Novel efficient anticancer agents and DNA-intercalators of 1,2,3-triazol-1,8-naphthalimides: Design, synthesis, and biological activity

Article abstract of DOI:10.1016/j.tet.2011.01.063

Two novel series of 3-1,2,3-triazol-1,8-naphthalimides 5a-e, 7a-e were synthesized easily by employing 'click reaction'. Their bioactivities were evaluated. Compounds 5a-e were found to be more toxic against MCF-7 cells while 7a-e were more potent against

Full text of DOI:10.1016/j.tet.2011.01.063

Tetrahedron 67 (2011) 2299e2304
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Novel efficient anticancer agents and DNA-intercalators of 1,2,3-triazol-
1,8-naphthalimides: design, synthesis, and biological activity
,
a
a
a
a,b,
Xiaolian Li a , Yanjie Lin , Yukun Yuan , Kai Liu , 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:
Two novel series of 3-1,2,3-triazol-1,8-naphthalimides 5aee, 7aee were synthesized easily by employing
‘click reaction’. Their bioactivities were evaluated. Compounds 5aee were found to be more toxic against
MCF-7 cells while 7aee were more potent against 7721 cells, in particular 7a, the IC50 value of which
against cell lines of MCF-7 and 7721 was 0.348 mM and 0.258 mM, respectively. Due to the phenyl group
linked to 1,2,3-triazole, compound 5a not only showed higher DNA affinity but also more efficient DNA
damaging ability than compound 7a.
Received 10 December 2010
Received in revised form 17 January 2011
Accepted 21 January 2011
Available online 27 January 2011
Keywords:
Triazole
Ó 2011 Elsevier Ltd. All rights reserved.
Intercalation
Anticancer
Naphthalimides
1. Introduction
in anticancer field.1e3 As shown in Fig. 1, Compound (a) as aroma-
tase inhibitor could reduce the growth-stimulatory effect of es-
Triazole derivatives had attracted much attention in chemistry,
biology, and medicine fields because of their stable metabolism,
high selectivity, and less adverse reaction. They were widely used
as antifungal agents, anticonvulsant agents, and especially popular
trogens in estrogen-dependent breast cancer.4 Compound (b)
effectively inhibited epithelia proliferation.5 Contragestazol (c) had
outstanding effect on suppressing the Oophoroma cells.6 All these
compounds were under clinical trial for cancer therapy.
N
N
N
N
H3CO
N
Cl
Cl
CH2CH3
N
HN
N
NC
CN
N
Cl
(a)
(b)
(c)
OH
R
N
R
N
O
O
O
O
O
N
O
S
N
NH2
NO2
(d)
(e)
(f)
Fig. 1. Some excellent compounds of triazole and naphthalimide derivatives.
* Corresponding authors. E-mail address: xiaolianlidlut@gmail.com (X. Li).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.01.063

2300
X. Li et al. / Tetrahedron 67 (2011) 2299e2304
In oncotherapy area, DNA is often referred to be one of the most
naphthalimides 5aee and 7aee. Structures of all the compounds
were confirmed by 1H NMR, HRMS, and IR spectra. The above ex-
periments provided an approach of the linkage of 1,2,3-triazole to
3-site of naphthalimide by ‘click reaction’ with high yields and
simple purification steps, which could further expand the variety of
naphthalimide derivatives.
promising biological targets of developing anti-tumor agents to
specifically constrain tumor cell growth.7 Design and synthesis of
novel and effective DNA-targeted compounds, especially DNA-
intercalators have important theoretical significance and applica-
tion value. Studying the interaction between DNA-intercalating
molecules and DNA, in particular, effects of structural characters of
molecular on the interaction, could offer novel insights into the
design of new DNA targeting anti-tumor drugs.8 Naphthalimide
was a significant DNA-targeted matrix for its planar chromophore
and modifiable structure. Successful examples including Amona-
fide (d), NI (e), and 2-aminothiazonaphthalimides (f).9e11
O
O
O
O
O
O
O
O
O
II
I
V
NO
NH
N
3
2
1
O
O
Fusing heterocycles to naphthalene nucleus had been widely
reported, but few attentions had been paid to the linkage of func-
tional rings with a single covalent bond,12 much less combination of
1,2,3-triazole and naphthalimides. 1,2,3-Triazole compounds do not
exist in natural substances, but they have been artificially synthe-
sized with many ways due to their attractive features, such as large
dipole moment,13 stable to metabolic degradation, capable of hy-
drogen bonding,14 and they also could react with protein in dif-
ferent forms. What is more, it is often referred as the classical
bioisosteres of amide for its similar space structure and electrical
effect to amide.15 It is known that 3-amino-naphthalimide (Amo-
nafide), which had been used in clinic II, was effective to various
mammary cancers.16 Unfortunately its adverse side effects blocked
its further research. Herein, our group continued to expand the
diversity of naphthalimide derivatives, so novel series of 3-1,2,3-
triazol-1,8-naphthalimides 5aee and 7aee (Fig. 2) were designed
and synthesized. 1,2,3-Triazole instead of amino was linked to 3-
site of naphthalimide by ‘click reaction’, which was a mildness
approach with high yields under environmental-friendly condi-
tion.17 In doing so, we hoped that new properties could be endowed
to the whole molecule and the horizon for designing naph-
thalimides could be broadened.
