Synthesis and biological evaluation of indole-based, anti-cancer agents inspired by the vascular disrupting agent 2-(3′-hydroxy-4′- methoxyphenyl)-3-(3″,4″,5″-trimethoxybenzoyl)-6-methoxyindole (OXi8006)

Article abstract of DOI:10.1016/j.bmc.2013.07.028

The discovery of a 2-aryl-3-aroyl indole-based small-molecule inhibitor of tubulin assembly (referred to as OXi8006) inspired the design, synthesis, and biological evaluation of a series of diversely functionalized analogues. In the majority of examples, the pendant 2-aryl ring contained a 3-hydroxy-4-methoxy substitution pattern, and the fused aryl ring featured a 6-methoxy group. Most of the variability was in the 3-aroyl moiety, which was modified to incorporate methoxy (33-36), nitro (25-27), halogen (28-29), trifluoromethyl (30), or trifluoromethoxy (31-32) functionalities. In two analogues (34 and 36), the methoxy substitution pattern in the fused aryl ring varied, while in another derivative (35) the phenolic moiety was translocated from the pendant 2-aryl ring to position-7 of the fused aryl ring. Each of the compounds were evaluated for their cytotoxicity (in vitro) against the SK-OV-3 (ovarian), NCI-H460 (lung), and DU-145 (prostate) human cancer cell lines and for their ability to inhibit tubulin assembly. Four of the compounds (30, 31, 35, 36) proved to be potent inhibitors of tubulin assembly (IC₅₀ <5 μM), and three of these compounds (31, 35, 36) were strongly cytotoxic against the three cancer cell lines. The most active compound (36) in this series, which incorporated a methoxy group at position-7, was comparable in terms of inhibition of tubulin assembly and cytotoxicity to the lead compound OXi8006.

Full text of DOI:10.1016/j.bmc.2013.07.028

Accepted Manuscript
Synthesis and biological evaluation of indole-based, anti-cancer agents inspired
by the vascular disrupting agent 2-(3′-hydroxy-4′-methoxyphenyl)-3-(3′ ′,4′ ′,
5′ ′-trimethoxybenzoyl)-6-methoxyindole (OXi8006)
Matthew T. MacDonough, Tracy E. Strecker, Ernest Hamel, John J. Hall, David
J. Chaplin, Mary Lynn Trawick, Kevin G. Pinney
PII:
S0968-0896(13)00648-2
DOI:
http://dx.doi.org/10.1016/j.bmc.2013.07.028
BMC 10992
Reference:
To appear in:
Bioorganic & Medicinal Chemistry
Received Date:
Revised Date:
Accepted Date:
16 May 2013
3 July 2013
11 July 2013
Please cite this article as: MacDonough, M.T., Strecker, T.E., Hamel, E., Hall, J.J., Chaplin, D.J., Trawick, M.L.,
Pinney, K.G., Synthesis and biological evaluation of indole-based, anti-cancer agents inspired by the vascular
disrupting agent 2-(3′-hydroxy-4′-methoxyphenyl)-3-(3′ ′,4′ ′,5′ ′-trimethoxybenzoyl)-6-methoxyindole
(OXi8006), Bioorganic & Medicinal Chemistry (2013), doi: http://dx.doi.org/10.1016/j.bmc.2013.07.028
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Synthesis and biological evaluation of indole-based, anti-cancer
agents inspired by the vascular disrupting agent 2-(3 -hydroxy-4 -
methoxyphenyl)-3-(3 ,4 ,5 -trimethoxybenzoyl)-6-methoxyindole
(OXi8006)
Matthew T. MacDonough,a Tracy E. Strecker,a Ernest Hamel,b John J. Hall,a David J.
Chaplin,c Mary Lynn Trawick,a and Kevin G. Pinneya*
a Department of Chemistry and Biochemistry, Baylor University, One Bear Place #97348,
Waco, Texas, 76798-7348, USA
b Screening Technologies Branch, Developmental Therapeutics Program, Division of
Cancer Treatment and Diagnosis, National Cancer Institute, Frederick National
Laboratory for Cancer Research, National Institutes of Health, Frederick, Maryland,
21702, USA
c Oxigene Inc., 701 Gateway Boulevard, Suite 210, South San Francisco, California,
94080, USA
*Corresponding Author. Tel: +1-254-710-4117 Fax +1-254-710-4272. E-mail:
Kevin_Pinney@baylor.edu.
1 of 48

ABSTRACT.
The discovery of a 2-aryl-3-aroyl indole-based small-molecule inhibitor of tubulin
assembly (referred to as OXi8006) inspired the design, synthesis, and biological
evaluation of a series of diversely functionalized analogues. In the majority of examples,
the pendant 2-aryl ring contained a 3-hydroxy-4-methoxy substitution pattern, and the
fused aryl ring featured a 6-methoxy group. Most of the variability was in the 3-aroyl
moiety, which was modified to incorporate methoxy (33-36), nitro (25-27), halogen (28-
29), trifluoromethyl (30), or trifluoromethoxy (31-32) functionalities. In two analogues
(34 and 36), the methoxy substitution pattern in the fused aryl ring varied, while in
another derivative (35) the phenolic moiety was translocated from the pendant 2-aryl ring
to position-7 of the fused aryl ring. Each of the compounds were evaluated for their
cytotoxicity (in vitro) against the SK-OV-3 (ovarian), NCI-H460 (lung), and DU-145
(prostate) human cancer cell lines and for their ability to inhibit tubulin assembly. Four
of the compounds (30, 31, 35, 36) proved to be potent inhibitors of tubulin assembly (IC50
< 5 M), and three of these compounds (31, 35, 36) were strongly cytotoxic against the
three cancer cell lines. The most active compound (36) in this series, which incorporated
a methoxy group at position-7, was comparable in terms of inhibition of tubulin assembly
and cytotoxicity to the lead compound OXi8006.
Keywords: Vascular disrupting agent (VDA), inhibitor of tubulin assembly,
functionalized indole, combretastatin.
2 of 48

1. Introduction
The exploration and assessment of the tumor microenvironment and its
physiology have revealed a number of prospective molecular targets for selective
therapeutic intervention by small-molecule anti-cancer agents. A well-established target
is the dynamic tubulin-microtubule protein system. Microtubules are structurally
characterized as biopolymers composed of -tubulin heterodimers.1-5 The dynamic
assembly and disassembly of microtubules is linked to a variety of cellular functions,
including cell shape, intracellular motility, cellular division, and apoptosis.1-5 More
recently, certain small-molecule inhibitors of tubulin assembly have been identified as
vascular disrupting agents (VDAs).6 These compounds selectively disrupt tumor
vasculature by interfering with the tubulin-microtubule protein system of the endothelial
cells lining tumor microvessels, which sets in motion a cascade of cell signaling events
leading to morphology changes (rounding up) of these endothelial cells. This results in
the occlusion of the vessels, which limits tumor blood flow. This in turn restricts the
oxygen and nutrients vital for tumor survival. The vascular network feeding tumors is
distinct from normal tissue vasculature and incorporates branching that is often
unsystematic and convoluted.7-9 In addition, increased rates of tumor cell proliferation
coupled with underdeveloped endothelium, in contrast to normal tissue vasculature, has
established tumor vasculature as a selective therapeutic target for anti-cancer agents.9
This approach has led to the development of a class of therapeutics referred to as vascular
targeting agents (VTAs). This class is further subdivided into two discrete sub-classes
centered upon distinct mechanism(s) of action: vascular disrupting agents (VDAs) and
angiogenesis inhibiting agents (AIAs).10 VDAs damage existing tumor vasculature while
AIAs impede new tumor vessel formation.10-12 VDAs can be further divided into two
3 of 48

