4-(3-Methoxyphenyl)-1-substituted-4H-[1,2,4]triazolo[4,3-a] quinazolin-5-ones: New class of H1-antihistaminic agents

Article abstract of DOI:10.1691/ph.2008.8670

A series of 1-substituted-4-(3-methoxyphenyl)-4H-[1,2,4]triazolo[4,3-a] quinazolin-5-ones were synthesized by the cyclization of 2-hydrazino-3-(3- methoxyphenyl)-3H-quinazolin-4-one with various electrophile. The starting material 2-hydrazino-3-(3-methoxy

Full text of DOI:10.1691/ph.2008.8670

ORIGINAL ARTICLES
Medicinal Chemistry Research Laboratory1, MNR College of Pharmacy, Sangareddy; Department of Pharmaceutical Chemistry2,
Patel College of Pharmacy, Bhopal; Medicinal & Process Chemistry Division3, Central Drug Research Institute, Lucknow, India.
4-(3-Methoxyphenyl)-1-substituted-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-
ones: new class of H1-antihistaminic agents
V. Alagarsamy1, H. K. Sharma2, P. Parthiban1, J. C. Hanish Singh1, S. Thirusenthil Murugan 1, V. Raja Solomon3
Received July 17, 2008, accepted September 16, 2008
Prof. Dr. Veerachamy Alagarsamy, Medicinal Chemistry Research Laboratory,
MNR College of Pharmacy, Sangareddy 502 294, India
drvalagarsamy@gmail.com
Pharmazie 64: 5–9 (2009)
doi: 10.1691/ph.2008.8670
A series of 1-substituted-4-(3-methoxyphenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-ones were synthe-
sized by the cyclization of 2-hydrazino-3-(3-methoxyphenyl)-3H-quinazolin-4-one with various electro-
phile. The starting material 2-hydrazino-3-(3-methoxyphenyl)-3H-quinazolin-4-one was synthesized from
3-methoxy aniline by an innovative route. Title compounds were tested for their in vivo H1-antihistaminic
activity on guinea pigs; all the tested compounds protected the animals from histamine induced broncho-
spasm significantly. Compound 1-methyl-4-(3-methoxyphenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-one
(II) emerged as the most active compound of the series and was more potent (72.76%) than the refer-
ence standard chlorpheniramine maleate (71%). Compound II showed negligible sedation (10%) when
compared to chlorpheniramine maleate (25%). Hence it could serve as prototype molecule for further
development as a new class of H1-antihistaminic agents.
Table 1: Characterization data of 4-(3-methoxyphenyl)-1-sub-
stituted-4H-[1,2,4] triazolo[4,3-a] quinazolin-5-ones
1. Introduction
A common feature of first generation compounds includes
two aryl or heteroaryl rings linked to an aliphatic tertiary
amine via the side chain (e.g. diphenhydramine and phe-
niramine) (Estelle et al. 1991; Simons 1993; Simons and
Simons 1999), the second-generation compounds (terfe-
nadine and cetirizine) (Van der Goot et al. 1991; Simons
and Simons 1994) also contain many of the structural
features of first generation compounds. The real break-
through of non-sedative antihistamines came in the early
eighties of twentieth century when the discovery of mod-
ern antihistamines, was found to exhibit potent antihista-
minic activity without sleep-inducing effect (Carr and
Meyer 1982). Condensed heterocycles containing new
generation of H1-antihistamines (e.g. loratadine, azelastine
and flazelastine) that do not possess the above mentioned
pharmacophore for H1-antihistamines gave way for the
discovery of many novel antihistamines temelastine and
mangostin (Hopp et al. 1985; Chairungsrilerd et al. 1996).
A literature survey reveals excellent antihistaminic activity
in quinazolines and condensed quinazolines (Rao and
Reddy 1992; Buyuktimkin et al. 1989; Alagarsamy et al.
2002, 2004). In view of these facts and to continue our
structure activity relationship (SAR) study efforts in the
search of quinazoline derivatives as potent antihistamines
with least sedation, we aimed to synthesis of a series
of 1,2,4-triazolo-4H-[4,3-a]quinazolin-5-ones compounds
containing 3-methoxyphenyl substitution at position 4 and
alkyl/alicyclic amines substitution at position 1. The title
compounds were synthesized by cyclization of 2-hydrazi-
OCH3
O
N
N
N
N
R
Compd.
