Synthesis and structure-activity relationships of N2-alkylated quaternary β-carbolines as novel antitumor agents

Article abstract of DOI:10.1016/j.ejmech.2013.04.031

A series of novel N²-alkylated quaternary β-carbolines was synthesized by modification of position-1, 2, 7 and 9 of β-carboline nucleus with various alkyl and arylated alkyl substituents, and their cytotoxic activities in vitro and antitumor potencies in mice were evaluated. Compound 3m was found to be the most potent antitumor agent. SARs analysis revealed that (1) the substituents in position-2 and 9 of β-carboline nucleus played a vital role in modulation of antitumor activity; (2) the benzyl and 3-phenylpropyl substituents in position-2 and 9 of β-carboline ring were the optimal substituents giving rise to significant antitumor agent. These compounds might be a novel promising class of antitumor agents with clinical development potential.

Full text of DOI:10.1016/j.ejmech.2013.04.031

European Journal of Medicinal Chemistry 65 (2013) 21e31
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and structureeactivity relationships of N2-alkylated
quaternary -carbolines as novel antitumor agents
b
,
c
c
c
c
a
Guoxian Zhang a, Rihui Cao a , Liang Guo , Qin Ma , Wenxi Fan , Xuemei Chen , Jianru Li ,
*
Guang Shao a, Liqin Qiu a, Zhenghua Ren b
,
*
a School of Chemistry and Chemical Engineering, Sun Yat-sen University, 135 Xin Gang West Road, Guangzhou 510275, PR China
b School of Life Science, Sun Yat-sen University, 135 Xin Gang West Road, Guangzhou 510275, PR China
c Xinjiang Huashidan Pharmaceutical Co. Ltd., 175 He Nan East Road, Urumqi 830011, PR China
a r t i c l e i n f o
a b s t r a c t
A series of novel N2-alkylated quaternary
b-carbolines was synthesized by modification of position-1, 2, 7
Article history:
Received 22 January 2013
Received in revised form
26 March 2013
Accepted 13 April 2013
Available online 23 April 2013
and 9 of
tivities in vitro and antitumor potencies in mice were evaluated. Compound 3m was found to be the most
potent antitumor agent. SARs analysis revealed that (1) the substituents in position-2 and 9 of -car-
boline nucleus played a vital role in modulation of antitumor activity; (2) the benzyl and 3-phenylpropyl
substituents in position-2 and 9 of -carboline ring were the optimal substituents giving rise to signif-
b-carboline nucleus with various alkyl and arylated alkyl substituents, and their cytotoxic ac-
b
b
icant antitumor agent. These compounds might be a novel promising class of antitumor agents with
clinical development potential.
Keywords:
Synthesis
Ó 2013 Elsevier Masson SAS. All rights reserved.
b
-Carboline
Cytotoxic
Antitumor
Structureeactivity relationships
1. Introduction
position-1, 2, 7 and 9 of
determining their antitumor effects; (iii) the N2-benzyl substituted
quaternary -carbolines represented the most interesting anti-
b-carboline nucleus played a vital role in
b-Carbolines are of great interest due to their broad spectrum of
b
biochemical effects and pharmaceutical functions [1]. In particular,
there have been intense research efforts in recent years in the
tumor potencies (Fig. 1) [22,24,26,27,32].
Polo-like kinases (PLK) play an essential role in the ordered
execution of mitotic events, and accumulating evidence demon-
strates that PLK are attractive targets for anticancer drugs [33e38].
Our recent investigations on the mechanism of action of N2-benzyl
design and development of
b-carbolines as a new class of antitumor
agents [2e9]. -Carbolines are initially discovered to exert their
b
antitumor effects by intercalating into DNA [10,11]. Subsequent
investigations suggested that this class of compounds might exert
their antitumor effects through multiple mechanisms of action,
such as inhibiting Topo I and II (topoisomerase I and II) [12e14],
CDK (cyclin-dependent kinase) [4,15,16], MK-2 (mitogen activated
protein kinase-activated protein kinase 2) [17], kinesin-like protein
Eg5 [18] and IKK (I-Kappa-B kinase) [19].
substituted quaternary
b-carbolines revealed that this class of
compounds was new and potent PLK inhibitors with potential for
cancer treatment [39,40].
In a continuing effort to develop novel b-carbolines endowed
with better pharmacological profiles and elucidate the antitumor
structureeactivity relationships (SARs) of N2-alkylated quaternary
Our group had previously reported the synthesis of a large
b-carbolines in finer detail, in the present investigation, we re-
number of
antitumor activities in vitro and in vivo [20e32]. Structureeactivity
relationships (SARs) analysis unraveled that (i) -carbolines had
b
-carboline derivatives and the evaluation of their
ported the synthesis, in vitro evaluation, in vivo efficacies and
detailed structureeactivity relationships for the N2-alkylated qua-
b
ternary b-carbolines with various alkyl and arylated alkyl sub-
potent antitumor activities and the potencies were correlated to
both the planarity of the molecule and the presence of the ring
substituents; (ii) the introduction of appropriate substituents into
stituents appending to positon-1, 2, 7 and 9.
2. Chemistry
The preparation of N2-alkylated quaternary
b-carbolines 3aem,
4aek, 8aed and 10aed followed a common synthetic scheme from
compounds 2aem, 7aed and 10aed by the addition of alkyl halide
* Corresponding authors. Tel.: þ86 20 84110918; fax: þ86 20 84112245.
E-mail addresses: caorihui@mail.sysu.edu.cn (R. Cao), renzhh@mail.sysu.edu.cn
(Z. Ren).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2013.04.031

22
G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
-
Br
COOC2H5
N+ CH2
CONHCHCH2CH2SCH3
N
N+ CH2
Br
CH2
-
N
C4H9
Lovo IC50=20 µM
32
786-0 IC50=1.7 µM
8b
-
Br
-
N+ CH2
Br
N+ CH2
N
(H2C)3O
N
(CH2)3
C2H5
OCH3
KB IC50 <1.5 µM
5f
BGC-823 IC50=0.46 µM
19
Fig. 1. The chemical structure of the representative reported N2-benzylated quaternary
b-carbolines.
in refluxing ethyl acetate [26,27] (Schemes 1e4). Unfortunately, the
same synthetic procedure was used for the preparation of N2-iso-
propyl (4l), isobutyl (4m) and penta-3-yl (4n) substituted quater-
described as antitumor agents in our previous reports [32]. The
chemical structures of all the newly synthesized target compounds
were characterized by MS, HRMS, 1H NMR and 13C NMR.
nary
(Scheme 2). 1-Substituted 1,2,3,4-tetrahydro-
carboxylic acids 5aed and 1-substituted -carbolines 6aed were
prepared according to previously reported general procedure
[21,25] using -tryptophan and appropriate aldehydes as starting
materials (Scheme 3). The intermediates 2aem and 7aed, bearing
various alkyl groups in postion-9 of -carboline nucleus, were
synthesized from compounds 1 and 6aed by the action of sodium
hydride in dry DMF followed by addition of the appropriate alky-
lating and arylating agents in 63e87% yield [20] (Scheme 1 and
Scheme 3). The preparation of compounds 10aed has been already
b
-carbolines but failed to afford the expected target products
b
-carboline-3-
3. Results and discussion
b
3.1. Cytotoxicity in vitro
L
The cytotoxic potencies of N2-alkylated quaternary
b-carbolines
b
3aem, 4aek, 8aed and 10aed against a panel of human tumor cell
lines were investigated and compared with the reference drugs
cisplatin. The human tumor cell line panel consisted of breast car-
cinoma (MCF-7), liver carcinoma (HepG2), prostate carcinoma
(22RV1), colon carcinoma (HT-29), renal carcinoma (769-P),
Br
N+ CH2
ii
N
N
N
N
N
H
R9
R9
1
3a-m
2a-m
a R9=CH3
b R9=C2H5
c R9=CH(CH3)2
g R9=n-C6H13
d R9=CH2CH=CH2
h R9=n-C8H17
e R9=n-C4H9
f R9=CH2CH(CH3)2
j R9=
i R9=
CH2
k R9=
CH2
F
CH2
Cl
l R9=
CH2
m R9=
OCH3
(CH2)3
Reagents and conditions: (i) DMF, NaH, appropriate alkyl halide, stirred at room
temperature, 0.5-4 h; (ii) ethyl acetate, benzyl bromide, reflux, 5-10 h.
Scheme 1. Synthesis of N2-alkylated quaternary
b-carbolines 3aem.

G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
23
Next, we examined the influence of the substituents in position-
9 of -carboline ring on cytotoxic potencies. The data collected in
Table 1 showed that compounds 3gem, bearing long chain alkyl or
arylated alkyl substituents in position-9 of -carboline nucleus,
showed moderate to significant cytotoxic effects, and compounds
bearing a n-hexyl (3g), n-octyl (3h) and 3-phenylpropyl (3m)
X
i
N+ R2
b
N
N
N
b
(CH2)3
(CH2)3
substituent group in position-9 of
the most potent cytotoxic agents with IC50 value of lower than
20 M against all tumor cell lines tested, while compounds 3aef,
b-carboline ring were found to be
4a-k
2l
m
bearing short chain or branch chain alkyl substituent in position-9,
were only found to exhibit marginal cytotoxic activities against
most tumor cell lines investigated. These results suggested that the
long chain alkyl and arylated alkyl substituent might be facilitated
their cytotoxic potencies.
c R2=n-C4H9
a R2=CH3
b R2=C2H5
d R2=n-C6H13
e R2=n-C8H17
f R2=n-C10H21
Thirdly, we evaluated the effect of various substituents in
g R2=
CH2
h R2=
F
b
-carboline ring on cytotoxic activities in these N2-
CH2
position-2 of
alkylated quaternary
4dek having long chain alkyl or arylated alkyl substituents in
position-2 of -carboline nucleus were very active, and compounds
4d and 4k bearing a n-hexyl and 3-phenylpropyl substituent in
position-9 of -carboline ring, respectively, were found to be the
most potent cytotoxic agents with all IC50 value of lower than
5.0 M against all tumor cell lines tested. Unfortunately, com-
pounds 4aec with a methyl, ethyl and n-butyl group appended to
the position-9 of -carboline ring, respectively, were less active
b
-carbolines. Table 1 showed that compounds
Cl
i R2=
CH2
b
j R2=
NO2
(CH2)2
b
k R2=
X=I or Br
(CH2)3
m
b
than compounds 4dek. These results suggested that the long chain
alkyl and arylated alkyl substituent might play a vital role in
determining their cytotoxic potencies, and the n-hexyl and 3-
phenylpropyl substituent were more favorable.
The cytotoxic potency of compounds 8aed bearing a methyl,
phenyl, 4-methoxyphenyl and thiophen-3-yl group in position-1 of
X
N+ R2
N
N
N
(CH2)3
(CH2)3
b-carboline ring, respectively, was comparable to compound 3m.