distinct groups: biologics and small-molecules. One strategy focuses on the development
of indole-based small-molecule VDAs that bind at the colchicine site, named after the
natural product originally described as binding at the site (Figure 1)13 and whose
interaction with tubulin led to the original isolation of the protein.14 Synthetic and
biological studies with indole-based, colchicine site VDAs were originally prompted by
the discovery of the potent natural products combretastatin A-4 (CA4) and
combretastatin A-1 (CA1) that were isolated from the African bush willow tree,
Combretum caffrum, by Pettit and co-workers (Figure 1).15-16 CA4 emerged as a
benchmark VDA, and its corresponding prodrug salt CA4P (ZybrestatTM) was the first
small-molecule tubulin binding VDA to enter clinical trials.17-19 Although no VDA is yet
in routine clinical use, several small-molecule VDAs interacting at the colchicine site are
in clinical trials.17-21
OCH3
H3CO
H3CO
O
H3CO
H3CO
CH3
H3CO
H3CO
N
O
H
R2
R1
H3CO
OCH3
OH
OCH3
O
N
H3CO
OCH3
colchicine
OCH3
H
CA4: R1 = OH; R2 = H
CA1: R1 = R2 = OH
OXi8006
OCH3
HO
OCH3
OCH3
H3CO
H3CO
H3CO
H3CO
OCH3
H3CO
H3CO
O
O
O
O
O
H3CO
OCH3
CH3
OCH3
OCH3
O
H3CO
N
H
H3CO
S
H3CO
H3CO
OH
BPR0L075
1
2
BNC105
Figure 1. Selected colchicine site tubulin binding agents.
VDAs derived from the combretastatin family demonstrate potent
antiproliferative activity in various human cancer cell lines in vitro through the inhibition
4 of 48

of tubulin polymerization.22-31 These findings led us and others to explore indole-based
compounds for potential VDA and antitubulin activities by incorporating into their design
structural similarities to the combretastatin series. Our work led to the potent compound
2-(3 -hydroxy-4 -methoxyphenyl)-3-(3 ,4 ,5 -trimethoxybenzoyl)-6-methoxyindole
(referred to as OXi8006),32-35 and Flynn36 has subsequently pursued this compound
(through a separate synthetic route) and structurally similar, highly active compounds.
Because OXi8006 potently inhibits tubulin assembly (IC50 = 1.1 M) and cell growth (for
example, GI50 = 3.45 nM against SK-OV-3 cells), we initiated further structural studies.
As an initial finding, a water-soluble, disodium phosphate prodrug salt, OXi8007,
demonstrated distinct in vivo VDA activity in a study employing a SCID mouse model
bearing an orthotopic PC-3 (prostate) tumor as imaged by color Doppler ultrasound.37
Herein, we report the synthesis and biological evaluation of a series of
functionalized analogues of OXi8006 in an effort to further explore the molecular space
inherent to 2-aryl-3-aroyl indole-based anti-cancer agents. Our finding32-35 that OXi8006
is a potent tubulin binding agent combined with the work of Hseih38 with BPR0L075
(Figure 1) provided preliminary structural parallels defining distinct associations between
the stilbene aryl rings of CA4 and the aryl and aroyl rings of OXi8006 and BPR0L075.
These correlations were further expanded by our previous identification of
benzo[b]thiophene 1 and benzo[b]furan 2 as tubulin interacting compounds39-42 and the
subsequent studies by Flynn leading to the benzofuran-based BNC105 (Figure 1), a VDA
currently undergoing clinical trials.43-45 A narrow but focused literature survey of
inhibitors of tubulin assembly that incorporate the indole molecular template confirms the
importance of the 3-(3
-trimethoxybenzoyl)indole functionality while allowing for
5 of 48

structural diversity within the indole core (Figure 2). This is exemplified by structures
that include variation in alkoxy substitution (structure I, Fig. 2),38 halogen incorporation
(structures I and III),38,46 heterocyclic substitution at the 2-position (structure IV),47 and
derivatives of BRP0L075 (such as compound II).48
OCH3
OCH3
H3CO
H3CO
H3CO
H3CO
R1 = H
R2 = 4-OCH3, 5-OCH3,
7-OCH3, 5,6-di-OCH3, 6-F,
6-OH, 6-OEt, 6-OPr, 6-OiPr
O
O
R2
R1
R1 = CH3
R2 = 5-OCH3, 6-OCH3
N
H
N
H3CO
H
OH
II
I
OCH3
OCH3
H3CO
H3CO
H3CO
H3CO
X
R = pyrole, imidizole, furan,
thiophene, oxazole, Ph, Ar-F,
pyridine, naphthyl, cyclobutyl,
cyclopentyl, cyclohexyl,
X = Br, Cl, or OCH3
R = H, COOMe, or COOEt
O
O
R
R
N
N
H
H
III
IV
Figure 2. Structural diversity within the 3-(3
space
-trimethoxybenzoyl)indole molecular
The potent inhibition of tubulin assembly and cytotoxicity of OXi8006 and BPR0L075,
in addition to the previous studies with benzo[b]thiophene and benzo[b]furan derivatives,
led to the present study, which investigates a small collection of diversely modified 2-
aryl-3-aroyl indole-based analogues to gain further insight into the structural features of
OXi8006 that are most important for biological activity (inhibition of tubulin assembly
and cytotoxicity).
2. Results and discussion
6 of 48

2.1 Chemistry
The synthetic route to derivatized OXi8006 analogues 25-36 involved the
previously described bromoacetophenone 337 and commercially available
bromoacetophenone 4 as key intermediates. 2-Aryl substituted indoles 5-11 were
prepared by condensation of bromoacetophenone 3 or 4 with suitable anilines under
Bischler-Mohlau conditions49-50 (Scheme 1). Further modification of 2-aryl indole 8 by
selective demethoxylation in the presence of ionic liquid [TMAH][Al2Cl7]51 (generated
from AlCl3 and trimethylamine hydrochloride (TMAH)) and microwave irradiation
yielded the phenolic 2-aryl indole 9, which was subsequently protected as its
corresponding TBS derivative 10 (Scheme 2). The regioselectivity of the demethylation
reaction was confirmed by X-ray crystallographic analysis of TBS indole 10 (see
Supplementary data). Treatment of 2-aryl indoles 5-11 with appropriate functionalized
benzoyl chloride derivatives resulted in 2-aryl-3-aroyl indole analogues 12-24 through a
benzoylation reaction. Final desilylation with TBAF provided the parent 2-aryl-3-aroyl
free phenol indole analogues 25-36.
Scheme 1. Synthetic route to OXi8006 analogues from bromoacetophenones 3 and 4.
7 of 48

O
Cl
NH2
R2
N, N-dimethylaniline
R3
o-dichlorobenzene
170 o
O
Br
R1
R2
150-170 o
44-69%
C
C
R1
N
H
20-94%
OCH3
3: R1 = OTBS
4: R1 = H
5: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3
6: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OTBS
7: R1 = 3'-OTBS, 4'-OCH3, R2 = 4,5,6-tri-OCH3
8: R1 = 4'-OCH3, R2 = 6,7-di-OCH3
10: R1 = 4'-OCH3, R2 = 6-OCH3, 7-OTBS
11: R1 = 3'-OTBS, 4'-OCH3, R2 = 6,7-di-OCH3
R3
R3
O
O
TBAF
THF, 0 oC
R2
R2
R1
R1
N
N
H
19%-quant.
H
12: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',4'',5''-tri-OCH3
13: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',5''-di-NO2
14: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 4''-NO2
OXi8006: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',4'',5''-tri-OCH3
25: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',5''-di-NO2
26: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 4''-NO2
15: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 3''-NO2
27: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 3''-NO2
16: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',4'',5''-tri-F
17: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 4''-F
28: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',4'',5''-tri-F
29: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 4''-F
18: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',5''-di-CF3
19: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 3''-OCF3
20: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OCH3, R3 = 4''-OCF3
21: R1 = 3'-OTBS, 4'-OCH3, R2 = 6-OTBS, R3 = 3'',4'',5''-tri-OCH3
22: R1 = 3'-OTBS, 4'-OCH3, R2 = 4,5,6-tri-OCH3, R3 = 3'',4'',5''-tri-OCH3
23: R1 = 4'-OCH3, R2 = 6-OCH3, 7-OTBS, R3 = 3'',4'',5''-tri-OCH3
24: R1 = 3'-OTBS, 4'-OCH3, R2 = 6,7-di-OCH3, R3 = 3'',4'',5''-tri-OCH3
30: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 3'',5''-di-CF3
31: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 3''-OCF3
32: R1 = 3'-OH, 4'-OCH3, R2 = 6-OCH3, R3 = 4''-OCF3
33: R1 = 3'-OH, 4'-OCH3, R2 = 6-OH, R3 = 3'',4'',5''-tri-OCH3
34: R1 = 3'-OH, 4'-OCH3, R2 = 4,5,6-tri-OCH3, R3 = 3'',4'',5''-tri-OCH3
35: R1 = 4'-OCH3, R2 = 6-OCH3, 7-OH, R3 = 3'',4'',5''-tri-OCH3
36: R1 = 3'-OH, 4'-OCH3, R2 = 6,7-di-OCH3, R3 = 3'',4'',5''-tri-OCH3
Scheme 2. Synthetic route to modified indole 10.
[TMAH][Al2Cl7]
OCH3
OCH3
µW 80 o
C
N
N
H
H3CO
H3CO
H
71%
OCH3
OH
8
9
DMAP, Et3N, TBSCl
OCH3
N
H
CH2Cl2, 0 o
45%
C
H3CO
OTBS
10
2.2 Biological Evaluation
8 of 48

