Synthesis and biological activities of new furo[3,4-b]carbazoles: Potential topoisomerase II inhibitors

Article abstract of DOI:10.1016/j.ejmech.2010.09.003

New 1,5-Dihydro-4-(substituted phenyl)-3H-furo[3,4-b]carbazol-3-ones were synthesised via a key step Diels-Alder reaction under microwave irradiation. 3-Formylindole was successfully used in a 6-step synthesis to obtain those complex heterocycles. The Diels-Alder reaction generating the carbazole ring was optimised under thermal conditions or microwave irradiation. After cleavage of functional groups, DNA binding, topoisomerase inhibition and cytotoxic properties of the new-formed furocarbazoles were investigated. These carbazoles do not present a strong interaction with the DNA, and do not modify the relaxation of the DNA in the presence of topoisomerase I or II except for one promising compound. This compound is a potent topoisomerase II inhibitor, and its cellular activity is not moderated compared to etoposide. The synthesis of these molecules allowed the generalisation of the method using indole and 5-OBn indole and several benzaldehydes. The synthesis of these molecules produced chemical structures endowed with promising cytotoxic and topoisomerase II inhibition activities.

Full text of DOI:10.1016/j.ejmech.2010.09.003

European Journal of Medicinal Chemistry 45 (2010) 5428e5437
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and biological activities of new furo[3,4-b]carbazoles: Potential
topoisomerase II inhibitors
,
Youssef Hajbi a, Cléopatra Neagoie a b, Bérenger Biannic a, Aurélie Chilloux a, Emeline Vedrenne a,
,
Brigitte Baldeyrou c, Christian Bailly c, Jean-Yves Mérour a, Sorin Rosca b, Sylvain Routier a
**
,
*
,
Amélie Lansiaux c
a Institut de Chimie Organique et Analytique, Université d’Orléans, CNRS UMR 6005, B.P. 6759, 45067 Orléans Cedex 2, France
b Universitatea Politehnica, 313, Splaiul Independentei, 77206 Bucuresti, Romania
c INSERM U-837, Centre Oscar Lambret, Université Lille Nord de France, Faculté de Médecine de Lille, IRCL, 59045 Lille, France
a r t i c l e i n f o
a b s t r a c t
Article history:
New 1,5-Dihydro-4-(substituted phenyl)-3H-furo[3,4-b]carbazol-3-ones were synthesised via a key step
DielseAlder reaction under microwave irradiation. 3-Formylindole was successfully used in a 6-step
synthesis to obtain those complex heterocycles. The DielseAlder reaction generating the carbazole ring
was optimised under thermal conditions or microwave irradiation. After cleavage of functional groups,
DNA binding, topoisomerase inhibition and cytotoxic properties of the new-formed furocarbazoles were
investigated. These carbazoles do not present a strong interaction with the DNA, and do not modify the
relaxation of the DNA in the presence of topoisomerase I or II except for one promising compound. This
compound is a potent topoisomerase II inhibitor, and its cellular activity is not moderated compared to
etoposide. The synthesis of these molecules allowed the generalisation of the method using indole and 5-
OBn indole and several benzaldehydes. The synthesis of these molecules produced chemical structures
endowed with promising cytotoxic and topoisomerase II inhibition activities.
Received 4 June 2010
Received in revised form
27 August 2010
Accepted 1 September 2010
Available online 15 September 2010
Keywords:
Carbazoles
Synthesis
Azatoxin
Microwave
Topoisomérase II
Inhibition cytotoxicity
Ó 2010 Elsevier Masson SAS. All rights reserved.
1. Introduction
O
O
R
Lignans are natural products which can be isolated from a wide
range of plants. The synthesis of such scaffolds is important as they
exhibit great antiviral activities [1]. Some of them proved to be
promising tools for the fight against cancer: podophyllotoxin and
its glycosylated analogues etoposide and teniposide, for instance,
are pro-apoptotic drugs strongly inhibiting tubulin polymerisation
and topoisomerase II [2e4].
This enzyme has raised considerable attention due to its crucial
role in the cell cycle and DNA replication. A lot of well-known
compounds, such as mitoxantrone, inhibit its activity, but drug
resistance prompted chemists to design new inhibitors by
exchanging the quinonic chromophore for another. In lignans
chemical series, naphthalenic analogues such as I, where the non-
aromatic central ring was suppressed, were developed; they exhibit
a good activity against the topoisomerase II (Fig. 1) [7].
O
OH
O
HO
OH
O
O
O
O
O
O
O
N
N
H
O
O
O
OMe
MeO
OMe
MeO
OMe
MeO
OMe
podophyllotoxin
OMe
azatoxin
OH
etoposide R = CH3
teniposide R =
S
MeO
MeO
O
O
R1
O
O
N
H
O
* Corresponding author. Tel.: þ33 238 49 48 53; fax: þ33 238 41 72 81.
** Corresponding author. Tel.: þ33 320 29 59 53; fax: þ33 320 16 92 29.
E-mail addresses: sylvain.routier@univ-orleans.fr (S. Routier), a-lansiaux@
o-lambret.fr (A. Lansiaux).
R
II
O
I
Fig. 1. The most representative lignans and derivatives.
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.09.003

Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
CO2H
5429
Cl
O
O
O
CHO
H
R1
R1
R1
II
+
DA
N
N
N
R
R
H
SO2Ph
SO2Ph
11-15
1, 2
26-30
9, 10
R
31-36
Fig. 2. Retrosynthetic scheme.
Azatoxin, an indolic heterolignan, has also proved to be a good
topoisomerase II inhibitor [5,6]. Based on our interests in
designing indolocarbazole analogues as topoisomerase I inhibi-
tors, we aimed to develop new DNA topoisomerase II inhibitors
[8]. We thought that the frameworks of azatoxin and compound
of type I could be combined to generate tetrahydrofuro[3,4-b]
carbazole such as II, in which the indole ring is fused to the
aromatic central ring.
2. Chemistry
2.1. Preparation of the indolic skeletons type IV
3-Formylindole 1 and 3-formyl-5-benzyloxyindole 2 [10] were
first protected with a benzenesulphonyl group using benzenesul-
phonyl chloride (1.2 eq.) in the presence of BnEt3NþClꢀ and NaOH.
The protection of 1 was carried out at room temperature, whereas
reflux conditions were necessary for indole 2: compounds 3 [11]
and 4 were both obtained in good yield (Scheme 1).
We hoped that this structure could result from an intra-
molecular DielseAlder reaction (DA, Fig. 2) [9]. Precursors 31e36
CO2Me
CHO
CHO
R1
R1
R1
b
a
N
N
H
N
SO2Ph
SO2Ph
1 R1 = H
2 R1 = OBn
5 R1 = H
6 R1 = OBn
3 R1= H
4 R1 = OBn
Cl
OH
R1
d
R1
c
N
N
SO2Ph
SO2Ph
7 R1 = H
8 R1 = OBn
9 R1 = H
10 R1 = OBn
Scheme 1. (a) BnEt3Nþ, Clꢀ (cat.), NaOH (3.0 eq.), PhSO2Cl (1.2 eq.), CH2Cl2, r.t., 2 h, from 1: 0 ꢁC to r.t., 3 84%, from 2: 0 ꢁC to reflux, 4 81%; (b) PPh3 ¼ CHCOOCH3 (3 eq.), toluene,
reflux, 12 h, from 3: 5 98%, from 4: 6 93%; (c) DibalH (2.5 eq.), toluene, 0 ꢁC to r.t., from 5: 2 h, 7 quant., from 6: 2 h 30, 8 quant.; (d) SOCl2 (1.9 eq.), benzotriazole (1.9 eq.), CH2Cl2, r.t.,
15 min., from 7: 9 quant, from 8: 10 quant.
could be obtained from indolic chloro derivatives (R ¼ Cl) and
alkynes 26e30. Therefore, indoles 1e2 and benzaldehydes 11e15
constituted the starting materials. The first issue was the choice of
an appropriate indolic protecting group. As the target II exhibits
a base-sensitive lactone, synthesis involving a Boc group or even
better, no protecting group was first envisaged.
Unfortunately, the synthesis of indoles IV without any protect-
ing group failed in our work, and the Boc group was prematurely
released during the synthetic pathway. These results prompted us
to use the robust benzenesulphonyl group. The first studies were
realised with 3-formylindole and 2,4,5-trimethoxybenzaldehyde.
Herein, we present the results of our method applied to indole
reacting with a wide range of benzaldehydes. Results obtained with
5-OBn indole 2 are also discussed.
A Wittig reaction was next performed in toluene under reflux
conditions using a slight excess of (carbethoxymethylene) tri-
phenylphosphorane (3.0 eq.) to give compounds 5 [12] and 6 in
98 and 93% yields respectively. The ester moieties were then
reduced with DibalH, affording alcohols 7 and 8 in quantitative
yields [13]. Chlorination was then realised using thionyl chloride
in the presence of benzotriazole, quantitatively affording
compounds 9 and 10 [14].
2.2. Preparation of the propynoic acids type V
We then focused our efforts on the CoreyeFuchs alkyne meth-
odology [15]. Benzaldehydes 10e15 were treated with PPh3 and
CBr4 to afford geminated dibromo alkenes 16e20 in very good

5430
Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
yields (Table 1, entries 1e5, Scheme 2). The triple bond formation
was then obtained via a twofold elimination using n-BuLi at ꢀ78 ꢁC.
The lithium acetylide intermediates were quenched in situ with
methyl chloroformate at the same temperature, leading to methyl
esters 21e25 in excellent yields (entries 6e10).
