Synthesis of threo-(±)-9,9-dibenzoylsecoisolariciresinol and its isomer

Article abstract of DOI:10.3184/030823410X12869011963454

The total synthesis of threo-(±)-9,9-dibenzoylsecoisolariciresinol and its isomer based on two Stobbe reactions as C-C bond-forming steps used a protected vanillin and diethyl; succinate to give the skeleton of lignan, followed by reduction to afford threo-and meso-(±)-secoisolariciresinol Both were treated with benzoyl chloride to obtain the natural product threo-(±)-9,9-dibenzoylsecoisolariciresinol and Its isomer meso-(±)-9,9-dibenzoylsecoisolariciresinol for the first time.

Full text of DOI:10.3184/030823410X12869011963454

606 RESEARCH PAPER
NOVEMBER, 606–609
JOURNAL OF CHEMICAL RESEARCH 2010
Synthesis of threo-( )-9,9-dibenzoylsecoisolariciresinol and its isomer
* and Yanling Wen
Yamu Xia
College of Chemical Engineering, Qingdao University of Science andTechnology, Qingdao 266042, P. R. China
The total synthesis of threo-( )-9,9-dibenzoylsecoisolariciresinol and its isomer based on two Stobbe reactions as
C–C bond-forming steps used a protected vanillin and diethyl; succinate to give the skeleton of lignan, followed by
reduction to afford threo- and meso-( )-secoisolariciresinol Both were treated with benzoyl chloride to obtain the
natural product threo-( )-9,9-dibenzoylsecoisolariciresinol and Its isomer meso-( )-9,9-dibenzoylsecoisolariciresinol
for the first time.
Keywords: lignan, 9,9-dibenzoylsecoisolariciresinol, dibenzylbutane
Lignans are a diverse family of biologically active plant metab-
olites that contain two phenylpropanoid units as the key struc-
tural components.1 Lignans are found in all parts of plants,
including the roots, stems, leaves, fruit, and seeds and they
exhibit a wide range of biological activities.2–5 Some natural
products have been used medicinally for thousands of years.
In many cases, the active principle of lignan-based traditional
medicines is not known, and a detailed study of the active
principles may provide useful leads in the development of
new pharmaceutical agents.6–11 In 2009, the new lignan 9,9-
dibenzoylsecoisolariciresinol (1) was isolated from the aerial
parts of Maytenus apurimacensis which belongs to the Celas-
traceae family and is used in South American folk medicine.
9,9-Dibenzoylsecoisolariciresinol has the classic lignan skele-
ton and it seems likely that it is formed by metabolism of a
naturally occurring lignan in an as yet unproven fashion.12
The core of 9,9-dibenzoylsecoisolariciresinol is the dibenz-
ylbutane. A great deal of effort has been put into synthetic
work on lignans of this type.13–15 Among them, the alkylation
of β-substituted γ-butyrolactone with an appropriate benzylic
halide is the most widely used.16 Gezginci reported the synthe-
sis of meso-nordihydroguaiaretic acid from 3,4-dimethoxy-
phenyl acetone using a low-valency Ti-induced carbonyl−
coupling reaction of the ketone as the key step.17 Rao has
described the synthesis of analogues of (–)-saururenin from