The series of 2-aryl-3-aroyl indole analogues (Fig. 3) were evaluated for their
cytotoxicity against the SK-OV-3, NCI-H460, and DU-145 human cancer cell lines
(Table 1) and for their ability to inhibit tubulin assembly (Table 2). The two most active
compounds (35 and 36) in the series featured substitution at position-7 in the fused aryl
ring. Compound 36 (7-methoxy) was comparable to OXi8006 in terms of both
cytotoxicity (sub-micromolar) and inhibition of tubulin assembly (IC50 = 1.1 M), and
analogue 35, in which the hydroxyl group was transposed from the pendant 2-aryl ring to
position-7 of the fused aryl ring, was nearly equipotent. Replacement of the 6-methoxy
group with a 6-hydroxy moiety (analogue 33) resulted in a loss of antitubulin activity (>
20 M) and a significant decrease in cytotoxicity. All structural modifications in the 3-
aroyl moiety that replaced the 3,4,5-trimethoxy motif (inherent to OXi8006) with a
different functionality resulted in a decrease in cytotoxicity (compared to OXi8006 and
the reference stilbene compound, CA4). However, the 3,5-bis-trifluoromethyl analogue
(30) and the 3-trifluoromethoxy derivative (31) remained relatively good inhibitors of
tubulin assembly (3.1 and 3.7 M, respectively). Although selective fluorine substitution
in CA4 analogues has been generally well-tolerated,52 this trend did not carry forward to
this indole series of compounds. A 3,4,5-trifluoro analogue (28) demonstrated only
modest inhibition of tubulin assembly (7.5 M), while a 3-fluoro derivative (29) was
inactive (> 20 M) in this assay. Nitro-bearing analogues (25-27) were similarly inactive.
These results suggest the importance of the 3,4,5-trimethoxy substitution pattern in the 3-
aroyl moiety and appropriate substitution at positions 6 and 7 of the fused aryl ring for
maintaining potent cytotoxicity and inhibition of tubulin assembly in this series of
compounds.
9 of 48

NO2
F
O2N
F
O2N
O2N
F
O
O
O
O
OCH3
OH
OCH3
OH
OCH3
OH
OCH3
OCH3
OCH3
N
H
N
N
N
H3CO
H3CO
H3CO
H3CO
OH
OH
OH
H
H
H
25
26
27
28
CF3
F
F3CO
F3C
F3CO
O
O
O
O
OCH3
OH
OCH3
OH
OCH3
OH
N
N
N
N
H3CO
H3CO
H3CO
H3CO
H
H
H
H
29
30
31
32
OCH3
OCH3
OCH3
OCH3
H3CO
H3CO
H3CO
H3CO
H3CO
H3CO
H3CO
H3CO
H3CO
O
O
O
O
H3CO
OCH3
OCH3
OH
OCH3
N
N
H3CO
H3CO
N
N
HO
H3CO
H
H
OCH3
OH
H
H
OH
33
34
35
36
Figure 3. Molecular structures of synthesized 2-aryl-3-aroylindole analogues 25-36.
Table 1. Cytotoxicity against human cancer cell lines SK-OV-3, NCI-H460,
and DU-145
10 of 48

GI50 ( M) + SD Sulforhodamine B assaya
NCI-H460
Compound
SK-OV-3
DU-145
0.00533 + 0.00180
0.00345 + 0.000409
4.35 + 0.290
0.00449 + 0.0000648b
0.0379 + 0.00182
4.08 + 0.119
16.8 + 2.13
0.00484 + 0.000848b
0.0356 + 0.00107
5.52 + 0.106
8.16 + 4.41
CA4
OXi8006
25
21.1 + 2.45
26
2.65 + 1.94
15.7 + 1.64
7.11 + 2.16
27
19.8 + 3.95
5.54 + 0.505
49.6 + 3.20
10.0 + 9.83
28
15.0 + 9.60
10.0 + 4.21
29
1.45 + 0.365
2.86 + 0.104
3.57 + 0.508
2.35 + 0.159
2.910 + 0.4833
41.8 + 2.52
3.01 + 0.0829
2.99 + 0.235
3.21 + 0.294
3.401 + 1.471
28.3 + 18.0
30
0.283 + 0.0395
3.05 + 0.895
31
32
2.167 + 0.3657
25.1 + 0.262
33
34
0.264 + 0.0418
0.0119 + 0.00422
0.177 + 0.0245
0.992 + 0.320
0.309 + 0.0143
0.0181 + 0.000772
35
36
a Average of n > 3 independent determinations. b For additional data see refs. 15-16.
Table 2. Inhibition of tubulin polymerization and colchicine binding
Inhibition of colchicine binding (%)
+ SD
11 of 48

Inhibition of tubulin
Compound
polymerization IC50 ( M) + SD
1 M
88 + 2
40 + 0.2
nda
5 M
98 + 0.5
75 + 0.2
nd
1.3 + 0.07
1.1 + 0.04
> 20
CA4
OXi8006
25
> 20
nd
nd
26
19 + 0.8
7.5 + 2
> 20
nd
21 + 1
26 + 2
nd
27
nd
28
nd
29
3.1 + 0.2
3.7 + 0.4
> 20
nd
26 + 2
19 + 4
nd
30
nd
31
nd
32
> 20
nd
nd
33
> 20
nd
nd
34
1.0 + 0.1
1.1 + 0.4
51 + 0.4
31 + 4
85 + 0.7
67 + 3
35
36
a nd = not determined in this study.
3. Conclusion
In summary, the results of this study have significantly extended our knowledge
of functional group tolerability for 2-aryl-3-aroyl indole analogues. The most promising
new analogues (35, 36) demonstrated inhibition of tubulin assembly comparable to the
reference compounds OXi8006 and CA4, and future studies will evaluate these
compounds (as their corresponding water-soluble phosphate prodrug salts) for their
potential to function as VDAs.
4. Experimental
4.1 Chemistry
12 of 48

4.1.1 Materials and instrumentation
CH2Cl2 and tetrahydrofuran (THF) were used in their anhydrous forms, as
obtained from the chemical suppliers. Reactions were performed under an inert
atmosphere using nitrogen gas, unless specified otherwise. Thin-layer chromatography
(TLC) plates (precoated glass plates with silica gel 60 F254, 0.25 mm thickness) were
used to monitor reactions. Purification of intermediates and products was carried out with
a flash purification system (Biotage Isolera 1 or 4) using silica gel (200-400 mesh, 60 Å)
prepacked columns. Reactions carried out under microwave irradiation were performed
with a Biotage Initiator Microwave Synthesizer. Intermediates and products synthesized
were characterized on the basis of their 1H NMR (500 MHz), 13C NMR (125 MHz), and
19F NMR (470 MHz) spectroscopic data using a Varian VNMRS 500 MHz instrument.
Spectra were recorded in CDCl3, (CD3)2SO, or (CD3)2CO. All of the chemical shifts are
expressed in ppm ( ), coupling constants (J) are presented in Hz, and peak patterns are
reported as broad (br), singlet (s), doublet (d), triplet (t), double doublet (dd), double
triplet (dt), triplet of triplets (tt), doublet of doublets of doublets (ddd), and multiplet (m).
Purity of the final compounds was further analyzed at 25 oC using an Agilent 1200 HPLC
system with a diode-array detector ( = 190-400 nm), a Zorbax XDB-C18 HPLC column
(4.6 mm - 150 mm, 5 µm), and a Zorbax reliance cartridge guard-column; solvent A:
acetonitrile, solvent B: H2O; gradient: 10%A / 90%B to 100%A / 0%B over 0 to 40 min;
post-time 10 min; flow rate 1.0 mL/min; injection volume 20 µL; monitored at
wavelengths of 210, 254, 230, 280, and 360 nm. Mass spectrometry was carried out
under positive ESI (electrospray ionization) using a Thermo scientific LTQ Orbitrap
Discovery instrument.
13 of 48

