Novel heterocyclic family of phenyl naphthothiazole carboxamides derived from naphthalimides: Synthesis, antitumor evaluation, and DNA photocleavage

Article abstract of DOI:10.1016/j.bmc.2005.02.045

A new heterocyclic family of (2-(dimethylamino)ethyl)-2-substituted phenylnaphtho[2,1-d]thiazole-5-carboxamides modified from naphthalimides was designed, synthesized, and quantitatively evaluated as antitumor agents and photonucleases. All these compound

Full text of DOI:10.1016/j.bmc.2005.02.045

Bioorganic & Medicinal Chemistry 13 (2005) 3149–3155
Novel heterocyclic family of phenyl naphthothiazole
carboxamides derived from naphthalimides: synthesis,
antitumor evaluation, and DNA photocleavage
Zhigang Li,a Qing Yangb and Xuhong Qiana,c,
*
aState Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
bDepartment of Bioscience and Biotechnology, Dalian University of Technology, Dalian 116012, China
cShanghai Key Laboratory of Chemical Biology, East China University of Science and Technology, Shanghai 200237, China
Received 31 January 2005; revised 21 February 2005; accepted 22 February 2005
Available online 19 March 2005
Abstract—A new heterocyclic family of (2-(dimethylamino)ethyl)-2-substituted phenylnaphtho[2,1-d]thiazole-5-carboxamides modi-
fied from naphthalimides was designed, synthesized, and quantitatively evaluated as antitumor agents and photonucleases. All these
compounds were found to be more cytotoxic against P388 than against A549. B3 (m-NO2) was found to be the strongest inhibitor
for P388 with IC50 of 1.49 lM, while B2 was the most cytotoxic compound against A549 with IC50 of 12 lM. B4 (p-CH3), the most
efficient DNA photocleaver, showed detectable DNA cleavage at 0.5 lM and total cleavage from form I to 100% form II at 50 lM.
The photocleaving mechanism was changed with the modification to be via superoxide anion and radical.
ꢀ 2005 Elsevier Ltd. All rights reserved.
1. Introduction
(b)
(a)
N
N
Naphthalimides form a famous class of intercalating
agents that consists of a flat, generally p-deficient aro-
matic or heteroaromatic system, which binds to DNA
by insertion between base pairs of the double helix.
Many of them have not only shown high antitumor
activities upon a variety of murine and human tumor
cells1 but also capabilities of generating a multitude of
reactive intermediates that resulted in DNA
photocleavage.2,3
HN
O
O
N
O
A1, B1 R = H
A2, B2 R = p-OCH3
A3, B3 R = m-NO2
A4, B4 R = P-CH3
N
N
S
S
R
R
Figure 1. Structures of the reported and novel designed compounds.
Various attempts made to modify the naphthalimide
units to promote their DNA antitumor and photocleav-
ing abilities are focused on incorporating substituents or
on fusing five or six membered (phenyl or heterocyclic)
rings on the naphthalene skeletons.1–3 The larger aro-
matic ring system was proved to account for the higher
affinity for DNA and consequently for higher antitumor
and photocleaving activities. A family of phenyl thiazo-
naphthalimide intercalators, A1–A4 (Fig. 1a), has been
reported as efficient photonucleases in our previous re-
search2f whose photocleavage was caused by the
naphthalimide-thiazole radicals produced via excited
triplet state.
In our continued efforts to developsimple but efficient
antitumor and photocleaving agents, we proposed a no-
vel molecular design of modifying the reported photo-
nucleases, A1–A4, to corresponding ring-opened
models of phenyl naphthothiazole carboxamides, B1–B4
(Fig. 1b), whose planar tri-cyclic ring systems may
also intercalate into DNA to show medical or biological
Keywords: Phenyl naphthothiazole carboxamides; Photocleavage;
Cytotoxicity; Synthesis; Antitumor; DNA cleavage.
*
Corresponding author. Tel.: +86 411 83673466; fax: +86 411
83673488; e-mail addresses: xhqian@dlut.edu.cn; xhqian@ecust.
edu.cn
0968-0896/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.02.045

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Z. Li et al. / Bioorg. Med. Chem. 13 (2005) 3149–3155
potential. Furthermore, the functional phenyl thiazole
groups proven active in DNA photocleavage2f were re-
mained. The aminoalkyl side chain serving as DNA
groove binder and/or external electrostatic binder was
inferred to be more flexible to increase the affinity with
DNA.
glacial acetic acid containing benzaldehyde (e.g., B1)
immediately, then refluxed for 4 h to get phenyl
naphthothiazole-5-carboxylic acid 6. Finally, the corre-
sponding naphthoyl chloride was prepared from the ob-
tained acid by refluxing for 20 h in a mixture of thionyl
chloride and chloroform, then the naphthoyl chloride
condensed with N,N-dimethylethylenediamine in dichlo-
romethane to form the desired product (Scheme 1a).
