Design and preparation of aza-analogues of benzo[c]phenanthridine framework with cytotoxic and antiplasmodial activities

Article abstract of DOI:10.1016/j.ejmech.2010.03.006

Benzo[c]phenanthridine alkaloids represent interesting lead for the discovery of new potential antiplasmodial and/or anticancer drugs. In this field, a novel library of aza-analogs of benzo[c]phenanthroline framework derivatives was designed and prepared. Although these compounds did not have specific antiplasmodial activities, some of them displayed specific in vitro activity against two cancer lines especially compound 24 with an IC₅₀ against the MCF7 line of 0.6 μM.

Full text of DOI:10.1016/j.ejmech.2010.03.006

European Journal of Medicinal Chemistry 45 (2010) 2854e2859
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design and preparation of aza-analogues of benzo[c]phenanthridine framework
with cytotoxic and antiplasmodial activities
Ange-Désiré Yapi a, Nicolas Desbois a, Jean-Michel Chezal b, Olivier Chavignon b, Jean-Claude Teulade b,
,
Alexis Valentin c, Yves Blache d
*
a Laboratoire de chimie organique et thérapeutique, EA 3660 Unité de Molécules d’Intérêt Biologique, Faculté de Pharmacie, 7 boulevard Jeanne d’Arc, BP 89700, 21079 Dijon, France
b Université de Clermont-Ferrand, Faculté de Pharmacie, EA 4231, F-63001, France
c UMR 152 IRD-UPS, Pharmacochimie des Substances Naturelles et Pharmacophores redox, Faculté de Pharmacie, Toulouse, France
d Laboratoire MAPIEM EA 4323, Université du Sud Toulon-Var, BP 20132, 83957 La Garde Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Benzo[c]phenanthridine alkaloids represent interesting lead for the discovery of new potential anti-
plasmodial and/or anticancer drugs. In this field, a novel library of aza-analogs of benzo[c]phenan-
throline framework derivatives was designed and prepared. Although these compounds did not have
specific antiplasmodial activities, some of them displayed specific in vitro activity against two cancer
Received 9 November 2009
Received in revised form
1 March 2010
Accepted 3 March 2010
Available online 12 March 2010
lines especially compound 24 with an IC50 against the MCF7 line of 0.6 mM.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Keywords:
Antiplasmodial
Cytotoxicity
Heck coupling
benzo[c]phenanthridine analogues
1. Introduction
and number of nitrogen atoms. As an example, 5-aza-analogues
of benzo[c]phenanthridines were designed as new top-
oisomerase I-targeting anticancer agents [6], while, in the same
time, aza-analogues of the marine pyrroloquinoline alkaloids
wakayin and tsitsikammamines were also reported as potential
antitumor agents, and many works were conducted around
ellipticine skeleton showing the influences of additional nitrogen
atoms [7,8]. Concurrently, in the field of antiplasmodial
compounds, we have previously reported some studies con-
cerning the synthesis and biological activities of azaphenan-
thridines showing the impact of the position of the nitrogen
atom [9,10], and these results finally led us to design new con-
formationally restricted analogs of primaquine with a 1,10-phe-
nanthroline framework [11].
As a continuation of these investigations, we initiated a project
aimed to design new libraries of azaphenanthridines related to the
benzo[c]phenanthridine class. In this context, we were interested
in developing an efficient and general strategy for the preparation
of series A, B, C from diverses amino(iso)quinolines as starting
materials. Among the different routes, we focused our attention in
the intramolecular arylearyl coupling reaction involving palladium
reagents which has been already used for the preparation of many
condensed heteroatomic compounds including benzo[c]phenan-
thridines [12e15].
Benzo[c]phenanthridine bases are distributed in Papaveraceous
and Rutaceous plants. They have a long history, dating back to their
first report in 1839 [1]. Among them, nitidine 1 an alkaloid isolated
from Rutaceous plants, was reported to exhibit a strong antima-
larial activity against a range of chloroquine-sensitive and -resis-
tant strains of P. falciparum and showed no cross-resistance with
chloroquine [2]. Concurrently, nitidine as well as others benzo[c]
phenanthridine alkaloïds, is well known to exhibit anticancer
activities by acting as topoisomerases inhibitors [3,4]. As a conse-
quence of this, structureeactivity relationships were developed in
order to enhance the selectivity of such compounds. In this way,
synthetic benzo[c]phenanthridines were tested in vitro for anti-
malarial activity showing that fagaronine 2 was relatively inactive
while O-Methyl fagaronine 3 was 6e30 times more potent than 2
[5]. In contrast, the fully synthetic analogue 4 was equally active
and this gave encouragement that analogue design could give
compounds with increased biological potency (Fig. 1).
In this field too, works were conducted with the aim of
designing new analogues by studying the impact of the position
* Corresponding author.
E-mail address: blache@univ-tln.fr (Y. Blache).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.03.006

A.-D. Yapi et al. / European Journal of Medicinal Chemistry 45 (2010) 2854e2859
2855
Table 1
preparation of secondary amides.
