Synthesis of Novel Jusbetonin Analogues and Their Cytotoxicity against Tumor Cell

Article abstract of DOI:10.1002/jhet.2381

Six novel analogues of bioactive natural indolo[3,2-b]quinoline alkaloid glycoside jusbetonin were designed and synthesized, employing polyphosphoric acid mediated cyclization and two different amidation strategies on introduction of tetra-O-acetyl-β-d-gl

Full text of DOI:10.1002/jhet.2381

Month 2015
Synthesis of Novel Jusbetonin Analogues and Their Cytotoxicity against
Tumor Cell
a
b
a
a
a
*
Shixu Liu, Junxiu Meng, Wei Zhang, Shengbiao Wan, and Tao Jiang
aKey Laboratory of Marine Drugs, Ministry of Education of China, School of Pharmacy, Ocean University of China,
Qingdao, 266003, China
bNowa Pharmceuticals Co, Ltd., Suzhou, 215121, China
*
E-mail: jiangtao@ouc.edu.cn
Received April 12, 2014
DOI 10.1002/jhet.2381
Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com).
Six novel analogues of bioactive natural indolo[3,2-b]quinoline alkaloid glycoside jusbetonin were
designed and synthesized, employing polyphosphoric acid mediated cyclization and two different amidation
strategies on introduction of tetra-O-acetyl-β-D-glucosamine to tetracyclic carboxylic acids.
J. Heterocyclic Chem., 00, 00 (2015).
INTRODUCTION
jusbetonin analogues by introducing sugar derivatives onto
the 7-position and 9-position of the indoquinoline core via
new strategies. Six analogues of jusbetonin were synthe-
sized by amidation of several tetracyclic carboxylic acids
and aminosugar donors.
Jusbetonin, the first natural indolo[3,2-b]quinoline alka-
loid glycoside isolated from the leaf extract of Justicia
betonica, has a unique structure containing β-D-glucose
[1]. Many natural bioactive indolo[3,2-b]quinoline alka-
loids exhibited anti-plasmodial, anti-inflammatory, and es-
pecially antitumor activity [2]. As one member under the
spotlight of indoloquinoline alkaloid family, cryptolepine
was found having potent DNA-interacting activity [3–5],
topoisomerase II [6,7], and telomerase inhibitory activity
[8]. Many analogues of cryptolepine have been synthesized
and evaluated for noticeable biological activity [9–15].
Because of the inspiring biological activity of the indolo
[3,2-b]quinoline alkaloid, we published the total synthesis
of the natural product jusbetonin together with several
analogues. In our previous work on jusbetonin, the key syn-
thetic step was to synthesize 10H-indolo[3,2-b]quinolin-9-
ol at first before introduction of several sugar derivatives
to 9-position of compound a (Fig. 1). Biological assay re-
vealed that all synthesized analogues of jusbetonin had
moderate proliferation inhibitory rate from 21% to 38%
on the human breast cancer cell line (MDA-231) at a
concentration of 1μM [16]. This result attracted us to ex-
ploit an efficient approach to afford a new series of indolo
[3,2-b]quinoline glycosides for further SAR investigation.
Herein, we report a new method to synthesize a series of
RESULTS AND DISCUSSION
The synthetic route of compounds 4, 5, 6, 7, and 8 is
shown in Scheme 1. Acylation of o-aminobenzoic acid
by chloroacetyl chloride gave 2-(2-chloroacetamido)
benzoic acid 1 in 90% yield. Compound 1 reacted with
4-aminobenzoic acid in NaHCO3 (aq.) solution at 80°C
to afford the corresponding compound 2 in 48% yield. Cy-
clization of compound 2 in polyphosphoric acid (PPA) at
130°C for 3 h gave key intermediate 3 in 51% yield. Inter-
mediate 3 reacted with thionyl chloride to form acyl chlo-
ride intermediate, which was used for thebnext step after
removing excess of thionyl chloride [17]. Acyl chloride
intermediates reacted with two different aminosugar
donors 2-amino-1,3,4,6-tetra-O-acetyl-β-D-glucosamine
hydrochloride and 1-amino-2,3,4,6-tetra-O-acetyl-β-D-
glucosamine, respectively, gave compounds 4 and 5 in
moderate yield. Further catalytic hydrodechlorination [18]
of compounds 4 and 5 gave another two jusbetonin ana-
logues 6 and 7. Deacetylation of compound 5 with sodium
© 2015 HeteroCorporation

S. Liu, J. Meng, W. Zhang, S. Wan, and T. Jiang
Vol 000
glucosamine hydrochloride gave jusbetonin analogues 14
and 15, respectively.
The proliferation inhibition activities of these compounds
against the MDA-231 breast cancer cell line at 25, 50, and
100μM were measured using a 3-(4,5-dimethylthioazol-2-
yl)-2,5-diphenyltetrazolium bromide cell viability assay.
The data showed that compound 7 possessed the most potent
proliferation inhibitory activity. The chlorination products 3
and 5 were less active than compound 7 without chlorine in
position 11 of the indoloquinoline ring. Interestingly,
deacetylation of compound 5 to 8 led to loss of activity.