Structures of the final products were all identified by
1H NMR, HRMS, IR. The above experiments also pro-
vided a new way to synthesize (substituted) phenyl
naphthothiazole carboxamide systems which may have
potential in other fields. However, compared with those
of (substituted) naphthalic anhydrides, the reacting abil-
ity of phenyl thiazonaphthalic anhydride 72f decreased
which was possibly caused by the introduction of het-
erocyclic atoms and/or the enlargement of the conjuga-
tion area resulting in the decarbonylation reaction
mediated by red mercuric oxide not taking place
(Scheme 1b).
2. Results and discussion
2.1. Synthesis and spectra
The replacement by mercury of one of the carbonyl
groups in naphthalic anhydride derivatives has long
been known,4 but the mercuric oxide mediated decarb-
onylation of 4-bromo-3-nitro-1,8-naphthalic anhydride5
has not been reported. When 4-bromo-3-nitro-1,8-naph-
thalic anhydride reacted with red mercuric oxide and
acetic acid according to the methods4 used in other
(substituted) naphthalic anhydrides, two isomers, 4-bro-
mo-3-nitro-1-naphthoic acid 3 and 4-bromo-3-nitro-8-
naphthoic acid 4 were obtained with the ratio of 4:1
via 1H NMR, and pure 4-bromo-3-nitro-1-naphthoic
acid 3 was obtained after recrystallization from acetic
acid. The obtained pure acid 3 refluxed in water with
sodium disulfide for 8 h to form 4-mercapto-3-amino-
1-naphthoic acid 5 whose solution was dropped into
It was found that compounds, B1, B2, B4, had slight dif-
ference in either emission wavelength (394, 396, 395 nm,
respectively) or absorption wavelength (358, 360,
359 nm, respectively). Due to the nitro groupꢀs elec-
tron-withdrawing effect, the maximal absorption of B3
was found to decrease to 348 nm, while its emission
O
OH
O
O
O
O
HO
O
O
O
O
(a)
Hg
Br
Hg
b
a
+
+
NO2
NO2
NO2
NO2
NO2
HO
Br
Br
Br
Br
1
4
2
3
H
O
HO
O
HO
O
O
N
N
c
d
f, g
e
NO2
NH2
N
N
Br
S
S
SH
3
5
6
O
O
O
O
O
O
HO
O
O
O
O
(b)
a, b
e
d
NO2
NH2
N
N
Br
S
SH
S
6
7
Scheme 1. Synthesis of target (2-(dimethylamino)ethyl)-2-phenyl naphtho[2,1-d]thiazole-5-carboxamide (e.g., B1). Reagents and conditions: (a) HgO
(red), NaOH, AcOH, H2O, reflux 4 days, 98% yield; (b) concentrated HCl, reflux 2 h; (c) recrystallized with AcOH, 40% yield; (d) Na2S2, H2O, 4 h;
(e) benzaldehyde, AcOH, N2, reflux 4 h, 65% yield; (f) SOCl2, CHCl3, Et3N; (g) N,N-dimethylethylenediamine, CH2Cl2, 20 h.

Z. Li et al. / Bioorg. Med. Chem. 13 (2005) 3149–3155
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Table 1. Spectra data,a,b photocleaving activityc,d and cytotoxicity (A-549e, P388f) of compounds
Compd
UV kmax/nm (lge)
FL kmax/nm (U)
Photocleaving activityc,d
Cytotoxicity (IC50, lM)
A549e P388f
I%
II%
B1
B2
B3
B4
358 (3.73)
360 (3.91)
348 (3.32)
359 (4.37)
376 (3.85)
386 (3.76)
384 (3.78)
376 (3.90)
394 (0.003)
396 (0.009)
405 (0.001)
395 (0.005)
425 (0.006)
491 (0.017)
447 (0.009)
412 (0.002)
29
22
35
0
71
78
206
12
2.36
2.16
1.49
2.66
NT
NT
NT
NT
65
870
408
NT
NT
NT
NT
100
96
2f
A1
2f
A2
4
53
57
58
47
43
2f
A3
2f
A4
42
NT, not tested.