O
III
R
N
6
O
O
O
O
O
IV
N
N
N
H NR
VI
N
N
N
N
N
N
R
4
5a-e
O
O
N
N
N
N
7a-e
a
R=CH CH N(CH )
R=CH CH OH
b
e
R=CH CH N(CH CH )
c
R=CH CH CH CH
d
R=CH CH N(CH CH ) NH
Scheme 1. Synthesis of 1,2,3-triazole-naphthalimides 5aee and 7aee. Reagents and
conditions: (I) 10% Pd/C, H2, DMF, 60 ꢀC, 86.7% yield; (II) NaNO2, HCl, CH3COOH, NaN3,
H2O, 0e5 ꢀC, 86.9% yield; (III) phenylacetylene, CuSO4$5H2O, sodium-ascorbate, H2O/
BuOH, rt, 92.3% yield; (IV) RNH2, CH3CH2OH, refluxed; (V) acetylene, CuSO4$5H2O,
sodium-ascorbate, H2O/t-BuOH, rt, 92.3% yield; (VI) RNH2, CH3CH2OH, refluxed.
The UVevis and Fluorescent data of 5aee and 7aee were
measured and shown in Table 1. The different substitutes of 5aee
and 7aee were found to have only slight effect on the UVevis
spectra, with the similar value of intensities around 4.15. Maximal
absorption of 5aee was slightly higher than that of 7aee because of
the impact of phenyl. It also can be seen that the maximal emission
of these compounds was around 400 nm and corresponding fluo-
rescence quantum yields of 5aee were low relatively. Such low
yields might be caused by the 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 and naphthalimide.
R
R
O
O
N
O
O
N
N
N
N
N
N
N
7a R=CH2CH2N(CH3)2
5a R=CH2CH2N(CH3)2
7b
7c
7d
R=CH2CH2N(CH2CH3)2
R=CH2CH2CH2CH3
R=CH2CH2OH
5b
5c
5d
R=CH2CH2N(CH2CH3)2
R=CH2CH2CH2CH3
R=CH2CH2OH
Table 1
UVevis and fluorescent data of 5aee and 7aee
R=CH2CH2N(CH2CH2)2NH
7e
R=CH2CH2N(CH2CH2)2NH
5e
Fb
)
Stokes’
shift/nm
Excitation
a
a
Compound
UV lmax
(lg
FL lmax
(
3)
wavelength l/nm
Fig. 2. The structures of 1,2,3-triazol-naphthalimide derivatives.
5a
5b
5c
5d
5e
7a
7b
7c
7d
7e
342 (4.15)
342 (4.16)
343 (4.18)
343(4.17)
342 (4.11)
339 (4.27)
338 (4.15)
339 (4.18)
338 (4.17)
339 (4.11)
401 (<0.001)
399 (<0.001)
400 (<0.001)
401 (<0.001)
400 (<0.001)
402 (0.006)
402 (0.005)
403 (0.008)
403 (0.004)
404 (0.003)
59
57
57
58
58
63
64
64
65
65
342
342
343
343
342
339
338
339
338
339
2. Results and discussion
2.1. Synthesis and spectra
Preparation processes of all these compounds 5aee and 7aee
were shown in Scheme 1. 3-Nitro-1,8-naphthalic anhydride 1 was
reduced with hydrogen to afford compound 2.18 Afterward, com-
pound 2 was reacted with sodium nitrite in glacial acetic acid and
concentrated hydrochloric acid at 0e5 ꢀC for 1 h, subsequently
sodium azide was dropped into the mixture and compound 3 was
obtained. Cyclization of 3-azido-naphthalic (3) with alkyne under
copper(II) and sodium-ascorbate catalysis yielded compound 4 and
6 with high yield. Without further purification, the obtained an-
hydride compounds were condensed with the corresponding
amine in ethanol to form the corresponding targeted
a
In absolute ethanol.
