The novel anti-tumor agents of 4-triazol-1,8-naphthalimides: Synthesis, cytotoxicity, DNA intercalation and photocleavage

Article abstract of DOI:10.1016/j.ejmech.2011.01.050

A novel series of 4-(4-phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalimide derivatives had been synthesized easily by employing "click reaction". For anti-tumor activity in vitro, all the compounds were found to be more toxic against MCF-7 than Hela and 7721 cells. 4a, 4b and 4e Showed improved cytotoxic activity against MCF-7 cells over Amonafide, in particular compound 4a, with an IC₅₀ could amount to 10^-7 M. The UV-vis spectra and Circular Dichroism titration indicated that the compounds behaved as effective DNA-intercalating agents. The investigation of their photo-damaging ability illuminated that these compounds could damage DNA effectively into form II and even form III.

Full text of DOI:10.1016/j.ejmech.2011.01.050

European Journal of Medicinal Chemistry 46 (2011) 1274e1279
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
The novel anti-tumor agents of 4-triazol-1,8-naphthalimides: Synthesis,
cytotoxicity, DNA intercalation and photocleavage
,
a
a
a
a
a,b,
Xiaolian Li a , Yanjie Lin , Qianqian Wang , Yukun Yuan , Hua Zhang , Xuhong Qian
*
**
a State Key Laboratory of Fine Chemicals, Dalian University of Technology, PO Box 89, 158 Zhongshan Road, Dalian 116012, China
b Shanghai Key Laboratory of Chemical Biology, School of Pharmacy, East China University of Science and Technology, PO Box 544, 130 Meilong Road, Shanghai 200237, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of 4-(4-phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalimide derivatives had been synthesized
easily by employing “click reaction”. For anti-tumor activity in vitro, all the compounds were found to be
more toxic against MCF-7 than Hela and 7721 cells. 4a, 4b and 4e Showed improved cytotoxic activity
against MCF-7 cells over Amonafide, in particular compound 4a, with an IC50 could amount to 10ꢀ7 M.
The UVevis spectra and Circular Dichroism titration indicated that the compounds behaved as effective
DNA-intercalating agents. The investigation of their photo-damaging ability illuminated that these
compounds could damage DNA effectively into form II and even form III.
Received 10 December 2010
Received in revised form
17 January 2011
Accepted 25 January 2011
Available online 3 February 2011
Keywords:
Triazole
Ó 2011 Elsevier Masson SAS. All rights reserved.
Intercalation
Anticancer
Naphthalimides
1. Introduction
features since its first synthesis more than 100 years ago. 1,2,3-
Triazoles have large dipole moment [5]. They are stable to meta-
DNA is a nucleic acid that contains the genetic instructions
specifying the biological development of all cellular forms of life.
DNA is often referred to as one of the most promising biological
target of developing anti-tumor agents to specifically constrain
tumor cell growth [1]. Design and synthesis of novel and potent
DNA-targeted compounds have important theoretical significance
and application value in chemistry, biology and medicine fields.
Such compounds include DNA-alkylating agents, DNA groove
binders and DNA intercalators. DNA-intercalating molecules are
those which intercalate DNA base pairs via electron-deficient
planar chromophores with flexible side chains. These specially
designed groups confer DNA sequence selectivity and allow
aromatic heterocycles to position at proper sites or interact with
topoisomerases so as to interfere with DNA replication and tran-
scription [2e4]. Acridine, naphthodiazine and anthraquinone are
all famous intercalating matrixes.
bolic degradation, capable of hydrogen bonding [6] and could react
with protein in different forms. What’s more, 1,2,3-triazoles were
often regarded as the classical bioisosteres of amide for their
similar space structure and electronic effect to amide [7]. These
1,2,3-triazole compounds have been reported to be significant
antimicrobial, antimalarial, antitubercular, anti-HIV agents and
cannabinoid CB1 receptor antagonists [8]. In recent years, more
and more attention has been paid to their anti-tumor activities.
