Benzofuran-isatin conjugates as potent VEGFR-2 and cancer cell growth inhibitors

Article abstract of DOI:10.1002/jhet.3795

A series of benzofuran-isatin conjugates 6a-l and 7a,b tethered by various alkyl linkers were synthesized and evaluated for their VEGFR-2 inhibitory activity and in vitro activity against a panel of cancer cell lines. Seven of them were comparable with or

Full text of DOI:10.1002/jhet.3795

Received: 1 September 2019
DOI: 10.1002/jhet.3795
Revised: 4 October 2019
Accepted: 11 October 2019
C O M M U N I C A T I O N
Benzofuran‐isatin conjugates as potent VEGFR‐2 and cancer
cell growth inhibitors
Yulin Zou
The Third Clinical Medical College of the
Abstract
Three Gorges University, Gezhouba
A series of benzofuran‐isatin conjugates 6a‐l and 7a,b tethered by various alkyl
linkers were synthesized and evaluated for their VEGFR‐2 inhibitory activity
Central Hospital of Sinopharm, Yichang
443002, Hubei, China
and in vitro activity against a panel of cancer cell lines. Seven of them were
Correspondence
Yulin Zou, The Third Clinical Medical
College of the Three Gorges University,
Gezhouba Central Hospital of Sinopharm,
Yichang 443002, Hubei, China.
comparable with or better than Sunitinib against all tested cancer cells, demon-
strating benzofuran‐isatin conjugates were potential anticancer candidates.
The mechanism study revealed that VEGFR‐2 was at least one of the targets
for this kind of conjugates. The structure‐activity relationship demonstrated
that the carbon spacer between benzofuran and isatin moieties, substituents
on the C‐2 position of benzofuran moiety, and substituents on C‐3 as well as
C‐5 position of isatin motif influenced the anticancer activity significantly,
and the enriched structure‐activity relationship may provide an insight for
rational design of more effective conjugates.
Email: zouyulin1213@163.com
1 | INTRODUCTION
clinical practice for fighting against various cancers.[5–
8]
The conjugates bearing benzofuran and isatin moie-
The World Health Organization (WHO) estimated that
around one in five people globally will develop cancer
through their lifetime, and one in eight men and one in
11 women will succumbed to this deadliest disease.[1,2]
Obviously, cancer represents a substantial threat to human
being. Anticancer agents are critical for the control and
eradication of cancer, but the severe anticancer scenario
and the emergence of drug resistant especially multidrug‐
resistant cancers have already put a heavy burden on the
world health system.[3,4] To reduce the significant disabil-
ity, suffering, and deaths caused by cancer especially
drug‐resistant cancer worldwide, new anticancer agents
are needed.
Benzofuran and isatin derivatives were reported
to possess potential anticancer activity, and some
benzofuran/isatin derivatives that are exemplified by
Fruquintinib (benzofuran derivative, inhibitor of vascu-
lar endothelial growth factor receptors/VEGFRs) and
Sunitinib (isatin derivative, a multitargeted receptor
tyrosine kinase inhibitor) have already been used in
ties simultaneously may also employ the mechanisms
of action of benzofuran and isatin, so these conjugates
may have the capacity to enhance the activity against
drug‐resistant cancers. The structure‐activity relation-
ship (SAR) demonstrated that the carbon spacer
between benzofuran and isatin moieties, substituents
on the C‐2 position of benzofuran moiety, and substitu-
ents on C‐3 as well as C‐5 position of isatin motif influ-
enced the biological activity greatly, and the length of
the carbon spacer was positively correlated with the
anticancer activity.[9–13]
Based on the above research results, a series of
benzofuran‐isatin conjugates tethered by alkyl linkers
were designed, synthesized, and evaluated for their
VEGFR‐2 inhibitory activity and in vitro activity against
a panel of cancer cell lines (including doxorubicin‐
resistant breast cancer MCF‐7/MCF‐7/DOX and
multidrug‐resistant DU‐145 prostate cancer cells) in this
paper. The SAR was discussed to provide an insight for
rational design of more effective conjugates.
J Heterocyclic Chem. 2019;1–7.
wileyonlinelibrary.com/journal/jhet
© 2019 Wiley Periodicals, Inc.
1

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TABLE 1 Chemical structures and yields of benzofuran‐isatin
conjugates 6a‐l and 7a,b
2 | RESULTS AND DISCUSSION
The alkyl‐linked benzofuran‐isatin conjugates 6a‐l and
7a,b could be obtained by the route described in Scheme 1.