With quinine sulfate in sulfuric acid as quantum yield standard (
b
F
¼0.55).
2.2. Cytotoxicity
The anti-tumor activity of the compounds 5aee and 7aee was
evaluated in vitro against MCF-7 (human mammary cancer cell),
Hela (human cervical carcinoma cell), and 7721 (human liver

X. Li et al. / Tetrahedron 67 (2011) 2299e2304
2301
cancer cell) by MTT tetrazolium assay. The IC50 values were listed in
Table 2 and activities of Amonafide were as a control. It can be seen
from Table 2 that compounds 5aee were to be more toxic against
MCF-7 than Hela and 7721 cells, and 5a bearing N,N-dimethyl-
ethylenediamine was the most effective compound. Its inhibition
abilities against three cell lines were 5.6-fold, 2.4-fold, and 8.5-fold
higher than that of Amonafide under the same experimental con-
ditions, respectively. Unlike 5aee, compounds 7aee were more
toxic against 7721 than MCF-7 and Hela cells, especially 7d had 2.9-
fold and 5.4-fold more selectively for 7721 than cell lines of MCF-7
and Hela. To further analyze the data in Table 2, the strong re-
semblance between 5aee and 7aee was found that their potent
were closely related with the side chains, which further demon-
strated that the presence of a basic terminal group in the side chain
was essential for cytotoxic activity.19 Compounds 5c,d and 7c,d
whose side chains had no basic terminal were less active than
Amonafide. The better cytotoxic activity of 5aec, 5e, and 7aec, 7e
hinted that 1,2,3-triazole could enhance the cytotoxicity and im-
prove anti-tumor ability of naphthalimides compared to the ac-
tivities with the famous Amonafide.
shifts indicating that compound can insert into the base pairs of
DNA. Its binding constant was calculated with the following
equation:
ꢀ
ꢁ
ꢀ
ꢁ
ꢀ
ꢀ
ꢁꢁ
½DNAꢁ= 3a
ꢂ
3f ¼ ½DNAꢁ= 3b
ꢂ
3f þ 1= Kb 3b
ꢂ
3f
3
addaverage molar extinction coefficient of the solution (A/C5a
)
Kbddthe binding constant
3
bddmolar extinction coefficient of totally binding 5a
fddmolar extinction coefficient of free 5a
3
Kb could be calculated out with the equation. In this way, the
binding constant of 5a with DNA was 5.10ꢃ105 Mꢂ1, which was
relatively higher during DNA-intercalation, indicating that 5a had
a good ability of DNA affinity.23
The Scatchard binding constant between CT-DNA and com-
pound 7a was determined by Fluorescence spectroscopy technique
(in 30 mM TriseHCl buffer, pH 7.5).24 As shown in Fig. 4, the
emission intensity of the 7a was strong quenched and had a slightly
350
Table 2
f5
f4
f5CT
Anti-tumor activities of compounds against MCF-7, Hela, and 7721 cells
300
Compound
Cytotoxicity (IC50, mM)
f3
f4CT
f2
f3CT
f1
MCF-7
Hela
7721
250
5a
5b
5c
5d
5e
7a
7b
7c
0.301
0.862
>100
33.71
1.0
0.348
0.692
>100
45.6
0.725
0.775
>100
71.4
0.194
0.357
0.78
0.502
>100
>100
>100
2.55
0.258
0.354
>100
15.6
200
f2CT
f1CT
150
100
>100
85
7d
7e
50
0
24.6
1.68
1.55
1.73
1.28
4.27
Amonafide
360
380
400
420
440
460
480
500
2.3. DNA intercalating property
wavelength(nm)
DNA intercalating property of compound 5a and 7a, which was
typical for all compounds was evaluated. As 5a had very weak
fluorescence, its UVevis spectra was used to investigate the in-
teraction between the compound and DNA.20 If the compound can
intercalate DNA, the UVevis curve of their complex will be induced
bathochromic shift and hypochromicity.21,22 UVevis curve of 5a
was shown in Fig. 3. As DNA concentration was increased, 5a
showed significant hypochromicities and slight bathochromic
Fig. 4. Fluorescence spectra before and after interaction of compound 7a and CT-DNA.
