Cytotoxicity and DNA binding property of phenanthrene imidazole with polyglycol side chains

Article abstract of DOI:10.1016/j.bmcl.2012.08.079

A series of phenanthrene imidazole with polyglycol side chain (2a-2c and 3a-3c) were synthesized and characterized by IR, NMR and MS. The cytotoxicity of 2a-2c and 3a-3c against cancer cell lines (HL-60, BGC-823, Bel-7402 and KB) in vitro were measured using MTT method. The DNA binding properties of 3a-3c were investigated by UV, fluorescence, CD spectroscopies and thermal denaturation. The results indicate that 2a exhibits higher cytotoxicity than cisplatin against BGC-823 and Bel-7402 cell lines, 3b and 3c exhibit higher cytotoxicity than 2b and 2c against BGC-823, Bel-7402 and KB cell lines. The cytotoxic effect of 2a-2c decrease with the increase of side chains length, the cytotoxic effect of 3a-3c increased with the increasing length of side chains against BGC-823, Bel-7402 and KB cell lines. Compounds 3a-3c intercalated DNA with a vertical orientation in the intercalation pocket. The binding constants of 3a-3c with Ct-DNA are 1.68 × 10⁶, 1.51 × 10⁶ and 0.709 × 10⁶ M^-1, respectively. The binding affinity of 3a-3c with Ct-DNA trended to decrease with the increasing length of polyglycol side chains.

Full text of DOI:10.1016/j.bmcl.2012.08.079

Bioorganic & Medicinal Chemistry Letters 22 (2012) 6347–6351
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Cytotoxicity and DNA binding property of phenanthrene imidazole with
polyglycol side chains
Shuxiang Wang a,b, Hongdong Li a, Chao Chen a, Jinchao Zhang a,b, , Shenghui Li a,b, Xinying Qin a,
⇑
a
Xiaoliu Li a,b, , Kerang Wang
⇑
a Chemical Biology Key Laboratory of Hebei Province, College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China
b Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding 071002, 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 phenanthrene imidazole with polyglycol side chain (2a–2c and 3a–3c) were synthesized and
characterized by IR, NMR and MS. The cytotoxicity of 2a–2c and 3a–3c against cancer cell lines (HL-60,
BGC-823, Bel-7402 and KB) in vitro were measured using MTT method. The DNA binding properties of
3a–3c were investigated by UV, fluorescence, CD spectroscopies and thermal denaturation. The results
indicate that 2a exhibits higher cytotoxicity than cisplatin against BGC-823 and Bel-7402 cell lines, 3b
and 3c exhibit higher cytotoxicity than 2b and 2c against BGC-823, Bel-7402 and KB cell lines. The cyto-
toxic effect of 2a–2c decrease with the increase of side chains length, the cytotoxic effect of 3a–3c
increased with the increasing length of side chains against BGC-823, Bel-7402 and KB cell lines. Com-
pounds 3a–3c intercalated DNA with a vertical orientation in the intercalation pocket. The binding con-
stants of 3a–3c with Ct-DNA are 1.68 Â 106, 1.51 Â 106 and 0.709 Â 106 MÀ1, respectively. The binding
affinity of 3a–3c with Ct-DNA trended to decrease with the increasing length of polyglycol side chains.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 1 June 2012
Revised 17 August 2012
Accepted 21 August 2012
Available online 30 August 2012
Keywords:
Phenanthrene imidazole derivatives
Polyglycol side chain
Binding property
Cytotoxicity
In recent years, studies on the small molecule DNA binding
agents towards their application on various biological responses
particularly anticancer activity is an active area of research.1,2 Var-
ious types of interaction of these small molecules with DNA have
been known. An electrostatic interaction that extends the nega-
tively charged phosphates outside the DNA double helix, interaction
with grooves of DNA, and intercalation model in which the base
pairs of DNA unwind to accommodate the intercalating agent are
some important binding modes. These binding interactions with
DNA are of interest in the development of drugs, new biochemical
tools, etc. Phenanthrene imidazole showed favorable properties
such as stability, ease of synthesis, a high extinction coefficient
and tuneable absorption and emission properties,3 which was com-
monly utilized in optical sensors and probes, such as endo/exo-11-
(4-(1H-phenanthro[9,10-d]imidazol-2-yl)phenoxy)undecylbicyclo
[2.2.1] hept-5-ene-2-carboxylat (A) and 2-[4-(diphenylamino) phe-
nyl]-1H-phenanthro[9,10-d]imidazole (B) (Fig. 1). Cote et al.4
designed and synthesized a series of substituted phenanthrene imi-
dazoles as anti-inflammatory and analgesic. Compound MF63
(Fig. 1) has been identified as a novel potent, selective and orally ac-
tive mPGES-1 inhibitor and exhibited a significant analgesic effect
with dosed at 30 and 100 mg/kg.
