Synthesis, anticancer activity and apoptosis inducing ability of bisindole linked pyrrolo[2,1-c][1,4]benzodiazepine conjugates

Article abstract of DOI:10.1016/j.bmcl.2011.10.080

A series of bisindole-pyrrolobenzodiazepine conjugates (5a-f) linked through different alkane spacers was prepared and evaluated for their anticancer activity. All compounds exhibited significant anticancer potency and the most potent compounds 5b and 5e

Full text of DOI:10.1016/j.bmcl.2011.10.080

Bioorganic & Medicinal Chemistry Letters 22 (2012) 571–578
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis, anticancer activity and apoptosis inducing ability of bisindole linked
pyrrolo[2,1-c][1,4]benzodiazepine conjugates
⇑
Ahmed Kamal , Y.V.V. Srikanth, M. Janaki Ramaiah, M. Naseer Ahmed Khan, M. Kashi Reddy, Md. Ashraf,
⇑
A. Lavanya, S.N.C.V.L. Pushpavalli, Manika Pal-Bhadra
Division of Organic Chemistry, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of bisindole–pyrrolobenzodiazepine conjugates (5a–f) linked through different alkane spacers was
prepared and evaluated for their anticancer activity. All compounds exhibited significant anticancer
potency and the most potent compounds 5b and 5e were taken up for detailed studies on MCF-7 cell line.
Cell cycle effects were examined apart from investigating the inhibition of tubulin polymerization for com-
Received 2 August 2011
Revised 5 October 2011
Accepted 24 October 2011
Available online 31 October 2011
pounds 2a, 2b, 5b and 5e at 2 lM. FACS analysis showed that at higher concentrations (4 and 8 lM) there
was an increase of sub-G1 phase cells and decrease of G2/M phase cells, thus indicating that compounds 5b
and 5e are effective in causing apoptosis in MCF-7 cells. It was also observed that compounds 5b and 5e
showed the down regulation of histone deacetylase protein levels such as HDAC1, 2, 3, 8 and increase in
the levels of p21, followed by apoptotic cell death. The apoptotic nature of these compounds was further
evidenced by increased expression of cleaved-PARP and active caspase-7 in MCF-7 cells.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Bisindoles
Pyrrolobenzodiazepine
Anticancer activity
Tubulin polymerization
HDACs
p21
PARP
Caspase-7
Indole derivatives have been found to exhibit anticancer activ-
ity by interacting with different intracellular targets. Naturally
occurring as well as synthetic indolocarbazoles indicated inhibi-
tory activity against cyclin-dependent kinases (CDKs) and antipro-
liferative activities in a variety of cell lines.1,2 Indole-3-carbinol
(I3C, 1, Fig. 1), a dietary component found predominantly in crucif-
erous vegetables, is known to exhibit antiproliferative as well as
apoptotic activities against various cancer cells,3 and presently en-
tered phase I and II clinical trials for breast cancer prevention.4
Moreover, 1 itself does not possess anticancer activity, but due to
the formation of active metabolites in the stomach by gastric juice
mainly 3,30-bisindolyl methane (BIM) a major metabolite may be
responsible for its in vivo anticancer effects.5 Recently, bisindolyl
maleimides have been identified as NAD+-dependent histone
deacetylase (HDAC) inhibitors.6 More recently, 1,1-bis(30-indo-
lyl)-1-(p-hydroxyphenyl)methane (2b) has been reported to exhi-
bit antiproliferative and apoptotic effect in pancreatic cancer
cells in vitro as well as in vivo.7 Furthermore, bisindolyl methane
moiety linked hydroxamic acids and related compounds act as
HDAC inhibitors.8,9 In addition, bisindoles and a number of indole
derivatives are well known to possess potent anticancer activ-
ity.10–14
Pyrrolo[2,1-c][1,4]benzodiazepines (PBDs), are an important
class of sequence selective DNA-interactive agents that bind
covalently to guanine bases within the minor groove of DNA.15
Well-known members of this group16,17 include anthramycin,
tomaymycin, sibiromycin, limazepine and DC-81 (3). Recently, a
PBD dimer (SJG-136) has entered the phase II clinical trial.18
Although PBDs have shown high antitumour activity, significant
cardiotoxicity hampers their clinical applications.19 Accordingly,
there has been considerable interest in the design of various PBD
conjugates by linking this scaffold to other DNA interactive agents
with a view to enhance the anticancer activity while decreasing
side effects.20–23 Recently, Wang and co-workers synthesized
indole-PBD conjugates (4) exhibiting anticancer activity by induc-
ing apoptosis through mitochondrial mediated pathway.24
Furthermore, we have not only been involved in the develop-
ment of new synthetic strategies25 for the preparation of PBD ring
system but also in the design of structurally modified PBDs and
their hybrids.26–28 In continuation to our efforts in search of potent
molecules that exhibit anticancer activity,29–31 and based on the
interesting biological activities of bisindoles, we designed and syn-
thesized bisindole linked PBD’s (5) to explore their potential as
anticancer agents. It is expected that combination of two active
pharmacophores with in a single molecule would enhance the
anticancer activity by an additive or synergistic effect. Therefore,
we coupled an active moiety of known antitumour bisindolyl
methane derivative (2) through their 3- and 4-hydroxyl groups
⇑
Corresponding authors. Tel.: +91 40 27193157; fax: +91 40 27193189.
E-mail addresses: ahmedkamal@iict.res.in (A. Kamal), manika@iict.res.in
(M. Pal-Bhadra).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.10.080

