Synthesis of new mixed phenol/heterocyclic derivatives and studies of their activity as inhibitors of Bax/Bcl-xL interaction

Article abstract of DOI:10.1016/j.tet.2013.11.060

We describe here the synthesis of a series of new molecules containing phenol and heteroaromatic moieties, compounds, which have been evaluated for their ability to inhibit Bax/Bcl-xL interactions in BRET assays. Among them, a triazole derivative 13, exhibit a very promising activity, being more potent than the reference compounds acylpyrogallol 1 and ABT 737. These preliminary results demonstrate that derivatives of this family can be attractive to develop new molecules with potent anticancer activity.

Full text of DOI:10.1016/j.tet.2013.11.060

Tetrahedron 70 (2014) 301e311
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of new mixed phenol/heterocyclic derivatives and studies
of their activity as inhibitors of Bax/Bcl-xL interaction
,
c
,
d
b
b,c
Duc Duy Vo a, Fabien Gautier b , Sophie Barille-Nion , Philippe Juin
,
ꢀ
e
a,
*
ꢀ
ꢀ
Nicolas Levoin , Rene Gree
a
ꢀ
ꢀ ꢀ
Universite de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226, Avenue du General Leclerc, 35042 Rennes Cedex, France
UMR 892 INSERM/6299 CNRS/Universite de Nantes, Team 8 “Cell Survival and Tumor Escape in Breast Cancer”, Institut de Recherche Therapeutique de
b
ꢀ
ꢀ
ꢀ
l’Universite de Nantes, 8 quai Moncousu, BP 70721, 44007 Nantes Cedex 1, France
c
ꢀ
ꢀ
Institut de Cancerologie de l’Ouest, Centre de Lutte contre le Cancer Rene Gauducheau, Boulevard Jacques Monod, 44805 Saint Herblain-Nantes Cedex,
France
d
ꢀ
ꢀ
Plateforme IMPACT, Biogenouest Institut de Recherche Therapeutique de l’Universite de Nantes, 8 quai Moncousu, BP 70721, 44007 Nantes Cedex 1,
France
e
ꢀ
Bioprojet-Biotech, 4 rue du Chesnay Beauregard, BP 96205, 35762 Saint Gregoire, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 August 2013
Received in revised form 13 November 2013
Accepted 18 November 2013
Available online 22 November 2013
We describe here the synthesis of a series of new molecules containing phenol and heteroaromatic
moieties, compounds, which have been evaluated for their ability to inhibit Bax/Bcl-xL interactions in
BRET assays. Among them, a triazole derivative 13, exhibit a very promising activity, being more potent
than the reference compounds acylpyrogallol 1 and ABT 737. These preliminary results demonstrate that
derivatives of this family can be attractive to develop new molecules with potent anticancer activity.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Polyphenol
Cycloaddition
Heterocycles
Cancer
Apoptosis
Bcl-xL
1. Introduction
expression, in particular, is a marker of chemoresistance6 and its
interaction with Bax is critical to maintain cancer cell survival7,8
Escape from apoptosis by cancer cells is considered as a very
important contribution to carcinogenesis.1 The overexpression of
the antiapoptotic Bcl-2 family of proteins (typically Bcl-2, Bcl-xL,
Mcl-1) is frequently observed in cancer cells and is implicated in
their aberrant survival and their resistance to current treatments.2
Inhibition of apoptosis by Bcl-2 homologs relies in great part on
their ability to physically interact with proapoptotic members of
the Bcl-2 family, the multi-domain proteins Bax and Bak and their
upstream effectors the BH3-only proteins. Thus, antiapoptotic Bcl-2
proteins inhibitors, such as ABT 737 and its orally available equiv-
alent, navitoclax that disrupt these interactions in cancer cells, are
of therapeutic interest as they are expected to trigger cell death by
themselves and/or to sensitize cells to chemotherapy.3e5 Bcl-xL
(Fig. 1).
NO2
NH
O
S
O
N
HN
O
N
N
S
Cl
ABT-737
OH
HO
HO
O
OH
O
HO
O
OH
OH
OH
OH
R-(-)-Gossypol
O
1
* Corresponding author. Tel.: þ33 (0)2 23 23 57 15; fax: þ33 (0)2 23 23 69 78;
ꢀ
e-mail address: rene.gree@univ-rennes1.fr (R. Gree).
Fig. 1. Selected inhibitors of Bcl-2 and/or BcL-xL proteins.
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.11.060

302
D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
Polyphenol derivatives are widely used in medicinal chemistry,
O
O
including for anticancer agents.9 For instance, gossypol, which
showed good activities towards Bcl-xL, Bcl-2, and Mcl-1 has en-
tered into clinical trials,10 and various analogues of gossypol have
been designed.11 The derivative 1 demonstrated good activities
against Bcl-2 and Mcl-1.11d It induced apoptosis and cell death as
a single agent in several cancer cell lines. Later developments
showed that the activity can be improved by changing the isopropyl
group of 1 into more bulky groups.11d Molecular docking studies
reported in the literature gave strong indications that for these
series of molecules, the different phenolic OH groups and the
benzophenone carbonyl have important interactions with the
amino acids inside the binding pockets of the antiapoptotic pro-
teins.11 Further, recent results have established that other ana-
logues, based on TW-37 and derivatives, exhibit very promising
properties against Mcl-1.12
O
O
O
O
O
O
O
O
O
a
b
R
R
R
OH
R'
R'
R'
4 (90%)
5 (48%)
6 (95%)
7 (75%)
2: R = R' = Me
3: R = pFPh; R' = H
O
8: R=R'=Me, R''=Bn (85%)
9: R=H, R'=pFPh, R"=Bn (92%)
O
O
O
N
N
c
N
R''
6, 7
10: R=R'=Me,
R
(91%)
R"=
COOEt
R'
OH
OH
HO
O
As part of our program towards new anticancer molecules,13
we reported recently a preliminary structureeactivity relation-
ship study on selected polyphenol derived molecules. We have
first shown that 1 was able to act as Bcl-xL inhibitor. Then, we
have demonstrated that the use of a p-fluorobenzyl group to re-
place the isopropyl substituent in position 5 resulted in an in-
crease of activity (Fig. 2, compound A2). Finally we have
established that the phenol at position 3 had a key role regarding
disruption of Bax/Bcl-xL interaction.14,15 In continuation of these
studies, it appeared interesting to explore the possibility of
replacing the central aromatic ring by either five-membered or
six-membered heteroaromatic systems. In this publication we will
describe the synthesis of representative examples in the two se-
ries: the triazole analogues (for series B) and several hetero-
aromatic compounds (pyrimidines, pyrimidone, and pyridine for
series C). We investigated their ability to inhibit Bax/Bcl-xL in-
teraction, using a previously reported Bioluminescence Resonance
Energy Transfer (BRET) assay in whole live cells.14 We wanted to
analyze if the new polyphenol derivatives retained the ability of
gossypol to interfere with the BH3 binding activity of anti-
apoptotic Bcl-xL protein and because disruption of this in-
teraction is critical to promote cell death.7 Finally, we will briefly
analyze our results by using molecular docking studies.
N
HO
OH
N
N
N
d
N
R''
+
N
R''
R
8, 9
R
O
R'
O
R'
12: R=R'=Me, R''=Bn (25%)
11: R=R'=Me, R''=Bn (17%)
13: R=H, R'=pFPh, R''=Bn (24%) 14: R=H, R'=pFPh, R''=Bn (8%)
Scheme 1. Synthesis of the first series of triazoles derivatives. Reagents and condi-
tions: (a) ethynylmagnesiumbromide, THF, 0 ꢀCert; (b) IBX, DMSO/CHCl3 1/1, 80 ꢀC; (c)
R00N3, CuSO4, Na ascorbate, CHCl3, reflux; (d) BBr3, DCM, ꢁ78 ꢀCert.
OH
O
HO
OR
N
O
O
HO2C
N
N
HO2C
N
N
b
a
N
10
3
3
O
O
16a: R = H 41%
15 90%
16b: R = Me 13%
O
HO
O
O
OH
O
O
O
HO
OR
N
b
N
N
N
HN
c
HN
N
15
N
3
3
OH
3
O
O
O
HO
O
OH
18a: R = H 56%
17 18%
18b: R = Me 20%
5
R
Scheme 2. Synthesis of the second series of triazoles 16 and 18. Reagents and con-
ditions: (a) LiOH, MeOH, 50 ꢀC; (b) BBr3, DCM, ꢁ78 ꢀCert; (c) p-MeOPhNH2, DCC,
DMAP, DCM, rt.
R'
OH
R1
OH
A
HO
OH
HO
OH
N
N
N
X
"
R
N
1: R = R' = Me
R
R
R2
A2: R = pFPh; R' = H
O
R'
O
R'
C
B
Fig. 2. Design of our target molecules.
To explore possible polar interactions inside the binding
pockets of the Bcl-xL protein, it appeared of interest to introduce
functional polar groups on the R00 chain. Therefore, the reaction of
2. Results and discussions
6 with a u-functionalized azide was performed to give the triazole
The synthesis of the triazoles is based on the use of the ‘click
chemistry’,16 as described in Schemes 1 and 2. The key in-
termediates are the propargylic ketones 6 and 7, easily prepared in
two steps and 85% and 36% yield, respectively, from the known
aldehydes 2 and 3.14 Then, reaction with benzyl azide under
copper catalysis gave the desired triazoles 8 and 9. A final
deprotection step afforded mixtures of fully deprotected de-
rivatives 11 and 13 with monoprotected compounds 12 and 14,
separated by silica gel chromatography. For the latter molecules,
the position of the remaining methoxy group, in para position to
the carbonyl substituent, was established by extensive NMR
studies.
10. Saponification gave acid 15 and, after deprotection, a mixture
of 16a and 16b separated by chromatography. On the other hand
coupling with p-methoxyaniline gave amide 17 and, after depro-
tection, the polyphenols targets 18a and 18b were separated by
chromatography.
Based on literature data on the use of bistriazoles as pep-
tidomimetics,17 it appeared interesting to prepare also some
bistriazoles derivatives of this type and this has been per-
formed following the route indicated in Scheme 3. Protection
of the propargylic alcohol 4 gave TBS ether 19, which was
subjected to the addition of the
u-functionalized azide
affording triazole 20.