R
Mol. formula
Mp oC (% yield)
I
––H
C16H12N4O2
C17H14N4O2
C18H16N4O2
C19H18N4O2
239–241 (78)
287–288 (73)
265–267 (80)
274–276 (74)
II
––CH3
III
IV
V
––CH2CH3
––(CH2) 2CH3
––CH2Cl
C17H13ClN4O2 296–298 (81)
VI
C21H21N5O2
C22H23N5O2
C21H21N5O3
255–256 (74)
220–262 (76)
219–221 (72)
N
VII
VIII
IX
N
N
N
N
O
C21H22N6O2
C22H24N6O2
260–262 (70)
245–246 (78)
NH–CH3
NH–CH3
X
Pharmazie 64 (2009) 1
5

ORIGINAL ARTICLES
no-3-(3-methoxyphenyl)-3H-quinazolin-4-one (6) with var-
backs; it is a multi step process, it requires prolonged re-
action time (37 h) and the yield is also very low (27%).
Hence, this method needed to be improved. Aqueous so-
dium hydroxide (20 mol solution) was used as a base in-
stead of anhydrous K2CO3 and dimethyl sulphoxide
(DMSO) was substituted for acetone as the reaction sol-
vent (Scheme). The use of DMSO as the reaction solvent
enhanced the rate of reaction and the use of alkali in high-
er concentration helped in preventing the hydrolysis of the
intermediate probably, due to less solvation. These modifi-
cation not only curtails the reaction time from 37 h to
26 h, also increased the yield from 27% to 85%. Thus
3-methoxy aniline (1) treated with carbon disulphide and
sodium hydroxide in dimethyl sulphoxide to give sodium
dithiocarbamate, which was methylated with dimethyl sul-
fate to afford the dithiocarbamic acid methyl ester (2).
Compound 2 on reflux with methyl anthranilate (3) in
ethanol yielded the desired 3-(3-methoxyphenyl)-2-thioxo-
2,3-dihydro-1H-quinazolin-4-one (4) via the thiourea inter-
mediate in good yield (82%). The product obtained was
cyclic and not an open chain thiourea 3a. The 3-(3-meth-
oxyphenyl)-2-methylsulfanyl-3H-quinazolin-4-one (5) was
obtained by dissolving 4 in 2% alcoholic sodium hydro-
xide solution and methylating with dimethyl sulphate with
stirring at room temperature. Nucleophilic displacement of
methylthio group of 5 with hydrazine hydrate was carried
out using ethanol as solvent to afford 2-hydrazino-3-(3-
methoxyphenyl)-3H-quinazolin-4-one (6). The long dura-
tion of reaction (35 h) required might be due to the pre-
ious electrophiles. Compound 6 was synthesized from 3-
methoxy aniline (1) by a novel innovative route. Spectral
data (IR, NMR and mass spectra) confirmed the structures
of the synthesized compounds; the purity of these com-
pounds was ascertained by microanalysis (Table 1). The
synthesized compounds were tested for their in vivo H1-
antihistaminic activity on conscious guinea pigs. As seda-
tion is one of the major side effects associated with anti-
histamines, the test compounds were also evaluated for
their sedative potentials, by measuring the reduction in
locomotor activity using actophotometer.
2. Investigations and results
The key intermediate 3-(3-methoxyphenyl)-2-thioxo-2,3-
dihydro-1H-quinazolin-4-one (4) was prepared by reflux-
ing methyl anthranilate with 3-methoxyphenyl isothiocya-
nate in ethanol. However, this route is not attractive as the
preparation of 3-methoxyphenyl isothiocyanate required
for the reaction is a tedious and time consuming process;
and the yield was also low. An alternate route was at-
tempted to synthesize 4. In this route, 3-methoxy aniline
(1) was reacted with carbon disulphide and anhydrous po-
tassium carbonate in acetone to give potassium dithiocar-
bamate, which was methylated with dimethyl sulphate to
afford dithiocarbamic acid methyl ester (2). Compound 2
on reflux with methyl anthranilate (3) yielded 4. This pro-
cess of synthesizing 4 suffers from the following draw-
Scheme
OCH3
OCH3
OCH3
_
+
Na
S
DMSO
SCH3
S
DMS
N
H
CS2 / NaOH
N
H
S
NH2
2
1
O
OCH3
EtOH
OCH3
NH2
3
OCH3
OCH3
OCH3
NH
O
O
O
NaOH/EtOH
DMS
N
N
N
H
S
N
SCH3
N
H
S
3a
5
4
EtOH
NH2NH2.H2O
OCH3
-
OCH3
O
O
One Carbon Donors
N
N
N
R
N
NHNH2
I - X
N
N
6
6
Pharmazie 64 (2009) 1

ORIGINAL ARTICLES
Table 2: Antihistaminic and sedative-hypnotic activity of compounds (I–X)
Compd.