As far as we know, phenanthrene imidazole was rare as antican-
cer agent. Here, we design and synthesize a series of phenanthrene
imidazole derivatives. These compounds contain a different length
of polyglycol side chains and a planar chromophore. The polyglycol
side chains can form H-bonds with biomacromolecules by the –OH
groups, which may increased the binding affinity between com-
pounds and DNA,5–7 and the planar of phenanthrene imidazole
may insert into two base pairs in the DNA helix, resulting in mis-
coding and possible cell death.8
As shown in Scheme 1, compounds 2a–2c were synthesized by
condensation reaction of 5,6-phenanthrenequinone with various
4-(polyglycol)-benzaldehyde and NH4OAc in acetic acid.3 Com-
pounds 3a–3c were obtained by methylation reaction of 2a–2c.
All of them were characterized by IR, NMR and MS spectrometry.9
The cytotoxicity of 2a–2c and 3a–3c were preliminarily evaluated
against different tumor cell lines, including HL-60 (immature gran-
ulocyte leukemia), Bel-7402 (liver carcinoma), BGC-823 (gastrocar-
cinoma) and KB (nasopharyngeal carcinoma). It is well known that
Cl
NC
NC
H
N
H
N
H
N
O
O
N
11
N
N
N
O
⇑
Corresponding authors. Tel./fax: +86 312 507 9005 (J.Z.); tel./fax: +86 312 597
1116 (X.L.).
B
MF63
A
E-mail addresses: jczhang6970@yahoo.com.cn (J. Zhang), wsxhbu6564@126.-
Figure 1. Phenanthrene imidazole derivatives in optical sensors and anti-
com, lixl@hbu.edu.cn (X. Li).
inflammatory.
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.08.079

6348
S. Wang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 6347–6351
O
O
OH
OH
n
n
O
O
2a n = 0
2b n = 1
2c n = 2
3a n = 0
3b n = 1
3c n = 2
O
O
O
OHC
n
OH
O
I
N
N
N
NH
a
b
Scheme 1. The route of synthesis 2a–2c and 3a–3c (a) HOAc, NH4OAc, reflux, 3 h; (b) THF, CH3I, reflux, 20 h.
the DNA phosphoric acid skeleton is negatively charged with elec-
tricity. The compounds 3a–3c have a net positive charge due to N-
methylation, which enhance their water-solubility and may en-
hance the binding affinity of 3a–3c with DNA. So compounds 3a–
3c were selected to explore the binding affinity with calf thymus
DNA (ct-DNA).