D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
303
O
O
O
O
O
O
O
N
O
O
O
O
O
O
O
N
EtO2C
N
N
a
b
b
EtO
N
a
19
4
HN
33
3
69%
70%
OTBS
19 94%
OTBS
20 96%
OTBS
OTBS
32
O
O
O
OH
O
O
O
O
O
O
d, e, f
N
N
N
N
O
c
N
HO
O
O
N
e
c, d
N
O
O
O
O
3
3
53%
HN
OTBS
21 55%
O
HN
14%
(2 steps)
22 20%, 3 steps
O
35
OH
34
HO
OR'
O
O
g
N
N
N
N
Scheme 5. Synthesis of the pyrimidone 35. Reagents and conditions: (a) t-BuLi, Et2O,
ꢁ78 ꢀC then ClCOOEt, ꢁ78 ꢀCert; (b) benzamidine, Na2CO3, CH3CN, reflux; (c) TBAF,
THF, rt; (d) IBX, DMSO/CHCl3 1/1, 80 ꢀC; (e) BBr3, DCM, ꢁ78 ꢀCert.
N
N
R
R
3
3
R = Bn
N
N
b
N
N
O
O
N
O
O
N
R = Bn
24a: R' = H 8%
23 80%
24b: R' = Me 8%
A pyridine was also prepared by using the BohlmanneRatz re-
action19 under the conditions described by Bagley (Scheme 6).20
Condensation of the propargylic ketone 25 with ethyl acetoace-
tate and ammonia with catalysis by iodine gave the pyridine 36 in
70% yield. Reaction with BF3$OEt2 gave the lactone 37 and after
a final deprotection step the target 38 was isolated in 44% yield.
Scheme 3. Synthesis of the bistriazoles derivatives 24. Reagents and conditions: (a)
TBSCl, Im, DMAP, DCM, rt; (b) RN3, CuSO4, Na ascorbate, acetone, reflux; (c) DIBAL-H,
THF, ꢁ78 ꢀC; (d) ethynylmagnesiumbromide, THF, 0 ꢀCert; (e) TBAF, THF, rt; (f) IBX,
DMSO/CHCl3 1/1, 80 ꢀC; (g) BBr3, DCM, ꢁ78 ꢀCert.
Dibal-H mediated reduction gave the aldehyde 21, which was
transformed, via the same two-step sequence, into the propargylic
ketone 22. This relatively unstable intermediate was used directly
for the next step where addition of benzyl azide gave the bis tri-
azole 23. Deprotection gave a mixture of the target molecules 24a
and 24b, however in poor yields (8% each, after separation by
chromatography).
The synthesis of the pyrimidines takes also advantage of the
chemistry of propargylic ketones, as indicated in Scheme 4. Met-
alation of propargylic ether 19, followed by trapping with pBr-
benzaldehyde and oxidation with IBX, gave the key intermediate
25. Then, reaction with acetamidine or benzamidine afforded the
desired pyrimidines 26 and 27 in 60% and 75% yield, respectively. A
TBAF-mediated deprotection, followed by oxidation with IBX, gave
the ketones 28 and 29 in 83% overall yield. A final deprotection step
using BBr3 afforded the target molecules, again as mixtures of the
fully deprotected derivatives 30a and 31a with the monoprotected
analogues 30b and 31b, separated by chromatography.
R
O
O
O
O
O
O
O
N
a
R
70%
OTBS
OTBS
R = p-BrPh
EtO
O
36
25
OH
O
R
R
HO
OH
O
O
c
b
N
N
44%
66%
O
38
O
O
37
O
R=p-BrPh
Scheme 6. Synthesis of the pyridine 38. Reagents and conditions: (a) ethyl acetoace-
tate, NH4OAc, (cat) I2, EtOH, 50 ꢀC; (b) BF3$OEt2, THF, 50 ꢀC; (c) BBr3, DCM, ꢁ78 ꢀCert.
3. Results of BRET assays
R'
O
O
O
O
O
O
O
O
O
O
N
N
The biological activity of synthesized molecules was evalu-
ated using a BRET assay, as previously described.14 Results for
the triazoles are reported in Fig. 3. If we consider first the series
a, b
c
R
R
R = p-BrPh
R = p-BrPh
OTBS
OTBS
19
OTBS
25 50%, 2 steps
26: R'=Me 60%
27: R'=Ph 75%
R'
OH
R'
O
O
HO
O
OR''
O
N
N
e
BRET Activity
d, b
N
N
26
27
2.0
O
Br
Br
30a: R'=Me, R''=H 21%
30b: R'=Me, R''=Me 10%
31a: R'=Ph, R''=H 13%
31b: R'=Ph, R''=Me 13%
28 R'=Me 83%
29 R'=Ph 83%
1.6
1.2
0.8
0.4
0.0
Scheme 4. Synthesis of the pyrimidines 30 and 31. Reagents and conditions: (a) t-BuLi,
Et2O, ꢁ78 ꢀC then RCHO, ꢁ78 ꢀCert; (b) IBX, DMSO/CHCl3 1/1, 80 ꢀC; (c) amidine
derivatives, Na2CO3, CH3CN, reflux; (d) TBAF, THF, rt; (e) BBr3, DCM, ꢁ78 ꢀCert.
A pyrimidone18 was also prepared by the route indicated in
Scheme 5. The ester 32 was prepared in 70% yield from 19 by
metalation and trapping with ethyl chloroformate. Then, reaction
with benzamidine gave the pyrimidone 33 in 69% yield. Starting
from 33, the same sequence of reactions as described for the py-
rimidines afforded the ketone 34. The final deprotection proved to
be difficult and only the monoprotected derivative 35 could be
obtained, albeit in low yield (14% after chromatography).
Compounds
Fig. 3. BRET activity regarding disruption of Bax/Bcl-xL interaction, for the triazoles
series (Unt: not treated).

304
D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
i
with the Pr chain, we see that the introduction of the triazole
unit is not beneficial since compounds 11 and 12 are less active
than the acylpyrogallol reference molecule 1. Replacement of
the benzyl group with more polar substituents, like in 16a and
18a, is leading to inactive compounds. On the other hand, the bis
triazole derivatives 24a and 24b are also nonactive molecules.
A
i
We have shown previously that replacement of the Pr unit by
a p-fluorobenzyl substituent improved the activity of the acyl-
pyrogallol-type molecules affording a compound as active as the
ABT 737. This proved to be true also here since the analogue
bearing this side chain 13 was found to be very active: it is not
only better than the acylpyrogallol 1 but also much more active
than the classical reference in these series, the ABT 737. Al-
though less potent, the monomethoxy analogue 14 is still in the
same range of activity as the ABT 737.
B
The results for the six-membered analogues are reported in
Fig. 4. Pyrimidine 30b, pyrimidone 35, and pyridine 38 exhibit an
activity in the same range as the acylpyrogallol reference com-
pound 1 but they are less active than the ABT 737. On the other
hand 30a and 31a are inactive compounds.
BRET Activity
2.0
1.6
1.2
0.8
0.4
0.0
Fig. 5. (A) Docking of reference compound 1 in the Bcl-xL binding site. The protein is
represented by its Connolly surface, colored according to the electrostatic potential,
from red (negative) to blue (positive). (B) Putative binding mode of reference com-
pound A2.
The triazoles have very similar binding mode (Fig. 6). The small
increase of affinity for compound 13 versus A2 is probably due to
the reduced hydrophobicity of the molecule, in a solvent-exposed
binding site (clog P¼ꢁ0.2 for triazole vs 1.8 for phenyl). On the
contrary, the polyphenol of pyrimidines can’t form any HB. Burying
Compounds
Fig. 4. BRET activity regarding disruption of Bax/Bcl-xL interaction, for the six-
membered derivatives (NT: not treated).
i
of the Pr in the hydrophobic cavity forced the hydroxyls to be
solvent-exposed (Fig. 7A). The polyphenol of pyridine compound
38 is also away from Glu96, but the g-butyrolactone is able to form
HB with Arg100, and the bromophenol suits well to the hydro-
phobic cavity (Fig. 7B).
Determination of the ligand-binding site resulted from a pipe-
line of molecular modeling protocols involving pharmacophore
definition, protein flexibility analysis, and ligand docking.21 The
identified region corresponds roughly to the tetrahydro-naphtalen-
1-ol’s site 2, or Ile85 binding crevice of Bak peptide.4a Docking of
the present series suggested that molecules share a common
binding mode. However, the precise interacting amino acids vary
between compounds. The inhibitors are always inserted in the
subcavity edged by Glu96, Tyr195, Trp137, and Glu92. Glu96 often
forms hydrogen bonds (HB) with the polyphenol of the ligands, and
Tyr195 is often engaged in p-stacking interaction. Fig. 5A shows the
predicted binding mode of reference compound 1, forming 2 HB
with Glu96, one with Arg100, and its phenolic ring stacked with
Tyr195. The diphenyl-ether fills the cavity formed by Asn136,
i
Phe191, and Trp137. The Pr group is relatively solvent-exposed.
Although sharing the same chemical scaffold, reference com-
pound A2 undergoes a slight translation in the binding site, with
ꢁ
a polyphenol centroïd displacement of 1.5 A. The HB with Glu96 is
conserved, but Tyr195 makes now
p-stacking with the p-fluo-
rophenyl, whose fluorine forms halogen bond with Glu92 (Fig. 5B).
A HB is gained between the ketone and Tyr101. These novel in-
teractions explain certainly the higher affinity of compound A2 as
compared to compound 1.
Fig. 6. Docking of triazole 13. Key amino acids are labeled, and precise intermolecular
interactions symbolized by dotted lines.

D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
305
tetramethylsilane (TMS), using [
reference. 13C NMR spectra:
using [
were designated as singlet (s), doublet (d), triplet (t), quadruplet
(q), multiplet (m) or br (broad). Mass spectral analyses have been
d
(CHCl3)¼7.26 ppm] as internal
A
d
(C) are given in ppm relative to TMS,
(CDCl3)¼77.0 ppm] as internal reference. Multiplicities
d
ꢀ
performed at the Centre Regional de Mesures Physiques de l’Ouest
(CRMPO) in Rennes (France).