Tian Laijin [9] synthesized triorganotin 2-phenyl-1,2,3-triazole-4-
carboxylates which were more active than clinically widely used
cis-platin. Sanghee Kim [10] replaced the amide bond of ceramide
with non-hydrolyzable 1,2,3-triazole, and obtained new analogs
showing higher cytotoxicity which might be the results of
apoptosis. Ahmed Kamal [11] designed 1,2,3-triazole-linked pyr-
rolobenzodiazepine to be used as DNA-alkylating and cross-linking
agents. The compounds exhibited promising DNA-binding affinity
and anticancer activity in selected human cancer cell lines. By
introducing the 1,2,3-triazole residues to nucleoside, Yu Jin-Lan
[12] reported that those compounds modified with a triazole
ring significantly improved activity towards a broad range of
tumor cell lines.
1,2,3-Triazole compounds do not exist in natural substances, but
this heterocycle has received wide research due to its attractive
* Corresponding author. State Key Laboratory of Fine Chemicals, Dalian University
of Technology, PO Box 89, 158 Zhongshan Road, Dalian 116012, China. Tel.: þ86 411
82987178; fax: þ86 411 83673488.
Owing to the planar ring systems of naphthalimide derivatives,
both their DNA intercalative and anti-tumor abilities have been
widely studied. Great efforts had been made to fuse heterocycles to
naphthalene nucleus [13], while few reports on linking functional
** Corresponding author. Shanghai Key Laboratory of Chemical Biology, School of
Pharmacy, East China University of Science and Technology, PO Box 544, 130 Mei-
long Road, Shanghai 200237, China. Tel.:+86 21 64253589; fax: +86 21 64252603.
E-mail addresses: xiaolianlidlut@gmail.com (X. Li), xhqian@ecust.edu.cn (X. Qian).
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.01.050

X. Li et al. / European Journal of Medicinal Chemistry 46 (2011) 1274e1279
1275
Table 1
R
N
,
UVevisa and fluorescent dataa b of 4aee.
O
O
Compound
UV lmax/nm
(log
FL lmax/nm(
F
)
Stokes’
shift/nm
Excitation
wavelength l/nm
3
)
4a R=CH2CH2N(CH3)2
4a
4b
4c
4d
4e
343 (4.21)
344 (4.19)
343 (4.13)
344 (4.20)
343 (4.16)
400 (<0.001)
401 (<0.001)
399 (<0.001)
400 (<0.001)
399 (<0.001)
57
58
56
57
56
343
344
343
344
343
4b
4c
4d
R=CH2CH2N(CH2CH3)2
R=CH2CH2CH2CH3
N
R=CH2CH2OH
R=CH2CH2N(CH2CH2)2NH
N
4e
a
N
In absolute ethanol.
b
With quinine sulfate in sulfuric acid as quantum yield standard (
F
¼ 0.55).
emissions were at 400 nm and fluorescence quantum yields of
these compounds were relatively low. Such low yields might be the
result of rapid non-radicalization transitions, such as IST from
a singlet to the triplet, vibrational relaxation and internal or
external conversion due to the vitality of single bond connecting
triazole with naphthalimide.
Fig. 1. The structures of 4-(4-phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalimide derivatives.
heterocycle rings to the naphthalimide. In addition, usually the
naphthalimides with substitution at 4-position only show very
weak anti-tumor activity. Herein, we revealed a novel series
of 4-(4-phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalimide derivatives
4aee (Fig. 1), expecting the 4-phenyl-[1,2,3]-triazole could improve
the biological activities while reducing drug resistance. Moreover,
pseudoaromatic nature of 1,2,3-triazole might change the distri-
bution of electrons and endow new properties to the whole
molecule.
2.2. Cytotoxicity
The anti-tumor activity of the compounds 4aee, were evaluated
in vitro against MCF-7 (human mammary cancer cell), Hela (human
cervical carcinoma cell) and 7721 (human liver cancer cell) cells by
MTT tetrazolium assay. The IC50 values were listed in Table 2 and
the activities of Amonafide were as a control. All the compounds
were found to be more toxic against MCF-7 cells than Hela and 7721
cells. 4a, Bearing N,N-dimethylethylenediamine, was the most
effective one. It’s inhibition of cell growth of MCF-7, Hela and 7721
cells were 5.2-fold, 1.7-fold and 9.2-fold higher than that found for
Amonafide under the same experimental conditions, respectively.