572
A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
OH
HO
N
OH
H
H3CO
N
N
H
N
H
N
H
O
1
2b
3
N
O
O
H
( )
n
HN
N
H3CO
O
N
NH
( )6
H3CO
O
H
N
H
O
HN
N
n = 4-6
O
4
5a-f
Figure 1. Chemical structures of indole-3-carbinol (1), bisindole (2b), DC-81 (3), indole-PBD conjugate (4) bisindole–PBD conjugates (5a–f).
to 3 via different alkyl spacers (Fig. 2). The in vitro cytotoxicity and
other biological investigations of these conjugates on MCF-7 cell
line in regulating HDACs as well as CDK inhibitor p21 were carried
out.
These conjugates 5a–f were evaluated for their anticancer activ-
ity in selected human cancer cell lines of lung, breast, oral, colon,
prostate and ovary by using sulforhodamine B (SRB) method. All
these compounds 5a–f exhibited anticancer potency with GI50 val-
The preparation of bisindole intermediates (2a,b) was accom-
plished by following a novel method recently developed in our
laboratory.32 Reaction of substituted hydroxy benzaldehydes
(7a,b) with indole in acetonitrile using aluminium triflate as a
catalyst afford the phenol substituted derivatives (2a,b) as illus-
trated in Scheme 1. The synthesis of C8-linked bisindole–PBD
conjugates (5a–f) was carried out from the (2S)-N-{4-[3-bro-
moalkoxy-5-methoxy-2-nitrobenzoyl} pyrrolidine-2-carboxalde-
hyde-diethylthioacetal (8), which has been prepared by the
methods reported in our earlier studies33–36 and phenolic bisin-
dole precursors (2a,b) using K2CO3 in acetone provided the nitro
thioacetal intermediates 9a–f. Finally, these upon reduction with
SnCl2ꢀ2H2O in refluxing methanol followed by thiol deprotection
by HgCl2/CaCO3 in CH3CN–H2O at room temperature afforded
the desired PBD conjugates 5a–f.37
ues ranging from 0.11 to 30.8
adriamycin38 and DC-81 demonstrated GI50 values in the range
of <0.1ꢁ14.7 M and 0.10–2.37 M concentrations, respectively.
Interestingly all the compounds are active in human breast cancer
cell line (MCF-7) with GI50 values ranging from 0.14 to 2.01
(Table 1). Compounds 5b and 5e in which the PBD moiety was
linked, to bisindole substituted phenolic group by odd number of
alkyl spacers (n = 3) exhibit better anticancer potency than their
counterparts with even number of decreased alkyl spacer length
(5a and 5d; n = 2) and increased in the length of alkyl spacer (5c
and 5f; n = 4). All the synthesized compounds have displayed
significant anticancer potency against breast cancer cell line
lM, whereas the positive controls
l
l
l
M
(MCF-7) with GI50 values in the range of 0.14–2.01 lM.
With a view to understand the cytotoxic nature of some of the
active compounds, MTT cytotoxicity assay was performed by
OH
HO
N
H
H3CO
N
O
N
H
N
H
3
2b
anticancer PBD
anticancer bisindole
variable alkyl spacer
O
O
N
H
H3CO
N
O
N
H
N
H
5a-f
predicted novel hybrids as
potential anticancer agents
Figure 2. Design of bisindole–PBD conjugates (5a–f) as potential anticancer agents.

