The preparation and evaluation of 1-substituted 1,2,3,4-tetrahydro- and 3,4-dihydro-β-carboline derivatives as potential antitumor agents

Article abstract of DOI:10.1248/cpb.53.32

A series of 1-substituted 1,2,3,4-tetrahydro- and 3,4-dihydro-β- carboline derivatives have been synthesized and evaluated for antitumor activity against murine P-388 and human tumor cell lines, KB-16, A-549 and HT-29. All of the compounds prepared, excep

Full text of DOI:10.1248/cpb.53.32

32
Chem. Pharm. Bull. 53(1) 32—36 (2005)
Vol. 53, No. 1
The Preparation and Evaluation of 1-Substituted 1,2,3,4-Tetrahydro- and
b
3,4-Dihydro- -carboline Derivatives as Potential Antitumor Agents
Ya-Ching SHEN,* Ching-Yeu CHEN, Pei-Wen HSIEH, Chang-Yih DUH, Yat-Min LIN, and Chin-Lien KO
Institute of Marine Resources, National Sun Yat-sen University; 70 Lien-Hai Rd., Kaohsiung, Taiwan, Republic of China.
Received June 17, 2004; accepted September 22, 2004
A series of 1-substituted 1,2,3,4-tetrahydro- and 3,4-dihydro-b-carboline derivatives have been synthesized
and evaluated for antitumor activity against murine P-388 and human tumor cell lines, KB-16, A-549 and HT-
29. All of the compounds prepared, except for 19, showed significant cytotoxicity. Among them, compound 29
exhibited the most potent activity against all tested tumor cell lines. There was an apparent lack of correlation
regarding cytotoxicity between 1,2,3,4-tetrahydro- and 3,4-dihydro-b-carbolines. This study is the first to dis-
cover compound 29 as a potential lead for the development of future anticancer agents. The mode of inhibition
for compound 29 was proposed.
Key words 1,2,3,4-tetrahydro-b-carboline; 3,4-dihydro-b-carboline; antitumor agent
Table 1 shows the biological results for compounds 4—29
and manzamine A (3) as tested against murine P-388
(leukemia) and human tumor cell lines, including KB-16
(nasopharyngeal carcinoma), A-549 (lung adenocarcinoma)
and HT-29 (colon adenocarcinoma) in vitro. All of the com-
pounds exhibited promising activity except for 19, which had
no activity toward the four tumor cell lines. Among them,
compound 29 exhibited the most potent activity against all
tested tumor cells. For P-388 inhibitory activity, compounds
8 and 29 were more potent than or comparable to 3. Com-
pounds 4, 12, 14, 15, 25 and 28 showed potent to moderate
activity. As for KB-16 cell cytotoxicity, compound 29 was
equal in potency to manzamine A (3). Compounds 8 and 21
have lower ID50 values, while the others were less active.
Compounds 12, 22 and 24 possessed specific inhibition
against A-549 and HT-29 tumor cells.
There was an apparent lack of correlation between 1,2,3,4-
tetrahydro-b-carbolines and 3,4-dihydro-b-carbolines in the
preliminary cytotoxicity tests. For example, comparison of
the biological data of compounds 6 and 19, as well as com-
pounds 16 and 29, revealed that B compounds (17—29) are
not always superior to A compounds (4—16). Both com-
pounds 29 and 19, which contain a 3,4-dihydro-b-carboline
skeleton showed notable difference in activity. The reason for
Marine natural products which contain a b-carboline
skeleton are widely distributed in marine invertebrates.1—3)
The discovery of natural b-carboline metabolites as potent
antitumor and antiviral agents has stimulated great interest in
the synthetic and pharmacological studies of b-carboline
derivatives.4—6) Particularly interesting targets include such
compounds as eudistomins7,8) and manzamines,9,10) which
were isolated from marine tunicates and sponges, respec-
tively. As a class, the oxathiazepine containing eudistomines
exhibited potent inhibitory activity toward DNA virus HSV-1.
In addition, the antiviral eudistomines C (1) and E (2) were
also found active against HSV-2, the Vaccinia virus and RNA
viruses.11) The novel structures of manzamines, however,
were reported to possess potent antitumor,12,13) antibacterial,
antifungal, and anti-HIV activities.14) The most active was
manzamine A (3), a principal metabolite from several species
of sponges, which showed cytotoxicity against murine P-388
cells at 0.07 mg/ml.15) Our previous report has revealed that
manzamine A—D and H exhibited potent cytotoxicities
against human KB-16, A-549 and HT-29 tumor cell lines.16)
The common b-carboline or 1,2,3,4-tetrahydro-b-carboline
moieties appear to be important for the biological activity.
In order to investigate the essential structural features for the
antitumor activity of manzamine A (3), the synthesis of
1-substituted 1,2,3,4-tetrahydro- and 3,4-dihydro-b-carboline
derivatives were initiated. The difficult isolation of manza-
mine A (3) from sponge and its limited source make this
current program more important and significant. A facile
synthetic method by the application of Pictet–Spengler reac-
tion17—20) and DDQ oxidation21) allowed the preparation of
compounds 4—29. Herein, we wish to report the preparation,
characterization and biological evaluation of 1-substituted
1,2,3,4-tetrahydro- and 3,4-dihydro-b-carboline derivatives.
Results and Discussion
As summarized in Chart 1, compounds 4—16 were syn-
thesized from tryptamine (I) and substituted benzaldehydes
via Pictet–Spengler cyclization. Subsequent oxidation of
1,2,3,4-tetrahydro-b-carbolines (4—16, A compounds) by
DDQ furnished 3,4-dihydro-b-carboline derivatives (17—29,
B compounds). The spectral data for 4—29 are illustrated in
Experimental.
