4- And 5-aroylindoles as novel classes of potent antitubulin agents

Article abstract of DOI:10.1021/jm070557q

A novel series of 4- and 5-aroylindole derivatives was prepared and evaluated for antitumor activity. Several compounds showed excellent antiproliferative activity as inhibitors of tubulin polymerization. Compounds 13,14,15, and 18, with IC₅₀ v

Full text of DOI:10.1021/jm070557q

4548
J. Med. Chem. 2007, 50, 4548-4552
4- and 5-Aroylindoles as Novel Classes of Potent Antitubulin Agents
Jing-Ping Liou,† Chang-Ying Wu,† Hsing-Pang Hsieh,¶ Chi-Yen Chang,‡ Chi-Ming Chen,† Ching-Chuan Kuo,‡ and
Jang-Yang Chang*,‡,§
College of Pharmacy, Taipei Medical UniVersity, Taipei 110, Taiwan, Republic of China, DiVision of Biotechnology and Pharmaceutical
Research, National Health Research Institutes, Miaoli, Taiwan, Republic of China, Institute of Cancer Research, National Health Research
Institutes, Taipei 114, Taiwan, Republic of China, and DiVison of Hematology/Oncology, Department of Internal Medicine,
Tri-SerVice General Hospital, National Defense Medical Center, Taipei 114, Taiwan, Republic of China
ReceiVed May 13, 2007
A novel series of 4- and 5-aroylindole derivatives was prepared and evaluated for antitumor activity. Several
compounds showed excellent antiproliferative activity as inhibitors of tubulin polymerization. Compounds
13, 14, 15, and 18, with IC50 values of 1.9, 1.1, 1.2, and 1.8 µM, respectively, exhibited more potent inhibition
of tubulin polymerization than colchicine. They also displayed antiproliferative activity, with IC50 values
ranging from 10 to 43 nM in a variety of human cell lines from different organs.
Introduction
One of the recognized targets in oncology is represented by
microtubules.1 Microtubule-targeting agents such as taxanes and
vinca alkaloids have played a central role in the treatment of
diverse human cancers over the past decade.2 However, many
clinically useful chemotherapy drugs face substantial limitations,
such as drug resistance, high systemic toxicity, complex
syntheses, and isolation procedures. This has encouraged
scientists to develop new antimitotic agents. Recent research
reported compounds targeting the colchicine-binding domain
can act as vascular-disrupting agents, rapidly depolymerizing
microtubules of newly formed vasculatures to block the blood
supply to tumors,3 for example, drug candidates 2, 3, and 5
(Figure 1).
The encouraging antivascular/anticancer activity of compound
Figure 1.
2 has stimulated significant interest in a number of diverse
ligands designed and prepared to mimic combretastatins,4 for
Results and Discussion
instance, z-aminostilbene,5 benzophenone,6 benzothiophene,7
benzofuran,8 indole,9 indazole,10 carbazole,11 thiophene,12 and
indolinone13 moieties. Numbers of indole-containing compounds
demonstrate strong antiproliferative and antitubulin activity.9,14
Analysis of these combretastatin A-4 analogues or derivatives
shows that the 3,4,5-trimethoxybenzoyl group or 3,4,5-tri-
methoxyphenyl group seems to play an important role for
activity in this series. On the basis of these observations, we
attempted to explore the structure-activity relationships between
the indoles moiety and the aroyl group. Using the indole skeleton
as a motif coupled with the 3,4,5-trimethoxybenzoyl group at
different positions provided the regioisomers of aroylindoles
and allowed evaluation of bioactivity. We herein describe the
synthesis and structure-activity relationships of 4- and 5-aroylin-
doles as potent antitubulin agents in continuation of our search
for anticancer agents (Figure 2).
Chemistry. The general method for the synthesis of aroylin-
doles 6-21 is depicted in Scheme 1. The 1-aroylindole,
compound 6, was synthesized by treating indole with 3,4,5-
trimethoxybenzoyl chloride in the presence of KOt-Bua in 85%
yield. The preparation of 2-, 3-, 4-, 5-, 6-, and 7-aroylindoles
(7-12) involved a four-step reaction sequence, with an overall
yield of 30-41%. N1-protection of various commercially
available indole-carboxyaldehydes (23-28) with benzenesulfo-
nyl chloride yielded the corresponding indole-1-sulfonamides.
