Conformationnally restricted naphthalene derivatives type isocombretastatin A-4 and isoerianin analogues: Synthesis, cytotoxicity and antitubulin activity

Article abstract of DOI:10.1016/j.ejmech.2012.03.001

A novel series of dihydronaphtalene, tetrahydronaphtalene and naphtalene derivatives as restricted analogues of isoCA-4 were designed, synthesized and evaluated for their anticancer properties. High cell growth inhibition against four tumour cell lines was observed at a nanomolar level with dihydronaphtalenes 1d, e and 1h, tetrahydronaphtalene 2c and naphtalene 3c. Structure-activity relationships are also considered. These compounds exhibited a significant inhibitory activity toward tubulin polymerization (IC₅₀ = 2-3 μM), comparable to that of isoCA-4. The effect of the lead compounds 1e and 2c on the cancer cells tested was associated with cell cycle arrest in the G ₂/M phase. Docking studies reveal that these compounds showed a binding mode similar to those observed with their non-constraint isoCA-4 and isoerianin congeners.

Full text of DOI:10.1016/j.ejmech.2012.03.001

European Journal of Medicinal Chemistry 52 (2012) 22e32
Contents lists available at SciVerse ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Conformationnally restricted naphthalene derivatives type isocombretastatin A-4
and isoerianin analogues: Synthesis, cytotoxicity and antitubulin activity
,
a
a
b
Evelia Rasolofonjatovo a, Olivier Provot a , Abdallah Hamze , Jordi Rodrigo , Jérome Bignon ,
*
Joanna Wdzieczak-Bakala b, Déborah Desravines b, Joëlle Dubois b, Jean-Daniel Brion a, Mouad Alami a
,
*
a Univ. Paris-Sud, CNRS, BioCIS-UMR 8076, LabEx LERMIT, Laboratoire de Chimie Thérapeutique, Faculté de Pharmacie, 5 rue J.-B. Clément, Châtenay-Malabry F-92296, France
b Institut de Chimie des Substances Naturelles, UPR 2301, CNRS avenue de la terrasse, F-91198 Gif sur Yvette, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of dihydronaphtalene, tetrahydronaphtalene and naphtalene derivatives as restricted
analogues of isoCA-4 were designed, synthesized and evaluated for their anticancer properties. High cell
growth inhibition against four tumour cell lines was observed at a nanomolar level with dihy-
dronaphtalenes 1d, e and 1h, tetrahydronaphtalene 2c and naphtalene 3c. Structureeactivity relation-
ships are also considered. These compounds exhibited a significant inhibitory activity toward tubulin
Received 27 January 2012
Received in revised form
28 February 2012
Accepted 1 March 2012
Available online 9 March 2012
polymerization (IC50 ¼ 2e3
mM), comparable to that of isoCA-4. The effect of the lead compounds 1e and
2c on the cancer cells tested was associated with cell cycle arrest in the G2/M phase. Docking studies
reveal that these compounds showed a binding mode similar to those observed with their non-
constraint isoCA-4 and isoerianin congeners.
Keywords:
Combretastatin A-4
isoCA-4
Cytotoxicity
Antimitotic
Ó 2012 Elsevier Masson SAS. All rights reserved.
Tubulin
Restricted analogues
1. Introduction
(CA-4, Fig. 1), a cis-stilbene extracted from the South African willow
Combretum caffrum [11,12] is arguably the most studied substance
Microtubules found in cytoskeleton of almost all eukaryotic cell
types are hollow tubes formed by self-assembly of and -tubulin
that displays a nanomolar level of cytotoxicity against a variety of
human cancer cells, including multidrug resistant cell lines [13,14].
a
b
heterodimers. They are directly involved in a variety of cellular
functions, such as cell movement, transport of organelles inside the
cell, maintenance of cell shape as well as mitosis and cell replication.
Consequently, perturbation of tubulin assembly/disassembly is
a popular target for new chemotherapeutic agents [1,2]. The vinca
alkaloids, typified by vinblastine and vincristine which inhibit
microtubules assembly [3] as well as the taxanes, such as paclitaxel
and docetaxel which promoted microtubules polymerization and
inhibits microtubules depolymerization [4,5], are the mostly used
antimicrotubules agents introduced in clinical oncology [6].
However, despite their potent antitumour activities, these drugs
have undesirable side effects [7,8] and are subject to multidrug
resistance [9,10]. These last decades, there has been a strong
enthusiasm for discovering tubulin polymerization inhibitors of
small size, easy synthesis and low side effects. Combretastatin A-4
CA-4 binds at or near colchicine binding site of b-tubulin and
strongly interferes with the assembly of tubulin, leading to cell death
[15]. It also exerts highly selective effects in proliferating endothelial
cells and, as a consequence, demonstrates strong suppressive
activity on tumour blood flow leading to tumour necrosis [16]. Two
derivatives are currently in clinical trials: CA-4 disodium phosphate
CA-4P [17,18], a water soluble prodrug of CA-4 and the amino-
combretastatin prodrug AVE-8062 (3) [19,20]. To date, CA-4P [21]
either as a single agent or in combination therapy is undergoing
several advanced clinical trials worldwide for the treatment of age-
related macular degeneration or anaplastic thyroid cancer.
Despite its remarkable anticancer activity, the main disadvan-
tage of CA-4 is the ready isomerization of the Z-double bond to its
inactive trans-form during storage, administration [22] and
metabolism [23]. In an ongoing project aimed at developing novel
tubulin assembly inhibitors [24e29], we recently discovered iso-
combretastatin A-4 (isoCA-4), a structural isomer of the natural
product, which holds biological activities comparable to that of CA-
4 [30]. This substance having a 1,1-diarylethylene scaffold is easy to
synthesize [31e33] at a multi grams scale without the need to
* Corresponding authors. Tel.: þ33 1 46 83 58 47; fax: þ33 1 46 83 58 28.
E-mail addresses: olivier.provot@u-psud.fr (O. Provot), mouad.alami@u-psud.fr
(M. Alami).
0223-5234/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2012.03.001

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
23
Fig. 1. Representative tubulin binding agents and general structure of the synthesized analogues 1e3.
control the olefin geometry and then definitively solving the
Z-double bond isomerization problem [34].
catalysis [30,41,42] to afford the key intermediates 1a, b. By securing
the required skeleton for the dihydronaphtalene analogues, the stage
was ready for the installation of various functionalities in place of the
bromine atom. The C(sp2)e-NH2 bond of 1d and 1i was formed from 1a
and 1b, respectively, using sodium azide as the amino source [43,44]
in the presence of a catalytic amountof CuI. Treating 1a, bwith KOH in
the presence of Pd2dba3, tBuXPhos in a mixture dioxane/H2O: 1/1 at
90 ꢀC [45] delivered in good yields the C30-hydroxy substituted
analogues 1e (63%) and 1h (62%). For the introduction of alkyne
substituents on the B-aromatic ring [36], we examined the
SonogashiraeLinstrumelle reaction [46] of 1a with propargylic and
homopropargylic alcohols. The coupling reaction of these alcohols
with 1a proceeded in the presence of PdCl2(PPh3)2 and CuI catalysts
under microwave irradiation (MWI) at 120 ꢀC to give the corre-
sponding alkynes 1f, g in good yields. Similarly, 1a underwent Heck
coupling with methyl acrylate using [1,3-bis(2,6-diisopropylphenyl)
imidazol-2-ylidene](3-chloropyridyl)palladium(II) dichloride (PEP-
PSI) as the catalyst in NMP at 140 ꢀC to afford the corresponding
30methyl (E)-cinnamate 1j in an unoptimized 35% yield.
Having achieved the preparation of dihydronaphtalenes 1, we
next focused our attention on their catalytic reduction to give
restricted isoerianin analogues 2. Thus, 4-aryltetrahydronaphtalenes
2aee were obtained in acceptable yields using H2 in the presence of
Pd/C in MeOH. Finally, aromatization of compound 1a into naph-
talene derivative 3a was attempted using a variety of oxidizing
species, including Pd/C, SeO2, o-chloranil, p-chloranil, and SO3-
pyridine complex. However, the oxidation reactions were unsuc-
cessful and gave 3a in very poor yields (<10%). After several trials, we
found that the oxidation of 1a with DDQ in CH2Cl2 afforded the
desired naphtalene 3a but in a moderate 33% yield. Introduction of
various substituents on 3a was next achieved in a similar manner as
described above for 1dej from 1a, b. Using a similar route for the
synthesis of 1d, dihydronaphtalene 1l bearing a NH2 substituent at
the C7 position was prepared from 7-bromo-6-methoxytetralone 4c
[47] for structureeactivity relation study (Scheme 2).