Cyclization of ethyl 3‐(4‐substituted phenyl)‐3‐oxopro
panoates 1 and benzoquinone in presence of copper (II)
triflate (Cu (OTf)2) provided the benzofuran interme
diates 2, which were then alkylated with 1,2‐
dibromoethane, 1,3‐dibromopropane, 1,4‐dibromobutane,
1,5‐dibromopentane, or 1,6‐dibromohexane 3 with NaH
as base, yielding the key intermediates 4. The benzo
furan‐isatin conjugates 6a‐l were obtained by treatment
of 5‐substituted isatin 5 with benzofuran intermediates 4
with potassium carbonate (K2CO3) as base. Finally,
condensation of conjugate 6l with the requested amine
hydrochlorides in the presence of sodium bicarbonate
(NaHCO3) gave the imine‐containing benzofuran‐isatin
conjugates 7a,b.
The chemical structures and yields of desired
benzofuran‐isatin conjugates 6a‐l and 7a,b were pre-
sented in Table 1, and the 1H NMR, 13C NMR, and HRMS
spectra were attached in the supporting information
The synthesized benzofuran‐isatin conjugates 6a‐l and
7a,b along with Sunitinib as positive control were evalu-
ated for their VEGFR‐2 inhibitory activity by homoge-
neous time‐resolved fluorescence (HTFR) assay and
in vitro anticancer activities against breast cancer cells
Compound
n
R1
R2
R3
Yield, %
6a
6b
6c
6d
6e
6f
1
1
1
1
2
2
2
2
3
4
5
5
5
5
F
H
O
28
37
21
29
42
36
33
25
22
30
37
34
57
39
F
OMe
F
O
F
O
H
F
O
H
H
O
F
H
O
6g
6h
6i
OMe
OMe
OMe
OMe
H
H
O
F
O
H
O
6j
H
O
6k
6l
F
O
F
OMe
OMe
OMe
O
7a
7b
F
NOH
NOEt
F
MCF‐7, MCF‐7/DOX, prostate cancer cells DU‐145 and
MDR DU‐145 by MTT assay, and half maximal inhibitory
concentration (IC50) values were listed in Table 2.
As shown in Table 2, all conjugates exhibited promis-
ing VEGFR‐2 inhibitory activity (IC50: 0.23‐4.17 μM) and
SCHEME 1 Synthesis of benzofuran‐isatin conjugates 6a‐l and 7a,b

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3
TABLE 2 VEGFR‐2 inhibitory activity and anticancer activities
of benzofuran‐isatin conjugates 6a‐l and 7a,b
TABLE 3 In vitro cytotoxicity of benzofuran‐isatin conjugates 6a‐
l and 7a,b toward HEK‐293 cells
IC50 (μM)
Compd.
CC50, μg/mL
VEGFR‐ MCF‐ MCF‐7/DOX DU‐
MDR DU‐
145
6a
64
512
128
32
Compd.
2
7
145
6b
6a
6b
6c
6d
6e
6f
1.43
0.86
1.01
0.78
0.39
0.56
0.49
0.23
0.74
0.64
0.38
0.55
4.17
3.22
80.3
76.6
95.7
99.6
63.2
67.5
55.3
86.7
77.2
49.4
56.6
47.6
99.5
78.8
18.9
72.4
79.1
90.0
85.1 >100
80.4 88.3
99.8 >100
>100 >100
85.1
72.4
6c
6d
6e
256
128
256
64
>100
6f
83.3
71.1
89.9
95.5
80.6
75.3
76.9
70.1
84.6
79.3
6g
6h
6i
6g
6h
6i
90.4 >100
>100 >100
96.7
128
512
256
128
32
6j
89.1
84.4
71.3
68.4
6k
6l
6j
79.5
71.6
69.9
6k
6l
7a
7b
64
7a
7b
>100
>100
>100
84.2 >100
>100
Sunitinib
64
89.9
29.4
>100
Sunitinib 0.24
considerable in vitro activity against breast cancer cells
MCF‐7, MCF‐7/DOX, prostate cancer cells DU‐145, and
MDR DU‐145 (IC50: 47.6 to >100 μM). The SAR revealed
that the carbon spacer between isatin and benzofuran
moieties, substituents on the C‐3 and C‐5 positions of
isatin skeleton, and substituent on the para‐position of
phenyl at C‐2 position of benzofuran motif influenced
the VEGFR‐2 inhibitory activity and anticancer activity
significantly. The electron‐donating group at para‐
position of phenyl on C‐2 position (R1) of benzofuran
motif and electron‐withdrawing group at C‐5 position
(R2) of isatin skeleton were beneficial to the activity. The
ketone‐containing conjugates 6a‐l conjugates showed
higher activity toward VEGFR‐2 and cancer cells than
the oxime analogs 7a,b, implying introduction of oxime
into C‐3 position (R3) was harmful to the activity. The
length of the carbon spacer was in positive correlation
with the anticancer activity, and conjugates with five‐ or
six‐carbon linkers demonstrated the highest activity. The
SAR was depicted in Figure 1.
