Synthesis, antimalarial and antibacterial activities of 3-amino acid- and aryl amine-substituted 2-methyl- 3H-quinalzolin-4-ones

Article abstract of DOI:10.1007/s00044-009-9245-1

A new series of 2-methyl-3H-quinazolinones substituted at the third position with amino acids (2-5) and aryl amine (6, 7) was designed, synthesized, and analyzed by infrared, NMR, and mass spectral analysis. Further, the compounds were screened for their in vivo antimalarial activity using the rodent malaria parasite Plasmodium yoelii (N-67) with the Swiss mice model. The compounds were also tested for their antibacterial activity. Birkhaueser Boston 2009.

Full text of DOI:10.1007/s00044-009-9245-1

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2010) 19:993–999
DOI 10.1007/s00044-009-9245-1
ORIGINAL RESEARCH
Synthesis, antimalarial and antibacterial activities
of 3-amino acid- and aryl amine-substituted 2-methyl-
3H-quinalzolin-4-ones
•
Subramania Nainar Meyyanathan
•
Mamillapalli Ramu Bhojraj Suresh
Received: 6 March 2009 / Accepted: 26 August 2009 / Published online: 6 October 2009
¨
Ó Birkhauser Boston 2009
Abstract A new series of 2-methyl-3H-quinazolinones substituted at the third
position with amino acids (2–5) and aryl amine (6, 7) was designed, synthesized,
and analyzed by infrared, NMR, and mass spectral analysis. Further, the compounds
were screened for their in vivo antimalarial activity using the rodent malaria parasite
Plasmodium yoelii (N-67) with the Swiss mice model. The compounds were also
tested for their antibacterial activity.
Keywords Quinazolinone Á Antimalarial Á Plasmodium yoelii Á Swiss mice model Á
Antibacterial
Introduction
The search for novel antimalarial drugs for treatment as well as for prophylaxis is of
great concern in light of the current worldwide resurgence of malaria. Quinazolines
and condensed quinazolines have received the attention of medicinal chemists due
to their wide range of biological activities (Alagarsamy et al., 2004), which include
mainly anti-infective activities, such as antibacterial (Alagarsamy et al., 2000) and
antifungal activities, CNS activities such as analgesic (Nigam et al., 1990), anti-
inflammatory (Koizomi and Marakuni 1917), anticonvulsant (Manabu et al., 1990)
activities, and antimalarial activities (Michael and Leann 1998; Mei-Lin et al.,
1998; Kaylene, 1999; Joshi et al., 2005). The quinazolin-4-one motif-based drugs
that are on the market are known to possess side effects. In the present study it was
envisaged that a drug molecule possessing the above-mentioned pharmacophore
S. N. Meyyanathan (&) Á M. Ramu Á B. Suresh
Department of Pharmaceutical Analysis, J.S.S. College of Pharmacy, Post Box No. 20,
Rocklands, Ooty 643001, Tamilnadu, India
e-mail: meyys@rediffmail.com; meyys@hotmail.com

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Med Chem Res (2010) 19:993–999
may be of advantage for antimalarial activity, because it is known to possess a broad
spectrum of antimicrobial activity.
Chemistry
The quinazolin-4-ones incorporated with biologically friendly amino acids such as
glycine (2), L-lysine (3), L-cysteine (4), and L-glutamic acid (5) were synthesized
according to the route given in Scheme 1. The intention in designing a quinazolin-4-
one motif incorporated with amino acids was to enhance the pharmacokinetic
parameters such as PKa and water solubility apart from nontoxic metabolites.
In general, anthranilic acid was acetylated using an acetylating reagent such as
acetic anhydride to form N-acetyl anthranilic acid (1). The N-acetyl anthranilic acid
was further treated with amino acid or aryl amine to cyclize in the presence of
phosphorous pentoxide, to give the final compounds shown in Table 1. Compounds
were analyzed based on infrared (IR), 1H-NMR, and mass profiles. Elemental
analysis was also performed for carbon, hydrogen, nitrogen, and oxygen. Calculated
and found values were within 0.4% variance.
General
Melting points were determined in open capillaries on a LABINDIA digital melting-
point apparatus and are uncorrected. IR spectra were recorded on a Perkin-Elmer
FTIR 283, spectrophotometer using KBr disks and are expressed as cm-1. 1H-NMR
spectra were recorded on a Bruker DRX-300 (300 MHz, FTNMR) using CDCl3 as
solvent and TMS as internal standard and are expressed as d ppm. Mass spectra
(MS) were determined on Shimadzu LCMS 2010A, using ESI ionization technique
in the positive mode (M ? 1). Elemental analysis was performed using an Elemental
Scheme 1 Compound scheme
O
(CH3CO)2O
CH3COONa
NH2
N
H
COOH
COOH
(1)
Amino acid or
aromatic amine
P2O5, CH3COOH
N
N R
O
(2-7)

