Regioselective hydrostannation of diarylalkynes directed by a labile ortho bromine atom: An easy access to stereodefined triarylolefins, hybrids of combretastatin A-4 and isocombretastatin A-4

Article abstract of DOI:10.1016/j.ejmech.2010.05.007

A series of triarylolefins bearing the combretastatin A-4 and the isocombretastatin A-4 cores were synthesized and evaluated. The cooperative ortho-effect of a labile bromine atom in the regioselective hydrostannation of unsymmetrical diarylalkynes leadin

Full text of DOI:10.1016/j.ejmech.2010.05.007

European Journal of Medicinal Chemistry 45 (2010) 3617e3626
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Regioselective hydrostannation of diarylalkynes directed by a labile ortho bromine
atom: An easy access to stereodefined triarylolefins, hybrids of combretastatin A-4
and isocombretastatin A-4
Evelia Rasolofonjatovo a, Olivier Provot a, Abdallah Hamze a, Jérome Bignon b, Sylviane Thoret b,
,
Jean-Daniel Brion a, Mouâd Alami a
*
a University Paris-Sud, CNRS, BioCIS-UMR 8076, 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 series of triarylolefins bearing the combretastatin A-4 and the isocombretastatin A-4 cores were
synthesized and evaluated. The cooperative ortho-effect of a labile bromine atom in the regioselective
hydrostannation of unsymmetrical diarylalkynes leading to stereodefined triarylolefins is presented.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Received 22 April 2010
Received in revised form
3 May 2010
Accepted 5 May 2010
Available online 12 May 2010
Dedicated to our colleague Pr. Claude
Combet-Farnoux
Keywords:
Palladium
Alkyne
Ortho-directing effect
Hydrostannation
Olefin
Combretastatin
1. Introduction
caffrum [9,10] is the most studied substance as a highly potent
inhibitor of tubulin assembly [11e13]. Moreover, CA-4 displays
The microtubule system of eukaryotic cells is an important
target for the development of anticancer agents. Consequently,
perturbation of normal tubulin assembly/disassembly is a popular
target for new chemotherapeutic agents [1,2] Examples of clinically
used antimitotic agents are paclitaxel, which promoted microtu-
bules polymerization and inhibits microtubules depolymerization,
and vincristine which inhibits microtubules assembly [3,4].
However, despite their potent antitumor activities, these drugs
have undesirable side effects [5,6] and are subject to multidrug
resistance [7,8].
strong cytotoxicities (nanomolar level) against a large panel of
human cancer cells, including multidrug-resistant cell lines [14,15].
Additionally, CA-4P [16e19] the water-soluble prodrug of CA-4, as
well as AC-7739 and its amino acid derivative AVE-8062 [20] have
beendemonstrated tocause a rapidand selective vascular shutdown
in established tumors in vivo, consistent with an antivascular
mechanismof action[21e27]. Currently, CA-4P [28]eitheras 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 (Fig. 1).
In recent years, there has been more and more interest in the
search of antitumor molecules of easy synthesis, with high efficacy
and low side effects. Combretastatin A-4 (CA-4), a naturally occur-
ring stilbene, extracted from the South African willow Combretum
Despite their remarkable anticancer activity, these Z-stilbene
compounds are prone to double bond isomerization during storage
and administration. The E-isomers display dramatically reduced
inhibition of cancer cell growth and tubulin assembly [29]. In our
efforts to discover novel tubulin assembly inhibitors [30e32], we
recently found that isocombretastatin A-4 (isoCA-4), the third and
“forgotten” structural isomer of the natural product, displayed bio-
logical activities comparable to that of CA-4 [33,34]. This substance
* Corresponding author.
E-mail address: mouad.alami@u-psud.fr (M. Alami).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.05.007

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E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
(1.2 eq) in THF at room temperature in the presence of PdCl2(PPh3)2
(1 mol%) to give vinylstannane 3 in good yield (79%) [44e47]. Subse-
quent direct coupling of 3 with 3,4,5-trimethoxy-iodobenzene under
modified Stille conditions [48] provided a moderate 54% isolated yield
of 1a. In order to increase the overall yield of 1a, we next evaluated
a halodestannylation [49]-Negishi coupling sequence [50,51]. Iodo-
destannylation of 3 with molecular iodine in CH2Cl2 at room
temperature furnished cleanly and rapidly the desired electrophilic
species 4, which upon reaction with 3,4,5-trimethoxyphenylzinc
chloride in the presence of a catalytic amountof PdCl2(PPh3)2 (5 mol%)
provided the target olefin 1a in a quantitative yield. This result clearly
indicated that the two steps iododestannylation-Negishi sequence
was more efficient than the direct Stille coupling of 3.
3'
MeO
MeO
R
MeO
MeO
R
A
B
OMe
OMe
OMe
OMe
R = OH (CA-4)
R = OH (isoCA-4)
R = NH2 (isoNH2CA-4)
R = F (isoFCA-4)
R = OP(O)(ONa)2 (CA-4P)
R = NH2 (AC-7739)
R = NH-Ser-H (AVE-8062)
isoCA-4
R4
R6
HO
OMe
According to this two steps sequence (iodolysis/Negishi
coupling) depicted in Scheme 2, the synthesis of other targets
triarylolefins 1beh was envisioned from the hydrostannation of
unsymmetrical diarylalkynes. In previous studies, we have repor-
ted that in the case of ortho substituted diarylalkynes, the ortho
substituent, regardless of its electronic nature, directed the trib-
R5
R3
R1
MeO
HO
MeO
OMe
OMe
CA-4
utyltin addition to afford a single
a-vinylstannane. We opted to
R2 R3
OMe
MeO
use this ortho-directing effect (ODE) [52,53] concept to prepare
the hybrids 1beh according to the retrosynthetic pathway
depicted in Scheme 3. To control the regioselectivity of the
hydrostannation reaction, we needed first to prepare diarylalkynes
5 bearing an ortho substituent able to exclusively directed the
HeSn bond addition across the triple bond, and therefore to
provide a single vinylstannane. To this end we have choosen as
ortho-directing group (oDG) a bromine atom, as this substituent
would be easy to introduce but also easy to remove at the end of
the synthesis by metal-halogen exchange reaction followed by
hydrolysis.
Diarylalkynes 5aed bearing an ortho bromine atom were
prepared according to Scheme 4. 5a was synthesized from terminal
alkyne 6a by SonogashiraeLinstrumelle (SeL) coupling with 3-
bromo-4-iodoanisole, readily obtained by regioselective iodination
of 3-bromoanisole (94%). For the preparation of diarylalkynes
5bed, the synthetic route involves the bromination of 3,4,5-tri-
methoxy-iodobenzene with molecular Br2 or MPHT [54] to provide
7 followed by sequential SeL coupling reactions.
hybrids 1
1h
Fig. 1. Representative tubulin binding agents and general structure of the synthesized
hybrids 1.
having a 1,1-diarylethylene scaffold is easy to synthesize [35,36] at
a multi grams scale without the need to control the olefin geometry.
By structural modifications on the B ring, we have also identified
other promising antiproliferative agents such as isoFCA-4 and iso-
NH2CA-4 (Fig. 1) [37]. In addition, these apoptosis inductors
substances were found to inhibit microtubules formation and to
induce cell cycle arrest in G2/M phase. To combine the anticancer
effects of CA-4 and isoCA-4 within a single substance (e.g.; 1h), we
have synthesized a variety of hybrids 1 that bear, from one hand, the
basic skeleton of CA-4 and, on the other hand, the one of isoCA-4
(Fig.1). Moreover, thesecompounds 1 maybe regarded asTamoxifen
[38] or trisubstituted Combretastatin analogues of high anti-
proliferative activity [39e41]. The potencies of newly synthesized
trisubstituted olefins 1 were evaluated for their capacity to inhibit
cancer cellular growth and, to act as potential antimitotic agents.
The palladium-catalyzed hydrostannation reaction was next
applied to ortho substituted diarylalkynes 5aed (Scheme 5). As
expected, a total regiochemical control was achieved by the pres-
ence of ortho bromine atom substituent. The reaction provide
2. Results and discussion
exclusively
a-vinylstannanes 8aed where the Bu3Sn group is
proximal to the ortho substituted aryl nucleus.
The strategy envisioned to prepare the target triarylolefins 1
involves a three step-sequence by achieving a regioselective
hydrostannation of diarylalkynes (Scheme 1). Further direct Stille
reaction or sequential iodolysis-Negishi coupling would provide 1.