From Table 3, all conjugates 6a‐l and 7a,b displayed
acceptable cytotoxicity toward normal human embryonic
kidney (HEK‐293) cells with CC50 in a range of 32 to
516 μg/mL, and majority of them were less toxic than
the reference Sunitinib (CC50: 64 μg/mL). The structure‐
cytotoxicity relationship suggested that incorporation of
oxime or ethyloxime into the C‐3 position could increase
the cytotoxicity when compared with unsubstituted
analogs.
Among them, seven conjugates 6b, 6e, 6f, and 6i‐l
(IC50: 47.6‐96.7 μM) possessed broad spectrum against
all tested cancer cell lines, and the activity was in the
same level with that of the reference Sunitinib (IC50:
18.9‐84.2 μM) against MCF‐7, MCF‐7/DOX, and DU‐145
cancer cells but higher than that of Sunitinib (IC50:
>100 μM) against MDR DU‐145 cells. Moreover, these
seven conjugates also showed low cytotoxicity toward
HEK‐293 cells. Based on the above facts, the
benzofuran‐isatin conjugates could act as lead molecules
for further investigations.
FIGURE 1 The anticancer structure‐
activity relationship (SAR) of benzofuran‐
isatin conjugates [Color figure can be
viewed at wileyonlinelibrary.com]

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3 | CONCLUSIONS
4.1 | Ethyl 5‐(2‐(2,3‐dioxoindolin‐1‐yl)
ethoxy)‐2‐(4‐fluorophenyl)benzofuran‐3‐
carboxylate (6a)
In summary, 14 benzofuran‐isatin conjugates tethered via
various alkyl linkers were synthesized, and their VEGFR‐
2 inhibitory activity and in vitro anticancer activity and
cytotoxicity toward normal cells were evaluated in this
paper. Seven of them were comparable with or better
than Sunitinib against all tested cancer cells, demonstrat-
ing benzofuran‐isatin conjugates are potential anticancer
candidates. The mechanism study revealed that VEGFR‐2
is at least one of the targets for this kind of conjugates.
The SAR proved that the anticancer activity of the con-
jugates was closely related to the carbon spacer between
isatin and benzofuran moieties, substituents on the C‐3
and C‐5 positions of isatin skeleton, and substituent on
the para‐position of phenyl at C‐2 position of benzofuran
motif, and the enriched SAR may be useful for further
design of this kind of conjugates.
Yellow solid, yield: 28%. 1H NMR (400 MHz, DMSO‐d6) δ
1.32 (3H, t, J = 8.0 Hz, CO2CH2CH3), 4.10‐4.15 (4H, m,
2×‐CH2‐), 4.32 (2H, q, J = 8.0 Hz, CO2CH2CH3), 6.98
(1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.15 (1H, t, J = 8.0 Hz,
Ar‐H), 7.36‐7.43 (4H, m, Ar‐H), 7.56 (1H, d, J = 4.0 Hz,
Ar‐H), 7.60 (1H, d, J = 8.0 Hz, Ar‐H), 7.70 (1H, t,
J = 4.0 Hz, Ar‐H), 8.00‐8.04 (2H, m, Ar‐H). 13C NMR
(101 Hz, DMSO‐d6) δ 183.67, 165.93, 163.31, 160.12,
158.80, 155.81, 151.49, 148.73, 138.57, 132.39, 132.30,
127.66 (JC‐F = 189 Hz), 124.82, 123.67, 117.93, 115.93,
114.91, 112.62, 111.88, 106.07, 100.00, 66.23, 61.00,
49.07, 14.40.
