidone against pentylenetetrazol
(PTZ)-induced seizures (Armarego, 1963; Bhaduri et al.,
1964; Salimath et al., 1956), Chart 1. In spite of the fact that
literally hundreds of quinazolinones related to compound 1
have been synthesized and tested for their anticonvulsant
activity, none of those drugs are currently in use. A persistent
problem with those compounds arises from the fact that
nearly every derivative tested exhibited neurotoxicity values
(TD50’s) which are less or slightly higher than the effective
doses (ED50’s), (Barthwal et al., 1973). Consequently, the
protective index (PI) corresponding to TD50/ED50 is too low.
The discovery of 3-tolyl-4(3H)-quinazolinones, which pos-
sessed an adequate separation between the anticonvulsant
and the sedative properties, inspired the synthesis of a series
of 2-[2-oxo-2-(4-pyridyl)-ethyl]-3-aryl-4(3H)-quinazoli-
nones (3, 4) with a single ortho substituent. Compounds 3
and 4 showed remarkable protection against maximal elec-
troshock and subcutaneous metrazol-induced seizures,
Chart 1 (Wolfe et al., 1990).
A. S. El-Azab Á G. S. Hassan Á O. A. Al-Deeb
Department of Pharmaceutical Chemistry, College of Pharmacy,
King Saud University, Riyadh 11451, Saudi Arabia
A. S. El-Azab
Department of Organic Chemistry, Faculty of Pharmacy,
Al-Azhar University, Cairo 11884, Egypt
S. G. Abdel-Hamide
Department of Pharmaceutical Chemistry, College of Pharmacy,
Salman Bin Abdulaziz University, Alkharj, Saudi Arabia
M. M. Sayed-Ahmed Á T. M. El-Hadiyah Á O. A. Al-Shabanah
Department of Pharmacology, College of Pharmacy, King Saud
University, Riyadh 11451, Saudi Arabia
G. S. Hassan
Department of Medicinal Chemistry, Faculty of Pharmacy,
Mansoura University, Mansoura 35516, Egypt
H. I. El-Subbagh (&)
Department of Pharmaceutical Chemistry, Faculty
of Pharmaceutical Sciences & Pharmaceutical Industries,
Future University, Cairo 12311, Egypt
e-mail: subbagh@yahoo.com
The present study is a continuation to the previous
efforts aiming to locate novel synthetic anticonvulsant lead
123

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Med Chem Res (2013) 22:2815–2827
Chart 1 Structures of literature
cited anticonvulsants
O
O
N
O
N
Cl
N
N
N
CH3
CH3
CH3
CH3
CH3
N
O
N
1
2
3
O
N
N
O
N
Cl
I
N
CH2COOH
O
S
N
5
4
¨
compound(s) (Loscher and Nau, 1985; Swinyard et al.,
1986; Archana and Kumar, 2002; Welch et al., 2001).
Some new quinazoline analogs prepared in our laboratory
possessed remarkable anticonvulsant activity, showing
100 % protection against PTZ-induced clonic convulsion
(Elmazar et al., 1993; El-Subbagh et al., 2011; Abdel-
Hamide et al., 2001), such as 6-iodo-3-benzyl-4-oxo-3H-
quinazoline-2-thioacetic acid (5, ED50 73.1 mg/kg). Based
on these considerations, new series of quinazoline analogs
is designed to accommodate thioacetic acid hydrazide at
C-2, which then used to produce cyclic-imines. Phenyl or
benzyl moiety was introduced to position 3- and electron
donating CH3 group or electron withdrawing NO2 group to
position 6- to investigate their electronic effect on activity
(A). Another new series is designed to accommodate sul-
fur-containing aryl moiety, such as thiophone at position
2-(B), and either oxygen or nitrogen connected to a free
amino group to position 3-(C). The 3-amino function was
then used to produce the cyclic-imines D. Meanwhile, the
2-thioacetic acid hydrazide moiety of A was moved to
position 4- and used to synthesize the cyclic-imines E,
Chart 2. These structure alterations, and modifications, are
known to contribute to the anticonvulsant activity of the
quinazoline nucleus (Armarego, 1963; Bhaduri et al., 1964;
Salimath et al., 1956; Barthwal et al., 1973; Wolfe et al.,
1990). Such structural alteration is expected to enhance the
anticonvulsant potency and produce compounds with rea-
sonable protective index (PI).
bromoacetate in boiling acetone. Upon refluxing compound 7
with hydrazine hydrate in boiling ethanol, a mixture of two
unexpected products were obtained, namely 2-hydrazinyl-6-
methyl-3-phenyl-quinazolin-4(3H)-one (8) and 2-hydrazinyl-
6-methyl-quinazolin-4(3H)-one (9), which were separated by
the use of column chromatography (20 % EtOH/Hexane). As
an attempt to circumvent this problem and to avoid getting
these unexpected products and reach the target intermediate
10, compound 7 was stirred at room temperature for a long
period of time with hydrazine hydrate. This attempt ended up
with fruition and 2-(6-methyl-4-oxo-3-phenyl-3,4-dihy-
droquinazolin-2-yl-thio)aceto-hydrazide (10) was obtained in
goodyieldandconsiderablepurity. Compound10 wasreacted
with substituted phathalic anhydride or 1,8-naphthalic anhy-
dride in acetic acid to give N-(substituted-phthalimido)-2-(3-
phenyl-4-oxo-6-methyl-3H-quinazolin-2-yl)thioacetamide
(11–13) and N-(1,8-naphthalimido)-2-(3-phenyl-4-oxo-6-
methyl-3H-quinazolin-2-yl)thioacetamide (14) (Scheme 1;
Table 1). Upon treating 10 with other anhydrides, such as
succinic, malic and tetrahydro-phathalic anhydrides under
the same condition, the starting material 10 was always
recovered unreacted. Unfortunately, when more drastic
condition was employed, such as fusion, the starting material
2-mercapto-6-methyl-3-phenyl-quinazolin-4(3H)-one (6)
was obtained with the elimination of the 2-thioacetohyd-
razide moiety, Scheme 1. 2-Mercapto-6-methyl-3-benzyl-4-
oxo-quina-zoline (15) was alkylated with ethylbromoacetate
to produce the thioalkyl ester 16. Interaction of the latter
compound with hydrazine hydrate in absolute ethanol led to
the formation of the acetic acid hydrazide analog 17. The
acid hydrazide 17 was allowed to react with substituted
phthalic, 1,8-naphthalic, and succinic anhydrides in boiling
acetic acid to give 1-substituted phthalimido, 1,8-naphtha-
