Synthesis and cytotoxic activities of a series of novel N -methyl-bisindolylmaleimide amide derivatives

Article abstract of DOI:10.1080/10286020.2013.877452

A novel series of N-methyl-bisindolylmaleimides were synthesized and evaluated for their inhibitory activities against nine tumor cell lines. Some of the compounds showed an interesting activity against the tested cell lines. The most potent compounds 5e

Full text of DOI:10.1080/10286020.2013.877452

This article was downloaded by: [University of Waterloo]
On: 16 December 2014, At: 00:13
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Asian Natural Products
Research
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/ganp20
Synthesis and cytotoxic activities
of a series of novel N-methyl-
bisindolylmaleimide amide derivatives
Ke Wanga & Zhan-Zhu Liua
a State Key Laboratory of Bioactive Substance and Function of
Natural Medicines, Institute of Materia Medica, Peking Union
Medical College and Chinese Academy of Medical Sciences,
Beijing, 100050, China
Published online: 23 Jan 2014.
Click for updates
To cite this article: Ke Wang & Zhan-Zhu Liu (2014) Synthesis and cytotoxic activities of a series of
novel N-methyl-bisindolylmaleimide amide derivatives, Journal of Asian Natural Products Research,
16:3, 296-303, DOI: 10.1080/10286020.2013.877452
To link to this article: http://dx.doi.org/10.1080/10286020.2013.877452
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Journal of Asian Natural Products Research, 2014
Vol. 16, No. 3, 296–303, http://dx.doi.org/10.1080/10286020.2013.877452
Synthesis and cytotoxic activities of a series of novel
N-methyl-bisindolylmaleimide amide derivatives
Ke Wang and Zhan-Zhu Liu*
State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of
Materia Medica, Peking Union Medical College and Chinese Academy of Medical Sciences,
Beijing 100050, China
(Received 29 September 2013; final version received 16 December 2013)
A novel series of N-methyl-bisindolylmaleimides were synthesized and evaluated for
their inhibitory activities against nine tumor cell lines. Some of the compounds showed
an interesting activity against the tested cell lines. The most potent compounds 5e and
5j displayed antiproliferative activity with 50% inhibitory concentration values in the
mM range against some tested cell lines.
Keywords: bisindolylmaleimide; conjugate; cytotoxic activity
1. Introduction
2. Results and discussion
The family of bisindolylmaleimides natu-
ral products is extremely interesting owing
to the broad spectrum of biological
properties that they possess, including
antimicrobial, hypotensive, cell cytotox-
icity, and inhibition of platelet aggregation
[1–4]. Furthermore, bisindolylmaleimide
derivatives [5–7], such as enzastaurin
(LY317615), have entered clinical trials
for the treatment of cancer [8,9] (Figure 1).
Previously, we reported the synthesis
and cytotoxic evaluation of a series
of novel N-methyl-bisindolylmaleimide
amino acid ester conjugates [10–12]. In
this article, as part of our ongoing studies
concerning the preparation of potential
antitumor compounds, we designed and
synthesized a series of novel N-methyl-
bisindolylmaleimides derivatives. The
antiproliferative activities of these com-
pounds against nine tumor cell lines were
evaluated.
2.1 Chemistry
Bisindolylmaleimides 5a–5m were pre-
pared as shown in Scheme 1. Compound 2
was synthesized following the method
described in the literature [13,14]. Indolyl-
lithium was coupled with N-methyl-
dibromomaleimide 2 to afford the bisindo-
lylmaleimide 3. Alkylation of bisindolyl-
maleimide 3 with 2-bromoethylamine in the
presence of NaH gave amine 4 [15].
Compound 4 was coupled with various
acids in the presence of 4-(dimethylamino)
pyridine (DMAP) and 1-(3-dimethylamino-
propyl)-3-ethylcarbodi-imide hydrochlo-
ride (EDC) to give the target compound 5
(Scheme 1).