The cytotoxicity of phenanthrene imidazole derivatives 2a–2c
and 3a–3c against HL-60, BGC-823, Bel-7402 and KB cell lines
in vitro were measured with MTT (3-(4,5-dimethylthiazol-2-yl)-
2,5-diphenyltetrazolium bromide) method. As shown in Table 1,
peaks show obvious hypochromicity and bathochromic shift (Table
2), which implies that 3a–3c may insert into the base pairs of DNA
as DNA-intercalating agents.10 Using the nonlinear least-squares
curve fitting method11 by fitting the experimental data of the max-
imum absorption changes, the binding constants of 3a–3c with Ct-
DNA were obtained to be 1.68 Â 106, 1.51 Â 106 and 0.709 Â 106 M
À1, respectively, which suggested that the length of the side chains
had slight influenced on the DNA binding properties and indicated
that the binding affinity trended to decrease with the increasing
length of polyglycol side chains for the tested compounds. For
compounds 3a–3c, though the DNA binding affinity decreased,
the cytotoxicity enhanced with the increase of the length of the
polyglycol side chain may be the polyglycol side chain improves
the solubility of phenanthrene imidazoles.
most compounds showed lower IC50 values (<30 lM) and exerted
cytotoxic effects with selectivity against tested carcinoma cell
lines. Compound 2a with the side chain of 4-(2-hydroxy-glycol)-
phenyl exhibited potent cytotoxicity against BGC-823 and Bel-
7402 cell lines with the IC50 values of 6.36 and 4.65
l
M, which
The fluorescence properties were performed to investigate the
interactions between 3a–3c and Ct-DNA in phosphate buffer
(1 mM, pH 7.5) containing 20 mM NaCl, 5% DMSO at 25 °C. As
shown in Figure 3, the fluorescence spectra of 3a–3c show a broad
emission band around 400 nm. Upon addition of Ct-DNA, the fluo-
rescence emission intensity of 3a–3c decreases due to forming the
complex between Ct-DNA and compounds and changing the
molecular rearrangements and energy transfer.12 Furthermore,
the maximum emission bands are blue shifted by about 3 nm,
which implies that the phenanthrene imidazole backbones of 3a–
3c enter Ct-DNA-stacking region with low polarity.13,14 These spec-
tral characteristic also indicated that 3a–3c intercalated into the
bases of the Ct-DNA.15,16 The observed fluorescence intensities
were quantified by plotting F/F0 as a function of Ct-DNA concentra-
tions, where F0 and F are the fluorescence intensity without and
with Ct-DNA, respectively. Stern-Volmer analysis17 gives insight
into the efficiency of fluorescence reduction of 3a–3c with the
increasing concentrations of Ct-DNA, which are calculated18,19 as
9.95 Â 103, 9.88 Â 103 and 6.61 Â 103 MÀ1 (Fig. 3, inset), respec-
tively, which indicate that the fluorescence of 3a–3c are sensitive
to the Ct-DNA concentrations. This result was in agreement with
the UV–vis analysis.
CD is a useful technique to investigate the conformational
changes in DNA morphology during small molecules-DNA interac-
tions. As shown in Figure 4, the CD spectrum of free Ct-DNA
showed a negative band at 247 nm due to the polynucleotide helic-
ity, and a positive band at 277 nm due to the base staking, which
indicated that the Ct-DNA existed in the right-band B form.20,21
Upon addition of compounds 3a–3c, the intensity of the positive
band increases at 277 nm and without significant wavelength
change. Additionally, weak positive induced circular dichroisms
(ICD) signals were observed in the region of the characteristic
absorption of the phenanthrene imidazole derivatives (350–
500 nm), which indicated that 3a–3c intercalated DNA with a ver-
tical orientation in the intercalation pocket.22
was better than that of positive control drug (cisplatin). The order
of IC50 value of 2a–2c were 2c > 2b > 2a against BGC-823, Bel-7402
and KB cell lines, indicating that the cytotoxic effect of 2a–2c de-
creases with the increase of side chains length. Although, the cyto-
toxicity of 3a have some decrease comparing with that of 2a,
compounds 3b and 3c showed obviously enhanced cytotoxicity
comparing with that of 2b and 2c against BGC-823, Bel-7402 and
KB cell lines. Compound 3c exhibited the best cytotoxicity against
BGC-823, Bel-7402 and KB cell lines among the compounds 3a–3c.