Compounds 4b and 4e, with different basic chains, were also more
toxic to MCF-7 and 7721 than Amonafide. The improved cytotoxic
activity of 4a, 4b, 4e, hinted that 1,2,3-triazole could enhance the
cytotoxicity and improve anti-tumor ability of naphthalimides on
comparing the activities with the famous Amonafide. The inactivity
of 4c and 4d were in accordance with previous study that the
presence of a basic terminal group in the side chain was essential
for cytotoxic activity. Any decrease in the basicity of this terminal
nitrogen leads to less active products [15]. Compounds 4c and 4d
both had no nitrogen atom in their side chains, so their potencies
were weaker than Amonafide. The subacidity of hydroxyl group
made 4d to be the weakest poison to the cell lines.
2. Results and discussion
2.1. Chemistry and spectra data
These compounds were synthesized via Cu (II) catalyzed Huis-
gen dipolar cycloaddition alkynes with organic azides, which was
an example of “click” chemistry for its mild reaction conditions,
high yield and simple purification steps [14]. The synthetic route
was shown in Scheme 1. The commercially available 4-bromo-1,8-
naphthalic anhydride 1 was reacted with sodium azide in DMF at
room temperature for 3 h to gave compound 2, which was further
reacted with phenylacetylene by “Click” reaction to afford
compound 3. Without any purification, the obtained naphthalic
anhydride was condensed with corresponding amine in ethanol for
3 h under refluxing to give the designed compounds 4aee. After
separation with careful column chromatography, each pure tar-
geted product was obtained. Structures of all these final products
were confirmed by using 1H NMR, HRMS and IR.
2.3. DNA-intercalating property
The UVevis and Fluorescent data of 4aee were displayed in
Table 1. The different substitutes were found to have slight effect on
the UVevis spectra, with maximal absorptions around 343 nm and
similar intensities around 4.2. It can be seen that the maximal
2.3.1. UVevis titration
As 4aee had very weak fluorescence, UVevis spectrum was
used to investigate the interaction between the compounds and
DNA [16]. It is widely accepted that if the compound could inter-
calate DNA, the UVevis curve of their complex will be induced
bathochromic shift and hypochromicity [17,18]. The UVevis spectra
of 4a, the efficient cytotoxic among compounds, was measured
R
N
O
O
O
O
O
O
O
O
O
O
O
III
II
I
Table 2
N
N
Br
N3
N
Anti-tumor activities of compounds against MCF-7, Hela and 7721 cells.
N
N
N
Compound
Cytotoxicity (IC50
MCF-7
, mm)
3
1
4a-e
2
Hela
7721
4a
4b
4c
4d
0.323
1.09
19.51
>100
0.836
1.68
1.02
0.463
1.892
32.92
>100
1.545
4.27
a
R=CH2CH2N(CH3)2
R=CH2CH2OH
b
R=CH2CH2N(CH2CH3)2
c
R=CH2CH2CH2CH3
26.88
19.56
>100
96.7
e
d
R=CH2CH2N(CH2CH2)2NH
Scheme 1. Synthesis of 4aee. Reagents and conditions: (I) NaN3, DMF, rt, 3 h, 89%; (II)
acetylene benzene, CuSO4, sodium ascorbate, H2O/BuOH, 12 h, 91.6%; (III) RNH2,
CH3CH2OH, refluxed, 3 h.
4e
Amonafide
1.73

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X. Li et al. / European Journal of Medicinal Chemistry 46 (2011) 1274e1279
[DNA]/(3a
ꢀ
3f) ¼ [DNA]/(3b
ꢀ
3f) þ 1/(Kb
(
3b
ꢀ
3f))
0.8
0.6
0.4
0.2
0.0
3a-average molar extinction coefficient of the solution (A/C4a),
Kb-the binding constant, 3b-molar extinction coefficient of totally
binding 4a, 3f-molar extinction coefficient of free 4a.