Interestingly, replacement of the hydrogen atom in position-7 of
compound 8a with butoxy (10a), penta-3-yloxy (10b), octyloxy
(10c) and 3-phenylpropoxy (10d) group resulted in significant
4l-n
n
R2=CH(CH2CH3)2
2l
enhance the activity with IC50 value of lower than 5.0
mM against
l R2=CH(CH3)2
m
R2=CH2CH(CH3)2
X=I or Br
most tumor cell lines tested. These results indicated that intro-
ducing an alkoxy substituent into position-7 of
facilitated cytotoxic potency.
b-carboline ring
Reagents and conditions: (i) ethyl acetate, alkyl halide, reflux, 5-10 h.
3.2. Assessment of acute toxicity
Scheme 2. Synthesis of N2-alkylated quaternary
b-carbolines 4aek.
The LD50 values for acute toxicity of the selected N2-alkylated
quaternary -carbolines in mice after administration by i.p. route
were summarized in Table 2. All the tested N2-alkylated quaternary
-carbolines resulted in acute toxic manifestation. Animals showed
a decrease in locomotor activity after the administration of various
N2-alkylated quaternary
-carbolines. Death occurred mostly in the
b
malignant melanoma (A375), ovarian carcinoma (SK-OV-3),
esophageal carcinoma (Eca-109), gastric carcinoma (BGC-823) and
Lewis lung carcinoma (LLC). The results were summarized inTable 1.
The first analysis of the structureeactivity relationships con-
cerned a general comparison of the cytotoxic activities among the
b
b
high dosage group with 10e20 min after injection. All surviving
animals returned to normal in the next day. Autopsy of the animals
that died in the course of experiment and the necropsy findings in
surviving animals at the end of experimental period (14 days)
revealed no obvious changes in any organs.
four class of N2-alkylated quaternary
b-carbolines described in this
report. Obviously, all compounds showed significant and selective
cytotoxic activities against prostate carcinoma (22RV1) and Lewis
lung carcinoma (LLC) cell lines with IC50 values lower than 10
mM.
Compounds 3aem bearing various alkyl groups in position-9 of
b-
Of all investigated N2-alkylated quaternary
pound 8a having a methyl group in position-1 of
exhibited remarkable acute toxicity with LD50 value of 2.5 mg kgꢀ1
b-carbolines, com-
carboline ring displayed marginal to significant cytotoxic potencies.
Similarly, compounds 4aek having different alkyl substituents in
b
-carboline ring
.
position-2 of
b
-carboline nucleus exhibited weak to strong cyto-
Replacement of the methyl group in postion-1 of compound 8a
with a 4-methoxyphenyl substituent gave compound 8c which
toxic effects against tumor cell lines. In addition, introduction of an
additional group into position-1 of compound 3m led to com-
pounds 8aed, which displayed excellent cytotoxic activities.
Interestingly, replacement of the hydrogen atom in position-7
of compound 8a by various alkoxy groups to yield compounds
10aed represented the most interesting class of cytotoxic agents
exhibited lower acute toxicity with LD50 value of 6.25 mg kgꢀ1
.
Incorporating a penta-3-yloxy (10b) and 3-phenylpropoxy (10d)
group into position-7 of -carboline ring also resulted in decrease
the acute toxicity with LD50 value of 6.25 and 3.75 mg kgꢀ1
b
,
respectively. Compound 3m with a benzyl group appended to
position-2 displayed significant acute toxicity with LD50 value of
8.9 mg kgꢀ1. Replacement of the benzyl group in postion-2 of
with IC50 values lower than 5.0
lines investigated.
mM against most human tumor cell

24
G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
Scheme 3. Synthesis of N2-alkylated quaternary
b-carbolines 8aed.
compound 3m with a 4-fluorobenzyl (4g) and 3-chlorobenzyl (4h)
substituent demonstrated weaker acute toxicities with LD50 value
of over 12.5 and 30.0 mg kgꢀ1, respectively. In comparison with
compound 3m, compound 2i bearing a benzyl group in positon-9
exhibited lower acute toxicity. These results suggested that
As shown in Table 2, all the tested N2-alkylated quaternary
b-
carbolines displayed moderate to strong antitumor activities in
animal models. Sarcoma 180 was more susceptible to all tested
compounds than Lewis lung cancer. Interestingly, compounds 3m,
4g and 8a exhibited remarkable antitumor activities with the tu-
mor inhibition rate of over 50% against mice bearing Sarcoma 180
at dose 1.75, 2.5 and 0.5 mg kgꢀ1, respectively. Particularly, com-
pound 3m was found to be the most potent antitumor agent with
the tumor inhibition rate of 63.5 and 60.6% against mice bearing
Sarcoma 180 and Lewis lung cancer, respectively. Replacement of
the benzyl group of compound 3m in postion-2 with a 4-
fluorobenzyl (4g) and 3-chlorobenzyl (4h) substituent reduced
antitumor potencies with the tumor inhibition rate of 51.5 and
56.6% against mice bearing Sarcoma 180, respectively. In compar-
ison with compound 3m, compounds 8a and 8c with a methyl and
appropriate substituent in position-1 of b-carboline ring might play
an important role in determining acute toxicity.
3.3. Evaluation of antitumor activity
Eight N2-alkylated quaternary
b-carbolines were selected for
evaluation in vivo against mice bearing Sarcoma 180 and Lewis lung
cancer and compared with the reference drugs Cyclophosphamide
(CTX). The tumor inhibition rates of all investigated N2-alkylated
quaternary
b
-carbolines were summarized in Table 2.
-
Br
i
N+ CH2
N
R7O
R7O
N
N
CH3
CH3
(CH2)3
(CH2)3
9a-d
10a-d
c R7=n-C8H17
b R7=CH(CH2CH3)2
a R7=n-C4H9
d R7=
(CH2)3
Reagents and conditions: (i) ethyl acetate, benzyl bromide, reflux, 5-10 h.
Scheme 4. Synthesis of N2-alkylated quaternary
b-carbolines 10aed.

G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
25
Table 1
Cytotoxic activities of 3aem, 4aek, 8aed and 10aed in vitroc (IC50
, m
Ma).
Compds
MCF-7b
HepG2
22RV1
HT-29
769-P
A375
SK-OV-3
Eca-109
BGC-823
LLC
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
8a
>100
>100
54.8
72.6
34.1
39.2
11.1
4.1
18.7
17.8
20.3
18.7
14.4
75.6
98.7
38.7
3.9
2.9
<2.0
9.7
14.3
24.5
12.5
3.7
>100
>100
58.7
67.8
29.0
36.6
13.9
6.5
34.6
23.4
16.5
15.9
7.9
8.4
5.6
3.6
<2.0
<2.0
9.6
<2.0
2.9
5.7
3.5
4.2
4.8
3.2
4.3
2.5
3.4
2.2
4.3
6.9
4.3
59.1
>100
>100
>100
83.8
87.7
16.0
10.9
42.5
28.9
26.9
19.2
7.6
97.3
54.2
62.7
2.3
18.6
31.3
9.1
22.5
38.5
30.8
21.9
19.8
11.6
2.7
<2.0
8.7
6.0
37.3
54.3
24.5
11.3
19.6
28.4
6.8
3.1
7.8
4.7
7.0
55.2
27.6
6.6
12.6
4.7
27.7
7.3
3.2
16.9
10.5
7.9
19.9
4.4
>100
>100
15.8
<2.0
5.9
57.0
12.2
13.8
17.4
8.4
10.8
7.6
<2.0
5.2
14.6
NDe
ND
ND
ND
10.2
95.9
36.7
7.6
21.4
8.6
35.7
13.9
5.1
32.7
35.4
23.3
54.3
11.7
60.0
55.5
41.5
2.5
22.8
23.2
5.3
7.9
7.6
8.1
5.3
6.8
5.1
13.2
>100
61.5
>100
68.1
60.7
5.2
2.5
38.7
6.3
20.3
17.8
8.5
40.6
88.0
15.4
2.3
7.4
57.0
8.1
8.4
5.1
<2.0
4.6
<2.0
8.0
<2.0
<2.0
<2.0
<2.0
<2.0
4.2
3.9
2.4
4.3
<2.0
<2.0
<2.0
15.7
8.1
3.5
7.6
4.9
9.5
8.7
90.8
92.1
45.5
4.3
19.9
34.2
13.4
2.5
<2.0
<2.0
14.3
21.9
8.3
41.5
45.1
12.2
2.9
<2.0
<2.0
10.4
24.6
12.3
12.2
3.2
4.7
<2.0
10.4
19.0
19.9
14.0
4.0
5.8
4.8
3.3
36.7
4.1
9.7
5.6
4.0
4.9
1.8
3.7
1.8
8.4
16.5
12.6
3.3
9.8
6.5
2.2
39.7
10.4
9.4
6.9
<2.0
3.2
4.0
4.1
2.5
3.9
14.0
3.3
5.3
<2.0
<2.0
<2.0
<2.0
<2.0
3.1
ND
ND
ND
ND
3.4
7.0
3.7
2.2
29.2
3.8
1.8
5.3
6.6
12.5
14.6
10.8
2.4
31.3
3.4
2.0
3.4
2.0
8.2
8.5
5.9
8b
8c
3.0
<2.0
14.6
2.9
<1.5
1.8
<2.0
27.9
1.5
<1.5
<1.5
<1.5
6.4
12.3
27.2
ND
ND
ND
8d
9ad
9bd
9cd
9dd
Cisplatin
3.4
3.1
3.9
3.8
7.2
<1.5
<1.5
2.3
2.9
8.9
ND
11.6
2.5
11.4
5.8
5.4
a
Cytotoxicity as IC50 for each cell line, is the concentration of compound which reduced by 50% the optical density of treated cells with respect to untreated cells using the
MTT assay.
b
Cell lines include breast carcinoma (MCF-7), liver carcinoma (HepG2), prostate carcinoma (22RV1), colon carcinoma (HT-29), renal carcinoma (769-P), malignant mel-
anoma (A375), ovarian carcinoma (SK-OV-3), esophageal carcinoma (Eca-109), gastric carcinoma (BGC-823) and Lewis lung carcinoma (LLC).
c
Data represent the mean values of three independent determinations.
See Ref. [32].
Not determined.
d
e
4-methoxyphenyl group appended to position-1, respectively,
displayed lower antitumor effects. A similar tendency also applied
to compounds 10b and 10d bearing an additional penta-3-yloxy
and 3-phenylpropoxy group in position-7, respectively. These re-
sults suggested that (1) the antitumor potencies of N2-alkylated
position-9, the benzyl group in position-2 were the optimal com-
bination for enhancing the antitumor potencies of b-carbolines.