limido, and succinimido analogs 18–22 (Scheme 2,
Table 1). The same behavior noticed with the hydrazide 10
toward the used anhydrides also occurred to hydrazide 17
affording either the starting material 15 or the isolation of 17
Results and discussion
Chemistry
2-(Ethoxycarbonyl-methylthio)-3-phenyl-4-oxo-6-methyl-
(3H)-quinazoline (7) was prepared by reacting 2-mercapto-
6-methyl-3-phenyl-4-oxo-(3H)-quinazoline (6) with ethyl
123

Med Chem Res (2013) 22:2815–2827
2817
Chart 2 General structures of
the new designed
anticonvulsants
O
N
O
N
O
N
I
NH2
S
X
R
S
I
N
N
X
O
H
N
N
O
S
O
C
A
B
X = NO2, CH3
R = Ph, Bn
X = O, NH
O
H
N
O
O
O
N
N
I
O
I
N
N
O
O
N
N
S
S
E
D
Anticonvulsant screening
upon work up unreacted. The 2-sulfhydryl function of 23 and
24 was alkylated with ethylbromoacetate to afford the thi-
oalkyl ester analogs 25 and 26, respectively. Attempts to
prepare the corresponding acid hydrazides 27 and 28 failed;
instead, the starting materials 23 and 24 were retrieved or the
corresponding 2-hydrazino analogs 29 and 30 were obtained
depending on the amount of hydrazine hydrate used and the
duration of reaction under reflux. It seems that the strong
electron withdrawing effect of the 6-NO2 group facilitates
the cleavage of the alkyl side chain or the replacement of the
sulfur side chain attached to the 2- position of the quinazoline
nucleus to give the hydrazine analogs 29 and 30. Reaction of
the 2-hydrazino analog 30 with 1,8-naphthalic anhydride in
boiling acetic acid afforded the corresponding cyclic-imide
analog 31 (Scheme 3; Table 1). The key benzoxazone
intermediate 35 was prepared by the reaction of 2-iodo-
anthranilic acid 32 with 2-thiophenecarbonyl chloride 33 to
obtain the amide 34, which was refluxed in acetic anhydride
to afford compound 35. Condensation of 35 with hydrazine
hydrate afforded 3-amino derivative 36. Compound 36 was
reacted with benzoyl chloride in pyridine to afford the
benzamide analog 37 also with various anhydrides in acetic
acid to afford the corresponding compounds 38–40,
respectively (Scheme 4; Table 1). The intermediate 35 was
heated under reflux with formamide to afford 2-(2-thieno)-6-
iodo-3,4-dihydroquinazolin-4-one (42). Alkylation of the
latter compound with ethyl bromoacetate in boiling acetone
affords the O-alkyl derivative 43. Interaction of 43 with
hydrazine hydrate in absolute ethanol at room temperature
led to the formation of hydrazide derivative 44. The reaction
of compound 44 with substituted phthalic anhydrides or 1,8-
naphthalic anhydride affords substituted phthalimido and
naphthalimido analogs 45–48 (Scheme 4, Table 1). The
same behavior of 10 and 17 toward succinic, malic, and
tetrahydro-phathalic anhydrides was also observed in the
case of the hydrazide 44 affording either the starting material
42 or the isolation of 44 upon work up, unreacted.
Four animal models were adopted to evaluate the anticon-
vulsant potency, namely: pentylenetetrazole (PTZ)-, maximal
electroshock (MES)-, picrotoxin (Pic)-, and bicuculline (Bic)-
induced convulsions. The anticonvulsant activities of the new
synthesized compounds against pentylenetetrazole (PTZ)-
induced seizures are shown in Table 2. PTZ (85 mg/kg, s.c.)
was given 30 min after the administration of each of the tested
compounds (1.5 mmol, i.p.). Only six compounds (6, 12, 21,
36, 37, and 38) resulted in 70–100 % protection against PTZ-
induced seizures. On the other hand, ten compounds showed
minimal (30 %) protection against PTZ-induced convulsions.
Two compounds (10 and 17) produced 100 % mortality
within 4–7 min before the administration of PTZ. The
remaining 21 compounds showed no anticonvulsant activity
against PTZ-induced seizures. Compounds 12, 21, and 38
produced 70, 30, and 30 % protection against MES-induced
tonic extension seizure, respectively (Table 2). These
findings suggest that those compounds possess the ability
to prevent the spread of seizure discharge throughout
neuronal tissues and to raise seizure threshold. Compounds
6, 36, and 37 proved to be inactive in such test. Picrotoxin is
a chloride channel blocker producing depolarization and
clonic convulsions. All the tested compounds produced
80–100 % protection against picrotoxin-induced convul-
sions suggesting that those compounds may act as GABAA
receptor agonist by increasing chloride influx via brain
chloride channels (Table 2). Bicuculline is a GABAA
receptor blocker inducing clonic convulsions. All the tes-
ted compounds produced 100 % protection against bicu-
culline-induced convulsions suggesting that the active
compounds may act directly as GABAA receptor agonist or
indirectly by increasing GABA synthesis or its release as a
brain inhibitory neurotransmitter (Table 2). A dose
response curve for the moderately active compounds 12
and the remarkably active anticonvulsant agents 38 was
123

2818
Med Chem Res (2013) 22:2815–2827
Scheme 1 Synthetic route for
the preparation of the target
compounds 11–14
O
N
H3C
N
SH
6
BrCH2COOEt
Acetone,K2CO3
O
N
O
N
O
H3C
H3C
H3C
N
NH
NH2NH2
+
N
S
NHNH2
N
NHNH2
O
OEt
EtOH,reflux
7
8
9
NH2NH2
EtOH,r.t.
O
N
O
H3C
N
O
N
O
X
H3C
S
N
O
O
N
S
O
NH
O
NH
10
O
H2N
X
O
O
O
11: X = H
12: X = tetrachloro
13: X = tetrabromo
O
N
H3C
N
S
N
O
O
NH
O
14
Structure activity correlations
performed along with the median effective (ED50), median
sedative (TD50), protective index (PI), and the acute tox-
icity determination (LD50). Results are shown in Table 3.
Compounds 12 and 38 showed ED50 values of 457 and
251 mg/kg, TD50 values of 562 and 447 mg/kg, PI (95 %
CL) values of 1.22 and 1.78, LD50 (95 % CL) values of
1,288 and 1,380 mg/kg, and TI (95 % CL) values of 2.82
and 5.50, respectively. Compound 38 proved to be almost
twofold more active than the standard drug sodium
valproate.