The relative reactivities of compounds 4 and 5 suggested that
C-2 amino substituted glucosamine is more helpful than C-1
amino substituted glucosamine to the antitumor activity of
indoloquinoline carboxylic acid (Table 1).
In conclusion, six novel jusbetonin analogues were syn-
thesized successfully using two different synthetic strate-
gies. Primary investigation on antitumor activity of these
jusbetonin analogues showed that compound 7 possessed
the most potent proliferation inhibitory activity. Besides,
acetylated glucosamine was helpful to increase the antitu-
mor activity via improving liposolubility.
Figure 1. Structures of 11-chloro-10H-indolo[3,2-b]quinolin-9-ol (a) and
jusbetonin.
methoxide in methanol gave sugar derivative 8 in 90%
yield (Scheme 1).
A different strategy was used for the synthesis of com-
pounds 14 and 15 (Scheme 2). We found that if the carbox-
ylic acid of di-ester 10 were not fully protected by methyl
group, the following cyclization in PPA was very compli-
cated. But di-ester 10 could be synthesized in extremely
high yield and then used for cyclization in PPA proceeding
in high yield as well as easier workup. Then, coupling re-
agent system (EDC/HOBt/DMAP) [19] was used for the
amidation. Because of its easier workup, facile amidation,
and high yield for every step, this synthetic strategy had ob-
vious advantage over the former strategy for the synthesis
of jusbetonin analogues 4, 5, 6, 7, and 8 (Scheme 1). Thus,
di-ester 10 was chosen as the substrate of cyclization to fa-
cilitate the tetracyclic system. Acylation of methyl anthrani-
late by bromoacetyl bromide gave intermediate 9 in 91%
yield. Compound 9 reacted with methyl anthranilate in
DMF at 85°C to afford ester 10 in 92% yield. Cyclization
of ester 10 in PPA at 100°C for 3 h gave key immediate
11 in 86% field. Hydrolysis of compound 11 in aqueous po-
tassium hydroxide solution gave carboxylic acid 12. Car-
boxylic acid 12 reacted with phosphorus oxychloride to
afford carboxylic acid 13. Amidation of carboxylic acids
12 and 13 with 2-amino-1,3,4,6-tetra-O-acetyl-β-D-
EXPERIMENTAL
All reactions were monitored by thin-layer chromatography,
on aluminum sheets (silica gel 60-F254, E. Merck). Compounds
were visualized by UV light. NMR spectra were recorded on a
Jeol JNM–ECP spectrometer at 600 MHz for 1H NMR and
151 MHz for 13C NMR with TMS as the internal standard. Chem-
ical shifts are expressed in δ (ppm). Column chromatography was
carried out using silica gel (200–300 mesh). Silica-gel chromatog-
raphy solvents were of analytical grade. Electrospray ionization
mass spectrometry (ES-MS) experiment was carried out in a Q-
TOF UltimaTM Global mass spectrometer (Micromass UK Ltd.,
Scheme 1. Synthetic route of novel jusbetonin analogues 4, 5, 6, 7, and 8.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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Synthesis of Novel Jusbetonin Analogues and Their Cytotoxicity against Tumor Cell
Scheme 2. Synthetic route of novel jusbetonin analogues 14 and 15.
Manchester, UK). All reaction solvents were dried prior to use ac-
cording to standard procedures. All chemicals and reagents were
obtained from Alfa Aesar, Acros or Sinopharm Chemical Reagent
Co, Ltd. (China). The primary screening for proliferation inhibi-
tion activities of compounds was tested in vitro against the human
breast cancer cell line (MDA-231) with standard method of
3-(4,5-dimcthylthioazol-2-yl)-2,5–diphenyl-tetrazolium bromide.
2-(2-Chloroacetamido)benzoic acid (1). To a solution of o-
aminobenzoic acid (16.46 g, 120.00 mmol) in DMF (200 mL) was
added a solution of chloroacetyl chloride (14.91 g, 132.03 mmol)
in THF (50 mL) dropwise below 25°C. This reaction mixture
was stirred at room temperature for 24 h before it was poured
onto 1000 mL of water. The white precipitate was collected by
filtration, dried on vacuum, and purified by column
chromatography (SiO2, eluted with EtOAc/petrol, 1/1) to give a
white solid (23.13 g, 10.83 mmol, 90%). 1H NMR (DMSO-d6,
600 MHz) δ: 13.80 (bs, 1H, COOH), 11.84 (bs, 1H, NH), 8.54
(d, 1H, J = 7.8Hz, Ar–H), 8.03 (dd, 1H, J = 7.8, 1.9 Hz, Ar–H),
7.66–7.63 (m, 1H, Ar–H), 7.24–7.21 (m, 1H, Ar–H), 4.47 (s,
1H, CH2); 13C NMR (DMSO-d6, 151 MHz) δ: 169.9, 165.8,
140.5, 134.8, 131.8, 124.0, 120.4, 117.4, 44.0. TOF MS (ES–):
m/z (relative intensity), 212.0 (100%) [M À H]–; HRMS (ES–):
m/z [M À H]– calcd for C9H7ClNO3:212.0114; found 212.0107.