At the outset of this work, the synthesis of triarylolefin 1a (Scheme
2) was first examined from symmetrically diarylalkyne 2 easily
available by SonogashiraeLinstrumelle coupling reaction [42,43].
Palladium-catalyzed hydrostannation of 2 was achieved using Bu3SnH
Further iodolysis of 8aed was achieved as described for 3 and
vinyl iodides 9aed were isolated in excellent yields (70e99%) as
pure (E)-isomers. For the Negishi cross coupling reaction, organo-
zinc species were generated by transmetallation from Grignard
reagents at 0 ꢀC using ZnCl2 except for the synthesis of 10f.
In this case, the organozinc species was generated after lith-
iation of 2-fluoro-4-iodoanisole followed by transmetallation with
R4
R5
SnBu3
R6
R3
R2
R1
R3
R3
MeO
OMe
R2
R3
OMe
R2
MeO
R1 R3
MeO
R1 R3
OMe
Direct Stille or
Regioselective
hydrostannation
1
sequential iodolysis/Negishi coupling
Scheme 1. Retrosynthetic pathway leading to triarylolefins 1.

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
3619
SnBu3
I
(a)
(b)
OMe
MeO
Iodolysis
Hydrostannation
MeO
OMe
MeO
OMe
OMe
2
3
4
MeO
Stille
coupling (d)
Negishi
(c) coupling
OMe
MeO
OMe
1a
Scheme 2. Reagents and conditions: (a) PdCl2(PPh3)2 (2 mol%), Bu3SnH, (1.2 equiv), THF, 79%. (b) I2 (1 equiv), CH2Cl2, 74%. (c) 3,4,5-(OMe)3C6H2ZnCl (2.2 equiv), PdCl2(PPh3)2 (5 mol
%), THF, 99%. (d) 3,4,5-(OMe)3C6H2I (0.9 equiv), Pd(PPh3)4 (5 mol%), CuI (10 mol%), CsF (2 equiv), DMF, 60 ꢀC, 54%.
ZnCl2 as above. As shown in Scheme 5, all organozinc reagents were
successfully coupled with the vinyl iodides 9aed in good yields
(50e99%). Finally, removal of the ortho bromo directing group was
achieved by halogenemetal exchange reaction using n-butyl-
lithium followed by quenching with aqueous HCl. Subsequent
MOM- or TBDMS-ether cleavage furnished the expected triar-
ylolefins 1beh as pure isomers.
The cytotoxic activity of 12 newly synthesized triarylolefins
against human colon carcinoma cell line (HCT-116) was firstly
evaluated using isoCA-4 [33] and CA-4 [55] as reference
compounds. The IC50 values corresponding to the concentration of
studied compounds leading to 50% decrease in HCT-116 cell growth
are presented in Table 1.
Newly synthesized ortho-brominated analogues 10 were not
cytotoxic. As it can be observed, most of the triarylolefins 1
retained a light cancer cell growth-inhibitory activity at a micro-
molar range. In particular, best inhibition results were obtained
with hybrids 1eeh bearing the greatest resemblance to CA-4 and
isoCA-4. However, the cytotoxicities of these triarylolefins are not
comparable with those of CA-4 and isoCA-4, even though all
derivatives of type 1 carry a CA-4 and a isoCA-4 (for 1h) moiety in
their structure.
were dissolved in DMSO, incubated at 37 ꢀC for 10 min and at 0 ꢀC
for 5 min before evaluation of the tubulin assembly rate.
Triarylolefins were tested at different concentrations and the
IC50 was calculated only for compounds inhibiting tubulin
assembly by more than 50% at 9.0 ꢁ 10ꢂ6 M. The tubulin assembly
assay was realized according to a slightly modified Guénard’s
protocol [56]. The tested analogues show a moderate potency
(micromolar level) related to the references compounds CA-4 and
isoCA-4. When comparing the inhibition of tubulin polymerization
versus the cell growth-inhibitory effect, we do not find a good
correlation for most of the active compounds except for the hybrid
1h. This hybrid most closely resembling CA-4 and isoCA-4 in
structure displayed a potent antimitotic activity and a weak cyto-
toxicity (Table 1).
2.1. Conclusion
The aim of this work was to devise a synthetic strategy to
prepare stereodefined triarylolefins 1 as CA-4 and isoCA-4 hybrids
and to evaluate the influence of the double bond substitution on
antitumor activity. From a chemical perspective, the “traceless use”
of an ortho bromo substituent to regioselectively control the
addition of tributyltin hydride on internal alkynes leading to
stannylated stilbenes precursors of trisubstituted olefins 1 is
notable. The new CA-4 and isoCA-4 analogues were evaluated for
their cell growth inhibition and antitubulin activity. Some of these
These trisubstituted olefinic combretastatin analogues were
next evaluated as tubulin polymerization inhibitors. All samples
compounds showed interesting antitubulin activities (8 mM) but are
less cytotoxic than CA-4 and isoCA-4, indicating that the nature of
the olefin substitution in combretastatin series plays an important
role on activity.
R3
R3
oDG
R2
oDG
Cleavage
3. Experimental
R1
R2
R1
3.1. General considerations
1b-h
Tetrahydrofuran (THF) and diethylether were distilled from
sodium-benzophenone ketyl. Piperidine, and triethylamine were
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 following abreviation are
used: m (multiplet), s (singlet), bs (broad singlet), d (doublet). 13C
chemical shifts are reported in ppm from the central peak of
Iodolysis
Negishi
regioselective
hydrostannation
under oDG control
oDG
SnBu3
β
α
α
oDG
R1
R2
5
R1
R2
exclusive α-isomer
Scheme 3. Retrosynthetic pathway leading to triarylolefins 1beh.

3620
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
OMe
OMe
OMe
OMe
OMe
Br
OMe
OMe
OMe
(a)
(b)
I
MeO
OMe
6a
5a
(c)
Br
OMe
OMe
OMe
Br
OMe
R
Br
OMe
OMe
OMe
(d)
(b)
I
OMe
OMe
MeO
7
6b
5b-d
b: R = H
c: R = OSitBuMe2
d: R = OMOM
Scheme 4. Synthesis of ortho bromodiarylalkynes 5. Reagents and conditions: (a) (i) HC^CSiMe3 (1.5 equiv), CuI (10 mol%), PdCl2(PPh3)2 (5 mol%), piperidine, 20 ꢀC; (ii) K2CO3,
MeOH, 92%. (b) ArI (0.7 equiv), CuI (10 mol%), PdCl2(PPh3)2 (5 mol%), Et3N/THF (1/1), 60 ꢀC, 5a: 80%; 5b: 86%, 5c: 66%, 5d: 80%. (c) Br2, AcOH, 92%. (d) (i) HC^CSiMe3 (1.5 equiv), CuI
(10 mol%), PdCl2(PPh3)2 (5 mol%), Et3N/THF (1/1), 60 ꢀC, (ii) K2CO3, MeOH, 72%.
deuteriochloroform (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.
3.1.1. 3-Bromo-4-iodoanisole
A stirred solution of 3-bromoanisole (500 mg, 2.15 mmol), HgO
(354 mg, 1.63 mmol), Ac2O (0.1 mL) in CH2Cl2 (10 mL) was refluxed
for 30 min. Then, I2 (709 mg, 2.79 mmol) was added by 6 portions
every 30 min. After refluxing for 12 h and filtration over a pad of
celite, the filtrate was washed with a saturated Na2S2O3 solution.
The aqueous layer was extracted with CH2Cl2 (3 ꢁ 10 mL) and the
Scheme 5. Synthesis of triarylolefins 1beh. Reagents and conditions: (a) PdCl2(PPh3)2 (2 mol%), Bu3SnH, (1.2 equiv), THF. (b) I2 (1 equiv), CH2Cl2, 20 ꢀC. (c) ArZnCl (2.2 equiv),
PdCl2(PPh3)2 (5 mol%), THF. (d) (i) n-BuLi (4.5 equiv), THF, ꢂ78 ꢀC. (ii) HCl 1 M, 0.5 h, 20 ꢀC.

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
3621
Table 1
Cytotoxicity of isoCA on HCT-116 human cancer cell line and antitubulin activities.