a In absolute ethanol.
b With quinine sulfate in sulfuric acid as quantum yield standard (U = 0.55).
c,d The concentration used for B1–B4 in photocleaving activity evaluation was 50 lM, while that for A1–A4 was 100 lM.
e Cytotoxicity (CTX) against human lung cancer cell (A549) was measured by sulforhodamine B dye-staining method.7
f CTX against murine leukemia cells (P388) was measured by microculture tetrazolium-formazan method.8
wavelength had a red-shift to 405 nm. Compared with
those of their corresponding naphthalimides, A1–A4,2f
(Table 1), values of both the emission wavelength and
the absorption wavelength of B1–B4 are blue-shifted
due to the reduction of their conjugation areas and elec-
tronic pushing–pulling ICT (intramolecular charge
transfer) effects caused by the decarbonylation reaction.
spectra method (Fig. 3) instead of fluorescence quench-
ing technique. In the process of adding calf thymus
DNA into the compound solution, absorption intensi-
ties decreased with the increase of DNA concentrations.
2.3. Antitumor evaluation
The antitumor activities in vitro (under scattered light) of
these compounds were evaluated by sulforhodamine B
(SRB) assay7 against A549 (human lung cancer cell)
and MTT tetrazolium dye assay8 against P388 (murine
leukemia cell), respectively (Table 1). The IC50 represents
the drug concentration (micromolar) required to inhibit
cell growth by 50%. All these compounds were found to
be more cytotoxic against P388 than against A549 with
IC50 ranging from 1.49 lM to 870 lM. No obvious corre-
lation was found between their DNA affinity or photo-
cleaving abilities (shown as follows) and antitumor
activities. B3, the most cytotoxic compound against
P388 with IC50 of 1.49 lM, showed the weakest photo-
cleaving ability. B2 was found to be the strongest growth
inhibitor for A549 with IC50 of 12 lM. However, the
modification of such agents for potent antitumor drugs
seems to be not very successful in that many other re-
ported efficient naphthalimides inhibited the tumor cells
in nanomolar orders.1 However, these data indicated
2.2. DNA-intercalating property
The Scatchard binding constants for compounds, B1, B2
and B4, to calf thymus DNA (buffered in 20 mM Tris–
HCl buffer, pH 7.5) were determined to be
6.39 · 104 Mꢀ1, 1.22 · 105 Mꢀ1, and 7.36 · 104 Mꢀ1
,
respectively, according to the method of fluorescence
quenching technique (Fig. 2).6 A more stable complex
of DNA and B2 was inferred to be formed by hydrogen
bond between the oxygen atom on the phenyl ring and
the hydrogen atom in base pairs of DNA molecule
which may account for the higher constant value of
B2 (1.22 · 105 Mꢀ1).
The constant of B3 was not measured due to its weak
fluorescence, however, the intercalation experiment of
B3 was carried out by using an electronic absorption
Figure 2. Fluorescence spectra before and after interaction of com-
pound B2 and calf thymus DNA. Curves F and F–CT corresponded to
compound B2 before and after being mixed with DNA. Numbers 1–4
indicated the concentration of B2, 5, 10, 20, 40 lM, respectively. DNA
applied was 50 lM (bp).
Figure 3. Interaction of B3 (50 lM) and calf thymus DNA. Absorption
changes of B3 during addition of calf thymus DNA (0, 50, 100,
200 lM) (bp) in 20 mM Tris–HCl (pH 7.5) solution.

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Z. Li et al. / Bioorg. Med. Chem. 13 (2005) 3149–3155
the importance of the six membered piperidinedione ring
in naphthalimides on their antitumor activities.
by A1.2f These data proved our rational design for effi-
cient DNA photocleaver. Additionally, the photocleav-
ing ability of B4 increased remarkably with the
prolongation of photo-irradiation time (Fig. 4c), show-
ing it was a time-dependent cleavage process. No dam-
age was observed in the absence of light (lane 3),
proving UV lightꢀs function as trigger to initiate the
DNA strand scission.