These sulfonamides were subjected to a Grignard reaction with
(3,4,5-trimethoxyphenyl) magnesium bromide followed by
pyridinium dichromate (PDC) oxidation, and the reaction
sequence was completed by NaOH-mediated deprotection to
afford the desired aroylindoles 7-12. The N1-alkyl-substituted
compounds 13-17 were synthesized in 65-86% yields from
compound 9 or 10 by allowing them to react with the
corresponding alkyl halide at room temperature, utilizing KOt-
Bu as base. Compound 18, with a hydroxymethyl group at the
N1-position, was prepared in 82% yield by treatment of
compound 10 with KOt-Bu in THF, followed by stirring with
37% formaldehyde at room temperature. The 1-alkylcarboxylic
* To whom correspondence should be addressed. J. Y. Chang, Institute
of Cancer Research, National Health Research Institutes, Room 7111, 7F,
National Defense Medical Center, 161, Min-Chuan East Road, Sec. 6, Taipei
114, Taiwan. Phone: 886-2-2653-4401 ext. 25110. Fax: 886-2-2792-9654.
E-mail: jychang@nhri.org.tw.
† College of Pharmacy, Taipei Medical University.
¶ Division of Biotechnology and Pharmaceutical Research, National
Health Research Institutes.
a Abbreviations: KOt-Bu, potassium tert-butoxide; PDC, pyridinium
dichromate; CH3CN, acetonitrile; Cs2CO3, cesium carbonate; DMF, N,N-
dimethylformamide; THF, tetrahydrofuran; MDR, multidrug-resistant;
LiOH, lithium hydroxide.
‡ Institute of Cancer Research, National Health Research Institutes.
§ Divison of Hematology/Oncology, Department of Internal Medicine,
Tri-Service General Hospital, National Defense Medical Center.
10.1021/jm070557q CCC: $37.00 © 2007 American Chemical Society
Published on Web 08/08/2007

Brief Articles
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4549
Scheme 1a
Figure 2.
acids 19 and 20 were obtained through a two-step synthesis.
Treatment of compound 10 with potassium tert-butoxide, KI,
and methyl bromoacetate in CH3CN at reflux followed by
hydrolysis with LiOH in MeOH afforded the desired 19 in 65%
yield (two steps). Michael addition of compound 10 to methyl
acrylate at room temperature in the presence of Cs2CO3 followed
by hydrolysis with LiOH/MeOH obtained the 1-(3-propanoic
acid)-5-aroylindole 20 in 74% yield (two steps). Compound 10
was treated with 2-dimethylaminoethyl chloride hydrochloride
in DMF in the presence of KOt-Bu and KI to afford the N1-
alkylamino-substituted compound 21 in 48% yield.
Biological Evaluation. (A) In Vitro Cell Growth Inhibitory
Activity. The synthesized aroylindoles 6-21 were evaluated
for their antiproliferative activities against five types of human
cancer cell lines, oral epidermoid carcinoma KB cells, colorectal
carcinoma HT29 cells, non small cell lung carcinoma H460
cells, and two stomach carcinoma TSGH, MKN45 cells, as well
the MDR-positive cell line KB-VIN10, with overexpressed P-gp
170/MDR (Table 1).
We first evaluated the effect of the 3,4,5-trimethoxybenzoyl
group substitution on the indole ring for cytotoxic activity.
Compounds 6-12 with a 3,4,5-trimethoxybenzoyl group at the
C-1, C-2, C-3, C-4, C-5, C-6, and C-7 positions, respectively,
on the indole ring were evaluated for antiproliferative activity.
The SAR information indicates that the 3,4,5-trimethoxybenzoyl
group located at the C-4 or C-5 position of the indole ring
resulted in the best activity. Shifting the group to the C-6 or
C-7 position resulted in moderate activity, while changing to
a Reagents and conditions: (a) 3,4,5-trimethoxybenzoyl chloride, KOt-
Bu, THF, rt; (b) (i) NaOH, PhSO2Cl, Bu4NHSO4, CH2Cl2, rt; (ii) (3,4,5-
trimethoxyphenyl)magnesium bromide, 0-25 °C; (iii) pyridinium dichro-
mate (PDC), CH2Cl2, molecular sieves, rt; (iv) 3N NaOH, EtOH,
reflux; (c) alkyl halide or HCHO, KOt-Bu, THF, rt; (d) (i) methyl
bromoacetate, KOt-Bu, KI, CH3CN, reflux; (ii) LiOH, MeOH, H2O, reflux;
(e) (i) ethyl acrylate, Cs2CO3, CH3CN, rt; (ii) LiOH, MeOH, H2O, reflux;
(f) 2-dimethylaminoethyl chloride hydrochloride, KOt-Bu, KI, DMF, 100-
120 °C.
