Synthesis, saccharide-binding and anti-cancer cell proliferation properties of arylboronic acid derivatives of indoquinolines

Article abstract of DOI:10.1111/j.1747-0285.2011.01196.x

A facile synthesis of a series of saccharide-binding arylboronic acid derivatives of indoloquinoline was described. The key synthetic steps were polyphosphoric acid-mediated cyclization, chlorinative aromatization, and amidation. Mass spectrometry experim

Full text of DOI:10.1111/j.1747-0285.2011.01196.x

ª 2011 John Wiley & Sons A/S
doi: 10.1111/j.1747-0285.2011.01196.x
Chem Biol Drug Des 2011; 78: 816–825
Research Article
Synthesis, Saccharide-Binding and Anti-cancer
Cell Proliferation Properties of Arylboronic Acid
Derivatives of Indoquinolines
in solution (5,6). Based on this, many boronic acids have been used
as saccharide sensors (7–13), transmembrane transporters (14–16),
and phenylboronic acid-based insulin release controller (16).
Junxiu Meng, Shaoqing Yu, Shengbiao
Wan, Sumei Ren, Tao Jiang*
Key Laboratory of Marine Drugs, Ministry of Education of China,
School of Pharmacy, Ocean University of China, Qingdao 266003,
China
Most recently, one of the benzylic amine-derived diboronic acid
compounds was established as potential sensors for sLex that has
been associated with liver and colon cancers (17,18). This diboronic
acid compound could stain sLex-expressing HEPG2 cells at 5 lM,
but could not stain either non-sLex-expressing COS7 cells or Ley-
expressing HEP3B cells. This represents the first example in which
a boronic acid derivative showed highly specific binding to sLex-
expressing cancer cell surfaces. Further investigation showed that
both sialic acid and fucose were necessary saccharides of sLex for
the high-specific binding. These studies implicated that boronic acid
derivatives can bind to specific carbohydrate sequences on cancer
cell surfaces. These studies inspire us to design novel boronic acid
derivatives that not only bind to specific carbohydrate sequences on
cancer cell surfaces but also inhibit cancer cell proliferations.
*Corresponding author: Tao Jiang, jiangtao@ouc.edu.cn
A facile synthesis of a series of saccharide-binding
arylboronic acid derivatives of indoloquinoline
was described. The key synthetic steps were po-
lyphosphoric acid-mediated cyclization, chlorin-
ative
aromatization,
and
amidation.
Mass
spectrometry experiments revealed these syn-
thetic arylboronic acid derivatives of indoquino-
lines could bind to biologically important
carbohydrates (sialic acid, fucose, glucose, and
galactose) by forming boronate di-esters in alka-
line aqueous solution. Most of the arylboronic acid
derivatives of indoquinolines inhibited human
breast cancer cell (MDA–231) proliferation at a
concentration of 5 lM, whereas the compound 17
exhibited highest percentages (76.74%) of the can-
cer cell proliferation inhibition.
We chose indoquinoline alkaloid family as lead compounds to make
boronic acid derivatives. As members of indoquinoline alkaloid fam-
ily, cryptolepine and quindoline (19) (Figure 1) were found in the
roots of the African plant Cryptolepis sanguinolenta which is a kind
of shrub used for treatment of malaria and other diseases in central
and west Africa (20). Modern biological experiment study revealed
cryptolepine possessed anti-plasmodial (21), anti-inflammatory (22–
24), and especially antitumor activity. Cell growth inhibition assay
showed that cryptolepine displayed potent cytotoxic activities
against P388 murine leukemia cells (IC50 = 0.94 lM) and HL-60
human leukemia cells (IC50 = 3.20 lM) (25). Further mechanistic
investigation at the molecular level demonstrated that crytolepine
had DNA-interacting activity (26–28), topoisomerase II (29,30) and
telomerase inhibitory activity (28,31). Most recently, many quindo-
line analogs were synthesized and found having potent telomerase
inhibitory activity (32,33).
Key words: anti-cancer cell proliferation, indoloquinoline, boronic
acid, saccharide
Received 4 May 2010, revised 13 July 2011 and accepted for publica-
tion 16 July 2011
As a common chemical moiety, cis-1, 2- and cis-1, 3-diols could be
found in saccharide which existing on the surfaces of cells. These
cis-1, 2- and cis-1, 3-diol moieties also show the potential to carry
necessary information for cell–cell recognition and communications.
More importantly, certain carbohydrates of cell surface are associated
with the development and progression of many types of cancers (1).
For instance, surface and serum of cancer cells have a higher concen-
tration of sialic acid (N-acetyl-neuraminic-acid) (2). Fucose is
over-expressed in many human malignancies, especially on specific
glycoproteins, glycolipids, certain mucins, and putative cell adhesion
ligands found on cancer cell surfaces. In normal cells, these func-
tional saccharides are expressed at a relatively low level (3). Boronic
acids are known to covalently react with cis-1, 2- or cis-1, 3-diols by
forming five- or six-membered cyclic esters (4). As both a biological
molecule and an important diol (1, 2 or 1, 3)-containing compound,
saccharides show similar binding property with various boronic acids
Owing to the properties of boronic acids and indoquinolines above
mentioned, we anticipated that introducing arylboronic acid to indo-
quinoline may improve its cancer-targeted selectivity and anti-
cancer cell proliferation activity via its reversible covalently binding
with over-expressed saccharide on cancer cell surfaces. Herein, we
synthesized and tested a series of arylboronic acid-derived indoquin-
oline analogs of quindoline for their anti-cancer cell proliferation
properties. Covalent binding between boronic acid and biologically
important saccharides and saccharide derivative (sialic acid, fucose,
816

Bioactivity of Arylboronic Acid Derivatives of Indoquinolines
acid (22.27 g, 104.25 mmol) slowly. After CO2 was released, this
reaction mixture was stirred at 80 ꢁC for 25 h. Aqueous HCl
(0.1 M) was added to the reaction mixture to let the pH arrives at
2 after the reaction mixture was cooled down. Messy white precipi-
tate was formed, filtered, and purified by column chromatography
H
N
N
N
N
CH3
Quindoline
Cryptolepine
(SiO2, eluted with MeOH ⁄ CHCl3, 1 ⁄ 5) to give white solid (15.80 g,
1
Figure 1: Structures of natural products crytolepine and quindo-
line.
