Synthesis and antioxidant evaluation of desmethylxanthohumol analogs and their dimers

Article abstract of DOI:10.1016/j.ejmech.2016.09.024

Four ring-closed analogs of natural prenylated chalcone desmethylxanthohumol (1) and their dimers were synthesized from the commercially available 1-(2,4,6-trihydroxyphenyl)ethan-1-one in five and six linear steps, respectively. The structures of the eigh

Full text of DOI:10.1016/j.ejmech.2016.09.024

Accepted Manuscript
Synthesis and antioxidant evaluation of desmethylxanthohumol analogs and their
dimers
Yuou Teng, Xuzhe Li, Ke Yang, Xuehui Li, Zijun Zhang, Luyao Wang, Zhijie Deng,
Binbin Song, Zhihong Yan, Yongmin Zhang, Kui Lu, Peng Yu
PII:
S0223-5234(16)30754-1
10.1016/j.ejmech.2016.09.024
EJMECH 8890
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 18 May 2016
Revised Date: 7 September 2016
Accepted Date: 8 September 2016
Please cite this article as: Y. Teng, X. Li, K. Yang, X. Li, Z. Zhang, L. Wang, Z. Deng, B. Song, Z. Yan,
Y. Zhang, K. Lu, P. Yu, Synthesis and antioxidant evaluation of desmethylxanthohumol analogs and
their dimers, European Journal of Medicinal Chemistry (2016), doi: 10.1016/j.ejmech.2016.09.024.
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ACCEPTED MANUSCRIPT
Graphical Abstract
Four ring-closing analogs of natural prenylated chalcone Desmethylxanthohumol (1) and their
dimers were synthesized. The antioxidant activities of these new chalcone derivatives were
evaluated in the PC12 cell model of hydrogen peroxide (H O )-induced oxidative damage.
2
2

ACCEPTED MANUSCRIPT
Synthesis and Antioxidant Evaluation of
Desmethylxanthohumol Analogs and their Dimers
a
a
a
a
a
a
Yuou Teng , Xuzhe Li , Ke Yang , Xuehui Li , Zijun Zhang , Luyao Wang ,
a
a
a
b
a*
a*
Zhijie Deng , Binbin Song , Zhihong Yan , Yongmin Zhang , Kui Lu , Peng Yu
a
China International Science and Technology Cooperation Base of Food
Nutrition/Safety and Medicinal Chemistry, Sino-French Joint Lab of Food
Nutrition/Safety and Medicinal Chemistry, Key Laboratory of Industrial
Fermentation Microbiology of Ministry of Education, Tianjin Key Laboratory of
Industry Microbiology, Tianjin University of Science and Technology, Tianjin
3
00457, China
b
Université Pierre et Marie Curie-Paris 6, Institut Parisien de Chimie Moléculaire
UMR CNRS 8232, 4 place Jussieu, 75005, Paris, France
*
Corresponding author. Tel.: +86 22 60912562, E-mail: lukui@tust.edu.cn
Tel.: +86 22 60912562, E-mail: yupeng@tust.edu.cn
1

ACCEPTED MANUSCRIPT
Abstract:
Four ring-closed analogs of natural prenylated chalcone
desmethylxanthohumol (1) and their dimers were synthesized from the
commercially available 1-(2,4,6-trihydroxyphenyl)ethan-1-one in five
and six linear steps, respectively. The structures of the eight new
1
13
derivatives were confirmed using H NMR, C NMR and HRMS. The
antioxidant activity of the new chalcone derivatives were evaluated in a
PC12 cell model of H O -induced oxidative damage. The SAR studies
2
2
suggested that the catechol motif was essential for the antioxidant activity.
Moreover, the dimers showed better antioxidant activity than their
corresponding monomers did. Among them, compound 14d was the most
potent and increased PC12 cell viability from 25% to 85%. Flow
cytometric analysis showed that compound 14d, the most potent
compound, decreased the apoptotic PC12 cell percentage and
significantly reduced the LDH release and 8-OHdG generation but
increased the GSH levels in H O -treated PC12 cells. Furthermore,
2
2
compound 14d had a higher FRAP value than that of gallic acid. It also
+
reduced the stable ABTS free radical with a lower EC than that of
5
0
gallic acid.
Keywords: Synthesis; Chalcone; Desmethylxanthohumol; Dimer;
Antioxidant
2

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1
. Introduction
Chalcones with a prenyl group or a benzopyran moiety are widely
distributed in fruits, vegetables, tea, and soy-based foodstuff and display
a wide spectrum of biological activities [1]. Desmethylxanthohumol (1), a
prenylated hydroxychalcone, first isolated from hop cones (Humulus
lupulus L.) by Schulz in 1988 [2] showed antiplasmodial [3],
antiproliferative [4,5], and antioxidant bioactivities [6]. Isobavachromene
(
2) isolated from the twigs of Dorstenia mannii by Ngadjui et al. [7] in
998 showed antibacterial [8, 9], anticancer [10], antimalarial [11], and
antioxidant activities [12].
1
(insert Scheme 1)
Oxidative stress can cause cell injury and death, which may be related
to numerous diseases and conditions such as liver damage [13], aging
14], cancer [15], stroke [16], myocardial infarction [17], Alzheimer's
[
disease [18], and Parkinson's disease[19]. However, there is still no
agreement on whether oxidants trigger these and other diseases, or are
produced as a secondary consequence of the diseases. Nevertheless,
whether oxidative stress can be considered as a cause or consequence of
some diseases, it is important to develop new antioxidant drugs.
As mentioned above, desmethylxanthohumol (1) and isobavachromene
(
2) showed antioxidant activity and 2 could be considered as the
ring-closed analog of 1. Some biflavonoids have been reported to exhibit
3

ACCEPTED MANUSCRIPT
better bioactivities than their monomers do [20]. Therefore, dimerization
of chalcones might increase their activities. Hydrogen peroxide (H O ) is
2
2
a major reactive oxygen species (ROS) with high cellular membrane
permeability. The PC12 cell line was derived from a rat
pheochromocytoma of the adrenal medulla, and H O -induced oxidative
2
2
damage to these cells constitutes a useful in vitro model system for
evaluating the antioxidant properties of compounds [21, 22].
H O -induced cytotoxicity in PC12 cells results in effects including
2
2
increased rate of apoptosis, membrane damage with lactate
dehydrogenase (LDH) release, nuclear damage with
-hydroxy-2'-deoxyguanosine (8-OHdG) generation, and decreased
cellular glutathione (GSH) levels.
8
In this study, we synthesized desmethylxanthohumol (1) analogs and
their respective dimers and subsequently evaluated the antioxidant
activity in the H O -induced PC12 cell oxidative damage model. The
2
2
antioxidant properties of a selected analog, compound 14d, and its
potential molecular mechanism were also investigated.
2
. Chemistry
Desmethylxanthohumol (1) is a commercially available compound and,
therefore, we synthesized its ring-closed analog, which could also be
considered as an analog of Isobavachromene (2) (Scheme 1). The
4

