Synthesis and bioactivity evaluation of 3-hydroxy-3-(phenylethynyl)indol-2- one analogues

Article abstract of DOI:10.1002/jhet.58

A series of propargylic alcohol was synthesized by the addition of phenylacetylene to isatin and its N-substituted derivatives for the first time. This reaction involves activation of zinc reagent via coordination with carbonyl substrates that behave ''li

Full text of DOI:10.1002/jhet.58

March 2009
Synthesis and Bioactivity Evaluation
of 3-Hydroxy-3-(phenylethynyl)indol-2-one Analogues
217
Gang Chen,a,b Ye Wang,c Suo Gao,a Hong-Ping He,a Shun-Lin Li,a
Jian-Xin Zhang,c Jian Ding,d and Xiao-Jiang Haoa,c*
aState Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of
Botany, Chinese Academy of Sciences, Kunming 650204, People’s Republic of China
bCollege of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an,
Shaanxi 710065, People’s Republic of China
cKey Laboratory of Chemistry for Natural Products of Guizhou Province and Chinese Academy of
Sciences, Guiyang 550002, People’s Republic of China
dShanghai Institutes for Biological Sciences, Shanghai 201203, People’s Republic of China
*E-mail: haoxj@mail.kib.ac.cn
Received December 11, 2007
DOI 10.1002/jhet.58
Published online 13 April 2009 in Wiley InterScience (www.interscience.wiley.com).
A series of propargylic alcohol was synthesized by the addition of phenylacetylene to isatin and its
N-substituted derivatives for the first time. This reaction involves activation of zinc reagent via coordi-
nation with carbonyl substrates that behave ‘‘ligand like.’’ The bioactivities on protective effect on the
apoptosis of PC12 cells induced by H2O2 and cytotoxicity against lung cancer A549 and P388 cell line
of these compounds were investigated, and several compounds showed potent activities.
J. Heterocyclic Chem., 46, 217 (2009).
INTRODUCTION
In this article, we describe the addition of phenyl-acety-
lene to isatin and (N-substituted) isatins promoted by
Et2Zn without employing specific ligands to form 3-
hydroxy-3-(phenylethynyl)indol-2-one analogues (Scheme
1). Furthermore, the bioactivity on neuroprotection and
antitumor of these isatin derivatives was evaluated for the
first time.
The reactions, which lead to carbon–carbon bond for-
mation by addition of nucleophiles to carbonyl group
electrophiles, are of great importance in the continuing
development of efficient processes for synthesis. Addition
of acetylides to carbonyl substrates has attracted the atten-
tion of organic chemists and is still a very active field of
organic reactions. The reaction gives access to prepara-
tion of propargylic alcohols, which are well known as ver-
satile building blocks in the synthesis of complex natural
products [1,2] and can be transformed into other func-
tional groups, such as chalcones [3], and oxasilacyclo-
pentene [4,5]. The addition of alkynes to ketones is also a
very useful practical strategy to create tertiary alcohols
with a new stereogenic center [6–8].
RESULTS AND DISCUSSION
Chemistry. The in situ generated ZnMe2-acetylides
from Me2Zn and acetylides have been used in a direct
addition process with aldehydes and ketones without the
employment of specific ligands [18]. In our preliminary
studies, the reaction was carried out at room tempera-
ture. Unfortunately, the outcome was found very com-
plex (by TLC), and the desired product was in a low
yield after purification by flash chromatography. Higher
yields were obtained at lower temperatures. Also, a vari-
ety of substrates were examined at 0ꢀC, and the results
are summarized in Table 1.
Some natural products with the structure of propargylic
alcohol showed potent bioactivities, such as panaxyno1
(PNN), which performs potent activities on neuro-protec-
tion [9] and antitumor [10]. Isatin has been found in many
natural products, with the function of modulating bio-
chemical processes [11–13]. The advances in the use of
isatin for organic synthesis and a survey of its biological
activities are continuously reported [14–16]. In 1963,
Ried reported the synthesis of 3-hydroxy-3-(phenyl-ethy-
nyl)indol-2-one for the first time, with a low yield of 28%
[17]. But in the following years, there was no further
attention paid to the synthesis and its bioactivity.