50.27 mmol, 48%). H NMR (DMSO-d6, 600 MHz) d: 13.57 (1H, bs,
COOH), 12.17 (1H, bs, COOH), 11.91(1H, bs, NH), 7.94 (1H, dd,
J = 7.8, 1.9 Hz, ArH), 7.71 (2H, d, J = 9.2Hz, ArH), 7.62–7.59 (1H,
m, ArH), 7.24 (1H, t, J = 6.0 Hz, CH2NH), 7.16–7.13 (1H, m, ArH),
6.64 (2H, d, J = 8.7 Hz, ArH), 3.96 (1H, s, CH2NH). 13C NMR
(DMSO-d6, 151 MHz) d: 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)H]). HRMS (ES)): m ⁄ z [M)H])
calculated exact mass for C16H13N2O5: 313.0824; found 313.0834.
glucose, and galactose) in aqueous solution was also studied by
mass spectrometry technique.
Experimental Section
Reagents and instruments
All reactions were monitored by thin-layer chromatography, on alumi-
num sheets (silica gel 60–F254, E. Merck). Compounds were visual-
ized by UV light. NMR spectra were recorded on a Jeol JNM–ECP
10,11-Dihydro-11-oxo-5H-indolo[3,2-b]quinoline-
7-carboxylic acid (3)
1
spectrometer at 600 MHz for H NMR and 151 MHz for 13C NMR
To a flask charged with mechanical stirrer were added compound 2
(7.45 g, 23.70 mmol) and polyphosphoric acid (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 yellow solid (3.38 g, 12.15 mmol, 51%). 1H NMR (DMSO-d6,
600 MHz) d: 12.74 (1H, bs), 12.68 (1H, s, NH), 12.10 (1H, s, NH),
9.00 (1 H, d, 1.4 Hz, ArH), 8.36 (1 H, dd, J = 8.3, 1.4 Hz, ArH), 8.04
(1H, dd, J = 8.7, 1.4 Hz, ArH), 7.74 (1H, d, J = 7.8 Hz, ArH), 7.72–
7.69 (1H, m, ArH), 7.57 (1H, d, J = 8.2 Hz, ArH), 7.32 (1H, ddd,
J = 8.3, 7.8, 1.4 Hz, ArH). 13C NMR (DMSO-d6, 151 MHz) d: 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 inten-
sity), 279.1 (100%) [M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated
exact mass for C16H11N2O3: 279.0770; found 279.0761.
with TMS as the internal standard. Chemical shifts are expressed in
d (ppm). Column chromatography was carried out using silica gel
(200–300 mesh). Silica gel chromatography solvents were of analyti-
cal grade. Electrospray ionization mass spectrometry (ESI–MS) experi-
ment was carried out in a Q–TOF Ultimaꢀ Global mass spectrometer
(Micromass UK Ltd., Manchester, UK). All reaction solvents were
dried prior to use according to standard procedures. All chemicals
and reagents were obtained from Alfa Aesar (Ward Hill, MA, USA),
Acros (New Jersey, USA) or Sinopharm Chemical Reagent Co, Ltd.
(Shanghai, China). The tumor inhibiting effect of compounds was
tested in vitro by using the human breast cancer cell line (MDA–231)
with standard method of MTT.
Synthesis
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 filtered,
dried on vacuum, and purified by column chromatography (SiO2, eluted
with EtOAc ⁄ petrol, 1 ⁄ 1) to give white solid (23.13 g, 10.83 mmol,
11-Chloro-10H-indolo[3,2-b]quinoline-7-
carboxylic acid (4)
To a flask charged with phosphoryl chloride (80 mL) was added com-
pound 3 (2.47 g, 8.88 mmol). This mixture was refluxed for 28 h, and
then poured onto 500 mL of water. Dark green precipitate was fil-
tered, dried on vacuum, and purified by column chromatography (SiO2,
eluted with MeOH ⁄ CHCl3, 1 ⁄ 10) to give yellow solid (0.90 g,
1
1
90%). H NMR (DMSO-d6, 600 MHz) d: 13.80 (1H, bs, COOH), 11.84
3.03 mmol, 34%). HNMR (DMSO-d6, 600 MHz) d: 12.21 (1H, s, NH),
(1H, bs, NH), 8.54 (1H, d, J = 7.8Hz, ArH), 8.03 (1H, dd, J = 7.8 Hz,
J = 1.9 Hz, ArH), 7.66–7.63 (1H, m, ArH), 7.24–7.21 (1H, m, ArH),
4.47 (1H, s, CH2). 13C NMR (DMSO-d6, 151 MHz) d: 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)H]). HRMS (ES)): m ⁄ z [M)H])
calculated exact mass for C9H7ClNO3:212.0114; found 212.0107.
8.93 (1H, s, ArH), 8.31 (2H, t, J = 8.7 Hz, ArH), 8.27 (1H, d,
J = 8.7 Hz, ArH), 7.81 (1H, t, J = 7.0 Hz, ArH), 7.77 (1H, t, J = 7.0 Hz,
ArH), 7.67 (1H, d, J = 8.7 Hz, ArH). 13C NMR (DMSO-d6, 151 MHz) d:
164.9, 146.5, 146.4, 144.6, 130.2, 129.9, 127.9, 127.7, 127.2, 124.3,
122.8, 122.1, 121.7, 121.6, 119.2, 112.6. TOF MS (ES+): m ⁄ z (relative
intensity), 297.1 (100%) [M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calcu-
lated exact mass for C16H10N2O3: 297.0431; found 297.0431.
2-({[(4-Carboxyphenyl)amino]acetyl}amino)
benzoic acid (2)
10H-indolo[3,2-b]quinoline-7-carboxylic acid (5)
To a solution of NaHCO3 (35.53 g, 417.00 mmol) and sodium bisul-
fite (0.50 g, 4.81 mmol) in H2O (400 mL) were added p-aminobenzo-
ic acid (21.44 g, 156.38 mmol) and 2-(2-chloroacetamido)benzoic
Ten percentage of Pd ⁄ C (0.84 g) was added to a solution of
compound
4 (0.73 g, 2.46 mmol) and triethylamine (2.50 mL,
18.01 mmol) in MeOH ⁄ THF (1:1, 180 mL). The mixture was reacted
Chem Biol Drug Des 2011; 78: 816–825
817

Meng et al.
under hydrogen atmosphere at room temperature for 24 h. Pd ⁄ C
catalyst was filtered. Solvent was removed under reduced pressure.