Compound
Method A
Method B
10
11
12
13
14
44%
90%
22%
82%
47%
72%
10%
85%
82%
28%
Method A: iodobenzoic acid, oxalyl chloride.
Method B: 2-iodobenzoic acid, EDCI, DMAP.
2.2. Biology
2.2.1. Antiplasmodial activities
Two strains of P. falciparum were used to evaluate the in vitro
antiplasmodial activities of compounds 20e26: The chloroquine
(CQ)-resistant FcB1-Columbia and F32 CQ-sensitive strains. Para-
sites were cultured according to the method originally described by
Trager and Jensen [16e18]. For each in vitro test, the parasite culture
was incubated with the tested compound at growing dilutions for
48 h. Results summarized in Table 2 showed that all tetracyclic
compounds exhibited lower in vitro antiplasmodial activities than
primaquine or chloroquine.
Fig. 1. Structure of nitidine 1, fagaronine derivatives 2e4 and targeted libraries A, B, C.
2. Results and discussion
2.1. Chemistry
Conversion of amino(iso)quinolines 5e9 listed in Scheme 1 to
tertiary amides 15e19 was investigated using two methods A and B
(Scheme 1, Table 1). Using method A, 2-iodobenzoic acid was first
converted in situ into the corresponding acyl chloride which was
then allowed to react with the amines 5e9 in presence of trie-
thylamine. This method was efficient only for the preparation of 11,
13 and 14. Preparation of 10e14 was finally optimized by using the
2.2.2. Cytotoxic activities [19]
Two cell lines were used MCF7 (human breast carcinoma) and
the Vero cells (monkey kidney epithelial cells). Except compounds
20, 21, all compounds exhibited interesting activities. Furthermore,
it can be highlighted that compound 22 is not selective (similar
activities against both Plasmodium and cancer cell lines).
alternative method
B (2-iodobenzoic acid, EDCI$HCl, DMAP).
Structural elucidations of 10e14 were easily achieved by 1H and 13
C
Although interpretation of these results in terms of SAR is
difficult at this stage, some elements could be highlighted when
comparing geometries of compounds 20e26. Interestingly, two
groups of compounds came out. The first group constituted of
twisted compounds 20, 22, 23, 26 (Fig. 2) exhibiting mild anti-
plasmodial activities, while the second group is constituted of flat
compounds 21, 24, 25 (Fig. 3). Among them, 21, 24 were the less
active against the two strains of P. falciparum tested, while
compound 25 was ten fold more active. However, the latter rep-
resented a particular case in which the conformation was twisted
after protonation. In addition, when considering the less active flat
structures 21, 24 against P. falciparum, one 21 was not cytotoxic
against the cell lines tested, while a particular interest arised when
considering 24. This compound exhibited better activities than
doxorubicin against the two cell lines and in a similar way (more
active on MCF7 than on Vero cell line, Table 3).
As these compounds are potential intercalating as well as anti-
topoisomerases agents, it can be highlighted that the position of the
nitrogen atom is crucial for the activity. At this stage only few struc-
tural features of the molecules can be taken in account: repartition of
electron densities (Fig. 4) and localisation of H-bonding site (nitrogen
atom). Thesetwo properties may have a greatimpactontargeting and
on the stabilization of biological complexes DNA/drug and/or DNA/
topo/drug. In the case of 24, the electron rich domain related to the
quinolinic nitrogen and located on the nitrogen appeared more
available to implicate this position in H-bonding, while in the case of
21, this domain is more enclosed inside the aromatic framework.
Furthertheoreticalstudiesaswellasexperimentalstudiesconcerning
the interaction of 21 and 24 with DNA and topoisomerases will be
necessary in order to refine such hypothesis.
NMR experiments, in particular because of the presence of the
quaternary carbons of the amide function near 170 ppm.
Subsequently, the secondary amides 10e14 were alkylated by
treatment with sodium hydride followed by methyl iodide. The
resulting tertiary amides 15e19 were obtained in moderate to good
yields (40e84%) as mixtures of rotamers. In each case, one rotamer
was preponderant but not identified. These mixtures were used for
the subsequent steps.
The palladium catalyzed reaction of 15e19 was evaluated using
Pd(OAc)2, PBu3, Ag2CO3 in refluxing DMF. The reaction smoothly
proceeded to give regioselectively the corresponding tetracycles
with 16, 19 to give 22, 26 while in the case of 18, low yield was
obtained and finally the reaction was optimized by using PPh3 to
give 25 in 74% yield. Concerning the two last amides 15, 17 reac-
tions were found to lead to the two regioisomers (respectively 20,
21 for 15 and 23, 24 for 16). Discrimination between the two
regioisomers 20, 21 was achieved by 1H NMR showing for 20
a deshielded singlet at 9.22 ppm corresponding to H-6 while in
the case of 23, 24, the 1H NMR spectrum of 24 showed two
singlets at 7.79 and 8.92 ppm, respectively attributed to H-5 and
H-12. In addition all structures were confirmed by 13C NMR and
mass spectroscopy data (Scheme 2).