4.2. Preparation of phenolic triazole-containing compounds
11e14, 16a, 16b, 18a, 18b, 24a, 24b
4.2.1. Propargylic alcohol 4. To a solution of aldehyde 2 (1 g,
4.2 mmol) in THF (5 ml) under nitrogen at 0 ꢀC was added dropwise
ethynyl magnesium bromide (8.4 ml, 2 equiv, 0.5 M in THF). The
reaction mixture was stirred for 2 h. The reaction mixture was
quenched with a saturated ammonium chloride solution and
extracted with Et2O. The combined organic layer was dried over
MgSO4 and concentrated under reduced pressure. The crude
product was purified on a silica gel column using a 9/1 mixture of
pentane/EA as eluent to afford 4 (1 g, 90%) as a light yellow viscous
B
oil. 1H NMR (300 MHz, CDCl3)
d
(ppm): 7.09 (s, 1H), 5.54 (dd, J¼7.2,
2.4 Hz, 1H), 4.00 (s, 3H), 3.90 (s, 3H), 3.88 (s, 3H), 3.28 (st, J¼6.9 Hz,
1H), 3.14 (d, J¼7.2 Hz, 1H, OH) 2.63 (d, J¼2.3 Hz, 1H), 1.20 (d,
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 151.5, 149.2, 146.0,
137.7, 128.8, 119.4, 84.1, 73.9, 61.4, 61.2, 61.1, 60.5, 26.9, 23.4. HRMS
(EIþ): C15H20O4 Mþ m/z, calcd 264.1362, found 264.1355.
4.2.2. Propargylic alcohol 5. Procedure used for compound 4 was
applied for compound 5. The reaction was performed with 3
(761 mg, 2.5 mmol), 0.5 M of ethynyl magnesium bromide solution
in THF (7.5 ml, 1.5 equiv) and THF (5 ml) to afford 5 (394 mg, 48%) as
Fig. 7. (A) Predicted binding mode of pyrimidine 30a. (B) Docking of pyridine 38.
a light yellow viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm): 7.14
In conclusion, synthetic strategies based on the use of prop-
argylic derivatives allowed efficient preparations of the mixed
heteroaromatic-polyphenol target molecules. Some of these com-
pounds (triazole, pyrimidone, pyridine) appear as attractive new
structures for further design of Bax/Bcl-xL inhibitors. Especially the
triazole 13, which is more potent than ABT 737 in disrupting Bax/
Bcl-xL interaction, is a promising hit for extended biological stud-
ies. Molecular docking gave a rationale for the interactions of these
molecules with Bcl-xL and will be of much use for optimization of
their inhibitory properties. Corresponding studies are under de-
velopment in our groups and will be reported in due course.
(dd, J¼5.5, 8.6 Hz, 2H), 7.00 (s, 1H), 6.97 (t, J¼8.7 Hz, 2H), 5.50 (d,
J¼1.7 Hz,1H), 3.98 (s, 3H), 3.89 (s, 2H), 3.88 (s, 3H), 3.72 (s, 3H), 3.03
(br s, 1H), 2.61 (d, J¼2.3 Hz, 1H). 13C NMR (75 MHz, CDCl3)
d (ppm):
161.3 (d, J¼243.7 Hz), 152.3, 150.2, 146.3, 136.4 (d, J¼3.2 Hz), 130.1
(d, J¼7.8 Hz), 130.0, 128.8, 123.2,115.0 (d, J¼21.2 Hz), 83.9, 74.0, 61.2,
61.1, 60.6, 60.5, 35.2. 19F NMR (282.4 MHz, CDCl3)
d
(ppm): ꢁ117.5.
HRMS (ESIþ): C19H19O4FNa [MþNa]þ m/z, calcd 353.1165,
found 353.1165.
4.3. General procedure 1 for oxidation with IBX, example:
preparation of compound 6
4. Experimental section
4.1. General information
4.3.1. Propargylic ketone 6. A solution of alcohol 4 (1.46 g,
6.2 mmol), IBX (4.66 g, 3 equiv) in a 1/1 mixture of CHCl3/DMSO
(10 ml) was heated under reflux for 2 h until total consumption of
alcohol. After cooling down, the mixture was poured into water and
filtered on Celite. The solution was then extracted with Et2O,
washed with water and brine. The combined organic layers were
dried over MgSO4 and concentrated under reduced pressure. The
crude product was purified on a silica gel column using a 9/1
mixture pentane/ether as eluent to afford 6 (1.42 g, 95%) as a yellow
All reagents were obtained commercially and used without
further purification. All reactions have been carried out under
a nitrogen atmosphere and anhydrous conditions. The solvents
used were freshly distilled under anhydrous conditions, unless
otherwise specified. The reaction mixtures have been magnetically
stirred with Teflon stirring bars, and the temperatures were mea-
sured externally. Reactions that require anhydrous conditions have
been carried out by using oven dried (120 ꢀC, 24 h) glassware.
Yields refer to chromatographically and spectroscopically (1H and
13C NMR) homogeneous materials, and the reactions have been
monitored by thin layer chromatography (TLC), carried out on
0.25 mm Merck silica gel plates (60 F254). The eluents used were
mixtures of pentane and ethyl acetate (EA), with detection by UV
light, or a p-anisaldehyde staining solution. Acros silica gel (60,
particle size 0.040e0.063 mm) was used for column chromatog-
raphy. Nuclear magnetic resonance (NMR) spectra have been
recorded with Bruker Avance 400 and 300 spectrometers. 1H NMR
oil. 1H NMR (300 MHz, CDCl3)
d (ppm): 7.64 (s,1H), 3.99 (s, 3H), 3.98
(s, 3H), 3.90 (s, 3H), 3.40 (s, 1H), 3.26 (st, J¼6.9 Hz, 1H), 1.23 (d,
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 175.1, 156.8, 153.6,
146.1, 137.6, 125.9, 123.8, 82.5, 78.9, 61.5, 61.1, 60.7, 27.0, 23.0. HRMS
(EIþ): C15H28O4 Mþ. m/z, calcd 262.1205, found 262.1202.
4.3.2. Propargylic ketone 7. According to general procedure 1, the
reaction was performed with 5 (374 mg, 1.13 mmol), IBX (476 mg,
1.5 equiv), and a 3/1 mixture CHCl3/DMSO (4 ml) to afford 7
(278 mg, 75%) as a yellow oil. 1H NMR (300 MHz, CDCl3)
d (ppm):
7.55 (s, 1H), 7.14 (dd, J¼5.4, 8.7 Hz, 2H), 6.96 (t, J¼8.7 Hz, 2H), 3.96
(s, 3H), 3.89 (s, 2H), 3.87 (s, 3H), 3.82 (s, 3H), 3.37 (s, 1H). 13C NMR
spectra:
d
(H) are given in parts per million relative to
(75 MHz, CDCl3)
d
(ppm): 174.8, 161.3 (d, J¼244.0 Hz), 157.2, 154.6,

306
D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
146.3, 135.9 (d, J¼3.2 Hz), 130.0 (d, J¼7.8 Hz), 127.5, 125.8, 115.1 (d,
J¼21.2 Hz), 82.4, 79.1, 61.6, 60.8, 60.7, 35.4. 19F NMR (282.4 MHz,
5H), 5.79 (s, 2H), 3.29 (st, J¼6.9 Hz, 1H), 1.27 (d, J¼6.9 Hz, 6H). 13
C
NMR (75 MHz, CDCl3)
d (ppm): 188.4, 152.6, 151.3, 149.1, 136.3,
CDCl3)
d
(ppm): ꢁ117.2. HRMS (ESIþ): C19H17O4FNa [MþNa]þ m/z,
132.2, 130.2, 129.8, 129.4, 129.2, 127.8, 123.2, 112.9, 54.6, 27.8, 23.0.
HRMS (ESIþ): C19H19N3O4Na [MþNa]þ m/z, calcd 376.1273,
found 376.1261.
calcd 351.1008, found 351.1009.
4.4. General procedure 2 for click chemistry, example: prep-
aration of compound 8
4.5.2. Triazole 12. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.70 (s, 1H),
8.65 (s, 1H), 8.15 (s, 1H), 7.48e7.33 (m, 5H), 5.61 (s, 2H), 5.57 (br s,
4.4.1. Triazole 8. A solution of propargyl ketone
2.82 mmol), benzyl azide (413 mg,1.1 equiv), copper (II) sulfate (36 mg,
0.05 equiv), sodium ascorbate (282 l, 0.1 equiv, 1 M in H2O) in CHCl3
6
(740 mg,
1H), 4.04 (s, 3H), 3.25 (st, J¼6.9 Hz, 1H), 1.25 (d, J¼6.9 Hz, 6H). 13
C
NMR (75 MHz, CDCl3)
d (ppm): 187.8, 151.0, 150.8, 148.4, 136.6,
m
133.5, 133.2, 129.4, 129.2, 128.5, 128.4, 121.6, 114.5, 60.6, 54.5, 27.2,
23.3. HRMS (ESIþ): C20H21N3O4Na [MþNa]þ m/z, calcd 390.1430,
found 390.1433.
(3 ml) was stirred under reflux for 2 h. After cooling down, the mixture
was added 25% NH4OH solution and then extracted with ethyl acetate.