Purification of the residue by flash column chromatography (SiO2,
eluted with MeOH ⁄ CHCl3, 1 ⁄ 7) to give yellow solid (0.50 g,
1.91 mmol, 78%). 1H NMR (DMSO-d6)d: 12.43 (1H, s, NH), 9.18
(1H, s, ArH), 8.80(1H, s, ArH), 8.37 (1H, d, J = 8.2 Hz, ArH), 8.31
(1H, t, J = 7.8 Hz, ArH), 8.29 (1H, dd, J = 8.7 Hz, 1.4 Hz, ArH),
7.88 (1H, t, J = 7.8 Hz, ArH), 7.74 (2H, d, J = 7.8 Hz, ArH). TOF
MS (ES+): m ⁄ z (relative intensity), 263.1 (100%) [M + H]+. HRMS
(ES+): m ⁄ z [M + H]+ calculated exact mass for C16H11N2O2:
263.0821; found 263.0810.
cipitate was filtered, washed with water, dried on high vacuum, and
purified by column chromatography (SiO2, eluted with MeOH ⁄ CHCl3,
1 ⁄ 20) to give yellow solid (0.93 g, 3.18 mmol, 86%). 1H NMR (DMSO-
d6, 600 MHz) d: 12.65 (1H, s, NH), 10.57 (1H, s, CONH), 8.53 (1 H, d,
J = 7.8 Hz, ArH), 8.37 (1H, d, J = 7.8 Hz, ArH), 8.15 (1H, d, J = 7.8,
0.9 Hz, ArH), 7.75–7.71 (2H, m, ArH), 7.40 (1H, t, J = 7.8 Hz, ArH),
7.34–7.32 (1H, m, ArH). 13C NMR (DMSO-d6, 151 MHz) d: 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 inten-
sity), 293.1 (100%) [M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated
exact mass for C17H13N2O3: 293.0926; found 293.0928.
Methyl 2-(2-bromoacetamido)benzoate (6)
Methyl 11-chloro-10H-indolo[3,2-b]quinoline-9-
carboxylate (9)
To a solution of methyl anthranilate (4.97 g, 32.90 mmol) in a 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. Thirteen milliliters of DMF was
then added to make the solid dissolved. This reaction mixture was
stirred at room temperature for 17 h, and then poured onto 50 mL
of H2O. White precipitate was formed, filtered, and recrystallized in
EtOAc ⁄ petrol to give white solid (8.18 g, 30.06 mmol, 91%). 1H
NMR (600 MHz, CDCl3) d: 11.71 (1H, s, NH), 8.68 (1H, dd,
J = 8.7 Hz, 1.1 Hz, ArH), 8.07 (1H, dd, J = 8.0 Hz, 1.6 Hz, ArH),
7.58 (1H, ddd, J = 8.7 Hz, 7.3 Hz, 1.6 Hz, ArH), 7.15 (1 H, ddd,
J = 7.8 Hz, 7.3 Hz, 1.1 Hz, ArH), 4.03 (2H, s, CH2Br), 3.96 (3H, s,
CH3).13C NMR (151 MHz, CDCl3) d:168.5, 165.0, 140.7, 134.7,
131.1, 123.5, 120.5, 115.9, 52.6, 29.7 ppm. TOF MS (ES+): m ⁄ z (rela-
tive intensity), 583.2 [2M + K]+ (100%). HRMS (ES+): m ⁄ z [M + H]+
calculated exact mass for C10H11BrNO3: 271.9917; found 271.9922.
To a flask charged with phosphoryl chloride (100 mL) was added
compound 8 (1.02 g, 3.49 mmol). This mixture was refluxed for
18 h, and then poured onto 500 mL of water after most of phos-
phoryl chloride was removed under reduced pressure. Yellow precip-
itate was filtered, dried on vacuum, and Recrystallization
1
(MeOH ⁄ CHCl3) gave yellow solid (0.97 g, 3.12 mmol, 89%). H NMR
(DMSO-d6, 600 MHz) d: 11.65 (s, 1H, NH); 8.66 (1H, d, J = 7.8 Hz,
ArH); 8.35 (1H, dd, J = 8.2, 0.9 Hz, ArH); 8.31 (1H, dd, J = 7.8 Hz,
0.90 Hz, ArH); 8.25 (1H, dd, J = 7.8, 0.9 Hz, ArH); 7.83 (1H, m,
ArH); 7.80 (1H, m, ArH); 7.50 (1H, t, J = 7.3 Hz, ArH); 4.04 (3H, s,
OCH3). 13C NMR (DMSO-d6, 151 MHz) d: 166.1, 145.1, 144.5,
142.7, 131.6, 129.9, 129.4, 127.7, 127.0, 123.9, 123.3, 122.5, 120.5,
119.4, 113.2, 52.42. TOF MS (ES+): m ⁄ z (relative intensity), 311.1
(100%) [M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated exact mass
for C17H13ClN2O2: 311.0587; found 311.0575.
Dimethyl 2,2¢-[(1-oxoethane-1,2-
diyl)diimino]dibenzoate (7)
Methyl 10H-indolo[3,2-b]quinoline-9-carboxylate
(10)
The solution of methyl 2-(2-bromoacetamido)benzoate (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 fil-
tered, dried on high vacuum, and purified by column chromatogra-
phy (SiO2, eluted with EtOAc ⁄ petrol, 1 ⁄ 1) to give white solid
Ten percentage of Pd ⁄ C (0.40 g) was added to a solution of com-
pound 9 (0.85 g, 2.74 mmol) and triethylamine (2.0 mL, 14.41 mmol)
in MeOH ⁄ THF (1:1, 100 mL). The mixture was reacted under hydro-
gen atmosphere at room temperature for 24 h. Pd ⁄ C catalyst was
filtered. Solvent was removed under reduced pressure. Recrystalliza-
tion of the residue (MeOH ⁄ THF) to give yellow solid (0.70 g,
2.53 mmol, 92%). 1H NMR (DMSO-d6, 600 MHz) d: 11.98 (1H, s,
NH); 8.91–8.77 (2H, m, ArH); 8.38–8.31 (3H, m, ArH); 7.87 (1H, d,
J = 5.94 Hz, ArH); 7.73 (t, J = 5.94 Hz, 1H, ArH); 7.49 (1H, t,
J = 7.3 Hz, ArH); 4.04 (3H, s, OCH3). 13C NMR (DMSO-d6,
151 MHz) d: 165.8, 142.9, 133.17, 132.4, 128.3, 127.9, 126.6, 126.0,
119.6, 112.7, 52.3. TOF MS (ES+): m ⁄ z (relative intensity), 277.1
(100%) [M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated exact mass
for C17H13N2O2: 277.0977; found 277.0970.