In the present study, structure activity correlations of the
obtained results revealed that the anticonvulsant activity
is embedded in the designed quinazolines. The starting
material 2-mercapto-6-methyl-3-phenyl-4-oxo-(3H)-quinaz-
oline (6) showed 70 % protection against PTZ-induced
convulsions. Replacement of the 3-phenyl of 6 by 3-benzyl
function produced compound 15 with total loss of activity.
In the 3-phenyl series, the replacement of the 2-sulfhydryl
123

Med Chem Res (2013) 22:2815–2827
2819
investigation (36, 37, and 38). The 3-amino analog 36
showed 100 % protection against PTZ-induced convul-
sions. Benzoylation of the 3-amino function of 36 gave the
benzamido analog 37 with preserved magnitude of activity.
The introduction of phthalimido function at position 3-
produced 38 with 100 % protection. Increasing the bulki-
ness of the substituents at position, 3- such as the tetra-
chloro- and tetrabromo-phthalimido analogs 39 and 40 as
well as 1,8-naphthalimido analog 41, produced inactive
compounds. Moving such substituents to position 4- of the
quinazoline nucleus, to be connected through ether linkage,
produced compounds 45–48, which were devoid of any
anticonvulsant activity.
Table 1 Physicochemical properties of the synthesized compounds
Compd. Solvent
Yield MP (°C) Molecular formula
7
EtOH
EtOH
EtOH
EtOH
AcOH
AcOH
AcOH
AcOH
EtOH
Dioxane
AcOH
AcOH
AcOH
AcOH
AcOH
EtOH
EtOH
75
50
60
60
65
50
45
53
69
50
35
60
50
35
39
75
69
130–35
174–5
198–9
287–90
189–91
254–5
293–4
182–4
153–5
[300
C19H18N2O3S
15H14N4O
C9H10N4O
8
C
9
10
11
12
13
14
16
17
18
19
20
21
22
25
26
29
30
31
38
39
40
41
45
46
47
48
C17H16N4O2S
C25H18N4O4S
C25H14Cl4N4O4S
C25H14Br4N4O4S
C29H20N4O3S
C20H20N2O3S
C18H18N4O2S
C26H20N4O4S
C26H16Cl4N4O4S
C26H16Br4N4O4S
C30H22N4O4S
C22H20N4O4S
C18H15N3O5S
C19H17N3O5S
C14H11N5O3
144–45
253–5
247–8
[300
Conclusion
The present study netted three compounds with 100 %
protection against PTZ-induced seizures which are 3-
amino-6-iodo-2-(thiophen-2-yl)-quinazolin-4(3H)-one (36),
N-[6-iodo-4-oxo-2-(thiophen-2-yl)quinazolin-3(4H)-yl]-
benzamide (37), and 2-[6-iodo-4-oxo-2-(thiophen-2-yl)-
quinazolin-3(4H)-yl]-isoindoline-1,3-dione (38), Chart 3.
Those compounds possess the ability to prevent the spread
of seizure discharge throughout neuronal tissues and to
raise seizure threshold. Those compounds proved to act as
GABAA receptor agonist by increasing chloride influx via
brain chloride channels or by increasing GABA synthesis
and its release as a brain inhibitory neurotransmitter. The
protective index (PI) of 38 proved to be 1.78 which insured
an adequate separation between the anticonvulsant activity
and the sedation property. Structure activity correlation of
the investigated quinazolines proved that the electron-
donating 6-CH3 function contribute to the anticonvulsant
activity rather than the electron-withdrawing 6-NO2 group.
The 3-phenyl moiety contributes to the activity rather than
the 3-benzyl function; the 2-thioacetamido moiety proved
important for activity. In the 3-phenyl series, phthalimido-
2-thioacetamide group preserved the anticonvulsant
potency rather than the 1,8-naphthalimido-2-thioacetamide
function; the opposite was noticed in the 3-benzyl series
where 1,8-naphthalimido-2-thioacetamide preserved the
potency rather than the phthalimido-2-thioacetamide
function. The obtained active compounds could be used as
lead template for future investigation and derivatization.
[300
174–5
165–6
193–5
202–4
271–3
237–39
197–96
299–300
190–92
178–80
[300
EtOH-benzene 60
EtOH-benzene 65
C15H13N5O3
C27H17N5O5
C20H10IN3O3S
AcOH
AcOH
AcOH
AcOH
AcOH
AcOH
AcOH
AcOH
AcOH
38
43
65
70
69
77
48
32
42
C
C
C
C
C
C
C
20H6Cl4IN3O3S
20H6Br4IN3O3S
24H12IN3O3S
20H13IN4O3S
22H9Cl4IN4O4S
22H9Br4IN4O4S
26H15IN4O4S
[300
285–6
function of 6 by N-(tetrachloro-phthalimido)-2-thioaceta-
mide moiety preserved the anticonvulsant activity (com-
pound 12 with its 70 % protection against PTZ-induced
convulsions), while its replacement with N-(1,8-naphtha-
limido)-2-thioacetamide led to 14 with total loss of activ-
ity. The contrary was observed in the 3-benzyl series,
compound 21 with its N-(1,8-naphthalimido)-2-thioaceta-
mide showed 70 % protection against PTZ-induced con-
vulsions, while its N-tetrachloro-phthalimido analogs 19
and 20 showed no sign of anticonvulsant activity.
