Synthesis and antimicrobial activity of polyhalobenzonitrile quinazolin-4(3H)-one derivatives

Article abstract of DOI:10.1016/j.bmcl.2013.08.068

A novel series of polyhalobenzonitrile quinazolin-4(3H)-one derivatives were synthesized and characterized by NMR, IR, MS, and HRMS spectra. All of the newly prepared compounds were screened for antimicrobial activities against four strains of bacteria (Gram-positive bacterial: Staphylococcus aureus and Bacillus cereus; Gram-negative bacterial: Escherichia coli and Pseudomonas aeruginosa) and one strain of fungi (Candida albicans). Among the synthesized compounds, 5-(dimethylamino)-8-(2,4,5-trichloro-isophthalonitrile) quinazolin-4(3H)-one (7k) exhibited significant activity towards Gram-positive bacterial, Gram-negative bacterial, and the fungi strains. The MIC (0.8-3.3 μg/mL) and MBC (2.6-7.8 μg/mL) for this compound were close to those of nofloxacin, chlorothalonil, and fluconazole, making it the most potent antimicrobial agents in the series.

Full text of DOI:10.1016/j.bmcl.2013.08.068

Bioorganic & Medicinal Chemistry Letters 23 (2013) 5958–5963
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and antimicrobial activity of polyhalobenzonitrile
quinazolin-4(3H)-one derivatives
a
c
b,
Li-Ping Shi a, , Kun-Ming Jiang a, , Jun-Jie Jiang b, Yi Jin a, , Yun-Hai Tao , Ke Li , Xing-Hong Wang
⇑
⇑
,
Jun Lin a,
⇑
a Key Laboratory of Medicinal Chemistry for Natural Resource (Yunnan University), Ministry Education, School of Chemical Science and Technology, Yunnan University,
Kunming 650091, PR China
b Institute of Microbiology, Yunnan University, Kunming 650091, PR China
c Yunnan Tumor Research Institute, The Third Affiliated Hospital of Kunming Medical University, Kunming 650118, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 June 2013
Revised 24 July 2013
Accepted 14 August 2013
Available online 23 August 2013
A novel series of polyhalobenzonitrile quinazolin-4(3H)-one derivatives were synthesized and character-
ized by NMR, IR, MS, and HRMS spectra. All of the newly prepared compounds were screened for antimi-
crobial activities against four strains of bacteria (Gram-positive bacterial: Staphylococcus aureus and
Bacillus cereus; Gram-negative bacterial: Escherichia coli and Pseudomonas aeruginosa) and one strain of
fungi (Candida albicans). Among the synthesized compounds, 5-(dimethylamino)-8-(2,4,5-trichloro-
isophthalonitrile) quinazolin-4(3H)-one (7k) exhibited significant activity towards Gram-positive bacte-
rial, Gram-negative bacterial, and the fungi strains. The MIC (0.8–3.3 lg/mL) and MBC (2.6–7.8 lg/mL) for
this compound were close to those of nofloxacin, chlorothalonil, and fluconazole, making it the most
potent antimicrobial agents in the series.
Keywords:
Polyhalobenzonitrile quinazolin-4(3H)-one
Synthesis
Antimicrobial activity
Gram-positive bacterial
Gram-negative bacterial
Fungi strains
Ó 2013 Elsevier Ltd. All rights reserved.
Quinazoline is the most commonly encountered heterocyclic
compound in medicinal chemistry due to its broad range of
pharmacological activities. Many of its derivatives are used as
medicines and display antimicrobial,1 antifungal,2 anti-HIV,3
anti-tobacco mosaic virus (anti-TMV),4 anticancer,5 anti-tubercu-
lar,6 anti-inflammatory,7 antidepressant,8 anticonvul-sant,8,9
hypolipidemic,10 analgesic,11 antiulcer,12 or immunotropic
activities. They also act as inhibitors of protein tyrosine kinase
inhibitors, thymidylate synthase,13 and poly(ADP-ribose) polymer-
ase (PARP).14 As pesticides, they are used as both insecticides15 and
fungicides. Quinazolinones are an excellent reservoir of bioactive
substances. The quinazolin-4(3H)-one structural motifs have
attracted a great deal of interest due to their accessibility, diverse
chemical reactivity, and wide range of previously mentioned
biological uses. Several bio-active natural products, such as febrifu-
gine and isofebrifugine,16 contain quinazolinone moieties with
potential antimalarial activity.
