Tetrahydropyrrolization of Resveratrol and Other Stilbenes Improves Inhibitory Effects on DNA Oxidation

Article abstract of DOI:10.1002/cmdc.201600205

The inhibitory effect of resveratrol on DNA oxidation caused by 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH) was found to be enhanced if the C=C bond in resveratrol was converted into tetrahydropyrrole by reaction with azomethine ylide (CH₂=N⁺(CH₃)CH₂^?). This encouraged us to explore whether the inhibitory activities of other stilbenes could also be increased by the same method. We found that the inhibitory effects of the tetrahydropyrrole derivatives on AAPH-induced oxidation of DNA were higher than those of the corresponding stilbenes, because the tetrahydropyrrole motif can provide hydrogen atoms to be abstracted by radicals. Therefore, the tetrahydropyrrolization offered an advantage for enhancing the antioxidant effects of stilbenes. Notably, (CH₃)₃SiCH₂N(CH₃)CH₂OCH₃(in the presence of CF₃COOH) and (CH₃)₃NO (in the presence of LiN(iPr)₂) can be used to generate azomethine ylide for the tetrahydropyrrolization of stilbenes containing electron-withdrawing and -donating groups, respectively.

Full text of DOI:10.1002/cmdc.201600205

DOI: 10.1002/cmdc.201600205
Full Papers
Tetrahydropyrrolization of Resveratrol and Other Stilbenes
Improves Inhibitory Effects on DNA Oxidation
Liang-Liang Bao and Zai-Qun Liu*[a]
The inhibitory effect of resveratrol on DNA oxidation caused
by 2,2’-azobis(2-amidinopropane hydrochloride) (AAPH) was
found to be enhanced if the C=C bond in resveratrol was con-
verted into tetrahydropyrrole by reaction with azomethine
ylide (CH2=N+(CH3)CH2ꢀ). This encouraged us to explore
whether the inhibitory activities of other stilbenes could also
be increased by the same method. We found that the inhibito-
ry effects of the tetrahydropyrrole derivatives on AAPH-in-
duced oxidation of DNA were higher than those of the corre-
sponding stilbenes, because the tetrahydropyrrole motif can
provide hydrogen atoms to be abstracted by radicals. There-
fore, the tetrahydropyrrolization offered an advantage for en-
hancing the antioxidant effects of stilbenes. Notably,
(CH3)3SiCH2N(CH3)CH2OCH3 (in the presence of CF3COOH) and
(CH3)3NO (in the presence of LiN(iPr)2) can be used to generate
azomethine ylide for the tetrahydropyrrolization of stilbenes
containing electron-withdrawing and -donating groups, re-
spectively.
Introduction
Stilbenes are usually found in plants and herbs[1] and are at the
convergence point of biological and medicinal investigations
because of their abilities to defend against oxidative stress.[2] In
particular, resveratrol attracts much research attention, as it is
able to protect neurological systems,[3] treat cancers,[4] delay
aging and angiogenesis,[5] and prevent cardiovascular diseas-
es.[6] In addition to the aforementioned pharmacological activi-
ties, the antioxidant effect of resveratrol plays a key role in
treating various other diseases.[7] However, it is worth noting
that resveratrol may also play a pro-oxidative role in some
cases.[8] Recently, some efforts have been dedicated to decreas-
ing the side effects of resveratrol. As shown in Figure 1, a CꢀC
coupling reaction was performed on cis-resveratrol to give a hy-
droxy-appended phenanthrene, which can inhibit DNA cleav-
generation of azomethine ylide. Meanwhile, theoretical calcula-
tions revealed that the hydrogen atoms at the a-position of
tetrahydropyrrole can be abstracted by radicals.[14] In light of
the aforementioned background, as shown in Figure 2, we
herein provide a cycloaddition pathway for constructing the
tetrahydropyrrole moiety based on the C=C bond in stilbene
(prepared in advance by Wittig–Horner reaction)[15] and azome-
thine ylide.[16] We therefore evaluated and compared the inhib-
itory effects of stilbenes and the corresponding tetrahydropyr-
role derivatives on oxidation of DNA caused by 2,2’-azobis(2-
amidinopropanehydrochloride) (AAPH; R-N=N-R, R=ꢀCMe2C(=
NH)NH2).
age efficiently.[9] Additionally, a 3,4,5-trimethoxyphenyl-substi- Results and Discussion
tuted 1,3,4-oxadiazole moiety in combination with stilbene can
increase the activity against phytopathogenic fungi.[10]
Inhibitory effects of resveratrol and its tetrahydropyrrole
derivative
The structure of a naturally occurring pyrrole derivative, la-
mellarin (see Figure 1), provided us with an approach for en-
hancing the antioxidant effect of stilbene.[11] Meanwhile, ample
evidence suggests that nitrogen-rich polyheterocycles may
generate abundant bioactivities.[12] But, to the best of our
knowledge, there have been few reports to date on bioactivi-
ties of tetrahydropyrrole derivatives of resveratrol and other
stilbenes,[13] because tetrahydropyrrolization is related to the
Ample evidence indicates the benefits of resveratrol on
health,[17] but some controversy still exists regarding the active
function of resveratrol.[18] For example, resveratrol may repair
DNA damage in the presence of CuI[19] through an acid/base-
promoted pro-oxidant reaction.[20] The shortcomings of resver-
atrol encouraged us to start our research by testing the effect
of resveratrol on peroxyl radical-induced DNA oxidation,
during which the decomposition of AAPH can provide a peroxyl
C
radical (ROO ) with a stable rate (Rg) at 378C: Rg =(1.4ꢁ0.2)ꢀ
[a] L.-L. Bao, Prof. Dr. Z.-Q. Liu
10ꢀ6 [AAPH] sꢀ1 [21]
.
As shown in Figure 3, in the control experi-
Department of Organic Chemistry, College of Chemistry,
Jilin University, No. 2519 Jiefang Road, Changchun 130021 (China)
E-mail: zaiqun-liu@jlu.edu.cn
ment, the increase in the absorbance of thiobarbituric acid re-
active species (TBARS) means that many more oxidative prod-
ucts are generated from DNA damage with the increase in re-
action time. However, in the presence of resveratrol, TBARS
were not formed for a period, then formation recovered as in
the control experiment. Thus, resveratrol (27) can hinder DNA
Supporting information for this article can be found under http://
dx.doi.org/10.1002/cmdc.201600205: NMR spectra of the synthesized
compounds, variation in TBARS absorbance during reaction period, and
relationship between inhibition period (tinh) and antioxidant concentra-
tion.
ChemMedChem 2016, 11, 1 – 10
1
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 1. Recently developed stilbene derivatives.