It can be found from Table 1 that the temperature
deeply effects the reaction of the addition of phenyl-
acetylene to (N-methyl) isatin. The reaction at relatively
higher temperature (rt) gave poor yield, and the yields
increased as the temperature is decreased, and the yield
C
V
2009 HeteroCorporation

218
G. Chen, Y. Wang, S. Gao, H.-P. He, S.-L. Li, J.-X. Zhang, J. Ding, and X.-J. Hao
Vol 46
Scheme 1
Scheme 2
was highest at 0ꢀC. Significantly, lower temperatures
such as ꢁ10ꢀC did not improve the yield.
In consideration of the accepted mechanism for ligand-
assisted addition of Et2Zn to aldehydes, Pier et al. [18]
investigated the possibility that a zinc-ketone complex
acts as a bifunctional catalyst, bringing together an addi-
tional 1 equiv of ketone and zinc reagent in a bicyclic
transition state (TS). On the basis of the proposed mecha-
nism, we assumed that this reaction involves activation of
the zinc reagent via coordination with isatins. The acti-
vated TS are shown in Scheme 2. In the TS (G), two mol-
ecules of (N-substituted) isatin behaved in a ‘‘ligand like’’
fashion to activate a phenylacetylene by two oxygen
atoms coordinating with two Zn as bridged-atoms. The
addition of activated phenylacetylene to a neighbor car-
bonyl formed H, and F was released into another cycle.
The desired product (I) is provided through hydrolysis in
the final step of the reaction.
apoptosis of PC12 cells induced by H2O2 and cytotoxic-
ity against A549 and P388 cell line at various concen-
trations by the reported methods [19,20]. The neuropro-
tection and cytotoxicity in vitro screening results are
shown in Table 2.
Because the substrates have more than one coordina-
tive and reactive point, the TS might be more complex,
which lead to several side reactions, the addition of
ethyl to isatins can be considered as an example. We
could find the yields were very low in entries 7 and 11
because of the more reactive substrates. (N-Acyl) isatins
(entries 12 and 13) were also introduced into this reac-
tion, but the product was too complex to determine
whether there was a desired product.
From the table, we find that compounds 4, 5, and 6
showed potent activity, which were more effective than
VE ((ꢂ) a-Tocophreol), with the percentage of 46.62,
65.93, and 35.89% at 2 lg/mL respectively, as com-
pound 5 was not cytotoxic against PC12 cell under the
concentration of 2–200 lg/mL, whereas compounds 4
and 6 showed some cytotoxicity. Other compounds were
either inactive or cytotoxic against PC12 cell. The
results of in vitro cytotoxicity of compounds 2–9 against
A549 and P388 cell line were given in Table 3.
Biological activity. Compounds 2–9 were screened
for their biological activities on protective effect on the
From the results, it was found that almost all com-
pounds could inhibit both cancer cells effectively at the
concentration of 100 lM. Compounds 6 and 8 showed
Table 1
Alkynylation of (N-substituted)isatins with phenylacetylene using
Et2Zn as promoter.
Table 2
Protective effect on the apoptosis of PC12 cells induced by H2O2.