Curves F and F-CT corresponded to compound 7a before and after being mixed with
DNA. Numbers 1e5 indicated the concentration of 7a, 2, 5, 10, 20, 40
DNA applied was 50 M.
mM, respectively.
m
bathochromic shift upon the addition of CT-DNA, suggesting that
the transition of energy or electron was occurred between com-
pounds and the base pairs of DNA. Its Scatchard binding constant
was determined to be 3.51ꢃ105 Mꢂ1 (Fig. 5), which was a little lower
80000
70000
60000
50000
40000
30000
20000
10000
0
0.00
0.05
0.10
0.15
0.20
0.25
r
Fig. 3. Interaction of 5a and calf thymus DNA. Absorption changes of 5a during ad-
Fig. 5. Scatchard plots of spectrophotometric titration of CT-DNA to 7a in TriseHCl
dition of calf thymus DNA (0, 50, 100, 200
mM) in 30 mM TriseHCl (pH 7.5) solution.
buffer.

2302
X. Li et al. / Tetrahedron 67 (2011) 2299e2304
than N-(N0,N0-dimethylamino-ethyl)-3-(4-phenyl-[1,2,3]-triazol-1-
yl)-naphthalimide (5a). The results suggested that the 5aeDNA
3. Conclusions
complex was more stable with the aid of large
tems formed by the phenyl linked to the 1,2,3-triazole of 5a.
p
-conjugated sys-
The present work focused on the design, synthesis, and quan-
titative evaluation of two kinds of 1,2,3-triazol-1,8-naphthalimide
derivatives as anti-tumor and DNA-photocleaving agents. An easy
approach of linkage of 1,2,3-triazole or 4-phenyl-1,2,3-triazole
rings to the 3-site of naphthalimide instead of amino by using ‘click
reaction’ was offered. This reconstruction improved the cytotoxic-
ity of the compounds. Based on the testing of anti-tumor activity,
5aee were found to be more cytotoxic against MCF-7 than cell lines
of Hela and 7721 while 7aee had a more selectivity on 7721 cells. In
particular, compound 5a, bearing N,N-dimethylethylenediamine
with the values of IC50 against three cell lines was 5.6-fold, 2.4-fold,
and 8.5-fold lower than that of Amonafide, and other compounds
bearing aminoalkyl side chains were all more potent than Amo-
nafide. Under the impact of phenyl, compound 5a not only showed
the higher DNA binding affinity (the binding constant was
5.10ꢃ105 Mꢂ1) but also more efficient DNA damaging ability than
compound 7a.
2.4. DNA photo-damaging property
Besides the anti-tumor activities and binding abilities of these
novel naphthalimides with DNA, their photodamage abilities to
DNA under light irradiation were also evaluated. The gel mobility
assay is sensitive to change of DNA length or conformation, since
the electrophoretic mobility of nucleic acid is proportional to the
length of the nucleic acid molecules. Therefore, DNA damaging
activities of all compounds were evaluated in 20 mM TriseHCl (pH
7.5) in the presence of supercoiled plasmid DNA pBR322 under the
irradiation with 365 nm-UV light for 2 h. All the compounds could
apparently cleave the closed supercoiled DNA into relaxed and
open circular form (form II) according to Fig. 6. Compared lane 3
and lane 7, it is easily found that 5a had a higher DNA damaging
ability than 7a indicating that the phenyl in 5a could assist it with
a more efficient approach for action between compound and DNA.
4. Experimental section
4.1. Materials and methods
All the solvents were analytical grade. The CT-DNA and the
closed supercoiled pBR322 DNA was purchased from Takara Bio-
tech Co., Ltd (Dalian).
Fig. 6. Agarose gel (1%) electrophoresis assay of plasmid pBR322 DNA cleaved by
compounds 5aee and 7aee. Lane 1: DNA alone (no hv); lane 2: DNA alone; lanes
3e12: DNA and compounds 5aee, 7aee at concentration of 100 mM, respectively.
Irradiation for 2 h in 30 mM TriseHCl (pH 7.5).
