Synthesis and in vitro antiproliferative activity of new 11-aminoalkylamino-substituted chromeno[2,3-b]indoles

Article abstract of DOI:10.1016/j.ejmech.2012.10.023

To search for new biological activities of the chromeno[2,3-b]indoles, the 5-oxa analog of the indolo[2,3-b]quinolines that are known to have a potent antitumor activity, a series of 11-amino derivatives with various substituents at the C-2 position were

Full text of DOI:10.1016/j.ejmech.2012.10.023

European Journal of Medicinal Chemistry 58 (2012) 441e451
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and in vitro antiproliferative activity of new 11-aminoalkylamino-
substituted chromeno[2,3-b]indoles
a
b
a
a
a
a
ꢀ
Wei Peng , Marta Switalska , Li Wang , Zhen-Wu Mei , Yoshiki Edazawa , Cui-Qing Pang ,
**
Ibrahim El-Tantawy El-Sayed a c, Joanna Wietrzyk b , Tsutomu Inokuchi
,
,
a,
*
a Division of Chemistry and Biotechnology, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
b Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, 12, R. Weigl Street, 53-114 Wroclaw, Poland
c Chemistry Department, Faculty of Science, El Menoufeia University, Shebin El Koom, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
To search for new biological activities of the chromeno[2,3-b]indoles, the 5-oxa analog of the indolo[2,3-
b]quinolines that are known to have a potent antitumor activity, a series of 11-amino derivatives with
various substituents at the C-2 position were prepared. The synthesis of the chromeno[2,3-b]indole
structure involves the cyclization of 2-phenoxy-3-indolecarboxylates 3, accessible from the indole-
3-carboxylate 1 and phenols 2, producing the chromeno[2,3-b]indol-11(6H)-ones 4, which is followed by
dehydroxychlorination with phosphorus oxychloride to afford the 11-chlorochromeno[2,3-b]indoles 5.
The treatment of 5 with various amines produced the corresponding 11-aminated chromeno[2,3-b]
Received 3 April 2012
Received in revised form
10 October 2012
Accepted 15 October 2012
Available online 24 October 2012
Keywords:
indoles 6, while some of the 11-u-aminoalkylamino derivatives 6 were transformed into the 11-u-sul-
Chromeno[2,3-b]indole
Aminoalkylamino-substituted indole
derivatives
Antiproliferative activity
MV4-11
fonylaminoalkylamino derivatives 8. The antiproliferative activity of these 11-aminochromeno[2,3-b]
indoles 6 and 8 in vitro were tested using MV4-11 (human leukemia), A549 (lung cancer), HCT116 (colon
cancer), and the normal mice fibroblast (BALB/3T3) and their potencies were described.
Ó 2012 Elsevier Masson SAS. All rights reserved.
HCT116
1. Introduction
Based on our studies on the antimalarial testing, we found that
chromeno[2,3-b]indole derivative IV (1-(3-(2-methoxychromeno
Recently, several examples of the tetracyclic ring system of the
indolo[2,3-b]quinoline (neocryptolepine, I, Fig. 1) and 5-methyl-
5H-indolo[3,2-b]quinoline (cryptolepine, II, Fig. 1) [1] have been
extensively studied for medicinal applications [2e7]. Among their
various biological properties, the antitumor activities have attrac-
ted considerable attention [8e10]. In this regard, several cryptole-
pine and neocryptolepine analogs have shown potent cytotoxicity
against several human cell lines due to their intercalating nature
with DNA. The competitive inhibition of human topoisomerase II
disrupts the normal DNA replication, leading to the apoptotic cell
death [9,11e15]. In order to decrease the cytotoxic effect of these
indolo[2,3-b]quinoline derivatives on the normal cell lines, we
attempted to bioisosterically modify the indolo[2,3-b]quinoline
structure to the 5-oxa analogs of I, that is, the chromeno[2,3-b]
indoles III (Fig. 1).
[2,3-b]indol-11-ylamino)propyl)-3-phenylurea) was considerably
less toxic compared with the indolo[2,3-b]quinoline structure V (1-
(3-(2-methoxy-5-methyl-5H-indolo[2,3-b]quinolin-11-ylamino)
propyl)-3-phenylurea) in vitro cytotoxicity with L-6 cells (rat
skeletal myoblasts) (Fig. 2).
Until now, there are few reports on the synthesis and biological
evaluation of the chromeno[2,3-b]indole derivatives III. One
example deals with the formation of 7-methylchromeno[2,3-b]
indole as a possible structure from the decomposition of the dia-
zonium sulfate prepared from 3-o-aminobenzylidene-7-
methyloxindole [16]. Some patents claimed that this type of
heterocyclic ring structure acts as one of candidates for modulating
RNA-binding proteins [17] as well as other purposes [18]. To the best
of our knowledge, no effort has been devoted to developing new
anticancer agents using the chromeno[2,3-b]indole as the lead
compound. In this paper, we report the synthesis and anti-
proliferative activity of new chromeno[2,3-b]indole derivatives
bearing aminoalkylamino side chain at the C-11 position. We
incorporated basic aminoalkylamino side chains into chromeno
[2,3-b]indole skeleton, which is similar to role of the basic side chain
* Corresponding author. Tel.: þ81 86 251 8210; fax: þ81 86 251 8021.
** Corresponding author.
E-mail addresses: wietrzyk@iitd.pan.wroc.pl (J. Wietrzyk), inokuchi@cc.
okayama-u.ac.jp (T. Inokuchi).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.10.023

442
W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
N
D
C
N
A
B
N
CH3
N
CH3
N
O
II, Cryptolepine
III, Chromeno[2,3-b]indole
I, Neocryptolepine
Fig. 1. Chemical structures of neocryptolepine (I), cryptolepine (II) and chromeno[2,3-b]indole (III).
that proved to be an important element for the antimalarial and
anticancer activities of isomeric indoloquinoline structure [19e21].
We subsequently examined the aminations of 5 bearing various
substituents R1 at the C-2 position, which is 5a, H; 5b, Cl; 5c, Br; and
5d, MeO. We employed various primary amines, which can be
categorized as
u-aminoalkylamines, u-(N,N-dialkylamino)alkyl-
2. Results and discussion
amines, -hydroxyalkylamines, cyclic amines, arylamines, and
u
tryptamine. Thus, the heating of 5aed with appropriate amines
followed by treatment with ammoniaemethanol produced the
corresponding adducts 6aex (Scheme 2).
The adducts of the aminoalkylamines 6a and 6n were further
transformed into the sulfonamides [26] 8aef upon treatment with
various sulfonyl chlorides 7aec as shown in Scheme 3.
Structures of 11-aminoalkylaminochromeno[2,3-b]indoles 6 as
well as their precursors 3e5 were confirmed by comparison with
11-aminoalkylamino-5-methylindolo[2,3-b]quinolines and their
precursors, which were synthesized to find promising antimalarial
and anticancer agents [27,28]. Thus, for example, in the conversion
of 5d (R1 ¼ MeO) to 6s, introduction of 3-aminopropylamino group
at C-11 of the chromeno[2,3-b]indole skeleton was confirmed by
2.1. Chemistry
With regard to chemistry, our retrosynthetic analysis of chro-
meno[2,3-b]indoles 6 suggested that 11-chlorochromeno[2,3-b]
indoles 5 would be a promising intermediate for installation of the
amino groups at the C-11 position by addition of amine and elim-
ination of chloride ion (Scheme 1). A similar mode of amination was
realized on the related system of 9-chlorotacrine derivatives [22].
To this end, we examined the chlorination of the chromeno[2,3-b]
indol-11(6H)-ones 4.
Several methods for the preparation of 4 have been reported by
the Claisen condensation of oxyindole and the salicylic ester fol-
lowed by cyclization [23,24], and later, by cyclization of the 20-
aminoisoflavones. However, as shown in Scheme 2, the method
based on the cyclization of the 2-phenoxyindole-3-carboxylates
available from the indole-3-carboxylate and phenols by Engqvist
and Bergman are of value for the present purpose from a divergent
point of view [25].
Methyl indole-3-carboxylate 1 was combined with phenols 2 via
chlorination with N-chlorosuccinimide (NCS) in the presence of 1,4-
dimethylpiperazine, giving the 2-phenoxy-3-indolecarboxylate 3.
Our attempt at the intramolecular acylation of 3 by heating in
boiling diphenyl ether without a catalyst was not successful.
However, the conversion was attained by heating in poly-
phosphoric acid, affording the desired chromeno[2,3-b]indol-
11(6H)-one 4 in good yields. Upon treatment with POCl3, the ketone
the signals at
d 1.82, 3.17, and 4.26 ppm due to the 3-
aminopropylamino unit. Furthermore, the substitution of Cl atom
with amino group at the C-11 caused the upfield shift of the signals
due to MeO group from
d 3.90 to 3.82 ppm, which would be
ascribable to more electron donating nature of amino group than Cl
atom. Similar trend of upfield shift was observed in the formation
of N-(3-aminopropyl)-2-methoxy-5-methyl-5H-indolo[2,3-b]qui-
nolin-11-amine (d 3.82 ppm due to MeO) from the corresponding
11-chloro-2-methoxy-5-methylindolo[2,3-b]quinoline precursor (
d
4.02 ppm due to MeO) [28].
3. Pharmacology
4
underwent dehydroxychlorination to give the desired 11-
3.1. Antiproliferative activity in vitro against MV4-11 cell line
chlorochromeno[2,3-b]indoles 5, smoothly. Assignment of 1H
NMR signals of 4 and 5 were deduced based on NMR analysis data
including COSY and by analogy with signals of indole.
The results of the cytotoxic activity in vitro were expressed as
IC50 e the concentration of the compound (in mM) that inhibits
O
Ph
O
Ph
N
H
N
H
N
H
HN
N
N
HN
O
H
MeO
MeO
N
N
Me
IV
V
Cytotoxicity L-6, IC50 (µM)
2.7
169.4
Fig. 2. In vitro cytotoxicity with L-6 cells (rat skeletal myoblasts).

W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
443
O
O
Cl
NR2R3
11
9
10
11
11
1
R1
8
D
R1
2
R1
C
A
B
7
N
H
N
3
O
N
O5
6
4
6, 11-Amino-
chromeno[2,3-b]indole
5, 11-Chloro-
chromeno[2,3-b]indole
4, Chromeno[2,3-b]indol-
11(6H)-one
Scheme 1. Retrosynthetic analysis of chromeno[2,3-b]indoles.
proliferation of the cells by 50% as compared to the untreated
control cells. The IC50 values were separately calculated for each
experiment and the mean standard deviation (ꢀSD) were pre-
sented in Tables 1e3.
Among the sulfonamide derivatives 8 (Table 2), the compounds
substituted at C-11 position with 1, -diamines mono-
u
benzenesulfonated (i.e. 8b and 8e) led to the lowest activity
against the MV4-11 cells. The benzenesulfonamides (8b and 8e)
showed 3e10 times lower antiproliferative properties than the
methanesulfonamides (8a and 8d) or naphthalene-2-sulfonamide
compounds (8c and 8f).
The results of the studies on the antiproliferative activity of the
11-alkylaminated
chromeno[2,3-b]indoles
against
human
leukemia MV4-11 cells are summarized in Tables 1 and 2. The
criterion of the antiproliferative activity of the tested compounds
which we used is an IC50 below 10 mM [29].