4.1.2. 2-(3 -tert-Butyldimethylsilyloxy-4 -methoxyphenyl)-6-methoxyindole (5)37
To a solution of m-anisidine (2.05 mL, 18.4 mmol) dissolved in N,N-
dimethylaniline (20 mL) at 170 oC was added dropwise bromoacetophenone 3 (2.0 g, 5.6
mmol) in EtOAc (5 mL). The reaction mixture was stirred at 170 oC for 12 h. Upon
completion of the reaction, the reaction mixture was cooled to room temperature and
extracted with EtOAc (3 x 50 mL). The combined organic extract was dried over Na2SO4
and concentrated under reduced pressure. Purification by flash chromatography using a
prepacked 25 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 12%A /
88%B (4 CV), 12%A / 88%B 100%A / 0%B (10 CV), 100%A / 0%B (2.6 CV); flow
rate: 25 mL/min; monitored at 254 and 280 nm] resulted in the desired 2-phenylindole
derivative 5 (1.49 g, 3.88 mmol, 69%, Rf = 0.48 (50:50 hexanes:EtOAc)) as light tan
1
crystals. H NMR (CDCl3, 500 MHz): 8.11 (br s, 1H, NH), 7.47 (d, J = 8.5 Hz, 1H,
ArH), 7.16 (dd, J = 2.0 Hz, 8.5 Hz 1H, ArH), 7.13 (d, J = 2.5 Hz, 1H, ArH), 6.90 (d, J =
8.5 Hz, 1H, ArH), 6.89 (d, J = 2.5 Hz, 1H, ArH), 6.79 (dd, J = 2.5 Hz, 8.5 Hz, 1H, ArH),
6.64 (dd, J = 1.0 Hz, 2.0 Hz 1H, ArH), 3.86 (s, 3H, OCH3), 3.84 (s, 3H, OCH3), 1.04 (s,
9H, C(CH3)3), 0.21 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 156.3, 150.5,
145.4, 137.4, 136.9, 125.8, 123.7, 120.9, 118.2, 117.8, 112.4, 109.9, 98.6, 94.5, 55.6,
55.4, 25.7, 18.5, -4.6.
4.1.3. 2-(3 -tert-Butyldimethylsilyloxy-4 -methoxyphenyl)-6-tert-
butyldimethylsilyloxyindole (6)
To a solution of 3-(tert-butyldimethylsilyloxy)aniline (2.06 g, 9.21 mmol) in N,N-
dimethylaniline (20 mL) at 170 oC was added compound 3 (1.00 g, 2.79 mmol) dropwise
14 of 48

in EtOAc (5 mL). The reaction mixture was stirred at 170 oC for 12 h. Upon completion
of the reaction, the reaction mixture was cooled to room temperature and extracted with
EtOAc (3 x 50 mL). The combined organic extract was dried over Na2SO4 and
concentrated under reduced pressure. Purification by flash chromatography using a
prepacked 100 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 2%A /
98%B (4 CV), 2%A / 98%B 20%A / 80%B (10 CV), 20%A / 80%B (2 CV); flow rate:
40 mL/min; monitored at 254 and 280 nm] resulted in the desired 2-phenylindole 6 (0.59
1
g, 1.23 mmol, 44%, Rf = 0.39 (90:10 hexanes:EtOAc)) as a brown solid. H NMR
(CDCl3, 500 MHz): 8.09 (br s, 1H, NH), 7.37 (d, J = 8.5 Hz, 1H, ArH), 7.10 (d, J = 1.5
Hz, 1H, ArH), 7.01 (dd, J = 1.5 Hz, 8.5 Hz, 1H, ArH), 6.82 (s, 1H, ArH), 6.72 (d, J = 8.5
Hz, 1H, ArH), 6.67 (dd, J = 1.5 Hz, 8.5 Hz, 1H, ArH), 6.54 (s, 1H, ArH), 3.70 (s, 3H,
OCH3), 1.02 (s, 9H, C(CH3)3), 1.01 (s, 9H, C(CH3)3), 0.20 (s, 6H, Si(CH3)2), 0.18 (s, 6H,
Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 150.7, 150.6, 145.4, 137.7, 137.3, 126.0,
124.5, 120.6, 118.5, 118.0, 114.6, 112.4, 101.8, 98.7, 55.4, 25.93, 25.89, 18.6, 18.4, -4.3,
-4.5. HPLC: 25.45 min., purity at 254 nm >99%. HRMS (ESI+): m/z calculated for
C27H42NO3Si2 [M+H]+ 484.2698, found 484.2698.
4.1.4. 2-(3 -tert-Butyldimethylsilyloxy-4 -methoxyphenyl)-4,5,6-trimethoxyindole (7)
To a solution of 3,4,5-trimethoxyaniline (0.336 g, 1.84 mmol) in N,N-
dimethylaniline (20 mL) at 170 oC was added compound 3 (0.20 g, 0.56 mmol) dropwise
in EtOAc (5 mL). The reaction mixture was stirred at 170 oC for 12 h. Upon completion
of the reaction, the reaction mixture was cooled to room temperature and extracted with
EtOAc (3 x 50 mL). The combined organic extract was dried over Na2SO4 and
concentrated under reduced pressure. Purification by flash chromatography using a
15 of 48

prepacked 50 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 7%A /
93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A / 40%B (2 CV); flow rate:
40 mL/min; monitored at 254 and 280 nm] resulted in the desired 2-phenylindole 7 (0.14
1
g, 0.32 mmol, 58%, Rf = 0.31 (70:30 hexanes:EtOAc)) as colorless crystals. H NMR
(CDCl3, 500 MHz): 8.06 (br s, 1H, NH), 7.15 (dd, J = 2.0 Hz, 8.5 Hz, 1H, ArH), 7.10
(d, J = 2.0 Hz, 1H, ArH), 6.90 (d, J = 8.5 Hz, 1H, ArH), 6.70 (dd, J = 1.0 Hz, 2.0 Hz, 1H,
ArH), 6.66 (d, J = 0.5 Hz, 1H, ArH), 4.13 (s, 3H, OCH3), 3.90 (s, 3H, OCH3), 3.88 (s, 3H,
OCH3), 3.84 (s, 3H, OCH3), 1.03 (s, 9H, C(CH3)3), 0.19 (s, 6H, Si(CH3)2). 13C NMR
(CDCl3, 125 MHz): 151.0, 150.6, 145.6, 145.5, 136.4, 135.8, 133.9, 125.8, 118.3, 117.9,
116.6, 112.5, 96.3, 89.8, 61.6, 60.9, 56.2, 55.2, 25.9, 18.5, -4.6. HPLC: 20.17 min.,
purity at 254 nm 94.2%. HRMS (ESI+): m/z calculated for C24H34NO5Si [M+H]+
444.2201, found 443.2200.
4.1.5. 2-(4 -Methoxyphenyl)-6,7-dimethoxyindole (8)
To a solution of 2,3-dimethoxyaniline (0.92 mL, 6.85 mmol) dissolved in N,N-
dimethylaniline (10 mL) was added 4-methoxybromoacetophenone 4 (0.79 g, 3.43
mmol). The solution was heated to reflux and stirred at 150 oC for 12 h. Upon
completion of the reaction, the reaction mixture was cooled to room temperature and
extracted with EtOAc (3 x 50 mL). The combined organic extract was dried over Na2SO4
and concentrated under reduced pressure. Purification by flash chromatography using a
prepacked 100 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 5%A /
95%B (4 CV), 5%A / 95%B 40%A / 60%B (10 CV), 40%A / 60%B (4 CV); flow rate:
40 mL/min; monitored at 254 and 280 nm] resulted in the desired 6,7-dimethoxy-2-
phenylindole 8 (0.50 g, 1.76 mmol, 51%, Rf = 0.35 (80:20 hexanes:EtOAc)) as a tan
16 of 48