1
(5.68 g, 16.59 mmol, 92%). H NMR (600 MHz, CDCl3) d: 11.66 (1H,
bs, NH); 8.75 (1H, dd, J = 8.3, 1.0 Hz, ArH), 8.42 (1H, t, J = 5.5 Hz,
NH), 7.97 (1H, dd, J = 7.8, 1.9 Hz, ArH), 7.94 (1H, dd, J = 8.2,
1.9 Hz, ArH), 7.54–7.52 (1H, m, ArH), 7.36–7.33 (1H, m, ArH),
7.09–7.06 (1H, m, ArH), 6.71–6.69 (1H, m, ArH), 6.61 (1H, d,
J = 8.3 Hz, ArH), 4.10 (2H, d, J = 6.0 Hz, CH2), 3.12 (3H, s, CH3),
3.72 (3H, s, CH3). 13C NMR (151 MHz, CDCl3) d: 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]+ calculated exact
mass for C18H19N2O5: 343.1294; found 343.1281.
10H-indolo[3,2-b]quinoline-9-carboxylic acid (11)
To a solution of KOH (3.30 g, 58.81 mmol) in H2O (50 mL) was
added compound 10 (0.70 g, 2.53 mmol). This suspension was stir-
red for 8 h at 40 ꢁC and then yellow solution was formed. After
the reaction was complete, the solution was neutralized with con-
centrated HCl slowly over ice bath. The product appeared as yellow
precipitate which was filtered, dried over high vacuum to give solid
(0.55 g, 2.10 mmol, 83%).
Methyl 10,11-dihydro-11-oxo-5H-indolo[3,2-b]
quinoline-9-carboxylate (8)
To a flask equipped with stirrer were added compound 7 (1.27 g,
3.71 mmol) and PPA (25 g, 73.98 mmol). This reaction mixture was stir-
red at 100 ꢁC for 3 h and then poured onto 600 mL of H2O. Yellow pre-
818
Chem Biol Drug Des 2011; 78: 816–825

Bioactivity of Arylboronic Acid Derivatives of Indoquinolines
1H NMR (DMSO-d6, 600 MHz) d: 11.72 (1H, s, NH), 8.75 (1H, d,
chromatography (SiO2, eluted with MeOH ⁄ CHCl3, 1 ⁄ 10) to give
yellow solid (0.64 g, 1.61 mmol, 79%). 1H NMR (DMSO-d6,
600 MHz) d: 12.62 (1H, s, NH), 10.73 (1H, bs, NH), 10.46 (1H, s,
CONH), 8.46 (1H, dd, J = 7.8, 0.9 Hz, ArH), 8.36 (1H, dd,
J = 7.8 Hz, 0.9 Hz, ArH), 8.31 (1H, dd, J = 7.8, 0.9 Hz, ArH); 8.14
(1H, d, J = 0.9 Hz, ArH), 8.05 (bs, 2H, BOH), 7.94–7.92 (1H, m,
ArH), 7.76 (1H, d, J = 7.8 Hz, ArH), 7.74–7.71 (1H, m, ArH), 7.61–
7.59 (1H, m, ArH), 7.41 (1H, t, J = 7.8 Hz, ArH); 7.38 (1H, t,
J = 8.7 Hz, ArH), 7.35–7.32 (1H, m, ArH). 13C NMR (DMSO-d6)d:
167.2, 165.4, 139.3, 137.9, 136.8, 131.1, 129.8, 128.8, 127.6, 127.1,
126.8, 125.2, 125.0, 123.1, 123.0, 122.8, 120.9, 118.8, 118.0 117.9,
117.8. TOF MS (ES+): m ⁄ z (relative intensity), 398.1 (100%)
[M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated exact mass for
C16H10N2O2: 398.1312; found 398.1319.
J = 6.4 Hz, ArH), 8.62 (1H, s, ArH), 8.30 (1H, d, J = 8.3 Hz, ArH),
8.26 (1H, d, J = 7.8 Hz, ArH), 8.2 (1H, d, J = 8.3 Hz, ArH), 7.79
(1H, t, J = 6.90 Hz, ArH), 7.66 (1H, t, J = 7.3 Hz, ArH), 7.44 (1H, t,
J = 7.8 Hz, ArH). 13C NMR (DMSO-d6, 151 MHz) d: 167.4, 143.2,
133.0, 132.0, 128.0, 127.4, 126.8, 126.7, 125.6, 119.2, 113.5. TOF
MS (ES+): m ⁄ z (relative intensity), 263.1 (100%) [M + H]+. HRMS
(ES+): m ⁄ z [M + H]+ calculated exact mass for C17H13N2O2:
311.0587; found 311.0575.
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 8 (1.76 g, 6.02 mmol). This suspension was stirred for
8 h and solution was formed. After the reaction was complete, the
solution was neutralized with concentrated HCl slowly over ice
bath. The product appeared as yellow precipitate which was fil-
tered, dried over high vacuum to give solid (1.24 g, 4.46 mmol,
3-(11-Chloro-10H-indolo[3,2-b]quinoline-7-
carboxamido)phenylboronic acid (15)
To a solution of 10,11-dihydro-11-oxo-5H-indolo[3,2-b]quinoline-7-
carboxylic acid 3 (0.56 g, 2.01 mmol) in DMSO (15 mL) were added
HOBt (0.54 g, 4.00 mmol), DMAP (0.60 g, 4.91 mmol), and EDC.HCl
(0.42 g, 2.19 mmol) separately. Thirty minutes later, to this reaction
mixture was added 3-aminophenylboronic acid (0.27 g, 1.97 mmol)
in one portion. Twenty milliliters of water was added after the
reaction mixture was stirred at room temperature for 46 h. Yellow
precipitate formed was filtered, washed with water for three times,
dried on vacuum, and purified by column chromatography (SiO2,
eluted with MeOH ⁄ CHCl3, 1 ⁄ 10) to give yellow solid (0.22 g,
0.55 mmol, 27%). 1H NMR (DMSO-d6, 600 MHz) d: 12.67 (1H, s,
NH), 12.07 (1H, s, NH), 10.28 (1H, s, CONH), 8.89 (1H, s,
J = 1.4 Hz, ArH), 8.37 (1H, d, J = 7.8 Hz, ArH), 8.12 (1H, dd,
J = 8.7 Hz, 1.8 Hz, ArH), 8.10 (d, J = 1.4 Hz, 1H, ArH), 8.07 (bs,
2H, BOH), 7.90–7.88 (1H, m, ArH), 7.75 (1H, d, J = 7.8 Hz, ArH),
7.72–7.70 (1H, m, ArH), 7.58 (1H, d, J = 8.7 Hz, ArH), 7.56 (1H, d,
J = 7.3 Hz, ArH), 7.35 (1H, t, J = 7.8 Hz, ArH), 7.33–7.31 (1H, m,
ArH). 13C NMR (DMSO-d6, 151 MHz) d: 167. 5, 165.9, 139.9, 139.2,
138.7, 131.0, 129.5, 129.3, 127.6, 126.6, 126.5, 126.0 125.2, 123.8,
123.1, 122.5, 122.3, 120.8, 117.9, 115.7, 112.0. TOF MS (ES+): m ⁄ z
(relative intensity), 398.1 (100%) [M + H]+. HRMS (ES+): m ⁄ z
[M + H]+ calculated exact mass for C22H17BN3O4 398.1312; found
398.1314.