The order of IC50 value of 3a–3c were 3a > 3b > 3c against BGC-
823, Bel-7402 and KB cell lines, indicating that the cytotoxic effect
of 3a–3c enhanced with the increase of side chains length.
In addition to cytotoxicity study, the DNA binding properties
were investigated by UV–vis, fluorescence, circular dischroism
(CD) spectroscopy and DNA thermal denaturation experiment.
Since compounds 2a–2c exhibit poor solubility in buffer solution
and can be dissolved only in a few solvents such as DMSO and
DMF, we selected compounds 3a–3c as the DNA binders to detect
the binding properties of 3a–3c with Ct-DNA.
The DNA binding properties of 3a–3c with Ct-DNA were inves-
tigated by UV–vis spectra in phosphate buffer (1 mM, pH 7.5) con-
taining 20 mM NaCl, 5% DMSO (volume ratio) at 25 °C. The
maximum absorption intensity of 3a–3c overlaped with Ct-DNA
at about 260 nm, so the absorption wavelength was selected at
300–400 nm to eliminate the interference of Ct-DNA. As shown
in Figure 2, the absorption intensity of 3a–3c decreased with the
increasing concentrations of Ct-DNA, and the maximum absorption
Table 1
Cytotoxicity data for 3a–3c (IC50 SD, lM)
Compound
BGC-823
Bel-7402
KB
7.03 0.46
30.69 0.94
44.62 0.84
14.45 0.71
10.95 0.68
9.12 0.72
2.65 0.33
HL-60
2a
2b
2c
3a
3b
3c
Cisplatin
6.36 0.34
22.47 0.83
24.21 0.91
10.74 0.75
9.35 0.69
7.01 0.47
6.48 0.24
4.65 0.16
18.11 0.73
27.95 0.82
14.07 0.75
10.74 0.63
10.55 0.77
8.12 0.20
11.28 0.89
8.14 0.67
11.93 0.78
24.83 0.87
12.10 0.76
15.63 0.85
2.89 0.18
Additional evidence for intercalation into the DNA was obtained
from thermal denaturation studies. It is well known that the dou-
ble-helical structure of DNA is very stable due to hydrogen bonding
and base stacking interactions. When heating, the double helix

S. Wang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 6347–6351
6349
(a)
(b)
(c)
(a)
0.25
0.20
0.15
0.10
0.05
0.00
2000
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
1600
1200
ε
ε
3
4
0
1
2
0
10
20
30
[DNA]×104 / M
5
[DNA]× 10 / M
800
400
0
350
400
450
500
550
600
320
330
340
350
360
370
380
Wavelength/nm
Wavelength/nm
(b)
(c)
2000
1600
1200
800
400
0
1.0
0.8
0.6
0.4
0.25
0.20
0.15
0.10
0.05
0.00
1.0
0.8
0.6
ε
0.4
ε
0.2
0
0.2
10
20
30
0.0
0
5
[DNA]× 10 / M
1
3
2
[DNA]×104 / M
0.0000
0.0001
0.0002
0.0003
350
400
450
500
550
600
Wavelength/nm
320
330
340
350
360
370
380
Wavelength/nm
2400
2000
1600
1200
800
400
0
1.0
0.8
0.6
0.4
0.25
0.20
0.15
0.10
0.05
0.00
1.0
0.8
ε
0.6
0.2
0
ε
10
20
30
0.4
5
[DNA]× 10 / M
0.2
0
2
3
1
[DNA]×104 / M
350
400
450
500
550
600
Wavelength/nm
320
330
340
350
360
370
380
Figure 3. Fluorescence spectral of 3a–3c in the absence and presence of Ct-DNA
Fluorescence spectral changes of 3a (a, kex = 320 nm), 3b (b, kex = 320 nm) and 3c (c,
kex = 320 nm) at the concentration of 4.0 Â 10À5 M upon addition of Ct-DNA (arrow:
Wavelength/nm
0–400 lM) in phosphate buffer (1 mM, pH 7.5) containing 20 mM NaCl, 5% DMSO at
Figure 2. UV–vis spectra of 3a–3c in the absence and presence of Ct-DNA. UV–Vis
spectra of 3a (a), 3b (b) and 3c (c) at the concentration of 4.0 Â 10À5 M upon
25 °C. The excitation slit width and emission slit width are 5.0 nm. Inset: Stern-
Volmer plots for the observed fluorescence decrease on addition of Ct-DNA to
phenanthrene imidazole derivatives.