The combined organic phases were dried over MgSO4 and concen-
trated in vacuo. The product was purified on a silica gel column with
a 7/3 mixture of pentane/AcOEt as eluent to afford 8 (950 mg, 85%) as
4.5.3. Triazole 13. According to general procedure 3, the reaction
was performed with 9 (270 mg, 0.59 mmol), 1 M of BBr3 solution in
DCM (5.9 ml, 10 equiv) and DCM (10 ml) to afford 13 (60 mg, 24%)
and 14 (20 mg, 8%) as yellow solids. 1H NMR (300 MHz, CDCl3)
awhite solid.1H NMR (300 MHz, CDCl3)
d(ppm): 8.06(s,1H), 7.42e7.30
(m, 5H), 7.23 (s, 1H), 5.59 (s, 2H), 3.94 (s, 3H), 3.89 (s, 3H), 3.82 (s, 3H),
3.26 (st, J¼6.9 Hz, 1H), 1.22 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d
(ppm): 12.81 (br s,1H), 8.50 (s,1H), 8.07 (s,1H), 7.36e7.26 (m, 5H),
7.18 (dd, J¼5.4, 8.8 Hz, 2H), 6.88 (t, J¼8.7 Hz, 2H), 5.55 (s, 2H), 3.91
(s, 2H). 13C NMR (75 MHz, CDCl3)
(ppm): 187.2, 161.1 (d,
d
(ppm): 187.2, 154.7, 151.1, 148.7, 145.9, 137.3, 133.8, 129.3, 129.1, 128.3,
127.8, 127.1, 122.3, 61.8, 61.1, 60.6, 54.4, 27.0, 23.2. HRMS (ESIþ):
d
C
22H25N3O4Na [MþNa]þ m/z, calcd 418.1743, found 418.1742.
J¼244.0 Hz), 152.0, 150.3, 148.3, 136.5 (d, J¼3.2 Hz), 133.6, 131.3,
129.9 (d, J¼7.8 Hz), 129.2, 129.1, 128.2, 128.1, 126.4, 119.8, 114.9 (d,
J¼21.3 Hz), 114.6, 112.3, 54.3, 34.8. 19F NMR (282.4 MHz, CDCl3)
4.4.2. Triazole 9. According to general procedure 2, the reaction
was performed with 7 (231 mg, 0.7 mmol), CuSO4$5H2O (8.75 mg,
d
(ppm): ꢁ117.4. HRMS (ESIþ): C23H18N3O4FNa [MþNa]þ m/z, calcd
0.05 equiv), 1 M sodium ascorbate solution (70
azide (140.5 mg, 1.5 equiv), and CHCl3 (4 ml) to afford 9 (297 mg,
92%) as a white solid. 1H NMR (300 MHz, CDCl3)
(ppm): 8.03 (s,
ml, 0.1 equiv), benzyl
442.1179, found 442.1177.
d
4.5.4. Triazole 14. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.82 (s, 1H),
1H), 7.43e7.37 (m, 3H), 7.34e7.27 (m, 2H), 7.18e7.12 (m, 3H), 6.93
(d, J¼8.7 Hz, 2H), 5.58 (s, 2H), 3.90 (s, 2H), 3.86 (s, 3H), 3.84 (s, 3H),
8.60 (s, 1H), 8.12 (s, 1H), 7.42e7.33 (m, 5H), 7.19 (dd, J¼5.4, 8.8 Hz,
2H), 6.94 (t, J¼8.7 Hz, 2H), 5.60 (s, 2H), 5.59 (br s, 1H), 3.93 (s, 2H),
3.78 (s, 3H). 13C NMR (75 MHz, CDCl3)
d
(ppm): 186.7, 161.3 (d,
3.88 (s, 3H). 13C NMR (75 MHz, CDCl3)
d (ppm): 187.6, 161.3 (d,
J¼243.7 Hz), 155.1, 152.1, 148.5, 146.2, 136.2 (d, J¼3.2 Hz), 133.7,
130.2 (d, J¼7.8 Hz), 129.6, 129.3, 129.1, 128.3, 127.6, 127.0, 125.9,
115.0 (d, J¼21.2 Hz), 61.8, 60.7, 60.6, 54.4, 35.3. 19F NMR (282.4 MHz,
J¼244.0 Hz), 152.0, 151.0, 148.3, 136.8 (d, J¼3.2 Hz), 136.7, 133.5,
130.0 (d, J¼7.8 Hz), 129.4, 129.3, 128.5, 128.4, 125.5, 125.2, 114.9 (d,
J¼21.3 Hz), 114.2, 60.3, 54.5, 35.7. 19F NMR (282.4 MHz, CDCl3)
CDCl3)
d
(ppm): ꢁ117.5. HRMS (ESIþ): C26H24N3O4Na [MþNa]þ m/z,
d
(ppm): ꢁ117.3. HRMS (ESIþ): C24H20N3O4FNa [MþNa]þ m/z, calcd
calcd 484.1643, found 484.1646.
456.1336, found 456.1334.
4.4.3. Triazole 10. According to general procedure 2, the reaction
was performed with 6 (660 mg, 2.52 mmol), CuSO4$5H2O (31.5 mg,
4.5.5. Triazole 15. A solution of triazole 10 (306 mg, 0.73 mmol)
with LiOH (61.3 mg, 2 equiv) in MeOH (2 ml) was stirred at 40 ꢀC for
1 h. After cooling down to rt, the mixture was neutralized with
a 10% HCl solution, and then extracted with EA. The combined or-
ganic layers were dried over MgSO4 and concentrated under re-
duced pressure to give triazole acid 15 (257 mg, 90%) as a white
0.05 equiv),1 M sodium ascorbate solution (252
(435 mg, 1.1 equiv), and CHCl3 (3 ml) to afford 10 (987 mg, 91%) as
a colorless viscous oil. 1H NMR (300 MHz, CDCl3)
(ppm): 8.17 (s,
ml, 0.1 equiv), azide
d
1H), 7.23 (s, 1H), 4.52 (t, J¼6.9 Hz, 2H), 4.14 (q, J¼7.2 Hz, 2H), 3.94 (s,
3H), 3.89 (s, 3H), 3.83 (s, 3H), 3.26 (st, J¼6.9 Hz, 1H), 2.38 (t,
J¼6.9 Hz, 2H), 2.28 (qn, J¼6.9 Hz, 2H), 1.26 (t, J¼7.2 Hz, 3H), 1.21 (d,
solid. 1H NMR (300 MHz, CDCl3)
d (ppm): 9.06 (br s,1H), 8.21 (s,1H),
7.23 (s, 1H), 4.54 (t, J¼6.9 Hz, 2H), 3.93 (s, 3H), 3.88 (s, 3H), 3.82 (s,
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 187.1, 172.1, 154.6,
3H), 3.26 (st, J¼6.9 Hz, 1H), 2.44 (qn, J¼6.9 Hz, 2H), 2.29 (t, J¼6.9 Hz,
151.1, 148.4, 145.9, 137.3, 127.9, 127.4, 122.3, 61.8, 61.1, 60.8, 60.6,
49.5, 30.5, 27.0, 25.3, 23.2, 14.2. HRMS (ESIþ): C21H29N3O6Na
[MþNa]þ m/z, calcd 442.1954, found 442.1953.
2H), 1.20 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 187.1,
177.1, 154.8, 151.1, 148.3, 145.9, 137.5, 127.8, 127.6, 122.3, 61.9, 61.2,
60.7, 49.4, 30.2, 27.0, 25.1, 23.3. HRMS (ESIþ): C19H25N3O6Na
[MþNa]þ m/z, calcd 414.1641, found 414.1638.
4.5. General procedure 3 for demethylation with BBr3, ex-
ample: preparation of compounds 11 and 12
4.5.6. Triazole 16a. According to general procedure 3, the reaction
was performed with 15 (60 mg, 0.15 mmol), 1 M of BBr3 solution in
DCM (2.0 ml, 13.3 equiv) and DCM (3 ml). A purification on silica gel
(eluent: pentane/EA 7/3) afford 16a (22 mg, 41%) and 16b (7 mg,
To a solution of compound 8 (178 mg, 0.45 mmol) was added
dropwise BBr3 (5.4 ml, 12 equiv, 1 M in CH2Cl2) in CH2Cl2 (4 ml) at
ꢁ78 ꢀC under nitrogen. The reaction mixture was allowed to come
back to rt and stirred for 6 h in dark. The mixture was then cooled
again to 0 ꢀC and after addition of water, it was diluted with CH2Cl2,
stirred for 1 h before extraction with CH2Cl2. The combined organic
layers were dried over MgSO4 and concentrated under reduced
pressure. The crude product was purified on a silica gel column
using a 7/3 mixture pentane/EA as eluent to afford polyphenolic
compounds 11 (40 mg, 25%) and 12 (28 mg, 17%) as yellow solids.
13%) as yellow solids. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.85 (s,
1H), 8.70 (s, 1H), 8.26 (s, 1H), 6.15 (br s, 1H), 5.62 (br s, 1H), 4.55 (m,
J¼6.7 Hz, 2H), 3.24 (m, J¼6.9 Hz, 1H), 2.46e2.26 (m, 4H), 1.29 (d,
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 187.4, 172.6, 150.2,
148.7, 148.4, 130.4, 128.6, 127.3, 123.0, 112.5, 51.9, 49.5, 30.3, 27.2,
25.3, 22.5. HRMS (ESIþ): C16H19N3O6Na [MþNa]þ m/z, calcd
372.1172, found 372.1170.
4.5.7. Triazole 16b. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.75 (s,
4.5.1. Triazole 11. 1H NMR (300 MHz, acetone-d6)
1H), 8.76 (s, 1H), 8.71 (s, 1H), 8.52 (s, 1H), 8.02 (s, 1H), 7.35e7.23 (m,
d
(ppm): 12.93 (s,
1H), 8.66 (s, 1H), 8.27 (s, 1H), 5.61 (br s, 1H), 4.55 (t, J¼6.7 Hz, 2H),
4.05 (s, 3H), 3.25 (st, J¼6.9 Hz, 1H), 2.47e2.24 (m, 4H), 1.26 (d,

D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
307
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d
(ppm): 187.8, 172.5, 151.0,
to afford 20 (464 mg, 96%) as a white solid. 1H NMR (300 MHz,
CDCl3) (ppm): 7.30 (s, 1H), 7.13 (s, 1H), 6.24 (s, 1H), 4.36 (t,
J¼6.9 Hz, 2H), 4.12 (q, J¼7.2 Hz, 2H), 3.86 (s, 3H), 3.84 (s, 3H), 3.75 (s,
3H), 3.24 (m, J¼6.9 Hz, 1H), 2.30 (t, J¼6.9 Hz, 2H), 2.18 (m, J¼6.9 Hz,
2H), 1.23 (t, J¼7.2 Hz, 3H), 1.17 (d, J¼6.9 Hz, 3H), 1.16 (d, J¼6.9 Hz,
3H), 0.87 (s, 9H), 0.02 (s, 3H), 0.01 (s, 3H). 13C NMR (75 MHz, CDCl3)
150.8, 148.3, 136.6, 133.2, 128.7, 121.6, 114.6, 60.6, 51.9, 49.6, 30.3,
27.3, 25.3, 23.3. HRMS (ESIþ): C17H21N3O6Na [MþNa]þ m/z, calcd
386.1328, found 386.1328.
d
4.5.8. Triazole 17. A solution of triazole acid 15 (237 mg,
0.61 mmol), DCC (138 mg, 1.1 equiv), DMAP (4.7 mg, 0.06 equiv) in
CH2Cl2 (3 ml) was stirred for 15 min at rt. To the mixture was then
added p-methoxyaniline (113 mg, 1.5 equiv) and it was stirred
overnight at rt. The mixture was then concentrated under reduced
pressure and purified on a silica gel column to afford triazole amide
17 (55 mg, 18%) as a light yellow viscous oil. 1H NMR (300 MHz,
d
(ppm): 172.4, 152.8, 150.4, 148.2, 145.6, 137.3, 131.8, 121.1, 118.6,
61.1, 60.9, 60.6, 60.5, 49.0, 30.6, 26.7, 25.8, 25.5, 23.6, 23.5, 18.2, 14.2,
ꢁ4.9, ꢁ5.0. HRMS (ESIþ): C27H45N3O6SiNa [MþNa]þ m/z, calcd
558.2975, found 558.2972.