Time Temp. Yield
(ꢀC)
Entry
R
(h)
(%)
Compound
Inhibition of apoptosis
of PC12 cells induced
by H2O2 (%)
1
2
H
12
12
12
12
24
12
12
12
12
12
12
12
12
12
0
25
10
0
38.7
8.1
1
2
2
2
2
3
4
5
6
7
8
9
/
Inhibition of PC12 cell
(%)
CH3
CH3
CH3
CH3
C2H5
(CH2)2CH3
(CH2)3CH3
(CH2)5CH3
CH2CHCH2
Bn
3
4
31.3
58.1
51.6
66.7
60
Compound 200 lM 20 lM 2 lM 200 lM 20 lM 2 lM
5
ꢁ10
6
7
0
2
3
55.56
54.36
18.77
0.00
18.43 26.61
3.59 15.02
–
–
–
0
–
0
0
8
9
0
0
70.2
71.3
40.5
67.9
35.8
/
4
5
0
3.53
0
–
44.20
43.70 46.62
62.88 65.93
0
10
11
12
13
14
0
0
6
7
90.06
89.33
89.51
29.56
14.67
5.66
7.41
14
5.63
2.99
2.36
9.07
–
–
–
–
0
0
0
0
35.89
0
CH2CO2C2H5
COCH3
COCH3CH3
0
8
0
0
0
9
VE
0
22.46
/
/
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

March 2009
Synthesis and Bioactivity Evaluation
of 3-Hydroxy-3-(phenylethynyl)indol-2-one Analogues
219
Table 3
In vitro cytotoxicity against A549 and P388 cell line.
35.2, 12.4; MS (ESI): m/z 300 (M þ Naþ). HR-ESI-MS: m/z
300.1006 (calcd. for C18H15NNaOþ2 300.1000); Anal. Calcd
for C18H15NO2: C, 77.96; H, 5.45; N, 5.05. Found: C, 77.78;
H, 5.41, N, 5.11.
P388 (%)
A459 (%)
1-Propyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (4).
1H NMR (CDCl3, 400 MHz), d: 7.62 (1H, d, J ¼ 7.6 Hz),
7.27–7.45 (6H, m), 7.16 (1H, t, J ¼ 7.6 Hz), 6.89 (1H, d, J ¼
7.6 Hz), 3.78 (2H, m), 3.75 (1H, s), 1.31 (3H, t, J ¼ 7.2 Hz).
13C NMR (CDCl3, 100 MHz), d: 173.5, 142.2, 132.0, 130.4,
129.2, 128.9, 128.1, 124.9, 123.5, 121.7, 108.9, 86.2, 85.6,
35.2, 12.4; MS (ESI): m/z 314 (M þ Naþ). HR-ESI-MS: m/z
314.1158 (calcd. for C19H17NNaOþ2 314.1157); Anal. Calcd
for C19H17NO2: C, 78.33; H, 5.88; N, 4.81. Found: C, 78.30;
H, 5.76, N, 4.45.
Compound
100 lM
10 lM
100 lM
10 lM
2
3
4
5
6
7
8
9
48.7
54.6
54.0
17.8
97.2
61.4
68.7
97.9
9.4
4.5
10.1
8.1
0
2.5
5.6
14.4
75.6
58.5
50.7
55.8
95.3
76.5
76.0
85.9
12.2
0
0
0
3.7
9.8
14.2
3.2
1
1-Butyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (5). H
NMR (CDCl3, 400 MHz), d: 7.62 (1H, d, J ¼ 7.2 Hz), 7.25–
7.44 (6H, m), 7.14 (1H, t, J ¼ 7.6 Hz), 6.87 (1H, d, J ¼ 8.0
Hz), 3.83 (1H, s), 3.68 (2H, m), 7.74 (2H, m), 0.98 (3H, t,
J ¼ 7.2 Hz); 13C NMR (CDCl3, 100 MHz), d: 173.7, 142.3,
132.1, 130.3, 129.2, 128.9, 128.1, 124.9, 123.5, 121.7, 108.9,
86.2, 85.7, 33.2, 25.7, 12.8; MS (ESI) m/z: 328 (M þ Naþ).
HR-ESI-MS: m/z 328.1318 (calcd. for C20H19NNaOþ2 328.1313);
Anal. Calcd for C20H19NO2: C, 78.66; H, 6.27; N, 4.59. Found:
C, 78.67; H, 6.33, N, 4.42.
potent activity, with the inhibition percentage of 97.2,
95.3 and 97.9, 85.9, only compound 5 was inactive
against P388.