Saururus cernuus, along with (–)-austrobailignan-5 by regi-
oselective cleavage of the methylenedioxyphenyl groups.18
Here, we first report an efficient route for the synthesis of
natural product threo-( )-9,9-dibenzoylsecoisolariciresinol (1)
and its isomer meso-( )-9,9-dibenzoylsecoisolariciresinol (2).
The syntheses were based on a strategy involving Stobbe con-
densation to give the skeleton of the lignan, and the resolution
of threo- and meso-isomers, followed by treatment with
benzoyl chloride to obtain the target compound.
is outlined in Scheme 2. It was anticipated that condensation
of 3 with diethyl succinate would furnish 4, which after the
second condensation of with 3 to form (E)-5 and subsequent
hydrogenation with a 10% palladium on charcoal catalyst,
gave a readily separable mixture of meso-secoisolariciresinol
(6a) and threo-( )-secoisolariciresinol (6b). Acylation of
meso-( )-6a or threo-( )-6b with benzoyl chloride produced
meso-( )-9,9-dibenzoylsecoisolariciresinol (2) or threo-( )-
9,9-dibenzoylsecoisolariciresinol (1).
Our investigations began with cheap vanillin as a raw mate-
rial. The 4-hydroxyl group of vanillina was protected with
benzyl chloride to afford the product 3. Compound 3 under-
went a Stobbe condensation with diethyl succinate in the pres-
ence of sodium ethoxide in ethanol to produce compound 4.
The trans-(E)-configuration of the olefinic double bond was
evident from the appearance of the deshielded vinylic proton at
δ7.87 in its 1H NMR spectrum.19 Compound 4 was methylated
with diazomethane in methanol to yield the diester 7. The
second Stobbe condensation of 7 with 3 in methanol with
the presence of sodium methoxide yielded compound 8. The
1
deshielded vinylic proton at δ7.96 in the H NMR spectrum
of 8 again indicated the trans-(E)-configuration for both the
olefinic double bonds.20 Compound 8 was again methylated to
produce a diester 9. Treatment of 9 with LiAlH4/AlCl3 afforded
the unsaturated diol 5, followed by hydrogenation with a 10%
palladium on charcoal catalyst to produce a readily separable
mixture (approximate 1) of diols meso-secoisolariciresinol
(6a) and threo-( )-secoisolariciresinol (6b). threo-( )-6b had
consistently larger Rf values than those of the corresponding
meso-6a, and each pair was easily separated by flash column
chromatography over silica gel. The configuration of threo-
( )-6b was agreement with those reported in the literature.21
The 4-hydroxyl group of meso-( )-6a or threo-( )-6b was
protected with benzyl chloride to afford meso-( )-10a or threo-
( )-10b. After acylation of meso-( )-10a or threo-( )-10b
with benzoyl chloride, and then hydrogenation, natural
product meso-( )-9,9-Dibenzoylsecoisolariciresinol (2) or
threo-( )-9,9-Dibenzoylsecoisolariciresinol (1) was obtained
Results and discussion
Our approach to the synthesis of the natural product threo-( )-
9,9-dibenzoylsecoisolariciresinol (1) and its meso-isomer (2)
Scheme 1
* Correspondent. E-mail: sdjndb@163.com