2-({[(4-Carboxyphenyl)amino]acetyl}amino)benzoic acid
(2). To a solution of NaHCO3 (35.53 g, 417.00 mmol) and
sodium bisulphite (0.50 g, 4.81 mmol) in H2O (400 mL) were
added p-aminobenzoic acid (21.44 g, 156.38 mmol) and 2-(2-
chloroacetamido)benzoic acid (22.27 g, 104.25 mmol) slowly.
After CO2 was released, this reaction mixture was stirred at 80°C
for 25 h. 0.1M aqueous HCl was added to the reaction mixture to
let the pH arrive at 2 after the reaction mixture was cooled down.
Messy white precipitate was formed, filtered and purified by
column chromatography (SiO2, eluted with MeOH/CHCl3, 1/5)
to give a white solid (15.80 g, 50.27 mmol, 48%). 1H NMR
(DMSO-d6, 600 MHz) δ: 13.57 (1H, bs, COOH), 12.17 (bs, 1H,
COOH), 11.91 (bs, 1H, NH), 7.94 (dd, 1H, J = 7.8, 1.9 Hz, Ar–
H), 7.71 (d, 2H, J = 9.2 Hz, Ar–H), 7.62–7.59 (m, 1H, Ar–H),
7.24 (t, 1H, J = 6.0 Hz, CH2NH), 7.16–7.13 (m, 1H, Ar–H), 6.64
(d, 2H, J = 8.7 Hz, Ar–H), 3.96 (s, 1H, CH2NH); 13C NMR
(DMSO-d6, 151 MHz) δ: 169.9, 169.2, 167.4, 151.9, 140.5,
134.2, 131.1, 122.8, 119.4, 118.6, 116.0, 111.5, 48.0; TOF MS
(ES–): m/z (relative intensity), 313.0 (100%) [M À H]–; HRMS
(ES–): m/z [M À H]– calcd for C16H13N2O5: 313.0824; found
313.0834.
10,11-Dihydro-11-oxo-5H-indolo[3,2-b]quinoline-7-carboxylic
acid (3). To a flask charged with mechanical stirrer were added
compound 2 (7.45 g, 23.70 mmol) and PPA (70 g, 207.14 mmol).
This reaction mixture was stirred at 130°C for 3 h and then poured
onto 800 mL of H2O. Dark green precipitate was filtered, washed
with water, dried on high vacuum, and purified by column
chromatography (SiO2, eluted with MeOH/CHCl3, 1/5) to give a
yellow solid (3.38 g, 12.15 mmol, 51%). 1H NMR (DMSO-d6,
600 MHz) δ: 12.74 (bs, 1H), 12.68 (s, 1H, NH), 12.10 (s, 1H, NH),
9.00 (d, 1 H, 1.4 Hz, Ar–H), 8.36 (dd, 1 H, J=8.3, 1.4Hz, Ar–H),
8.04 (dd, 1H, J = 8.7, 1.4 Hz, Ar–H), 7.74 (d, 1H, J = 7.8 Hz,
Table 1
Proliferation inhibition activities of synthesized compounds against
tumor cell line MDA-231.
Inhibitory rate (%)
Compound
25 μM
50 μM
100 μM
3
4
7
5
8
20.85
11.03
26.08
25.52
3.93
32.46
34.20
59.45
34.63
4.57
42.07
50.35
63.49
39.00
7.32
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S. Liu, J. Meng, W. Zhang, S. Wan, and T. Jiang
Vol 000
Ar–H), 7.72–7.69 (m, 1H, Ar–H), 7.57 (d, 1H, J = 8.2 Hz, Ar–H),
7.32 (ddd, 1H, J = 8.3, 7.8, 1.4 Hz, Ar–H); 13C NMR (DMSO-d6,
151 MHz) δ: 168.5, 145.3, 144.2, 143.4, 131.6, 129.4, 129.3,
127.3, 126.7, 125.4, 123.6, 122.4, 122.2, 120.2, 118.6, 116.7.
TOF MS (ES+): m/z (relative intensity), 279.1 (100%) [M+ H]+;
HRMS (ES+): m/z [M + H]+ calcd for C16H11N2O3: 279.0770;
found 279.0761.
(t, J = 9.66 Hz, 1H, H-2′), 4.23–4.19 (m, 2H, H-5′, H-6′-1), 4.05–
4.02 (m, 1H, H-6′-2), 2.03 (s, 3H, CH3CO), 2.02 (s, 3H,
CH3CO), 1.97 (s, 3H, CH3CO), 1.92 (s, 3H, CH3CO); TOF MS
(ES+): m/z (relative intensity), 592.3 (100%) [M + H]+; HRMS:
calcd for C30H30N3O10 [M + H]+ 592.1931, found 592.1951.