the C1-C3 position decreased the activity drastically. Notably,
4-aroylindoles (9) and 5-aroylindoles (10), namely, 4-(3′,4′,5′-
trimethoxybenzoyl)indole and 5-(3′,4′,5′-trimethoxybenzoyl)-
indole, respectively, showed IC50 values of 46-112 nM against
five different human cancer cell lines, which was >2-fold more
potent than the 6- and 7-aroylindoles (compounds 11 and 12,
respectively) and >10-fold more potent than 1-, 2-, and
3-aroylindoles (compounds 6, 7, and 8, respectively). Interest-
ingly, the 3′,4′,5′-trimethoxybenzoyl group located on the
benzene part of the indole ring (C-4-C-7 positions) seems to
be preferable to its location on the pyrrole part of the indole
ring (C-1-C-3 position) (9, 10, 11, and 12 vs 6, 7, and 8). In
the 1-aroylindole and 3-aroylindole series, compound 6 and 8,
respectively, exhibit weak cytotoxicity with an IC50 value of
Table 1. IC50 Values (nM ( SDa) of Compounds 6-21 and Colchicine
cell type (IC50 nM ( SDa)
cmpd
KB
KB-vin10
H460
HT29
TSGH
MKN45
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
>10 000
2900 ( 150
1600 ( 110
50.7 ( 8
104 ( 15
510 ( 21
310 ( 25
22.1 ( 6
13.6 ( 1
36 ( 1
1900 ( 120
1800 ( 240
39 ( 7
520 ( 69
>10 000
5200 ( 380
12 ( 2
>10 000
2800 ( 120
1500 ( 70
51.4 ( 2
111 ( 6
>10 000
2100 ( 250
1700 ( 70
53.8 ( 7
112 ( 12
520 ( 120
295 ( 19
28.8 ( 3
14.1 ( 1
38 ( 4
2000 ( 520
1600 ( 120
39 ( 6
530 ( 77
>10 000
5100 ( 620
19 ( 3
9600 ( 510
1700 ( 280
1000 ( 120
46.4 ( 4
8400 ( 350
1800 ( 320
1100 ( 130
54.4 ( 6
5200 ( 420
1500 ( 80
980 ( 90
49.1 ( 8
88 ( 11
480 ( 22
210 ( 11
21.6 ( 4
11.2 ( 3
31 ( 4
680 ( 33
470 ( 51
33 ( 4
396 ( 38
>10 000
2900 ( 320
13 ( 1
100 ( 7
103 ( 8
452 ( 8
330 ( 18
250 ( 24
22.4 ( 4
10.5 ( 2
32 ( 6
1800 ( 350
1200 ( 210
34 ( 3
460 ( 58
>10 000
4600 ( 310
430 ( 31
310 ( 18
26.9 ( 3
13.4 ( 2
41 ( 3
1500 ( 180
1100 ( 320
43 ( 8
548 ( 81
>10 000
4900 ( 610
284 ( 12
26.1 ( 2
12.5 ( 3
40 ( 2
2100 ( 480
1600 ( 150
35 ( 4
476 ( 16
>10 000
4900 ( 210
120 ( 4
colchicine
a SD: standard deviation. All experiments were independently performed at least three times.

4550 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Brief Articles
Table 2. Inhibition of Tubulin Polymerization and Colchicine Binding
by Compounds 9-10, 13-15, 18, Colchicine, and CA4
1-10 µM, but their activity could be significantly improved to
the nanomolar range by the introduction of methoxy groups at
the C-5 and C-6 positions of the indole moiety, respectively.9a
A similar phenomenon was also observed in the case of the
2-aroylindole (7) series, where the introduction of a methoxy
group at the C-5 position resulted in improvement of IC50 values
tubulina
colchicine bindingb
cmpd
IC50 ( SD (µM)
(% ( SD)
9
10
13
14
15
18
2.0 ( 0.2
2.2 ( 0.3
1.9 ( 0.2
1.1 ( 0.1
1.2 ( 0.3
1.8 ( 0.2
2.9 ( 0.4
1.3 ( 0.2
74 ( 3
71 ( 4
75 ( 3
84 ( 2
81 ( 3
78 ( 4
9b
to the nM level.