polyhalobenzonitriles derivatives are reportedly used as pesticides,
for example Bromoxynil (I) is used as a herbicide and Chlorothalo-
nil (II) is used as a fungicide.17 Additionally, polyhalobenzonitriles
may enhance the activity with other structural fragment and may
result in novel biological applications. Our previous reports have
explored the antimicrobial (III),18 antitumor (IV),19 and anti-HIV
activities of polyhalo-benzonitrile substituted derivatives, and all
were found to have good bioactivities (Fig. 1).
F
OH
NC
CN
F
Br
Br
N
H
Cl
CN
Antimicrobial Compound (III)
Bromoxynil (I)
F
Cl
F
CN
F
On the other hand, organic halide derivatives play important
role in drug research. In particular, polyhalobenzonitriles have at-
tracted much attention because of their biological activity. Some
O
Cl
Cl
CN
EtO
HN
Antitumor Compound (IV)
Figure 1. Biologically active polyhalobenzonitrile compounds.
Cl
CN
NH
CN
⇑
Corresponding authors. Tel./fax: +86 871 6503 3215.
E-mail addresses: jinyi@ynu.edu.cn (Y. Jin), wxihong@sina.com (X.-H. Wang),
linjun@ynu.edu.cn (J. Lin).
Chlorothalonil (II)
These authors contributed equally to this work.
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.08.068

L.-P. Shi et al. / Bioorg. Med. Chem. Lett. 23 (2013) 5958–5963
5959
Table 1
Prompted by the varied biological activities of quinazolin-
Optimization of reaction conditionsa
4(3H)-one derivatives, and understanding the importance of or-
ganic halide compounds, we synthesized potential antimicrobial
agents containing two biodynamic moieties: a polyhalobenzonitri-
le and 5-arylamine(or alkylamine)-8-amino-quinazolin-4(3H)-one.
The newly synthesized compounds, 3m–n, 4a–l, 7a–l, 8a–e, 9 and
10, were screened for their in vitro antibacterial and antifungal
activity, and we also determined their logP and molar refractivity
(MR). The bioactive assay showed that most of the tested com-
pounds displayed variable inhibitory effects on the growth of the
Gram-positive bacterial strain, Gram-negative bacterial strains, or
fungal strain.
The route employed for synthesis of the target compounds is
shown in Scheme 1. Compounds 3a–n were obtained with a
60–80% yield by SNAr nucleophilic substitution of alkylamine or
arylamine with 5-chloro-8-nitro-quinazolin-4(3H)-one (1) in
THF:DMF (3:1) at 80 °C for 12 h.20 Then compounds 3a–l were sub-
jected to direct hydrogen reduction in THF to give the intermedi-
ates compounds 4a–l. For the compounds 7a–l, the deacid
reagent promoted the SNAr nucleophilic substitution of poly-
halobenzonitrile 5 or 6 in different solvents, reaction times, and
temperatures (Table 1). Finally, we concluded that the best reaction
conditions for the target molecules 7a–l were THF/DMF (7:1) as the
solvent and K2CO3 as the deacid reagent under 75 °C for 2 h, result-
ing in an isolated product with a moderate yield (35–70%).
Entry
Solventb
Time (h)
T (°C)
Alkalic
Yieldd (%)
1
2
3
4
5
6
7
8
THF
THF
DMF
DMF
Methanol
Methanol
Toluene
Toluene
THF+DMF(1:1)
THF+DMF(1:1)
THF+DMF(4:1)
THF+DMF(4:1)
THF+DMF(7:1)
THF+DMF(7:1)
THF+DMF(7:1)
THF+DMF(7:1)
THF+DMF(7:1)
THF+DMF(7:1)
THF+DMF(7:1)
THF+DMF(7:1)
2
2
0.5
0.25
2
2
2
2
1
1
1
1
1
1
1
1
1
25
75
25
75
25
75
25
75
25
75
25
75
25
75
75
75
75
75
75
75
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NaOH
NaH
N.R.