4. Conclusions
In summary, a series of N2-alkylated quaternary
was designed and synthesized by modification of position-1, 2, 7
and 9 of -carboline nucleus with various alkyl and arylated alkyl
b
-carbolines
quaternary
b-carbolines depended upon the presence and location
and nature of the substituent which were introduced into the
carboline ring system; (2) the 3-phenylpropyl substituent in
b
-
b
substituents. Some of compounds were proved to be potent anti-
tumor agents, and Sarcoma 180 was more susceptible to this class
of compounds than Lewis lung cancer. SARs analysis indicated that
Table 2
(1) the antitumor potencies of N2-alkylated quaternary
b-carbo-
Acute toxic effects of the selected N2-alkylated quaternary
b-carbolines in mice and
antitumor activities of these compounds against mice bearing Sarcoma 180 and
Lewis lung cancer.
lines were substituent-dependence; (2) the substituents in
position-2 and 9 played a vital role in modulation of their antitumor
activities; (3) the benzyl and 3-phenylpropyl substituents in
Compds
LD50
Dosage
Tumor inhibition rate (%)
(mg kgꢀ1
)
(mg kgꢀ1
)
position-2 and 9 of
b-carboline nucleus, respectively, were the
Sarcoma
180
Lewis lung
carcinoma
optimal groups giving rise to significant antitumor agents. Syn-
thesis of analogs of compound 3m is in progress with an aim to
further improve the pharmacological profiles for preclinical testing.
3i
3m
4g
4h
8a
19.5
8.9
4.0
1.75
2.5
6.0
0.5
1.25
1.2
0.63
30
45.9
62.1
51.5
43.5
51.0
41.4
41.5
46.1
85.6
48.5
59.2
ND
12.5
30.0
2.50
6.25
6.25
3.75
ND
5. Experimental section
33.1
23.9
28.0
33.7
87.3
8c
10ba
10da
CTX
5.1. Reagents and general methods
All reagents were purchased from commercial suppliers and were
dried and purified when necessary. The following intermediates,
a
See Ref. [32].

26
G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
b
-carboline 1 [20], 9-methyl-
b
-carboline 2a [20], 9-ethyl-
-carboline 2e [20], 9-benzyl- -carboline 2i [20], 2,9-
-carboline 6a
b
-carboline
NCH2CH[CH3]2); 13C NMR (75 MHz, CDCl3):
132.5, 128.3, 128.2, 121.9, 121.1, 119.6, 114.6, 109.9, 51.1, 29.3, 20.9.
d 141.5, 138.9, 136.9,
2b [20], 9-butyl-
dibenzyl-
b
b
b-carboliniumbromate3i[22], and1-methyl-
b
[22], were prepared according to the described procedures. Com-
pounds 9aed and 10aed are known compounds [32].
5.2.4. 9-Hexyl-b-carboline (2g)
Yellow oil (1.02 g, 79%) was obtained. ESI-MS m/z: 253.0
Melting points were determined in capillary tubes on an elec-
trothermal PIF YRT-3 apparatus and without correction. ESI-MS
spectra were obtained from VG ZAB-HS spectrometer. 1H NMR and
13C NMR spectra were recorded on a Mercury-Plus 300 spectrometer
at 300 MHz and 75 MHz respectively, using TMS as internal standard
and CDCl3 or DMSO-d6 as solvent. Chemical shifts are reported in
[M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.87 (s, 1H, ArH); 8.45 (d,
J ¼ 6.3 Hz, 1H, ArH); 7.94 (d, J ¼ 5.4 Hz, 1H, ArH); 7.57 (t, J ¼ 8.1 Hz,
1H, ArH); 7.45 (d, J ¼ 8.1 Hz, 1H, ArH); 7.29e7.24 (m, 1H, ArH); 4.33
(t,
J
¼
7.2 Hz, 2H, NCH2[CH2]4CH3); 1.94e1.84 (m, 2H,
NCH2CH2[CH2]3CH3); 1.30 (m, 6H, NCH2CH2[CH2]3CH3); 0.86 (t,
J ¼ 6.9 Hz, 3H, NCH2[CH2]4CH3). 13C NMR (75 MHz, CDCl3):
d 141.1,
d
(ppm) downfield from an internal solvent peak and coupling con-
138.8, 136.5, 132.1, 128.3, 121.9, 121.1, 119.5, 114.5, 109.5, 43.4, 31.7,
29.3, 27.1, 22.8, 14.3.
stants, J in Hertz. Elemental analyses (C, H and N) were carried out on
an Elementar Vario EL CHNS Elemental Analyzer. HRMS were ob-
tained from ESI-Q-TOF maxis 4G spectrometer. Silica gel F254 were
used in analytical thin-layer chromatography (TLC) and silica gel
were used in column chromatography respectively.
5.2.5. 9-Octyl-b-carboline (2h)
White solid (1.05 g, 75%) was obtained, mp 46e47 ꢁC. ESI-MS m/
z: 280.9 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.88 (s, 1H, ArH);
8.45 (d, J ¼ 5.4 Hz, 1H, ArH); 8.14 (d, J ¼ 7.8 Hz, 1H, ArH); 7.96 (d,
J ¼ 5.1 Hz, 1H, ArH); 7.59 (t, J ¼ 5.1 Hz, 1H, ArH); 7.46 (d, J ¼ 8.4 Hz,
1H, ArH); 4.40e4.33 (t, J ¼ 7.2 Hz, 2H, NCH2[CH2]6CH3); 1.97e1.85
5.2. General procedure for the preparation of 9-substituted b-
carboline derivatives (2cem)
(m,
2H,
NCH2CH2[CH2]5CH3)
1.46e1.20
(m,
10H,
NCH2CH2[CH2]5CH3); 0.86 (t, J ¼ 6.6 Hz, 3H, NCH2[CH2]6CH3). 13C
A mixture of
b
-carbolines 1 (5 mmol) and anhydrous DMF
NMR (75 MHz, CDCl3): d 141.3,139.0,136.7,132.3,128.4,122.0,121.2,
(50 ml) was stirred at room temperature until clear, and then 60%
NaH (0.3 g, 7.5 mmol) and alkyl halide (10e15 mmol) were added.
The mixture was stirred at room temperature for 0.5e4 h. After
completion of the reaction as indicated by TLC, the solution was
poured into H2O (150 ml), and extracted with ethyl acetate. The
combined organic phase was made acidic with concentrated hy-
drochloric acid. Upon removal of solvent, the residue was crystal-
lized from acetone to afford yellow solid. The solid was dissolved in
water and made basic with sodium bicarbonate, and the aqueous
mixture extracted with ethyl acetate. The organic phase was
washed with water and brine, then dried over anhydrous sodium
sulfate, filtered and evaporated. The resulting oil was purified by a
column chromatography, using a mixture of acetone and petroleum
ether (1:4) as an eluent, to successfully afford the intermediates
2cem in good yield.
119.6, 114.7, 109.7, 43.7, 32.1, 29.7, 29.5, 27.6, 23.0, 14.5.
5.2.6. 9-(4-Fluorobenzyl)- -carboline (2j)
b
Yellow solid (0.81 g, 59%) was obtained, mp 109e112 ꢁC. ESI-
MS m/z: 276.8 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.82 (s,
1H, ArH); 8.48 (d, J ¼ 5.4 Hz, 1H, ArH); 8.17 (d, J ¼ 4.8 Hz, 1H, ArH);
7.98 (d, J ¼ 5.1 Hz, 1H, ArH); 7.57 (t, J ¼ 5.1 Hz, 1H, ArH); 7.42 (d,
J ¼ 5.1 Hz, 1H, ArH); 7.31 (t, J ¼ 5.1 Hz, 1H, ArH); 7.15e7.08 (m, 2H,
ArH); 6.99e6.91 (m, 2H, ArH); 5.55 (s, 2H, NCH2Ph[4-F]). 13C NMR
(75 MHz, CDCl3):
d 164.0, 160.8, 141.4, 139.7, 136.7, 132.4, 128.8,
128.4, 128.3, 122.2, 121.5, 120.3, 116.2, 116.0, 115.9, 114.8, 110.0,
109.8, 46.5.
5.2.7. 9-(3-Chlorobenzyl)-b-carboline (2k)
White solid (1.22 g, 84%) was obtained, mp 94e95 ꢁC. ESI-MS m/
z: 293.0 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.83 (s, 1H, ArH);
5.2.1. 9-Isopropyl-
b-carboline (2c)
8.51 (d, 1H, J ¼ 5.1 Hz, ArH); 8.20 (d, 1H, J ¼ 7.8 Hz, ArH); 8.01 (d, 1H,
J ¼ 5.1 Hz, ArH); 7.61e7.56 (m,1H, ArH); 7.42 (d,1H, J ¼ 7.8 Hz, ArH);
7.35e7.31 (m, 1H, ArH); 7.25e7.16 (m, 3H, ArH); 7.01(d, 1H,
J ¼ 7.2 Hz, ArH); 5.55 (s, 2H, NCH2Ph[3-Cl]). 13C NMR (75 MHz,
Yellow oil (0.75 g, 70%) was obtained. ESI-MS m/z: 210.9
[M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 9.04 (s, 1H, ArH); 8.43 (d,
J ¼ 5.1 Hz, 1H, ArH); 8.16 (d, J ¼ 8.1 Hz, 1H, ArH); 8.00 (d, J ¼ 4.5 Hz,
1H, ArH); 7.61e7.56 (m, 2H, ArH); 7.30e7.26 (m, 1H, ArH); 5.08e
5.02 (m, 1H, NCH[CH3]2); 1.75 (d, J ¼ 6.9 Hz, 6H, NCH[CH3]2). 13C
CDCl3):
d 141.3, 139.4, 138.4, 136.5, 134.9, 131.9, 130.4, 128.8, 128.2,
126.6, 124.6, 122.1, 121.3, 120.2, 114.7, 109.5, 46.4.
NMR (75 MHz, CDCl3):
d 140.5, 138.5, 135.8, 133.3, 129.0, 128.3,
122.0, 121.5, 119.6, 114.8, 110.8, 47.5, 21.4.
5.2.8. 9-(4-Methoxybenzyl)- -carboline (2l)
b
White solid (1.20 g, 86%) was obtained, mp 134e136 ꢁC. ESI-MS
5.2.2. 9-Allyl- -carboline (2d)
b
m/z: 288.9 [M þ H]þ; 1H NMR (300 MHz, CDCl3):
d 8.85 (s, 1H, ArH);
Yellow oil (0.65 g, 63%) was obtained. ESI-MS m/z: 208.9
8.46 (d, J ¼ 5.1 Hz, 1H, ArH); 8.16 (d, J ¼ 7.8 Hz, 1H, ArH); 7.98 (d,
J ¼ 5.1 Hz, 1H, ArH); 7.59e7.44 (m, 2H, ArH); 7.32e7.27 (m, 1H,
ArH); 7.12e7.08 (m, 2H, ArH); 6.81e6.78 (m, 2H, ArH), 5.52 (s, 2H,
NCH2Ph[4-OCH3]); 3.75 (s, 3H, OCH3). 13C NMR (75 MHz, CDCl3):
[M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.85 (s, 1H, ArH); 8.47 (d,
J ¼ 6.6 Hz, 1H, ArH); 8.16 (d, J ¼ 8.1 Hz, 1H, ArH); 7.98 (d, J ¼ 5.1 Hz,
1H, ArH); 7.59 (t, J ¼ 7.2 Hz, 1H, ArH); 7.46 (d, J ¼ 8.4 Hz, 1H, ArH);
7.29 (t, J ¼ 7.2 Hz, 1H, ArH); 6.07e5.92 (m, 1H, NCH2CH]CH2);
5.23e5.03 (m, 2H, NCH2CH]CH2); 5.03e5.98 (m, 2H, NCH2CH]
d
159.4, 141.5, 139.4, 136.8, 132.6, 128.7, 128.6, 128.0, 122.1, 121.5,
120.1, 114.8, 114.5, 110.0, 55.6, 46.8.