By structural modifications on the B-ring, we have also identified
other promising antiproliferative agents such as isoNH2CA-4 and
isoFCA-4 (Fig. 1) [35,36]. We also demonstrated that the bioisosteric
replacement of the (Z)-1,2-ethylene by the 1,1-ethylene could beapply
successfully to natural combretastatins CA-2, CA-3 and CA-5 [30]. On
the basis of these bioisosteric considerations, we also showed that
isoerianinderivatives having a 1,1-diarylethane scaffold were as active
as the natural product erianin [37]. A set of molecular docking calcu-
lations was performed with isoCA-4 as well as isoerianin which
showed a binding pose similar to those observed with CA-4 and the
co-crystallized DAMA-colchicine in the colchicine binding site [38]. In
addition, the dihedral angles between the planes of the two A/B-
aromatic nucleus in isoCA-4 and isoerianin (68ꢀ and 77ꢀ, respec-
tively) [30,37] were found to be close to that of CA-4 (53ꢀ) [39]. From
allof theseconsiderations,weareplanningtorationalizethesynthesis
of three new series of rigid analogues of isoCA-4 and isoerianin
namely, 4-aryldihydronaphtalenes 1 (e.g.; dihedral angle ¼ 69ꢀ for
1e), 4-aryltetrahydronaphtalenes 2 (e.g.; dihedral angle ¼ 79ꢀ for 2c)
and 1-arylnaphtalenes 3 (e.g.; dihedral angle ¼ 70ꢀ for 3d) with
reduced mobility of the B-ring. We hypothesized that constrained
analogues 1e3 with dihedral angles close to those of isoCA-4 and
isoerianin would be as active as their non restricted congeners. In this
paper we would like to describe the synthesis and evaluation of
compounds 1e3 in terms of inhibition of tubulin assembly along with
cytotoxicity studies against various cancer cell lines.
2. Results and discussion
2.1. Chemistry
Scheme 1 outlines the convergent synthetic routes followed for
the synthesis of the novel restricted-analogues 1e3. The projected
incorporation of a variety of substituents at the C3 position of the
~
B-ring trusts in the tractability of a C-Br bond, which can further be
engaged into diverse coupling reactions. Thus, the preparation of the
pivotal brominated precursors 1a and 1b was achieved from 5-
bromo-6-methoxytetralone 4b [40] which was heated in EtOH at
50 ꢀC with TsNHNH2 in the presence of PTSA. The resulting N-tosyl-
hydrazone 5b was next coupled with aryl iodides under palladium
2.2. Biological results
In vitro antiproliferative activity of the synthesized naphthalene
derivatives 1e3 was first determined against the human colon
carcinoma cell line (HCT116) using CA-4 [48] and isoCA-4 [30] and

24
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
Scheme 1. Synthesis of compounds 1e3. Reagents and conditions: (i) pTsNHNH2 (1.2 equiv), PTSA (0.2 equiv), MgSO4 (1 equiv), EtOH, 50 ꢀC (ii) ArI (1.1 equiv), Pd2dba3 (10 mol%),
XPhos (20 mol%), LiOtBu (2.2 equiv), dioxane 90 ꢀC in a sealed tube. (iii) 3,4,5-trimethoxyiodobenzene (1.1 equiv), Pd2dba3 (10 mol%), XPhos (20 mol%), LiOtBu (2.2 equiv), dioxane
90 ꢀC in a sealed tube. (iv) NaN3 (2 equiv), CuI 10 mol%, DMEDA (15 mol%), sodium ascorbate (5 mol%), DMSO/H2O: 5/1, 60 ꢀC (v) KOH (5 equiv), Pd2dba3 (10 mol%), tBuXPhos
(20 mol%), dioxane/H2O: 1/1, 90 ꢀC in a sealed tube. (vi) Alkyne (1.2 equiv), PdCl2(PPh3)2 (5 mol%), PPh3 (10 mol%), CuI (10 mol%), Et2NH (2 equiv), DMF, MWI, 120 ꢀC (vii) Methyl
acrylate (10 equiv), PEPPSI (5 mol%), K2CO3 (2 equiv), NMP 140 ꢀC in a sealed tube. (viii) H2, Pd/C in MeOH. (ix) DDQ (1.2 equiv), CH2Cl2, 20 ꢀC.
isoerianin [37] as reference compounds. The results of this study are
summarized in Table 1. On the exception of the amino derivative 3c
(GI50 ¼ 55 nM), naphtalene compounds 3 displayed only modest
antiproliferative activity, which was affected with halogen (Br, 3a),
alkynol (3e, 3f), alkene (3g) and alkyl (3h) substituents at the C5
position. In contrast, dihydronaphtalenes 1 were significantly more
active than their aromatic congeners. In particular, dihy-
dronaphtalenes 1d and 1e [49] bearing the greatest resemblance to
isoNH2CA-4 and isoCA-4, respectively, displayed a high anti-
proliferative activity at a nanomolar level (GI50 ¼ 7 and 85 nM). By
comparison with 1d, the introduction of an amino substituent at
the C7 position failed to improve the cytotoxic activity profile of 1l.
One note that compounds 1h and 1i bearing two methoxy groups
on the A-ring retained an important cytotoxicity in comparison
with 1e and 1d, respectively. Nevertheless, on the contrary with
previous reports [36], decreased cytotoxic activity was observed
with dihydronaphtalenes 1f, g and 1j bearing alkynol or alkene
substituents at the C5 position.
The reduction of 1 into tetrahydronaphtalenes 2 as restricted
isoerianin analogues led to compounds that displayed similar
cytotoxic activities in comparison with isoerianin (GI50 ¼ 28 nM)
and with their dihydronaphtalenes precursors. For example, 2c
with a GI50 value of 20 nM was slightly more active than restricted
isoCA-4 1e (85 nM), while the amino derivative 2b was about ten
Scheme 2. Synthesis of compounds 1k, l. Reagents and conditions: (i) pTsNHNH2 (1.2 equiv), PTSA (0.2 equiv), MgSO4 (1 equiv), EtOH, 50 ꢀC (ii) 3,4,5-trimethoxyiodobenzene (1.1
equiv), Pd2dba3 (10 mol%), XPhos (20 mol%), LiOtBu (2.2 equiv), dioxane 90 ꢀC in a sealed tube. (iii) NaN3 (2 equiv), CuI (10 mol%), DMEDA (15 mol%), sodium ascorbate (5 mol%),
DMSO/H2O: 5/1, 60 ꢀC.

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
25
Table 1
Cytotoxicity of compounds 1e3 against HCT116 cells.a
NH2
MeO
MeO
Br
MeO
MeO
MeO
Cpnd
OMe
OMe
OMe
OMe
OMe
OMe
1a
1b
1d
1c
Cytotoxicity GI50b [nM]
320 ꢁ 30
950 ꢁ 80
300 ꢁ 30
7 ꢁ 0.8
OH
OH
MeO
MeO
MeO
OH
MeO
MeO
MeO
MeO
OH
OMe
OMe
OMe
OMe
Cpnd
OMe
OMe
OMe
OMe
1f
1g
1h
1e
Cytotoxicity GI50b [nM]
85 ꢁ 6
250 ꢁ 22
600 ꢁ 50
70 ꢁ 6
CO2Me
NH2
MeO
MeO
MeO
MeO
MeO
OMe
OMe
Cpnd
OMe
OMe
OMe
OMe
1i
1j
2a
1l
Cytotoxicity GI50b [nM]
20 ꢁ 2
700 ꢁ 65
Ncc
70 ꢁ 6
NH2
MeO
MeO
OH
(CH2)4OH
OMe
MeO
MeO
MeO
MeO
OMe
OMe
Cpnd
OMe
OMe
OMe
2b
2c
2d
2e
Cytotoxicity GI50b [nM]
70 ꢁ 6
20 ꢁ 1.5
1700 ꢁ 100
250 ꢁ 28
Br
MeO
MeO
MeO
MeO
NH2
OH
MeO
MeO
MeO
OMe
OMe
Cpnd
OMe
MeO
OMe
OMe
OMe
OMe
OMe
3c
3d
3a
3b
Cytotoxicity GI50b [nM]
800 ꢁ 70
800 ꢁ 60
55 ꢁ 6
250 ꢁ 30
CO2Me
OMe
OH
MeO
MeO
MeO
MeO
(CH2)3OH
OMe
MeO
MeO
OH
MeO
MeO
OMe
OMe
Cpnd
OMe
OMe
OMe
OMe
3h
3g
3e
3f
Cytotoxicity GI50b [nM]
5500 ꢁ 500
Ncc
Ncc
Ncc
OH
MeO
OMe
MeO
OMe
isoCA-4
isoerianin
CA-4
3 ꢁ 0.2d
28 ꢁ 2
2 ꢁ 0.1d
a
HCT116: human colon carcinoma cells.
b
c
GI50 is the concentration of compound needed to reduce cell growth by 50% following 72 h cell treatment with the tested drug (average of three experiments).
GI50 value not calculated owing to the low activity of the compound.
The GI50 values for isoCA-4, isoerianin and CA-4 were determined in this study.
d

26
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
fold less active than its dihydronaphtalene analogue 1d. These
results indicated that rigidifying isoCA-4 or isoerianin with the
dihydro- or tetrahydronaphtalene system did not alter the reported
SAR. These preliminary in vitro cytotoxic results prompted us to
evaluate the most promising molecules in these series against other
human cancer cell lines. The GI50 values of selected compounds
obtained with K562 (chronic mylogenous leukaemia), H1299 (non-
small lung human carcinoma) and MDA-MB231 (human breast) cell
lines are summarized in Table 2.
Results from the cytotoxicity study provide evidence that
dihydronaphtalenes 1d, 1e, 1h, 1i which retained a high level of
cytotoxicity against HCT116 (Table 1) cells were also strongly
cytotoxic against H1299, MDA-MB231 and K562 cancer cell lines.