1
solid. H NMR (CDCl3, 500 MHz): 8.61 (br s, 1H, NH), 7.61 (d, J = 8.7 Hz, 2H, ArH),
7.28 (d, J = 8.5 Hz, 1H, ArH), 6.97 (d, J = 8.7 Hz, 2H, ArH), 6.87 (d, J = 8.6 Hz, 1H,
ArH), 6.66 (d, J = 2.1 Hz, 1H, ArH), 4.09 (s, 3H, OCH3), 3.97 (s, 3H, OCH3), 3.85 (s, 3H,
OCH3). 13C NMR (CDCl3, 125 MHz): 159.2, 147.1, 138.0, 134.2, 131.3, 126.4, 126.0,
125.3, 115.3, 114.5, 108.5, 98.8, 61.1, 57.4, 55.4. HPLC: 15.30 min., purity at 254 nm
90.6%. HRMS (ESI+): m/z calculated for C17H18NO3 [M+H]+ 284.1281, found 284.1282.
4.1.6. 2-(4 -Methoxyphenyl)-6-methoxy-7-hydroxyindole (9)
Trimethoxyindole 8 (0.61 g, 2.16 mmol) was dissolved in a solution of
[Al2Cl7][TMAH] (6.3 mL, 3.13 mmol, 0.496 M in CH2Cl2). The reaction mixture was
sealed and subjected to microwave irradiation at 80 oC for 1 h. Upon completion of the
reaction, the reaction mixture was diluted with NaHCO3 and extracted with CH2Cl2 (3 x
20 mL). The combined organic extract was dried over Na2SO4 and concentrated under
reduced pressure. Purification by flash chromatography using a prepacked 100 g silica
column [solvent A: EtOAc; solvent B: hexanes; gradient: 7%A / 93%B (4 CV), 7%A /
93%B 60%A / 40%B (10 CV), 60%A / 40%B (2 CV); flow rate: 40 mL/min;
monitored at 254 and 280 nm] resulted in the desired 6-methoxy-7-hydroxy-2-
phenylindole 9 (0.42 g, 1.55 mmol, 71%, Rf = 0.36 (70:30 hexanes:EtOAc)) as a tan
1
solid. H NMR ((CD3)2CO, 500 MHz): 10.11 (br s, 1H, NH), 7.85 (d, J = 8.7 Hz, 2H,
ArH), 7.66 (s, 1H, OH), 6.98 (m, 3H, ArH), 6.81 (d, J = 8.5 Hz, 1H, ArH), 6.66 (d, J =
2.2 Hz, 1H, ArH), 3.83 (s, 3H, OCH3), 3.81 (s, 3H, OCH3). 13C NMR ((CD3)2CO, 125
MHz): 159.9, 142.5, 138.8, 133.1, 128.4, 127.2, 127.1, 126.5, 115.0, 111.3, 108.9, 99.0,
58.3, 55.7. HPLC: 13.47 min., purity at 254 nm 85.8%. HRMS (ESI+): m/z calculated
for C16H16NO3 [M+H]+ 270.1125, found 270.1129.
17 of 48

4.1.7. 2-(4 -Methoxyphenyl)-6-methoxy-7-tert-butyldimethylsilyloxyindole (10)
To a solution of free phenol indole 9 (0.08 g, 0.28 mmol) in CH2Cl2 (5 mL) at 0 oC
was added Et3N (0.04 mL, 0.31 mmol) and DMAP (0.01 g, 0.11 mmol). The reaction
mixture was stirred for 10 min, and TBSCl (0.05 g, 0.31 mmol) was added gradually.
The solution was allowed to warm to room temperature over 12 h. Upon completion of
the reaction, water (10 mL) was added, and the reaction mixture was extracted with
CH2Cl2 (3 x 50 mL). The combined organic extract was dried over Na2SO4 and
concentrated under reduced pressure. Purification by flash chromatography using a
prepacked 25 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 2%A /
98%B (4 CV), 2%A / 98%B 20%A / 80%B (10 CV), 20%A / 80%B (5.2 CV); flow
rate: 35 mL/min; monitored at 254 and 280 nm] resulted in the TBS indole product 10
1
(0.05 g, 0.02 mmol, 45%, Rf = 0.64 (70:30 hexanes:EtOAc))) as a light tan solid. H
NMR (CDCl3, 500 MHz): 8.03 (br s, 1H, NH), 7.53 (d, J = 8.7, 2H, ArH ), 7.13 (d, J =
8.5 Hz, 1H, ArH), 6.98 (d, J = 8.7 Hz, 2H, ArH), 6.80 (d, J = 8.5 Hz, 1H, ArH), 6.61 (d, J
= 2.2 Hz, 1H, ArH), 3.86 (s, 6H, OCH3), 1.11 (s, 9H, C(CH3)3), 0.24 (s, 6H, Si(CH3)2).
13C NMR (CDCl3, 125 MHz): 159.3, 145.2, 137.5, 131.2, 130.2, 126.2, 125.9, 125.6,
114.6, 112.9, 108.5, 99.0, 57.0, 55.5, 26.3, 18.8, -4.2. HPLC: 21.73 min., purity at 254
nm 93.7%. HRMS (ESI+): m/z calculated for C22H30NO3Si [M+H]+ 384.1989, found
384.1990.
4.1.8. 2-(3 -tert-Butyldimethylsilyloxy-4 -methoxyphenyl)-6,7-dimethoxyindole (11)
To a solution of 2,3-dimethoxyaniline (2.19 mL, 16.3 mmol) dissolved in N,N-
dimethylaniline (20 mL) was added bromoacetophenone 3 (2.93 g, 8.16 mmol). The
18 of 48

solution was heated to reflux and stirred at 150 oC for 12 h. Upon completion of the
reaction, the reaction mixture was cooled to room temperature and extracted with EtOAc
(3 x 50 mL). The combined organic extract was dried over Na2SO4 and concentrated
under reduced pressure. Purification by flash chromatography using a prepacked 50 g
silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 5%A / 95%B (4 CV),
5%A / 95%B 40%A / 60%B (10 CV), 40%A / 60%B (2 CV); flow rate: 50 mL/min;
monitored at 254 and 280 nm] resulted in the desired 6,7-dimethoxy-2-phenylindole 11
1
(1.43 g, 3.47 mmol, 43%, Rf = 0.40 (80:20 hexanes:EtOAc)) as a tan solid. H NMR
(CDCl3, 500 MHz): 8.63 (br s, 1H, NH), 7.33 (d, J = 8.5 Hz, 1H, ArH), 7.28 (d, J = 2.2
Hz, 1H, ArH), 7.26 (dd, J = 8.5 Hz, 2.2 Hz 1H, ArH), 6.92 (dd, J = 8.4 Hz, 1.4 Hz, 2H,
ArH), 6.71 (d, J = 2.2 Hz, 1H, ArH), 4.15 (s, 3H, OCH3), 4.01 (s, 3H, OCH3), 3.88 (s, 3H,
OCH3), 1.15 (s, 9H, C(CH3)3), 0.31 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz):
150.7, 147.1, 145.4, 137.9, 134.2, 131.2, 126.0, 125.7, 118.4, 118.1, 115.2, 112.3, 108.7,
99.0, 60.9, 57.3, 55.4, 25.8, 18.5, -4.5. HPLC: 21.28 min., purity at 254 nm >99%.
HRMS (ESI+): m/z calculated for C23H32NO4Si [M+H]+ 414.2095, found 414.2095.
4.1.9. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 ,5 dinitrobenzoyl)-6-
methoxyindole (13)
To a solution of compound 5 (0.50 g, 1.30 mmol) in o-dichlorobenzene (20 mL)
was added 3,5-dinitrobenzoylchloride (0.45 g, 1.90 mmol). The reaction mixture was
heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark colored solid was subjected to flash chromatography
using a prepacked 50 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient:
7%A / 93%B (4 CV), 7%A / 93%B 60%A / 40%B (11 CV), 60%A / 40%B (2 CV);
19 of 48

flow rate: 40 mL/min; monitored at 254 and 280 nm] resulting in TBS-indole 13 as a pale
1
yellow powder (0.40 g, 0.69 mmol, 53%, Rf = 0.59 (70:30 hexanes:EtOAc)). H NMR
(CDCl3, 500 MHz): 8.85 (t, J = 2.0 Hz, 1H, ArH), 8.62 (d, J = 2.0 Hz, 2H, ArH), 8.60
(br s, 1H, NH) 8.15 (d, J = 8.5 Hz, 1H, ArH), 7.00 (dd, J = 2.0 Hz, 8.5 Hz, 1H, ArH),
6.95 (d, 2.0 Hz, 1H, ArH), 6.87 (dd, J = 2.0 Hz, 8.0 Hz, 1H, ArH), 6.61 (d, J = 8.5 Hz,
1H, ArH), 6.56 (d, J = 2.5 Hz, 1H, ArH), 3.90 (s, 3H, OCH3), 3.70 (s, 3H, OCH3), 0.89 (s,
9H, C(CH3)3), 0.00 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 187.3, 158.1,
152.1, 147.8, 145.3, 145.1, 143.1, 136.5, 129.1, 123.5, 123.4, 122.7, 122.4, 122.3, 120.1,
112.8, 112.5, 111.8, 95.0, 55.9, 55.5, 25.6, 18.4, -4.8. HPLC: 20.28 min., purity at 254
nm 93.1%. HRMS (ESI+): m/z calculated for C29H32N3O8Si [M+H]+ 578.1953, found
578.1950.
4.1.10. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(4 -nitrobenzoyl)-6-
methoxyindole (14)
To a solution of compound 5 (0.20 g, 0.52 mmol) in o-dichlorobenzene (10 mL)
was added 3-nitrobenzoylchloride (0.15 g, 0.78 mmol). The reaction mixture was heated
to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple distillation,
and the resulting dark colored solid was subjected to flash chromatography using a
prepacked 100 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 7%A /
93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A / 40%B (8.8 CV); flow
rate: 40 mL/min; monitored at 254 and 280 nm] resulting in TBS-indole 14 as a yellow
1
powder (0.14 g, 0.28 mmol, 51%, Rf = 0.36 (70:30 hexanes:EtOAc)). H NMR (CDCl3,
500 MHz): 8.37 (br s, 1H, NH), 8.06 (d, J = 8.5 Hz, 1H, ArH), 7.97 (d, J = 8.5 Hz, 2H,
ArH) 7.69 (d, J = 8.5 Hz, 2H, ArH), 6.97 (dd, J = 2.0 Hz, 8.5 Hz, 1H, ArH), 6.93 (d, J =
20 of 48