2.4. DNA photocleavage
The cleavage abilities of compounds, B1–B4, were evalu-
ated using closed supercoiled pBR322 DNA as substrate
under photo-irradiation with a transluminator (360 nm)
at a distance of 20 cm at 0 ꢁC for 3 h under aerobic con-
ditions, and no cleavage was observed without the light
irradiation. The photocleaving efficiency of plasmid
DNA was defined by the percentage of obtained nicked
circular form (form II) converted from supercoiled form
(form I) which could be visible on 1% agarose gel by
electrophoresis. As shown in Figure 4a, all these com-
pounds photocleaved plasmid DNA from form I to
form II efficiently. B4 was found to be more efficient
(100% form II) than its analogues under identical condi-
tions. The concentration-dependent experiment of B4
exhibited detectable cleavage (21% form II) at concen-
tration of 0.5 lM and total cleavage from form I to
100% form II at concentration of 50 lM (Fig. 4b). Also
at concentration of 100 lM, B4 cleaved plasmid DNA
completely to generate much smaller linear fragments
which were invisible on the agarose gel (Fig. 4b, lane
8). It was obvious that B1–B4 photocleaved DNA more
efficiently than their corresponding naphthalimides, A1–
A4,2f through comparison of the obtained percentage of
form II, even though the concentration used for A1–A4
was 100 lM, two times as high as that for B1–B4 (Table
1). The most efficient naphthalimide A1 showed detect-
able (19% form II) and total photocleavage (100% form
II) of supercoiled pBR322 DNA at 5 and 100 M, respec-
tively. Only 67% form II DNA was obtained at 50 lM
Photocleavage can be via a variety of mechanisms
involving free radical, electron transfer and singlet oxy-
gen. In order to establish the reactive species responsible
for cleavage of the plasmid DNA, B4 and B3 were cho-
sen as example compounds to perform mechanistic
experiments by addition of histidine (singlet oxygen
quencher), dithiothreitol (DTT, superoxide anion scav-
enger), ethanol (radical scavenger), respectively (Fig.
5a and b). It was clear that DTT and ethanol retarded
the photocleavage process as for both B3 and B4 (lane
5, 6), indicating superoxide anion and radical were most
possibly responsible for the DNA cleavage. In our cases,
the damage to DNA by these compounds was possibly
through both superoxide anions generated through elec-
tron transfer from the chromophores to oxygen, and
radicals produced by the C@N bond in phenyl thiazole
groupand/or the C @O bond via photo-excited3 (n–p*)
state under photo-irradiation. The mechanism was
found to be different from that of A1–A4, whose photo-
cleavage was only via radicals produced via excited
triplet state.2f
Electron densities of the phenyl thiazonaphthalene chro-
mophores were relatively higher than those of the corre-
sponding naphthalimides due to the reduction of one
strong electron-withdrawing group, carbonyl group.
The higher chromophoresꢀ electron densities were in-
ferred to grant B1–B4 stronger abilities of transferring
electrons, which were from their chromophores to oxy-
gen to form superoxide anions responsible for photo-
cleavage under photo-activation, consequently, B1–B4
exhibited higher photocleavage abilities with the emer-
gence of superoxide anion species than A1–A4.
Figure 4. Photocleavage of closed supercoiled pBR322 DNA in the
buffer of Tris–HCl (20 mM, pH 7.5). (a) Photocleavage of pBR322
DNA by different compounds (50 lM) for 3 h; lane 1, DNA alone (no
hm); lane 2, DNA alone; lane 3–6, compounds, B1–B4, individually and
DNA. (b) Photocleavage of DNA by B2 at various concentrations for
3 h. lane 1, DNA alone (no hm); lane 2, DNA alone; lane 3–7, B2 at
concentration of 0.5, 1, 5, 10, 50, 100 lM, respectively. (c) Photoclea-
vage of DNA by B2 (50 lM) at various time intervals. lane 1, DNA
alone (no hm); lane 2, DNA alone; lane 3–7, 0, 30, 60, 120, 180 min,
respectively.
Figure 5. Effect of additives on the photocleavage of closed super-
coiled pBR322 DNA by: (a) compound B4 (30 lM) and (b) B3 (50 lM)
in the buffer of Tris–HCl (20 mM, pH 7.5) for 3 h. lane 1, DNA alone
(no hm); lane 2, DNA alone; lane 3, DNA, and compound B4 or B3;
lane 4–6, DNA and compound in the presence of histidine (12 mM),
dithiothreitol (DTT, 60 mM), ethanol (3.4 M), respectively.