OMe
Br
MeO
OMe
OMe
OMe
Br
Br
MeO
MeO
OMe
OMe
Compounds
TBDMSO
MeO
OMe
OMe
OMe
OMe
MeO
MeO
MeO
10c
10a
10b
>10ꢂ5
>10ꢂ5
NA
>10ꢂ5
NA
a
Cytotoxicity IC50 [M]
ITPb IC50
M]
[m
NAc
MeO
OMe
OMe
MeO
OMe
OMe
MOMO
OMe
Br
MeO
MOMO
MeO
OMe
OMe
Compounds
MeO
OMe
OMe
MeO
MeO
OMe
10g
1b
1a
a
Cytotoxicity IC50 [M]
ITPb IC50
M]
>10ꢂ5
8.0
>10ꢂ5
8.1
>10ꢂ5
NA
[m
OMe
Me
OMe
OMe
OMe
HO
OMe
OMe
HO
OMe
OMe
Compounds
MeO
MeO
MeO
MeO
MeO
MeO
1d
1e
1c
>10ꢂ5
8.0
>10ꢂ5
7.8
3 ꢁ 10ꢂ6
a
Cytotoxicity IC50 [M]
ITPb IC50
M]
[m
NA
F
OMe
HO
OMe
HO
OMe
OMe
HO
OMe
OMe
HO
OMe
OMe
Compounds
MeO
MeO
MeO
MeO
MeO
MeO
1f
1g
1h
8 ꢁ 10ꢂ6
8 ꢁ 10ꢂ6
5 ꢁ 10ꢂ6
a
Cytotoxicity IC50 [M]
ITPb IC50
M]
[m
NA
NA
8.5
References
CA-4
isoCA-4
2 ꢁ 10ꢂ9
2.1
2 ꢁ 10ꢂ9
1.0
a
Cytotoxicity IC50 [M]
ITPb IC50
[mM]
a
IC50 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 ¼ Inhibition of Tubulin Polymerization; IC50 is the concentration of compound required to inhibit 50% of the rate of microtubule assembly (average of three
b
experiments).
c
NA, non active.
combined organic layers were dried with MgSO4 and evaporated to
dryness. Purification by flash chromatography (cyclohexane)
afforded the titled compound.
Yield: 92%. TLC: Rf 0.68 (cyclohexane/EtOAc: 8/2). IR (neat) nmax
cmꢂ1: 2935, 1562, 1472, 1421, 1371, 1297, 1233, 1102, 1003. 1H NMR
(300 MHz, CDCl3) ppm 7.26 (m, 1H), 7.19 (s, 1H), 3.87 (s, 3H), 3.87
(s, 3H), 3.84 (s, 3H).
/
d
Yield: 94%. TLC: Rf 0.68 (cyclohexane/Et2O: 95/5). IR (neat) nmax
/
cmꢂ1: 2933, 2831, 2361, 2183, 2013, 1579, 1556, 1463, 1436, 1384,
1285, 1260, 1225, 1182, 1093, 1034, 1001. 1H NMR (300 MHz, CDCl3)
3.1.3. 1-Ethynyl-3,4,5-trimethoxybenzene (6a)
To stirred solution of iodo-3,4,5-trimethoxybenzene
d
ppm 7.68 (d, J ¼ 8.8 Hz, 1H), 7.19 (d, J ¼ 2.8 Hz, 1H), 6.59 (dd,
a
J ¼ 2.8 Hz, J ¼ 8.8 Hz, 1H), 3.77 (s, 3H).
(10 mmol) in piperidine (15 mL) was added, CuI (190 mg, 1 mmol),
PdCl2(PPh3)2 (351 mg, 0.5 mmol) and trimethylsilylacetylene
(15 mmol). The stirred mixture was kept for a night at room
temperature and was then treated with HCl 10% (20 mL). After
extraction with CH2Cl2 (3 ꢁ 15 mL), the organic layers were dried
with MgSO4 and evaporated to dryness. Next, the crude mixture
was diluted in MeOH (15 mL) containing K2CO3 (15 mmol). After
stirring for 1 h at room temperature, the black mixture was
concentrated under vacuum and treated with a diluted HCl solution
until pH ¼ 6. The aqueous layer was extracted with CH2Cl2
3.1.2. 2-Bromo-1-iodo-3,4,5-trimethoxybenzene (7)
Br2 (192 mg) was slowly added to a solution of 1-iodo-3,4,5-
trimethoxybenzene (1.47 g; 5 mmol) in AcOH (10 mL) and the
mixture was stirred over night. After neutralization with NaOH
(1 N), the reaction product was extracted with EtOAc (3 ꢁ 10 mL).
The organic solutions were dried with MgSO4 and evaporated to
dryness. Purification by flash chromatography (cyclohexane/EtOAc:
9/1) afforded the titled compound.

3622
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
(3 ꢁ 30 mL) and the combined organic layers were dried with
MgSO4 and evaporated to dryness. Purification by flash chroma-
tography afforded 6a.
(75 MHz, CDCl3) d ppm 159.9, 152.6, 151.3, 143.7, 133.2, 120.9, 115.1,
114.1, 112.6, 111.6, 93.2, 86.9, 61.3, 61.1, 56.3, 55.4. MS (APCI) m/z:
377.0 ((M þ H)þ, 79Br), 379.0 ((M þ H)þ, 81Br).
Yield: 82%. TLC: Rf 0.47 (cyclohexane/EtOAc: 8/2). IR (neat) nmax
/
cmꢂ1: 3242, 2989, 2939, 2023, 1967, 1576, 1501, 1450, 1427, 1410,
3.2.3. (5-(2-(2-Bromo-3,4,5-trimethoxyphenyl)ethynyl)-2-
methoxyphen-oxy)(tert-butyl)dimethylsilane (5c)
1329, 1232, 1180, 1125, 1034, 998, 955, 832, 773. 1H NMR (300 MHz,
CDCl3)
d
ppm 6.72 (s, 2H), 3.85 (s, 6H), 3.83 (s, 3H), 3.02 (s, 1H). 13
C
Yield: 66%. TLC: Rf 0.35 (cyclohexane/EtOAc: 9/1). IR (neat) nmax/
NMR (75 MHz, CDCl3)
d
ppm 153.1 (2C), 123.68, 117.05, 114.99,
cmꢂ1: 2931, 2855, 2211, 1566, 1508, 1477, 1443, 1413, 1384, 1360,
1288, 1257, 1233, 1189, 1151, 1132, 1107, 1043, 1023. 1H NMR
109.35 (2C), 105.21, 83.73, 76.26, 60.99, 56.17 (2C). MS (APCI) m/z:
193.22 (M þ H)þ.
(300 MHz, CDCl3)
d
ppm 7.00 (dd, J ¼ 1.9 Hz, J ¼ 8.3 Hz, 1H), 6.88 (d,
J ¼ 1.7 Hz, 1H), 6.73 (s, 1H), 6.64 (d, J ¼ 8.4 Hz, 1H), 3.74 (s, 3H), 3.73
3.1.4. Synthesis of 2-bromo-1-ethynyl-3,4,5-trimethoxybenzene
(6b)
(s, 3H), 3.70 (s, 3H), 3.66 (s, 3H), 0.83 (s, 9H), 0.00 (s, 6H). 13C NMR
(75 MHz, CDCl3) d ppm 152.6, 151.9, 151.3, 144.8, 143.6, 125.9, 123.9,
To a stirred solution of 7 (10 mmol) in THF (15 mL) and Et3N
(15 mL) was added, CuI (190 mg, 1 mmol), PdCl2(PPh3)2 (351 mg,
0.5 mmol) and trimethylsilylacetylene (15 mmol). The stirred
mixture was kept for a night at room temperature and was then
treated with HCl 10% (20 mL). After extraction with CH2Cl2
(3 ꢁ 15 mL), the organic layers were dried with MgSO4 and evap-
orated to dryness. Next, the crude mixture was diluted in MeOH
(15 mL) containing K2CO3 (20 mmol). After stirring for 1 h at room
temperature, the black mixture was concentrated under vacuum
and treated with a diluted HCl solution until pH ¼ 6. The aqueous
layer was extracted with CH2Cl2 (3 ꢁ 30 mL) and the combined
organic layers were dried with MgSO4 and evaporated to dryness.
Purification by flash chromatography afforded 6b.
120.8, 115.1, 112.6, 111.7, 111.5, 93.2, 86.5, 61.2, 60.9, 56.2, 55.4, 25.7
(3C), 18.5, ꢂ4.6 (2C). MS (APCI) m/z: 509.1 (M þ H)þ. Anal. calcd for
5c (C24H31BrO5Si): C, 56.80; H, 6.16. Found: C, 56.65; H, 6.05.
3.2.4. 4-(2-(2-Bromo-3,4,5-trimethoxyphenyl)ethynyl)-1-methoxy-
2-(methoxymethoxy)benzene (5d)
Yield: 80%. Anal. calcd for 5d (C20H21BrO6): C, 54.93; H, 4.84.