2.5 Hz, 1H, ArH), 6.75 (m, 2H, ArH), 6.58 (d, J = 8.0 Hz, 1H, ArH), 3.89 (s, 3H, OCH3),
3.71 (s, 3H, OCH3), 0.97 (s, 9H, C(CH3)3), 0.07 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125
MHz): 190.9, 157.8, 152.1, 148.9, 145.6, 145.2, 144.4, 136.5, 130.3, 124.1, 123.7,
123.0, 122.69, 122.67, 121.7, 113.0, 112.3, 111.7, 94.9, 55.9, 55.6, 25.8, 18.6, -4.6.
HPLC: 20.23 min., purity at 254 nm >99%. HRMS (ESI+): m/z calculated for
C29H33N2O6Si [M+H]+ 533.2102, found 533.2100.
4.1.11. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 -nitrobenzoyl)-6-
methoxyindole (15)
To a solution of compound 5 (0.10 g, 0.26 mmol) in o-dichlorobenzene (10 mL)
was added 3-nitrobenzoylchloride (0.07 g, 0.39 mmol). The reaction mixture was heated
to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple distillation,
and the resulting dark colored solid was subjected to flash chromatography using a
prepacked 25 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient: 12%A /
88%B (4 CV), 12%A / 88%B 100%A / 0%B (10 CV), 100%A / 0%B (2.8 CV); flow
rate: 25 mL/min; monitored at 254 and 280 nm] resulting in TBS-indole 15 as pale
1
yellow crystals (0.13 g, 0.25 mmol, 94%, Rf = 0.63 (50:50 hexanes:EtOAc)). H NMR
(CDCl3, 500 MHz): 9.15 (br s, 1H, NH), 8.30 (t, J = 2.0 Hz, 1H, ArH), 8.06 (ddd, J =
1.0 Hz, 2.0 Hz, 8.0 Hz, 1H, ArH) 8.03 (d J = 9.5 Hz, 1H, ArH), 7.88 (dt, J = 1.0 Hz, 8.0
Hz, 1H, ArH), 7.29 (t, J = 8.0 Hz, 1H, ArH), 6.92 (dd, J = 2.0 Hz, 7.0 Hz, 1H, ArH), 6.91
(d, J = 2.0 Hz, 1H, ArH), 6.78 (dd, J = 2.0 Hz, 8.0 Hz, 1H, ArH), 6.66 (d, J = 2.5 Hz, 1H,
ArH), 6.50 (d, J = 8.5 Hz, 1H, ArH), 3.82 (s, 3H, OCH3), 3.65 (s, 3H, OCH3), 0.91 (s, 9H,
C(CH3)3), 0.00 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 190.4, 157.6, 151.7,
147.4, 144.9, 144.6, 141.3, 136.6, 135.0, 128.9, 125.4, 124.7, 124.1, 123.4, 122.7, 122.3,
21 of 48

122.0, 112.4, 112.3, 111.6, 94.9, 55.7, 55.4, 25.7, 18.4, -4.7. HPLC: 20.13 min., purity
at 254 nm >99%. HRMS (ESI+): m/z calculated for C29H33N2O6Si [M+H]+ 533.2102,
found 533.2100.
4.1.12. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 ,4 ,5 -
trifluorobenzoyl)-6-methoxyindole (16)
To a solution of compound 5 (0.61 g, 1.59 mmol) in o-dichlorobenzene (10 mL)
was added 3,4,5-trifluorobenzoylchloride (3.12 mL, 2.38 mmol). The reaction mixture
was heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark colored solid was subjected to flash chromatography
using a prepacked 100 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient:
7%A / 93%B (4 CV), 7%A / 97%B 60%A / 40%B (10 CV), 60%A / 40%B (5.5 CV);
flow rate: 40 mL/min; monitored at 254 and 280 nm] resulting in TBS-indole 16 as a
1
white powder (0.70 g, 1.29 mmol, 81%, Rf = 0.48 (50:50 hexanes:EtOAc)). H NMR
(CDCl3, 500 MHz): 8.44 (br s, 1H, NH), 7.95 (d, J = 9.0 Hz, 1H, ArH), 7.25 (m, 2H,
ArH) 6.94 (dd, J = 2.5 Hz, 8.5 Hz, 1H, ArH), 6.91 (d, J = 2.0 Hz, 1H, ArH), 6.83 (dd, J =
2.0 Hz, 8.0 Hz, 1H, ArH), 6.79 (d, J = 2.0 Hz, 1H, ArH), 6.70 (d, J = 8.5 Hz, 1H, ArH),
3.87 (s, 3H, OCH3), 3.78 (s, 3H, OCH3), 0.97 (s, 9H, C(CH3)3), 0.09 (s, 6H, Si(CH3)2).
13C NMR (CDCl , 125 MHz): 189.1, 157.7, 152.1, 150.6 (ddd, JC-F = 3.1 Hz, 10.0 Hz,
3
250.0 Hz), 145.4, 143.5, 141.8 (dt, JC-F = 15.5 Hz, 255.9 Hz), 136.5, 135.6 (d, JC-F = 3.9
Hz), 124.4, 123.2, 122.8, 121.4, 121.6, 114.1 (dd, JC-F = 5.1 Hz, 16.9 Hz), 112.3, 112.2,
112.0, 94.8, 55.9, 55.6, 25.7, 18.5, -4.8. 19F NMR (CDCl3, 470 MHz): -134.0 (dd, J =
7.5 Hz, 21.2 Hz, 2F, ArF), -155.6 (tt, J = 6.6 Hz, 20.2 Hz, 1F, ArF). HPLC: 21.32 min.,
22 of 48

purity at 254 nm >99%. HRMS (ESI+): m/z calculated for C29H30F3NNaO4Si [M+Na]+
564.1788, found 564.1786.
4.1.13. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(4 -fluorobenzoyl)-6-
methoxyindole (17)
To a solution of compound 5 (0.10 g, 0.26 mmol) in o-dichlorobenzene (10 mL)
was added 4-fluorobenzoylchloride (0.05 mL, 0.39 mmol). The reaction mixture was
heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark colored solid was subjected to flash chromatography
using a prepacked 25 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient:
12%A / 88%B (4 CV), 12%A / 88%B 100%A / 0%B (10 CV), 100%A / 0%B (2 CV);
flow rate: 25 mL/min; monitored at 254 and 280 nm] resulting in TBS-indole 17 as pale
1
yellow crystals (0.09 g, 0.18 mmol, 69%, Rf = 0.73 (50:50 hexanes:EtOAc)). H NMR
(CDCl3, 500 MHz): 8.59 (br s, 1H, NH), 7.88 (d, J = 9.5 Hz, 1H, ArH), 7.65 (dt, J = 2.5
Hz, 9.0 Hz, 1H, ArH) 7.64 (dt, J = 2.0 Hz, 9.0 Hz, 1H, ArH), 6.89 (m, 2H, ArH), 6.82
(m, 4H, ArH), 6.60 (d, J = 8.0 Hz, 1H, ArH), 3.84 (s, 3H, OCH3), 3.73 (s, 3H, OCH3),
0.96 (s, 9H, C(CH3)3), 0.08 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 191.7,
164.8 (d, JC-F = 251 Hz), 157.4, 151.7, 145.1, 142.8, 136.4, 136.09, 136.06, 132.2 (d, JC-F
= 9 Hz), 124.6, 123.4, 123.1, 122.4, 121.6, 114.9 (d, JC-F = 22 Hz), 113.0, 111.8, 94.7,
55.8, 55.5, 25.8, 18.6, -4.6. 19F NMR (CDCl3, 470 MHz): -108.1 (m, 1F, ArF). HPLC:
20.59 min., purity at 254 nm >99%. HRMS (ESI+): m/z calculated for C29H33FNO4Si
[M+H]+ 506.2157, found 506.2155.
23 of 48