On the basis of these results, that the 5-aroylindole core
demonstrating substantial antiproliferative activity, the N1-
substituted 5-aroylindoles, compounds 14-21, were synthesized
and evaluated for activity. To understand the steric effect of
alkyl substituents at the N1-position of 5-aroylindoles, the
methyl-, ethyl-, propyl-, and isopropyl-substituted compounds
14, 15, 16, and 17, respectively, were prepared. Compound 14,
with a methyl group, displayed an apparent increase in activity
with a mean IC50 value of 12 nM, being 8-10-fold more potent
than the parent compound. However, compound 15, with an
ethyl group, retained substantial cytotoxicity, but a further
increase in the bulkiness of the substituent resulted in a drastic
decrease in potency to the micromolecular range, thus revealing
that the steric effect of the substitutions at the N1-position of
5-aroylindoles influences cell growth inhibitory activities. The
potency improvement by adding a methyl group at the N1-
position observed in the 5-aroylindole series intrigued us to
explore whether the 4-aroylindoles also exhibit this effect. A
resemblance in the 4-aroylindole series showed that compound
13, with an additional methyl group as compared to parent 9,
demonstrated an increased growth inhibition by a 1-2-fold
magnitude in all six cell lines. Notably, compound 13 displayed
IC50 values of 21-29 nM in five human cancer cells. In an
attempt to increase the polarity of this series structure, com-
pounds 18, 19, 20, and 21, with hydroxy, carboxylic acid, and
amine functionalities, were prepared and evaluated for their cell
growth inhibitory activity. The SAR data revealed that the
activity of compounds with a polar group at the N1-position of
a 5-aroylindole seems to be correlated with the steric effect.
Compound 18, with a methyl alcohol substitution, showed
substantially increased antiproliferative activity, with an IC50
value of 34-43 nM against five human cancer cell lines, and
was comparable to the 1-ethyl-5-(3′,4′,5′-trimethoxybenzoyl)-
indole (15). The N1-alkylcarboxylic acid-substituted compounds
19 and 20, modified with methylcarboxylic acid and ethyl
carboxylic acid groups, displayed decreased antiproliferative
activity relative to 10. The ethanoic acid derivative 19 was 5-fold
less potent than the parent, while the propanoic acid derivative
20 showed a dramatic loss of activity. The 2-(N,N-dimethyl-
amino)ethyl substitution at the N1-position of parent (10) gave
compound 21, which resulted in decreased activity to micro-
molar IC50 values.
colchicine
CA4
89 ( 2
a Inhibition of tubulin polymerization.15 b Inhibition of [3H] colchicine
binding.15,16 Tubulin was at 1 µM and both [3H]colchicine and inhibitor
were at 5 µM.
in Table 2 revealed that 4- and 5-aroylindoles derivatives were
bound to the colchicine binding site.
Conclusion
The 4- and 5-aroylindole derivatives have been identified as
a novel class of potent antitubulin agents acting through the
colchicine binding site on microtubules. The lead compound
14 exhibits antiproliferative activity, with IC50 values ranging
from 10 to 15 nM in a diverse set of human cancer cell lines
from different organs, including the MDR-positive resistant line
(KB-vin10). It also demonstrates greater antitubulin activity than
colchicine and comparable activity to combretastatin A-4. The
SAR information indicated that the 3,4,5-trimethoxybenzoyl
substituent at position-4 or -5 of the indole ring contributed to
a significant extent to maximal activity, rather than the other
positions, such as positions 1-3 and 6-7 (9 and 10 vs 6, 7, 8,
11, and 12). Adding a methyl group at the N1-position in the
4- and 5-aroylindoles increases potency in both series (13 and
14). But a further increase in the bulkiness of the N1-position
of 5-aroylindoles resulted in a tendency to decrease activity (16,
17, 19, and 20 vs 10). In summary, 4-aroylindoles (13) and
5-aroylindoles (14, 15, and 18) constitute a strong antimitotic
agent with the potential to be further investigation for cancer
treatment.
Experimental Section
General Procedure for the Preparation of 4- and 5-Aroylin-
doles (9, 10). 4-(3′,4′,5′-Trimethoxybenzoyl)indole (9). Benze-
nesulfonyl chloride (1.76 mL, 13.77 mmol) was added slowly to a
well-stirred suspension of 4-formylindole (25) (1 g, 6.88 mmol),
potassium hydroxide (1.16 g, 20.66 mmol), and tetra-n-butylam-
monium hydrogen sulfate (0.23 g, 0.68 mmol) in CH2Cl2 (20 mL)
at room temperature. After 18 h, the reaction mixture was quenched
with saturated NaHCO3 (30 mL) and extracted with EtOAc (3 ×
20 mL). The combined organic layers were dried over MgSO4 and
evaporated in vacuum to give a residue, which was purified by
silica gel chromatography (ethyl acetate/n-hexane ) 1:1) to afford
the N1-phenylsulfonamide-indoles product. The N1-sulfonamide
compound was dissolved in THF (20 mL) and cooled to 0 ˚C with
stirring. A solution of 3,4,5-trimethoxyphenylmagnesium bromide
(10.33 mL, 1.0 M in THF, prepared in advance) was added dropwise
to the reaction mixture over 10 min with vigorous stirring for 1 h.