2.2 Pharmacology
By the MTT assay, cytotoxicity of these
derivatives was evaluated against nine
human cancer cell lines: human intestinal
*Corresponding author. Email: liuzhanzhu@imm.ac.cn
q 2014 Taylor & Francis

Journal of Asian Natural Products Research
297
H
N
H
N
O
O
O
O
H
N
O
O
N
H
N
N
N
N
Cl
Cl
O
N
H
N
H
OH
HO
OH
O
N
enzastaurin (LY317615)
Rebeccamycin
Figure 1. Structures of typical bisindolylmaleimides.
Arcyriarubin A
N
O
O
N
O
O
N
c
d
O
O
a
b
N
N
N
H
N
H
N
H
Br
Br
1
2
3
4
H2N
N
O
O
e
N
N
H
HN
O
R
5
R-(5a–5n) :
N
5a=
5b=
5g=
5l=
5c=
5h=
5d=
5e=
5j=
O
O
O
N
O
O
NO2
O
O
N
N
O
N
5f=
5i=
N
H
5k=
5m=
N
O
F
Scheme 1. Reagents and conditions: (a) NBS, THF, (b) HNO3, 46%; (c) indole, LiHMDS, toluene,
73%; (d) BrCH2CH2NH2, NaH, DMF, 808C, 48%; (e) EDC, DMAP, CH2Cl2, 50–90%.

298
K. Wang and Z.-Z. Liu
adenocarcinoma (HCT-8), human hepa-
toma cell (BEL-7402), human ovarian
carcinoma (A2780), human breast carci-
noma (MCF-7), non-small-cell lung carci-
noma (A549), human gastric carcinoma
(BGC-823), human kidney carcinoma
(Ketr3), oral squamous cell carcinoma
(KB), and human cervical carcinoma cell
(HeLa). The results of cytotoxicity studies
are summarized in Table 1.
8.32mM, but it showed moderate or weak
activity against the other cell lines with IC50
values of40–100 mM. Compound5iwith2-
indolyl group displayed cytotoxic activities
against MCF-7 and KB cell lines, with IC50
values of 12.95 and less than 10mM, but it
showed moderate cytotoxic activities
against A549, BGC-823, Ketr3, and HeLa
cell lines with IC50 values of 38–72mM.
In conclusion, a series of novel aryl-
and heteroaryl-N-methyl-bisindolylmalei-
mides were prepared. Some compounds
showed antiproliferative activity and
selectivity against nine human cancer cell
lines. Further studies on the mechanism of
action and the structure–activity relation-
ship of these compounds are in progress
and will be reported in due course.
The data in Table 1 indicate that some
compounds exhibited moderate to higher
antiproliferative activity against the tested
cancer cells than the control compound.
Bearingonemethoxylgrouponthearomatic
derivatives, compound5jexhibited the most
potent inhibitory activity against HCT-8,
MCF-7, A549,KB, andHeLacelllines,with
the 50% inhibitory concentration (IC50)
values of 0–10 mM. Compound 5j showed
moderate activity against BEL-7402,
A2780, BGC-823, and Ketr3 cell lines,
with IC50 values of 15–25 mM (Table 1).
Changing the methoxyl group from the
ortho (5j) to the para (5k) position reduced
cytotoxicity to an IC50 value of higher than
100 mM. Bearing two or three methoxyl
groups on the aromatic derivatives, com-
pound 5a was inactive to all tumor cell lines.
Compound 5c only exhibited cytotoxicity
against Ketr3 cell line with IC50 value of
59.43 mM. Compound 5b bearing a nitro
group exhibited inhibitory activities against
KB cell line with an IC50 value of 4.26mM,
while compound 5b was inactive to all the
other tumor cell lines.
3. Experimental
3.1 General experimental procedures
NMR spectra were recorded on a Varian
Oxford 300 (1H: 300 MHz, 13C: 75MHz) or
Varian Oxford 400 (1H: 400 MHz, 13C:
100 MHz) (Varian, Palo Alto, CA, USA),
chemical shifts (d) are expressed in ppm,
and the following abbreviations are used:
singlet (s), doublet (d), triplet (t), doubled
doublet (dd), and multiplet (m). HR-MS
were carried out by using Agilent LC/MSD
TOF (Santa Clara, CA, USA). Starting
materials, reagents, and solvents were
purchased from commercial suppliers and
purified before use.