Kb could be calculated and the binding constant of 4a with DNA
was 2.95 ꢁ 105 Mꢀ1, showing good DNA affinity. The similar binding
constant to other naphthalimides told that the triazole ring did not
have big influence on the intercalating ability of naphthalimide
unit. Excellent cytotoxicity would result from the efficient action on
the enzyme relating with DNA replication and transcription.
DNA
2.3.2. Circular Dichroism titration
Circular Dichroism (CD) is a powerful and reliable tool to
determine the conformation of biomacromolecule. The CD spec-
trum of free CT-DNA has a negative band at 247 nm due to the
helicity, and a positive band at 279 nm due to the base stacking,
which is the characteristic of DNA in the right-hand B form [19,20].
When exploring the interaction between DNA and DNA-targeted
compounds, messages in two aspects can be seen from CD spectra:
the changes in DNA’s CD and the Induced Circular Dichroism (ICD)
of compounds, from which the binding mode can be deduced,
providing technique to confirm the mechanism of interaction.
4b was chosen to illustrate the CD spectra at different ratio. Both
the changes of DNA and ICD of 4b were obtained. When R(4b/
DNA) ꢂ 0.20 (Fig. 3A), the CD spectrum of DNA underwent changes
in both the positive and negative bands without significant
300
320
340
360
380
400
Wavelength(nm)
Fig. 2. Interaction of 4a and calf thymus DNA. Absorption changes of 4a (100
during addition of calf thymus DNA (0, 50, 100, 200
solution.
mM)
mM) in 30 mM TriseHCl (pH 7.5)
(Fig. 2). As DNA concentration was increased, the curve showed
significant hypochromicities and slight bathochromic shifts indi-
cating compound 4a can insert into the base pairs of DNA. Its’
binding constant was calculated with the following equation:
Fig. 3. Titration CD spectra of CT-DNA by 4b at different R ratio in TriseHCl buffer (pH ¼ 7.0). The CT-DNA concentration is 50
mM. The value of R(4b/DNA) is (a) free DNA (b) 0.02
(c) 0.04 (d) 0.10 (e) 0.16 (f) 0.20 (g) 0.30 (h) 0.40 (i) 0.60 (j) 0.80 (k) 1.00 (l) 1.2 (m) 1.40. Insert the amplificatory induced CD spectra.

X. Li et al. / European Journal of Medicinal Chemistry 46 (2011) 1274e1279
1277
wavelength change. The decrease of negative bands and increase of
positive bands manifested that 4b intercalated into the base pairs of
DNA, causing the base pairs to separate vertically, thereby distort-
ing the sugarphosphate backbone and changing the degree of
rotation between successive base pairs and transforming DNA to
A-like conformation [21]. The appearance of small negative ICD
signal at 350 nm suggested that 4b intercalated DNA with its long
axis parallel to the base pair long axis [22]. When 0.20 < R(4b/
< 0.80 (Fig. 3B), change trends of CD spectra were continued.
DNA)
When R ¼ 0.80, the positive band reached the highest peak.
However, a new positive ICD at 360 nm emerged gradually while
the negative ICD signal at 350 nm disappeared gradually. The
positive ICD band increased by a big margin, implying another
binding model happened and the molecule started to stack along
the surface of DNA [23,24]. When R(4b/DNA) > 0.80 (Fig. 3C), the
reduction of the positive band of DNA and the constancy of the
negative band and ICD demonstrated that electrostatic stacking
was the only combination manner. The disagreement between the
turning point in intrinsic CD and ICD could be explained: when
R ¼ 0.20e0.80, intercalation dominated the process and aggrega-
tion began; when R > 0.80, the DNA had been saturated with 4b, so
4b could not insert into the base pairs but accumulated on the
surface of DNA.