addition of Ct-DNA (arrow: 0–400 lM for 3a–3c) in phosphate buffer (1 mM, pH
7.5) containing 20 mM NaCl, 5%DMSO at 25 °C. Inset: the fitting plots of the binding
constants for 3a–3c with Ct-DNA obtained at the maximum absorption band.
dissociates into single strands due to the breaking of hydrogen
bonding and stacking interactions. The temperature, at which a
half of a DNA sample is melted, is known as the melting tempera-
ture (Tm). A change of Tm may be observed if a molecule binds with
DNA.23 Thus the thermal behavior of DNA in the presence of phen-
anthrene imidazole derivatives provides useful information on the
conformational changes and the strength of the DNA-compound
complexes. The melting curves of Ct-DNA in the absence and pres-
ence of 3a–3c are illustrated in Figure 5 and Table 3, respectively.
The Tm value for the free Ct-DNA is 68.7 °C. Upon addition of 3a–
Table 2
Binding constants (K) and photometric properties of 3a–3c with Ct-DNA
a
a
Compound Hypochromicity
(%)
Bathochromic shift
(nm)
K
(MÀ1 cmÀ1
)
3a
3b
3c
21.2
21.7
26.4
3.5
3.5
3.0
1.68 Â 106
1.51 Â 106
0.709 Â 106
a
Obtained at kmax
.

6350
S. Wang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 6347–6351
Furthermore, the binding properties of 3a–3c with Ct-DNA were
12
10
8
Ct-DNA
investigated by UV–vis, fluorescence and CD spectra and thermal
denaturation experiment. The results showed that compounds
3a–3c intercalated DNA with a vertical orientation in the intercala-
tion pocket. The binding constants of 3a–3c with Ct-DNA are
3a+Ct-DNA
3b+Ct-DNA
3c+Ct-DNA
6
4
1.68 Â 106, 1.51 Â 106 and 0.709 Â 106 MÀ1
, respectively. The
binding affinity of 3a–3c with Ct-DNA trended to decrease with
2
0
the increasing length of polyglycol side chains.
1.0
0.5
-2
-4
-6
-8
-10
Acknowledgments
0.0
-0.5
-1.0
This work was supported by the National Basic Research 973
Program (No. 2010CB534913), the Special Foundation for State
Major New Drug Research Program of China (No. 2009ZX09103-
139), the Natural Science Foundation of Hebei Province (No.
B2011201135), the Nature Science Foundation for Distinguished
Young Scholars of Hebei Province (No. B2011201164), the Key
Basic Research Special Foundation of Technology Ministry of Hebei
Province (Grant No. 11966412D), the Key Research Project Founda-
tion of Department of Education of Hebei Province (No.
ZD2010142), the Technology Research and Development Founda-
tion of Hebei Province (No. 11276431), the Joint Research Funda-
tion of the Natural Science Foundation of Hebei Province and
China Shiyao Pharmaceutical Group Co., Ltd. (B2011201174).
380
400
420
Wavelength/nm
240
270
Wavelength/nm
300
330
Figure 4. CD spectral of Ct-DNA in the absence and presence of 3a–3c CD spectra of
Ct-DNA (6.0 Â 10À5 M) and in presence of 3a–3c (2.0 Â 10À5 M) in phosphate buffer
(10 mM, pH 7.5) containing 20 mM NaCl, 5% DMSO at 25 °C.