Replacing the phthalimido or naphthalimido nucleus by
succinimide retained some of the activity as shown in
compound 22 with 30 % protection against PTZ-induced
convulsions. Replacement of the 6-CH3 function of the
quinazoline ring by 6-NO2 produced the inactive analog
31, which implies that electron donating functions favor the
activity rather than electron withdrawing moieties. In the
6-iodo-2-thieno-quinazoline series, three compounds
proved to be the most active anticonvulsants in the present
Experimental
Unless otherwise specified, all chemicals were of com-
mercial grade, used without further purification and were
obtained from Aldrich Chemical Co. (Milwaukee, WI,
USA). Solvents used for work ups were dried over MgSO4,
filtered, and removed on a rotary evaporator. Elemental
123

2820
Med Chem Res (2013) 22:2815–2827
Scheme 2 Synthetic route for
the preparation of the target
compounds 18–22
O
O
N
H3C
H3C
BrCH2COOEt
N
N
Acetone,K2CO3
N
S
SH
O
16
15
OEt
NH2NH2
EtOH,reflux
O
O
O
O
N
H3C
N
H3C
N
O
N
S
S
O
Aceticacid
O
O
NH
N
NH
H2N
O
17
22
O
O
O
O
O
X
Aceticacid
O
Aceticacid
O
N
O
N
H3C
H3C
N
N
S
N
S
N
O
O
O
NH
O
NH
O
O
X
18:
X = H
19: X = tetrachloro
20: X = tetrabromo-
21
analyses were performed at College of Pharmacy, Central
Laboratory, King Saud University. IR spectra (KBr) were
measured using a Mattson 5000 FT-IR Spectrophotometer
(m cm-1). Mass spectral (MS) data were obtained on a
according to reported procedures (Al-Obaid et al., 2009;
Al-Omar et al., 2004; Al-Rashood et al., 2006; Al-Omary
et al., 2010). Male Swiss albino mice (SWR) weighing
25–30 g, were obtained from the Animal Care Center,
College of Pharmacy, King Saud University, Riyadh, Saudi
Arabia, and were housed in metabolic cages under con-
trolled environmental conditions (25 °C and a 12 h light/
dark cycle). Animals had free access to pulverized standard
rat pellet food and tap water unless otherwise indicated.
The protocol of this study has been approved by Research
Ethics Committee of College of Pharmacy, King Saud
University, Riyadh, Kingdom of Saudi Arabia.
1
Shimadzu GC/MS QP 5000 apparatus. H and 13C NMR
spectra obtained at 400 and 100 MHz on a JEOL instru-
ment, respectively, using TMS as internal standard. Thin
layer and flash chromatography were performed using E.
Merck Silica gel (230–400 mesh). Preparative thin layer
chromatography was performed on Harrison model 7924 A
chromatotron using Analtech silica gel GF rotors. Com-
pounds 6, 15, 23, 24, 34–37, and 42–44 were prepared
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Med Chem Res (2013) 22:2815–2827
2821
Scheme 3 Synthetic route for
the preparation of the target
compound 31
O
N
O
N
O
N
O2N
NH2NH2,EtOH
R
S
N
O2N
R
O2N
R
S
N
N
BrCH2COOEt
SH
O
O
HN
NH2
23:
24: R = Bn
R = Ph
25:
R = Ph
26: R = Bn
27: R = Ph
28: R = Bn
OEt
O
N
O
O
O
O2N
O
N
N
O2N
R
N
NH
NH
NH2
N
O
O
29:
R = Ph
30: R = Bn
31
Chemistry
1H, NH, D2O exchangeable), 7.72 (s, 1H, Ar–H), 7.42 (d,
1H, J = 8.0 Hz, Ar–H), 7.24 (d, 1H, J = 8.0 Hz, Ar–H),
5.41 (s, 2H, NH2, D2O exchangeable), 4.36 (s, 1H, NH,
D2O exchangeable), 2.34 (s, 3H, CH3). 13C NMR: 20.9,
116.7, 124.8, 125.8, 131.2, 135.8, 146.9, 152.6, 161.3.
2-(Ethoxycarbonylmethyl)-thio-3-phenyl-4-oxo-6-methyl-
3H-quinazoline (7)
A mixture of 2-mercapto-3-phenyl-4-oxo-6-methyl-3H-
quinazoline (6, 2.68 g, 0.01 mol), ethylbromoacetate
(2.51 g, 0.015 mol), and anhydrous potassium carbonate
(2.0 g) in dry acetone (50 ml) was heated under reflux for
12 h. The reaction mixture was filtered while hot and the
filtrate was concentrated in vacuo to give the crude prod-
uct, which was crystallized from ethanol (Table 1). IR
(KBr, m cm-1): 1,741 and 1,693 (2 C=O). 1H NMR
(CDCl3): d 1.32 (t, 3H, J = 7 Hz, CH3CH2O), 2.49 (s, 3H,
CH3), 3.9 (s, 2H, S–CH2CO), 4.25 (q, 2H, J = 7 Hz,
CH3CH2), 7.37–7.39 (m, 2H, Ar–H), 7.48 (d, 1H,
J = 8.5 Hz, Ar–H), 7.55–7.58 (m, 4H, Ar–H), 8.04 (s, 1H,
Ar–H).
2-(6-Methyl-4-oxo-3-phenyl-3,4-dihydro-quinazolin-2-yl-
thio)acetohydrazide (10)
A solution of 2-(ethoxycarbonylmethyl)thio-3-phenyl-4-
oxo-6-methyl-3H-quinazo-line (7, 3.5 g, 0.01 mol) and
hydrazine hydrate (85 %, 3 ml) in ethanol (30 ml) was
stirred at room temperature for 7 days. The obtained solid
was filtered and dried to give compound 10. IR (KBr,
m cm-1): 1,741 and 1,693 (C=O). 1H NMR, (DMSO-d6): d
9.32 (s, 1H, NH, D2O exchangeable), 7.78 (s, 1H, Ar–H),
7.65(d, 1H, J = 8.0 Hz, Ar–H), 7.57–7.53 (m, 4H, Ar–H),
7.45 (d, 2H, J = 5.0 Hz, Ar–H), 4.31(s, 2H, NH2, D2O
exchangeable), 3.85 (s, 2H, CH2), 2.43 (s, 3H, CH3). 13C
NMR: 21.2, 34.9, 119.7, 126.3, 126.4, 129.9, 130.4, 136.0,
136.5, 145.8, 156.1, 156.8, 161.1, 166.7, 171.3.
2-Hydrazinyl-6-methyl-3-phenyl-quinazolin-4(3H)-one (8)
and 2-Hydrazinyl-6-methyl-quinazolin-4(3H)-one (9)
A solution of 2-(ethoxycarbonylmethyl)-thio-3-phenyl-4-
oxo-6-methyl-3H-quinazoline (7, 3.0 g, 0.01 mol) and
hydrazine hydrate (85 %, 3 ml) in ethanol (30 ml) was
heated under reflux for 1 h. The obtained solid was filtered,
dried, and chromatographed (silica gel, 100 g, elution with
N-(Substituted-phthalimido)-2-[(3-phenyl-4-oxo-6-
methyl-3H-quinazolin-2-yl)-thio]acet amide (11–13)
and N,N-(1,8-naphthalimido)-2-[(3-phenyl-4-oxy-6-
methyl-3H-quinazolin-2-yl)-thio]acetamide (14)
1
EtOAc-Hexan 1:8 v/v) to give compounds 8 and 9. H
A mixture of 10 (1.7 g, 0.005 mol) and the appropriate
anhydride (0.007 mol) was heated under reflux for 18 h.