Med Chem Res (2010) 19:993–999
995
Table 1 Final compounds
Compounds
R
Yield (%)
46.2
N
2
CH2COOH
N R
O
3
4
40.1
NH2
COOH
39.14
COOH
COOH
SH
5
46.8
COOH
6
7
70.34
NO2
OH
72.8
Vario EL III (Carloerba 1108). Reactions were monitored by TLC using silica gel
type 60 F254 of E. Merck with 4% methanol in chloroform as the mobile phase. TLC
plates were visualized in UV and with iodine vapors.
Procedure for the preparation of N-acetyl anthranilic acid (1)
Anthranilic acid (1 mol) was mixed with an equimolar quantity of sodium acetate
and acetic anhydride (1.15 mol) and refluxed on a sand bath for 1 h. The reaction

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Med Chem Res (2010) 19:993–999
mixture was then poured into a beaker containing water; the crude solid product
separated was filtered and dried. The dried crude product was recrystallized from
aqueous alcohol to get a brownish-yellow crystalline solid (4.7 g; 72.2%); m.p.,
210°C. IR (KBr) cm-1: 3367 (N–H), 2902 (CH3), 1677 (CONH), 1718 (COOH),
1611 (C=C), 1218 (C–N), 1121 (C–O).
Procedure for the preparation of 3-amino acid-substituted 3H-quinazolin-4-ones
(2–5)
To a solution of N-acetyl anthranilic acid (1 mol) in 20 ml of hot glacial acetic acid
was added a phosphorus pentoxide (1.15 mol) and a corresponding amino acid
(1.15 mol). The reaction mixture was refluxed for 3 h and the reaction monitored by
TLC. Then the reaction mixture was poured into a beaker containing 100 ml of
hydrochloric acid; crude products which separated out were filtered and dried.
Crude products were recrystallized with aqueous ethanol. Further, the compounds
were purified by column chromatography using silica gel (60-120) as the stationary
phase and acetonitrile/ethyl acetate/methanol at a ratio of 1:1:1 as the mobile phase
and are shown in Table 1.
2-(2-Methyl-4-oxo-4H-quinazolin-3-yl)-ethanoic acid (2)
Melting point, 201°C. IR (KBr) cm-1: 3458 (OH), 2884 (CH3), 1720 (COOH), 1677
(CONH), 1630 (C=C), 1588 (C=N), 1215 (C–N),1105 (C–O). H-NMR (CDCl3,
1
300 MHz) d: 2.11 (3H, s, CH3), 4.14 (2H, s, CH2), 7.73–8.11(4H, m, ArH), 11.0
(1H, s, COOH). ESI-MS m/z: 219.2 (M ? 1), 214, 167, 241, 82.
2-Amino-6-(2-methyl-4-oxo-4H-quinazolin-3-yl)-hexanoic acid (3)
Melting point, 197°C. IR (KBr) cm-1; 3470 (OH), 2897 (CH3), 1723 (COOH), 1680
(CONH), 1631 (C=C), 1598 (C=N), 1210 (C–N), 1121 (C–O). H-NMR (CDCl3,
1
300 MHz) d: 1.91 (3H, s, CH3), 2.29–3.03 (8H, m, CH2), 3.2 (1H, t, CH), 3.49 (1H,
t, CH), 4.35 (2H, t, NH2), 7.65–7.91 (4H, m, ArH), 11.1 (1H, s, COOH). ESI-MS m/
z: 290.2 (M ? 1), 264, 177, 128.
3-Mercapto-3-(2-methyl-4-oxo-4H-quinazolin-3-yl)-propionic acid (4)
Melting point, 226°C. IR (KBr) cm-1: 3469 (OH), 2890 (CH3), 2590 (SH), 1721
(COOH), 1671 (CONH), 1630 (C=C), 1579 (C=N), 1219 (C–N), 1119 (C–O). H-
1
NMR (CDCl3, 300 MHz) d: 2.19 (3H, s, CH3), 1.7 (1H, t, SH), 2.94 (2H, q, CH2),
3.89 (1H, t, CH), 7.72–8.16 (4H, m, ArH), 11.1 (1H, s, COOH). ESI-MS m/z: 265.2
(M ? 1), 250, 197, 119, 80.
2-(2-Methyl-4-oxo-4H-quinazolin-3-yl)-pentandioic acid (5)
Melting point, 213°C. IR (KBr) cm-1: 3481 (OH), 2907 (CH3), 1723 (COOH), 1680
(CONH), 1630 (C=C), 1589 (C=N), 1209 (C–N), 1112 (C–O). H-NMR (CDCl3,
1