Figure 2. General procedures for the tetrahydropyrrolization of stilbenes and the preparation of tetrahydropyrrole derivatives of resveratrol (28).
oxidation for an inhibitory period (tinh). The relationship be-
tween the tinh and the concentration of resveratrol (Figure 3B)
is quantitatively expressed by Equation (1):
The coefficient in Equation (2) includes the initiation rate of
the radical-induced oxidation (Ri) and the stoichiometric factor
(n) of the antioxidant. The stoichiometric factor (n) is the
number of radical propagations terminated by one molecule
of the antioxidant. The coefficient in Equation (1) is equivalent
to n/Ri in Equation (2). It is difficult to measure the initiation
rate (Ri) of DNA oxidation directly. However, as both the DNA
sodium salt and AAPH are water-soluble compounds, and
tinh ¼ 1:10 ðꢁ0:04Þ ½27ꢂ þ 38:62 ðꢁ3:05Þ
ð1Þ
Chemical kinetics proved that the tinh generated by an anti-
oxidant correlates proportionally with the concentration of the
antioxidant, as shown as Equation (2):[21]
C
ROO derived from the decomposition of AAPH initiates DNA
oxidation in the water phase, it is safely to assume that the ini-
tiation rate (Ri) of DNA oxidation is equal to the radical genera-
tion rate (Rg); therefore, Ri =Rg =1.4ꢀ10ꢀ6 ꢀ40 mmsꢀ1
=
tinh ¼ ðn=RiÞ ½antioxidantꢂ
ð2Þ
&
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
2
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
Figure 3. A) Absorbance of TBARS in AAPH-induced oxidation of DNA in the presence of various concentrations of resveratrol (27) and its tetrahydropyrrole
derivative 28 and B) the relationship between the inhibition period (tinh) and compound concentration.
3.36 mmminꢀ1.[22] The stoichiometric factor (n) of resveratrol is
tinh ¼ 1:35 ðꢁ0:05Þ ½28ꢂ þ 44:65 ðꢁ1:96Þ
ð3Þ
the product of the coefficient in Equation (1) and Ri
(3.36 mmminꢀ1); therefore, 1.10 (ꢁ0.04)ꢀ3.36=3.7 (ꢁ0.2). As
a result, resveratrol can terminate 3.7 radical propagations
during the protection of DNA against AAPH-induced oxidation.
A method has been reported to measure oxygen radical ab-
sorbance capacity (ORAC) using fluorescein (FL) as a fluorescent
probe.[23] In the case of vitamin E or Trolox, used as a reference,
ORAC-FL measurement led to an antioxidative effectiveness in
relation to the standard antioxidant. On the other hand, the
benefit of the presented method is to bridge chemically kinetic
expression [Eq. (2)] with the biological experimental material
(DNA used herein), leading to a quantitative expression of the
antioxidant effectiveness using a stoichiometric factor (n). The
stoichiometric factor (n) does not correlate with the measure-
ment condition, because Rg takes the temperature (378C) into
account, while the antioxidant concentration acts as the varia-
ble parameter in Equation (2). We examined the stoichiometric
factor (n) of Trolox; however, it cannot generate tinh in the
same manner as compounds 2 and 13. Trolox decreases the
oxidation rate of DNA instead of temporarily inhibiting this oxi-
dation for a period of time. Therefore, Trolox does not gener-
ate the stoichiometric factor (n) needed.[24]
Accordingly, the stoichiometric factor (n) of 28 was obtained
as 4.6 (ꢁ0.2), which is higher than that of resveratrol (3.7).
Therefore, it could be concluded that tetrahydropyrrolization
enhanced the antioxidant effect of resveratrol.
Tetrahydropyrrolization of other stilbenes
We attempted to synthesize a series of tetrahydropyrrole deriv-
atives of stilbenes to determine whether tetrahydropyrroliza-
tion could be a suitable protocol for increasing the antioxidant
effects of stilbenes. Stilbenes with electron-donating or -with-
drawing groups were prepared by using Wittig–Horner reac-
tion, then trimethylamine-N-oxide was used as the precursor
ꢀ
of CH2=N+(CH3)CH2 to carry out the cycloaddition. As shown
in Figure 4, a single hydroxy group at the ortho-, para-, and
meta-positions in stilbene gave 3, 5, and 7, respectively. Using
the structure of 3, a chloride, bromide, or nitro group was
linked with the para-position of hydroxy group to afford 9, 11,
and 13, respectively. Furthermore, a bromide was allocated at
the ortho-position of another benzene ring in 3 to give 17.
Using the structure of 17, a chloride, bromide, or nitro group
was attached to the para-position of hydroxy group to afford
19, 21, and 23, respectively. In addition, a vanillin was applied
to perform a Wittig–Horner reaction to give 15, to which a bro-
mide was added at the ortho-position of another benzene ring
to access 25. Subsequently, the aforementioned stilbenes react
with (CH3)3NO in the presence of LiN(iPr)2 to give tetrahydro-
pyrrole derivatives, 2, 4, 6, 8, 10, 12, 16, 18, and 26, respective-
ly.
Pyrrolization is able to improve the antioxidant function of
some proteins,[25] while some natural pyrrole derivatives such
as lamellarin (Figure 1) also exhibit tumor growth inhibitory ac-
tivities.[26] As shown in Figure 2, the aforementioned back-
ground motivated us to react resveratrol with azomethine
ylide (CH2=N+(CH3)CH2ꢀ), which is derived from treatment of
trimethylamine-N-oxide with lithium diisopropylamide (LDA).
The tetrahydropyrrolization of trans-resveratrol generated 28,
in which double phenyl groups located on two sides of the
tetrahydropyrrole form a raceme. It is worth noting that the
hydroxy groups in resveratrol should be protected by
CH3OCH2Cl (forming 27’) to avoid oxidation during the cyclo-
addition process. The CH3OCH2- protecting group can be readi-
ly removed under acidic conditions. Subsequently, as shown in
Figure 3, the inhibitory effect of a tetrahydropyrrole derivative
of resveratrol 28 on AAPH-induced oxidation of DNA was mea-
sured, and the quantitative relationship between the concen-
tration of 28 and tinh is expressed by Equation (3):
Unfortunately, compounds 14, 20, 22, and 24 failed to be
synthesized using trimethylamine-N-oxide as the precursor of
CH2=N+(CH3)CH2ꢀ. We found that the corresponding stil-
benes—13, 19, 21, and 23—containing electron-withdrawing
groups (-NO2, -Cl, and -Br) did not undergo cycloaddition with
(CH3)3NO in the presence of LiN(iPr)2. Thus, another precursor
was evaluated for cycloaddition with these stilbenes.
(CH3)3SiCH2Cl was heated in CH3NH2, followed by addition of
HCHO and CH3OH to afford (CH3)3SiCH2N(CH3)CH2OCH3 (see
Figure 2).[27] After the hydroxy groups in 13, 19, 21, and 23
were
acetylated,
these
stilbenes
reacted
with
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
3
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Figure 4. Stilbenes and tetrahydropyrrole derivatives synthesized in this work.
(CH3)3SiCH2N(CH3)CH2OCH3 in the presence of CF3COOH to
afford desired products, 14, 20, 22, and 24, respectively. Fortu-
nately, the acetate on the hydroxy group could be simultane-
ously removed during the cycloaddition process.
