A facile and rapid access to resveratrol derivatives and their radioprotective activity

Article abstract of DOI:10.1016/j.bmcl.2016.07.018

A facile and rapid access to resveratrol derivatives has been achieved based on palladium-catalyzed oxidative Heck reaction of aryl boronic acids with styrenes followed by demethylation in moderate to good yields. A series of resveratrol derivatives with various functional groups has been synthesized easily. The radioprotective activity of synthesized compounds has also been evaluated using rat thymocytes. The results revealed that some resveratrol derivatives efficiently protected the thymocytes from radiation-induced apoptosis.

Full text of DOI:10.1016/j.bmcl.2016.07.018

Bioorganic & Medicinal Chemistry Letters 26 (2016) 3886–3891
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
A facile and rapid access to resveratrol derivatives and their
radioprotective activity
b,
a
a,
Saori Uzura a, Emiko Sekine-Suzuki b, , Ikuo Nakanishi , Motohiro Sonoda , Shinji Tanimori
⇑
⇑
⇑
a Department of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuencho, Sakai, Osaka 599-8241, Japan
b Quantitative RedOx Sensing Team (QRST), Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences (NIRS), National Institutes
for Quantum and Radiological Science and Technology (QST), Inage-ku, Chiba 263-8555, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A facile and rapid access to resveratrol derivatives has been achieved based on palladium-catalyzed
oxidative Heck reaction of aryl boronic acids with styrenes followed by demethylation in moderate to
good yields. A series of resveratrol derivatives with various functional groups has been synthesized easily.
The radioprotective activity of synthesized compounds has also been evaluated using rat thymocytes. The
results revealed that some resveratrol derivatives efficiently protected the thymocytes from radiation-
induced apoptosis.
Received 7 June 2016
Revised 4 July 2016
Accepted 6 July 2016
Available online 7 July 2016
Keywords:
Resveratrol
Ó 2016 Elsevier Ltd. All rights reserved.
Synthesis
Oxidative Heck reaction
Radioprotector
Recently, polyhydroxylated stilbenes and its congeners have
attracted much attention due to the significance of their biological
activity.1 Among them, resveratrol [1, (E)-3,5,40-trihydroxystilbene,
Fig. 1], a naturally occurring phytoalexin present in grapevines,
pines, and legumes but also in pomegranates, soy beans, and in
peanuts,2 is recognized to be a representative of trans-polyphenolic
stilbenes. Resveratrol shows a plethora of remarkable biological
properties such as antifungal,3 antibacterial,4 antiviral,5 anti-
cancer,6,7 estrogenic,8 platelet anti-aggregating,9 and heart protect-
ing activities.10,11 For these reasons, many synthetic methods for
polyhydroxylated stilbenes has been appeared which include
Wittig reaction,12 traditional Heck reaction,13 cross-metathesis,14
Perkin reaction,15 and Hunsdiecker–Suzuki strategy.16 However,
the application of oxidative Heck reaction17 using aryl boronic
acids and styrenes as starting materials has not been appeared
yet. It was assumed that such method would result in a facile
access to polymethoxylated and polyhydroxylated stilbene deriva-
tives due to the easy availability of boronic acid derivatives as
commercial sources.
Figure 1. Structure of resveratrol (1).