Found: C, 54.83; H, 4.80. TLC: Rf 0.20 (cyclohexane/EtOAc: 9/1). IR
(neat) nmax/cmꢂ1: 2942, 1556, 1514, 1478, 1421, 1382, 1364, 1317,
1246, 1198, 1151, 1131, 1104, 1074, 1047. 1H NMR (300 MHz, CDCl3)
d
ppm 7.28 (d, J ¼ 1.9 Hz,1H), 7.17 (dd, J ¼ 2.3 Hz, J ¼ 8.8 Hz,1H), 6.84
(s, 1H), 6.80 (d, J ¼ 8.4 Hz, 1H), 5.18 (s, 2H), 3.84 (s, 6H), 3.83 (s, 3H),
3.80 (s, 3H), 3.47 (s, 3H). 13C NMR (75 MHz, CDCl3)
ppm 152.6,
d
Yield: 72%. TLC: Rf 0.17 (cyclohexane/EtOAc: 95/5). IR (neat)
151.3, 150.5, 146.2, 143.7, 126.6, 120.7, 119.3, 115.3, 112.6, 111.7, 95.5,
93.0, 86.7, 61.3, 60.9, 56.3, 56.2, 55.9. MS (APCI) m/z: 437.28
((M þ H)þ, 79Br), 439.0 ((M þ H)þ, 81Br).
nmax/cmꢂ1: 3291, 2938, 1555, 1477, 1424, 1383, 1336, 1241, 1195,
1166,1105, 1041, 1004. 1H NMR (300 MHz, CDCl3)
d
ppm 6.73 (s, 1H),
3.75 (s, 3H), 3.73 (s, 3H), 3.70 (s, 3H), 3.17 (s, 1H). 13C NMR (75 MHz,
CDCl3) ppm 155.2, 152.6, 119.3, 112.9, 112.6, 80.9, 61.3, 61.0, 56.2
d
3.3. General procedure for the hydrostannation of diarylalkynes
(two C missing).
Tributyltin hydride (12 mmol) was added dropwise at room
temperature to a solution of PdCl2(PPh3)2 (0.1 mmol) and alkyne
(10 mmol) in THF (15 mL). The dark brown reaction mixture was
stirred for 90 min. Then, the solution was concentrated in vacuo.
Purification by flash chromatography on silica gel gave the desired
products 3 and 8aed.
3.2. Synthesis of internal alkynes 5
To a mixture of required aryl iodide (0.7 mmol), PdCl2(PPh3)2
(0.1 mmol), CuI (0.15 mmol), TEA (10 mL) in THF (10 mL) was added
dropwise under an argon atmosphere, a solution of 6a or 6b
(1.0 mmol). The mixture was stirred at 60 ꢀC for a night. Then Et2O
(20 mL) was added to the crude and the mixture was filtered over
a short pad of celite. The organic layer was washed with brine
(5 mL) twice, separated, dried over MgSO4, filtered, and concen-
trated. Purification by flash chromatography afforded internal
alkynes 5aed.
3.3.1. (E)-(1,2-bis(4-Methoxyphenyl)vinyl)tributylstannane (3)
Yield: 79%. TLC: Rf 0.82 (cyclohexane/Et2O: 95/5). IR (neat) nmax
cmꢂ1: 2954, 2920, 2361, 2162, 1965, 1604, 1503, 1462, 1376, 1279,
1242, 1173, 1106, 1071, 1038. 1H NMR (300 MHz, CDCl3)
6.87 (d,
/
d
J ¼ 8.7 Hz, 2H), 6.82 (d, J ¼ 8.8 Hz, 2H), 6.73 (d, J ¼ 8.7 Hz, 2H), 6.55
(d, J ¼ 8.7 Hz, 2H), 6.48 (s, 1H), 3.68 (s, 3H), 3.60 (s, 3H), 1.45e1.35
(m, 6H), 1.29e1.15 (m, 6H), 0.92e0.76 (m, 5H). 13C NMR (75 MHz,
3.2.1. 5-(2-(2-Bromo-4-methoxyphenyl)ethynyl)-1,2,3-
trimethoxybenzene (5a)
CDCl3) d 158.1, 157.2, 146.8, 138.1, 137.8, 130.6, 130.4 (2C), 127.5 (2C),
Yield: 80%. Anal. calcd for 5a (C18H17BrO4): C, 57.31; H, 4.54.
Found: C, 57.18; H, 4.39. TLC: Rf 0.14 (cyclohexane/EtOAc: 9/1). IR
(neat) nmax/cmꢂ1: 3751, 2935, 1601, 1572, 1506, 1457, 1437, 1409,
1351, 1287, 1268, 1221, 1182, 1123, 1027. 1H NMR (300 MHz, CDCl3)
114.1 (2C), 113.3 (2C), 55.2, 55.1, 30.6 (3C), 29.0 (3C), 27.5 (3C), 13.7
(3C).
3.3.2. (E)-(1-(2-Bromo-4-methoxyphenyl)-2-(3,4,5-
trimethoxyphenyl) vinyl)tributylstannane (8a)
d
ppm 7.45 (d, J ¼ 8.6 Hz, 1H), 7.15 (d, J ¼ 2.5 Hz, 1H), 6.83 (dd,
J ¼ 2.6 Hz, J ¼ 8.7 Hz, 1H), 6.78 (s, 2H), 3.87 (s, 6H), 3.86 (s, 3H), 3.80
(s, 3H). 13C NMR (75 MHz, CDCl3)
ppm 159.9, 153.2, 138.9, 133.9,
Yield: 78%. TLC: Rf 0.29 (cyclohexane/EtOAc: 9/1). 1H NMR
d
(300 MHz, CDCl3)
d
ppm 7.17 (d, J ¼ 2.2 Hz, 1H), 6.87 (d, J ¼ 8.4 Hz,
126.3, 118.3, 117.9, 117.5, 113.6, 108.8, 92.3, 87.1, 61.0, 56.2, 55.7.MS
1H), 6.82 (dd, J ¼ 2.2 Hz, J ¼ 8.4 Hz, 1H), 6.57 (s, 1H), 6.26 (s, 2H),
(APCI) m/z: 377.0 ((M þ H)þ, 79Br), 379.0 ((M þ H)þ, 81Br).
3.78 (s, 6H), 3.59 (s, 6H), 1.49 (m, 6H), 1.29 (m, 6H), 0.95 (m, 6H), 0.
87 (m, 9H). 13C NMR (75 MHz, CDCl3)
d ppm 158.0, 152.8 (2C), 148.9,
3.2.2. 2-Bromo-3,4,5-trimethoxy-1-(2-(4-methoxyphenyl) ethynyl)
benzene (5b)
139.1, 138.7, 137.2, 133.2, 128.4, 121.7, 117.7, 114.5, 106.0, 60.9, 55.8
(3C), 28.9 (3C), 27.5 (3C), 13.8 (3C), 10.9 (3C).
Yield: 86%. Anal. calcd for 5b (C18H17BrO4): C, 57.31; H, 4.54.
Found: C, 57.11; H, 4.35. TLC: Rf 0.30 (cyclohexane/Et2O: 9/1). IR
(neat) nmax/cmꢂ1: 2936, 2218, 1736, 1604, 1578, 1551, 1511, 1477,
1462, 1427, 1383, 1358, 1295, 1250, 1174, 1098, 1030. 1H NMR
3.3.3. (E)-(1-(2-Bromo-3,4,5-trimethoxyphenyl)-2-(4-
methoxyphenyl) vinyl)tributylstannane (8b)
Yield: 92%. TLC: Rf 0. 2 (cyclohexane/Et2O: 95/5). IR (neat) nmax
/
(300 MHz, CDCl3)
d
ppm 7.51 (d, J ¼ 8.3 Hz, 2H), 6.90 (s, 2H), 6.89 (d,
cmꢂ1: 2928, 2847, 2168, 2029, 1973, 1604, 1554, 1508, 1476, 1420,
1378, 1319, 1286, 1248, 1175, 1161, 1106. 1H NMR (300 MHz, CDCl3)
J ¼ 10.2 Hz, 2H), 3.90 (s, 6H), 3.87 (s, 3H), 3.83 (s, 3H). 13C NMR

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
3623
d
ppm 6.95 (d, J ¼ 8.7 Hz, 2H), 6.68 (d, J ¼ 8.7 Hz, 2H), 6.57 (s, 1H),
3.4.3. (E)-1-(2-(2-Bromo-3,4,5-trimethoxyphenyl)-2-iodovinyl)-4-
methoxy benzene (9b)
6.31 (s, 1H), 3.91 (s, 6H), 3.74 (s, 3H), 3.73 (s, 3H), 1.52e1.43 (m, 6H),
1.35e1.23 (m, 6H), 0.98e0.93 (m, 6H), 0.87 (t, J ¼ 7.3 Hz, 9H). 13C
Yield: 85%. Anal. calcd for 9b (C18H18BrIO4): C, 42.80; H, 3.59.
