Synthesis of bisindolylmaleimides related to GF109203x and their efficient conversion to the bioactive indolocarbazoles

Article abstract of DOI:10.1039/b607504e

From a structure-activity relationship perspective, the new indolocarbazoles 11 and 12 have been synthesized and evaluated biologically as novel Chk1 inhibitors. Compounds 11 and 12 were synthesized in high yield from indole via bisindolylmaleimides 18 and 24. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b607504e

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www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis of bisindolylmaleimides related to GF109203x and their efficient
conversion to the bioactive indolocarbazoles
Sudipta Roy,a Alan Eastmanb and Gordon W. Gribble*a
Received 26th May 2006, Accepted 30th June 2006
First published as an Advance Article on the web 21st July 2006
DOI: 10.1039/b607504e
From a structure–activity relationship perspective, the new indolocarbazoles 11 and 12 have been
synthesized and evaluated biologically as novel Chk1 inhibitors. Compounds 11 and 12 were
synthesized in high yield from indole via bisindolylmaleimides 18 and 24.
Go¨6976 (5) abrogated S and G2 arrest at a concentration sub-
stantially lower than that required to inhibit PKC. Interestingly,
Introduction
Cell cycle checkpoints are activated in response to DNA damage
UCN-01 (1) did not demonstrate this selectivity for checkpoint
thereby delaying cell cycle progression in order to provide more
inhibition. Accordingly, we initiated a synthetic program to
time for DNA repair. Cell cycle arrest in G1 or S phase prevents
develop novel analogues rationally designed to overcome the
replication of damaged DNA, while arrest at G2 prevents damaged
obstacles observed with the other analogues. During our screening
chromosomes from being segregated in mitosis; thus preventing
to identify novel inhibitors of Chk1, we found that ICP-103 (6) is
also a potent checkpoint inhibitor.10 Therefore, we have focused
our investigation on this class of molecules as potential inhibitors
of Chk1. We synthesized two nitrile analogues of ICP-103, ICP-
106 (7) and ICP-109 (8), with variable lengths of the nitrile arm to
investigate the effect of the nitrile chain-length on Chk1 activity
(Fig. 2).11 We find that ICP-106 (7) and ICP-109 (8) are less potent
than ICP-103 (6) at abrogating DNA damage-induced cell cycle
arrest. From this activity data for the nitrile analogues 7 and 8,
it was found that a three-carbon nitrile chain provided maximum
activity. We then synthesized a novel amide analogue of ICP-103,
ICP-112 (9), bearing the same number of carbons in the amide
arm.11 However, in this latter study we found that a cyano group
is the more desirable functionality than an amide for activity since
ICP-112 (9) was found to be less active than ICP-103 (6).
In the course of our structure–activity relationship studies on
ICP-103 analogues, we have synthesized and tested two new
amine analogues related to the known PKC inhibitor GF109203x12
(Go¨6850, 10), ICP-121 (11) and ICP-125 (12) (Fig. 3). We wanted
to further explore the SAR by replacing the nitrile with an amine.
We decided to maintain the same three-carbon spacer between the
indole nitrogen and the functional group nitrogen as in ICP-103
(6) due to its high activity compared to ICP-106 (7) and ICP-109
(8).
the propagation of genetic abnormalities. Inhibition of the G2
checkpoint has attracted widespread interest because most cancer
cells have an inoperative G1 checkpoint. The activity of the G1
checkpoint is dependent on the p53 tumor suppressor protein
which is deleted or mutated in more than 50% of all cancers.
Although cells with defective p53 are unable to activate the G1
checkpoint in response to DNA damage, they retain the ability to
arrest in S and G2. This provides the cells with an opportunity
to repair their DNA and thereby survive and grow. The S and
G2 checkpoints are regulated by various kinases among which
checkpoint kinase 1 (Chk1) plays a major role. Inhibitors of Chk1
preferentially abrogate cell cycle arrest in p53-defective cells and
selectively sensitize cancer cells with mutated p53 to killing by
DNA-damaging agents. Therefore, combining a Chk1 inhibitor
with a DNA damaging agent should selectively drive p53-defective
cells into a premature and lethal mitosis.1
UCN-01 (1), the synthetic 7-hydroxy derivative of the non-
selective PKC inhibitor staurosporine (2),2 generated considerable
interest in our laboratory when it was found to be a potent inhibitor
of DNA damage-induced S and G2 cell cycle checkpoints, which
led to increased killing of tumor cells (Fig. 1).3 Although UCN-01
is well recognized as a protein kinase C inhibitor,4 this checkpoint
inhibition was attributed to its ability to inhibit Chk1.5 Unfortu-
nately, UCN-01 binds avidly to human serum proteins thereby
compromising its potential therapeutic activity.6 Accordingly,
we screened other indolocarbazoles to identify analogues with
improved therapeutic potential. Initially, a K252a (3) analogue,
ICP-1 (4), was synthesized and tested, and was found to overcome
the problem of protein binding but it had considerably reduced
potency.7
We herein describe the synthesis of compounds 11 and 12,
and briefly report the biological activity of these two novel
indolocarbazoles.