reported,20 only amifostine was authorized for clinical use by the
FDA. However, due to the side effect such as vomiting,21 amifostine
has not been widely utilized. For these reason along with the
Fukushima Daiichi nuclear disaster in Japan on 11 March 2011, it
is an urgent necessity to develop effective radioprotectors. Thus
we evaluated the effect of radioprotection of resveratrol deriva-
tives synthesized in this study based on the method developed
by our group.22
We first examined the reaction of 3,5-dimethoxyphenylboronic
acid 2a with 4-acetoxystyrene 3a to form (E)-4-(3,5-dimethoxys-
tyryl)phenyl acetate 4a23 (Table 1). When the mixture of com-
pounds 2a and 3a were treated with Pd(OAc)2 (10 mol %) and
sodium carbonate (2 equiv) under molecular oxygen in DMF at
50 °C for 3 h,17 the desired stilbene 4a was observed in a 80% iso-
lated yield (Table 1, entry 1). Other palladium catalysts were pro-
ven to be less effective (entries 2–5) except for the case utilizing
(CH3CN)2PdCl2 (entry 6), which showed a slight better conversion
(84%). For base variations, potassium carbonate was equally
Recently, a triacetylated resveratrol derivative has reported to
show an efficient protective effect against
c-irradiation-induced
death of mice.18 Radioprotectors are crucial for the cancer radia-
tion therapy to protect the normal tissue around the target
cancer.19 Although a large number of chemical compounds with
radioprotective effect in in vitro/vivo studies have so far
⇑
Corresponding authors.
http://dx.doi.org/10.1016/j.bmcl.2016.07.018
0960-894X/Ó 2016 Elsevier Ltd. All rights reserved.

S. Uzura et al. / Bioorg. Med. Chem. Lett. 26 (2016) 3886–3891
3887
Table 1
Optimization studies for the couple of boronic acid 2a with styrene 3aa
Entry
Pd catalyst
Base
Solvent
Time (h)
4a yieldb
%
1
2
3
4
5
6
7
8
Pd(OAc)2
PdCl2
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
K2CO3
Cs2CO3
DBU
Na2CO3
Na2CO3
Na2CO3
Na2CO3
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMSO
Dioxane
MeCN
DMF
3
3
24
24
24
3
80
70
58
38
34
84d
82
22
0
50
8
17
68
[Pd(
g
3-C3H5)Cl]2
PdCl2(PPh3)2
PdCl2(dppf)
(CH3CN)2PdCl2
(CH3CN)2PdCl2
(CH3CN)2PdCl2
(CH3CN)2PdCl2
(CH3CN)2PdCl2
(CH3CN)2PdCl2
(CH3CN)2PdCl2
(CH3CN)2PdCl2
3
24
24
24
24
24
18
9
10
11
12
13c
a
Reaction conditions: 3,5-Dimethoxyphenylboronic acid 2a (0.50 mmol), p-acetoxystyrene 3a (0.25 mmol), base (0.50 mmol), Pd catalyst (0.025 mmol), in solvent (1.3 ml)
at 50 °C under oxygen atmosphere.
b
Isolated yield.
5 mol % of (CH3CN)2PdCl2 was introduced.
Optimized conditions.
c
d
Table 2
Synthesis of polyhydroxylated stilbenes
a Reaction time for the synthesis of stilbenes.
b Reaction time for demethylation.

3888
S. Uzura et al. / Bioorg. Med. Chem. Lett. 26 (2016) 3886–3891
Table 3
Synthesis of miscellaneous stilbenes
a Reaction time for the synthesis of stilbenes.
b Reaction time for demethylation.
effective (entry 7). However, cesium carbonate afforded a lower
yield and no reaction took place when an organic base such as
DBU was applied (entries 8 and 9). As shown in entries 10 to 12,
the choice of solvent was found to be crucial for this transforma-
tion. When the reactions were performed in DMSO, dioxane, and
acetonitrile, the lower yields were observed. Moreover, lowering
the catalyst loading to 5 mol % resulted in the diminished yield
(entry 13).
with 5% CO2. After incubation, the size and number of thymocytes
were measured by the flow cytometer.
The radio-modification factors (RMF), which is defined as the
ratio of apoptotic cells with chemicals divided by the ratio of apop-
totic cells without chemicals, in order to quantify the radioprotec-
tive efficiency of the chemicals, are calculated and shown in
Table 4 and also in Figure 2 as a bar graph. The lower the RMF val-
ues of the compounds, the more effective their radioprotection is.