Z. Li et al. / Bioorg. Med. Chem. 13 (2005) 3149–3155
3153
Substituent effects on photocleavage were described by
the photocleavage ability order: B4 (p-CH3) > B2 (p-
OCH3) > B1(H) > B3 (m-NO2). Obviously, the com-
pounds with electron-donating groups (B2, B4) photo-
cleaved DNA more efficiently than B3 (m-NO2) with
electron-withdrawing group. The electron-donating
groups were believed to have stronger abilities to push
electrons so as to facilitate the electron transferring to
form superoxide anions. DTT inhibited the photoclea-
vage reaction of B4 more efficiently (form II: from
83% to 33%) than that of B3 (form II: from 67% to
41%) proving that superoxide anion was more easily
produced in the photocleavage course of B4 (lane 5).
As for B2, the hydrogen bond formed between the oxy-
gen atom on phenyl ring and base pairs of DNA prob-
ably inhibit the electron-donating ability of the
methyloxyl group, which might explain why B2 had a
stronger electron-donating groupbut had lower effi-
ciency in photocleavage than B4. By comparison, the re-
ported photocleavage order of A1 (H) > A4 (p-CH3) >
A3 (m-NO2) > A2 (p-OCH3)2f could partly prove that
superoxide anions might be not involved in photo-
cleavage reactions of A1–A4.
dium hydroxide (3.75 g, 94 mmol) and refluxed until
the solid material dissolved, a solution of HgO (red)
(6.6 g) in a mixture of H2O (10 mL) and AcOH (6 mL)
was added with stirring to result in slow evolution of
carbon dioxide. The reaction mixture refluxed for 96 h,
then cooled, and filtered. The highly insoluble yellow so-
lid was washed with water and dried under vacuum at
100 ꢁC overnight to give the mixture of 1 and 2 (15 g,
98% yield). Attempts to purify and separate the anhydro
compounds were unsuccessful. They are insoluble in or-
ganic solvents.
4.2.2. 4-Bromo-3-nitro-1-naphthoic acid (3). The ob-
tained precipitates, 1 and 2 were suspended in 80 mL
concentrated HCl, stirred, heated under reflux for 3 h.
Hot filtration gave the mixture of 4-bromo-3-nitro-1-
naphthoic acid 3 and 4-bromo-3-nitro-8-naphthoic acid
1
4 with ratio of 4:1 via H NMR. Pure 4-bromo-3-nitro-
1-naphthoic acid 3 was obtained after recrystallization
from acetic acid (3.4 g, 40% yield). Mp: 225.1–226 ꢁC.
1H NMR (DMSO-d6) d (ppm) 7.94 (m, J1 = 7.8 Hz,
J2 = 7.2 Hz, J2 = 7.6 Hz, 2H, 5-H, 8-H), 8.50
(J1 = 6.0 Hz, J2 = 7.2 Hz, J2 = 6.8 Hz, 2H, 6-H, 7-H),
8.94 (s, 1H, 2-H). ESI-MS (negative) m/z: 293.9
(MꢀH)+.
3. Conclusion
4.2.3. 2-Phenylnaphtho[2,1-d]thiazole-5-carboxylic acid
(6). Na2SÆ9H2O (4.32 g, 18 mmol) and S (1.152 g,
36 mmol) were refluxed in 50 mL H2O for 0.5 h till S
was all dissolved. Pure 4-bromo-3-nitro-1-naphthoic
acid 3 (1.18 g, 4 mmol) was added within 0.5 h and re-
fluxed for 8 h, the reaction mixture cooled and filtered
to get the dark red solution of 4-mercapto-3-amino-1-
naphthoic acid 5. Due to its instability in the air, it
was dropped into glacial acetic acid containing benzal-
dehyde (0.448 mL) immediately under the protection
of N2 and refluxed for 4 h, cooled, and poured into
1000 mL ice water, filtered, washed with water, and
dried under vacuum at 40 ꢁC over night to obtain the
brown solid of 2-phenylnaphtho[2,1-d]thiazole-5-carb-
oxylic acid 6. (0.75 g, 65% yield). Mp: 232–235 ꢁC.
ESI-MS (negative) m/z: 306.0 (MꢀH)+.
The present work demonstrated the design and synthesis
of compounds, B1–B4, as novel antitumor agents and
DNA photocleavers. All these compounds were found
to be more cytotoxic against P388 than against A549
with IC50 ranging from 1.49 to 870 lM. B3 (m-NO2)
was found to be the strongest inhibitor for P388 with
IC50 of 1.49 lM, while B2 was the most cytotoxic one
against A549 with IC50 of 12 lM. Compared with their
corresponding naphthalimide derivatives, these com-
pounds photocleaved DNA more efficiently. B4 (p-
CH3), the most efficient cleaver, showed detectable
DNA cleavage at 0.5 lM and total cleavage from form
I to form II at 50 lM. The mechanism experiments
showed the cleavage occurred to DNA might be via
superoxide anion and radical.