The formed precipitate was filtered while hot, dried, and
crystallized from acetic acid (Table 1). 11: IR (KBr,
NMR, (DMSO-d6) 8: d 8.54 (s, 1H, NH, D2O exchange-
able), 7.81 (s, 1H, Ar–H), 7.78 (d,2H, J = 8.0 Hz, Ar–H),
7.42–7,035 (m, 4H, Ar–H), 7.11 (t, 1H, J = 7.0 Hz, Ar–
H), 4.63 (s, 2H, NH2, D2O exchangeable), 2.38 (s, 3H,
CH3). 13C NMR: 20.9, 117.2, 119.7, 123.3, 125.5, 125.8,
128.9, 133.0, 136.0, 138.2, 145.8, 146.0, 162.0. 9: d 8.09 (s,
1
m cm-1): 3,242 (CONH), 1731, 1699 (2 C=O). H NMR,
(DMSO-d6), d 2.44 (s, 3H, CH3), 4.11 (s, 2H, SCH2CO),
7.47–814 (m, 12H, Ar–H), 11.04 (s, 1H, CONH). 12: IR
123

2822
Med Chem Res (2013) 22:2815–2827
O
O
O
I
I
OH
OH
Cl
+
S
NH
NH2
S
O
33
32
34
Ac2O
O
O
O
N
O
I
NH
S
I
I
HCONH2
N
O
NH
N
N
O
S
S
Cl
37
42
35
BrCH2COOEt
NH2NH2
O
O
OEt
O
X
O
O
N
N
X
O
I
O
I
NH2
S
I
N
N
N
O
O
N
N
S
S
43
38: X = H
39: X = tetrachloro
40: X = tetrabromo
36
O
O
O
NH2NH2
O
H
N
O
O
NHNH2
N
X
O
O
O
N
O
X
I
I
O
S
I
O
S
O
O
N
N
N
O
N
N
N
S
41
45: X = H
44
O
46:
47:
X = tetrachloro
X = tetrabromo
O
O
O
H
N
N
O
I
O
S
O
N
N
48
Scheme 4 Synthetic route for the preparation of the target compounds 37–48
(KBr, m cm-1): 3,446 (NH), 1787, 1756, 1636 (3 C=O). 1H
NMR, (DMSO-d6), d 2.45 (s, 3H, CH3), 4.11 (s, 2H,
SCH2CO), 7.46–7.56 (m, 2H, Ar–H), 7.59–7.61 (m, 4H,
Ar–H), 7.71 (s, 1H), 11.28 (s, 1H, CONH, exchangeable).
MS: (M-C8Cl4NO2) m/z = 326 (4.35 %), M-C8Cl4HNO2,
m/z = 311 (7.4 %), M-C9Cl4HN2O3, m/z = 283 (6.4 %),
123

Med Chem Res (2013) 22:2815–2827
2823
(2.51 g, 0.015 mol), and anhydrous potassium carbonate
(2.0 g) in dry acetone (50 ml) was heated under reflux for
18 h. The reaction mixture was filtered while hot, and the
filtrate was concentrated in vacuo to give the crude product
Table 2 Potential anticonvulsant activity of the newly synthesized
compounds at dose of 1.5 mmol each, against PTZ, MES, and Pic and
Bic-induced clonic convulsions
Compd.
% Protectiona
PTZb
1
MESc
Picd
Bice
which was crystallized from ethanol (Table 1). H NMR
(CDCl3), d 1.88 (t, 3H, J = 7 Hz, CH3CH2O), 2.43 (s, 3H,
CH3), 4.08 (s, 2H, SCH2CO), 4.12 (q, 3H, J = 7 Hz), 5.33
(s, 2H, CH2Ph), 7.28 (t, 2H, J = 7 Hz, Ar–H), 7.33–7.38
(m, 2H, Ar–H), 7.68 (d, 1H, J = 8. 5 Hz), 7.8–8.5 (m, 3H,
Ar–H).
6
70
70
0.0
70
30
nt
80
70
80
nt
100
100
100
nt
12
21
70
22
30
24
30
nt
nt
nt
29
30
nt
nt
nt
2-[(3-Benzyl)-4-oxo-6-methyl-3H-quinazolin-2-yl)-
thio]acetyl hydrazide (17)
31
30
nt
nt
nt
36
100
100
100
30
0.0
0.0
30
nt
100
80
100
nt
100
100
100
nt
37
A solution of the ester 16 (3.68 g, 0.01 mol) and hydrazine
hydrate (85 %, 3 ml) in ethanol (40 ml) was heated under
reflux for 2 h. The obtained solid was filtered, dried, and
38
40
43
30
nt
nt
nt
1
recrystallized from dioxane (Table 1). H NMR (DMSO-
44
30
nt
nt
nt
d6): d 2.44 (s, 3H, CH3), 3.93 (s, 2H, SCH2CO), 4.31 (b,
2H, NH2), 5.34 (s, 2H, CH2Ph), 7.27–7.40 (m, 4H, Ar–H),
7.58 (d, 1H, J = 8 Hz, Ar–H), 7.81–7.84 (m, 1H, Ar–H),
8.16 (d, 1H, J = 8 Hz, Ar–H), 9.37 (s, 1H, CONH).