CH2). 13C NMR (75 MHz, CDCl3):
d
141.2, 139.2, 136.5, 132.3, 131.9,
128.5, 122.0, 121.2, 119.4, 117.5, 114.7, 109.7, 45.7.
5.2.9. 9-(3-Phenylpropyl)-b-carboline (2m)
White solid (1.25 g, 87%) was obtained, mp 99e100 ꢁC. ESI-MS
5.2.3. 9-Isobutyl-
b
-carboline (2f)
m/z: 286.9 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.83 (s, 1H,
White solid (0.82 g, 73%) was obtained, mp 61e63 ꢁC. ESI-MS m/
ArH); 8.48 (d,1H, J ¼ 5.1 Hz, ArH); 8.17 (d,1H, J ¼ 7.5 Hz, ArH); 7.97e
7.99 (m, 1H, ArH); 7.58e7.62 (m, 1H, ArH); 7.18e7.41 (m, 7H, ArH);
4.42 (t, 2H, J ¼ 6.9 Hz, NCH2CH2CH2Ph); 2.73e2.77 (2H, m,
NCH2CH2CH2Ph); 2.27e2.31 (m, 2H, NCH2CH2CH2Ph). 13C NMR
z: 224.9 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.87 (s, 1H, ArH);
8.45 (d, J ¼ 5.4 Hz, 1H, ArH); 8.15 (d, J ¼ 8.1 Hz, 1H, ArH); 7.96 (d,
J ¼ 5.4 Hz, 1H, ArH); 7.58 (t, J ¼ 7.2 Hz, 1H, ArH); 7.47 (d, J ¼ 5.1 Hz,
1H, ArH); 7.30e7.25 (m, 1H, ArH); 4.18 (d, J ¼ 7.5 Hz, 2H, NCH2CH
[CH3]2); 2.47e2.33 (m, 1H, NCH2CH[CH3]2); 1.00 (d, J ¼ 6.6 Hz, 6H,
(75 MHz, CDCl3):
d 141.2, 140.8, 139.2, 136.5, 132.3, 128.8, 128.5,
126.5, 122.1, 121.3, 119.8, 114.8, 109.7, 42.9, 33.5, 30.6.

G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
27
5.3. General procedure for the preparation of 1-substituted
carboline (6bed)
b
-
by a column chromatography, using a mixture of ethyl acetate and
petroleum ether 5:1 as an eluent, to successfully afford the target
products in good yield.
A mixture of L-tryptophan (20.4 g, 100 mmol), acetic acid
(300 ml) and the appropriate aldehydes (100 mmol) was refluxed
for 3 h, then cooled and adjusted pH to 5 with concentrated
ammonium hydroxide, the precipitated product was collected by
filtration and washed well with water and dried to provide the
intermediates 1,2,3,4-tetrahydro-b-carboline-3-carboxylic acid
5bed. Further purification was not necessary and used directly for
5.4.1. 1-Methyl-9-(3-phenylpropyl)-b-carboline (7a)
White solid (1.31 g, 87%) was obtained, mp 120e121 ꢁC. ESI-MS
m/z: 300.8 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.30 (d,
J ¼ 5.1 Hz, 1H, ArH); 8.10 (d, J ¼ 7.8 Hz, 1H, ArH); 7.82 (d, J ¼ 5.1 Hz,
1H, ArH); 7.54 (t, J ¼ 7.8 Hz, 1H, ArH); 7.35e7.17 (m, 7H, ArH); 4.54
(t, J ¼ 7.8 Hz, 2H, NCH2CH2CH2Ph); 2.92 (s, 3H, CH3); 2.78 (t,
the next steps.
J
¼
7.5 Hz, 2H, NCH2CH2CH2Ph); 2.24e2.12 (m, 2H,
1,2,3,4-Tetrahydro-
b-carboline-3-carboxylid
acid
5be
NCH2CH2CH2Ph). 13C NMR (75 MHz, CDCl3):
d 141.5, 141.4, 140.8,
d (10 mmol) was diluted to 100 ml with water, and then heated to
boiling. To the hot solution was added potassium dichromate (15 g)
and acetic acid (20 ml). The brown suspension was heated for
20 min and then cooled under the tap. After treating the cold so-
lution with sodium sulfite to remove the excess oxidizing agent, the
mixture was made definitely alkaline with sodium hydroxide. The
solution was extracted exhaustively with ethyl acetate (1000 ml),
the extracts dried over anhydrous sodium sulfate, and the solvent
removed. The residue was crystallized from anhydrous ethanol to
provide the compounds 6bed in good yield.
138.2, 135.2, 129.1, 128.8,128.6,128.2, 126.5, 121.6, 121.5, 119.8, 113.1,
109.8, 44.4, 33.4, 32.3, 23.7.
5.4.2. 1-Phenyl-9-(3-phenylpropyl)-b-carboline (7b)
White solid (1.52 g, 84%) was obtained, mp 100e103 ꢁC. ESI-MS
m/z: 362.8 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.52 (d,
J ¼ 4.5 Hz, 1H, ArH); 8.17 (d, J ¼ 7.8 Hz, 1H, ArH); 7.97 (d, J ¼ 5.1 Hz,
1H, ArH); 7.65e7.52 (m, 6H, ArH); 7.34e7.11 (m, 5H, ArH); 6.94 (d,
J ¼ 7.2 Hz, 2H, ArH); 3.99 (t, J ¼ 8.1 Hz, 2H, NCH2CH2CH2Ph); 2.13 (t,
J ¼ 7.8 Hz, 2H, NCH2CH2CH2Ph); 1.77e1.64 (m, 2H, NCH2CH2CH2Ph).
13C NMR (75 MHz, CDCl3):
d 144.5, 142.2, 141.1, 140.4, 138.6, 134.3,
5.3.1. 1-Phenyl-
b
-carboline (6b)
130.6,129.6,128.7, 128.7,128.5,128.4,126.3,121.9,121.7,120.1,114.0,
110.4, 44.6, 33.3, 30.8.
Yellow solid (15.4 g, 63%) was obtained, mp 244e250 ꢁC. ESI-MS
m/z: 244.9 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.57 (d,
J ¼ 5.4 Hz, 1H, ArH); 8.50 (s, 1H, NH) 8.16 (d, J ¼ 7.8 Hz, 1H, ArH);
5.4.3. 1-(4-Methoxylphenyl)-9-(3-phenylpropyl)-b-carboline (7c)
7.99e7.92 (m, 3H, ArH); 7.62e7.45 (m, 5H, ArH); 7.31 (t, J ¼ 7.8 Hz,
Yellow oil (1.61 g, 82%) was obtained. ESI-MS m/z: 393.9
1H, ArH). 13C NMR (75 MHz, CDCl3):
d
143.2, 140.6, 139.7, 138.7,
[M þ H]þ. 1H NMR (300 MHz, CDCl3):
8.50 (d, J ¼ 5.1 Hz, 1H, ArH);
d
133.7, 130.0, 129.3, 129.0, 128.7, 128.3, 122.0, 120.4, 114.0, 111.8.
8.16 (d, J ¼ 7.8 Hz, 1H, ArH); 7.94 (d, J ¼ 5.1 Hz, 1H, ArH); 7.58e7.52
(m, 3H, ArH); 7.35e7.11 (m, 5H, ArH); 7.06 (d, J ¼ 8.7 Hz, 2H, ArH);
6.93 (d, J ¼ 6.9 Hz, 2H, ArH); 4.05 (t, J ¼ 7.8 Hz, 2H, NCH2CH2CH2Ph);
3.92 (s, 3H, OCH3); 2.18 (t, J ¼ 7.2 Hz, 2H, NCH2CH2CH2Ph); 1.75e
5.3.2. 1-(4-Methoxyphenyl)- -carboline (6c)
b
White solid (18.3 g, 67%) was obtained, mp 135e142 ꢁC. ESI-MS
m/z: 274.8 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d
8.55e8.50 (m,
1.65 (m, 2H, NCH2CH2CH2Ph). 13C NMR (75 MHz, CDCl3):
d 160.0,
2H, ArH, NH); 8.15 (d, J ¼ 7.8 Hz, 1H, ArH); 7.93e7.87 (m, 3H, ArH);
7.58e7.47 (m, 2H, ArH); 7.30 (t, J ¼ 7.5 Hz, 1H, ArH); 7.10 (d,
J ¼ 8.4 Hz, 2H, ArH); 3.90 (s, 3H, OCH3). 13C NMR (75 MHz, CDCl3):
144.3, 142.3, 141.0, 138.6, 134.4, 132.7, 130.8, 130.6, 128.6, 128.3,
126.22, 121.8, 121.8, 120.1, 113.9, 113.7, 110.4, 55.7, 44.5, 33.3, 30.7.
d
160.2, 142.9, 140.9, 138.9, 133.6, 130.6, 130.1, 129.7, 128.7, 121.9,
5.4.4. 9-(3-Phenylpropyl)-1-(thiophen-3-yl)-b-carboline (7d)
120.3, 114.7, 113.6, 112.0, 55.7.
Yellow solid (1.34 g, 73%) was obtained, mp 146e148 ꢁC. ESI-MS
m/z: 369 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
8.67 (d, J ¼ 6.0 Hz,
d
5.3.3. 1-(Thiophen-3-yl)- -carboline (6d)
b
1H, ArH); 8.42 (d, J ¼ 6.0 Hz, 1H, ArH); 8.27 (d, J ¼ 7.8 Hz, 1H, ArH);
7.84e7.74 (m, 2H, ArH); 7.64e7.63 (dd, J ¼ 3.6, 1.2 Hz, 1H, ArH);
7.51e7.47 (m, 1H, ArH); 7.44 (d, J ¼ 8.1 Hz, 1H, ArH); 7.34 (dd, J ¼ 5.1,
3.6 Hz, 1H, ArH); 7.26e7.15 (m, 3H, ArH); 6.98 (m, 2H, ArH); 4.20e
4.16 (t, J ¼ 7.2 Hz, 2H, NCH2CH2CH2Ph); 2.36e2.32 (t, J ¼ 7.2 Hz, 2H,
NCH2CH2CH2Ph); 1.90e1.82 (m, 2H, NCH2CH2CH2Ph). 13C NMR
Yellow solid (10.5 g, 42%) was obtained, mp 154e157 ꢁC. ESI-MS
m/z: 250.8 [M þ H]þ. 1H NMR (300 MHz, CDCl3):
d 8.80 (s, 1H, NH),
8.48 (d, J ¼ 5.1 Hz, 1H, ArH); 8.12 (d, J ¼ 7.8 Hz, 1H, ArH); 7.87 (d,
J ¼ 5.4 Hz, 1H, ArH); 7.74 (d, J ¼ 3.6 Hz, 1H, ArH); 7.58e7.46 (m, 3H,
ArH); 7.36e7.27 (m, 1H, ArH); 7.20 (t, J ¼ 4.5 Hz, 1H, ArH). 13C NMR
(75 MHz, CDCl3):
d
143.0, 140.9, 139.3, 137.3, 132.5, 130.6, 128.8,
(75 MHz, CDCl3): d 142.2, 140.8, 138.3, 137.0, 134.9, 131.0, 128.7,
128.2, 127.4, 125.4, 122.0, 121.9, 120.6, 114.0, 112.1.
