Synthesis, in vitro antimicrobial and cytotoxic activities of novel pyrimidine-benzimidazol combinations

Article abstract of DOI:10.1016/j.bmcl.2014.04.037

A series of novel 4-substituted-2-{[(1H-benzo[d]imidazol-2-yl)methyl] thio}-6-methylpyrimidine derivatives were designed, synthesized and evaluated for their cytotoxic activities against four human cancer cell lines and inhibitory activities against five type culture strains in vitro. Some of synthetic pyrimidine-benzimidazol combinations showed good inhibitory activities against Stenotrophomonas maltophilia, especially compounds 7b and 7c. Compounds 7a and 7d exhibited enhanced activities against MGC-803 in vitro, when compared to 5-Fu.

Full text of DOI:10.1016/j.bmcl.2014.04.037

Bioorganic & Medicinal Chemistry Letters 24 (2014) 2741–2743
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis, in vitro antimicrobial and cytotoxic activities of novel
pyrimidine–benzimidazol combinations
Peng-Ju Chen, Ang Yang, Yi-Fei Gu, Xiao-Song Zhang, Kun-Peng Shao, Deng-Qi Xue, Peng He,
⇑
⇑
Teng-Fei Jiang, Qiu-Rong Zhang , Hong-Min Liu
New Drug Research & Development Center, School of Pharmaceutical Sciences, Zhengzhou University, No. 100, KeXue DaDao, Zhengzhou 450001, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel 4-substituted-2-{[(1H-benzo[d]imidazol-2-yl)methyl] thio}-6-methylpyrimidine deriv-
atives were designed, synthesized and evaluated for their cytotoxic activities against four human cancer
cell lines and inhibitory activities against five type culture strains in vitro. Some of synthetic pyrimidine–
benzimidazol combinations showed good inhibitory activities against Stenotrophomonas maltophilia,
especially compounds 7b and 7c. Compounds 7a and 7d exhibited enhanced activities against
MGC-803 in vitro, when compared to 5-Fu.
Received 12 February 2014
Revised 26 March 2014
Accepted 9 April 2014
Available online 18 April 2014
Keywords:
Pyrimidine
Ó 2014 Published by Elsevier Ltd.
Benzimidazole
Synthesis
Antimicrobial
Cytotoxic activities
Pyrimidines play an important role in the drug discovery pro-
cess, and have considerable pharmacological and chemical signif-
icance. Literature survey shows that a large number of pyrimidine
derivatives are found to be associated with diverse types of bio-
logical activities, such as antimicrobial,1–3 antiviral4 and antitu-
mor.5–10 On the other hand, benzimidazole is also known to be
an important scaffold in various biologically active molecules,
possessing antitumor,11–13 topoisomerases inhibitors,14–16 anti-
helminthic, antiviral and antibacterial17,18 activities.
It is well-known that the application of combinatorial
approaches toward the synthesis of drugs is a powerful tool in
helping to speed up drug development. On the basis of extensive
research, it has been considerably worthwhile to prepare some
new chemical entities containing benzimidazole and pyrimidine
moieties. To better understand the structure–activity relationship
of pyrimidine–benzimidazol combinations, herein we report the
synthesis of novel pyrimidine–benzimidazol combinations in mod-
erate yields. Besides, we have evaluated their antimicrobial
activities against Staphylococcus aureus, Bacillus subtilis, Escherichia
coli, Stenotrophomonas maltophilia and Candida albicans, and their
cytotoxic activities against MGC-803, MCF-7, EC-109 and PC-3
cancer cell lines in vitro.
The synthesis of the target compounds were finally obtained
in five steps from available ethyl acetoacetate and o-phenylene-
diamine. The synthetic route was shown in Scheme 1. In earlier
report,19 the compound (2) was prepared by the reaction of
ethyl acetoacetate and thiourea in the presence of potassium
hydroxide in ethanol heated to 125 °C by microwave. In this Let-
ter, we also synthesized the compound in a higher yield under
the condition of reflux in the presence of potassium hydroxide
in ethanol at 85 °C for 3 h. The compound (4) was obtained by
the reaction of 3 with chloroacetyl chloride in thin hydrochloric
acid.20 The next part of this synthesis involved the preparation of
the compound (5) by condensation of 2 with 4 in the mixed sol-
vent of water and dioxane. Subsequently, 5 was halogenated by
the reaction with POCl3 and PCl3 to yield the compound (6). The
highly activated intermediate was then reacted with different
substituents to obtain compounds 7a–o. The results were sum-
marized in Table 1. Finally, all the structures of 7a–o were fully
characterized by 1H NMR, 13C NMR and HRMS.
Next, every target compound was screened for antimicrobial
activity. The microorganisms used in the study were Gram-positive
bacteria (Staphylococcus aureus, Bacillus subtilis), Gram-negative
bacteria (Escherichia coli, Stenotrophomonas maltophilia) and Fungi
(Candida albicans). The minimum inhibitory concentration (MIC)
of the target compounds was determined by broth microdilution
method21 and compared to two commercial antibiotics (Table 2).
From the Table 2 we can observe that some of the target com-
pounds show inhibitory activities against S. maltophilia with the
⇑
Corresponding authors. Tel.: +86 371 67781896 (Q.-R.Z.), +86 371 67781739
(H.-M.L.).
E-mail addresses: zqr406@sina.com (Q.-R. Zhang), liuhm@zzu.edu.cn (H.-M. Liu).
http://dx.doi.org/10.1016/j.bmcl.2014.04.037
0960-894X/Ó 2014 Published by Elsevier Ltd.