N.R.
<10.0
<10.0
N.R.
N.R.
N.R.
N.R.
<10.0
<10.0
25.5
27.4
25.0
62.4
<10.0
<10.0
<10.0
<10.0
47.2
N.R.
9
10
11
12
13
14
15
16
17
18
19
20
t-BuOK
EtONa
Cs2CO3
Et3N
1
1
1
a
8-Amino-5-(phenylamino)quinazolin-4(3H)-one 4a (1 mmol) and 2,4,5,6-tet-
rachloroisophthalonitrile 6 (1 mmol).
b
The volume of solvent is 5 mL.
Alkali (2 mmol).
Isolated 7a yield.
c
d
The intermediates (3m and 3n) directly reacted with 2,4,5,6-tet-
rachloroisophthalonitrile (6) to give the polyhalobenzonitrile at the
5-substituted position of quinazolin-4(3H)-one (9 and 10)
(Scheme 2). The structures of all newly synthesized compounds
werecharacterizedbyIR, 1HNMR, 13CNMR, MS, andHRMSstudies.21
Of all of the compounds, 3m–n, 4a–l, 7a–l, 8a–e, 9, and 10 were
initially screened for in vitro antimicrobial activity against Gram-
positive bacterial strains (Staphyloccocus aureus ATCC 6538 [SA]
and Bacillus cereus ATCC 14579 [BC]), Gram-negative bacterial
strains (Escherichia coli ATCC 8099 [EC] and Pseudomonas aerugin-
osa ATCC 15442 [PA]), and a fungalstrain (Candida albicans ATCC
10231 [CA]) using the disk diffusion assay.22,23 Standard inoculums
(1–2 Â 107 c.f.u/ml 0.5 Mcfarland standards) were introduced onto
the surface of sterile agar plates, and a sterile glass spreader was
CN
Cl
Cl
Cl
Cl
NH2
Cl
Cl
CN
Cl
NC
NH
NH
R
NH
O
N
NH
CN
R
O
N
6
NH
THF+DMF(7:1);
K2CO3
NO2
3m: R=H
9: R=H
NO2
3n: R=CH3
10: R=CH3
Scheme 2. Synthetic pathway of compounds 9 and 10.
R1
O
R1
O
N
Cl
O
N
alkylamine
H2,Pd/C
THF
2
NH
or arylamine
NH
NH
THF+DMF, 80¡æ;
N
NO2
NO2
NH2
1
3a-n
4a-l
X
R1
O
NC
X
Y
5
:X=Cl,Y=Cl
NH
6:X=F,Y=Cl
X
CN
X
N
CN
X
NH
Y
7a-l
: X=Cl, Y=Cl
THF+DMF(7:1)
K2CO3
8a-c,e: X=F, Y=Cl
NC
Cl
F
Cl
R1 =
NH
NH
NH
NH
NH
NH
NH
f
c
e
d
g
n
b
a
NH2
NH
NH2
NH
N
N
N
NH
NH
l
k
h
m
j
i
Scheme 1. Synthetic pathway of compounds 7a–l, 8a–c and 8e.

5960
L.-P. Shi et al. / Bioorg. Med. Chem. Lett. 23 (2013) 5958–5963
used for even distribution of the inoculums. The disks, which mea-
sured 6 mm in diameter, were prepared from Whatman No. 1 filter
paper and sterilized by dry heat at 121 °C for 1 h. The sterile disks
ZOI[PA] = 15.0; and ZOI[CA] = 15.5) had comparably better activity
than the other compounds against all the bacterial and fungal
strains, and exhibited similar antimicrobial activities as the stan-
dard antibiotic drugs, norfloxacin (ZOI[BC] = 18.6; ZOI[SA] = 17.0;
ZOI[EC] = 20.0; ZOI[PA] = 16.8 and ZOI[CA] = 21.8) and chlorothalo-
nil (ZOI[BC] = 15.5; ZOI[SA] = 14.0; ZOI[EC] = 18.5; ZOI[PA] = 15.8
and ZOI[CA] = 17.0).
