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C. R. Chimie 21 (2018) 471e474Contents lists avaiComptes Rendus Chimie
www.sciencedirect.comPreliminary communication/CommunicationAutocatalytic synthesis of 3-ethyl-3-hydroxy-indole-2-ones
and their neuroprotection and antitumor activities'
evaluation
Gang Chen a, *, Jiao Lin a, Jie Zhang a, Ya Wu a, Xuefan Gu a, Xiaojiang Hao b, **,
Yu Zhang b
a College of Chemistry and Chemical Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 701165, PR China
b State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences,
Kunming 650204, PR Chinaa r t i c l e i n f o
Article history:
Received 30 October 2017
Accepted 15 February 2018
Available online 19 March 2018
Keywords:
Isatin
3-Ethyl-3-hydroxy-indole-2-one
Antitumor
Neuroprotection* Corresponding author.
** Corresponding author.
E-mail addresses: gangchen@xsyu.edu.cn (G. Ch
ac.cn (X. Hao).
https://doi.org/10.1016/j.crci.2018.02.009
1631-0748/© 2018 Académie des sciences. Publishea b s t r a c t
In this study, a series of 3-ethyl-3-hydroxy-indole-2-ones were synthesized through the
addition reaction of Et2Zn and N-substituted isatin by an autocatalytic process. The syn-
thesized compounds were characterized by NMR spectroscopy and mass spectrometry,
and the reaction mechanism was discussed. The antitumor and neuroprotection activities
of these compounds were evaluated. The results showed that several compounds display
protection activity on H2O2-induced apoptosis of PC12 cells, which are more effective than
that of (±)-a-tocopherol Vitamin E (VE). Moreover, these compounds also show antitumor
activity against A549 and P388 cell lines.
© 2018 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.1. Introduction
Alkaloids are versatile natural products with various
bioactivities, among which isatin (indole-2,3-dione, a kind
of endogenous indole alkaloid) present in mammalian tis-
sues and fluids has drawnmuch attention from the fields of
chemistry and biology [1]. It has been identified as a se-
lective inhibitor of monoamine oxidase B [2] and is an
interesting compound involved in nerve protection. Be-
sides, isatin derivatives have been reported with various
activities [3e5]. The 3-hydroxyindole moiety has been
found in many alkaloid natural products, such as welwi-
tindolinone C, 3-hydroxyglucoisatisin, dioxibrassinine, and
donaxaridine [6], and it has also been found in many bio-
logically active molecules such as convolutamydines [7]en), xjhao@mail.kib.
d by Elsevier Masson SAS. Aand convolutamydines A and B, which show potent anti-
tumor activity against HL-60 cell line. It is an important
structural motif in proteasome inhibitors [8]. With an
active carboxyl group, isatin can easily transform to 3-
hydroxyindole by an addition reaction [5,9]. We have re-
ported the synthesis and bioactivity of several kinds of
isatin derivatives [5,10,11]; to explore the bioactivity of the
derivatives, a series of newcompounds, 3-ethyl-3-hydroxy-
indole-2-ones, were synthesized by an addition reaction,
and then we studied the cytoprotectivity of H2O2-induced
apoptosis of PC12 cells and the antitumor activity against
A549 and P388 cell lines.2. Experimental section
2.1. Materials
The agents and solvents of analytical reagent gradewere
purchased from Xi'an Chemical Co, Ltd and were used
without any further purification. NMR characterizationwasll rights reserved.
G. Chen et al. / C. R. Chimie 21 (2018) 471e474472performed using a Bruker DRX-400 spectrometer, 400 MHz
for 1H and 100 MHz for 13C. Mass spectra were recorded
using a Micromass Platform spectrometer with electron
impact mode at 75 eV.2.2. Synthesis of 3-ethyl-3-hydroxy-indole-2-ones
The addition reaction of Et2Zn and common aldehyde
ketone has been used for long time, but it was used for the
first time in the addition of N-substituted isatin and Et2Zn.