Fig. 5. Effect of increasing amounts of compounds 4a and 4d on the relative viscosities
of CT-DNA at 25 ꢄC respectively. [DNA] ¼ 100
mM in TriseHCl (30 mM, pH 7.5). h is the
viscosity of DNA in the presence of the compounds and h0 is the absence of the
compounds.
2.4. DNA photo-damaging property
intercalation mechanism. According to Fig. 5, 4a aroused a greater
viscosity’s change than 4d did, in other words, 4a had a higher
capacity of DNA-damaging. The result was parallel to their activity
on tumor cells.
Besides the anti-tumor activities and binding abilities of these
novel naphthalimides with DNA, we are also interested in their
photo-damaging abilities to DNA under light irradiation. The gel
mobility assay is sensitive to changes in DNA length or conforma-
tion, since the electrophoretic mobility of nucleic acid is propor-
tional to the length of the nucleic acid molecules. Therefore,
DNA-damaging activities of 4aee were evaluated in 20 mM
TriseHCl (pH 7.5) in the presence of supercoiled plasmid DNA
pBR322 under the irradiation of 365 nm-UV light for 2 h. All the
compounds could cleave the closed supercoiled DNA into relaxed,
open circular form (Form II) and compounds 4aeb even could
cleave closed supercoiled plasmid DNA into linear Form III (Fig. 4),
indicating that 4-(4-phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalimide
derivatives also can be active photonucleases.
3. Conclusions
The present work demonstrated the design, synthesis and
quantitative evaluation of the 4-(4-phenyl-[1,2,3]-triazol-1-yl)-1,8-
naphthalimide derivatives as DNA-intercalating and DNA-photo-
cleaving agents. The easily method that introduce 1,2,3-triazole
ring to the 4 site of naphthalimide was offered. This reconstruction
improved the anticancer cytotoxicity of the compounds over
famous Amonafide, especially compound 4a with an IC50 amount-
ing to 10ꢀ7 M. Based on the Circular Dichroism titration, the binding
mode of 4b with CT-DNA was characterized. The binding process
displayed two steps depending on the ratio of C4b/[DNA]. When
R(4b/DNA) ꢂ 0.20, 4b intercalated into DNA and the intercalation
orientations were heterogeneous. While 0.20 < R(4b/DNA) < 0.80, the
stacking of 4b on DNA was available while intercalation was still
the dominant force. When R(4b/DNA) ꢃ 0.80, surface stacking became
the only binding mode. The investigation of their photo-damaging
ability illuminated that these compounds could efficient photo-
cleaved DNA into form II and even form III under 365 nm light
irradiation.
2.5. Viscosity measurement
To further assure the binding mode between drug and DNA, the
viscosity of complex of 4a and 4d with CT-DNA were taken into
study. Viscosity experiment was the most powerful tool to deter-
mine which binding mode occurred between compound and DNA
[25]. Accounting to Fig. 5, the viscosity of the complex mounted up
obviously with the increasing value of R(com/DNA), implying that the
distances between adjacent base pairs were largened and the helix
was unwound and stiffened, which was the distinct symbol of
4. Experimental
4.1. Materials and methods
All the solvents were analytical grade. The closed supercoiled
pBR322 DNA was bought from Takara Biotech Co. Ltd (Dalian). 1H
NMR was measured on a Bruker AV-400 spectrometer with chemical
shifts reported as ppm (in DMSO/CDCl3, TMS as internal standard).
Mass spectra were measured on a HP 1100 LCeMS spectrometer.
Melting points were determined with an X-6 micro-melting point
apparatus and were uncorrected. IR spectra were recorded on
a Nicolet Nexus 770 spectrometer. Fluorescence spectra were det-
ermined on a Hitachi F-4500. Absorption spectra were determined
on a PGENERAL TU-1901 UVevis spectrophotometer.