The lipophilicity of the compounds, which is seen as an impor-
tant parameter related to membrane permeation in biological sys-
tem, describes the main predictor for the activity.24 The octanol/
water partition coefficient logP, which is a measure of hydropho-
bicity/lipophilicity, was calculated using ChemDraw Ultra 10.0
software integrated with Cambridgesoft Software (Cambridgesoft
Corporation).25 The results obtained are shown in Table 2. The
calculated values of logP for polyhalobenzonitrile-substituted
compounds 7a–l, 8a–e, 9, and 10 were higher than that of the
non-polyhalobenzonitrile substituted compounds 3m, 4c–e, and
4g–k. The antimicrobial ZOI observed for polyhalobenzonitrile
substituted compounds is higher than that observed for the non-
polyhalobenzonitrile substituted compounds.
previously soaked in a known concentration (1000 lg/mL) of the
test compounds were placed in nutrient agar medium. Solvent
and growth controls were performed, using. norfloxacin- and chlo-
rothalonil-soaked disks as positive control, while DMSO-soaked
disks were used as negative control. The plates were incubated
for 24 h at 37 °C. Susceptibility was assessed on the basis of the
diameter of the zone of inhibition against Gram-positive and
Gram-negative strains of bacterial and the fungal strain. Inhibition
zones (ZOI) were measured and compared to the controls. The bac-
terial and fungal zones of inhibition values are shown in Table 2.
The inhibition results revealed that the polyhalobenzonitrile
substituted compounds 7a–l, 8a–e, 9, and 10 showed moderate
to good bacterial and fungal inhibitions, with ZOI up to 19.0 mm.
Of these compounds, having polyhalobenzonitrile at the 5-substi-
tuted position (such as 7a–l, 8a–e) or the 8-substituted position
(such as
9 and 10) on quinazolin-4(3H)-one compounds is
beneficial, as both can inhibit the growth of Gram-positive and
Gram-negative bacterial strains and the fungal strain. However,
non-polyhalobenzonitrile-substituted compounds 3m, 4c–e and
4g–k showed no significant inhibition of bacterial growth and fun-
gal growth for any of the strains tested. However, compounds 3n,
4a, 4b, and 4f showed some degree of inhibition for the bacterial
and fungal strains. This can be explained by the introduction of a
polyhalobenzonitrile at the quinazolin-4(3H)-one fragment, which
can increase the antimicrobial activity of compounds. Noticeably,
the compound 7k (ZOI[BC] = 18.0; ZOI[SA] = 14.3; ZOI[EC] = 19.0;
The molar refractivity (MR), which represents the size and
polarizability of a molecule by describing its steric effects, was also
calculated (using ChemDraw Ultra 10.0 software) to explain the
activity of the synthesized compounds. From the data shown
Table 2, it can be inferred that the higher value of molar refractivity
favors the activity ratio for quinazolin-4(3H)-one derivatives, such
as compounds 4a–l and 7a–l.
The minimum inhibitory concentration (MIC,
lg/mL) of anti-
bacterial activity for compounds 3n, 4a–b, 4f, 7a–k, 8a–e, 9, and
Table 2
Calculated logP and molar refractivity (MR) and antimicrobial evaluation of compounds 3m–n, 4a–l, 7a–l, 8a–e, 9 and 10 y determination of the ZOI
Compound
LogP
MR
Zone of inhibition (mm)
Gram-negative bacterial
Gram-positive bacterial
SA
Fungal strain
CA
BC
EC
PA
3m
3n
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
8a
8b
8c
8e
9
10
1.34
1.80
1.52
2.01
2.01
2.01
2.08
2.08
1.68
2.50
2.50
1.08
0.34
1.02
5.53
6.02
6.02
6.02
6.09
6.09
5.69
6.51
6.51
5.08
4.35
5.03
4.73
5.22
5.71
5.29
4.29
4.71
4.33
1.37
77.00
43.81.