1
67%). H NMR (DMSO-d6, 600 MHz) d: 13.64 (1H, bs, COOH), 12.68
(1H, s, NH), 10.22 (1H, s, CONH), 8.51 (1H, d, J = 7.8 Hz, ArH),
8.37 (1H, d, J = 7.8 Hz, ArH), 8.13 (1H, dd, J = 7.3, 1.0 Hz, ArH),
7.71–7.76 (2H, m, ArH), 7.38 (1H, t, J = 7.8 Hz, ArH), 7.35–7.33
(1H, m, ArH). 13C NMR (DMSO-d6, 151 MHz) d: 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]+ calculated exact mass for
C16H10N2O3: 279.0770; found 279.0772.
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, and then poured onto 500 mL of water. Yellow precipitate was
filtered, dried on vacuum. Recrystallization (MeOH ⁄ CHCl3) gave yel-
1
low solid (1.08 g, 3.64 mmol, 92%). H NMR (DMSO-d6, 600 MHz)
d: 10.43 (1H, s, NH), 8.59 (1H, d, J = 7.3, 1.4 Hz, ArH), 8.30–8.27
(2H, m, ArH), 8.22 (1H, d, J = 1.3 Hz, ArH), 7.82–7.79 (1H, m,
ArH), 7.78–7.75 (1H, m, ArH), 7.46 (1H, t, J = 7.3 Hz,ArH). 13C
NMR (DMSO-d6, 151 MHz) d: 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), 297.0 (100%) [M + H]+. HRMS
(ES+): m ⁄ z [M + H]+ calculated exact mass for C16H10N2O2:
297.0431; found 297.0441.
3-(11-Chloro-10H-indolo[3,2-b]quinoline-9-
carboxamido)phenylboronic acid (16)
To a solution of acid 13 (0.40 g, 1.35 mmol) in DMSO (25 mL) were
added CH2Cl (10 mL), HOBt (0.36 g, 2.70 mmol), DMAP (0.40 g,
3.38 mmol), EDC.HCl (0.28 g, 1.46 mmol) separately at 0 ꢁC. After
this mixture was stirred for 1 h, 3-aminophenylboronic acid (0.28 g,
2.04 mmol) was added in one portion. The reaction mixture was
stirred at room temperature for 39 h. Yellow precipitate was formed
after 50 mL of water was added to the reaction mixture. The yel-
low precipitate was filtered, washed with water (25 mL) twice,
dried over vacuum, and purified by column chromatography (SiO2,
eluted with MeOH ⁄ CHCl3, 1 ⁄ 8) to give yellow solid (0.21 g,
10,11-Dihydro-11-oxo-5H-indolo[3,2-b]quinoline-
9-carboxamido)phenylboronic acid (14)
To a solution of acid 12 (0.57 g, 2.05 mmol) in DMSO (15 mL) and
DCM (20 mL) were added HOBt (0.54 g, 4.00 mmol), DMAP (0.60 g,
4.91 mmol), and EDC.HCl (0.42 g, 2.19 mmol) separately. Thirty min-
utes later, to this reaction mixture was added 3-aminophenylboronic
acid (0.27 g, 1.97 mmol) in one portion. Twenty milliliters of water
was added after the reaction mixture was stirred at room tempera-
ture for 46 h. Yellow precipitate formed was filtered, washed with
water for three times, dried on vacuum, and purified by column
1
0.51 mmol, 38%). H NMR (DMSO-d6) d: 11.00 (1H, s, NH); 10.57
(1H, s, CONH); 8.59 (1H, d, J = 7.8 Hz, ArH); 8.40 (1H, d,
Chem Biol Drug Des 2011; 78: 816–825
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Meng et al.
J = 7.8 Hz, ArH); 8.33–8.30 (2H, m, ArH); 8.20 (1H, s, ArH); 8.12
(2H, s, BOH); 7.94 (1H, d, J = 7.8 Hz, ArH); 7.82 (1H, t, J = 6.8 Hz,
ArH); 7.78 (1H, t, J = 7.8 Hz, ArH); 7.63 (1H, d, J = 7.3 Hz, ArH);
7.51 (d, J = 7.3 Hz, 1H, ArH); 7.40 (d, J = 7.3 Hz, 1H, ArH). 13C
NMR (DMSO-d6) d: 165.2, 145.1, 144.3, 142.7, 137.9, 129.9, 129.7,
129.4, 129.0, 127.6, 127.4, 127.1, 126.8, 125.2, 123.8, 123.1, 122.9
122.3, 120.0, 118.9, 117.6. TOF MS (ES+): m ⁄ z (relative intensity),
416.1 (100%). HRMS (ES+): m ⁄ z [M + H]+ calculated exact mass for
C22H16BClN3O3: 416.0973; found 416.0963.
3-(10H-indolo[3,2-b]quinoline-9-
carboxamido)phenylboronic acid (19)
To a solution of compound 16 (0.13 g, 0.31 mmol) and triethyl-
amine (0.05 mL, 0.36 mmol) in MeOH (10 mL) was added 10%
Pd ⁄ C (0.12 g, 92% mol). This reaction mixture was stirred for 23 h
under hydrogen atmosphere at room temperature. Pd ⁄ C was fil-
tered. Solvent was removed under reduced pressure. Purification of
the residue by column chromatography (SiO2, eluted with
EtOAc ⁄ petrol, 1 ⁄ 3) to give yellow solid (0.075 g, 0.20 mmol, 65%).