Chart 1
∗ To whom correspondence should be addressed. e-mail: ycshen@mail.nsysu.edu.tw
© 2005 Pharmaceutical Society of Japan

January 2005
33
Table 1. Biological Evaluationa) of 1-Substituted 1,2,3,4-Tetrahydro-b-carboline and 3,4-Dihydro-b-carbolines
A
B
P-388
KB-16
A-549
HT-29
Compound
R
A
B
A
B
A
B
A
B
4
0.2
0.7
0.6
0.9
17
0.5
1.1
7.7
2.9
0.7
0.9
2.4
1.2
2.0
1.3
1.2
5
18
1.0
0.8
2.2
0.07
2.1
1.1
1.7
0.2
3.0
0.9
1.6
1.1
1.1
1.5
0.7
1.1
6
19
ꢀ50
ꢀ50
ꢀ50
7
20
4.8
0.3
50
3.0
1.3
8
21
1.8
9
22
0.6
2.8
0.7
1.1
0.8
0.6
2.7
2.7
0.5
0.5
2.7
10
23
ꢀ50
ꢀ50
ꢀ50
15
12
11
24
2.6
0.2
3.7
1.4
2.0
0.6
2.2
0.4
1.1
0.4
0.7
1.0
0.2
0.6
0.4
0.6
12
25
13
26
1.2
0.3
8.3
6.0
2.0
1.7
1.6
1.4
1.2
1.4
0.8
0.5
0.6
0.7
1.0
14
27
0.3
0.1
15
28
0.1
0.7
0.4
0.8
0.6
0.8
0.5
0.5
1.4
0.6
0.7
16
29
ꢁ0.001
ꢁ0.001
ꢁ0.001
ꢁ0.001
30 (paclitaxel)
3 (manzamineA)
ꢁ0.001
0.07
ꢁ0.001
ꢁ0.001
ꢁ0.001
0.03
ꢁ0.001
0.1
a) The concentration of compound inhibiting 50% (IC50, mg/ml) of the growth of tumor cell lines, P-388 (murine leukemia), KB-16 (human nasopharyngeal
carcinoma), A-549 (human lung adenocarcinoma) and HT-29 (human colon adenocarcinoma), after 3, 3, 6 and 6 d drug exposure. (— Not tested).
different degrees of activity might be explained by the differ- intercalate more easily with the DNA molecule, although
ences in bioavailability such as drug uptake and fate of there is no evidence to support this proposal.22) However,
metabolism. Compound 29 showed much better activity than recently the cytotoxic mechanism of 29 was first reported
that of 16, suggesting that the double bond between C-1 and and characterized as chromosome missegregation.23)
C-2 in 29 is critical in cytotoxicity. This double bond makes
Introducing the moiety of N-ethyl carbazole onto 3,4-dihy-
compound 29 into a planar structure, which may allow it to dro-b-carboline to give 29 seems to be a correct route to

34
Vol. 53, No. 1
reach the lead compound. However, stronger cytotoxicity (q, Me); HR-EI-MS m/z 291.1738 (Mꢄ, Calcd for C19H21N3, 291.1735).
1-(4ꢂ-N-Diethylphenyl)-1,2,3,4-tetrahydro-b-carboline (8): Pale yellow
may cause increased side effects and thus result in a lower
therapeutic index. Further biological evaluation of 1-substi-
tuted 1,2,3,4-tetrahydro- and 3,4-dihydro-b-carboline deriva-
tives as potential antitumor agents by application of mecha-
1
solid, mp 282—284 °C; H-NMR (300 MHz, CDCl3): d 5.04 (1H, s, H-1),
3.12 (1H, m, H-3a), 3.40 (1H, m, H-3b), 2.83 (2H, m, H-4), 7.15 (3H, over-
lap, H-5, 6, 7), 7.55 (1H, d, Jꢃ8.4 Hz, H-8), 8.05 (1H, s, H-9), 7.15 (2H, d,
Jꢃ9 Hz, H-2ꢂ, 6ꢂ), 6.63 (2H, d, Jꢃ9 Hz, H-3ꢂ, 5ꢂ), 1.17 (6H, t, Jꢃ7.1 Hz,
nism-based bioassay systems, such as the inhibition of CH2CH3), 3.35 (4H, q, Jꢃ7.1 Hz, CH2CH3); 13C-NMR (75 MHz, CDCl3):
d 57.3 (d, C-1), 42.7 (t, C-3), 22.4 (t, C-4), 109.3 (s, C-4a), 127.8 (s, C-4b),
121.3 (d, C-5), 119.0 (d, C-6), 118.0 (d, C-7), 110.8 (d, C-8), 1335.7 (s, C-
8a), 135.2 (s, C-9a), 127.4 (s, C-1ꢂ), 129.5 (d, C-2ꢂ, 6ꢂ), 111.6 (d, C-3ꢂ, 5ꢂ),
147.6 (s, C-4ꢂ), 12.5 (q, CH2CH3), 44.3 (t, CH2CH3); EI-MS m/z 319 (96,
Mꢄ), 318 (100), 290 (28), 289 (29), 276 (19), 275 (17), 274 (12), 260 (5),
245 (9), 219 (11), 218 (39), 217 (41), 216 (12), 204 (5), 189 (5), 171 (28),
169 (14), 160 (10), 144 (13), 143 (21), 137 (18), 130 (15), 123 (14), 109
(14); HR-EI-MS m/z 319.2045 (Mꢄ, Calcd for C21H25N3, 319.2048).
1-(2ꢂ,4ꢂ-Dimethoxylphenyl)-1,2,3,4-tetrahydro-b-carboline (9): Pale yel-
low solid; mp 210—213 °C; IR (KBr) nmax 3410, 2950, 1615, 1505, 1465,
human topoisomerase I and II and animal antitumor tests, is
currently under investigation.
Experimental
General Methods All mp’s were taken on a Buchi mp B-540 appratus
and are uncorrected. UV and IR spectra were taken on a Hitachi V-3210 and
JASCO A-100 IR spectrophotometers, respectively. EI-MS spectra were
obtained on a MAT 112S-JMS D300 spectrometer using direct inlet systems.
1H- and 13C-NMR spectra were recorded on a Varian FT-300 spectrometer.
Analytical thin-layer chromatography (TLC) was carried out on Kiesel gel
GF254 plates, and detection was made under UV light. EM Kieselgel 60
(230—400 mesh ASTM) was used for column chromatography.
Synthesis of Compounds 4—16 To a stirred solution of tryptamine
(1.6 g, 1 mmol) and the appropriate substituted aldehyde (1 mmol) in toluene
(30 ml) at room temperature was slowly added trifloroacetic acid (TFA,
2 ml). The reaction mixture was stirred at room temperature for 2 d. After
evaporation of the solvent under vacuum, the residue was chromatographed
on a Si gel column (60 g) and eluted with a solvent mixture of CHCl3/MeOH
by the following ratios and volumes (99 : 1, 98 : 2, 97 : 3, 96 : 4, 95 : 5; each
100 ml), to afford compounds 4—16 with a yield which varied in the range
of 30—50%.