7-(1,3,4,6-Tetra-O-acetyl-β-D-glucosamino)-10H-indolo[3,2-b]
quinoline (7). Similar to the procedure described for compound 6,
1
7-(2,3,4,6-Tetra-O-acetyl-β-D-glucosamino)-11-chloro-10H-
indolo[3,2-b]quinoline (4). To a flask were added compound 3
(1.21 g, 4.35 mmol), thionyl chloride (40 mL), and catalytic
amount of DMF. The mixture was refluxed under nitrogen
atmosphere for 14 h. Excess of thionyl chloride was removed
under reduced pressure. DMF (10 mL), DCM (20 mL), DMAP
(1.06 g, 8.68 mmol), and 2,3,4,6-tetra-O-acetyl-β-D-glucosamine
were added to the residue, respectively. The reaction mixture
was stirred at room temperature under nitrogen atmosphere
overnight. After the solvent was removed under reduced
pressure, residue was purified by column chromatography
(SiO2, eluted with EtOAc/petrol, 2/1) to give a yellow solid
(0.65 g, 1.04 mmol, 24%). 1H NMR (DMSO-d6, 600 MHz)
δ: 12.22 (s, 1H, NH), 9.47 (d, J = 9.2 Hz, 1H, NH); 9.03
(s, 1H, Ar–H), 8.30–8.33 (m, 2H, Ar–H), 8.24 (dd,
J = 8.2 Hz, 1.4 Hz, 1H, Ar–H), 7.77–7.83 (m, 2H, Ar–H),
7.69 (d, J = 8.7 Hz, 1H,Ar–H), 5.75 (t, J = 9.2 Hz, 1H, H-1′),
5.46 (t, J = 9.6 Hz, 1H, H-3′), 5.22 (t, J = 9.6 Hz, 1H, H-4′),
4.97 (t, J = 9.6 Hz, 1H, H-2′), 4.19–4.22 (m, 2H, H-5′, H-6′-
1), 4.02–4.05 (m, 1H, H-6′-2), 2.03 (s, 3H, CH3CO), 2.01
(s, 3H, CH3CO), 1.97 (s, 3H, CH3CO), 1.92 (s, 3H,
CH3CO); TOF MS (ES+): m/z (relative intensity), 626.1
(100%) [M + H]+; HRMS (ES+): m/z [M + H]+ calcd for
C30H29ClN3O10 [M + H]+ 626.1541, found 626.1522.
7-(1,3,4,6-Tetra-O-acetyl-β-D-glucosamino)-11-chloro-10H-
indolo[3,2-b]quinoline (5). Prepared by a procedure similar to
that described for compound 4, using 1,3,4,6-tetra-O-acetyl-β-D-
glucosamine as the suger. 1H NMR (DMSO-d6, 600 MHz) δ:
12.17 (s, 1H, NH), 8.86 (s, 1H, Ar–H), 8.81 (d, J = 9.2 Hz, 1H,
NH), 8.32 (dd, J = 7.8, 0.96 Hz, 1H, Ar–H), 8.31 (dd, J = 9.8 Hz,
0.96 Hz, 1H, Ar–H), 8.18 (dd, J = 8.2 Hz, 1.9 Hz, 1H, Ar–H),
7.78–7.82 (m, 2H, Ar–H), 7.69 (d, J = 8.7 Hz, 2H, Ar–H), 5.98
(d, J = 8.7 Hz, 1H, H-1′), 5.43 (t, J = 9.6 Hz, 1H, H-3′), 5.02 (t,
J = 9.6 Hz, 1H, H-4′), 4.38–4.34 (m, 1H, H-2′), 4.27 (dd,
J = 12.4, 4.14 Hz, 1H, H-6′-1), 4.07–4.03 (m, 2H, H-5′, H-6′-2),
2.06 (s, 3H, CH3CO), 2.02 (s, 6H, CH3CO × 2), 1.87 (s, 3H,
CH3CO); TOF MS (ES+): m/z (relative intensity), 626.1 (100%)
[M + H]+; HRMS: calcd for C30H29ClN3O10 [M + H]+ 626.1541,
found 626.1565.