1H NMR (DMSO-d6, 600 MHz) d: 11.72 (1H, s, NH), 10.46 (1H, s,
CONH), 8.60 (1H, d, J = 7.3 Hz, ArH), 8.42 (1H, s, ArH), 8.38 (1H,
dd, J = 7.8, 1.0 Hz, ArH); 8.27 (1H, d, J = 1.38 Hz, ArH), 8.22 (1H,
d, J = 8.4 Hz, ArH), 8.12 (1H, d, J = 7.74 Hz, ArH), 8.06 (s, 2H,
BOH), 7.93 (1H dd, J = 7.8, 1.4 Hz, ArH), 7.69 (1H, ddd, J = 7.80,
1.38 Hz, ArH), 7.61–7.57 (2H, m, ArH), 7.43 (1H, t, J = 7.80 Hz,
ArH); 7.39 (1H, t, J = 7.80 Hz, ArH). 13C NMR (DMSO-d6, 151 MHz)
d: 165.3, 144.8, 143.8 142.7, 138.1, 132.8, 129.7, 128.8, 128.4,
127.7, 127.6, 126.9, 126.4, 125.2, 124.8, 122.7, 122.6, 118.6, 117.0,
114.5. TOF MS (ES+): m ⁄ z (relative intensity), 382.1 (100%)
[M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated exact mass for
C22H17BN3O3: 382.1363; found 382.1354.
3-(11-chloro-10H-indolo[3,2-b]quinoline-7-
carboxamido)phenylboronic acid (17)
To a solution of acid 4 (1.22 g, 4.11 mmol) in DMSO (25 mL) were
added CH2Cl (25 mL), HOBt (1.13 g, 8.36 mmol), DMAP (1.25g,
10.27 mmol), and EDC.HCl (0.84 g, 4.38 mmol) separately at 0 ꢁC.
After this mixture was stirred for 1 h, 3-aminophenylboronic acid
(0.58 g, 11.54 mmol) was added in one portion. The reaction mix-
ture was stirred at room temperature for 40 h. Yellow precipitate
was formed after 50 mL of water was added to the reaction mix-
ture. The yellow precipitate was filtered, washed with water
(25 mL) twice, dried over vacuum, and purified by column chroma-
tography (SiO2, eluted with MeOH ⁄ CHCl3, 1 ⁄ 10) to give yellow solid
(1.10 g, 2.64 mmol, 64%). 1H NMR (DMSO-d6, 600 MHz) d: 12.22
(1H, s, NH), 10.45 (1H, s, CONH), 9.18 (1H, s, ArH), 8.35 (1H, d,
J = 8.2 Hz, ArH), 8.34 (1H, d, J = 8.2 Hz, ArH), 8.32 (1H, d,
J = 7.3 Hz, ArH), 8.16 (1H, s, ArH), 8.07 (2H, s, BOH), 7.95–7.94
(1H, m, ArH), 7.83–7.81 (1H, m, ArH), 7.80–7.78 (1H, m, ArH),
7.73(1H, d, J = 8.3 Hz, ArH), 7.56 (1H, d, J = 7.3 Hz, ArH), 7.35
(1H, t, J = 7.8 Hz, ArH). 13C NMR (DMSO-d6, 150 MHz) d: 165.1,
146.0, 145.9, 144.2, 138.6, 130.7, 130.6, 129.4, 129.3, 127.5, 127.4,
126.8, 126.7, 123.81, 122.6, 122.4, 121.5, 120.8, 118.7, 111.8. TOF
MS (ES+): m ⁄ z (relative intensity), 416.1 (100%) [M + H]+. HRMS
(ES+): m ⁄ z [M + H]+ calculated exact mass for C22H16BClN3O3:
416.0973; found 416.0963.
Mass spectrometry section
The solution of compound 18 and fucose was made up by follow-
ing a general procedure: to a 5 mL vial with 4 mL of 1:1
MeOH ⁄ H2O were added boronic acid 18 (2 mg, 5 · 10)6 mol) and
fucose (2 mg, 1.11 · 10)5 mol). The pH of the solution was
adjusted to 11 using NaOH. The mass spectrometer was operated
in the negative ion mode. Prepared solution of compound 18 was
introduced into the ES–MS by loop injection (5 lM injection loop)
into
a flow stream of 1:1 acetonitrile ⁄ water with 0.1%
CH3COONH4.
Results and Discussions
3-(10H-indolo[3,2-b]quinoline-7-
Chemistry
carboxamido)phenylboronic acid (18)
Parent indoloquinoline cores named as indoloquinoline-7-carboxylic
acid and indoloquinoline-9-carboxylic acid were synthesized for the
first time. Tetracyclic conjugated system was accomplished via PPA-
mediated cyclization, followed by chlorinative aromatization and
hydrogenation (34–36). Coupling of 3-aminophenylboronic acid with
these carboxylic acids by classic amidation (37) gave arylboronic
acid–derived indoloquinolines using EDC ⁄ HOBt ⁄ DMAP as coupling
reagent.
To a solution of compound 5 (0.067 g, 0.26 mmol) in DMSO (25 mL)
were added HOBt (0.069 g, 0.51 mmol), DMAP (0.093 g,
0.76 mmol), EDC.HCl (0.054 g, 0.28 mmol) separately at 0 ꢁC. After
this mixture was stirred for 1 h, 3-aminophenylboronic acid
(0.039 g, 0.028 mmol) was added in one portion. The reaction mix-
ture was stirred at room temperature for 48 h. Yellow precipitate
was formed after 50 mL of water was added to the reaction mix-
ture. The yellow precipitate was filtered, washed with water
(25 mL) twice, dried over vacuum, and purified by column chroma-
tography (SiO2, eluted with MeOH ⁄ CHCl3, 1 ⁄ 8) to give yellow solid
The synthesis of indoloquinoline-7-carboxylic acid and its analogs
is shown in Scheme 1. Acylation of o-aminobenzoic acid by chlo-
roacetyl 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. Cyclization of compound 2 in PPA at 130 ꢁC for 3 h
gave key intermediate compound 3 in 51% field. Compound 3
underwent chlorinated aromatization by treatment of phosphorus
oxychloride to afford compound 4. Dechlorination of compound 4
via hydrogenation gave indoloquinoline-7-carboxylic acid 5 with a
yield of 78%.