Degree of
bronchoconstriction (s)
% Protection
Percent CNS depression
1 h
2 h
3 h
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
**
***
*
**
**
***
*
I
II
III
IV
V
VI
VII
VIII
391 ꢀ 6.92
70.33 ꢀ 1.89
72.76 ꢀ 1.36
70.48 ꢀ 1.02
69.39 ꢀ 1.69
68.21 ꢀ 1.81
68.98 ꢀ 1.01
68.64 ꢀ 1.82
70.10 ꢀ 1.73
70.85 ꢀ 1.83
71.63 ꢀ 1.49
ꢁ
7 ꢀ 1.45
10 ꢀ 1.92
12 ꢀ 1.49
13 ꢀ 1.87
14 ꢀ 1.28
10 ꢀ 1.54
13 ꢀ 1.93
14 ꢀ 1.49
15 ꢀ 1.68
15 ꢀ 1.03
16 ꢀ 1.46
4 ꢀ 0.59
6 ꢀ 1.35Ns
*
*
*
426 ꢀ 8.63
10 ꢀ 1.61
8 ꢀ 1.82
8 ꢀ 1.45
9 ꢀ 1.93
393 ꢀ 9.71
12 ꢀ 1.38
*
*
379 ꢀ 11.92
14 ꢀ 1.93
365 ꢀ 5.05
6 ꢀ 1.56Ns
5 ꢀ 1.30Ns
*
*
*
*
*
*
**
*
*
*
*
374 ꢀ 7.81
9 ꢀ 1.29
8 ꢀ 1.27
***
***
***
***
370 ꢀ 5.98
11 ꢀ 1.64
8 ꢀ 1.83
**
**
**
388 ꢀ 6.45
12 ꢀ 1.02
9 ꢀ 1.39
IX
X
398 ꢀ 7.60
12 ꢀ 1.48
9 ꢀ 1.67
*
*
409 ꢀ 8.11
13 ꢀ 1.02
10 ꢀ 1.83
Control
Chlorpheniramine
116 ꢀ 4.56
6 ꢀ 0.49
4 ꢀ 0.91
***
*
*
***
***
400 ꢀ 9.50
71.00 ꢀ 1.36
37 ꢀ 1.82
32.0 ꢀ 1.73
indicate not significant, as compared with respective control.
22 ꢀ 1.98
NS
*
**
***
Each value represents the mean ꢀ SEM (n ¼ 6). Significance levels p < 0.5, p < 0.1 and
p < 0.05 and
sence of the bulky aromatic ring at position 3, which
might have reduced the reactivity of quinazoline ring sys-
tem at C-2 position. The title compounds I–V were ob-
tained in fair to good yields through the cyclization of 6
with a variety of one carbon donors such as formic acid,
acetic acid, propionic acid, butyric acid and chloroacetyl
Log P ¼ 3.16 piperazinyl compound IX, Log P ¼ 3.54
and 4-methyl piperazinyl compound X, Log P ¼ 3.77) led
to further increase in activity. A comparison of the percen-
tage protection of compounds (I–X) with their correspond-
ing, calculated log P values (Table 1) found no correlation,
indicating that in vivo activity observed is not based on
liphophilicity alone.
1
chloride at reflux. The H NMR spectrum of I–V showed
the absence of NH and NH2 signals. Compounds VI–X
were obtained by the displacement of chloro of compound
V with various alicyclic amines like pyrrolidine, piperi-
dine, morpholine, piperazine and 4-methylpiperazine. All
the synthesized compounds were confirmed by spectral
data (IR, NMR and mass spectra). Elemental (C, H, N)
analysis satisfactorily confirmed elemental composition
and purity of the synthesized compounds (I–X).