In this study, 1 mmol Et2Zn solution and 10 mL toluene
were added in a dried flask protected under nitrogen at-
mosphere. The flask was placed into an ice-water bath
cooled to 0 C. Then 1mmol N-substituted isatinwas added
to the flask, and the resulting solutionwas stirred at 0 C for
4 h. After the mixture was warmed to room temperature,
the reaction was quenched by adding a 10 mL saturated
NH4Cl aqueous solution. The aqueous layer was extracted
with AcOEt (310 mL). The AcOEt solution was dried over
anhydrous Na2SO4, and concentrated by vacuum. The
target product was obtained by purification with silica gel
flash column chromatography (hexane:AcOEt ¼ 10:1 to
4:1). The reaction is summarized in Scheme 1.2.3. Biological activity screening
The synthesized compounds were screened for their
biological activities on protective activity of H2O2-induced
apoptosis of PC12 cells and antitumor activity against A549
and P388 cell lines by the reported methods [5,12].
3. Results and discussion
3.1. Chemistry
The structure, yield, NMR, and MS data of the synthe-
sized 3-ethyl-3-hydroxy-indole-2-ones compounds in this
study are summarized in Table 1. From the results, it was
found that all the reactions provide high yields except the
reaction of Et2Zn and N-2-oxo-2-ethoxy-ethyl isatin, which
gave a yield of 65%. The reason may be due to the carboxyl
group on the N-substitutent, which can react with Et2Zn.
Nakazaki et al. [13] have reported the reaction between
alkyllithium and N-phenyl isatin catalyzed by LiBr with a
yield of 68e98%. It should be noted that the reaction was
carried out at 78 C, and use of cosolvents was required.
Kumar et al. [14] investigated the reaction between tri-
alkylaluminumwithout any catalyst at 70 C and found the
reaction is very rapid and yields are high. But more tri-
alkylaluminum was needed than the reaction molar ratio,
isatin:organoaluminum¼ 1:2.N O
O
ZnEt 2+
(1) Tolu
(2) sat. 
R
Scheme 1. The synthesis of 3-ethyThe mechanism is described in Scheme 2. In this reac-
tion, the Zn2þ coordinates with the O atom of the carboxyl
group in isatin, by which the carboxyl group is activated.
Then the CH3CH2 attacks the C atom of the activated
carboxyl group, by a classical addition reaction process, and
a zinc salt intermediate is formed accordingly. Through a
similar process, the zinc salt activates another molecule of
isatin and initiates another addition reaction, which results
in a bi-oxindole zinc salt. Finally, the target product, 3-
ethyl-3-hydroxy-indole-2-one, was produced by the hy-
droxylation process in a saturated aqueous solution of
NH4Cl.3.2. Biological activity
PC12 cell line derives from rat adrenal medulla, which
has been used to get detailed information about diseases
related to brain, such as hypoxia and Parkinson's disease. In
our study, PC12 cell has been used to evaluate the neuro-
protection activity of oxindole compounds [11]. In this
article, the neuroprotection of the 3-ethyl-3-hydroxy-
indole-2-ones in vitro screening results was evaluated, and
the results are shown in Table 2. From the result, it was
found that compounds DNO-2, DNO-3, and DNO-5 show
some protection activity on the H2O2-induced apoptosis of
PC12 cells with the higher activity than that of VE ((±)-a-
tocopherol), with the percentage of 34.3%, 32.2%, and 28.8%
at 2 mM, respectively. Also they are almost noncytotoxic
against the PC12 cell at the concentration less than 2e
20 mM, whereas DNO-1, DNO-2, DNO-6, and DNO-7 show
high cytotoxicity at 200 mM. Concerning the structure of
these compounds, the 3-ethyl-3-hydroxy-indole-2-ones
with N-alkyl groups show high neuroprotection activity,
and they are not cytotoxic against PC12 cell at the con-
centration less than 2e20 mM. The unsaturated C]C bond
in the N-substituent group can enhance the protection
activity, whereas the ester group and phenyl group can
decrease the activity and lead to high cytotoxicity against
PC12 cell.