1
(0.033 g, 0.09 mmol, 35%). H NMR (DMSO-d6, 600 MHz) d: 12.19
(1H s, NH), 10.43 (1H, s, CONH), 9.22 (1H, s, ArH), 8.71 (1H, s,
ArH), 8.39 (H, dd, J = 8.3, 1.4 Hz, ArH), 8.30 (2H, d, J = 8.7 Hz,
ArH), 8.15 (1H, d, J = 1.4 Hz, ArH), 7.93 (1H, dd, J = 8.3, 1.4 Hz,
ArH), 7.86 (1H, t, J = 7.3Hz, ArH), 7.77 (1H, d, J = 8.7 Hz, ArH);
7.72 (1H, t, J = 7.8 Hz, ArH); 7.58 (1H, d, J = 7.3 Hz, ArH); 7.38
(1H, t, J = 7.80 Hz, ArH). TOF MS (ES+): m ⁄ z (relative intensity),
382.1 (100%) [M + H]+. HRMS (ES+): m ⁄ z [M + H]+ calculated exact
mass for C22H17BN3O3: 382.1363; found 382.1356.
820
Chem Biol Drug Des 2011; 78: 816–825

Bioactivity of Arylboronic Acid Derivatives of Indoquinolines
COOH
O
OH
NH2
O
OH
O
OH
H
H
N
N
c
a
b
Cl
N
H
O
O
2
1
O
Cl
H
H
N
H
N
N
e
d
N
N
N
H
5
COOH
4
COOH
3
COOH
Scheme 1: Reagents and conditions: (a)chloroacetyl chloride, DMF ⁄ dioxane, ice bath, then r.t., 90%; (b) NaHCO3, H2O, 85 ꢁC,48%; (c) poly
phosphoric acid, 130 ꢁC, 51%; (d) POCl3, reflux, 34%; (e) H2, Pd ⁄ C, Et3N, CH3OH, r.t., 51%.
OCH3
O
OCH3
O
OCH3
O
OCH3
NH2
O
H
N
H
N
c
b
a
N
H
Br
O
O
7
6
Cl
N
O
H
N
O
O
H
N
O
H
N
d
OCH3
OCH3
e
OCH3
N
N
H
9
10
8
O
H
N
f
OH
N
11
O
Cl
N
O
O
O
H
N
H
N
O
H
N
f
OH
OCH3
e
OH
N
H
12
N
H
13
8
Scheme 2: Reagents and conditions: (a) bromoacetyl bromide, DMF ⁄ dioxane, ice bath, then r.t., 91%; (b) DMF, 85 ꢁC, 92%; (c) poly phos-
phoric acid, 100 ꢁC, 86%; (d) POCl3, reflux, 89%; (e) H2, Pd ⁄ C, Et3N, CH3OH, 92%; (f) KOH, 40 ꢁC, 83%.
The synthetic routes of indoloquinoline-9-carboxylic acid 11 and
indoloquinoline-7-carboxylic acid 5 are slightly different (Scheme 2).
We found di-ester 7 could be synthesized in extremely high yield,
and then used for cyclization in PPA with high yield as well as eas-
ier workup. So di-ester 7 was chosen as substrate of cyclization to
facilitate the tetracyclic system. Acylation of methyl anthranilate by
bromoacetyl bromide gave intermediate 6 in 91% yield. Compound
6 reacted with methyl anthranilate in DMF at 85 ꢁC to afford ester
7 with 92% yield. Cyclization of ester 7 in PPA at 100 ꢁC for 3 h
gave key immediate 8 in 86% field. Chlorinated aromatization of
compound 8 with phosphorus oxychloride gave immediate 9 in
89% yield. Dechlorination of compound 9 via hydrogenation on
Pd ⁄ C in THF ⁄ CH3OH gave ester 10 in 92% yield. Hydrolysis of
ester 10 gave indoloquinoline-9-carboxylic acid 11 in 83% field.
Compounds 12 and 13 were obtained in a similar way.
Dechlorination ⁄ hydrogenation boronic acid compound 11 gave boro-
nic acid–derived indoloquinoline 19 in 65% yield (Scheme 4).
Mass spectrometry study
Biologically important saccharides and saccharide derivative (glu-
cose, galactose, fucose, and sialic acid) were used for binding study
of boronic acid–derived indoloquinolines and diol (1, 2 or 1, 3)-con-
taining carbohydrates in alkaline aqueous by using negative ion
electrospray and tandem mass spectroscopy (ES–MS and MS–MS)
scanning (38–40). Tandem mass spectra indicated formation of boro-
nate di-esters via covalent binding of six arylboronic acid–derived
indoquinolines and saccharides in alkaline aqueous solution, even
though we do not know the exact binding pattern of boronic acid
and saccharide (Table 1).
Five arylboronic acid–derived indoquinolines 14, 15, 16, 17, and
18 were obtained by amidation of tetracyclic carboxylic acids 12,
3, 13, 4, and 5, respectively, with 3-aminophenylboronic acid using
EDC ⁄ HOBt ⁄ DMAP as coupling reagent in medium yield from 19%
to 64% (Scheme 3).
In case of mass spectrometry study of fucose and compound 18 in
this paper, negative ion electrospray mass spectrum clearly showed
fucose–boronic acid di-ester's molecular ion which was further con-
firmed by its tandem mass spectroscopy (Figure 2). Parent ion m ⁄ z
508.01 corresponded to molecular ion of boronate di-ester (BS).
Chem Biol Drug Des 2011; 78: 816–825
821

Meng et al.
O
O
H
H
N
N
R1
R1
a
N
H
N
H
R2
: R1 = COOH, R2 = H
R2
14
15
: R1 = Bon, R2 = H
: R1 = H, R2 = Bon
12
3: R1 = H, R2 = COOH
H
R3
H
R3
H
N
N
R1
N
R1
O
a
N
N
B
HO
(Bon)
OH
R2
R2
13
: R1 = COOH, R2 = H, R3 = Cl
16
17
18
: R1 = Bon, R2 = H, R3 = Cl
4: R1 = H, R2 = COOH, R3 = Cl
: R1 = H, R2 = Bon, R3 = Cl
: R1 = H, R2 = Bon, R3 = H
5
: R1 = H, R2 = COOH, R3 = H
Scheme 3: Reagents and conditions: (a) EDC, HOBt, DMAP, DMSO, r.t., yield for 14 (19%); 15 (27%); 16 (38%); 17 (64%); 18 (35%),
respectively.