4.2 | Ethyl 2‐(4‐fluorophenyl)‐5‐(2‐(5‐
methoxy‐2,3‐dioxoindolin‐1‐yl)ethoxy)
benzofuran‐3‐carboxylate (6b)
4 | EXPERIMENTAL SECTION
Yellow solid, yield: 37%. 1H NMR (400 MHz, DMSO‐d6) δ
1.30 (3H, t, J = 8.0 Hz, CO2CH2CH3), 3.78 (3H, s, OMe),
4.09‐4.11 (2H, m, ‐CH2‐), 4.28‐4.34 (4H, m, ‐CH2‐ and
CO2CH2CH3), 6.98 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.12
(1H, d, J = 4.0 Hz, Ar‐H), 7.26‐7.41 (5H, m, Ar‐H), 7.58
(1H, d, J = 8.0 Hz, Ar‐H), 8.00‐8.04 (2H, m, Ar‐H). 13C
NMR (101 Hz, DMSO‐d6) δ 183.92, 163.31, 160.11,
158.83, 156.16, 155.80, 148.72, 145.34, 132.38, 132.29,
127.64, 125.91 (JC‐F = 173 Hz), 124.48, 118.34, 115.92,
115.70, 114.92, 113.00, 112.60, 109.69, 109.34, 108.90,
106.11, 66.28, 61.00, 29.71, 14.39.
Benzofuran‐3‐carboxylates 2 were synthesized by the pro-
cedure described in the literatures.[9,10] To a solution of
benzofuran‐3‐carboxylates
2 (10.0 mmol) in DMF
(50 mL), NaH (60%, 12.0 mmol) was added at 0°C. The
mixture was stirred at 0°C for 30 minutes, and then 1,2‐
dibromoethane, 1,3‐dibromopropane, 1,4‐dibromobutane,
1,5‐dibromopentane, or 1,6‐dibromohexane 3 (15.0 mmol)
were added. The mixture was stirred at room temperature
overnight. EtOH (10 mL) was added to quench the reac-
tion, and then H2O (100 mL) was added. The mixture
was extracted with EA (50 mL × 4), and then the com-
bined organic layers were washed with brine (20 mL × 2),
followed by concentration under reduced pressure. The
residue was purified by silica gel column chromatography
with PE:EA = 1:1 to give the key intermediates 4.
A mixture of intermediates 4 (1.0 mmol), 5‐substituted
isatins 5 (1.0 mmol), and K2CO3 (10.0 mmol) in DMF
(50 mL) was stirred at room temperature for 48 hours.
After filtration, the filtrate was concentrated under
reduced pressure, and the residue was purified by silica
gel column chromatography with PE:EA = 1:1 to give
the desired benzofuran‐isatin conjugates 6a‐l.
The conjugate 6l (0.6 mmol), the requested amine
hydrochlorides (1.0 mmol) and NaHCO3 (1.1 mmol) in
the mixture of THF (10 mL) and H2O (5 mL), was stirred
at 70°C for 12 hours. After cooling to room temperature,
the mixture was extracted with EA (10 mL × 4). The com-
bined organic layers were washed with brine (10 mL × 2),
and then concentrated under reduced pressure. The resi-
due was purified by silica gel column chromatography
4.3 | Ethyl 5‐(2‐(5‐fluoro‐2,3‐dioxoindolin‐
1‐yl)ethoxy)‐2‐(4‐fluorophenyl)benzofuran‐
3‐carboxylate (6c)
Yellow solid, yield: 21%. 1H NMR (400 MHz, DMSO‐d6) δ
1.30 (3H, t, J = 8.0 Hz, CO2CH2CH3), 4.12‐4.15 (2H, m, ‐
CH2‐), 4.28‐4.34 (4H, m, ‐CH2‐ and CO2CH2CH3), 6.98
(1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.12 (1H, d, J = 4.0 Hz,
Ar‐H), 7.39‐7.42 (5H, m, Ar‐H), 7.60 (1H, d, J = 8.0 Hz,
Ar‐H), 8.00‐8.04 (2H, m, Ar‐H). Elemental Anal. Calcd
(%) for C27H19F2NO6: C, 65.99; H, 3.90; N, 2.85; Found:
C, 65.91; H, 3.77; N, 2.59.
4.4 | Ethyl 5‐(2‐(5‐fluoro‐2,3‐dioxoindolin‐
1‐yl)ethoxy)‐2‐phenylbenzofuran‐3‐
carboxylate (6d)
1
with PE:EA
=
1:1 to give the imine‐containing
Yellow solid, yield: 29%. H NMR (400 MHz, CDCl3) δ
benzofuran‐isatin conjugates 7a,b.