Fig. 4. 1% Agarose gel electrophoresis assay of plasmid PBR 322DNA cleaved by
compounds 4aee. lane: DNA alone (no hv); lane 2: DNA alone; lanes 3e7: DNA and
compounds 4aee at concentration of 100
TriseHCl (pH 7.5).
mM, respectively. Irradiation for 2 h in 30 mM

1278
X. Li et al. / European Journal of Medicinal Chemistry 46 (2011) 1274e1279
4.2. Synthesis
4.2.3.3. N-Butyl-4-(4-phenyl-[1,2,3]-triazol-1-yl)-naphthalimide
(4c). Yield 87%, mp: 195.4e196.3 ꢄC. Chromatography solvent
(CH2Cl2/CH3OH, 50:1, v/v). IR (potassium bromide): 2955, 2768,
1701, 1656, 1591, 1429, 1378, 1351, 1239, 1160, 1120, 1011, 810 cmꢀ1
4.2.1. 4-Azido-1,8-naphthalic anhydride (2)
To a suspension of 4-bromo-1,8-naphthalic anhydride 1 (5.0 g,
18 mmol) in DMF (70 mL) at room temperature was added
a suspension of sodium azide (1.75 g, 27 mmol) in water (3 mL).
The mixture was stirred vigorously for 5 h at room temperature,
and the solution was poured into ice water. The precipitated
yellow solid was filtered to give 2 (3.8 g, 89% yield). mp:
185.6e186.9 ꢄC. IR (potassium bromide): 3030, 2150, 1777, 1736,
1H NMR (d6-DMSO, 400 MHz)
d
(ppm): 0.95 (t, J ¼ 7.2 Hz, 3H), 1.38
(m, 2H), 1.66 (dd, J ¼ 7.6 Hz, 2H), 4.08 (t, J ¼ 7.2 Hz, 2H), 7.42
(t, J ¼ 7.6 Hz, 1H), 7.53 (t, J ¼ 7.6 Hz, 2H), 8.00 (m, 3H), 8.16
(d, J ¼ 7.6 Hz, 1H), 8.30 (d, J ¼ 8.4 Hz, 1H), 8.63 (m, 2H), 9.32 (s, 1H).
13C NMR (d6-DMSO, 100 Hz)
d (ppm): 14.19, 20.28, 30.06, 55.36,
123.03,123.86,124.59,124.61,125.98,126.19,128.80,128.89,129.34,
129.49, 129.91, 130.43, 130.91, 132.03, 138.09, 147.56, 163.08, 163.61.
1606, 1510 cmꢀ1
.
HRMS-EI m/z: calcd for
C
24H20N4O2 (Mþ): 396.1586, found:
4.2.2. 4-(4-Phenyl-[1,2,3]-triazol-1-yl)- 1,8-naphthalic anhydride (3)
4-Azido-1,8-naphthalic anhydride 2 (2.0 g, 8.2 mmol) and
phenylacetylene (0.85 g, 8.2 mmol) were suspended in a 1:1
mixture of water and tert-butyl alcohol (50 mL). Sodium ascorbate
(176 mg, 0.8 mmol) was added, followed by copper (II) sulfate
pentahydrate (20 mg, 0.08 mmol). The heterogeneous mixture was
stirred vigorously overnight. The reaction mixture was poured into
ice water, and the yellowegreen precipitate was collected by
filtration. After washing the precipitate with cold water, it was
dried under vacuum to afford 3 (2.61 g, 91.6% yield) of pure product
as yellowegreen powder. mp: 262.5e263.6 ꢄC. IR (potassium
bromide): 3025, 2765, 1697, 1654, 1587, 1510, 1425 cmꢀ1 1H NMR
396.1591.