4.5.13. Triazole 21. To a solution of triazole ester 20 (416 mg,
0.78 mmol) in DCM (3 ml) at ꢁ78 ꢀC under nitrogen, was added
dropwise a 1 M DIBAL solution in hexane (0.78 ml, 1 equiv). The
reaction mixture was stirred and warmed up from ꢁ78 ꢀC to
ꢁ40 ꢀC for 2 h and 30 min. This mixture was quenched, at rt, with
a 1 M sodium tartrate solution and stirred for 30 min and then it
was extracted with DCM. The organic phase was concentrated in
vacuo and the product was purified on a silica gel column with
a 7/3 mixture of pentane/AcOEt as eluent to afford 21 (210 mg,
55%) as a colorless viscous oil. 1H NMR (300 MHz, CDCl3)
CDCl3)
d
(ppm): 8.18 (s, 1H), 8.00 (s, 1H), 7.37 (d, J¼9.0 Hz, 2H), 7.19
(s, 1H), 6.80 (d, J¼9.0 Hz, 2H), 4.54 (t, J¼6.2 Hz, 2H), 3.92 (s, 3H),
3.86 (s, 3H), 3.79 (s, 3H), 3.75 (s, 3H), 3.24 (st, J¼6.9 Hz, 1H),
2.39e2.26 (m, 4H), 1.18 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d
(ppm): 186.9, 169.5, 156.3, 154.6, 150.9, 148.1, 145.9, 137.5, 130.8,
127.9, 127.8, 122.1, 121.8, 114.0, 61.9, 61.0, 60.6, 55.4, 49.5, 33.0, 27.0,
25.9, 23.2. HRMS (ESIþ): C26H32N4O6Na [MþNa]þ m/z, calcd
519.2219, found 519.2220.
4.5.9. Triazole 18a. According to general procedure 3, the reaction
was performed with 17 (34.5 mg, 0.07 mmol), 1 M of BBr3 solution
in DCM (1.12 ml, 16 equiv) and DCM (3 ml). A purification by HPLC
on a reverse column using gradient mixture of ACN/H2O as eluent
afford 18a (16 mg, 56%) and 18b (6 mg, 20%) as yellow solids. 1H
d (ppm): 9.75 (s, 1H), 7.31 (s, 1H), 7.15 (s, 1H), 6.27 (s, 1H), 4.36 (t,
J¼6.9 Hz, 2H), 3.89 (s, 3H), 3.87 (s, 3H), 3.79 (s, 3H), 3.27 (st,
J¼6.9 Hz, 1H), 2.54 (t, J¼6.9 Hz, 2H), 2.21 (qn, J¼6.9 Hz, 2H), 1.21
(d, J¼6.9 Hz, 3H), 1.19 (d, J¼6.9 Hz, 3H), 0.91 (s, 9H), 0.05 (s, 3H),
0.04 (s, 3H). 13C NMR (75 MHz, CDCl3)
d (ppm): 200.5, 153.0,
NMR (300 MHz, acetone-d6)
d
(ppm): 12.99 (br s, 1H), 9.01 (br s,
150.4, 148.2, 145.6, 137.3, 131.8, 121.1, 118.6, 64.8, 61.1, 61.0, 60.5,
48.9, 40.3, 26.7, 25.8, 23.7, 23.6, 22.7, 18.3, ꢁ4.8, ꢁ4.9. HRMS
(ESIþ): C25H41N3O5SiNa [MþNa]þ m/z, calcd 514.2713,
found 514.2710.
1H), 8.79 (s, 1H), 8.72 (s, 1H), 7.45 (d, J¼8.8 Hz, 2H), 6.75 (d,
J¼8.8 Hz, 2H), 4.66 (t, J¼6.6 Hz, 2H), 3.28 (st, J¼6.9 Hz, 1H),
2.48e2.29 (m, 4H), 1.27 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, ace-
tone-d6) d (ppm): 188.5, 172.0, 170.0, 154.3, 151.3, 148.8, 132.4,132.3,
130.5, 127.8, 123.1, 121.8, 121.7, 115.9, 112.9, 50.5, 33.7, 27.8, 26.6,
23.3, 23.0. HRMS (ESIþ): C23H26N4O6Na [MþNa]þ m/z, calcd
477.1750, found 477.1752.
4.5.14. Triazole 22. Firstly procedure used for compound 4 was
applied. The reaction was performed with aldehyde 21 (290 mg,
0.59 mmol), 0.5 M of ethynyl magnesium bromide solution in THF
(2.4 ml, 2 equiv) and THF (7 ml) to afford alcohol intermediate
(199 mg) as a colorless viscous oil. Secondly, to a solution of this
alcohol (199 mg, 0.39 mmol) in THF (2 ml) at rt, was added
dropwise TBAF (0.77 ml, 2 equiv, 1 M in THF). The reaction mixture
was stirred at rt for 1 h and then quenched with a saturated
ammonium chloride solution. Then the mixture was extracted
with EA, dried over MgSO4, and concentrated under reduced
pressure. The residue was purified on a silica gel column chro-
matography using mixture pentane/EA 5/5 to afford diol in-
termediate (73 mg) as a colorless viscous oil. Lastly, this diol
intermediate (73 mg, 0.18 mmol) was oxidized by using general
procedure 1 with IBX (304 mg, 6 equiv) and the 1/1 mixture
CHCl3/DMSO (4 ml). Purification on silica gel (eluent: pentane/EA
7/3) afford dione 22 (48 mg, 20%, three steps) as a colorless vis-
cous oil. This relatively labile compound was used directly for the
4.5.10. Triazole 18b. 1H NMR (300 MHz, acetone-d6)
d (ppm): 12.84
(s, 1H), 8.99 (br s, 1H), 8.78 (s, 1H), 8.76 (s, 1H), 8.15 (br s, 1H), 7.80
(br s, 1H), 7.45 (d, J¼8.8 Hz, 2H), 6.75 (d, J¼8.8 Hz, 2H), 4.67 (t,
J¼6.5 Hz, 2H), 4.03 (s, 3H), 3.25 (st, J¼6.9 Hz, 1H), 2.48e2.30 (m,
4H), 1.24 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, acetone-d6)
d (ppm):
189.2,170.0,154.3,153.1,152.3,149.0,148.6,1333,132.5,130.9,121.8,
121.7,121.6, 115.9,115.8,115.5, 60.7, 50.6, 33.7, 27.9, 26.6, 23.7. HRMS
(ESIþ):
found 463.1592.
C22H24N4O6Na
[MþNa]þ
m/z,
calcd
463.1594,
4.5.11. Triazole 19. A solution of propargyl alcohol 4 (1.22 g,
4.62 mmol), TBSCl (834.4 mg, 1.2 equiv), imidazole (440 mg,
1.4 equiv), and DMAP (789 mg, 1.4 equiv) in CH2Cl2 (3 ml) was
stirred for overnight under nitrogen at rt. To the reaction mixture
was then added a saturated ammonium chloride solution and it
was extracted with CH2Cl2. The combined organic layers were dried
over Mg2SO4 and concentrated under reduced pressure. The crude
product was purified on a silica gel column using a 95/5 mixture
pentane/ether as eluent to afford 19 (1.64 g, 94%) as a colorless
next step. 1H NMR (300 MHz, CDCl3)
d (ppm): 8.17 (s, 1H), 7.24 (s,
1H), 4.49 (t, J¼6.9 Hz, 2H), 3.94 (s, 3H), 3.89 (s, 3H), 3.84 (s, 3H),
3.28 (s, 1H), 3.26 (st, J¼6.9 Hz, 1H), 2.71 (t, J¼6.9 Hz, 2H), 2.31 (qn,
J¼6.9 Hz, 2H), 1.21 (d, J¼6.9 Hz, 6H). HRMS (ESIþ): C21H25N3O5Na
[MþNa]þ m/z, calcd 422.1692, found 422.1690.
viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm): 7.24 (s, 1H), 5.73 (d,
J¼2.3 Hz, 1H), 3.92 (s, 3H), 3.90 (s, 3H), 3.87 (s, 3H), 3.27 (st,
J¼6.9 Hz, 1H), 2.49 (d, J¼2.2 Hz, 1H), 1.22 (d, J¼6.9 Hz, 3H), 1.20 (d,
J¼6.9 Hz, 3H), 0.93 (s, 9H), 0.18 (s, 3H), 0.11 (s, 3H). 13C NMR
4.5.15. Triazole 23. According to general procedure 2, the reaction
was performed with 32 (48 mg, 0.12 mmol), CuSO4$5H2O (3 mg,
0.10 equiv), 1 M sodium ascorbate solution (24
azide derivative (31.9 mg, 2 equiv), and CHCl3 (2 ml) to afford 33
(55 mg, 86%) as a white solid. 1H NMR (300 MHz, CDCl3)
(ppm):
ml, 0.2 equiv), benzyl
(75 MHz, CDCl3) d (ppm): 150.8,148.0,145.5,137.4,130.1,118.5, 85.5,
72.2, 61.1, 60.9, 60.5, 59.3, 26.7, 25.8, 23.6, 23.5, 18.3, ꢁ4.9. HRMS
d
(ESIþ): C21H34O4SiNa [MþNa]þ m/z, calcd 401.2124, found 401.2124.