These esters were then saponified, yielding propiolic acids
26e30 (entries 11e15). Reactions were achieved using LiOH at r.t. in
a mixture of THF/MeOH/H2O. Starting materials 21e25 completely
disappeared after 1 h. HCl (1 N) was then slowly added at 0 ꢁC to
reach pH ¼ 4. The desired carboxylic acids were isolated, without
any difficulty, in nearly quantitative yields. Acids 26e30 were thus
obtained from aldehydes 11e15 through a three-step sequence in
overall yields of 67e89%. This pathway proved to be highly efficient
as reactions could be performed in a multigram-scale with similar
yields.
2.3. Preparation of the esters of type III
The subsequent step involved a nucleophilic reaction between
chlorinated compounds 9 and 10 and the sodium salts of acids
26e30 (Scheme 3). These reactions were performed in the dark
using NaHCO3 in dry DMF, and appeared to be very sluggish. After
48 h, rapid neutralisation, extraction and purification afforded
compounds 31e36 in good yields (Table 2, entries 1e6). Unfortu-
nately, compound 36 proved to be too unstable to be fully
characterised.
O
O
R1
26-30
Table 1
9, 10
Preparation of 16e30.
a
R4
N
Entry
Compounds
R2
R3
R4
R
Product
Yield (%)
SO2Ph
1
2
3
4
5
6
7
8
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
H
OMe
H
H
OMe
H
OMe
H
H
OMe
H
H
OMe
H
OMe
eOCH2Oe
H
OMe
H
OMe
H
OMe
OMe
e
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
94 [16]
88 [17]
89 [18]
82 [18]
95 [19]
83 [20]
85
88 [21]
R2
R3
e
31-36
e
e
Scheme 3. For substitutions and yields see Table 2. (a) NaHCO3 (1.5 eq.), DMF, 48 h, r.t.,
26e30 (1.5 eq.).
OMe
H
OMe
OMe
e
Me
Me
Me
Me
Me
H
H
H
H
H
Table 2
9
eOCH2Oe
87 [22]
Preparation of 31e36.
10
11
12
13
14
15
OMe
OMe
H
OMe
eOCH2Oe
OMe OMe
OMe
H
OMe
OMe
96 [23]
95, 74a [24]
98, 73a
Entry
Compounds
R1
R2
R3
R4
Product
Yielda (%)
H
H
OMe
97, 76a [22]
95, 67a [25]
98, 89a [26]
1
2
3
4
5
6
9
9
9
9
9
26
27
28
29
30
27
H
H
OMe
H
OMe
eOCH2Oe
OMe
H
H
OMe
OMe
31
32
33
34
35
36
80
74
85
81
98
71
H
H
OMe
H
a
Overall yield calculated from aldehydes 11e15.
H
H
H
OBn
OMe
OMe
OMe
OMe
10
a
Yields are given for isolated products.
Br
COOR
2.4. Synthesis of 4-phenyl-3H-furo[3,4-b]carbazoles II
CHO
Br
b
a
2.4.1. DA and aromatisation steps
The DA reactions were first carried out under thermal condi-
tions in a sealed tube protected from light and under inert atmo-
sphere (Scheme 4) to provide the cycloadducts 37e41 in moderate
yields. Alternatively, the electrocyclisation was realised under
microwave irradiation at 150 ꢁC for 2 h 30. After precipitation, the
desired compounds 37e41 were isolated in good to quantitative
yields (Table 3, entries 1e5). The NMR data of 37e41 showed that
isomerisation of the new double bonds occurred, allowing the
formation of the indole core. Despite our efforts, we were unable to
obtain compound 42.
R2
R4
R2
R4
R2
R4
R3
R3
R3
16-20
11-15
21-25 R = Me
26-30 R = H
c
Scheme 2. For substitutions and yields see also Table 1. (a) PPh3 (3.0 eq.), CBr4 (1.5 eq.),
CH2Cl2, 0 ꢁC, 1 h then 11e15, r.t. 2 h; (b) n-BuLi (2.2 eq.), THF, ꢀ78 ꢁC, 1 h then ClCO2Me
(1.2 eq.), ꢀ78 ꢁC, 1 h; (c) LiOH (1.4 eq.), r.t., 1 h then HCl (1 N), 0 ꢁC, 1 h.
Two-step
O
O
procedure
R1
b
a
O
O
31-36
aromatization
N
DA
N
R4
R4
isomerization
PhO2S
PhO2S
43-47
37-42
R3
R3
R2
R2
One-pot
strategy
c
DA/aromatization
Scheme 4. For substitutions and yields see Table 3. (a) Toluene, MW, 150 ꢁC, 2 h 30; (b) Toluene, sealed tube, 150 ꢁC, MW, o-chloranil (2.0 eq.), 1 h 30; (c) one-pot reaction: (i)
toluene, MW, 150 ꢁC 1 h, (ii) o-chloranil (2.5 eq.), MW, 150 ꢁC, 35 min.

Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
5431
Table 3
O
O
Preparation of 43e47 via the two-step procedure.
Entry Compounds R1
R2
R3
R4
DA product Arom. product
O
O
a
(Yield (%))a (Yield (%))a
43 (76, 81b)
44 (77)
45 (70)
46 (66)
47 (75)
(e)
N
H
N
1
2
3
4
5
6
31
32
33
34
35
36
H
H
H
H
H
H
OMe
H
OMe
H
H
37 (81)
R4
R4
PhO2S
OMe 38 (74)
OMe OMe 39 (87)
eOCH2Oe 40 (70%)
48-52
43-47
H
R3
R3
R2
R2
OMe OMe OMe 41 (99)
OMe 42 (e)
OBn OMe
H
O
O
a
Yields are given for isolated products.
By heating in toluene 24 h.
b
O
O
b
Cycloadducts 37e41 (entries 1e5) were then aromatised in
N
H
N
H
OMe
OH
OMe
refluxing toluene using o-chloranil. Starting from 37, the reaction
afforded the cyclised furocarbazole 43 in 81% yield but yields
dropped with 32e35. Aromatisation was thus performed under
microwave irradiation for 1 h 30 and the furocarbazoles 43e46
were isolated in 66e77% yield (entries 1e5). As an alternative, we
realised a one-pot electrocyclisationearomatisation step under
microwave irradiation starting from 31 to 35, without isolating
intermediates 37e41 (Table 4). Brief optimisation of the conditions
afforded the fully aromatised compounds 43e47 after 1 h 35 in
pretty good yields (entries 1e5). Compound 46 was obtained in
only 26% yield, as its purification remained problematic.
53
52
OMe
HO
MeO
Scheme 5. For substitutions and yields see Table 4. (a) Method A or Method B; (b) BBr3
(1.0 eq.), CH2Cl2, ꢀ78 ꢁC, 1 h, 55%.
3. Biological activities
3.1. Topoisomerase inhibition and DNA binding
The structure of newly synthesised compounds 48e53 is close
to azatoxin, an indolic heterolignan, which has proven to be a top-
oisomerase II inhibitor. For these reasons these compounds were
tested for topoisomerase II inhibition and DNA binding. As shown
in Fig. 3, supercoiled plasmid DNA was treated with human top-
oisomerase II in the presence of the reference compound (etopo-
side) or compounds 48e53 at different concentrations. The DNA
relaxation/cleavage products were resolved by electrophoresis.
Inhibition of topoisomerase II was clearly specifically detected with
the reference compound (etoposide), which produced a marked
level of DNA double stranded breaks (Fig. 3A), corresponding to
linear DNA (lin). Among all 6 tested compounds only 53 was found
to stabilise the drugeDNA complex with an increase of the band
corresponding to linear DNA (double stranded breaks). Fig. 3B
Table 4
Preparation of 43e47 via the one-pot strategy.
Entry
Compounds
R1
R2
R3
R4
Product
Yielda (%)
1
2
3
4
5
31
32
33
34
35
H
H
H
H
H
H
OMe
H
H
OMe
OMe
43
44
45
46
47
88
70
75
26
95
OMe
OMe
OMe
eOCH2Oe
OMe OMe
a
Yields are given for isolated products.
2.4.2. Cleavage of benzenesulphonyl groups
Benzenesulphonyl groups were cleaved using a 6% Hg/Na
amalgam in the presence of a large excess of Na2HPO4 at ꢀ78 ꢁC
(Table 5, entries 1e5). After 1 h, the reaction mixtures were allowed
to reach ꢀ50 ꢁC for 30 min to finally give the desired compounds
48e52 in good yields [27]. As an alternative, treatment of 43e47
with a Bu4NF solution in toluene at 100 ꢁC for 1 h led to the same
derivatives 48e52 in similar yields [28] (Scheme 5).
In order to mime the etoposide pendular aromatic ring, we tried
the demethylation of the R3 methyl ether group but each assay
failed. Demethylation of the 3,4,5-trimethoxy derivative 52 (entry
6) was only performed using an equimolar amount of BBr3 at room
temperature to afford a mixture of demethylated compounds.
When the reaction was carried out at ꢀ78 ꢁC, a double demethy-
lation of hydroxy groups occurred, yielding 53 in an amount of 55%
(Table 5).
shows that 53, tested at different concentrations from 1 to 100 mM,
appeared to be less active than etoposide.
Fig. 3A and B also shows that, in high concentrations, 53 pres-
ents a supercoiled form (Sc) which represents a weak interaction
with DNA, while etoposide presents stabilisation of DNA top-
oisomerase II covalent complexes. But the drug showed minimal if
any interaction with DNA in the absence of the enzyme. In the same
way, 50, which differs from 53 by the absence of OMe in R4, did not
inhibit topoisomerase II, while it presented an interaction with the
DNA visualised by an increase in the supercoiled form at high
concentration. This weak DNA interaction is not bound to an
intercalation mechanism because any modification of the DNA
topology is visualised on relaxation agarose gels in the absence of
ethidium bromide in presence of 50 and 53 and any variation of the
melting temperature of calf thymus DNA is visualised (data not
shown). The result from this topoisomerase assay established that
compound 53 is a highly potent topoisomerase II poison in vitro,
with a weak interaction with DNA, and that the OMe in R4 is
necessary for this inhibition.