4.2.3.4. N-(2-Hydroxy-ethyl)-4-(4-phenyl-[1,2,3]-triazol-1-yl)-naph-
thalimide (4d). Yield 80%, mp: 216.8e217.9 ꢄC. Chromatography
solvent (CH2Cl2/CH3OH, 5:1, v/v). IR (potassium bromide): 3600,
1793, 1660, 1588, 1505, 1447, 1350, 1239, 1156, 1115, 1011, 820 cmꢀ1
1H NMR (d6-DMSO, 400 MHz)
d
(ppm): 3.67 (t, J ¼ 5.6 Hz, 2H), 4.18
(t, J ¼ 5.6 Hz, 2H), 4.86 (t, J ¼ 5.6 Hz, 1H), 7.42 (t, J ¼ 6.8 Hz, 1H), 7.54
(t, J ¼ 7.2 Hz, 2H), 8.00 (m, 3H), 8.16 (d, J ¼ 7.6 Hz, 1H), 8.31 (d,
J ¼ 8.4 Hz, 1H), 8.63 (m, 2H), 9.33 (s, 1H). 13C NMR (d6-DMSO,
100 Hz) d (ppm): 42.09, 57.73,122.65, 123.48,124.08, 124.15, 125.52,
128.33, 128.46, 128.88. 129.07, 129.39, 129.95, 130.38, 131.51, 137.54,
147.09, 162.75, 163.28. HRMS-EI m/z: calcd for C22H16N4O3 (Mþ):
384.1222, found: 384.1119.
(d6-DMSO, 400 MHz)
d
(ppm): 7.43 (t, J ¼ 8.0 Hz, 1H), 7.54
(t, J ¼ 8.0 Hz, 2H), 8.03 (m, 3H), 8.21 (d, J ¼ 8.0 Hz, 1H), 8.66
(d, J ¼ 8.0 Hz, 1H), 8.70 (d, J ¼ 8.0 Hz, 1H), 9.38 (s, 1H). HRMS-EI: m/
z: calcd for C20H11N3O3 (Mþ): 341.0800, found: 341.0778.
4.2.3.5. N-(2-(Piperazin-1-yl)ethyl)-4-(4-phenyl-[1,2,3]-triazol-1-
yl)-naphthalimide (4e). Yield 75%, mp: 241.5e242.3 ꢄC. Chromatog-
raphy solvent (CH2Cl2/CH3OH, 10:1, v/v). IR (potassium bromide):
2930,1703,1670,1610,1597,1515,1430,1222,1151,1050, 830 cmꢀ11H
4.2.3. General procedure for preparation of compounds 4aee
A suspension of 4-(4-Phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalic
anhydride 3 (0.45 g, 1.3 mmol) was treated with corresponding
alkylamine (0.3 ml) in absolute EtOH (15 ml) and the reaction
mixture was heated at reflux temperature for 3 h. The reaction
mixture was cooled and the solvent was removed under reduced
pressure and the crude mixture was purified by silica gel
chromatography.
NMR (d6-DMSO, 400 MHz) d(ppm): 2.49 (m, 4H, NHCH2), 2.60
(t, J ¼ 6.8 Hz, 2H), 2.74 (m, 4H, NCH2), 4.20 (t, J1 ¼ 6.8 Hz, 2H), 7.42
(t, J ¼ 7.6Hz,1H), 7.54 (t, J ¼ 7.6Hz, 2H), 8.00 (m, 3H), 8.16 (d, J ¼ 8.0 Hz,
1H), 8.31 (d, J ¼ 8.0 Hz, 1H), 8.63 (m, 2H), 9.33 (s, 1H). HRMS-EI m/z:
calcd for C26H24N6O2 (Mþ): 452.1961, found: 452.1975.
4.3. Spectroscopic measurements
4.2.3.1. N-(2-(Dimethylamino)ethyl)-4-(4-phenyl-[1,2,3]-triazol-1-
yl)-naphthalimide (4a). Yield 85%, mp: 172.3e173.6 ꢄC. Chro-
matographic solvent (CH2Cl2/CH3OH, 10:1, v/v). IR (potassium
bromide): 2950, 2765, 1697, 1654, 1587, 1425, 1378, 1349, 1238,
The compounds were dissolved in absolute DMSO to give
10ꢀ5 M solutions. Following spectra testing were read with Shi-
madzu UV for absorption spectra and with PerkineElmer LS 50 for
fluorescence spectra.