We herein attempt to explain the reason why
(CH3)3SiCH2N(CH3)CH2OCH3 should be applied to perform the
cycloaddition of stilbenes with electron-withdrawing groups. A
hydrogen atom from (CH3)3NO is directly abstracted by
&
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
4
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
LiN(iPr)2 to afford CH2=N+(CH3)CH2ꢀ, which accepts the elec-
trons from the C=C of stilbene during the cycloaddition. Thus,
the electron-donating group in stilbene is beneficial for elec-
trons in C=C to transfer to CH2=N+(CH3)CH2ꢀ. On the other
tron-donating group (such as -OCH3) can largely enhance the
antioxidant effect of the tetrahydropyrrole derivative. This phe-
nomenon can also be found by comparing the n value of 26
(2.1) with that of 25 (0.9). This is in line with the traditional
conclusion that electron-donating groups are able to increase
antioxidant activity. Compared with the n value of 4 (2.7), the
low n value of 18 (1.8) indicates that the bromide atom on an-
other phenyl group cannot ameliorate the inhibitory effect of
the tetrahydropyrrole derivative. Also, the n value of 10 (2.6)
was close to that of 20 (2.4), and the n value of 12 (3.3) ap-
proached that of 22 (3.4), revealing that a bromide atom on
another phenyl group could not provide additional antioxidant
effects for tetrahydropyrrole derivatives. In contrast, the differ-
ence between the n values of 18 (1.8) vs. 17 (1.2), 20 (2.4) vs.
19 (1.7), and 24 (0.5) vs. 23 (0.1) were not as large as other
pairs of stilbenes and tetrahydropyrroles. Therefore, a bromide
atom on another phenyl group results in an average of the n
values of the stilbene/tetrahydropyrrole pair. Interestingly, the
n value of 22 (3.4) was much higher than that of the corre-
sponding stilbene, 21 (0.7), implying that two bromide atoms
located on different phenyl groups largely increases the antiox-
idant effect of the tetrahydropyrrole derivative. This is in agree-
ment with our previous finding that bromide atoms play an
antioxidative role in protecting DNA against AAPH-induced ox-
idation.[29] Therefore, tetrahydropyrrolization, in combination
with an electron-donating group, is able to improve the anti-
oxidant effects of stilbenes. Meanwhile, the potential antioxi-
dant effect derived from a bromide atom is worth exploring in
future work.
hand, the (CH3)3Si- and -OCH3 groups must be dissociated from
ꢀ
(CH3)3SiCH2N(CH3)CH2OCH3 in order to form CH2=N+(CH3)CH2
.
The bond dissociation energy of C-Si is 72 kcalmolꢀ1, while
that of CꢀO is 86 kcalmolꢀ1. Thus, the C-Si is readily dissociat-
ed to form a carbanion (ꢀCH2N(CH3)CH2OCH3). Next, the elec-
tron in the carbanion transfers to the C=C in stilbene. A stil-
bene with an electron-withdrawing group is beneficial for ac-
cepting the electron from CH2=N+(CH3)CH2ꢀ. This is in line
with a previous report in which a substrate with an electron-
withdrawing group prefers to undergo cycloaddition with an
azomethine ylide derived from a silane precursor.[28]
Inhibitory effects of tetrahydropyrrole derivatives of other
stilbenes
The stoichiometric factors (n) of stilbenes and tetrahydropyr-
role derivatives are outlined in Figure 5. The n values of all tet-
rahydropyrrole derivatives were found to be higher than those
of the corresponding stilbenes, demonstrating that tetrahydro-
pyrrolization actually enhances the antioxidant effect of stil-
benes. A decreasing trend was found when comparing the n
values of 4, 6, and 8 (2.7, 1.8, and 1.3, respectively). This result
indicated that the antioxidant effect of a single hydroxy group
follows the order: ortho->para->meta with regard to the po-
sition on the phenyl group in the tetrahydropyrrole derivatives.
The n value of 4 (2.7) is similar to that of 10 (2.6), implying
that introduction of a chloride atom onto the phenyl group
did not markedly affect the antioxidant effect of a tetrahydro-
pyrrole derivative. The high n value of 12 (3.3) revealed that
the bromide atom was beneficial for the antioxidant effect of
the tetrahydropyrrole derivative, but this positive effect of bro-
mide was invalid for stilbenes, because the n value of 11 is 1.9
and therefore approaching that of 9 (1.6). On the other hand,
the low n value of 14 (1.4) means that the nitro electron-with-
drawing group could not increase the antioxidant effect of the
compound, 13 only decreased the TBARS formation rate with-
out generating a tinh value, and 23 and 24 (both containing
-NO2) possessed the lowest n values (0.1 and 0.5, respectively).
On the contrary, the n value of 16 (3.7) is higher than that of
the corresponding stilbene 15 (1.5), indicating that an elec-
Antioxidant effect derived from the tetrahydropyrrolization
To clarify the function of the tetrahydropyrrole moiety, we se-
lected compounds 1 and 2 for a comparison of the antioxidant
effects. As shown in Figure 3S, the addition of 1 (even at
400 mm) did not increase the absorbance of TBARS during the
oxidation of DNA. However, the addition of 2 (at 400 mm)
slows the increase in the rate of TBARS absorbance; thus, 2 is
able to hinder the oxidation of DNA, although tinh cannot be
generated. The tetrahydropyrrole moiety can thereby be re-
garded as the contributor to the antioxidant effect of 2. In ad-
dition, 2 is a suitable compound for exploring the antioxidant
mechanism, because no other substituents are involved to
cover the function of the tetrahydropyrrole moiety.
A previous report revealed a theoretical possibility
for converting the tetrahydropyrrole scaffold into pyr-
role through a decreasing process of the transition
energy.[30] Meanwhile, it was proven that the hydro-
gen atoms at the a-position of tetrahydropyrrole are
readily abstracted by radicals, resulting in eventual
aromatization.[14] As shown in Figure 6, the 1H NMR
spectrum of 2 indicates that the peaks at 3.56, 3.39,
and 3.15 ppm were assigned to the hydrogen atoms
on the tetrahydropyrrole moiety, while the peak at
2.67 ppm was assigned to a hydrogen atom from
CH3 in the tetrahydropyrrole moiety (NꢀCH3). Further
Figure 5. The stoichiometric factor (n) of stilbenes and their tetrahydropyrrole derivatives
and resveratrol (27) and its tetrahydropyrrole derivative 28.
investigations focused on the preparation of a pyrrole
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
5
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
Conclusions
Conversion of the double bond in stilbene into a tetrahydropyr-
role moiety by reaction with azomethine ylide enhanced the
antioxidant effect of stilbene, because the tetrahydropyrrole
moiety provides hydrogen atoms to be abstracted by radicals.
In addition, the antioxidant effects of tetrahydropyrrole deriva-
tives can be further improved by attaching an electron-donat-
ing
group
to
the
phenyl
groups.
Essentially,
(CH3)3SiCH2N(CH3)CH2OCH3 (in CF3COOH) was used as the pre-
ꢀ
cursor of CH2=N+(CH3)CH2 to react with stilbenes involving
electron-withdrawing groups, while (CH3)3NO (in lithium diiso-
ꢀ
propylamide) was a popular precursor of CH2=N+(CH3)CH2 for
the tetrahydropyrrolization of other stilbenes. In the continued
quest for novel antioxidants, tetrahydropyrrolization may offer
an advantage for enhancing the effectiveness of other double-
bond-containing antioxidants.