Similarly, tetrahydronaphtalenes 2aec as well as naphtalene
derivative 3c displayed an equivalent level of cytotoxicity against
the three tested cancer cells (30 < GI50 < 150 nM).
To confirm that the antiproliferative activities of these
compounds, like those in the isoCA-4 [30] and isoerianin series
[37], were related to an interaction with the microtubule system,
these selected compounds were evaluated for their inhibitory
effects on tubulin assembly (Table 2). Except for dihy-
dronaphtalenes 2a and 2b, the results demonstrated that the drug
cytotoxicity correlated with the inhibition of tubulin polymeri-
zation. For instance, dihydronaphatalenes 1d, 1e, 1h, 1i, tetrahy-
dronaphtalene 2c and naphtalene 3c were found to be as active as
isoCA-4 and CA-4, displaying an IC50 at a micromolar level. One
note that naphthol derivative 3d, bearing the greatest resem-
2.3. Docking study
These results clearly demonstrated that tubulin is the target of
these compounds; however, the specific binding site on tubulin was
not investigated, for example, by use of a radiolabeled colchicine
displacement assay. Nevertheless, a set molecular docking calcu-
lations was performed with 5-OH naphtalene derivatives to
investigate the possible binding mode of 2c, 1e and 3d which were
docked in the colchicine binding site of tubulin. For this purpose,
the X-ray structure of tubulin DAMA-colchicine complex (Code
PDB: 1sa0) [38] was used. Fig. 2 illustrates from one hand, the
docking-derived superimposition of 2c and 1e, with isoCA-4 (blue),
and on the other hand, the superimposition of 3d with isoerianin
(green). As expected, these compounds showed a binding pose
similar to the one observed with the reference compounds isoCA-4
and isoerianin with the trimethoxyphenyl ring placed in proximity
of Cys241 and the OH substituent of the B-ring (naphtalene, dihy-
dro- and tetrahydronaphtalene) which forms a hydrogen-bond
with Val181. These binding parallels and the dihedral angles
values of 2c (79ꢀ), 1e (69ꢀ) and 3d (70ꢀ) probably rationalise the
potency observed for these drugs in their tubulin effects which are
seen to be close to that reported for isoCA-4 (dihedral angle ¼ 68ꢀ)
[30] and isoerianin (dihedral angle ¼ 77ꢀ) [37].
3. Conclusion
We designed and synthesized by a convergent strategy, three
new classes of synthetic inhibitors of tubulin polymerization based
on the molecular skeleton of dihydronaphtalenes 1, tetrahy-
dronaphtalenes 2 and naphtalenes 3. These restricted analogues of
isoCA-4 and isoerianin were evaluated for their antiproliferative
activity against various human cancer cell lines. The lead
compounds, dihydronaphtalenes 1eeh, tetrahydronaphtalenes 2b,
c and to a lesser extent naphtalene 3c displayed potent cytotoxic-
ities with GI50 ranging from 15 to 110 nM. In these three series, six
of the most cytotoxic compounds were evaluated for effects on
blance to isoCA-4, showed
a reduced antitubulin activity
(IC50 ¼ 6.9
m
M) which was consistent with the results of the
growth inhibitory effect (310 nM < GI50 < 500 nM).
Because molecules exhibiting effects on tubulin polymerization
causes the alteration of cell cycle parameters, the effect of tetra-
hydronaphtalene 2c, dihydronaphtalene 1e, and naphtalene 3d on
MDA-MB231, K562, HCT116 and H1299 cellular cycle was investi-
gated. The fluorescent propidium iodide intercalates with the DNA
and hence, the amount of fluorescence measured per cell is
proportional to the DNA content. Cells were harvested after 24 h
and analysed for DNA content by flow cytometry. Table 3 shows
that a significant increased in G2/M peak is observed after treat-
ment of the four cell lines with tetrahydronaphtalene 2c at a low
concentration (5.10ꢂ9 M). Similarly, dihydronaphtalene 1e as well
as naphtalene derivative 3d arrest the majority of cells in the G2/M
phase of the cell cycle but at concentrations smoothly superiors
(10ꢂ8 M and 5.10ꢂ7 M, respectively).
tubulin polymerization and the IC50 values in a nearly range of 3 mM
are comparable to that of isoCA-4. The three most potent inhibitors
of tubulin assembly having the greatest resemblance to isoCA-4, 2c,
1e and 3d induced a prevalent block of cells in G2/M phase of the
cell cycle at nanomolar concentrations. In addition, docking studies
revealed that these compounds adopted an orientation similar to
that of isoCA-4 and isoerianin in the colchicine binding site. Bio-
logical results obtained in this study demonstrate that structural
Table 2
Cytotoxicities of selected compounds against different human cancer cell lines and inhibition of tubulin polymerization (ITP).
a
Compound
GI50 [nM]
Inhibition of tubulin
polymerization
Non-small lung
human carcinoma (H1299)
Human breast
cancer (MDA-MB231)
Chronic mylogenous
leukaemia (K562)
b
IC50
[mM]
1d
1e
1h
1i
2a
2b
2c
3c
30 ꢁ 2
32 ꢁ 2.5
33 ꢁ 2
85 ꢁ 5
20 ꢁ 1.5
20 ꢁ 1
70 ꢁ 6
100 ꢁ 7
70 ꢁ 3
30 ꢁ 2
60 ꢁ 4
500 ꢁ 35
4 ꢁ 0.5
40 ꢁ 5
3 ꢁ 0.3
180 ꢁ 14
15 ꢁ 0.8
20 ꢁ 1.5
200 ꢁ 12
150 ꢁ 10
110 ꢁ 9
55 ꢁ 3
2.1 ꢁ 0.2
1.9 ꢁ 0.2
2.0 ꢁ 0.2
3.1 ꢁ 0.5
Ncc
32 ꢁ 2
80 ꢁ 7
45 ꢁ 3
Ncc
30 ꢁ 2.5
90 ꢁ 7
3.0 ꢁ 0.3
2.0 ꢁ 0.3
6.9 ꢁ 0.8
2.2 ꢁ 0.2d
3.2 ꢁ 0.3d
1.0 ꢁ 0.2d
85 ꢁ 5
3d
310 ꢁ 25
3 ꢁ 0.4
38 ꢁ 3
380 ꢁ 25
5 ꢁ 4
isoCA-4
isoerianin
CA-4
20 ꢁ 1.5
4 ꢁ 0.3
5 ꢁ 0.4
a
GI50 is the concentration of compound needed to reduce cell growth by 50% following 72 h cell treatment with the tested drug (average of three experiments).
ITP, inhibition of tubulin polymerization; IC50 is the concentration of compound required to inhibit 50% of the rate of microtubule assembly (average of three experiments).
IC50 value not calculated owing to the low activity of the compound.
b
c
d
The GI50 and IC50 values for isoCA-4, isoerianin and CA-4 were determined in this study.

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
27
Table 3
Evaluation of G2/M arrest in MDA-MB231, K562, HCT116 and H1299 cells exposed to 2c, 1e and 3d.
Untreated cells
2c: 5.10ꢂ9
M
1e: 10ꢂ8
M
3d: 5.10ꢂ7
M
MDA-MB231 cells
K562 cells
HCT116 cells
H1299 cells
restrictions at this portion of isoCA-4 offers various premises for the
design of novel heterocycle-containing restricted isoCA-4 deriva-
tives. Synthesis and biological evaluation of such compounds are
under investigation in our laboratory and will be reported in due
course.
following abbreviations are used:
m
(multiplet),
s
(singlet),
d (doublet), br s (broad singlet), t (triplet). 13C chemical shifts are
reported in ppm from the central peak of CDCl3 (77.14). IR spectra
were measured on a Bruker Vector 22 spectrophotometer (neat,
cmꢂ1). Elemental analyses were performed with a PerkineElmer
240 analyser. Mass spectra were obtained with a LCT Micromass
spectrometer. Analytical TLC was performed on Merck precoated
silica gel 60F plates. Merck silica gel 60 (230e400 mesh) was used
for column chromatography.
4. Experimental
4.1. General considerations
Triethylamine was distilled from potassium hydroxide under
argon prior to use. The compounds were all identified by usual
physical methods, i.e. 1H NMR, 13C NMR, IR, MS and elemental
analysis. 1H and 13C NMR spectra were measured in CDCl3 with
a Bruker Avance 300. 1H chemical shifts are reported in ppm from
an internal standard TMS or of residual chloroform (7.27 ppm). The
4.2. Bromination of 6-methoxytetralone was achieved according to
literature to give 4b and 4c [40]
4.2.1. 5-Bromo-6-methoxytetralone (4b)
Yield: 49%. TLC: Rf 0.52 (cyclohexane/EtOAc: 9/1). IR (neat) nmax
/
cmꢂ1: 3904, 3232, 1664, 1568, 1458, 1415, 1352, 1327, 1280, 1232,

28
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
Fig. 2. Docked pose of 2c, 1e and 3c overlayed with isoCA-4 and isoerianin in the tubulin binding site.