Many isatin derivatives have been reported displaying
high antitumor activity [15,16]. In this article, the antitumor
activity of these compounds against A549 and P388 cell
lines was screened, and the results are summarized in Table
3. From this table, we can find that almost all compounds
show inhibition against both cancer cells at the concen-
tration of 100 mM. DBO-3, DBO-4, DBO-5, DBO-6, and DBO-
7 show high activity against A459 cell line, with the inhi-
bition percentagemore than 50% at 100 mM. Concerning the
structures of these compounds, the long chains contribute
to the high activity against the A459 cell line, and the
highest activity of DNO-6 may be due to the ester group in
the N-substituent group.ene
aqu. NH 4Cl N O
R
HO
l-3-hydroxy-indole-2-ones.
Table 1
The structure, yield, NMR, and MS of the synthesized 3-ethyl-3-hydroxy-
indole-2-ones.
Compound structure and
the number
Yield
(%)
NMR and MS
N O
HO
DBO-1
89 1H NMR (CDCl3, 400 MHz), d: 7.38
(1H, d, J¼ 7.6 Hz), 7.34 (1H, t,
J¼ 7.6 Hz), 7.11 (1H, t, J¼ 7.6 Hz),
6.85 (1H, d, J¼ 7.6 Hz), 3.20 (3H, s),
3.04 (1H, s), 1.99e2.07 (1H, m),
0.75 (3H, t, J¼ 7.6 Hz); 13C NMR
(CDCl3, 100 MHz), d: 178.3, 143.5,
129.7, 129.5, 128.7, 123.8, 123.1,
108.3, 31.4, 26.1, 7.5; MS (ESI) m/z:
214 (Mþ)
N O
HO
DBO-2
92 1H NMR (CDCl3, 400 MHz), d: 7.39
(1H, d, J¼ 7.2 Hz), 7.32 (1H, t,
J¼ 7.6 Hz), 7.10 (1H, t, J¼ 7.6 Hz),
6.86 (1H, d, J¼ 7.6 Hz), 3.75e3.85
(1H, m), 3.63e3.71 (1H, m), 3.45
(1H, br), 2.00e2.03 (2H, m), 1.26
(3H, t, J¼ 7.2 Hz) 0.72 (3H, t,
J¼ 7.6 Hz); 13C NMR (CDCl3,
100 MHz), d: 178.2, 143.6, 129.8,
129.5, 128.4, 124.0, 122.9, 108.4,
34.6, 31.7, 12.6, 7.6; MS (ESI) m/z:
228 (Mþ)
N O
HO
DBO-3
93 1H NMR (CDCl3, 400 MHz), d: 7.44
(1H, d, J¼ 7.2 Hz), 7.32 (1H, t,
J¼ 7.6 Hz), 7.10 (1H, t, J¼ 7.6 Hz),
6.85 (1H, d, J¼ 7.6 Hz), 3.76e3.80
(1H, m), 3.58e3.62 (1H, m), 3.21
(1H, br), 2.00e2.04 (2H, m), 1.70
e1.73 (2H, m), 1.32e1.38 (2H, m),
0.91 (3H, t, J¼ 7.2 Hz), 0.73 (3H, t,
J¼ 7.6 Hz); 13C NMR (CDCl3,
100 MHz), d: 178.1, 143.3, 129.7,
129.0, 123.9, 122.8, 108.5, 39.8,
31.6, 26.9, 22.4, 13.1, 7.6; MS (ESI)
m/z: 256 (Mþ)
N O
HO
DBO-4
88 1H NMR (CDCl3, 400 MHz), d: 7.38
(1H, d, J¼ 7.6 Hz), 7.32 (1H, t,
J¼ 7.6 Hz), 7.10 (1H, t, J¼ 7.6 Hz),
6.86 (1H, d, J¼ 8.0 Hz), 3.72e3.80
(1H, m), 3.57e3.65 (1H, m), 3.13