8.19 (s, 1H), 7.98 (s, 1H), 7.38e7.32 (m, 3H), 7.30e7.24 (m, 2H), 7.20
(s, 1H), 5.54 (s, 1H), 4.52 (t, J¼7.2 Hz, 2H), 3.91 (s, 3H), 3.86 (s, 3H),
3.80 (s, 3H), 3.24 (st, J¼6.9 Hz, 1H), 3.18 (t, J¼7.2 Hz, 2H), 2.37 (m,
J¼7.2 Hz, 2H), 1.18 (d, J¼6.9 Hz, 6H). 13C NMR (125 MHz, CDCl3)
4.5.12. Triazole 20. According to general procedure 2, the reaction
was performed with 19 (343 mg, 0.91 mmol), CuSO4$5H2O
(11.4 mg, 0.05 equiv), 1 M sodium ascorbate solution (91
ml,
d (ppm): 193.1, 187.2, 154.6, 147.6, 145.9, 137.3, 133.6, 129.3, 129.2,
0.1 equiv), azide derivative (270 mg, 1.9 equiv), and acetone (2 ml)
128.4, 128.0, 127.4, 125.6, 122.3, 61.9, 61.1, 60.6, 54.5, 49.7, 35.7, 27.0,

308
D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
24.2, 23.3. HRMS (ESIþ): C28H32N6O5Na [MþNa]þ m/z, calcd
After cooling down to rt, the mixture was filtered and concen-
trated in vacuo. The product was purified on a silica gel column
with a 8/2 mixture of pentane/AcOEt as eluent to afford pyrim-
idine 26 (110 mg, 60%) as a colorless viscous oil. 1H NMR
555.2332, found 555.2330.
4.5.16. Triazole 24a. According to general procedure 3, the reaction
was performed with 23 (53 mg, 0.1 mmol), 1 M BBr3 solution in
DCM (1.2 ml, 12 equiv) and DCM (3 ml). A purification by HPLC on
a reverse column using gradient mixture of ACN/H2O as eluent
afford 24a (4 mg, 8%) and 24b (4 mg, 8%) as yellow solids. 1H NMR
(300 MHz, CDCl3)
d
(ppm): 7.96 (d, J¼8.7 Hz, 2H), 7.81 (s, 1H),
7.64 (d, J¼8.7 Hz, 2H), 7.03 (s, 1H), 6.07 (s, 1H), 3.89 (s, 3H), 3.87
(s, 3H), 3.86 (s, 3H), 3.24 (st, J¼6.9 Hz, 1H), 2.72 (s, 3H), 1.20 (d,
J¼6.9 Hz, 3H), 1.14 (d, J¼6.9 Hz, 3H), 0.94 (s, 9H), 0.07 (s, 3H),
(300 MHz, CDCl3)
d
(ppm): 12.80 (br s, 1H), 8.69 (s, 1H), 8.28 (s, 1H),
ꢁ0.03 (s, 3H). 13C NMR (75 MHz, CDCl3)
d (ppm): 173.7, 167.5,
7.96 (s, 1H), 7.41e7.38 (m, 3H), 7.32e7.26 (m, 2H), 6.20 (br s, 1H),
5.57 (br s, 1H), 5.56 (s, 2H), 4.56 (t, J¼7.2 Hz, 2H), 3.26e3.22 (m, 3H),
2.43 (qn, J¼7.2 Hz, 2H), 1.29 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz,
163.1, 150.8, 149.0, 145.8, 137.3, 136.6, 132.1, 128.7, 125.1, 119.4,
109.6, 72.0, 61.1, 61.0, 60.5, 26.9, 26.2, 25.8, 23.6, 23.5, 18.2, ꢁ4.9,
ꢁ5.0. HRMS (ESIþ): C30H41N2O4BrSiNa [MþNa]þ m/z, calcd
623.1917, found 623.1921.
CDCl3)
d (ppm): 193.1, 187.4, 150.1, 148.6, 148.3, 147.6, 133.4, 130.3,
129.4, 129.3, 128.5, 128.4, 127.2, 125.4, 123.1, 112.5, 54.6, 49.8, 36.7,
27.3, 24.1, 22.5. HRMS (ESIþ): C25H26N6O5Na [MþNa]þ m/z, calcd
513.1862, found 513.1860.
4.6.3. Pyrimidine 27. Procedure used for compound 26 was applied
for compound 27. The reaction was performed with 25 (110 mg,
0.2 mmol), benzamidine hydrochloride (37.6 mg, 1.2 equiv), Na2CO3
(50.9 mg, 2.4 equiv), and CH3CN (2 ml) to afford 27 (98 mg, 75.4%)
4.5.17. Triazole 24b. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.75 (br s,
1H), 8.65 (s, 1H), 8.30 (s, 1H), 7.96 (s, 1H), 7.41e7.38 (m, 3H),
7.32e7.26 (m, 2H), 5.57 (br s, 1H), 5.56 (s, 2H), 4.57 (t, J¼7.2 Hz, 2H),
4.05 (s, 3H), 3.26e3.22 (m, 3H), 2.44 (qn, J¼7.2 Hz, 2H), 1.25 (d,
as a colorless viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm):
8.58e8.50 (m, 2H), 8.11 (d, J¼8.6 Hz, 2H), 7.89 (s, 1H), 7.68 (d,
J¼8.6 Hz, 2H), 7.51e7.44 (m, 3H), 7.06 (s, 1H), 6.22 (s, 1H), 3.92 (s,
3H), 3.90 (s, 3H), 3.86 (s, 3H), 3.23 (st, J¼6.9 Hz, 1H), 1.20 (d,
J¼6.9 Hz, 3H), 1.13 (d, J¼6.9 Hz, 3H), 0.96 (s, 9H), 0.10 (s, 3H), 0.00 (s,
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 193.1, 187.9, 151.0,
150.8, 148.2, 147.6, 136.6, 133.4, 133.2, 129.4, 129.3, 128.7, 128.4,
125.4, 121.7, 114.6, 60.6, 54.6, 49.8, 35.6, 27.3, 24.1, 23.3. HRMS
3H). 13C NMR (75 MHz, CDCl3)
d (ppm): 174.0, 163.6, 163.1, 150.6,
(ESIþ):
found 527.2019.
C26H28N6O5Na
[MþNa]þ
m/z,
calcd
527.2019,
149.0, 145.7, 137.9,137.4,136.6,132.1,131.3,130.5,128.7,128.3,125.2,
119.4, 110.2, 71.8, 61.2, 61.1, 60.5, 26.8, 25.8, 23.6, 23.5, 18.2, ꢁ4.9,
ꢁ5.0. HRMS (ESIþ): C35H43N2O4BrSiNa [MþNa]þ m/z, calcd
685.2073, found 685.2074.
4.6. Preparation of phenolic pyrimidine-containing com-
pounds 30a, 30b, 31a, 31b
4.7. General procedure 4 for deprotection of OTBS to OH, ex-
4.6.1. Propargylic ketone 25. To a solution of propargyl derivative
19 (1.04 g, 2.75 mmol) in THF (10 ml) at ꢁ78 ꢀC under argon, was
added dropwise t-BuLi (1.78 ml, 1.1 equiv, 1.6 M in pentane). The
mixture was stirred for 30 min. Then a solution of p-bromo-
benzaldehyde (560 mg, 1.1 equiv) in THF (2 ml) was added at
ꢁ78 ꢀC. The reaction mixture was allowed to warm up slowly to rt
and stirred for 4 h and then quenched with a saturated ammo-
nium chloride solution. The mixture was extracted with Et2O or
EA. The combined organic layers were dried over MgSO4 and
concentrated under reduced pressure. The crude product was
purified on a silica gel column using a 9/1 mixture pentane/EA as
eluent to afford the alcohol intermediate (857 mg, 55%) as a col-
orless viscous oil. Alcohol intermediate: 1H NMR (300 MHz, CDCl3)
ample: first step for preparation of compound 28
To a solution of pyrimidine 26 (254 mg, 0.42 mmol) in THF (4 ml)
was added dropwise at rt TBAF (0.84 ml, 2 equiv, 1 M in THF). The
reaction mixture was stirred at rt for 1 h and then quenched with
a saturated ammonium chloride solution. Then the mixture was
extracted with EA, dried over MgSO4, and concentrated under re-
duced pressure to afford the alcohol as a crude product, which was
used as such for the next step.
4.7.1. Pyrimidine 28. Previous alcohol prepared from general
procedure 4 (0.42 mmol, expected) was oxidized by using general
procedure 1 with IBX (235 mg, 2 equiv) and the 3/1 mixture
CHCl3/DMSO (4 ml) to afford 28 (170 mg, 83%, two steps) as a light
d
(ppm): 7.50e7.40 (m, 4H), 7.20 (s, 1H), 5.80 (d, J¼2.4 Hz, 1H), 5.45
(s, 1H), 3.89 (s, 3H), 3.88 (s, 3H), 3.87 (s, 3H), 3.23 (m, J¼6.9 Hz,1H),
2.24 (d, J¼2.4 Hz, 1H), 1.21 (d, J¼6.9 Hz, 3H), 1.20 (d, J¼6.9 Hz, 3H),
0.92 (s, 9H), 0.15 (s, 3H), 0.10 (s, 3H). 13C NMR (75 MHz, CDCl3)
yellow viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm): 8.07 (d,
J¼8.7 Hz, 2H), 7.89 (s, 1H), 7.65 (d, J¼8.7 Hz, 2H), 7.40 (s, 1H), 3.98
(s, 3H), 3.82 (s, 3H), 3.61 (s, 3H), 3.27 (st, J¼6.9 Hz, 1H), 2.82 (s, 3H),
d
(ppm): 150.8, 148.0, 145.5, 139.6, 137.4, 131.2, 129.9, 128.4, 122.2,
1.24 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 194.2,
118.6, 88.8, 83.1, 64.0, 61.1, 61.0, 60.5, 59.6, 26.8, 25.8, 23.6, 23.5,
18.3, ꢁ4.9. Prepared alcohol intermediate (857 mg, 1.52 mmol)
was oxidized by using general procedure 1 with IBX (1.28 g,
3 equiv) and a 1/1 mixture CHCl3/DMSO (4 ml) to afford 25
167.9, 164.6, 164.2, 156.4, 152.5, 145.5, 137.6, 135.5, 132.2, 128.8,
125.8, 125.4, 123.1, 110.8, 61.1, 60.9, 60.4, 27.1, 26.2, 23.2. HRMS
(ESIþ):
found 485.1071.