1188, 904, 826, 776, 729, 638. 1H NMR (300 MHz, CDCl3)
d
ppm 8.06
J ¼ 6.0 Hz, 2H), 2.52e2.47 (m, 2H), 2.37 (s, 3H), 1.77 (m, 2H). 13C
(d, J ¼ 8.7 Hz, 1H), 6.88 (d, J ¼ 8.7 Hz, 1H), 3.97 (s, 3H), 3.03 (t,
NMR (75 MHz, DMSO) d 156.21, 152.15, 143.14, 140.06, 136.50,
J ¼ 6.2 Hz, 2H), 2.66e2.54 (m, 2H), 2.14 (m, 2H). 13C NMR (75 MHz,
129.39 (2C), 127.61 (2C), 126.37, 124.76, 112.31, 110.58, 56.39, 29.29,
25.12, 21.03, 20.86.
CDCl3) d 196.9, 159.8, 145.6, 128.5, 127.7, 113.1, 109.7, 56.6, 38.1, 30.6,
22.6. MS (APCI, m/z) 255.1 ([M þ H]þ, 79Br), 257.0 ([M þ H]þ, 81Br).
4.3.2. N0-(7-Bromo-6-methoxy-3.4-dihydronaphtalen-1(2H)-ylidene)
-4-methylbenzenesulfonohydrazide (5c)
4.2.2. 7-Bromo-6-methoxytetralone (4c)
Yield: 7%. Rf 0.45 (cyclohexane/EtOAc: 9/1). IR (neat) nmax/cmꢂ1
:
Yield: 98%. M.p. 236 ꢀC Rf 0.5 (cyclohexane/EtOAc: 7/3). IR (neat)
3628, 3238, 1668, 1568, 1459, 1413, 1352, 1327, 1283, 1260, 1232,
1188, 902, 778, 733, 640. 1H NMR (300 MHz, CDCl3)
ppm 8.21 (s,
1H), 6.69 (s, 1H), 3.94 (s, 3H), 2.91 (t, J ¼ 6.0 Hz, 2H), 2.75e2.41 (m,
2H), 2.12 (m, 2H). 13C NMR (75 MHz, CDCl3)
196.0, 159.6, 159.4,
nmax/cmꢂ1: 2249, 1054, 1025, 1016, 992, 821, 701, 654. 1H NMR
d
(300 MHz, DMSO) d ppm 10.39 (br s, 1H), 7.92e7.70 (m, 3H), 7.42 (d,
J ¼ 7.8 Hz, 2H), 6.91 (s, 1H), 3.84 (s, 3H), 3.35e3.30 (m, 2H),
d
2.76e2.59 (m, 2H), 2.38 (s, 3H), 1.85e1.65 (m, 2H). 13C NMR
151.4, 145.9, 132.6, 110.8, 56.4, 38.5, 29.9, 23.2. MS (APCI, m/z) 255.0
([M þ H]þ, 79Br), 257.0 ([M þ H]þ, 81Br).
(75 MHz, DMSO) d 156.3, 152.1, 143.8, 141.8, 136.7, 129.9 (2C), 128.8,
127.9 (2C), 126.0, 112.5, 109.3, 56.8, 29.1, 25.9, 21.5, 21.4.
4.3. General procedure for the formation of N-tosylhydrazones
4.4. General procedure for the coupling of N-tosylhydrazones with
aryl iodides
To a solution of tetralone 4b, c (1 mmol), PTSA (0.2 mmol) and
MgSO4 (1 mmol) in ethanol (20 mL) was added 4-
methylbenzenesulfonohydrazide (1.2 mmol). The resulting
mixture was stirred under reflux for 2 h. After cooling at room
temperature, the medium was diluted with EtOAc and filtered over
a pad of Celite. The solvent was next removed and the residue was
purified by crystallization in ethanol to afford 5b, c.
To a dioxane (2 mL) solution of N-tosylhydrazone (0.24 mmol),
tBuOLi (0.53 mmol), Pd2dba3 (0.02 mmol), and XPhos (0.04 mmol)
was added the required aryl iodide (0.24 mmol). The mixture was
stirred at 90 ꢀC for 5 h CH2Cl2 (5 mL) was then added to the cooled
mixture which was filtered over a pad of Celite. After concentration,
the residue was purified by silica gel chromatography to yield
1aec, 1k.
4.3.1. N0-(5-Bromo-6-methoxy-3.4-dihydronaphtalen-1(2H)-
ylidene)-4-methylbenzenesulfonohydrazide (5b)
4.4.1. 8-Bromo-7-methoxy-4-(3,4,5-trimethoxyphenyl)-1,2-
Yield: 100%. M.p. 212.1 ꢀC Rf 0.5 (cyclohexane/EtOAc: 7/3). IR
dihydronaphtalene (1a)
(neat) nmax/cmꢂ1: 2249, 1054, 1025, 1006, 821, 758, 623. 1H NMR
Yield: 76%. Rf 0.4 (cyclohexane/EtOAc: 7/3). IR (neat) nmax/cmꢂ1
:
(300 MHz, DMSO)
7.40 (d, J ¼ 8.1 Hz, 2H), 7.01 (d, J ¼ 8.9 Hz, 1H), 3.85 (s, 3H), 2.75 (t,
d
ppm 10.51e10.03 (br s, 1H), 7.85e7.73 (m, 3H),
2931, 1591, 1421, 1331, 1267, 1204, 1154, 1062, 994, 906, 857, 729,
648. 1H NMR (300 MHz, CDCl3)
d
6.90 (d, J ¼ 8.5 Hz, 1H), 6.60 (d,

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
29
J ¼ 8.5 Hz, 1H), 6.45 (s, 2H), 5.91 (t, J ¼ 4.6 Hz, 1H), 3.81 (s, 6H), 3.77
4.5.2. 6-Methoxy-1-(3,4,5-trimethoxyphenyl)naphtalene (3b)
Yield: 99%. Rf 0.3 (cyclohexane/EtOAc: 8/2). IR (neat) nmax/cmꢂ1
2934,1672,1579,1499,1410,1374,1335,1235,1168,1124,1031,1007,
910, 835, 789, 730, 700, 667, 647. 1H NMR (300 MHz, CDCl3)
7.86
(s, 6H), 2.96 (t, J ¼ 7.9 Hz, 2H), 2.33 (dt, J ¼ 4.8 Hz, J ¼ 7.9 Hz, 2H). 13C
:
NMR (75 MHz, CDCl3)
d 154.9, 153.0 (2C), 139.2, 138.2, 137.3, 136.4,
129.8, 125.4, 125.4, 113.6,108.8, 105.9 (2C), 60.9, 56.3, 56.1 (2C), 28.1,
23.0. MS (APCI, m/z) 405.7 ([M þ H]þ, 79Br), 407.2 ([M þ H]þ, 81Br).
Anal. Calcd for C20H21BrO4: C 59.27, H 5.22, found C 59.10, H 5.09.
d
(d, J ¼ 9.3 Hz, 1H), 7.75 (d, J ¼ 8.2 Hz, 1H), 7.48 (t, J ¼ 7.5 Hz,1H), 7.30
(d, J ¼ 7.1 Hz, 1H), 7.21 (d, J ¼ 1.9 Hz, 1H), 7.12 (dd, J ¼ 9.3 Hz,
J ¼ 1.9 Hz, 1H), 6.70 (s, 2H), 3.95 (s, 6H), 3.88 (s, 6H). 13C NMR
4.4.2. 8-Bromo-4-(3,5-dimethoxyphenyl)-7-methoxy-1,2-dihydrona-
(75 MHz, CDCl3) d 157.5, 152.9 (2C), 140.2, 137.3, 136.5, 135.1, 127.6,
phtalene (1b)
127.1,126.5,125.9,124.5,118.7,107.2 (2C),106.1, 60.9, 56.2 (2C), 55.3.
MS (APCI, m/z) 325.2 [M þ H]þ. Anal. Calcd for C20H20O4: C 74.06, H
6.21, found C 73.80, H 6.13.
Yield: 84%. Rf 0.47 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 2931, 1591, 1421, 1267, 1204, 1154, 1062, 906, 729, 648. 1H
NMR (300 MHz, CDCl3)
/
d
6.98 (d, J ¼ 8.5 Hz, 1H), 6.66 (d, J ¼ 8.5 Hz,
1H), 6.49e6.40 (m, 3H), 6.00 (t, J ¼ 4.7 Hz, 1H), 3.88 (s, 3H), 3.79 (s,
4.6. General procedure for the preparation of anilines 1d, 1i, 1l
and 3c
6H), 3.12e2.94 (m, 2H), 2.49e2.28 (m, 2H). 13C NMR (75 MHz,
CDCl3)
d 160.62 (2C), 154.9, 142.8, 139.2, 138.1, 129.7, 125.5, 115.8,
113.6, 108.8, 106.9 (2C), 99.4, 56.3, 55.3 (2C), 28.1, 23.0. MS (APCI, m/
z) 375.15 ([M þ H]þ, 79Br), 377.36 ([M þ H]þ, 81Br). Anal. Calcd for
C19H19BrO3: C 60.81, H 5.10, found C 60.54, H 4.99.
A solution of 1a, 1b, 1k or 3a (1 mmol), NaN3 (2 mmol), CuI
(0.1 mmol), DMEDA (0.15 mmol) and sodium ascorbate 0.05 mmol
in a mixture of DMSO/H2O: 5/1 was stirred at 60 ꢀC in a sealed tube.