4.2.4. N-(2-(Dimethylamino)ethyl)-2-phenylnaphtho[2,1-d]-
thiazole-5-carboxamide (B1). 2-Phenylnaphtho[2,1-d]thi-
azole-5-carboxylic acid 6 (0.75 g) was treated with
thionyl chloride (15 mL) and DMF (1 drop) in CHCl3
(15 mL) at reflux temperature for 20 h. After removal
of the solvent and excess thionyl chloride, the crude so-
lid, and N,N-dimethyl ethyl diamine (0.5 mL) were com-
bined in 25 mL CH2Cl2. The mixture cooled in an ice
bath while Et3N (0.55 mL) was added dropwise with
stirring. The stirring continued for 20 h at room temper-
ature. Removal of solvent and separated on silica gel
chromatography (CH2Cl2/MeOH, 6:1, v/v) to afford
the pure product B1 (0.45 g, 51% yield). Mp: 186–
187 ꢁC. 1H NMR (CDCl3-d6) d (ppm): 2.33 (s, H,
NCH3), 2.66 (t, J1 = 6 Hz, J2 = 5.2 Hz, 2H, NCH2),
3.69 (d, J1 = 4 Hz, 2H, CONHCH2), 7.02 (s, 1H,
CONH), 7.52 (d, J = 5.2 Hz, 3H, 30-H, 40-H, 50-H),
7.62 (m, J1 = 7.6 Hz, J2 = 8 Hz, J3 = 7.6 Hz, J4 =
7.6 Hz, 2H, 7-H, 8-H), 8.05 (d, J1 = 7.6 Hz, 9-H), 8.13
(t, J1 = 2 Hz, J2 = 3.2 Hz, 2H, 10-H, 60-H), 8.26 (s, 1H,
4. Experimental
4.1. Materials
1
All the solvents were of analytic grade. H NMR was
measured on a Bruker AV-400 spectrometer with chem-
ical shifts reported as parts per million (in DMSO/
CDCl3-d6, TMS as an internal standard). Mass spectra
were measured on a HP 1100 LC-MS spectrometer.
Melting points were determined by an X-6 micro-melt-
ing point apparatus and uncorrected. Absorption spec-
tra were determined on PGENERAL TU-1901 UV–vis
spectrophotometer.
4.2. Synthesis
4.2.1. Anhydro-8-hydroxylmercuri-1-naphthoic acids (1
and 2). 4-Bromo-3-nitro-1,8-naphthalic anhydride
(9.66 g, 30 mmol) was suspend in 100 mL aqueous so-

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Z. Li et al. / Bioorg. Med. Chem. 13 (2005) 3149–3155
4-H), 8.50 (d, J = 8 Hz, 1H, 6-H). HRMS (ESI): calcd
10, 20, 40 lM, one contained calf thymus DNA
50 lM, the other contained no DNA but had the
same concentration of chemical as control. All the
above solution was shaken for 3 days at 25 ꢁC in
the dark. Fluorescence wavelength and intensity
area of samples were measured.
for C22H22N3OS (M+H)+: 376.1484. Found: 376.1475.
IR (KBr): 3285, 2921, 2850, 1635, 1536, 761 cmꢀ1
.
4.2.5. N-(2-(Dimethylamino)ethyl)-2-(4-methoxyphenyl)
naphtha[2,1-d]thiazole-5-carboxamide (B2). Prepared in
a similar manner as that in B1, 4-methoxybenzaldehyde
was used here instead of benzaldehyde and separated on
silica gel chromatography (CH2Cl2/MeOH, 4:1, v/v).
(b) Solution of B3 (0.25 mL), in DMSO (10ꢀ3 M)
mixed with 20 mM Tris–HCl (pH 7.5) to 5 mL.
Then, one group of samples were prepared in the
concentration of chemical at 50 lM, one did not
contain calf thymus DNA as control, the others
contained DNA with the concentration of 50, 100,
200 lM, respectively. All the above solution was
shaken for 3 days at 25 ꢁC in the dark. Absorption
spectra of samples were measured.