Melting points were determined by an X-6 micro-melting point
apparatus and were uncorrected. Infrared (IR) spectra were mea-
sured on a Nicolet 20DXB FR-I infrared spectrometer, with samples
analyzed as KBr disks. High-resolution mass spectra (HRMS) were
obtained on a HPLC Q-TOF MS (Micro) spectrometer. The purity of
compounds was checked by ascending TLC on Merck’s silica gel
plates (0.25 mm) with fluorescent baking. NMR measurements
(data reported in ppm) were performed on a Varian INOVA spec-
trometer operating at 400 MHz or an AVANCE spectrometer oper-
2.5. Viscosity measurement
To further assure the binding mode of drug and DNA, com-
pounds 5a and 7a were studied on CT-DNA viscosity. The viscosity
of mixture was increased obviously on the addition of compounds
according to Fig. 7, which powerfully proved that compounds could
intercalate into DNA and then caused the distance between adja-
cent base pairs to be largened and the helix to be unwound and
stiffened, and so the viscosity increased.25 It could be seen that 5a
aroused a greater viscosity’s change than 7a did, in other words,
compound 5a had a higher DNA damaging capacity. The result was
parallel to their DNA binding constants.
ating at 500 MHz, respectively. Chemical shifts
d are reported in
parts per million downfield from tetramethylsilane, J values are in
hertz, and the splitting patterns were designated as follows: s,
singlet; d, doublet; t, triplet; q, quartet; m, multiplet; b, broad. UV
spectra were recorded on HP 8453 UVevisible spectrophotometer.
4.2. Synthesis
4.2.1. 3-Amino-naphthalic anhydride (2). 3-Nitro-naphthalic anhy-
dride (7.5 g) and Pd/C (1.2 g) were suspended in DMF (100 mL)
under 1.5 MPa hydrogen gas and were stirred at 60 ꢀC for 3 h, then
cooled and the catalyzer Pd/C was removed by filtration. The filter
cake was washed by DMF until filtrate was achromatic. The
obtained filtrate was poured into the icewater and the yellow
precipitation (5.7 g) was gained. Yield (86.7%). Mp: >300 ꢀC.
4.2.2. 3-Azido-naphthalic anhydride (3). 3-Amino-naphthalic an-
hydride (4.1 g) was suspended in the mixture of concentrated HCl
(30 mL) and AcOH (30 mL). A solution of sodium nitrite (3.5 g) in
water (15 mL) was added dropwise within 20 min. After stirring
reaction for 1 h under the temperature not beyond 5 ꢀC, the solu-
tion of NaN3 (3.1 g) in water (10 mL) was added dropwise within
0.5 h under the ice-water bath condition. Withdrew the ice-water
bath, the reaction mixture was continued stirred for 2 h at room
temperature. Then the yellow precipitation was obtained when the
mixture was poured into icewater (300 mL). The desired compound
(4.0 g) was obtained after filtration, washing, and drying. Yield:
Fig. 7. Effect of increasing amounts of compounds 5a and 7a on the relative viscosities
of CT-DNA at 25 ꢀC, respectively. [DNA]¼100
mM in TriseHCl (30 mM, pH 7.5). h is the
86.9%, 1H NMR (CDCl3-d6, 400 MHz):
7.88 (d, J¼1.6 Hz, 1H), 8.3 (d, J¼8.0 Hz, 1H), 8.27 (d, J¼1.6 Hz, 1H),
d
(ppm): 7.84 (t, J¼8.0 Hz, 1H),
viscosity of DNA in the presence of the compounds and h0 is in the absence of the
compounds.

X. Li et al. / Tetrahedron 67 (2011) 2299e2304
2303
8.55 (d, J¼8.0 Hz, 1H). IR (KBr, cmꢂ1): 3050, 2155, 1770, 1730, 1601,
1521. HRMS (m/z): C12H5N3O3, calcd: 239.0331, found: 239.0324.
found: 384.1230. IR (KBr, cmꢂ1): 3630, 1710, 1655, 1600, 1510, 1450,
1330, 1230, 1156, 1112, 1015, 825.
4.2.3. 3-(4-Phenyl-[1,2,3]-triazol-1-yl)-1,8-naphthalic
anhydride
4.2.8. N-(2-Piperazin-1-yl-ethyl)-3-(4-phenyl-[1,2,3]-triazol-1-yl)-
naphthalimide (5e). Prepared and purified in a similar manner as
that in 5a, 2-piperazin-1-yl-ethylamine was used here instead of
N0,N0-dimethylethane-1,2-diamine and separated on silica gel
chromatography (CH2Cl2/CH3OH, 5:1, v/v) to get pure 5e. Yield:
(4). Combination of the 3-azido-1,8-naphthalic anhydride (2.0 g)
and phenylacetylene (0.85 g) dissolved into the mixture of t-BuOH
(25 mL) and water (25 mL). Then sodium-ascorbate (176 mg) and
CuSO4$5H2O (20 mg) were added. The mixture was stirred for 8 h
in dark at room temperature, which was traced by TCL until the
reaction completed. The mixture was poured into the icewater and
the appeared yellow precipitate was filtered, washed, and dried.