Table 5
Entry
Compounds
R1
R2
R3
R4
Product
Yielda (%)
1
2
3
4
5
6
43
44
45
46
47
52
H
H
H
H
H
H
H
OMe
H
H
OMe
OH
OMe
H
OMe
eOCH2Oe
OMe
OH
H
OMe
OMe
48
49
50
51
52
53
71,b 81c
74,b 70c
70,b 72c
70,b 79c
82,b 75c
55
3.2. Cytotoxic activity
¼ OMe
OMe
To gain an insight into the involvement of topoisomerase II
inhibition in the cytotoxicity of the compounds, their anti-
proliferative activity was assessed using the HL60/MX2 cell line
resistant to mitoxantrone, which displays altered catalytic activity
a
Yields are given for isolated products.
b
Method A: Na2HPO4 (excess), 6% Na/Hg amalgam, ꢀ78 ꢁC, 1 h to ꢀ50 ꢁC, 30 min.,
THF/MeOH 1/1.
c
Method B: Bu4NF, toluene, 90 ꢁC, 1 h.

5432
Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
Fig. 3. Effect of compounds on the relaxation of plasmid DNA by human topoisomerase II. Native supercoiled PUC19 (350 ng, lane plasmid) was incubated with 4 units top-
oisomerase II in the absence (lane Topo II) or presence of tested compound at the indicated concentration. (A) Selected compounds displaying detectable DNA breaks at 20 and
50
mM. Etoposide was used at 20 (left) and 50
mM (right). (B) Comparison of most potent compound 53 with 50 and reference compound (etoposide) from 1 to 100
m
M. DNA samples
were separated by electrophoresis on a 1% agarose gel containing 1
relaxed.
mg/mL ethidium bromide. Gels were photographed under UV light. Nck: nicked; Sc: supercoiled; Lin: linear; Rel:
and reduced levels of topoisomerase II [28]. The HL60/MX2 cell line
displays an atypical multidrug resistance profile with a decreased
expression and activity of topoisomerase II. When evaluated on the
HL60 cell line, compound 53 displayed a high cytotoxicity in the
submicromolar range (IC50 ¼ 150 nM), higher than etoposide
(IC50 ¼ 490 nM). Compound 53 was also cytotoxic on HL60/MX2
(IC50 ¼ 170 nM). This weak resistance index may be explained by its
binding to the enzyme at a different site from that of mitoxantrone
or by a specific kinetics. No obvious relationship was found
between cytotoxicity and topoisomerase II inhibition. This was also
demonstrated for other topoisomerase II inhibitors in the literature
[29,30] and could be a contribution of different cellular activities.
(weak index of resistance). Additional mechanisms and/or targets
could be involved. The development of this molecule could be
interesting because of the different spectrum of actions from eto-
poside, which is frequently prescribed in oncology and for which
toxicities and resistance have been observed.
5. Experimental section
1H NMR and 13C NMR spectra were recorded on a Bruker DPX
250 or 400 MHz instrument using CDCl3 or DMSO-d6. The chemical
shifts are reported in ppm (d scale) and all coupling constants (J)
values are in hertz (Hz). The splitting patterns are designated as
follows: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet),
and dd (doublet doublet). Melting points are uncorrected. IR
absorption spectra were obtained on a PerkineElmer PARAGON
1000 PC and values were reported in cmꢀ1. MS spectra (Ion Spray)
were performed on a PerkineElmer Sciex PI 300. HRMS were per-
formed by the Centre Commun de Spectrométrie de Masse (Cler-
mont Ferrand, France). Monitoring of the reactions was performed
using silica gel TLC plates (silica Merck 60 F254). Spots were
visualised by UV light at 254 nm and 356 nm. Column chromatog-
raphy was performed using silica gel 60 (0.063e0.200 mm, Merck).
4. Conclusion
In this paper we described the preparation of new furocarba-
zoles starting from formylindoles and various benzaldehydes. Our
straightforward and efficient synthesis gave access to esters which
were then readily used in a 6p-electrocyclisation/aromatisation
reaction. This key step was performed under microwave irradia-
tions and could be realised through a one-pot process. After the
furocarbazoles deprotection and the methyl ether cleavage, the
compounds obtained were evaluated as potent anticancer agents.
Compared to azatoxin, where the benzylic asymmetric carbon
confers a T-shape to the molecule, the rigidity of our models was
enhanced and the pendular phenyl ring appeared to be orthogonal
to the central furocarbazole. This difference of structure could
explain the lack of activity of 52.
Finally, compound 53, which bears more donor/acceptor hy-
drogen bonds on the pendular phenyl ring, is a particularly inter-
esting compound. It strongly inhibits the topoisomerase II in vitro,
but less than etoposide, and interacts differently with the DNA. To
remove substitutions from the phenyl group of the molecule prob-
ably decreases the steric dimensions of the compound and facili-
tates the interaction with the topoisomerase II. On the other hand,
compound 53 presents a more significant cytotoxic effect than
etoposide and seems independent to the topoisomerase II inhibition
5.1. 1-Benzenesulphonyl-5-benzyloxy-3-formylindole (4)
Benzyltriethylammonium chloride (0.12 g, 0.5 mmol) and fine
powdered sodium hydroxide (2.8 g, 70 mmol) were added to 1,2-
dichloroethane (30 mL) under argon at r.t. A solution of 5-benzyloxy-
3-formylindole 2 (5.63 g, 22.4 mmol) in 1,2-dichloroethane (30 mL)
was added at 0 ꢁC. Benzenesulphonyl chloride (3.33 mL, 26 mmol)
was then added dropwise at 0 ꢁC and the reaction mixture was
stirred under reflux for 2 h. The mixture was cooled to r.t. and
filtered. Water (50 mL) was added to the filtrate, which was extrac-
ted withCH2Cl2 (30 mL). The organiclayer was dried over MgSO4 and
the expected product 4 was crystallised from EtOAc as a white solid
(4.29 g, 81%). Mp 145e147 ꢁC; IR (KBr, cmꢀ1
1680, 1446, 909, 725; 1H NMR (DMSO-d6, 250 MHz)
)
n
3120, 3100, 2830,
5.09 (s, 2H),
d

Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
5433
7.07 (dd, 1H, J ¼ 2.5 Hz, J ¼ 8.7 Hz), 7.20e7.70 (m, 8H), 7.85 (d, 2H,
J ¼ 7.5 Hz), 7.93 (d, 2H, J ¼ 8.8 Hz), 8.18 (s,1H), 10.06 (s,1H, CHO); 13C
129.4 (Cq),129.7 (2CH),131.4 (CH),132.1 (CH),134.5 (CH),137.0 (Cq),
155.5 (Cq); MS (IS) 420.5 (M þ H)þ; 442.5 (M þ Naþ).
NMR (DMSO-d6, 62.5 MHz) d 70.7 (CH2),105.3 (CH),114.1 (CH),116.7
(CH), 122.4 (Cq), 127.0 (2CH), 127.3 (Cq), 127.6 (2CH), 128.0 (2CH),
128.3 (Cq),128.6 (CH),129.7 (2CH),134.6 (CH),136.2 (Cq),136.5 (CH),
137.4 (Cq), 156.9 (Cq), 185.4 (CHO); MS (IS) 392 (M þ Hþ).
5.6. 1-Benzenesulphonyl-3-chloropropenyl-1H-indole (9)
A solution 1.5 M of benzotriazole (1.786 g, 15 mmol) and SOCl2
(1.09 mL, 15 mmol) in dry CH2Cl2 (10 mL) was prepared. This solu-
tion (6.7 mL) was added dropwise at 0 ꢁC to a solution of 7 (2.5 g,
8.0 mmol) in dry CH2Cl2 (50 mL). The reaction mixture was stirred at
r.t. for 15 min and filtered. The filtrate was dried in vacuo to afford
compound 9 as an orange solid (2.60 g, quant.). Degradation was
observed during the flash chromatography operation. Mp
5.2. (E)-3-(1-Benzenesulphonyl-1H-indol-3-yl)-acrylic acid methyl
ester (5)
To a solution of 3 (4.7 g, 16.5 mmol) in dry toluene (100 mL) was
portionwise added carbethoxymethylene triphenylphosphorane
(16.55 g, 49.5 mmol). The reaction mixture was heated overnight
under reflux. The solvent was removed under reduced pressure and
the crude residue was purified by flash chromatography (petro-
leum ether/EtOAc 5/5) to afford compound 5 as a white solid
(5.52 g, 98%). All spectral data were in agreement with previous
reports [12].
139e141 ꢁC; IR (KBr, cmꢀ1
NMR (CDCl3, 250 MHz)
) n
1659, 1447, 1363, 1177, 953, 743; 1H
4.26 (d, 2H, J ¼ 7.2 Hz), 6.40 (dt, 1H,
d
J ¼ 7.2 Hz, J ¼ 16.0 Hz), 6.73 (d, 1H, J ¼ 16.0 Hz), 7.26e7.48 (m, 5H),
7.62 (s,1H), 7.72 (d,1H, J ¼ 7.5 Hz), 7.88 (d, 2H, J ¼ 8.6 Hz), 8.00 (d,1H,
J ¼ 7.3 Hz); 13C NMR (CDCl3, 62.5 MHz)
d 44.5 (CH2),118.2 (Cq),112.6
(CH),119.2 (CH),122.6 (CH),124.0 (CH),125.0 (CH),125.6 (2CH),127.2
(CH),127.5 (CH),128.2 (2CH),131.0 (CH),132.8 (Cq),134.3 (CH),136.8
(Cq); MS (IS) 331.5 (M þ Hþ, 35Cl) and 333.5 (M þ Hþ, 37Cl).