1.0
Ct-DNA
3a+Ct-DNA
0.8
3b+Ct-DNA
3c+Ct-DNA
References and notes
0.6
1. Demeunynck, M.; Bailly, C.; Wilson, W. D. DNA and RNA Binders: From Synthesis
to Nucleic Acid Complexes; Wiley-VCH: Weinheim, 2003.
0.4
0.2
0.0
2. Tiekink, E. R. T.; Gielen, M. Metallotherapeutic Drugs and Metal-based Diagnostic
Agents: The Use of Metals in Medicine; John Wiley & Sons, 2005.
3. Steck, E. A.; Day, A. R. J. Am. Chem. Soc. 1943, 65, 452.
4. Côté, B.; Boulet, L.; Brideau, C.; Claveau, D.; Ethier, D.; Frenette, R.; Gagnon, M.;
Giroux, A.; Guay, J.; Guiral, S.; Mancini, J.; Martins, E.; Massé, F.; Méthot, N.;
Riendeau, D.; Rubin, J.; Xu, D.; Yu, H.; Ducharme, Y.; Friesen, R. W. Bioorg. Med.
Chem. Lett. 2007, 17(24), 6816.
5. Huang, T.; Wang, X. D.; Wei, Y. B.; Huang, S. L.; Huang, Z. S.; Tan, J. H.; An, L. K.;
Wu, J. Y.; Chan, A. S. C.; Gu, L. Q. Eur. J. Med. Chem. 2008, 43, 973.
6. Ruchelman, A. L.; Singh, S. K.; Ray, A.; Wu, X. H.; Yang, J. M.; Li, T. K.; Liu, A.;
Leroy, F.; Liu, L. F.; LaVoie, E. J. Bioorg. Med. Chem. 2003, 11, 2061.
7. Van der Graaf, W.; Vries, E. D. Anticancer Drugs 1990, 1, 109.
50
55
60
65
70
75
80
85
Temperature (°C )
Figure 5. DNA melting curves for Ct-DNA in the absence and presence of 3a–3c
8. Kamal, A.; Ramu, R.; Khanna, G. B. R.; Saxena, A. K.; Shanmugavel, M.; Pandita,
R. M. Bioorg. Med. Chem. Lett. 2004, 14(19), 4907.
DNA melting curves for Ct-DNA (5.0 Â 10À5 M) (j) and in presence of 3a ( ), 3b (
)
and 3c ( ) with concentration of 5.0 Â 10À6 M in phosphate buffer (1 mM, pH 7.5)
9. 2a: A light yellow solid; yield: 70.2%; mp >250 °C; IR (KBr, cmÀ1): 3520 (O–H),
3311 (N–H), 3062–3008 (C–H, Ph), 1150–1060 (C–O–C). 1H NMR (600 MHz,
DMSO-d6, TMS): d (ppm) 8.85 (d, J = 8.3 Hz, 2H, ArH), 8.63 (d, J = 6.9 Hz, 2H,
ArH), 8.33 (d, J = 8.8 Hz, 2H, ArH), 7.72 (t, J = 7.5 Hz, 2H, ArH), 7.62 (t, J = 7.0 Hz,
2H, ArH), 7.15 (d, J = 8.8 Hz, 2H, ArH), 4.11 (t, J = 5.0 Hz, 2H, CH2), 3.78 (t,
containing 2 mM NaCl, 5% DMSO.