3. Conclusion
A
library of benzophenanthridine-like compounds have
Scheme 1. Preparation of tertiary amides; (i) method A or method B, (ii) NaH, CH3I.
been synthesized. Although these compounds did not have

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A.-D. Yapi et al. / European Journal of Medicinal Chemistry 45 (2010) 2854e2859
Scheme 2. Synthesis of compounds 20e26 through Heck coupling strategy.
Table 2
IC50 (mM) of compounds 20e26 on two P. falciparum strains tested.
permitting structureeactivity relationships studies are under
investigation.
Compounds
F32
FcB1
20
21
22
23
24
25
26
PMQ
CQ
DOX
32.7 ꢀ 2.7
354.6 ꢀ 1.5
17.6 ꢀ 4.8
96.1 ꢀ 16.3
123.0 ꢀ 8.0
36.3 ꢀ 1.2
61.0 ꢀ 5.4
6.83 ꢀ 1.66
0.046
14.8 ꢀ 0.9
180.7 ꢀ 16.0
22.3 ꢀ 8.8
80.7 ꢀ 10.8
153.8 ꢀ 5.4
38.2 ꢀ 1.0
54.8 ꢀ 5.2
6.87 ꢀ 1.69
0.155
4. Experimental protocols
4.1. Chemistry
All column chromatographies were performed with Merck
neutral aluminum oxide 90 standardized (63e200
mm) or silica gel
(Acros organic, 60 Å, 35e70 m). All thinlayer chromatographies
m
NT
NT
were performed on Fluka aluminum oxide plates (with fluorescent
indicator 254 nm) or Merck silica gel 60F254 plates. Melting points
were determined on a Reichert-JungeKoffler apparatus and are not
corrected. NMR spectra (300 MHz for 1H and 75 MHz for 13C) were
recorded on a Bruker Avance 300 instruments using CDCl3 or MeOD
PMQ, primaquine; CQ, chloroquine; DOX, doxorubicine; NT, not tested.
specific antiplasmodial activities, further studies are now
needed in order to confirm the potentiality of compound 24 for
designing new leads as potential anticancer drugs. For
this purpose, regioselective access to this class of compounds
as solvent. Chemical shifts were reported in ppm (d) downfield
Fig. 2. lowest energy of the twisted conformations of compounds 20 (up left), 22 (up right), 23 (down left), 26 (down right).

A.-D. Yapi et al. / European Journal of Medicinal Chemistry 45 (2010) 2854e2859
2857
Fig. 3. lowest energy of the flat conformations of compounds 21 (up left), 24 (up middle), 25 (up right) and their protonated forms (down).
0 ꢁC. A solution of amino(iso)quinoline 5e9 (0.72 g, 5.0 mmol) in dry
dichloromethane (20 mL) was added dropwise and distilled trie-
thylamine (0.76 g, 7.5 mmol) was added at the same temperature.
The reaction mixture was stirred for another 1 h at 0 ꢁC. The reaction
was gradually allowed to reflux. After completion of the reaction
(TLC, Al2O3, CH2Cl2), the product was then diluted with a Na2CO3
saturated solution (35 mL). The product was then four times
extracted with dichloromethane/2-propanol (3:1, 40 mL). The
product was then dried with anhydrous sodium sulphate, filtered
and evaporated. The residue was purified by column chromatog-
raphy (Al2O3, CH2Cl2) to give the pure corresponding compound.
Procedure B: A mixture of amino(iso)quinoline 5e9 (0.72 g, 5.0
mmol), 2-iodobenzoic acid (1.86 g, 7.5 mmol), EDCIeHCl (1.44 g, 7.5
mmol) and DMAP (92 mg, 0.75 mmol) in dichloromethane (30 mL)
was stirred at room temperature for 24 h. The precipitate was then
washed with 5% HCl solution (5 mL) and dissolved in Na2CO3
saturated solution (10 mL).
Table 3
IC50 M) of compounds 20e26 on MCF7 and vero cell line.
(
m
Compounds
MCF7
Vero
20
21
22
23
24
25
26
PMQ
CQ
DOX
30.9 ꢀ 4.6
153.8 ꢀ 4.2
12.5 ꢀ 8.8
11.5 ꢀ 1.7
0.6 ꢀ 0.15
16.5 ꢀ 0.5
11.9 ꢀ 1.6
NT
22.3 ꢀ 1.15
42.0 ꢀ 4.24
3.5 ꢀ 0.1
1.75 ꢀ 0.78
2.85 ꢀ 0.35
3.35 ꢀ 0.64
2.3 ꢀ 0.2
NT
NT
NT
7.4 ꢀ 1.6
0.41 ꢀ 0.05
PMQ, primaquine; CQ, chloroquine; DOX, doxorubicine; NT, not tested.
from TMS. All the coupling constants (J) are in hertz. ESI-MS
analyses were performed on a Bruker Esquire 6000 instrument.
Analytical analysis were not reported because amides were not
stable enough, and results of these analysis were not significant,
especially for the iodo derivatives. However, all compounds were
successfully analyzed by SM (2 decimals), NMR and checked for
their degrees of purity by HPLC before proceeding biological tests.