The mixture was quenched with ice water, neutralized with saturated
NH4Cl solution, and extracted with EtOAc (15 mL × 2) and CH2-
Cl2 (15 mL × 2). The combined organic extracts was dried over
MgSO4 and evaporated to give a crude residue, which was dissolved
in CH2Cl2 (60 mL). Molecular sieves (4 Å, 5.2 g) and pyridinium
dichromate (5.20 g, 13.78 mmol) were added to the reaction mixture
with stirring at room temperature for 16 h. The reaction mixture
was diluted with diethyl ether (40 mL) and stirred for another 1 h,
and then filtered through a pad of celite and washed three times by
(B) Inhibition of Tubulin Polymerization and Colchicine
Binding Activity. To investigate whether the 4- and 5-aroylin-
doles were tubulin inhibitors through the colchicine-binding
domain, compounds 9, 10, 13, 14, 15, 18, and reference
compounds (colchicine and combretastatin A-4) were evaluated
for antitubulin activities and colchicine binding activities (Table
2). The data showed that 4- and 5-aroylindoles have good
antitubulin activity and correlated with their cellular growth
inhibitory activity. As shown in Table 2, compounds 9, 10, 13-
15, 18 were effective in inhibiting tubulin assembly, with IC50
values of 2.0, 2.2, 1.9, 1.1, 1.2, and 1.8 µM, respectively. These
values were comparable or superior to the reference compounds,
combretastatin A-4 and colchicine (IC50 ) 1.3 and 2.9,
respectively). In the [3H] colchicine-competing assay, our data

Brief Articles
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18 4551
CH2Cl2 (50 mL). The filtrate was concentrated in vacuum, and the
residue was further treated with 3 N sodium hydroxide (23 mL,
68.88 mmol) in EtOH (30 mL) and heated at reflux for 16 h. The
solution was evaporated and extracted with EtOAc (20 mL × 2)
and CH2Cl2 (20 mL × 2). The combined organic layers were dried
and evaporated to give a residue that was purified by silica gel
flash column chromatography (ethyl acetate/n-hexane ) 1:1) and
recrystallized (CH2Cl2/EtOAc) to afford compound 9, yield 39%;
7.66 (d, J ) 8.4 Hz, 1H), 8.06 (s, 1H). 13C NMR (100 MHz, CDCl3)
δ 56.1, 60.9, 69.8, 104.1, 107.5, 109.4, 124.1, 124.9, 128.3, 129.0,
129.7, 133.7, 138.0, 141.3, 152.6, 196.8. MS (EI) m/z 341 (M+,
65%), 311 (100%). HRMS (EI) calcd for C19H19NO5 (M+),
341.1257; found, 341.1260. Anal. (C19H19NO5‚0.5H2O) C, H, N.
Acknowledgment. This research were supported by the
National Science Council of the Republic of China (Grant No.
NSC 95-2320-B-038-008 and NSC 95-2752-B-400-001-PAE),
and National Health Research Institutes, Taiwan (Grant No.
95A1CAPP06-1).
1
mp 94.8-95.2 ˚C. H NMR (400 MHz, CDCl3) δ 3.84 (s, 6H),
3.95 (s, 3H), 6.94 (m, 1H), 7.14 (s, 2H), 7.22 (t, J ) 8.0 Hz, 1H),
7.31 (t, J ) 2.8 Hz, 1H), 7.47 (d, J ) 7.6 Hz, 1H), 7.59 (d, J ) 7.6
Hz, 1H), 8.99 (s, 1H). 13C NMR (100 MHz, CDCl3) δ 56.1, 60.9,
103.1, 107.6, 115.5, 120.5, 124.0, 126.5, 127.2, 129.1, 134.0, 136.5,
141.5, 152.6, 196.6. MS (EI) m/z 311 (M+, 100%), 144 (95%),
116 (38%). HRMS (EI) calcd for C18H17NO4 (M+), 311.1162;
found, 311.1160. Anal. (C18H17NO4‚0.25H2O) C, H, N.
Supporting Information Available: Spectral data of com-
pounds 6-8, 11, 12, 16, 17, 19-21 and experimental procedures
for synthesis and biological evaluations. This material is available
free of charge via the Internet at http://pubs.acs.org.