As for the six heterocyclic derivatives,
compound 5e with 2-pyridyl group exhib-
ited broad-spectrum inhibitory activities
against the tested cell lines, with IC50 values
of 0–35mM except for A2780 and BGC-
823. Compound 5d with 4-pyridyl group
and compound 5f with 3-pyridyl group
exhibited inhibitory activities against all the
tested cell lines, with IC50 values of 10–
35mM. Compound 5h with 2-pyrazinyl
group displayed cytotoxic activities against
HCT-8, MCF-7, Ketr3, and KB cell lines,
with IC50 values of 10.98, 14.62, 24.34, and
3.2 Cytotoxicity assay
The tumor cell lines panel consisted of
BCT-8, BEL-7402, A2780, MCF-7, A549,
BGC-823, Ketr3, KB, and HeLa. Human
cancer cells were cultured in PRMI1640 or
DMEM/F12 supplemented with 10% fetal
bovine serum, containing penicillin and
streptomycin at 378C and humidified at 5%
CO2. Briefly, cells were plated in the
appropriate media on 96-well plates
in a 100 ml total volume at a density of
1–2.5 £ 104 cells/ml and were allowed to

Journal of Asian Natural Products Research
299

300
K. Wang and Z.-Z. Liu
adhere for 24h before treatment with tested
drugs in dimethyl sulfoxide (DMSO)
solution (1025, 1026, 1027 mol/l final
concentration). Triplicate wells were treated
with media and agents. Cell viability was
assayed after 96 h of continuous drug
exposure with a tetrazolium compound [3-
(4,5-dimethylthiazol-2-yl)-5-(3-carboxy-
methoxyphenyl)-2-(4-sulfophenyl)-2H-tet-
razolium salt; MTT (0.5mg/ml, 100ml),
Ameresco Corp., Solon, OH, USA] in fresh
medium. After the medium was removed,
150 ml of DMSO was added to each well.
The plates were gently agitated until the
color of the reaction mixture was uniform,
and OD570 was determined using a micro-
plate reader (Wellscan MK3, Labsystems
Dragon, Helsinki, Finland). Microsoft Excel
2003 was used for data analysis. Media-only
treated cells served as the indicator of 100%
cell viability. IC50 was defined as the
concentration that reduced the absorbance
of the untreated wells by 50% of vehicle in
the MTT assay. Assays were performed in
triplicate on three independent experiments.
J ¼ 5.4 Hz), 7.82 (s, 1H), 7.43 (d, 1H,
J ¼ 2.7 Hz), 7.55 (d, 1H, J ¼ 8.4 Hz), 7.37
(m, 3H), 6.97 (m, 3H), 6.77 (dd, 2H,
J ¼ 7.8, 3.9 Hz), 6.63 (m, 2H), 4.43 (t, 2H,
J ¼ 5.4 Hz), 3.78 (s, 3H), 3.74 (s, 3H),
3.61 (m, 2H), 3.04 (s, 3H). 13C NMR
(DMSO-d6, 100 MHz): d 171.7 ( £ 2),
166.3, 151.2, 148.1, 135.9 ( £ 2), 132.3,
129.2, 127.1, 126.6, 126.2, 125.9, 125.3,
121.7, 121.6, 121.2, 121.1, 120.3, 119.5,
119.4, 111.7, 110.8, 110.6, 110.1, 105.6,
105.1, 55.5, 55.4, 45.1, 38.9, 23.9. HR-
ESI-MS: m/z 549.2141 [M þ H]þ (calcd
for C32H29N4O5, 549.2132).