The product was then extracted with dichloromethane (3 ꢂ 30
mL), the organic layer was then dried with anhydrous sodium
sulphate, filtered and evaporated. The residue was purified by
column chromatography (Al2O3, CH2Cl2) to give the title compound.
4.1.1.1. N-(3-quinolinyl)-2-iodobenzamide (10). Prepared from 3-
aminoquinoline by the procedure A (44%) or by procedure B (72%),
mp 204e206 ꢁC; Rf 0.20 (Al2O3, CH2Cl2); 1H NMR (CDCl3/MeOD,
4.1.1. Typical procedure for preparation of N-(iso)quinolyl-2-iodo-
benzamides 10e14
Procedure A: Oxalyl chloride (2.30 g, 18.1 mmol) was added to
a mixture of 2-iodobenzoic acid (1.50 g, 6.05 mmol) in dry
dichloromethane (40 mL), and the mixture was heated to reflux
under nitrogen with stirring for 3 h. The mixture was concentrated
to dryness under vacuum. The acid chloride was redissolved in dry
dichloromethane (40 mL) and the solution was taken and cooled to
300 MHz)
d
7.20 (m, 1H), 7.50 (m, 2H), 7.60 (t, 1H, J ¼ 7.5 Hz), 7.69
(t, 1H, J ¼ 7.5 Hz), 7.89 (d, 1H, J ¼ 7.5 Hz), 7.94 (d, 1H, J ¼ 7.5 Hz), 7.99
(d,1H, J ¼ 7.5 Hz), 8.86 (s,1H), 8.97 (s,1H); 13C NMR (CDCl3, 75 MHz)
d
92.4, 124.5, 127.4, 127.9, 128.2, 128.4, 128.6 (2C), 129.0, 131.2, 131.8,
140.2, 141.4, 143.8, 145.5, 167.9; MS (ESI, m/z) 397.03 (M þ Naþ),
375.09 (M þ Hþ)
Fig. 4. Electrostatic potential surfaces for compounds 21 (left) and 24 (right). The values are color-coded onto the total electron density surface, with colors toward red indicating
electron rich regions of the molecule (charge range from ꢃ0.08327 (red) to þ0.08327 (blue). (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article).

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A.-D. Yapi et al. / European Journal of Medicinal Chemistry 45 (2010) 2854e2859
4.1.1.2. N-(5-quinolinyl)-2-iodobenzamide (11). Prepared from 5-
aminoquinoline by the procedure A (90%) or by procedure B (10%);
mp 226e228 ꢁC; Rf 0.18 (Al2O3, CH2Cl2); 1H NMR (MeOD, 300 MHz)
4.1.2.3. N-methyl-N-(6-quinolinyl)-2-iodobenzamide (17). Prepared
from 12. (45%); oil; Rf 0.30 (SiO2, CH2Cl2: MeOH; 95:5); 1H NMR
(major rotamer) (CDCl3, 300 MHz)
d
3.57 (s, 3H), 6.76 (t, 1H, J ¼ 7.5
d
7.16 (t, 1H, J ¼ 8 Hz), 7.49 (m, 2H), 7.56 (d, 1H, J ¼ 8 Hz), 7.79
(m, 2H), 7.90 (m, 2H), 8.60 (d, 1H, J ¼ 7.5 Hz), 8.80 (d, 1H, J ¼ 4 Hz);
13C NMR (MeOD, 75 MHz)
93.3, 122.5, 124.9, 125.7, 128.0, 129.2,
Hz), 7.06 (m, 2H), 7.33 (m, 1H), 7.49 (d, 1H, J ¼ 7.5 Hz), 7.58 (m, 2H),
7.89 (d, 1H, J ¼ 7.5 Hz), 7.98 (d, 1H, J ¼ 7.5 Hz), 8.82 (m, 1H); MS (ESI,
m/z) 411.04 (M þ Naþ), 389.12 (M þ Hþ).
d
129.5, 130.7, 132.4, 134.0, 134.4, 140.9, 144.1, 149.3, 151.5, 171.8; MS
(ESI, m/z) 397.04 (M þ Naþ), 375.10 (M þ Hþ).
4.1.2.4. N-methyl-N-(8-quinolinyl)-2-iodobenzamide (18). Prepared
from 13. (74%); mp 100e102 ꢁC; Rf 0.30 (SiO2, CH2Cl2: MeOH; 95:5);
1H NMR (major rotamer) (CDCl3, 300 MHz)
d 3.59 (s, 3H), 6.65 (m,
4.1.1.3. N-(6-quinolinyl)-2-iodobenzamide (12). Prepared from 6-
aminoquinoline by the procedure A (22%) or by procedure B (85%);
mp 200e202 ꢁC; Rf 0.22 (Al2O3, CH2Cl2); 1H NMR (CDCl3, 300 MHz)
2H), 6.89 (d, 1H, J ¼ 7.5 Hz), 7.30 (t, 1H, J ¼ 7.5 Hz), 7.41 (m, 1H), 7.55
(d,1H, J ¼ 7.5 Hz), 7.61 (d, 1H, J ¼ 7.5 Hz), 7.73 (d,1H, J ¼ 7.5 Hz), 8.06
(d, 1H, J ¼ 7.5 Hz), 9.00 (m, 1H); MS (ESI, m/z) 411.04 (M þ Naþ),
389.10 (M þ Hþ).