Sedative-hypnotic activity was determined by measuring
the reduction in locomotor activity using an actophot-
ometer (Dews 1953; Kuhn and Van Maanen 1961) on
swiss albino mice. The results of sedative-hypnotic activ-
ity indicate that all the test compounds were found to ex-
hibit only negligible sedation (8–13%), whereas the refer-
ence standard chlorpheniramine maleate showed 25%
sedation.
The compounds containing the 1,4-disubstituted
[1,2,4]triazoloquinazoline ring system (I–X) were evalu-
ated for their in vivo antihistaminic activity. Histamine
causes bronchospasm and the guinea pigs are most sus-
ceptible animals for histamine, hence protection against
histamine-induced bronchospasm on conscious guinea
pigs method was adopted to determine the antihistaminic
potential of the test compounds (Van Arman et al. 1961).
The advantage of this method is that it is a non-invasive
method and the animals are recovered after the experi-
ment. As the test compounds could not be converted to
water-soluble form, in vitro evaluation for antihistaminic
activity could not be performed.
All the test compounds were found to exhibit good anti-
histaminic activity (Table 2). Percentage protection data
showed that all compounds of the series show significant
protection in the range of 68–72%. Pharmacological stu-
dies indicated that different substituents over the first posi-
tion of the triazoloquinazoline ring exerted various biolo-
gical activity. The presence of a methyl group (compound
II, Log P ¼ 3.19) showed better activity than the unsubsti-
tuted compound (compound I, Log P ¼ 2.51), with in-
creased lipophilicity (i.e., ethyl compound III, Log
P ¼ 3.76) activity retained, further increase in lipophilicity
(i.e., propyl compound IV, Log P ¼ 4.18) leads to de-
crease in activity. Replacement of a proton of the methyl
group by chloro (compound V, Log P ¼ 3.68) showed
further decrease in activity. Replacement of a proton of
the methyl group by alicyclic amines (pyrrolidinyl and pi-
peridinyl compound VI, Log P ¼ 4.10 and VII, Log
P ¼ 4.51, respectively) showed increase in activity over
the chloro substituent. Placement of alicyclic amines with
additional hetero atom (morpholinyl compound VIII,
3. Discussion
In summary the synthesis of a new series of 1-substituted-4-
(3-methoxyphenyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-
ones has been described. In this study, the intermediate
compound of 3-(3-methoxyphenyl)-2-thioxo-2,3-dihydro-
1H-quinazolin-4-one has been synthesized by a new inno-
vative route with improved yield. These derivatives have
exhibited promising antihistaminic activity against hista-
mine-induced bronchospasm in conscious guinea pigs mod-
el. Among the test compounds 1-methyl-4-(3-methoxyphe-
nyl)-4H-[1,2,4]triazolo[4,3-a]quinazolin-5-one (II) was the
most active antihistaminic agent, which was more potent
than the reference standard chlorpheniramine maleate and
could therefore serve as a lead molecule for further modifi-
cation to obtain a clinically useful novel class of antihista-
minic agents.
4. Experimental
4.1. Chemistry
Melting points (mp) were determined in open capillaries on a Thomas Ho-
over melting point apparatus and are uncorrected. The IR spectra were
recorded in film or in potassium bromide disks on a Perkin-Elmer 398
spectrometer. The 1H NMR spectra were recorded on a DPX-300 MHz
Bruker FT-NMR spectrometer. The chemical shifts were reported as parts
per million (d ppm) tetramethylsilane (TMS) as an internal standard. Mass
spectra were obtained on a JEOL-SX-102 instrument using fast atom bom-
bardment (FAB positive). Elemental analysis was performed on a Perkin-
Elmer 2400 C, H, N analyzer and values were within the acceptable limits
(ꢀ0.4%) of the calculated values. The progress of the reaction was moni-
tored on readymade silica gel plates (Merck) using chloroform-methanol
(9 : 1) as a solvent system. Iodine was used as a developing agent. Spectral
data (IR, NMR and mass spectra) confirmed the structures of the synthe-
Pharmazie 64 (2009) 1
7

ORIGINAL ARTICLES
sized compounds and the purity of these compounds was ascertained by
111.9, 125.9, 126.9, 129.7, 129.9, 131.8, 132.7, 134.9, 135.9, 138.9,
147.8, 158.9, 160.5; MS (m/z, %): 320 (Mþ, 80), 262 (60), 186 (56), 168
(71), 148 (29), 144 (44).
microanalysis. All chemicals and reagents were obtained from Aldrich
(USA), Lancaster (UK) or Spectrochem Pvt.Ltd (India) and were used
without further purification.