C24H26N2O4Br
[MþH]þ
m/z,
calcd
485.1076,
(770 mg, 90%) as a yellow oil. 1H NMR (300 MHz, CDCl3)
d (ppm):
7.99 (d, J¼8.7 Hz, 2H), 7.60 (d, J¼8.7 Hz, 2H), 7.22 (s, 1H), 5.94 (s,
1H), 3.95 (s, 3H), 3.90 (s, 3H), 3.88 (s, 3H), 3.28 (st, J¼6.9 Hz, 1H),
1.21 (d, J¼6.9 Hz, 3H), 1.20 (d, J¼6.9 Hz, 3H), 0.95 (s, 9H), 0.21 (s,
4.7.2. Pyrimidine 29. Firstly, according to general procedure 4, the
reaction was performed with pyrimidine 27 (98 mg, 0.15 mmol),
1 M TBAF solution in THF (0.165 ml, 1.1 equiv) and THF (3 ml) to
afford the alcohol as a crude product used directly for the next step.
Secondly, this alcohol was oxidized by using general procedure 1
with IBX (126 mg, 3 equiv) and the 1/1 mixture CHCl3/DMSO (2 ml)
to afford 29 (67 mg, 83%, two steps) as a light yellow viscous oil. 1H
3H), 0.12 (s, 3H). 13C NMR (75 MHz, CDCl3)
d (ppm): 176.7, 151.3,
148.1, 145.6, 137.7, 135.6, 131.9, 131.0, 129.5, 128.2, 118.6, 96.1, 81.3,
61.1, 61.0, 60.5, 59.8, 26.8, 25.7, 23.6, 23.5, 18.3, ꢁ4.7, ꢁ5.0. HRMS
(ESIþ): C28H37O5BrSiNa [MþNa]þ m/z, calcd 583.1491,
found 583.1496.
NMR (300 MHz, CDCl3)
d (ppm): 8.56e8.52 (m, 2H), 8.21 (d,
J¼8.7 Hz, 2H), 8.04 (s, 1H), 7.70 (d, J¼8.7 Hz, 2H), 7.52e7.44 (m, 3H),
4.6.2. Pyrimidine 26. To a solution of propargylic ketone 25
(172 mg, 0.31 mmol) in CH3CN (2 ml) were added sodium car-
bonate (78.4 mg, 2.4 equiv) and acetamidine hydrochloride
(35 mg, 1.2 equiv). The solution was stirred under reflux for 1.5 h.
7.46 (s, 1H), 4.01 (s, 3H), 3.84 (s, 3H), 3.59 (s, 3H), 3.32 (st, J¼6.9 Hz,
1H), 1.27 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 194.4,
164.5, 164.3, 163.9, 156.1, 152.6, 145.6, 137.5, 137.1, 135.6, 132.2, 131.1,
128.9, 128.6, 128.5, 126.0, 125.9, 123.2, 111.4, 61.3, 61.2, 60.5, 27.2,

D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
309
23.3. HRMS (ESIþ): C29H27N2O4BrNa [MþNa]þ m/z, calcd 569.1052,
ꢁ5.1. HRMS (ESIþ): C24H38O6SiNa [MþNa]þ m/z, calcd 473.2335,
found 569.1053.
found 473.2336.
4.7.3. Pyrimidine 30a. According to general procedure 3, the re-
action was performed with 28 (154 mg, 0.32 mmol), 1 M BBr3
solution in DCM (3 ml, 9 equiv) and DCM (3 ml). A purification by
HPLC on a reverse column using gradient mixture of ACN/H2O as
eluent afford 30a (30 mg, 21%) and 30b (14 mg, 10%) as yellow
4.8.2. Pyrimidone 33. To a solution of propargylic ester 32
(141 mg, 0.31 mmol) in EtOH (3 ml) were added sodium carbonate
(79 mg, 2.4 equiv) and benzamidine hydrochloride (58.2 mg,
1.2 equiv). The solution was stirred under reflux for 1.5 h. After
cooling down to rt, the mixture was filtered and concentrated in
vacuo. The product was purified on a silica gel column with a 8/2
mixture of pentane/AcOEt as eluent to afford to afford 33 (114 mg,
solids. 1H NMR (400 MHz, CDCl3)
d
(ppm): 8.06 (d, J¼8.7 Hz, 2H),
8.00 (s, 1H), 7.68 (d, J¼8.7 Hz, 2H), 7.50 (s, 1H), 3.19 (st, J¼6.9 Hz,
1H), 2.93 (s, 3H), 1.19 (d, J¼6.9 Hz, 6H). 13C NMR (100 MHz, CDCl3)
69%) as a colorless viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm):
d
(ppm): 194.2, 167.6, 165.2, 162.7, 150.1, 149.6, 135.1, 132.4, 130.6,
13.10 (br s, 1H), 8.23e8.09 (m, 2H), 7.58e7.38 (m, 3H), 7.00 (s, 1H),
6.77 (s, 1H), 6.01 (s, 1H), 3.99 (s, 3H), 3.91 (s, 3H), 3.86 (s, 3H), 3.22
(st, J¼6.9 Hz, 1H), 1.17 (d, J¼6.9 Hz, 3H), 1.13 (d, J¼6.9 Hz, 3H), 0.92
(s, 9H), 0.10 (s, 3H), ꢁ0.07 (s, 3H). 13C NMR (75 MHz, CDCl3)
128.9, 127.1, 126.4, 123.0, 112.8, 112.1, 26.8, 25.9, 22.3. HRMS
(ESIþ): C21H19N2O4BrNa [MþNa]þ m/z, calcd 465.0426,
found 465.0424.
d
(ppm): 171.8, 166.2, 156.1, 150.6, 149.0, 145.5, 137.5, 132.2, 131.7,
4.7.4. Pyrimidine 30b. 1H NMR (400 MHz, CDCl3)
d
(ppm): 8.06 (d,
130.7, 128.8, 127.8, 119.6, 107.8, 70.5, 61.3, 61.1, 60.5, 26.8, 25.8,
23.5, 23.4, 18.2, ꢁ5.0, ꢁ5.1. HRMS (ESIþ): C29H40N2O5SiNa
[MþNa]þ m/z, calcd 547.2604, found 547.2600.
J¼8.7 Hz, 2H), 8.03 (s, 1H), 7.68 (d, J¼8.7 Hz, 2H), 7.62 (s,1H), 4.07 (s,
3H), 3.22 (m, J¼6.9 Hz, 1H), 2.91 (s, 3H), 1.18 (d, J¼6.9 Hz, 6H). 13
C
NMR (100 MHz, CDCl3)
d (ppm): 194.3, 167.7, 165.2, 162.4, 151.2,
150.6, 137.0, 135.1, 133.2, 132.4, 128.9, 126.4, 121.6, 114.3, 112.7, 60.7,
27.0, 26.0, 23.1. HRMS (ESIþ): C22H21N2O4BrNa [MþNa]þ m/z, calcd
479.0582, found 479.0581.
4.8.3. Pyrimidone 34. Firstly, according to general procedure 4,
the reaction was performed with pyrimidin-4-one 33 (114 mg,
0.22 mmol), 1 M TBAF solution in THF (0.66 ml, 3 equiv) and THF
(3 ml) to afford the alcohol crude product. This intermediate was
used directly in the next step. Then, this alcohol was oxidized by
using general procedure 1 with IBX (92.4 mg, 1.5 equiv) and the
5/1 mixture THF/DMSO (6 ml) to afford 34 (47.3 mg, 53%, two
4.7.5. Pyrimidine 31a. According to general procedure 3, the re-
action was performed with 29 (65 mg, 0.12 mmol), 1 M BBr3 solu-
tion in DCM (1.44 ml, 12 equiv) and DCM (2 ml). A purification on
silica gel (eluent: pentane/EA 7/3) afford 31a (8 mg, 13%) and 31b
steps) as a yellow viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm):
(8 mg, 13%) as yellow solids. 1H NMR (300 MHz, CDCl3)
d
(ppm):
13.45 (br s, 1H), 8.31e8.25 (m, 2H), 7.59e7.47 (m, 3H), 7.37 (s,
1H), 6.84 (s, 1H), 3.98 (s, 3H), 3.85 (s, 3H), 3.71 (s, 3H), 3.28 (st,
J¼6.9 Hz, 1H), 1.24 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
12.55 (br s, 1H), 8.67e8.61 (m, 2H), 8.19 (d, J¼8.7 Hz, 2H), 8.10 (s,
1H), 7.96 (s, 1H), 7.70 (d, J¼8.7 Hz, 2H), 7.58e7.50 (m, 3H), 6.24 (br s,
1H), 5.67 (br s, 1H), 3.24 (st, J¼6.9 Hz, 1H), 1.20 (d, J¼6.9 Hz, 6H). 13
C
d (ppm): 193.1, 165.9, 162.8, 157.0, 156.0, 152.4, 145.5, 137.5, 132.4,
NMR (75 MHz, CDCl3)
d
(ppm): 194.5, 165.0, 163.6, 163.2, 150.3,
131.3, 129.0, 127.9, 125.8, 122.8, 111.3, 61.4, 61.1, 60.6, 27.1, 23.2.
HRMS (ESIþ): C23H24N2O5Na [MþNa]þ m/z, calcd 431.1577,
found 431.1579.