5-(3′,4′,5′-Trimethoxybenzoyl)indole (10). The title compound
was obtained in 41% overall yield from 5-formylindole (26) and
3,4,5-trimethoxyphenylmagnesium bromide; mp 147.2-148.1 ˚C.
1H NMR (400 MHz, CDCl3) δ 3.85 (s, 6H), 3.94 (s, 3H), 6.62-
6.63 (m, 1H), 7.09 (s, 2H), 7.27-7.28 (m, 1H), 7.44 (d, J ) 8.4
Hz, 1H), 7.75 (dd, J ) 8.4, 1.5 Hz, 1H), 8.16 (s, 1H), 9.55 (s, 1H).
MS (EI) m/z 311 (M+, 100%), 195 (39%), 144 (90%). HRMS (EI)
calcd for C18H17NO4 (M+), 311.1145; found, 311.1151. Anal.
(C18H17NO4) C, H, N.
General Procedure for the Preparation of 1-Substituted
4- and 5-Aroylindoles Derivatives (13-15, 18). 1-Methyl-4-
(3′,4′,5′-trimethoxybenzoyl)indole (13). Potassium tert-butoxide
(0.36 g, 3.21 mmol) was added to a solution of 9 (0.5 g, 1.60 mmol)
in THF (20 mL) under vigorous stirring at room temperature.
Stirring was continued for 20 min followed by the addition of
iodomethane (0.5 mL, 8.03 mmol). After 3 h, the reaction mixture
was evaporated and extracted with EtOAc (15 mL × 2) and CH2-
Cl2 (15 mL × 2). The combined organic layers were dried over
MgSO4 and evaporated to give a residue, which was purified by
silica gel chromatography (ethyl acetate/n-hexane ) 1:3) to afford
compound 13, yield 86%; mp 105.2-106.7 ˚C. 1H NMR (400 MHz,
CDCl3) δ 3.85 (s, 6H), 3.86 (s, 3H), 3.94 (s, 3H), 6.85 (d, J ) 3.2
Hz, 1H), 7.13 (s, 2H), 7.19 (d, J ) 3.2 Hz, 1H), 7.27 (t, J ) 7.6
Hz, 1H), 7.47 (d, J ) 7.2 Hz, 1H), 7.55 (d, J ) 7.6 Hz, 1H). 13C
NMR (100 MHz, CDCl3) δ 33.0, 56.2, 60.9, 101.8, 107.6, 113.4,
120.2, 123.6, 127.8, 129.4, 130.9, 134.0, 137.3, 141.5, 152.7, 196.3.
MS (EI) m/z 325 (M+, 100%), 282 (17%), 158 (49%). HRMS (EI)
calcd for C19H19NO4 (M+), 325.1332; found, 325.1323. Anal.
(C19H19NO4) C, H, N.
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2006, 49, 5372-5376. (i) Zhang, Q, Peng, Y.; Wang, X. I.; Keenan,
S. M.; Arora, S.; Welsh, W. J. Highly Potent Triazole-Based
Tubulin Polymerization Inhibitors. J. Med. Chem. 2007, 50, 749-
754.
1-Methyl-5-(3′,4′,5′-trimethoxybenzoyl)indole (14). The title
compound was obtained in 84% yield from 10 and iodomethane;
1
mp 119.6-120.8 ˚C. H NMR (400 MHz, CDCl3) δ 3.84 (s, 3H),
3.84 (s, 6H), 3.94 (s, 3H), 6.60 (d, J ) 2.8 Hz, 1H), 7.08 (s, 2H),
7.14 (d, J ) 3.2 Hz, 1H), 7.39 (d, J ) 8.4 Hz, 1H), 7.79 (dd, J )
8.8, 1.6 Hz, 1H), 8.14 (d, J ) 1.6 Hz, 1H). 13C NMR (100 MHz,
CDCl3) δ 33.0, 56.2, 60.8, 102.8, 107.4, 108.9, 123.7, 125.0, 127.5,
129.1, 130.3, 134.1, 138.8, 141.1, 152.6, 196.3. MS (EI) m/z 325
(M+, 100%), 158 (43%). HRMS (EI) calcd for C19H19NO4 (M+),
325.1328; found, 325.1321. Anal. (C19H19NO4) C, H, N.
(5) Chang, J. Y.; Yang, M. F.; Chang, C. Y.; Chen, C. M.; Kuo, C. C.;
Liou, J. P. 2-Amino and 2′-Aminocombretastatin Derivatives as
Potent Antimitotic Agents. J. Med. Chem. 2006, 49, 6412-
6415.