1.41 (3H, t, J = 8.0 Hz, CO2CH2CH3), 4.22 (2H, t,

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5
J = 8.0 Hz, ‐CH2‐), 4.35‐4.41 (4H, m, ‐CH2‐ and
CO2CH2CH3), 6.86 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.16‐
7.24 (4H, m, Ar‐H), 7.40 (1H, d, J = 8.0 Hz, Ar‐H), 7.50
(1H, d, J = 4.0 Hz, Ar‐H), 7.62‐7.65 (2H, m, Ar‐H), 8.01‐
8.05 (2H, m, Ar‐H). Elemental Anal. Calcd (%) for
C27H20FNO6: C, 68.50; H, 4.26; N, 2.96; Found: C, 68.27;
H, 4.11; N, 2.73.
4.8 | Ethyl 5‐(3‐(5‐fluoro‐2,3‐dioxoindolin‐
1‐yl)propoxy)‐2‐phenylbenzofuran‐3‐
carboxylate (6h)
Yellow solid, yield: 25%. 1H NMR (400 MHz, DMSO‐d6) δ
1.28 (3H, t, J = 8.0 Hz, CO2CH2CH3), 2.08‐2.17 (2H, m, ‐
CH2‐), 3.88‐3.92 (2H, m, ‐CH2‐), 3.88‐3.92 (2H, m, ‐CH2‐),
4.11‐4.17 (2H, m, ‐CH2‐), 4.48 (2H, q, J = 4.0 Hz,
CO2CH2CH3), 7.10 (1H, d, J = 8.0 Hz, Ar‐H), 7.23‐7.27
(1H, m, Ar‐H), 7.39‐7.67 (6H, m, Ar‐H), 7.76‐7.95 (3H,
m, Ar‐H). Elemental Anal. Calcd (%) for C29H24FNO6:
C, 67.31; H, 4.67; N, 2.71; Found: C, 67.11; H, 4.53; N,
2.54.
4.5 | Ethyl 5‐(2‐(5‐fluoro‐2,3‐dioxoindolin‐
1‐yl)ethoxy)‐2‐phenylbenzofuran‐3‐
carboxylate (6e)
1
Yellow solid, yield: 42%. H NMR (400 MHz, CDCl3) δ
1.32 (3H, t, J = 8.0 Hz, CO2CH2CH3), 2.25‐2.32 (2H, m,
‐CH2‐), 4.00‐4.05 (2H, m, ‐CH2‐), 4.21‐4.27 (2H, m, ‐
CH2‐), 4.48 (2H, q, J = 8.0 Hz, CO2CH2CH3), 6.92‐7.11
(3H, m, Ar‐H), 7.42‐7.66 (7H, m, Ar‐H), 7.79‐7.87 (1H,
m, Ar‐H), 7.62‐7.65 (2H, m, Ar‐H), 8.00‐8.03 (1H, m, Ar‐
H). Elemental Anal. Calcd (%) for C28H23NO6: C, 71.63;
H, 4.94; N, 2.98; Found: C, 71.55; H, 4.87; N, 2.71.
4.9 | Ethyl 5‐((6‐(3‐(2‐
carbamothioylhydrazono)‐5‐fluoro‐2‐
oxoindolin‐1‐yl)hexyl)oxy)‐2‐(4‐
methoxyphenyl)benzofuran‐3‐carboxylate
(6i)
1
Purple solid, yield: 22%. H NMR (400 MHz, CDCl3) δ
1.32 (3H, t, J = 8.0 Hz, CO2CH2CH3), 1.72‐1.88 (4H, m,
2×‐CH2‐), 3.67‐3.75 (5H, m, ‐CH2‐ and OMe), 3.85 (3H,
s, OCH3), 4.04 (2H, t, J = 4.0 Hz, ‐CH2‐), 4.32 (2H, q,
J = 8.0 Hz, CO2CH2CH3), 6.94 (1H, dd, J = 4.0, 8.0 Hz,
Ar‐H), 7.06‐7.14 (4H, m, Ar‐H), 7.22 (1H, dd, J = 4.0,
8.0 Hz, Ar‐H), 7.40 (1H, d, J = 5.0 Hz, Ar‐H), 7.52 (1H,
d, J = 8.0 Hz, Ar‐H), 7.94‐7.96 (2H, m, Ar‐H). 13C NMR
(101Hz, CDCl3) δ 184.17, 163.61, 161.41, 161.21, 158.59,
156.12 (2C), 148.25, 144.89, 131.38, 127.96, 124.25,
121.72, 118.43, 114.41, 114.12 (2C), 112.23, 112.18,
109.66, 107.66, 105.78, 68.01, 60.79, 56.30, 55.83, 26.49,
23.97, 14.44.