NMR (75 MHz, CDCl3)
d
ppm 158.4, 153.1, 151.2, 146.5, 142.0, 140.4,
Found: C, 42.59; H, 3.37. TLC: Rf 0.21 (cyclohexane/EtOAc: 95/5). 1H
137.9, 130.2, 129.9 (2C), 113.4 (2C), 107.2, 105.9, 61.3, 60.9, 55.9, 55.1,
28.9 (3C), 27.3 (3C), 13.7 (3C), 10.8 (3C). MS (APCI) m/z: 669.0
(M þ H)þ.
NMR (300 MHz, CDCl3)
6.65 (d, J ¼ 8.7 Hz, 2H), 6.62 (s, 1H), 3.93 (s, 3H), 3.91 (s, 3H), 3.79 (s,
3H), 3.74 (s, 3H). 13C NMR (75 MHz, CDCl3)
ppm 159.5, 151.9, 145.6,
d
ppm 7.31 (s, 1H,), 6.81 (d, J ¼ 8.7 Hz, 2H),
d
138.8, 136.0, 133.6, 130.3 (2C), 128.6, 113.5 (2C), 107.2, 106.5, 90.7,
3.3.4. (E)-(5-(2-(2-Bromo-3,4,5-trimethoxyphenyl)-2-
(tributylstannyl) vinyl)-2-methoxyphen-oxy)(tert-butyl)dimethyl
silane (8c)
60.93, 60.6, 56.1, 55.4. MS (ESI) m/z: 528.8 (M þ Naþ).
3.4.4. (E)-(5-(2-(2-Bromo-3,4,5-trimethoxyphenyl)-2-iodovinyl)-2-
methoxyphen-oxy)(tert-butyl)dimethyl silane (9c)
Yield: 75%. TLC: Rf 0.58 (cyclohexane/EtOAc: 9/1). IR (neat) nmax
cmꢂ1: 3836, 2929, 2854, 1556, 1506, 1463, 1423, 1380, 1281, 1231,
1139, 1109, 1013. 1H NMR (300 MHz, CDCl3)
ppm 7.00 (dd,
/
Yield: 99%. TLC: Rf 0.50 (cyclohexane/EtOAc: 9/1). 1H NMR
d
(300 MHz, CDCl3)
d
ppm 7.26 (s, 1H), 6.67 (d, J ¼ 8.4 Hz, 1H), 6.62 (s,
J ¼ 1.9 Hz, J ¼ 8.3 Hz,1H), 6.88 (d, J ¼ 1.7 Hz,1H), 6.73 (s,1H), 6.64 (d,
1H), 6.56 (dd, J ¼ 8.4 Hz, J ¼ 2.2 Hz, 1H), 6.36 (d, J ¼ 2.2 Hz, 1H), 3.91
J ¼ 8.4 Hz, 1H), 3.74 (s, 3H), 3.73 (s, 3H), 3.70 (s, 3H), 3.66 (s, 3H),
(s, 3H), 3.80 (s, 3H), 3.78 (s, 3H), 3.74 (s, 3H), 0,99 (s, 9H), 0,15 (s,
0.83 (s, 9H), 0.00 (s, 6H). 13C NMR (75 MHz, CDCl3)
d
ppm 152.5,
6H). 13C NMR (75 MHz, CDCl3)
d ppm 153.3, 151.8, 151.14, 144.6,
151.5,149.7, 146.2, 144.6, 142.8, 142.3, 138.9, 127.9, 123.3, 120.1, 111.2,
107.3, 61.3, 60.6, 56.4, 55.4, 29.1 (3C), 27.5 (3C), 25.9 (3C), 18.6, 13.5
(3C), 8.07 (3C), ꢂ2.7 (2C).
143.1, 142.1, 138.7, 129.7, 123.1, 119.9, 111.3, 109.0, 107.9, 92.2, 61.2,
61.1, 56.1, 55.3, 25.6 (3C), 16.4, ꢂ4.8 (2C). MS (ESI) m/z: 659.0
(M þ Naþ). Anal. calcd for 9c (C24H32BrIO5Si): C, 45.37; H, 5.08.
Found: C, 45.17; H, 4.98.
3.3.5. (E)-(1-(2-Bromo-3,4,5-trimethoxyphenyl)-2-(4-methoxy-3-
(methoxymethoxy)phenyl)vinyl)tributyl stannane (8d)
3.4.5. (E)-2-Bromo-1-(1-iodo-2-(4-methoxy-3-(methoxymethoxy)
Yield: 75%. TLC: Rf 0.28 (cyclohexane/EtOAc: 9/1). IR (neat) nmax
cmꢂ1: 2916, 1737, 1373, 1234, 1044. 1H NMR (300 MHz, CDCl3)
ppm 6.76 (s, 1H), 6.64 (s, 2H), 6.47 (s, 1H), 6.25 (s, 1H), 4.85 (s, 2H),
/
phenyl) vinyl)-3,4,5-trimethoxybenzene (9d)
Yield: 88%. TLC: Rf 0.49 (cyclohexane/EtOAc: 8/2). IR (neat) nmax
/
d
cmꢂ1: 2984, 1737, 1373, 134, 1044. 1H NMR (300 MHz, CDCl3)
d
ppm
3.82 (s, 3H), 3.80 (s, 3H), 3.72 (s, 3H), 3.65 (s, 3H), 3.27 (s, 3H),
7.27 (s, 1H), 6.72e6.61 (m, 3H), 6.63 (s, 1H), 4.92 (s, 2H), 3.92 (s, 6H),
1.45e1.36 (m, 6H), 1.27e1.15 (m, 6H), 0.91e0.85 (m, 6H), 0.79 (t,
3.82 (s, 3H), 3.80 (s, 3H), 3.34 (s, 3H). 13C NMR (75 MHz, CDCl3)
J ¼ 7.2 Hz, 9H). 13C NMR (75 MHz, CDCl3)
d
ppm 153.1, 151.2, 148.7,
d ppm 153.4,151.8,149.4,146.1,143.1,141.9,138.5,129.7,123.4,115.2,
110.9, 108.8, 107.8, 95.2, 92.6, 61.1, 61.0, 56.2, 55.8 (2C). Anal. calcd
for 9d (C20H22BrIO6): C, 42.50; H, 3.92. Found: C, 42.38; H, 3.88.
147.1, 145.8, 141.8, 140.4, 137.7, 130.5, 123.4, 116.1, 111.0, 107.0, 105.8,
95.1, 60.9, 60.7, 55.9, 55.6, 28.8 (3C), 27.2 (3C), 13.5 (3C), 10.8 (3C).
3.5. General procedure for the PdCl2(PPh3)-catalyzed cross coupling
reaction of vinyl iodides with arylzinc reagents
3.4. General procedure for the iodination of 3 and 8aed
To
a
CH2Cl2 (15 mL) solution containing vinylstannane
To a solution of vinyl iodides 4 or 9aed, PdCl2(PPh3)2 (5 mol%) in
THF was added at room temperature, ArZnCl (2 equiv.) prepared by
transmetallation from the corresponding Grignard reagent
(2.2 equiv.) and anhydrous ZnCl2 (3 equiv.). The reaction was stirred
at room temperature and monitored by TLC until complete
consumption of starting materials. The reaction was hydrolyzed at
0 ꢀC with aqueous HCl (1 N), extracted with Et2O, the organic extract
was dried over MgSO4 and the solvent was removed in vacuo. Puri-
fication by flash chromatography afforded olefins 1a, 10aeg.
(0.39 mmol) was added in one portion I2 (0.39 mmol) at 0 ꢀC. The
mixture was then stirred at rt until the disappearance of the
starting material (judged by TLC). Then a saturated Na2S2O3 solu-
tion (10 mL) was added to the mixture which was extracted with
CH2Cl2 (3 ꢁ 10 mL). The combined organic layers were dried with
MgSO4 and evaporated to dryness. Purification by flash chroma-
tography afforded terminal alkynes 4 and 9aed.