1-(4ꢂ-Chlorophenyl)-1,2,3,4-tetrahydro-b-carboline (4): White solid; mp
165 °C; 1H-NMR (300 MHz, CDCl3): d 5.09 (1H, s, H-1), 3.11 (1H, m,
H-3a), 3.28 (1H, m, H-3b), 2.85 (2H, m, H-4), 7.17 (3H, overlap, H-5, 6, 7),
7.57 (1H, d, Jꢃ8.4 Hz, H-8), 7.87 (1H, s, NH-9), 7.20 (2H, d, Jꢃ7.8 Hz,
H-2ꢂ, 6ꢂ), 7.31 (2H, d, Jꢃ7.8 Hz, H-3ꢂ, 5ꢂ), 13C-NMR (75 MHz, CDCl3):
d 57.1 (d, C-1), 42.4 (t, C-3), 22.3 (t, C-4), 110.2 (s, C-4a), 133.7 (s, C-4b),
121.8 (d, C-5), 119.4 (d, C-6), 118.2 (d, C-7), 110.8 (d, C-8), 140.3 (s, C-8a),
135.9 (s, C-9a), 127.2 (s, C-1ꢂ), 129.8 (d, C-2ꢂ, 6ꢂ), 128.9 (d, C-3ꢂ, 5ꢂ), 133.9
(s, C-4ꢂ); EI-MS m/z 282 (100, Mꢄ), 281 (72), 255 (13), 254 (17), 253 (39),
252 (30), 219 (25), 218 (92), 217 (80), 189 (9), 171 (81), 169 (18), 154 (9),
144 (21), 143 (20), 130 (10), 123 (15), 115 (22), 109 (51); HR-EI-MS m/z
282.0926 (Mꢄ, Calcd for C17H15N2Cl, 282.0924).
1300, 1160, 1040, 835, 715 cmꢅ1 1H-NMR (300 MHz, CDCl3): d 5.54
;
(1H, s, H-1), 3.11 (1H, m, H-3a), 3.27 (1H, m, H-3b), 2.84 (2H, m, H-4),
7.23 (1H, d, Jꢃ6.8 Hz, H-5), 7.13 (2H, overlap, H-6, 7), 7.53 (1H, d,
Jꢃ6.8 Hz, H-8), 7.78 (1H, s, H-9), 6.53 (1H, d, Jꢃ2.4 Hz, H-3ꢂ), 6.37 (1H,
d, Jꢃ8.7, 2.4 Hz, H-5ꢂ), 6.93 (1H, d, Jꢃ8.7 Hz, H-6ꢂ), 3.79, 3.87 (6H,
s, OMe); 13C-NMR (75 MHz, CDCl3): d 50.6 (d, C-1), 42.0 (t, C-3), 22.5
(t, C-4), 110.1 (s, C-4a), 127.4 (s, C-4b), 121.4 (d, C-5), 119.2 (d, C-6),
118.0 (d, C-7), 110.7 (d, C-8), 135.7 (s, C-8a), 134.6 (s, C-9a), 122.3 (s, C-
1ꢂ), 98.8 (d, C-3ꢂ), 104.0 (d, C-5ꢂ), 110.7 (d, C-6ꢂ), 55.4, 55.6 (q, OMe); EI-
MS m/z 308 (100, Mꢄ), 307 (73), 279 (31), 278 (43), 264 (12), 249 (13),
248 (30), 233 (9), 217 (7), 204 (18), 191 (8.4), 171 (38), 154 (17), 143 (21),
130 (13), 115 (15), 102 (13), 95 (9), 77 (13), 69 (22); HR-EI-MS m/z
308.1523 (Mꢄ, Calcd for C19H20N2O2, 308.1526).
1-(3ꢂ,4ꢂ-Dimethoxylphenyl)-1,2,3,4-tetrahydro-b-carboline (10): Pale yel-
1
low solid; mp ꢀ300 °C; H-NMR (300 MHz, CDCl3): d 5.04 (1H, s, H-1),
3.10 (1H, m, H-3a), 3.32 (1H, m, H-3b), 2.89 (2H, m, H-4), 7.12 (3H, over-
lap, H-5, 6, 7), 7.56 (1H, d, Jꢃ5.7 Hz, H-8), 8.32 (1H, s, H-9), 6.80 (1H, H-
2ꢂ), 6.75 (1H, d, Jꢃ8.1 Hz, H-5ꢂ), 6.78 (1H, d, Jꢃ8.1 Hz, H-6ꢂ), 3.70 (3H, s,
3ꢂ-OMe), 3.84 (3H, s, 4ꢂ-OMe); 13C-NMR (75 MHz, CDCl3) d 57.9 (d, C-1),
42.9 (t, C-3), 22.3 (t, C-4), 109.7 (s, C-4a), 134.2 (s, C-4b), 121.4 (d, C-5),
120.5 (d, C-6), 119.0 (d, C-7), 111.2 (d, C-8), 135.8 (s, C-8a), 134.5 (s, C-
9a), 127.2 (s, C-1ꢂ), 110.8 (d, C-2ꢂ), 148.6 (s, C-3ꢂ), 149.0 (s, C-4ꢂ), 110.8
(d, C-5ꢂ), 118.0 (d, C-6ꢂ), 55.7, 55.6 (q, OMe); EI-MS m/z 308 (100, Mꢄ),
307 (82), 291 (9.4), 279 (19), 264 (8), 249 (15), 248 (43), 233 (9), 217 (9),
204 (20), 191 (11), 171 (64), 154 (20), 143 (16), 130 (9), 115 (12), 102 (14),
95 (9), 77 (8); HR-EI-MS m/z 308.1528 (Mꢄ, Calcd for C19H20N2O2,
308.1525).