Experimental Section
Materials and instrumentation
AAPH and naked DNA sodium salt were purchased from Acros Or-
ganics (Geel, Belgium) and used as received. Solvents and reagents
used in synthesis were obtained commercially and used as such
unless noted otherwise. All products were identified by 1H and
13C NMR spectroscopy using a Bruker Avance III 400 MHz spectrom-
eter. The NMR spectra are provided in the Supporting Information.
The purity of all products was detected by high performance liquid
chromatography as higher than 98%, and molecular weights were
determined by high-resolution mass spectrometry (HRMS) with
electrospray ionization (ESI) as the ionization mode using an Agi-
lent 1290-micrOTOF QII spectrometer.
Figure 6. 1H NMR spectra of compound 1 and its pyrrole and tetrahydropyr-
role derivatives.
Tetrahydropyrrolization of resveratrol
trans-3-(3,5-Dihydroxyphenyl)-4-(4-hydroxyphenyl)-1-methylpyr-
rolidine (28): The synthesis of compound 28 involved protection
of the hydroxy groups of resveratrol and cycloaddition by trime-
thylamine-N-oxide. Sodium hydride (70% in mineral oil, 275 mg,
8 mmol) was added to tetrahydrofuran (THF; 15 mL) at 08C under
nitrogen, and a THF solution of trans-resveratrol (27, 456 mg,
2 mmol) was added dropwise and stirred for 30 min, followed by
dropwise addition of CH3OCH2Cl (886 mg, 11 mmol) and stirring for
24 h at room temperature. After THF was removed under vacuum,
the residue was dissolved in water. The aqueous phase was ex-
tracted with EtOAc. The combined EtOAc layers were washed with
saturated NaCl aqueous solution and dried over Na2SO4. After the
organic solvent was evaporated, the residue was purified by flash
column chromatography with petroleum ether/EtOAc as the
eluent to afford (E)-1,3-dimethoxy-5-(4-methoxystyryl)benzene (27’)
in 30% yield (219 mg): 1H NMR (400 MHz, CDCl3): d=7.46 (d, J=
8.6 Hz, 2H), 7.06 (d, J=16.4 Hz, 1H), 7.05 (d, J=8.6 Hz, 2H), 6.93
(d, J=16.4 Hz, 1H), 6.88 (d, J=2.0 Hz, 2H), 6.66 (t, J=2.0 Hz, 1H),
5.22 (s, 6H), 3.53 (s, 6H), 3.52 ppm (s, 3H).
derivative of 2 in order to observe the variation in chemical
shifts of the aforementioned hydrogen atoms. Attempt to aro-
matize 2 using MnO2 led to a novel NMR spectrum (see
Figure 6) in which the peaks of the hydrogen atoms in the tet-
rahydropyrrole scaffold (around 3.56–3.15 ppm) almost disap-
peared. Instead, the peak of the hydrogen atom on the pyrrole
scaffold was found at 6.75 ppm (hydrogen atom on the aro-
matic ring), while the peak of the hydrogen atom at NꢀCH3
shifted from 2.67 to 3.74 ppm (CH3 on the aromatic ring).
In the case of 2 (dissolved in DMSO as the stock solution),
combined with AAPH (dissolved in PBS solution) and incubat-
ed at 378C (as the measurement of inhibiting DNA oxidation
except that DNA is not added) for a period, the oxidative prod-
1
uct was extracted with EtOAc. The H NMR spectrum of the ox-
idative product indicated the characteristic peaks of the hydro-
gen atoms on the pyrrole scaffold and NꢀCH3, at 6.84 and
C
3.75 ppm, respectively. Thus, ROO derived from the decompo-
trans-3-(3,5-Dimethoxymethoxyphenyl)-4-(4-methoxymethoxy-
phenyl)-1-methylpyrrolidine (28’): Compound 27’ (108 mg,
0.3 mmol) and trimethylamine-N-oxide (33.8 mg, 0.45 mmol) were
dissolved in THF (3 mL). The trimethylamine-N-oxide was prepared
by oxidizing a 33% aqueous solution of (CH3)3N (25 mL) with
a 30% aqueous solution of H2O2 (20 mL) at 08C and stirring for
sition of AAPH can oxidize the tetrahydropyrrole moiety to
form a pyrrole scaffold. This procedure results in an antioxidant
effect for tetrahydropyrrole derivatives of stilbenes.
&
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
6
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
24 h. The solvents were then evaporated under vacuum. Lithium
diisopropylamide (LDA, dissolved in heptane/THF at 2m, 0.9 mL,
1.8 mmol) was added dropwise at 08C under nitrogen and stirred
for 3 h. After completion of the reaction, as indicated by thin-layer
chromatography (TLC), water (10 mL) was added, and heptane and
THF were removed under vacuum. The residue was dissolved in
EtOAc (15 mL), and the aqueous layer was extracted with EtOAc
(2ꢀ10 mL). The combined EtOAc layers were washed with saturat-
ed NaCl aqueous solution and dried over Na2SO4. After the organic
solvent was evaporated, the residue was purified by flash column
chromatography with petroleum ether/ EtOAc as the eluent to
10H), 3.56 (t, J=5.7 Hz, 2H), 3.43–3.36 (m, 2H), 3.19–3.11 (m, 2H),
2.67 ppm (s, 3H); 13C NMR (100 MHz, CDCl3): d=128.9, 128.8, 128.5,
127.5, 126.5, 64.1, 53.5, 42.5 ppm; HRMS (ESI): calcd for [M+H]+ of
C17H20N: 238.1596, found: 238.1596.
(E)-2-Styrylphenol (3): light-yellow solid (yield: 61%, 723 mg).
trans-1-Methyl-3-(2- hydroxyphenyl)-4-phenylpyrrolidine (4):
1
light-yellow oil (yield: 47%, 60 mg): H NMR (400 MHz, CDCl3): d=
7.34 (t, J=7.4 Hz, 2H), 7.25 (d, J=7.4 Hz, 3H), 7.15 (t, J=7.5 Hz,
1H), 6.95 (d, J=8.0 Hz, 1H), 6.85 (d, J=7.5 Hz, 1H), 6.69 (t, J=
7.3 Hz, 1H), 3.66 (t, J=8.6 Hz, 1H), 3.62–3.54 (m, 1H), 3.34–3.28 (m,
1H), 3.25 (d, J=9.8 Hz, 1H), 2.85 (t, J=8.8 Hz, 1H), 2.57 (s, 3H),
2.47 ppm (t, J=9.6 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=156.0,
143.2, 130.0, 128.7, 128.3, 127.3, 126.7, 118.4, 117.8, 64.5, 61.9, 53.0,
51.6, 40.1 ppm; HRMS (ESI): calcd for [M+H]+ of C17H20NO:
254.1545, found: 254.1531.
1
afford compound 28’ as a brown oil (yield: 41%, 51 mg): H NMR
(400 MHz, CDCl3): d=7.14 (d, J=8.6 Hz, 2H), 6.93 (d, J=8.7 Hz,
2H), 6.58 (t, J=2.2 Hz, 1H), 6.54 (d, J=2.2 Hz, 2H), 5.14 (s, 2H),
5.10 (s, 4H), 3.46 (s, 3H), 3.45 (s, 6H), 3.35 (dd, J=19.0 Hz, 8.2 Hz,
2H), 3.15 (dd, J=17.7 Hz, 9.8 Hz, 2H), 2.91–2.84 (m, 2H), 2.48 ppm
(s, 3H); HRMS (ESI): calcd for [M+H]+ of C23H32NO6: 418.2230,
found: 418.2202.