After 12 h, the medium was cooled, quenched with NH4Cl and
extracted with EtOAc (3 ꢃ 10 mL). The combined organic layers
were dried over MgSO4, filtered and evaporated to dryness. Puri-
fication by flash chromatography afforded compounds 1d, 1i, 1l
and 3c.
4.4.3. 7-Methoxy-4-(3,4,5-trimethoxyphenyl)-1,2-dihydronaphtalene
(1c)
Yield: 75%. Rf 0.57 (cyclohexane/EtOAc: 8/2). IR (neat) nmax
cmꢂ1: 2934, 2834, 1589, 1496, 1453, 1421, 1358, 1301, 1278, 1249,
1203, 1150, 1117, 1062, 1039, 1000. 1H NMR (300 MHz, CDCl3)
6.93
/
d
(d, J ¼ 8.5 Hz, 1H), 6.71 (d, J ¼ 2.6 Hz, 1H), 6.59 (dd, J ¼ 2.6 Hz,
J ¼ 8.5 Hz, 1H), 6.49 (s, 2H), 5.89 (t, J ¼ 4.7 Hz, 1H), 3.82 (s, 3H), 3.77
(s, 6H), 3.74 (s, 3H), 2.76 (t, J ¼ 7.9 Hz, 2H), 2.31 (m, 2H). 13C NMR
4.6.1. 2-Methoxy-5-(3,4,5-trimethoxyphenyl)-7,8-dihydronahtalen-
1-amine (1d)
Yield: 59%. Rf 0.6 (cyclohexane/EtOAc: 5/5). IR (neat) nmax/cmꢂ1
:
(75 MHz, CDCl3)
d
158.6, 152.9, 139.5, 138.6 (2C), 137.1, 136.7, 128.1,
3663, 3324, 2974,1659,1088,1045. 1H NMR (300 MHz, CDCl3)
d 6.52
126.7, 124.8, 113.8, 110.8, 105.7 (2C), 60.9, 56.1 (2C), 55.3, 28.8, 23.4.
MS (APCI, m/z) 327.9 [M þ H]þ. Anal. Calcd for C20H22O4: C 73.60, H
6.79, found C 73.54, H 6.69.
(d, J ¼ 8.4 Hz, 1H), 6.48 (s, 2H), 6.43 (d, J ¼ 8.4 Hz, 1H), 5.84 (t,
J ¼ 4.6 Hz, 1H), 3.81 (s, 3H), 3.77 (s, 3H), 3.76 (s, 6H), 2.60 (t,
J ¼ 7.9 Hz, 2H), 2.34 (m, 2H), NH2 not seen. 13C NMR (75 MHz, CDCl3)
d
152.9 (2C), 147.2, 140.1, 137.3, 132.7, 128.3, 124.2, 121.2, 116.7, 107.2,
4.4.4. 6-Bromo-7-methoxy-4-(3,4,5-trimethoxyphenyl)-1,2-dihydr-
onaphtalene (1k)
106.2 (2C), 61.0, 56.2 (2C), 55.7, 23.0, 21.7 (1C missing). MS (APCI, m/
z) 342.2 [M þ H]þ. Anal. Calcd for C20H23NO4: C 70.36, H 6.79, N 4.10
found C 70.01, H 6.48, N 3.98.
Yield: 78%. Rf 0.47 (cyclohexane/EtOAc: 8/2). IR (neat) nmax
/
cmꢂ1: 2934, 2833, 1580, 1505, 1490, 1465, 1449, 1411, 1360, 1337,
1255, 1237, 1166, 1126, 1018, 1003, 907, 730, 646. 1H NMR (300 MHz,
4.6.2. 5-(3,5-Dimethoxyphenyl)-1-amino-2-methoxy-1,2-dihydron-
CDCl3)
3.92 (s, 3H), 3.90 (s, 3H), 3.85 (s, 6H), 2.81 (t, J ¼ 7.8 Hz, 2H), 2.39 (m,
2H). 13C NMR (75 MHz, CDCl3)
154.5, 153.1 (2C), 138.7, 137.7, 137.3,
135.9,130.1,129.3,125.7,111.7,108.6,105.6 (2C), 60.9, 56.3, 56.1 (2C),
28.5, 23.2. MS (APCI, m/z) 405,1 ([M þ H]þ, 79Br), 407.4 ([M þ H]þ,
81Br). Anal. Calcd for C20H21BrO4: C 59.27, H 5.22, found C 59.00, H
5.03.
d
6.78 (s, 1H), 6.66 (s, 1H), 6.53 (s, 2H), 6.00 (t, J ¼ 4.6 Hz, 1H),
aphtalene (1i)
Yield: 73%. Rf 0.8 (cyclohexane/EtOAc: 7/3). IR (neat) nmax/cmꢂ1
:
d
3669, 3324, 2974, 1670, 1088, 1045. 1H NMR (300 MHz, CDCl3)
6.49e6.42 (m, 4H), 6.35 (t, J ¼ 2.3 Hz, 1H), 5.84 (t, J ¼ 4.6 Hz, 1H),
3.75 (s, 3H), 3.72 (m, 2H), 3.69 (s, 6H), 2.58 (t, J ¼ 7.9 Hz, 2H), 2.32
(m, 2H). 13C NMR (75 MHz, CDCl3)
160.5 (2C), 147.2, 143.8, 140.1,
d
d
132.7, 128.2, 124.3, 121.2, 116.8, 107.0 (3C), 99.4, 55.7, 55.5 (2C), 23.0,
21.7. MS (APCI, m/z) 312.9 [M þ H]þ. Anal. Calcd for C19H21NO3: C
73.29, H 6.80, N 4.50 found C 73.04, H 6.62, N 4.40.
4.5. Synthesis of 3a and 3b
A CH2Cl2 solution (30 mL) of 1a or 1c (500 mg, 4.93 mmol) and
DDQ (1.34 g, 5.91 mmol) was stirred at room temperature for 1 h.
The medium was next washed three times with water and brine.
The organic layer was dried over MgSO4, filtered and evaporated to
dryness. Purification by flash chromatography afforded 3a, b.
4.6.3. 3-Methoxy-8-(3,4,5-trimethoxyphenyl)-5,6-dihydronaphtalen-
2-amine (1l)
Yield: 72%. Rf 0.6 (cyclohexane/EtOAc: 5/5). IR (neat) nmax/cmꢂ1
:
2934, 2251, 2157, 1978, 1578, 1508, 1462, 1410, 1366, 1339, 1285,
1243, 1214, 1158, 1124, 1006, 909, 823, 731. 1H NMR (300 MHz,
CDCl3)
d
6.68 (s, 1H), 6.55 (s, 2H), 6.49 (s, 1H), 5.94 (t, J ¼ 4.6 Hz, 1H),
4.5.1. 1-Bromo-2-methoxy-5-(3,4,5-trimethoxyphenyl)naphthalene
(3a)
3.89 (s, 3H), 3.87 (s, 3H), 3.84 (s, 6H), 2.76 (t, J ¼ 7.7 Hz, 2H), 2.35 (m,
2H), NH2 not seen. 13C NMR (75 MHz, CDCl3) 153.0 (2C), 146.5,
145.9, 139.7, 137.1, 133.4, 128.0, 127.8, 125.2, 113.6, 110.5, 105.9 (2C),
61.0, 56.3 (2C), 55.8, 28.2, 23.9. MS (APCI, m/z) 342.0 [M þ H]þ. Anal.
Calcd for C20H23NO4: C 70.36, H 6.79, N 4.10 found C 69.88, H 6.39, N
3.89.
Yield: 33%. Rf 0.42 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 3663, 3324, 2974, 2934, 1672, 1659, 1579, 1499, 1088, 1045,
730, 700. 1H NMR (300 MHz, CDCl3)
/
d
8.28 (d, J ¼ 8.6 Hz, 1H), 7.92
(d, J ¼ 9.2 Hz, 1H), 7.59 (dd, J ¼ 8.6, 7.0 Hz, 1H), 7.35 (dd, J ¼ 7.0,
1.1 Hz, 1H), 7.23 (d, J ¼ 9.4 Hz, 1H), 6.66 (s, 2H), 4.03 (s, 3H), 3.95 (s,
3H), 3.87 (s, 6H). 13C NMR (75 MHz, CDCl3)
d
153.8, 153.1 (2C), 140.7,
4.6.4. 2-Methoxy-5-(3,4,5-trimethoxyphenyl)naphtalen-1-amine
137.5, 136.2, 133.6, 128.3, 127.5, 127.3, 126.0, 125.3, 113.5, 109.1, 107.4
(2C), 61.1, 57.1, 56.3 (2C). MS (APCI, m/z) 403.1 ([M þ H]þ, 79Br),
405.1 ([M þ H]þ, 81Br). Anal. Calcd for C20H19BrO4: C 59.57, H 4.75,
found C 59.41, H 4.63.