1-(4ꢂ-Bromophenyl)-1,2,3,4-tetrahydro-b-carboline (5): Pale yellow solid,
1
mp 226—228 °C; C17H15N2Br; H-NMR (300 MHz, CDCl3): d 5.10 (1H, s,
H-1), 3.12 (1H, m, H-3a), 3.30 (1H, m, H-3b), 2.87 (2H, m, H-4), 7.18 (3H,
overlap, H-5, 6, 7), 7.65 (1H, d, Jꢃ6.9 Hz, H-8), 7.74 (1H, s, NH-9), 7.17
(2H, d, Jꢃ8.4 Hz, H-2ꢂ, 6ꢂ), 7.47 (2H, d, Jꢃ8.4 Hz, H-3ꢂ, 5ꢂ); 13C-NMR
(75 MHz, CDCl3): d 57.3 (d, C-1), 42.5 (t, C-3), 22.4 (t, C-4), 110.3 (s, C-
4a), 133.6 (s, C-4b), 121.9 (d, C-5), 119.4 (d, C-6), 118.2 (d, C-7), 110.8
(d, C-8), 140.8 (s, C-8a), 135.9 (s, C-9a), 127.2 (s, C-1ꢂ), 130.2 (d, C-2ꢂ, 6ꢂ),
131.8 (d, C-3ꢂ, 5ꢂ), 122.0 (s, C-4ꢂ); EI-MS m/z 328 (43), 327 (37, Mꢄ), 326
(48), 325 (34), 299 (17), 297 (18), 219 (28), 218 (100), 217 (93), 216 (30),
189 (9), 171 (64), 169 (17), 144 (19), 143 (21), 130 (15), 123 (27), 109 (55);
HR-EI-MS m/z 326.0418 (Mꢄ, Calcd for C17H15N2Br, 326.0420).
1-(2ꢂ,5ꢂ-Dimethoxylphenyl)-1,2,3,4-tetrahydro-b-carboline (11): Pale yel-
low solid; mp ꢀ300 °C; IR (KBr) nmax 3410, 2950, 1680, 1505, 1465, 1135,
1045, 750 cmꢅ1; 1H-NMR (300 MHz, CDCl3): d 5.64 (1H, s, H-1), 3.20 (1H,
m, H-3a), 3.32 (1H, m, H-3b), 2.88 (2H, m, H-4), 7.23 (1H, d, Jꢃ6.8 Hz, H-
5), 7.12 (2H, overlap, H-6, 7), 7.52 (1H, d, Jꢃ6.8 Hz, H-8), 7.85 (1H, s, H-
9), 6.90 (1H, d, Jꢃ8 Hz, H-3ꢂ), 6.83 (1H, dd, Jꢃ8, 2 Hz, H-4ꢂ), 6.71 (1H, d,
Jꢃ2 Hz, H-6ꢂ), 3.67, 3.81 (6H, s, OMe); 13C-NMR (75 MHz, CDCl3) d 51.2
(d, C-1), 42.0 (t, C-3), 21.8 (t, C-4), 109.8 (s, C-4a), 129.7 (s, C-4b), 121.7
(d, C-5), 119.3 (d, C-6), 118.1 (d, C-7), 110.8 (d, C-8), 127.1 (s, C-1ꢂ), 111.8
(d, C-3ꢂ), 113.6 (d, C-4ꢂ), 115.5 (d, C-6ꢂ), 55.7, 56.2 (q, OMe); EI-MS m/z
308 (100, Mꢄ), 307 (56), 292 (4), 279 (21), 264 (6), 249 (23), 248 (67), 233
(15), 217 (12), 204 (24), 191 (7.7), 171 (79), 169 (20), 154 (17), 144 (30),
1-(4ꢂ-Nitrophenyl)-1,2,3,4-tetrahydro-b-carboline (6): Yellow solid, mp
79 °C; 1H-NMR (300 MHz, CDCl3): d: 5.28 (1H, s, H-1), 3.17 (1H, m,
H-3a), 3.28 (1H, m, H-3b), 2.87 (2H, m, H-4), 7.27 (1H, d, Jꢃ7.5 Hz, H-5),
7.17 (2H, t, Jꢃ7.5 Hz, H-6, 7), 7.57 (1H, d, Jꢃ7.5 Hz, H-8), 7.87 (1H, s,
NH-9), 7.50 (2H, d, Jꢃ8.7 Hz, H-2ꢂ, 6ꢂ), 8.18 (2H, d, Jꢃ8.7 Hz, H-3ꢂ, 5ꢂ), 143 (27), 130 (18), 115 (18), 102 (15), 69 (39); HR-EI-MS m/z 308.1527
13C-NMR (75 MHz, CDCl3): d 57.1 (d, C-1), 42.2 (t, C-3), 22.4 (t, C-4),
(Mꢄ, Calcd for C19H20N2O2, 308.1525).
1-(3ꢂ,5ꢂ-Dimethoxylphenyl)-1,2,3,4-tetrahydro-b-carboline (12): Pale yel-
110.8 (s, C-4a), 127.1 (s, C-4b), 122.2 (d, C-5), 119.7 (d, C-6), 118.4 (d, C-
7), 110.9 (d, C-8), 147.6 (s, C-8a), 135.6 (s, C-9a), 136.0 (s, C-1ꢂ), 129.4 (d, low solid; mp 215—218 °C; IR (KBr) nmax 3420, 2910, 1605, 1465, 1350,
C-2ꢂ, 6ꢂ), 123.9 (d, C-3ꢂ, 5ꢂ), 149.3 (s, C-4ꢂ); EI-MS m/z 293 (82, Mꢄ), 292 1305, 1155, 1065, 845, 785 cmꢅ1; 1H-NMR (300 MHz, CDCl3): d 5.03 (1H,
(45), 264 (31), 247 (20), 218 (80), 217 (100), 216 (38), 204 (11), 189 (10),
171 (68), 169 (13), 154 (8), 144 (17), 143 (20), 130 (11), 115 (21), 109 (23);
HR-EI-MS m/z 293.1168 (Mꢄ, Calcd for C17H15N3O2, 293.1166).
s, H-1), 3.11 (1H, m, H-3a), 3.35 (1H, m, H-3b), 2.91 (2H, m, H-4), 7.15
(3H, overlap, H-5, 6, 7), 7.56 (1H, d, Jꢃ7 Hz, H-8), 8.13 (1H, s, H-9), 6.47
(2H, d, Jꢃ2.1 Hz, H-2ꢂ, 6ꢂ), 6.44 (1H, d, Jꢃ2.1 Hz, H-4ꢂ), 3.71 (6H,
s, OMe); 13C-NMR (75 MHz, CDCl3): d 58.3 (d, C-1), 43.0 (t, C-3), 22.3 (t,
C-4), 109.8 (s, C-4a), 127.3 (s, C-4b), 121.6 (d, C-5), 119.2 (d, C-6), 118.1
(d, C-7), 110.8 (d, C-8), 144.1 (s, C-8a), 135.8 (s, C-9a), 134.2 (s, C-1ꢂ),
106.5 (d, C-2ꢂ, 6ꢂ), 161.1 (s, C-3ꢂ, 5ꢂ), 100.0 (d, C-4ꢂ), 55.3 (q, OMe); EI-
MS m/z 308 (100, Mꢄ), 307 (64), 279 (38), 278 (37), 264 (11), 249 (17),
248 (30), 233 (10), 220 (9), 217 (9), 204 (21), 191 (10), 171 (85), 154 (13),
144 (17), 130 (10), 115 (16), 102 (13), 95 (9), 77 (10); HR-EI-MS m/z
308.1526 (Mꢄ, Calcd for C19H20N2O2, 308.1525).