4.1.14. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 ,5 -bis-
trifluoromethylbenzoyl)-6-methoxyindole (18)
To a solution of compound 5 (0.20 g, 0.52 mmol) in o-dichlorobenzene (15 mL)
was added 3,5-bis-trifluoromethylbenzoyl chloride (0.14 mL, 0.78 mmol). The reaction
mixture was heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by
simple distillation, and the resulting dark colored solid was subjected to flash
chromatography using a prepacked 50 g silica column [solvent A: EtOAc; solvent B:
hexanes; gradient: 7%A / 93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A
/ 40%B (2 CV); flow rate: 40 mL/min; monitored at 254 and 280 nm] resulting in TBS-
indole 18 as pale orange crystals (0.26 g, 0.42 mmol, 81%, Rf = 0.47 (70:30
1
hexanes:EtOAc)). H NMR (CDCl3, 500 MHz): 8.70 (br s, 1H, NH), 8.07 (d, J = 9.0
Hz, 1H, ArH), 8.03 (s, 2H, ArH) 7.74 (s, 1H, ArH), 6.96 (dd, J = 2.5 Hz, 9.0 Hz, 1H,
ArH), 6.92 (d, J = 2.0 Hz, 1H, ArH), 6.85 (dd, J = 2.0 Hz, 8.0 Hz, 1H, ArH), 6.65 (d, J =
8.5 Hz, 1H, ArH), 6.62 (d, J = 2.5 Hz, 1H, ArH), 3.86 (s, 3H, OCH3), 3.71 (s, 3H, OCH3),
0.91 (s, 9H, C(CH3)3), 0.00 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 189.5,
157.8, 152.0, 145.3, 144.5, 141.5, 136.6, 131.3 (q, JC-F = 33 Hz), 129.7 (m), 124.47 (q,
JC-F = 7 Hz), 124.46, 124.0, 123.1 (q, JC-F = 275 Hz), 122.9, 122.7, 122.5, 122.2, 112.4,
112.1, 94.9, 55.8, 55.5, 25.6, 18.4, -4.8. 19F NMR (CDCl3, 470 MHz): -62.8 (s, 6F,
CF3). HPLC: 22.22 min., purity at 254 nm 96.3%. HRMS (ESI+): m/z calculated for
C31H32F6NO4Si [M+H]+ 624.1999, found 624.1997.
4.1.15. (2-(3 -tert-Butyldimethylsilyloxy-4 -methoxyphenyl)-3-(3 -
trifluoromethoxybenzoyl)-6-methoxyindole (19)
24 of 48

To a solution of compound 5 (1.14 g, 2.97 mmol) in o-dichlorobenzene (15 mL)
was added 3-trifluoromethoxybenzoylchloride (0.70 mL, 4.45 mmol). The reaction
mixture was heated to reflux at 170 oC for 12 h. The o-dichlorobenzene was removed by
simple distillation, and the resulting dark green colored solid was subjected to flash
chromatography using a prepacked 50 g silica column [solvent A: EtOAc; solvent B:
hexanes; gradient: 7%A / 93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A
/ 40%B (2 CV); flow rate: 40 mL/min; monitored at 254 and 280 nm] resulting in TBS-
indole 19 as a yellow powder (1.21 g, 2.11 mmol, 71%, Rf = 0.43 (70:30
1
hexanes:EtOAc)). H NMR (CDCl3, 500 MHz): 8.31 (br s, 1H, NH), 7.96 (d, J = 8.4
Hz, 1H, ArH), 7.52 (dt, J = 1.3 Hz, 7.5 Hz, 1H, ArH) 7.48 (s, 1H, ArH), 7.17 (t, J = 7.8
Hz, 1H, ArH), 7.13 (d, J = 8.2 Hz, 1H, ArH), 6.93 (m, 2H, ArH), 6.81 (m, 2H, ArH), 6.62
(d, J = 9.0 Hz, 1H, ArH), 3.88 (s, 3H, OCH3), 3.73 (s, 3H, OCH3), 0.97 (s, 9H, C(CH3)3),
0.08 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 191.8, 157.4, 151.6, 148.8, 144.9,
144.1, 142.1, 136.6, 129.2, 128.0, 124.3, 123.6, 123.5, 122.9, 122.2, 122.0, 121.4, 120.4
(q, JC-F = 256 Hz), 112.6, 112.0, 111.6, 94.8, 55.7, 55.3, 25.7, 18.4, -4.7. 19F NMR
(CDCl3, 470 MHz): -57.8 (s, 3F, OCF3). HPLC: 21.53 min., purity at 254 nm >99%.
HRMS (ESI+): m/z calculated for C30H33F3NO5Si [M+H]+ 572.2075, found 572.2071.
4.1.16. (2-(3 -tert-Butyldimethylsilyloxy-4 -methoxyphenyl)-3-(4 -
trifluoromethoxybenzoyl)-6-methoxyindole (20)
To a solution of compound 5 (1.14 g, 2.97 mmol) in o-dichlorobenzene (15 mL)
was added 3-trifluoromethylbenzoylchloride (0.70 mL, 4.45 mmol). The reaction
mixture was heated to reflux at 170 oC for 12 h. The o-dichlorobenzene was removed by
simple distillation, and the resulting dark green colored solid was subjected to flash
25 of 48

chromatography using a prepacked 50 g silica column [solvent A: EtOAc; solvent B:
hexanes; gradient: 7%A / 93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A
/ 40%B (1.1 CV); flow rate: 40 mL/min; monitored at 254 and 280 nm] resulting in TBS-
indole 20 as a yellow powder (0.92 g, 1.61 mmol, 54%, Rf = 0.43 (70:30
1
hexanes:EtOAc)). H NMR (CDCl3, 500 MHz): 8.29 (br s, 1H, NH), 8.00 (d, J = 8.6
Hz, 1H, ArH), 7.64 (d, J = 8.7 Hz, 2H, ArH) 6.97 (d, J = 8.0 Hz, 2H, ArH), 6.93 (m, 2H,
ArH), 6.83 (d, J = 2.2 Hz, 1H, ArH), 6.73 (dd, J = 2.2 Hz, 8.3 Hz, 1H, ArH), 6.58 (d, J =
8.4 Hz, 1H, ArH), 3.88 (s, 3H, OCH3), 3.73 (s, 3H, OCH3), 0.98 (s, 9H, C(CH3)3), 0.10 (s,
6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 191.9, 157.3, 151.6, 151.0, 144.8, 144.1,
138.4, 136.6, 131.3, 124.2, 123.8, 122.8, 122.2, 121.4, 120.3 (q, JC-F = 256 Hz), 119.7,
112.6, 111.9, 111.3, 94.8, 55.6, 55.1, 25.6, 18.4, -4.8. 19F NMR (CDCl3, 470 MHz): -
57.7 (s, 3F, OCF3). HPLC: 21.61 min., purity at 254 nm >99%. HRMS (ESI+): m/z
calculated for C30H33F3NO5Si [M+H]+ 572.2075, found 572.2075.
4.1.17. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 ,4 ,5 -
trimethoxybenzoyl)-6-tert-butyldimethylsiloxyindole (21)
To a solution of compound 6 (0.19 g, 0.39 mmol) in o-dichlorobenzene (20 mL)
was added 3,4,5-trimethoxybenzoylchloride (0.13 g, 0.58 mmol). The reaction mixture
was heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark colored solid was subjected to flash chromatography
using a prepacked 50 g silica column [solvent A: EtOAc; solvent B: hexanes; gradient:
7%A / 93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A / 40%B (2 CV);
flow rate: 40 mL/min; monitored at 254 and 280 nm] resulting in di-TBS-indole 21 as a
1
pale yellow powder (0.04 g, 0.59 mmol, 20%, Rf = 0.33 (70:30 hexanes:EtOAc)). H
26 of 48