Then the target compound (2.65 g) was obtained. Yield: 92.3%. Mp:
76%. Mp: 250.2e251.7 ꢀC. 1H NMR (DMSO-d6, 400 MHz):
d (ppm):
2.50 (m, 4H, NHCH2), 2.60 (t, J¼6.4 Hz, 2H), 2.76 (m, 4H, NCH2), 4.19
(t, J¼6.4 Hz, 2H), 7.41 (t, J¼7.2 Hz,1H), 7.53 (t, J¼7.6 Hz, 2H), 7.96 (m,
3H), 8.52 (m, 2H), 8.95 (s, 1H), 9.01 (s, 1H), 9.63 (s, 1H). HRMS (m/z):
C26H24N6O2, calcd: 452.1961, found: 452.1986. IR (KBr, cmꢂ1): 2919,
1700, 1662, 1625, 1590, 1519, 1436, 1234, 1149, 1041, 840.
>300 ꢀC. 1H NMR (DMSO-d6, 400 MHz):
1H), 7.31 (t, J¼7.2 Hz, 2H), 7.62 (m, 3H), 8.21 (m, 2H), 8.41 (s, 1H),
8.62 (s, 1H), 9.01 (s, 1H). HRMS (m/z): C20H11N3O3, calcd: 341.0800,
found: 341.0789.
d
(ppm): 7.25 (t, J¼7.2 Hz,
4.2.9. N-(N0,N0-Dimethylamino-ethyl)-3-([1,2,3]-triazol-1-yl)-naph-
thalimide (7a). Prepared and purified in a similar manner as that in
5a, acetylene instead of phenylacetylene was used here, and sep-
arated on silica gel chromatography (CH2Cl2/CH3OH, 10:1, v/v) to
get pure 7a. Yield: 83%. Mp: 226.3e227.5 ꢀC. 1H NMR (DMSO-d6,
4.2.4. N-(N0,N0-Dimethylamino-ethyl)-3-(4-phenyl-[1,2,3]-triazol-1-
yl)-naphthalimide (5a). A suspension of 3-(4-Phenyl-[1,2,3]-tri-
azol-1-yl)-1,8-naphthalic anhydride 4 (0.47 g) was treated with
excess N0,N0-dimethylethane-1,2-diamine (0.3 mL) in absolute
EtOH (15 mL). The mixture was heated at reflux temperature until
the reaction was completed (TLC). After removing organic solvent
under reduced pressure, the crude mixture was purified by flash
chromatography (silica gel, CH2Cl2/CH3OH, 10:1, v/v) to afford the
0.46 g yellow solid 5a. Yield: 83%. Mp: 205.3e206.1 ꢀC. 1H NMR
400 MHz):
d
(ppm): 2.24 (s, 6H), 2.51 (t, J¼6.8 Hz, 2H), 4.18 (t,
J¼6.8 Hz, 2H), 7.96 (t, J¼7.6 Hz, 1H), 8.10 (d, J¼1.2 Hz, 1H), 8.53 (m,
2H), 8.93 (d, J¼2.4 Hz, 1H), 9.02 (d, J¼2.0 Hz, 1H), 9.16 (d, J¼1.2 Hz,
1H). HRMS (m/z): C18H17N5O2, calcd: 335.1382, found: 335.1382. IR
(KBr, cmꢂ1): 2923, 2815, 2771, 1700, 1656, 1627, 1598, 1471, 1381,
1292, 1240, 1174, 1058, 890, 790.
(DMSO-d6, 400 MHz):
d
(ppm): 2.25 (s, 6H), 2.57 (t, J¼6.8 Hz, 2H),
4.17 (t, J¼6.8 Hz, 2H), 7.40 (t, J¼7.2 Hz, 1H), 7.51 (t, J¼7.6 Hz, 2H),
7.95 (m, 3H), 8.50 (m, 2H), 8.92 (s, 1H), 8.99 (s, 1H), 9.59 (s, 1H).
HRMS (m/z): C24H21N5O2, calcd: 411.1695, found: 411.1703. IR (KBr,
cmꢂ1): 2942, 2775, 1698, 1662, 1596, 1477, 1384, 1338, 1261, 1238,
1151, 1043, 883, 781.