4.1.7. Synthesis of 4-(3-methoxyphenyl)-1-propyl-4H-[1,2,4] triazolo [4,3-
4.1.1. Synthesis of 3-(3-methoxyphenyl)-2-thioxo-2,3-dihydro-1H-quinazo-
a] quinazolin-5-one (IV)
lin-4-one (4)
IR: 1678 (C¼O), 1612 (C¼N) cmꢁ1
.
1H NMR (CDCl3): d 0.80–0.92 (t,
A solution of 3-methoxy aniline (1, 0.02 mol) in dimethyl sulphoxide
(10 ml) was stirred vigorously. To this were added carbon disulphide
(1.6 ml; 0.026 mol) and aqueous sodium hydroxide 1.2 ml (20 molar solu-
tion) drop wise during 30 min with stirring. Dimethyl sulphate (0.02 mol)
was added gradually keeping the reaction mixture stirring in freezing mix-
ture for 2 h. The reaction mixture was then poured into ice water. The
solid obtained was filtered, washed with water, dried and recrystallized
from ethanol. Methyl anthranilate (0.01 mol) and the above prepared N-(3-
methoxyphenyl)-methyl dithiocarbamic acid (0.01 mol), were dissolved in
ethanol (20 ml). To this anhydrous potassium carbonate (100 mg) was
added and refluxed for 23 h. The reaction mixture was cooled in ice and
the solid separated was filtered and purified by dissolving in 10% alco-
holic sodium hydroxide solution and re-precipitated by treating with dilute
hydrochloric acid. The solid obtained was filtered, washed with water,
dried and recrystallized from ethanol. Yield ¼ 85%, mp 255–256 ꢂC. IR:
2 H, CH2CH2CH3), 1.21–1.32 (sext, 2 H, CH2CH2CH3), 1.63–1.72 (t, 3 H,
CH2CH2CH3), 3.11 (s, 3 H, OCH3), 7.60–8.11 (m, 8 H, ArH). MS (m/z,
%): 334 (Mþ, 75), 320 (75), 306 (34), 262 (65), 186 (60), 168 (41), 148
(29), 144 (33).
4.1.8. Synthesis of 1-chloromethyl-4-(3-methoxyphenyl)-4H-[1,2,4] triazolo
[4,3-a] quinazolin-5-one (V)
IR: 1688 (C¼O), 1609 (C¼N) cmꢁ1
.
1H NMR (CDCl3): d 3.22 (s, 3 H,
OCH3), 3.83 (s, 2 H, CH2), 7.21–7.73 (m, 8 H, ArH); 13C NMR (CDCl3):
d 33.7, 54.9, 103.1, 106.9, 111.7, 126.2, 126.7, 128.9, 129.5, 131.2,
132.9, 135.3, 136.9, 139.8, 147.5, 159.5, 161.3; MS (m/z, %): 340 (Mþ,
95), 342 (M þ 2, 31), 262 (65), 186 (60), 168 (41), 148 (29), 144 (33).
4.1.9. Synthesis of 4-(3-methoxyphenyl)-1-(pyrrolidinyl)-4H-[1,2,4] triazolo
[4,3-a] quinazolin-5-one (VI)
3312 (NH), 1690 (C¼O), 1210 (C¼S) cmꢁ1
.
1H NMR (CDCl3): d 3.10 (s,
3 H, OCH3), 7.31–7.92 (m, 8 H, ArH), 10.53 (br s, 1 H, NH); MS (m/z,
%): 284 (Mþ, 100), 254 (54), 178 (75), 148 (35).