(1H, s), 1.90e2.18 (2H, m), 1.60
e1.66 (2H, m), 1.34e1.45 (4H, m),
0.95 (3H, t, J¼ 7.6 Hz), 0.73 (3H, t,
J¼ 7.6 Hz); 13C NMR (CDCl3,
100 MHz), d: 178.1, 143.1, 129.9,
129.5, 123.9, 122.8, 108.6, 40.0,
31.7, 31.4, 27.3, 26.6, 22.5, 13.9,
7.6; MS (ESI) m/z: 284 (Mþ)
N O
HO
DBO-5
85 1H NMR (CDCl3, 400 MHz), d: 7.40
(1H, d, J¼ 7.6 Hz), 7.31 (1H, td,
J¼ 7.6, 1.2 Hz), 7.10 (1H, t,
J¼ 7.6 Hz), 6.84 (1H, d, J¼ 8.0 Hz),
5.79e5.85 (1H, m), 5.20e5.26 (2H,
m), 4.25 (1H, dd, J¼ 15.6, 7.6 Hz),
4.20 (1H, dd, J¼ 15.6, 7.6 Hz), 3.11
(1H, s), 2.03 (2H, q, J¼ 7.6 Hz), 0.76
(3H, t, J¼ 7.6 Hz); 13C NMR (CDCl3,
100 MHz), d: 178.1, 142.8, 131.2,
129.7, 129.5, 123.9, 123.1, 117.7,
109.3, 42.3, 31.7, 7.7; MS (ESI) m/z:
240 (M þ Naþ)
(continued on next page)
Table 1 (continued )
Compound structure and
the number
Yield
(%)
NMR and MS
N O
HO
O
OC2H5
DBO-6
65 1H NMR (CDCl3, 400 MHz), d: 7.39
(1H, d, J¼ 7.6 Hz), 7.31 (1H, t,
J¼ 7.16 Hz), 7.13 (1H, t, J¼ 7.6 Hz),
6.72 (1H, d, J¼ 7.6 Hz), 4.62 (1H, d,
J¼ 17.6 Hz), 4.18e4.27 (3H, m), 3.0
(1H, s), 2.04 (2H, q, J¼ 7.2 Hz), 1.25
(3H, t, J¼ 7.2 Hz), 0.77 (3H, t,
J¼ 7.6 Hz); 13C NMR (CDCl3,
100 MHz), d: 178.1, 167.5, 142.2,
129.6, 129.5, 124.0, 123.4, 108.3,
61.8, 41.3, 31.7, 14.1, 7.5; MS (ESI)
m/z: 286 (M þ Naþ)
N O
HO
DBO-7
87 1H NMR (CDCl3, 400 MHz), d: 7.39
(1H, d, J¼ 7.6 Hz), 7.19e7.30 (6H,
m), 7.07 (1H, d, J¼ 8.0 Hz), 5.02
(1H, d, J¼ 15.6 Hz), 4.76 (1H, d,
J¼ 15.6 Hz), 3.06 (1H, s), 2.03e3.01
(2H, m), 0.79 (3H, t, J¼ 7.6 Hz); 13C
NMR (CDCl3, 100 MHz), d: 178.4,
142.7, 129.7, 129.5, 128.8, 128.6,
127.7, 127.6, 126.7, 123.9, 123.1,
109.4, 43.8, 31.7, 7.7; MS (ESI) m/z:
290 (Mþ)
Scheme 2. The reaction between Et2Zn and N-substituted isatin.
Table 2
Inhibitory and protective effects of 3-ethyl-3-hydroxy-indole-2-ones on
PC12 cell.
Compound Inhibitory effecta (%) Protective effectb (%)
200 mM 20 mM 2 mM 200 mM 20 mM 2 mM
DBO-1 23.6 0 0 e 25.1 15.4
DBO-2 33.9 0 0 e 36.5 34.3
DBO-3 0 0 0 0 37.7 32.2
DBO-4 0 0 0 49.0 8.4 2.7
DBO-5 0 0 5.7 0 53.9 28.8
DBO-6 37.6 16.5 9.3 e 0 1.8
DBO-7 84.4 11.9 5.9 e 0 11.9
VE 0.0 22.5
a Inhibition against PC12 cell growth.
b Protective effect on the H2O2-induced apoptosis of PC12 cells.
G. Chen et al. / C. R. Chimie 21 (2018) 471e474 473
Table 3
In vitro cytotoxicity against A549 and P388 cell lines.