1
Mp: 194–195 ꢁC. H NMR (CDCl3-d6) d (ppm): 2.92
(s, 6H, NCH3), 3.44 (s, 2H, NCH2), 3.86 (s, 3H,
OCH3), 3.98 (s, 2H, CONHCH2), 6.92 (d, J = 8.8 Hz,
2H, 30-H, 50-H), 7.46 (m, J1 = 7.6 Hz, J2 = 8.8 Hz,
J3 = 8.8 Hz, J4 = 6.4 Hz, 2H, 7-H, 8-H), 7.82 (d,
J = 7.6 Hz, 6-H), 7.89 (d, J = 8.4 Hz, 2H, 20-H, 60-H),
8.30 (s, 1H, 4-H), 8.33 (d, J = 8 Hz, 1H, 9-H), 8.57 (s,
1H, CONH). HRMS (ESI): calcd for C23H24N3O2S
(M+H)+: 406.1545. Found: 406.1554. IR (KBr): 3285,
4.2.10. Cytotoxic activity in vitro. The prepared com-
pounds have been submitted to Shanghai Institute of
Materia Medica for testing their cytotoxicities in vitro.
2921, 2850, 1635, 1606, 827 cmꢀ1
.
4.2.6. N-(2-(Dimethylamino)ethyl)-2-(3-nitrophenyl) naph-
tho[2,1-d]thiazole-5-carboxamide (B3). Prepared in a sim-
ilar manner as that in B1, 3-nitrobenzaldehyde was used
here instead of benzaldehyde and separated on silica gel
chromatography (CH2Cl2/MeOH, 3:1, v/v). Mp: 225.1–
226 ꢁC. 1H NMR (DMSO-d6) d (ppm): 2.50 (s, H,
NCH3), 2.58 (s, 2H, NCH2), 3.50 (s, 2H, CONHCH2),
7.69 (t, J1 = 8.1 Hz, J2 = 7.2 Hz, 1H, 8-H), 7.753 (t,
J1 = 7.8 Hz, J2 = 7.2 Hz, 1H, 7-H), 7.90 (t, J1 = 8.1 Hz,
J2 = 7.2 Hz, 1H, 50-H), 8.22 (d, J = 6 Hz, 2H, 20-H, 9-
H), 8.39 (d, J = 8.2 Hz, 2H, 40-H, 60-H), 8.54 (d,
J = 7.9 Hz 1H, 6-H), 8.86 (s, 1H, 4-H), HRMS (ESI):
calcd for C22H21N4O3S (M+H)+): 421.1334. Found:
421.1332. IR (KBr): 3272, 2947, 2859, 1639, 1532,
4.2.11. Photocleavage of supercoiled pBR322 DNA. Two
hundred and fifty nanograms of pBR322 DNA (form I),
1 lL solution of chemical in organic solvent and 20 mM
Tris–HCl (pH 7.5) were mixed to 10 lL, then irradiated
for 3 h with light (360 nm) using lampplaced at 20 cm
from sample. The samples were analyzed by gel electro-
phoresis in 1% agarose gel which was stained with ethi-
dium bromide. Supercoiled DNA runs at position I,
nicked DNA at position II.
Acknowledgments
Financial support by the National Key Project for Basic
Research (2003CB114400) and under the auspices of
National Natural Science Foundation of China is
greatly appreciated.
1344, 760 cmꢀ1
.
4.2.7. N-(2-(Dimethylamino)ethyl)-2-p-tolylnaphtho[2,1-d]-
thiazole-5-carboxamide (B4). Prepared in a similar
manner as that in B1, 4-methylbenzaldehyde was used
here instead of benzaldehyde and separated on silica
gel chromatography (CH2Cl2/MeOH, 6:1, v/v). Mp:
References and notes
1
1. (a) Bran˜a, M. F.; Cacho, M.; Gradillas, A.; Pascual-Teresa,
B.; Ramos, A. Curr. Pharm. Des. 2001, 7, 1745; (b) Bran˜a,
M. F.; Ramos, A. Curr. Med. Chem.: Anti-cancer Agents
2001, 1, 237; (c) Sami, S. M.; Dorr, R. T.; Alberts, D. S.;
Remers, W. A. J. Med. Chem. 1993, 36, 765; (d) Sami, S.
M.; Dorr, R. T.; Alberts, D. S. J. Med. Chem. 2000, 43,
3067; (e) Bran˜a, M. F.; Cacho, M.; Garcia, M. A. J. Med.
Chem. 2002, 45, 5813; (f) Bran˜a, M. F.; Cacho, M.; Garcia,
M. A. J. Med. Chem. 2004, 47, 1391.
2. (a) Qian, X.; Yao, W. Tetrahedron Lett. 2001, 42, 6175; (b)
Qian, X.; Mao, P.; Yao, W.; Guo, X. Tetrahedron Lett.