Results and discussion
Towards the synthesis of 11, we alkylated the indole nitrogen
with 1,3-dibromopropane13 in the presence of KOH to furnish
13 (Scheme 1). A small amount (10%) of 1-allylindole was
also recovered from the reaction mixture. Compound 13 was
then treated with di-tert-butyl-iminodicarboxylate and caesium
carbonate to produce fully protected amine 14 in 99% yield. The
key starting material 14 can be prepared alternatively using 15 with
sodium hydride in DMF–THF. Compound 15 was synthesized
More recently, we found that Go¨6976 (5) is a very potent check-
point inhibitor even in the presence of human serum,8 and this
has also been attributed to the inhibition of Chk1.9 Additionally,
aDepartment of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
E-mail: ggribble@dartmouth.edu; Fax: 603-646-3946; Tel: 603-646-3118
bDepartment of Pharmacology and Toxicology, Dartmouth Medical School,
Hanover, NH 03755, USA
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Fig. 1 Indolocarbazoles 1–4.
Fig. 2 Go¨6976 analogues.
Fig. 3 GF109203x analogues.
from 1,3-dibromopropane and di-tert-butyl-iminodicarboxylate
in the presence of sodium hydride.14 N-Alkylation of indole-3-
acetic acid using methyl iodide in the presence of excess sodium
hydride gave 1-methylindole-3-acetic acid (16) in 94% yield.10
Amine 14 was treated with oxalyl chloride in dichloromethane to
furnish the glyoxylyl chloride which was immediately treated with
1-methylindole-3-acetic acid (16) in the presence of triethylamine
to produce anhydride 17 in 30% yield in two steps from 14
(Scheme 2).15 Loss of one Boc group was observed during this
reaction sequence. The anhydride 17 was subsequently converted
to the imide 18 by exposure to HMDS and MeOH in DMF
in 99% yield.16 During our synthesis of ICP-106 (7), we found
that the final oxidative cyclization was quite challenging for the
bisindolylmaleimide with substituents present on both N-12 and
N-13.17 Low yields are registered in most cases and the isolation
of the final product is difficult from the complex reaction mixture.
However, in some cases, palladium(II) trifluoroacetate was found
to be superior for this cyclization.11 To our delight, heating
Scheme 1
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Scheme 2
bisindolylmaleimide 18 in DMF in the presence of palladium(II)
Experimental
trifluoroacetate gave 19 in 80% yield. Finally, deprotection of the
Boc-group using an ethereal solution of 1M HCl in methanol gave
the target compound 11 in essentially quantitative yield.
Melting points were determined with a Mel-Temp Laboratory
Device apparatus and are uncorrected. IR spectra were recorded
on a Perkin-Elmer 600 series FTIR spectrophotometer. H-and
1
Our target compound 12 was synthesized in a similar fashion.
Boc-Protection of 3-bromopropylamine hydrobromide furnished
20 in 92% yield (Scheme 3).18 Compound 20 was then used
to alkylate indole to give compound 21. Compound 21 was
methylated with iodomethane in the presence of sodium hydride to
produce 22. Fully protected amine 22 was subjected to the coupling
reaction with 1-methylindole-3-acetic acid (16) which produced
the desired anhydride 23 in 32% yield. Conversion of anhydride 23
to imide 24 was achieved using HMDS and MeOH in 99% yield.
Bisindolylmaleimide 24 was then subjected to the challenging
oxidative cyclization reaction using palladium(II) trifluoroacetate.
To our extreme satisfaction, we obtained the desired product 25 in
excellent yield. This is the highest yield we have obtained so far for
this otherwise capricious cyclization step. Finally, deprotection of
the Boc group furnished the target compound 12.
In work to be reported separately, we find that ICP-125 (12)
exhibits high potency in an assay using flow cytometry analysis.
Thus, ICP-125 (12) abrogates S phase arrest at 100 nM indicating
the compound is inhibiting Chk1. However, ICP-121 (11) was
tested up to 10 lM and found to be inactive in the same assay.
These values can be compared to the efficacy of Go¨6976 (5) of
30 nM and efficacy of ICP-103 (6) of 100 nM in the same assay.
In summary, we have synthesized ICP-125 (12) and find it to be
a potent Chk1 inhibitor. We have found that Pd(II) catalyzed ox-
idative cyclization is much more effective for bisindolylmaleimides
bearing an amine group. Also, we find that a secondary amine or
a nitrile are more desirable than a primary amine or amide on the
chain. Work is in progress in our laboratory with other nitrogen-
bearing functionalities and these will be reported in due course.