Compound P388 (%) A459 (%)
100 mM 10 mM 100 mM 10 mM
DBO-1 38.9 20.5 40.5 8.2
DBO-2 36.8 19.0 47.3 9.8
DBO-3 32.6 16.7 55.8 13.9
DBO-4 20.0 6.7 64.1 14.1
DBO-5 13.6 13.7 62.0 14.4
DBO-6 35.4 17.1 70.2 12.6
DBO-7 22.8 21.3 54.8 9.5
G. Chen et al. / C. R. Chimie 21 (2018) 471e4744744. Conclusions
A series of 3-ethyl-3-hydroxy-indole-2-ones were syn-
thesized through the autocatalytic addition reaction of
Et2Zn and N-substituted isatin and characterized by NMR
and MS. The antitumor and neuroprotection activities of
these compounds were evaluated and showed protection
activity on the apoptosis of PC12 cells induced by H2O2,
which are more effective than that of (±)-a-tocopherol
Vitamin E (VE) at 2 and 20 mM.Moreover, these compounds
also showed antitumor activity against A549 and P388 cell
lines.
Acknowledgments
This research was financially supported by the grants
from National Science Foundation of China (50874092) and
Scientific Research Program Funded by Shaanxi Provincial
Education Department (16JS094). The authors would like tothank Professor Allan Prior, Daniel K. Inouye College of
Pharmacy, University of Hawaii at Hilo, for the language
revision.References
[1] V. Glover, M.A. Reveley, M. Sandler, Biochem. Pharmacol. 29 (1980)
467.
[2] V. Glover, A. Medvedev, M. Sandler, Life Sci. 57 (1995) 2073.
[3] S.E. Webber, J. Tikhe, S.T. Worland, S.A. Fuhrman, T.F. Hendrickson,
D.A. Matthews, R.A. Love, A.K. Patick, J.W. Meador, R.A. Ferre,
E.L. Brown, D.M. DeLisle, C.E. Ford, S.L. Binford, J. Med. Chem. 39
(1996) 5072.
[4] K. Parthasarathy, C. Praveen, C. Balachandran, P. Senthil kumar,
S. Ignacimuthu, P.T. Perumal, Bioorg. Med. Chem. Lett. 23 (2013)
2708.
[5] G. Chen, Y. Wang, S. Gao, H.P. He, S.L. Li, J.X. Zhang, J. Ding, X.J. Hao, J.
Heterocycl. Chem. 46 (2009) 217.
[6] T. Kawasaki, M. Nagaoka, T. Satoh, A. Okamoto, R. Ukon, A. Ogawa,
Tetrahedron 60 (2004) 3493.
[7] Y. Kamano, H.P. Zhang, Y. Ichihara, H. Kizu, K. Komiyama, G.R. Pettit,
Tetrahedron Lett. 36 (1995) 2783.
[8] B.K. Albrecht, R.M. Williams, Org. Lett. 5 (2003) 197.
[9] G. Chen, Y. Wang, H.P. He, S. Gao, X.S. Yang, X.J. Hao, Heterocycles 68
(2006) 2327.
[10] G. Chen, H.P. He, J. Ding, X.J. Hao, Heterocycl. Commun. 15 (2009)
355.
[11] G. Chen, Y. Wang, X.J. Hao, S. Zh Mu, Q.Y. Sun, Chem. Cent. J. 5 (2011)
37.
[12] T.J. Mosmann, J. Immunol. Methods 65 (1983) 55.
[13] A. Nakazaki, A. Mori, S. Kobayashi, T. Nishikawa, Tetrahedron Lett.
53 (2012) 7131.
[14] G.S. Kumar, P. Ramesh, A.S. Kumar, A. Swetha, H.M. Meshram, Tet-
rahedron Lett. 54 (2013) 5048.
[15] P.S. Prathima, P. Rajesh, J.V. Rao, U.S. Kailash, B. Sridhar, M.M. Rao,
Eur. J. Med. Chem. 84 (2014) 155.
[16] W.M. Eldehna, A. Altoukhy, H. Mahrous, H.A. Abdel-Aziz, Eur. J. Med.
Chem. 90 (2015) 684.


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