3.4.1. (E)-1-Iodo-1,2-bis(4-methoxyphenyl)ethene (4)
Yield: 74%. Anal. calcd for 4 (C16H15IO2): C, 52.48; H, 4.13. Found:
C, 52.24; H, 4.07. TLC: Rf 0.68 (cyclohexane/EtOAc: 8/2). IR (neat)
nmax/cmꢂ1: 2932, 2938, 1596, 1568, 1504, 1462, 1440, 1421, 1286,
3.5.1. (E)-5-(1,2-Bis(4-methoxyphenyl)vinyl)-1,2,3-
trimethoxybenzene (1a)
Yield: 99%. Anal. calcd for 1a (C25H26O5): C, 73.87; H, 6.45.
Found: C, 73.77; H, 6.38. TLC: Rf 0.31 (cyclohexane/EtOAc: 8/2). IR
(neat) nmax/cmꢂ1: 2930, 1603, 1576, 1507, 1463, 1412, 1332, 1285,
1245, 1174, 1161, 1109, 1024. 1H NMR (300 MHz, CDCl3)
d ppm 7.22
(s, 1H), 7.18 (d, J ¼ 8.7 Hz, 2H), 6.80 (d, J ¼ 8.9 Hz, 2H), 6.74 (d,
J ¼ 8.7 Hz, 2H), 6.57 (d, J ¼ 8.9 Hz, 2H), 3.73 (s, 3H), 3.65 (m, 3H). 13C
1238, 1173, 1119, 1028. 1H NMR (300 MHz, CDCl3)
d ppm 7.13 (d,
NMR (75 MHz, CDCl3)
d
ppm 159.3, 158.8, 140.3, 135.6, 130.2 (2C),
J ¼ 8.7 Hz, 2H), 6.99 (d, J ¼ 8.7 Hz, 2H), 6.87 (d, J ¼ 8.8 Hz, 2H), 6.81
130.1, 129.9 (2C), 114.0 (2C), 113.5 (2C), 96.1, 55.3, 55.2. MS (CI) m/z:
(s, 1H), 6.69 (d, J ¼ 8.8 Hz, 2H), 6.53 (s, 2H), 3.86 (s, 3H), 3.85 (s, 3H),
365.9 (M þ Hþ).
3.79 (s, 6H), 3.76 (s, 3H). 13C NMR (75 MHz, CDCl3)
d ppm 158.9,
158.3, 152.8 (2C), 140.4, 139.9, 137.6, 132.5, 131.7 (2C), 130.7 (2C),
130.2, 126.9, 113.9 (2C), 113.4 (2C), 104.9 (2C), 60.9, 56.1 (3C), 55.2.
MS (CI) m/z: 407.2 (M þ Hþ).
3.4.2. (E)-2-Bromo-1-(1-iodo-2-(3,4,5-trimethoxyphenyl)vinyl)-4-
methoxy benzene (9)
Yield: 70%. Anal. calcd for 9a (C18H18BrIO4): C, 42.80; H, 3.59.
Found: C, 42.74; H, 3.57. TLC: Rf 0.13 (cyclohexane/EtOAc: 9/1). 1H
3.5.2. (Z)-5-(1-(2-Bromo-4-methoxyphenyl)-2-(3,4,5-
NMR (300 MHz, CDCl3)
d
ppm 7.32 (s, 1H), 7.19 (d, J ¼ 8.5 Hz, 1H),
trimethoxyphenyl) vinyl)-1,2,3-trimethoxybenzene (10a)
7.15 (d, J ¼ 2.6 Hz, 1H), 6.86 (dd, J ¼ 8.5 Hz, J ¼ 2.6 Hz, 1H), 6.14 (s,
Yield: 95%. Anal. calcd for 10a (C27H29BrO7): C, 59.46; H, 5.36.
Found: C, 59.29; H, 5.24. TLC: Rf 0.13 (cyclohexane/EtOAc: 8/2). IR
(neat) nmax/cmꢂ1: 2936, 2836, 1578, 1506, 1452, 1418, 1334, 1283,
2H), 3.78 (s, 3H), 3.77 (s, 3H), 3.57 (s, 6H). 13C NMR (75 MHz, CDCl3)
d
ppm 160.0, 152.9, 142.8, 137.8, 135.9, 132.2, 130.7, 123.2118.4, 114.4,
105.4 (2C), 94.5, 60.8, 55.8, 55.7 (2C). MS (APCI) m/z: 500.0
1229, 1186, 1122, 1032, 1004. 1H NMR (300 MHz, CDCl3)
d
ppm 7.23
(M þ Hþ).
(d, J ¼ 2.5 Hz, 1H), 7.13 (d, J ¼ 8.5 Hz, 1H), 6.91 (dd, J ¼ 8.5 Hz,

3624
E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
J ¼ 2.5 Hz, 1H), 6.71 (s, 1H), 6.54 (s, 2H), 6.26 (s, 2H), 3.92 (s, 3H),
(neat) nmax/cmꢂ1: 2937, 1514, 1481, 1385, 1262, 1156, 1132, 1106,
1079, 1009. 1H NMR (300 MHz, CDCl3)
ppm 7.09e7.03 (m, 1H),
3.81 (s, 3H), 3.80 (s, 6H), 3.79 (s, 6H), 3.60 (s, 3H). 13C NMR (75 MHz,
d
CDCl3)
d
ppm 159.6, 153.4 (2C), 153.0 (2C), 152.8, 139.9, 137.6, 137.3,
7.02e6.98 (m, 1H), 6.92 (s, 1H), 6.87 (d, J ¼ 8.6 Hz, 1H), 6.76 (d,
J ¼ 10.4 Hz, 1H), 6.74 (s, 1H), 6.56 (s, 1H), 4.94 (s, 2H), 3.95 (s, 3H),
3.92 (s, 3H), 3.88 (s, 3H), 3.83 (s, 3H), 3.74 (s, 3H). 13C NMR (75 MHz,
133.1, 132.5, 132.3, 128.7, 124.9, 118.7, 114.2, 106.2 (2H), 104.0 (2C),
60.9, 60.8, 56.3, 56.1 (2C), 55.6 (2C). MS (APCI) m/z: 547.0 (M þ Hþ).
CDCl3)
d
ppm 153.6, 152.3 (1C, d, J ¼ 244.9 Hz), 151.9, 148.9, 146.9,
3.5.3. (Z)-1-(1-(2-Bromo-3,4,5-trimethoxyphenyl)-2-(4-
methoxyphenyl) vinyl)-4-methoxybenzene (10b)
146.8, 146.0, 142.6, 137.4, 136.0, 134.8, 129.7, 127.6, 124.2, 122.2,
116.1, 113.9 (1C, d, J ¼ 19.3 Hz), 113.1, 111.2, 110.6, 110.0, 95.2, 61.2,
61.1, 56.3, 56.2, 55.9, 55.8. MS (APCI) m/z: 441.0 (M þ Hþ).
Yield: 99%. Anal. calcd for 10b (C25H25BrO5): C, 61.86; H, 5.19.
Found: C, 61.65; H, 5.04. TLC: Rf 0.41 (cyclohexane/EtOAc: 8/2). 1H
NMR (300 MHz, CDCl3)
d
ppm 7.20 (d, J ¼ 8.4 Hz, 2H), 6.90 (s,1H), 6.82
3.5.8. (Z)-1-(1,2-Bis(4-methoxy-3-(methoxymethoxy)phenyl)
vinyl)-2-bromo-3,4,5-trimethoxybenzene (10g)
Yield: 54%. Anal. calcd for 10g (C29H33BrO9): C, 57.53; H, 5.49.
Found: C, 57.08; H, 5.10. TLC: Rf 0.20 (cyclohexane/EtOAc: 7/3). IR
(neat) nmax/cmꢂ1: 2984, 1737, 1373, 1235, 1045. 1H NMR (300 MHz,
(d, J ¼ 8.7 Hz, 2H), 6.78 (d, J ¼ 8.7 Hz, 2H), 6.61 (d, J ¼ 8.4 Hz, 2H), 6.48
(s, 1H), 3.96 (s, 3H), 3.92 (s, 3H), 3.81 (s, 3H), 3.75 (s, 3H), 3.72 (s, 3H).
13C NMR (75 MHz, CDCl3)
d ppm 159.0,158.5,153.4,151.8,142.5,138.2,
136.9, 134.0, 130.1 (2C), 129.8, 127.5 (2C), 126.8, 113.8 (2C), 113.6 (2C),
110.8, 110.2, 61.4, 61.2, 56.2, 55.3, 55.2. MS (ESI) m/z: 485.2 (M þ Hþ).