A mixture of 1-chloromethyl-4-(3-methoxyphenyl)-4H-[1,2,4]triazolo[4,3-
a] quinazolin-5-one (V) (0.01 mol) and pyrrolidine (0.05 mole) and anhy-
drous potassium carbonate (100 mg) in dioxan (25 ml) were taken in a
round bottomed flask and refluxed for 29 h, cooled and poured into ice
water. The solid obtained was filtered, washed with water, dried and re-
crystallized from ethanol-benzene (50 : 50). IR: 1695 (C¼O), 1612 (C¼N)
C
15H12N2O2S
4.1.2. Synthesis of 3-(3-methoxyphenyl)-2-methylsulfanyl-3H-quinazolin-4-
one (5)
The 3-(3-methoxyphenyl)-2-thioxo-2,3-dihydro-1H-quinazolin-4-one (4,
0.01 mol) was dissolved in 40 ml of 2% alcoholic sodium hydroxide solu-
tion. To this dimethyl sulphate (0.01 mol) was added drop wise with stir-
ring. The stirring was continued for 1 h, the reaction mixture was then
poured into ice water. The solid obtained was filtered, washed with water,
dried and recrystallized from an ethanol-chloroform (75 : 25) mixture.
cmꢁ1 1H NMR (CDCl3): d 1.31–1.52 (m, 4 H, NCH2CH2), 1.84–2.02 (m,
.
4 H, NCH2CH2), 2.95 (s, 3 H, OCH3), 3.45 (s, 2 H, CH2), 7.04–7.63 (m,
8 H, ArH). MS (m/z, %): 375 (Mþ, 100), 262 (55), 186 (50), 168 (41),
148 (44), 144 (33).
Adopting this procedure compounds VII–X were prepared.
Yield ¼ 86%, mp 155–156 ꢂC. IR: 1690 (C¼O) cmꢁ1
.
1H NMR (CDCl3):
4.1.10. Synthesis of 4-(3-methoxyphenyl)-1-(piperidinyl)-4H-[1,2,4] triazolo
[4,3-a] quinazolin-5-one (VII)
d 2.85 (s, 3 H, SCH3), 3.34 (s, 3 H, OCH3), 7.23–7.72 (m, 8 H ArH); MS
(m/z, %): 298 (Mþ, 76), 300 (89), 270 (55), 194 (47), 148 (100), 136 (35).
IR: 1693 (C¼O), 1603 (C¼N) cmꢁ1
.
1H NMR (CDCl3) d 1.00–1.32 (m,
C
16H14N2O2S
6 H, CH2-piperidinyl), 1.90–2.11 (m, 4 H, CH2-piperidinyl), 2.83 (s, 3 H,
OCH3), 3.21 (s, 2 H, CH2), 7.62–8.14 (m, 8 H, ArH); 13C NMR (CDCl3) :
d 24.3, 24.9 (2C), 51.7 (2C), 53.7, 103.9, 107.5, 111.9, 126.9, 127.9,
129.5, 129.9, 130.8, 131.7, 134.9, 137.5, 138.9, 147.9, 155.9, 161.9; MS
(m/z, %): 389 (Mþ, 80), 262 (55), 186 (50), 168 (41), 148 (44), 144 (33).
4.1.3. Synthesis of 2-hydrazino-3-(3-methoxyphenyl)-3H-quinazolin-4-one (6)
The 3-(3-methoxyphenyl)-2-methylsulfanyl-3H-quinazolin-4-one (5,
0.01 mol) was dissolved in ethanol (25 ml). To this hydrazine hydrate
(99%) (0.1 mol) and anhydrous potassium carbonate (100 mg) was added
and refluxed for 35 h. The reaction mixture was cooled and poured into
ice water. The solid obtained was filtered, washed with water, dried and
recrystallized from a chloroform-benzene (25 : 75) mixture. Yield ¼ 79%,
4.1.11. Synthesis of 4-(3-methoxyphenyl)-1-(morpholinyl)-4H-[1,2,4] tria-
zolo[4,3-a] quinazolin-5-one (VIII)
mp 211–213 ꢂC. IR: 3368, 3210 (NHNH2), 1678 (C¼O) cmꢁ1
;
1H NMR
IR: 1691 (C¼O), 1610 (C¼N) cmꢁ1
.
1H NMR (CDCl3): d 1.22–1.41 (m,
4 H, NCH2CH2O), 2.00–2.22 (m, 4 H, NCH2CH2O), 2.74 (s, 3 H, OCH3),
3.34 (s, 2 H, CH2), 7.23–7.74 (m, 8 H, ArH); MS (m/z, %): 391 (Mþ,
100), 262 (50), 186 (45), 168 (40), 148 (34), 144 (23).