1-Ethyl-5-(3′,4′,5′-trimethoxybenzoyl)indole (15). The title
compound was obtained in 76% yield from 10 and iodoethane; mp
(6) (a) Liou, J. P.; Chang, C. W.; Song, J. S.; Yeh, C. F.; Hung, H. H.;
Liu, S. H.; Hsieh, H. P. Synthesis and Structure-Activity Relation-
ship of 2-Aminobenzophenone Derivatives as Antimitotic Agents.
J. Med. Chem. 2002, 45, 2556-2562. (b) Liou, J. P.; Chang, J. Y.;
Chang, C. W.; Chang, C. Y.; Mahindroo, N.; Hsieh, H. P. Synthesis
and Structure-Activity Relationships of 3-Aminobenzophenones as
Antimitotic Agents. J. Med. Chem. 2004, 47, 2897-2905.
(7) (a) Romagnoli, R.; Baraldi, P. G.; Carrion, M. D.; Cara, C. L.; Preti,
D.; Fruttarolo, F.; Pavani, M. G.; Tabrizi, M. A.; Tolomeo, M.;
Grimaudo, S.; Cristina, A. D.; Balzarini, J.; Hadfield, J. A.; Brancale,
A.; Hamel, E. Synthesis and Biological Evaluation of 2- and
3-Aminobenzo[b]thiophene Derivatives as Antimitotic Agents and
Inhibitors of Tubulin Polymerization. J. Med. Chem. 2007, 50, 2273-
2277. (b) Pinney, K. G.; Bounds A. D.; Dingeman, K. M.; Mocharla,
V. P.; Pettit, G. R.; Bai, R.; Hamel, E. A New Anti-Tubulin Agent
Containing the Benzo[b]thiophene Ring System. Bioorg. Med. Chem.
Lett. 1999, 9, 1081-1086.
1
103.5-104.3 ˚C. H NMR (400 MHz, CDCl3) δ 1.50 (t, J ) 7.6
Hz, 3H), 3.87 (s, 6H), 3.94 (s, 3H), 4.22 (q, J ) 7.6 Hz, 2H), 6.60
(d, J ) 3.2 Hz, 1 H), 7.08 (s, 2H), 7.21 (d, J ) 3.2 Hz, 1H), 7.42
(d, J ) 8.8 Hz, 1H), 7.79 (dd, J ) 8.8, 1.6 Hz, 1H), 8.14 (d, J )
1.6 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ 15.4, 41.1, 56.2, 60.8,
102.9, 107.4, 109.0, 123.5, 125.2, 127.7, 128.6, 129.1, 134.1, 137.8,
141.1, 152.6, 196.2. MS (EI) m/z 339 (M+, 85%), 172 (100%).
HRMS (EI) calcd for C20H21NO4 (M+), 339.1463; found, 339.1467.
Anal. (C20H21NO4) C, H, N.
1-Hydroxymethyl-5-(3′,4′,5′-trimethoxybenzoyl)indole (18).
The title compound was obtained in 82% yield from 10 and 37%
1
formaldehyde; mp 162.1-163.2 ˚C. H NMR (400 MHz, CDCl3)
δ 3.82 (s, 6H), 3.93 (s, 3H), 5.65 (s, 2H), 6.57 (d, J ) 3.2 Hz, 1H),
7.02 (s, 2H), 7.26 (d, J ) 3.6 Hz, 1H), 7.48 (d, J ) 8.8 Hz, 1H),

4552 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 18
Brief Articles
(8) Flynn, B. L.; Hamel, E.; Jung, M. K. One-Pot Synthesis of Benzo-
[b]furan and Indole Inhibitors of Tubulin Polymerization. J. Med.
Chem. 2002, 45, 2670-2673.
(12) (a) Romagnoli, R.; Baraldi, P. G.; Pavani, M. G.; Tabrizi, M. A.;
Preti, D.; Fruttarolo, F.; Piccagli, L.; Jung, M. K.; Hamel, E.; Borgatti,
M.; Gambari, R. Synthesis and Biological Evaluation of 2-Amino-
3-(3′,4′,5′-trimethoxybenzoyl)-5-aryl Thiophenes as a New Class of
Potent Antitubulin Agents. J. Med. Chem. 2006, 49, 3906-3915.
(b) Cara, C.; Preti, D.; Fruttarolo, F.; Pavani, M. G.; Tabrizi, M. A.;
Tolomeo, M.; Grimaudo, S.; Balzarini, J.; Jordan, M. A.; Hamel, E.