Having identified the optimal conditions (Table 1, entry 6), we
next investigated the synthesis of polyhydroxylated stilbenes by
the coupling reactions followed by deprotection with the use of
boron tribromide (Table 2).24 As shown in Table 2, a series of poly-
hydroxylated stilbenes with hydroxyl group at various positions
have been synthesized from readily available aryl boronic acid
and styrenes in moderate to good yields.
Moreover, resveratrol derivatives with various functional
groups at 40-position were also synthesized along the same meth-
ods by applying a series of 4-substituted styrenes (Table 3).
Finally, we examined the radioprotective effect of the resvera-
trol derivatives using an assessment method, which we have
recently reported.22 This method assesses the radioprotective
effect of compounds by measuring cell death, such as apoptosis,
induced by radiation in rat thymocytes.
In Table 4, 1a (1 mM), 1b, 1c, 1e, 1k, 1l (100
lM), 4a (100 lM),
4b (1 mM), 4c (100 M), 4g (100 M), 4i (1 M), and 4o (1 mM)
l
l
l
significantly protected the thymocytes against radiation-induced
apoptosis without toxicity. The structure–activity relationship for
these results has been unclear at this time. For instance, the corre-
lation of lipophilicity of these compounds with their radioprotec-
tive activity has not been observed. The substituent at 40-position
would not give little influence to the activity (1a, 1k and 1l except
for 4o). The number of methoxy and hydroxyl groups seems to be
influenced the activity (4f, 4g, and 4l). Further study has been
required for elucidation of structure–activity relationship.
These results suggest that some resveratrol derivatives can effi-
ciently act as radioprotector.
In conclusions, a facile access to resveratrol derivatives has been
accomplished based on oxidative Heck reaction from readily avail-
able chemicals under mild reaction conditions. In this study, we
demonstrated the radioprotective effect of resveratrol derivatives
using normal cells, such as rat thymocytes. Some resveratrol
derivatives efficiently protect cells against radiation with low tox-
icity. These data suggest the beneficial use of novel resveratrol
Thymocytes from rats were placed in cell culture medium sup-
plemented with 10% fetal bovine serum. Each resveratrol deriva-
tive25 was dissolved in DMSO as a cosolvent and applied to the
cell suspensions (1, 10, 100 lM, or 1 mM), the thymocytes were
pretreated with either DMSO 0.1% or the resveratrol derivative
with DMSO 0.1% as a cosolvent. After irradiation of 2 Gy of X-rays
at a rate of 1.2 Gy/min, the cells were incubated for 4 h at 37 °C
derivatives as
radiotherapy.
a protector for normal tissues in the cancer

S. Uzura et al. / Bioorg. Med. Chem. Lett. 26 (2016) 3886–3891
3889
2
1.5
1
**
**
**
**
**
**
*
0.5
0
*
*
**
*
*
*
*
*
*
*
1a
1b
1c
1d
1e
1f
1g
1h
1k
1l
1m
1n
-0.5
2
1.5
1
** **
**
**
**
0.5
0
*
*
4p
4a
4b
4c
4d
4e
4f
4g
4h
4l
4n
4o
4i
-0.5
** high protection (0.5 > RMF) and no toxicity (toxicity < 5), * N.A: no analysis
(high toxicity, toxicity > 10), The RMF values of the compounds with radioprotective
activity are smaller than 1.0.
Figure 2. RMF and toxicity of the resveratrol derivatives. N.A: no analysis (high toxicity, toxicity >10). **High protection (0.5 >RMF) and no toxicity (toxicity <5), *N.A: no
analysis (high toxicity, toxicity >10), The RMF values of the compounds with radioprotective activity are smaller than 1.0.