45
30
nt
nt
nt
46
30
nt
nt
nt
47
30
nt
nt
nt
Sod. valproate
100
100
100
100
a
Compounds 10 and 17 showed 100 % mortality
b
Compounds 7,10, 11, 13–20, 23, 25, 26, 30, 34, 35, 39, 41,42, and
48 showed no anticonvulsant activity against PTZ-induced
N-(Substituted phthalimido)-2-[(3-benzyl-4-oxo-6-methyl-
3H-quinazolin-2-yl)thio]-acetamide (18–20), N,N-(1,8-
naphthalimido)-2-[(3-benzyl-4-oxo-6-methyl-3H-quina-
zolin-2-yl)-thio]acetamide (21) and N-(succinamido)-2-
[(3-benzyl-4-oxo-6-methyl-3H-quinazolin-2-yl)-
thio]acetamide (22)
convulsions
c
MES maximal electroshock test, was applied 30 min after the
administration of each compound
d
Pic picrotoxin (3.15 mg/kg, s.c.) was given 30 min after the
administration of each compound
e
Bic bicuculline (2.7 mg/kg, s.c.) was given 30 min after the
administration of each compound
A mixture of compound 17 (1.77 g, 0.005 mol) and
appropriate anhydride (0.007 mol) and fused sodium ace-
tate (1.0 g) in glacial acetic acid (30 ml) was heated under
reflux for 18 h. The formed precipitate was filtered while
M-C10Cl4H3N2O3, m/z = 269 (8 %), M-C10Cl4H3N2O3S,
m/z = 237 (7.6 %). 13: 1H NMR, (DMSO-d6): d 11.16
(s, 1H, NH, D2O exchangeable), 7.89 (s, 1H, Ar–H),
7.59–7.46 (m, 7H, Ar–H), 4.12 (s, 2H, CH2), 2.45 (s, 3H,
CH3). 13C NMR: 21.2, 34.4, 119.7, 121.7, 126.2, 126.8,
129.4, 129.9, 130.0, 130.5, 136.2, 136.5, 137.9, 145.7,
155.5, 161.1, 161.4, 167.1. 14: IR (KBr, m cm-1): 3,251
1
hot, dried, and crystallized from acetic acid (Table 1). H
NMR(DMSO-d6): 18: d 2.45 (s, 3H, CH3), 4.22 (s, 2H,
SCH2CO), 5.34 (s, 2H, CH2Ph), 7.28–7.32 (m, 4H, Ar–H),
7.69–7.54 (m, 4H, Ar–H), 8.06 (d, 2H, J = 2 Hz, Ar–H),
8.12 (d, 2H, J = 2 Hz, Ar–H), 11.03 (s, 1H, CONH). 19: d
2.50 (s, 3H, CH3), 4.25 (s, 2H, SCH2CO), 5.35 (s, 2H,
CH2Ph), 7.29–7.34 (m, 4H, Ar–H), 7.50 (t, 1H, J = 7 Hz,
Ar–H), 7.9 (d, 1H, J = 7.5 Hz, Ar–H), 7.66 (d, 1H,
J = 7.5 Hz, Ar–H), 8.12 (d, 1H, J = 7.5 Hz, Ar–H), 11.07
(bs, 1H, NHCO). 20: d 2.50 (s, 3H, CH3), 4.25 (s, 2H,
SCH2CO), 5.35 (s, 2H, CH2Ph), 7.28–7.36 (m, 5H, Ar–H),
7.50 (t, 1H, J = 7.5 Hz, Ar–H), 7.9–7.97 (m, 2H, Ar–H
and NH), 8.18 (d, 1H, J = 8 Hz, Ar–H). 21: IR (KBr,
m cm-1): 3,424 (NH), 1785, 1772, 1668 (3 C=O), Ms: m/z 534
(20 %). 22: d 2.45 (s, 3H, CH3), 2.89 (s, 4H, COCH2CO),
3.98 (s, 2H, SCH2CO), 5.78 (s, 2H, CH2Ph), 7.2–8.1 (m,
8H, Ar–H), 11.76 (s, 1H, NH).
1
(CONH), 1740, 1687 (2 C=O). H NMR, (DMSO-d6), d
2.46 (s, 3H, CH3), 4.21 (s, 2H, SCH2CO), 7.47–7.49 (m,
2H, Ar–H), 7.61 (d, 3H, Ar–H), 7.73–7.78 (m, 2H, Ar–H),
7.89–7.93 (m, 3H, Ar–H), 8.58 (d, 4H, Ar–H), 11.11 (s,
1H, CONH).
2-(Ethoxycarbonylmethyl)thio-3-benzyl-4-oxo-6-methyl-
3H-quinazoline (16)
A mixture of 2-mercapto-3-benzyl-4-oxo-6-methyl-3H-
quinazoline (15, 2.82 g, 0.01 mol), ethylbromoacetate
123

2824
Med Chem Res (2013) 22:2815–2827
Table 3 Dose response curve, ED50, TD50, PI, LD50, and TI for compounds 12 and 38
Compd.a Dose
(mmol/kg) (mg/kg)
Dose
%
%
%
%
%
EDf50 (mg/kg) TD5f 0 (mg/kg) PIg LD50 (mg/kg)
TIh
PTZ Chimb MESc Picd Bice
12
38
a
1.5
912
456
228
114
748
374
187
94
70
100
30
70
70
50
20
0.0
100
70
457 (363–575) 562 (447–708) 1.22 1,288 (920–1,803) 2.82
0.75
0.37
0.18
1.5
50
10
30
0.0
0.0
80
0.0
0.0
30
10
0.0
100
70
0.0
100 100
251 (200–316) 447 (355–562) 1.78 1,380 (1,030–1,849) 5.50
0.75
0.37
0.18
30
0.0
0.0
0.0
50
50
20
40
10
0.0
30
30
0.0
0.0
Each dose of selected compounds was tested using 10 animals and the percentage of animals protected was recorded and the anticonvulsant
activity was calculated
b
Chim chimney test, was applied 15, and 25 min after the administration of each compound
c
MES maximal electroshock test, was applied 30 min after the administration of each compound
d
Pic picrotoxin (3.15 mg/kg, s.c.) was given 30 min after the administration of each compound
e
Bic bicuculline (2.7 mg/kg, s.c.) was given 30 min after the administration of each compound
f
ED50 and TD50: median effective and median sedative doses, respectively
g
PI protective index = TD50/ED50
h
TI Therapeutic index = LD50/ED50
Chart 3 List of structures of
the active anticonvulsant agents
O
O
N
O
O
N
O
N
N
NH
S
NH2
S
I
I
I
O
N
N
N
S
37
36
38
2-(Ethoxycarbonylmethyl)-thio-3-phenyl-4-oxo-6-nitro-
3H-quinazoline (25) and 2-(ethoxy carbonylmethyl)-thio-3-
benzyl-4-oxo-6-nitro-3H-quinazoline (26)
2H, CH2Ph), 7.16–7.31 (m, 6H, Ar–H), 8.22 (m, 1H, Ar–H),
8.61 (s, 1H, Ar–H).