A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
573
OH
CHO
CHS(C2H5)2
Br
O
NO2
( )
n
(i)
+
+
N
O
N
H
H3CO
OH
N
H
N
H
7a: 3-OH
7b: 4-OH
2a: 3-OH
2b: 4-OH
6
8
n = 2-4
(ii)
CHS(C2H5)2
O
NO2
( )n
O
N
O
H3CO
HN
9a-f
n = 2-4
HN
(iii),(iv)
N
O
( )n
O
H
N
H3CO
HN
O
5a-f
HN
5a: 3_O_(CH2)n_ ; n = 2
_
5b: 3_O_(CH2)n_ ; n = 3
_
_
5c
5d
;
;
: 3 O (CH2)n_
n = 4
n = 2
_
_
: 4 O (CH2)n_
5e: 4_O_(CH2)n_ ; n = 3
5f: 4_O_(CH2)n
; n = 4
Scheme 1. Reagents and conditions: (i) Al(OTf)3, dry acetonitrile, rt, 1–2 h, 93–95%; (ii) K2CO3, acetone, reflux, 24 h, 84–88%; (iii) SnCl2ꢀ2H2OꢀMeOH, reflux, 3 h, 89–95%; (iv)
HgCl2, CaCO3, CH3CN/H2O (4:1) rt, 8 h, 40–52%.
Table 1
Anticancer activity (GI50 values in l
M)a for compounds 5a–f in selected human cancer cell lines
Code
MCF-7b
Zr-75-1b
A2780c
Colo205d
SiHae
A549f
KBg
h
h
h
h
5a
5b
5c
5d
5e
5f
DC-81
ADR
2.01
0.19
2.01
0.18
0.14
0.14
0.17
<0.1
—
—
—
27.00
0.18
2.29
2.07
0.11
2.46
0.14
<0.1
28.50
0.16
2.30
24.0
26.1
—
0.11
14.7
—
—
—
—
—
—
h
h
2.20
30.8
2.49
0.18
2.30
30.1
2.30
0.13
h
h
h
26.50
0.12
2.40
29.0
0.16
h
h
h
h
—
—
—
2.37
<0.1
0.16
1.90
0.17
0.16
13.01
a
b
c
50% Growth inhibition and the values are mean of three determinations.
Breast cancer.
Ovarian cancer.
Colon cancer.
Cervix cancer.
Lung cancer.
Oral cancer.
d
e
f
g
h
GI50 values not attained at the concentrations used. ADR stands for adriamycin.
treating MCF-7 cells with compounds 3, 2a, 2b, 5b and 5e at differ-
ent concentrations ranging from 2 to 8 M for 24 h. It is observed
that compounds 5b and 5e cause almost 50% of cell death at 2
To investigate the effect of bisindole–PBD conjugates on the cell
cycle progression of human breast cancer cell line (MCF-7), the
DNA content of the cell nuclei was measured by flow cytometric
analysis. MCF-7 cells were treated with compounds 3, 2a, 2b, 5b
l
lM
concentrations. Further these compounds are slightly higher cyto-
toxic than the positive control DC-81 (3), 2a and 2b (Fig. 3).
and 5e at 2 lM concentration which resulted in accumulation of