4.6 | Ethyl 5‐(3‐(2,3‐dioxoindolin‐1‐yl)
propoxy)‐2‐(4‐fluorophenyl)benzofuran‐3‐
carboxylate (6f)
Yellow solid, yield: 36%. 1H NMR (400 MHz, DMSO‐d6) δ
1.31 (3H, t, J = 8.0 Hz, CO2CH2CH3), 2.13 (2H, t,
J = 8.0 Hz, ‐CH2‐), 3.89 (2H, t, J = 4.0 Hz, ‐CH2‐), 4.12
(2H, t, J = 4.0 Hz, ‐CH2‐), 4.33 (2H, q, J = 8.0 Hz,
CO2CH2CH3), 6.98 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.11
(1H, t, J = 4.0 Hz, Ar‐H), 7.24 (1H, d, J = 8.0 Hz, Ar‐
H), 7.37‐7.42 (3H, m, Ar‐H), 7.54‐7.64 (3H, m, Ar‐H),
8.01‐8.05 (2H, d, J = 8.0 Hz, Ar‐H). Elemental Anal.
Calcd (%) for C28H22FNO6: C, 68.99; H, 4.55; N, 2.87;
Found: C, 68.83; H, 4.37; N, 2.69.
4.10 | Ethyl 2‐(4‐fluorophenyl)‐5‐((5‐(5‐
methoxy‐2,3‐dioxoindolin‐1‐yl)pentyl)oxy)
benzofuran‐3‐carboxylate (6j)
Yellow solid, yield: 30%. 1H NMR (400 MHz, DMSO‐d6) δ
1.32 (3H, t, J = 8.0 Hz, CO2CH2CH3), 1.50‐1.53 (2H, m, ‐
CH2‐), 1.66‐1.71 (2H, m, ‐CH2‐), 1.78‐1.81 (2H, m, ‐CH2‐),
3.69 (2H, t, J = 8.0 Hz, ‐CH2‐), 3.99 (2H, t, J = 4.0 Hz, ‐
CH2‐), 4.32 (2H, q, J = 8.0 Hz, CO2CH2CH3), 6.94 (1H,
dd, J = 4.0, 8.0 Hz, Ar‐H), 7.05‐7.13 (3H, m, Ar‐H), 7.20
(1H, d, J = 8.0 Hz, Ar‐H), 7.40 (1H, d, J = 4.0 Hz, Ar‐
H), 7.54 (2H, d, J = 8.0 Hz, Ar‐H), 7.64 (1H, td, J = 4.0,
8.0 Hz, Ar‐H), 7.93‐7.97 (2H, m, Ar‐H). 13C NMR
(101Hz, DMSO‐d6) δ 183.97, 163.62, 161.40, 158.53,
156.23, 151.18, 148.23, 138.62, 131.38, 127.97, 124.90,
123.55 (JC‐F = 181 Hz), 121.74, 117.91, 114.41, 114.11,
112.21, 111.16, 107.68, 105.67, 68.35, 60.78, 55.83 (2C),
28.84, 27.01, 23.37, 14.45.
4.7 | Ethyl 5‐(3‐(5‐methoxy‐2,3‐
dioxoindolin‐1‐yl)propoxy)‐2‐
phenylbenzofuran‐3‐carboxylate (6g)
Yellow solid, yield: 33%. 1H NMR (400 MHz, DMSO‐d6) δ
1.32 (3H, t, J = 8.0 Hz, CO2CH2CH3), 2.14‐2.17 (2H, m, ‐
CH2‐), 3.86 (3H, s, OMe), 3.97 (2H, t, J = 8.0 Hz, ‐CH2‐),
4.11 (2H, t, J = 8.0 Hz, ‐CH2‐), 4.32 (2H, q, J = 8.0 Hz,
CO2CH2CH3), 6.92 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.08‐
7.16 (3H, m, Ar‐H), 7.22 (1H, d, J = 8.0 Hz, Ar‐H), 7.38‐
7.40 (2H, m, Ar‐H), 7.56 (1H, d, J = 12.0 Hz, Ar‐H),
7.72 (1H, d, J = 8.0 Hz, Ar‐H), 7.95‐7.98 (2H, m, Ar‐H).