Most of the studied compounds of the series 6 meet this crite-
rion (the IC50 values of these compounds were between 0.12 and
Similarly, research on structureecytotoxic activity relationship
of 5H- and 6H-indolo[2,3-b]quinoline series showed that their
activity rely on the presence, position, and type of substituent. The
6,11-dimethyl-6H-indolo[2,3-b]quinolone, which is an inactive
isomer of 5,11-dimethyl-5H-indolo[2,3-b]quinoline (DIMIQ), can
acquire activity after introduction of appropriate substituents.
Since the chromeno[2,3-b]indoles can have a similar isoelectronic
structure with that of indolo[2,3-b]quinolines, it is meaningful to
discuss effect of the substituent on the chromeno[2,3-b]indoles by
analogy with the case of indolo[2,3-b]quinolines. On the other
hand, introduction of proper alkylaminoalkyl substituents into
biologically active derivatives can favor its activity and selectivity in
DNA binding [11,12].
9.20 mM) (Table 1). The most active (with IC50 below 1.02 mM) were
compounds with substitution by H, Cl, Br and MeO at the C-2
position bearing the simple 1,3-diamino or 1,4-diamino side chain
at the C-11 position (compounds 6a, 6b, 6f, 6g, 6n, 6o and 6s) and
compounds 6m and 6v. The antiproliferative activities of these
compounds are higher than activity of known anticancer drug used
e cisplatin (IC50: 2.82
mM). The substitution of the 1,4-diamino
chain at the C-11 position (6b, 6g, 6o) appeared to increase the
activity compared to the corresponding 1,3-diamino ones (6a, 6f,
6n). On the other hand, some compounds substituted at the C-11
position with alkylmonoamines (i.e. 6h, 6j, 6l, 6p and 6r) led to the
lowest activity against the MV4-11 cells. Among the 11-morpholino
substituted derivatives, compounds with substitution by 2-H, 2-Cl,
2-Br (6e, 6j, 6r) showed the lowest activity, whereas the 2-MeO
substituted compound 6v led to a marked increase in the anti-
3.2. Antiproliferative activity in vitro against A549, HCT116 and
BALB/3T3 cell lines
To study the antiproliferative activity against the human A549
and HCT116 cancer cell lines and against the BALB/3T3 normal
mouse fibroblast, nine of the most active compounds: 6a, 6b, 6f, 6g,
proliferative potency (IC50: 0.38 mM).
O
O
OH
R1
O
OMe
ii
OMe
R1
i
N
H
O
R1
N
H
N
H
O
3a, R1 = H,
b, R1 = Cl,
c, R1 = Br,
d, R1 = OMe
4a, R1 = H,
b, R1 = Cl,
c, R1 = Br,
d, R1 = OMe
1
2a, R1 = H,
b, R1 = Cl,
c, R1 = Br,
d, R1 = OMe
R2
O
Cl
O
R1
R1
iii
iv
N
N
6a-e, R1 = H,
f-m, R1 = Cl,
n-r, R1 = Br,
s-x, R1 = OMe
5a, R1 = H,
b, R1 = Cl,
c, R1 = Br,
d, R1 = OMe
Scheme 2. Synthesis of 11-chlorochromeno[2,3-b]indoles 5aed and their 11-aminated derivatives 6aex. Reagents and conditions: i) (a) NCS, 1,4-dimethylpiperazine, CH2Cl2, 0 ꢁC,
2 h; (b) trichloroacetic acid, 2aed, room temperature, 2 h; ii) PPA, 130 ꢁC, 2 h; iii) POCl3, reflux, 6e12 h; iv) appropriate amine, 80 ꢁC, 1e4 h.

444
W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
O
R3
O
S
N
H
HN
O
NH2
HN
O
R1
R1
O
O
R3
i
S
Cl
N
N
6a, R1 = H,
6n, R1 = Br
7a, R3 = Me,
b, R3 = Ph,
8a-c, R1 = H, R3 = Me, Ph, Naph
8d-f, R1 = Br, R3 = Me, Ph, Naph
c, R3 = Naph
Scheme 3. Synthesis of sulfonamides 8aef. Reagents and conditions: i) 7aec, Et3N, DMF, 0 ꢁC to room temperature, 2e4 h.
6m, 6n, 6o, 6s and 6v were chosen (Table 3). Compounds 6g, 6s and
6v revealed a selective activity against the colon cancer cells
HCT116. The antiproliferative activity of these three compounds
was 3e5 times higher against the HCT116 cells than against the
lung cancer cells A549. The antiproliferative activity of these
compounds against cancer cells is higher or similar to activity of
cisplatin used as control agent (Table 3). All the tested derivatives
are, generally, cytotoxic against cancer cell lines A549 and HCT116,
with higher IC50 value than that against the human leukemia MV4-
11 cell line. Compounds 6a, 6f and 6g are selective against cancer
cell lines, while the cytotoxicity was 2e5 times lower against
normal cell line BALB/3T3. The tested compounds 6s and 6v
expressed about 5 times lower IC50 value against lung cancer cell
line HCT116, compared to A549 or BALB/3T3. The selective activity
of these compounds suggests a recommendation for further studies
of this usefulness as potential anticancer compounds.
4. Conclusion
We have described the design and synthesis of a series of novel
11-aminochromeno[2,3-b]indole
derivatives,
whose
anti-
proliferative activity were evaluated using the MV4-11 (human
leukemia), A549 (human lung cancer), HCT116 (human colon
cancer), and normal mice fibroblast (BALB/3T3) cell lines. Only
a few of the tested compounds showed a very high antiproliferative
activity, especially against the MV4-11 leukemia cell line (i.e., 6s,
IC50: 0.12 mM) and HCT116 cell line (i.e., 6v, IC50: 1.70 mM). These
results indicated that the 11-aminoalkylamino group is important
for their activity. Moreover, in the 3-aminopropylamino analogs,
a marked increase in potency is observed with the addition of a Cl
or a MeO group at the C-2 position. These results help to further
understand the critical molecular requirements that lead to the
antiproliferative properties of the chromeno[2,3-b]indole series.
5. Experimental
3.3. Spectroscopic characterization of 6s interacting with DNA
All commercial chemicals and solvents were used without
further purification. Reactions were monitored by thin layer chro-
matography (TLC) on silica gel plates (60 F254) and flash chroma-
tography was performed on silica gel (230e400 mesh) using
a gradient solvent system. The 1H and 13C NMR spectra were
measured on a Varian INOVA-600 spectrometer (600 MHz) with
Molecular modeling and in vitro tests showed that neo-
cryptolepine and its analogs were able to intercalate DNA strongly
and inhibited topoisomerase II activity [11,13]. However, it is
possible that the cellular enzyme, which is inhibited in vitro by the
compound, is not its primary target in the intact cell. As showed
Humeniuk et al. the cells resistant to topoisomerase II poison (HL-
60/MX2), etoposide, were still sensitive to some neocryptolepine
derivatives [14].
UVevisible spectroscopy is the most common and convenient
way to study interaction between small molecule and nucleic acid.
Generally, red shift (or blue shift) and hypochromic (or hyper-
chromic) effect are observed in the absorption spectra if molecules
interact with DNA. So, the DNA binding ability of representative
compound 6s was investigated by UVevis absorption.
CDCl3 or DMSO-d6 as the solvent. Chemical shifts (d ppm) were
determined using tetramethylsilane (TMS) as the internal standard
and the coupling constants (J) are given in hertz. Melting points
were determined on a J-Science RFS-10 hot stage microscope. High
resolution mass spectra were obtained on a Bruker micrOTOF II-
SKA spectrometer. Elemental analyses were measured on a Perkin
Elmer 2400 II elemental analyzer.
The DNA binding study of the chromeno[2,3-b]indole derivative
6s was performed using UVevis absorption spectroscopy with
salmon fish sperm DNA in phosphate buffer (pH 7.0) at 20 ꢁC. The
red shift and hypochromic effect were observed in the absorption
spectra while the DNA solution was gradually added to the solution
of the compound 6s. The results in Fig. 3(a) show that the
absorption band at 349 nm for 6s decrease while increasing the
DNA concentration. The maximum absorption shifts from 349 nm
to a longer wavelength at 353 nm. The intercalation binding of
a small molecule with DNA commonly results in hypochromism
and red shift phenomenon of the maximum absorption according
to Barton’s results [30], suggesting that compound 6s interacts with
DNA through the intercalation mode. The binding constant K of 6se
DNA was calculated as 2.79 ꢂ 104 L molꢃ1 according to double-
reciprocal equation [31]. The large K value of 6s suggested
a strong binding ability toward DNA which might result in the anti-
proliferative activity.
5.1. Chemistry: general and methods
5.1.1. Methyl 2-phenoxy-1H-indole-3-carboxylate (3a)
A
suspension of methyl indole-3-carboxylate (1, 2.08 g,
11.9 mmol) in CH2Cl2 (50 ml) was cooled to 0 ꢁC under argon and
treated sequentially with 1,4-dimethylpiperazine (0.75 g,
6.6 mmol) and N-chlorosuccinimide (1.75 g, 13.1 mmol) in one
portion. The resulting solution was stirred for 2 h at 0 ꢁC and then
a solution of phenol (2a, 2.30 g, 24.5 mmol) and trichloroacetic acid
(0.50 g, 3.1 mmol) in CH2Cl2 (50 ml) was added and the solution
was stirred at room temperature for 2 h. The reaction mixture was
washed with aq. NaHCO3 (10%), aq. HCl (1 M) and water. The
organic layer was dried over MgSO4. The product 3a was isolated as
white solids by chromatography (SiO2, hexaneeAcOEt 5:1 V/V);
yield: 2.39 g (75%). Mp: 138e140 ꢁC [lit. mp: 161e162 ꢁC]; Rf ¼ 0.64
(hexaneeAcOEt 3:1 V/V); 1H NMR (CDCl3):
d
3.78 (s, 3H, COOMe),
7.06 (dd, J ¼ 7.7, 1.2 Hz, 1H, ArH), 7.15 (t, J ¼ 7.8 Hz, 2H, 2ꢂ ArH),

W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
Table 1 (continued)
445
Table 1
Antiproliferative activity of 11-alkylaminated chromeno[2,3-b]indoles 6 against
human leukemia MV4-11 cell line.
Compound
R1
R2
MV4-11
IC50 M)
R1
R2
MV4-11
IC50 M)
(
m
Compound
(m
Cisplatin
2.82 ꢀ 0.45
1.02 ꢀ 0.10
NEt2
6q
6r
Br
Br
4.93 ꢀ 0.26
N
H
N
H
NH2
NH2
6a
H
H
H
25.26 ꢀ 0.78
N
O
6b
6c
0.76 ꢀ 0.10
7.66 ꢀ 2.05
N
H
N
H
NH2
OH
6s
6t
MeO
MeO
0.12 ꢀ 0.07
7.26 ꢀ 0.37
N
H
OH
N
H
NEt2
6d
H
6.02 ꢀ 1.25
N
H
NEt2
6u
6v
MeO
MeO
3.45 ꢀ 0.49
0.38 ꢀ 0.05
N
H
6e
6f
H
9.20 ꢀ 2.20
0.86 ꢀ 0.15
N
O
N
H
NH2
Cl
N
O
NH2
6g
6h
Cl
Cl
0.76 ꢀ 0.15
>30.60
N
H
6w
6x
MeO
MeO
3.04 ꢀ 1.06
4.35 ꢀ 0.85
NH
N
H
N
H
OH
Ph
N
H
NEt2
6i
6j
Cl
Cl
7.00 ꢀ 0.34
>29.52
N
H
7.19e7.29 (m, 3H, 3ꢂ ArH), 7.33 (t, J ¼ 8.1 Hz, 2H, 2ꢂ ArH), 8.12 (d,
J ¼ 7.6 Hz, 1H, ArH), 8.56 (br s, 1H, NH); 13C NMR (CDCl3):
d
50.9,
N
O
92.6, 110.8, 117.4 (2C), 121.2, 122.2, 122.6, 124.4, 125.7, 129.92, 129.93
(2C),151.6,156.2,164.4. Anal. calcd for C16H13NO3: C 71.90, H 4.90, N
5.24. Found: C 71.95, H 4.57, N 5.23. HRMS (ESI) calcd for C16H12NO3
[M ꢃ H]ꢃ: 266.0823, found 266.0801.