2742
P.-J. Chen et al. / Bioorg. Med. Chem. Lett. 24 (2014) 2741–2743
OH
O
O
N
OH
N
a
Cl
R
O
N
2
SH
N
N
N
N
1
S
N
c
S
S
N
N
d
e
N
N
H
CH3
N
H
N
H
CH3
CH3
NH2
NH2
H
N
5
6
7
b
Cl
N
3
4
Scheme 1. Reagents and conditions: (a) Thiourea, KOH/EtOH, 85 °C; (b) Chloroacetyl chloride, 5 N HCl, reflux; (c) KOH, H2O/dioxane (2:1), 55–60 °C; (d) POCl3, PCl3, 110 °C;
(e) isopropanol, 85 °C.
Table 1
Table 3
Reaction yields (%) of products 7a–o with different groups
In vitro cytotoxic activities of the target compounds against four human cancer cell
lines
Compound
R
Yield %
Compounds
IC50
MCF-7
(lM)
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
4-F-C6H4-NH
4-Cl-C6H4-NH
4-Br-C6H4-NH
72.3
61.1
76.6
67.5
71.4
83.5
77.5
73.4
81.1
61.2
66.9
68.2
58.8
85.3
59.8
MGC-803
EC-109
PC-3
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
5-Fu
5.77
42.19
33.63
38.04
56.49
61.11
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
7.76
69.46
20.43
42.94
57.29
69.79
34.37
>100
>100
>100
>100
>100
>100
>100
>100
>100
24.14
56.17
35.98
37.09
55.98
67.39
70.82
>100
>100
>100
>100
>100
>100
>100
>100
>100
4.68
4-CH3-C6H4-NH
4-OCH3-C6H4-NH
2-OCH3-C6H4-NH
3-CF3-C6H4-NH
OH-(CH2)2-NH
[OH-(CH2)2]2-NH
NH2-CS-NH-NH
(CH3)2-CH-NH
Piperidin-1-yl
28.24
26.82
7.39
51.08
56.24
>100
>100
>100
>100
>100
>100
>100
>100
31.27
8.13
Piperazin-1-yl
Morpholin-4-yl
N-Benzylmethylamine
Table 2
In vitro antimicrobial activities MIC data (
l
g/ml) of synthetic compounds
Bacteria
E. cc
Compounds
Fungal
C. ae
bioactivity, especially Cl and Br. For instance, Compound 7b shows
inhibitory activity against S. aureus with the MIC of 8 g/ml,
B. subtilis (128 g/ml), E. coli (128 g/ml), S. maltophilia (2 g/ml)
and C. albicans (64 g/ml).
S. aa
B. sb
S. md
l
l
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
32
8
16
32
64
64
32
2
4
8
16
8
8
64
8
64
l
l
128
128
64
32
32
>128
>128
>128
>128
>128
>128
128
>128
>128
0.25
/
128
128
32
128
32
>128
64
64
>128
>128
>128
>128
>128
>128
0.125
/
l
Finally, all the target compounds were evaluated for the cyto-
toxic activities against four human cancer cell lines, MCF-7 (human
breast cancer cell line), MGC-803 (human gastric cancer cell line),
EC-109 (human esophageal cancer cell line) and PC-3(human pros-
tate cancer cell line) using MTT assay method. The IC50 values (con-
centration required to inhibit tumor cell proliferation by 50%) have
been showed in Table 3 and the proverbial anticancer drug
5-fluorouracil (5-Fu) serves as the positive control medicine. From
the screening results in Table 3, it has been observed that com-
pounds 7a–e exhibits anticancer activities against all the human
cancer cell lines used in the study, in particular, compounds 7a
64
64
>128
>128
>128
>128
>128
>128
>128
>128
>128
128
0.5
128
>128
>128
>128
128
128
32
8
64
128
128
32
64
32
32
16
0.25
/
7k
7l
7m
7n
7o
LEVf
FCZh
>128
>128
128
g
/
/
2
(5.77 lM) and 7d (7.39 lM) exerts enhanced cytotoxic activities
a
b
c
against MGC-803 in contrast with 5-Fu. In addition the results
show that the series of target compounds have the similar SAR
concerning antimicrobial activities and cytotoxic activities in vitro.
To summary, a series of novel 4-substituted-2-{[(1H-benzo[d]
imidazol-2-yl)methyl] thio}-6-methylpyrimidine derivatives were
synthesized. Some of the target compounds showed inhibitory
activities against S. maltophilia, particularly compounds 7b and
7c. But the cytotoxic activities were not enough good, only the
compounds 7a and 7d exhibited enhanced activities against
MGC-803 as compared with 5-Fu in vitro.
S.a: Staphylococcus aureus.
B.s: Bacillus subtilis.
E.c: Escherichia coli.
S.m: Stenotrophomonas maltophilia.
C.a: Candida albicans.
LEV: levofloxacin, positive control drug.
No detection.
d
e
f
g
h
FCZ: fluconazole, positive control drug.
MIC of 2–128 lg/ml, and compounds 7a–e have antimicrobial
activities against all species of Gram-positive, Gram-negative bac-
teria and Fungi used in the study. Studies on structure–activity
relationship (SAR) shows that introduction of aromatic amines at
pyrimidine ring is beneficial for the bioactivity. Besides, the aniline
containing a para-substituted group is more beneficial for the
Acknowledgments
This work was supported by the National Natural Science Foun-
dation of China (Project No. 81172937).

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2743
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