2002, 43, 2995; (c) Yao, W.; Qian, X.; Hu, Q. Tetrahedron
Lett. 2000, 41, 7711; (d) Li, Y.; Xu, Y.; Qian, X. Bioorg.
Med. Chem. Lett. 2003, 13, 3513; (e) Qian, X.; Li, Y.; Xu,
Y. Bioorg. Med. Chem. Lett. 2004, 14, 2665; (f) Li, Y.; Xu,
Y.; Qian, X. Tetrahedron Lett. 2004, 45, 1247; (g) Xu, Y.;
Qian, X. Bioorg. Med. Chem. 2003, 11, 5427.
3. (a) Satio, I.; Takayama, M.; Sakurai, T. J. Am. Chem. Soc.
1994, 116, 2653; (b) Satio, I.; Takayama, M. J. Am. Chem.
Soc. 1995, 117, 5590; (c) Satio, I.; Takayama, M.; Sugiy-
ama, H.; Nakatani, K. J. Am. Chem. Soc. 1995, 117, 6406.
4. (a) Leuck, B. G.; Perkins, R. P.; Whitmore, F. C. J. Am.
Chem. Soc. 1929, 51, 1831; (b) Whitmore, F. C.; Fox, A. L.
J. Am. Chem. Soc. 1929, 51, 3363; (c) Bailey, R. J.;
189–190 ꢁC. H NMR (CDCl3-d6) d (ppm): 2.39 (s, H,
NCH3), 2.43 (s, 3H, CH3), 2.73 (t, J = 5.6 Hz, 2H,
NCH2), 3.70 (d, J = 5.6 Hz, 2H, CONHCH2), 7.16 (s,
1H, CONH), 7.30 (d, J = 8 Hz, 2H, 30-H, 50-H), 7.58
(m, J1 = 5.6 Hz, J2 = 8.4 Hz, J3 = 8 Hz, J4 = 7.2 Hz,
2H, 7-H, 8-H), 7.98 (d, J = 8 Hz, 3H, 1-H, 20-H, 60-H),
8.24 (s, 1H, 4-H), 8.459 (d, J = 8 Hz, 1H, 6-H). HRMS
(ESI): calcd for C23H24N3OS (M+H+): 390.1640.
Found: 390.1618. IR (KBr): 3273, 2922, 2852, 1634,
1537, 820 cmꢀ1
.
4.2.8. 2-Phenyl thiazonaphthalic anhydride (7). Prepared
in a similar manner as that in 2-phenylnaphtho[2,1-d]-
thiazole-5-carboxylic acid 6, 4-bromo-3-nitro-1,8-
naphthalic anhydride was used here instead of
4-bromo-3-nitro-1-naphthoic acid 3.
4.2.9. Intercalation studies of compounds to CT-DNA
(a) Solution of compound B1, B2, B4 (0.1 mL) in
DMSO (10ꢀ3–10ꢀ4 M) mixed with 20 mM Tris–
HCl (pH 7.5) to 5 mL. Then, two groups of samples
were prepared in the concentration of chemical at 5,

Z. Li et al. / Bioorg. Med. Chem. 13 (2005) 3149–3155
3155
Schechter, H. J. Am. Chem. Soc. 1983, 105, 6096; (d)
Rosowsky, A.; Wright, J. E.; Vaidya, C. M.; Forsch, R. A.;
Bader, H. J. Med. Chem. 2000, 43, 1620; (e) Yamada, K.;
Rice, K. C.; Flippen-Anderson, J. L. J. Med. Chem. 1996,
39, 1967; (f) Duffy, K. J.; Darcy, M. G.; Delorme, E. J.
Med. Chem. 2001, 44, 3730.
6. Gupta, M.; Ali, R. J. Biochem. 1984, 95, 1253.
7. Skehan, P.; Storeny, R.; Scudiero, D.; Monks, A.; McMa-
hon, J.; Vistica, D.; Warren, J. T.; Bokesc, H.; Kenney, S.;
Boyd, M. R. J. Natl. Cancer Inst. 1990, 82, 1107.
8. Kuroda, M.; Mimaki, Y.; Sashida, Y.; Hirano, T.; Oka, K.;
Dobashi, A.; Li, H.; Harada, N. Tetrahedron 1997, 53,
11549.
5. Yao, W.; Qian, X. Dyes Pigments 2001, 48, 43.