2-Hydrazino-6-nitro-3-phenyl-4-oxo-3H-quinazoline (29)
and 2-hydrazino-6-nitro-3-benzyl-4-oxo-3H-quinazoline
(30)
A mixture of 2-mercapto-3-phenyl-4-oxo-6-nitro-3H-qui-
nazoline 23 or 2-mercapto-3-benzyl-4-oxo-6-nitro-3H-qui-
nazoline 24 (0.01 mol), ethylbromoacetate (2.51 g, 0.015
mol) and anhydrous potassium carbonate (2.0 g) in dry ace-
tone (50 ml) was heated under reflux for 12 h. Solvents were
evaporated and the obtained residue was recrystallized from
theappropriatesolvent(Table 1).25:IR(KBr,m cm-1):1724,
A mixture of 25 or 26 (0.01 mol) and hydrazine hydrate
(0.03 mol) in ethanol (40 ml) was heated under reflux for 1 h.
The reaction mixture was cooled; the obtained solid was fil-
tered and recrystallized from ethanol–benzene (Table 1). 1H
NMR (DMSO-d6), 29: d 3.36 (s, 2H, NHNH2), 7.5–7.6 (m,
1H, Ar–H), 7.7 (t, 1H, J = 7.5 Hz, Ar–H), 7.84 (t, 1H,
J = 7 Hz, Ar–H), 8.09–8.18 (dd, 1H, J = 8 Hz, Ar–H), 8.28
(d, 1H, J = 7.5 Hz, Ar–H), 8.78 (d, 1H, J = 3.5 Hz, Ar–H),
8.87(s, 1H, Ar–H), 9.09(s, 1H, Ar–H), 12.36(s, 1H, NHNH2),
30: d 3.34 (brs, 2H, NHNH2), 5.22 (s, 2H, CH2Ph), 7.16–7.32
(m, 7H, Ar–H, and NHNH2), 8.22–8.24 (m, 1H, Ar–H), 8.61
(s, 1H, Ar–H).
1
1701 (2 C=O), H NMR(DMSO-d6): d 1.31 (t, 3H, J =
7 Hz, OCH2CH3), 3.95 (s, 2H, SCH2CO), 4.2 (q, 2H,
J = 7 Hz, OCH2CH3), 7.38–7.4 (m, 2H, Ar–H), 7.61 (t, 3H,
J = 3 Hz, Ar–H), 7.69 (d, 1H, J = 9 Hz, Ar–H), 8.51–8.54
(dd, 1H, J = 2.5 Hz, Ar–H), 9.09 (d, 1H, J = 2.5 Hz, Ar–H),
26: IR (KBr, m cm-1): 3,087 (CH), 1730, 1683 (2 C=O). 1H
NMR (DMSO-d6): d 1.29 (t, 3H, J = 8 Hz, OCH2CH3), 3.97
(s, 2H, SCH2CO), 4.16 (q, 2H, J = 8 Hz, OCH2CH3), 5.23 (s,
123

Med Chem Res (2013) 22:2815–2827
2825
1H NMR (DMSO-d6): d 4.76 (s, 2H, OCH2CO), 7.26–7.27
(m, 1H, thiophene-H), 7.70 (d, 1H, J = 8.5 Hz, thiophene-
H), 7.84 (d, 1H, 8.5 Hz, thiophene-H), 7.83-7.99 (m, 4H,
Ar–H), 8.18–8.22 (m, 2H, Ar–H), 8.65 (d, 1H, J = 1.5 Hz,
Ar–H), 11.03 (s, 1H, NHCO). 46: IR (KBr, m cm-1): 3,246
2-(1,8-Naphthalimidoamino)-6-nitro-3-benzyl-4-oxo-3H-
quinazoline (31)
Equimolar amounts of compound 30 and 1,8-naphthalic
anhydride (10.01 mol) was refluxed in acetic acid (30 ml) and
fused sodium acetate (2.0 g) for 24 h. The reaction mixture
was concentrated to its half volume and filtered while hot. The
resulting solid was crystallized from acetic acid (Table 1).
(DMSO-d6): d 5.48(s, 2H, CH2Ph), 7.36–7.93 (m, 8H, Ar–H),
8.52–8.62 (m, 6H, Ar–H), 11.2 (s, 1H, NH).
1
(NH), 1802, 1758, 1654 (3 C=O). H NMR (DMSO-d6): d
5.43 (s, 2H, OCH2CO), 7.25 (s, 1H, Ar–H), 7.69 (d, 1H,
J = 8.5 Hz, thiophene-H), 7.83 (d, 1H, J = 3.5 Hz, thio-
phene-H), 8.16–8.21 (m, 2H, Ar–H), 8.61 (s, 1H, Ar–H),
12.00 (s, 1H, NHCO, exchangeable). 13C NMR: 64.4,
116.3, 126.6, 128.9, 129.4, 129.5, 131.0, 132.0, 132.6,
139.7, 143.5, 150.8, 161.0, 164.5, 167.0. 47: IR (KBr,
m cm-1): 3,212 (NH), 1791, 1751, 1654 (3 C=O). 1H NMR
(DMSO-d6): d 5.43 (s, 2H, OCH2CO), 7.25 (s, 1H), 7.69 (d,
1H, J = 8.5 Hz, thiophene-H), 7.82–8.21 (m, 2H), 8.62 (s,
1H, Ar–H), 11.34 (s, 1H, NHCO, exchangeable). 13C
NMR: 64.4, 92.5, 116.3, 121.8, 128.9, 129.4, 129.5, 131.0,
132.0, 132.6, 138.0, 143.0, 143.5, 150.8, 156.6, 161.3,
164.5, 166.9. 48: 1H NMR (DMSO-d6): d 5.46 (s, 2H,
OCH2CO), 7.70–8.70 (m, 12H, Ar–H), 11.25 (s, 1H,
NHCO, exchangeable). 13C NMR: 64.6, 119.5, 122.1,
127.9, 128.0, 130.2, 132.0, 132.1, 132.7, 133.0, 135.8,
135.9, 143.5, 150.9, 156.6, 161.2, 162.1, 164.0, 166.4,
172.4.