ACCEPTED MANUSCRIPT
mono-MOM protected 2',4',6'-trihydroxyacetophenone (5) was readily
synthesized
from
the
commercially
available
2
',4',6'-trihydroxyacetophenone by treatment with chloromethyl methyl
ether and ethyldiisopropylamine followed by regioselective deprotection
under acidic conditions. Compound 5 was converted to chalcones (8a-d)
by cyclization with 3-methyl-2-butenal followed by aldol condensation
with four different substituted benzaldehydes (6a-d). Full deprotection of
8
a-d by 3N hydrochloric acid (HCl) in methanol (MeOH) and
tetrahydrofuran (THF) produced the chalcones 9a-d at a 16%-38% yield.
It is noteworthy that compounds 9a-d were not stable and partly
decomposed in the acid condition.
(insert Scheme 2)
Following the generation of the key intermediate 6, we attempted to
synthesize the corresponding dimers of compound 9a by condensation
with polyformaldehyde followed by aldol and deprotection reactions.
However, the desired product was not obtained. To reduce the steric effect
of the substrate, the corresponding de-MOM product 11 was evaluated.
Fortunately, the desired dimer, 12 was obtained at 71% yield and was
subsequently transformed into the bichalcones (14a-d) using a similar
approach to that used for the monomers.
(insert Scheme 3)
3
. Results and discussion
5

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Before the antioxidant activity analysis of our newly synthesized
compounds, the toxicity of compound 1 and its ring-closed analog
compound 9a was evaluated using normal human umbilical vein
endothelial cells (HUVECs) and rat pheochromocytoma cells (PC12).
Firstly, the toxicity of compounds 1 and 9a against the HUVECs was
evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (MTT) assay. The half-minimal inhibitory concentration (IC )
5
0
was determined to reflect the toxicity and a lower value indicates a higher
cytotoxicity. The result revealed that the IC of compounds 1 and 9a in
5
0
HUVECs was 18.92 and 41.15 µΜ, respectively
(insert Table 1).
The cytotoxicity of compounds 1 and 9a against the PC12 cells was
then determined, and both compounds showed high toxicity at 200 µΜ
Figure 1). Furthermore, 9a only has a slight effect on cell proliferation at
00 µΜ while 1 showed considerable toxicity against PC12 cells at the
(
1
same concentration, suggesting that cyclizing the prenyl group of
chalcone 1 to benzopyran decreased its toxicity against PC12 cells.
(insert Figure 1)
Based on this information, the ring-closed analogs (compounds 9a-d)
were synthesized, and their antioxidant activity was evaluated in
H O -damaged PC12 cells at a concentration of 100 µΜ. Gallic acid was
2
2
used as a positive control, and the results are illustrated in Figure 2. The
6

ACCEPTED MANUSCRIPT
viability of PC12 cells decreased to 25.47% after a 2-h exposure to 100
µM H O . Compounds 9b and 9d, which possess 2, 3-dihydroxyl
2
2
substituted phenyl group and 2, 3, 4-trihydroxyl substituted phenyl
groups, respectively, showed antioxidant activity. The viability of the
9
b-pretreated PC12 cells was 54.46%. Moreover, 9d, which was the most
potent compound, protected the PC12 cells against H O oxidation by
2
2
8
4.02% at 100 µΜ, which was comparable to protection shown by gallic
acid (88.88%). However, 9a and 9c, which possess 4-hydroxyl
substituted phenyl group and 2, 4-dihydroxyl substituted phenyl groups,
did not exhibit any antioxidant activity.
(insert Figure 2)
As we mentioned above, some dimers show better bioactivities than
their monomers do. Therefore, we tested the antioxidant activities of 9a
and its dimer 14a, which did indeed show superior bioactivity to that of
the monomer, 9a (Figure 3).
(insert Figure 3)
These encouraging results above led us to synthesize the dimers of
1
4b-d and subsequently evaluate their antioxidant activity (Figure 4). The
bioassay showed that unlike their monomers, all the respective dimers
possessed antioxidant activity. Moreover, the results were in agreement
with our previous reports that dimers often show better antioxidant
activity than their corresponding monomers (14b-d versus 9b-d,
7

ACCEPTED MANUSCRIPT
respectively). Among those dimers, 14b and 14d protected the PC12 cells
against H O oxidation by 78% and 85% respectively at 100 µΜ.
2
2
(insert Figure 4)
The effects of the test compounds on cell viability are shown in Table
2
. After carefully analyzing the structures of 9a-d and those of 14a-d, we
found that the catechol motif was essential for the antioxidant activity.
We think that compared to the 4-hydroxyl phenyl and 2,4-dihydroxyl
phenyl groups, the 2,3-dihydroxyl phenyl and 2,3,4-trihydroxyl phenyl
groups can be more easily oxidized to o-quinone during the H O -induced
2
2
oxidation process.
The structure-activity relationship (SAR) studies of these compounds
identified the novel prenylated chalcone derivative, compound 14d, as a
highly potent antioxidant compound. Then, the molecular mechanism by
which compound 14d exerts its antioxidant activity was investigated.
As shown in Table 2, treatment with H O (100 µM) for 2 h markedly
2
2
decreased the cell viability. Hwang et al. [23] reported that oxidative
stress induces apoptosis rather than necrosis in PC12 cells. The effect of
compound 14d on the morphological alterations in H O -injured PC12
2
2
cells was evaluated to confirm, whether the treatment with H O could
2
2
induce apoptosis in PC12 cells and whether compound 14d could inhibit
this effect. The results (Figure 5A) showed that treatment with H O (100
2
2
µM) for 2 h markedly increased the typical apoptotic cell morphology
8