CDCl3)
d
ppm 7.22 (d, J ¼ 1.5 Hz, 1H), 6.91 (s, 1H), 6.81 (d, J ¼ 2.0 Hz,
2H), 6.80e6.70 (m, 3H), 6.56 (s, 1H), 5.19 (d, J ¼ 0.9 Hz, 2H), 4.92 (s,
3.5.4. (Z)-(5-(2-(2-Bromo-3,4,5-trimethoxyphenyl)-2-(4-
methoxyphenyl) vinyl)-2-methoxyphen-oxy)(tert-butyl)dimethyl
silane (10c)
Yield: 77%. Anal. calcd for 10c (C31H39BrO6Si): C, 60.48; H, 6.39.
Found: C, 60.32; H, 6.30. TLC: Rf 0.14 (cyclohexane/EtOAc: 9/1). IR
(neat) nmax/cmꢂ1: 2203, 2149, 2073, 2020, 1985, 1605, 1570, 1497,
1440, 1388, 1275, 1243, 1178, 1136, 1109, 1040, 1012. 1H NMR
2H), 3.93 (s, 3H), 3.89 (s, 3H), 3.84 (s, 3H), 3.80 (s, 3H), 3.72 (s, 3H),
3.48 (s, 3H), 3.35 (s, 3H). 13C NMR (75 MHz, CDCl3)
d ppm 153.5,
151.8, 149.5, 148.8, 146.3, 145.9, 142.5, 138.2, 136.5, 134.2, 129.9,
126.9, 124.1, 121.0, 116.1, 115.0, 111.5, 111.2, 110.7, 110.2, 95.9, 95.2,
61.1, 60.9, 56.2, 56.2, 55.9, 55.8, 55.8. MS (ESI) m/z: 627.2 (M þ Naþ,
79Br), 629.2 (M þ Naþ, 81Br).
(300 MHz, CDCl3)
d
ppm 7.22 (d, J ¼ 7.9 Hz, 2H), 6.88 (s, 1H), 6.84 (d,
3.6. Typical procedure for the synthesis of triarylolefins 1beh
J ¼ 7.9 Hz, 2H), 6.67 (s, 2H), 6.56 (s, 1H), 6.49 (s, 1H), 3.95 (s, 3H),
3.91 (s, 3H), 3.80 (s, 3H), 3.75 (s, 3H), 3.72 (s, 3H), 0.92 (s, 9H), 0.03
To a cooled solution (ꢂ78 ꢀC) of 10aeg (0.25 mmol) in THF
(5 mL) was added a 2.5 M hexane solution of n-BuLi (0.5 mL,
1.25 mmol) over 2 min. After 30 min at ꢂ78 ꢀC the solution was
allowed to warm to rt then HCl 1 N (5 mL) was added and stirring
was continued for 1 h. The aqueous phase was separated and
extracted with EtOAc, the organic extract was dried over MgSO4
and the solvent was removed in vacuo. Purification by flash chro-
matography afforded triarylolefins 1beh.
(s, 6H). 13C NMR (75 MHz, CDCl3)
d ppm 158.9, 153.3, 151.8, 150.3,
144.4, 142.4, 138.1, 136.8, 134.1, 130.0, 127.5 (2C), 126.9, 123.6, 120.8,
113.8 (2C), 111.4, 110.7, 110.0, 61.2, 61.1, 56.1, 55.3, 55.3, 25.6 (3C),
18.3, ꢂ6.1 (2C). MS (APCI) m/z: 617.1 (M þ Hþ).
3.5.5. (Z)-2-Bromo-3,4,5-trimethoxy-1-(2-(4-methoxy-3-
(methoxymethoxy) phenyl)-1-p-tolylvinyl)benzene (10d)
Yield: 72%. TLC: Rf 0.50 (cyclohexane/EtOAc: 7/3). IR (neat) nmax
/
cmꢂ1: 2190, 1512, 1263, 1106, 1008. 1H NMR (300 MHz, CDCl3)
3.6.1. (E)-1,2,3-Trimethoxy-5-(1-(4-methoxyphenyl)-2-(3,4,5-
trimethoxy phenyl)vinyl)benzene (1b)
Yield: 91%. Anal. calcd for 1b (C27H30O7): C, 69.51; H, 6.48.
Found: C, 69.41; H, 6.35. TLC: Rf 0.46 (cyclohexane/EtOAc: 8/2). IR
(neat) nmax/cmꢂ1: 2954, 2922, 1573, 1505, 1482, 1463, 1417, 1376,
1327, 1280, 1223, 1184, 1125, 1030, 1010. 1H NMR (400 MHz, CDCl3)
d
ppm 7.22 (d, J ¼ 8.3 Hz, 1H), 7.12 (d, J ¼ 8.1 Hz, 1H), 6.99 (s, 1H),
6.80 (d, J ¼ 1.6 Hz,1H), 6.76 (t, J ¼ 5.2 Hz,1H), 6.73 (d, J ¼ 8.4 Hz,1H),
6.58 (s, 1H), 4.95 (s, 2H), 3.95 (s, 3H), 3.92 (s, 3H), 3.83 (s, 3H), 3.74
(s, 3H), 3.38 (s, 3H), 2.04 (s, 3H). 13C NMR (75 MHz, CDCl3)
d ppm
153.5, 151.8, 148.8, 145.9, 142.4, 138.7, 138.3, 137.1, 136.6, 130.0 (2C),
129.1, 127.5 (2C), 126.2, 124.1, 116.1, 111.1, 110.6, 110.1, 95.2, 61.1, 61.0,
56.2, 55.9, 55.8. MS (APCI) m/z: 551.0 (M þ Naþ, 79Br), 553.1
(M þ Naþ, 81Br). Anal. calcd for 10d (C27H29BrO6): C, 61.25; H, 5.52.
Found: C, 61.31; H, 5.52.
d
ppm: 7.16 (d, J ¼ 8.7 Hz, 2H), 6.89 (d, J ¼ 8.7 Hz, 2H), 6.71 (s, 1H),
6.55 (s, 2H), 6.29 (s, 2H), 3.93 (s, 3H), 3.86 (s, 3H), 3.82 (s, 3H), 3.80
(s, 6H), 3.59 (s, 6H). 13C NMR (100 MHz, CDCl3)
ppm: 159.1, 153.4,
d
152.9 (2C), 152.6 (2C), 141.8, 139.3, 137.6, 132.9, 132.4, 131.7 (2C),
127.5, 114.1 (2C), 106.7 (2C), 104.9 (2C), 60.9, 56.3, 56.1 (2C), 55.7
(2C), 55.3. MS (ESI) m/z: 467.3 (M þ Hþ).
3.5.6. (Z)-2-(1-(2-Bromo-3,4,5-trimethoxyphenyl)-2-(4-methoxy-
3-(methoxymethoxy)phenyl)vinyl) naphthalene (10e)
Yield: 72%. Anal. calcd for 10e (C30H29BrO6): C, 63.72; H, 5.17.
Found: C, 63.45; H, 5.00. TLC: Rf 0.13 (cyclohexane/EtOAc: 8/2). IR
(neat) nmax/cmꢂ1: 2989, 1737, 1373, 1236, 1045. 1H NMR (300 MHz,
3.6.2. (Z)-1-Methoxy-4-(2-(4-methoxyphenyl)-1-(3,4,5-
trimethoxyphenyl) vinyl)benzene (1c)
Yield: 65%. Anal. calcd for 1c (C25H26O5): C, 73.87; H, 6.45.
Found: C, 73.73; H, 6.36. TLC: Rf 0.40 (cyclohexane/EtOAc: 8/2). IR
(neat) nmax/cmꢂ1: 2934, 1605, 1577, 1508, 1461, 1410, 1280, 1237,
CDCl3)
d
ppm 7.81 (d, J ¼ 9.2 Hz, 1H), 7.81e7.50 (m, 2H), 7.63 (d,
J ¼ 1.8 Hz, 1H), 7.61 (dd, J ¼ 1.9 Hz, J ¼ 3.7 Hz, 1H), 7.44 (d, J ¼ 9.4 Hz,
1H), 7.44 (dd, J ¼ 1.9 Hz, J ¼ 3.1 Hz, 1H), 6.86 (d, J ¼ 1.9 Hz, 1H), 6.82
(dd, J ¼ 1.9 Hz, J ¼ 8.5 Hz, 1H), 6.66 (s, 1H)6.76 (d, J ¼ 8.4 Hz, 1H). 13C
1175, 1124, 1032. 1H NMR (300 MHz, CDCl3)
d ppm 7.28 (d,
J ¼ 8.8 Hz, 2H), 6.97 (d, J ¼ 8.8 Hz, 2H), 6.86 (d, J ¼ 8.8 Hz, 2H), 6.81
NMR (75 MHz, CDCl3)