EXPERIMENTAL
In an oven-dried flask connected to a nitrogen/vacuum line
was placed phenylacetylene (1.6 mmol) followed by the slow
addition of Et2Zn 1M solution in toluene (1.5 mmol, 1.5 mL)
(2.5 mmol Et2Zn for isatin). The resulting solution was stirred
at room temperature for 1 h and then cooled to 0ꢀC with an
ice-water bath. The (N-substituted) isatin (1 mmol) was added
to the reaction mixture. The resulting solution was stirred at
0ꢀC for 12 h, and then warmed to room temperature. The reac-
tion was quenched with water (10 mL). The mixture was
stirred for 10 min and then filtered over Celite. The mixture
evaporated under reduced pressure and was purified by flash
chromatography (silica gel, petroleum ether/ethyl acetate ¼
10: 1–4: 1).
1
1-Hexyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (6). H
NMR (CDCl3, 400 MHz), d: 7.61 (1H, d, J ¼ 7.6 Hz), 7.43
(2H, m), 7.37 (1H, t, J ¼ 8.0 Hz), 7.30 (2H, m), 7.15 (1H, t,
J ¼ 7.6 Hz), 6.88 (2H, d, J ¼ 8.0 Hz), 3.71 (2H, t, J ¼ 6.8
Hz), 3.64 (1H, s), 1.70 (3H, m), 1.25–1.38 (5H, m), 0.87 (3H,
t, J ¼ 7.2 Hz); 13C NMR (CDCl3, 100 MHz), d: 173.9, 142.4,
132.1, 130.1, 129.0, 128.9, 128.2, 124.9, 123.5, 121.8, 109.1,
86.1, 85.6, 69.5, 48.6, 40.0, 31.1, 28.9, 26.8, 22.3; MS (ESI):
m/z 356 (M þ Naþ). HR-ESI-MS: m/z 356.1625 (calcd. for
C22H23NNaOþ2 356.1626); Anal. Calcd for C22H23NO2: C,
79.25; H, 6.95; N, 4.20. Found: C, 79.31; H, 6.78, N, 4.41.
1
1-Allyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (7). H
1
NMR (CDCl3, 400 MHz), d: 7.62 (1H, d, J ¼ 7.6 Hz), 7.44
(2H, d, J ¼ 7.6 Hz), 7.26–7.36 (4H, m), 7.15 (1H, t, J ¼ 7.6
Hz), 6.86 (1H, d, J ¼ 7.6 Hz), 5.85 (1H, m), 5.26 (2H, m),
4.36 (2H, m), 3.80 (1H, s); 13C NMR (CDCl3, 100 MHz), d:
173.8, 143.0, 130.6, 133.1, 131.3, 129.2, 128.4, 128.2, 124.9,
123.6, 121.4, 118.8, 109.4, 86.2, 85.5, 69.5, 43.3; MS (ESI):
m/z 312 (M þ Naþ). HR-ESI-MS: m/z 312.9997 (calcd. for
C19H15NNaOþ2 312.1000); Anal. Calcd for C19H15NO2: C,
78.87; H, 5.23; N, 4.84. Found: C, 78.66; H, 5.15, N, 4.77.
1-Benzyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (8).
1H NMR (CDCl3, 400 MHz), d: 7.62 (1H, d, J ¼ 7.2 Hz),
7.45 (2H, d, J ¼ 7.6 Hz), 7.23–7.33 (4H, m), 7.12 (1H, t, J ¼
7.6 Hz), 6.72 (1H, d, J ¼ 7.6 Hz), 4.94 (2H, s), 3.80 (1H, s);
13C NMR (CDCl3, 100 MHz), d: 174.1, 142.2, 135.0, 132.0,
130.3, 128.9, 128.8, 128.2, 127.7, 127.1, 124.8, 123.7, 121.6,
108.9, 86.5, 85.5, 69.6, 44.1. MS (ESI): m/z 362 (M þ Naþ).