7-(2,3,4,6-Tetra-O-acetyl-β-D-glucosamino)-10H-indolo
[3,2-b]quinoline (6). To a solution of compound 4 (205 mg,
0.32 mmol) in MeOH/THF (30 mL/30 mL) were added
triethylamine (32 mg, 0.32 mmol) and 10% Pd/C (40 mg). This
reaction mixture was stirred under hydrogen atmosphere at room
temperature for 24 h. Catalyst was filtered before the solvent was
removed to give yellow residue, which was purified by column
chromatography (SiO2, eluted with EtOAc/petrol, 2/1) to give a
yellow solid (113 mg, 0.19 mmol, 59%). 1H NMR (DMSO-d6,
600 MHz) δ: 11.80 (s, 1H, NH), 9.43 (d, J = 9.18 Hz, 1H, NH),
9.03 (s, 1H, Ar–H), 8.38 (s, 1H, Ar–H), 8.22 (d, J = 8.7 Hz, 1H,
Ar–H), 8.20 (dd, J = 8.7, 1.8 Hz, 1H, Ar–H), 8.16 (d, J = 8.22 Hz,
1H, Ar–H), 7.69–7.22 (m, 1H, Ar–H), 8.24 (dd, J = 8.24, 1.38 Hz,
1H, Ar–H), 7.72–7.69 (m, 2H, Ar–H), 7.64 (d, J = 8.7 Hz, 1H,
Ar–H), 7.59–7.62 (m, 1H, Ar–H); 5.74 (t, J = 9.18 Hz, 1H, H-1′),
5.45 (t, J = 9.6 Hz, 1H, H-3′), 5.23 (t, J = 9.6 Hz, 1H, H-4′), 4.97
7 was prepared by using compound 5 as the starting material. H
NMR (DMSO-d6, 600 MHz) δ: 11.78 (s, 1H, NH), 8.88 (s, 1H,
Ar–H), 8.79 (d, J = 9.12 Hz, 1H, NH), 8.38 (s, 1H, Ar–H), 8.22
(d, J= 8.7 Hz, 1H, Ar–H), 8.17–8.13 (m, 2H, Ar–H), 7.72–7.70
(m, 1H, Ar–H), 7.66 (d, J = 8.7 Hz, 1H, Ar–H ), 7.62–7.60
(m, 1H, Ar–H), 5.99 (d, J = 8.7 Hz, 1H, H-1′), 5.45 (t,
J = 9.6 Hz, 1H, H-3′), 5.04 (t, J = 9.6 Hz, 1H, H-4′), 4.40–
4.35 (m, 1H, H-2′), 4.30–4.27 (m, 1H, H-6′-1), 4.09–4.04
(m, 2H, H-5′, H-6′-1), 2.06 (s, 3H, CH3CO), 2.03 (s, 3H,
CH3CO), 2.02 (s, 3H, CH3CO), 1.87 (s, 3H, CH3CO); TOF
MS (ES+): m/z (relative intensity), 592.2 (100%) [M + H]+;
HRMS: calcd for C30H30N3O10 [M + H]+ 592.1931, found
592.1957.
7-(D-glucosamino)-11-chloro-10H-indolo[3,2-b]quinoline
(8). To a solution of compound 5 (46 mg, 0.073mmol) in
THF/MeOH (5 mL / 15 mL) was added 27.5% sodium methoxide
solution in THF (1 mL, 6.62 mmol) at 0°C. After stirring at room
temperature for 2 h, the resulting precipitate was collected and
washed with MeOH to obtain compound 8 (30 mg, 0.066 mmol,
90%) as yellow powder. 1H NMR (DMSO-d6, 600 MHz) δ: 12.12
(s, 1H, NH), 9.08 (s, 1H, Ar–H), 8.36 (d, J = 6.4 Hz, 1H, NH),
8.33 (d, J = 7.8 Hz, 1H, Ar–H), 8.30 (d, J= 7.8 Hz, 1H, Ar–H),
8.24 (dd, J= 8.4 Hz, 1.3 Hz, 1H, Ar–H), 7.83–7.77 (m, 2H, Ar–H),
7.66 (d, J= 8.4 Hz, 1H, Ar–H), 5.16 (t, J = 3.2 Hz, 1H, H-1′), 4.99
(s, 2H, OH), 4.76 (s, 1H, OH), 4.48 (s, 1H, OH), 3.88–3.54 (m,
2H, H-3′, H-4′), 3.70–3.67 (m, 2H, H-2′, H-5′), 3.56–3.54 (m, 1H,
H-6′-1), 3.24 (m, 1H, H-6′-1); TOF MS (ES+): m/z (relative
intensity), 458.09 (100%) [M + H]+; HRMS: calcd for
C22H21ClN3O6 [M + H]+ 458.1119, found 458.1118.
Methyl 2-(2-bromoacetamido)benzoate (9). To a solution of
methyl anthranilate (4.97g, 32.90 mmol) in DMF (13 mL) was
added a solution of bromoacetyl bromide (7.34 g, 36.39 mmol) in
1, 4-dioxane (8 mL) dropwise below 5°C. During addition, white
solid was formed. DMF (13 mL) was then added to make the
solid dissolve. This reaction mixture was stirred at room
temperature for 17 h and then poured onto 50mL of H2O. White
precipitate was formed, filtered, and recrystallized in EtOAc/petrol
to give a white solid (8.18 g, 30.06mmol, 91%). 1H NMR
(600 MHz, CDCl3) δ: 11.71 (s, 1H, NH), 8.68 (dd, 1H, J = 8.7,
1.1 Hz, Ar–H), 8.07 (dd, 1H, J = 8.0, 1.6Hz, Ar–H), 7.58 (ddd,
1H, J = 8.7, 7.3, 1.6 Hz, Ar–H), 7.15 (ddd, 1 H, J = 7.8, 7.3,
1.1 Hz, Ar–H), 4.03 (s, 2H, CH2Br), 3.96 (s, 3H, CH3); 13C NMR
(151 MHz, CDCl3): δ (ppm) 168.5, 165.0, 140.7, 134.7, 131.1,
123.5, 120.5, 115.9, 52.6, 29.7; TOF MS (ES+): m/z (relative
intensity), 583.2 [2M + K]+ (100%). HRMS (ES+): m/z [M + H]+
calcd for C10H11BrNO3: 271.9917; found 271.9922.