13C-NMR spectra were recorded on either a Varian XL-300 or
500 Fourier transform NMR spectrometer. Both low- and high
resolution mass spectra were carried out at the Mass Spectrometry
Laboratory, School of Chemical Sciences, University of Illinois at
Urbana Champaign. Anhydrous THF and CH2Cl2 were prepared
by a solvent purification system. All other solvents (analytical
grade) including anhydrous solvents and reagents were used
as received. All experiments were performed under a nitrogen
atmosphere unless otherwise stated.
1-(3-Bromopropyl)-1H-indole (13)
To a stirred solution of indole (1.17 g, 10 mmol) and freshly
powdered KOH (88%, 0.64 g, 10 mmol) in DMF (25 mL) was
added 1,3-dibromopropane (6.06 g, 30 mmol) in DMF (25 mL)
in one portion. The mixture was stirred at rt for 24 h. Water
(100 mL) was added and extracted with ether (3 × 75 mL). The
organic phase was washed with water (100 mL), dried (MgSO4)
and concentrated in vacuo. The residue was purified by column
chromatography on silica gel (initially pet. ether; then 15 : 1 pet.
ether : ether) to furnish the desired product (1.21 g, 51%) as a
colorless oil: IR (thin film): 3051, 2939, 1611, 1511, 1461, 1314,
1
1258, 1229, 742 cm−1; H-NMR (CDCl3): d 7.71–7.73 (m, 1H),
7.45 (d, 1H, J = 8.3 Hz), 7.29–7.32 (m, 1H), 7.19–7.22 (m, 2H),
6.58 (d, 1H, J = 2.9 Hz), 4.38 (t, 2H, J = 6.3 Hz), 3.35 (t, 2H,
J = 6.3 Hz), 2.39 (2H, qn, J = 6.3 Hz); 13C-NMR (CDCl3): d
135.9, 128.8, 128.1, 121.8, 121.2, 119.6, 109.4, 101.6, 44.0, 32.8,
30.7.
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Scheme 3
A small amount of 1-allylindole was recovered as a colorless
oil19 (0.16 g, 10%) which came in earlier fractions during column
chromatography: H-NMR (CDCl3): d 7.78–7.82 (m, 1H), 7.44–
(CDCl3): d 3.68–3.73 (m, 2H), 3.39 (t, 2H, J = 6.7 Hz), 2.08–2.18
(m, 2H); 13C-NMR (CDCl3): d 152.6, 82.7, 45.4, 32.3, 30.6, 28.2.
1
Bis(1,1-dimethylethyl)[3-(1H-indolyl)propyl]imidodicarbonate (14)
7.47 (m, 1H), 7.33–7.38 (m, 1H), 7.24–7.30 (m, 1H), 7.20 (d,
1H, J = 3.2 Hz), 6.04–6.16 (m, 1H), 5.29–5.34 (m, 1H), 5.16–
5.24 (m, 1H), 4.79–4.82 (m, 2H); 13C-NMR (CDCl3): d 136.2,
133.6, 128.8, 128.0, 121.7, 121.1, 119.6, 117.3, 109.7, 101.5,
48.9.
From 13. Compound 13 (0.26 g, 1.1 mmol), di-tert-butyl-
iminodicarboxylate (0.22 g, 1 mmol) and caesium carbonate
(0.33 g, 1 mmol) in DMF (10 mL) were stirred for 6 h at
70 ◦C. Water (40 mL) was added and extracted with ethyl acetate
(3 × 25 mL). The organic phase was washed with water (2 ×
25 mL) and dried (Na2SO4). The solvent was evaporated and the
residue was purified by column chromatography on silica gel (4 :
1 hexanes : ethyl acetate) to furnish the desired product (0.37 g,
99%) as a colorless oil.
Bis(1,1-dimethylethyl)(3-bromopropyl)imidodicarbonate (15)
To a stirred solution of di-tert-butyl-iminodicarboxylate (1.09 g,
5 mmol) in THF : DMF (40 mL, 3 : 1) was added sodium hydride
(60% dispersion in mineral oil, 0.21 g, 5.25 mmol). The mixture was
heated at 65 ◦C for 2.5 h, 1,3-dibromopropane (2.3 mL, 22.5 mmol)
was added, and the mixture was stirred for 3 h. It was cooled to 0◦C
and ether (50 mL) was added. Excess hydride was destroyed by the
dropwise addition of water. The organic phase was washed with
water (2 × 50 mL) and dried (MgSO4). The solvent was evaporated
and the residue was purified by column chromatography on silica
gel (initially 98 : 2 hexanes : ether; then 1 : 1 hexanes : ether) to
yield the desired product (1.06 g, 63%) as a colorless oil: IR (thin
From 15. To a stirred suspension of NaH (60% dispersion in
mineral oil, 0.22 g, 5.5 mmol) in DMF (15 mL) at 0 ◦C was added
dropwise a solution of indole (0.41 g, 3.5 mmol) in DMF (10 mL).