5.3. (E)-3-(1-Benzenesulphonyl-1H-5-benzyloxyindol-3-yl)-acrylic
acid methyl ester (6)
5.7. 1-Benzenesulphonyl-5-benzyloxy-3-chloropropenyl-1H-indole
Compound 6 was isolated as a white solid (93%) starting from 4
(10)
and using the procedure described for the preparation of compound
5. Mp 225e227 ꢁC; IR (KBr, cmꢀ1
)
n
3097, 1675, 1425, 1204, 953; 1H
Compound 10 was isolated as a yellow solid (quant.) starting
from 8 and using the procedure described for the preparation of
NMR (CDCl3, 250 MHz)
d 3.81 (s, 3H, CH3), 5.09 (s, 2H), 6.42 (d, 1H,
J ¼ 16.0 Hz), 7.06 (dd, 1H, J ¼ 2.5 Hz, J ¼ 16.0 Hz), 7.23e7.41 (m, 3H),
compound 9. Mp 184e186 ꢁC; IR (KBr, cmꢀ1
)
n
2961,1518,1435,1171,
7.42e7.72 (m, 5H), 7.81e7.92 (m, 3H), 8.02 (d, 2H, J ¼ 7.0 Hz), 8.50
968; 1H NMR (CDCl3, 250 MHz)
d
4.33 (dd, 2H, J ¼ 1.0 Hz, J ¼ 6.5 Hz),
(s, 1H); 13C NMR (CDCl3, 62.5 MHz)
d
51.0 (CH3), 69.8 (CH2), 104.5
5.06 (s, 2H), 6.33 (dt, 1H, J ¼ 6.5 Hz, J ¼ 17.0 Hz), 6.62 (d, 1H,
J ¼ 17.0 Hz), 76.99e7.01 (m, 1H), 7.21 (d, 1H, J ¼ 2.5 Hz), 7.31e7.82
(m, 8H), 7.83e7.89 (m, 3H), 8.12 (dd, 1H, J ¼ 3.1 Hz, J ¼ 6.6 Hz); 13C
(CH), 114.3 (CH), 115.2 (CH), 117.5 (CH), 117.8 (Cq), 126.8 (CH), 127.7
(2CH), 127.8 (Cq), 128.4 (2CH), 128.7 (2CH), 129.3 (CH), 129.9 (Cq),
131.4 (2CH), 131.5 (CH), 134.9 (Cq), 135.5 (CH), 137.0 (Cq), 155.8 (Cq),
166.8 (CO); MS (IS) 336 (M þ Naþ).
NMR (CDCl3, 62.5 MHz)
d 44.3 (CH2), 69.5 (CH2), 104.6 (CH), 113.7
(CH), 118.5 (Cq), 112.8 (CH), 119.7 (CH), 122.6 (CH), 125.0 (CH), 125.6
(2CH), 127.2 (2CH), 127.5 (Cq), 128.2 (2CH), 128.8 (2CH), 129.8 (Cq),
131.3 (CH), 133.1 (Cq), 133.0 (CH), 136.8 (Cq), 153.9 (Cq); MS (IS)
438.5 (M þ Hþ, 35Cl) and 440.5 (M þ Hþ, 37Cl).
5.4. 3-(Benzenesulphonyl-1H-indol-3-yl)-prop-2-en-1-ol (7)
To a solution of 5 (4.5 g,13 mmol) in dry toluene under argonwas
added dropwise at 0 ꢁC a solution of DibalH (20% in toluene, 29.8 mL,
32.5 mmol). The reaction mixture was stirred at r.t. for 2 h and the
reaction mixture was slowly hydrolysed at 0 ꢁC with water (30 mL).
Aluminium salts were filtered and the solvent was removed under
reduced pressure. The aqueous phase was extracted with EtOAc
(2 ꢂ 20 mL). The organic layer was dried with MgSO4, filtered and
evaporated to dryness. A flash chromatography (petroleum ether/
EtOAc 7/3) afforded the compounꢀd1 7 as a yellow solid (3.91 g,
5.8. General procedure for the preparation of 2,2-dibromovinyl
benzenes 16e20
A solution of CBr4 (1.5 eq.) in dry CH2Cl2 was stirred under argon
at r.t. PPh3 (3.0 eq.) was added portionwise slowly. The reaction
mixture was stirred for 1 h and then cooled to 0 ꢁC. A solution of
benzaldehydes 11e15 (1.0 eq.) in dry CH2Cl2 was then added and
the mixture was stirred for 2 h at r.t. The reaction mixture was
filtered. The filtrate was hydrolysed with water. After extraction,
the aqueous layer was extracted with CH2Cl2. The combined
organic layers were dried over MgSO4 and solvent was removed
under reduced pressure. The crude product was purified by flash
chromatography to afford compounds 16e20. All spectral data
were in agreement with previous reports [16e20].
quant.). Mp 102e104 ꢁC; IR (KBr, cm
) n 3397,1655,1447,1176, 973;
1H NMR (CDCl3, 250 MHz)
d
4.12 (d, 2H, J ¼ 6.4 Hz), 6.47 (dt, 1H,
J ¼ 6.4 Hz, J ¼ 16.1 Hz), 6.69 (d, 1H, J ¼ 16.1 Hz), 7.43e7.60 (m, 6H),
7.73 (d,1H, J ¼ 7.2 Hz), 7.87 (d, 2H, J ¼ 9.5 Hz), 7.99 (d,1H, J ¼ 7.2 Hz);
13C NMR (CDCl3, 62.5 MHz)
d 64.0 (CH2),113.9 (CH),120.3 (Cq),120.5
(CH), 121.8 (CH), 123.8 (CH), 124.0 (CH), 125.2 (CH), 126.9 (CH), 129.1
(Cq),129.4 (CH),130.1 (CH),134.0 (CH),135.6 (Cq),138.1 (Cq); MS (IS)
336.5 (M þ Naþ).
5.9. General procedure for the preparation of propynoic methyl
esters 21e25
5.5. 3-(1-Benzenesulphonyl-1H-5-benzyloxyindol-3-yl)-prop-2-
en-1-ol (8)
A solution of 2,2-(dibromovinyl)-benzenes 16e20 in dry THF
(1 eq.) was stirred under argon at r.t. A solution of n-BuLi (2.5 M in
hexane, 2.2 eq.) was added dropwise at ꢀ78 ꢁC and the reaction
mixture was next stirred at r.t. for 1 h and then cooled to ꢀ78 ꢁC. At
that point, methyl chloroformate (1.2 eq.) was added to the solu-
tion. After 1 h at r.t., the solvent was concentrated under reduced
pressure. EtOAc and a saturated aqueous solution of ammonium
chloride were added. After extractions with EtOAc, the combined
organic layers were dried over MgSO4 and the solvent removed
under reduced pressure. The crude product was purified by flash
Compound 8 was isolated as a yellow solid (quant.) starting
from 6 and using the procedure described for the preparation of
compound 7. Mp 211e212 ꢁC; IR (KBr, cmꢀ1
)
n
3364, 1658, 1435,
4.33 (d, 2H, J ¼ 5.0 Hz), 5.06
(s, 2H), 6.33 (dt, 1H, J ¼ 5.0 Hz, J ¼ 17.0 Hz), 6.62 (d, 1H, J ¼ 17.0 Hz),
7.01e7.62 (m, 14H); 13C NMR (CDCl3, 62.5 MHz)
61.7 (CH2), 69.7
1171, 968; 1H NMR (CDCl3, 250 MHz)
d
d
(CH2),104.3 (CH), 114.3 (CH), 114.4 (Cq), 108.8 (CH),120.4 (Cq),126.6
(2CH), 127.7 (CH), 127.8 (CH), 128.4 (2CH), 128.6 (Cq), 128.8 (2CH),

5434
Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
chromatography (petroleum ether/EtOAc 8/2) to afford compounds
21e25. All spectral data were in agreement with previous reports
[21e24].
5.15. 3,5-Dimethoxyphenylpropynoic-3-(1-benzenesulphonyl-1H-
indol-3-yl)-allyl ester (32)
Compound 32 was isolated as a yellow solid starting from 27
in 74% yield after purification by flash chromatography (petro-
5.10. (3,5-Dimethoxybenzene)-propynoic acid methyl ester (22)
leum ether/EtOAc 9:1). Mp 149e151 ꢁC; IR (KBr, cmꢀ1
)
n
3111,
3019, 2376, 1714, 1642, 1307, 1243, 1150, 1110, 765; 1H NMR
(CDCl3, 400 MHz)
Compound 22 was obtained starting from 17 as a yellow solid in
85% yield. Mp 104e106 ꢁC; IR (KBr) cmꢀ1 3022, 2202, 1732, 1215,
d
3.70 (s, 6H), 4.82 (d, 2H, J ¼ 6.6 Hz), 6.30 (dt,
1H, J ¼ 6.6 Hz, J ¼ 16 Hz), 6.47 (t, 1H, J ¼ 2.4 Hz), 6.70 (d, 1H,
J ¼ 16 Hz), 7.19e7.30 (m, 3H), 7.35 (t, 2H, J ¼ 8.0 Hz), 7.45e7.48
(m, 1H), 7.57 (s, 1H), 7.65 (d, 1H, J ¼ 8.0 Hz), 7.80 (d, 2H,
J ¼ 8.0 Hz), 7.92 (d, 2H, J ¼ 8.0 Hz); 13C NMR (CDCl3, 100 MHz)
1046, 767, 669, 508; 1H NMR (DMSO, 250 MHz)
d 3.35 (s, 3H), 3.78
(s, 6H), 6.69 (t, 1H, J ¼ 2.5 Hz), 6.81 (d, 2H, J ¼ 2.5 Hz); 13C NMR
(CDCl3, 62.9 MHz)
d 54.8 (CH3), 54.9 (2CH3), 79.5 (Cq), 81.9 (Cq),
104.9 (2CH), 106.9 (CH), 140.8 (Cq), 142.4 (2Cq), 160.7 (CO); MS (IS)
d
55.6 (2CH3), 66.9 (CH2), 79.8 (Cq), 86.8 (Cq), 104.4 (CH), 110.7
221 (M þ Hþ).