3.3.2 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-3-
yl]-indol-1-yl}-ethyl)-4-nitro-benzamide
(5b)
Yield 89.9%; red solid. 1H NMR (DMSO-
d6, 300 MHz): d 11.66 (s, 1H), 8.54 (t, 1H,
J ¼ 5.1 Hz), 8.26 (d, 2H, J ¼ 9.0 Hz), 7.97
(d, 2H, J ¼ 9.0 Hz), 7.86 (s, 1H), 7.75 (d,
1H, J ¼ 2.7 Hz), 7.53 (d, 1H, J ¼ 8.1 Hz),
7.34 (d, 1H, J ¼ 8.4 Hz), 7.01 (t, 1H,
J ¼ 7.5 Hz), 6.95 (t, 1H, J ¼ 7.5 Hz), 6.77
(t, 2H, J ¼ 8.4 Hz), 6.61 (m, 2H), 4.48
(t, 2H, J ¼ 5.7 Hz), 3.67 (m, 2H), 3.04
(s, 3H). 13C NMR (DMSO-d6, 100 MHz):
d 171.7, 171.6, 165.1, 149.0, 139.9, 135.9
( £ 2), 132.2, 129.2, 128.6 ( £ 2), 127.2,
126.2, 125.9, 125.3, 123.5 ( £ 2), 121.7,
121.6, 121.2, 121.0, 119.5, 119.4, 111.7,
110.0, 105.6, 105.2, 99.3, 44.9, 38.9, 23.9.
HR-ESI-MS: m/z 534.1756 [M þ H]þ
(calcd for C30H24N5O5, 534.1772).
3.3 Preparation of compounds 5a–5m
A mixture of amine 4 (1 equiv.), DMAP
(1.2equiv.), EDC (1.2equiv.), and anhy-
drous CH2Cl2 was stirred at room tempera-
ture, and then aromatic acid (1.2equiv.) was
added and the mixture was stirred at room
temperature for 4–6 h. After completion of
the reaction as indicated by TLC, CH2Cl2
was removed on the rotary evaporator to
give a red solid. The solid obtained was
purified by silica gel column chromatog-
raphy with ethyl acetate/petroleum ether as
the eluent to give compounds 5a–5m.
Yields: 50–90%.
3.3.3 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-3,4,5-trimethoxy-
benzamide (5c)
Yield 72.0%; red solid. 1H NMR (DMSO-
d6, 300 MHz): d 11.65 (s, 1H), 8.56 (m,
1H), 7.83 (s, 1H), 7.72 (d, 1H, J ¼ 2.7 Hz),
7.55 (d, 1H, J ¼ 8.1 Hz), 7.33 (d, 1H,
J ¼ 8.1 Hz), 7.08 (s, 2H), 7.02 (t, 1H,
J ¼ 7.5 Hz), 6.94 (t, 1H, J ¼ 7.5 Hz), 6.76
3.3.1 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-3,4-dimethoxy-
benzamide (5a)
Yield 78.4%; red solid. 1H NMR (DMSO-
d6, 300 MHz): d 11.67 (s, 1H), 8.49 (t, 1H,

Journal of Asian Natural Products Research
301
(m, 2H), 6.58 (m, 2H), 4.43 (m, 2H), 3.75 (s,
6H), 3.62 (m, 5H), 3.02 (s, 3H). 13C NMR
(DMSO-d6, 125 MHz): d 171.7 ( £ 2),
166.3, 152.5 ( £ 2), 139.9, 135.9, 135.9,
132.3, 129.6, 129.2, 127.0, 126.2, 125.8,
125.3, 121.8, 121.6, 121.3, 121.1, 119.5,
119.4, 111.7, 110.1, 105.6, 105.1, 104.8
( £ 2), 60.0, 55.9 ( £ 2), 45.1, 40.1, 23.9.
HR-ESI-MS: m/z 579.2237 [M þ H]þ
(calcd for C33H31N4O6, 579.2238).
m/z 490.1877 [M þ H]þ (calcd for
C29H24N5O3, 490.1874).