Synthesis and Biological Evaluation of 2-(3′,4′,5′-Trimethoxyben-
zoyl)-3-amino-5-aryl Thiophenes as a New Class of Tubulin Inhibi-
tors. J. Med. Chem. 2006, 49, 6425-6428.
(13) Andreani, A.; Burnelli, S.; Granaiola, M.; Leoni, A.; Locatelli, A.;
Morigi, R.; Rambaldi, M.; Varoli, L.; Kunkel, M. W. Antitumor
Activity of Substituted E-3-(3,4,5-Trimethoxybenzylidene)-1,3-di-
hydroindol-2-ones. J. Med. Chem. 2006, 49, 6922-6924.
(14) Bacher, G.; Nickel, B.; Emig, P.; Vanhoefer, U.; Seeber, S.; Shandra,
A.; Klenner, T.; Beckers, T. D-24851, A Novel Synthetic Microtubule
Inhibitor, Exerts Curative Antitumoral Activity In Vivo, Shows
Efficacy Toward Multidrug-Resistant Tumor Cells and Lacks Neu-
rotoxicity. Cancer Res. 2001, 61, 392-399.
(15) Chang, J. Y.; Hsieh, H. P.; Chang, C. Y.; Hsu, K. S.; Chiang, Y. F.;
Chen, C. M.; Kuo, C. C.; Liou, J. P. 7-Aroyl-aminoindoline-1-
sulfonamides as a Novel Class of Potent Antitubulin Agents. J. Med.
Chem. 2006, 49, 6656-6659.
(9) (a) Liou, J. P.; Chang, Y. L.; Kuo, F. M.; Chang, C. W.; Tseng, H.
Y.; Wang, C. C.; Yang, Y. N.; Chang, J. Y.; Lee, S. J.; Hsieh, H. P.
Concise Synthesis and Structure-Activity Relationships of Com-
bretastatin A-4 Analogues, 1-Aroylindoles and 3-Aroylindoles, as
Novel Classes of Potent Antitubulin Agents. J. Med. Chem. 2004,
47, 4247-4257. (b) Mahboobi, S.; Pongratz, H.; Hufsky, H.;
Hockemeyer, J.; Frieser, M.; Lyssenko, A.; Paper, D. H.; Bu¨rger-
meister, J.; Bo¨hmer, F. D.; Fiebig, H. H.; Burger, A. M.; Baasner,
S.; Beckers, T. Synthetic 2-Aroylindole Derivatives as a New Class
of Potent Tubulin-Inhibitory Antimitotic Agents. J. Med. Chem. 2001,
44, 4535-4553. (c) Martino, G. D.; Edler, M. C.; Regina, G. L.;
Coluccia, A.; Barbera, M. C.; Barrow, D.; Nicholson, R. I.; Chiosis,
G.; Brancale, A.; Hamel, E.; Artico, M.; Silvestri, R. New Arylth-
ioindoles: Potent Inhibitors of Tubulin Polymerization. 2. Structure-
Activity Relationships and Molecular Modeling Studies. J. Med.
Chem. 2006, 49, 947-954. (d) Liou, J. P.; Mahindroo, N.; Chang,
C. W.; Guo, F. M.; Lee, S. W. H, Tan, U. K.; Yeh, T. K.; Kuo, C.
C.; Chang, Y. W.; Lu, P. H.; Tung, Y. S.; Lin, K. T.; Chang, J. Y.;
Hsieh, H. P. Structure-Activity Relationship Studies of 3-Aroylin-
doles as Potent Antimitotic Agents. ChemMedChem 2006, 1, 1106-
1118.
(10) Duan, J. X.; Meng, F.; Lan, L.; Hart, C.; Matteucci, M. Potent
Antitubulin Tumor Cell Cytotoxins Based on 3-Aroyl Indazoles. J.
Med. Chem. 2007, 50, 1001-1006.
(11) Hu, L.; Li, Z. R.; Li, Y.; Qu, J.; Ling, Y. H.; Jiang, J. D.; Boylin, D.
W. Synthesis and Structure-Activity Relationships of Carbazole
Sulfonamides as a Novel Class of Antimitotic Agents Against Solid
Tumors. J. Med. Chem. 2006, 49, 6273-6282.
(16) Kuo, C. C.; Hsieh, H. P.; Pan, W. Y.; Chen, C. P.; Liou, J. P.; Lee,
S. J.; Chang, Y. L.; Chen, L. T.; Chang, J. Y. BPR0L075, a Novel
Synthetic Indole Compound with Antitumoral Activity In Vivo.
Cancer Res. 2004, 64, 4621-4628.
JM070557Q