(CDCl3): d 3.54 (s, 3 H, OCH3), 5.33 (s, 2 H, NH2), 7.32–7.81 (m, 8 H,
ArH), 9.30 (s, 1 H, NH); 13C NMR (CDCl3): d 53.9, 103.8, 108.7, 112.9,
120.2, 121.3, 126.5, 127.7, 128.3, 129.8, 131.9, 132.4, 146.9, 159.8,
162.7; MS (m/z, %): 282 (Mþ, 89), 252 (76), 176 (45), 160 (56), 146
(34).
C
15H14N4O2
4.1.12. Synthesis of 4-(3-methoxyphenyl)-1-(piperazinyl)-4H-[1,2,4] triazo-
lo[4,3-a] quinazolin-5-one (IX)
IR: 1685 (C¼O), 1614 (C¼N) cmꢁ1. H NMR (CDCl3): d 1.0–1.2 (m, 4 H,
4.1.4. Synthesis of 4-(3-methoxyphenyl)-4H-[1,2,4] triazolo [4,3-a] quina-
zolin-5-one (I)
1
NCH2CH2NH), 1.60–1.83 (m, 4 H, NCH2CH2NH), 2.84 (s, 3 H, OCH3),
3.33 (s, 2 H, CH2), 7.63–8.14 (m, 8 H, ArH), 9.05 (s, 1 H, NH); 13C NMR
(CDCl3): d 44.7 (2C), 51.9 (2C), 53.7, 104.1, 107.5, 111.9, 126.7, 127.7,
129.8, 129.9, 131.9, 132.9, 133.9, 137.6, 139.8, 147.5, 157.9, 161.9; MS (m/z,
%): 390 (Mþ, 90), 262 (60), 186 (55), 168 (50), 148 (44), 144 (33).
The 2-hydrazino-3-(3-methoxyphenyl)-3H-quinazolin-4-one (6) (0.01 mol)
and formic acid (25 ml) were placed in a round bottomed flask and re-
fluxed for 35 h, cooled and poured into ice water. The solid obtained was
filtered, washed with water, dried and recrystallized from ethanol. IR: 1685
(C¼O), 1612 (C¼N) cmꢁ1
.
1H NMR (CDCl3): d 2.90 (s, 3 H, OCH3),
7.00–7.31 (m, 4 H, ArH), 7.82 (s, 1 H, ArH), 8.02–8.34 (m, 4 H, ArH);
13C NMR (CDCl3): d 54.2, 102.7, 108.9, 112.7, 126.4, 127.8, 129.5,
129.9, 131.6, 132.3, 134.6, 136.4, 139.9, 148.9, 159.8, 160.9; MS (m/z,
%): 292 (Mþ, 100), 262 (75), 186 (50), 168 (70), 148 (25), 144 (50).
Adopting this procedure compounds II–V were prepared.
4.1.13. Synthesis of 4-(3-methoxyphenyl)-1-(4-methylpiperazinyl)-4 H-
[1,2,4] triazolo [4,3-a] quinazolin-5-one (X)
IR: 1688 (C¼O), 1608 (C¼N) cmꢁ1
.
1H NMR (CDCl3): d 1.0–1.2 (m,
4 H, NCH2CH2N), 1.74–1.90 (m, 4 H, NCH2CH2N), 2.02 (s, 3 H, CH3),
2.95 (s, 2 H, OCH3), 3.21 (s, 2 H, CH2), 7.20–7.73 (m, 8 H, ArH);
13C NMR (CDCl3): d 41.9, 46.8 (2C), 53.6 (2C), 54.9, 103.5, 106.9,
111.7, 125.7, 126.9, 128.9, 129.7, 131.9, 132.9, 133.9, 137.6, 139.8,
147.5, 157.9, 161.0; MS (m/z, %): 404 (Mþ, 100), 262 (65), 186 (50), 168
(48), 148 (44), 144 (40).
4.1.5. Synthesis of 4-(3-methoxyphenyl)-1-methyl-4H-[1,2,4] triazolo [4,3-
a] quinazolin-5-one (II)
IR: 1680 (C¼O), 1611 (C¼N) cmꢁ1
;
1H NMR (CDCl3): d 2.5 (s, 3 H,
CH3), 3.3 (s, 3 H, OCH3), 7.3–7.8 (m, 8 H, ArH). MS (m/z, %): 306 (Mþ,
75), 262 (75), 275 (60), 186 (50), 168 (70), 148 (25), 144 (50).