(CH), 113.9 (CH), 119.6 (Cq), 120.5 (CH), 120.7 (Cq), 123.4 (CH),
123.8 (CH), 124.9 (CH), 125.3 (2CH), 126.3 (CH), 126.9 (2CH), 128.8
(Cq), 129.4 (2CH), 135.6 (Cq), 138.1 (Cq), 153.8 (Cq), 160.7 (2Cq),
162.6 (CO); HRMS (ESI) calculated for C28H24NO6S 502.1324,
found 502.1315 (M þ Hþ).
5.11. General procedure to obtain the propynoic acids 26e30
To a solution of propynoic methyl esters 21e25 in THF/H2O/
MeOH (4/1/1) at r.t., was added LiOH$H2O (1.4 eq.). The reaction
mixture was stirred overnight at r.t. EtOAc was added and the
reaction mixture was acidified at pH ¼ 4 with an aqueous solution
of HCl (1 N). After extraction of the aqueous layers by EtOAc, the
combined organic layers were dried over MgSO4 and filtered, and
the solvent was removed under reduced pressure to afford
compounds 21e25. These compounds, which appeared to be very
pure, were used in the next step without further purification. All
spectral data were in agreement with previous reports [25e27].
5.16. 3,4-Dimethoxyphenylpropynoic-3-(1-benzenesulphonyl-1H-
indol-3-yl)-allyl ester (33)
Compound 33 was isolated as a yellow solid starting from 28
in 85% yield after purification by flash chromatography (petro-
leum ether/EtOAc 8:2). Mp 63e65 ꢁC; IR (KBr, cmꢀ1
)
n
2935, 2206,
1701, 1596, 1512, 1445, 1370, 1248, 1225, 1133, 978, 744, 685; 1H
NMR (CDCl3, 250 MHz) 3.85 (s, 3H), 3.88 (s, 3H), 4.88 (d, 2H,
d
J ¼ 6.5 Hz), 6.34 (dt, 1H, J ¼ 6.5 Hz, J ¼ 16 Hz), 6.75e6.84 (m, 2H),
7.06 (d, 1H, J ¼ 1.7 Hz), 7.20e7.60 (m, 6H), 7.64 (s, 1H), 7.70 (d, 1H,
J ¼ 7.0 Hz), 7.86 (d, 2H, J ¼ 7.0 Hz), 7.99 (d, 1H, J ¼ 7.7 Hz); 13C NMR
5.12. (3,5-Dimethoxybenzene)-propynoic acid (27)
(CDCl3, 62.9 MHz)
d 56.0 (CH3), 66.6 (CH2), 79.7 (Cq), 87.7 (Cq),
Compound 27 was obtained starting from 22 as a yellow solid
in 98% yield. Mp 131e133 ꢁC; IR (KBr, cmꢀ1
)
n
3019, 2947, 2602,
111.0 (CH), 111.2 (Cq), 113.7 (CH), 115.3 (CH), 119.6 (Cq), 120.4 (CH),
123.4 (CH), 123.7 (CH), 124.8 (2CH), 125.2 (CH), 126.0 (CH), 126.8
(2CH), 127.3 (CH), 128.7 (Cq), 129.3 (CH), 134.0 (CH), 135.5 (Cq),
137.9 (Cq), 148.7 (Cq), 151.6 (Cq), 154.0 (CO); HRMS (ESI) calcu-
lated for C28H23NO6SNa 524.1144, found 524.1128 (M þ Naþ).
2217, 1709, 1587, 1451, 1348, 1208, 1160, 1068, 832; 1H NMR
(CDCl3, 250 MHz)
d
3.79 (s, 6H), 6.56 (t, 1H, J ¼ 2.5 Hz), 6.74 (d,
2H, J ¼ 2.5 Hz), 8.91 (s, 1H); 13C NMR (CDCl3, 62.5 MHz)
d 55.6
(2CH3), 79.5 (Cq), 89.1 (Cq), 104.8 (CH), 110.9 (2CH), 120.3 (Cq),
158.3 (2Cq), 160.7 (CO); MS (IS) 205.0 (M ꢀ Hþ).
5.17. 3,4-Methylenedioxyphenylpropynoic-3-(1-benzenesulphonyl-
1H-indol-3-yl)-allyl ester (34)
5.13. General procedure for the preparation of esters 31e36
Compound 34 was isolated as a yellow solid starting from 29
in 81% yield after purification by flash chromatograꢀp1hy (petro-
2196, 1710, 1449, 1339, 1242, 678; 1H NMR (CDCl3, 250 MHz)
A solution of acids 21e25 (3.0 eq.) and NaHCO3 (1.5 eq.) in dry
DMF was stirred under argon and in the dark at r.t. for 1 h. 3-
chloropropenyl 9 or 10 (1.0 eq.) was added in one portion and the
reaction mixture was stirred for 48 h. Water was then added and
the solution was extracted with EtOAc and purified quickly on a pad
of silica gel (petroleum ether/AcOEt 7/3) to afford the esters 31e36,
which were immediately used in the DA step.
leum ether/EtOAc 9:1). Mp 71e73 ꢁC; IR (KBr, cm
) n 2938,
d
4.87 (d, 2H, J ¼ 6.4 Hz), 6.00 (s, 2H), 6.34 (dt, 1H, J ¼ 6.4 Hz,
J ¼ 16.0 Hz), 6.75e681 (m, 2H), 6.98 (d, 1H, J ¼ 1.5 Hz), 7.13 (dd,
1H, J ¼ 1.5 Hz, J ¼ 8.0 Hz), 7.26e7.52 (m, 5H), 7.64 (s, 1H), 7.71 (d,
1H, J ¼ 7.2 Hz), 7.86 (d, 2H, J ¼ 7.2 Hz), 7.98 (d, 1H, J ¼ 7.7 Hz); 13C
NMR (CDCl3, 62.9 MHz)
d 66.7 (CH2), 79.5 (Cq), 87.3 (Cq), 101.8
5.14. 4-Methoxyphenylpropynoic-3-(1-benzenesulphonyl-1H-
indol-3-yl)-allyl ester (31)
(CH2), 108.8 (CH), 112.4 (Cq), 112.5 (CH), 113.7 (CH), 119.6 (Cq),
120.4 (CH), 123.4 (CH), 123.8 (2CH), 124.8 (CH), 125.2 (CH), 126.0
(CH), 126.8 (2CH), 128.7 (Cq), 128.9 (CH), 129.3 (CH), 134.0 (CH),
135.5 (Cq), 137.9 (Cq), 147.6 (Cq), 150.1 (Cq), 153.9 (CO); HRMS
(ESI) calculated for C27H19NO6SNa 508.0847, found 508.0831
(M þ Naþ).
Compound 31 was isolated after purification by flash chroma-
tography (petroleum ether/EtOAc 8:2) as a yellow solid starting
from 26 in 96% yield. Mp 95e97 ꢁC; IR (KBr, cmꢀ1
)
n
2954, 2210,1697,
1603, 1446, 1364, 1156, 948, 739, 684; 1H NMR (CDCl3, 250 MHz)
d
3.83 (s, 3H), 4.90 (d, 2H, J ¼ 6.5 Hz), 6.35 (dt, 1H, J ¼ 6.5 Hz,
5.18. 3,4,5-Trimethoxyphenylpropynoic-3-(1-benzenesulphonyl-
1H-indol-3-yl)-allyl ester (35)
J ¼ 16.0 Hz), 6.76 (d, 1H, J ¼ 16.0 Hz), 6.86 (d, 2H, J ¼ 8.7 Hz),
7.26e7.56 (m, 7H), 7.59 (s, 1H), 7.75 (d, 1H, J ¼ 7.0 Hz), 7.87 (d, 2H,
J ¼ 7.2 Hz), 7.99 (d,1H, J ¼ 7.7 Hz); 13C NMR (CDCl3, 62.9 MHz)
d
55.5
Compound 35 was isolated as a white solid starting from 30 in
98% yield after purification by column chromatography (petro-
(CH3), 66.7 (CH2), 77.3 (Cq), 80.0 (Cq), 87.8 (Cq),111.3 (Cq),113.9 (CH),
114.4 (CH),119.7 (Cq),120.5 (CH),123.6 (CH),123.8 (CH),124.9 (2CH),
125.3 (2CH), 126.1 (CH), 126.9 (2CH), 128.8 (Cq), 129.4 (2CH), 134.1
(CH), 135.1 (CH), 138.1 (Cq), 154.2 (Cq), 161.7 (CO); MS (IS) 472.5
(M þ Hþ).
leum ether/EtOAc 8:2). Mp 153e155 ꢁC; IR (KBr, cmꢀ1
)
n
3450,
3100, 3000, 2220, 1750, 1715, 1640, 1245, 1300, 1150, 1100, 760; 1H
NMR (CDCl3, 400 MHz) 3.84 (s, 6H), 3.88 (s, 3H), 4.90 (d, 2H,
J ¼ 6.4 Hz), 6.41 (dt, 1H, J ¼ 6.4 Hz, J ¼ 16 Hz), 6.76e683 (m, 1H),
d

Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
5435
6.84 (s, 2H), 7.26e7.55 (m, 5 H), 7.65 (s, 1H), 7.72 (d, 1H,
J ¼ 8.0 Hz), 7.80 (d, 2H, J ¼ 7.6 Hz), 8.00 (d, 1H, J ¼ 8.0 Hz); 13C NMR
(Cq), 147.4 (Cq), 149.5 (Cq), 167.6 (CO); HRMS calculated for
C28H23NO6SNa 524.1144, found 524.1147 (M þ Naþ).