d ppm 153.6, 151.9, 149.0, 146.0, 142.6, 138.8,
(s, 1H), 6.68 (d, J ¼ 8.8 Hz, 2H), 6.42 (s, 2H), 3.91 (s, 3H), 3.82 (s, 3H),
138.6,136.4,133.5,132.7,129.9,128.9,128.3,127.9,127.5,126.1,125.9,
125.5,124.4,124.3,116.3,111.2,110.8,110.2, 95.2, 61.2, 61.1, 56.2, 55.9,
55.8. MS (APCI) m/z: 587.2 (M þ Naþ, 79Br), 589.1 (M þ Naþ, 81Br).
3.76 (s, 3H), 3.69 (s, 6H). 13C NMR (75 MHz, CDCl3)
d ppm 159.1,
158.3, 153.5 (2C), 139.9, 137.3, 136.2, 135.9, 130.8 (2C), 130.6, 128.5
(2C), 125.9, 113.6 (2C), 113.4 (2C), 107.4 (2C), 61.1, 56.1 (2C), 55.3,
55.2. MS (APCI) m/z: 407.3 (M þ Hþ).
3.5.7. (Z)-2-Bromo-1-(1-(3-fluoro-4-methoxyphenyl)-2-(4-
methoxy-3-(methoxymethoxy)phenyl)vinyl)-3,4,5-
trimethoxybenzene (10f)
3.6.3. (Z)-2-Methoxy-5-(2-(4-methoxyphenyl)-2-(3,4,5-
trimethoxyphenyl) vinyl)phenol (1d)
Yield: 50%. Anal. calcd for 10f (C27H28BrFO7): C, 57.56; H, 5.01.
Found: C, 57.50; H, 4.98. TLC: Rf 0.33 (cyclohexane/EtOAc: 7/3). IR
Yield: 99%. Anal. calcd for 1d (C25H26O6): C, 71.07; H, 5.20.
Found: C, 70.95; H, 6.14. TLC: Rf 0.36 (cyclohexane/EtOAc: 8/2). IR

E. Rasolofonjatovo et al. / European Journal of Medicinal Chemistry 45 (2010) 3617e3626
3625
(neat) nmax/cmꢂ1: 3335, 1561, 1411, 803. 1H NMR (300 MHz, CDCl3)
supplier’s instructions. HCT-116 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
d
ppm 7.12 (d, J ¼ 8.8 Hz, 2H), 6.7 (d, J ¼ 8.8 Hz, 2H), 6.61 (s,1H), 6.51
(d, J ¼ 2 Hz, 1H), 6.47 (d, J ¼ 8.5 Hz,1H), 6.38 (dd, J ¼ 8.5 Hz, J ¼ 2 Hz,
1H), 6.27 (s, 2H), 3.76 (s, 3H), 3.68 (s, 3H), 3.67 (s, 3H), 3.55 (s, 6H).
13C NMR (75 MHz, CDCl3)
d ppm 159.1, 153.2 (2C), 145.4, 144.9,
140.4, 137.4, 135.9, 135.8, 131.1, 128.5 (2C), 125.9, 121.5, 115.5, 113.6
(2C), 110.2, 107.5 (2C), 61.0, 56.1 (2C), 55.7, 55.3. MS (APCI) m/z:
423.2 (M þ Hþ).
seeded in 96-well plates (5 ꢁ 103 cells/well) containing 50
mL
growth medium. After 24 h of culture, the cells were supplemented
with 50
0.1% in each preparation). After 72 h of incubation, 20
was added for 2 h before recording fluorescence (
m
L of the tested compound dissolved in DMSO (less than
L of resazurin
ex ¼ 560 nm,
m
l
3.6.4. (Z)-2-Methoxy-5-(2-p-tolyl-2-(3,4,5-trimethoxyphenyl)
vinyl)phenol (1e)
lem ¼ 590 nm) using a Victor microtiter plate fluorimeter
Yield: 92%. Anal. calcd for 1e (C25H26O5): C, 73.87; H, 6.45.
Found: C, 73.68; H, 6.34. TLC: Rf 0.33 (cyclohexane/EtOAc: 6/4). IR
(neat) nmax/cmꢂ1: 3650, 2227, 2173, 2082, 2004, 1581, 1510, 1279,
(PerkineElmer,USA). The IC50 corresponds 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.
1126. 1H NMR (300 MHz, CDCl3)
(d, J ¼ 8.0 Hz, 2H), 6.74 (s, 1H), 6.59 (d, J ¼ 2.0 Hz, 1H), 6.56 (d,
J ¼ 8.4 Hz, 1H), 6.47 (dd, J ¼ 2.0 Hz, J ¼ 8.8 Hz, 1H), 6.35 (s, 2H), 3.84
(s, 3H), 3.77 (s, 3H), 3.65 (m, 6H), 2.29 (s, 3H). 13C NMR (75 MHz,
d
ppm 7.17 (d, J ¼ 9.0 Hz, 2H), 7.05
3.7.2. Tubulin binding assay
Sheep brain tubulin was purified according to the method of
Shelanski [57] by two cycles of assemblyedisassembly and then
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
and recorded continuously by turbidimetry at 350 nm in a UV
spectrophotometer equipped with a thermostatted cell at 37 ꢀC.
The GI50 value of each compound was determined as the concen-
tration which decreased the maximum assembly rate of tubulin by
50% compared to the rate in the absence of compound. The GI50
values for all compounds were compared to the GI50 of Ca-4 and
isoCA-4 and measured the same day under the same conditions.
CDCl3)
d ppm 153.6 (2C), 145.6, 145.1, 140.9, 140.5, 137.4 (2C), 136.1,
131.2,129.1 (2C),127.4 (2C),126.9,121.8,115.8,110.3,107.6 (2C), 61.2,
56.3 (2C), 56.0, 21.3. MS (APCI) m/z: 407.0 (M þ Hþ).
3.6.5. (Z)-2-Methoxy-5-(2-(naphthalen-2-yl)-2-(3,4,5-
trimethoxyphenyl) vinyl)phenol (1f)
Yield: 95%. Anal. calcd for 1f (C28H26O5): C, 76.00; H, 5.92.
Found: C, 75.84; H, 5.97. TLC: Rf 0.35 (cyclohexane/EtOAc: 8/2). IR
(neat) nmax/cmꢂ1: 2983, 1737, 1373, 1235, 1054. 1H NMR (300 MHz,
CDCl3)
d
ppm 7.81 (d, J ¼ 9.2 Hz, 1H), 7.81e7.50 (m, 2H), 7.63 (d,
J ¼ 1.8 Hz, 1H), 7.61 (dd, J ¼ 1.9 Hz, J ¼ 3.7 Hz, 1H), 7.44 (d, J ¼ 9.4 Hz,
1H), 7.44 (dd, J ¼ 1.9 Hz, J ¼ 3.1 Hz, 1H), 6.86 (d, J ¼ 1.9 Hz, 1H), 6.82
(dd, J ¼ 1.9 Hz, J ¼ 8.5 Hz,1H), 6.66 (s,1H), 6.76 (d, J ¼ 8.4 Hz,1H). 13C
Acknowledgments
NMR (75 MHz, CDCl3)
d ppm 153.7 (2C), 145.8, 145.2 (2C), 141.0,
140.8, 137.7, 135.9, 133.5, 132.9, 131.1, 128.4, 127.8, 127.7, 126.6, 126.3,
126.0, 125.6, 121.9, 115.8, 110.3, 107.7 (2C), 61.3, 56.3 (2C), 56.0.
The authors gratefully acknowledge support of this project by
CNRS and MNSER for doctoral fellowships to E. R.
3.6.6. (E)-5-(2-(3-Fluoro-4-methoxyphenyl)-2-(3,4,5-
trimethoxyphenyl) vinyl)-2-methoxyphenol (1g)
References
Yield: 53%. Anal. calcd for 1g (C25H25FO6): C, 68.17; H, 5.72.
Found: C, 68.01; H, 5.66. TLC: Rf 0.20 (cyclohexane/EtOAc: 7/3). IR
(neat) nmax/cmꢂ1: 3650, 2983, 2190, 1739, 1373, 1239, 1047. 1H NMR
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1H), 6.63 (d, J ¼ 8.3 Hz, 1H), 6.53 (dd, J ¼ 1.9 Hz, J ¼ 8.4 Hz, 1H), 6.40
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d
ppm 6.88 (d, J ¼ 1.6 Hz,1H), 6.75e6.73 (m, 2H), 6.69 (s,1H), 6.57 (d,
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145.6, 145.4, 145.1, 140.5, 137.5, 136.9, 135.9, 131.1, 126.5, 121.7, 119.4,
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