HR-ESI-MS: m/z 362.1157 (calcd. for C23H17NNaO2þ
362.1157); Anal. Calcd for C23H17NO2: C, 81.40; H, 5.05; N,
4.13. Found: C, 81.51; H, 5.13, N, 4.22.
3-Hydroxy-3-(phenylethynyl)indolin-2-one (1). H NMR
(CD3OD, 400 MHz), d: 7.50 (1H, d, J ¼ 7.2 Hz), 7.43 (2H, m),
7.30–7.33 (4H, m), 7.10 (1H, m), 6.91 (1H, d, J ¼ 8.0 Hz);
13C NMR (CDCl3, 100 MHz), d: 177.6, 142.4, 132.8, 132.2,
131.3, 130.0, 129.5, 125.6, 124.2, 123.3, 111.5, 87.3, 86.3;
MS (ESI): m/z 272 (M þ Naþ). HR-ESI-MS: m/z 272.0684
(calcd. for C16H11NNaO2þ 272.0687); Anal. Calcd for
C16H11NO2: C, 77.10; H, 4.45; N, 5.62. Found: C, 77.33;
H, 4.14, N, 5.52.
1-Methyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (2).
1H NMR (CDCl3, 400 MHz), d: 7.62 (1H, d, J ¼ 6.8 Hz),
7.43 (2H, d, J ¼ 6.8 Hz), 7.38 (1H, t, J ¼ 7.6 Hz), 7.24–7.30
(3H, m), 7.16 (1H, t, J ¼ 7.6 Hz), 6.85 (1H, d, J ¼ 8.0 Hz),
4.05 (1H, s), 3.23 (3H, s); 13C NMR (CDCl3, 100 MHz), d:
173.9, 142.9, 132.0, 130.5, 128.9, 128.8, 128.2, 124.7, 123.7,
121.5, 108.8, 86.3, 85.4, 69.5, 26.6; MS (ESI): m/z 286 (M þ
Naþ). HR-ESI-MS: m/z 286.08849 (calcd. for C17H13NNaOþ2
286.0844); Anal. Calcd for C17H13NO2: C, 77.55; H, 4.98; N,
5.32. Found: C, 77.43; H, 4.77, N, 5.23.
1
1-Ethyl-3-hydroxy-3-(phenylethynyl)indolin-2-one (3). H
Ethyl-2-(3-hydroxy-2-oxo-3-(phenylethynyl)indolin-1-yl)-
1
NMR (CDCl3, 400 MHz), d: 7.62 (1H, d, J ¼ 7.6 Hz), 7.27–
7.45 (6H, m), 7.16 (1H, t, J ¼ 7.6 Hz), 6.89 (1H, d, J ¼
7.6 Hz), 3.78 (2H, m), 3.75 (1H, s), 1.31 (3H, t, J ¼ 7.2 Hz).
13C NMR (CDCl3, 100 MHz), d: 173.5, 142.2, 132.0, 130.4,
129.2, 128.9, 128.1, 124.9, 123.5, 121.7, 108.9, 86.2, 85.6,
acetate (9). H NMR (CDCl3, 400 MHz), d: 7.64 (1H, d, J ¼
7.6 Hz), 7.43 (2H, d, J ¼ 7.2 Hz), 7.25–7.37 (4H, m), 7.17
(1H, t, J ¼ 7.6 Hz), 7.66 (1H, d, J ¼ 8.0 Hz), 4.48 (2H, s),
4.21 (2H, q, J ¼ 7.2 Hz), 3.76 (1H, s), 1.25 (3H, t, J ¼ 7.2
Hz); 13C NMR (CDCl3, 100 MHz), d: 173.8, 167.1, 141.2,
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G. Chen, Y. Wang, S. Gao, H.-P. He, S.-L. Li, J.-X. Zhang, J. Ding, and X.-J. Hao
Vol 46
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358.1055); Anal. Calcd for C20H17NO4: C, 71.63; H, 5.11; N,
4.18; O, 19.08. Found: C, 71.58; H, 5.20, N, 4.23.
Acknowledgment. This work was financially supported by Gov-
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Science Research Plan Projects of Shaanxi Science and Technol-
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