3.3.6 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-nicotinamide (5f)
1
Yield 73.5%; red solid. H NMR (CDCl3,
300 MHz): d 8.87 (s, 1H), 8.58 (s, 2H), 7.70
(s, 1H), 7.55 (s, 1H), 7.24 (m, 3H), 7.07 (t,
1H, J ¼ 7.5 Hz), 7.00 (t, 1H, J ¼ 7.5 Hz),
6.90 (t, 1H, J ¼ 7.5 Hz), 6.81 (m, 3H), 6.64
(t, 1H, J ¼ 7.5 Hz), 6.40 (t, 1H, J ¼ 6.0 Hz),
4.38 (t, 2H, J ¼ 6.0 Hz), 3.74 (m, 2H), 3.17
(s, 3H). 13C NMR (CDCl3, 100 MHz): d
172.5, 172.4, 166.1, 156.0, 150.0, 141.4,
136.3, 135.9, 130.9, 129.6, 128.7, 126.4,
125.2, 122.8, 122.6, 122.3, 121.7, 121.2,
120.6, 120.4, 120.1, 115.3, 111.5, 109.3,
107.0, 106.8, 45.5, 40.5, 24.2. HR-ESI-MS:
m/z 490.1866 [M þ H]þ (calcd for
C29H24N5O3, 490.1874).
3.3.4 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-isonicotinamide
(5d)
Yield67.4%. 1HNMR(CDCl3,300 MHz):d
9.29 (s, 1H), 8.61 (s, 1H), 8.54 (d, 1H,
J ¼ 2.4 Hz), 7.87 (d, 1H, J ¼ 7.8 Hz), 7.59
(d, 1H, J ¼ 2.1 Hz), 7.51 (s, 1H), 7.27 (m,
1H), 7.21 (m, 2H), 7.03 (m, 2H), 6.95 (t, 1H,
J ¼ 6.0 Hz), 6.68 (m, 4H), 4.30 (t, 2H,
J ¼ 5.1 Hz), 3.63 (m, 2H), 3.10 (s, 3H). 13
C
3.3.7 2,3-Dihydro-benzo[1,4]dioxine-2-
carboxylic acid (2-{3-[4-(1H-indol-3-yl)-
1-methyl-2,5-dioxo-2,5-dihydro-1H-
NMR (CDCl3, 100 MHz): d 172.4, 172.4,
166.0, 151.4, 147.4, 136.3, 136.0, 135.7,
131.3, 130.0, 128.7, 127.8, 127.1, 126.2,
125.1, 123.6, 122.6, 122.4, 122.3, 121.7,
120.4, 120.0, 111.5, 109.4, 106.7, 106.5,
45.5, 40.3, 24.1. HR-ESI-MS: m/z 490.1863
[M þ H]þ (calcd for C29H24N5O3,
490.1874).
pyrrol-3-yl]-indol-1-yl}-ethyl)-amide (5g)
1
Yield 66.2%; red solid. H NMR (CDCl3,
300 MHz): d 8.92 (s, 1H), 7.62 (d, 1H,
J ¼ 2.4 Hz), 7.46 (s, 1H), 7.25 (m, 2H), 7.04
(m, 3H), 6.88 (m, 3H), 6.74 (m, 5H), 4.62
(dd, 1H, J ¼ 6.6, 2.7 Hz), 4.42 (dd, 1H,
J ¼ 11.4, 2.7 Hz), 4.23 (t, 2H, J ¼ 5.7 Hz),
3.3.5 Pyridine-2-carboxylic acid (2-{3-
[4-(1H-Indol-3-yl)-1-methyl-2,5-dioxo-
2,5-dihydro-1H-pyrrol-3-yl]-indol-1-yl}-
ethyl)-amide (5e)
4.07 (m, 1H), 3.57 (m, 2H), 3.15 (s, 3H). 13
C
NMR (CDCl3, 100 MHz): d 172.4, 172.3,
167.9, 143.1, 141.4, 136.1, 135.9, 131.3,
128.5, 127.6, 127.1, 126.2, 125.1, 122.5,
122.4, 122.3, 122.3, 121.8, 121.7, 120.4,
120.0, 117.5, 117.0, 111.35, 109.2, 106.8,
106.5, 64.9, 60.3, 45.3, 39.4, 24.1. HR-ESI-
MS: m/z 547.1954 [M þ H]þ (calcd for
C32H27N4O5, 547.1976).