(E)-4-Styrylphenol (5): light-yellow solid (yield: 59%, 688 mg).
trans-1-Methyl-3-(4-hydroxyphenyl)- 4-phenylpyrrolidine (6):
1
light-yellow oil (yield: 32%, 41 mg): H NMR (400 MHz, CDCl3): d=
trans-3-(3,5-Dihydroxyphenyl)-4-(4-hydroxyphenyl)-1-methylpyr-
rolidine (28): A 38% HCl aqueous solution (120 mL) was added to
a methanolic solution (1.2 mL) of 28’ (16.7 mg, 0.04 mmol), and the
mixture was stirred at room temperature for 24 h. The solvent was
then removed under vacuum to afford compound 28 as a brown
oil (yield ~100%, 11 mg): 1H NMR (400 MHz, [D6]DMSO): d=7.07
(dd, J=25.3 Hz, 6.1 Hz, 2H), 6.69 (d, J=6.1 Hz, 2H), 6.12 (s, 2H),
6.08 (s, 1H), 3.79 (s, 2H), 3.38 (m, 2H), 3.26 (s, 2H), 2.93 ppm (s,
3H); 13C NMR (100 MHz, [D6]DMSO): d=158.9, 157.2, 143.9, 129.0,
115.8, 106.1, 104.4, 101.9, 64.3, 61.3, 51.3, 49.6, 41.5 ppm; HRMS
(ESI): calcd for [M+H]+ of C17H20NO3: 286.1443, found: 286.1432.
7.25–7.10 (m, 5H), 6.95 (d, J=8.3 Hz, 2H), 6.72 (d, J=8.4 Hz, 2H),
3.47–3.38 (m, 2H), 3.38–3.31 (m, 1H), 3.28 (dd, J=9.9 Hz, 7.4 Hz,
1H), 3.05 (td, J=13.3 Hz, 8.3 Hz, 2H), 2.59 ppm (s, 3H); 13C NMR
(100 MHz, CDCl3): d=155.8, 141.6, 131.9, 128.1, 127.2, 126.3, 114.9,
63.5, 63.2, 53.1, 52.5, 41.5 ppm; HRMS (ESI): calcd for [M+H]+ of
C17H20NO: 254.1545 [M+H]+, found: 254.1537.
(E)-3-Styrylphenol (7): light-yellow solid (yield: 85%, 997 mg).
trans-1-Methyl-3-(3-hydroxyphenyl)- 4-phenylpyrrolidine (8):
1
light-yellow oil (yield: 62%, 78 mg): H NMR (400 MHz, CDCl3): d=
7.27–7.17 (m, 5H), 7.11 (t, J=7.8 Hz, 1H), 6.76 (s, 1H), 6.71 (d, J=
7.9 Hz, 2H), 3.52–3.38 (m, 2H), 3.24 (dd, J=9.6 Hz, 7.7 Hz, 1H), 3.17
(dd, J=9.8 Hz, 8.0 Hz, 1H), 3.01 (dd, J=9.8 Hz, 7.7 Hz, 1H), 2.92
(dd, J=9.5 Hz, 8.3 Hz, 1H), 2.51 ppm (s, 3H); 13C NMR (100 MHz,
CDCl3): d=157.2, 143.5, 141.6, 129.6, 128.5, 127.5, 126.6, 119.0,
114.7, 114.3, 63.7, 63.6, 52.8, 52.7, 42.6 ppm; HRMS (ESI): calcd for
[M+H]+ of C17H20NO: 254.1545, found: 254.1532.
General method for the synthesis of 1–12, 15–18, 25, and 26:
Syntheses of (E)-1,2-diphenylethene (1) and trans-1-methyl-3,4-di-
phenylpyrrolidine (2) were used as examples. Diethyl benzyl-
phosphonate (2736 mg, 12 mmol) was prepared by heating benzyl
bromide (22 g, 125 mmol) and triethyl phosphite (25 g, 150 mmol)
in acetonitrile (60 mL) at 1408C for 16 h and then drying the mix-
ture under vacuum. The resulting residue was used directly by dis-
solving in THF (5 mL), then adding sodium hydride (823 mg, 70%
in mineral oil, 24 mmol) and a THF solution of benzaldehyde (5 mL,
636 mg, 6 mmol) at ꢀ108C over 20 min under nitrogen. The tem-
perature was allowed to rise to room temperature, and the mixture
was stirred for 3 h. After completion of the reaction as indicated by
TLC, water (10 mL) was added. The THF solution was evaporated
under vacuum, and the residue was dissolved in EtOAc (20 mL).
The aqueous layer was extracted with EtOAc (2ꢀ15 mL), and the
combined organic layers were washed with saturated NaCl solution
and dried over Na2SO4. After the organic solvent was evaporated,
the residue was purified by silica gel chromatography with petrole-
um ether/EtOAc as the eluent to afford compound 1 as a white
crystalline solid (yield: 74%, 799 mg).
(E)-4-Chloro-2-styrylphenol (9): white solid (yield: 59%, 817 mg).
trans-1-Methyl-3-(2-hydroxy-4-
chlorophenyl)-4-phenylpyrroli-
1
dine (10): brown oil (yield: 55%, 78 mg): H NMR (400 MHz, CDCl3):
d=7.35 (t, J=7.3 Hz, 2H), 7.23 (d, J=7.3 Hz, 3H), 7.08 (d, J=
8.5 Hz, 1H), 6.85 (d, J=8.6 Hz, 1H), 6.81 (s, 1H), 3.66 (t, J=8.7 Hz,
1H), 3.56 (s, 1H), 3.24 (d, J=8.8 Hz, 2H), 2.88 (t, J=8.6 Hz, 1H),
2.59 (s, 3H), 2.50 ppm (t, J=9.8 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d=154.8, 129.3, 128.8, 128.0, 127.3, 127.0, 122.6, 119.1, 64.4, 61.6,
52.5, 51.3, 40.0 ppm; HRMS (ESI): calcd for [M+H]+ of C17H19NOCl:
288.1155, found: 288.1151.
(E)-4-Bromo-2-styrylphenol (11): light-yellow solid (yield: 60%,
986 mg). trans-1-Methyl-3-(2- hydroxy-4-bromophenyl)-4-phenyl-
1
pyrrolidine (12): brown oil (yield: 48%, 96 mg): H NMR (400 MHz,
CDCl3): d=7.35 (t, J=7.2 Hz, 2H), 7.28–7.18 (m, 4H), 6.95 (s, 1H),
6.80 (d, J=8.5 Hz, 1H), 3.65 (t, J=8.7 Hz, 1H), 3.57–3.49 (m, 1H),
3.22 (d, J=9.4 Hz, 2H), 2.85 (t, J=8.8 Hz, 1H), 2.57 (s, 3H),
2.47 ppm (t, J=9.8 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=155.4,
142.8, 132.1, 130.9, 128.8, 127.3, 126.9, 119.7, 109.8, 64.6, 61.7, 52.7,
51.5, 40.0 ppm; HRMS (ESI): calcd for [M+H]+ of C17H19NOBr:
332.0650, found: 332.0644.