After stirring the mixture at 0 ◦C for 30 min, a solution of 15
(1.59 g, 4.7 mmol) in DMF : THF (20 mL, 1 : 1) was added. The
mixture was allowed to reach rt and stirring was continued for
36 h. It was then cooled to 0 ◦C and water (50 mL) was added very
slowly. The aqueous layer was extracted with ethyl acetate (2 ×
50 mL). The organic phase was washed with water (3 × 50 mL)
and brine (50 mL), and dried (Na2SO4). The crude product was
1
film): 3265, 2973, 1688, 1490, 1297, 1118, 1076 cm−1; H-NMR
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purified by column chromatography on silica gel (4 : 1 hexanes :
ethyl acetate) to yield the desired product (0.65 g, 50%) as a
colorless oil.
1,1-Dimethylethyl(3-{3-[2,5-dihydro-4-(1-methyl-1H-indol-3-yl)-
2,5-dioxo-1H-pyrrol-3-yl]-1H-indol-1-yl}propyl)carbamate (18)
To a stirred solution of 17 (0.25 g, 0.5 mmol) in DMF (2.5 mL)
at rt was added HMDS (1.1 mL, 5 mmol) and methanol (0.1 mL,
2.5 mmol). The flask was tightly sealed and the mixture was stirred
at rt for 24 h. The mixture was poured into water (25 mL) and
extracted with ethyl acetate (2 × 25 mL) and dried (MgSO4). The
solvent was evaporated and the residue was purified by column
chromatography on silica gel (95 : 5 dichloromethane : methanol)
to yield the desired product (246 mg, 99%) as a dark red solid: mp
112–114 ◦C; IR (thin film): 2969, 1755, 1703, 1610, 1531, 1333,
IR (thin film): 2977, 2933, 1787, 1745, 1696, 1366, 1146, 1126,
1
740 cm−1; H-NMR (CDCl3): d 7.62–7.64 (m, 1H), 7.33 (d, 1H,
J = 8.3 Hz), 7.19–7.22 (m, 1H), 7.13 (d, 1H, J = 2.9 Hz), 7.08–7.12
(m, 1H), 4.16 (t, 2H, J = 7.1 Hz), 3.65 (t, 2H, J = 7.1 Hz), 2.14
(qn, 2H, J = 7.3 Hz), 1.46 (s, 18H); 13C-NMR (CDCl3): d 152.6,
136.0, 128.8, 127.8, 121.6, 121.2, 119.4, 109.3, 101.4, 82.7, 44.3,
44.1, 29.7, 28.2; LRMS (EI): m/z 374 (M+), 218, 201, 173, 144,
130 (100%); HRMS (EI): calcd for C21H30N2O4: 374.2206, found:
374. 2197.
1
1170, 740 cm−1; H-NMR (DMSO-d6): d 10.93 (s, 1H), 7.86 (s,
1H), 7.76 (s, 1H), 7.45 (d, 1H, J = 8.2 Hz), 7.40 (d, 1H, J = 8.2
Hz), 6.97–7.04 (m, 3H), 6.89 (d, 1H, J = 7.9 Hz), 6.61–6.70 (m,
3H), 4.23 (t, 2H, J = 6.7 Hz), 3.86 (s, 3H), 2.90 (q, 2H, J = 6.1 Hz),
1.83 (qn, 2H, J = 6.6 Hz, 1.38 (s, 9H); LRMS (ESI+): m/z 521
[M + Na]+, 499 [M + H]+; HRMS (ESI+): calcd for C29H31N4O4
[M + H]: 499.2345, found: 499.2341.
1-Methyl-1H-indole-3-acetic acid (16)
To a stirred suspension of NaH (6.0 g, 150 mmol, 60% mineral
oil dispersion) in THF (125 mL) at 0 ◦C was added a solution
of indole-3-acetic acid (5.25 g, 30 mmol) in THF (50 mL). After
stirring the mixture for 30 min at 0 ◦C, a solution of methyl iodide
(14.2 g, 100 mmol) in THF (50 mL) was added dropwise. The
mixture was allowed to slowly reach rt and stirring was continued
for 16 h. The reaction mixture was then cooled to 0 ◦C and
excess hydride was carefully destroyed by slow addition of MeOH
(5 mL) with vigorous stirring, followed by cold water until a clear
yellow solution resulted. Ether (100 mL) was added. The aqueous
phase was separated, acidified with 6 N HCl and extracted with
dichloromethane (3 × 100 mL). The combined dichloromethane
extracts were dried (Na2SO4) and concentrated to about 40–
50 mL. Pet. ether was then added slowly until a brownish
colored solid completely precipitated out. The crude solid was
recrystallized from ethanol to give the desired product (5.33 g,
94%) as a pale brown solid: mp 127–128 ◦C (lit20 127–129 ◦C); IR
(thin film): 3059, 2933, 1699, 1617, 1474 cm−1; 1H-NMR (CDCl3):
d 7.64–7.62 (m, 1H), 7.34–7.26 (m, 2H), 7.19–7.15 (m, 1H), 7.07 (s,
1H), 3.83 (s, 2H), 3.78 (s, 3H); 13C-NMR (CDCl3): d 178.8, 137.0,
128.1, 127.7, 122.0, 119.5, 119.1, 109.5, 106.2, 32.9, 31.2.