ACCEPTED MANUSCRIPT
such as cell shrinkage, blebbing, or both. Morphological changes in the
compound 14d-treated PC12 cells suggested that it significantly protected
them against H O -induced cell injury. These results indicate that
2
2
compound 14d might protect PC12 cells against oxidative stress injury
caused by H O .
2
2
(insert Table 2)
To further study the effects of compound 14d on apoptosis of
pretreated H O -damaged PC12 cells, they were double-labeled with
2
2
Annexin V-FITC and propidium iodide (PI) and then analyzed using flow
+
-
cytometry (Figure 5B). The apoptotic rate (Annexin V /PI and Annexin
+
+
V /PI ) of the untreated H O -damaged PC12 cells was 77.6% while that
2
2
of the compound 14d-treated cells decreased to 3.8% of the total cells
compared to 13.9% observed in the gallic acid-treated control cells. These
results suggest that compound 14d protected the H O -injured PC12 cells
2
2
against apoptosis.
(insert Figure 5)
The effects of compound 14d for the release of LDH, generation of
-OHdG, and GSH activity were assessed. The cells were pretreated with
0 µM compound 14d or gallic acid for 30 min and then incubated with
8
1
H O (100 µM, 2 h). LDH is a stable cytoplasmic enzyme present in all
2
2
cells, and is rapidly released into the culture medium when the plasma
membrane is damaged by an oxidant [24]. An increased LDH activity in
9

ACCEPTED MANUSCRIPT
culture supernatant indicates an increase in the number of dead or plasma
membrane-damaged cells. As shown in Figure 6A, treatment with H O2
2
markedly increased the LDH level (P < 0.01) from 238.73 to 479.77 U/L.
However, pre-incubation with gallic acid and compound 14d significantly
decreased the LDH levels to 326.59 and 251.45 U/L (P < 0.05 and P <
0
.01), respectively.
DNA damage is one of the earliest recognized and most extensively
studied manifestations of oxygen toxicity in biology. In nuclear and
mitochondrial DNA, 8-hydroxy-2'-deoxyguanosine (8-OHdG) is one of
the predominant forms of free radical-induced oxidative lesions and,
therefore, has been widely used as a biomarker for oxidative stress and
carcinogenesis [25]. As shown in Figure 6B, the 8-OHdG level in PC12
cells exposed to H O significantly increased (123.97 ng/L, P < 0.01)
2
2
compared to that in the control group (47.12 ng/L). However,
pretreatment of PC12 cells with compound 14d decreased 8-OHdG levels
(P < 0.01) to 62.80 ng/L, which was better than the effect of gallic acid
treatment (85.70 ng/L).
Antioxidant nutrients such as GSH act as the primary defense
mechanisms that protect living systems from oxidative damage [26].
Exposure of PC12 cells to H O significantly (P < 0.01) reduced the GSH
2
2
level (Figure 6C) from 127.85 to 59.93 µmol/gprot, whereas pretreatment
1
0

ACCEPTED MANUSCRIPT
with gallic acid and compound 14d attenuated this effect (99.73 or 105.71
µmol/gprot, respectively.
(insert Figure 6)
The antioxidant activity of compound 14d was evaluated using the
ferric
reducing
antioxidant
power
(FRAP)
and
2
,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assays
and the results are shown in Table 3. Compound 14d exhibited better
activity in the FRAP assay than the positive control, gallic acid did
(648.44 and 531.02 mg/mM, equivalent amounts of vitamin C [Vc],
respectively). The scavenging activity of compound 14d against the
ABTS radical was also evaluated and expressed as the half-maximal
effective concentration (EC ). Compound 14d exhibited a high ABTS
50
radical scavenging activity with an EC of 0.54 mM, which was slightly
5
0
less than that of gallic acid (0.35 mM). This result suggests that
compound 14d possesses potent in vitro antioxidant properties.
4
. Conclusions
In summary, ring-closed analogs (9a-d) of the natural prenylated
chalcone desmethylxanthohumol (1) and their dimers (14a-14d) were
synthesized from the commercially available
-(2,4,6-trihydroxyphenyl)ethan-1-one (3) in five and six linear steps
1
1
1

ACCEPTED MANUSCRIPT
respectively. The biological activity evaluation illustrated the following. 1)
The ring-closed analog, 9a showed a lower toxicity than compound 1 did
on HUVECs and PC12 cells. 2) Compounds bearing 2,3-dihydroxyl
phenyl and 2,3,4-trihydroxyl phenyl groups showed better antioxidant
activity than their counterparts with 4-hydroxyl phenyl and
2
,4-dihydroxyl phenyl groups did. 3) The dimers showed better
antioxidant activity than their corresponding monomers did. 4) The most
potent compound, 14d protected the PC12 cell against H O oxidation by
2
2
8
5% at 100 µΜ, which was comparable to the activity shown by gallic
acid. 5) Pretreatment with compound 14d significantly prevented the
H O -induced apoptosis. 6) Compound 14d exhibited protective effects
2
2
on the release of LDH (a plasma membrane damage marker), production
of 8-OHdG (a DNA damage marker), and a decrease in GSH (an
antioxidant enzyme).
Studies are currently underway to clarify the mechanism of action of
compound 14d and identify its target molecule. Although compound 14d
showed a superior antioxidant activity in vitro to that of its parent
structure, the chalcones, the molecular mechanism of this action is still
unclear. Therefore, it is necessary to further study the in vivo antioxidant
action and associated mediating pathways of compound 14d in animal
models [27-29].
1
2

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. Experimental section
5
5
.1. Chemistry
All commercial materials and reagents were used without further
purification, unless otherwise stated. All solvents were distilled prior to
use. The solvents for reaction were distilled to remove water over Na or
CaH . All reactions were carried out in oven-dried glassware under an
2
inert atmosphere (nitrogen or argon). For chromatography, 200-300 mesh
1
13
silica gel (Qingdao, China) was employed. H and CNMR spectra were
recorded at 400 MHz and 100 MHz with a Brucker ARX 400
1
spectrometer. The chemical shifts (δ) for H NMR spectra were given in
parts per million (ppm) referenced to the residual proton signal of the
duterated solvent (CDCl at δ = 7.26 ppm, DMSO-d at δ = 2.50 ppm and
3
6
Acetone-d at δ = 2.05 ppm); coupling constants were expressed in hertz
6
1
3
(
Hz). C NMR spectra were referenced to the carbon signal of CDCl (δ
3
=
77.0 ppm), DMSO-d (δ = 40.0 ppm) and Acetone-d (δ = 30.0 ppm
6
6
and 206.0 ppm). The following abbreviations are used to describe NMR
signals: s = singlet, d = doublet, t = triplet, m = multiple, and dd = doublet
of doublets. HRMS were recorded on Bruker Daltonics, Inc. APEXIII 7.0
TESLA FTMS (ESI). Known products were characterized by comparing
1
to their corresponding H-NMR reported in the literatures.
5
.1.1. 1-(2-hydroxy-4,6-bis(methoxymethoxy)phenyl)ethan-1-one (4)
1
3