72.77
78.67
78.67
78.67
77.38
77.38
73.18
84.57
84.57
71.96
60.04
N
15.0
9.5
6.0
N
N
N
6.0
6.0
N
6.0
N
N
N
5.3
N
8.0
N
N
N
6.5
N
6.5
N
N
7.8
14.7
N
9.0
6.5
N
N
6.0
N
N
N
13.5
N
10.0
N
N
N
N
N
N
N
N
N
N
10.3
N
10.0
9.5
9.5
9.0
10.5
10.0
7.0
N
16.8
7.0
8.5
N
N
N
6.5
6.0
N
6.3
N
N
N
7.8
8.5
6.0
11.0
12.5
10.3
10.5
9.0
9.0
9.0
10.8
11.5
9.0
19.0
6.0
N
9.7
9.3
9.0
7.0
9.0
18.5
20.0
N
N
69.64
6.0
7.3
10.0
10.0
9.7
9.3
8.8
8.5
11.5
8.5
10.0
9.7
14.3
7.7
8.9
10.3
9.8
9.7
7.3
9.3
14.0
17.0
7.5
11.3
9.0
10.0
12.0
9.5
8.7
11.0
9.4
10.0
8.7
15.0
7.5
9.5
9.5
10.0
12.0
6.7
9.5
15.8
16.8
121.88
127.78
127.78
127.78
126.49
126.49
122.29
133.68
133.68
121.07
109.15
118.75
113.48
119.38
125.28
118.09
130.10
134.52
55.90
11.7
10.5
11.0
11.0
9.0
9.0
18.0
11.0
10.3
15.0
18.0
6.0
15.5
N
6.0
6.0
7.5
9.5
8.5
N
7.5
17.0
21.8
10.8
10.0
10.4
11.2
10.7
15.5
18.6
Chlorothalonil
Norfloxacin
86.98
N: No inhibition zone.

L.-P. Shi et al. / Bioorg. Med. Chem. Lett. 23 (2013) 5958–5963
5961
10 were determined using the liquid dilution method.26,27 Chlorot-
halonil, norfloxacin and fluconazole were used as a standard drug
for the comparison of antibacterial activity (Table 2). Test com-
pounds and positive control drugs were prepared in dimethyl sulf-
oxide solution at concentrations of 0.98, 1.95, 3.91, 7.81, 15.63,
SA] = 0.7
l
g/mL; MIC[EC] = 1.0
l
g/mL; MIC[PA] = 1.3
l
g/mL), and
5-(dimethylamino)-8-(2,4,5-trichloro-isophthalonitrile) quinazolin-
4(3H)-one (7k, MIC[BC] = 0.5 g/mL; MIC[SA] = 0.7 g/mL;
MIC[EC] = 1.0 g/mL; MIC[PA] = 1.3 g/mL) were identified as
l
l
l
l
having potent antibacterial activity against Gram-positive and
31.25, 62.5, 125, 250, 500, and 1000 lg/mL. Inoculums of the bac-
Gram-negative bacterial strains, with the same level of antibacterial
terial cultures were also prepared. Inoculums and sterile water
were added to series of tubes each containing 1 mL of a test com-
pound solution at the 11 different concentrations listed above. The
tubes were incubated for 24 h and carefully observed for the pres-
ence of turbidity. The minimum concentration at which no growth
was observed was taken as the MIC value (Table 3).
activity as the standard antibiotic chlorothalonil (MIC[BC] = 0.7
l
l
g/
g/
mL; MIC[SA] = 1.3
mL) and norfloxacin (MIC[BC] = 0.6
MIC[EC] = 0.5 g/mL; MIC[PA] = 0.7
l
g/mL; MIC[EC] = 0.5
l
g/mL; MIC[PA] = 1.7
lg/mL; MIC[SA] = 1.2 lg/mL;
l
l
g/mL).
Compounds 7f, 7g, and 7i–k were also examined for antifungal
activity by determining the MIC value using the liquid dilution
method.26,27 Chlorothalonil and the antifungal drug fluconazole
were used as a positive controls. All five of these test compounds
were identified as the most potent antifungal agents against fungal
strains, with compound 7k actually showing more inhibitory activ-
ities than the positive control.