1,1-Dimethylethyl[12-(3-aminopropyl)-12,13-dihydro-13-methyl-
5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7-(6H)-
dione]carbamate (19)
A mixture of 18 (25 mg, 0.05 mmol) and palladium(II) triflu-
oroacetate (84 mg, 0.25 mmol) in DMF (3 mL) was heated at
90 ◦C for 2.5 h. The mixture was cooled to rt and ethyl acetate
(25 mL) was added. The organic phase was washed with 0.5 N
HCl (50 mL), water (50 mL) and dried (Na2SO4). The solution was
filtered through Hyflo and purified by column chromatography on
silica gel (95 : 5 dichloromethane : methanol) to yield the desired
product (20 mg, 80%) as a yellow fluorescent solid: mp 213–215 ◦C
(dec); IR (thin film): 3203, 1755, 1698, 1575, 1450, 1317, 1163,
1
745 cm−1; H-NMR (DMSO-d6): d 11.12 (s, 1H), 9.10–9.14 (m,
2H), 7.87 (d, 1H, J = 8.2 Hz), 7.75 (d, 1H, J = 8.2 Hz), 7.60–7.67
(m, 2H), 7.38–7.43 (m, 2H), 6.76 (t, 1H, J = 5.3 Hz), 4.79 (t, 2H,
J = 7.5 Hz), 4.21 (s, 3H), 2.65 (q, 2H, J = 6.1 Hz), 1.67 (qn,
2H, J = 6.9 Hz), 1.24 (s, 9H); LRMS (ESI+): m/z 497 [M + H]+;
HRMS (ESI+): calcd for C29H29N4O4 [M + H]: 497.2189, found:
497.2169.
1,1-Dimethylethyl(3-{3-[2,5-dihydro-4-(1-methyl-1H-indol-3-yl)-
2,5-dioxo-3-furanyl]-1H-indol-1-yl}propyl)carbamate (17)
To a stirred solution of 14 (0.37 g, 1.0 mmol) in dichloromethane
(10 mL) at 0 ◦C was added dropwise oxalyl chloride (0.09 mL,
1.05 mmol). After stirring for 45 min at 0 ◦C, the solvent was evap-
orated in vacuo. The residue was redissolved in dichloromethane
(10 mL) and added dropwise to a stirred solution of 16
(0.19 g, 1.0 mmol) and triethylamine (0.28 mL, 2 mmol) in
dichloromethane (5 mL) at rt. The mixture was stirred at rt for 10 h.
The solvent was evaporated and the crude residue was purified by
column chromatography on silica gel (98 : 2 dichloromethane :
methanol) to furnish t◦he desired product (149 mg, 30%) as a dark
red solid: mp 99–101 C; IR (thin film): 2977, 1817, 1750, 1704,
1527, 1252, 1171, 740 cm−1; 1H-NMR (DMSO-d6): d 7.98 (s, 1H),
7.88 (s, 1H), 7.52 (d, 1H, J = 8.2 Hz), 7.47 (d, 1H, J = 8.2 Hz),
7.07–7.11 (m, 2H), 6.97–7.00 (m, 2H), 6.78 (t, 1H, J = 7.6 Hz),
6.69–6.73 (m, 2H), 4.25 (t, 2H, J = 6.7 Hz), 3.89 (s, 3H), 2.90 (q,
2H, J = 6.4 Hz), 1.83 (qn, 2H, J = 6.7 Hz), 1.38 (s, 9H); LRMS
(EI): m/z 499 (M+), 425, 399 (100%), 356, 312, 283, 269, 249, 191,
158, 107, 77; HRMS (EI): calcd for C29H29N3O5: 499.2107, found:
499.2112.
