Synthesis of novel, azasugar-modified anthraquinone derivatives and their cytotoxicity

Article abstract of DOI:10.1016/j.cclet.2014.05.029

A series of novel, azasugar-modified 2-monosubstituted, 2,6- and 2,7-bissubstituted anthraquinone derivatives have been synthesized by the nucleophilic substitution of N-alkylamino azasugar with mono-, bis(2-chloroacetamido)anthraquinones. Their cytotoxic activities against HeLa and MCF-7 cells were preliminarily evaluated and compound 9a with mono-azasugar pendant at 2-position showed similar activity to the control drug (Cisplatin).

Full text of DOI:10.1016/j.cclet.2014.05.029

G Model
CCLET 3010 1–3
Chinese Chemical Letters xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
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Original article
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Synthesis of novel, azasugar-modified anthraquinone
derivatives and their cytotoxicity
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Q1 Ping-Zhu Zhang , Hai-Long Yang , Cui-Cui Li , Zhi-Chao Xia , Xiao-Man Wang ,
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Hua Wei , Rui-Xue Rong , Zhi-Ran Cao , Ke-Rang Wang , Hua Chen , Xiao-Liu Li
*
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Key Laboratory of Chemical Biology of Hebei Province, College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China
Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding 071002, China
Department of Immunology, School of Basic Medical Science, Hebei University, Baoding 071002, China
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c
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, azasugar-modified 2-monosubstituted, 2,6- and 2,7-bissubstituted anthraquinone
derivatives have been synthesized by the nucleophilic substitution of N-alkylamino azasugar with
mono-, bis(2-chloroacetamido)anthraquinones. Their cytotoxic activities against HeLa and MCF-7 cells
were preliminarily evaluated and compound 9a with mono-azasugar pendant at 2-position showed
similar activity to the control drug (Cisplatin).
Received 31 March 2014
Received in revised form 12 May 2014
Accepted 14 May 2014
Available online xxx
ß 2014 Xiao-Liu Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords:
Anthraquinone
Azasugar
Cytotoxic activity
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1. Introduction
between the nitrogen atom and phosphate ester of the side chains 33
and the G-quadruplex grooves. In order to improve the binding 34
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The human telomeric G-quadruplexes DNA refers to the four
stranded structures formed by the guanine-rich DNA sequences,
which presents in the telomeres of eukaryotic chromosomes [1].
Telomeres have a crucial function in restricting the proliferative
capacity of normal cells. However in most tumor cells, telomerase
activity has been acquired and over-expressed, which resulted in
the unlimited growth of the tumor cells [2]. In recent years, G-
quadruplexes DNA has become a potential target for new
anticancer drugs [3–5]. The G-quadruplex ligands can induce
DNA molecules to form stable G-quadruplex structures, then to
inhibit the activity of the telomerase, resulting in rapid apoptosis of
the cancer cell [3,4]. In order to improve the selectivity and reduce
the side effects of DNA-interactive anticancer drugs, many
researchers have focused their interests on designing and
synthesis of DNA G-quadruplex ligands [6–9]. To date, several
drugs based on DNA G-quadruplex ligands have been in clinical
trials, such as Quarfloxin and BRACO-19 (Fig. 1) [10,11].
capacity and selectivity of ligand to G-quadruplex DNA by synergy 35
of multi-site and multimode, scientists paid more attention to the 36
synthesis of anthraquinone derivatives. Stephen Neidle et al., 37
reported on a series of DNA G-quadruplex ligands based on 38
anthraquinone derivatives, and found that 2,6- and 2,7-bis 39
aminoacyl substituted anthraquinones showed a preference for 40
triplex and quadruplex DNA vs. duplex DNA [12].
41
It is well known that carbohydrates play diverse and crucial 42
roles in a wide variety of biological systems [13]. The anthraqui- 43
none and carbohydrate conjugates, as anticancer drugs, have been 44
widely and successfully used in the clinic, such as Doxorubicin and 45
Sabarubicin (Fig. 1), and an investigation has also revealed that the 46
glycosyl moiety could improve the selectivity of the G-quadruplex 47
DNA [14]. On the other hand, azasugar (iminosugar), as a kind of 48
carbohydrate mimic, has remarkable biological properties [15], 49
especially because its nitrogen atom can interact with the 50
phosphate ester chain by electrostatic interaction under physio- 51
logical conditions. Ranjan and coworkers found that aminosugars 52
were also identified as G-quadruplex DNA ligand by binding with 53
the quadruplex grooves [16]. However, the glycosyl modified 54
G-quadruplex ligands have rarely been reported. Herein we 55
designed and synthesized series novel azasugar-modified anthra- 56
quinones derivatives at 2-, 2,6- and 2,7-positions with different 57
lengths of the linking chains. Their structures were characterized 58
by NMR and HRMS analysis. Their cytotoxic activities against 59
Anthraquinone derivatives are one of the earliest G-quadruplex
DNA ligands. For example, BSU1051 (Fig. 1) can inhibit the
telomerase activity through
p–p interactions with the terminal
G-tetrad of quadruplex, and the electrostatic interaction
a
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Corresponding author.
E-mail address: lixl@hbu.cn (X.-L. Li).
http://dx.doi.org/10.1016/j.cclet.2014.05.029
001-8417/ß 2014 Xiao-Liu Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
1
Please cite this article in press as: P.-Z. Zhang, et al., Synthesis of novel, azasugar-modified anthraquinone derivatives and their
cytotoxicity, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.05.029