ACCEPTED MANUSCRIPT
1
-(2,4,6-trihydroxyphenyl)ethan-1-one (16.8 g, 100 mmol) in dry
CH Cl (500 mL) were added DMF (20 mL). The mixture was cooled to
2
2
0
°C and N,N-diethylpropan-2-amine (39.3 g, 250 mmol) was added
slowly. After addtion chloro(methoxy)methane (17.7 g, 220 mmol) in dry
CH Cl (100 mL) was added dropwised. The reaction mixture was
2
2
warmed to room temperature and stirred for 6 h. The reaction was
quenched with NH Cl (aq) and extracted with CH Cl (3x500 mL). The
4
2
2
combined organic layers were washed with brine, dried over Na SO and
2
4
concentrated under reduced pressure. The crude product was purified by
column chromatography on silica (petroleum ether/ethyl acetate 20:1) to
1
afford a compound 4 (21.0 g, 82%) as a colorless oil. H NMR (400 MHz,
CDCl ) δ 13.66 (s, 1H), 6.17 (s, 2H), 5.19 (s, 2H), 5.10 (s, 2H), 3.46 (s,
3
1
3
3
1
5
H), 3.41 (s, 3H), 2.58 (s, 3H). C NMR (100 MHz, CDCl ) δ 203.1,
3
66.8, 163.4, 160.3, 106.8, 97.0, 94.4, 93.9, 93.9, 56.6, 56.3, 32.9.
.1.2 1-(2,6-dihydroxy-4-(methoxymethoxy)phenyl)ethan-1-one (5)
Compound 4 (2.56 g, 10.0 mmol) in MeOH (50 mL) was cooled to
°C. Then 2N HCl (10 mL) was added dropwised. After addition, the
0
reaction mixture was warmed to 40 °C and stirred for 3h. The reaction
was quenched with NaHCO (aq) and extracted with EtOAc (3x100 mL).
3
The combined organic layers were washed with brine, dried over Na SO4
2
and concentrated under reduced pressure. The crude product was purified
by column chromatography on silica (petroleum ether/ethyl acetate 10:1)
1
4

ACCEPTED MANUSCRIPT
1
to afford a compound 5 (1.30 g, 61%) as a white solid. H NMR (400
MHz, DMSO) δ 12.26 (s, 2H), 6.02 (s, 2H), 5.17 (s, 2H), 3.36 (s, 3H),
1
3
2
9
5
1
.58 (s, 3H). C NMR (100 MHz, DMSO) δ 203.8, 164.4, 163.6, 105.8,
5.1, 93.9, 56.3, 33.0.
.1.3
-(7-hydroxy-5-(methoxymethoxy)-2,2-dimethyl-2H-chromen-8-yl)et
han-1-one (6)
Compound 5 (2.12 g, 10.0 mmol) in dry pyridine (20 mL) was added
-Methyl-2-butenal (1.26 g, 15.0 mmol). The reaction was heated to
20 °C for 16h. The mixture was cooled and pyridine was removed by
3
1
distillation under reduced pressure. The residue was dissolved in CH Cl2
2
(20 mL) and poured into 1N HCl (20 mL). The organic phase was washed
with NaHCO (aq) (10 mL) and brine, dried over Na SO and
3
2
4
concentrated under reduced pressure. The crude product was purified by
column chromatography on silica (petroleum ether/ethyl acetate 50:1) to
1
afford a compound 6 (2.09 g, 75%) as a yellow oil. H NMR (400 MHz,
CDCl ) δ 13.64 (s, 1 H), 6.58 (d, J = 10.0 Hz, 1 H), 6.20 (s, 1 H), 5.43 (d,
3
J = 10.0 Hz, 1 H), 5.20 (s, 2 H), 3.47 (s, 3 H), 2.67 (s, 3 H), 1.50 (s, 6 H).
1
3
C NMR (100 MHz, CDCl ) δ 202.4, 164.9, 157.4, 155.4, 123.8, 115.5,
3
1
05.5, 102.2, 93.9, 93.2, 77.0, 55.5, 32.2, 26.9.
5
.1.4 4-(methoxymethoxy)benzaldehyde (7a)
1
5

ACCEPTED MANUSCRIPT
4
-hydroxybenzaldehyde (1.22 g, 10 mmol) in dry CH Cl (10 mL)
2
2
was cooled to 0 °C. Then NaH (900 mg, 15 mmol) was added. After
addition, chloro(methoxy)methane (965 mg, 12 mmol) in dry CH Cl (10
2
2
mL) was added dropwised. The reaction was warmed to room
temperature and stirred for 24 h. The reaction was quenched with NH Cl
4
(
aq) and extracted with CH Cl (3x10 mL). The combined organic layers
2
2
were washed with brine, dried over Na SO and concentrated under
2
4
reduced pressure. The crude product was purified by column
chromatography on silica (petroleum ether/ethyl acetate 20:1) to afford a
1
compound 7a (1.50 g, 90%) as a colorless oil. H NMR (400 MHz,
CDCl ) δ 9.89 (s, 1H), 7.83(d, J = 8.8 Hz, 2H), 7.14(d, J = 8.8 Hz, 2H),
3
1
3
5
1
.25(s, 2H), 3.49(s, 3H). C NMR (100 MHz, CDCl ) δ 190.8 , 162.2 ,
3
31.8 , 130.7 , 116.3 , 94.1 , 56.3 .
5
.1.5 2,3-bis(methoxymethoxy)benzaldehyde (7b)
2
,3-dihydroxybenzaldehyde (1.38 g, 10 mmol) in dry CH Cl (10
2
2
mL) was cooled to 0 °C. Then NaH (1.80 g, 30 mmol) was added. After
addition, chloro(methoxy)methane (1.93 g, 24 mmol) in dry CH Cl (10
2
2
mL) was added dropwised. The reaction was warmed to room
temperature and stirred for 24 h. The reaction was quenched with NH Cl
4
(
aq) and extracted with CH Cl (3x10 mL). The combined organic layers
2
2
were washed with brine, dried over Na SO and concentrated under
2
4
reduced pressure. The crude product was purified by column
1
6