(3c)
Yield: 46%. Rf 0.33 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 3663, 3324, 2974, 2934, 1672, 1659, 1579, 1088, 1045. 1H NMR
(300 MHz, CDCl3)
7.72 (d, J ¼ 8.5 Hz, 1H), 7.36 (m, 2H), 7.20 (d,
/
d

30
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
J ¼ 7.0 Hz, 1H), 7.12 (d, J ¼ 9.2 Hz, 1H), 6.62 (s, 2H), 4.27 (br s, 2H),
4.8.1. 4-(2-Methoxy-5-(3,4,5-trimethoxyphenyl)-7,8-dihydronaph-
talen-1-ul)but-3-yn-1-ol (1f)
3.89 (s, 3H), 3.87 (s, 3H), 3.79 (s, 6H). 13C NMR (75 MHz, CDCl3)
d
153.1 (2C), 142.6, 140.8, 137.2, 137.0, 129.8, 127.7, 124.6 (2C), 124.4,
Yield: 41%. Rf 0.6 (cyclohexane/EtOAc: 4/6). IR (neat) nmax/cmꢂ1
:
120.1, 116.9, 113.4, 107.3 (2C), 61.1, 56.7, 56.3 (2C). MS (APCI, m/z)
362 [M þ Na]þ. Anal. Calcd for C20H21NO4: C 70.78, H 6.24, N 4.13,
found C 70.55, H 6.15, N 4.01.
2922, 1590, 1489, 1413, 1353, 1267, 1128, 905, 812, 738. 1H NMR
(300 MHz, CDCl3)
d
6.97 (d, J ¼ 8.6 Hz, 1H), 6.63 (d, J ¼ 8.6 Hz, 1H),
6.53 (s, 2H), 5.98 (t, J ¼ 4.5 Hz,1H), 3.89 (s, 3H), 3.87 (s, 3H), 3.84 (m,
8H), 3.02 (t, J ¼ 7.8 Hz, 2H), 2.81 (t, J ¼ 6.0 Hz, 2H), 2.39 (m, 2H), OH
not seen. 13C NMR (75 MHz, CDCl3) 159.3 (2C), 152.9, 140.6, 139.2,
137.1, 136.5, 128.2, 126.2, 125.3, 111.2 (2C), 107.3, 105.7, 95.1, 77.7,
61.1, 60.9, 56.1, 55.8 (2C), 26.3, 24.4, 23.0. MS (APCI, m/z) 395.6
[M þ H]þ. Anal. Calcd for C24H26O5: C 73.08, H 6.64, found C 72.79, H
6.38.
4.7. General procedure for the preparation of naphtols 1e, 1h
and 3d
A solution of 1a, b, and 3a (1 mmol), KOH (5 mmol), Pd2dba3
(0.1 mmol) and tBuXPhos (0.2 mmol) in a mixture of dioxane/H2O:
1/1 was stirred at 90 ꢀC in a sealed tube. After 1 h, the medium was
cooled to room temperature, quenched with NH4Cl and extracted
with EtOAc (3 x 10 mL). The combined organic layers were then
dried over MgSO4, filtered and evaporated to dryness. Purification
by flash chromatography afforded compounds 1e, 1h and 3d.
4.8.2. 3-(2-Methoxy-5-(3,4,5-trimethoxyphenyl)-7,8-dihydronapht-
alen-1-yl)prop-2-yn-1-ol (1g)
Yield: 25%. Rf 0.57 (cyclohexane/EtOAc: 4/6). IR (neat) nmax
cmꢂ1: 2922,1590,1489,1413,1353,1267,1128, 905, 805, 726, 649.1H
NMR (300 MHz, CDCl3)
/
d
7.00 (d, J ¼ 8.6 Hz, 1H), 6.64 (d, J ¼ 8.6 Hz,
1H), 6.53 (s, 2H), 5.99 (t, J ¼ 4.3 Hz,1H), 4.61 (s, 2H), 3.89 (s, 3H), 3.87
(s, 3H), 3.84 (s, 6H), 3.04 (t, J ¼ 7.7 Hz, 2H), 2.38e2.19 (m, 2H). OH not
seen. 13C NMR (75 MHz, CDCl3) 159.3, 152.9 (2C), 141.2, 139.1, 137.1,
136.5,127.9,126.7,125.4,110.4,107.4,105.8 (2C), 95.8, 80.2, 60.9, 56.1
(2C), 55.8, 51.9, 26.2, 22.9. MS (APCI, m/z) 381.8 [M þ H]þ. Anal. Calcd
for C23H24O5: C 72.61, H 6.36, found C 72.56, H 6.12.
4.7.1. 2-Methoxy-5-(3,4,5-trimethoxyphenyl)-7,8-dihydronaphtalen-
1-ol (1e)
Yield: 63%. Rf 0.52 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 2941, 2177, 1581, 1489, 1355, 1234, 1126, 905, 726, 652, 610.
1H NMR (300 MHz, CDCl3)
/
d
6.63 (d, J ¼ 8.5 Hz, 1H), 6.59 (d,
J ¼ 8.5 Hz, 1H), 6.56 (s, 2H), 5.97 (t, J ¼ 4.6 Hz, 1H), 5.72 (s, 1H), 3.89
(s, 6H), 3.84 (s, 6H), 2.89 (t, J ¼ 7.9 Hz, 2H), 2.38 (m, 2H). 13C NMR
4.8.3. 3-(2-Methoxy-5-(3,4,5-trimethoxyphenyl)naphtalen-1-yl)
but-3-yn-1-ol (3e)
(75 MHz, CDCl3)
d
153.0 (2C), 146.0, 142.1, 139.7, 137.0, 129.1, 125.5,
122.4, 117.6, 107.4, 106.1 (2C), 61.1, 56.3 (2C), 56.1, 23.0, 20.4, (1 C
missing). MS (APCI, m/z) 343.2 [M þ H]þ. Anal. Calcd for C20H22O5: C
70.16, H 6.48, found C 70.00, H 6.32.
Yield: 52%. Rf 0.22 (cyclohexane/EtOAc: 6/4). IR (neat) nmax
cmꢂ1: 2934, 1580, 1501, 1463, 1409, 1320, 1266, 1236, 1183, 1124,
1060, 1005, 910, 850, 730, 686. 1H NMR (300 MHz, CDCl3)
8.27 (d,
/
d
J ¼ 8.4 Hz, 1H), 7.90 (d, J ¼ 9.4 Hz, 1H), 7.60e7.48 (m, 1H), 7.31 (d,
J ¼ 6.8 Hz, 1H), 7.19 (d, J ¼ 9.4 Hz, 1H), 6.66 (s, 2H), 4.01 (s, 3H),
3.98e3.89 (m, 5H), 3.87 (s, 6H), 2.92 (t, J ¼ 6.1 Hz, 2H), OH not seen.
13C NMR (75 MHz, CDCl3) 158.7, 152.9 (2C),140.5, 137.3, 136.2, 134.9,
127.9, 126.8, 126.7, 124.9 (2C), 112.4, 107.3 (2C), 106.5, 96.4, 77.3,
61.2, 60.9, 56.5, 56.2 (2C), 24.6. MS (APCI, m/z) 393.3 [M þ H]þ. Anal.
Calcd for C24H24O5: C 73.45, H 6.16, found C 73.34, H 6.02.
4.7.2. 5-(3,5-Dimethoxyphenyl)-2-methoxy-7,8-dihydronaphtalen-
1-ol (1h)
Yield: 62%. Rf 0.46 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 2934, 1590, 1489, 1353, 1276, 1204, 1152, 1095, 1069, 826. 1H
NMR (300 MHz, CDCl3)
/
d
6.60 (s,1H), 6.58 (d, J ¼ 2.3 Hz,1H), 6.50 (d,
J ¼ 2.3 Hz, 2H), 6.44 (t, J ¼ 2.3 Hz, 1H), 5.98 (t, J ¼ 4.7 Hz, 1H), 5.71 (s,
1H), 3.88 (s, 3H), 3.79 (s, 6H), 2.88 (t, J ¼ 8.0 Hz, 2H), 2.37 (m, 2H).
13C NMR (75 MHz, CDCl3)
d
160.6 (2C), 145.9, 143.4, 142.1, 140.0,
4.8.4. 3-(2-Methoxy-5-(3,4,5-trimethoxyphenyl)naphthalen-1-yl)
129.0, 125.7, 122.4, 117.6, 107.4, 107.0 (2C), 99.5, 56.1, 55.5 (2C), 23.0,
20.4. MS (APCI, m/z) 313.2 [M þ H]þ. Anal. Calcd for C19H20O4: C
73.06, H 6.45, found C 72.99, H 6.39.
prop-2-yn-1-ol (3f)
Yield: 49%. Rf 0.14 (cyclohexane/EtOAc: 2/8). IR (neat) nmax/cmꢂ1
:
2922, 1501, 1463, 1413, 1267, 1128, 905, 805, 726, 649. 1H NMR
(300 MHz, CDCl3)
d
8.35 (d, J ¼ 8.4 Hz,1H), 8.00 (d, J ¼ 9.4 Hz,1H), 7.63
4.7.3. 2-Methoxy-5-(3,4,5-trimethoxyphenyl)naphtalen-1-ol (3d)
(dd, J ¼ 8.4 Hz, J ¼ 7.0 Hz,1H), 7.39 (d, J ¼ 7.0 Hz,1H), 7.26 (d, J ¼ 9.5 Hz,
1H), 6.73 (s, 2H), 4.80 (s, 2H), 4.08 (s, 3H), 4.01 (s, 3H), 3.94 (s, 6H), OH
not seen. 13C NMR (75 MHz, CDCl3) 158.1 (2C), 152.1, 139.8, 135.3,
134.2,127.9,126.1,125.9,124.2,124.0,115.5,106.3 (2C), 96.2, 79.3, 60.2,
55.6, 55.4 (2C), 51.3, two C missing. MS (APCI, m/z) 379.5 [M þ H]þ.