d
7.13 (t, 1H, J ¼ 7.5 Hz), 7.42 (m, 2H), 7.55 (d, 1H, J ¼ 7.5 Hz), 7.69
(d, 1H, J ¼ 9 Hz), 7.89 (d, 1H, J ¼ 7.5 Hz), 8.09 (d, 1H, J ¼ 9 Hz), 8.19
(m, 2H), 8.55 (s, 1H), 8.82 (d, 1H, J ¼ 4.5 Hz); 13C NMR (CDCl3, 75
4.1.2.5. N-methyl-N-(5-isoquinolinyl)-2-iodobenzamide (19). Prepa
red from 14. (45%); mp 180e182 ꢁC; Rf 0.30 (SiO2, CH2Cl2: MeOH;
MHz)
d 92.4, 116.6, 121.8, 123.2, 128.4, 128.6, 128.9, 130.3, 131.7,
135.5, 136.2, 140.1, 141.8, 145.6, 149.5, 167.6; MS (ESI, m/z) 397.01
95:5); 1H NMR (major rotamer) (CDCl3, 300 MHz)
d 3.58 (s, 3H),
(M þ Naþ), 375.10 (M þ Hþ).
6.75 (m, 3H), 7.43 (t, H, J ¼ 7.5 Hz), 7.64 (d, 1H, J ¼ 7.5 Hz), 7.77
(d, 1H, J ¼ 7.5 Hz), 7.83 (m, 2H), 8.69 (m, 1H), 9.25 (s, 1H); MS (ESI,
m/z) 411.10 (M þ Naþ), 389.10 (M þ Hþ).
4.1.1.4. N-(8-quinolinyl)-2-iodobenzamide (13). Prepared from 8-
aminoquinoline by the procedure A (82%) or by procedure B (82%);
mp 157e159 ꢁC; Rf 0.90 (Al2O3, CH2Cl2); 1H NMR (CDCl3, 300 MHz)
4.1.3. Typical procedure for Heck cyclisation
d
7.17 (t, 1H, J ¼ 7.5 Hz), 7.45 (m, 2H), 7.61 (m, 3H), 7.96 (d, 1H,
J ¼ 7.5 Hz), 8.17 (d, 1H, J ¼ 7.5 Hz), 8.77 (s, 1H,), 8.94 (s, 1H, J ¼ 6
Hz), 10.15 (s, 1H, NH); 13C NMR (CDCl3, 75 MHz)
92.8, 116.9, 121.8,
To a solution of N-methyl-N-((iso)quinolinyl)-2-iodo-benza-
mides 15e19 (110 mg, 0.28 mmol) in dry DMF (4 mL) were
successively added Pd(OAc)2 (12 mg, 0.054 mmol), Bu3P (23 mg,
0.11 mmol) and Ag2CO3 (154 mg, 0.56 mmol). The mixture was
refluxed for 30 min and the reaction mixture was diluted with ether
and the precipitate was removed by filtration. The filtrate was
diluted with dichloromethane (30 mL) and washed with water (3 ꢂ
30 mL) and brine (30 mL). The organic layer was then dried with
anhydrous sodium sulphate, filtered and evaporated. The mixture
was purified using column chromatography (Al2O3, CH2Cl2).
d
122.2, 127.4, 128.1, 128.3, 128.4, 131.4, 134.3, 136.4, 138.6, 140.3,
142.3, 148.4, 167.4; MS (ESI, m/z) 397.04 (M þ Naþ), 375.10
(M þ Hþ).
4.1.1.5. N-(5-isoquinolinyl)-2-iodobenzamide (14). Prepared from
5-aminoisoquinoline by the procedure A (47%) or by procedure B
(28%); mp 205e207 ꢁC; Rf 0.18 (Al2O3, CH2Cl2); 1H NMR (MeOD, 300
MHz)
d
7.27 (t, 1H, J ¼ 8 Hz), 7.57 (t, 1H, J ¼ 8 Hz), 7.67 (d, 1H, J ¼ 8
Hz), 7.79 (t, 1H, J ¼ 8 Hz), 8.01 (d, 1H, J ¼ 8 Hz), 8.08 (d, 1H, J ¼ 8 Hz),
4.1.3.1. 7-Methyl-7H-dibenzo[c,f][1,7]naphthyridin-8-one (20). Prep
ared from compound 15 (56%); mp 238e240 ꢁC; Rf 0.30 (Al2O3,
8.14 (m, 2H), 8.50 (d, 1H, J ¼ 6 Hz), 9.30 (s, 1H); 13C NMR (MeOD, 75
MHz)
d 92.1, 116.0, 125.9, 126.7, 127.3, 127.8, 127.9, 129.0, 131.0 (2C),
CH2Cl2); 1H NMR (CDCl3, 300 MHz)
d
4.02 (s, 3H), 7.73 (m, 3H), 7.88
(t, 1H, J ¼ 7.5 Hz), 8.23 (m, 1H), 8.69 (d, 1H, J ¼ 7.5 Hz), 8.77 (m, 2H),
9.22 (s, 1H); 13C NMR (CDCl3, 75 MHz)
30.1, 119.5, 123.4, 125.3,
131.6, 139.4, 141.7, 142.0, 151.9, 169.6; MS (ESI, m/z) 397.04
(M þ Naþ), 375.10 (M þ Hþ).
d
127.5, 127.7, 128.0, 129.2, 129.4, 130.3, 130.8, 131.9, 132.2 (2C), 139.8,
144.8, 161.2; MS (ESI, m/z) 283.19 (M þ Naþ).