Med Chem Res (2010) 19:993–999
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300 MHz) d: 2.32 (3H, s, CH3), 2.95–3.11 (4H, m, (CH2)2), 4.52 (1H, t, CH), 7.74–
8.19 (4H, m, ArH), 11.08 (1H, s, COOH), 11.28 (1H, s, COOH). ESI-MS m/z:
305.23 (M ? 1), 289, 234, 186, 98.
Procedure for the preparation of compounds 6 and 7
To a solution of N-acetyl anthranilic acid (1 mol) in 20 ml of hot glacial acetic acid
was added a mixture of phosphorus pentoxide (1.15 mol) and aromatic amine
(1 mol). The reaction mixture was refluxed for 3 h, then poured into a beaker
containing 100 ml of 1 N sodium bicarbonate solution. The crude products which
separated out were filtered and dried. Dried crude products were recrystallized with
aqueous ethanol to get pure compounds and are shown in Table 1.
1-(2-Methyl-4-oxo-4H-quinazolin-3-yl)-4-nitro benzene (6)
Melting point, 124°C. IR (KBr) cm-1: 2991 (CHAr), 2913 (CH3), 1680 (CONH),
1629 (C=C), 1585 (C=N), 1550 (NO2), 1202 (C–N), 1109 (C–O). 1H-NMR (CDCl3,
300 MHz) d: 2.21 (3H, s, CH3), 7.71–8.39 (4H, m, ArH), 7.90 (2H, d, ArH), 8.17
(2H, d, ArH), 10.9 (1H, s, COOH). ESI-MS m/z: 282.15 (M ? 1), 267, 211, 184,
111, 74.
1-(2-Methyl-4-oxo-4H-quinazolin-3-yl)-4-hydroxy benzene (7)
Melting point, 190°C. IR (KBr) cm-1: 3342 (OH), 2991 (CHAr), 2907 (CH3),1680
(CONH), 1627 (C=C), 1585 (C=N), 1550 (NO2), 1214 (C–N), 1109 (C–O). H-
1
NMR (CDCl3, 300 MHz) d: 2.07 (3H, s, CH3), 7.84–8.31 (4H, m, ArH), 7.47 (2H, d,
ArH), 7.51 (2H, d, ArH), 7.90 (2H, d, ArH), 8.9 (1H, s, OH). ESI-MS m/z: 253.2
(M ? 1), 217, 176, 112, 81.
Pharmacology
Procedure for in vivo antimalarial screening
The in vivo efficacy of synthetic compounds was evaluated against a rodent malaria
parasite Plasmodium yoelii (N-67) in the Swiss mice model (Neerja and Puri 2004;
Singh et al., 2002, 2004; Puri and Naresh 2000). Random-bred Swiss mice
(23 2 g) of either gender were obtained from breeding colonies at the laboratory
animal facilities at CDRI, Lucknow, India. Each animal was inoculated intraper-
itoneally with 1 9 107 P. yoelii parasitized red blood cells (RBCs) and the day of
inoculation was designated Day 0. Animals were maintained on a commercial pellet
diet and water ad libitum under standard housing conditions.
Aqueous suspensions of the synthetic compounds were prepared after making a
paste with a few drops of Tween-80. The volume was adjusted so as to obtain the
required 200 mg/kg dose in a volume of 0.5 ml. The treatment was administered
intraperitoneally, once daily for 4 consecutive days, day 0 to day 3, to groups of five