1-(4ꢂ-N-Dimethylphenyl)-1,2,3,4-tetrahydro-b-carboline (7): Pale yellow
1
solid, mp 235—237 °C; H-NMR (300 MHz, CDCl3): d 5.11 (1H, s, H-1),
3.14 (1H, m, H-3a), 3.44 (1H, m, H-3b), 2.84 (2H, m, H-4), 7.56 (1H, d,
Jꢃ7.0 Hz, H-5), 7.14 (2H, overlap, H-6, 7), 7.75 (1H, d, Jꢃ7.5 Hz, H-8),
7.17 (2H, d, Jꢃ8.4 Hz, H-2ꢂ, 6ꢂ), 6.69 (2H, d, Jꢃ8.4 Hz, H-3ꢂ, 5ꢂ), 2.95 (6H,
s, Me); 13C-NMR (75 MHz, CDCl3) d 53.0 (d, C-1), 41.2 (t, C-3), 25.9
(t, C-4), 113.2 (s, C-4a), 127.2 (s, C-4b), 122.1 (d, C-5), 119.5 (d, C-6),
118.8 (d, C-7), 112.0 (d, C-8), 136.4 (s, C-8a), 132.9 (s, C-9a), 122.1
(s, C-1ꢂ), 127.4 (d, C-2ꢂ, 6ꢂ), 112.9 (d, C-3ꢂ, 5ꢂ), 149.4 (s, C-4ꢂ), 40.7
1-(3ꢂ,4ꢂ,5ꢂ-Trimethoxylphenyl)-1,2,3,4-tetrahydro-b-carboline (13): Pale

January 2005
35
1
yellow solid, mp 161 °C; H-NMR (300 MHz, CDCl3): d 5.85 (1H, s, H-1),
3.59 (1H, m, H-3a), 3.68 (1H, m, H-3b), 3.29 (2H, m, H-4), 7.32 (1H, d,
Jꢃ8 Hz, H-5), 7.16 (1H, t, Jꢃ8 Hz, H-6), 7.11 (1H, Jꢃ8 Hz, H-7), 7.55 (1H,
d, Jꢃ8 Hz, H-8), 6.73 (2H, s, H-2ꢂ, 6ꢂ), [3.71 (9H, s, OMe)]; 13C-NMR
(75 MHz, CDCl3): d 56.1 (d, C-1), 41.7 (t, C-3), 51.5 (t, C-4), 109.4 (s, C-
4a), 126.7 (s, C-4b), 122.4 (d, C-5), 119.7 (d, C-6), 118.4 (d, C-7), 111.1 (d,
C-8), 136.2 (s, C-8a), 133.3 (s, C-9a), 128.6 (s, C-1ꢂ), 106.1 (d, C-2ꢂ, 6ꢂ),
153.4 (s, C-3ꢂ, 5ꢂ), 153.8 (s, C-4ꢂ), 56.1 (q, 3ꢂ, 5ꢂ-OMe), 60.7 (q, 4ꢂ-OMe);
EI-MS m/z 338 (100, Mꢄ), 337 (67), 309 (17), 279 (14), 278 (39), 262 (6.7),
247 (9), 234 (7.8), 219 (6.9), 204 (6.7), 191 (10), 180 (12), 171 (69), 169
(24), 154 (13), 144 (20), 130 (11), 115 (15), 109 (12), 77 (11), 69 (54); HR-
EI-MS m/z 338.1629 (Mꢄ, Calcd for C20H22N2O3, 338.1630).
292.1085 (MꢄHꢄ, Calcd for C17H14N3O2, 292.1086).
1-(4ꢂ-N-Dimethylphenyl)-3,4-dihydro-b-carboline (20): Yellow solid, mp
1
150 °C; H-NMR (300 MHz, CD3OD): d 3.94 (2H, t, Jꢃ7.8 Hz, H-3), 3.31
(2H, overlap, H-4), 7.55 (1H, d, Jꢃ8.4 Hz, H-5), 7.21 (1H, t, Jꢃ7.5 Hz, H-
6), 7.40 (1H, t, Jꢃ7.5 Hz, H-7), 7.75 (1H, d, Jꢃ8.1 Hz, H-8), 7.81 (2H, d,
Jꢃ9.0 Hz, H-2ꢂ, 6ꢂ), 6.94 (2H, d, Jꢃ9.0 Hz, H-3ꢂ, 5ꢂ), 3.16 (6H, s, NMe2);
HR-EI-MS m/z 289.1581 (Mꢄ, Calcd for C19H19N3, 289.1578).
1-(4ꢂ-N-Diethylphenyl)-3,4-dihydro-b-carboline (21): Yellow solid, mp
244—246 °C; 1H-NMR (300 MHz, CDCl3): d 3.83 (2H, dd, Jꢃ7.8, 15.3 Hz,
H-3), 3.09 (2H, t, Jꢃ7.2, 15.0 Hz, H-4), 7.62 (1H, d, Jꢃ8.4 Hz, H-5), 7.20
(1H, t, Jꢃ7.8 Hz, H-6), 7.38 (1H, t, Jꢃ7.8 Hz, H-7), 7.68 (1H, d, Jꢃ7.8 Hz,
H-8), 10.6 (1H, br s, NH-9), 7.94 (2H, d, Jꢃ9.0 Hz, H-2ꢂ, 6ꢂ), 6.55 (2H,
d, Jꢃ9.0 Hz, H-3ꢂ, 5ꢂ), 1.08 (6H, t, Jꢃ6.9 Hz, CH2CH3), 3.23 (4H,
q, Jꢃ6.9 Hz, CH2CH3); HR-EI-MS m/z 317.1889 (Mꢄ, Calcd for C19H18N3,
317.1892).