ACCEPTED MANUSCRIPT
chromatography on silica (petroleum ether/ethyl acetate 15:1) to afford a
1
compound 7b (1.90 g, 84%) as a colorless oil. H NMR (400 MHz,
CDCl3) δ 10.47 (s, 1H), 7.50 (dd, J = 8.0, 1.6 Hz, 1H), 7.41 (dd, J = 8.0,
1
3
1
5
.6 Hz, 1H), 7.17-7.11 (m, 1H), 5.26 (s, 2H), 5.23 (s, 2H), 3.58 (s, 3H),
13
.52 (s, 3H). C NMR (100 MHz, CDCl ) δ 190.2, 150.1, 149.9, 130.6,
3
24.6, 122.3, 120.9, 99.7, 95.3, 57.9, 56.4.
.1.6 2,4-bis(methoxymethoxy)benzaldehyde (7c)
2
,4-dihydroxybenzaldehyde (1.38 g, 10 mmol) in dry CH Cl (10
2
2
mL) was cooled to 0 °C. Then NaH (1.80 g, 30 mmol) was added. After
addition, chloro(methoxy)methane (1.93 g, 24 mmol) in dry CH Cl (10
2
2
mL) was added dropwised. The reaction was warmed to room
temperature and stirred for 24 h. The reaction was quenched with NH Cl
4
(
aq) and extracted with CH Cl (3x10 mL). The combined organic layers
2
2
were washed with brine, dried over Na SO and concentrated under
2
4
reduced pressure. The crude product was purified by column
chromatography on silica (petroleum ether/ethyl acetate 15:1) to afford a
1
compound 7c (1.94 g, 86%) as a colorless oil. H NMR (400 MHz,
CDCl ) δ 10.27 (s, 1H), 7.73 (d, J = 8.8 Hz, 1H), 6.76 (d, J = 2.0 Hz, 1H),
3
6
3
1
5
.66-6.69 (m, 1H), 5.21 (s, 2H), 5.15 (s, 2H), 3.45 (s, 3H), 3.41 (s,
1
3
H). C NMR (100 MHz, CDCl ) δ 188.4, 163.5, 161.3, 130.2, 120.2,
3
09.5, 102.6, 94.7, 94.2, 56.6, 56.4.
.1.7 2,3,4-tris(methoxymethoxy)benzaldehyde (7d)
1
7

ACCEPTED MANUSCRIPT
2
,3,4-trihydroxybenzaldehyde (1.54 g, 10 mmol) in dry CH Cl (10
2
2
mL) was cooled to 0 °C. Then NaH (2.10 g, 35 mmol) was added. After
addition, chloro(methoxy)methane (2.57 g, 32 mmol) in dry CH Cl (10
2
2
mL) was added dropwised. The reaction was warmed to room
temperature and stirred for 24 h. The reaction was quenched with NH Cl
4
(
aq) and extracted with CH Cl (3x10 mL). The combined organic layers
2
2
were washed with brine, dried over Na SO and concentrated under
2
4
reduced pressure. The crude product was purified by column
chromatography on silica (petroleum ether/ethyl acetate 15:1) to afford a
1
compound 7d (2.70 g, 94%) as a colorless oil. H NMR (400 MHz,
CDCl ) δ 10.29 (s, 1H), 7.61 (d, J = 8.8 Hz, 1H), 7.04 (d, J = 8.8 Hz, 1H),
3
5
3
1
.27 (s, 2H), 5.27 (s, 2H), 5.15 (s, 2H), 3.62 (s, 3H), 3.58 (s, 3H), 3.51 (s,
1
3
H). C NMR (100 MHz, CDCl ) δ 188.9 , 156.6 , 154.2 , 138.9 , 124.9 ,
3
24.4 , 111.3 , 100.3 , 98.8 , 94.8 , 57.9 , 57.4 , 56.5 .
5
.1.8
(E)-1-(7-hydroxy-5-(methoxymethoxy)-2,2-dimethyl-2H-chromen-8-y
l)-3-(4-(methoxymethoxy)phenyl)prop-2-en-1-one (8a)
Compound 6 (0.10 g, 0.36 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7a (72 mg, 0.43 mmol) was added. The reaction was heated to
0 °C for 6h. After cooling down to 0 °C, 2N HCl was added to the
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
5
1
8

ACCEPTED MANUSCRIPT
1
to give compound 8a (0.13 g, 83%) as a red solid. H NMR (400 MHz,
CDCl ) δ 14.0 (s, 1H), 8.02 (d, J = 15.6 Hz, 1H), 7.76 (d, J = 15.6 Hz,
3
1
H), 7.55 (d, J = 8.8 Hz, 2H), 7.07 (d, J = 8.8 Hz, 2H), 6.62 (d, J = 10.0
Hz, 1H), 6.24 (s, 1H), 5.47 (d, J = 10.0 Hz, 1H), 5.22 (s, 4H), 3.493 (s,
1
3
3
1
1
5
H), 3.489 (s, 3H), 1.54 (s, 6H). C NMR (100 MHz, CDCl ) δ 193.0,
3
66.9, 159.0, 158.5, 155.8, 142.3, 129.9, 129.4, 125.6, 124.8, 116.8,
16.6, 107.0, 103.6, 95.3, 94.3, 94.2, 78.0, 56.5, 56.2, 28.0.
.1.9
(E)-3-(2,3-bis(methoxymethoxy)phenyl)-1-(7-hydroxy-5-(methoxymet
hoxy)-2,2-dimethyl-2H-chromen-8-yl)prop-2-en-1-one (8b)
Compound 6 (0.10 g, 0.36 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7b (98 mg, 0.43 mmol) was added. The reaction was heated to
0 °C for 6h. After cooling down to 0 °C, 2 NHCl was added to the
5
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 8b (0.15 g, 86%) as a red solid. H NMR (400 MHz,
CDCl ) δ 14.05 (s, 1H), 8.23 (d, J = 16.0 Hz, 1H), 8.08 (d, J = 16.0 Hz,
3
1
1
5
6
H), 7.33 (d, J = 8.0 Hz, 1H), 7.19 (d, J = 8.8 Hz, 1H), 7.08 (t, J = 8.0 Hz,
H), 6.61 (d, J = 10.0 Hz, 1H), 6.25 (s, 1H), 5.47 (d, J = 10.0 Hz, 1H),
.22 (s, 4H), 5.19 (s, 2H), 3.64 (s, 3H), 3.51 (s, 3H), 3.49 (s, 3H), 1.54 (s,
1
3
H). C NMR (100 MHz, CDCl ) δ 192.0, 165.9, 157.6, 154.9, 149.5,
3
1
9