4.1.2Typical procedure for preparation of N-methyl-N-(iso)quinolyl-
2-iodo-benzamides (15e19)
A solution of iodobenzamide (0.30 g, 0.80 mmol) in sodium
hydride (64 mg, 1.61 mmol) (60% dispersed in mineral oil), and dry
DMF (5 mL) was prepared at 0 ꢁC. The iodomethane (136 mg, 0.96
mmol) was then added, slowly, to the reaction mixture at 0 ꢁC. The
reaction mixture was stirred at room temperature for 20 min. The
solution was diluted with dichloromethane (10 mL) and then
washed with water (3 ꢂ 20 mL). The organic layer was dried with
anhydrous sodium sulphate, filtered, and evaporated. The product
was then purified using column chromatography on silica gel
(CH2Cl2: MeOH; 95:5) to give two rotamers.
4.1.3.2. 6-Methyl-6H-dibenzo[b,h][1,5]naphthyridin-5-one (21). Pre
pared from compound 15 (6%); mp 220e222 ꢁC (lit [20]. 219e220
ꢁC); Rf 0.70 (Al2O3, CH2Cl2); 1H NMR (CDCl3, 300 MHz)
d 3.84 (s, 3H),
7.56 (t, 1H, J ¼ 7.5 Hz), 7.72 (m, 2H), 7.85 (m, 3H), 8.19 (d, 1H, J ¼ 7.5
Hz), 8.51 (d, 1H, J ¼ 7.5 Hz), 9.06 (d, 1H, J ¼ 7.5 Hz); 13C NMR (CDCl3,
75 MHz)
d 29.7, 118.1, 124.5, 127.1, 127.3, 127.5, 128.1, 128.3 (2C),
129.3, 130.4, 132.4, 132.8, 134.4, 139.6, 144.0, 161.1; MS (ESI, m/z)
283.05 (M þ Naþ).
4.1.3.3. 5-Methyl-5H-benzo[c][1,7]phenanthrolin-6-one (22). Prep
ared from 16 (80%); mp 159e161 ꢁC; Rf 0.80 (Al2O3, CH2Cl2); 1H
4.1.2.1. N-methyl-N-(3-quinolinyl)-2-iodobenzamide (15). Prepared
from 10. (84%); mp 156e158 ꢁC; Rf 0.40 (SiO2, CH2Cl2: MeOH; 95:5);
NMR (CDCl3, 300 MHz)
d
4.02 (s, 3H), 7.43 (m, 1H), 7.63 (t, 1H, J ¼ 9
Hz), 7.80 (t, 1H, J ¼ 9 Hz), 7.99 (d, 1H, J ¼ 8.5 Hz), 8.30 (d, 1H, J ¼ 8.5
1H NMR (major rotamer) (CDCl3, 300 MHz)
d 3.62 (s, 3H), 6.82 (t,1H,
Hz), 8.47 (d,1H, J ¼ 9 Hz), 8.55 (d,1H, J ¼ 9 Hz), 8.69 (d,1H, J ¼ 9 Hz),
J ¼ 7.5 Hz), 7.16 (m, 2H), 7.64 (m, 4H), 7.98 (m, 2H), 8.71 (s, 1H); MS
8.93 (d, 1H, J ¼ 4.5 Hz); 13C NMR (CDCl3, 75 MHz)
d 40.7, 117.3, 119.3,
(ESI, m/z) 411.05 (M þ Naþ), 389.10 (M þ Hþ).
119.8, 122.2, 123.6, 125.2, 125.4, 128.4, 128.6, 132.9, 133.4 (2C), 135.9,
149.3, 150.3, 164.3; MS (ESI, m/z) 283.04 (M þ Naþ), 283.20
(M þ Hþ).
4.1.2.2. N-methyl-N-(5-quinolinyl)-2-iodobenzamide (16). Prepared
from 11. (40%); mp 117e119 ꢁC; Rf 0.36 (SiO2, CH2Cl2: MeOH; 95:5);
1H NMR (major rotamer) (CDCl3, 300 MHz)
d
3.58 (s, 3H), 6.78
4.1.3.4. 6-Methyl-6H-benzo[a][4,7]phenanthrolin-5-one (23). Prepa
red from 17 (70%); mp 249e251 ꢁC; Rf 0.22 (Al2O3, CH2Cl2); 1H NMR
(m, 3H), 7.55 (m, 2H), 7.62 (m, 2H), 7.95 (d, 1H, J ¼ 7.5 Hz), 8.40
(d, 1H, J ¼ 8.5 Hz), 8.95 (d, 1H, J ¼ 4 Hz); MS (ESI, m/z) 411.09
(M þ Naþ), 389.09 (M þ Hþ).