Table 4
RMF and toxicity of the resveratrol derivatives
Compound (lM)
RMF (protectivity)
Toxicity
Compound (
lM)
RMF (protectivity)
Toxicity
1a
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
0.93
1.06
0.59
ꢀ0.34**
0.9
<5
<5
<5
<5
<5
<5
<5
10<
<5
<5
<5
10<
<5
<5
<5
<5
<5
<5
<5
10<
4a
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
0.82
0.85
0.31**
ꢀ0.15
1.4
<5
<5
<5
5<, <10
<5
<5
<5
<5
<5
<5
<5
5<, <10
<5
<5
<5
<5
<5
<5
l
l
M
M
l
l
M
M
1b
1c
1d
1e
4b
4c
4d
4e
lM
0.9
lM
1.2
l
M
0.3**
N.A.
1.2
l
M
1.1
0.2**
0.8
lM
1.3
lM
0.6
l
M
0.4**
N.A.
1.4
l
M
0.3**
0.1
1.0
1.1
1.1
1.5
0.8
1.0
0.7
0.5
lM
1.2
1.6
0.6
2.2
lM
l
M
l
M
1
1
10
100
1000
lM
1.3
10
100
1000
lM
l
M
ꢀ0.3**
N.A.
l
M
<5
5<, <10
(continued on next page)

3890
S. Uzura et al. / Bioorg. Med. Chem. Lett. 26 (2016) 3886–3891
Table 4 (continued)
Compound (lM)
RMF (protectivity)
Toxicity
Compound (
lM)
RMF (protectivity)
Toxicity
1f
1
1.7
<5
4f
1
0.7
<5
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
l
l
M
M
N.A.
N.A.
N.A.
0.4
0.7
0.5
N.A.
0.6
1.1
1.2
1.1
0.94
1.06
0.11**
N.A.
0.89
0.81
ꢀ0.22**
N.A.
0.56
0.47
N.A.
N.A.
1.14
1.01
0.91
N.A.
10<
10<
10<
5<, <10
<5
5<, <10
10<
<5
<5
<5
<5
<5
<5
10<
<5
<5
<5
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
1
10
100
1000
l
l
M
M
1.2
0.9
0.7
1.3
<5
<5
<5
<5
<5
<5
5<, <10
<5
<5
<5
<5
<5
<5
5<, <10
5<, <10
<5
1g
1h
1k
1l
4g
4h
4i
lM
lM
1.3
l
M
l
M
ꢀ0.2**
0.2
1.1
1.0
1.3
lM
lM
l
M
l
M
1.5
0.4**
1.0
lM
lM
l
M
l
M
0.4
0.3
4l
1.34
1.26
N.A.
N.A.
0.99
0.86
0.52
0.07
0.53
0.98
0.72
ꢀ0.37**
1.25
1.21
0.99
1.05
lM
lM
<5
l
M
<5
l
M
10<
10<
<5
5<, <10
5<, <10
5<, <10
5<, <10
<5
<5
<5
<5
<5
10<
5<, <10
5<, <10
10<
10<
<5
<5
<5
10<
1m
1n
4n
4o
4p
lM
lM
l
M
lM
10
100
1000
lM
lM
l
M
l
M
lM
l
M
<5
<5
**
High protection (0.5 >RMF) and no toxicity (toxicity <5), N.A: no analysis (high toxicity, toxicity >10).
7. Schneider, Y.; Vincent, F.; Duranton, B.; Badolo, L.; Gosse, F.; Bergmann, C.;
Seiler, N.; Raul, F. Cancer Lett. 2000, 158, 85.
Acknowledgments
8. Bowers, J. L.; Tyulmenkov, V. V.; Jernigan, S. C.; Klinge, C. M. Endocrinology
2000, 141, 3657.
9. Wang, Z. R.; Huang, Y. Z.; Zou, J. G.; Cao, K. J.; Xu, Y. N.; Wu, J. M. Int. J. Mol. Med.
2002, 9, 77.
10. Wu, J. M.; Wang, Z. R.; Hsieh, T. C.; Bruder, J. L.; Zou, J. G.; Huang, Y. Z. Int. J. Mol.
Med. 2001, 8, 3.
This work was financially supported by JSPS KAKENHI Grant
Number 25410051 and 26460056. We thank Ms. M. Ueno and
Mr. Y. Ogawa for their help in the measurements of the radiopro-
tective activity.