Compound
1 (369 mg, 2 mmol) and trimethylamine-N-oxide
(225 mg, 3 mmol) were dissolved in THF (10 mL), followed by drop-
wise addition of lithium diisopropylamide (6 mL, dissolved in hep-
tane/THF at 2m, 12 mmol) at 08C under nitrogen. The mixture was
stirred for 3 h. After completion of the reaction as indicated by
TLC, water (10 mL) was added. The THF solution was evaporated
under vacuum, and the residue was dissolved in EtOAc (15 mL).
The aqueous layer was extracted with EtOAc (2ꢀ10 mL). The com-
bined organic layers were washed with saturated NaCl solution
and dried over Na2SO4. After the organic solvent was evaporated,
the residue was purified by silica gel chromatography with petrole-
um ether/EtOAc as the eluent to afford compound 2 as a yellow
(E)-2-Methoxy-4-styrylphenol (15): white solid (yield: 72%,
649 mg). trans-1-Methyl-3-(3- methoxy-4-hydroxyphenyl)-4-phe-
nylpyrrolidine (16): light-yellow oil (yield: 58%, 99 mg): 1H NMR
(400 MHz, CDCl3): d=7.29 (d, J=7.2 Hz, 2H), 7.23 (d, J=7.3 Hz,
3H), 6.81 (d, J=8.0 Hz, 1H), 6.73 (s, 1H), 6.70 (d, J=8.1 Hz, 1H),
3.83 (s, 3H), 3.38 (dd, J=14.6 Hz, 8.2 Hz, 2H), 3.19 (q, J=8.3 Hz,
1
oil (yield: 16%, 75 mg): H NMR (400 MHz, CDCl3): d=7.43–7.11 (m,
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
7
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Full Papers
2H), 2.94 (t, J=8.2 Hz, 2H), 2.52 ppm (s, 3H); 13C NMR (100 MHz,
CDCl3): d=146.8, 144.5, 142.4, 134.2, 128.5, 127.5, 126.5, 120.0,
114.4, 110.1, 63.9, 63.7, 55.8, 53.5, 53.2, 42.5 ppm; HRMS (ESI): calcd
for [M+H]+ of C18H22NO2: 284.1651, found: 284.1643.
(s, 1H), 7.21 (d, J=7.2 Hz, 3H), 6.92 (d, J=9.1 Hz, 1H), 3.75–3.66
(m, 1H), 3.50 (t, J=10.5 Hz, 1H), 3.39 (d, J=7.3 Hz, 1H), 3.29–3.20
(m, 1H), 2.93 (t, J=12.3 Hz, 1H), 2.63 (s, 3H), 2.54 ppm (t, J=
9.9 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=171.2, 142.2, 137.3,
131.0, 129.0, 128.7, 125.9, 124.9, 122.9, 118.4, 61.0, 60.4, 52.6, 51.3,
44.1 ppm; MALDI-TOF mass: calcd for [M]+ of C17H18N2O3:
298.1320; found: 298.7640.
(E)-2-(2-Bromostyryl)phenol (17): white solid (yield: 67%,
1104 mg). trans-1-Methyl-3-(2- hydroxyphenyl)-4-(2-bromophe-
nyl)pyrrolidine (18): light-yellow oil (yield: 53%, 71 mg): 1H NMR
(400 MHz, CDCl3): d=7.54 (dd, J=8.0 Hz, 1.0 Hz, 1H), 7.42 (dd, J=
7.8 Hz, 1.6 Hz, 1H), 7.38–7.32 (m, 1H), 7.12 (tdd, J=8.9 Hz, 8.1 Hz,
1.7 Hz, 2H), 6.93 (d, J=8.1 Hz, 1H), 6.81 (dd, J=7.5 Hz, 1.4 Hz, 1H),
6.66 (td, J=7.4 Hz, 1.1 Hz, 1H), 4.13 (ddd, J=10.1 Hz, 8.1 Hz,
4.5 Hz, 1H), 3.71 (t, J=8.8 Hz, 1H), 3.41 (dd, J=7.5 Hz, 4.7 Hz, 1H),
3.28 (d, J=9.8 Hz, 1H), 2.94 (t, J=8.7 Hz, 1H), 2.57 (s, 3H),
2.37 ppm (t, J=9.9 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=155.9,
133.2, 130.0, 129.9, 128.4, 128.2, 128.0, 124.7, 118.4, 117.7, 63.7,
61.9, 51.5, 50.5, 40.3 ppm; HRMS (ESI): calcd for [M+H]+ of
C17H19NOBr: 334.0630, found: 334.0617.
The aforementioned (CH3)3SiCH2N(CH3)CH2OCH3 was prepared by
heating (CH3)3SiCH2Cl (12 mL, 82 mmol) and 30% CH3NH2 aqueous
solution (27.6 mL, 164 mmol) in a hydrothermal reactor at 858C for
12 h, and the organic layer was distilled at 90–1008C to obtain
(CH3)3SiCH2NHCH3. Then, (CH3)3SiCH2NHCH3 (20 g, 172 mmol) was
added to a 37% HCHO aqueous solution (14 g, 172 mmol) at
ꢀ58C, the reaction was stirred for 30 min, and then CH3OH (7 mL,
172 mmol) and K2CO3 (18 g, 112 mmol) were added, and the mix-
ture was stirred for an additional 1 h. The organic layer was sepa-
rated, and K2CO3 (1.2 g, 8.5 mmol) was added at ꢀ58C and stirred
for 1 h. The reaction mixture was filtered, and 5 ꢂ molecular sieves
(E)-4-(2-Bromostyryl)-2-methoxyphenol (25): light-yellow solid
(yield: 51%, 1096 mg). trans-1-Methyl-3-(3-methoxy-4-hydroxy-
phenyl)-4-(2-bromophenyl)pyrrolidine (26): brown oil (yield: 41%,
were
added
to
the
liquid
phase.
The
resulting
(CH3)3SiCH2N(CH3)CH2OCH3 was stored at 48C and used directly.
1
trans-1-Methyl-3-(2-hydroxy-4-chlorophenyl)-4-(2-bromophenyl)-
pyrrolidine (20): light-yellow oil (yield: 66%, 120 mg): 1H NMR
(400 MHz, CDCl3): d=7.55 (d, J=7.9 Hz, 1H), 7.40–7.32 (m, 2H),
7.12 (t, J=7.3 Hz, 1H), 7.07 (d, J=8.6 Hz, 1H), 6.84 (d, J=8.5 Hz,
1H), 6.80 (s, 1H), 4.17–4.06 (m, 1H), 3.70 (t, J=8.8 Hz, 1H), 3.35 (s,
1H), 3.25 (d, J=9.9 Hz, 1H), 2.95 (dd, J=18.3 Hz, 10.0 Hz, 1H), 2.57
(s, 3H), 2.39 ppm (t, J=9.9 Hz, 1H); 13C NMR (100 MHz, CDCl3): d=
154.8, 141.1, 133.3, 130.9, 129.3, 128.5, 128.2, 128.1, 124.7, 122.7,
118.9, 63.3, 61.5, 50.7, 50.0, 40.2 ppm; HRMS (ESI): calcd for [M+
H]+ of C17H18NOClBr: 368.0240, found: 368.0238.