ACCEPTED MANUSCRIPT
1
1
45.4, 136.3, 129.8, 127.4, 123.9, 123.5, 119.0, 117.0, 115.7, 106.0,
02.6, 98.4, 94.3, 94.2, 93.3, 77.0, 56.9, 55.5, 55.3, 27.0 .
5
.1.10
(E)-3-(2,4-bis(methoxymethoxy)phenyl)-1-(7-hydroxy-5-(methoxymet
hoxy)-2,2-dimethyl-2H-chromen-8-yl)prop-2-en-1-one (8c)
Compound 6 (0.10 g, 0.36 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7c (98 mg, 0.43 mmol) was added. The reaction was heated to
0 °C for 6h. After cooling down to 0 °C, 2 NHCl was added to the
5
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 8c (146 mg, 84%) as a red solid. H NMR (400 MHz,
CDCl ) δ 14.16 (s, 1H), 8.21 (d, J = 15.6 Hz, 1H), 8.02 (d, J = 15.6 Hz,
3
1
H), 7.60 (d, J = 8.8 Hz, 1H), 6.87 (d, J = 2.4 Hz, 1H), 6.76 (dd, J = 8.8
Hz, 2.4 Hz, 1H), 6.62 (d, J = 10.0 Hz, 1H), 6.24 (s, 1H), 5.47 (d, J = 10.0
Hz, 1H), 5.26 (s, 2H), 5.22 (s, 2H), 5.20 (s, 2H), 3.51 (s, 3H), 3.50 (s, 3H),
1
3
3
1
.49 (s, 3H), 1.54 (s, 6H). C NMR (100 MHz, CDCl ) δ 193.0, 166.9,
3
58.6, 155.9, 150.5, 146.4, 137.4, 130.8, 128.4, 125.0, 124.5, 120.0,
118.0, 116.7, 107.0, 103.6, 99.5, 95.3, 95.2, 94.3, 78.0, 58.0, 56.5, 56.3,
2
8.0.
5
.1.11
E)-1-(7-hydroxy-5-(methoxymethoxy)-2,2-dimethyl-2H-chromen-8-y
l)-3-(2,3,4-tris(methoxymethoxy)phenyl)prop-2-en-1-one (8d)
(
2
0

ACCEPTED MANUSCRIPT
Compound 6 (0.10 g, 0.36 mmol) in EtOH (3 mL) was cooled to
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
0
compound 7d (123 mg, 0.43 mmol) was added. The reaction was heated
to 50 °C for 6h. After cooling down to 0 °C, 2 NHCl was added to the
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 8d (180 mg, 91%) as a red solid. H NMR (400 MHz,
CDCl ) δ 14.2 (s, 1H), 8.16 (d, J = 15.6 Hz, 1H), 8.04 (d, J = 15.6 Hz,
3
1
H), 7.39 (d, J = 8.8 Hz, 1H), 7.00 (d, J =8.8 Hz, 1H), 6.61 (d, J = 10.0
Hz, 1H), 6.24 (s, 1H), 5.47 (d, J = 10.0 Hz, 1H), 5.25 (s, 2H), 5.21 (s, 2H),
5
3
1
1
2
5
.20 (s, 2H), 5.16 (s, 2H), 3.64 (s, 3H), 3.62 (s, 3H), 3.52 (s, 3H), 3.49 (s,
13
H), 1.54 (s, 6H). C NMR (100 MHz, CDCl ) δ192.9, 166.9, 158.5,
3
55.8, 153.0, 150.9, 139.7, 137.5, 126.7, 124.9, 124.7, 122.5, 116.8, 111.9,
07.0, 103.5, 100.0, 98.8, 95.3, 95.0, 94.3, 78.0, 58.1, 57.4, 56.5, 56.4,
8.0.
.1.12
(E)-1-(5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl)-3-(4-hydroxyph
enyl)prop-2-en-1-one (9a)
Compound 8a (50 mg, 0.12 mmol) in MeOH (4 mL) and THF (1
mL) was added. The reaction mixture was cooled to 0 °C, then 2N HCl (1
mL) was added. After addtion, the mixture was heated to 60 °C for 30
min. The mixture was poured in cold NaHCO (aq) and extracted with
3
EtOAc (3x10 mL). The combined organic layers were washed with brine,
2
1

ACCEPTED MANUSCRIPT
dried over Na SO and concentrated under reduced pressure. The crude
2
4
product was purified by column chromatography on silica (petroleum
ether/ethyl acetate 4:1) to afford a compound 9a (15 mg, 38%) as a red
1
solid. H NMR (400 MHz, DMSO) δ 13.84 (s, 1H), 10.83 (s, 1H), 10.17
(s, 1H), 7.84 (d, J = 16.0 Hz, 1H), 7.64 (d, J = 16.0 Hz, 1H), 7.55 (d, J =
8
1
.6 Hz, 2H), 6.87 (d, J = 8.6 Hz, 2H), 6.52 (d, J = 10.0 Hz, 1H), 5.96 (s,
1
3
H), 5.57 (d, J = 10.0 Hz, 1H), 1.49 (s, 6H). C NMR (100 MHz, DMSO)
δ 192.4, 165.3, 160.5, 160.1, 155.9, 143.3, 130.8, 126.4, 125.1, 124.0,
16.9, 116.5, 105.6, 102.5, 96.2, 78.1, 28.0; HRMS (ESI) m/z: Calcd for
1
-
C H O [M-H] 337.1081; found, 337.1086.
2
0
17
5
5
.1.13
(E)-1-(5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl)-3-(2,3-dihydrox
yphenyl)prop-2-en-1-one (9b)
Compound 8b (50 mg, 0.102 mmol) in MeOH (4 mL) and THF (1
mL) was added. The reaction mixture was cooled to 0 °C, then 3N HCl (1
mL) was added. After addtion, the mixture was heated to 60 °C for 30
min. The mixture was poured in cold NaHCO (aq) and extracted with
3
EtOAc (3x10 mL). The combined organic layers were washed with brine,
dried over Na SO and concentrated under reduced pressure. The crude
2
4
product was purified by column chromatography on silica (petroleum
ether/ethyl acetate 2:1) to afford a compound 9b (6 mg, 16%) as a red
1
solid. H NMR (400 MHz, DMSO) δ 13.83 (s, 1H), 10.83 (s, 1H), 9.70 (s,
2
2