574
A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
Figure 3. The in vitro cytotoxicity assay for bisindole–PBD conjugates. The MCF-7 cells were treated with various concentrations of compounds 3, 2a, 2b, 5b and 5e and MTT
assay was conducted which reveals the viable cells present after compound treatment. The values were found to be statistically significant with ⁄⁄p <0.01, ⁄⁄⁄p <0.001 when
compared to control untreated cells. Error bars represent the mean standard deviation (SD) of at least three measurements.
Table 2
Cell cycle distribution of MCF-7 cell line at different concentrations (2, 4 and 8 lM of compounds DC-81 (3), 2a, 2b, 5b, and 5e
Compound
Conc. (
lM)
G0
3.03 0.15
G1
S
G2/M
Control
3
2a
2b
5b
5e
Control
3
2a
2b
5b
5e
Control
3
2a
2b
5b
5e
2
2
2
2
2
2
4
4
4
4
4
4
8
8
8
8
8
8
47.01 1.00
55.11 1.55
51.23 1.12
53.85 0.79
38.86 0.74
40.67 0.76
65.60 0.61
70.84 1.23
50.56 0.51
49.65 1.51
70.29 1.44
68.33 0.39
65.60 0.61
57.74 0.65
45.99 0.99
46.19 1.30
60.92 0.81
46.11 1.87
15.25 0.48
8.02 0.23
9.86 0.32
9.26 0.65
15.42 0.76
9.08 0.22
5.90 0.32
8.56 0.87
9.41 0.52
9.78 1.07
8.26 0.35
6.95 0.06
5.90 0.32
4.53 0.50
10.02 0.96
8.99 0.017
5.26 0.47
2.32 0.24
34.71 1.51
33.79 0.73
36.03 0.95
33.7 0.25
42.67 1.34
46.67 1.34
25.38 0.78
11.31 0.30
36.3 0.59
35.56 0.75
10.74 1.50
8.60 0.45
25.38 0.78
8.05 0.92
37.97 1.01
37.97 1.29
8.99 1.04
1.41 0.32
3.14 0.52
2.80 0.26
3.16 0.28
2.98 0.48
3.57 0.35
3.11 0.11
9.27 0.28
3.63 0.63
5.01 1.02
10.70 0.3
16.11 0.3
3.11 0.11
29.68 0.59
6.03 0.11
7.05 0.99
24.81 0.50
50.15 1.73
34%, 36%, 33%, 42% and 45% of cells in G2/M phase, when compared
to untreated cells. Further treatment of these compounds at higher
concentrations (4 and 8 lM) for 24 h resulted in larger accumula-
confirming cell cycle arrest at G2/M phase (Fig. 5). DC-81 (3), the
standard PBD molecule did not show any effect on tubulin as it
causes G1 cell cycle arrest (Supplementary data Fig. S1).
tion of sub-G1 populated cells with a concomitant decrease in the
G2/M phase especially in compounds 3, 5b and 5e. However, the
intermediates 2a and 2b have shown only G2/M phase arrest at
Histones are the nuclear core proteins that regulate transcrip-
tion and cell cycle progression41 and inhibition of HDACs is a prom-
ising novel strategy in human cancer therapy.42 HDAC depletion is
known to activate CDK inhibitors p21 as well as p27 and trigger the
G2/M cell cycle arrest.43 To understand the molecular events in-
volved in G2/M phase arrest, the effect on the expression levels of
histones and CDK inhibitor p21, which plays a vital role in cell cycle
progression was also investigated in MCF-7 cells. Thus MCF-7 cells
were treated with compounds trichostatin A (TSA, the standard
all the concentrations (2, 4 and 8 lM) (Table 2). Therefore increase
of cells in sub-G1 clearly showed that these hybrid compounds are
effective in causing apoptosis in MCF-7 cells as shown in (Figs. 4a
and 4b). Similar observations were previously found for the indole-
PBD conjugate (IN6CPBD).24
Generally, inhibition of tubulin polymerization was associated
with cell cycle arrest at G2/M phase transition by interrupting mi-
totic spindle formation.39 From the previous reports, it is well
known that molecules that alter the microtubule polymerization,
cause mitotic arrest which ultimately leads to apoptosis.40 Thus
the effect of these compounds 3, 2a, 2b, 5b and 5e on the tubulin
HDAC inhibitor), 3, 2a, 2b, 5b and 5e at 2 lM concentrations for
24 h and cell lysates were collected, subjected to Western blotting.
Results indicate that down regulation of HDACs protein levels such
as HDAC1, 2, 3, 8 were observed when compared to the untreated
control cells. Moreover compounds 5b and 5e selectively induced
significant increase in the protein levels of p21 and similar observa-
tions were found in the study response of estrogen receptor (ER)-
positive MCF-7 cells and effect of HDAC inhibitors44 (Figs. 6a, 6b
and 6c).
cytoskeleton and its integrity was examined at 2
nocodazole as the standard. The cells were fixed and stained after
24 h with FITC conjugated -tubulin antibody. Interestingly, dis-
ruption of tubulin polymerization was observed in this assay, thus
lM by taking
a