Dimethyl 2,2′-[(1-oxoethane-1,2-diyl)diimino]dibenzoate
(10). A solution of methyl 2-(2-bromoacetamido)benzoate 9
(4.93 g, 18.12 mmol) and methyl anthranilate (10.88 g,
71.98 mmol) in DMF (18 mL) was stirred at 85°C for 13 h. This
reaction mixture was then poured onto 200 mL of H2O. The
white precipitate was filtered, dried on high vacuum, and
purified by column chromatography (SiO2, eluted with
EtOAc/petrol, 1/1) to give a white solid (5.68 g, 16.59 mmol,
1
92%). H NMR (600 MHz, CDCl3) δ: 11.66 (bs, 1H, NH); 8.75
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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Synthesis of Novel Jusbetonin Analogues and Their Cytotoxicity against Tumor Cell
(dd, 1H, J = 8.3, 1.0 Hz, Ar–H), 8.42 (t, 1H, J = 5.5 Hz, NH), 7.97
(dd, 1H, J = 7.8, 1.9 Hz, Ar–H), 7.94 (dd, 1H, J = 8.2, 1.9 Hz, Ar–
H), 7.54–7.52 (m, 1H, Ar–H), 7.36–7.33 (m, 1H, Ar–H), 7.09–
7.06 (m, 1H, Ar–H), 6.71–6.69 (m, 1H, Ar–H), 6.61 (d, 1H,
J = 8.3 Hz, Ar–H), 4.10 (d, 2H, J = 6.0 Hz, CH2), 3.12 (s, 3H,
OCH3), 3.72 (s, 3H, OCH3) ppm. 13C NMR (151 MHz, CDCl3):
δ 169.8, 167.9, 150.1, 140.5, 134.8, 134.5, 131.7, 130.9, 123.0,
120.6, 116.5, 116.0, 111.9, 111.5, 52.1, 51.8, 48.6; TOF MS
(ES+): m/z (relative intensity), 343.1 (100%) [M + H]+. HRMS
(ES+): m/z [M + H]+ calcd for C18H19N2O5: 343.1294; found
343.1281.
297.0 (100%) [M + H]+; HRMS (ES+): m/z [M + H]+ calcd for
C16H10ClN2O2: 297.0431; found 297.0441.
9-(1,3,4,6-Tetra-O-acetyl-β-D-glucosamino)-10,11-dihydro-
11-oxo-5H-indolo[3,2-b]quinoline (14). To a solution of
compound 12 in DMSO/DCM (20 mL/20 mL) were added HOBt
(0.54 g, 4.00 mmol), DMAP (0.31 g, 2.54 mmol), and EDC
(0.42 g, 2.71 mmol), respectively, over ice bath. This reaction
mixture was stirred at room temperature 15 h. Removal of the
solvent gave yellow residue, which was purified by column
chromatography (SiO2, eluted with EtOAc/petrol, 2/1) to give a
yellow solid (0.93 g, 3.18 mmol, 86%). 1H NMR (DMSO-d6,
600 MHz) δ: 12.63 (s, 1H, NH), 10.41 (s, 1H, NH), 8.94 (d,
J = 8.7 Hz, 1H, NH), 8.44 (d, 1H, J = 8.3 Hz, Ar–H), 8.36 (d,
J = 7.8 Hz, 1H, Ar–H), 7.94 (d, J = 7.3 Hz, 1H, Ar–H), 7.71–7.75
(m, 2H, Ar–H), 7.40 (t, J = 7.8 Hz, 1H, Ar–H), 7.33 (td, J = 7.8,
1.4 Hz, 1H, Ar–H), 6.00 (d, J = 8.7 Hz, 1H, H-1′), 5.47 (t,
J = 10.1 Hz, 1H, H-3′), 5.06 (t, J = 10.1 Hz, 1H, H-4′), 4.37–4.33
(m, J = 8.7 Hz, 1H, H-2′), 4.27 (dd, J = 12.8 Hz, 4.6 Hz, 1H, H-
6′-1), 4.04–4.07 (m, 2H, H-5′, H-6′-2), 2.05 (s, 3H, CH3CO),
2.02 (s, 3H, CH3CO), 2.01 (s, 3H, CH3CO), 1.86 (s, 3H,
CH3CO); TOF MS (ES+): m/z (relative intensity), 608.1 (100%)
[M + H]+; HRMS (ES+): m/z [M + H]+ calcd for C16H10N2O2:
608.1880; found 608.1905.
