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Published on the web June 4, 2011
Novel Synthetic Azaacridine Analogues as Topoisomerase 1 Inhibitors
Xudong Luan,1,2 Chunmei Gao,1 Qinsheng Sun,1 Chunyan Tan,1 Hongxia Liu,1 Yibao Jin,1,2 and Yuyang Jiang*1,2,3
1The Guangdong Province Key Laboratory of Chemical Biology, the Graduate School at Shenzhen,
Tsinghua University, Lishui Road, Shenzhen 518055, P. R. China
2Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China
3School of Medicine, Tsinghua University, Beijing 100084, P. R. China
(Received April 21, 2011; CL-110340; E-mail: jiangyy@sz.tsinghua.edu.cn)
Novel azaacridine analogues were synthesized and their
COOH
COOH
N
OCH3
N
antiproliferative activities against K562 and HepG-2 cell lines
were evaluated, among which compound 5a was found to
display good cytotoxicity. UV-visible spectral absorbance
measurements showed that 5a can bind with calf thymus DNA
(ct DNA). A relaxation assay indicated that 5a inhibits
topoisomerase 1 activity.
(i)
+
Cl
N
H
OCH3
Cl
Cl
H2N
1
2
3
Cl
R
NH
N
OCH3
(iii)
N
OCH3
(ii)
Cl
N
Cl
N
4
5a–5e
Cancer can significantly affect people’s health and develop-
ment of anticancer agents, such as DNA-interacting agents which
can distort the helix and affect the activity of topoisomerases, has
attracted great attention.1 Topoisomerase 1 (topo 1), one of the
topoisomerases is essential for cell proliferation and it has been
regarded as an important target for cancer.2 However, topo 1
inhibitors are relatively rare and some of them have severe side
effects. The success of camptosar and topotecan as topo 1
inhibitors, which have been approved and extensively used for
anticancer therapy, has inspired a new search for additional
agents as topo 1 inhibitors for cancer treatment.3
Scheme 1. Synthesis of azaacridine derivatives 5. Reagents and
conditions: (i) K2CO3, Cu, DMF, 130 °C; (ii) POCl3, 140 °C;
(iii) various anilines, CHCl3, EtOH, concd HCl.
Table 1. Antiproliferative activity of compounds against tumor
cell
IC50/µM
Compound
R
K562
15.9
HepG-2
18.9
H3C
5a
Azaacridine derivatives have been studied extensively in
organic chemistry and pharmaceutical fields, most of which have
been used as antibacterial,4 antimalarial,5 and antiparasitic,6
while little attention has been paid to the exploration of
azaacridines as antitumor7 and particularly topo 1 inhibitory
agents. As part of our efforts in the design and synthesis of
compounds with potent antitumor activities, especially hetero-
cyclic compounds,8 a series of acridine derivatives with
antitumor activity have been developed, some of which showed
topo 1 inhibitory activity.9 Herein, we report the preparation and
evaluation of the antitumor activity of an additional series of
azaacridine analogs with substituent(s) at the anilino ring. The
inhibition effect of the compounds on topo 1 activity was also
detected.
OH
5b
>50
38.5
>50
>50
5.4
>50
>50
>50
>50
NDa
1.9
H3CO
5c
H3CO
5d
H3CO
N
H3CO
5e
Imatinib
Colchicin
NDa
aND: not detected.
The synthetic route to the target compounds 5a-5e is shown
in Scheme 1. An Ullmann reaction was carried out by heating
2,4-dichlorobenzoic acid (1) with 5-amino-2-methoxypyridine
(2) in the presence of Cu to afford the corresponding anthranilic
acid 3. Then 3 was stirred with POCl3 giving the 9-chloroacri-
dine derivative 4. The reaction of 4 with aniline derivatives in
the presence of a few drops of concentrated hydrogen chloride
afforded the desired compounds 5a-5e, the structures of which
in DMSO in quintuplet for 48 h. After treatment, the cells were
incubated with 15 ¯L of MTT [3-(4,5-dimethylthiazol-2-yl)-
2,5-diphenyltetrazolium bromide from Sigma] solution
(5 mg mL¹1) for 4 h. The formazan precipitate was dissolved
in 100 ¯L DMSO and the absorbance at 490 nm was measured
by a Benchmark microplate reader (Molecular Devices Corpo-
ration). IC50 values are the concentration at which cell growth
was inhibited by 50%. The results are depicted in Table 1.
Imatinib and colchicin were used as the positives control.
Compound 5a with methyl substitute at the para-position on the
aniline ring displayed good antiproliferative activity with IC50
values of 15.9 and 18.9 ¯M against K562 and HepG-2 cells
respectively in vitro, while the other four compounds 5b-5e
exhibited weaker or no activity against these two cell lines.
1
were confirmed by H NMR and high-resolution MS.13
The ability of compounds to inhibit cell growth was
evaluated against K562 leukemia cells and hepatoma HepG-2
cells by MTT assay. The cells were suspended at a concentration
of 1.5 © 105 cells/mL and seeded in 96-well microtiter plates at
37 °C in a humidified atmosphere with 5% CO2. The cells were
then treated with various concentrations of compound dissolved
Chem. Lett. 2011, 40, 728-729
© 2011 The Chemical Society of Japan
Luan, Xudong