11. Babich, H.; Reisbaum, A. G.; Zuckerbraun, H. L. Toxicol. Lett. 2000, 114, 143.
12. Mizuno, C. S.; Ma, G.; Khan, S.; Patny, A.; Avery, M. A.; Rimando, A. M. Bioorg.
Med. Chem. 2008, 16, 3800.
Supplementary data
13. (a) Guiso, M.; Marra, C.; Farina, A. Tetrahedron Lett. 2002, 43, 597; (b) Feffery,
T.; Ferber, B. Tetrahedron Lett. 2003, 44, 193; (c) Andrus, M. B.; Liu, J.; Meredith,
E. L.; Nartey, E. Tetrahedron Lett. 2003, 44, 4819; (d) Yamada, Y. M. A.; Takeda,
K.; Takahashi, H.; Ikegami, S. Tetrahedron 2004, 60, 4097; (e) Moro, A. V.;
Cardoso, F. S. P.; Correia, C. R. D. Tetrahedron Lett. 2008, 49, 5668; (f) Iijima, T.;
Makabe, H. Biosci. Biotechnol. Biochem. 2009, 71, 2547.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2016.07.
018.
14. Ferré-Filmon, K.; Delaude, L.; Demonceau, A.; Noels, A. F. Eur. J. Org. Chem.
2005, 3319.
15. Sinha, A. K.; Kumar, V.; Sharma, A.; Sharma, A.; Kumar, R. Tetrahedron 2007, 63,
11070.
References and notes
1. (a) Gorham, J. The Chemistry of the Stilbenoids; Chapman & Hall: London, 1995;
See, for instances (b) Garo, E.; Hu, J.-F.; Goering, M.; Hough, G.; O’Neil-Johnson,
M.; Eldridge, G. J. Nat. Prod. 2007, 70, 968; (c) Siles, R.; Ackley, J. F.; Hadimani,
M. B.; Hall, J. J.; Mugabe, B. E.; Guddneppanavar, R.; Monk, K. A.; Chapuis, J.-C.;
Petit, G. R.; Chaplin, D. J.; Edvardsen, K.; Trawick, M. L.; Garner, C. M.; Pinney, K.
G. J. Nat. Prod. 2008, 71, 313; (d) Gosslau, A.; Pabbaraja, S.; Knapp, S.; Chen, K. Y.
Eur. J. Pharmacol. 2008, 587, 25; (e) Frémont, L. Life Sci. 2000, 66, 663; (f) Baur, J.
A.; Sinclair, D. A. Nat. Rev. Drug Disc. 2006, 5, 493; (g) Quideau, S.; Deffieux, D.;
Pouységu, L. Angew. Chem., Int. Ed. 2012, 51, 6824, Angew. Chem. 2012, 124,
6930; (h) Novelle, M. G.; Wahl, D.; Diéguez, C.; Bernier, M.; deCabo, R. Ageing
Res. Rev. 2015, 21, 1; (i) Park, E.-J.; Pezzuto, J. M. Biochim. Biophys. Acta Mol. Basis
Dis. 2015, 1852, 1071; (j) Jang, M.; Cai, L.; Udeani, G. O.; Slowing, K. V.; Thomas,
C. F.; Beecher, C. W. W.; Fong, H. H. S.; Farnsworth, N. R.; Mehta, D. R. G.; Moon,
R. C.; Pezzuto, J. M. Science 2015, 275, 218.
2. For a monograph, see: Resveratrol in Health and Disease; Aggarwall, B. B.,
Shishodia, S., Eds.; Taylor & Francis: Boca Ra- ton, FL, USA, 2006.