A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
575
Figure 4a. Effect of bisindole–PBD conjugates on cell cycle. MCF-7 cells were treated with compounds 3, 2a, 2b, 5b and 5e at various concentrations 2, 4 and 8
lM for 24 h. At
2
l
M the cells showed G2/M cell cycle arrest and increased concentration caused accumulation of more cells in sub G1, indicating apoptosis, DC-81(3) is the positive control.
Whereas starting material 2a and 2b continued to show G2/M phase arrest at 2, 4 and 8 M. One of three independent experiment values have been depicted.
l
Figure 4b. The graph depicting the percentage of apoptosis after treatment of compounds 3, 2a, 2b, 5b and 5e at 2, 4 and 8
lM concentrations for 24 h. The values were found
to be statistically significant with ⁄⁄⁄p <0.001 when compared to control untreated cells. Error bars represent the mean SD of at least three measurements.
Previous studies by Twiddy et al.45 have discovered that caspase-
7 and PARP play an important role in causing apoptosis in human
breast cancer cells. To prove whether these conjugates cause apop-
tosis, MCF-7 cells were treated with compounds 3, 2a, 2b, 5b and 5e
24 h) (Fig. 7). This finding confirms the apoptosis inducing nature
of these compounds.
The synthesis and evaluation of anticancer activity of a new ser-
ies of bisindole–PBD conjugates has been investigated. Most of the
compounds have exhibited potent anticancer activity against se-
lected human cancer cell lines. Cell cycle effects were examined
apart from investigating the inhibition of tubulin polymerization
at 8
analysis. A signal for cleaved-PARP and activated capase-7 was de-
tected in MCF-7 samples treated with these compounds (8 M,
lM concentration and cell lysates were subjected to Western
l

576
A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
Figure 5. Effect of bisindole–PBD conjugates on tubulin polymerization. MCF-7 cells were exposed to 3, 2a, 2b, 5b, 5e, and nocodazole at 2 lM concentration for 24 h and
followed by tubulin staining. ‘Noc’ represents nocodazole, used as a positive control.
Figure 6a. Effect of bisindole–PBD conjugates on various proteins involved on class I HDACs and p21. MCF-7 cells were treated with compounds TSA, 3, 2a, 2b, 5b and 5e for
24 h and cell lysates were subjected to Western blotting for p21, HDAC1, 2, 3 and 8. b-Actin used as a loading control.

A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
577
Figure 6b. Effect of bisindole–PBD conjugates on HDAC-1 protein. Compounds TSA, 3, 2a, 2b, 5b and 5e were subjected to HDAC-1 photometric assay (Enzo Kit). Here TSA
was used as standard chemical. The lesser O.D indicates the higher HDAC inhibitory activity. The values were found to be statistically significant with ⁄⁄⁄p <0.001 when
compared to control untreated cells. Error bars represent the mean SD of at least three measurements.
Figure 6c. Effect of bisindole–PBD conjugates on HDAC-8 protein. Compounds TSA, 3, 2a, 2b, 5b and 5e were subjected to HDAC-8 fluorometry based assay (Enzo Kit). Here
TSA was used as standard chemical. The lesser O.D indicates the higher HDAC inhibitory activity. The values were found to be statistically significant with ⁄⁄⁄p <0.001 when
compared to control untreated cells. Error bars represent the mean SD of at least three measurements.
Figure 7. Effect of compounds on apoptosis, MCF-7 cells were treated with compounds 3, 2a, 2b, 5b and 5e at 8 lM concentrations for 24 h. The cells were then processed
and lysates were subjected to Western blotting analysis using antibodies against active caspase-7 and cleaved-PARP which are indicators of apoptosis. b-Actin used as a
loading control. Results shown are indicative of three individual experiments.
for compounds 3,2a, 2b, 5b and 5e. Thus, we provided the evidence
that these newly synthesized hybrid molecules inhibited growth of
human breast carcinoma MCF-7 cells by inducing apoptosis. The
apoptotic death was associated with down regulation of histone
protein levels such as HDAC1, 2, 3, 8 and increased levels of p21.
Further HDAC reduction was associated with an initiation of DNA
damage that triggered apoptosis followed by cell death. In addi-
tion, we have observed increased expression of cleaved-PARP and