6k
Cl
7.57 ꢀ 2.04
NH
5.1.2. Methyl 2-(4-chlorophenoxy)-1H-indole-3-carboxylate (3b)
Yield: 84%, white solids; mp: 154e155 ꢁC; Rf ¼ 0.86 (hexanee
N
H
AcOEt 1:1 V/V); 1H NMR (CDCl3):
d 3.79 (s, 3H, COOMe), 6.93e
7.03 (m, 2H, 2ꢂ ArH), 7.21e7.33 (m, 5H, 5ꢂ ArH), 8.08e8.17 (d,
N
H
J ¼ 7.2 Hz, 1H, ArH), 8.42 (br s, 1H, NH); 13C NMR (CDCl3):
d 51.0,
6l
Cl
Cl
Br
>32.39
93.3, 110.8, 118.1 (2C), 121.4, 122.4, 123.0, 125.5, 129.3, 129.85 (2C),
129.88, 150.7, 155.2, 164.1. Anal. calcd for C16H12ClNO3: C 63.69, H
4.01, N 4.64. Found: C 63.90, H 3.71, N 4.47. HRMS (ESI) calcd for
Me
N
6m
6n
0.63 ꢀ 0.05
0.97 ꢀ 0.24
16H11ClNO3 [M ꢃ H]ꢃ: 300.0433, found 300.0407.
N
C
5.1.3. Methyl 2-(4-bromophenoxy)-1H-indole-3-carboxylate (3c)
Yield: 90%, white solids; mp: 156e158 ꢁC; Rf ¼ 0.72 (hexanee
N
H
NH2
AcOEt 2:1 V/V); 1H NMR (CDCl3):
d 3.79 (s, 3H, COOMe), 6.92 (m,
2H, 2ꢂ ArH), 7.22e7.33 (m, 3H, 3ꢂ ArH), 7.40e7.47 (m, 2H, 2ꢂ ArH),
8.12 (d, J ¼ 8.4 Hz, 1H, ArH), 8.48 (br s, 1H, NH); 13C NMR (CDCl3):
NH2
d
51.0, 93.3, 110.8, 116.7, 118.5 (2C), 121.4, 122.4, 123.0, 125.5, 129.9,
6o
6p
Br
Br
0.72 ꢀ 0.07
>26.94
N
H
132.8 (2C), 150.6, 155.8, 164.2. Anal. calcd for C16H12BrNO3: C 55.51,
H 3.49, N4.05. Found: C 55.40, H 3.31, N 3.81. HRMS (ESI) calcd for
C
C
16H11BrNO3 [M(79Br)
ꢃ
H]ꢃ: 343.9928, found 343.9897;
16H11BrNO3 [M(81Br) ꢃ H]ꢃ: 345.9902, found 345.9881.
N
H
OH

446
W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
Table 2
5.1.5. Preparation of chromeno[2,3-b]indol-11(6H)-one (4a)
Antiproliferative activity of sulfonamide derivatives 8 against human leukemia
MV4-11 cell line.
Compound 3a (0.20 g, 0.75 mmol) was heated in polyphosphoric
acid (PPA, 2 g) at 130 ꢁC for 2 h. The reaction mixture was allowed to
cool to 80 ꢁC and water (80 ml) was added. The solids thus formed
was isolated by filtration, washed with water and dried, giving 4a as
gray solids; yield: 168 mg (94%). Mp: 342e344 ꢁC [lit. mp: 344e
Compound R1
R2
MV4-11
IC50 M)
(m
Cisplatin
2.82 ꢀ 0.45
349 ꢁC (decomp.)]; 1H NMR (DMSO-d6):
d
7.26e7.36 (m, 2H, 2ꢂ
O
O
ArH), 7.47e7.56 (m, 2H, 2ꢂ ArH), 7.72e7.76 (m, 1H, ArH), 7.78e7.82
S
8a
8b
H
H
7.74 ꢀ 1.46
(m,1H, ArH), 8.10 (d, J ¼ 7.2 Hz,1H, ArH), 8.25 (dd, J ¼ 7.8, 1.2 Hz,1H,
N
H
N
Me
ArH), 12.88 (s, 1H, NH); 13C NMR (DMSO-d6):
d 98.7, 111.8, 117.7,
H
O
120.4, 121.9, 122.0, 123.5, 123.6, 125.0, 125.6, 131.9, 132.9, 153.5,
155.8, 171.6. HRMS (ESI) calcd for C15H8NO2 [M ꢃ H]ꢃ: 234.0561,
found 234.0540.
O
S
>23.17
N
H
N
H
5.1.6. 2-Chlorochromeno[2,3-b]indol-11(6H)-one (4b)
Yield: 91%, gray solids; mp: >370 ꢁC (decomp.); 1H NMR
(DMSO-d6): 7.30 (t, J ¼ 7.8 Hz, 1H, C9-H), 7.34 (t, J ¼ 7.8 Hz, 1H, C8-
H), 7.50 (d, J ¼ 7.8 Hz, 1H, C7-H), 7.80 (d, J ¼ 9.0 Hz, 1H, C4-H), 7.83
(d,d, J ¼ 9.0, 2.4 Hz, 1H, C3-H), 8.09 (d, J ¼ 7.8 Hz,1H, C10-H), 8.14 (d,
O
O
S
S
8c
H
2.41 ꢀ 1.06
N
H
N
H
J ¼ 2.4 Hz, 1H, C1-H), 12.99 (s, 1H, NH); 13C NMR (DMSO-d6):
d 98.8,
111.9, 120.1, 120.5, 121.6, 122.2, 123.9, 124.6, 124.8, 129.4, 132.0,
132.5, 152.0, 155.8, 170.2. HRMS (ESI) calcd for
C15H7ClNO2
O
O
[M ꢃ H]ꢃ: 268.0171, found 268.0151.
8d
8e
Br
Br
6.22 ꢀ 1.25
>19.59
N
H
N
H
Me
5.1.7. 2-Bromochromeno[2,3-b]indol-11(6H)-one (4c)
Yield: 82%, gray solids; mp: >370 ꢁC; 1H NMR (DMSO-d6): 7.31
(t, J ¼ 7.8 Hz, 1H, C9-H), 7.35 (t, J ¼ 7.8 Hz, 1H, C8-H), 7.51 (d,
J ¼ 7.8 Hz, 1H, C7-H), 7.76 (d, J ¼ 9.0 Hz, 1H, C4-H), 7.96 (d,d, J ¼ 9.0,
2.4 Hz, 1H, C3-H), 8.09 (d, J ¼ 7.8 Hz, 1H, C10-H), 8.29 (d, J ¼ 2.4 Hz,
O
O
S
N
H
N
H
1H, C1-H), 12.99, 13.07 (s, 1H, NH); 13C NMR (DMSO-d6):
d 98.8,
112.0,117.3,120.4,120.5,121.7,122.2,124.0, 125.2,127.7,132.0,135.4,
152.5, 155.9, 170.2. HRMS (ESI) calcd for 15H7BrNO2
O
O
C
S
[M(79Br)
ꢃ
H]ꢃ: 311.9666, found 311.9651; C15H7BrNO2
8f
Br
5.75 ꢀ 0.50
N
H
N
H
[M(81Br) ꢃ H]ꢃ: 313.9640, found 313.9621.
5.1.8. 2-Methoxychromeno[2,3-b]indol-11(6H)-one (4d)
Yield: 84%, gray solids; mp: 265e271 ꢁC (decomp.); 1H NMR
(DMSO-d6):
d
3.89 (s, 3H, OMe), 7.28 (t, J ¼ 7.8 Hz, 1H, C9-H), 7.28 (t,
J ¼ 7.8 Hz, 1H, C8-H), 7.38 (d,d, J ¼ 9.0, 3.0 Hz, 1H, C3-H), 7.48 (d,
J ¼ 7.8 Hz,1H, C7-H), 7.65 (d, J ¼ 3.0 Hz,1H, C1-H), 7.70 (d, J ¼ 9.0 Hz,
1H, C4-H), 8.10 (d, J ¼ 7.8 Hz, 1H, C10-H), 12.82 (s, 1H, NH); 13C NMR
5.1.4. Methyl 2-(4-methoxyphenoxy)-1H-indole-3-carboxylate (3d)
Yield: 80%, white solids; mp: 135e136 ꢁC; Rf ¼ 0.74 (hexanee
AcOEt 1:1 V/V); 1H NMR (CDCl3):
d 3.79 (s, 3H, OMe), 3.85 (s, 3H,
(DMSO-d6):
d 55.7, 98.4, 106.6, 111.7, 119.1, 120.4, 120.8, 121.8, 121.9,
COOMe), 6.85e6.92 (m, 2H, 2ꢂ ArH), 7.05e7.11 (m, 2H, 2ꢂ ArH),
123.6, 124.2, 132.0, 147.9, 155.9, 156.2, 171.4. HRMS (ESI) calcd for
C
7.16e7.22 (m, 2H, 2ꢂ ArH), 7.25 (m, 1H, ArH), 8.10 (d, J ¼ 7.9 Hz, 1H,
16H10NO3 [M ꢃ H]ꢃ: 264.0666, found 264.0658.
ArH), 8.28 (br s, 1H, NH); 13C NMR (CDCl3):
d 50.9, 55.7, 91.3, 110.6,
115.05, 115.07, 119.55, 119.58, 121.1, 122.2, 122.3, 125.9, 129.7, 148.9,
153.1, 156.8, 164.6. Anal. calcd for C17H15NO4: C 68.68, H 5.09, N4.71.
Found: C 68.09, H 4.67, N 4.85. HRMS (ESI) calcd for C17H14NO4
[M ꢃ H]ꢃ: 296.0928, found 296.0902.
5.1.9. 11-Chlorochromeno[2,3-b]indole (5a)
A solution of 4a (0.69 g, 2.9 mmol) in POCl3 (18 ml) was refluxed
for 6e12 h. The reaction mixture was cooled and poured into ice.
The solids thus formed were isolated by filtration, washed with
water and a cold aqueous saturated NaHCO3, dried. The product
was purified by chromatography (SiO2, hexaneeAcOEt 3:1 V/V)
giving 5a as red solids; yield: 471 mg (63%). Mp: 205e207 ꢁC;
Table 3
Antiproliferative activity of 11-alkylaminated chromeno[2,3-b]indoles against
normal mice fibroblast BALB/3T3 and against cancer cell lines A549 and HCT116.