(CDCl3, 100 MHz)
d 56.3 (2CH3), 61.1 (CH3), 66.8 (CH2), 79.8 (Cq),
87.3 (Cq), 110.5 (CH), 113.8 (CH), 114.1 (Cq), 119.6 (Cq), 120.4 (CH),
123.4 (CH), 123.8 (2CH), 124.9 (CH), 125.3 (CH), 126.3 (CH), 126.9
(2CH), 128.7 (Cq), 129.4 (2CH), 134.0 (CH), 135.5 (Cq), 138.0 (Cq),
141.1 (Cq), 153.2 (2Cq), 153.9 (CO); HRMS (ESI) calculated for
C29H26NO7S 532.1424, found 532.1430 (M þ Hþ).
5.23. 4-(Benzo[d][1,3]dioxol-5-yl)-5-benzenesulphonyl-1H-furo
[3,4-b]carbazol-3(4H,5H,10H)-one (40)
Compound 40 was isolated as a yellꢀow1 solid starting from 34 in
70% yield. Mp 234e236 ꢁC; IR (KBr, cm
) n 2903, 1737, 1603, 1445,
1366,1243,1227,1175,1087, 753, 686; 1H NMR (DMSO-d6, 250 MHz)
5.19. General procedure for the preparation of N-benzenesulphonyl
furocarbazol-3(4H,5H,10H)-ones 37e41
d
2.55 (t, 1H, J ¼ 16.9 Hz), 3.00 (dd, 1H, J ¼ 7.7 Hz, J ¼ 16.9 Hz),
3.34e3.51 (m, 1H), 4.02 (dd, 1H, J ¼ 7.5 Hz, J ¼ 9.2 Hz), 4.67 (t, 1H,
J ¼ 9.2 Hz), 5.97 (s, 2H), 6.69 (d, 1H, J ¼ 8.0 Hz), 6.80e6.94 (m, 2H),
7.11e7.57 (m, 8H), 8.09 (d, 1H, J ¼ 8.0 Hz); 13C NMR (DMSO-d6,
A solution of esters 31e36 (0.17 mmol) in toluene (2.5 mL) was
heated at 150 ꢁC for 2 h 30 under microwave irradiation. After
cooling at 0 ꢁC overnight, the precipitate was filtered and washed
with pentane to give the desired products 37e41.
62.9 MHz) d 26.4 (CH), 36.8 (CH2), 69.9 (CH2),101.2 (CH2),107.1 (CH),
111.5 (CH), 117.9 (CH), 119.5 (CH), 120.0 (CH), 125.0 (2CH), 125.3
(2CH),126.4 (CH), 127.3 (CH),127.8 (Cq),128.3 (Cq),128.5 (CH),129.1
(CH), 129.9 (Cq), 133.4 (CH), 136.5 (Cq), 139.0 (Cq), 141.2 (Cq), 146.5
(Cq), 148.1 (Cq), 167.4 (CO); HRMS (ESI) calculated for C27H20NO6S
486.1011, found 486.0993 (M þ Hþ).
5.20. 4-(4-Methoxyphenyl)-5-benzenesulphonyl-1H-furo[3,4-b]
carba zol-3(4H,5H,10H)-one (37)
Compound 37 was isolated as a pale beige solid starting from 31
5.24. 5-Benzenesulphonyl-4-(3,4,5-trimethoxyphenyl)-1H-furo
[3,4-b]carbazol-3(4H,5H,10H)-one (41)
in 81% yield. Mp 225e227 ꢁC; IR (KBr, cmꢀ1
)
n
3105, 2985,1751,1247,
1130, 1131, 756; 1H NMR (DMSO-d6, 250 MHz)
d
2.56 (t, 1H,
J ¼ 16.6 Hz), 3.00 (dd, 1H, J ¼ 7.7 Hz, J ¼ 16.6 Hz), 3.38e3.52 (m, 1H),
3.83 (s, 3H), 4.02 (dd,1H, J ¼ 7.5 Hz, J ¼ 9.1 Hz), 4.69 (t,1H, J ¼ 9.1 Hz),
6.81 (d, 2H, J ¼ 8.7 Hz), 7.18e7.45 (m, 10H), 8.09 (d, 1H, J ¼ 8.4 Hz);
Compound 41 was isolated as a yellꢀo1w solid starting from 35 in
99% yield. Mp 215e217 ꢁC; IR (KBr, cm
) n 2941, 1737, 1606, 1445,
1362, 1215, 1174, 1089, 756, 686; 1H NMR (CDCl3, 250 MHz)
d 2.58
13C NMR (DMSO-d6, 100 MHz)
d
25.0 (CH2), 36.1 (CH), 55.0 (CH3),
(t, 1H, J ¼ 17.0 Hz), 3.09 (dd, 1H, J ¼ 7.7 Hz, J ¼ 17.0 Hz), 3.43e3.59
(m, 1H), 3.76 (s, 6H), 3.89 (s, 3H), 4.06 (dd, 1H, J ¼ 7.7 Hz, J ¼ 9.0 Hz),
4.73 (t, 1H, J ¼ 9.0 Hz), 6.64 (s, 2H), 7.26e7.47 (m, 8H), 8.08 (d, 1H,
69.7 (CH2),112.0 (CH),117.3 (CH),120.4 (CH),120.6 (CH),125.5 (2CH),
126.4 (2CH), 126.7 (2CH), 127.2 (2CH), 128.9 (Cq), 129.3 (Cq), 131.6
(Cq), 131.9 (Cq), 134.1 (Cq), 134.3 (CH), 138.7 (Cq), 140.4 (Cq), 140.4
(Cq), 159.1 (Cq), 167.4 (CO); HRMS (ESI) calculated for C27H22NO5S
472.1219, found 472.1223 (M þ Hþ).
J ¼ 8.2 Hz); 13C NMR (CDCl3, 62.9 MHz)
d 26.2 (CH2), 37.0 (CH), 56.2
(2CH3), 61.0 (CH3), 69.9 (CH2), 108.7 (CH), 117.5 (CH), 120.1 (CH),
120.2 (Cq), 125.1 (2CH), 126.2 (CH), 127.2 (2CH), 128.5 (2CH), 128.8
(Cq), 128.8 (Cq), 129.1 (Cq), 133.5 (CH), 137.0 (Cq), 138.6 (Cq), 138.9
(Cq), 141.0 (Cq), 142.2 (Cq), 151.9 (2Cq), 167.4 (CO); HRMS (ESI)
calculated for C29H26NO7S 532.1430, found 532.1423 (M þ Hþ).
5.21. 5-Benzenesulphonyl-4-(3,5-dimethoxyphenyl)-1H-furo[3,4-b]
carbazol-3(4H,5H,10H)-one (38)
Compound 38 was isolated as a whꢀit1e solid starting from 32 in
1589, 1446, 1362, 1203, 1150, 1026, 759, 685; 1H NMR (DMSO-d6,
5.25. General procedures for the preparation of furocarbazoles
43e47
74% yield. Mp 235e237 ꢁC; IR (KBr, cm
)
n
3064, 3007, 1739, 1607,
400 MHz)
d
2.60 (t, 1H, J ¼ 17.2 Hz), 3.11 (dd, 1H, J ¼ 8.0 Hz,
Method A: A solution of derivatives 37e42 (0.41 mmol) and
o-chloranil (0.2 g, 0.82 mmol) in toluene was irradiated under
microwave for 1 h 30. After cooling at 4 ꢁC for 12 h, the reaction
mixture was filtered and the precipitate washed with pentane, then
dried under vacuum. Method B: A solution of 31e36 (0.19 mmol) in
toluene was heated at 150 ꢁC for 1 h under microwave irradiation
(Biotage initiator apparatus), then o-chloranil (0.48 mmol) was
added and the mixture irradiated at 150 ꢁC for an additional
35 min. After evaporation of the solvent, the residue was dissolved
in a small amount of Et2O, and the precipitate was filtered and dried
under reduced pressure.
J ¼ 17.2 Hz), 3.34e3.56 (m, 1H), 3.70 (s, 6H), 4.06 (dd, 1H, J ¼ 7.6 Hz,
J ¼ 9.0 Hz), 4.67 (t, 1H, J ¼ 9.0 Hz), 6.46e6.52 (m, 3H), 7.30e7.46
(m, 6H), 7.50e7.56 (m, 2H), 7.94 (d,1H, J ¼ 8.4 Hz); 13C NMR (DMSO-
d6, 100 MHz)
d 24.5 (CH2), 35.9 (CH), 54.8 (2CH3), 69.1 (CH2), 100.1
(Cq), 109.1 (CH), 116.6 (CH), 120.0 (CH), 121.3 (Cq), 124.7 (CH), 125.7
(2CH), 126.5 (2CH), 128.3 (2CH), 128.6 (Cq), 130.0 (Cq), 133.3 (Cq),
135.0 (CH), 135.4 (Cq), 137.9 (CH), 139.7 (Cq), 139.9 (Cq), 158.5 (2Cq),
167.4 (CO); HRMS (ESI) calculated for C28H23NO6SNa 524.1132, found
524.1136 (M þ Naþ).