1-(6ꢂ-Nitro-1ꢂ-piperoyl)-1,2,3,4-tetrahydro-b-carboline (14): Yellow solid,
mp 267 °C; H-NMR (300 MHz, CDCl3): d 5.66 (1H, s, H-1), 3.17 (1H, m,
1
H-3a), 3.25 (1H, m, H-3b), 2.89 (2H, m, H-4), 7.23 (1H, d, Jꢃ7.6 Hz, H-5),
7.16 (2H, overlap, H-6, 7), 7.56 (1H, d, Jꢃ7.6 Hz, H-8), 8.04 (1H, s, H-9),
6.77 (1H, s, H-2ꢂ), 7.39 (1H, s, H-5ꢂ), 6.01 (2H, d, Jꢃ4.2 Hz, OCH2O); 13C-
NMR (75 MHz, CDCl3): d 52.4 (d, C-1), 42.0 (t, C-3), 22.1 (t, C-4), 111.1
(s, C-4a), 127.0 (s, C-4b), 122.0 (d, C-5), 119.5 (d, C-6), 118.3 (d, C-7),
110.9 (d, C-8), 136.0 (s, C-8a), 134.1 (s, C-9a), 132.6 (s, C-1ꢂ), 109.9 (d, C-
2ꢂ), 151.7 (s, C-3ꢂ), 147.3 (s, C-4ꢂ), 104.9 (s, C-5ꢂ), 143.7 (s, C-6ꢂ), 102.9 (t,
OCH2O); EI-MS m/z 337 (6, Mꢄ), 335 (6.7), 320 (9), 319 (70), 303 (56),
290 (93), 289 (100), 275 (6), 261 (24), 244 (11), 232 (13), 216 (9), 204 (33),
203 (19), 191 (18), 171 (20), 151 (18), 144 (32), 130 (53), 115 (50), 102
(52), 101 (22), 89 (20), 77 (25); HR-EI-MS m/z 337.1066 (Mꢄ, Calcd for
C18H15N3O4, 337.1064).
1-(2ꢂ,4ꢂ-Dimethoxylphenyl)-3,4-dihydro-b-carboline (22): Yellow solid,
mp 165—168 °C; 1H-NMR (300 MHz, CDCl3): d 4.07 (2H, t, Jꢃ8.4 Hz,
H-3), 3.10 (2H, t, Jꢃ8.4 Hz, H-4), 7.54 (1H, d, Jꢃ8.4 Hz, H-5), 7.41 (1H,
dd, Jꢃ8.4 Hz, H-6), 7.34 (1H, t, Jꢃ8.4 Hz, H-7), 7.63 (1H, d, Jꢃ8.4 Hz,
H-8), 6.53 (1H, d, Jꢃ1.8 Hz, H-3ꢂ), 6.57 (1H, d, Jꢃ7.2, 1.8 Hz, H-5ꢂ), 7.19
(1H, d, Jꢃ7.2 Hz, H-6ꢂ), 3.82, 3.84 (6H, s, OMe); HR-EI-MS m/z 306.1365
(Mꢄ, Calcd for C19H18N2O2, 306.1368).
1-(3ꢂ,4ꢂ-Dimethoxylphenyl)-3,4-dihydro-b-carboline (23): Yellow solid,
mp 288—290 °C; 1H-NMR (300 MHz, CDCl3): d 3.98 (2H, t, Jꢃ7.8 Hz,
H-3), 2.96 (2H, t, Jꢃ7.8 Hz, H-4), 7.40 (1H, d, Jꢃ8.4 Hz, H-5), 7.20 (1H,
d, Jꢃ8.4 Hz, H-6), 7.66 (1H, d, Jꢃ8.4 Hz, H-8), 7.30 (1H, d, Jꢃ1.8 Hz,
H-2ꢂ), 6.86 (1H, d, Jꢃ7.8 Hz, H-5ꢂ), 7.15 (1H, d, Jꢃ7.8 Hz, H-6ꢂ), 3.77,
3.82, 3.84 (6H, s, OMe); HR-EI-MS m/z 306.1366 (Mꢄ, Calcd for
C19H18N2O2, 306.1368).
1-(2ꢂ,5ꢂ-Dimethoxylphenyl)-1,2,3,4-dihydro-b-carboline (24): Yellow
solid, mp 175—176 °C; 1H-NMR (300 MHz, CDCl3): d 4.11 (2H, t,
Jꢃ8.6 Hz, H-3), 2.99 (2H, t, Jꢃ8.6 Hz, H-4), 7.34 (1H, d, Jꢃ8.1 Hz, H-5),
7.27 (1H, t, Jꢃ7.4 Hz, H-6), 7.15 (1H, t, Jꢃ7.4 Hz, H-7), 7.63 (1H, d,
Jꢃ8.1 Hz, H-8), 8.50 (1H, br s, H-9), 7.00 (2H, s, H-3ꢂ, 4ꢂ), 7.06 (1H, s,
H-6ꢂ), 3.81 (6H, s, OMe); HR-EI-MS m/z 306.1370 (Mꢄ, Calcd for
C19H18N2O2, 306.1368).
1-(3ꢂ,5ꢂ-Dimethoxylphenyl)-3,4-dihydro-b-carboline (25): Yellow solid,
mp 111—113 °C; 1H-NMR (300 MHz, CDCl3): d 4.05 (2H, t, Jꢃ8.4 Hz, H-
3), 2.98 (2H, t, Jꢃ8.4 Hz, H-4), 7.37 (1H, d, Jꢃ8.1 Hz, H-5), 7.18 (1H, t,
Jꢃ7.5 Hz, H-6), 7.31 (1H, t, Jꢃ7.5 Hz, H-7), 7.66 (1H, d, Jꢃ8.1 Hz, H-8),
8.38 (1H, s, H-9), 6.88 (2H, d, Jꢃ2.1 Hz, H-2ꢂ, 6ꢂ), 6.58 (1H, dd, Jꢃ2.4,
2.1 Hz, H-4ꢂ), 3.83 (6H, s, OMe); HR-ESI-MS m/z 307.1450 (MꢄHꢄ,
Calcd for C19H19N2O2, 307.1447).