1162, 1118, 1012, 786 cmꢀ1 1H NMR (d6-DMSO, 400 MHz)
d (ppm):
2.25 (s, 6H), 2.57 (t, J ¼ 6.8 Hz, 2H), 4.20 (t, J ¼ 6.8 Hz, 2H), 7.44
(t, J ¼ 7.6 Hz, 1H), 7.54 (t, J ¼ 7.2 Hz, 2H), 8.01 (m, 3H), 8.18
(d, J ¼ 7.6 Hz, 1H), 8.33 (d, J ¼ 8.0 Hz, 1H), 8.62 (d, J ¼ 6.8 Hz, 1H),
8.68 (d, J ¼ 8.0 Hz, 1H), 9.32 (s, 1H). 13C NMR (d6-CDCl3, 100 Hz)
4.4. Viscosity experiments
Calf thymus DNA was dissolved in TriseHCl buffer (30 mM, pH
7.5) and left at 4 ꢄC overnight. It was treated in an ultrasonic bath
for 10 min, and the insoluble material was filtered through a PVDF
d
(ppm): 38.47, 45.85, 57.01, 122.00, 122.98, 123.51, 123.90, 126.00,
126.48, 128.65, 128.90, 129.14, 129.58, 129.69, 130.77, 132.31,
138.49, 148.48, 163.19, 163.71. HRMS-EI m/z: calcd for C24H21N5O2:
411.1695, found: 411.1705.
membrane filter (pore size of 0.45
mm). The final concentration of
CT-DNA was 100 M. Viscometric titrations were performed
m
with an Ubbelodhe viscometer immersed in a thermostated bath
maintained at 25 (ꢅ0.1) ꢄC. The flow times were measured with
a digital stopwatch. Each sample was measured three times, and an
4.2.3.2. N-(2-(Diethylamino)ethyl)-4-(4-phenyl-[1,2,3]-triazol-1-yl)-
naphthalimide (4b). Yield 82%, mp: 171.6e172.5 ꢄC. Chromatog-
raphy solvent (CH2Cl2/CH3OH, 10:1, v/v). IR (potassium bromide):
2930, 2765, 1700, 1655, 1590, 1430, 1378, 1350, 1239, 1162, 1119,
average flow time was calculated. Data is presented as (
[complex]/[DNA], where is the viscosity of DNA in the presence of
complex and
0 is the viscosity of DNA alone. Viscosity values were
calculated from the observed flowing time of DNA-containing
h/ ) vs
h0 1/3
h
1011, 790 cmꢀ1 1H NMR (d6-DMSO, 400 MHz)
d
(ppm): 0.96
h
(t, J ¼ 7.2 Hz, 6H), 2.53 (m, 4H), 2.68 (t, J ¼ 7.2 Hz, 2H), 4.13
(t, J ¼ 7.2 Hz, 2H), 7.42 (t, J ¼ 7.6 Hz, 1H), 7.53 (t, J ¼ 7.6 Hz, 2H),
8.01 (m, 3H), 8.15 (d, J ¼ 7.6 Hz, 1H), 8.30 (d, J ¼ 8.4 Hz, 1H), 8.60
solutions (t) corrected for that of the buffer alone (t0),
h
¼ (t ꢀ t0).
(m, 2H), 9.31 (s, 1H). 13C NMR (d6-CDCl3, 100 Hz)
d
(ppm): 12.78,
4.5. DNA cleavage assays
40.17, 47.85, 56.01, 121.90, 122.87, 123.41, 123.80, 125.87, 126.28,
128.64, 128.90, 129.24, 129.56, 129.59, 130.67, 132.22, 138.31,
148.43, 163.09, 163.52. HRMS-EI m/z: calcd for C26H25N5O2 (Mþ):
439.2008, found: 439.2005.
The plasmid DNA cleavage experiments were performed using
pBR322 DNA in TriseHCl buffer. Reactions were performed by
incubating DNA (0.05 mM bp) at 37 ꢄC in the dark in the presence/

X. Li et al. / European Journal of Medicinal Chemistry 46 (2011) 1274e1279
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We are grateful to the National Natural Science Foundation of
China (20536010), Program for Changjiang Scholars and Innovative
Research Team in University (IRT07110), and interdiscipline project
of Dalian University of Technology.
(b) V.V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem. Int.
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