1
Yield 71.7%; red solid. H NMR (CDCl3,
300 MHz): d 8.86 (s, 1H), 8.45 (d, 1H,
J ¼ 1.8 Hz), 8.20 (d, 2H, J ¼ 7.5 Hz), 7.82
(t, 1H, J ¼ 7.5 Hz), 7.71 (s, 1H), 7.61 (s,
1H), 7.39 (m, 2H), 7.27 (d, 1H, J ¼ 7.5 Hz),
7.02 (m, 4H), 7.75 (m, 2H), 4.38 (t, 2H,
J ¼ 6.0 Hz), 3.79 (q, 2H, J ¼ 6.0 Hz), 3.16
(s, 3H). 13C NMR (CDCl3, 100 MHz): d
172.5, 172.4, 164.9, 149.2, 148.2, 137.4,
136.1, 135.9, 131.6, 128.3, 127.5, 127.4,
126.4, 126.4, 125.3, 122.5, 122.4, 122.2,
122.1, 121.8, 120.3, 120.2, 111.2, 109.5,
107.1, 106.4, 46.0, 39.3, 24.1. HR-ESI-MS:
3.3.8 Pyrazine-2-carboxylic acid(2-{3-
[4-(1H-indol-3-yl)-1-methyl-2,5-dioxo-
2,5-dihydro-1H-pyrrol-3-yl]-indol-1-yl}-
ethyl)-amide (5h)
1
Yield 76.2%; red solid. H NMR (CDCl3,
300 MHz): d 9.40 (s, 1H), 8.76 (s, 1H),

302
K. Wang and Z.-Z. Liu
8.70 (s, 1H), 8.40 (s, 1H), 7.89 (t, 1H,
J ¼ 6.0 Hz), 7.75 (s, 1H), 7.60 (s, 1H), 7.26
(m, 2H), 7.02 (m, 3H), 6.91 (d, 1H,
J ¼ 8.4 Hz), 6.75 (m, 2H), 4.40 (s, 2H),
3.3.11 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-4-methoxy-
benzamide (5k)
3.81 (q, 2H, J ¼ 6.0 Hz), 3.16 (s, 3H). 13
C
1
Yield 73.6%; red solid. H NMR (CDCl3,
NMR (CDCl3, 100 MHz): d 172.4, 172.3,
163.6, 147.5, 144.2, 143.9, 142.6, 136.1,
135.9, 131.4, 128.3, 127.5, 127.4, 126.5,
125.3, 122.6, 122.5, 122.3, 121.8, 120.4,
120.1, 111.3,109.4, 107.2, 106.6,45.8, 39.4,
24.1. HR-ESI-MS: m/z 491.1819 [M þ H]þ
(calcd for C28H23N6O3, 491.1826).
300 MHz): d 8.72 (s, 1H), 7.70 (d, 1H,
J ¼ 2.4 Hz), 7.55 (m, 3H), 7.31 (m, 2H),
7.05 (m, 3H), 6.84 (m, 4H), 6.69 (t, 1H,
J ¼ 8.1 Hz), 6.08 (t, 1H, J ¼ 6.0 Hz), 4.35
(t, 2H, J ¼ 5.7 Hz), 3.81 (s, 3H), 3.70 (q,
2H, J ¼ 6.0 Hz), 3.18 (s, 3H). 13C NMR
(CDCl3, 125 MHz): d 172.4, 172.4, 167.5,
162.3, 136.4, 135.9, 131.3, 128.8 ( £ 2),
128.4, 127.8, 127.5, 126.4, 126.2, 125.2,
122.6 ( £ 2), 122.3, 121.8, 120.5, 120.1,
113.8 ( £ 2), 111.4, 109.6, 107.2, 106.6,
55.4, 46.0, 40.4, 24.2. HR-ESI-MS: m/z
3.3.9 1H-Indole-2-carboxylic acid (2-{3-
[4-(1H-indol-3-yl)-1-methyl-2,5-dioxo-
2,5-dihydro-1H-pyrrol-3-yl]-indol-1-yl}-
ethyl)-amide (5i)
519.2025
C31H27N4O4, 519.2027).