Anal. Calcd for C23H22O5: C 73.00, H 5.86, found C 72.87, H 5.76.
Yield: 82%. Rf 0.39 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 2936, 1579, 1500, 1461, 1403, 1340, 1235, 1123, 1073, 1005,
896, 797, 729. 1H NMR (300 MHz, CDCl3)
/
d
8.20 (d, J ¼ 7.0 Hz, 1H),
7.53e7.44 (m, 2H), 7.31 (dd, J ¼ 7.0 Hz, J ¼ 1.2 Hz, 1H), 7.22 (d,
J ¼ 9.3 Hz, 1H), 6.70 (s, 2H), 4.00 (s, 3H), 3.94 (m, 3H), 3.87 (s, 6H),
OH not seen. 13C NMR (75 MHz, CDCl3)
d 153.0 (2C), 141.2, 139.9,
139.8, 137.2, 136.8, 127.8, 125.2, 125.0, 124.5, 121.0, 118.0, 113.1, 107.3
(2C), 61.1, 57.2, 56.3 (2C). MS (APCI, m/z) 341 [M þ H]þ. Anal. Calcd
for C20H20O5: C 70.57, H 5.92, found C 70.30, H 5.67.
4.9. General procedure for the synthesis of compounds 1j and 3g
A NMP solution of 1a or 3a (1 mmol), methyl acrylate (10 mmol),
PEPPSI (0.05 mmol) and K2CO3 (2 mmol) was stirred at 140 ꢀC in
a sealed tube. After 1 h, the medium was cooled down to room
temperature, quenched with NH4Cl and extracted with EtOAc
(3 ꢃ 10 mL). The combined organic layers were then dried over
MgSO4, filtered, and the solvent was then removed. Purification by
flash chromatography afforded compounds 1j and 3g.
4.8. General procedure for the synthesis of alkynes 1f, 1g, 3e and 3f
A DMF solution of 1a and 3a (1 mmol), alkyne (1.2 mmol),
PdCl2(PPh3)2 (0.05 mmol), PPh3 (0.1 mmol), CuI (0.05 mmol) and
Et2NH (2 mmol) was stirred at 120 ꢀC under microwave irradiation.
After 25 min, the medium was cooled down to room temperature,
quenched with NH4Cl and extracted with EtOAc (3 ꢃ 10 mL). The
combined organic layers were then dried over MgSO4, filtered and
evaporated to dryness. Purification by flash chromatography
afforded compounds 1f, 1g, 3e and 3f.
4.9.1. Methyl-3-(2-methoxy-5-(3,4,5-trimethoxyphenyl)-7,8-
dihydronaphtalen-1-yl)acrylate (1j)
Yield: 35%. 0.41 Rf (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 2945, 2500, 1714, 1579, 1504, 1463, 1412, 1352, 1252, 1169,
1124, 1007, 911. 1H NMR (300 MHz, CDCl3)
7.99 (d, J ¼ 16.2 Hz, 1H),
/
d

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
31
7.05 (d, J ¼ 8.6 Hz, 1H), 6.69 (d, J ¼ 8.6 Hz, 1H), 6.53 (s, 2H), 6.45 (d,
4.10.4. 4-(2-Methoxy-5-(3,4,5-trimethoxyphenyl)-5,6,7,8-
tetrahydronaphtalen-1-yl)butan-1-ol (2d)
J ¼ 16.2 Hz,1H), 6.01 (t, J ¼ 4.1 Hz,1H), 3.88 (s, 3H), 3.84 (s, 3H), 3.83
(s, 6H), 3.81 (s, 3H), 2.96 (t, J ¼ 7.7 Hz, 2H), 2.33 (m, 2H). 13C NMR
(75 MHz, CDCl3) 167.9, 157.7, 153.0 (2C), 139.6, 139.1, 138.1, 137.1,
136.7, 128.6, 127.9, 125.1, 123.4, 121.8, 107.8, 105.8 (2C), 60.9, 56.1
(2C), 55.5, 51.6, 25.3, 23.2. MS (APCI, m/z) 411.8 [M þ H]þ. Anal.
Calcd for C24H26O6: C 70.23, H 6.38, found C 70.11, H 6.31.
Yield: 34%. Rf 0.31 (cyclohexane/EtOAc: 6/4). IR (neat) nmax
cmꢂ1: 2004, 1589, 1492, 1459, 1280, 1234, 1154, 1126, 1064, 1007,
806, 730, 613. 1H NMR (300 MHz, CDCl3)
6.71 (d, J ¼ 8.4 Hz, 1H),
/
d
6.63 (d, J ¼ 8.4 Hz, 1H), 6.31 (s, 2H), 4.04e3.94 (m, 1H), 3.84 (s, 3H),
3.78 (s, 9H), 3.71 (t, J ¼ 6.6 Hz, 1H), 2.82 (t, J ¼ 6.6 Hz, 2H), 2.68 (dd,
J ¼ 12.7 Hz, J ¼ 6.4 Hz, 2H), 2.16e1.48 (m, 10H). 13C NMR (75 MHz,
CDCl3) 155.6,153.1 (2C),143.6,136.5,136.3,131.9,128.5,128.4,108.4,
106.1 (2C), 63.0, 60.9, 56.2 (2C), 55.6, 46.4, 33.0, 32.8, 26.8, 25.4,
25.4, 21.5. MS (APCI, m/z) 423.3 [M þ Na]þ. Anal. Calcd for
C24H32O5: C 71.97, H 8.05, found C 71.59, H 7.83.
4.9.2. Methyl-3-(2-methoxy-5-(3,4,5-trimethoxyphenyl)naphtalen-
1-yl)acrylate (3g)
Yield: 22%. Rf 0.44 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 3976, 3412, 2939, 2185, 1713, 1579, 1503, 1464, 1414, 1278,
1171, 1153, 1126, 1063, 1008, 806. 1H NMR (300 MHz, CDCl3)
8.38
/
d
(d, J ¼ 16.2 Hz, 1H), 8.20 (d, J ¼ 8.9 Hz, 1H), 7.96 (d, J ¼ 8.9 Hz, 1H),
7.54 (t, J ¼ 7.2 Hz,1H), 7.33 (d, J ¼ 7.2 Hz, 1H), 7.24e7.10 (m, 1H), 6.77
(d, J ¼ 16.2 Hz, 1H), 6.66 (s, 2H), 3.99 (s, 3H), 3.94 (s, 3H), 3.87 (s,
9H). 13C NMR (75 MHz, CDCl3) 168.4, 156.5, 153.1 (2C), 141.1, 138.3,
137.4,136.5,133.3,129.9,127.3,126.9,124.9,123.4,123.1,116.9,112.7,
107.3 (2C), 77.2, 61.1, 56.3 (2C), 51.8. MS (APCI, m/z) 409.7 [M þ H]þ.
Anal. Calcd for C24H24O6: C 70.57, H 5.92, found C 70.21, H 5.68.
4.10.5. 1-(3,5-Dimethoxyphenyl)-6-methoxy-1,2,3,4-tetrahydronap-
htalene (2e)
Yield: 72%. Rf 0.25 (cyclohexane/EtOAc: 8/2). IR (neat) nmax
cmꢂ1: 2939, 2835, 2049, 2000, 1595, 1501, 1462, 1427, 1323, 1254,
1204, 1154, 1064, 832, 697. 1H NMR (300 MHz, CDCl3)
6.80 (d,
/
d
J ¼ 8.3 Hz, 1H), 6.68e6.54 (m, 2H), 6.31 (t, J ¼ 2.3 Hz, 1H), 6.26 (d,
J ¼ 2.2 Hz, 2H), 3.99 (t, J ¼ 6.7 Hz, 1H), 3.78 (s, 3H), 3.75 (s, 6H),
2.96e2.71 (m, 2H), 2.20e2.03 (m, 1H), 1.95e1.79 (m, 2H), 1.79e1.65
(m, 1H). 13C NMR (75 MHz, CDCl3) 160.5 (2C), 157.6, 150.2, 138.6,
131.4, 131.3, 113.2, 112.1, 107.1 (2C), 97.6, 55.2 (2C), 55.2, 45.2, 33.1,
30.1, 21.0. MS (APCI, m/z) 299.1 [M þ H]þ. Anal. Calcd for C19H22O3:
C 76.48, H 7.43, found C 76.09, H 7.23.
4.10. General procedure for catalytic hydrogenation
A solution of suitable precursor (50 mg) and Pd/C (5 mg) in
MeOH (8 mL) was stirred under a H2 atmosphere at room
temperature. After 4 h, the medium filtered over a pad of Celite and
the solvent was removed in vacuo. Purification by flash chroma-
tography afforded compounds 2aee and 3h.