147 mg): H NMR (400 MHz, CDCl3): d=7.60 (d, J=7.8 Hz, 1H), 7.48
(d, J=8.0 Hz, 1H), 7.32 (t, J=7.6 Hz, 1H), 7.07 (t, J=7.6 Hz, 1H),
6.80 (d, J=8.1 Hz, 1H), 6.76 (s, 1H), 6.70 (d, J=8.1 Hz, 1H), 4.15
(dd, J=18.3 Hz, 8.4 Hz, 1H), 3.83 (s, 3H), 3.68 (dd, J=17.4 Hz,
9.4 Hz, 1H), 3.56–3.49 (m, 1H), 3.36 (t, J=9.6 Hz, 1H), 3.20–3.08 (m,
1H), 2.98 (t, J=9.7 Hz, 1H), 2.66 ppm (s, 3H); 13C NMR (100 MHz,
CDCl3): d=146.7, 144.8, 132.9, 128.4, 128.2, 125.0, 120.1, 114.4,
110.2, 63.2, 62.3, 56.0, 51.4, 50.0, 42.2 ppm; HRMS (ESI): calcd for
[M+H]+ of C18H21NO2Br: 362.0756, 364.0735, found: 364.0742.
General method for the synthesis of 13, 14, and 19–24: The syn-
thesis of (E)-4-nitro-2-styrylphenol (13) and trans-1-methyl-3-(2-hy-
droxy-4-nitrophenyl)-4-phenylpyrrolidine (14) was used as an ex-
ample. Diethyl benzylphosphonate (2736 mg, 12 mmol) was added
to THF (5 mL), followed by the addition of sodium hydride
(823 mg, 70% in mineral oil, 24 mmol) at ꢀ108C under nitrogen.
Then, a THF solution of 2-hydroxy-5-nitrobenzaldehyde (5 mL,
1002 mg, 6 mmol) was added dropwise over 20 min. The tempera-
ture was allowed to rise to room temperature and stirred for 3 h to
afford 13. Prior to tetrahydropyrrolization, the hydroxy group of 13
was protected by acetylation. Acetic anhydride (1836 mg,
18 mmol) was added and stirred for 6 h. After completion of the
reaction as indicated by TLC, water (10 mL) was added. The THF
was evaporated under vacuum, and the residue was dissolved in
EtOAc (20 mL). The aqueous layer was extracted with EtOAc (2ꢀ
15 mL). The combined organic layers were washed with saturated
NaCl solution and dried over Na2SO4. After the organic solvent was
evaporated, the residue was purified by silica gel chromatography
with EtOAc/petroleum ether as the eluent to afford (E)-4-nitro-2-
styrylphenyl acetate in 43% yield. (E)-4-Nitro-2-styrylphenyl acetate
(141 mg, 0.5 mmol) was then suspended in THF (5 mL) at 338C,
and CF3COOH (2 drops) was added at ꢀ58C under nitrogen.
(CH3)3SiCH2N(CH3)CH2OCH3 (1 mL) was then added dropwise to the
reaction mixture and stirred for 3 h. After completion of the reac-
tion as indicated by TLC, the THF was evaporated under vacuum,
and EtOAc and water (20 mL each) were added. The organic layer
was collected, and the aqueous layer was extracted with EtOAc
(2ꢀ15 mL). The combined organic layers were washed with satu-
rated NaCl solution and dried over Na2SO4. After the organic sol-
vent was evaporated, the residue was purified by silica gel chroma-
tography with petroleum ether/EtOAc as the eluent to afford 14 as
a yellow oil (yield: 92%, 137 mg): 1H NMR (400 MHz, CDCl3): d=
8.44 (s, 1H), 8.05 (d, J=9.0 Hz, 1H), 7.47 (d, J=12.8 Hz, 1H), 7.31
trans-1-Methyl-3-(2-hydroxy-4-bromophenyl)-4-(2-bromophe-
nyl)pyrrolidine (22): brown oil (yield: 76%, 156 mg): 1H NMR
(400 MHz, CDCl3): d=7.56 (d, J=8.0 Hz, 1H), 7.40–7.32 (m, 2H),
7.21 (d, J=8.6 Hz, 1H), 7.13 (dd, J=9.3 Hz, 5.0 Hz, 1H), 6.93 (s, 1H),
6.80 (d, J=8.5 Hz, 1H), 4.13–4.05 (m, 1H), 3.70 (t, J=8.8 Hz, 1H),
3.35 (d, J=5.4 Hz, 1H), 3.24 (d, J=9.9 Hz, 1H), 2.93 (t, J=8.8 Hz,
1H), 2.56 (s, 3H), 2.37 ppm (t, J=9.8 Hz, 1H); 13C NMR (100 MHz,
CDCl3): d=155.4, 141.7, 133.3, 132.2, 131.0, 128.4, 128.2, 128.1,
124.7, 119.7, 109.8, 63.6, 61.7, 51.3, 50.4, 40.0 ppm; HRMS (ESI):
calcd for [M+H]+ of C17H18NOBr2: 411.9735, found: 411.9732.
trans-1-Methyl-3-(2-hydroxy-4-nitrophenyl)-4-(2-bromophenyl)-
pyrrolidine (24): yellow oil (yield: 72%, 136 mg): 1H NMR
(400 MHz, CDCl3): d=8.05 (d, J=8.9 Hz, 1H), 7.80 (s, 1H), 7.57 (d,
J=7.9 Hz, 1H), 7.38 (s, 2H), 7.15 (s, 1H), 6.93 (d, J=8.9 Hz, 1H),
4.09 (s, 1H), 3.74 (t, J=8.8 Hz, 1H), 3.51 (d, J=21.0 Hz, 1H), 3.26 (d,
J=9.9 Hz, 1H), 3.04 (s, 1H), 2.63 (s, 3H), 2.46 ppm (d, J=7.7 Hz,
1H); 13C NMR (100 MHz, CDCl3): d=163.5, 141.2, 138.9, 133.4,
130.5, 128.7, 128.2, 128.0, 126.2, 125.0, 124.6, 118.4, 63.3, 61.1, 51.6,
50.2, 39.5 ppm; MALDI-TOF mass: calcd for [M]+ of C17H17N2O3Br:
378.0400, found: 378.7140.
AAPH-induced oxidation of DNA
AAPH-induced oxidation of DNA was performed in a mixture of
DNA (final concentration: 2.24 mgmLꢀ1) dissolved in phosphate-
buffered saline (PBS; 8.1 mm Na2HPO4, 1.9 mm NaH2PO4, 10.0 mm
EDTA, pH 7.4) and AAPH (final concentration: 40.0 mm, dissolved in
PBS). A mixture of DNA, AAPH, and various concentrations of a stil-
bene or a tetrahydropyrrole derivative (stock solution dissolved in
DMSO) were aliquoted into test tubes, with each containing 2.0 mL
of the aforementioned mixture. The control experimental system
&
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
8
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Papers
´
[7] I. Chrza˛scik, Crit. Rev. Anal. Chem. 2009, 39, 70–80.