6-Iodo-2-thieno-3-substituted phthalimido-4-(3H)-
quinazolinone (38–40) and 6-iodo-2-thieno-3-
naphthalimido-4-(3H)-quinazolinone (41)
Amixtureofcompound36 (3.69 g,0.01 mol)andappropriate
anhydride (0.015 mol) and fused sodium acetate (1.0 g) in
acetic acid (30 ml) was heated under reflux for 6 h. The
formed precipitate was filtered while hot, dried, and crystal-
lized from acetic acid (Table 1). 38: 1H NMR; (DMSO-d6), d
7.17–7.23 (m, 1H), 7.50 (d, 1H, J = 8 Hz thiophene-H), 7.61
(d, 1H, J = 8.5 Hz thiophene-H), 7.87–8.27 (m, 6H, thio-
phene-H), 8.39 (d, 1H, J = 8.0 Hz, Ar–H). I.R. 1799, 1751,
1700 (3 C=O). 13C NMR: 92.3, 122.3, 128.5, 129.5, 130.3,
132.8, 134.3, 135.2, 137.2, 145.4, 146.5, 149.0, 150.6, 158.5,
164.7, 170.2. 39: IR (KBr, m cm-1): 1797, 1702, 1645 (3
C=O). 1H NMR; (DMSO-d6), d 7.18-7.19 (m, 1H, thiophene-
H), 7.62 (d, 1H, J = 2.5 thiophene-H), 7.89–7.91 (m, 1H,
thiophene-H), 8.01–8.05 (m, 1H, Ar–H), 8.33 (d, 1H,
J = 9 Hz, Ar–H), 8.37-8.39 (m, 1H, Ar–H). 13C NMR: 94.0,
120.8, 126.3, 129.7, 130.3, 130.7, 133.0, 133.2, 134.5, 135.6,
141.4, 145.7, 146.1, 148.5, 165.9, 160.7. 40: IR (KBr,
m cm-1): 1769, 1751, 1693 (3 C=O). 1H NMR; (DMSO-d6), d
7.23–7.24 (m, 1H, thiophene-H), 7.47 (d, 1H, J = 8.5 Hz,
thiophene-H), 7.89–7.9 (m, 1H, thiophene-H), 8.07-8.09 (m,
1H, Ar–H), 8.38–8.39 (m, 1H, Ar–H), 8.42–8.43 (m, 1H, Ar–
H), 13C NMR: 93.4, 122.8, 124.8, 128.4, 129.8, 131.3, 133.3,
134.5, 135.3, 144.4, 145.2, 146.4, 150.3, 157.3, 158.5, 172.5.
41: d 7.22–7.23 (m, 1H, Ar–H), 7.46 (m, 1H, J = 8.5 Hz,
thiophene-H). 7.89–7.94 (m, 3H, thiophene-H and Ar–H),
8.07–8.09 (dd, 1H, J = 2, 7 Hz, Ar–H), 8.38–8.39 (m, 1H,
Ar–H), 8.42–8.43 (m, 1H, Ar–H), 8.53–8.57 (m, 4H, Ar–H).
Anticonvulsant screening
The test compounds were freshly dissolved in 99 %
DMSO. In a preliminary screening, compounds were used
at dose level of 1.5 mol/kg, i.p. Pentylene-tetrazole (PTZ)
was freshly dissolved in 0.9 % NaCl and used at dose level
of 85 mg/kg, s.c. This dose was found to be the minimum
dose which induced 100 % clonic convulsion. Picrotoxin
(Pic) was freshly dissolved in 1 ml 0.1 N warmed HCl and
the final volume was made up with 0.9 % NaCl. It has been
used at dose level of 3.15 mg/kg sc and was given 30 min
after the test compounds. Bicuculline (Bic) was freshly
dissolved in 1 ml 0.1 N warmed HCl and the final volume
was made up with 0.9 % NaCl. It has been used at dose
level of 2.7 mg/kg s.c. and was given 30 min after the test
compounds. Sodium valproate was freshly dissolved in
0.9 % NaCl and used at a dose level of 200 mg/kg
(1.38 mmol/kg) s.c., 30 min after the test compounds.
N-(1-Substituted-phthalimido)-2-[(2-thieno-6-iodo-
quinazolin-4-yl)oxo]acetamide (45–47) and
naphthalimido-2-[(2-thieno-6-iodo-quinazolin-4-
yl)oxo]acetamide (48)
Pentylenetetrazole (PTZ)-induced convulsion
Pentylenetetrazole seizure threshold test is one of the well-
known chemical tests used to evaluate the potential anti-
convulsant activity of the tested compounds according to
White et al., 1995. Each compound was tested in 10 mice
and was given i.p. at dose level of 1.5 mmol. 30 min later,
animals received PTZ (85 mg/kg, s.c.) and observed for
30 min. A single 5-s episode of clonic spasms was taken as
A
mixture of 2-(6-iodo-2-(thiophen-2-yl)quinqzolin-4-
yloxy)acetohydrazide (44, 4.26 g, 0.01 mol), the appro-
priate anhydride (1.5 g, 0.01 mol) in acetic acid (30 ml)
was heated under reflux for 18 h. The formed precipitate
was filtered while hot, dried and crystallized (Table 1). 45:
123

2826
Med Chem Res (2013) 22:2815–2827
a threshold seizure. Compounds 6, 12, 21, 36, 37, and 38
produced 100 % protection against PTZ-induced seizures.
Those active compounds were further tested against max-
imal electroshock seizure (MES), picrotoxin, and bicucul-
line-induced clonic convulsions to explore the involvement
of GABA receptors in their anticonvulsant activity.
climb up backwards in a glass tube of 25-cm length and
3-cm inner diameter within 30 s was recorded and taken as
a measure of neurologic deficits. Normal mice climb up in
5–10 s. (Cheymol et al., 1961; Buckley and Dorato, 2009).
Determination of LD50 and dose–response curve
Several doses of compounds 12 and 38 which produced
70–100 % protection against MES, Pic, and Bic-induced
convulsion were used to construct a dose–response curve.
Also, LD50 for compounds 12 and 38 was determined by
the Spearman–Karber method in which the doses were
selected at equal logarithmic intervals White et al., 1995.
Effect of tested compounds against the maximal
electroshock (MES)-induced convulsion
The MES is one of the electrical tests used to evaluate
anticonvulsant activity according to White et al., 1995.
MES that induced 100 % maximal seizures was found to
be 50 mA alternating current of 100 Hz frequency for
0.2 s, using ECT UNIT (model number 7801, UGO Basile,
Varese, Italy). 1.5 mmol of the tested compounds (6, 12,
21, 36, 37, and 38), which produced 100 % protection
against PTZ-induced seizures, were injected i.p. 30 min
later, mice were restrained by hand and subjected to elec-
tric shock through their ears, and released immediately
following electrical stimulation to permit observation of
the maximal seizure. The maximal seizure typically con-
sists of a short period of initial tonic flexion and a pro-
longed period of tonic extension (especially the hind limb).
Protection was defined as the complete absence of hind
limb tonic extension.
Acknowledgments The financial support of King Abdulaziz City for
Science and Technology, Grant AR-25-53, is greatly acknowledged.
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