12-(3-Aminopropyl)-12,13-dihydro-13-methyl-5H-indolo[2,3-a]-
pyrrolo[3,4-c]carbazole-5,7-(6H)-dione hydrochloride (11)
To a solution of 19 (15 mg, 0.03 mmol) in methanol (2 mL) at rt
was added dropwise 1 M HCl in ether (9 mL). The mixture was
stirred at rt for 5 h. The solvent was evaporated and the residue
was recrystallized from methanol to furnish◦the desired product
1
(12.8 mg, 99%) as a yellow solid: mp >300 C (dec.); H-NMR
(DMSO-d6): d 11.18 (s, 1H), 9.16 (d, 1H, J = 7.6 Hz), 9.13 (d, 1H,
J = 7.9 Hz), 7.97 (d, 1H, J = 8.5 Hz), 7.80 (d, 1H, J = 8.2 Hz),
7.65–7.70 (m, 5H), 7.44 (t, 2H, J = 7.6 Hz), 4.89 (t, 2H, J = 7.3
Hz), 4.25 (s, 3H), 2.46–2.49 (m, 2H), 1.78 (qn, 2H, J = 7.6 Hz);
13C-NMR (DMSO-d6): d 170.8, 170.7, 144.9, 143.7, 133.3, 131.8,
127.7, 127.5, 124.9, 124.5, 122.9, 121.8, 121.5, 121.2, 121.1, 120.1,
119.6, 118.7, 112.4, 111.4, 45.6, 36.8; LRMS (ESI+): m/z 397
[(M − HCl) + H]+; HRMS (ESI+): calcd for C24H21N4O2 [(M −
HCl) + H]: 397.1665, found: 397.1662.
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1,1-Dimethylethyl(3-bromopropyl)carbamate (20)
J = 8.3 Hz), 7.24–7.30 (m, 1H), 7.14–7.20 (m, 2H), 6.56 (d, 1H, J =
2.7 Hz), 4.18 (t, 2H, J = 7.2 Hz), 3.32 (t, 2H, J = 6.8 Hz), 2.88 (s,
3H), 2.07–2.16 (m, 2H), 1.51 (s, 9H); 13C-NMR (CDCl3): d 156.1,
136.1, 129.0, 127.9, 121.8, 121.3, 119.6, 109.5, 101.5, 79.9, 46.7,
44.1, 34.5, 28.7; LRMS (EI): m/z 288 (M+), 232, 215, 156, 144, 131
(100%), 117; HRMS (EI): calcd for C17H24N2O2: 288.1838, found:
288.1844.
To a stirred solution of 3-bromopropylamine hydrobromide
(2.20 g, 10 mmol) and Boc-anhydride (2.18 g, 10 mmol) in
dichloromethane (50 mL) at 0 ◦C was added dropwise triethy-
lamine (2.89 mL, 20 mmol). The solution was stirred at the same
temperature for 15 min. The mixture was allowed to reach rt and
stirred for 7 h. The mixture was washed with water (2 × 50 mL)
and dried (Na2SO4). The solvent was evaporated and the residue
was purified by column chromatography on silica gel (initially
hexanes; then 1 : 1 hexanes : ethyl acetate) to furnish the desired
product (2.19 g, 92%) as a colorless oil which slowly solidified at
−4 ◦C: mp: 38–40 ◦C (lit.21 33–34 ◦C); IR (thin film): 3252, 2969,
1,1-Dimethylethyl(3-{3-[2,5-dihydro-4-(1-methyl-1H-indol-3-yl)-
2,5-dioxo-3-furanyl]-1H-indol-1-yl}propyl)methylcarbamate (23)
To a stirred solution of 22 (1.44 g, 5 mmol) in dichloromethane
(50 mL) at 0 ◦C was added dropwise oxalyl chloride (0.45 mL,
5.1 mmol). The mixture was stirred at the same temperature
for 20 min. Then the solvent was evaporated and the residue
was redissolved in dichloromethane (50 mL) and added dropwise
to a stirred solution of 16 (0.95 g, 5 mmol) and triethylamine
(1.52 mL, 10 mmol) in dichloromethane (20 mL) at rt. The
solution was stirred for 12 h. The solvent was evaporated and
the residue was purified by column chromatography on silica gel
(98 : 2 dichloromethane : methanol) to furnish the desired product
(0.81 g, 32%) as a dark-red solid: mp 81–83 ◦C; IR (thin film):
1
1685, 1490, 1450, 1298, 1119, 1076 cm−1; H-NMR (CDCl3): d
3.44 (t, 2H, J = 6.6 Hz), 3.27 (t, 2H, J = 6.6 Hz), 2.04 (qn, 2H,
J = 6.6 Hz), 1.44 (s, 9H); 13C-NMR (CDCl3): d 156.1, 32.9, 31.0,
28.6, 27.6.