The results obtained for the Gram-positive bacterial and Gram-
negative bacterial showed that all the test compounds exhibited
weak to good level of antibacterial activity, as determined by the
MIC values. Non-polyhalobenzonitrile-substituted compounds
(3n, 4a–b, and 4f), 5-(2,4,5-trichloroisophthalonitrile)-substituted
quinazolin-4(3H)-one (9 and 10), and 8-(5-chloro-2,4-difluoro-
isophthalonitrile)-substituted quinazolin-4(3H)-one (8a–e)
showed reduced antibacterial properties as compared to 8-(2,4,
5-trichloro-isophthalonitrile)-substituted quinazolin-4(3H)-one
(7a–k). This further indicates that introducing polyhalobenzonitrile
substituents, especially 2,4,5-trichloroisophthalonitrile, at 8-sub-
stitued quinazolin-4(3H)-one can improve their antibacterial
activities. For the 8-(2,4,5-trichloro-isophthalonitrile)-substituted
quinazolin-4(3H)-one (7a–k), all of these compounds exhibited
good inhibition against the Gram-positive bacterial BC and SA. It is
worth noting that 5-alkylamine-substituted quinazolin-4(3H)-one
(7j and 7k) and 5-haloaniline-substituted quinazolin-4(3H)-one
(7f and 7g) showed much stronger inhibition against Gram-negative
bacterial than 5-methylaniline- or 5-aniline-substituted quinazo-
lin-4(3H)-one (7a–d, 7h). Three compounds, 5-(o-fuloroaniline)-
8-(2,4,5-trichloro-isophthalonitrile) quinazo-lin-4(3H)-one (7g,
The minimum bactericidal concentration (MBC, lg/mL) against
Gram-positive bacterial and antifungal activity against fungal
strains for compounds 7f, 7g, and 7i–k also was determined
(Table 3). To determine the minimum bactericidal concentration,
0.1 mL was taken from each tube and spread on agar plates. The
number of c.f.u was counted after 18–24 h of incubation at 35 °C.
MBC was defined as the lowest drug concentration at which
99.9% of the inoculums were killed.
All five compounds (7f, 7g, and 7i–k) showed moderate to good
antibacterial activity against Gram-positive bacterial and antifungal
activity as compared to the positive controls chlorothalonil, norflox-
acin, and fluconazole, respectively. Two compounds (7g and 7j)
exhibited antibacterial activity that was as strong as chlorothalonil
and norfloxacin, but did not show as strong inhibition of fungal
activity as fluconazole. Only the compound 7k (MBC[BC] = 3.3
mL; MBC[SA] = 2.6 g/mL; MBC[CA] = 7.8 g/mL) displayed good
antifungal activity, which was greater than that observed for the po-
sitive control norfloxacin (MBC[BC] = 6.5 g/mL; MBC[SA] = 5.2 g/
mL), and fluconazole (MBC[CA] = 15.6 g/mL).