4.2.10. N-(N0,N0-Diethylamino-ethyl)-3-([1,2,3]-triazol-1-yl)-naph-
thalimide (7b). Prepared and purified in a similar manner as that in
5b, acetylene instead of phenylacetylene was used here, and sep-
arated on silica gel chromatography (CH2Cl2/CH3OH, 10:1, v/v) to
get pure 7b. Yield: 85%. Mp: 200.5e201.5 ꢀC. 1H NMR (DMSO-d6,
400 MHz):
d
(ppm): 0.97 (t, J¼6.8 Hz, 6H), 2.56 (m, 6H), 4.13 (t,
4.2.5. N-(N0,N0-Diethylamino-ethyl)-3-(4-phenyl-[1,2,3]-triazol-1-
yl)-naphthalimide (5b). Compound 5b was prepared and purified in
a similar manner as that in 5a, N0,N0-diethylethane-1,2-diamine was
used here instead of N0,N0-dimethylethane-1,2-diamine (CH2Cl2/
CH3OH, 10:1, v/v). Yield: 81%. Mp: 191.1e192.3 ꢀC. 1H NMR (DMSO-
J¼6.8 Hz, 2H), 7.95 (t, J¼7.6 Hz, 1H), 8.10 (s, 1H), 8.52 (m, 2H), 8.93
(d, J¼2 Hz, 1H), 9.02 (d, J¼2 Hz, 1H), 9.16 (s, 1H). HRMS (m/z):
C20H21N5O2, calcd: 363.1695, found: 363.1701. IR (KBr, cmꢂ1): 2925,
2811, 2750, 1711, 1651, 1616, 1601, 1462, 1376, 1276, 1233, 1168, 1043,
891, 793.
d6, 400 MHz):
d
(ppm): 0.97 (t, J¼7.2 Hz, 6H), 2.50 (m, 4H), 2.68 (t,
J¼7.2 Hz, 2H), 4.12 (t, J¼7.2 Hz, 2H), 7.42 (t, J¼7.6 Hz, 1H), 7.52 (t,
J¼7.6 Hz, 2H), 7.98 (m, 3H), 8.50 (m, 2H), 8.93 (d, J¼2.0 Hz, 1H), 9.0
(d, J¼2.4 Hz, 1H), 9.62 (s, 1H). HRMS (m/z): C26H25N5O2, calcd:
439.2008, found: 439.2001. IR (KBr, cmꢂ1): 2971, 2803, 1702, 1664,
1627, 1517, 1477, 1380, 1361, 1290, 1257, 1203, 1172, 1050, 881, 765.
4.2.11. N-Butyl-3-([1,2,3]-triazol-1-yl)-naphthalimide (7c). Prepared
and purified in a similar manner as that in 5c, acetylene instead of
phenylacetylene was used here, and separated on silica gel chro-
matography (CH2Cl2/CH3OH, 50:1, v/v) to get pure 7c. Yield: 86%.
Mp: 191.9e193.1 ꢀC. 1H NMR (DMSO-d6, 400 MHz):
d (ppm): 0.94 (t,
J¼7.6 Hz, 3H), 1.37 (m, 2H), 1.64 (m, 2H), 4.05 (t, J¼7.2 Hz, 2H), 7.94
(t, J¼8.0 Hz, 1H), 8.10 (s, 1H), 8.50 (m, 2H), 8.89 (d, J¼2.0 Hz, 1H),
8.99 (d, J¼2.0 Hz, 1H), 9.15 (s, 1H). HRMS (m/z): C18H16N4O2, calcd:
320.1273, found: 320.1278. IR (KBr, cmꢂ1): 2930, 2825, 2750, 1706,
1655, 1613, 1601, 1451, 1376, 1280.
4.2.6. N-Butyl-3-(4-phenyl-[1,2,3]-triazol-1-yl)-naphthalimide
(5c). Prepared and purified in a similar manner as that in 5a,
butylamine was used here instead of N0,N0-dimethylethane-1,2-di-
amine and separated on silica gel chromatography (CH2Cl2/CH3OH,
50:1, v/v) to get pure 5c. Yield: 85%. Mp: 195.4e196.7 ꢀC. 1H NMR
(DMSO-d6, 400 MHz):
d
(ppm): 0.94 (t, J¼7.2 Hz, 3H), 1.37 (m, 2H),
4.2.12. N-(2-Hydroxy-ethyl)-3-([1,2,3]-triazol-1-yl)-naphthalimide
(7d). Prepared and purified in a similar manner as that in 5d,
acetylene instead of phenylacetylene was used here, and separated
on silica gel chromatography (CH2Cl2/CH3OH, 5:1, v/v) to get pure
7d. Yield: 79%. Mp: 257.3e258.6 ꢀC. 1H NMR (DMSO-d6, 400 MHz):
1.64 (m, 2H), 4.05 (t, J¼7.6 Hz, 2H), 7.41 (t, J¼7.6 Hz, 1H), 7.52 (t,
J¼7.6 Hz, 2H), 7.97 (m, 3H), 8.51 (m, 2H), 8.93 (d, J¼1.6 Hz, 1H), 9.0
(d, J¼2.4 Hz, 1H), 9.62 (s, 1H). HRMS (m/z): C24H20N4O2, calcd:
396.1586, found: 396.1590. IR (KBr, cmꢂ1): 2950, 1708, 1669, 1630,
1510, 1472, 1378, 1361, 1293, 1245, 1201, 1172, 1055, 883, 780.