[M þ H]þ
(calcd
for
1
Yield 80.2%; red solid. H NMR (CDCl3,
300 MHz): d 9.64 (s, 1H), 8.74 (s, 1H),
7.53 (m, 3H), 7.35 (d, 1H, J ¼ 8.4 Hz),
7.24 (m, 3H), 7.05 (m, 4H), 6.89 (d, 1H,
J ¼ 8.4 Hz), 6.74 (m, 2H), 6.59 (s, 1H),
6.47 (t, 1H, J ¼ 6.0 Hz), 4.26 (t, 2H,
J ¼ 4.8 Hz), 3.66 (m, 2H), 3.14 (s, 3H).
13C NMR (CDCl3, 125 MHz): d 172.5,
172.3, 161.9, 136.4, 136.3, 135.9, 131.2,
130.1, 128.4, 127.9, 127.6, 127.4, 126.5,
125.3, 124.8, 122.7, 122.3, 122.1, 121.9,
120.8, 120.6, 120.2, 111.9, 111.3, 109.4,
107.3, 106.7, 103.3, 46.2, 37.0, 24.2. HR-
ESI-MS: m/z 528.2016 [M þ H]þ (calcd
for C32H25N5O3, 528.2030).
3.3.12 3-(4-Fluoro-phenyl)-N-(2-{3-[4-
(1H-indol-3-yl)-1-methyl-2,5-dioxo-2,5-
dihydro-1H-pyrrol-3-yl]-indol-1-yl}-
ethyl)-acrylamide (5l)
1
Yield 63.4%; red solid. H NMR (CDCl3,
300 MHz): d 8.86 (s, 1H), 7.69 (d, 1H,
J ¼ 2.7 Hz), 7.47 (d, 1H, J ¼ 15.6Hz), 7.40
(m, 5H), 7.18 (d, 1H, J ¼ 7.8 Hz), 7.13 (d,
1H, J ¼ 7.5 Hz), 7.05(m, 3H), 6.84(m, 2H),
6.74 (t, 1H, J ¼ 8.1 Hz), 5.97 (d, 1H,
J ¼ 15.6 Hz), 5.61 (t, 1H, J ¼ 5.7 Hz),
4.27 (t, 2H, J ¼ 5.4 Hz), 3.58 (q, 2H,
J ¼ 5.7 Hz), 3.16 (s, 3H). 13C NMR
(CDCl3, 125 MHz): d 172.4, 172.3, 166.3,
162.6, 140.3, 136.3, 136.1, 131.3, 131.0,
130.9, 129.7, 129.7, 128.8, 128.0, 127.4,
126.5, 125.1, 122.7, 122.3, 122.1, 120.6,
120.1, 119.9, 116.0, 115.8, 111.5, 109.5,
107.1, 106.5, 45.9, 40.1, 24.2. HR-ESI-MS:
m/z 533.1993 [M þ H]þ (calcd for
C32H26FN4O3, 533.1983).
3.3.10 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-2-methoxy-
benzamide (5j)
1
Yield 75.7%; red solid. H NMR (CDCl3,
300 MHz): d 8.74 (s, 1H), 8.19 (dd, 1H,
J ¼ 8.1, 1.8 Hz), 7.92 (t, 1H, J ¼ 5.4 Hz),
7.76 (d, 1H, J ¼ 2.4 Hz), 7.58 (s, 1H), 7.38
(m, 3H), 7.16 (d, 1H, J ¼ 8.1 Hz), 7.04 (m,
3H), 6.84 (m, 3H), 6.70 (t, 1H,
J ¼ 7.5 Hz), 4.36 (t, 2H, J ¼ 5.7 Hz),
3.76 (q, 2H, J ¼ 5.7 Hz), 3.46 (s, 3H),
3.19 (s, 3H). HR-ESI-MS: m/z 519.2019
[M þ H]þ (calcd for C31H27N4O4,
519.2027).