Table 3
J = 4.7 Hz, 2H, CH2), 13C NMR (150 MHz, DMSO-d6)
d (ppm) 60.03, 70.16,
Average Tm and
DTm for Ct-DNA in the absence and in presence of 3a–3c
115.25, 122.52, 123.52, 125.44, 127.44, 127.86, 128.32, 149.85, 160.06. MS
(ESI) m/z: 355.1 [M+H]+. 2b: A yellow solid; yield: 84.5%; mp >250 °C; IR (KBr,
Compound
Tm(°C)
DTm(°C)
cmÀ1): 3680 (O–H), 3280 (N–H), 3032–3008 (C–H, Ph),1150–1060 (C–O–C). 1
H
Ct-DNA
3a
3b
68.7
73.5
72.9
72.7
—
4.8
4.2
4.0
NMR (600 MHz, DMSO-d6, TMS): d (ppm) 8.85 (d, J = 8.3 Hz, 2H, ArH), 8.61 (d,
J = 6.7 Hz, 2H, ArH), 8.30 (d, J = 8.7 Hz, 2H, ArH), 7.72 (t, J = 7.5 Hz, 2H, ArH),
7.62 (t, J = 7.6 Hz, 2H, ArH), 7.17 (d, J = 8.7 Hz, 2H, ArH), 4.22 (t, J = 9.0 Hz, 2H,
CH2), 3.8 (t, J = 9.0 Hz, 2H, CH2), 3.54 (t, J = 3.3 Hz, 4H, CH2), 13C NMR (150 MHz,
DMSO-d6) d (ppm) 60.73, 67.87, 69.39, 70.98, 115.27, 122.46, 123.68, 125.44,
127.51, 127.95, 128.21, 149.83, 159.85. MS (ESI) m/z: 399.2 [M+H]+. 2c: A white
solid; yield: 82.5%; mp >250 °C; IR (KBr, cmÀ1): 3500 (O–H), 3301 (N–H), 3020–
3008 (C–H, Ph),1150–1060 (C–O–C). 1H NMR (600 MHz, DMSO-d6, TMS): d
(ppm) 8.98 (d, J = 8.4 Hz, 2H, ArH), 8.64 (d, J = 7.9 Hz, 2H, ArH), 8.28 (d,
J = 8.8 Hz, 2H, ArH), 7.88 (t, J = 7.5 Hz, 2H, ArH), 7.80 (t, J = 7.6 Hz, 2H, ArH), 7.36
(d, J = 8.7 Hz, 2H, ArH), 4.29 (t, J = 8.4 Hz, 2H, CH2), 3.84 (t, J = 9.0 Hz, 2H, CH2),
3.65 (t, J = 9.6 Hz,2H, CH2), 3.58 (t, J = 9.6 Hz, 2H, CH2), 3.51 (t, J = 10.2 Hz, 2H,
CH2), 3.46 (t, J = 10.8 Hz,2H, CH2), 13C NMR (150 MHz, DMSO-d6) d (ppm) 60.7,
67.81, 69.40, 70.27, 70.48, 72.86, 115.34, 122.33, 123.58, 125.51, 127.50,
127.94, 128.20, 149.76, 159.89. MS (ESI) m/z: 443.2 [M+H]+. 3a: A orange solid;
yield: 31.9%; mp >250 °C; IR (KBr, cmÀ1): 3520 (O–H), 3042–3012 (C–H,
Ph),1100–1040 (C–O–C). 1H NMR (600 MHz, DMSO-d6, TMS): d (ppm) 9.11 (d,
J = 9.2 Hz, 2H, ArH), 8.76 (d, J = 9.1 Hz, 2H, ArH), 7.92–7.89 (m, 4H, ArH), 7.84 (d,
J = 8.6 Hz, 2H, ArH), 7.38 (d, J = 8.6 Hz, 2H, ArH), 4.27 (s, 6H, CH3), 4.19 (t,
J = 4.7 Hz, 2H, CH2), 3.80 (t, J = 4.4 Hz, 2H, CH2). 13C NMR (150 MHz, DMSO-d6) d
(ppm) 38.3, 40.5, 59.9, 70.6, 113.3, 116.2, 120.8, 121.2, 123.1, 125.2, 126.6,
128.5, 129.0, 129.8, 133.7, 149.8, 162.5; MS (ESI) m/z: 383.2 [MÀI]+. 3b:A
brown solid; yield: 40.3%; mp >250 °C; IR (KBr, cmÀ1): 3500 (O–H), 3069–3008