NMR (CDCl3, 500 MHz): 8.31 (br s, 1H, NH), 7.90 (d, J = 8.5 Hz, 1H, ArH), 6.99 (s,
2H, ArH) 6.94 (dd, J = 2.0 Hz, 8.5 Hz, 1H, ArH), 6.89 (d, J = 2.0 Hz, 1H, ArH), 6.82
(dd, J = 2.0 Hz, 8.5 Hz, 1H, ArH), 6.76 (d, J = 2.5 Hz, 1H, ArH), 6.70 (d, J = 8.0 Hz, 1H,
ArH), 3.79 (s, 3H, OCH3), 3.75 (s, 3H, OCH3), 3.69 (s, 6H, OCH3), 1.01 (s, 9H, C(CH3)3),
0.94 (s, 9H, C(CH3)3), 0.22 (s, 6H, Si(CH3)2), 0.04 (s, 6H, Si(CH3)2). 13C NMR (CDCl3,
125 MHz): 191.8, 153.0, 152.6, 151.7, 145.2, 142.3, 141.3, 136.5, 134.6, 125.2, 123.9,
122.3, 121.9, 116.7, 112.9, 111.8, 107.4, 105.1, 101.6, 60.9, 56.1, 55.5, 25.9, 25.8, 18.46,
18.45, -4.2, -4.8. HPLC: 23.31 min., purity at 254 nm 90.6%. HRMS (ESI+): m/z
calculated for C37H52NO7Si2 [M+H]+ 678.3277, found 678.3279.
4.1.18. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 ,4 ,5 -
trimethoxybenzoyl)-4,5,6-trimethoxyindole (22)
To a solution of compound 7 (0.05 g, 0.11 mmol) in o-dichlorobenzene (10 mL)
was added 3,4,5-trimethoxybenzoylchloride (0.04 g, 0.17 mmol). The reaction mixture
was heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark green colored solid was subjected to flash
chromatography using a prepacked 25 g silica column [solvent A: EtOAc; solvent B:
hexanes; gradient: 12%A / 88%B (4 CV), 12%A / 88%B 100%A / 0%B (10 CV),
100%A / 0%B (2 CV); flow rate: 25 mL/min; monitored at 254 and 280 nm] resulting in
TBS-indole 22 as a pale yellow powder (0.03 g, 0.05 mmol, 46%, Rf = 0.50 (50:50
1
hexanes:EtOAc)). H NMR (CDCl3, 500 MHz): 8.25 (br s, 1H, NH), 7.19 (s, 2H, ArH),
6.99 (dd, J = 2.5 Hz, 8.5 Hz, 1H, ArH) 6.88 (d, J = 2.5 Hz, 1H, ArH), 6.75 (d, J = 8.0 Hz,
1H, ArH), 6.69 (s, 1H, ArH), 3.90 (s, 3H, OCH3), 3.85 (s, 3H, OCH3), 3.82 (s, 3H,
OCH3), 3.76 (s, 3H, OCH3), 3.74 (s, 6H, OCH3), 3.72 (s, 3H, OCH3), 0.93 (s, 9H,
27 of 48

C(CH3)3), 0.04 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125 MHz): 193.4, 152.9, 152.1,
151.4, 146.4, 145.3, 142.2, 137.8, 136.6, 134.2, 132.4, 124.7, 121.1, 120.5, 116.7, 114.4,
112.3, 107.6, 89.8, 61.4, 61.0, 60.8, 56.4, 56.3, 55.6, 25.8, 18.5, -4.7. HPLC: 18.60
min., purity at 254 nm 90.7%. HRMS (ESI+): m/z calculated for C34H44NO9Si [M+H]+
638.2780, found 638.2780.
4.1.19. 2-(4 -Methoxyphenyl)-3-(3 ,4 ,5 -trimethoxybenzoyl)-6-methoxy-7-tert-
butyldimethylsilyloxyindole (23)
To a solution of compound 10 (0.05 g, 0.13 mmol) in o-dichlorobenzene (10 mL)
was added 3,4,5-trimethoxybenzoylchloride (0.05 g, 0.20 mmol). The reaction mixture
was heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark green colored solid was subjected to flash
chromatography using a prepacked 25 g silica column [solvent A: EtOAc; solvent B:
hexanes; gradient: 10%A / 90%B (4 CV), 10%A / 90%B 80%A / 20%B (10 CV),
80%A / 20%B (2 CV); flow rate: 25 mL/min; monitored at 254 and 280 nm] resulting in
TBS-indole 23 as a yellow powder (0.06 g, 0.10 mmol, 76%, Rf = 0.36 (60:40
1
hexanes:EtOAc)). H NMR (CDCl3, 500 MHz): 8.20 (br s, 1H, NH), 7.56 (d, J = 8.7
Hz, 1H, ArH), 7.26 (d, J = 9.0 Hz, 2H, ArH) 6.96 (s, 2H, ArH), 6.94 (d, J = 8.7 Hz, 1H,
ArH), 6.78 (d, J = 8.6 Hz, 2H, ArH), 3.88 (s, 3H, OCH3), 3.80 (s, 3H, OCH3), 3.76 (s, 3H,
OCH3), 3.70 (s, 6H, OCH3), 1.09 (s, 9H, C(CH3)3), 0.26 (s, 6H, Si(CH3)2). 13C NMR
(CDCl3, 125 MHz): 192.0, 160.2, 152.6, 146.0, 142.8, 141.3, 134.9, 130.3, 129.99,
129.95, 125.0, 124.8, 114.4, 114.2, 113.4, 109.9, 107.5, 61.0, 56.7, 56.2, 55.5, 26.3, 18.8,
-4.1. HPLC: 20.21 min., purity at 254 nm >99%. HRMS (ESI+): m/z calculated for
C32H39NNaO7Si [M+Na]+ 600.2388, found 600.2383.
28 of 48

4.1.20. 2-(3 -tert-Butyldimethylsiloxy-4 -methoxyphenyl)-3-(3 ,4 ,5 -
trimethoxybenzoyl)-6,7-dimethoxyindole (24)
To a solution of compound 11 (0.25 g, 0.60 mmol) in o-dichlorobenzene (10 mL)
was added 3,4,5-trimethoxybenzoylchloride (0.15 g, 0.66 mmol). The reaction mixture
was heated to reflux at 160 oC for 12 h. The o-dichlorobenzene was removed by simple
distillation, and the resulting dark green colored solid was subjected to flash
chromatography using a prepacked 50 g silica column [solvent A: EtOAc; solvent B:
hexanes; gradient: 7%A / 93%B (4 CV), 7%A / 93%B 60%A / 40%B (10 CV), 60%A
/ 40%B (5.2 CV); flow rate: 50 mL/min; monitored at 254 and 280 nm] resulting in TBS-
indole 24 as a yellow powder (0.08 g, 0.14 mmol, 23%, Rf = 0.17 (70:30
1
hexanes:EtOAc)). H NMR (CDCl3, 500 MHz): 8.53 (br s, 1H, NH), 7.71 (d, J = 8.5
Hz, 1H, ArH), 6.98 (m, 4H, ArH) 6.77 (d, J = 2.0 Hz, 1H, ArH), 6.73 (d, J = 8.5 Hz, 1H,
ArH), 4.06 (s, 3H, OCH3) 3.96 (s, 3H, OCH3), 3.79 (s, 3H, OCH3), 3.76 (s, 3H, OCH3),
3.69 (s, 6H, OCH3), 0.94 (s, 9H, C(CH3)3), 0.03 (s, 6H, Si(CH3)2). 13C NMR (CDCl3, 125
MHz): 191.8, 152.6, 151.8, 148.0, 145.2, 142.8, 141.3, 134.6, 134.0, 130.2, 125.2,
125.1, 122.3, 122.2, 116.8, 113.1, 111.8, 110.4, 107.4, 61.3, 60.9, 57.3, 56.1, 55.5, 25.8,
18.5, -4.7. HPLC: 19.24 min., purity at 254 nm >99%. HRMS (ESI+): m/z calculated
for C33H41NNaO8Si [M+Na]+ 630.2494, found 630.2491.
4.1.21. 2-(3 -Hydroxy-4 -methoxyphenyl)-3-(3 ,5 -dinitrobenzoyl)-6-methoxyindole
(25)
To a well-stirred solution of compound 13 (0.40 g, 0.69 mmol) in THF (10 mL) at
0 oC was added tetrabutylammonium fluoride (TBAF) (1.03 mL, 1.03 mmol, 1 M in
29 of 48