128.4, 128.1, 127.2, 126.8, 126.0, 121.7, 121.3, 120.1, 114.2, 110.2, 44.2,
33.0, 30.6.
5.4. General procedure for the preparation of 1,9-disubstituted b-
carbolines (7aed)
5.5. General procedure for the preparation of N2-alkylated
b-
carbolinium bromides or iodides (3aem, 4aek, 8aed)
A mixture of 1-substituted
b-carbolines 6aed (5 mmol) and
anhydrous DMF (30 ml) was stirred at room temperature until
clear, and then 60% NaH (10 mmol) and halogenated alkane (10e
15 mmol) were added. The mixture was stirred at room tempera-
ture. After completion of the reaction as indicated by TLC, the so-
lution was poured into H2O (150 ml), and extracted with ethyl
acetate. The organic phase was made acidic with concentrated
hydrochloric acid. Upon removal of solvent, the residue was crys-
tallized from acetone to afford yellow solid. The solid was dissolved
in water and made basic with sodium bicarbonate, and the aqueous
mixture extracted with ethyl acetate. The organic phase was
washed with water and brine, then dried over anhydrous sodium
sulfate, filtered and evaporated. The residue crude oil was purified
A mixture of b-carboline (2.0 mmol) and alkyl halide (30e
50 mmol) in ethyl acetate (50 ml) was refluxed for 5e10 h. After
completion of the reaction as indicated by TLC, the solution was
cooled and filtered to afford yellow solid. The solid was recrystal-
lized from ethanol.
5.5.1. 2-Benzyl-9-methyl-b-carbolinium bromide (3a)
Yellow crystals (0.49 g, 90%) were obtained, mp > 250 ꢁC. ESI-
MS 273.2 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.85 (s,
1H, ArH); 8.80 (d, J ¼ 6.6 Hz, 2H, ArH); 8.48 (d, J ¼ 8.1 Hz, 1H, ArH);
7.87 (d, J ¼ 8.7 Hz, 3H, ArH); 7.61e7.27 (m, 6H, ArH); 5.93 (s, 2H,
NþCH2Ph); 4.09 (s, 3H, NCH3). 13C NMR (75 MHz, DMSO-d6):
d 145.1,

28
G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
136.5, 135.5, 132.8, 132.7, 132.1, 129.7, 129.6, 129.1, 129.0, 124.0,
122.3, 119.2, 118.5, 111.6, 63.8, 30.9. HRMS (ESI) calcd for C19H17BrN2
273.1386 [M ꢀ Br]þ, found 273.1392.
1H, ArH); 8.77 (s, 2H, ArH), 8.43 (d, J ¼ 8.1 Hz, 1H, ArH); 7.88e7.75
(m, 2H, ArH); 7.57 (d, J ¼ 6.6 Hz, 2H, ArH), 7.47e7.32 (m, 4H, ArH),
5.96 (s, 2H, NþCH2Ph); 4.58 (t, J ¼ 6.9 Hz, 2H, NCH2[CH2]4CH3);
1.85e1.72 (m, 2H, NCH2CH2[CH2]3CH3); 1.26e1.05 (m, 6H,
NCH2CH2[CH2]3CH3); 0.71 (t, J ¼ 6.9 Hz, 3H, NCH2[CH2]4CH3). 13C
5.5.2. 2-Benzyl-9-ethyl-b-carbolinium bromide (3b)
Yellow crystals (0.55 g, 96%) were obtained, mp > 250 ꢁC. ESI-MS
NMR (75 MHz, DMSO-d6): d 144.7, 136.1, 135.6, 132.9, 132.8, 132.3,
1
287.2 m/z [M ꢀ Br]þ. H NMR (300 MHz, DMSO-d6):
d
9.89 (s, 1H,
129.6, 129.0, 128.8, 124.3, 122.4, 119.4, 118.7, 111.8, 63.7, 44.2, 31.2,
29.0, 26.3, 22.3, 14.2. HRMS (ESI) calcd for C24H27BrN2 343.2169
[M ꢀ Br]þ, found 343.2177.
ArH); 8.79 (d, J ¼ 14.7 Hz, 2H, ArH); 8.50 (d, J ¼ 8.1 Hz,1H, ArH); 7.97e
7.82 (m, 3H, ArH); 7.65e7.35 (m, 5H, ArH); 5.92 (s, 2H, NþCH2Ph); 4.66
(q, J ¼ 6.9 Hz, 2H, NCH2CH3); 1.41 (t, J ¼ 7.2 Hz, 3H, NCH2CH3).13C NMR
(75 MHz, DMSO-d6):
d
144.3, 135.6, 135.6, 133.0, 132.9, 132.5, 129.6,
5.5.8. 2-Benzyl-9-octyl-b-carbolinium bromide (3h)
129.1, 128.8, 124.4, 122.4, 119.5, 118.7, 111.7, 63.9, 14.4. Analysis (calcd,
found for C20H19BrN2): C (65.40, 65.65), H (5.21, 5.31), N (7.63, 7.53).
Yellow crystals (0.64 g, 86%) were obtained, mp 196e198 ꢁC. ESI-
MS 371.3 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.92 (s, 1H,
ArH); 8.81 (q, J ¼ 6.6 Hz, 2H, ArH); 8.49 (d, J ¼ 8.1 Hz, 1H, ArH); 7.87
(d, J ¼ 8.1 Hz, 2H, ArH); 7.58e7.35 (m, 6H, ArH); 5.94 (s, 2H,
NþCH2Ph); 4.61 (t, J ¼ 6.9 Hz, 2H, NCH2[CH2]6CH3); 1.84e1.80 (m, 2H,
NCH2CH2[CH2]5CH3); 1.20e1.12 (m, 10H, NCH2CH2[CH2]5CH3); 0.77
(t, J ¼ 6.9 Hz, 3H, NCH2[CH2]6CH3). 13C NMR (75 MHz, DMSO-d6):
5.5.3. 2-Benzyl-9-isopropyl-b-carbolinium bromide (3c)
Yellow crystals (0.58 g, 97%) were obtained, mp > 250 ꢁC. ESI-
MS 301.2 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.87 (s,
1H, ArH); 8.82 (d, J ¼ 6.3 Hz, 1H, ArH); 8.75 (d, J ¼ 6.3 Hz, 1H, ArH);
8.50 (d, J ¼ 8.1 Hz, 1H, ArH); 8.03 (d, J ¼ 8.4 Hz, 1H, ArH); 7.83 (t,
J ¼ 7.8 Hz, 1H, ArH); 7.56e7.36 (m, 6H, ArH); 5.94 (s, 2H, NþCH2Ph);
5.35e5.26 (m, 1H, NCH[CH3]2); 1.71 (d, J ¼ 6.9 Hz, 6H, NCH[CH3]2).
d
144.6, 136.1, 135.7, 132.9, 132.8, 132.3, 129.6, 129.1, 128.8, 124.3,
122.4, 119.4, 118.7, 111.8, 63.7, 44.2, 31.5, 29.1, 28.9, 26.7, 22.4, 14.3.
HRMS (ESI) calcd for C26H31BrN2 371.2482 [M ꢀ Br]þ, found 371.2501.
13C NMR (75 MHz, DMSO-d6):
d 143.8, 135.7, 134.9, 132.9, 132.8,
132.7, 129.6, 129.5, 128.9, 124.4, 122.3, 119.9, 118.6, 113.0, 63.7, 48.7,
20.9. Analysis (calcd, found for C21H21BrN2): C (66.15, 66.36), H
(5.55, 5.63), N (7.35, 7.24).
5.5.9. 9-(4-Fluorobenzyl)-2-benzyl-b-carbolinium bromide (3j)
Yellow crystals (0.67 g, 91%) were obtained, mp 250e251 ꢁC. ESI-
MS 367.2 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.97 (s,1H,
ArH); 8.86 (s, 2H, ArH); 8.51 (d, J ¼ 8.1 Hz, 1H, ArH); 7.91 (d,
J ¼ 8.4 Hz, 1H, ArH); 7.81 (d, J ¼ 11.4 Hz, 1H, ArH); 7.58e7.29 (m, 8H,
ArH); 7.16e7.06 (m, 2H, ArH); 5.94 (s, 2H, NþCH2Ph); 5.87 (s, 2H,
5.5.4. 2-Benzyl-9-allyl-b-carbolinium bromide (3d)
Yellow crystals (0.55 g, 92%) were obtained, mp > 250 ꢁC. ESI-MS
1
299.2 m/z [M ꢀ Br]þ. H NMR (300 MHz, DMSO-d6):
d
9.83 (s, 1H,
NCH2Ph[4-F]). 13C NMR (75 MHz, DMSO-d6):
d 163.4, 161.0, 144.6,
ArH); 8.82 (d, J ¼ 6.6 Hz, 2H, ArH); 8.51 (d, J ¼ 8.1 Hz, 1H, ArH); 7.92e
7.80 (m, 2H, ArH); 7.57e7.35 (m, 6H, ArH); 6.11e5.97 (m, 1H,
NCH2CH]CH2); 5.92 (s, 2H, NþCH2Ph); 5.27 (d, J ¼ 5.1 Hz, 2H,
NCH2CH]CH2); 5.18e5.06 (m, 2H, NCH2CH]CH2).13C NMR (75 MHz,
136.3, 135.6, 133.6, 133.0, 132.9, 132.6, 129.9, 129.8, 129.6, 129.1,
128.9, 124.5, 122.7, 119.8, 118.9, 116.2, 116.0, 112.1, 63.9, 46.7. HRMS
(ESI) calcd for C25H20Br FN2 367.1605 [M ꢀ Br]þ, found 367.1614.
DMSO-d6):
d
144.7, 136.1, 135.5, 133.3, 132.9, 132.7, 132.4, 129.6, 129.1,
5.5.10. 9-(3-Chlorobenzyl)-2-benzyl-b-carbolinium bromide (3k)
128.8,124.4,122.6,119.6,118.8,118.3,112.0, 63.9, 46.3. Analysis (calcd,
found for C21H19BrN2): C (66.50, 66.70), H (5.05, 5.17), N (7.39, 7.28).
Yellow crystals (0.65 g, 70%) were obtained, mp 267e269 ꢁC; EI-
MS m/z 383.0 [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 10.08 (s,
1H, ArH); 8.95 (d, J ¼ 8.1 Hz, 2H, ArH); 8.58 (d, J ¼ 8.1 Hz, 1H, ArH);
7.95 (d, J ¼ 8.1 Hz, 1H, ArH); 7.86e7.90 (m, 1H, ArH); 7.57e7.60 (m,
2H, ArH); 7.51e7.55 (m,1H, ArH); 7.31e7.46 (m, 6H, ArH); 7.20e7.22
5.5.5. 2-Benzyl-9-butyl-b-carbolinium bromide (3e)
Yellow crystals (0.68 g, 85%) were obtained, mp 225e227 ꢁC.
ESI-MS 315.0 m/z [M ꢀ Br]þ. 1H NMR (500 MHz, DMSO-d6):
d
10.05
(m, 1H, ArH); 5.98 (s, 2H, NþCH2Ph); 5.94 (s, 2H, NCH2Ph[3-Cl]). 13
C
(s, 1H, ArH); 8.85e8.88 (m, 2H, ArH); 8.54 (d, J ¼ 8.0 Hz, 1H, ArH);
7.96 (d, J ¼ 9.0 Hz, 1H, ArH); 7.86e7.89 (m, 1H, ArH); 7.39e7.61 (m,
6H, ArH); 6.01 (2H, s, NþCH2Ph); 4.65 (t, J ¼ 7.5 Hz, 2H,
NCH2CH2CH2CH3); 1.83e1.86 (m, 2H, NCH2CH2CH2CH3); 1.30e1.35
NMR (75 MHz, DMSO-d6): d 144.1, 140.7, 135.8, 133.3, 132.4, 132.1,
131.8, 130.6, 129.0, 128.3, 127.9, 127.0, 125.7, 123.8, 121.7, 119.0, 118.1,
111.3, 63.0, 32.2. Analysis (calcd, found for C25H20BrClN2): C (64.74,
64.38), H (4.35, 4.39), N (6.04, 6.10).
(m, 2H, NCH2CH2CH2CH3); 0.88e0.91 (m, 3H, NCH2CH2CH2CH3). 13
C
NMR (75 MHz, DMSO-d6):
d
144.7, 136.1, 136.0, 133.1, 132.8, 132.3,
5.5.11. 9-(4-Methoxybenzyl)-2-benzyl-b-carbolinium bromide (3l)
129.7, 129.6, 129.2, 124.5, 122.4, 119.6, 118.9, 112.0, 63.6, 44.4, 31.6,
20.5, 14.5. Analysis (calcd, found for C22H23BrN2): C (66.84, 66.48),
H (5.86, 5.90), N (7.09, 6.96).
Yellow crystals (0.64 g, 71%) were obtained, mp > 250 ꢁC. ESI-
MS m/z: 378.9 (M ꢀ Br)þ. 1H NMR (300 MHz, DMSO-d6):
d 9.99
(s, 1H, ArH); 8.83e8.84 (m, 2H, ArH); 8.48 (d, J ¼ 8.1 Hz, 1H, ArH);
7.93 (d, J ¼ 8.4 Hz, 1H, ArH); 7.78e7.84 (m, 1H, ArH); 7.38e7.56 (m,
6H, ArH); 7.25 (d, J ¼ 8.4 Hz, 2H, ArH); 6.79e6.82 (m, 2H, ArH); 5.95
(s, 2H, NþCH2Ph); 5.79 (s, 2H, NCH2Ph[4-OCH3]); 3.65 (s, 3H, OCH3).
5.5.6. 2-Benzyl-9-isobutyl-b-carbolinium bromide (3f)
Yellow crystals (0.57 g, 90%) were obtained, mp 240e242 ꢁC.
ESI-MS 315.2 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.92
13C NMR (75 MHz, DMSO-d6):
d 159.5, 144.5, 136.1, 136.0, 133.5,
(s, 1H, ArH); 8.80 (d, J ¼ 13.8 Hz, 2H, ArH); 8.50 (d, J ¼ 8.1 Hz, 1H,
ArH); 7.96 (d, J ¼ 8.4 Hz, 1H, ArH); 7.84 (t, J ¼ 7.8 Hz, 1H, ArH); 7.57e
7.34 (m, 6H, ArH); 5.93 (s, 2H, NþCH2Ph); 4.43 (d, J ¼ 7.5 Hz, 2H,
NCH2CH[CH3]2); 2.37e2.24 (m, 1H, NCH2CH[CH3]2); 0.89 (d,
J ¼ 6.6 Hz, 6H, NCH2CH[CH3]2). 13C NMR (75 MHz, DMSO-d6):
132.8, 132.7, 129.7, 129.6, 129.4, 129.3, 128.6, 124.5, 122.6, 119.8,
119.0, 114.7, 112.4, 63.6, 55.9, 47.2. HRMS (ESI) calcd for
C
26H23BrN2O 379.1805 [M ꢀ Br]þ, found 379.1832.
5.5.12. 9-(3-Phenylpropyl)-2-benzyl-b-carbolinium bromide (3m)
d
145.0, 136.4, 135.7, 132.9, 132.7, 132.2, 129.6, 129.4, 128.8, 124.2,
Yellow crystals (0.84 g, 92%) were obtained, mp 218e219 ꢁC. ESI-
122.3,119.3, 118.7,112.2, 63.6, 50.9, 28.9, 20.2. Analysis (calcd, found
for C22H23BrN2): C (66.84, 66.39), H (5.86, 5.88), N (7.09, 6.87).
MS 376.9 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.98 (s,1H,
ArH); 9.82 (s, 2H, ArH); 8.49e8.51 (m, 1H, ArH); 7.84e7.92 (m, 2H,
ArH); 7.59e7.61 (m, 2H, ArH); 7.40e7.50 (m, 4H, ArH); 7.04e7.14
(m, 5H, ArH); 5.98 (s, 2H, NþCH2Ph); 4.71 (t, J ¼ 4.2 Hz, 2H,
NCH2CH2CH2Ph); 2.67 (t, J ¼ 4.8 Hz, 2H, NCH2CH2CH2Ph); 2.18e
2.24 (m, 2H, NCH2CH2CH2Ph). 13C NMR (75 MHz, DMSO-d6):
5.5.7. 2-Benzyl-9-hexyl-b-carbolinium bromide (3g)
Yellow crystals (0.66 g, 96%) were obtained, mp 218e219 ꢁC. ESI-
MS 343.3 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.95 (s,

G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
29
d
144.6, 141.5, 136.1, 136.0, 133.1, 132.7, 132.4, 129.7, 129.3, 128.7,
(d, J ¼ 8.1 Hz, 1H, ArH); 7.96e7.78 (m, 3H, ArH); 7.48 (t, J ¼ 7.2 Hz,1H,
128.6, 126.3, 124.5, 122.4, 119.7, 118.8, 111.9, 63.6, 44.5, 33.1, 30.9.
Analysis (calcd, found for C27H25BrN2): C (70.90, 70.79), H (5.51,
5.61), N (6.12, 6.14).
ArH); 7.18e7.05 (m, 5H, ArH); 4.70 (d,
J
¼
6.6 Hz, 2H,
NþCH2[CH2]6CH3); 4.65 (t, J ¼ 6.6 Hz, 2H, NCH2CH2CH2Ph); 2.64 (t,
J ¼ 7.5 Hz, 2H, NCH2CH2CH2Ph); 2.24e2.10 (m, 2H, NCH2CH2CH2Ph);
2.02e1.96 (m, 2H, NþCH2CH2[CH2]5CH3); 1.28e1.18 (m, 10H,
5.5.13. 9-(3-Phenylpropyl)-2-methyl-
b
-carbolinium iodide (4a)
NþCH2CH2[CH2]5CH3); 0.78 (t, J ¼ 6.7 Hz, 3H, NþCH2[CH2]6CH3). 13
C
Yellow crystals (0.57 g, 95%) were obtained, mp 208e210 ꢁC. ESI-
NMR (75 MHz, DMSO-d6): d 144.4, 141.3, 135.9, 133.0, 132.5, 132.2,
MS 301.2 m/z [M ꢀ I]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.54 (s, 1H,
128.9, 128.6, 128.4, 126.3, 124.2, 122.2, 119.5, 118.3, 111.7, 61.2, 44.0,
32.7, 31.7, 31.5, 30.5, 28.9, 28.8, 25.9, 22.4, 14.3. HRMS (ESI) calcd for
ArH); 8.73 (d, J ¼ 6.3 Hz, 1H, ArH); 8.58 (d, J ¼ 6.3 Hz, 1H, ArH); 8.47
(d, J ¼ 8.1 Hz,1H, ArH); 7.84 (q, J ¼ 8.4 Hz, 2H, ArH); 7.46 (d, J ¼ 7.8 Hz,
1H, ArH); 7.23e7.05 (m, 5H, ArH); 4.63 (t, J ¼ 6.9 Hz, 2H,
NCH2CH2CH2Ph); 4.47 (s, 3H, NþCH3); 2.65 (t, J ¼ 7.5 Hz, 2H,
NCH2CH2CH2Ph); 2.23e2.10 (m, 2H, NCH2CH2CH2Ph). 13C NMR
C
28H35IN2 399.2795 [M ꢀ I]þ, found 399.2805.
5.5.18. 9-(3-Phenylpropyl)-2-decyl-b-carbolinium iodide (4f)
Yellow crystals (0.39 g, 46%) were obtained, mp 125e126 ꢁC. ESI-
(75 MHz, DMSO-d6):
d
144.3, 141.3, 135.7, 133.8, 132.4, 131.9, 129.7,
MS 427.4 m/z [M ꢀ I]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.79 (s, 1H,
128.7,128.5,126.3,124.1,122.2,119.4,117.9,111.7, 48.3, 43.9, 32.7, 30.4.
ArH); 8.71e8.66 (m, 2H, ArH); 8.38 (d, J ¼ 8.1 Hz,1H, ArH); 7.78e7.70
(m, 2H, ArH); 7.36 (t, J ¼ 7.2 Hz, 1H, ArH); 7.12e6.93 (m, 5H, ArH);
4.74 (t, J ¼ 6.9 Hz, 2H, NþCH2[CH2]7CH2CH3); 4.61 (t, J ¼ 6.9 Hz, 2H,
NCH2CH2CH2Ph); 2.62 (t, J ¼ 7.5 Hz, 2H, NCH2CH2CH2Ph); 2.11e1.95
(m, 4H, NCH2CH2CH2Ph, NþCH2CH2[CH2]7CH3); 1.27e0.97 (m, 14H,
HRMS (ESI) calcd for C21H21IN2 301.1699 [M ꢀ I]þ, found 301.1717.
5.5.14. 9-(3-Phenylpropyl)-2-ethyl-b-carbolinium iodide (4b)
Yellow crystals (0.60 g, 95%) were obtained, mp 164e165 ꢁC. ESI-
MS 315.2 m/z [M ꢀ I]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.64 (s, 1H,
NþCH2CH2[CH2]7CH3); 0.65 (t, J ¼ 6.6 Hz, 3H, NþCH2[CH2]8CH3). 13
C
ArH); 8.78 (d, J ¼ 6.3 Hz, 1H, ArH); 8.70 (d, J ¼ 6.6 Hz, 1H, ArH); 8.49
(d, J ¼ 8.1 Hz, 1H, ArH); 7.93e7.79 (m, 2H, ArH); 7.47 (t, J ¼ 7.2 Hz,
1H, ArH); 7.19e7.04 (m, 5H, ArH); 4.73 (t, J ¼ 7.2 Hz, 2H,
NCH2CH2CH2Ph); 4.65 (q, J ¼ 7.2 Hz, 2H, NþCH2CH3); 2.66
NMR (75 MHz, DMSO-d6): d 149.1, 146.3, 146.2, 140.6, 137.8, 137.4,
137.0, 133.9, 133.4, 133.3, 131.1, 129.1, 127.1, 124.3, 123.2, 116.6, 66.1,
49.1, 37.7, 36.7, 35.8, 34.3, 34.1, 34.0, 31.0, 27.5, 19.4. HRMS (ESI) calcd
for C30H39IN2 427.3108 [M ꢀ I]þ, found 427.3117.
(t,
J
¼
7.5 Hz, 2H, NCH2CH2CH2Ph); 2.24e2.11 (m, 2H,
NCH2CH2CH2Ph); 1.64 (t, J ¼ 7.2 Hz, 3H, NþCH2CH3). 13C NMR
5.5.19. 2-(4-Fluorobenzyl)-9-(3-phenylpropyl)-b-carbolinium
(75 MHz, DMSO-d6):
d
144.3, 141.3, 135.9, 132.6, 132.4, 132.1, 128.7,
chloride (4g)
128.6, 128.5, 126.3, 124.2, 122.2, 119.4, 118.3, 111.7, 56.8, 44.0, 32.7,
30.4, 17.5. Analysis (calcd, found for C22H23IN2): C (59.74, 60.55), H
(5.24, 5.47), N (6.33, 6.09).
Yellow crystals (0.61 g, 77%) were obtained, mp 214e216 ꢁC. ESI-
MS 395.3 m/z [M ꢀ Cl]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.97 (s,1H,
ArH); 8.84e8.74 (m, 2H, ArH); 8.46 (d, J ¼ 8.1 Hz, 1H, ArH); 7.92e
7.79 (m, 2H, ArH); 7.74e7.65 (m, 2H, ArH); 7.46 (t, J ¼ 7.2 Hz, 1H,
ArH); 7.26 (t, J ¼ 8.7 Hz, 2H, ArH); 7.14e6.95 (m, 5H, ArH); 5.93 (s,
2H, NþCH2Ph[4-F]); 4.69 (t, J ¼ 6.9 Hz, 2H, NCH2CH2CH2Ph); 2.64 (t,
5.5.15. 9-(3-Phenylpropyl)-2-butyl-b-carbolinium bromide (4c)
Yellow crystals (0.64 g, 93%) were obtained, mp 178e180 ꢁC. ESI-
MS 343.2 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.65 (s,
J
¼
7.2 Hz, 2H, NCH2CH2CH2Ph); 2.27e2.09 (m, 2H,
1H, ArH); 8.78 (d, J ¼ 6.3 Hz, 1H, ArH); 8.70 (d, J ¼ 6.3 Hz, 1H, ArH);
8.49 (d, J ¼ 8.1 Hz, 1H, ArH); 7.94e7.79 (m, 2H, ArH); 7.47 (t,
J ¼ 7.2 Hz, 1H, ArH); 7.18e7.06 (m, 5H, ArH); 4.72e4.63 (m, 4H,
NCH2CH2CH2Ph, NþCH2CH2CH2CH3); 2.65 (t, J ¼ 7.5 Hz, 2H,
NCH2CH2CH2Ph); 2.24e2.10 (m, 2H, NCH2CH2CH2Ph); 2.07e1.92
(m, 2H, NþCH2CH2CH2CH3); 1.39e1.25 (m, 2H, NþCH2CH2CH2CH3);
0.93 (t, J ¼ 7.2 Hz, 3H, NþCH2CH2CH2CH3). 13C NMR (75 MHz,
NCH2CH2CH2Ph). 13C NMR (75 MHz, DMSO-d6):
d 144.7, 141.2, 136.1,
132.7, 132.0, 131.5, 129.3, 128.6, 128.3, 126.2, 124.3, 122.4, 119.5,
118.6, 116.5, 116.3, 111.8, 62.9, 44.1, 32.7, 30.3. HRMS (ESI) calcd for
C
27H24ClFN2 395.1918[M ꢀ Cl]þ, found 395.1927.
5.5.20. 2-(3-Chlorobenzyl)-9-(3-phenylpropyl)-b-carbolinium
bromide (4h)
DMSO-d6):
d
144.3, 141.3, 135.8, 132.9, 132.5, 132.1, 128.8, 128.6,
Yellow crystals (0.91 g, 92%) were obtained, mp 194e195 ꢁC. ESI-
128.4, 126.2, 124.2, 122.2, 119.4, 118.2, 111.7, 60.9, 44.0, 33.7, 32.6,
MS 412.0 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.99 (s,1H,
30.5, 19.3, 13.9. HRMS (ESI) calcd for
C24H27BrN2 343.2169
ArH); 8.84 (d, J ¼ 8.1 Hz, 2H, ArH); 8.53 (d, J ¼ 8.1 Hz, 1H, ArH); 7.96
(d, J ¼ 8.1 Hz, 1H, ArH); 7.91e7.87 (m, 1H, ArH); 7.79e7.78 (m, 1H,
ArH); 7.62e7.47 (m, 4H, ArH); 7.15e7.04 (m, 5H, ArH); 5.99 (2H, s,
NþCH2Ph[3-Cl]); 4.75 (t, 2H, J ¼ 7.2 Hz, NCH2CH2CH2Ph); 2.68 (t, 2H,
[M ꢀ Br]þ, found 343.2178.
5.5.16. 9-(3-Phenylpropyl)-2-hexyl-b-carbolinium bromide (4d)
Yellow crystals (0.56 g, 76%) were obtained, mp 170e172 ꢁC. ESI-
J ¼ 7.2 Hz, NCH2CH2CH2Ph); 2.24e2.20 (m, 2H, NCH2CH2CH2Ph). 13
C
MS 371.3 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.75 (s, 1H,
NMR (75 MHz, DMSO-d6): d 144.2, 140.7, 135.5, 133.5, 132.4, 132.2,
ArH); 8.72 (d, J ¼ 6.3 Hz, 1H, ArH); 8.66 (d, J ¼ 6.3 Hz, 1H, ArH); 8.42
(d, J ¼ 8.1 Hz, 1H, ArH); 7.85e7.73 (m, 2H, ArH); 7.48e7.36
(t, J ¼ 7.8 Hz 1H, ArH); 7.07 (m, 5H, ArH); 4.71 (t, J ¼ 7.2 Hz, 2H,
NþCH2[CH2]4CH3); 4.63 (t, J ¼ 6.9 Hz, 2H, NCH2CH2CH2Ph); 2.64
131.9, 130.9,129.0,128.3,128.0,127.8, 127.1, 125.7, 123.8,121.8, 119.0,
118.2, 111.3, 62.2, 32.2, 29.8.
5.5.21. 2-(4-Nitrobenzyl)-9-(3-phenylpropyl)-b-carbolinium
(t,
J
¼
7.2 Hz, 2H, NCH2CH2CH2Ph); 2.19e2.05 (m, 2H,
chloride (4i)
NCH2CH2CH2Ph); 2.03e1.96 (m, 2H, NþCH2CH2[CH3]3CH3); 1.31e
Yellow crystals (0.69 g, 76%) were obtained, mp 152e153 ꢁC. ESI-
1.21 (m, 6H, NþCH2CH2[CH2]3CH3); 0.75 (t,
J
d
¼
6.6 Hz, 3H,
144.4, 141.3, 136.0,
MS m/z: 422.9 [M ꢀ Cl]þ. 1H NMR (300 MHz, DMSO-d6):
d 10.11 (s,
NþCH2[CH2]4CH3). 13C NMR (75 MHz, DMSO-d6):
1H, ArH); 8.86e8.87 (m, 2H, ArH); 8.51(d, J ¼ 7.8 Hz, 1H, ArH);
8.27e8.23 (m, 2H, ArH); 7.94e7.79 (m, 4H, ArH); 7.51e7.49 (m, 1H,
ArH); 7.15e7.04 (m, 5H, ArH); 6.16 (s, 2H, NþCH2Ph[4-NO2]); 4.71 (t,
133.0, 132.6, 132.2, 128.9, 128.6, 128.4, 126.3, 124.2, 122.3, 119.5, 118.2,
111.7, 61.2, 43.9, 32.7, 31.6, 31.0, 30.5, 25.6, 22.3,14.2. HRMS (ESI) calcd
for C26H31BrN2 371.2482 [M ꢀ Br]þ, found 371.2485.
J
¼
7.5 Hz, 2H, NCH2CH2CH2Ph); 2.66 (t,
NCH2CH2CH2Ph); 2.21e2.17 (2H, m, NCH2CH2CH2Ph). 13C NMR
(75 MHz, DMSO-d6): 148.2, 144.7, 143.0, 141.5, 136.2, 133.3, 132.8,
J
¼
7.2 Hz, 2H,
5.5.17. 9-(3-Phenylpropyl)-2-octyl-
b
-carbolinium iodide (4e)
d
Yellow crystals (0.38 g, 47%) were obtained, mp 147e148 ꢁC. ESI-
132.5, 130.6, 130.0, 128.6, 128.5, 126.3, 124.5, 122.4, 119.6, 118.9,
111.9, 62.4, 44.5, 33.0, 30.9. HRMS (ESI) calcd for C27H24ClN3O2
422.1863 [M ꢀ Cl]þ, found 422.1872.
MS 399.4 m/z [M ꢀ I]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.64 (s, 1H,
ArH); 8.78 (d, J ¼ 6.3 Hz, 1H, ArH); 8.69 (d, J ¼ 6.3 Hz, 1H, ArH); 8.49

30
G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
5.5.22. 9-(3-Phenylpropyl)-2-(phenethyl)-
b
-carbolinium bromide (4j)
(m, 2H, NCH2CH2CH2Ph). 13C NMR (75 MHz, DMSO-d6):
d 161.9,
145.3, 141.1, 140.4, 135.4, 135.3, 134.9, 134.3, 132.9, 132.1, 129.2,
128.9, 128.8, 128.4, 127.5, 126.4, 124.2, 122.7, 120.6, 119.4, 117.8,
115.0, 112.0, 60.6, 56.2, 44.6, 32.6, 31.2. Analysis (calcd, found for
Yellow crystals (0.34 g, 43%) were obtained, mp 180e182 ꢁC. ESI-
MS 391.3 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.52 (s,1H,
ArH); 8.75 (d, J ¼ 6.3 Hz, 1H, ArH); 8.64 (d, J ¼ 6.6 Hz, 1H, ArH); 8.47
(d, J ¼ 8.1 Hz, 1H, ArH); 7.85 (q, J ¼ 8.4 Hz, 2H, ArH); 7.46 (t,
J ¼ 6.6 Hz, 1H, ArH); 7.25e7.01 (m, 10H, ArH); 4.97 (t, J ¼ 6.9 Hz, 2H,
NþCH2CH2Ph); 4.59 (t, J ¼ 6.9 Hz, 2H, NCH2CH2CH2Ph); 3.36 (t,
C34H31BrN2O): C (72.47, 71.75), H (5.54, 5.82), N (4.97, 4.81).
5.5.27. 1-(Thiophen-3-yl)-9-(3-phenylpropyl)-2-benzyl-b-
J
¼
7.2 Hz, 2H, NþCH2CH2Ph); 2.58 (t,
J
¼
7.8 Hz, 2H,
carbolinium bromide (8d)
NCH2CH2CH2Ph); 2.09e1.99 (m, 2H, NCH2CH2CH2Ph). 13C NMR
(75 MHz, DMSO-d6): 144.4, 141.3, 136.7, 135.6, 133.0, 132.6, 132.1,
Yellow crystals (0.98 g, 91%) were obtained, mp 146e148 ꢁC. ESI-MS
d
459.0 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 9.07e9.00 (m,
129.3, 129.0, 128.7, 128.5, 127.4, 126.3, 124.2, 122.3, 119.4, 118.1, 111.7,
61.9, 43.9, 37.4, 32.7, 30.5. HRMS (ESI) calcd for C28H27BrN2
391.2169 [M ꢀ Br]þ, found 391.2165.
2H, ArH); 8.64 (d, J ¼ 8.1 Hz, 1H, ArH); 8.18 (dd, J ¼ 5.1, 1.2 Hz, 1H, ArH);
7.95e7.86 (m, 2H, ArH); 7.59e7.52 (m, 2H, ArH); 7.39 (dd, J ¼ 5.1, 3.6 Hz,
1H, ArH); 7.37e7.30 (m, 3H, ArH); 7.29e7.22 (m, 2H, ArH); 7.20e7.09
(m, 3H, ArH); 7.05e7.02 (m, 2H, ArH); 5.71 (s, 2H, NþCH2Ph); 4.03e3.55
(m, 2H, NCH2CH2CH2Ph); 2.38e2.17 (m, 2H, NCH2CH2CH2Ph); 1.90e
5.5.23. 2,9-Di(3-phenylpropyl)-b-carbolinium bromide (4k)
Yellow crystals (0.31 g, 38%) were obtained, mp 120e121 ꢁC. ESI-
1.69 (m, 2H, NCH2CH2CH2Ph). 13C NMR (75 MHz, DMSO-d6):
d 144.2,
MS 405.3 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.90 (s,
140.7, 137.4, 135.5, 133.5, 132.4, 132.2, 131.9, 130.9, 129.0, 128.3, 128.0,
127.8, 127.1, 125.7, 123.8, 121.8, 119.0, 118.2, 111.3, 62.2, 43.5, 32.2, 29.8.
1H, ArH); 8.70 (m, 2H, ArH); 8.37 (d, J ¼ 8.1 Hz, 1H, ArH); 7.80e7.64
(m, 2H, ArH); 7.48e7.43 (m, 1H, ArH); 7.16e6.90 (m, 10H, ArH); 4.85
(t, J ¼ 6.9 Hz, 2H, NþCH2CH2CH2Ph); 4.59 (t, J ¼ 6.9 Hz, 2H,
NCH2CH2CH2Ph); 2.67 (t, J ¼ 7.2 Hz, 2H, NþCH2CH2CH2Ph); 2.62 (t,
5.6. Cytotoxicity assays in vitro
J
¼
7.5 Hz, 2H, NCH2CH2CH2Ph); 2.40e2.31 (m, 2H,
Cytotoxicity assays in vitro were carried out using 96 microtitre
plate cultures and MTTstaining according tothe procedures described
by Cao et al. [20]. Briefly, cells were grown in RPMI-1640 medium
NþCH2CH2CH2Ph); 2.21e2.11 (m, 2H, NCH2CH2CH2Ph). 13C NMR
(75 MHz, DMSO-d6): 144.3, 141.4, 140.9, 135.8, 133.0, 132.4, 132.1,
d
129.0, 128.7, 128.6, 128.5, 128.4, 126.3, 126.2, 124.2, 122.1, 119.4,
118.2, 111.6, 60.9, 43.9, 33.2, 32.6, 32.2, 30.6. HRMS (ESI) calcd for
containing 10% (v/v) fetal calf serum and 100
m
g mlꢀ1 penicillin and
100
m
g mlꢀ1 streptomycin. Cultures were propagated at 37 ꢁC in a
C
29H29BrN2 405.2325 [M ꢀ Br]þ, found 405.2343.
humidified atmosphere containing 5% CO2. Cell lines were obtained
from Shanghai Institute of Biochemistry and Cell Biology, Chinese
Academy of Science. DMSO was used as the solution for drugs. Final
concentration of DMSO in the growth medium was 2% (v/v) or lower,
concentration without effect on cell replication. In all of these exper-
iments, three replicate wells were used to determine each point.
5.5.24. 9-(3-Phenylpropyl)-2-benzyl-1-methyl-b-carbolinium
bromide (8a)
Yellow crystals (0.74 g, 78%) were obtained, mp 234e236 ꢁC. ESI-MS
390.9 m/z[M ꢀ Br]þ.1H NMR (300 MHz, DMSO-d6):
8.85 (d, J¼ 6.6 Hz,
d
1H, ArH); 8.78 (d, J ¼ 6.6 Hz, 1H, ArH); 7.93e7.80 (m, 2H, ArH); 7.49 (t,
J ¼ 7.2 Hz, 1H, ArH); 7.43e7.34 (m, 3H, ArH); 7.25e7.10 (m, 7H, ArH);
6.07 (s, 2H, NþCH2Ph); 4.71 (t, J ¼ 7.5 Hz, 2H, NCH2CH2CH2Ph); 3.01 (s,
3H, CH3); 2.69 (t, J ¼ 7.5 Hz, 2H, NCH2CH2CH2Ph); 2.15e2.03 (m, 2H,
5.7. Assay of acute toxicities
Acute toxicity assay was performed according to the method
described by Cao et al. [20]. Briefly, healthy C57BL/6 mice (9e12
weeks) weighing 18e22 g were housed in rooms where the temper-
ature was approximately 24 ꢂ 2 ꢁC, with a relative humidity 60e70%,
and in 12 h lightedark cycle. The sterile food and water were provided
according to institutional guidelines. All animals were provided by
Laboratory Animal Center of Sun Yat-sen University. All animal pro-
cedures were approved by the Animal Ethical Committee of the Sun
Yat-sen University. Prior to each experiment, mice were fastened
overnight and allowed free access to water. Various doses of the N2-
NCH2CH2CH2Ph). 13C NMR (75 MHz, DMSO-d6):
d 145.6, 141.6, 141.4,
136.1, 135.5, 135.3, 133.5, 132.7, 129.8, 128.9, 128.9, 127.4, 126.6, 124.1,
122.7, 119.6, 116.5, 112.2, 60.8, 45.7, 32.7, 32.5, 17.3. HRMS (ESI) calcd for
C
28H27BrN2 391.2169 [M ꢀ Br]þ, found 391.2185.
5.5.25. 9-(3-Phenylpropyl)-2-benzyl-1-phenyl-b-carbolinium
bromide (8b)
Yellow crystals (0.48 g, 53%) were obtained, mp 148e150 ꢁC. ESI-
MS 453.4 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d 8.94 (d,
J ¼ 6.6 Hz, 1H, ArH); 8.89 (d, J ¼ 6.6 Hz, 1H, ArH); 8.57 (d, J ¼ 8.1 Hz,
1H, ArH); 7.89e7.71 (m, 3H, ArH); 7.67e7.55 (m, 4H, ArH); 7.55e
7.46 (m, 1H, ArH); 7.32e7.16 (m, 5H, ArH); 7.11 (t, J ¼ 7.2 Hz, 1H,
ArH); 7.01 (d, J ¼ 6.9 Hz, 2H, ArH); 6.92e6.85 (m, 2H, ArH); 5.65 (s,
2H, NþCH2Ph); 3.56 (t, J ¼ 7.5 Hz, 2H, NCH2CH2CH2Ph); 2.01 (t,
J ¼ 7.8 Hz, 2H, NCH2CH2CH2Ph); 1.70e1.55 (m, 2H, NCH2CH2CH2Ph).
alkylated quaternary b
-carbolines ranging from 1.0 to 100 mg kgꢀ1
dissolved in 0.5% carboxymethyl cellulose sodium (CMC-Na) salt so-
lution were given via intraperitoneal (i.p.) to different groups of
healthy C57BL/6mice, and each groupcontained 10 mice(5 males and
5 females). After the administration of the compounds, mice were
observed continuously for the first 2 h for any gross behavioral
changes and deaths, then intermittently for the next 24 h and occa-
sionally thereafter for 14 days, and for the onset of any delayed effects.
All animals were sacrificed at the 14th day after drug administration
and checked macroscopically for possible damage to the heart, liver
and kidneys. Mice of immediate death following drug administration
were also examined for any possible organ damage. LD50 values were
calculated graphically as described [41].
13C NMR (75 MHz, DMSO-d6):
d 145.3, 141.1, 140.1, 135.3, 134.5,
133.0, 132.1, 130.5, 129.6, 129.2, 128.9, 128.8, 128.8, 128.5, 127.5,
126.4, 124.2, 122.7, 119.3, 117.9, 112.0, 60.8, 44.5, 32.4, 31.2. HRMS
(ESI) calcd for C33H29BrN2 453.2325 [M ꢀ Br]þ, found 453.2340.
5.5.26. 1-(4-Methoxyphenyl)-9-(3-phenylpropyl)-2-benzyl-b-
carbolinium bromide (8c)
Yellow crystals (0.45 g, 47%) were obtained, mp 182e183 ꢁC. ESI-
MS 483.4 m/z [M ꢀ Br]þ. 1H NMR (300 MHz, DMSO-d6):
d
9.01e8.95
5.8. Assay of antitumor activity
(m, 2H, ArH); 8.56 (d, J ¼ 7.8 Hz, 1H, ArH); 7.83e7.73 (m, 2H, ArH);
7.53 (d, J ¼ 8.4 Hz, 2H, ArH); 7.45e7.38 (m, 1H, ArH); 7.27e7.23 (m,
3H, ArH); 7.19e7.12 (m, 4H, ArH); 7.09e6.90 (m, 5H, ArH); 5.72 (s,
2H, NþCH2Ph); 3.86 (s, 3H, OCH3); 3.68e3.62 (m, 2H,
NCH2CH2CH2Ph); 2.09 (t, 2H, J ¼ 7.5 Hz, NCH2CH2CH2Ph); 1.63e1.49
Antitumor activity against Lewis lung cancer and Sarcoma 180
was performed as described by Cao et al. [20] with a slightly
modification. Briefly, Lewis lung cancer and S180 sarcoma cell lines
were provided by Shanghai Institute of Pharmaceutical Industry.

G. Zhang et al. / European Journal of Medicinal Chemistry 65 (2013) 21e31
31
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This work was supported by MEGA-Project (2009ZX09102-004)
and the Natural Science Foundation of China (21102187) and the
Fundamental Research Funds for the Central Universities
(11lgpy11) and Xinjiang Huashidan Pharmaceutical Co. Ltd.
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