G Model
CCLET 3010 1–3
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P.-Z. Zhang et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
Fig. 1. The structures of some G-quadruplex ligands and antitumor drugs based on the anthraquinone derivatives.
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human epithelial cervical cell (HeLa) and human breast cancer
cells (MCF-7) were preliminarily evaluated.
azasugars 5a–c were obtained. Then through the nucleophilic
substitution of N-alkylamino azasugar 5a–c with the correspond-
ing chloroacetamidoanthraquinone (6, 7, 8), the targeted com-
pounds 9–11 were obtained (experimental procedures and
characterization data for compounds 4–11 and cytotoxicity
analyses, please see Supporting information).
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2. Experimental
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2.1. Instruments
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Melting points were measured on a SGW X-4 micro melting
point apparatus and are uncorrected. H NMR, C NMR spectra
were measured on a RT-NMR Bruker AVANCE 600 (600 MHz)
3. Results and discussion
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N-Alkylamino azasugars 5a–c were synthesized using
mannitol as the starting material (Scheme 1). Compound 3 was
obtained through benzylidenation and bistrifluoromethanesul-
D-
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spectrometer using tetramethylsilane (Me
4
Si) as the internal
standard. High-resolution mass spectra (HRMS) were recorded on
a FTICR-MS (Ionspec 7.0T) mass spectrometer in the electrospray-
ionization (ESI) mode. The microwave assisted reactions were
carried out on a DISCOVER S-Class Auto Focused Microwave
Synthesis System (CEM Corporation, USA). Thin-layer chromatog-
phonation of
D-mannitol according to the procedure in the
literature [17]. Then nucleophilic substitution of N-Boc-diamine
to compound 3 produced the N-Boc-alkylamino benzylidene
azasugars 4a–c in yields of 78–80%. Then compounds 4a–c in a
solution of concentrated hydrochloric acid/1,4-dioxane (1:1, v/v)
were refluxed for 24 h to remove the benzylidene and Boc group
and afford the N-alkylamino azasugars 5a–c in yields of 75%, 77%
and 76%, respectively.
The starting materials, 2-aminoanthraquinone and 2,6-diami-
noanthraquinone, are commercially available, and the 2,7-diami-
noanthraquinone was prepared from anthrone according to the
literature [18]. Compounds 6–8 were prepared by the acylation
from the corresponding aminoanthraquinones with chloroacyl
chloride according to the reported procedure [18], followed by
the nucleophilic substitution with the N-alkylamino azasugar,
5a–c, to afford the targeted compounds 9–11 (Scheme 2). The
nucleophilic substitution of 2-chloroacetamidoanthraquinone (6)
raphy (TLC) was performed on precoated plates (Qingdao GF254
with detection by UV light or with phosphomolybdic acid in EtOH/
O followed by heating. Column chromatography was performed
using a SiO (Qingdao 300–400 mesh).
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2.2. Synthesis and cytotoxicity analyses
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Compounds 5a-c N-alkylamino azasugars were synthesized
using
D-mannitol as the starting material, benzylidenation and
bistrifluoromethanesulphonation of
D-mannitol to obtain com-
pound 3. Then nucleophilic substitution of N-Boc-diamine
to compound 3 produced the N-Boc-alkylamino benzylidene
azasugars 4a–c. Following the deprotection the N-alkylamino
2 4 2 2 2
Scheme 1. Synthesis of N-alkylamino azasugars 5a–c. Reagents and conditions: (i) benzaldehyde, H SO , DMF, r.t. 5 d; (ii) Tf O, Py., CH Cl ; (iii) N-Bocdiamine, THF, TEA,
reflux, 78–82%; (iv) hydrochloric acid/1,4-dioxane (1:1, v/v), reflux, 75–77%.
Please cite this article in press as: P.-Z. Zhang, et al., Synthesis of novel, azasugar-modified anthraquinone derivatives and their
cytotoxicity, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.05.029