149.2, 136.8, 135.4, 132.3, 131.4, 130.6, 128.9, 128.7, 128.5, 127.3,
126.3, 123.5, 113.4, 112.0, 26.7, 22.6. HRMS (ESIþ): C26H22N2O4Br
[MþH]þ m/z, calcd 505.0763, found 505.0768.
4.8.4. Pyrimidone 35. According to general procedure 3, the re-
action was performed with 34 (47.3 mg, 0.11 mmol), 1 M BBr3 so-
lution in DCM (1 ml, 9 equiv) and DCM (5 ml). A purification on
silica gel (eluent: pentane/EA 7/3) afford 35 (6 mg, 14%) as orange
4.7.6. Pyrimidine 31b. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.49 (br
s, 1H), 8.68e8.61 (m, 2H), 8.19 (d, J¼8.7 Hz, 2H), 7.91 (s, 1H), 7.70 (d,
J¼8.7 Hz, 2H), 7.58e7.49 (m, 3H), 5.70 (br s, 1H), 4.10 (s, 3H), 3.25
(st, J¼6.9 Hz, 1H), 1.17 (d, J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
solid. 1H NMR (300 MHz, CDCl3)
d (ppm): 12.92 (br s, 1H), 12.25 (s,
d
(ppm): 195.0, 165.1, 163.7, 163.0, 151.2, 136.8, 135.3, 133.1, 132.3,
1H), 8.30 (d, J¼7.1 Hz, 2H), 7.65e7.54 (m, 3H), 7.60 (s, 1H), 6.94 (s,
131.5, 128.9, 128.7, 128.5, 126.4, 122.0, 113.9, 113.4, 60.8, 26.8, 23.3.
HRMS (ESIþ): C27H24N2O4Br [MþH]þ m/z, calcd 519.0919,
found 519.0917.
1H), 5.67 (br s, 1H), 4.08 (s, 3H), 3.23 (st, J¼6.9 Hz, 1H), 1.15 (d,
J¼6.9 Hz, 6H). 13C NMR (75 MHz, CDCl3)
d (ppm): 194.9,165.0,161.2,
157.0, 151.3, 151.1, 136.8, 133.0, 132.8, 131.1, 129.2, 127.8, 121.3, 113.8,
113.6, 60.7, 26.9, 23.2. HRMS (ESIþ): C21H20N2O5Na [MþNa]þ m/z,
calcd 403.1264, found 403.1264.
4.8. Preparation of phenolic pyrimidone-containing com-
pound 34
4.9. Preparation of phenolic pyridine-containing compound
38
4.8.1. Propargylic ketone 32. To
a solution of 19 (991 mg,
2.62 mmol) in Et2O (15 ml) at ꢁ78 ꢀC under argon, was added
dropwise t-BuLi (1.8 ml, 2.2 equiv, 1.6 M in pentane). The mixture
was stirred for 30 min and then ClCO2Et (0.3 ml, 1.2 equiv) was
added dropwise at ꢁ78 ꢀC. The reaction mixture was allowed to
warm up slowly to rt and it was stirred overnight and then
quenched with a saturated ammonium chloride solution. The
mixture was extracted with Et2O. The combined organic layers
were dried over MgSO4 and concentrated under reduced pres-
sure. The crude product was purified on a silica gel column using
the 8/2 mixture pentane/Et2O as eluent to give the desired
4.9.1. Pyridine 36. To a stirred solution of NH4OAc (1.3 g, 20 equiv)
and ethyl acetoacetate (214 ml, 2 equiv) in 15 ml EtOH at rt after 2 h
and 30 min, was added 25 (475 mg, 0.85 mmol). The mixture was
stirred at rt overnight. I2 (43.2 mg, 0.2 equiv) was added and this
mixture was stirred for another hour at 50 ꢀC. It was then quenched
with a saturated sodium thiosulfate solution. The mixture was
extracted with EA, the organic phases dried over MgSO4, and
concentrated under reduced pressure. The crude product was pu-
rified on a silica gel column using the 9/1 mixture pentane/EA as
eluent to afford the desired product 36 (398 mg, 70%) as a colorless
product 32 (840 mg, 70%). 1H NMR (300 MHz, CDCl3)
7.17 (s, 1H), 5.80 (s, 1H), 4.20 (q, J¼7.1 Hz, 2H), 3.92 (s, 3H), 3.88
(s, 3H), 3.86 (s, 3H), 3.25 (d, J¼6.9 Hz, 1H), 1.28 (t, J¼7.1 Hz, 3H),
0.92 (s, 9H), 0.18 (s, 3H), 0.09 (s, 3H). 13C NMR (75 MHz, CDCl3)
d (ppm):
viscous oil. 1H NMR (300 MHz, CDCl3)
d (ppm): 7.95 (s, 1H), 7.89 (d,
J¼8.6 Hz, 2H), 7.60 (d, J¼8.6 Hz, 2H), 7.03 (s, 1H), 6.24 (s, 1H),
4.36e4.10 (m, 2H), 3.83 (s, 3H), 3.80 (s, 3H), 3.63 (s, 3H), 3.25 (st,
J¼6.9 Hz, 1H), 2.59 (s, 3H), 1.27 (t, J¼7.2 Hz, 3H), 1.20 (d, J¼6.9 Hz,
d
(ppm): 153.6, 151.2, 148.0, 145.5, 137.5, 128.3, 118.5, 88.2, 75.7,
61.9, 61.1, 61.0, 60.5, 59.4, 26.8, 25.7, 23.5, 23.4, 18.2, 14.0, ꢁ4.7,
3H),1.18 (d, J¼6.9 Hz, 3H), 0.92 (s, 9H), 0.05 (s, 3H), ꢁ0.01 (s, 3H). 13
C

310
D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
NMR (125 MHz, CDCl3)
d
(ppm): 168.0, 155.3, 155.0, 151.1, 149.1,
References and notes
145.7, 136.7, 132.0, 130.6, 128.7, 125.7, 123.8, 120.7, 116.2, 69.2, 61.2,
61.1, 60.4, 60.2, 29.7, 26.8, 25.9, 25.8, 23.6, 23.5, 23.1, 18.3, 14.0, ꢁ4.8,
ꢁ4.9. HRMS (ESIþ): C34H47NO6BrSiNa [MþH]þ m/z, calcd 672.2356,
found 672.2358.
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in CH3CN (5 ml) at rt under nitrogen was added dropwise
€
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50 ꢀC and stirred for 1 h before quenching with water at rt and
then extracted with EA. The organic layer was washed with sat-
urated NaCl, dried over MgSO4. After evaporation of the solvent,
the residue was purified on a silica gel column using the 8/2
mixture pentane/EA as eluent to afford the desired product 37
(150 mg, 66%) as a colorless viscous oil. 1H NMR (400 MHz, CDCl3)
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d
(ppm): 7.92 (d, J¼8.6 Hz, 2H), 7.59 (d, J¼8.6 Hz, 2H), 7.55 (s, 1H),
6.68 (s, 1H), 6.56 (s, 1H), 3.90 (s, 3H), 3.88 (s, 3H), 3.85 (s, 3H), 3.21
(m, J¼6.9 Hz, 1H), 2.99 (s, 3H), 1.16 (d, J¼6.9 Hz, 3H), 1.11 (d,
J¼6.9 Hz, 3H). 13C NMR (100 MHz, CDCl3)
d (ppm): 169.5, 160.4,
159.6, 159.5, 152.7, 150.1, 146.3, 138.2, 137.1, 132.1, 129.2, 124.8,
123.3, 119.5, 118.4, 111.6, 78.3, 61.2, 61.0, 60.6, 27.1, 23.4, 23.3, 21.1.
HRMS (ESIþ): C26H26NO5BrNa [MþNa]þ m/z, calcd 534.0886,
found 534.0887.
4.9.3. Pyridine 38. According to general procedure 3, the reaction
was performed with 37 (50 mg, 0.1 mmol), 1 M BBr3 solution in
DCM (1 ml, 10 equiv) and DCM (5 ml) to afford 38 (20 mg, 44%) as
brown solid. 1H NMR (300 MHz, acetone-d6)
d (ppm): 8.13 (d,
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J¼8.8 Hz, 2H), 7.86 (s, 1H), 7.67 (d, J¼8.8 Hz, 2H), 7.62 (br s, 1H), 6.74
(s, 1H), 6.57 (s, 1H), 3.18 (m, J¼6.9 Hz, 1H), 2.88 (s, 3H), 1.14 (d,
J¼6.9 Hz, 3H), 1.09 (d, J¼6.9 Hz, 3H). 13C NMR (100 MHz, acetone-
d6)
d (ppm): 171.0, 163.3, 160.4, 160.3, 146.9, 145.2, 139.3, 133.8,
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22.0. HRMS (ESIþ): C23H21NO5Br [MþH]þ m/z, calcd 470.0603,
found 470.0605.
4.10. BRET assay
Hela cells were seeded on 6-well plates and transfected with
200 ng/well of plasmid pRLuc-Bax coding for BRET donor and 1 mg/
well of peYFP-Bcl-xL coding for BRET acceptor (or with pCMV-Bcl-
xL for control). Twenty-four hours after transfection, cells were
trypsinized and re-seeded into white 96 flat well plate, incubated
ꢀ
Pouysegu, L. Angew. Chem., Int. Ed. 2011, 50, 586.
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emission at 485 nm and 530 nm was measured consecutively by
using the Mithras fluorescence-luminescence detector LB 940
(Berthold) after adding the luciferase substrate, coelenterazine H
(Uptima) at a final concentration of 5 mM. BRET ratios were calcu-
lated as described.22
Acknowledgements
ꢀ ꢀ
ꢀ
We thank Laboratoires Servier and Societe de Chimie Thera-
peutique for a fellowship to D.D.V. We thank the Ligue contre le
Cancer for support to this research. We thank CNRS, INSERM,
University of Rennes 1 and University of Nantes for financial
support. We thank Mr. O. Tasseau for fruitful discussions.
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ꢀ
Supplementary data
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ꢀ
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Supplementary data associated with this article (characteriza-
tion data: 1H and 13C NMR spectra) are available. Supplementary
data related to this article can be found at http://dx.doi.org/10.1016/
j.tet.2013.11.060.

D.D. Vo et al. / Tetrahedron 70 (2014) 301e311
311
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