1-(2ꢂ-Fluorenyl)-1,2,3,4-tetrahydro-b-carboline (15): Yellow solid; mp
ꢀ300 °C; IR (KBr) nmax 3540, 2990, 1680, 1710, 1465, 745 cmꢅ1; 1H-NMR
(300 MHz, CDCl3): d 5.23 (1H, s, H-1), 3.17 (1H, m, H-3a), 3.41 (1H, m,
H-3b), 2.94 (2H, m, H-4); 13C-NMR (75 MHz, CDCl3): d 58.3 (d, C-1), 43.0
(t, C-3), 22.6 (t, C-4), 110.2 (s, C-4a), 127.5 (s, C-4b), 121.7 (d, C-5), 119.4
(d, C-6), 118.3 (d, C-7), 110.9 (d, C-8), 143.9 (s, C-8a), 134.8 (s, C-9a),
125.1 (s, C-1ꢂ), 135.9 (s, C-2ꢂ), 125.1 (d, C-3ꢂ), 120.0 (d, C-4ꢂ), 141.2 (s, C-
4ꢂa), 141.8 (s, C-4ꢂb), 120 (d, C-5ꢂ), 126.9 (d, C-6ꢂ), 126.8 (d, C-7ꢂ), 125.1
(d, C-8ꢂ), 143.5 (s, C-8ꢂa), 36.9 (t, C-9ꢂ); EI-MS m/z 336 (100, Mꢄ), 335
(87), 334 (60), 307 (73), 306 (86), 304 (50), 292 (14), 171 (52), 152 (55),
143 (26), 115 (28); HR-EI-MS m/z 336.1626 (Mꢄ, Calcd for C24H20N2,
336.1625).
1-(9ꢂ-Ethyl-3ꢂ-carbazole)-1,2,3,4-tetrahydro-b-carboline (16): Yellow
solid; mp 242 °C; IR (KBr) nmax 3470, 2930, 1465, 1390, 750 cmꢅ1 1H-
;
NMR (300 MHz, CDCl3): d 6.04 (1H, s, H-1), 3.56 (1H, m, H-3a), 3.66 (1H,
m, H-3b), 3.18 (1H, m, H-4a), 3.28 (1H, m, H-4b); 13C-NMR (CDCl3)
d 59.2 (d, C-1), 42.3 (t, C-3), 19.8 (t, C-4), [110.2 (s, C-4a), 127.5 (s, C-4b),
121.7 (d, C-5), 119.4 (d, C-6), 118.3 (d, C-7), 110.9 (d, C-8), 143.9 (s, C-8a),
125.1 (s, C-1ꢂ), 135.9 (s, C-2ꢂ), 125.1 (d, C-3ꢂ), 120.0 (d, C-4ꢂ), 141.2 (s, C-
4ꢂa), 141.8 (s, C-4ꢂb), 120 (d, C-5ꢂ), 126.9 (d, C-6ꢂ), 126.8 (d, C-7ꢂ), 125.1
(d, C-8ꢂ), 143.5 (s, C-8ꢂa), 36.9 (t, C-9ꢂ)]; EI-MS m/z 365 (100, Mꢄ), 364
(8), 336 (46), 335 (45), 319 (8), 306 (18), 223 (5.7), 208 (7.3), 183 (18), 171
(39), 160 (51), 153 (18), 144 (15), 130 (5), 115 (11); HR-EI-MS m/z
365.1897 (Mꢄ, Calcd for C25H23N3, 365.1894).
1-(3ꢂ,4ꢂ,5ꢂ-Trimethoxylphenyl)-3,4-tetrahydro-b-carboline (26): Yellow
solid, mp 251 °C; 1H-NMR (300 MHz, CDCl3): d 4.06 (2H, dd, Jꢃ8.1,
16.5 Hz, H-3), 3.01 (2H, dd, Jꢃ8.1, 16.5 Hz, H-4), 7.43 (1H, d, Jꢃ8.1 Hz,
H-5), 7.22 (1H, dd, Jꢃ8.1, 7.8 Hz, H-6), 7.36 (1H, t, Jꢃ7.8 Hz, H-7), 7.69
(1H, d, Jꢃ7.8 Hz, H-8), 8.28 (1H, br s, H-9), 6.99 (2H, s, H-2ꢂ, 6ꢂ), 3.92
(9H, s, OMe); HR-EI-MS m/z 336.1476 (Mꢄ, Calcd for C20H20N2O3,
336.1473).
Synthesis of Compounds 17—29 To a stirred solution of compound A
(4—16, 0.03 mmol) in EtOH (1 ml) and CHCl3 (3 ml) at room temperature
was added 2,3-dichloro-5,6-dicyanobezoquinone (DDQ, 40 mg). The reac-
tion mixture was stirred for 30 min. After concentration, the residue was
subjected to prep. TLC and developed with CHCl3/MeOH (10 : 1) to yield
compound B (17—29, 30—75%).
1-(6ꢂ-Nitro-1ꢂ-piperoyl)-3,4-dihydro-b-carboline (27): Yellow solid, mp
1
191—193 °C; H-NMR (300 MHz, CDCl3): d 4.08 (2H, t, Jꢃ8.6 Hz, H-3),
3.06 (2H, t, Jꢃ8.6 Hz, H-4), 7.30 (1H, overlap, H-5), 7.20 (2H, overlap, H-
6, 7), 7.65 (1H, d, Jꢃ7.8 Hz, H-8), 8.11 (1H, s, H-9), 6.94 (1H, s, H-2ꢂ),
7.63 (1H, s, H-5ꢂ), 6.19 (2H, s, OCH2O); HR-EI-MS m/z 335.0903 (Mꢄ,
Calcd for C18H13N3O4, 335.0907).
1-(4ꢂ-Chlorophenyl)-3,4-dihydro-b-carboline (17): Yellow solid, mp
1-(2ꢂ-Fluorenyl)-3,4-dihydro-b-carboline (28): Yellow solid, mp 121—
123 °C; 1H-NMR (300 MHz, CDCl3): d 3.03 (2H, t, Jꢃ7.8 Hz, H-3), 4.09
(2H, t, Jꢃ7.8 Hz, H-4), 3.99 (2H, s, H-9ꢂ), 7.20 (1H, t), 7.35 (1H, t), 7.40
(3—4H, m), 7.58 (1H, d), 7.66 (1H, d, Jꢃ7.8 Hz), 7.80 (1H, d), 7.83 (1H,
d), 7.88 (1H, d, Jꢃ8 Hz), 8.00 (1H, s); HR-EI-MS m/z 334.1468 (Mꢄ,
Calcd for C24H18N2, 334.1471).