9-(1,3,4,6-Tetra-O-acetyl-β-D-glucosamino)-11-chloro-10H-
indolo[3,2-b]quinoline (15). Similar to the procedure described
for compound 14, 15 was prepared using compound 13
as the starting material. 1H NMR (DMSO-d6, 600 MHz) δ: 10.72
(s, 1H, NH), 9.05 (d, J = 9.2 Hz, 1H,NH), 8.55 (d, J = 7.3 Hz, 1H,
Ar–H), 8.28 (td, J = 7.8, 1.0 Hz, 2H, Ar–H), 8.08 (dd, J = 7.8,
0.9 Hz, 1H, Ar–H), 7.75–7.82 (m, 2H, Ar–H), 7.49 (t, J = 7.8 Hz,
H, Ar–H), 6.03 ( d, J = 7.8 Hz, 1H,H-1′), 5.50 (t, J = 9.6 Hz, 1H,
H-3′), 5.07 (d, J = 9.6 Hz, 1H, H-4′), 4.39–4.32 (m, 1H, H-2′),
4.30 (dd, J = 11.9 Hz, 4.1 Hz, 1H, H-6′-1), 4.07–4.10 (m, 2H, H-
5′, H-6′-1), 2.07 (s, 3H, CH3CO), 2.06 (s, 3H, CH3CO), 2.04 (s,
3H, CH3CO), 1.91 (s, 3H, CH3CO); 13C NMR (DMSO-d6,
151 MHz) δ: 170.1, 169.8, 169.3, 167.0, 166.6, 145.0, 144.3,
142.6, 129.5, 129.4, 128.2, 127.5, 126.9, 125.5, 123.8, 123.0,
122.3, 120.2, 118.9, 116.0, 91.8, 72.3, 71.5, 68.1, 61.5, 52.5,
20.6, 20.5, 20.3; TOF MS (ES+): m/z (relative intensity), 626.1
(100%) [M + H]+; HRMS (ES+): m/z [M + H]+ calcd for
C30H29ClN3O10: 626.1541; found 626.1551.
Methyl 10,11-dihydro-11-oxo-5H-indolo[3,2-b]quinoline-9-
carboxylate (11). To a flask equipped with a stirrer were
added compound 10 (1.27 g, 3.71 mmol) and PPA (25 g,
73.98 mmol). This reaction mixture was stirred at 100°C for 3 h
and then poured onto 600 mL of ice-H2O. Yellow precipitate
was collected by filtration, washed with water, dried on high
vacuum, and purified by column chromatography (SiO2, eluted
with MeOH/CHCl3, 1/20) to give a yellow solid (0.93 g,
1
3.18 mmol, 86%). H NMR (600 MHz, CDCl3) δ: 12.65 (s, 1H,
NH), 10.57 (s, 1H, CONH ), 8.53 (d, 1 H, J = 7.8 Hz, Ar–H),
8.37 (d, 1H, J = 7.8 Hz, Ar–H), 8.15 (d, 1H, J = 7.8, 0.9 Hz, Ar–
H), 7.75–7.71 (m, 2H, Ar–H), 7.40 (t, 1H, J = 7.8 Hz, Ar–H),
7.34–7.32 (m, 1H, Ar–H); 13C NMR (DMSO-d6, 151 MHz) δ:
167.2, 166.3, 139.2, 136.5, 131.2, 129.9, 129.0, 127.3, 126.8,
125.2, 123.2, 122.4, 122.9, 119.0, 118.2, 117.9; TOF MS
(ES+): m/z (relative intensity), 293.1 (100%) [M + H]+; HRMS
(ES+): m/z [M + H]+ calcd for C17H13N2O3: 293.0926; found
293.0928.
10,11-Dihydro-11-oxo-5H-indolo[3,2-b]quinoline-9-carboxylic
acid (12). To a solution of KOH (3.71 g, 6.61 mmol) in H2O
(10 mL) was added compound 11 (1.76 g, 6.02mmol). The
resulting suspension was stirred for 8 h, and the mixture turned
clear. After the reaction was complete, the solution was
neutralized with concentrated HCl slowly over ice bath. The
product appeared as yellow precipitate, which was collected by
filtration and dried over high vacuum to give a yellow solid
(1.24 g, 4.46mmol, 67%). 1H NMR (DMSO-d6, 600 MHz) δ:
13.64 (bs, 1H, COOH), 12.68 (s, 1H, NH), 10.22 (s, 1H,
CONH), 8.51 (d, 1H, J = 7.8 Hz, Ar–H), 8.37 (d, 1H, J = 7.8 Hz,
Ar–H), 8.13 (dd, 1H, J = 7.3, 1.0 Hz, Ar–H), 7.71–7.76 (m, 2H,
Ar–H), 7.38 (t, 1H, J = 7.8 Hz, Ar–H), 7.35–7.33 (m, 1H, Ar–H);
13C NMR (DMSO-d6, 151 MHz) δ: 168.9, 139.4, 138.9, 132.6,
132.1, 132.0, 128.5, 124.8, 123.3, 121.8, 121.2, 120.1, 119.0,
117.7, 114.9; TOF MS (ES+): m/z (relative intensity), 279.1
(100%) [M+ H]+; HRMS (ES+): m/z [M + H]+ calcd for
C16H11N2O3: 279.0770; found 279.0772.
Acknowledgments. This work was financially supported by the
Natural Science Foundation of China (Grant No. 21171154) and
the Key International Cooperation Project of CMST (Grant No.
2013 DFG32160).
11-Chloro-10H-indolo[3,2-b]quinoline-9-carboxylic
acid
(13). To a flask charged with phosphoryl chloride (60 mL) was
added compound 12 (1.10 g, 3.95 mmol). This mixture was
refluxed for 6 h. The mixture was allowed to cool to room
temperature and then poured onto 500 mL of ice-water. The
resulting precipitate was collected by filtration and dried under
vacuum. The resulting solid was dissolved in MeOH/CHCl3.
Evaporation of the solvent slowly gave a yellow solid (1.08 g,
REFERENCES AND NOTES
[1] Subbaraju, G. V.; Kavitha, J.; Rajasekhar, D.; Jimenez, J. I.