ACCEPTED MANUSCRIPT
1
7
H), 9.19 (s, 1H), 8.04 (d, J = 16.0 Hz, 1H), 7.64 (d, J =16.0 Hz, 1H),
.01 (d, J = 8.0 Hz, 1H), 6.85 (d, J = 8.0 Hz, 1H), 6.70-6.74 (m, 1H), 6.50
(d, J = 10.0 Hz, 1H)，5.9,5 (s, 1H), 5.54 (d, J = 10.0 Hz, 1H), 1.48 (s,
1
3
6
H). C NMR (100 MHz, DMSO) δ 192.8, 165.8, 160.3, 156.1, 146.4,
1
46.3, 139.2, 126.9, 125.3, 122.8, 119.8, 119.3, 117.4, 116.8, 105.8, 102.6,
-
9
6.2, 78.3, 27.8; HRMS (ESI) m/z: Calcd for C H O [M-H] 353.1031;
2
0
17
6
found, 353.1041.
5
.1.14
(E)-1-(5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl)-3-(2,4-dihydrox
yphenyl)prop-2-en-1-one (9c)
Compound 8c (50 mg, 0.102 mmol) in MeOH (4 mL) and THF (1
mL) was added. The reaction mixture was cooled to 0 °C, then 3N HCl (1
mL) was added. After addtion, the mixture was heated to 60 °C for 30
min. The mixture was poured in cold NaHCO (aq) and extracted with
3
EtOAc (3x10 mL). The combined organic layers were washed with brine,
dried over Na SO and concentrated under reduced pressure. The crude
2
4
product was purified by column chromatography on silica (petroleum
ether/ethyl acetate 2:1) to afford a compound 9c (10 mg, 27%) as a red
1
solid. H NMR (400 MHz, DMSO) δ 14.21 (s, 1H), 10.74 (s, 1H), 10.31
(s, 1H), 9.98 (s, 1H), 8.05 (d, J = 15.6 Hz, 1H), 7.85 (d, J = 15.6 Hz, 1H),
7
1
.34 (d, J = 8.4 Hz, 1H), 6.50 (d, J = 10.0 Hz, 1H), 6.41 (d, J = 2.4 Hz,
H), 6.35-6.30 (m, 1H), 5.92 (s, 1H), 5.53 (d, J = 10.0 Hz, 1H), 1.49 (s,
2
3

ACCEPTED MANUSCRIPT
1
3
6
1
1
3
H). C NMR (100 MHz, DMSO) δ 192.8 , 166.0 , 161.7, 159.9, 159.8,
56.1, 140.6, 132.2, 125.1, 123.3, 117.0, 114.2, 108.5, 105.6, 103.2,
-
02.5, 96.2, 78.1, 27.7; HRMS (ESI) m/z: Calcd for C H O [M-H]
2
0
17
6
53.1031; found, 353.1034.
5
.1.15
(E)-1-(5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl)-3-(2,3,4-trihydr
oxyphenyl)prop-2-en-1-one (9d)
Compound 8d (50 mg, 0.09 mmol) in MeOH (4 mL) and THF (1
mL) was added. The reaction mixture was cooled to 0 °C, then 3N HCl (1
mL) was added. After addtion, the mixture was heated to 60 °C for 30
min. The mixture was poured in cold NaHCO (aq) and extracted with
3
EtOAc (3x10 mL). The combined organic layers were washed with brine,
dried over Na SO and concentrated under reduced pressure. The crude
2
4
product was purified by column chromatography on silica (petroleum
ether/ethyl acetate 2:1) to afford a compound 9d (6 mg, 18%) as a red
1
solid. H NMR (400 MHz, DMSO) δ 14.12 (s, 1H), 10.73 (s, 1H), 9.84 (s,
1
1
H), 9.24 (s, 1H), 8.61 (s, 1H), 7.99 (d, J = 16.0 Hz, 1H), 7.90 (d, J =
6.0 Hz, 1H), 6.92 (d, J = 8.8 Hz, 1H), 6.49 (d, J = 10.0 Hz, 1H), 6.41 (d,
1
3
J = 8.8 Hz, 1H), 5.93 (s, 1H), 5.53 (d, J = 10.0 Hz, 1H), 1.48 (s, 6H). C
NMR (100 MHz, DMSO) δ 192.7, 165.9, 160.0, 156.0, 149.6, 148.1,
1
40.8, 133.5, 125.2, 123.4, 120.6, 116.9, 115.2, 108.6, 105.7, 102.5, 96.2,
2
4

ACCEPTED MANUSCRIPT
8.1, 27.8; HRMS (ESI) m/z: Calcd for C H O [M-H] 369.0980; found,
-
7
3
20
17
7
69.0981.
.1.16 1-(5,7-dihydroxy-2,2-dimethyl-2H-chromen-8-yl)ethan-1-one
5
(11)
Compound 6 (557 mg, 2.0 mmol) in MeOH (10 mL) was cooled to
0
°C, then 3N HCl (2.5 mL) was added. After addtion, the mixture was
heated to 60 °C for 6h. The mixture was poured in cold NaHCO (aq) and
3
extracted with EtOAc (3x20 mL). The combined organic layers were
washed with brine, dried over Na SO and concentrated under reduced
2
4
pressure. The crude product was purified by column chromatography on
silica (petroleum ether/ethyl acetate 20:1) to afford a compound 11 (250
1
mg, 53%) as a yellow solid. H NMR (400 MHz, DMSO) δ 13.55 (s, 1H),
1
1
1
5
1
0.83 (s, 1H), 6.47 (d, J = 10.0 Hz, 1H), 5.90 (s, 1H), 5.52 (d, J = 10.0 Hz,
13
H), 2.58 (s, 3H), 1.45 (s, 6H). C NMR (100 MHz, DMSO) δ 203.0,
65.3, 160.4, 157.0, 125.2, 116.7, 105.1, 102.3, 95.8, 78.3, 33.3, 27.8.
.1.17
,1'-(methylenebis(5,7-dihydroxy-2,2-dimethyl-2H-chromene-6,8-diyl
))bis(ethan-1-one) (12)
Compound 11 (234 mg, 1.0 mmol) in CH Cl (10 mL) was added
2
2
polyformaldehyde (15 mg, 0.5 mmol). The reaction mixture was heated
to 60 °C for 8h. Solvent was removed under reduced pressure and the
residue was purified by by column chromatography on silica (petroleum
2
5