5.22. 5-Benzenesulphonyl-4-(3,4-dimethoxyphenyl)-1H-furo[3,4-
b] carbazol-3(4H,5H,10H)-one (39)
5.26. 9-Benzenesulphonyl-4-(4-methoxyphenyl)-1,5-dihydro-3H-
furo [3,4-b]carbazol-3-one (43)
Compound 39 was isolated as a yellꢀow1 solid starting from 33 in
87% yield. Mp 205e207 ꢁC; IR (KBr, cm
)
n
2940, 1737, 1580, 1445,
Compound 43 was isolated as a white solid from 37 (Method A)
in 76% yield or from 31 (Method B) in 88% yield. Mp 234e236 ꢁC; IR
1361, 1235, 1173, 1023, 755, 686; 1H NMR (CDCl3, 250 MHz)
d 2.50
(t, 1H, J ¼ 17.0 Hz), 3.02 (dd, 1H, J ¼ 7.5 Hz, J ¼ 17.0 Hz), 3.39e3.55
(m, 1H), 3.83 (s, 3H), 3.87 (s, 3H), 4.02e4.13 (m, 1H), 4.68 (t, 1H,
J ¼ 9.0 Hz), 6.71 (d, 1H, J ¼ 8.5 Hz), 6.94 (d, 1H, J ¼ 8.5 Hz), 7.04
(s, 1H), 7.21e7.44 (m, 8H), 8.07 (d, 1H, J ¼ 8.5 Hz); 13C NMR (CDCl3,
(KBr, cmꢀ1
)
n
2934, 1746, 1610, 1514, 1446, 1349, 1239, 1177, 1023,
763, 685; 1H NMR (CDCl3, 400 MHz)
d
3.86 (s, 3H), 5.31 (s, 2H), 6.84
(d, 2H, J ¼ 8.8 Hz), 7.12e7.21 (m, 4H), 7.33e7.43 (m, 4H), 7.53 (t, 1H
J ¼ 8.8 Hz), 7.77 (s, 1H), 7.81 (d, 1H, J ¼ 7.6 Hz), 8.16 (d, 1H,
62.9 MHz)
d
26.3 (CH2), 36.9 (CH), 55.7 (CH3), 56.0 (CH3), 69.9 (CH2),
J ¼ 8.0 Hz); 13C NMR (CDCl3, 100 MHz)
d 55.2 (CH3), 67.5 (CH2), 111.7
109.1 (CH),114.6 (CH),117.7 (CH),119.3 (Cq),120.0 (CH),123.8 (2CH),
125.1 (CH), 126.3 (2CH), 127.2 (CH), 128.4 (CH), 129.0 (Cq), 129.6
(Cq), 133.4 (CH), 133.5 (Cq), 136.6 (Cq), 139.1 (Cq), 141.1 (Cq), 142.2
(CH), 112.9 (CH), 119.7 (CH), 120.7 (CH), 125.7 (2CH), 126.0 (Cq),
126.3 (2CH), 127.5 (Cq), 128.4 (2CH), 129.3 (2CH), 131.9 (Cq), 132.0
(CH), 133.2 (CH), 135.0 (Cq), 136.4 (Cq), 136.8 (Cq), 140.1 (Cq), 143.4

5436
Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
(Cq), 144.9 (Cq), 159.6 (Cq), 169.2 (CO); HRMS calculated for
(Cq), 128.5 (2CH),128.8 (Cq), 129.4 (CH),133.3 (CH), 134.1 (Cq),136.0
(Cq), 137.7 (Cq), 138.2 (Cq), 140.2 (Cq), 143.3 (Cq), 144.5 (Cq), 152.2
(2Cq), 169.1 (CO); HRMS calculated for C29H23NO7SNa 552.1093,
found 552.1088 (M þ Naþ).
C27H20NO5S 470.1062, found 470.1063 (M þ Hþ).
5.27. 9-Benzenesulphonyl-4-(3,5-dimethoxyphenyl)-1,5-dihydro-
3H-furo[3,4-b]carbazol-3-one (44)
Compound 44 was isolated as a pale grey solid from 38 (Method
A) in 77% yield or from 32 (Method B) in 70% yield. Mp 235e237 ꢁC;
5.31. General procedure for the preparation of NH-furocarbazoles
48e52
IR (KBr, cmꢀ1
)
n
2940, 1737, 1582, 1446, 1360, 1212, 1088, 945, 756,
684; 1H NMR (DMSO-d6, 250 MHz)
d
3.73 (s, 6H), 5.42 (s, 2H), 6.46
Method A: see also reference [9]. Method B: A solution of 43e47
(0.21 mmol) and TBAF (1 M solution in THF, 0.42 mmol) in toluene
(5 mL) was heated at 90 ꢁC for 1 h. The resulting solutionwas cooled
to room temperature and solvent was removed in vacuo. The crude
product was purified by flash column chromatography (petroleum
ether/EtOAc 8/2), to give the desired compounds.
(t,1H, J ¼ 2.2 Hz), 6.62 (d, 2H, J ¼ 2.2 Hz), 7.15 (d, 2H, J ¼ 7.2 Hz), 7.24
(t, 2H, J ¼ 8.2 Hz), 7.44e7.51 (m, 2H), 7.58e7.65 (m, 1H), 8.06 (dd,
2H, J ¼ 4.5 Hz, J ¼ 7.2 Hz), 8.24 (s, 1H); 13C NMR (DMSO-d6,
100 MHz)
d 55.0 (2CH3), 67.4 (CH2), 99.5 (CH), 109.2 (CH), 113.5
(CH), 119.1 (CH), 121.4 (2CH), 125.9 (2CH), 126.0 (Cq), 127.2 (Cq),
128.8 (2CH), 128.9 (Cq), 129.3 (CH), 133.3 (CH), 133.8 (Cq), 135.2
(CH), 135.5 (Cq), 135.8 (Cq), 138.6 (Cq), 142.3 (Cq), 145.9 (Cq), 159.1
(2Cq), 168.4 (CO); HRMS calculated for C28H22NO6S 500.1168, found
500.1151 (M þ Hþ).
5.32. 4-(4-Methoxyphenyl)-1,5-dihydro-3H-furo[3,4-b]carbazol-3-
one (48)
5.28. 9-Benzenesulphonyl-4-(3,4-dimethoxyphenyl)-1,5-dihydro-
3H-furo[3,4-b]carbazol-3-one (45)
Compound 48 was isolated as a yellow solid from 43 following
Method A in 71% yield ꢀo1r following Method B in 81% yield.
1111, 828, 756; 1H NMR (DMSO-d6, 250 MHz)
d 3.87 (s, 3H), 5.46 (s,
Mp >250 ꢁC; IR (KBr, cm
) n 3326, 2936, 1732, 1580, 1410, 1237,
Compound 45 was isolated as a pale brown solid from39 (Method
A) in 70% yield or from 33 (Method B) in 75% yield. Mp >250 ꢁC; IR
2H), 7.12 (d, 2H, J ¼ 8.7 Hz), 7.19e7.25 (m, 1H), 7.47e7.56 (m, 4H),
(KBr, cmꢀ1
) n
3024, 1747, 1327, 1212, 1041, 751, 670, 514; 1H NMR
8.24 (d, 1H, J ¼ 7.7 Hz), 8.30 (s, 1H), 11.07 (s, 1H); 13C NMR (acetone-
(CDCl3, 250 MHz)
d
3.83 (s, 3H), 3.92 (s, 3H), 5.32 (s, 2H), 6.74 (d, 1H,
d6, 62.9 MHz) d 55.1 (CH3), 68.0 (CH2), 111.9 (CH), 112.1 (CH), 113.6
J ¼ 8.7 Hz), 6.99 (d, 2H, J ¼ 8.7 Hz), 7.16e7.28 (m, 4H), 7.36e7.44
(CH), 117.8 (Cq), 119.2 (CH), 121.2 (2CH), 124.0 (Cq), 125.0 (Cq), 127.5
(2CH), 128.1 (Cq), 131.4 (CH), 137.7 (Cq), 138.4 (Cq), 142.2 (Cq), 159.1
(Cq), 165.7 (Cq), 170.0 (CO); HRMS calculated for C21H16NO3
330.1130, found 330.1115 (M þ Hþ).
(m, 2H), 7.53 (t, 1H, J ¼ 7.7 Hz), 7.82 (t, 2H, J ¼ 7.7 Hz), 8.15 (d, 1H,
J ¼ 8.0 Hz); 13C NMR (CDCl3, 62.9 MHz)
d 55.7 (CH3), 56.0 (CH3), 67.5
(CH2),109.8 (CH),111.8 (CH),114.5 (CH),119.4 (CH),120.8 (CH),122.3
(Cq), 123.7 (CH), 125.5 (2CH), 126.0 (Cq), 126.1 (2CH), 127.2 (Cq),
128.4 (CH), 129.3 (CH), 133.2 (CH), 134.6 (Cq), 136.2 (Cq), 137.3 (Cq),
140.0 (Cq), 143.4 (Cq), 144.7 (Cq), 147.9 (Cq), 149.1 (Cq), 169.1 (CO);
HRMS calculated for C28H22NO6S 500.1168, found 500.1167
(M þ Hþ).
5.33. 4-(3,5-Dimethoxyphenyl)-1,5-dihydro-3H-furo[3,4-b]
carbazol-3-one (49)
Compound 49 was isolated as a yellow solid from 44 following
Method A in 74% yield ꢀo1r following Method B in 70% yield.