Rf ¼ 0.63 (hexaneeAcOEt 1:1 V/V); 1H NMR (CDCl3):
d 7.30e7.36
(m, 1H, ArH), 7.49e7.59 (m, 2H, 2ꢂ ArH), 7.66e7.76 (m, 3H, 3ꢂ
Compound
BALB/3T3
IC50 M)
A549
IC50
HCT116
IC50 M)
ArH), 8.12e8.19 (m, 1H, ArH), 8.20e8.25 (m, 1H, ArH); 13C NMR
(
m
(
mM)
(m
(CDCl3):
d 117.8, 118.5, 119.4, 122.5, 123.0, 123.1, 123.8, 124.8, 125.5,
Cisplatin
6a
6b
6f
6g
6m
6n
6o
6s
6v
8.7 ꢀ 0.97
13.42 ꢀ 0.65
12.08 ꢀ 1.28
10.10 ꢀ 1.10
10.95 ꢀ 1.50
16.78 ꢀ 5.25
8.94 ꢀ 0.84
9.55 ꢀ 0.81
6.87 ꢀ 1.74
8.73 ꢀ 2.27
9.87 ꢀ 2.4
4.26 ꢀ 1.44
3.90 ꢀ 1.38
5.59 ꢀ 1.38
5.56 ꢀ 1.88
10.80 ꢀ 1.04
6.19 ꢀ 1.67
7.36 ꢀ 2.24
9.29 ꢀ 1.10
10.62 ꢀ 0.54
8.5 ꢀ 0.54
5.70 ꢀ 1.30
7.20 ꢀ 3.34
3.28 ꢀ 0.89
2.03 ꢀ 0.77
9.68 ꢀ 3.01
4.19 ꢀ 1.13
6.74 ꢀ 1.64
1.93 ꢀ 0.24
1.70 ꢀ 0.54
130.5, 132.6, 138.4, 151.2, 151.7, 163.1. Anal. calcd for C15H8ClNO: C
71.02, H 3.18, N 5.52. Found: C 70.97, H 2.90, N 5.29.
5.1.10. 2,11-Dichlorochromeno[2,3-b]indole (5b)
Yield: 53%, red solids; mp: 190e192 ꢁC; Rf ¼ 0.52 (hexanee
AcOEt 2:1 V/V); 1H NMR (CDCl3):
d
7.35e7.39 (t, J ¼ 7.8 Hz, 1H,
C9-H), 7.58e7.61 (t, J ¼ 7.8 Hz, 1H, C8-H), 7.70e7.71 (m, 2H, C3-H,
C4-H), 7.71e7.74 (d, J ¼ 7.8 Hz, 1H, C-7H), 8.16 (m, 1H, C1-H), 8.22e
8.26 (d, J ¼ 7.8 Hz, 1H, C10-H); 13C NMR (CDCl3):
d 119.3, 119.4, 119.7,

W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
447
Fig. 3. (a) UVevis absorption spectra of compound 6s and 6seDNA at 20 ꢁC. C6s ¼ 39
mol/l, CDNA ¼ 0.00, 0.50, 1.00, 1.50, 1.93, 2.40, 2.84, 3.28, 3.71, 4.14, 4.56, 4.97, 5.37, 5.77, 6.16,
m
6.55, 6.92, 7.30, 7.66
mmol/l for curve 1e19 in pH 7.0 phosphate buffer solution; (b) The plot of A0/(A0 ꢃ A) vs 1/[DNA] for 6seDNA. Double-reciprocal equation: Eq. (1).
122.5,123.0,123.5,124.1,124.9,130.8,131.2,132.7,137.4,149.4,151.0,
162.5. Anal. calcd for C15H7Cl2NO: C 62.53, H 2.45, N 4.86. Found: C
62.52, H 2.14, N 4.55.
NH and NH2), 4.02 (t, J ¼ 7.2 Hz, 2H, NHCH2), 7.11 (t, J ¼ 7.2 Hz, 1H,
ArH), 7.23 (t, J ¼ 7.2 Hz, 1H, ArH), 7.45e7.52 (m, 2H, 2ꢂ ArH), 7.69
(dd, J ¼ 8.5, 1.2 Hz, 1H, ArH), 7.75 (t, J ¼ 7.2 Hz, 1H, ArH), 7.87 (d,
J ¼ 7.6 Hz, 1H, ArH), 8.45 (dd, J ¼ 8.2, 0.9 Hz, 1H, ArH); 13C NMR
5.1.11. 2-Bromo-11-chlorochromeno[2,3-b]indole (5c)
(DMSO-d6): d 27.5, 29.8, 40.9, 47.2, 95.3, 115.8, 117.7, 117.9, 119.8,
Yield: 51%, red solids; mp: 193e194 ꢁC; Rf ¼ 0.68 (hexanee
121.8, 123.70, 123.74 (2C), 124.0, 132.0, 148.3, 148.7, 150.8, 164.0.
HRMS (ESI) calcd for C19H18N3O [M ꢃ H]ꢃ: 304.1455, found
304.1439.
AcOEt 1:1 V/V); 1H NMR (CDCl3):
d
7.33e7.37 (t, J ¼ 7.2 Hz, 1H,
C9-H), 7.55e7.59 (t, J ¼ 6.6 Hz, 1H, C8-H), 7.60e7.63 (d, J ¼ 8.4 Hz,
1H, C7-H), 7.69 (d, J ¼ 8.4 Hz, 1H, C4-H), 7.82 (dd, J ¼ 8.4, 2.4 Hz, 1H,
C3-H), 8.20 (d, J ¼ 7.8 Hz, 1H, C10-H), 8.27 (d, J ¼ 2.4 Hz, 1H, C1-H);
5.2.3. 3-(Chromeno[2,3-b]indol-11-ylamino)propan-1-ol (6c)
Yield: 68%, yellow solids; mp: 204e205 ꢁC; 1H NMR (DMSO-d6):
13C NMR (CDCl3):
d 117.9,119.5,120.1,122.7,123.2,123.5,124.1,127.9,
130.9, 131.2, 135.4, 137.0, 150.0, 151.4, 162.6. Anal. calcd for
15H7BrClNO: C 54.17, H 2.12, N 4.21. Found: C 54.03, H 1.92, N 3.93.
d
1.95 (quint, J ¼ 6.2 Hz, 2H, CH2CH2CH2), 3.54 (q, J ¼ 6.0 Hz, 2H,
C
NHCH2), 4.13 (q, J ¼ 6.2 Hz, 2H, CH2OH), 4.72 (t, J ¼ 4.7 Hz, 1H, OH),
7.11 (t, J ¼ 7.2 Hz,1H, ArH), 7.25 (t, J ¼ 7.2 Hz,1H, ArH), 7.44e7.53 (m,
2H, 2ꢂ ArH), 7.67e7.72 (m, 1H, ArH), 7.75 (t, J ¼ 7.2 Hz, 1H, ArH),
7.94 (d, J ¼ 7.8 Hz, 1H, ArH), 8.12 (br s, 1H, NH), 8.40 (dd, J ¼ 8.2,
5.1.12. 11-Chloro-2-methoxychromeno[2,3-b]indole (5d)
Yield: 67%, red solids; mp: 169e171 ꢁC; Rf ¼ 0.64 (hexaneeAcOEt
1:1 V/V); 1H NMR (CDCl3):
d
3.90 (s, 3H, OMe), 7.23 (dd, J ¼ 9.6,
1.17 Hz, 1H, ArH); 13C NMR (DMSO-d6):
d 32.6, 45.2, 58.3, 95.6, 115.7,
3.0 Hz, 1H, C3-H), 7.28 (t, J ¼ 7.2 Hz, 1H, C8-H), 7.46 (d, J ¼ 3.0 Hz, 1H,
C1-H), 7.52 (t, J ¼ 7.8 Hz, 1H, C9-H), 7.58 (d, J ¼ 9.0 Hz, 1H, C10-H),
7.64 (d, J ¼ 7.8 Hz, 1H, C4-H), 8.17 (d, J ¼ 7.8 Hz, 1H, C7-H); 13C NMR
117.8, 117.9, 119.8, 122.0, 123.6, 123.7, 123.7, 124.0, 132.1, 148.3, 148.8,
150.8, 164.0. HRMS (ESI) calcd for C18H15N2O2 [M ꢃ H]ꢃ: 291.1139,
found 291.1123.
(CDCl3):
d 55.9, 107.0, 118.7, 118.9, 119.3, 120.5, 122.6, 122.6, 123.0,
123.8, 130.5, 137.7, 145.7, 152.4, 156.3, 163.4. Anal. calcd for
16H10ClNO2: C 67.74, H 3.55, N 4.94. Found: C68.00, H 3.21, N 4.79.
5.2.4. N-(5-(Diethylamino)pentan-2-yl)chromeno[2,3-b]indol-11-
amine (6d)
C
Yield: 78%, yellow solids; mp: 136e139 ꢁC; 1H NMR (DMSO-d6):
d
0.72 (t, J ¼ 7.0 Hz, 6H, 2ꢂ CH2CH3),1.18e1.33 (m, 2H, CH2CH2NEt2),
5.2. General procedure for the synthesis of 11-aminochromeno[2,3-
b]indole (6aex)
1.55 (d, J ¼ 6.2 Hz, 3H, Me), 1.67e1.86 (m, 2H, CH(Me)CH2CH2),
2.10e2.25 (m, 6H, CH2NEt2 and 2ꢂ CH2CH3), 4.65 (m, 1H, CH), 7.14
(t, J ¼ 7.2 Hz,1H, ArH), 7.26 (t, J ¼ 7.2 Hz, 1H, ArH), 7.48 (d, J ¼ 7.2 Hz,
1H, ArH), 7.52 (t, J ¼ 7.2 Hz, 1H, ArH), 7.71 (t, J ¼ 7.9 Hz, 2H, 2ꢂ ArH),
7.77 (t, J ¼ 7.2 Hz, 1H, ArH), 7.81 (d, J ¼ 9.7 Hz, 1H, NH), 8.52 (d,
11-Chlorochromeno[2,3-b]indole (5aed) (0.3 mmol) and an
excess of the appropriate aminoalkylamine (1.5 mmol) were heated
together at 80 ꢁC for 1e4 h. TLC monitoring was used to ensure the
completion of the reaction. The resulting brown crude oil was
purified by flash chromatography using AcOEte2 N ammonia in
MeOH (9:1) as an eluent to give pure product as yellow solids.
J ¼ 8.2 Hz,1H, ArH); 13C NMR (DMSO-d6):
d 11.4 (2C), 21.8, 23.4, 35.1,
46.0 (2C), 51.6, 52.0, 95.6, 115.7, 117.8, 118.1, 119.9, 121.5, 123.6, 123.7,
123.8, 124.1, 132.2, 148.2, 148.9, 150.8, 164.2. HRMS (ESI) calcd for
C
24H28N3O [M ꢃ H]ꢃ: 374.2238, found 374.2214.