G Model
CCLET 3010 1–3
P.-Z. Zhang et al. / Chinese Chemical Letters xxx (2014) xxx–xxx
3
Scheme 2. Synthesis of compounds 9–11. Reagents and conditions: DMF, DIPEA, KI, M.W., 55 8C, 20 min, 30–60%.
Table 1
The cytotoxic activities of compounds 9–11.
Cell lines
Cytotoxicity (IC50
, mmol/L)
9
a
9b
9c
10a
10b
10c
44.1 Æ 0.04
11a
35.43 Æ 0.08
11b
44.2 Æ 0.04
11c
75.7 Æ 0.04
Cisplatin
HeLa
96.0 Æ 0.03
33.3 Æ 0.03
>100
85.1 Æ 0.03
>100
>100 >100
20.4 Æ 0.12
16.9 Æ 1.36
MCF-7
17.3 Æ 0.218
>100 27.3 Æ 0.31
>100
>100
>100
>100
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and N-ethylamino azasugar 5a was studied to optimize the
reaction conditions with different solvents, temperature, the acid-
binding agent, the amount of additive KI, as well as microwave
irradiation. It was found that although the reaction with normal
heating at 80 8C for 24 h provided compound 6 only in 10% yield,
the microwave irradiation could remarkably improve the reaction
efficiency with a few minutes of irradiation. Thus, the microwave
assisted reaction of compound 6 and N-alkylamino azasugar 5a
(2.0 equiv.) was carried out in DMF, in the presence of DIPEA and
KI, under microwave irradiation at 55 8C for 20 min to afford
compound 9 in a yield of 60%. Similarly, compounds 9b–11c were
obtained in yields of 30–59%.
The cytotoxicity of the novel, azasugar-modified anthraquinone
derivatives 9–11 against HeLa cell lines (human cervical cancer
cells) and MCF-7 (human breast cancer cells) in vitro were
examined with comparison to the control drug (cisplatin). As
shown in Table 1, the compounds showed lower cytotoxic activity
against HeLa and Mcf-7 cells, however, compounds 9a and 10b
exhibit good selective toxicity against MCF-7, and especially
compound 9a with mono-azasugar conjugate at the 2-position
exhibited a similar activity to MCF-7 as the control drug (cisplatin).
For all compounds, the mono- and di-substituted position and the
lengths of the chain between anthraquinone and azasugar all
influenced the cytotoxic activities.
Appendix A. Supplementary data
150
Supplementary data associated with this article can be found, in 151
the online version, at http://dx.doi.org/10.1016/j.cclet.2014.05.029. 152
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Acknowledgments
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This work was supported by the National Natural Science
Foundation of China (Nos. 21372059 and 21172051), the Hebei Key
Basic Research (No. 12966417D), the Hebei Natural Science
Foundation (No. B2012201041) and the Foundation of Hebei
Education Department (No. YQ2013006).
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Please cite this article in press as: P.-Z. Zhang, et al., Synthesis of novel, azasugar-modified anthraquinone derivatives and their
cytotoxicity, Chin. Chem. Lett. (2014), http://dx.doi.org/10.1016/j.cclet.2014.05.029