Elemental Anal. Calcd (%) for C29H25NO7: C, 69.73; H,
5.04; N, 2.80; Found: C, 69.60; H, 4.88; N, 2.62.

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110.33, 108.03, 68.65, 62.29, 60.90, 29.05, 27.41, 26.47,
25.71, 14.38.
4.11 | Ethyl 5‐((6‐(2,3‐dioxoindolin‐1‐yl)
hexyl)oxy)‐2‐phenylbenzofuran‐3‐
carboxylate (6k)
1
4.14 | Ethyl 5‐((6‐(3‐(ethoxyimino)‐5‐
methoxy‐2‐oxoindolin‐1‐yl)hexyl)oxy)‐2‐(4‐
fluorophenyl)benzofuran‐3‐carboxylate
(7b)
Purple solid, yield: 37%. H NMR (400 MHz, CDCl3) δ
1.33 (3H, t, J = 8.0 Hz, CO2CH2CH3), 1.50‐1.58 (4H,
m, 2×‐CH2‐), 1.76‐1.79 (2H, m, ‐CH2‐), 1.86‐1.91 (2H,
m, ‐CH2‐), 3.75 (2H, t, J = 8.0 Hz, ‐CH2‐), 4.12 (2H, t,
J = 8.0 Hz, ‐CH2‐), 4.52 (2H, q, J = 8.0 Hz,
CO2CH2CH3), 6.86 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H),
7.08 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.25‐7.33 (2H, m,
Ar‐H), 7.49‐7.67 (5H, m, Ar‐H), 7.72 (1H, d, J = 4.0
Hz, Ar‐H), 7.87‐8.00 (2H, m, Ar‐H). Elemental Anal.
Calcd (%) for C31H29NO6: C, 72.78; H, 5.71; N, 2.74;
Found: C, 72.71; H, 5.58; N, 2.44.
1
Yellow solid, yield: 39%. H NMR (400 MHz, DMSO‐d6)
δ 1.28‐1.48 (6H, t, NOCH2CH3 and CO2CH2CH3), 1.56‐
1.86 (8H, m, 4×‐CH2‐), 3.77 (2H, t, J = 8.0 Hz, ‐CH2‐),
3.90 (3H, s, ‐OMe), 4.05 (2H, t, J = 8.0 Hz, ‐CH2‐),
4.41 (2H, q, J = 8.0 Hz, CO2CH2CH3), 4.56 (2H, q,
J = 8.0 Hz, NOCH2CH3), 6.80 (1H, dd, J = 4.0,
12.0 Hz, Ar‐H), 6.92 (1H, dd, J = 4.0, 12.0 Hz, Ar‐H),
7.03 (1H, d,
J = 8.0 Hz, Ar‐H), 7.10 (1H, t,
J = 4.0 Hz, Ar‐H), 7.40 (1H, d, J = 8.0 Hz, Ar‐H),
7.54 (1H, d, J = 4.0 Hz, Ar‐H), 7.74 (1H, dd, J = 4.0,
8.0 Hz, Ar‐H), 8.00‐8.03 (2H, m, Ar‐H). Elemental Anal.
Calcd (%) for C34H35N2O7: C, 67.76; H, 5.85; N, 4.65;
Found: C, 67.51; H, 5.57; N, 4.39.
4.12 | Ethyl 5‐((6‐(5‐fluoro‐2,3‐
dioxoindolin‐1‐yl)hexyl)oxy)‐2‐(4‐
fluorophenyl)benzofuran‐3‐carboxylate (6l)
1
Yellow solid, yield: 34%. H NMR (400 MHz, DMSO‐d6)
δ 1.31 (3H, t, J = 8.0 Hz, CO2CH2CH3), 1.39‐1.51 (4H,
m, 2×‐CH2‐), 1.62‐1.65 (2H, m, ‐CH2‐), 1.73‐1.75 (2H,
m, ‐CH2‐), 3.67 (2H, t, J = 8.0 Hz, ‐CH2‐), 4.03 (2H, t,
J = 8.0 Hz, ‐CH2‐), 4.33 (2H, q, J = 4.0 Hz,
CO2CH2CH3), 7.00 (1H, dd, J = 4.0, 12.0 Hz, Ar‐H),
7.24 (1H, dd, J = 4.0, 8.0 Hz, Ar‐H), 7.36‐7.45 (4H, m,
Ar‐H), 7.53 (1H, td, J = 4.0, 8.0 Hz, Ar‐H), 7.58 (1H,
d, J = 8.0 Hz, Ar‐H), 8.01‐8.05 (2H, m, Ar‐H). 13C
NMR (101 Hz, DMSO‐d6) δ 183.39, 163.99, 162.41,
160.00 (JC‐F = 238 Hz), 158.57, 157.68, 156.36, 148.51,
147.45, 132.36, 132.27, 127.65, 126.04 (JC‐F = 161 Hz),
124.58, 124.34, 115.90, 115.68, 115.06, 112.58, 112.51,
108.94, 105.63, 100.00, 68.45, 60.96, 29.05, 27.13, 26.44,
25.73, 14.39.