lg/
l
l
MIC[BC] = 0.7
MIC[PA] = 1.7
l
l
g/mL; MIC[SA] = 0.8
g/mL), 5-(piperidin-1-yl)-8-(2,4,5-trichloro-isopht-
lg/mL; MIC[EC] = 6.5 lg/mL;
l
l
halonitrile) quinazolin-4(3H)-one (7j, MIC[BC] = 0.5
lg/mL; MIC[-
l
Table 3
Antimicrobial activity (MIC and MBC, [
l
g/mL]) of compounds 3n, 4a, 4b, 4f, 7a–k, 8a–e, 9, 10
Minimum inhibitory concentration (MIC) ( g/mL)
Gram-negative bacterial
Compound
l
Minimum bactericidal concentration (MBC) (
lg/mL)
Gram-positive bacterial
Fungal strain
CA
Gram-positive bacterial
SA
Fungal strain
BC
SA
EC
PA
BC
CA
3n
4a
4b
4f
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
8a
20.8
125.0
166.7
N
0.5
0.5
1.0
0.7
83.3
0.5
0.7
0.8
0.7
0.5
0.8
500.0
52.1
291.7
41.7
41.7
52.1
0.7
10.4
208.0
250.0
N
125.0
52.1
5.2
10.4
4.7
0.7
0.8
15.6
0.8
0.7
3.3
20.8
208.3
250.0
N
250.0
125.0
104.2
104.2
333.3
7.8
6.5
83.3
7.8
1.0
1.3
20.8
250.0
416.7
N
83.4
83.4
N
52.1
416.7
20.8
1.7
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
41.7
6.5
—
31.3
6.5
3.3
—
—
—
—
—
—
—
—
—
—
31.3
6.5
—
31.3
4.6
2.6
—
—
—
—
—
—
—
—
—
—
—
1.7
1.7
—
5.2
2.6
0.5
—
—
—
—
—
31.3
52.1
—
52.1
41.7
7.8
—
—
—
—
—
N
20.8
1.3
2.0
N
N
500.0
208.3
416.7
500.0
125.0
416.7
1.7
8b
8c
8e
9
208.3
500
20.8
250.0
500.0
1.3
208.3
500.0
208.3
166.7
416.7
0.5
—
—
—
—
—
—
—
—
10
—
0.7
—
—
—
—
7.8
—
Chlorothalonil
Norfloxacin
Fluconazole
1.7
6.5
—
2.0
5.2
—
0.6
—
1.2
—
0.5
—
0.7
—
2.0
15.6
N: No inhibition in MIC or MBC.
—: No test.

5962
L.-P. Shi et al. / Bioorg. Med. Chem. Lett. 23 (2013) 5958–5963
Alkylamine or
Arylamine
N
O
N
R1
O
N
Cl
O
NH
R1= :
NH
NH
Dimethylamino > Piperidyl > p-Fluoroaniline
> m-Chloroaniline > Methylaniline > Aniline
best
CN
Cl
CN
X
Cl
NH
Cl
N
X
NH
Y
NH
X
NC
7k
X = Cl >
best
F
NC
Best Potent Compound
NC
X
Y
X
CN
Figure 2. Structure–activity relationship of polyhalobenzonitrile quinazolin-4(3H)-oneReferences.
3. Pandeya, S. N.; Sriram, D.; Nath, G.; De Clercq, E. Pharm. Acta. Helv. 1999, 74,
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In conclusion, in this study we described an efficient method
for the preparation of polyhalobenzonitrile quinazolin-4(3H)-one
derivatives. All the compounds 7a–l, 8a–e, 9, and 10 were tested
for their in vitro antibacterial activity against BC, SA, EC, and PA
and for their antifungal activity against Candida albicans (ATCC
10231). Most of the synthesized compounds exhibited weak to
good activity against Gram-positive and Gram-negative bacterial,
as well as the fungal strain. Compounds 7g (MIC[BC] = 0.7
l
g/mL;
g/mL; MBC[CA] = 52.1 g/
g/mL; MBC[BC] =
g/
g/mL MBC[CA] =
g/mL) appeared to be more effective than the other com-
pounds (MIC = 10–500 g/mL)against the four bacterial and one
MIC[CA] = 1.7
mL), 7j (MIC[BC] = 0.5
6.5
mL; MIC[CA] = 0.5
7.8
l
g/mL; MBC[BC] = 6.5
l
l
lg/mL; MIC[CA] = 2.6 l
l
g/mL; MBC[CA] = 41.7
lg/mL), and 7k (MIC[BC] = 0.8 l
lg/mL; MBC[BC] = 3.3
l
l
l
fungal strains. From a structure–activity relationship, we can con-
clude that polyhalobenzonitrile substitution improved the biolog-
ical activity of these compounds against Gram-positive bacterial,
Gram-negative bacterial, and fungal strains. The introduction of
haloaniline or simple alkylamine into the 5-substituted position
of quinazolin-4(3H)-one and 2,4,5-trichloro-isophthalonitrile into
the 8-substituted position of quinazolin-4(3H)-one, both of which
make the compound 7k as the best poten compound for antimi-
crobial activity in all synthetic derivatives (Fig. 2). These biologi-
cal effects will be helpful in designing more potent antimicrobial
agents.