1
102—104 °C; H-NMR (300 MHz, CDCl3): d 4.06 (2H, t, Jꢃ8.3 Hz, H-3),
2.99 (2H, t, Jꢃ8.3 Hz, H-4), 7.39 (1H, d, Jꢃ7.7 Hz, H-5), 7.32 (1H, dd,
Jꢃ7.7, 7.2 Hz, H-6), 7.20 (1H, dd, Jꢃ7.8, 7.2 Hz, H-7), 7.67 (1H, d,
Jꢃ7.8 Hz, H- 8), 8.04 (1H, s, NH-9), 7.49 (2H, d, Jꢃ8.6 Hz, H-2ꢂ, 6ꢂ), 7.71
(2H, d, Jꢃ8.6 Hz, H-3ꢂ, 5ꢂ); HR-EI-MS m/z 280.0764 (Mꢄ, Calcd for
C17H13N2Cl, 280.0767).
1-(9ꢂ-Ethyl-3ꢂ-carbazole)-3,4-dihydro-b-carboline (29): Yellow solid, mp
1
1-(4ꢂ-Bromophenyl)-3,4-dihydro-b-carboline (18): Yellow solid, mp
175—177 °C; H-NMR (300 MHz, CDCl3): d 3.01 (2H, m, H-3), 2.60 (2H,
1
102—104 °C; H-NMR (300 MHz, CDCl3): d 4.05 (2H, t, Jꢃ7.6 Hz, H-3),
m, H-4), 1.41 (3H, t, Jꢃ7.2 Hz, CH2CH3), 4.32 (2H, q, Jꢃ7.2 Hz, CH2CH3),
7.0—7.6 (m), 8.00 (1H, d), 8.11 (1H, s); HR-EI-MS m/z 363.1724 (Mꢄ,
Calcd for C25H21N3, 363.1735).
2.98 (2H, t, Jꢃ7.6 Hz, H-4), 7.39 (1H, d, Jꢃ8.0 Hz, H-5), 7.31 (1H, d,
Jꢃ8.0 Hz, H-6), 7.20 (1H, t, Jꢃ7.2 Hz, H-7), 7.60 (1H, d, Jꢃ7.2 Hz, H-8),
8.00 (1H, s, NH-9), 7.47 (4H, s, H-2ꢂ, 3ꢂ, 5ꢂ, 6ꢂ); HR-EI-MS m/z 325.0342
(Mꢄ, Calcd for C17H13N2Br, 325.0340).
Biological Assay The cytotoxic activities of compounds against P-388,
KB-16, A-549, and HT-29 cells were assayed by the MTT {3-(4,5-di-
methylthiazole-2-yl)-2,5-diphenyltetrazolium bromide} colorimetric assay
with some modifications.24) Each cell line was plated at 1000 cells/well in
96-well microtiter plates. Two-fold serial dilutions of tested compounds
were added to the cells, and P-388, KB-16, A549, and HT29 cells were enu-
merated using MTT after 3, 3, 6 and 6 d, respectively. MTT (50 ml, 1 mg/ml)
1-(4ꢂ-Nitrophenyl)-3,4-dihydro-b-carboline (19): Yellow solid, mp 211—
213 °C; 1H-NMR (300 MHz, CDCl3): d 4.12 (2H, t, Jꢃ8.6 Hz, H-3), 2.99
(2H, t, Jꢃ8.6 Hz, H-4), 7.41 (1H, d, Jꢃ7.7 Hz, H-5), 7.34 (1H, t, Jꢃ7.8 Hz,
H-6), 7.22 (1H, t, Jꢃ7.8 Hz, H-7), 7.68 (1H, d, Jꢃ7.8 Hz, H-8), 7.95 (2H, d,
Jꢃ8.4 Hz, H-2ꢂ, 6ꢂ), 8.37 (2H, d, Jꢃ8.4 Hz, H-3ꢂ, 5ꢂ); HR-ESI-MS m/z

36
Vol. 53, No. 1
was added to each well, and the plates were incubated at 37 °C for 5 h. For-
mazan crystals were redissolved in DMSO (Merck) for 10 min with shaking,
and plates were then immediately read on a microtiter plate reader (Dynat-
ech) at 540 nm. The ID50 was defined as the concentration of test compound
resulting in a 50% reduction of absorbance compared to untreated cells in
the MTT assay. Manzamine A (3) and Paclitaxel (30) were used as standard
compounds. Results are given in Table 1.
13567—13574 (1994).
10) Sakai R., Kohmoto S., Higa T., Jefford C. W., Bernardinelli G., Tetra-
hedron Lett., 28, 5493—5496 (1987).
11) Munro M. H. G., Luibrand R. T., Blunt J. W., “Bioorganic Marine
Chemstry,” Vol. I, ed. by Scheuer P. J., Springer-Verlag, N.Y., 1987,
pp. 103—105.
12) Ichiba T., Sakai R., Kohmoto S., Saucy G., Higa T., Tetrahedron Lett.,
29, 3083—3086 (1988).
Acknowledgments We thank Ms. Ho Chao Lein and Yu Shiu Ching of
the NSC Southern NMR and MS Instrument Center for measurement of
NMR an MS spectral data. This research was supported by grants from the
National Science Council, Republic of China (NSC 85-2321-B110-003 BH)
and by the National Institute of Health, Republic of China ( DOH 86-HR-
509) awarded to Y.-C.S.
13) Higa T., “Studies in Natural Product Chemistry,” Vol. 5, Part B, ed. by
Atta-Ur-Rahman, Elsevier Co., New York, 1989, pp. 346—353.
14) Yousaf M., Hammond N. L., Peng J., Wahyuono S., McIntosh K. A.,
Charman W. N., Mayer A. M. S., Hamann M. T., J. Med. Chem., 47,
3512—3517 (2004).
15) Sakai R., Higa T., Jefford C. W., Bernardinelli G., J. Am. Chem. Soc.,
108, 6404—6405 (1986).
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