5.29. 9-Benzenesulphonyl-4-(3,4-methylenedioxyphenyl)-1,5-
dihydro-3H-furo[3,4-b]carbazol-3-one (46)
Mp >250 ꢁC; IR (KBr, cm
) n 2936, 1701, 1596, 1512, 1414, 1369,
1303, 1175, 1133, 1021, 744; NMR (acetone-d6, 400 MHz)
d 3.83 (s,
Compound 46 was isolated as a yellow solid from 40 (Method A)
in 66% yield or from 34 (Method B) in 26% yield. Mp 240e242 ꢁC; IR
6H), 5.45 (s, 2H), 6.57 (t, 1H, J ¼ 2.2 Hz), 6.74 (d, 2H, J ¼ 2.2 Hz),
7.24e7.28 (m, 1H), 7.47e7.51 (m, 1H), 7.57 (d,1H, J ¼ 8.0 Hz), 8.26 (d,
1H, J ¼ 8.0 Hz), 8.30 (s, 1H), 10.43 (s, 1H); 13C NMR (acetone-d6,
(KBr, cmꢀ1
400 MHz)
) n
3019, 1215, 1045, 761, 669, 505; 1H NMR (CDCl3,
d
5.31 (s, 2H), 6.00 (s, 2H), 6.72 (d, 1H, J ¼ 12.8 Hz), 6.91
100 MHz) d 55.7 (2CH3), 68.9 (CH2), 101.0 (CH), 108.9 (CH), 112.6
(dd,1H, J ¼ 2.4 Hz, J ¼ 12.8 Hz), 7.00 (d,1H, J ¼ 2.4 Hz), 7.17e7.29 (m,
(CH),113.1 (CH),119.5 (Cq),120.4 (CH),122.0 (2CH),122.8 (Cq),125.3
(Cq), 128.5 (CH), 129.6 (Cq), 136.2 (Cq), 138.9 (Cq), 139.7 (Cq), 143.2
(Cq), 161.6 (2Cq), 170.3 (CO); HRMS calculated for C22H18NO4
360.1236, found 360.1219 (M þ Hþ).
4H), 7.38e7.45 (m, 2H), 7.53 (t, 1H, J ¼ 8.0 Hz), 7.79e7.84 (m, 2H),
8.17 (d,1H, J ¼ 13.2 Hz); 13C NMR (CDCl3,100 MHz)
d 67.5 (CH2),101.6
(CH2),107.6 (CH), 111.6 (CH),112.0 (CH),119.6 (CH),120.8 (CH),122.3
(Cq), 124.7 (CH), 125.7 (2CH), 126.3 (2CH), 126.5 (Cq), 127.2 (Cq),
128.5 (CH), 129.3 (CH), 133.3 (CH), 134.6 (Cq), 136.4 (Cq), 136.8 (Cq),
140.0 (Cq), 143.4 (Cq), 144.8 (Cq), 146.9 (Cq), 147.8 (Cq), 169.1 (CO);
HRMS calculated for C27H18NO6S 484.0855, found 484.0854
(M þ Hþ).
5.34. 4-(3,4-Dimethoxyphenyl)-1,5-dihydro-3H-furo[3,4-b]
carbazol-3-one (50)
Compound 50 was isolated as a yellow solid from 45 following
Method A in 70% yield or following Method B in 72% yield. Mp
5.30. 9-Benzenesulphonyl-4-(3,4,5-trimethoxyphenyl)-1,5-
dihydro-H-furo[3,4-b]carbazol-3-one (47)
212e214 ꢁC; IR (KBr, cmꢀ1
)
n
2944, 1712, 1588, 1513, 1367, 1301,
1167, 1143, 1017, 712; NMR (acetone-d6, 400 MHz) 3.84 (s, 3H),
d
Compound 47 was isolated as a yellow solid from 41 (Method A) in
75% yield or from 35 (Method B) in 95% yield. Mp 204e206 ꢁC; IR
3.92 (s, 3H), 5.45 (s, 2H), 7.01 (d, 1H, J ¼ 12.6 Hz), 7.08e7.11 (m, 2H),
7.22 (t, 1H, J ¼ 12.6 Hz), 7.45e7.56 (m, 2H), 8.26 (d, 1H, J ¼ 12.6 Hz),
(KBr, cmꢀ1
)
n
2936,1736,1581,1511,1446,1361,1224,1174,1123,1012,
8.31 (s, 1H), 11.11 (s, 1H); 13C NMR (acetone-d6, 100 MHz)
d 55.7
746, 685; 1H NMR (CDCl3, 250 MHz)
d
3.72 (s, 6H), 3.88 (s, 3H), 5.59
(CH3), 56.0 (CH3), 68.1 (CH2), 108.2 (CH), 110.7 (CH), 111.9 (CH), 112.3
(CH), 118.0 (Cq), 119.3 (CH), 121.2 (Cq), 121.3 (CH), 123.7 (Cq), 123.8
(CH), 126.5 (CH), 127.6 (Cq), 128.2 (Cq), 137.6 (Cq), 138.5 (Cq), 142.2
(Cq), 147.0 (Cq), 147.1 (Cq), 169.9 (CO); HRMS calculated for
C22H18NO4 360.1236, found 360.1245 (M þ Hþ).
(s, 2H), 7.21e7.28 (m, 6H), 7.36e7.42 (m, 2H), 7.51 (t, 1H, J ¼ 8.0 Hz),
7.83 (d, 2H, J ¼ 8.5 Hz), 8.12 (d, 1H, J ¼ 8.5 Hz); 13C NMR (CDCl3,
62.9 MHz) d 56.1 (2CH3), 61.1 (CH3), 67.5 (CH2),108.7 (CH),112.1 (CH),
118.9 (Cq), 119.2 (CH), 120.8 (CH), 125.4 (2CH), 126.0 (2CH), 126.9

Y. Hajbi et al. / European Journal of Medicinal Chemistry 45 (2010) 5428e5437
5437
5.35. 4-(3,4-Methylenedioxyphenyl)-1,5-dihydro-3H-furo[3,4-b]
Acknowledgements
carba zol-3-one (51)
This work was supported by grants from the Ligue Nationale
Française contre le Cancer (Comités du Nord et de l’inter-Région
Grand Ouest) and the Canceropôle Grand Ouest.
Compound 51 was isolated as a yellow solid from 46 following
Method A in 70% yieldꢀ1or following Method B in 79% yield.
Mp >250 ꢁC; IR (KBr, cm
) n 3308, 2900, 1735, 1499, 1442, 1325,
1226, 1111, 1031, 858, 745; 1H NMR (DMSO-d6, 250 MHz)
d 5.46 (s,
References
2H), 6.14 (s, 2H), 7.00 (dd, 1H, J ¼ 1.5 Hz, J ¼ 8.0 Hz), 7.08e7.11 (m,
2H), 7.19e7.26 (m, 1H), 7.45e7.56 (m, 2H), 8.25 (d, 1H, J ¼ 7.8 Hz),
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(2003) 854e864;
8.31 (s,1H),11.11 (s,1H); 13C NMR (DMSO-d6, 62.9 MHz)
d 68.1 (CH2),
101.1 (CH), 108.2 (CH2), 110.7 (CH), 111.9 (Cq), 112.3 (CH), 118.0 (Cq),
119.2 (Cq), 121.2 (CH), 121.3 (CH), 123.7 (CH), 123.8 (CH), 126.5
(Cq), 127.6 (CH), 128.2 (Cq), 137.6 (Cq), 138.4 (Cq), 142.2 (Cq), 147.0
(Cq), 147.1 (Cq), 169.9 (CO); HRMS calculated for C21H13NO4Na
366.0742, found 366.0747 (M þ Naþ).
5.36. 4-(3,4,5-Trimethoxyphenyl)-1,5-dihydro-3H-furo[3,4-b]car
bazol-3-one (52)
(b) J. Routier, M. Calancea, M. David, Y. Vallée, J.-N. Denis, Eur. J. Org. Chem.
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(1997) 678e684.
Compound 50 was isolated as a white solid from 47 following
Method A in 82% yield or following Method B in 75% yield [9].
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J. Med. Chem. 49 (2006) 789e799.
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5.37. 4-(3,4-Hydroxy-5-methoxyphenyl)-1,5-dihydro-3H-furo[3,4-
b]carbazol-3-one (53)
[11] V.O. Illi, Synthesis (1979) 136e139.
A solution of BBr3 (2.5 M in CH2Cl2, 17 mL) was added to a solu-
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73e84.
tion of 52 (50 mg, 0.128 mmol) in CH2Cl2(5 mL) at ꢀ78 ꢁC. Water
(5 mL) and CH2Cl2 (20 mL) were added after 1 h and the reaction
mixture was allowed to warm to r.t. After extraction, the organic
layer was washed with water (10 mL) and concentrated under
reduced pressure. The crude residue was purified by flash chro-
matography (petroleum ether to petroleum ether/EtOAc 7/3) to
afford compound 53 as a white solid (26 mg, 55%). Mp >250 ꢁC; IR
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(KBr, cmꢀ1
NMR (CDCl3, 250 MHz)
)
n
3512, 2932, 1714, 1532, 1437, 1317, 1123, 1034, 746; 1H
3.93 (s, 3H), 5.44 (s, 2H), 7.17 (t, 1H,
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d
J ¼ 7.9 Hz), 7.22 (t, 1H, J ¼ 7.9 Hz), 7.26e7.34 (m, 2H), 7.43e7.60 (m,
2H), 7.80 (s, 1H), 8.36 (br s, 1H); 13C HSQC NMR (CDCl3, 62.9 MHz)
d
56.4, 68.1, 106.3, 111.1, 111.4, 118.2, 119.9, 122.1, 122.4; HRMS
calculated for C21H16NO5 362.1028, found 362.1016 (M þ Hþ).
5.38. DNA binding measurements
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Cancer Res. 55 (1995) 1707e1716.
They were performed as previously described [31].
5.39. Topoisomerases inhibition assays
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R. Houssin, C. Bailly, J.-P. Hénichart, J. Med. Chem. 51 (2008) 3617e3629.
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A. Lansiaux, N. Guilbaud, T. Imbert, C. Bailly, Cancer Res. 68 (2008) 9845e9853.
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C. Bailly, R. Le Guével, C. Guillouzo, S. Routier, Org. Biomol. Chem. 6 (2008)
2108e2117.
They were performed as previously described [32].
5.40. Cell culture and survival assay
They were performed as previously described [33].
[33] C. Bailly, Methods Enzymol. 340 (2001) 610e623.