4.2. Pharmacology screening
The synthesized compounds were evaluated for antihistaminic and seda-
tive-hypnotic activities. The animals were maintained in colony cages at
25 ꢀ 2 ꢂC, relative humidity of 45–55%, under a 12 h light and dark cy-
cle; they were fed standard animal feed. All the animals were acclimatized
for a week before use. The Institutional Animal Ethics committee ap-
proved the protocol adopted for the experimentation of animals.
4.1.6. Synthesis of 1-ethyl-4-(3-methoxyphenyl)-4H-[1,2,4] triazolo [4,3-a]
quinazolin-5-one (III)
IR: 1690 (C¼O), 1615 (C¼N) cmꢁ1
8.23 (m, 8 H, ArH); 13C NMR (CDCl3): d 12.8, 18.9, 53.9, 102.9, 107.9,
.
1H NMR (CDCl3): d 1.52–1.64 (t,
3 H, CH2CH3), 2.11–2.24 (q, 2H, CH2CH3), 3.64 (s, 3 H, OCH3), 7.80–
8
Pharmazie 64 (2009) 1

ORIGINAL ARTICLES
4.2.1. Antihistaminic activity
References
A modification of the technique of Van Arman et al. (1961) was adopted
to determine the antihistaminic potential of the synthesized compounds.
Male Dunkin Hartley Guinea pigs (250–300 g) were fasted for 12 h. Six
animals were taken in each group. The test compounds, was administered
orally at a dose of 10 mg/kg in 1% CMC and challenged with histamine
aerosol (0.2% aqueous solution of histamine acid chloride 3 ml) in a vapo-
nephrin pocket nebulizer sprayed into a closed transparent cage. The re-
spiratory status reflecting the increasing degree of bronchoconstriction was
recorded. The time for onset of action was recorded. Animals remaining
stable for more than 6 min were considered protected against histamine-
induced bronchospasm. An intraperitoneal injection of chlorpheniramine
maleate (Avil; Hoechst, Mumbai, India) at a dose of 25 mg/kg was given
for the recovery of the test animals. The mean preconvulsion time of ani-
mals, treated with the test compounds was compared to control and is
expressed in terms of percentage protection (Table 2).
Alagarsamy V, Venkatesaperumal R, Vijayakumar S, Angayarkanni T, Pou-
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Percent protection ¼ [1ꢁ(T1/T2)] ꢃ 100
T2-preconvulsive time of test compound; T1-preconvulsive time of control.
The activity of the test compounds was compared with the standard anti-
histamine chlorpheniramine maleate.
Dews PB (1953) The measurement of the influence of drugs on voluntary
activity in mice. Br J Pharmacol 8: 46–48.
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4.2.2. Sedative-hypnotic activity
Reduction in locomotor activity was determined using actophotometer
(Dews 1953; Kuhn and Van Maanen 1961). Swiss albino mice were chosen
as test animals in a group of six. Basal activity score was taken and then
compounds I–X and standard chlorpheniramine maleate were administered
orally at the dose of 5 mg/kg in 1% CMC. Scores were recorded at 1, 2 and
3 h after the drug administration. The percent reduction in locomotor activ-
ity was calculated by the following formula and shown in Table 2.
% Reduction in motor activity ¼ [(AꢁB)/A] ꢃ 100
Where A-basal score, B-score after drug treatment.
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beta-alkoxyethyl and beta-(N,N-dialkylamino)ethyl-(3-aryl-3,4-dihydro-
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4.2.3. Statistical analysis
Statistical analysis of the biological activity of the synthesized compounds
on animals was evaluated using a one-way analysis of variance (ANOVA).
In all cases, post-hoc comparisons of the means of individual groups were
performed using Tukey’s test. A significance level of P < 0.05 denoted
significance in all cases. All values are expressed as mean ꢀ SD (standard
deviations). For statistical analysis we have used GraphPad Prism 3.0 ver-
sion. (GraphPad Prism 3.0 version, GraphPad Software, Inc.11452 El Ca-
mino Real, #215, San Diego, CA 92130 USA).
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Acknowledgements: The authors thank the head, department of Chemistry,
Indian Institute of Technology, Chennai for the mass spectral data and the
head, sophisticated analytical instrument facilities, Central Drug Research
Institute, Lucknow for NMR spectral data.
Pharmazie 64 (2009) 1
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