1,1-Dimethylethyl[3-(1H-indol-1-yl)propyl]carbamate (21)
To a stirred solution of NaH (60% dispersion in mineral oil, 0.24 g,
6 mmol) in DMF (25 mL) at 0 ◦C was added dropwise indole
(1.19 g, 5 mmol) dissolved in DMF (15 mL). After the addition,
the mixture was heated at 80 ◦C for 1 h. It was then cooled to
0 ◦C. Then, a solution of 20 (1.31 g, 5.5 mmol) in DMF (10 mL)
1
2973, 2932, 1816, 1752, 1689, 1528, 1255, 1147, 740 cm−1; H-
NMR (DMSO-d6): d 7.99 (s, 1H), 7.85 (s, 1H), 7.50 (t, 2H, J =
9.3 Hz), 7.06–7.14 (m, 2H), 7.01 (d, 1H, J = 8.1 Hz), 6.79 (t, 1H,
J = 7.5 Hz), 6.67–6.73 (m, 2H), 4.22 (t, 2H, J = 6.8 Hz), 3.89 (s,
3H), 3.14 (m, 2H), 2.74 (s, 3H), 1.93 (m, 2H), 1.28–1.39 (m, 9H);
LRMS (ESI+): m/z 536 [M + Na]+, 514 [M + H]+; HRMS (ESI+):
calcd for C30H32N3O5 [M + H]: 514.2342, found: 514.2336.
◦
was added dropwise and stirred at 0 C for 30 min. The mixture
was then allowed to reach rt and stirring was continued for 18 h.
The DMF was evaporated and the oily residue was dissolved
in ethyl acetate (100 mL). The organic phase was washed with
water (3 × 50 mL) and brine (50 mL), and dried (Na2SO4). The
solvent was evaporated and the residue was purified by column
chromatography on silica gel (2 : 1 hexanes : ethyl acetate) to
furnish the desired product (1.03 g, 75%) as a colorless oil: IR (thin
film): 3350, 2974, 2932, 1694, 1512, 1462, 1250, 1171, 742 cm−1;
1H-NMR (CDCl3): d 7.74 (d, 1H, J = 8.1 Hz), 7.38–7.41 (m, 1H),
7.28–7.33 (m, 1H), 7.19–7.24 (m, 1H), 7.16 (d, 1H, J = 3.3 Hz),
6.59 (d, 1H, J = 2.9 Hz), 4.78 (brs, 1H), 4.16 (t, 2H, J = 6.9 Hz),
3.12 (m, 2H), 2.01 (qn, 2H, J = 6.9 Hz), 1.56 (s, 9H); 13C-NMR
(CDCl3): d 156.1, 135.9, 128.7, 127.9, 121.6, 121.1, 119.4, 109.3,
101.3, 79.4, 43.7, 38.2, 30.5, 28.5; LRMS (EI): m/z 274 (M+), 218,
201, 156, 144, 130 (100%), 117; HRMS (EI): calcd for C16H22N2O2:
274.1681, found: 274.1685.
1,1-Dimethylethyl(3-{3-[2,5-dihydro-4-(1-methyl-1H-indol-3-yl)-
2,5-dioxo-1H-pyrrol-3-yl]-1H-indol-1-yl}propyl)methylcarbamate
(24)
To a stirred solution of anhydride 23 (257 mg, 0.5 mmol) in
DMF (2 mL) were added HMDS (1.1 mL, 5 mmol) and methanol
(0.1 mL, 2.5 mL). The reaction flask was tightly closed and the
mixture was stirred for 36 h. It was poured into cold water (50 mL)
and extracted with ethyl acetate (3 × 50 mL). The organic phase
was washed with water (2 × 50 mL) and dried (Na2SO4). The
solvent was evaporated and the residue was purified by column
chromatography on silica gel (95 : 5 dichloromethane : methanol)
to furnish the desired product (253 mg, 99%) as an orange-red
solid: mp 215–217 ◦C; IR (thin film): 3218, 2972, 1755, 1701, 1532,
1332, 1147, 739 cm−1; 1H-NMR (DMSO-d6): d 10.94 (s, 1H), 7.86
(s, 1H), 7.74 (s, 1H), 7.39–7.46 (m, 2H), 6.99–7.06 (m, 2H), 6.94
(d, 1H, J = 8.1 Hz), 6.68–6.72 (m, 2H), 6.58–6.63 (m, 1H), 4.19
(t, 2H, J = 6.8 Hz), 3.85 (s, 3H), 3.13 (m, 2H), 2.73 (s, 3H), 1.92
(m, 2H), 1.29–1.39 (m, 9H); LRMS (ESI+): m/z 513 [M + H]+;
HRMS (ESI+): calcd for C30H33N4O4 [M + H]: 513.2502, found:
513.2501.