ACCEPTED MANUSCRIPT
ether/ethyl acetate 50:1) to afford a compound 12 (170 mg, 71%) as a
1
yellow solid. H NMR (400 MHz, CDCl ) δ 15.81 (s, 2H), 9.43 (s, 2H),
3
6
6
1
.63 (d, J = 10.0 Hz, 2H), 5.43 (d, J = 10.0 Hz, 2H), 3.75 (s, 2H), 2.67 (s,
13
H), 1.47 (s, 12H). C NMR (100 MHz, CDCl ) δ 202.8, 160.2, 157.3,
3
54.9, 124.0, 116.0, 104.9, 104.0, 102.4, 77.1, 31.7, 26.9, 14.4.
5
.1.18
(2E,2'E)-1,1'-(methylenebis(5,7-dihydroxy-2,2-dimethyl-2H-chromen
e-6,8-diyl))bis(3-(4-(methoxymethoxy)phenyl)prop-2-en-1-one) (13a)
Compound 12 (0.24 g, 0.5 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7a (200 mg, 1.2 mmol) was added. The reaction was heated to
0 °C for 6h. After cooling down to 0 °C, 2N HCl was added to the
5
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 13a (343 mg, 88% ) as a red solid. H NMR (400 MHz,
CDCl ) δ 9.69 (s, 2H), 8.11 (d, J = 15.6 Hz, 2H), 7.82 (d, J = 15.6 Hz,
3
2
H), 7.56 (d, J = 8.8 Hz, 4H), 7.08 (d, J = 8.8 Hz, 4H), 6.68 (d, J = 10.0
Hz, 2H), 5.48 (d, J = 10.0 Hz, 2H), 5.22 (s, 4H), 3.82 (s, 2H), 3.49 (s, 6H),
1
3
1
1
1
.53 (s, 12H). C NMR (100 MHz, CDCl ) δ 192.7, 162.9, 159.1, 158.7,
3
55.3, 143.2, 130.1, 129.3, 125.0, 124.9, 117.4, 116.6, 106.6, 105.3,
03.8, 94.2, 78.1, 56.2, 28.0, 15.8.
5
.1.19
(2E,2'E)-1,1'-(methylenebis(5,7-dihydroxy-2,2-dimethyl-2H-chromen
2
6

ACCEPTED MANUSCRIPT
e-6,8-diyl))bis(3-(2,3-bis(methoxymethoxy)phenyl)prop-2-en-1-one)
(13b)
Compound 12 (0.24 g, 0.5 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7b (270 mg, 1.2 mmol) was added. The reaction was heated to
0 °C for 6h. After cooling down to 0 °C, 2N HCl was added to the
5
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 13b (367 mg, 82%) as a red solid. H NMR (400 MHz,
CDCl ) δ 9.70 (s, 2H), 8.30 (d, J = 16.0 Hz, 2H), 8.17 (d, J = 16.0 Hz,
3
2
H), 7.34 (dd, J = 8.0, 1.2 Hz, 2H), 7.20 (dd, J = 8.0, 1.2 Hz, 2H), 7.09 (t,
J = 8.0 Hz, 2H), 6.67 (d, J = 10.0 Hz, 2H), 5.48 (d, J = 10.0 Hz, 2H), 5.22
(s, 4H), 5.20 (s, 4H), 3.82 (s, 2H), 3.66 (s, 6H), 3.52 (s, 6H), 1.52 (s, 12H).
1
3
C NMR (100 MHz, CDCl ) δ 192.9, 163.0, 158.8, 155.4, 150.5, 146.5,
3
1
1
38.4, 130.7, 127.7, 125.1, 124.6, 120.1, 118.2, 117.2, 106.6, 105.3,
03.8, 99.5, 95.2, 78.2, 58.0, 56.3, 28.0, 15.8.
5
.1.20
(
2E,2'E)-1,1'-(methylenebis(5,7-dihydroxy-2,2-dimethyl-2H-chromen
e-6,8-diyl))bis(3-(2,4-bis(methoxymethoxy)phenyl)prop-2-en-1-one)
13c)
(
Compound 12 (0.24 g, 0.5 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7c (270 mg, 1.2 mmol) was added. The reaction was heated to
2
7

ACCEPTED MANUSCRIPT
5
0 °C for 6h. After cooling down to 0 °C, 2N HCl was added to the
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 13c (250 mg, 56%) as a red solid. H NMR (400 MHz,
CDCl ) δ 9.71 (s, 2H), 8.26 (d, J = 16.0 Hz, 2H), 8.09 (d, J = 16.0 Hz,
3
2
2
4
1
1
1
H), 7.60 (d, J = 8.8 Hz, 2H), 6.87 (d, J = 2.4 Hz, 2H), 6.76 (dd, J = 8.8,
.4 Hz, 2H), 6.68 (d, J = 10.0Hz, 2H), 5.47 (d, J = 10.0 Hz, 2H), 5.27 (s,
H), 5.20 (s, 4H), 3.82 (s, 2H), 3.52 (s, 6H), 3.50 (s, 6H), 1.52 (s,
1
3
2H). C NMR (100 MHz, CDCl ) δ 192.9, 163.0, 160.5, 158.6, 157.8,
3
55.3, 138.2, 128.4, 125.0, 124.7, 119.3, 117.4, 109.6, 106.6, 105.3,
03.7, 103.6, 94.8, 94.3, 78.0, 56.4, 56.3, 28.0, 15.8.
5
.1.21
(
2E,2'E)-1,1'-(methylenebis(5,7-dihydroxy-2,2-dimethyl-2H-chromen
e-6,8-diyl))bis(3-(2,3,4-tris(methoxymethoxy)phenyl)prop-2-en-1-one)
13d)
(
Compound 12 (0.24 g, 0.5 mmol) in EtOH (3 mL) was cooled to
0
°C. Then KOH (30% aq) (1 mL) was added slowly. After addtion,
compound 7d (340 mg, 1.2 mmol) was added. The reaction was heated to
0 °C for 6h. After cooling down to 0 °C, 2N HCl was added to the
5
reaction mixture until the pH = 5-6. The percipitate was filtered and dried
1
to give compound 13d (387 mg, 76%) as a red solid. H NMR (400 MHz,
CDCl ) δ 9.72 (s, 2H), 8.24 (d, J = 15.6 Hz, 2H), 8.13 (d, J = 15.6 Hz,
3
2
H), 7.40 (d, J = 8.8 Hz, 2H), 7.01 (d, J = 8.8 Hz, 2H), 6.66 (d, J = 10.0
2
8