3. Creasy, L. L.; Coffee, M. J. Am. Soc. Hortic. Sci. 1988, 113, 230.
4. Mahady, G. B. Oxidat. Stress Dis. 2006, 20, 465.
5. Docherty, J. J.; Fu, M. M. H.; Stiffler, B. S.; Limperos, R. J.; Pokabla, C. M.; DeLucia,
A. L. Antivir. Res. 1999, 43, 145.
16. Bazin, M. A.; Kihel, L. E.; Lancelot, J.-C.; Rault, S. Tetrahedron Lett. 2007, 48,
4347.
17. Jung, Y. C.; Mishra, R. K.; Yoon, C. H.; Jung, K. W. Org. Lett. 2003, 5, 2231.
18. Koide, K.; Osman, S.; Garner, A. L.; Song, F.; Dixon, T.; Greenberger, J. S.;
Epperly, M. W. ACS Med. Chem. Lett. 2011, 2, 270.
19. JASTRO (Japanese Society for Therapeutic Radiology and Oncology), Report;
JASTRO (Japanese Society for Therapeutic Radiology and Oncology), 2005.
20. (a) Weiss, J. F.; Landauer, M. R. Int. J. Radiat. Biol. 2009, 85, 539. and references
cited therein; (b)Radioprotectors: Chemical, Biological, and Clinical Perspectives;
Bump, E. A., Malaker, K., Eds.; CRC Press: Boca Raton, FL, 1997.
21. (a) Hosseinimehr, S. J. Drug Discovery Today 2007, 12, 794; (b) Kouvaris, J. R.;
Kouloulias, V. E.; Vlahos, L. J. Oncologist 2007, 12, 738.
22. Sekine-Suzuki, E.; Nakanishi, I.; Shimokawa, T.; Ueno, M.; Matsumoto, K.;
Murakami, T. Anal. Chem. 2013, 85, 7650.
23. Velder, J.; Ritter, S.; Lex, J.; Schmalz, H.-G. Synthesis 2006, 273.
24. General synthetic procedure of stilbenes 4: The mixture of styrene 3 (0.5 mmol)
and phenylboronic acid
2 (182 mg, 1.0 mmol), (CH3CN)2PdCl2 (13 mg,
0.05 mmol) and Na2CO3 (106 mg, 1.0 mmol) in DMF (2.5 mL) was stirred at
50 °C for 3–196 h under an oxygen balloon. The mixture was then diluted with
ethyl acetate (20 mL), and washed with aqueous NaCl solution (3 ꢁ 10 mL).
The organic layer was dried over anhydrous Na2SO4 and filtered. The filtrate
was concentrated in vacuo, and subjected to flash chromatography (ca. 5 g of
6. Jang, M. S.; Cai, E. N.; Udeani, G. O.; Slowing, K. V.; Thomas, C. F.; Beecher, C. W.
W.; Fong, H. H. S.; Farnsworth, N. R.; Kinghorn, A. D.; Mehta, R. G.; Moon, R. C.;
Pezzuto, J. M. Science 1997, 275, 218.

S. Uzura et al. / Bioorg. Med. Chem. Lett. 26 (2016) 3886–3891
3891
SiO2). Elution with hexanes/EtOAc afforded stilbene. General procedure for
demethylation of stilbene 4: In 6 mL of anhydrous methylene chloride, 200 mg
of methoxy-stilbene 4 (0.74 mmol) was dissolved and cooled to ꢀ10 °C under
argon. BBr3 (0.6 mL, 6.3 mmol, 17% in dichloromethane) in anhydrous
methylene chloride (5 mL) was added slowly, and the mixture was allowed
to reach to room temperature for 25 min–24 h. Water was added to destroy the
excess BBr3, and the mixture was extracted twice with ethyl acetate. The
organic extracts were washed with water and brine and dried, and the solvent
evaporated. The crude product was purified by column chromatography on
silica gel (20% EtOAc in hexane) yielding resveratrol and derivatives 1.
25. Due to the instability of compounds 1i, 1j, 1o 1p, 4j, 4k, and 4m along with the
low yields for the productions, their radioprotective effects have not been
evaluated yet. We continue the effort to seek the suitable conditions for the
synthesis of these compounds.