5.2.1. N-(3-Aminopropyl)chromeno[2,3-b]indol-11-amine (6a)
Yield: 93%, yellow solids; mp: 135e136 ꢁC; 1H NMR (DMSO-d6):
5.2.5. 11-Morpholinochromeno[2,3-b]indole (6e)
Yield: 62%, yellowish-orange solids; mp: 108e115 ꢁC (decomp.);
d
1.84 (quint, J ¼ 6.6 Hz, 2H, CH2CH2CH2), 2.79 (t, J ¼ 6.2 Hz, 2H,
1H NMR (DMSO-d6):
d
3.24 (t, J ¼ 4.8 Hz, 4H, 2ꢂ NCH2), 3.52 (t,
CH2NH2), 4.18 (t, J ¼ 6.5 Hz, 2H, NHCH2), 4.20e4.50 (br s, 3H, NH
and NH2), 7.08e7.13 (m, 1H, ArH), 7.21e7.26 (m, 1H, ArH), 7.44e7.51
(m, 2H, 2ꢂ ArH), 7.69 (dd, J ¼ 8.5, 1.2 Hz, 1H, ArH), 7.73e7.78 (m, 1H,
J ¼ 4.8 Hz, 4H, 2ꢂ CH2O), 6.86e6.96 (m, 3H, 3ꢂ ArH), 6.97e7.02 (m,
1H, ArH), 7.17 (d, J ¼ 7.9 Hz, 1H, ArH), 7.24 (d, J ¼ 8.4 Hz, 1H, ArH),
7.34e7.42 (m, 1H, ArH), 7.45 (dd, J ¼ 7.6, 1.5 Hz, 1H, ArH); 13C NMR
ArH), 7.96 (d, J ¼ 7.9 Hz, 1H, ArH), 8.34 (d, J ¼ 8.2 Hz, 1H, ArH); 13
C
(DMSO-d6):
d 50.2 (2C), 65.5 (2C), 99.1, 110.5, 116.8, 118.6, 118.7,
NMR (DMSO-d6):
d 31.7, 39.8, 47.1, 95.2, 115.7, 117.8, 117.9, 119.7,
120.7, 121.0, 126.4, 128.0, 130.4, 132.4, 132.8, 153.7, 157.3, 190.3.
HRMS (ESI) calcd for C19H17N2O3 [M þ OH]ꢃ: 321.1245, found
321.1231.
121.9, 123.7, 123.7, 123.8, 123.9, 132.0, 148.2, 148.7, 150.8, 163.9.
HRMS (ESI) calcd for C18H16N3O [M ꢃ H]ꢃ: 290.1299, found
290.1286.
5.2.6. N-(3-Aminopropyl)-2-chlorochromeno[2,3-b]indol-11-
amine (6f)
5.2.2. N-(4-Aminobutyl)chromeno[2,3-b]indol-11-amine (6b)
Yield: 90%, yellow solids; mp: 137e139 ꢁC; 1H NMR (DMSO-d6):
Yield: 82%, yellow solids; mp: 204e208 ꢁC; 1H NMR (DMSO-d6):
d
1.44 (quint, J ¼ 7.1 Hz, 2H, NHCH2CH2), 1.82 (quint, J ¼ 7.2 Hz, 2H,
d
1.84 (quint, J ¼ 6.0 Hz, 2H, CH2CH2CH2), 2.74 (t, J ¼ 6.0 Hz, 2H,
CH2CH2NH2), 2.55 (t, J ¼ 7.2 Hz, 2H, CH2NH2), 3.40e3.90 (br s, 3H,

448
W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
CH2NH2), 4.13 (t, J ¼ 6.6 Hz, 2H, NHCH2), 4.06e4.28 (br s, 3H, NH
and NH2), 7.11 (t, J ¼ 7.6 Hz, 1H, ArH), 7.25 (t, J ¼ 7.5 Hz, 1H, ArH),
7.46 (d, J ¼ 7.9 Hz, 1H, ArH), 7.71e7.75 (m, 1H, ArH), 7.76e7.81 (m,
1H, ArH), 7.93 (d, J ¼ 7.9 Hz, 1H, ArH), 8.47 (d, J ¼ 2.4 Hz, 1H, ArH);
J ¼ 8.2 Hz, 1H, ArH), 7.47 (d, J ¼ 7.6 Hz, 1H, ArH), 7.52 (d, J ¼ 7.9 Hz,
1H, ArH), 7.70e7.76 (m, 1H, ArH), 7.79 (dd, J ¼ 9.0, 2.2 Hz, 1H, ArH),
7.87 (d, J ¼ 7.9 Hz, 1H, ArH), 8.31 (t, J ¼ 6.0 Hz, 1H, NHCH2), 8.59 (d,
J ¼ 2.4 Hz, 1H, ArH), 10.83 (br s, 1H, NHindole); 13C NMR (DMSO-d6):
13C NMR (DMSO-d6):
d
32.1, 39.6, 46.7, 95.6, 117.3, 118.0, 119.7, 120.0,
d 25.8, 48.2, 94.8, 110.3, 111.4, 116.4, 117.1, 118.1, 118.3 (2C), 119.9,
122.2, 123.2, 123.7, 124.2, 127.9, 131.7, 147.1, 148.8, 149.4, 163.7.
HRMS (ESI) calcd for C18H15ClN3O [M ꢃ H]ꢃ: 324.0909, found
324.0895.
121.0 (2C), 122.2, 122.4, 123.0, 123.5, 124.9, 126.9, 128.7, 132.5, 136.1,
149.0, 149.1, 161.5. HRMS (ESI) calcd for C25H17ClN3O [M ꢃ H]ꢃ:
410.1066, found 410.1066.
5.2.7. N-(4-Aminobutyl)-2-chlorochromeno[2,3-b]indol-11-amine
(6g)
5.2.12. N-Allyl-2-chlorochromeno[2,3-b]indol-11-amine (6l)
Yield: 88%, yellow solids; mp: 220e225 ꢁC (decomp.); 1H NMR
Yield: 73%, yellow solids; mp: 186e188 ꢁC; 1H NMR (DMSO-d6):
(DMSO-d6):
d
4.61 (s, 2H, NHCH2), 5.32 (dd, J ¼ 10.8,1.2 Hz,1H, CH]
d
1.42 (quint, J ¼ 7.2 Hz, 2H, NHCH2CH2), 1.82 (quint, J ¼ 7.2 Hz, 2H,
CH2 (HeH cis)), 5.38 (dd, J ¼ 17.4, 1.8 Hz, 1H, CH]CH2 (HeH trans)), 6.19
(ddt, J ¼ 17.2, 10.4, 4.7 Hz, 1H, CH), 7.12 (td, J ¼ 7.8, 1.2 Hz, 1H, ArH),
7.27 (td, J ¼ 7.8, 1.2 Hz, 1H, ArH), 7.47 (d, J ¼ 7.8 Hz, 1H, ArH), 7.72e
7.77 (m, 1H, ArH), 7.78e7.86 (m, 2H, 2ꢂ ArH), 8.43 (br s, 1H, NH),
CH2CH2NH2), 2.53 (t, J ¼ 6.8 Hz, 2H, CH2NH2), 3.23e3.67 (br s, 3H,
NH and NH2), 4.00 (t, J ¼ 7.0 Hz, 2H, NHCH2), 7.13 (t, J ¼ 6.6 Hz, 1H,
ArH), 7.26 (t, J ¼ 7.2 Hz, 1H, ArH), 7.47 (d, J ¼ 7.6 Hz, 1H, ArH), 7.71e
7.74 (m, 1H, ArH), 7.76e7.80 (m, 1H, ArH), 7.85 (d, J ¼ 7.9 Hz, 1H,
8.62 (d, J ¼ 2.4 Hz, 1H, ArH); 13C NMR (DMSO-d6):
d 48.6, 96.1, 117.0,
ArH), 8.60 (d, J ¼ 2.4 Hz, 1H, ArH); 13C NMR (DMSO-d6):
d
27.4, 30.0,
117.2, 118.1, 119.7, 120.1, 122.3, 123.3 (2C), 124.5, 128.0, 131.8, 135.0,
147.5, 148.8, 149.4, 163.8. HRMS (ESI) calcd for C18H12ClN2O
[M ꢃ H]ꢃ: 307.0644, found 307.0643.
41.0, 47.4, 95.7, 117.4, 118.1, 119.7, 120.0, 122.1, 123.2, 123.6, 124.3,
127.9, 131.7, 147.2, 148.8, 149.4, 163.8. HRMS (ESI) calcd for
C
19H17ClN3O [M ꢃ H]ꢃ: 338.1066, found 338.1058.
5.2.13. 2-Chloro-11-(4-methyl-1,4-diazepan-1-yl)chromeno[2,3-b]
indole (6m)
5.2.8. 3-(2-Chlorochromeno[2,3-b]indol-11-ylamino)propan-1-ol
(6h)
Yield: 53%, yellowish-orange solids; mp: 170e173 ꢁC; 1H NMR
Yield: 72%, yellow solids; mp: 254e258 ꢁC (decomp.); 1H NMR
(DMSO-d6): d 1.90 (m, 2H, 6-CH2 diazepane), 2.46 (s, 3H, 4-Mediazepane),
(DMSO-d6):
d
1.95 (quint, J ¼ 6.5 Hz, 2H, CH2CH2CH2), 3.52 (t,
2.74 (t, J ¼ 5.4 Hz, 2H, 3-CH2 diazepane), 2.86 (t, J ¼ 5.1 Hz, 2H, 5-CH2
diazepane), 3.84 (t, J ¼ 5.1 Hz, 2H, 7-CH2 diazepane), 3.90 (t, J ¼ 5.4 Hz, 2H,
2-CH2 diazepane), 7.27 (t, J ¼ 5.4 Hz, 1H, ArH), 7.42 (t, J ¼ 7.8 Hz, 1H,
ArH), 7.53 (d, J ¼ 8.4 Hz,1H, ArH), 7.77e7.83 (m, 2H, 2ꢂ ArH), 7.90 (d,
J ¼ 5.6 Hz, 2H, NHCH2), 4.10 (t, J ¼ 6.8 Hz, 2H, CH2OH), 4.66 (br s, 1H,
OH), 7.12 (td, J ¼ 7.6, 1.2 Hz, 1H, ArH), 7.26 (td, J ¼ 7.6, 1.2 Hz, 1H,
ArH), 7.47 (dd, J ¼ 7.9, 0.6 Hz, 1H, ArH), 7.73e7.76 (m, 1H, ArH),
7.78e7.81 (m, 1H, ArH), 7.92 (d, J ¼ 7.9 Hz, 1H, ArH), 8.13 (br s, 1H,
J ¼ 8.4 Hz, 1H, ArH), 8.52 (s, 1H, ArH); 13C NMR (DMSO-d6):
d 30.3,
NH), 8.57 (d, J ¼ 2.4 Hz, 1H, ArH); 13C NMR (DMSO-d6):
d
32.6, 45.0,
47.3, 52.4, 53.1, 58.2, 58.5,112.2,118.4,119.8,120.8,121.4,122.3,123.9,
126.5, 127.2, 127.9, 131.4, 150.3, 150.7, 151.1, 164.7. HRMS (ESI) calcd
for C21H21ClN3O [M þ H]þ: 366.1368, found 366.1339.
58.1, 95.9, 117.2, 118.1, 119.7, 120.1, 122.2, 123.1, 123.6, 124.4, 128.0,
131.7, 147.2, 148.9, 149.4, 163.9. HRMS (ESI) calcd for C18H14ClN2O2
[M ꢃ H]ꢃ: 325.0749, found 325.0754.