21. Preparation
of
8-amino-5-(phenylamino)quinazolin-4(3H)-one
(4a).
Representative procedure: In 50 mL round-bottomed flask, compound 3a
(2.8 g, 10 mmol) was dissolved with 20 mL of tetrahydrofuran (THF), then
added 0.28 g (w/w) 10% Pd/C, reduced with hydrogen for 24 h. After the
completion of the reaction, Pd/C was filtered, and the solvent was evaporated
to give a pale yellow powder compound 4a 2.3 g (yield 92%). Compound 4a:
Yellow solid. Mp: 279–281 °C; IR (KBr): 3461, 3371, 3147, 3047, 2912, 1648,
Acknowledgments
1486, 1250, 1037, 757, 570 cmÀ1 1H NMR (500 MHz, DMSO-d6): d = 4.87 (br,
;
The National Natural Science Foundation of China (Nos.
20902079, 21262043, 81160384, 21262042 and U1202221) is
greatly appreciated for financial support. The authors thank the
High Performance Computing Center at Yunnan University for
use of the high performance computing platform.
2H, NH2), 6.65 (d, J = 7.3 Hz, 2H, ArH), 6.82 (d, J = 6.7 Hz, 1H, ArH), 7.18 (t,
J = 6.8 Hz, 2H, ArH), 7.26–7.30 (m, 2H, ArH), 7.80 (s, 1H, NCH@N), 9.01 (s, 1H,
NH), 11.98 (br, 1H, NH); 13C NMR (125 MHz, DMSO-d6): d = 115.7, 117.0, 120.0,
122.7, 123.2, 126.2, 129.0, 140.6, 141.1, 143.7, 163.4; HRMS (TOF ES+): m/z
calcd for C14H12N4O [M+H]+, 253.1089; found, 253.1082. Preparation of 2,4,5-
trichloro-6-(4-oxo-5-(phenylamino)-3,4-dihydroquinazolin-8-
ylamino)isophthaloni-trile (7a). Representative procedure: In 50 mL round-
bottomed flask, Polyhalogenated isophthalonitrile (0.26 g, 1 mmol) was
dissolved with 1 mL of DMF and 7 mL of THF, then added the Potassium
carbonate (0.14 g, 1 mmol) and compound 4a (0.252 g, 1 mmol) successively.
The mixted solution was stirred at 75 °C for about 1 h by TLC detected. After
the completion of the reaction, 50 mL of ethyl acetate was added, and washed
with 40 mL of saturated aqueous ammonium chloride solution and 40 mL of
brine. The organic phase was dried over anhydrous sodium sulfate, rotary
evaporated at vacuum and Silica gel column separate (Petro/AcOEt = 5:1) to get
the compound 7a (yield 60%). Compound 7a: Red solid. Mp: 260–263 °C; IR
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2013.08.
068.
(KBr): 3464, 3368, 3054, 2240, 1663, 1488, 1320, 1250, 758, 540 cmÀ1 1H NMR
;
References and notes
(500 MHz, DMSO-d6): d = 5.29 (s, 2H, NH), 6.67 (d, J = 8.0 Hz, 2H, ArH), 6.83 (t,
J = 7.2 Hz, 1H, ArH), 7.20 (t, J = 7.8 Hz, 2H, ArH), 7.45 (d, J = 8.7 Hz, 1H, ArH),
7.50 (d, J = 8.6 Hz, 1H, ArH), 8.11 (s, 1H, NCH@N), 8.35 (br, 1H, NH); 13C
NMR(125 MHz, DMSO-d6): d = 112.0, 112.6, 114.8, 115.9, 116.3, 117.8, 119.8,
123.4, 124.6, 126.0, 129.0, 133.8, 139.2, 139.3, 139.6, 142.3, 143.2, 143.3, 143.7,
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L.-P. Shi et al. / Bioorg. Med. Chem. Lett. 23 (2013) 5958–5963
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