J Nat Prod 2004, 67, 461.
[2] Juliani, H. R.; Simon, J. E.; Ho, C. T. African Natural
Plant Products: New Discoveries and Challenges in Chemistry and
Quality. Appiah, A. A. ACS Symposium Series, Chapter 13, Vol. 1021,
pp 231-239.
[3] Bonjean, K.; De Pauw-Gillet, M. C.; Defresne, M. P.; Colson, P.;
Houssier, C.; Dassonneville, L.; Bailly, C.; Wright, C.; Quetin-Leclercq, J.;
Angenot, L. Anticancer Res 1997, 17, 4068.
[4] Lisgarten, J. N.; Coll M.; Portugal, J.; Wright, C. W.; Aymami, J.
Nat Struct Biol 2002, 9, 57.
1
3.64 mmol, 92%). H NMR (DMSO-d6, 600 MHz) δ: 10.43 (s,
1H, NH), 8.59 (d, 1H, J = 7.3, 1.4 Hz, Ar–H), 8.30–8.27 (m,
2H, Ar–H), 8.22 (d, 1H, J = 1.3 Hz, Ar–H), 7.82–7.79 (m, 1H,
Ar–H), 7.78–7.75 (m, 1H, Ar–H), 7.46 (t, 1H, J = 7.3 Hz, Ar–
H); 13C NMR (DMSO-d6, 151 MHz) δ: 167.7, 145.1, 144.4,
143.2, 131.7, 129.6, 129.4, 127.5, 126.9, 126.4, 123.8, 122.9,
122.4, 120.4, 119.1; TOF MS (ES+): m/z (relative intensity),
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

S. Liu, J. Meng, W. Zhang, S. Wan, and T. Jiang
Vol 000
[5] Guittat, L.; Alberti, P.; Rosu, F.; Van Miert, S.; Thetiot, E.
Biochimie 2003, 85, 535.
[12] Seville, S.; Phillips, R. M.; Shnyder, S. D.; Wright, C. W.
Bioorg Med Chem 2007, 15, 6353.
[6] Bonjean, K.; De Pauw-Gillet, M. C.; Defresne, M. P.;
Colson, P.; Houssier, C.; Dassonneville, L.; Bailly, C.; Greimers, R.;
Wright, C.; Quetin-Leclercq, J.; Tits, M.; Angenot, L. Biochemistry
1998, 37, 5136.
[7] Bailly, C.; Laine, W.; Baldeyrou, B.; De, P. G.; Colson, P.;
Houssier, C.; Cimanga, K.; Van Miert, S.; Vlietinck, A. J.; Pieters, L. An-
ticancer Drug Des 2000, 10, 191.
[8] Guyen, B.; Schultes, C. M.; Hazel, P.; Mann, J.; Neidle, S. Org
Biomol Chem 2004, 2, 981.
[9] Yamato, M.; Takeuchi, Y.; Chang, M. R.; Hashigaki, K.;
Tsuruo, T.; Tashiro, T.; Tsukagoshi, S. Chem Pharm Bull 1990, 38,
3048.
[13] Woo, P. C.; Lau, S. K.; Wong, B. H.; Chan, K. H.; Hui, W. T.;
Kwan, G. S.; Peiris, J. S.; Couch, R. B.; Yuen, K. Y. Bioorg Med Chem
Lett 2010, 20, 7042.
[14] Boddupally, P. V. L.; Hahn, S.; Beman, C.; De, B.; Brooks, T. A.;
Gokhale, V.; Hurley, L. H. J Med Chem 2012, 55, 6076.
[15] Lavrado, J.; Borralho, P. M.; Ohnmacht, S. A.; Castro, R. E.;
Rodrigues, C. M. P.; Moreira, R.; Santos, D. J. V. A.; Neidle, S.; Paulo, A.
ChemMedChem 2013, 8, 1648.
[16] Zhang, Z. W.; Wang, S. X.; Wan, S. B.; Ren, S. M.; Li, W.;
Jiang, T. Carbohydr Res 2009, 344, 291.
[17] Lewis, A.; Ryan, M. D.; Gani, D. J Chem Soc Perkin Trans I
1998, 143, 3767.
[10] Takeuchi, Y.; Chang, M. R.; Hashigaki, K.; Yamato, M. Chem
Pharm Bull 1991, 39, 1629.
[18] Xia, C. H.; Xu, J.; Wu, W. Z.; Luo, Q.; Chen, J. P.; Zhang, Q.;
Liang, X. M. Appl Catal Environ 2003, 45, 281.
[11] Onyeibor, O.; Croft, S. L.; Dodson, H. I.; Feiz-Haddad, M.;
Kendrick, H.; Millington, N. J.; Parapini, S.; Phillips, R. M.; Seville, S.;
Shnyder, S. D.; Taramelli, D.; Wright, C. W. J Med Chem 2005, 48, 2701.
[19] Ormerod, D.; Willemsens, B.; Mermans, R.; Langens, J.;
Winderickx, G.; Kalindjian, S. B.; Buck, I. M.; Mcdonald, I. M. Org Pro-
cess Res Dev 2005, 9, 499.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet