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Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues
Accepted Manuscript Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues Tingting Xu, Liqiao Shi, Yani Zhang, Kaimei Wang, Ziwen Yang, Shaoyong Ke PII:
S0223-5234(19)30184-9
DOI:
https://doi.org/10.1016/j.ejmech.2019.02.060
Reference:
EJMECH 11152
To appear in:
European Journal of Medicinal Chemistry
Received Date: 22 January 2019 Revised Date:
19 February 2019
Accepted Date: 21 February 2019
Please cite this article as: T. Xu, L. Shi, Y. Zhang, K. Wang, Z. Yang, S. Ke, Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues, European Journal of Medicinal Chemistry (2019), doi: https://doi.org/10.1016/j.ejmech.2019.02.060. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical Abstract
Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues
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Tingting Xu,b† Liqiao Shi,a,† Ya-Ni Zhang,a,† Kaimei Wang,a Ziwen Yang,a,b,* Shaoyong Kea,*
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Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues Tingting Xu,b† Liqiao Shi,a,† Yani Zhang,a,† Kaimei Wang,a Ziwen Yang,a,b,* Shaoyong Kea,* a
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National Biopesticide Engineering Research Centre, Hubei Biopesticide Engineering Research Centre, Hubei Academy of Agricultural Sciences, Wuhan 430064, People’s Republic of China b College of Life Sciences, Wuhan University, Wuhan 430072, People’s Republic of China
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*Address correspondence to Shaoyong Ke: Hubei Biopesticide Engineering Research Centre, Hubei Academy of Agricultural Sciences, Wuhan 430064, People′s Republic of China; Tel: +86-27-59101956; E-mail: [email protected] or [email protected] (S. Ke), [email protected] (Z. Yang) † These authors contributed equally to this work.
Abstract: Pityriacitrin is a marine alkaloid with typical β-carboline scaffold, and which has been proven to exhibit diverse biological functions. During the course of our research for highly active compounds from natural products, the pityriacitrin have also been isolated and identified from a
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Chinese Burkholderia sp. NBF227. So, in order to explore the potential functional molecules, a series of β-carboline analogues derived from pityriacitrin were designed and synthesized, and their in vitro cytotoxic activities against SGC-7901, A875, HepG2, and MARC145 cell lines were
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evaluated. The results demonstrated that some of these β-carboline derivatives exhibited moderate
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to good cytotoxic activities, especially, compound 9o with a special sulfonyl group presented the highest inhibitory activities against all tested cell lines with the IC50 values of 6.82±0.98, 8.43±1.93, 7.69±2.17, 7.19±1.43 µM, respectively, which might be used as lead compound for discovery of novel cytotoxic agents. Keywords: Marine alkaloid, Pityriacitrin, Analogues, Synthesis, Biological evaluation, SARs
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1. Introduction Cancer is a major disease that seriously endangers human health [1,2]. Nowadays, the treatments for cancer mainly include surgical management, chemotherapy, radiotherapy,
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photodynamic therapy, photothermal therapy, gene therapy, and immunotherapy [3], however, chemotherapy remains the most important treatment method [4,5], and the development of novel molecules with unique structural features as anticancer drugs is still an important direction.
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Natural products are important sources of leading compounds for discovery of drugs [6-9] or
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agrochemicals [10-14], and many synthetic derivatives of natural products have extensive bioactivities, especially antitumor [15,16]. Alkaloids are classes of natural products widely distributed in plants with diverse structural features, and which play an important role in the field of medicinal chemistry and agrochemical industry [17-19]. Among these natural products,
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β-carboline alkaloids, a family of indole alkaloids [20-25], are with the unique tricyclic pyrido-[3,4-b]indole ring (Fig. 1), which belong to an important class of bioactive natural products
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distributed in nature.
Fig. 1. Representative natural β-carboline alkaloids.
Especially, pityriacitrin, a rare marine β-carboline alkaloid (Fig. 1) bearing an indole ring attached with a carbonyl group on C-1 position arouse the interest of researchers due to its unique structure and broad UV absorption [26-28]. Subsequently, some pityriacitrin analogues and derivatives have been isolated or prepared, and their potential biological implications have also 2
ACCEPTED MANUSCRIPT been investigated [29-33]. Recently, during the course of our research for active compounds from natural products, the pityriacitrin and pityriacitrin B have been isolated and identified from a Chinese Burkholderia sp. NBF227 (Fig. 2), and which also indicated obvious antifungal activities.
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However, the low fermentation levels limit the further research on exploring the potential applications for these natural compounds, and so the convenient synthetic methods for these β-carboline alkaloids have been investigated in our lab. In addition, as part of our medicinal
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chemistry program aimed at the discovery of potential cytotoxic agents, we wish to report herein
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the molecule design, convenient synthesis, and biological evaluation of a series of β-carboline
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amide derivatives derived from natural pityriacitrin (Fig. 2).
Fig. 2. Design strategy of β-carboline analogues derived from natural pityriacitrin.
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In this study, the pityriacitrin scaffold was used as a key unit and planned for the hybridization
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of amide pharmacophore [34-36] to the core structure as depicted in Fig. 2. Therefore, a series of novel β-carboline amide derivatives 9a-p were designed and synthesized as shown in Scheme 1, and their cytotoxic activities against several cell lines (SGC-7901, A875, HepG2, and MARC145) were evaluated by MTT colorimetric method, and the possible structure and activity relationships have also been summarized and discussed.
2. Results and discussion
3
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In this work, a series of novel β-carboline amide derivatives based on natural pityriacitrin were constructed by integrating β-carboline pharmacophore with amide function group. The synthesis
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of pityriacitrin, pityriacitrin B and the target β-carboline amide derivatives 9a-p was shown in
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Scheme 1.
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Scheme 1. Synthesis of β-carboline amide derivatives 9a-p. Reagents and conditions: a. SeO2, Dioxane/H2O; b. p-MePhSO3H, MeOH, 60 oC; c. SOCl2, MeOH; d. Compd 1, I2, DMSO; e. PhCH2CH2NH2, Dioxane, Reflux; f. 2N NaOH, MeOH, rt; g. NH2(CH2)nR, HOBt, EDCI, Et3N, DMF, rt.
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Firstly, the 1-(1H-indol-3-yl)ethanone 1 was selected as starting materials, and which was transformed into 2-(1H-indol-3-yl)-2-oxoacetaldehyde 2 via oxidation process. After this, the
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tryptophan 3 undergoes ring closure after condensation with the intermediate 2 via a similar transformation of Pictet–Spengler reaction, however, the UPLC-MS analyses demonstrate a tetrahydro-β-carboline derivative 4 (tR = 2.51 min, [M+H]+ 360.5) has been obtained as the majoring product (48%) along with pityriacitrin B (15%, tR = 3.64 min, [M+H]+ 356.4) and pityriacitrin (12%, tR = 3.90 min, [M+H]+ 312.4) under this condition. So, another method to prepare pityriacitrin and pityriacitrin B was investigated as described in Scheme 1. The heterocyclization reaction of compound 7 was treated with 1-(1H-indol-3-yl)ethanone 1 resulting 4
ACCEPTED MANUSCRIPT in methyl 1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylate 8 via a convenient condensation reaction. With the compound 8 in hand, the direct nucleophilic substitution reaction using 2-phenylethanamine was explored, unfortunately, this transformation was not work. Then
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the compound 8 was conveniently hydrolyzed to compound 5 (pityriacitrin B) in the presence of sodium hydroxide solution, and which can couple with various amines using HOBt/EDCI as coupling agents. All target β-carboline derivatives 9a-p gave satisfactory chemical analyses, and
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the chemical structures of the compounds were summarized in Table 1.
Table 1 Chemical structure of target β-carboline amide derivatives
16
9p
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9a 9b 9c 9d 9e 9f 9g 9h 9i 9j 9k 9l 9m 9n 9o
R
3-Indolyl 3-MeO-Ph 4-F-Ph 3,4-(MeO)2-Ph 3-OH-Ph Ph Ph 4-F-Ph 4-Me-Ph 3-Py 2-Py 3-MeO-4-OH-Ph 4-F-Ph 4-MeO-Ph MeSO2
Appearance
Mp (oC)
Yielda (%)
Yellow powder Yellowish needle crystal Turquoise powder Yellow powder Bright yellow powder Bright yellow powder Yellow powder Light yellow powder Light yellow powder Yellow powder Yellow powder Bright yellow powder Bright yellow powder Turquoise powder Yellow powder
172-173 102-104 211-213 109-111 142-143 115-116 129-131 219-221 221-223 139-141 137-139 203-204 130-132 132-133 141-143
72 56 62 77 72 78 64 73 75 70 81 65 61 67 71
Yellow powder
191-193
52
n
2 2 2 2 2 2 1 1 1 1 1 1 0 0 2
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Substituents
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Compd. No.
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a
Entry
Isolated yields.
2.2. Biological evaluation
2.2.1. Cytotoxic activities All prepared β-carboline amide derivatives 9a-p, pityriacitrin and pityriacitrin B were tested for
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ACCEPTED MANUSCRIPT their in vitro cytotoxic effects on SGC-7901 (Human gastric cancer), A875 (Human melanoma), HepG2 (Human hepatocellular liver carcinoma), and MARC145 (A subclone of African green monkey kidney cell line MA-104) cell lines by the standard MTT assay [37-39], and the results
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are summarized in Table 2 and 3. Table 2 Growth-inhibitory activity for target compounds Growth-inhibitory propertiesa
Compd. No.
SGC-7901b
A875b
HepG2b
MARC145b
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
6 5 8 9a 9b 9c 9d 9e 9f 9g 9h 9i 9j 9k 9l 9m 9n 9o 9p 5-FUc
43.17±2.84 62.97±9.03 48.60±1.80 76.60±8.12 39.33±7.49 76.73±4.04 22.10±2.54 88.33±2.78 84.53±3.70 79.00±4.13 78.80±2.59 63.97±2.18 70.07±3.98 69.53±3.01 83.10±4.06 33.97±5.88 41.20±7.15 88.47±0.74 82.73±4.13 79.87±6.31
59.10±2.17 72.17±3.71 36.80±7.87 77.83±2.14 16.64±8.46 33.90±6.89 0±0 87.47±2.81 77.13±4.55 75.53±2.32 68.07±2.72 26.97±6.12 74.23±2.54 70.67±5.12 81.67±5.66 20.70±6.30 72.07±6.67 87.93±1.72 83.90±2.88 61.03±3.40
30.50±5.34 78.40±8.21 62.70±6.11 74.40±7.04 40.13±7.89 72.43±2.97 31.73±5.81 86.90±3.49 82.33±4.62 77.30±4.85 73.90±2.36 63.87±8.02 82.80±5.71 79.57±6.61 80.87±0.55 34.83±3.42 44.83±2.66 87.30±2.78 78.97±5.33 72.60±5.24
34.60±17.25 71.95±3.04 35.85±11.53 66.95±5.02 48.35±0.64 63.00±3.96 38.40±0.57 83.15±7.28 79.75±6.29 67.40±1.84 63.80±4.67 55.00±1.98 73.80±0.42 66.15±5.44 79.10±3.82 47.45±5.44 41.95±3.82 90.15±2.62 83.20±2.69 66.70±0.42
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a
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Entry
The percentage of growth inhibition evaluated at the screening concentration of 40 µg/mL; Abbreviations: SGC-7901 – Human gastric cancer cell line; A875 – Human melanoma cell line; HepG2 – Human hepatocellular liver carcinoma cell line; MARC145 – A subclone of African green monkey kidney cell line MA-104; cUsed as a positive control.
b
As seen in Table 2, these novel β-carboline amide derivatives 9a-p displayed moderate to good inhibitory activities against all tested cell lines. The compounds directly derived from arylamines (9m and 9n, Entries 16-17) exhibited lower activities than the corresponding compounds from
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ACCEPTED MANUSCRIPT substituted benzylamines (9g-l, Entry 10-15) and phenylethylamines (9a-f, Entries 4-9). The compounds bearing 3-hydroxy group (9e) have obviously high activity than the compounds with 3-methoxyl substituent (9b). Notably, the compounds 9o and 9p (Entries 18 and 19) exhibited
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significant inhibitory activity against all tested cell lines with 78.97-90.15% growth inhibition at the concentration of 40 µg/mL. Also, it is interesting to note that compound 9l (Entry 15) with natural vanillylamine unit also showed good cytotoxicity (>79%) against all tested cell lines. The
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results of preliminary bioassay indicated that these β-carboline amide derivatives containing
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hydroxyphenyl, amino acids or sulfonyl group might be used as lead molecules for development of potential anticancer agents.
Furthermore, in order to investigate the highly potential compounds, the IC50 values for target compounds were also tested, and the results are shown in Table 3.
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Table 3 Cytotoxic activities (IC50s) of the compounds against various cell lines In vitro cytotoxicity IC50a (µM)
Entry
Compd. No.
1
6
2
5
3
8
4 5
A875b
HepG2b
MARC145b
>120
75.79±14.63
>120
>120
67.69±11.79
48.75±6.25
51.82±5.99
41.88±9.32
>100
>100
>100
>100
9a
38.56±1.47
50.36±6.54
41.03±6.15
44.09±8.47
9b
>80
>80
>80
>80
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SGC-7901b
6
9c
34.02±6.32
>80
38.53±9.30
48.76±4.96
7
9d
>75
>75
>75
>75
8
9e
17.65±5.84
11.91±0.80
8.63±3.31
13.77±3.75
9
9f
22.98±5.15
44.76±8.32
19.77±5.19
25.88±7.99
10
9g
39.87±7.14
56.37±5.40
36.24±6.62
42.82±2.39
11
9h
34.54±5.60
63.06±6.84
39.04±8.74
55.05±10.24
12
9i
65.98±4.43
>85
65.32±9.71
73.20±6.81
13
9j
33.13±9.52
25.18±6.65
18.49±2.56
20.80±5.44
14
9k
43.94±6.83
42.48±6.67
26.30±6.13
33.76±8.18
15
9l
16.18±2.31
8.47±2.96
11.08±3.33
21.77±6.94
16
9m
>85
>85
>85
>85
17
9n
>85
65.38±8.13
>85
>85 7
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9o
19
9p
20
c
5-FU
6.82±0.98
8.43±1.93
7.69±2.17
7.19±1.43
14.30±2.57
10.46±1.34
9.99±1.82
16.27±0.07
53.58±1.99
62.12±17.83
66.42±12.99
115.54±8.30
a
IC50 – Compound concentration required to inhibit tumor cell proliferation by 50%. Abbreviations: SGC-7901 – Human gastric cancer cell line; A875 – Human melanoma cell line; HepG2 – Human hepatocellular liver carcinoma cell line; MARC145 – A subclone of African green monkey kidney cell line MA-104. cUsed as a positive control.
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b
As indicated in Table 3, some of these β-carboline amide derivatives such as 9e, 9l, 9o, 9p exhibited higher inhibition activities compared to 5-FU. Compounds 9e and 9l containing an
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hydroxyphenyl unit have higher inhibitory effects on all cell lines, and the compound 9p
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containing a serine unit also exhibited significant activity. Especially, we also can find that compound 9o with a special sulfonyl group presented obviously highest inhibitory activities against all four cell lines, and the IC50 values are 6.82±0.98, 8.43±1.93, 7.69±2.17, 7.19±1.43 µM, respectively. However, the parent compounds pityriacitrin 6, pityriacitrin B 5, and the
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intermediate 8 were less effective. These interesting findings may provide some useful information for discovery of potential cytotoxicity agents derived from natural alkaloids.
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In addition, the dose-response analysis for highly potential compounds 9e, 9l, 9o, 9p and 5-FU was displayed in Fig. 3, and which indicated that these compounds inhibited the cell lines in a
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concentration-dependent manner.
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Fig. 3. Dose-response analysis of cell growth inhibition activity for compounds 9e, 9l, 9o, 9p and 5-FU (positive control) against SGC-7901 cells (upper left), A875 cells (upper right), HepG2 cells (lower left) and MARC145 cells (lower right). 2.2.2. Structure and activity relationships (SARs)
The structural modification of compounds is mainly focused on amide scaffold with different
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kinds of amines including substituted phenylethylamines (9a-f), substituted benzylamines (9g-l) and substituted arylamines (9m-n). In addition, two compounds with special sulfonyl group (9o)
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and amino acid unit (9p) were also synthesized to investigate the possible activity difference. According to in vitro results described in Table 2 and 3, the possible structure and activity
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relationships for these β-carboline amide derivatives can be obtained (Fig. 4).
Fig. 4. General structure-activity relationships for target β-carboline derivatives. 9
ACCEPTED MANUSCRIPT As the analysis in Fig. 4, we can conclude the basic rule that the compounds bearing substituted benzylamines (n = 1) are general present better activities than the compounds modified by substituted phenylethylamines (n = 2), and the activity for the compounds of these two systems
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are obviously superior to those of substituted arylamines (n = 0), which proved the importance of the linker between aromatic ring and amide. In addition, most of the β-carboline amide derivatives exhibit better activity than that of the parent compounds pityriacitrin B (5) and pityriacitrin (6),
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which indicate the amide bond is beneficial to increase the activity. For the compound containing
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amino acid unit, the compound 9p bearing a serine moiety present higher potential activity. From Table 3, we also can find that, within the series of amide derivatives (9a-n), it is clear that the compounds with hydroxyphenyl group (9l and 9e) are better than other corresponding compounds, which may be due to the polar of hydroxyphenyl group is favorable for the binding to target
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protein. In particular, it’s interesting that the compound containing a special sulfonyl group present the highest inhibitory activities. According to these findings, it can be speculated it would have been more interesting to test the other hydroxyphenyl substituted and sulfur-containing
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derivatives, and the special properties of hydroxylphenyl and sulfur groups will be helpful to
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increase the activity. These structure-activity relationships will be helpful for further structural optimization based on the β-carboline amide scaffold, and the most active compounds also can be considered as lead compounds for the development of more potent derivatives.
3. Conclusion In summary, a series of novel β-carboline amide derivatives derived from natural marine alkaloid were designed and synthesized. The in vitro bioassay demonstrated that some of the
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cytotoxic agents.
4. Materials and Methods 4.1. Instrumentation and chemicals
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All reagents from commercial sources were directly used without purification. Analytical
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thin-layer chromatography was carried out on silica gel GF254 by UV. Melting points (m.p.) were tested using a digital model X-5 apparatus. The infrared absorption spectra were recorded on a Thermo Nicolet FT-IR Avatar 330 instrument in KBr discs and are reported in cm-1. 1H NMR and 13
C NMR spectra were tested on a Bruker Avance III 600 MHz FT-NMR spectrometer using
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DMSO-d6 as the solvent and tetramethylsilane (TMS) as the internal standard. Mass spectra were performed on a WATERS ACQUITY UPLC® H-CLASS PDA (Waters®) instrument.
General
synthetic
procedure
for
methyl
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4.2.
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1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylate 8
To a solution of tryptophan 3 (10.21 g, 0.05 mmol) in anhydrous methanol (50 ml) was added dropwise thionyl chloride (7.14 g, 0.06 mmol) under ice-bath. After addition, the mixture was slowly heated to 50 oC overnight, and then the reaction solution was concentrated, filtered and washed with cool methanol to obtain the crude tryptophan methyl ester hydrochlorides 7, which were used for the next reaction without further purification. Iodine (2.54 g, 0.01 mol) was added to the solution of 1-(1H-indol-3-yl)ethanone 1 (1.59 g, 0.01 mol) in 15 mL of DMSO, and the
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ACCEPTED MANUSCRIPT resulting mixture was heated at 85-90 oC for 1.5 h. Then the obtained tryptophan methyl ester 7 (2.55 g, 0.01 mol) was added, and the solution was stirred at same temperature for 3-4 h. After completion of the reaction, the mixture was then cooled to room temperature followed by addition
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of water and extracted with ethyl acetate. The extract was washed with the aqueous of Na2S2O3, dried over Na2SO4, filtered and evaporated under reduced pressure. The residue was used for the next reaction without further purification. MS (ESI) m/z 370.4 (M+H)+, 392.4 (M+Na)+, calcd. for
General
synthetic
procedure
for
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4.3.
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C22H15N3O3 m/z = 369.1.
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid 5
To a solution of methyl 1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylate 8 (10 mmol) in methanol (15 mL) was added aqueous (15 mL) of sodium hydroxide (15 mmol), which
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were stirred at room temperature overnight, and detected by thin-layer chromatography. After the completion of reaction, the mixture was adjusted to pH 2-3 with dilute hydrochloric acid under and
the
precipitate
was
filtered
and
dried
to
obtain
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ice-bath,
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid 5. This compound was
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obtained following the above method as light brown powder, mp 302-303 oC, yield 76%. MS (ESI) m/z 356.4 (M+H)+, calcd. for C21H13N3O3 m/z = 355.1.
4.4. General synthetic procedure for the target compounds 9a-p
The typical process for the synthesis of target pityriacitrin-oriented β-carboline analogues 9a-p is
shown
as
following:
To
a
solution
of
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid 5 (1 mmol) in DMF (8 mL) 12
ACCEPTED MANUSCRIPT was added HOBt (1.5 mmol), EDCI (1.5 mmol), Et3N (2 mmol) and appropriate substituted amine (1.2 mmol), and then the mixture were stirred at room temperature overnight. After the completion of reaction, the water was added to the mixture, and which was extracted with ethyl acetate, and
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the organic layer was washed with water and brine, and dried with anhydrous Na2SO4. The solvent was removed to give crude target compounds, and which were purified by silica gel column-chromatography (ethyl acetate/petroleum ether) or recrystallization to give pure
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compounds. All the compounds were characterized by ESI-MS, 1H NMR and
13
C NMR
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spectroscopic data, and their physico-chemical properties and spectra data are as follows: N-(2-(1H-Indol-3-yl)ethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9a This compound was obtained following the above method as yellow powder, yield 72%, mp 172-173 oC; IR (νmax, KBr, cm-1): 3360, 2924, 1655, 1643, 1597, 1507, 1457, 1417, 1145, 1112,
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952, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.23 (s, 1H, NH), 12.21 (s, 1H, NH), 10.80 (s, 1H, ArH), 9.08 (s, 1H, ArH), 8.95 (d, J = 3 Hz,1H, ArH), 8.66 (t, J = 6 Hz, 1H, ArH), 8.55 (t, J = 6 Hz, 1H, ArH), 8.47 (d, J = 6 Hz,1H, ArH), 7.85 (d, J = 7.8 Hz,1H, ArH), 7.68-7.59 (m, 3H, ArH),
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7.36-7.30 (m, 4H, ArH), 7.25 (d, J = 1.8 Hz,1H, ArH), 7.07-7.04 (m, 1H, ArH), 6.97 (t, J = 6
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Hz,1H), 3.73 (q, J = 6 Hz, 2H, CH2), 3.08 (t, J = 6 Hz, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 187.39, 165.30, 142.52, 139.42, 138.60, 137.35, 136.82, 136.64, 136.35, 131.84, 129.59, 127.80, 127.42, 123.66, 123.12, 122.66, 122.06, 121.44, 120.99, 120.95, 118.94, 118.68, 117.14, 114.51, 113.64, 112.81, 112.32, 111.86, 40.54, 26.02; ESI-MS: calcd for C31H23N5O2 ([M+H]+), 498.2; found, 498.4. 1-(1H-Indole-3-carbonyl)-N-(3-methoxyphenethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9b This compound was obtained following the above method as yellowish needle crystal, yield 56%, 13
ACCEPTED MANUSCRIPT mp 102-104 oC; IR (νmax, KBr, cm-1): 3373, 3317, 2919, 2848, 1647, 1608, 1583, 1526, 1512, 1491, 1425, 1339, 1257, 1160, 1122, 1036, 952, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.23 (s, 1H, NH), 12.21 (s, 1H, NH), 9.06 (s, 1H, ArH), 8.89 (s, 1H, ArH), 8.57-8.53 (m, 2H, ArH), 8.46 (d,
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J = 12 Hz, 1H, ArH), 7.55 (d, J = 6 Hz, 1H, ArH), 7.65-7.60 (m, 2H, ArH), 7.35-7.31 (m, 3H, ArH), 7.18 (t, J = 6 Hz, 1H, ArH), 6.89 (d, J = 6 Hz, 1H, ArH), 6.85 (s, 1H, ArH), 6.74 (dd, J = 6 Hz, 1H, ArH), 3.68-3.62 (m, 5H, CH2 and OCH3), 2.94 (t, J = 8 Hz, 2H, CH2Ph); 13C NMR (150
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MHz, DMSO-d6): δ 187.39, 165.20, 159.78, 142.54, 141.48, 139.23, 138.57, 137.40, 136.69,
M AN U
136.26, 131.85, 129.88, 129.58, 127.42, 123.58, 122.66, 122.03, 121.34, 120.97, 117.04, 114.66, 114.50, 113.66, 112.81, 112.12, 55.27, 41.09, 35.96; ESI-MS: calcd for C30H24N4O3 ([M+H]+), 489.2; found, 489.5.
N-(4-Fluorophenethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9c
TE D
This compound was obtained following the above method as turquoise powder, yield 62%, mp 211-213 oC; IR (νmax, KBr, cm-1): 3220, 1655, 1590, 1491, 1439, 1335, 1220, 1132, 1100, 949, 741; 1H NMR (600 MHz, DMSO-d6) δ 12.27 (s, 1H, NH), 12.23 (s, 1H, NH), 9.05 (s, 1H, ArH),
EP
8.87 (s, 1H, ArH), 8.58-8.53 (m, 2H, ArH), 8.46 (d, J = 12 Hz, 1H, ArH), 7.55 (d, J = 6 Hz, 1H,
AC C
ArH), 7.64-7.59 (m, 2H, ArH), 7.36-7.31 (m, 5H, ArH), 7.09 (t, J = 6 Hz, 2H, ArH), 3.66 (q, J = 6 Hz, 2H, CH2), 2.96 (t, J = 8 Hz, 2H, CH2Ph); 13C NMR (150 MHz, DMSO-d6): δ 187.42, 165.24, 162.10, 160.49, 142.54, 139.21, 138.58, 137.42, 136.70, 136.26, 136.07, 131.84, 130.90, 130.85, 129.57, 127.41, 123.59, 122.66, 122.02, 120.97, 117.05, 115.61, 115.47, 114.52, 113.65, 112.81, 41.11, 35.02; ESI-MS: calcd for C29H21FN4O2 ([M+H]+), 477.2; found, 477.5. N-(3,4-Dimethoxyphenethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9d 14
ACCEPTED MANUSCRIPT This compound was obtained following the above method as yellow powder, yield 77%, mp 109-111 oC; IR (νmax, KBr, cm-1): 3323, 2933, 1651, 1601, 1514, 1491, 1461, 1440, 1336, 1260, 1140, 1025, 953, 745; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.23 (s, 1H, NH),
RI PT
9.05 (s, 1H, ArH), 8.88 (s, 1H, ArH), 8.54-8.45 (m, 3H, ArH), 7.84 (d, J = 12 Hz, 1H, ArH), 7.64-7.60 (m, 2H, ArH), 7.36-7.30 (m, 3H, ArH), 6.86-6.77 (m, 3H, ArH), 3.67-3.63 (m, 5H, CH2 and OCH3), 3.62 (s, 3H, OCH3), 2.90 (t, J = 9 Hz, 2H, CH2Ph); 13C NMR (150 MHz, DMSO-d6):
SC
δ 187.42, 165.14, 149.11, 147.70, 142.54, 139.23, 138.56, 137.39, 136.70, 136.25, 132.24, 131.86,
M AN U
129.58, 127.41, 123.59, 122.67, 122.02, 120.95, 118.59, 117.01, 114.53, 113.65, 112.85, 112.26, 55.82, 55.72, 41.24, 35.47; ESI-MS: calcd for C31H26N4O4 ([M+H]+), 519.2; found, 519.5. N-(3-Hydroxyphenethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9e This compound was obtained following the above method as bright yellow powder, yield 72%, mp
TE D
142-143 oC; IR (νmax, KBr, cm-1): 3392, 1599, 1512, 1491, 1437, 1336, 1235, 1153, 1120, 952, 743; 1H NMR (600 MHz, DMSO-d6) δ 12.23 (s, 1H, NH), 12.17 (s, 1H, NH), 9.30 (s, 1H, ArH), 9.06 (s, 1H, ArH), 8.91 (s, 1H, ArH), 8.60-8.53 (m, 2H, ArH), 8.46 (d, J = 12 Hz, 1H, ArH), 7.85
EP
(d, J = 6 Hz, 1H, ArH), 7.65-7.59 (m, 2H, ArH), 7.36-7.30 (m, 4H, ArH), 7.06 (t, J = 6 Hz, 1H,
AC C
ArH), 6.72 (t, J = 6 Hz, 2H, ArH), 6.59 (d, J = 12 Hz, 1H, ArH), 3.63 (q, J = 6 Hz, 2H, CH2), 2.87 (t, J = 6 Hz, 2H, CH2Ph);
13
C NMR (150 MHz, DMSO-d6): δ 187.39, 165.22, 157.87, 142.54,
141.30, 139.29, 138.65, 137.37, 136.68, 136.29, 131.85, 129.80, 129.58, 127.43, 123.63, 123.61, 122.66, 122.04, 120.98, 119.72, 119.61, 115.96, 114.50, 113.66, 112.81, 100.02, 41.25, 36.02; ESI-MS: calcd for C29H22N4O3 ([M+H]+), 475.2; found, 475.4. 1-(1H-Indole-3-carbonyl)-N-phenethyl-9H-pyrido[3,4-b]indole-3-carboxamide 9f This compound was obtained following the above method as bright yellow powder, yield 78%, mp 15
ACCEPTED MANUSCRIPT 115-116 oC; IR (νmax, KBr, cm-1): 3398, 1647, 1600, 1491, 1444, 1337, 1300, 1239, 1123, 952, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.27 (s, 1H, NH), 12.23 (s, 1H, NH), 9.06 (s, 1H, ArH), 8.87 (s, 1H, ArH), 8.57-8.53 (m, 2H, ArH), 8.46 (d, J = 12 Hz, 1H, ArH), 7.85 (d, J = 6 Hz, 1H,
RI PT
ArH), 7.64-7.60 (m, 2H, ArH), 7.32-7.27 (m, 7H, ArH), 7.17 (t, J = 6 Hz, 1H, ArH), 3.67 (q, J = 6 Hz, 2H, CH2), 2.97 (t, J = 6 Hz, 2H, CH2Ph); 13C NMR (150 MHz, DMSO-d6): δ 187.53, 165.18, 142.53, 139.91, 139.40, 138.58, 137.43, 136.71, 136.26, 131.84, 129.60, 129.11, 128.88, 127.47,
M AN U
calcd for C29H22N4O2 ([M+H]+), 459.2; found, 459.4.
SC
126.62, 123.61, 122.66, 122.03, 120.97, 117.04, 114.51, 113.65, 112.82, 41.16, 35.90; ESI-MS:
N-Benzyl-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9g This compound was obtained following the above method as yellow powder, yield 64%, mp 129-131 oC; IR (νmax, KBr, cm-1): 3614, 3441, 3382, 1651, 1599, 1535, 1491, 1434, 1337, 1300,
TE D
1242, 1125, 951, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (br, 2H, NH), 9.08 (t, J = 6 Hz, 2H, ArH), 8.97 (d, J = 2.4 Hz, 1H, ArH), 8.54-8.53 (m, 1H, ArH), 8.47 (d, J = 6 Hz, 1H, ArH), 7.85 (d, J = 8.4 Hz, 1H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.56 (m, 1H, ArH), 7.44-7.25 (m, 8H, ArH),
EP
4.65 (d, J = 6 Hz, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 187.40, 165.60, 142.54, 140.34,
AC C
139.28, 138.74, 137.54, 136.68, 136.33, 131.84, 129.58, 128.84, 127.60, 127.41, 127.17, 123.56, 122.65, 122.04, 120.98, 117.29, 114.51, 113.67, 112.76, 43.15; ESI-MS: calcd for C28H20N4O2 ([M+H]+), 445.2; found, 445.3. N-(4-Fluorobenzyl-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9h This compound was obtained following the above method as light yellow powder, yield 73%, mp 219-221 oC; IR (νmax, KBr, cm-1): 3420, 3390, 1667, 1603, 1508, 1458, 1427, 1356, 1302, 1250, 1122, 952, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.23 (s, 1H, NH), 16
ACCEPTED MANUSCRIPT 9.12-9.08 (m, 2H, ArH), 8.95 (d, J = 2.4 Hz, 1H, ArH), 8.54-8.53 (m, 1H, ArH), 8.47 (d, J = 6 Hz, 1H, ArH), 7.85 (d, J = 8.4 Hz, 1H, ArH), 7.65-7.57 (m, 2H, ArH), 7.49-7.46 (m, 2H, ArH), 7.35-7.30 (m, 3H, ArH), 7.21-7.18 (m, 2H, ArH), 4.62 (d, J = 6 Hz, 2H, CH2);
13
C NMR (150
RI PT
MHz, DMSO-d6): δ 187.40, 165.62, 142.54, 139.23, 138.78, 137.55, 136.68, 136.54, 136.32, 131.83, 129.63, 129.58, 127.41, 123.57, 122.65, 122.03, 117.29, 115.60, 115.46, 114.51, 113.67, 112.75, 42.46; ESI-MS: calcd for C28H19FN4O2 ([M+H]+), 463.1; found, 463.3.
SC
1-(1H-Indole-3-carbonyl)-N-(4-methylbenzyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9i
M AN U
This compound was obtained following the above method as light yellow powder, yield 75%, mp 221-223 oC; IR (νmax, KBr, cm-1): 3453, 3419, 3303, 1635, 1600, 1579, 1450, 1419, 1339, 1273, 1228, 1110, 939, 737; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (br, 2H, NH), 9.08 (s, 1H, ArH), 9.02 (t, J = 6 Hz, 1H, ArH), 8.95 (d, J = 6 Hz, 1H, ArH), 8.54-8.53 (m, 1H, ArH), 8.47 (d, J = 6
TE D
Hz, 1H, ArH), 7.85 (d, J = 7.8 Hz, 1H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.56 (m, 1H, ArH), 7.36-7.29 (m, 5H, ArH), 7.18 (d, J = 7.8 Hz, 2H, ArH), 4.60 (d, J = 6 Hz, 2H, CH2), 2.28 (s, 3H, CH3); 13C NMR (150 MHz, DMSO-d6): δ 187.40, 165.50, 142.54, 139.31, 138.69, 137.51, 137.28,
EP
136.68, 136.32, 136.18, 131.84, 129.58, 129.39, 127.62, 127.41, 123.56, 122.65, 122.04, 120.98,
AC C
117.26, 114.51, 113.67, 112.76, 42.88, 21.18; ESI-MS: calcd for C29H22N4O2 ([M+H]+), 459.2; found, 459.3.
1-(1H-Indole-3-carbonyl)-N-(pyridin-3-ylmethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9j This compound was obtained following the above method as yellow powder, yield 70%, mp 139-141 oC; IR (νmax, KBr, cm-1): 3185, 2360, 2341, 1652, 1599, 1521, 1491, 1445, 1337, 1239, 1126, 944, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.21 (s, 1H, NH), 9.20 (t, J = 6 Hz, 1H, ArH), 9.09 (s, 1H, ArH), 8.96 (s, 1H, ArH), 8.65 (d, J = 2.4 Hz, 1H, ArH), 8.55-8.53 17
ACCEPTED MANUSCRIPT (m, 1H, ArH), 8.48-8.45 (m, 2H, ArH), 7.86-7.84 (m, 2H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.56 (m, 1H, ArH), 7.41-7.29 (m, 4H, ArH), 4.66 (d, J = 6 Hz, 2H, CH2);
13
C NMR (150
MHz, DMSO-d6): δ 187.38, 165.83, 149.32, 148.50, 142.53, 139.11, 138.90, 137.62, 136.68,
RI PT
136.34, 135.88, 135.53, 131.80, 129.59, 127.41, 124.02, 123.56, 122.65, 122.04, 120.98, 117.33, 114.50, 113.67, 112.75, 40.97; ESI-MS: calcd for C27H19N5O2 ([M+H]+), 446.2; found, 446.4. 1-(1H-Indole-3-carbonyl)-N-(pyridin-2-ylmethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9k
SC
This compound was obtained following the above method as yellow powder, yield 81%, mp
M AN U
137-139 oC; IR (νmax, KBr, cm-1): 3215, 1648, 1597, 1570, 1515, 1460, 1335, 1300, 1233, 1121, 946, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.29 (s, 1H, NH), 12.25 (s, 1H, NH), 9.27 (t, J = 6 Hz, 1H, ArH), 9.12 (s, 1H, ArH), 9.05 (s, 1H, ArH), 8.60-8.55 (m, 2H, ArH), 8.49 (d, J = 6 Hz, 1H, ArH), 7.87-7.81 (m, 2H, ArH), 7.66-7.63 (m, 1H, ArH), 7.60-7.58 (m, 1H, ArH), 7.47 (d, J = 6 Hz,
TE D
1H, ArH), 7.37-7.29 (m, 4H, ArH), 4.78 (d, J = 6 Hz, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 187.39, 165.44, 158.32, 149.48, 142.57, 138.97, 138.46, 137.47, 137.34, 136.72, 131.91, 129.62, 127.48, 123.60, 122.69, 122.09, 121.61, 121.00, 117.26, 114.51, 113.70, 112.80, 44.76; ESI-MS:
EP
calcd for C27H19N5O2 ([M+H]+), 446.2; found, 446.4.
AC C
N-(4-Hydroxy-3-methoxybenzyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxami d 9l
This compound was obtained following the above method as bright yellow powder, yield 65%, mp 203-204 oC; IR (νmax, KBr, cm-1): 3286, 1651, 1599, 1514, 1490, 1424, 1355, 1274, 1114, 944, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.23 (s, 1H, NH), 9.10 (s, 1H, ArH), 8.95-8.92 (m, 2H, ArH), 8.82 (s, 1H, ArH), 8.53 (t, J = 6 Hz, 1H, ArH), 8.47 (d, J = 6 Hz, 1H, ArH), 7.85 (d, J = 7.8 Hz, 1H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.57 (m, 1H, ArH), 7.36-7.30 18
ACCEPTED MANUSCRIPT (m, 3H, ArH), 6.99 (d, J = 1.8 Hz, 1H, ArH), 6.85 (q, J = 6 Hz, 1H, ArH), 6.77 (d, J = 7.8 Hz, 1H, ArH), 4.55 (d, J = 6 Hz, 2H, CH2), 3.74 (s, 3H, OCH3); 13C NMR (150 MHz, DMSO-d6): δ 187.43, 165.39, 147.90, 145.85, 142.54, 139.36, 138.61, 137.52, 136.68, 136.30, 131.84, 131.07, 129.57,
RI PT
127.40, 123.57, 122.65, 122.04, 120.98, 120.95, 120.09, 117.25, 115.88, 114.54, 113.66, 112.77, 112.22, 56.04, 42.98; ESI-MS: calcd for C29H22N4O4 ([M+H]+), 491.2; found, 491.4.
N-(4-Fluorophenyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9m
SC
This compound was obtained following the above method as bright yellow powder, yield 61%, mp
M AN U
130-132 oC; IR (νmax, KBr, cm-1): 3422, 1652, 1600, 1508, 1425, 1234, 1122, 938, 832, 739; 1H NMR (600 MHz, DMSO-d6) δ 12.35 (s, 1H, NH), 12.27 (s, 1H, NH), 10.47 (s, 1H, NH), 9.18 (s, 1H, ArH), 9.11 (d, J = 6 Hz, 1H, ArH), 8.56-8.51 (m, 2H, ArH), 7.95-7.92 (m, 2H, ArH), 7.88 (d, J = 6 Hz, 1H, ArH), 7.65 (t, J = 6 Hz, 1H, ArH), 7.60-7.58 (m, 1H, ArH), 7.38-7.25 (m, 5H, ArH); C NMR (150 MHz, DMSO-d6): δ 187.17, 164.08, 142.58, 138.99, 138.74, 137.21, 136.61,
TE D
13
136.45, 135.68, 132.12, 127.49, 123.56, 122.70, 122.44, 122.39, 121.98, 120.92, 117.62, 115.87, 115.73, 114.54, 113.69, 112.84; ESI-MS: calcd for C27H17FN4O2 ([M+H]+), 449.1; found, 449.4.
EP
1-(1H-Indole-3-carbonyl)-N-(4-methoxyphenyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9n
AC C
This compound was obtained following the above method as turquoise powder, yield 67%, mp 132-133 oC; IR (νmax, KBr, cm-1): 3291, 1655, 1597, 1509, 1491, 1437, 1338, 1301, 1229, 1155, 1122, 1032, 960, 743; 1H NMR (600 MHz, DMSO-d6) δ 12.33 (s, 1H, NH), 12.29 (s, 1H, NH), 10.27 (s, 1H, NH), 9.17 (s, 1H, ArH), 9.10 (s, 1H, ArH), 8.55-8.50 (m, 2H, ArH), 7.88-7.81 (m, 3H, ArH), 7.67-7.59 (m, 2H, ArH), 7.38-7.30 (m, 3H, ArH), 7.00-6.98 (m, 2H, ArH), 3.78 (s, 3H, OCH3);
13
C NMR (150 MHz, DMSO-d6): δ 187.30, 163.63, 163.11, 159.09, 149.77, 142.64,
139.23, 138.59, 137.15, 136.62, 136.43, 132.34, 132.13, 129.75, 127.52, 123.57, 122.70, 122.03, 19
ACCEPTED MANUSCRIPT 121.08, 120.97, 117.46, 115.42, 114.98, 114.55, 114.40, 113.74, 112.85, 55.73; ESI-MS: calcd for C28H20N4O3 ([M+H]+), 461.2; found, 461.3. 1-(1H-Indole-3-carbonyl)-N-(2-(methylsulfonyl)ethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9o
RI PT
This compound was obtained following the above method as yellow powder, yield 71%, mp 141-143 oC; IR (νmax, KBr, cm-1): 3384, 1652, 1599, 1514, 1491, 1424, 1297, 1123, 946, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.26 (s, 1H, NH), 12.17 (s, 1H, NH), 9.09 (s, 1H, ArH), 8.97 (s,
SC
1H, ArH), 8.82-8.79 (m, 1H, ArH), 8.58-8.54 (m, 1H, ArH), 8.48 (d, J = 12 Hz, 1H, ArH), 7.86 (d,
M AN U
J = 6 Hz, 1H, ArH), 7.65-7.57 (m, 2H, ArH), 7.36-7.28 (m, 3H, ArH), 3.91 (q, J = 6 Hz, 2H, CH2), 3.51 (t, J = 9 Hz, 2H, CH2Ph), 3.14 (s, 3H, CH3);
13
C NMR (150 MHz, DMSO-d6): δ 187.29,
165.40, 142.55, 139.02, 138.72, 137.48, 136.73, 136.40, 131.86, 129.70, 127.45, 123.54, 122.68, 122.03, 121.00, 117.23, 114.36, 113.70, 112.83, 53.71, 46.16, 33.69; ESI-MS: calcd for
Methyl
TE D
C24H20N4O4S ([M+H]+), 461.1; found, 461.3.
2-(1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamido)-3-hydroxypropanoate 9p
EP
This compound was obtained following the above method as yellow powder, yield 52%, mp
AC C
191-193 oC; IR (νmax, KBr, cm-1): 3397, 2927, 1725, 1599, 1510, 1460, 1425, 1275, 1120, 960, 741; 1H NMR (600 MHz, DMSO-d6) δ 12.34 (s, 1H, NH), 12.31 (s, 1H, NH), 9.12 (s, 1H, ArH), 8.94 (d, J = 3 Hz, 1H, ArH), 8.75 (d, J = 8.4 Hz, 1H, ArH), 8.56-8.55 (m, 1H, ArH), 8.50 (d, J = 7.8 Hz, 1H, ArH), 7.87 (d, J = 8.4 Hz, 1H, ArH), 7.72-7.59 (m, 3H, ArH), 7.37-7.31 (m, 3H, ArH), 4.79-4.76 (m, 1H, CH), 4.00-3.97 (m, 1H, CH2), 3.91-3.89 (m, 1H, CH2), 3.75 (s, 3H, OCH3); 13C NMR (150 MHz, DMSO-d6): δ 187.22, 171.62, 164.81, 142.62, 138.14, 137.76, 137.18, 136.72, 136.49, 132.07, 129.70, 129.14, 127.44, 123.64, 122.75, 122.06, 121.09, 120.98, 117.21, 114.51, 20
ACCEPTED MANUSCRIPT 113.75, 112.88, 62.04, 55.06, 52.77; ESI-MS: calcd for C25H20N4O5 ([M+H]+), 457.1; found, 457.4.
RI PT
4.5. In vitro cytotoxicity assays
The in vitro cytotoxicities of the prepared β-carboline amide derivatives against several cell lines
(SGC-7901,
A875,
HepG2,
and
MARC145)
were
evaluated
using
the
SC
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay [37-39].
M AN U
Acknowledgment
This work was supported by National Key R&D Program of China (2017YFD0200502) and the Program for Leading Talents of Hubei Academy of Agricultural Sciences (HAAS), and the authors also thank the partial support from Hubei Agricultural Science Innovation Centre
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TE D
(2016-620-000-001-039).
EP
[1] R. Tandon, I. Singh, V. Luxami, N. Tandon, K. Paul, Recent advances and developments of in
AC C
vitro evaluation of heterocyclic moieties on cancer cell lines, Chem. Rec. 18 (2018) 1-33. [2] R.L. Siegel, K.D. Miller, A. Jemal, Cancer statistics, 2018, CA Cancer J. Clin. 68 (2018) 7-30. [3] D. Luo, K.A. Carter, D. Miranda, J.F. Lovell, Chemophototherapy: an emerging treatment option for solid tumors, Adv. Sci. (2016) 1600106.
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ACCEPTED MANUSCRIPT [5] Y. Sumii, N. Kotoku, A. Fukuda, T. Kawachi, M. Arai, M. Kobayashi, Structure-activity relationship and in vivo anti-tumor evaluations of dictyoceratin-A and -C, hypoxia-selective growth inhibitors from marine sponge, Mar. Drugs 13 (2015) 7419-7432.
RI PT
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SC
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M AN U
[8] T. Rodrigues, D. Reker, P. Schneider, G. Schneider, Counting on natural products for drug design, Nature Chem. 8 (2016) 531-541.
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TE D
[10] I. Boulogne, P. Petit, H. Ozier-Lafontaine, L. Desfontaines, G. Loranger-Merciris, Insecticidal and antifungal chemicals produced by plants: a review, Environ. Chem. Lett. 10 (2012) 325-347.
EP
[11] T.C. Sparks, D.R. Hahn, N.V. Garizi, Natural products, their derivatives, mimics and
AC C
synthetic equivalents: role in agrochemical discovery, Pest Manag. Sci. 73 (2017) 700-715. [12] B.C. Gerwick, T.C. Sparks, Natural products for pest control: an analysis of their role, value and future, Pest Manag. Sci. 70 (2014) 1169-1185.
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ACCEPTED MANUSCRIPT [15] V. Spanò, A. Attanzio, S. Cascioferro, A. Carbone, A. Montalbano, P. Barraja, L. Tesoriere, G. Cirrincione, P. Diana, B. Parrino, Synthesis and antitumor activity of new thiazole nortopsentin analogs, Mar. Drugs 14 (2016) 226.
RI PT
[16] S. Cascioferro, A. Attanzio, V.D. Sarno, S. Musella, L. Tesoriere, G. Cirrincione, P. Diana, B. Parrino, New 1,2,4-oxadiazole nortopsentin derivatives with cytotoxic activity, Mar. Drugs 17 (2019) 35.
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ACCEPTED MANUSCRIPT (2012) 2296-2299. [31] C. Tan, Y. Zhang, N. Kong, Y. Di, X. Hao, Further alkaloids from the leaves of Trigonostemon lii, Helv. Chim. Acta 98 (2015) 72-77.
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ACCEPTED MANUSCRIPT dehydroepiandrosterone: A convenient synthesis, antiproliferation activity, structure-activity relationships, and role of heterocyclic moiety, Sci. Rep. 7 (2017) 44439. [39] S. Ke, L. Shi, X. Cao, Q. Yang, Y. Liang, Z. Yang, Heterocycle-functional gramine analogues:
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Eur. J. Med. Chem. 54 (2012) 248-254.
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Solvent- and catalyst-free synthesis and their inhibition activities against cell proliferation,
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Figure captions:
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Table 1 Chemical structure of target β-carboline amide derivatives Table 2 Growth-inhibitory activity for target compounds Table 3 Cytotoxic activities (IC50s) of the compounds against various cell lines Fig. 1. Representative natural β-carboline alkaloids. Fig. 2. Design strategy of β-carboline analogues derived from natural pityriacitrin. Fig. 3. Dose-response analysis of cell growth inhibition activity for compounds 9e, 9l, 9o, 9p and 5-FU (positive control) against SGC-7901 cells (upper left), A875 cells (upper right), HepG2 cells (lower left) and MARC145 cells (lower right). Fig. 4. General structure-activity relationships for target β-carboline derivatives. Scheme 1. Synthesis of β-carboline amide derivatives 9a-p. Reagents and conditions: a. SeO2, Dioxane/H2O; b. p-MePhSO3H, MeOH, 60 oC; c. SOCl2, MeOH; d. Compd 1, I2, DMSO; e. PhCH2CH2NH2, Dioxane, Reflux; f. 2N NaOH, MeOH, rt; g. NH2(CH2)nR, HOBt, EDCI, Et3N, DMF, rt.
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Research highlights: 1. Novel carboline analogues derived from marine alkaloid pityriacitrin 2. Good cytotoxic activities compared with the reference drug
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3. The SARs analyses have been fully investigated
S0223-5234(19)30184-9
DOI:
https://doi.org/10.1016/j.ejmech.2019.02.060
Reference:
EJMECH 11152
To appear in:
European Journal of Medicinal Chemistry
Received Date: 22 January 2019 Revised Date:
19 February 2019
Accepted Date: 21 February 2019
Please cite this article as: T. Xu, L. Shi, Y. Zhang, K. Wang, Z. Yang, S. Ke, Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues, European Journal of Medicinal Chemistry (2019), doi: https://doi.org/10.1016/j.ejmech.2019.02.060. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical Abstract
Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues
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Tingting Xu,b† Liqiao Shi,a,† Ya-Ni Zhang,a,† Kaimei Wang,a Ziwen Yang,a,b,* Shaoyong Kea,*
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Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues Tingting Xu,b† Liqiao Shi,a,† Yani Zhang,a,† Kaimei Wang,a Ziwen Yang,a,b,* Shaoyong Kea,* a
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National Biopesticide Engineering Research Centre, Hubei Biopesticide Engineering Research Centre, Hubei Academy of Agricultural Sciences, Wuhan 430064, People’s Republic of China b College of Life Sciences, Wuhan University, Wuhan 430072, People’s Republic of China
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*Address correspondence to Shaoyong Ke: Hubei Biopesticide Engineering Research Centre, Hubei Academy of Agricultural Sciences, Wuhan 430064, People′s Republic of China; Tel: +86-27-59101956; E-mail: [email protected] or [email protected] (S. Ke), [email protected] (Z. Yang) † These authors contributed equally to this work.
Abstract: Pityriacitrin is a marine alkaloid with typical β-carboline scaffold, and which has been proven to exhibit diverse biological functions. During the course of our research for highly active compounds from natural products, the pityriacitrin have also been isolated and identified from a
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Chinese Burkholderia sp. NBF227. So, in order to explore the potential functional molecules, a series of β-carboline analogues derived from pityriacitrin were designed and synthesized, and their in vitro cytotoxic activities against SGC-7901, A875, HepG2, and MARC145 cell lines were
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evaluated. The results demonstrated that some of these β-carboline derivatives exhibited moderate
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to good cytotoxic activities, especially, compound 9o with a special sulfonyl group presented the highest inhibitory activities against all tested cell lines with the IC50 values of 6.82±0.98, 8.43±1.93, 7.69±2.17, 7.19±1.43 µM, respectively, which might be used as lead compound for discovery of novel cytotoxic agents. Keywords: Marine alkaloid, Pityriacitrin, Analogues, Synthesis, Biological evaluation, SARs
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1. Introduction Cancer is a major disease that seriously endangers human health [1,2]. Nowadays, the treatments for cancer mainly include surgical management, chemotherapy, radiotherapy,
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photodynamic therapy, photothermal therapy, gene therapy, and immunotherapy [3], however, chemotherapy remains the most important treatment method [4,5], and the development of novel molecules with unique structural features as anticancer drugs is still an important direction.
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Natural products are important sources of leading compounds for discovery of drugs [6-9] or
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agrochemicals [10-14], and many synthetic derivatives of natural products have extensive bioactivities, especially antitumor [15,16]. Alkaloids are classes of natural products widely distributed in plants with diverse structural features, and which play an important role in the field of medicinal chemistry and agrochemical industry [17-19]. Among these natural products,
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β-carboline alkaloids, a family of indole alkaloids [20-25], are with the unique tricyclic pyrido-[3,4-b]indole ring (Fig. 1), which belong to an important class of bioactive natural products
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distributed in nature.
Fig. 1. Representative natural β-carboline alkaloids.
Especially, pityriacitrin, a rare marine β-carboline alkaloid (Fig. 1) bearing an indole ring attached with a carbonyl group on C-1 position arouse the interest of researchers due to its unique structure and broad UV absorption [26-28]. Subsequently, some pityriacitrin analogues and derivatives have been isolated or prepared, and their potential biological implications have also 2
ACCEPTED MANUSCRIPT been investigated [29-33]. Recently, during the course of our research for active compounds from natural products, the pityriacitrin and pityriacitrin B have been isolated and identified from a Chinese Burkholderia sp. NBF227 (Fig. 2), and which also indicated obvious antifungal activities.
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However, the low fermentation levels limit the further research on exploring the potential applications for these natural compounds, and so the convenient synthetic methods for these β-carboline alkaloids have been investigated in our lab. In addition, as part of our medicinal
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chemistry program aimed at the discovery of potential cytotoxic agents, we wish to report herein
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the molecule design, convenient synthesis, and biological evaluation of a series of β-carboline
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amide derivatives derived from natural pityriacitrin (Fig. 2).
Fig. 2. Design strategy of β-carboline analogues derived from natural pityriacitrin.
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In this study, the pityriacitrin scaffold was used as a key unit and planned for the hybridization
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of amide pharmacophore [34-36] to the core structure as depicted in Fig. 2. Therefore, a series of novel β-carboline amide derivatives 9a-p were designed and synthesized as shown in Scheme 1, and their cytotoxic activities against several cell lines (SGC-7901, A875, HepG2, and MARC145) were evaluated by MTT colorimetric method, and the possible structure and activity relationships have also been summarized and discussed.
2. Results and discussion
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In this work, a series of novel β-carboline amide derivatives based on natural pityriacitrin were constructed by integrating β-carboline pharmacophore with amide function group. The synthesis
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of pityriacitrin, pityriacitrin B and the target β-carboline amide derivatives 9a-p was shown in
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Scheme 1.
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Scheme 1. Synthesis of β-carboline amide derivatives 9a-p. Reagents and conditions: a. SeO2, Dioxane/H2O; b. p-MePhSO3H, MeOH, 60 oC; c. SOCl2, MeOH; d. Compd 1, I2, DMSO; e. PhCH2CH2NH2, Dioxane, Reflux; f. 2N NaOH, MeOH, rt; g. NH2(CH2)nR, HOBt, EDCI, Et3N, DMF, rt.
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Firstly, the 1-(1H-indol-3-yl)ethanone 1 was selected as starting materials, and which was transformed into 2-(1H-indol-3-yl)-2-oxoacetaldehyde 2 via oxidation process. After this, the
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tryptophan 3 undergoes ring closure after condensation with the intermediate 2 via a similar transformation of Pictet–Spengler reaction, however, the UPLC-MS analyses demonstrate a tetrahydro-β-carboline derivative 4 (tR = 2.51 min, [M+H]+ 360.5) has been obtained as the majoring product (48%) along with pityriacitrin B (15%, tR = 3.64 min, [M+H]+ 356.4) and pityriacitrin (12%, tR = 3.90 min, [M+H]+ 312.4) under this condition. So, another method to prepare pityriacitrin and pityriacitrin B was investigated as described in Scheme 1. The heterocyclization reaction of compound 7 was treated with 1-(1H-indol-3-yl)ethanone 1 resulting 4
ACCEPTED MANUSCRIPT in methyl 1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylate 8 via a convenient condensation reaction. With the compound 8 in hand, the direct nucleophilic substitution reaction using 2-phenylethanamine was explored, unfortunately, this transformation was not work. Then
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the compound 8 was conveniently hydrolyzed to compound 5 (pityriacitrin B) in the presence of sodium hydroxide solution, and which can couple with various amines using HOBt/EDCI as coupling agents. All target β-carboline derivatives 9a-p gave satisfactory chemical analyses, and
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the chemical structures of the compounds were summarized in Table 1.
Table 1 Chemical structure of target β-carboline amide derivatives
16
9p
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9a 9b 9c 9d 9e 9f 9g 9h 9i 9j 9k 9l 9m 9n 9o
R
3-Indolyl 3-MeO-Ph 4-F-Ph 3,4-(MeO)2-Ph 3-OH-Ph Ph Ph 4-F-Ph 4-Me-Ph 3-Py 2-Py 3-MeO-4-OH-Ph 4-F-Ph 4-MeO-Ph MeSO2
Appearance
Mp (oC)
Yielda (%)
Yellow powder Yellowish needle crystal Turquoise powder Yellow powder Bright yellow powder Bright yellow powder Yellow powder Light yellow powder Light yellow powder Yellow powder Yellow powder Bright yellow powder Bright yellow powder Turquoise powder Yellow powder
172-173 102-104 211-213 109-111 142-143 115-116 129-131 219-221 221-223 139-141 137-139 203-204 130-132 132-133 141-143
72 56 62 77 72 78 64 73 75 70 81 65 61 67 71
Yellow powder
191-193
52
n
2 2 2 2 2 2 1 1 1 1 1 1 0 0 2
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Substituents
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Compd. No.
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a
Entry
Isolated yields.
2.2. Biological evaluation
2.2.1. Cytotoxic activities All prepared β-carboline amide derivatives 9a-p, pityriacitrin and pityriacitrin B were tested for
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ACCEPTED MANUSCRIPT their in vitro cytotoxic effects on SGC-7901 (Human gastric cancer), A875 (Human melanoma), HepG2 (Human hepatocellular liver carcinoma), and MARC145 (A subclone of African green monkey kidney cell line MA-104) cell lines by the standard MTT assay [37-39], and the results
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are summarized in Table 2 and 3. Table 2 Growth-inhibitory activity for target compounds Growth-inhibitory propertiesa
Compd. No.
SGC-7901b
A875b
HepG2b
MARC145b
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
6 5 8 9a 9b 9c 9d 9e 9f 9g 9h 9i 9j 9k 9l 9m 9n 9o 9p 5-FUc
43.17±2.84 62.97±9.03 48.60±1.80 76.60±8.12 39.33±7.49 76.73±4.04 22.10±2.54 88.33±2.78 84.53±3.70 79.00±4.13 78.80±2.59 63.97±2.18 70.07±3.98 69.53±3.01 83.10±4.06 33.97±5.88 41.20±7.15 88.47±0.74 82.73±4.13 79.87±6.31
59.10±2.17 72.17±3.71 36.80±7.87 77.83±2.14 16.64±8.46 33.90±6.89 0±0 87.47±2.81 77.13±4.55 75.53±2.32 68.07±2.72 26.97±6.12 74.23±2.54 70.67±5.12 81.67±5.66 20.70±6.30 72.07±6.67 87.93±1.72 83.90±2.88 61.03±3.40
30.50±5.34 78.40±8.21 62.70±6.11 74.40±7.04 40.13±7.89 72.43±2.97 31.73±5.81 86.90±3.49 82.33±4.62 77.30±4.85 73.90±2.36 63.87±8.02 82.80±5.71 79.57±6.61 80.87±0.55 34.83±3.42 44.83±2.66 87.30±2.78 78.97±5.33 72.60±5.24
34.60±17.25 71.95±3.04 35.85±11.53 66.95±5.02 48.35±0.64 63.00±3.96 38.40±0.57 83.15±7.28 79.75±6.29 67.40±1.84 63.80±4.67 55.00±1.98 73.80±0.42 66.15±5.44 79.10±3.82 47.45±5.44 41.95±3.82 90.15±2.62 83.20±2.69 66.70±0.42
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a
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Entry
The percentage of growth inhibition evaluated at the screening concentration of 40 µg/mL; Abbreviations: SGC-7901 – Human gastric cancer cell line; A875 – Human melanoma cell line; HepG2 – Human hepatocellular liver carcinoma cell line; MARC145 – A subclone of African green monkey kidney cell line MA-104; cUsed as a positive control.
b
As seen in Table 2, these novel β-carboline amide derivatives 9a-p displayed moderate to good inhibitory activities against all tested cell lines. The compounds directly derived from arylamines (9m and 9n, Entries 16-17) exhibited lower activities than the corresponding compounds from
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ACCEPTED MANUSCRIPT substituted benzylamines (9g-l, Entry 10-15) and phenylethylamines (9a-f, Entries 4-9). The compounds bearing 3-hydroxy group (9e) have obviously high activity than the compounds with 3-methoxyl substituent (9b). Notably, the compounds 9o and 9p (Entries 18 and 19) exhibited
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significant inhibitory activity against all tested cell lines with 78.97-90.15% growth inhibition at the concentration of 40 µg/mL. Also, it is interesting to note that compound 9l (Entry 15) with natural vanillylamine unit also showed good cytotoxicity (>79%) against all tested cell lines. The
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results of preliminary bioassay indicated that these β-carboline amide derivatives containing
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hydroxyphenyl, amino acids or sulfonyl group might be used as lead molecules for development of potential anticancer agents.
Furthermore, in order to investigate the highly potential compounds, the IC50 values for target compounds were also tested, and the results are shown in Table 3.
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Table 3 Cytotoxic activities (IC50s) of the compounds against various cell lines In vitro cytotoxicity IC50a (µM)
Entry
Compd. No.
1
6
2
5
3
8
4 5
A875b
HepG2b
MARC145b
>120
75.79±14.63
>120
>120
67.69±11.79
48.75±6.25
51.82±5.99
41.88±9.32
>100
>100
>100
>100
9a
38.56±1.47
50.36±6.54
41.03±6.15
44.09±8.47
9b
>80
>80
>80
>80
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SGC-7901b
6
9c
34.02±6.32
>80
38.53±9.30
48.76±4.96
7
9d
>75
>75
>75
>75
8
9e
17.65±5.84
11.91±0.80
8.63±3.31
13.77±3.75
9
9f
22.98±5.15
44.76±8.32
19.77±5.19
25.88±7.99
10
9g
39.87±7.14
56.37±5.40
36.24±6.62
42.82±2.39
11
9h
34.54±5.60
63.06±6.84
39.04±8.74
55.05±10.24
12
9i
65.98±4.43
>85
65.32±9.71
73.20±6.81
13
9j
33.13±9.52
25.18±6.65
18.49±2.56
20.80±5.44
14
9k
43.94±6.83
42.48±6.67
26.30±6.13
33.76±8.18
15
9l
16.18±2.31
8.47±2.96
11.08±3.33
21.77±6.94
16
9m
>85
>85
>85
>85
17
9n
>85
65.38±8.13
>85
>85 7
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9o
19
9p
20
c
5-FU
6.82±0.98
8.43±1.93
7.69±2.17
7.19±1.43
14.30±2.57
10.46±1.34
9.99±1.82
16.27±0.07
53.58±1.99
62.12±17.83
66.42±12.99
115.54±8.30
a
IC50 – Compound concentration required to inhibit tumor cell proliferation by 50%. Abbreviations: SGC-7901 – Human gastric cancer cell line; A875 – Human melanoma cell line; HepG2 – Human hepatocellular liver carcinoma cell line; MARC145 – A subclone of African green monkey kidney cell line MA-104. cUsed as a positive control.
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b
As indicated in Table 3, some of these β-carboline amide derivatives such as 9e, 9l, 9o, 9p exhibited higher inhibition activities compared to 5-FU. Compounds 9e and 9l containing an
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hydroxyphenyl unit have higher inhibitory effects on all cell lines, and the compound 9p
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containing a serine unit also exhibited significant activity. Especially, we also can find that compound 9o with a special sulfonyl group presented obviously highest inhibitory activities against all four cell lines, and the IC50 values are 6.82±0.98, 8.43±1.93, 7.69±2.17, 7.19±1.43 µM, respectively. However, the parent compounds pityriacitrin 6, pityriacitrin B 5, and the
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intermediate 8 were less effective. These interesting findings may provide some useful information for discovery of potential cytotoxicity agents derived from natural alkaloids.
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In addition, the dose-response analysis for highly potential compounds 9e, 9l, 9o, 9p and 5-FU was displayed in Fig. 3, and which indicated that these compounds inhibited the cell lines in a
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concentration-dependent manner.
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Fig. 3. Dose-response analysis of cell growth inhibition activity for compounds 9e, 9l, 9o, 9p and 5-FU (positive control) against SGC-7901 cells (upper left), A875 cells (upper right), HepG2 cells (lower left) and MARC145 cells (lower right). 2.2.2. Structure and activity relationships (SARs)
The structural modification of compounds is mainly focused on amide scaffold with different
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kinds of amines including substituted phenylethylamines (9a-f), substituted benzylamines (9g-l) and substituted arylamines (9m-n). In addition, two compounds with special sulfonyl group (9o)
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and amino acid unit (9p) were also synthesized to investigate the possible activity difference. According to in vitro results described in Table 2 and 3, the possible structure and activity
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relationships for these β-carboline amide derivatives can be obtained (Fig. 4).
Fig. 4. General structure-activity relationships for target β-carboline derivatives. 9
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are obviously superior to those of substituted arylamines (n = 0), which proved the importance of the linker between aromatic ring and amide. In addition, most of the β-carboline amide derivatives exhibit better activity than that of the parent compounds pityriacitrin B (5) and pityriacitrin (6),
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which indicate the amide bond is beneficial to increase the activity. For the compound containing
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amino acid unit, the compound 9p bearing a serine moiety present higher potential activity. From Table 3, we also can find that, within the series of amide derivatives (9a-n), it is clear that the compounds with hydroxyphenyl group (9l and 9e) are better than other corresponding compounds, which may be due to the polar of hydroxyphenyl group is favorable for the binding to target
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protein. In particular, it’s interesting that the compound containing a special sulfonyl group present the highest inhibitory activities. According to these findings, it can be speculated it would have been more interesting to test the other hydroxyphenyl substituted and sulfur-containing
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derivatives, and the special properties of hydroxylphenyl and sulfur groups will be helpful to
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increase the activity. These structure-activity relationships will be helpful for further structural optimization based on the β-carboline amide scaffold, and the most active compounds also can be considered as lead compounds for the development of more potent derivatives.
3. Conclusion In summary, a series of novel β-carboline amide derivatives derived from natural marine alkaloid were designed and synthesized. The in vitro bioassay demonstrated that some of the
10
ACCEPTED MANUSCRIPT compounds displayed good cytotoxic activities against SGC-7901, A875, HepG2, and MARC145 cell lines compared to the control, which might be developed as novel lead scaffold for potential
RI PT
cytotoxic agents.
4. Materials and Methods 4.1. Instrumentation and chemicals
SC
All reagents from commercial sources were directly used without purification. Analytical
M AN U
thin-layer chromatography was carried out on silica gel GF254 by UV. Melting points (m.p.) were tested using a digital model X-5 apparatus. The infrared absorption spectra were recorded on a Thermo Nicolet FT-IR Avatar 330 instrument in KBr discs and are reported in cm-1. 1H NMR and 13
C NMR spectra were tested on a Bruker Avance III 600 MHz FT-NMR spectrometer using
TE D
DMSO-d6 as the solvent and tetramethylsilane (TMS) as the internal standard. Mass spectra were performed on a WATERS ACQUITY UPLC® H-CLASS PDA (Waters®) instrument.
General
synthetic
procedure
for
methyl
EP
4.2.
AC C
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylate 8
To a solution of tryptophan 3 (10.21 g, 0.05 mmol) in anhydrous methanol (50 ml) was added dropwise thionyl chloride (7.14 g, 0.06 mmol) under ice-bath. After addition, the mixture was slowly heated to 50 oC overnight, and then the reaction solution was concentrated, filtered and washed with cool methanol to obtain the crude tryptophan methyl ester hydrochlorides 7, which were used for the next reaction without further purification. Iodine (2.54 g, 0.01 mol) was added to the solution of 1-(1H-indol-3-yl)ethanone 1 (1.59 g, 0.01 mol) in 15 mL of DMSO, and the
11
ACCEPTED MANUSCRIPT resulting mixture was heated at 85-90 oC for 1.5 h. Then the obtained tryptophan methyl ester 7 (2.55 g, 0.01 mol) was added, and the solution was stirred at same temperature for 3-4 h. After completion of the reaction, the mixture was then cooled to room temperature followed by addition
RI PT
of water and extracted with ethyl acetate. The extract was washed with the aqueous of Na2S2O3, dried over Na2SO4, filtered and evaporated under reduced pressure. The residue was used for the next reaction without further purification. MS (ESI) m/z 370.4 (M+H)+, 392.4 (M+Na)+, calcd. for
General
synthetic
procedure
for
M AN U
4.3.
SC
C22H15N3O3 m/z = 369.1.
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid 5
To a solution of methyl 1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylate 8 (10 mmol) in methanol (15 mL) was added aqueous (15 mL) of sodium hydroxide (15 mmol), which
TE D
were stirred at room temperature overnight, and detected by thin-layer chromatography. After the completion of reaction, the mixture was adjusted to pH 2-3 with dilute hydrochloric acid under and
the
precipitate
was
filtered
and
dried
to
obtain
EP
ice-bath,
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid 5. This compound was
AC C
obtained following the above method as light brown powder, mp 302-303 oC, yield 76%. MS (ESI) m/z 356.4 (M+H)+, calcd. for C21H13N3O3 m/z = 355.1.
4.4. General synthetic procedure for the target compounds 9a-p
The typical process for the synthesis of target pityriacitrin-oriented β-carboline analogues 9a-p is
shown
as
following:
To
a
solution
of
1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxylic acid 5 (1 mmol) in DMF (8 mL) 12
ACCEPTED MANUSCRIPT was added HOBt (1.5 mmol), EDCI (1.5 mmol), Et3N (2 mmol) and appropriate substituted amine (1.2 mmol), and then the mixture were stirred at room temperature overnight. After the completion of reaction, the water was added to the mixture, and which was extracted with ethyl acetate, and
RI PT
the organic layer was washed with water and brine, and dried with anhydrous Na2SO4. The solvent was removed to give crude target compounds, and which were purified by silica gel column-chromatography (ethyl acetate/petroleum ether) or recrystallization to give pure
SC
compounds. All the compounds were characterized by ESI-MS, 1H NMR and
13
C NMR
M AN U
spectroscopic data, and their physico-chemical properties and spectra data are as follows: N-(2-(1H-Indol-3-yl)ethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9a This compound was obtained following the above method as yellow powder, yield 72%, mp 172-173 oC; IR (νmax, KBr, cm-1): 3360, 2924, 1655, 1643, 1597, 1507, 1457, 1417, 1145, 1112,
TE D
952, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.23 (s, 1H, NH), 12.21 (s, 1H, NH), 10.80 (s, 1H, ArH), 9.08 (s, 1H, ArH), 8.95 (d, J = 3 Hz,1H, ArH), 8.66 (t, J = 6 Hz, 1H, ArH), 8.55 (t, J = 6 Hz, 1H, ArH), 8.47 (d, J = 6 Hz,1H, ArH), 7.85 (d, J = 7.8 Hz,1H, ArH), 7.68-7.59 (m, 3H, ArH),
EP
7.36-7.30 (m, 4H, ArH), 7.25 (d, J = 1.8 Hz,1H, ArH), 7.07-7.04 (m, 1H, ArH), 6.97 (t, J = 6
AC C
Hz,1H), 3.73 (q, J = 6 Hz, 2H, CH2), 3.08 (t, J = 6 Hz, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 187.39, 165.30, 142.52, 139.42, 138.60, 137.35, 136.82, 136.64, 136.35, 131.84, 129.59, 127.80, 127.42, 123.66, 123.12, 122.66, 122.06, 121.44, 120.99, 120.95, 118.94, 118.68, 117.14, 114.51, 113.64, 112.81, 112.32, 111.86, 40.54, 26.02; ESI-MS: calcd for C31H23N5O2 ([M+H]+), 498.2; found, 498.4. 1-(1H-Indole-3-carbonyl)-N-(3-methoxyphenethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9b This compound was obtained following the above method as yellowish needle crystal, yield 56%, 13
ACCEPTED MANUSCRIPT mp 102-104 oC; IR (νmax, KBr, cm-1): 3373, 3317, 2919, 2848, 1647, 1608, 1583, 1526, 1512, 1491, 1425, 1339, 1257, 1160, 1122, 1036, 952, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.23 (s, 1H, NH), 12.21 (s, 1H, NH), 9.06 (s, 1H, ArH), 8.89 (s, 1H, ArH), 8.57-8.53 (m, 2H, ArH), 8.46 (d,
RI PT
J = 12 Hz, 1H, ArH), 7.55 (d, J = 6 Hz, 1H, ArH), 7.65-7.60 (m, 2H, ArH), 7.35-7.31 (m, 3H, ArH), 7.18 (t, J = 6 Hz, 1H, ArH), 6.89 (d, J = 6 Hz, 1H, ArH), 6.85 (s, 1H, ArH), 6.74 (dd, J = 6 Hz, 1H, ArH), 3.68-3.62 (m, 5H, CH2 and OCH3), 2.94 (t, J = 8 Hz, 2H, CH2Ph); 13C NMR (150
SC
MHz, DMSO-d6): δ 187.39, 165.20, 159.78, 142.54, 141.48, 139.23, 138.57, 137.40, 136.69,
M AN U
136.26, 131.85, 129.88, 129.58, 127.42, 123.58, 122.66, 122.03, 121.34, 120.97, 117.04, 114.66, 114.50, 113.66, 112.81, 112.12, 55.27, 41.09, 35.96; ESI-MS: calcd for C30H24N4O3 ([M+H]+), 489.2; found, 489.5.
N-(4-Fluorophenethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9c
TE D
This compound was obtained following the above method as turquoise powder, yield 62%, mp 211-213 oC; IR (νmax, KBr, cm-1): 3220, 1655, 1590, 1491, 1439, 1335, 1220, 1132, 1100, 949, 741; 1H NMR (600 MHz, DMSO-d6) δ 12.27 (s, 1H, NH), 12.23 (s, 1H, NH), 9.05 (s, 1H, ArH),
EP
8.87 (s, 1H, ArH), 8.58-8.53 (m, 2H, ArH), 8.46 (d, J = 12 Hz, 1H, ArH), 7.55 (d, J = 6 Hz, 1H,
AC C
ArH), 7.64-7.59 (m, 2H, ArH), 7.36-7.31 (m, 5H, ArH), 7.09 (t, J = 6 Hz, 2H, ArH), 3.66 (q, J = 6 Hz, 2H, CH2), 2.96 (t, J = 8 Hz, 2H, CH2Ph); 13C NMR (150 MHz, DMSO-d6): δ 187.42, 165.24, 162.10, 160.49, 142.54, 139.21, 138.58, 137.42, 136.70, 136.26, 136.07, 131.84, 130.90, 130.85, 129.57, 127.41, 123.59, 122.66, 122.02, 120.97, 117.05, 115.61, 115.47, 114.52, 113.65, 112.81, 41.11, 35.02; ESI-MS: calcd for C29H21FN4O2 ([M+H]+), 477.2; found, 477.5. N-(3,4-Dimethoxyphenethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9d 14
ACCEPTED MANUSCRIPT This compound was obtained following the above method as yellow powder, yield 77%, mp 109-111 oC; IR (νmax, KBr, cm-1): 3323, 2933, 1651, 1601, 1514, 1491, 1461, 1440, 1336, 1260, 1140, 1025, 953, 745; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.23 (s, 1H, NH),
RI PT
9.05 (s, 1H, ArH), 8.88 (s, 1H, ArH), 8.54-8.45 (m, 3H, ArH), 7.84 (d, J = 12 Hz, 1H, ArH), 7.64-7.60 (m, 2H, ArH), 7.36-7.30 (m, 3H, ArH), 6.86-6.77 (m, 3H, ArH), 3.67-3.63 (m, 5H, CH2 and OCH3), 3.62 (s, 3H, OCH3), 2.90 (t, J = 9 Hz, 2H, CH2Ph); 13C NMR (150 MHz, DMSO-d6):
SC
δ 187.42, 165.14, 149.11, 147.70, 142.54, 139.23, 138.56, 137.39, 136.70, 136.25, 132.24, 131.86,
M AN U
129.58, 127.41, 123.59, 122.67, 122.02, 120.95, 118.59, 117.01, 114.53, 113.65, 112.85, 112.26, 55.82, 55.72, 41.24, 35.47; ESI-MS: calcd for C31H26N4O4 ([M+H]+), 519.2; found, 519.5. N-(3-Hydroxyphenethyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9e This compound was obtained following the above method as bright yellow powder, yield 72%, mp
TE D
142-143 oC; IR (νmax, KBr, cm-1): 3392, 1599, 1512, 1491, 1437, 1336, 1235, 1153, 1120, 952, 743; 1H NMR (600 MHz, DMSO-d6) δ 12.23 (s, 1H, NH), 12.17 (s, 1H, NH), 9.30 (s, 1H, ArH), 9.06 (s, 1H, ArH), 8.91 (s, 1H, ArH), 8.60-8.53 (m, 2H, ArH), 8.46 (d, J = 12 Hz, 1H, ArH), 7.85
EP
(d, J = 6 Hz, 1H, ArH), 7.65-7.59 (m, 2H, ArH), 7.36-7.30 (m, 4H, ArH), 7.06 (t, J = 6 Hz, 1H,
AC C
ArH), 6.72 (t, J = 6 Hz, 2H, ArH), 6.59 (d, J = 12 Hz, 1H, ArH), 3.63 (q, J = 6 Hz, 2H, CH2), 2.87 (t, J = 6 Hz, 2H, CH2Ph);
13
C NMR (150 MHz, DMSO-d6): δ 187.39, 165.22, 157.87, 142.54,
141.30, 139.29, 138.65, 137.37, 136.68, 136.29, 131.85, 129.80, 129.58, 127.43, 123.63, 123.61, 122.66, 122.04, 120.98, 119.72, 119.61, 115.96, 114.50, 113.66, 112.81, 100.02, 41.25, 36.02; ESI-MS: calcd for C29H22N4O3 ([M+H]+), 475.2; found, 475.4. 1-(1H-Indole-3-carbonyl)-N-phenethyl-9H-pyrido[3,4-b]indole-3-carboxamide 9f This compound was obtained following the above method as bright yellow powder, yield 78%, mp 15
ACCEPTED MANUSCRIPT 115-116 oC; IR (νmax, KBr, cm-1): 3398, 1647, 1600, 1491, 1444, 1337, 1300, 1239, 1123, 952, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.27 (s, 1H, NH), 12.23 (s, 1H, NH), 9.06 (s, 1H, ArH), 8.87 (s, 1H, ArH), 8.57-8.53 (m, 2H, ArH), 8.46 (d, J = 12 Hz, 1H, ArH), 7.85 (d, J = 6 Hz, 1H,
RI PT
ArH), 7.64-7.60 (m, 2H, ArH), 7.32-7.27 (m, 7H, ArH), 7.17 (t, J = 6 Hz, 1H, ArH), 3.67 (q, J = 6 Hz, 2H, CH2), 2.97 (t, J = 6 Hz, 2H, CH2Ph); 13C NMR (150 MHz, DMSO-d6): δ 187.53, 165.18, 142.53, 139.91, 139.40, 138.58, 137.43, 136.71, 136.26, 131.84, 129.60, 129.11, 128.88, 127.47,
M AN U
calcd for C29H22N4O2 ([M+H]+), 459.2; found, 459.4.
SC
126.62, 123.61, 122.66, 122.03, 120.97, 117.04, 114.51, 113.65, 112.82, 41.16, 35.90; ESI-MS:
N-Benzyl-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9g This compound was obtained following the above method as yellow powder, yield 64%, mp 129-131 oC; IR (νmax, KBr, cm-1): 3614, 3441, 3382, 1651, 1599, 1535, 1491, 1434, 1337, 1300,
TE D
1242, 1125, 951, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (br, 2H, NH), 9.08 (t, J = 6 Hz, 2H, ArH), 8.97 (d, J = 2.4 Hz, 1H, ArH), 8.54-8.53 (m, 1H, ArH), 8.47 (d, J = 6 Hz, 1H, ArH), 7.85 (d, J = 8.4 Hz, 1H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.56 (m, 1H, ArH), 7.44-7.25 (m, 8H, ArH),
EP
4.65 (d, J = 6 Hz, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 187.40, 165.60, 142.54, 140.34,
AC C
139.28, 138.74, 137.54, 136.68, 136.33, 131.84, 129.58, 128.84, 127.60, 127.41, 127.17, 123.56, 122.65, 122.04, 120.98, 117.29, 114.51, 113.67, 112.76, 43.15; ESI-MS: calcd for C28H20N4O2 ([M+H]+), 445.2; found, 445.3. N-(4-Fluorobenzyl-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9h This compound was obtained following the above method as light yellow powder, yield 73%, mp 219-221 oC; IR (νmax, KBr, cm-1): 3420, 3390, 1667, 1603, 1508, 1458, 1427, 1356, 1302, 1250, 1122, 952, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.23 (s, 1H, NH), 16
ACCEPTED MANUSCRIPT 9.12-9.08 (m, 2H, ArH), 8.95 (d, J = 2.4 Hz, 1H, ArH), 8.54-8.53 (m, 1H, ArH), 8.47 (d, J = 6 Hz, 1H, ArH), 7.85 (d, J = 8.4 Hz, 1H, ArH), 7.65-7.57 (m, 2H, ArH), 7.49-7.46 (m, 2H, ArH), 7.35-7.30 (m, 3H, ArH), 7.21-7.18 (m, 2H, ArH), 4.62 (d, J = 6 Hz, 2H, CH2);
13
C NMR (150
RI PT
MHz, DMSO-d6): δ 187.40, 165.62, 142.54, 139.23, 138.78, 137.55, 136.68, 136.54, 136.32, 131.83, 129.63, 129.58, 127.41, 123.57, 122.65, 122.03, 117.29, 115.60, 115.46, 114.51, 113.67, 112.75, 42.46; ESI-MS: calcd for C28H19FN4O2 ([M+H]+), 463.1; found, 463.3.
SC
1-(1H-Indole-3-carbonyl)-N-(4-methylbenzyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9i
M AN U
This compound was obtained following the above method as light yellow powder, yield 75%, mp 221-223 oC; IR (νmax, KBr, cm-1): 3453, 3419, 3303, 1635, 1600, 1579, 1450, 1419, 1339, 1273, 1228, 1110, 939, 737; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (br, 2H, NH), 9.08 (s, 1H, ArH), 9.02 (t, J = 6 Hz, 1H, ArH), 8.95 (d, J = 6 Hz, 1H, ArH), 8.54-8.53 (m, 1H, ArH), 8.47 (d, J = 6
TE D
Hz, 1H, ArH), 7.85 (d, J = 7.8 Hz, 1H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.56 (m, 1H, ArH), 7.36-7.29 (m, 5H, ArH), 7.18 (d, J = 7.8 Hz, 2H, ArH), 4.60 (d, J = 6 Hz, 2H, CH2), 2.28 (s, 3H, CH3); 13C NMR (150 MHz, DMSO-d6): δ 187.40, 165.50, 142.54, 139.31, 138.69, 137.51, 137.28,
EP
136.68, 136.32, 136.18, 131.84, 129.58, 129.39, 127.62, 127.41, 123.56, 122.65, 122.04, 120.98,
AC C
117.26, 114.51, 113.67, 112.76, 42.88, 21.18; ESI-MS: calcd for C29H22N4O2 ([M+H]+), 459.2; found, 459.3.
1-(1H-Indole-3-carbonyl)-N-(pyridin-3-ylmethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9j This compound was obtained following the above method as yellow powder, yield 70%, mp 139-141 oC; IR (νmax, KBr, cm-1): 3185, 2360, 2341, 1652, 1599, 1521, 1491, 1445, 1337, 1239, 1126, 944, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.21 (s, 1H, NH), 9.20 (t, J = 6 Hz, 1H, ArH), 9.09 (s, 1H, ArH), 8.96 (s, 1H, ArH), 8.65 (d, J = 2.4 Hz, 1H, ArH), 8.55-8.53 17
ACCEPTED MANUSCRIPT (m, 1H, ArH), 8.48-8.45 (m, 2H, ArH), 7.86-7.84 (m, 2H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.56 (m, 1H, ArH), 7.41-7.29 (m, 4H, ArH), 4.66 (d, J = 6 Hz, 2H, CH2);
13
C NMR (150
MHz, DMSO-d6): δ 187.38, 165.83, 149.32, 148.50, 142.53, 139.11, 138.90, 137.62, 136.68,
RI PT
136.34, 135.88, 135.53, 131.80, 129.59, 127.41, 124.02, 123.56, 122.65, 122.04, 120.98, 117.33, 114.50, 113.67, 112.75, 40.97; ESI-MS: calcd for C27H19N5O2 ([M+H]+), 446.2; found, 446.4. 1-(1H-Indole-3-carbonyl)-N-(pyridin-2-ylmethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9k
SC
This compound was obtained following the above method as yellow powder, yield 81%, mp
M AN U
137-139 oC; IR (νmax, KBr, cm-1): 3215, 1648, 1597, 1570, 1515, 1460, 1335, 1300, 1233, 1121, 946, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.29 (s, 1H, NH), 12.25 (s, 1H, NH), 9.27 (t, J = 6 Hz, 1H, ArH), 9.12 (s, 1H, ArH), 9.05 (s, 1H, ArH), 8.60-8.55 (m, 2H, ArH), 8.49 (d, J = 6 Hz, 1H, ArH), 7.87-7.81 (m, 2H, ArH), 7.66-7.63 (m, 1H, ArH), 7.60-7.58 (m, 1H, ArH), 7.47 (d, J = 6 Hz,
TE D
1H, ArH), 7.37-7.29 (m, 4H, ArH), 4.78 (d, J = 6 Hz, 2H, CH2); 13C NMR (150 MHz, DMSO-d6): δ 187.39, 165.44, 158.32, 149.48, 142.57, 138.97, 138.46, 137.47, 137.34, 136.72, 131.91, 129.62, 127.48, 123.60, 122.69, 122.09, 121.61, 121.00, 117.26, 114.51, 113.70, 112.80, 44.76; ESI-MS:
EP
calcd for C27H19N5O2 ([M+H]+), 446.2; found, 446.4.
AC C
N-(4-Hydroxy-3-methoxybenzyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxami d 9l
This compound was obtained following the above method as bright yellow powder, yield 65%, mp 203-204 oC; IR (νmax, KBr, cm-1): 3286, 1651, 1599, 1514, 1490, 1424, 1355, 1274, 1114, 944, 742; 1H NMR (600 MHz, DMSO-d6) δ 12.24 (s, 1H, NH), 12.23 (s, 1H, NH), 9.10 (s, 1H, ArH), 8.95-8.92 (m, 2H, ArH), 8.82 (s, 1H, ArH), 8.53 (t, J = 6 Hz, 1H, ArH), 8.47 (d, J = 6 Hz, 1H, ArH), 7.85 (d, J = 7.8 Hz, 1H, ArH), 7.65-7.62 (m, 1H, ArH), 7.58-7.57 (m, 1H, ArH), 7.36-7.30 18
ACCEPTED MANUSCRIPT (m, 3H, ArH), 6.99 (d, J = 1.8 Hz, 1H, ArH), 6.85 (q, J = 6 Hz, 1H, ArH), 6.77 (d, J = 7.8 Hz, 1H, ArH), 4.55 (d, J = 6 Hz, 2H, CH2), 3.74 (s, 3H, OCH3); 13C NMR (150 MHz, DMSO-d6): δ 187.43, 165.39, 147.90, 145.85, 142.54, 139.36, 138.61, 137.52, 136.68, 136.30, 131.84, 131.07, 129.57,
RI PT
127.40, 123.57, 122.65, 122.04, 120.98, 120.95, 120.09, 117.25, 115.88, 114.54, 113.66, 112.77, 112.22, 56.04, 42.98; ESI-MS: calcd for C29H22N4O4 ([M+H]+), 491.2; found, 491.4.
N-(4-Fluorophenyl)-1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9m
SC
This compound was obtained following the above method as bright yellow powder, yield 61%, mp
M AN U
130-132 oC; IR (νmax, KBr, cm-1): 3422, 1652, 1600, 1508, 1425, 1234, 1122, 938, 832, 739; 1H NMR (600 MHz, DMSO-d6) δ 12.35 (s, 1H, NH), 12.27 (s, 1H, NH), 10.47 (s, 1H, NH), 9.18 (s, 1H, ArH), 9.11 (d, J = 6 Hz, 1H, ArH), 8.56-8.51 (m, 2H, ArH), 7.95-7.92 (m, 2H, ArH), 7.88 (d, J = 6 Hz, 1H, ArH), 7.65 (t, J = 6 Hz, 1H, ArH), 7.60-7.58 (m, 1H, ArH), 7.38-7.25 (m, 5H, ArH); C NMR (150 MHz, DMSO-d6): δ 187.17, 164.08, 142.58, 138.99, 138.74, 137.21, 136.61,
TE D
13
136.45, 135.68, 132.12, 127.49, 123.56, 122.70, 122.44, 122.39, 121.98, 120.92, 117.62, 115.87, 115.73, 114.54, 113.69, 112.84; ESI-MS: calcd for C27H17FN4O2 ([M+H]+), 449.1; found, 449.4.
EP
1-(1H-Indole-3-carbonyl)-N-(4-methoxyphenyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9n
AC C
This compound was obtained following the above method as turquoise powder, yield 67%, mp 132-133 oC; IR (νmax, KBr, cm-1): 3291, 1655, 1597, 1509, 1491, 1437, 1338, 1301, 1229, 1155, 1122, 1032, 960, 743; 1H NMR (600 MHz, DMSO-d6) δ 12.33 (s, 1H, NH), 12.29 (s, 1H, NH), 10.27 (s, 1H, NH), 9.17 (s, 1H, ArH), 9.10 (s, 1H, ArH), 8.55-8.50 (m, 2H, ArH), 7.88-7.81 (m, 3H, ArH), 7.67-7.59 (m, 2H, ArH), 7.38-7.30 (m, 3H, ArH), 7.00-6.98 (m, 2H, ArH), 3.78 (s, 3H, OCH3);
13
C NMR (150 MHz, DMSO-d6): δ 187.30, 163.63, 163.11, 159.09, 149.77, 142.64,
139.23, 138.59, 137.15, 136.62, 136.43, 132.34, 132.13, 129.75, 127.52, 123.57, 122.70, 122.03, 19
ACCEPTED MANUSCRIPT 121.08, 120.97, 117.46, 115.42, 114.98, 114.55, 114.40, 113.74, 112.85, 55.73; ESI-MS: calcd for C28H20N4O3 ([M+H]+), 461.2; found, 461.3. 1-(1H-Indole-3-carbonyl)-N-(2-(methylsulfonyl)ethyl)-9H-pyrido[3,4-b]indole-3-carboxamide 9o
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This compound was obtained following the above method as yellow powder, yield 71%, mp 141-143 oC; IR (νmax, KBr, cm-1): 3384, 1652, 1599, 1514, 1491, 1424, 1297, 1123, 946, 744; 1H NMR (600 MHz, DMSO-d6) δ 12.26 (s, 1H, NH), 12.17 (s, 1H, NH), 9.09 (s, 1H, ArH), 8.97 (s,
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1H, ArH), 8.82-8.79 (m, 1H, ArH), 8.58-8.54 (m, 1H, ArH), 8.48 (d, J = 12 Hz, 1H, ArH), 7.86 (d,
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J = 6 Hz, 1H, ArH), 7.65-7.57 (m, 2H, ArH), 7.36-7.28 (m, 3H, ArH), 3.91 (q, J = 6 Hz, 2H, CH2), 3.51 (t, J = 9 Hz, 2H, CH2Ph), 3.14 (s, 3H, CH3);
13
C NMR (150 MHz, DMSO-d6): δ 187.29,
165.40, 142.55, 139.02, 138.72, 137.48, 136.73, 136.40, 131.86, 129.70, 127.45, 123.54, 122.68, 122.03, 121.00, 117.23, 114.36, 113.70, 112.83, 53.71, 46.16, 33.69; ESI-MS: calcd for
Methyl
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C24H20N4O4S ([M+H]+), 461.1; found, 461.3.
2-(1-(1H-indole-3-carbonyl)-9H-pyrido[3,4-b]indole-3-carboxamido)-3-hydroxypropanoate 9p
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This compound was obtained following the above method as yellow powder, yield 52%, mp
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191-193 oC; IR (νmax, KBr, cm-1): 3397, 2927, 1725, 1599, 1510, 1460, 1425, 1275, 1120, 960, 741; 1H NMR (600 MHz, DMSO-d6) δ 12.34 (s, 1H, NH), 12.31 (s, 1H, NH), 9.12 (s, 1H, ArH), 8.94 (d, J = 3 Hz, 1H, ArH), 8.75 (d, J = 8.4 Hz, 1H, ArH), 8.56-8.55 (m, 1H, ArH), 8.50 (d, J = 7.8 Hz, 1H, ArH), 7.87 (d, J = 8.4 Hz, 1H, ArH), 7.72-7.59 (m, 3H, ArH), 7.37-7.31 (m, 3H, ArH), 4.79-4.76 (m, 1H, CH), 4.00-3.97 (m, 1H, CH2), 3.91-3.89 (m, 1H, CH2), 3.75 (s, 3H, OCH3); 13C NMR (150 MHz, DMSO-d6): δ 187.22, 171.62, 164.81, 142.62, 138.14, 137.76, 137.18, 136.72, 136.49, 132.07, 129.70, 129.14, 127.44, 123.64, 122.75, 122.06, 121.09, 120.98, 117.21, 114.51, 20
ACCEPTED MANUSCRIPT 113.75, 112.88, 62.04, 55.06, 52.77; ESI-MS: calcd for C25H20N4O5 ([M+H]+), 457.1; found, 457.4.
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4.5. In vitro cytotoxicity assays
The in vitro cytotoxicities of the prepared β-carboline amide derivatives against several cell lines
(SGC-7901,
A875,
HepG2,
and
MARC145)
were
evaluated
using
the
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3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay [37-39].
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Acknowledgment
This work was supported by National Key R&D Program of China (2017YFD0200502) and the Program for Leading Talents of Hubei Academy of Agricultural Sciences (HAAS), and the authors also thank the partial support from Hubei Agricultural Science Innovation Centre
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Solvent- and catalyst-free synthesis and their inhibition activities against cell proliferation,
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Figure captions:
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Table 1 Chemical structure of target β-carboline amide derivatives Table 2 Growth-inhibitory activity for target compounds Table 3 Cytotoxic activities (IC50s) of the compounds against various cell lines Fig. 1. Representative natural β-carboline alkaloids. Fig. 2. Design strategy of β-carboline analogues derived from natural pityriacitrin. Fig. 3. Dose-response analysis of cell growth inhibition activity for compounds 9e, 9l, 9o, 9p and 5-FU (positive control) against SGC-7901 cells (upper left), A875 cells (upper right), HepG2 cells (lower left) and MARC145 cells (lower right). Fig. 4. General structure-activity relationships for target β-carboline derivatives. Scheme 1. Synthesis of β-carboline amide derivatives 9a-p. Reagents and conditions: a. SeO2, Dioxane/H2O; b. p-MePhSO3H, MeOH, 60 oC; c. SOCl2, MeOH; d. Compd 1, I2, DMSO; e. PhCH2CH2NH2, Dioxane, Reflux; f. 2N NaOH, MeOH, rt; g. NH2(CH2)nR, HOBt, EDCI, Et3N, DMF, rt.
27
ACCEPTED MANUSCRIPT
Research highlights: 1. Novel carboline analogues derived from marine alkaloid pityriacitrin 2. Good cytotoxic activities compared with the reference drug
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3. The SARs analyses have been fully investigated