5.2.14. N-(3-Aminopropyl)-2-bromochromeno[2,3-b]indol-11-
amine (6n)
5.2.9. 2-Chloro-N-(5-(diethylamino)pentan-2-yl)chromeno[2,3-b]
indol-11-amine (6i)
Yield: 95%, yellow solids; mp: 207 ꢁC (decomp.); 1H NMR (DMSO-
Yield: 82%, yellow solids; mp: 193e196 ꢁC; 1H NMR (DMSO-d6):
d6):
d
1.94 (quint, J ¼ 6.8 Hz, 2H, CH2CH2CH2), 2.80 (t, J ¼ 6.8 Hz, 2H,
d
0.73 (t, J ¼ 7.2 Hz, 6H, 2ꢂ CH2CH3), 1.16e1.35 (m, 2H, CH2CH2NEt2),
CH2NH2), 3.20e3.52 (br s, 3H, NH and NH2), 4.11 (t, J ¼ 6.8 Hz, 2H,
NHCH2), 7.13 (td, J ¼ 7.5, 1.2 Hz, 1H, ArH), 7.27 (td, J ¼ 7.8, 0.6 Hz, 1H,
ArH), 7.48 (dd, J ¼ 7.8, 0.7 Hz, 1H, ArH), 7.67 (d, J ¼ 8.8 Hz, 1H, ArH),
1.54 (d, J ¼ 6.5 Hz, 3H, Me), 1.65e1.86 (m, 2H, CH(Me)CH2CH2),
2.11e2.26 (m, 6H, CH2NEt2 and 2ꢂ CH2CH3), 4.63 (m, 1H, CH), 7.16
(t, J ¼ 7.5 Hz,1H, ArH), 7.28 (t, J ¼ 7.5 Hz, 1H, ArH), 7.49 (d, J ¼ 7.6 Hz,
1H, ArH), 7.69 (d, J ¼ 7.9 Hz, 1H, ArH), 7.73e7.76 (m, 1H, ArH), 7.78e
7.83 (m, 1H, ArH), 7.87 (d, J ¼ 9.7 Hz, 1H, NH), 8.69 (d, J ¼ 2.1 Hz, 1H,
7.90 (dd, J ¼ 8.8, 2.1 Hz, 2H, 2ꢂ ArH), 8.69 (d, J ¼ 2.4 Hz,1H, ArH); 13
C
NMR (DMSO-d6):
d 30.2, 38.1, 45.5, 95.9, 115.8, 117.8, 118.1, 120.0,
120.1,122.2,123.6,124.4,126.1,134.5,147.0,148.8,149.8,163.7. HRMS
(ESI) calcd for C18H15BrN3O [M(79Br) ꢃ H]ꢃ: 368.0404, found
368.0401; C18H15BrN3O [M(81Br) ꢃ H]ꢃ: 370.0378, found 370.0379.
ArH); 13C NMR (DMSO-d6):
d 11.4 (2C), 21.7, 23.4, 35.0, 46.0 (2C),
51.6, 52.1, 95.9, 117.2, 118.2, 119.7, 120.1, 121.7, 123.2, 123.5, 124.5,
128.0, 131.8, 146.9, 149.0, 149.4, 164.0. HRMS (ESI) calcd for
C
24H27ClN3O [M ꢃ H]ꢃ: 408.1848, found 408.1842.
5.2.15. N-(4-Aminobutyl)-2-bromochromeno[2,3-b]indol-11-
amine (6o)
5.2.10. 2-Chloro-11-morpholinochromeno[2,3-b]indole (6j)
Yield: 87%, yellow solids; mp: 116e123 ꢁC (decomp.); 1H NMR
Yield: 81%, yellowish-orange solids; mp: >300 ꢁC; 1H NMR
(CDCl3):
d
1.72 (quint, J ¼ 6.0 Hz, 2H, NHCH2CH2), 1.92 (quint,
(DMSO-d6):
d
3.06e3.10 (m, 4H, 2ꢂ NCH2), 3.74e3.78 (m, 4H, 2ꢂ
J ¼ 6.0 Hz, 2H, CH2CH2NH2), 2.90 (t, J ¼ 6.0 Hz, 2H, CH2NH2), 4.01 (t,
J ¼ 6.0 Hz, 2H, NHCH2), 5.41 (br s, 1H, NH2), 5.61 (br s, 1H, NH2), 7.16
(t, J ¼ 7.2 Hz, 1H, ArH), 7.36 (t, J ¼ 7.2 Hz, 1H, ArH), 7.43 (d, J ¼ 8.8 Hz,
1H, ArH), 7.60e7.64 (m,1H, ArH), 7.69 (d, J ¼ 7.8 Hz,1H, ArH), 7.83 (d,
J ¼ 7.9 Hz, 1H, ArH), 8.22 (d, J ¼ 2.4 Hz, 1H, ArH), 8.41 (br s, 1H, NH);
CH2O), 7.29e7.33 (m, 1H, ArH), 7.35 (td, J ¼ 7.6, 1.5 Hz, 1H, ArH), 7.51
(d, J ¼ 7.8 Hz, 1H, ArH), 7.82e7.86 (m, 2H, 2ꢂ ArH), 8.10 (d,
J ¼ 7.6 Hz, 1H, ArH), 8.16 (d, J ¼ 2.4 Hz, 1H, ArH); 13C NMR (DMSO-
d6): d 42.8 (2C), 63.3 (2C), 98.8, 111.9, 120.1, 120.5, 121.6, 122.1, 123.9,
124.6, 124.9, 129.4, 132.0, 132.6, 152.1, 155.9, 170.2. HRMS (ESI) calcd
13C NMR (CDCl3):
d 28.0, 30.2, 41.1, 48.4, 97.5,115.8,117.9,118.8,119.9,
for C19H16ClN2O3 [M þ OH]ꢃ: 355.0855, found 355.0812.
120.3, 121.8, 123.8, 125.0, 126.0, 133.9, 147.2, 149.3, 150.3, 164.6.
HRMS (ESI) calcd for C19H17BrN3O [M(79Br) ꢃ H]ꢃ: 382.0560, found
382.0549; C19H17BrN3O [M(81Br) ꢃ H]ꢃ: 384.0534, found 384.0529.
5.2.11. N-(2-(1H-Indol-3-yl)ethyl)-2-chlorochromeno[2,3-b]indol-
11-amine (6k)
Yield: 66%, yellow solids; mp: 279e282 ꢁC (decomp.); 1H NMR
5.2.16. 3-(2-Bromochromeno[2,3-b]indol-11-ylamino)propan-1-ol
(6p)
(DMSO-d6):
d
3.22 (t, J ¼ 7.5 Hz, 2H, NHCH2CH2), 4.29 (q, J ¼ 7.2 Hz,
2H, NHCH2CH2), 6.93 (t, J ¼ 7.2 Hz, 1H, ArH), 7.01e7.09 (m, 2H, 2ꢂ
Yield: 86%, yellow solids; mp: 248e253 ꢁC; 1H NMR (DMSO-d6):
ArH), 7.13 (d, J ¼ 2.1 Hz,1H, ArH), 7.25 (t, J ¼ 6.6 Hz,1H, ArH), 7.31 (d,
d
1.95 (quint, J ¼ 6.6 Hz, 2H, CH2CH2CH2), 3.52 (t, J ¼ 6.0 Hz, 2H,

W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
449
NHCH2), 4.09 (t, J ¼ 6.9 Hz, 2H, CH2OH), 4.65 (b rs, 1H, OH), 7.12 (td,
J ¼ 7.5, 1.2 Hz, 1H, ArH), 7.26 (td, J ¼ 7.5, 1.2 Hz, 1H, ArH), 7.47 (dd,
J ¼ 7.9, 0.6 Hz, 1H, ArH), 7.67 (d, J ¼ 8.8 Hz, 1H, ArH), 7.88e7.93 (m,
2H, 2ꢂ ArH), 8.15 (br s, 1H, NH), 8.69 (d, J ¼ 2.4 Hz, 1H, ArH); 13C
1.52e1.63 (m, 2H, CH2CH2NEt2), 1.73e1.88 (m, 2H, CH(Me)CH2CH2),
2.39 (m, 2H, CH2NEt2), 2.45 (m, 4H, 2ꢂ CH2CH3), 3.90 (s, 3H, OMe),
4.66 (m, 1H, CH), 5.83 (br s, 1H, NH), 7.19e7.27 (m, 2H, 2ꢂ ArH),
7.37e7.42 (m, 2H, 2ꢂ ArH), 7.60 (d, J ¼ 9.0 Hz, 1H, ArH), 7.71 (d,
J ¼ 7.9 Hz, 1H, ArH), 7.74 (d, J ¼ 7.9 Hz, 1H, ArH); 13C NMR (CDCl3):
NMR (DMSO-d6):
d 32.6, 45.0, 58.1, 95.9, 115.8, 117.7, 118.1, 120.0,
120.1, 122.2, 123.7, 124.3, 126.0, 134.5, 147.1, 148.8, 149.8, 163.8.
HRMS (ESI) calcd for C18H14BrN2O2 [M(79Br) ꢃ H]ꢃ: 369.0244,
found 369.0261; C18H14BrN2O2 [M(81Br) ꢃ H]ꢃ: 371.0218, found
371.0240.
d 11.3, 22.6, 23.7, 36.7, 46.8 (2C), 52.4 (2C), 52.6, 56.1, 100.2, 106.7,
116.4, 118.2, 118.9, 119.5, 119.5, 120.4, 121.0, 123.4, 125.6, 146.4, 147.7,
150.1, 155.5, 165.1. HRMS (ESI) calcd for C25H30N3O2 [M ꢃ H]ꢃ:
404.2344, found 404.2339.
5.2.17. 2-Bromo-N-(5-(diethylamino)pentan-2-yl)chromeno[2,3-b]
indol-11-amine (6q)
5.2.22. 2-Methoxy-11-morpholinochromeno[2,3-b]indole (6v)
Yield: 71%, yellowish-orange solids; mp: 188e193 ꢁC; 1H NMR
Yield: 65%, yellow solids; mp: 187e189 ꢁC; 1H NMR (DMSO-d6):
(CDCl3):
d
3.77 (t, J ¼ 4.2 Hz, 4H, 2ꢂ NCH2), 3.93 (s, 3H, OMe), 4.08 (t,
d
0.74 (t, J ¼ 7.0 Hz, 6H, 2ꢂ CH2CH3), 1.17e1.36 (m, 2H, CH2CH2NEt2),
J ¼ 4.2 Hz, 4H, 2ꢂ CH2O), 7.22e7.26 (m, 2H, 2ꢂ ArH), 7.47 (t,
J ¼ 7.5 Hz, 1H, ArH), 7.53 (d, J ¼ 2.6 Hz, 1H, ArH), 7.60 (dd, J ¼ 9.0,
2.8 Hz, 1H, ArH), 7.68 (d, J ¼ 7.6 Hz, 1H, ArH), 7.97 (d, J ¼ 7.9 Hz, 1H,
1.54 (d, J ¼ 6.0 Hz, 3H, Me), 1.67e1.85 (m, 2H, CH(Me)CH2CH2),
2.12e2.29 (m, 6H, CH2NEt2 and 2ꢂ CH2CH3), 4.63 (m, 1H, CH), 7.13e
7.19 (m, 1H, ArH), 7.25e7.30 (m, 1H, ArH), 7.49 (d, J ¼ 7.3 Hz, 1H,
ArH), 7.68 (t, J ¼ 8.8 Hz, 2H, 2ꢂ ArH), 7.88 (d, J ¼ 9.6 Hz,1H, NH), 7.91
(m, 1H, ArH), 8.80 (d, J ¼ 1.8 Hz, 1H, ArH); 13C NMR (DMSO-d6):
ArH); 13C NMR (CDCl3):
d 51.7 (2C), 55.9, 67.5 (2C), 108.9, 113.7,
118.8, 119.08, 119.14, 119.3, 121.3, 122.1, 123.7, 128.0, 146.8, 150.9,
151.2, 155.5, 165.6. HRMS (ESI) calcd for C20H17N2O3 [M ꢃ H]ꢃ:
333.1245, found 333.1218.
d
11.4 (2C), 21.7, 23.3, 35.1, 46.0 (2C), 51.6, 52.1, 95.8, 115.9, 117.7,
118.3, 120.0, 120.2, 121.7, 123.5, 124.5, 126.0, 134.6, 146.9, 148.9,
149.8, 164.0. HRMS (ESI) calcd for C24H27BrN3O [M(79Br) ꢃ H]ꢃ:
452.1343, found 452.1368; C24H27BrN3O [M(81Br) ꢃ H]ꢃ: 454.1317,
found 454.1356.