(CDCl3, 300 MHz)
7.79 (t, 1H, J ¼ 8 Hz), 7.85 (d, 1H, J ¼ 9 Hz), 8.21 (d, 1H, J ¼ 9 Hz), 8.43
d
3.91 (s, 3H), 7.52 (m, 1H), 7.64 (t, 1H, J ¼ 8 Hz),

A.-D. Yapi et al. / European Journal of Medicinal Chemistry 45 (2010) 2854e2859
2859
(d, 1H, J ¼ 9 Hz), 8.61 (d, 1H, J ¼ 8 Hz), 8.88 (d, 1H, J ¼ 4 Hz), 9.10
singly-excited configuration interaction. (RHF [Restricted
HartreeeFock], charge 1, spin multiplicity 1, lowest state, orbital
criterion, five occupied and five unoccupied orbitals.).
(d, 1H, J ¼ 8 Hz); 13C NMR (CDCl3, 75 MHz)
d 30.7, 113.7, 118.6, 121.4,
126.0, 126.6, 126.8, 127.8, 129.1, 131.2, 131.9, 133.1, 134.2, 136.5, 145.1,
148.5, 161.1; MS (ESI, m/z) 283.17 (M þ Naþ).
4.2. Biology
4.1.3.5. 6-Methyl-6H-quinolino[6,7-b]isoquinolin-7-one (24). Prepar
ed from 17 (5%); mp 225e226 ꢁC; Rf 0.40 (Al2O3, CH2Cl2); 1H NMR
P. falciparum was cultured according to the method described by
Trager and Jensen [16] with modifications [17]. Cultures were
synchronized by 5% D-sorbitol lysis (Merck, Darmstadt, Germany)
(MeOD, 300 MHz)
d
3.85 (s, 3H), 7.52 (m, 1H), 7.65 (t, 1H, J ¼ 8 Hz),
7.79 (s, 1H), 7.84 (t, 1H, J ¼ 8 Hz), 8.34 (d, 1H, J ¼ 8 Hz) 8.43 (d, 1H,
J ¼ 8 Hz), 8.50 (d, 1H, J ¼ 8 Hz), 8.83 (d, 1H, J ¼ 4.5 Hz), 8.92 (s, 1H);
[17]. In vitro antimalarial activity was evaluated by [3H]hypoxan-
thine (ICN, France) incorporation as already described [17,18].
Incubation time between parasite culture and the drugs was 48 h.
Cytotoxicity of the drugs was estimated with MCF7 and Vero cell
lines which were cultured in the same conditions as P. falciparum,
except for the 5% human serum which was replaced by 5% fetal calf
serum (Boehringer). After addition of drugs at various concentra-
tions, cell growth was estimated by [3H]hypoxanthine incorpora-
tion after 48 h incubation [19].
13C NMR (CDCl3/MeOD, 75 MHz)
d 30.2, 122.2, 122.8, 123.3, 123.9,
126.1, 129.3, 129.4, 129.8, 133.5, 133.8, 137.0, 137.1, 143.7, 150.3,
162.5; MS (ESI, m/z) 283.09 (M þ Naþ).
4.1.3.6. 5-Methyl-5H-benzo[c][1,10]phenanthrolin-6-one (25). Prepa
red from 18 (30% with PBu3, 74% with PPh3); mp 164e166 ꢁC; Rf
0.40 (Al2O3, CH2Cl2); 1H NMR (CDCl3, 300 MHz)
d 4.34 (s, 3H), 7.46
(m, 1H), 7.65 (m, 2H), 7.81 (t, 1H, J ¼ 8 Hz), 8.17 (d, 1H, J ¼ 8 Hz), 8.35
(m, 2H), 8.62 (d, 1H, J ¼ 8 Hz), 8.93 (d, 1H, J ¼ 4 Hz); 13C NMR (CDCl3,
75 MHz)
d 39.6, 119.2, 121.2, 121.5, 122.2, 122.6, 126.0, 128.4, 128.8,
References
129.4, 132.5, 133.4, 135.8, 135.9, 140.8, 147.2, 163.8 (CO); MS (ESI,
m/z) 283.09 (M þ Naþ).
[1] J.-M. Prost, Ann. Chem. 29 (1839) 120.
[2] D.M.N. Gakunju, E.K. Mberu, S.F. Dossaji, A.I. Gray, R.D. Waigh, P.G. Waterman,
W.M. Watkins, Antimicrob. Agents Chemother. 39 (1995) 2606e2609.
[3] H.-K. Wang, S.L. Morris-Natschke, K.-H. Lee, Med. Res. Rev. 17 (1997) 367e425.
[4] S.D. Fang, L.K. Wang, S.M. Hecht, J. Org. Chem. 58 (1993) 5025e5027.