1,1-Dimethylethyl[3-(1H-indol-1-yl)propyl]methylcarbamate (22)
To a stirred solution of NaH (60% dispersion in mineral oil, 0.26 g,
6.4 mmol) in THF (20 mL) at 0 ◦C was added dropwise a solution
of 21 (0.88 g, 3.2 mmol) in THF (10 mL). The mixture was
stirred at the same temperature for 45 min. Then iodomethane
(0.32 mL, 5.1 mmol) was added dropwise. After the addition, the
solution was slowly allowed to warm to rt and stirred for 20 h. The
solution was cooled to 0 ◦C and the excess hydride was destroyed
by the dropwise addition of ice-cold water. Dichloromethane
(100 mL) was added and the organic phase was washed with
water (2 × 50 mL) and brine (50 mL), and dried (Na2SO4). The
solvent was evaporated and the residue was purified by column
chromatography on silica gel (2 : 1 hexanes : ethyl acetate) to
furnish the desired product (0.77 g, 84%) as a yellowish oil: IR
(thin film): 2974, 2930, 1694, 1482, 1464, 1393, 1365, 1170, 1147,
1,1-Dimethylethyl{12-(3-aminopropyl)-12,13-dihydro-13-methyl-
5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7-(6H)-
dione}methylcarbamate (25)
A mixture of imide 24 (26 mg, 0.05 mmol) and palladium(II)
trifluoroacetate (84 mg, 0.25 mmol) in DMF (3 mL) was heated at
90 ◦C for 2 h. The mixture was cooled and poured into ethyl acetate
(25 mL). The organic phase was washed with 0.5 N HCl (50 mL),
1
741 cm−1; H-NMR (CDCl3): d 7.69–7.71 (m, 1H), 7.39 (d, 1H,
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water (2 × 50 mL), dried (Na2SO4) and filtered through Hyflo. The
filtrate was concentrated and purified by column chromatography
on silica gel (95 : 5 dichloromethane : methanol) to furnish the
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◦
desired product (24 mg, 94%) as a yellow solid: mp 208–210 C
(dec.); IR (thin film): 3221, 2973, 1755, 1716, 1694, 1450, 1316,
1
1158, 744 cm−1; H-NMR (acetone-d6): d 9.84 (s, 1H), 9.18–9.22
(m, 2H), 7.79 (d, 1H, J = 8.2 Hz), 7.69 (d, 1H, J = 8.2 Hz),
7.58–7.64 (m, 2H), 7.34–7.39 (m, 2H), 4.84 (m, 2H), 4.27 (s,
3H), 2.87 (m, 2H), 2.64 (s, 3H), 1.83–1.89 (m, 2H), 1.26–1.41 (m,
9H); LRMS (ESI+): m/z 533 [M + Na]+, 511 [M + H]+; HRMS
(ESI+): calcd for C30H30N4O4Na [M + Na]: 533.2165, found:
533.2169.
12,13-Dihydro-12-methyl-13-{3-[(1-methyl)amino]propyl}-5H-
indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7-(6H)-dione hydrochloride
(12)
6 E. Fuse, H. Tanii, N. Kurata, H. Kobayashi, Y. Shimada, T. Tamura,
Y. Sasaki, Y. Tanigawara, R. D. Lush, D. Headlee, W. D. Figg, S. G.
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To a stirred solution of 25 (15 mg, 0.03 mmol) in methanol (2 mL)
was added 1 M HCl in ether (9 mL). The mixture was stirred at
rt for 5 h. Then the solvent was evaporated and the residue was
purified by recrystallization from methanol to yield the desired
product (13.2 mg, 98%) as a yellow solid: mp >290 ◦C (dec.); 1H-
NMR (DMSO-d6): d 11.17 (s, 1H), 9.16 (d, 1H, J = 7.9 Hz), 9.12
(d, 1H, J = 7.9 Hz), 8.61 (brs, 2H), 7.97 (d, 1H, J = 8.2 Hz), 7.79
(d, 1H, J = 8.2 Hz), 7.64–7.69 (m, 2H), 7.44 (t, 2H, J = 7.5 Hz),
4.88 (t, 2H, J = 7.5 Hz), 4.25 (s, 3H), 2.67 (m, 2H), 2.35 (s, 3H),
1.83–1.87 (m, 2H); 13C-NMR (DMSO-d6): d 170.8, 170.7, 144.8,
143.6, 133.2, 131.7, 127.7, 127.5, 124.9, 124.5, 122.9, 121.8, 121.5,
121.2, 121.1, 120.2, 119.6, 118.7, 112.4, 111.4, 45.5, 45.4, 36.8,
32.3, 24.7; LRMS (ESI+): m/z 411 [(M − HCl) + H]+; HRMS
(ESI+): calcd for C25H23N4O2 [(M − HCl) + H]: 411.1821, found:
411.1817.
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Acknowledgements
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This investigation was supported in part by the donors of the
Petroleum Research Fund (PRF), administered by the American
Chemical Society, the National Institutes of Health (CA 82220),
and Wyeth.
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3234 | Org. Biomol. Chem., 2006, 4, 3228–3234
This journal is
The Royal Society of Chemistry 2006
©