5.2.23. N-(2-(1H-Indol-3-yl)ethyl)-2-methoxychromeno[2,3-b]
indol-11-amine (6w)
Yield: 66%, yellow solids; mp: 223e225 ꢁC; 1H NMR (DMSO-d6):
d
3.23 (t, J ¼ 7.5 Hz, 2H, NHCH2CH2), 3.91 (s, 3H, OMe), 4.32 (m, 2H,
5.2.18. 2-Bromo-11-morpholinochromeno[2,3-b]indole (6r)
NHCH2CH2), 6.92 (td, J ¼ 7.4, 1.0 Hz, 1H, ArH), 7.04 (m, 2H, 2ꢂ ArH),
7.14 (d, J ¼ 2.4 Hz, 1H, ArH), 7.23 (t, J ¼ 7.8 Hz, 1H, ArH), 7.31 (d,
J ¼ 7.9 Hz, 1H, ArH), 7.36 (dd, J ¼ 9.1, 2.9 Hz, 1H, ArH), 7.45 (d,
J ¼ 7.6 Hz, 1H, ArH), 7.52 (d, J ¼ 7.6 Hz, 1H, ArH), 7.63 (d, J ¼ 8.8 Hz,
1H, ArH), 7.87 (d, J ¼ 7.9 Hz, 1H, ArH), 7.92 (d, J ¼ 2.6 Hz, 1H, ArH),
8.27 (br s, 1H, NHCH2), 10.85 (br s, 1H, NHindole); 13C NMR (DMSO-
Yield: 69%, yellowish-orange solids; mp: 118e120 ꢁC; 1H NMR
(DMSO-d6):
d
3.25 (m, 4H, 2ꢂ NCH2), 3.52 (m, 4H, 2ꢂ CH2O), 6.89e
6.97 (m, 2H, 2ꢂ ArH), 7.02 (td, J ¼ 7.6, 1.2 Hz, 1H, ArH), 7.22 (d,
J ¼ 7.9 Hz, 1H, ArH), 7.26 (d, J ¼ 7.9 Hz, 1H, ArH), 7.48e7.51 (m, 2H,
2ꢂ ArH); 13C NMR (DMSO-d6):
d 50.5 (2C), 65.4 (2C), 99.5, 109.6,
110.6, 118.7, 119.0, 120.9, 121.2, 127.8, 129.5, 131.8, 132.9, 133.9, 154.1,
d6):
d 26.0, 47.7, 56.1, 95.7, 106.5, 110.6, 111.4, 116.1, 117.8, 118.2, 118.3,
155.7, 187.2. HRMS (ESI) calcd for C19H16BrN2O3 [M(79Br) þ OH]ꢃ:
118.8, 119.6 (2C), 121.0, 122.0, 122.9, 123.4, 124.1, 127.0, 136.1, 145.2,
399.0350, found 399.0350;
401.0324, found 401.0333.
C
19H16BrN2O3 [M(81Br)
þ
OH]ꢃ:
148.1, 148.8, 155.4, 164.2. HRMS (ESI) calcd for C26H20N3O2
[M ꢃ H]ꢃ: 406.1561, found 406.1539.
5.2.19. N-(3-Aminopropyl)-2-methoxychromeno[2,3-b]indol-11-
amine (6s)
5.2.24. 2-Methoxy-N-phenylchromeno[2,3-b]indol-11-amine (6x)
Yield: 95%, yellow solids; mp: 265e273 ꢁC (decomp.); 1H NMR
Yield: 77%, yellow solids; mp: 153e155 ꢁC; 1H NMR (CDCl3):
(DMSO-d6):
d
4.00 (s, 3H, OMe), 5.59 (d, J ¼ 8.2 Hz, 1H, NH), 6.82 (t,
d
1.51e1.80 (br s, 2H, NH2), 1.82 (quint, J ¼ 6.6 Hz, 2H, CH2CH2CH2),
J ¼ 7.8 Hz, 1H, ArH), 7.33 (d, J ¼ 7.8 Hz, 1H, ArH), 7.45e7.49 (m, 2H,
2ꢂ ArH), 7.49e7.57 (m, 5H, 5ꢂ ArH), 7.65 (dd, J ¼ 9.2, 2.8 Hz, 1H,
3.17 (m, 2H, CH2NH2), 3.83 (s, 3H, OMe), 4.26 (t, J ¼ 5.4 Hz, 2H,
NHCH2), 7.10e7.17 (m, 2H, 2ꢂ ArH), 7.30e7.35 (m, 2H, 2ꢂ ArH), 7.48
(d, J ¼ 9.1 Hz, 1H, ArH), 7.68 (dd, J ¼ 7.9, 0.6 Hz, 1H, ArH), 7.90 (d,
ArH), 8.00 (d, J ¼ 9.1 Hz, 1H, ArH), 8.45 (d, J ¼ 2.1 Hz, 1H, ArH); 13
C
NMR (DMSO-d6):
d 56.7, 95.2, 106.7, 112.5, 116.6, 119.4, 119.7, 122.1,
J ¼ 7.6 Hz, 1H, ArH), 9.23 (br s, 1H, NH); 13C NMR (CDCl3):
d
30.0,
123.4, 123.7, 125.3, 126.0, 127.5, 129.3, 129.6 (2C), 134.6, 138.9, 145.4,
150.8, 157.1, 158.5. HRMS (ESI) calcd for C22H15N2O2 [M ꢃ H]ꢃ:
339.1139, found 339.1119.
42.1, 50.2, 55.7, 96.5, 105.8, 116.3, 118.5, 118.7, 119.0, 119.6, 121.6,
123.8, 124.5, 145.9, 147.9, 149.4, 155.3, 165.1. HRMS (ESI) calcd for
C
19H18N3O2 [M ꢃ H]ꢃ: 320.1405, found 320.1385.
5.3. General procedure for the synthesis of sulfonamide (8aef)
5.2.20. 3-(2-Methoxychromeno[2,3-b]indol-11-ylamino)propan-1-
ol (6t)
A solution of compound 6a or 6n (0.2 mmol) in DMF (3 ml) was
cooled to 0 ꢁC under argon and to this was added sulfonyl chloride
(7aec, 0.24 mmol) and Et3N (0.4 mmol) sequentially. The resulting
solution was stirred for 2e4 h at 0 ꢁC to room temperature. The
reaction mixture was washed with sat. NaCl and CH2Cl2. The
organic layer was dried over MgSO4. The resulting crude oil was
purified by flash chromatography using AcOEte2 N ammonia in
MeOH (9:1) as an eluent to give pure product as yellow solids.
Yield: 91%, yellow solids; mp: 237e239 ꢁC; 1H NMR (DMSO-d6):
d
1.94 (quint, J ¼ 6.4 Hz, 2H, CH2CH2CH2), 3.50e3.56 (m, 2H,
NHCH2), 3.90 (s, 3H, OMe), 4.07e4.15 (m, 2H, CH2OH), 4.72 (t,
J ¼ 4.4 Hz, 1H, OH), 7.07e7.12 (m, 1H, ArH), 7.22e7.26 (m, 1H, ArH),
7.37 (dd, J ¼ 9.0, 2.8 Hz, 1H, ArH), 7.45 (d, J ¼ 7.9 Hz, 1H, ArH), 7.64
(d, J ¼ 9.0 Hz, 1H, ArH), 7.87 (d, J ¼ 2.6 Hz, 1H, ArH), 7.91 (d,
J ¼ 7.9 Hz, 1H, ArH), 8.10 (br s, 1H, NH); 13C NMR (DMSO-d6):
d 32.7,
45.1, 56.1, 58.3, 95.7, 106.4, 116.1, 117.8, 118.8, 119.5, 119.6, 122.0,
123.6, 124.0, 145.2, 148.1, 148.9, 155.4, 164.3. HRMS (ESI) calcd for
5.3.1. N-(3-(Chromeno[2,3-b]indol-11-ylamino)propyl)
methanesulfonamide (8a)
C
19H17N2O3 [M ꢃ H]ꢃ: 321.1245, found 321.1216.
Yield: 45%, yellow solids; mp: 129e133 ꢁC; 1H NMR (DMSO-d6):
5.2.21. N-(5-(Diethylamino)pentan-2-yl)-2-methoxychromeno[2,3-
b]indol-11-amine (6u)
d
2.08 (quint, J ¼ 6.8 Hz, 2H, CH2CH2CH2), 2.82 (s, 3H, SO2Me), 2.99e
3.06 (m, 2H, AreNHCH2), 4.21 (t, J ¼ 7.2 Hz, 2H, CH2NHeSO2), 7.13
(t, J ¼ 6.6 Hz, 1H, AreNH), 7.33 (t, J ¼ 7.2 Hz, 1H, ArH), 7.42 (t,
J ¼ 7.2 Hz, 1H, ArH), 7.58 (d, J ¼ 8.4 Hz, 1H, ArH), 7.65 (td, J ¼ 7.7,
Yield: 84%, yellow solids; mp: 155e156 ꢁC; 1H NMR (CDCl3):
d
0.94 (t, J ¼ 7.2 Hz, 6H, 2ꢂ CH2CH3), 1.49 (d, J ¼ 6.5 Hz, 3H, Me),

450
W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
1.3 Hz, 1H, ArH), 7.84 (dd, J ¼ 8.4, 1.0 Hz, 1H, ArH), 7.87e7.93 (m, 1H,
ArH), 8.05 (d, J ¼ 7.8 Hz, 1H, ArH), 8.74 (d, J ¼ 7.8 Hz, 1H, ArH), 9.52
NHCH2), 4.00 (t, J ¼ 6.8 Hz, 2H, CH2NHeSO2), 7.05e7.11 (m,1H, ArH),
7.23e7.28 (m,1H, ArH), 7.47 (d, J ¼ 7.8 Hz,1H, ArH), 7.60e7.65 (m, 2H,
2ꢂ ArH), 7.65e7.73 (m, 2H, 2ꢂ ArH), 7.76e7.89 (m, 3H, 2ꢂ ArH and
AreNH), 7.96e8.01 (m, 3H, 2ꢂ ArH and NHeSO2), 8.06 (d, J ¼ 8.4 Hz,
1H, ArH), 8.35 (s, 1H, ArH), 8.62 (d, J ¼ 1.8 Hz, 1H, ArH); 13C NMR
(br s, 1H, NHeSO2); 13C NMR (DMSO-d6):
d 29.6, 39.2, 39.5, 45.4,
93.5, 114.4, 115.6, 118.1, 121.1, 122.2, 122.9, 124.8, 125.2, 125.5, 133.8,
150.3, 152.6, 159.0, 162.3. HRMS (ESI) calcd for C19H18N3O3S
[M ꢃ H]ꢃ: 368.1074, found 368.1047.