[5] J.M. Nyangulu, S.L. Hargreaves, S.L. Sharples, S.P. Mackay, R.D. Waigh, O. Duval,
E.K. Mberu, W.M. Watkins, Bioorg. Med. Chem. 15 (2005) 2007e2010.
[6] Y. Yu, S.K. Singh, A. Liu, T.-K. Li, L.F. Liu, E.J. LaVoie, Bioorg. Med. Chem. 11
(2003) 1475e1491.
[7] L. Legentil, L. Benel, V. Bertrand, B. Lesur, E. Delfourne, J. Med. Chem. 49 (2006)
2979e2988.
[8] M.-J. Vilarem, J.-Y. Charcosset, F. Primaux, M.-P. Gras, F. Calvo, C.-J. Larsen,
Cancer Res. 45 (1985) 3906e3911.
[9] A.D. Yapi, M. Mustofa, A. Valentin, O. Chavignon, J.-C. Teulade, M. Mallié,
J.-P. Chapat, Y. Blache, Chem. Pharm. Bull. 48 (2000) 1886e1889.
[10] A.D. Yapi, A. Valentin, J.-M. Chezal, O. Chavignon, B. Chaillot, R. Gerhardt,
J.-C. Teulade, Y. Blache, Arch. Pharm. Chem. Life Sci. 339 (2006) 201e206.
[11] C. Sall, A.D. Yapi, N. Desbois, S. Chevalley, J.-M. Chezal, K. Tan, J.-C. Teulade,
A. Valentin, Y. Blache, Bioorg. Med. Chem. Lett. 18 (2008) 4666e4669.
[12] J. Tsuji, Palladium Reagents and Catalysts. John Wiley & Sons, Ltd., Chichester,
UK, 1995, pp. 125e527.
[13] J.J. Li, G.W. Gribble, Palladium in Heterocyclic Chemistry. Pergamon, Oxford,
2000.
[14] T. Harayama, Heterocycles 65 (2005) 697e713.
[15] G. Bringmann, D. Menche, Acc. Chem. Res. 34 (2001) 615e624.
[16] W. Trager, J.B. Jensen, Science 193 (1976) 673e675.
[17] F. Benoit, A. Valentin, Y. Pélissier, C. Marion, Z. Dakuyo, M. Mallié, J.-M. Bastide,
Trans. R. Soc. Trop. Med. Hyg. 89 (1995) 217e218.
[18] A. Valentin, F. Benoit-Vical, C. Moulis, E. Stanislas, M. Mallié, I. Fourasté,
J.-M. Bastide, Antimicrob. Agents Chemother. 41 (1997) 2305e2307.
[19] V. Jullian, C. Bonduelle, A. Valentin, L. Acebey, A.G. Duigou, M.F. Prévost,
M. Sauvain, Bioorg. Med. Chem. Lett. 15 (2005) 5065e5070.
[20] I.G. Hinton, F.G. Mann, J. Chem. Soc. (1959) 2043e2048.
4.1.3.7. 5-Methyl-5H-benzo[c][1,8]phenanthrolin-6-one (26). Prepa
red from 19 (63%); mp 148e150 ꢁC; Rf 0.18 (Al2O3, CH2Cl2); 1H NMR
(CDCl3, 300 MHz)
d
4.09 (s, 3H), 7.70 (t, 1H, J ¼ 8 Hz), 7.86 (m, 1H),
7.89 (d,1H, J ¼ 9 Hz), 8.19 (d, 1H, J ¼ 6 Hz), 8.36 (d, 1H, J ¼ 8 Hz), 8.43
(d, 1H, J ¼ 9 Hz), 8.59 (d, 1H, J ¼ 6 Hz), 8.61 (d, 1H, J ¼ 8 Hz), 9.32
(s, 1H); 13C NMR (CDCl3, 75 MHz)
d 40.3, 118.0, 120.3, 121.7, 122.5,
123.1, 126.0, 127.6, 128.8, 129.1, 129.4, 133.0, 133.1, 135.0, 142.6,
153.0, 164.0 (CO); MS (ESI, m/z) 283.16 (M þ Naþ).
Computational methods: Structure of compounds (20e26) was
built in HyperChem Release 8.0.5 pro for Windows (Hypercube Inc.
Gainesville, Florida).
The geometries were optimized using the semi-empirical AM1
programme in singly-excited configuration interaction. (RHF
[Restricted HartreeeFock], charge 0, spin multiplicity 1, lowest
state, orbital criterion, five occupied and five unoccupied orbitals.)
To an rms (root mean square) gradient of 0.01 in vacuo
(PolakeRibière method). For the protonated forms, the system was
first optimized in MMþ to an rms gradient of 0.5. Then a molecular
dynamics program was run for 1 ps, with 0.001 ps steps, relaxation
time 0.1 ps, to a simulation temperature of 300 K. This was followed
by MMþ geometry optimization to an rms gradient of 0.2. The
molecular dynamics run was repeated and a further MMþ protocol
was carried out to a gradient of rms 0.04. Finally, the geometries
were optimized using the semi-empirical AM1 programme in