578
A. Kamal et al. / Bioorg. Med. Chem. Lett. 22 (2012) 571–578
19. Cargill, C.; Bachmann, E.; Zbinden, G. J. Natl. Cancer Inst. 1974, 53, 481.
20. Kamal, A.; Reddy, K. S.; Khan, M. N. A.; Rajesh, S. V. C. R. N. C.; Ramaiah, M. J.;
Pushpavalli, S. N. C. V. L.; Srinivas, C.; Bhadra, M. P.; Chourasia, M.; Sastry, G. N.;
Juvekar, A.; Zingde, S.; Barkume, M. Bioorg. Med. Chem. 2010, 18, 4747.
21. Kamal, A.; Reddy, J. S.; Ramaiah, M. J.; Dastagiri, D.; Bharathi, E. V.; Azhar, M. A.;
Sultana, F.; Pushpavalli, S. N. C. V. L.; Bhadra, M. P.; Juvekar, A.; Sen, S.; Zingde,
S. Eur. J. Med. Chem. 2010, 45, 3924.
active caspase-7 proteins in MCF-7 cells. Further studies on bio-
chemical changes and molecular events involved in cell death
caused by these hybrids are underway.
Acknowledgments
22. Kamal, A.; Tekumalla, V.; Krishnan, A.; Bhadra, M. P.; Bhadra, U. Chem. Med.
Chem. 2008, 3, 794.
23. Kamal, A.; Khan, M. N. A.; Srikanth, Y. V. V.; Reddy, K. S.; Juvekar, A.; Sen, S.;
Kurian, N.; Zingde, S. Bioorg. Med. Chem. 2008, 16, 7804.
The authors Y.V.V.S. and M.A. thank UGC and M.K.R. thanks
CSIR, New Delhi for the award of research fellowships.
24. Wang, J. J.; Shen, Y. K.; Hu, W. P.; Hsieh, M. C.; Lin, F. L.; Hsu, M. K.; Hsu, M. H. J.
Med. Chem. 2006, 49, 1442.
Supplementary data
25. Damayanthi, Y.; Reddy, B. S. P.; Lown, J. W. J. Org. Chem. 1999, 64, 290.
26. (a) Kamal, A.; Laxman, E.; Ariffudin, M. Tetrahedron Lett. 2000, 41, 7743; (b)
Kamal, A.; Reddy, G. S. K.; Raghavan, S. Bioorg. Med. Chem. Lett. 2001, 13, 387;
(c) Kamal, A.; Reddy, P. S. M. M.; Reddy, D. R. Tetrahedron Lett. 2003, 44, 2857.
27. (a) Kamal, A.; Laxman, E.; Laxman, N.; Rao, M. V. Bioorg. Med. Chem. Lett. 2000,
10, 2311; (b) Kamal, A.; Reddy, B. S. N.; Reddy, G. S. K.; Ramesh, G. Bioorg. Med.
Chem. Lett. 2002, 12, 1933; (c) Kamal, A.; Ramulu, P.; Srinivas, O.; Ramesh, G.
Bioorg. Med. Chem. Lett. 2003, 13, 3517.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2011.10.080.
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cmꢁ1): 3407, 2936, 2874, 1604, 1487, 1433, 1264, 1220, 1017, 875, 743; (S)-8-
(5-(4-(di(1H-indol-3-yl)methyl) phenoxy)pentyloxy)-7-methoxy-2,3-dihydro-1H-
benzo[e]pyrrolo[1,2-a] [1,4]diazepin-5(11aH)-one (5e): Yield 49%; mp 127–
129 °C; 1H NMR (CDCl3, 300 MHz): d 7.99 (br s, 2H), 7.64 (s, 1H), 7.51 (d,
J = 4.0 Hz, 1H), 7.42–7.34 (m, 4H), 7.23 (dd, J = 6.6, 1.9 Hz, 2H), 7.15 (dt, J = 6.9,
0.9 Hz, 2H), 6.99 (dt, J = 6.9, 0.9 Hz, 2H), 6.85–6.76 (m, 3H), 6.67–6.63 (m, 2H),
5.83 (s, 1H), 4.12–4.05 (m, 2H), 4.04–3.92 (m, 2H), 3.91 (s, 3H), 3.87–3.71 (m,
3H), 2.00–1.72 (m, 6H), 1.63–1.47 (m, 4H); MS (LC) m/z 653 (M+1)+; IR (KBr)
(m
max/cmꢁ1): 3393, 2939, 1605, 1508, 1459, 1224, 1175, 1015, 746. The detail
spectral data of other compounds are available in Supplementary data.
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