(C–H, ph), 1100–1040 (C–O–C). 1H NMR (600 MHz, DMSO-d6, TMS): d (ppm)
9.12 (d, J = 9.6 Hz, 2H, ArH), 8.77 (d, J = 9.4 Hz, 2H, ArH), 7.92–7.90 (m, 4H, ArH),
7.84 (d, J = 8.7 Hz, 2H, ArH), 7.39 (d, J = 8.8 Hz, 2H, ArH), 4.31 (t, J = 9.0 Hz, 2H,
3c
3c, obvious changes in the DNA melting temperature were ob-
served. The Tm values increased to 73.5, 72.9 and 72.7 °C, respec-
tively, indicating that the insertion of compounds enhanced the
stability of the DNA double helix conformation and increased the
DNA melting temperature. The level of the increased melting tem-
perature (DTm) induced by DNA-compound interactions is 4.8, 4.2
and 4.0 °C, respectively. Compounds 3b and 3c possessed lower
DNA melting temperature than 3a. The result was in agreement
with the UV–vis and fluorescence analysis.
In conclusion, a series of novel phenanthrene imidazole deriva-
tives with various polyglycol side chains were synthesized by con-
densation and N-methylation reactions. The phenanthrene
imidazole derivatives showed cytotoxic effects with selectivity
against tested carcinoma cell lines. Compounds 2a and 3c exhibit
better cytotoxicity against BGC-823, Bel-7402 and KB cell lines.

S. Wang et al. / Bioorg. Med. Chem. Lett. 22 (2012) 6347–6351
6351
CH2), 4.27 (s, 6H, CH3), 3.85 (t, J = 9.0 Hz,2H, CH2), 3.56 (t, J = 3.0 Hz, 4H, CH3).
13C NMR (150 MHz, DMSO-d6) d (ppm) 38.3, 40.5, 60.7, 68.3, 69.2, 73.0, 113.4,
116.2, 121.2, 123.1, 125.3, 126.6, 128.5, 129.0, 129.8, 133.7, 149.7, 162.3. MS
(ESI) m/z: 427.2 [MÀI]+. 3c: A yellow solid; yield: 37.6%; mp >250 °C; IR (KBr,
cmÀ1): 3505 (O–H), 3072–3002 (C–H, Ph), 1100–1040 (C–O–C). 1H NMR
(600 MHz, DMSO-d6, TMS): d (ppm) 9.14 (d, J = 9.7 Hz, 2H, ArH), 8.79 (d,
J = 9.5 Hz, 2H, ArH), 7.94–7.91 (m, 4H, ArH), 7.85 (d, J = 8.7 Hz, 2H, ArH), 7.41 (d,
J = 8.7 Hz, 2H, ArH), 4.30 (t, J = 9.0 Hz, 2H, CH2), 4.29 (s, 6H, CH3), 3.85 (t,
J = 9.0 Hz,2H,CH2), 3.65 (t, J = 9.6 Hz, 2H, CH2), 3.58 (t, J = 9.6 Hz, 2H, CH2), 3.51
(t, J = 9.6 Hz, 2H, CH2), 3.46 (t, J = 5.2 Hz, 2H, CH2). 13C NMR (150 MHz, DMSO-
d6) d (ppm) 38.3, 40.6, 60.7, 68.3, 69.3, 70.3, 70.5, 72.9, 113.4, 116.2, 121.2,
123.1, 125.3, 126.6, 128.5, 129.0129.8, 133.7, 149.7, 162.3, MS (ESI) m/z: 471.2
[MÀI]+.
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