(DMSO-d6):
d 29.7, 39.9, 44.8, 96.2, 115.7, 117.6, 118.1, 119.9, 120.2,
122.1,122.3,123.6,124.5,125.9,127.3,127.6,127.8,128.7,129.1,129.4,
131.6, 134.1, 134.5, 137.2, 147.0, 148.9, 149.7, 163.8. HRMS (ESI) calcd
for C28H21BrN3O3S [M(79Br) ꢃ H]ꢃ: 558.0492, found 558.0472;
5.3.2. N-(3-(Chromeno[2,3-b]indol-11-ylamino)propyl)
benzenesulfonamide (8b)
Yield: 53%, yellow solids; mp: 215e219 ꢁC; 1H NMR (DMSO-d6):
C
28H21BrN3O3S [M(81Br) ꢃ H]ꢃ: 560.0467, found 560.0465.
d
1.93 (quint, J ¼ 6.9 Hz, 2H, CH2CH2CH2), 2.82 (q, J ¼ 6.5 Hz, 2H, Are
NHCH2), 4.01 (q, J ¼ 6.6 Hz, 2H, CH2NHeSO2), 7.11 (t, J ¼ 7.2 Hz, 1H,
ArH), 7.26 (t, J ¼ 7.2 Hz, 1H, ArH), 7.48 (m, 4H, 4ꢂ ArH), 7.56 (t,
J ¼ 7.2Hz,1H, ArH), 7.68(m, 4H, 3ꢂ ArH and AreNH), 7.76 (t, J ¼ 7.2 Hz,
1H, ArH), 7.86 (d, J ¼ 7.8 Hz, 1H, ArH), 7.98 (m, 1H, NHeSO2), 8.39 (d,
5.4. Biological assays
5.4.1. Cell lines
Established in vitro, human cancer cell lines: MV4-11 (biphe-
notypic B myelomonocytic leukemia), A549 (non-small cell lung
carcinoma), HCT116 (colorectal carcinoma) and normal mice
fibroblasts BALB/3T3 was used. All lines were obtained from
American Type Culture Collection (Rockville, Maryland, USA). All
the cell lines were maintained in the Institute of Immunology and
Experimental Therapy, Wroclaw, Poland.
J ¼ 8.4 Hz,1H, ArH); 13C NMR (DMSO-d6):
d 29.9, 39.8, 44.7, 96.0,115.7,
117.8, 118.0, 119.9, 122.0, 123.6, 123.7, 123.7, 124.2, 126.3 (2C), 129.1
(2C),132.1,132.3,140.1,148.2,148.9,150.7,164.0. HRMS (ESI) calcd for
C
24H20N3O3S [M ꢃ H]ꢃ: 430.1231, found 430.1214.
5.3.3. N-(3-(Chromeno[2,3-b]indol-11-ylamino)propyl)
naphthalene-2-sulfonamide (8c)
MV4-11 cells were cultured in RPMI 1640 medium (Gibco,
Scotland, UK), supplemented with 2 mM L-glutamine and 1.0 mM
1
Yield: 77%, yellow solids; mp: 206e207 ꢁC; H NMR (DMSO-d6):
d
1.94 (quint, J ¼ 6.9 Hz, 2H, CH2CH2CH2), 2.88 (m, 2H, AreNHCH2),
sodium pyruvate, 10% fetal bovine serum (all from SigmaeAldrich
Chemie GmbH, Steinheim, Germany). A549 and HCT116 cells
were cultured in the mixture of RPMI 1640 and Opti-MEM (1:1)
medium (Gibco, Scotland, UK), supplemented with 2 mM L-gluta-
mine and 5% fetal bovine serum. BALB/3T3 cells were cultured in
4.02 (t, J ¼ 7.0 Hz, 2H, CH2NHeSO2), 7.07 (t, J ¼ 7.2 Hz, 1H, ArH), 7.24
(t, J ¼ 7.2 Hz, 1H, ArH), 7.41e7.49(m, 2H, 2ꢂ ArH), 7.60e7.75 (m, 5H, 5ꢂ
ArH), 7.81e8.04 (m, 2H, AreNH and NHeSO2), 7.85 (d, J ¼ 7.9 Hz, 1H,
ArH), 8.00 (m, 2H, 2ꢂ ArH), 8.06 (d, J ¼ 8.2 Hz,1H, ArH), 8.32e8.38 (m,
2H, 2ꢂ ArH); 13C NMR (DMSO-d6):
d
29.9, 40.0, 44.7, 95.9, 115.7, 117.7,
Dulbecco’s medium (IIET, Wroclaw, Poland), supplemented with
117.9,119.9,122.0,122.1,123.7,123.7,124.1,127.3 (2C),127.5,127.8,128.7,
129.1, 129.4, 131.6, 132.1, 134.1, 137.2, 148.2, 148.8, 150.7, 164.0. HRMS
(ESI) calcd for C28H22N3O3S [M ꢃ H]ꢃ: 480.1387, found 480.1347.
2 mM
L-glutamine and 1.0 mM sodium pyruvate, 10% fetal bovine
serum. Each culture medium was supplemented with 100 units/ml
penicillin, and 100 mg/ml streptomycin (both from Polfa, Tarchomin
S.A., Poland). The cells were grown at 37 ꢁC with 5% CO2 humidified
5.3.4. N-(3-(2-Bromochromeno[2,3-b]indol-11-ylamino)propyl)
methanesulfonamide (8d)
atmosphere.
Yield: 51%, yellowsolids; mp: 268 ꢁC (decomp.); 1H NMR (DMSO-
5.4.2. Antiproliferative assay in vitro
d6):
d
2.06 (quint, J ¼ 6.8 Hz, 2H, CH2CH2CH2), 2.80 (s, 3H, SO2Me),
Test solutions of the compounds tested (1 mg/ml) were
3.02 (q, J ¼ 6.5 Hz, 2H, AreNHCH2), 4.20e4.28 (m, 2H, CH2NHeSO2),
7.04 (t, J ¼ 6.0 Hz,1H, AreNH), 7.40e7.46 (m,1H, ArH), 7.49e7.55 (m,
1H, ArH), 7.63 (d, J ¼ 7.6 Hz,1H, ArH), 7.92 (d, J ¼ 8.8 Hz,1H, ArH), 8.09
(d, J ¼ 7.9 Hz, 1H, ArH), 8.14 (dd, J ¼ 9.0, 2.2 Hz, 1H, ArH), 8.94 (s, 1H,
prepared by dissolving the substances in 100
ml DMSO (Sigmae
Aldrich, Germany) completed with 900
ml of tissue culture
medium. Afterward, the tested compounds were diluted in culture
medium to reach the final concentrations of 10, 1, 0.1, 0.01 and
0.001 mg/ml.
ArH), 9.76 (br s,1H, NHeSO2); 13C NMR (DMSO-d6):
d
29.1, 39.1, 45.9,
92.9, 113.2, 117.5, 118.3, 120.1, 120.5, 123.2, 123.4, 125.9, 134.3, 136.7,
149.2, 153.2, 157.4, 160.5. HRMS (ESI) calcd for C19H17BrN3O3S
Twenty-four hours before addition of the tested agents, the cells
were plated in 96-well plates (Sarstedt, USA) at a density of
[M(79Br)
ꢃ
H]ꢃ: 446.0179, found 446.0166; C19H17BrN3O3S
1 ꢂ 104 cells per well in 100
ml of culture medium. The cell cultures
[M(81Br) ꢃ H]ꢃ: 448.0154, found 448.0144.
were maintained at 37 ꢁC in humid atmosphere saturated with 5% CO2.
The in vitro cytotoxic effect of all agents was examined after 72 h
exposure of the cultured cells to varying concentrations (from 0.01
5.3.5. N-(3-(2-Bromochromeno[2,3-b]indol-11-ylamino)propyl)
benzenesulfonamide (8e)
to 10
mg/ml) of the tested compounds, using the SRB assay for
Yield: 52%, yellow solids; mp: 286e289 ꢁC (decomp.); 1H NMR
adherent cells (A549, HCT116, BALB/3T3) and MTT assay for
leukemia cells (MV4-11) to avoid rinsing out of the cells during
washing. Both assays were recommended by NCI as giving similar
results [32]. Each compound in given concentration was tested in
triplicates in each experiment, which was repeated 3e5 times.
(DMSO-d6):
d
1.93 (quint, J ¼ 6.9 Hz, 2H, CH2CH2CH2), 2.83 (m, 2H,
AreNHCH2), 4.00 (m, 2H, CH2NHeSO2), 7.12 (t, J ¼ 7.2 Hz, 1H, ArH),
7.27 (t, J ¼ 7.2 Hz, 1H, ArH), 7.48 (m, 3H, 3ꢂ ArH), 7.57 (m, 1H, ArH),
7.68 (m, 4H, 3ꢂ ArH and AreNH), 7.84 (d, J ¼ 7.8 Hz, 1H, ArH), 7.88e
7.93 (m, 1H, ArH), 8.02 (br s, 1H, NHeSO2), 8.66 (d, J ¼ 1.2 Hz, 1H,
ArH); 13C NMR (DMSO-d6):
d
29.7, 44.7, 96.3, 115.8, 117.7, 118.1,
5.4.3. MTT assay
120.0, 120.2, 122.3, 123.6, 124.5, 126.0, 126.3 (2C), 129.1 (2C), 132.3,
134.5, 140.1, 147.0, 149.0, 149.8, 163.8. HRMS (ESI) calcd for
For the last 3e4 h of incubation 20 ml of MTT solution were
added to each well (MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyl tetrazolium bromide; stock solution: 5 mg/ml, Sigmae
Aldrich, Germany). The mitochondria of viable cells reduce the
pale yellow MTT to a navy blue formazan: the more viable cells are
present in well, the more MTT will be reduced to formazan. When
C
C
24H19BrN3O3S [M(79Br)
ꢃ
H]ꢃ: 508.0336, found 508.0316;
24H19BrN3O3S [M(81Br) ꢃ H]ꢃ: 510.0310, found 510.0299.
5.3.6. N-(3-(2-Bromochromeno[2,3-b]indol-11-ylamino)propyl)
naphthalene-2-sulfonamide (8f)
incubation time was completed, 80 ml of the lysing mixture were
added to each well (lysing mixture: 225 ml dimethylformamide,
Yield: 89%, yellow solids; mp: 240e243 ꢁC; 1H NMR (DMSO-d6):
d
1.94 (quint, J ¼ 7.2 Hz, 2H, CH2CH2CH2), 2.88 (t, J ¼ 6.6 Hz, 2H, Are
POCh, Gliwice, Poland, 67.5 g sodium dodecyl sulfate, Sigmae

W. Peng et al. / European Journal of Medicinal Chemistry 58 (2012) 441e451
451
Aldrich, Germany, and 275 ml of distilled water). After 24 h, when
formazan crystals had been dissolved, the optical densities of the
samples were read on a Multiskan RC photometer (Labsystems,
Helsinki, Finland) at 570 nm wavelength. The background optical
density was measured in the wells filled with culture medium,
without the cells.
We are thankful to Prof. S. Nakashima for HRMS analyses and Prof. J.
Futami for UV measurements. We thank Koei Chemical Company
for a generous gift of various amines.
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4
ꢁC for 1 h and then washed five times with tap water. The back-
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l) and different amount of DNA were added (CDNA ¼ 0.00, 0.50, 1.00,
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A
3
3
1
G
G
¼
þ
ꢂ
G
(1)
A ꢃ A0
3
HꢃG ꢃ
3
3
HꢃG ꢃ
3
K½DNAꢄ
G
where A0 and A are the absorbances of 6s in the absence and
presence of DNA, respectively, and G and HeG are their absorption
coefficients, respectively. The double reciprocal plot of A0/(A0 ꢃ A)
versus 1/[DNA] was linear (R2 ¼ 0.9993 for 18 points) and the
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We are grateful to Okayama University for support and to the
Advanced Science Research Center for the NMR experiments and
EA analyses. We thank the Ministry of Education, Culture, Sports,
Science and Technology (MEXT) for the scholarship to W.P and L.W.