[8] C. A. de La Lastra, I. Villegas, Biochem. Soc. Trans. 2007, 35, 1156–1160.
[9] D.-J. Ding, X.-Y. Cao, F. Dai, X.-Z. Li, G.-Y. Liu, D. Lin, X. Fu, X.-L. Jin, B.
Zhou, Food Chem. 2012, 135, 1011–1019.
contained the same volume of DMSO (less than 0.5% of the total
volume) without the tested compounds dissolved. The test tubes
were incubated at 378C to initiate the oxidation of DNA, and three
were taken out every 2 h and cooled immediately in ice water.
Then, thiobarbituric acid (TBA; 1.0 mL, 1.00 g of TBA and 0.40 g of
NaOH dissolved in 100 mL PBS) and a 3.0% aqueous solution of tri-
chloroacetic acid (TCA; 1.0 mL) were added, and the mixture was
heated in boiling water for 15 min. After the test tubes were
cooled to room temperature, n-butanol (1.5 mL) was added and
shaken vigorously to extract TBARS, with absorbance measured at
535 nm. The absorbance of TBARS was plotted vs. the reaction
period.
[10] D. He, W. Jian, X. Liu, H. Shen, S. Song, J. Agric. Food Chem. 2015, 63,
1370–1377.
[11] J. B. Bharate, S. Singh, A. Wani, S. Sharma, P. Joshi, I. A. Khan, A. Kumar,
R. A. Vishwakarma, S. B. Bharate, Org. Biomol. Chem. 2015, 13, 5424–
5431.
[12] A. Domagala, T. Jarosz, M. Lapkowski, Eur. J. Med. Chem. 2015, 100,
176–187.
[13] M. Li, J. Xiong, Y. Huang, L.-J. Wang, Y. Tang, G.-X. Yang, X.-H. Liu, B.-G.
Wei, H. Fan, Y. Zhao, W.-Z. Zhai, J.-F. Hu, Tetrahedron 2015, 71, 5285–
5295.
[14] X.-N. Sun, Y.-Q. Qiu, S.-L. Sun, C.-G. Liu, Y.-Q. Du, Z.-M. Su, Sci. China
Chem. 2011, 54, 1086–1093.
Statistical analysis
[15] E. J. Seus, C. V. Wilson, J. Org. Chem. 1961, 26, 5243–5243.
[16] M. van der Linden, T. Roeters, R. Harting, E. Stokkingreef, A. S. Gelpke, G.
Kemperman, Org. Process Res. Dev. 2008, 12, 196–201.
[17] M. Zahid, M. Saeed, C. Beseler, E. G. Rogan, E. L. Cavalieri, Free Radical
Biol. Med. 2011, 50, 78–85.
[18] J. L. Bitterman, J. H. Chung, Cell. Mol. Life Sci. 2015, 72, 1473–1488.
[19] L.-F. Zheng, Q.-Y. Wei, Y.-J. Cai, J.-G. Fang, B. Zhou, L. Yang, Z.-L. Liu, Free
Radical Biol. Med. 2006, 41, 1807–1816.
All data were the average of at least three independent measure-
ments with an experimental error within 10%. The equations were
analyzed by one-way ANOVA using Origin 7.0 software, and p
<0.001 indicated a significance difference.
Acknowledgements
[20] G.-Y. Liu, J. Yang, F. Dai, W.-J. Yan, Q. Wang, X.-Z. Li, D.-J. Ding, X.-Y. Cao,
B. Zhou, Chem. Eur. J. 2012, 18, 11100–11106.
[21] V. W. Bowry, R. Stocker, J. Am. Chem. Soc. 1993, 115, 6029–6044.
[22] Y.-Z. Tang, Z.-Q. Liu, Cell Biochem. Funct. 2007, 25, 149–158.
[23] C. Lucas-Abellꢄn, M. T. Mercader-Ros, M. P. Zafrilla, M. I. Fortea, J. A. Ga-
baldꢅn, E. NfflÇez-Delicado, J. Agric. Food Chem. 2008, 56, 2254–2259.
[24] H.-W. Lai, Z.-Q. Liu, Eur. J. Med. Chem. 2014, 81, 227–236.
[25] F. J. Hidalgo, M. Alaiz, R. Zamora, Chem. Res. Toxicol. 2001, 14, 582–588.
[26] R. Liu, Y. Liu, Y.-D. Zhou, D. G. Nagle, J. Nat. Prod. 2007, 70, 1741–1745.
[27] J. E. Davoren, D. L. Gray, A. R. Harris, D. M. Nason, W. Xu, Synlett 2010,
16, 2490–2492.
Financial support from the Jilin Provincial Science and Technolo-
gy Department, China (20160101317JC) is gratefully acknowl-
edged. The authors declare no competing financial interests.
Keywords: antioxidants
·
cycloaddition
·
resveratrol
·
stilbenes · tetrahydropyrroles
[1] L. Li, N. P. Seeram, J. Agric. Food Chem. 2010, 58, 11673–11679.
[2] C. Chen, X. Jiang, W. Zhao, Z. Z. Zhang, Food Chem. Toxicol. 2013, 59,
8–17.
[3] S. Bastianetto, C. Mꢃnard, R. Quirion, Biochim. Biophys. Acta Gen. Subj.
2015, 1852, 1195–1201.
[28] A. Hosomi, Y. Sakata, H. Sakurai, Chem. Lett. 1984, 1117–1120.
[29] X.-R. Gong, G.-L. Xi, Z.-Q. Liu, Tetrahedron Lett. 2015, 56, 6257–6261.
[30] X. Chen, Q. Qiao, Z. Cai, Y. Jin, J. Jing, X. Sun, L. Sun, H. Cai, D. Feng,
Chin. J. Chem. 2009, 27, 1452–1458.
[4] C. K. Singh, M. A. Ndiaye, N. Ahmad, Biochim. Biophys. Acta Gen. Subj.
2015, 1852, 1178–1185.
[5] K. M. Kasiotis, H. Pratsinis, D. Kletsas, S. A. Haroutounian, Food Chem.
Toxicol. 2013, 61, 112–120.
Received: April 14, 2016
Revised: May 28, 2016
[6] M. Frombaum, S. L. Clanche, D. Bonnefont-Rousselot, D. Borderie, Bio-
chimie 2012, 94, 269–276.
Published online on && &&, 0000
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
9
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

FULL PAPERS
L.-L. Bao, Z.-Q. Liu*
&& – &&
Tetrahydropyrrolization of Resveratrol
and Other Stilbenes Improves
Inhibitory Effects on DNA Oxidation
Tricks with tetrapyrroles: Tetrahydro-
pyrrolization was found to enhance the
inhibitory effect of resveratrol on DNA
oxidation and was also found to in-
crease antioxidant effects of other stil-
benes. In the continued quest for novel
antioxidants, tetrahydropyrrolization
may offer an advantage for enhancing
the effectiveness of other double-bond-
containing antioxidants.
&
ChemMedChem 2016, 11, 1 – 10
www.chemmedchem.org
10
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!