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Med Chem Res (2010) 19:993–999
P. yoelii-infected mice. One group of five mice was administered the aqueous
vehicle used for preparing the suspension and served as untreated controls.
Thin blood smears were prepared from each animal on day 4, i.e., 24 h after the
last treatment dose, and again on day 7. The degree of infection was microscopically
recorded in terms of the number of P. yoelii-infected cells per 100 RBCs (i.e.,
percentage parasitemia). The mean value determined for each group of five mice
was used to calculate the percentage suppression of parasitemia with respect to the
untreated control group.
Antibacterial activity
In vitro antibacterial screening was performed for all six synthesized compounds
against S. aureus and E. coli by the cup plate method. Sterile nutrient agar plates
were prepared by pouring sterile agar into petri plates under aseptic conditions.
One-tenth milliliter of the standardized organism was spread onto agar plates. Holes
were prepared using a sterile borer 6 mm in diameter. Test compound solutions
were placed in each hole separately. Then the plates were incubated at 4°C for 1 h
to allow diffusion of the solution into the medium. Then all the bacterial plates were
incubated at 37°C for 24 h. The zone of inhibition was measured (mm) against the
standard kanamycin as a positive control and 10% DMSO in water as a solvent
control. The concentration of test compounds as well as standard kanamycin was
100 lg.
Results and discussion
In the present studies, four 3-amino acid-substituted 3H-quinazolin-4-ones (1–4)
were synthesized, and to compare and contrast the structure–activity relationships at
the third position, we synthesized another two compounds with the aryl group
incorporated at the third position of 3H-quinazolin-4-one. Their antimalarial activity
Table 2 Degree of parasitemia on days 4 and 7 in the six treated groups and relative suppression of
parasitemia compared to the control group
Compound Dose
No. of Mean % parasitemia on
Suppression of
parasitemia on
Mean survival
time SE (days)
(mg/kg) mice
Day 4
Day 7
Day 4
Day 7
2
200
200
200
200
200
200
5
5
5
5
5
5
5
10.50 1.60 17.20 0.00 15.05
9.78 1.30 17.50 1.70 20.87
11.90 1.77 25.00 3.00 3.72
9.60 1.73 18.45 1.35 22.33
10.43 0.47 25.50 2.50 15.61
10.52 1.33 16.80 0.00 14.89
11.79
10.25
NIL
5.38
NIL
13.85
–
6.60 0.98
6.80 1.39
7.40 1.03
7.80 0.97
7.00 1.82
6.80 0.58
8.20 0.86
3
4
5
6
7
Control
12.36 1.14 19.50 0.76
–
(–) Mice remained negative during the entire observation period

Med Chem Res (2010) 19:993–999
999
was evaluated pharmacologically against the rodent malaria parasite P. yoelii (N-
67) in the Swiss mice model. The degree of parasitemia on days 4 and 7 in the six
treated groups and the relative suppression of parasitemia compared to the control
group are summarized in Table 2. Although compounds 2, 3, 5, and 7 showed a
little antimalarial activity, surprisingly, the overall results revealed that none of the
six compounds possess significant or potential antimalarial activity. None of the
compounds showed antibacterial activity against either the gram-positive bacterium
S. aureus or the gram-negative bacterium E. coli at a concentration of 100 lg.
In conclusion, the entitled compounds did not show any antimalarial or
antibacterial activity, although better antimalarial and antibacterial activity was
anticipated.
Acknowledgments All the authors are grateful to Dr. A. K. Goel, Assistant Director, CDRI, Lucknow,
India, for helping us conduct the antimalarial evaluation. The authors are also grateful to Sri Shivarathree
Desikendra Mahaswamigalavaru of Suttur mutt for providing the facilities to carry out the synthetic work.
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