Fragment ions m ⁄ z 490.0 and 472.0 were the dehydration products
of boronate di-ester. Fragment ion m ⁄ z 380.0 corresponded to boro-
nic acid compound 18.
OH
OH
HO
B
B
O
H
OH
N
NH
Cl
N
a
O
H
N
NH
N
19
Biological assay
16
The anti-cancer cell proliferation activity of these indoquinoline
compounds against the human breast cancer cell line (MDA–231)
in vitro was tested at a concentration of 5 lM, using 3-(4, 5-
Scheme 4: Reagents and conditions: (a) H2, Pd ⁄ C, Et3N,
CH3OH, THF, r.t., 65%.
Table 1: Main fragment ions of boronate di-ester observed in MS–MS spectra
Compound (Mol. wt)
Fragment ions of boronate di-esters
14 (397.19)
540.1[M-H])
540.1[M-H])
524.2[M-H])
669.3[M-H])
504.0[M-H-2H2O])
396.0[M-glu-H])
540.1[M-H])
504.1[M-H-2H2O])
396.1[M-gal-H])
540.1[M-H])
506.2[M-H-H2O])
396.1[M-fuc-H])
524.2[M-H])
651.3[M-H-H2O])
396.2[M-sia-H])
669.3[M-H])
15 (397.19)
16 (415.64)
504.1[M-H-2H2O])
396.1[M-glu-H])
558.1[M-H])
504.1[M-H-2H2O])
396.1[M-gal-H])
558.0[M-H])
488.2[M-H-2H2O])
396.1[M-fuc-H])
542.1[M-H])
651.3[M-H-H2O])
396.1[M-sia-H])
687.3[M-H])
540.2[M-H-H2O])
522.2[M-H-2H2O])
414.1[M-glu-H])
558.1[M-H])
522.2[M-H-2H2O])
414.0[M-gal-H])
506.2[M-H-2H2O])
414.1[M-fuc-H])
669.7[M-H-H2O])
414.1[M-sia-H])
17 (415.64)
18 (381.19)
19 (381.19)
558.1[M-H])
542.1[M-H])
687.3[M-H])
540.2[M-H-H2O])
414.1[M-glu-H])
540.2[M-H-H2O])
522.2[M-H-2H2O])
414.1[M-gal-H])
524.0[M-H])
506.1[M-H-2H2O])
414.1[M-sia-H])
414.1[M-fuc-H])
508.0[M-H])
524.0[M-H])
653.1[M-H])
380.0[M-glu-H])
488.0[M-H-2H2O])
380.0[M-gal-H])
490.0[M-H-H2O])
472.0[M-H-2H2O])
380.0[M-fuc-H])
508.0[M-H])
635.1[M-H-H2O])
380.0[M-sia-H])
524.0[M-H])
524.0[M-H])
653.1[M-H])
380.0[M-glu-H])
488.0[M-H-2H2O])
380.0[M-gal-H])
490.0[M-H-H2O])
472.0[M-H-2H2O])
380.0[M-fuc-H])
635.1[M-H-H2O])
380.0[M-sia-H])
Abbreviations of glu, gal, fuc, and sia represent glucose, galactose, fucose, and sialic acid, respectively.
822
Chem Biol Drug Des 2011; 78: 816–825

Bioactivity of Arylboronic Acid Derivatives of Indoquinolines
M-FINALBORONFUCMSMS
20100304-M-FINALBORONFUCMSMS 27 (0.522)
TOF MSMS 508.00ES-
472.00
6.16e3
100
[M-H-2H2O]-
%
448.03
[M-H-H2O]-
380.01
[M-fucose-H]-
508.01
472.01
[M-H]-
490.05
472.07
448.05
340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 540
10
m/z
Figure 2: Electrospray tandem mass spectrum (MS–MS) of boronate di-ester formed by fucose and indoquinoline compound 18 in aque-
ous solution.
Conclusion
Table 2: Proliferation inhibition against tumor cell line MDA–
231 (MTT)
We have developed an efficient method for the synthesis of a
series of indoloquinoline carboxylic acids and their boronic acid
derivatives. The covalent binding between arylboronic acid–derived
indoquinolines and saccharides in alkaline aqueous solution was
confirmed using negative ion electrospray and tandem mass spec-
troscopy (ES–MS and MS–MS) techniques. Biological test of pro-
liferation inhibitory activity against the human breast cancer cell
line (MDA–231) revealed most of the arylboronic acid–derived
indoquinolines exhibited higher proliferation inhibitory activity
against the human breast cancer cell line (MDA–231) in vitro than
corresponding parent indoquinoline compounds without boronic
acid functional groups. Compound 17 exhibited best potent inhibi-
tory rate (76.74%) on the human breast cancer cell line (MDA–
231) at a concentration of 5 lM. Even though binding assay
revealed arylboronic acid–derived indoquinolines could only inter-
act covalently with some carbohydrates at pH 11 but not at physi-
ological pH, our anti-cancer cell proliferation results indicate that
the covalent interaction between synthetic indoquinolines possess-
ing arylboronic acid functional group and carbohydrates on the
surfaces of cancer cells might not be required for cancer cell pro-
liferation inhibition. Future work is needed to understand why
covalent binding is not required for cancer cell proliferation inhibi-
tion.
Compound (100 lM)
Proliferation inhibition (%)
12
7.88
17.18
58.77
49.25
48.29
34.59
34.8
3
13
4
5
11
14
15
33.4
16
17
48.69
76.12
96.99
64.61
0
18
19
Blank
Paclitaxel (10 nM)
79.1
dimethylthioazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell
viability assay. Paclitaxel (6 mg ⁄ mL) was used as positive control,
and the proliferation inhibition rate was 79.1% at the concentra-
tion of 10 nM. Results of the anti-tumor activity test revealed that
arylboronic acid–derived indoquinolines 14, 15, 16, 17, 18 had
better inhibitory effect on the human breast cancer cell line, com-
pared with corresponding indoquinoline carboxylic acids 12, 3,
13, 4, and 5. Among these arylboronic acid–derived indoquino-
lines possessing moderate inhibitory activity on tumor cells, com-
pound 17 exhibited best potent inhibitory rate (76.74%) on the
human breast cancer cell line (MDA–231) at a concentration of
5 lM (Table 2).
Acknowledgments
This work was financially supported by the Key International Coop-
eration Project of CMST (Grant No. 2008DFA31040).
Chem Biol Drug Des 2011; 78: 816–825
823

Meng et al.
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