3.3.13 N-(2-{3-[4-(1H-Indol-3-yl)-1-
methyl-2,5-dioxo-2,5-dihydro-1H-pyrrol-
3-yl]-indol-1-yl}-ethyl)-3-pyridin-2-yl-
acrylamide (5m)
1
Yield 67.0%; red solid. H NMR (CDCl3,
300 MHz): d 9.65 (s, 1H), 8.65 (d, 1H,

Journal of Asian Natural Products Research
303
[3] M. Prudhomme, Curr. Pharm. Des. 3, 265
(1997).
[4] H.J. Knolker and K.R. Reddy, Chem. Rev.
102, 4303 (2002).
[5] P.D. Davis, L.H. Elliott, W. Harris, C.H.
Hill, S.A. Hurst, E. Keech, M.K. Hari
Kumar, G. Lawton, J.S. Nixon, and S.E.
Wilkinson, J. Med. Chem. 35, 994 (1992).
[6] M.M. Faul, J.R. Gillig, M.R. Jirousek, L.
M. Ballas, T. Schotten, A. Kahl, and M.
Mohr, Bioorg. Med. Chem. Lett. 13, 1857
(2003).
[7] S. Roy, S. Roy, and G.W. Gribble, Org.
Lett. 21, 4975 (2006).
[8] H.L. Pearce and M.A. Miller, Adv.
Enzyme. Regul. 45, 229 (2005).
[9] H.A. Fine, L. Kim, C. Royce, D. Draper, I.
Haggarty, H. Ellinzano, P. Albert, P.
Kinney, L. Musib, and D. Thornton,
J. Clin. Oncol. 23, 1504 (2005).
[10] K. Wang, Z. Yan, N. Wang, and Z.Z. Liu,
Chin. Chem. Lett. 23, 462 (2012).
[11] K. Wang and Z. Liu, Eur. J. Med. Chem.
45, 4175 (2010).
[12] K. Wang, X.Y. Li, X.G. Chen, and Z.Z.
Liu, J. Asian Nat. Prod. Res. 12, 36
(2010).
[13] D.S. Choi, S. Huang, M. Huang, T.S.
Barnard, R.D. Adams, J.M. Seminario,
and J.M. Tour, J. Org. Chem. 63, 2646
(1998).
[14] M. Brenner, H. Rexhausen, B. Steffan,
and W. Steglich, Tetrahedron 10, 2887
(1988).
[15] B. Witulski and T. Schweikert, Synthesis
12, 1959 (2005).
J ¼ 3.9 Hz), 7.69 (m, 2H), 7.48 (d, 1H,
J ¼ 15.3 Hz), 7.43 (d, 1H, J ¼ 8.4 Hz),
7.32 (m, 4H), 7.16 (t, 1H, J ¼ 7.5 Hz),
7.08 (t, 1H, J ¼ 7.5 Hz), 6.97 (t, 1H,
J ¼ 7.2 Hz), 6.78 (m, 3H), 6.59 (d, 1H,
J ¼ 15.3 Hz), 5.37 (t, 1H, J ¼ 6.0 Hz),
4.15 (m, 2H), 3.43 (m, 2H), 3.15 (s, 3H).
13C NMR (CDCl3, 125 MHz): d 172.4,
172.3, 166.0, 153.2, 149.9, 139.8, 137.3,
136.5, 136.4, 131.4, 129.7, 129.0, 128.8,
128.4, 126.5, 125.3, 124.6, 124.3, 122.7,
122.5, 122.1, 120.9, 120.4, 115.6, 112.2,
109.5, 106.9, 106.6, 45.6, 40.4, 24.3. HR-
ESI-MS: m/z 516.2048 [M þ H]þ (calcd
for C31H26N5O3, 516.2030).
Acknowledgement
The research was financially supported by the
Beijing Key Laboratory of Active Substance
Discovery and Druggability Evaluation.
References
[1] G.W. Gribble and S.J. Berthel, Studies in
Natural Product Chemistry, edited by
Atta-ur-Rahman, (Elsevier, Amsterdam,
1993), Vol. 12, p. 365.
[2] P.D. Davis, C.H. Hill, E. Keech, G.
Lawton, J.S. Nixon, A.D. Sedgwick, J.
Wadsworth, D. Westmacott, and S.E.
Wilkinson, FEBS Lett. 259, 61 (1989).