4.10.6. 3-(2-Methoxy-5-(3,4,5-trimethoxyphenyl)naphtalen-1-yl)
propan-1-ol (3h)
Yield: 82%. Rf 0.2 (cyclohexane/EtOAc: 3/7). IR (neat) nmax/cmꢂ1
:
4.10.1. 6-Methoxy-1-(3,4,5-trimethoxyphenyl)-1,2,3,4-tetrahydron-
2932, 2035, 1582, 1501, 1462, 1415, 1332, 1257, 1126, 1040, 1007, 806,
aphthalene (2a)
730, 613. 1H NMR (300 MHz, CDCl3)
d
8.01 (d, J ¼ 8.6 Hz, 1H), 7.85 (d,
Yield: 76%. Rf 0.6 (cyclohexane/EtOAc: 8/2). IR (neat) nmax/cmꢂ1
:
J ¼ 9.4 Hz, 1H), 7.53 (dd, J ¼ 8.6 Hz, J ¼ 7.0 Hz, 1H), 7.31 (d, J ¼ 6.9 Hz,
1H), 7.24 (d, J ¼ 10.4 Hz,1H), 6.68 (s, 2H), 3.98 (s, 3H), 3.95 (s, 3H), 3.87
(s, 6H), 3.59 (t, J ¼ 5.8 Hz, 2H), 3.27 (t, J ¼ 7.0 Hz, 2H),1.98 (m, 2H), OH
not seen. 13C NMR (75 MHz, CDCl3) 154.2, 152.9 (2C), 140.9, 136.7,
133.3,127.7,126.2,125.9,124.3,122.8,122.5(2C),112.9,107.2(2C), 61.6,
60.9, 56.7, 56.2 (2C), 32.2, 20.6. MS (APCI, m/z) 383.8 [M þ H]þ. Anal.
Calcd for C23H26O5: C 72.23, H 6.85, found C 72.00, H 6.58.
2931, 1589, 1500, 1462, 1417, 1328, 1232, 1124, 1038, 1007, 908, 826,
727, 647. 1H NMR (300 MHz, CDCl3)
d
6.80 (d, J ¼ 8.3 Hz, 1H),
6.68e6.58 (m, 2H), 6.31 (s, 2H), 4.01e3.94 (m, 1H), 3.83 (s, 3H), 3.78
(s, 9H), 2.93e2.79 (m, 2H), 2.19e2.07 (m, 1H), 1.95e1.84 (m, 2H),
1.84e1.68 (m, 1H). 13C NMR (75 MHz, CDCl3) 157.7, 153.0 (2C), 143.5,
138.7,136.2, 131.6, 131.2, 113.3,112.1, 105.8 (2C), 60.9, 56.2 (2C), 55.3,
45.6, 33.6, 30.2, 21.5. MS (APCI, m/z) 329.1 [M þ H]þ. Anal. Calcd for
C20H24O4: C 73.15, H 7.37, found C 72.89, H 7.13.
4.11. Biology
4.10.2. 2-Methoxy-5-(3,4,5-trimethoxyphenyl)-5,6,7,8-tetrahydrona-
4.11.1. Cell culture and Proliferation assay
phtalen-1-amine (2b)
Cancer cell lines were obtained from the American type Culture
Collection (Rockville, MD) and were cultured according to the
supplier’s instructions. Briefly MDA-MB-231 and H1299 cells were
grown in Dulbecco minimal essential medium (DMEM) containing
4.5 g/L glucose supplemented with 10% FCS and 1% glutamine.
Human K562 leukaemia and HCT116 colorectal carcinoma cells
were grown in RPMI 1640 containing 10% FCS and 1% glutamine.
Cell lines were maintained at 37 ꢀC in a humidified atmosphere
containing 5% CO2. Cell viability was assessed using Promega
CellTiter-Blue TM reagent according to the manufacturer’s
instructions. Cells were seeded in 96-well plates (5 ꢃ 103 cells/
Yield: 47%. Rf 0.49 (cyclohexane/EtOAc: 6/4). IR (neat) nmax
cmꢂ1: 2933, 1600, 1492, 1458, 1233, 1127. 1H NMR (400 MHz, CDCl3)
6.60 (d, J ¼ 8.2 Hz,1H), 6.31 (d, J ¼ 8.1 Hz,1H), 6.32 (s, 2H), 3.99 (m,
/
d
1H), 3.83 (s, 3H), 3.83 (s, 3H), 3.78 (s, 6H), 2.59 (m, 2H), 2.07 (m,1H),
1.96 (m, 1H), 1.83e1.81 (m, 2H), NH2 not seen. The presence of an
impurity complicates the NMR spectra and despite our best efforts,
we were not able to obtain 2b with a satisfactory elemental analysis
13C NMR (100 MHz, CDCl3) 153.0 (2C), 145.1, 143.5, 136.2, 133.2,
132.3, 122.8, 119.6, 108.2, 106.0 (2C), 61.0, 56.2 (2C), 55.7, 46.0, 32.7,
24.7, 20.8. MS (APCI, m/z) 344.2 [M þ H]þ.
well) containing 50
cells were supplemented with 50
solved in DMSO (less than 0.1% in each preparation). After 72 h of
m
L growth medium. After 24 h of culture, the
4.10.3. 2-Methoxy-5-(3,4,5-trimethoxyphenyl)-5,6,7,7-tetrahydrona-
phtalen-1-ol (2c)
mL of the tested compound dis-
Yield: 50%. Rf 0.66 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
cmꢂ1: 3518, 2930, 2004, 1589, 1492, 1459, 1280, 1234, 1126, 907,
731, 624. 1H NMR (300 MHz, CDCl3)
J ¼ 8.5 Hz, 1H), 6.32 (s, 2H), 5.69 (br s, 1H), 3.96 (m, 1H), 3.86 (s, 3H),
3.84 (s, 3H), 3.79 (s, 6H), 2.96e2.65 (m, 2H), 2.17e1.73 (m, 4H). 13C
NMR (75 MHz, CDCl3) 153.0 (2C), 144.0, 143.4, 142.6, 133.0, 124.3,
120.9, 108.2, 105.9 (2C), 61.0, 56.2 (2C), 56.1, 45.9, 33.0, 23.3, 20.7
(one C missing). MS (APCI, m/z) 345.2 [M þ H]þ. Anal. Calcd for
C20H24O5: C 69.75, H 7.02, found C 69.51, H 6.85.
/
incubation, 20
fluorescence (
m
L of resazurin was added for 2 h before recording
l
ex ¼ 560 nm, em ¼ 590 nm) using a Victor
l
d
6.63 (d, J ¼ 8.5 Hz,1H), 6.39 (d,
microtiter plate fluorimeter (PerkineElmer, USA). The GI50 corre-
sponds to the concentration of the tested compound that caused
a decrease of 50% in fluorescence of drug treated cells compared
with untreated cells. Experiments were performed in triplicate. The
GI50 values for all compounds were compared to the GI50 of CA4,
isoCA-4 and isoerianin and measured the same day under the same
conditions.

32
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 52 (2012) 22e32
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dissolved in the assembly buffer containing 0.1 M MES, 0.5 mM
MgCl2, 1 mM EGTA, and 1 mM GTP, pH 6.6 (the concentration of
tubulin was about 2e3 mg/mL). Tubulin assembly was monitored
by fluorescence according to reported procedure [50] using DAPI as
fluorescent molecule. Assays were realized on 96-well plates
prepared with Biomek NKMC and Biomek 3000 from Beckman
Coulter and read at 37 ꢀC on Wallac Victor fluorimeter from Per-
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tubulin by 50% compared to the rate in the absence of compound.
The IC50 values for all compounds were compared to the IC50 of
CA4, isoCA-4 and isoerianin and measured the same day under the
same conditions.
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Acknowledgements
[28] N. L’Hermite, A. Giraud, O. Provot, J.-F. Peyrat, M. Alami, J.-D. Brion, Tetrahe-
dron 62 (2006) 11994e12002.
[29] A. Giraud, O. Provot, J.-F. Peyrat, M. Alami, J.-D. Brion, Tetrahedron 62 (2006)
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[30] S. Messaoudi, B. Tréguier, A. Hamze, O. Provot, J.-F. Peyrat, J.R. Rodrigo De
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M. Alami, Tetrahedron Lett. 52 (2011) 1036e1040.
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(2011) 4042e4045.
[34] M.A. Soussi, S. Aprile, S. Messaoudi, O. Provot, E. Del Grosso, J. Bignon,
J. Dubois, J.-D. Brion, G. Grosa, M. Alami, ChemMedChem 6 (2011) 1781e1788.
[35] A. Hamze, A. Giraud, S. Messaoudi, O. Provot, J.-F. Peyrat, J. Bignon, J.-M. Liu,
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4 (2009) 1912e1924.
The CNRS (Centre National de la Recherche Scientifique) is
gratefully acknowledged for financial support of this research. We
thank the MRES (Ministère de la Recherche et de l’Enseignement
Supérieur) for a financial fellowship to E.R. Our laboratory BioCIS-
UMR 8076 is a member of the Laboratory of Excellence LERMIT
supported by a grant from ANR (Agence Nationale de la Recherche,
ANR-10-LABX-33). The work on tubulin was supported by a grant
from ANR (ANR-09-BLAN-0071).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ejmech.2012.03.001.
[36] A. Hamze, E. Rasolofonjatovo, O. Provot, C. Mousset, D. Veau, J. Rodrigo,
J. Bignon, J.-M. Liu, J. Wdzieczak-Bakala, S. Thoret, J. Dubois, J.-D. Brion,
M. Alami, ChemMedChem 6 (2011) 2179e2191.
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