d
(ppm): 3.71 (d, J¼5.6 Hz, 2H), 4.35 (d, J¼5.2 Hz, 2H), 4.96 (s, 1H),
7.93 (t, J1¼8.0 Hz,1H), 8.09 (s, 1H), 8.51 (m, 2H), 8.89 (d, J¼2 Hz, 1H),
8.98 (d, J¼2.4 Hz, 1H), 9.16 (s, 1H). HRMS (m/z): C16H12N4O3, calcd:
308.0909, found: 308.0915. IR (KBr, cmꢂ1): 3660, 1706, 1651, 1607,
1518, 1432, 1330, 1235, 1152, 1111, 1012, 821.
4.2.7. N-(2-Hydroxy-ethyl)-3-(4-phenyl-[1,2,3]-triazol-1-yl)-naph-
thalimide (5d). Prepared and purified in a similar manner as that in
5a, 2-amino-ethanol was used here instead of N0,N0-dimethyl-
ethane-1,2-diamine and separated on silica gel chromatography
(CH2Cl2/CH3OH, 5:1, v/v) to get pure 5d. Yield: 79%. Mp:
4.2.13. N-(2-Piperazin-1-yl-ethyl)-3-([1,2,3]-triazol-1-yl)-naph-
thalimide (7e). Prepared and purified in a similar manner as that in
5e, acetylene instead of phenylacetylene was used here, and sep-
arated on silica gel chromatography (CH2Cl2/CH3OH, 4:1, v/v) to get
pure 7e. Yield: 77%. Mp: 250.2e251.7 ꢀC. 1H NMR (DMSO-d6,
257.3e258.6 ꢀC. 1H NMR (DMSO-d6, 400 MHz):
d (ppm): 3.61 (d,
J¼5.6 Hz, 2H), 4.20 (d, J¼5.2 Hz, 2H), 4.92 (s, 1H), 7.42 (t, J¼6.8 Hz,
1H), 7.53 (t, J¼6.8 Hz, 2H), 7.97 (m, 3 H), 8.52 (m, 2H), 8.93 (s, 1H),
9.00 (s, 1H), 9.60 (s, 1H). HRMS (m/z): C22H16N4O3, calcd: 384.1222,

2304
X. Li et al. / Tetrahedron 67 (2011) 2299e2304
400 MHz):
d
(ppm): 2.53 (m, 4H, NHCH2), 2.65 (t, J¼7.2 Hz, 2H),
a Microplate reader. All experiments were performed at least three
times and average of the percentage absorbance was plotted
against concentration. The results were expressed as percentage
relative to untreated control and IC50 value was calculated for each
compound.
2.78 (m, 4H, NCH2), 4.19 (t, J¼7.2 Hz, 2H), 7.92 (t, J¼7.6 Hz, 1H), 8.09
(s, 1H), 8.51 (m, 2H), 8.88 (d, J¼2.4 Hz, 1H), 8.99 (d, J¼2.0 Hz, 1H),
9.15 (s, 1H). HRMS (m/z): C20H20N6O2, calcd: 376.1648, found:
376.1645. IR (KBr, cmꢂ1): 2911, 1705, 1650, 1610, 1590, 1510, 1429,
1229, 1130, 1050, 833.
Acknowledgements
4.3. Spectroscopic measurements
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.
The compounds were dissolved in absolute DMSO at the con-
centration of 10ꢂ5 M. Following spectra testings were read with
Shimadzu UV for absorption spectra and with PerkineElmer LS 50
for fluorescence spectra.
Supplementary data
4.4. Viscosity experiments
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2011.01.063.
Calf thymus DNA was dissolved in TriseHCl buffer (30 mM, pH
7.5) and left at 4 ꢀC overnight. It was treated in an ultrasonic bath
for 10 min, and the insoluble material was filtered through a PVDF
References and notes
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