ORCID
Yulin Zou https://orcid.org/0000-0002-0540-8684
REFERENCES
[1] World Health Organization. 10 facts about cancer. https://
www.who.int/features/factfiles/cancer/en/
[2] World Health Organization. Cancer: Key facts. http://www.
who.int/news‐room/fact‐sheets/detail/cancer
[3] F. Gao, X. Zhang, T. F. Wang, J. Q. Xiao, Eur. J. Med. Chem.
2019, 165, 59.
[4] J. Y. Zhang, S. Wang, Y. Bai, Z. Xu, Eur. J. Med. Chem. 2019,
178, 341.
[5] N. M. Evdokimov, I. V. Magedov, D. McBrayer, A. Kornienko,
Bioorg. Med. Chem. Lett. 2016, 26, 1558.
4.13 | Ethyl 5‐((6‐(5‐fluoro‐3‐
[6] Z. Xu, S. J. Zhao, Z. S. Lv, F. Gao, Y. Wang, F. Zhang, L. Bai, J.
(hydroxyimino)‐2‐oxoindolin‐1‐yl)hexyl)
oxy)‐2‐phenylbenzofuran‐3‐carboxylate (7a)
L. Deng, Eur. J. Med. Chem. 2019, 162, 396.
[7] R. J. Nevagi, S. N. Dighe, S. N. Dighe, Eur. J. Med. Chem. 2015,
97, 561.
1
Yellow solid, yield: 57%. H NMR (400 MHz, DMSO‐d6)
[8] H. K. Shamsuzzaman, Eur. J. Med. Chem. 2015, 97, 483.
δ 1.32 (3H, t, J = 8.0 Hz, CO2CH2CH3), 1.37‐1.50 (4H,
m, 2×‐CH2‐), 1.61‐1.64 (2H, m, ‐CH2‐), 1.72‐1.75 (2H,
m, ‐CH2‐), 3.81 (2H, t, J = 8.0 Hz, ‐CH2‐), 4.02 (2H, t,
J = 8.0 Hz, ‐CH2‐), 4.43 (2H, q, J = 4.0 Hz,
CO2CH2CH3), 7.10 (1H, dd, J = 4.0, 12.0 Hz, Ar‐H),
7.30‐7.32 (1H, m, Ar‐H), 7.51‐7.94 (7H, m, Ar‐H), 13.68
(1H, s, NOH). 13C NMR (101 Hz, DMSO‐d6) δ 165.89,
163.32, 157.14 (JC‐F = 195 Hz), 155.19, 154.01, 151.00,
150.40, 130.81, 129.71, 129.33, 129.17, 128.65, 128.22,
124.05, 120.52, 116.22, 115.90, 114.27, 112.57, 110.69,
[9] F. Gao, H. Yang, T. Lu, Z. Chen, L. Ma, Z. Xu, P. Schaffer, G.
Lu, Eur. J. Med. Chem. 2018, 159, 277.
[10] F. Gao, T. Wang, M. Gao, X. Zhang, Z. Liu, S. Zhao, Z. Lv, J.
Xiao, Eur. J. Med. Chem. 2019, 165, 323.
[11] F. Gao, Z. Chen, L. Ma, L. Qiu, J. Lin, G. Lu, Bioorg. Med.
Chem. 2019, 27, 2652.
[12] Y. Zhang, R. Wang, T. Zhang, W. Yan, Y. Chen, Y. Zhang, M.
Zhou, Chin. Chem. Lett. 2019, 30, 653.
[13] Q. P. Diao, H. Guo, G. Q. Wang, J. Heterocyclic Chem. 2019, 56,
1687.

ZOU
7
SUPPORTING INFORMATION
How to cite this article: Zou Y. Benzofuran‐
isatin conjugates as potent VEGFR‐2 and cancer
cell growth inhibitors. J Heterocyclic Chem.
2019;1–7. https://doi.org/10.1002/jhet.3795
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.