JOURNAL OF CHEMICAL RESEARCH 2010 607
Scheme 2
Scheme 3
(E)-2-(4′-benzyloxy-3′-methoxybenzylidene)succinic acid (4): The
(Scheme 4). The spectroscopic data of natural product 1 was in
agreement with those found in the literature12.
compound 3 (72.6 g, 300 mmol) and diethylsuccinate (52.2 g,
300 mmol) were added to a solution of NaOEt (40.8 g, 600 mmol) in
EtOH (500 mL). The mixture was heated under reflux for 4 h, and the
ethanol was removed. The residue was cooled and acidified with HCl
(5 N). This was then extracted with EtOAc (3 × 70 mL). The EtOAc
layer was then re-extracted with saturated solution of NaHCO3
(300 mL). Acidification of the aq. NaHCO3 extract with HCl (5 N)
provided an oily layer, which was again extracted with EtOAc (3 ×
70 mL). The combined organic layer was dried over MgSO4 and
concentrated in vacuo. This residue was added to a solution of 20%
aqueous NaOH (500 mL) and refluxed for 3 h. After cooling to room
temperature, the mixture was washed with EtOAc (3 × 70 mL). The
solution was decolourised with active carbon and the mixture was
acidified with HCl (5 N) to yield white solids. The crude product
was crystallised from EtOH to give the diacid 4 as a yellow crystal
(120.0 g, 83%). m.p. 131−133 °C. 1H NMR (CDCl3, 500 MHz) δ: 3.57
(s, 2H, CH2), 3.86 (s, 3H, OCH3), 5.15 (s, 2H, ArCH2O), 6.68−7.43
(m, 8H, ArH), 7.87 (s, 1H, ArCH=C). EI−MS (m/z, %): 342 (M+, 26),
324 (12), 297 (27), 175 (16), 91 (100).
In summary, we have developed an efficient and practical
synthesis of a dibenzylbutyl benzoate lignan based on a
Stobbe reaction to construct the skeleton of lignan. The natural
product threo-( )-9,9-Dibenzoylsecoisolariciresinol(1) and its
isomer meso-( )-9,9-Dibenzoylsecoisolariciresinol (2) were
obtained by this route for the first time.
Experimental
Melting points were taken on Gallenkamp melting point apparatus
which are uncorrected. IR spectra were recorded on a Nicolet NEXUS
1
670 FT−IR. The HNMR and 13CNMR spectra were recorded on a
Bruker AM−500 MHz spectrometers. Mass spectra were recorded on
a ZAB−HS spectrometer. HRMS were obtained on a Bruker Daltonics
APEXII47e spectrometer. Flash column chromatography was per-
formed on silica gel (200–300 mesh) and TLC inspections on silica
gel GF254 plates.
4-Benzyloxy-3-methoxybenzaldehyde (3): A mixture of Vanillin
(60.8 g, 400 mmol), benzyl bromide and anhydrous potassium car-
bonate (83.2 g, 400 mmol) in acetone were stirred overnight at room
temperature. The reaction mixture was filtered, and the solvent was
removed in vacuo. The residue was crystallised from EtOH to give
the compound 3 as yellow crystals (92.0 g, 95%). m.p. 65−67 °C. 1H
NMR (DMSO−d6, 500 MHz) δ: 3.84 (s, 3H, OCH3), 5.16 (s, 2H,
ArCH2O), 6.87−7.54 (m, 8H, ArH), 9.85 (s, 1H, ArCHO).
(E)-Dimethyl
2-(4′-benzyloxy-3′-methoxybenzylidene)succinate
(7): The diacid 4 (68.4 g, 200 mmol) was added to an ice-cold solution
of excess CH2N2 in Et2O. The mixture was stirred for 12 h, and
concentrated in vacuo. Flash column chromatography of the residue
1
gave the diester 7 as a yellow oil (71.8 g, 97%). H NMR (CDCl3,
500 MHz) δ: 3.69 (s, 3H, COOCH3), 3.78 (s, 3H, COOCH3), 3.83
(s, 3H, OCH3), 5.15 (s, 2H, ArCH2O), 6.68−7.45 (m, 8H, ArH), 7.88

608 JOURNAL OF CHEMICAL RESEARCH 2010
Scheme 4
(s, 1H, ArCH=C). EI−MS (m/z, %): 370 (M+, 36), 338 (18), 307 (14),
175 (23), 91 (100).
the solvent was removed in vacuo and flash column chromatography
of the residue gave the colourless oil meso-secoisolariciresinol 6a
(3.69 g, 40.7%) and a white crystal threo-( )-secoisolariciresinol 6b
(4.1 g, 45.2%).
Trans-(E)-2,3-dis(4′-benzyloxy-3′-methoxybenzylidene)succinic
acid (8): Diester 7 (37.1 g, 100 mmol) on Stobbe condensation
(following the above mentioned procedure) with compound 3 (24.2 g,
100 mmol) gave a light-yellow solid which was purified by recrystal-
lisation from MeOH to yield product 8 (42.5 g, 75%). m.p. 151−
Meso-secoisolariciresinol 6a: IR (KBr/cm−1): 3310, 2910, 1498,
1
1251, 1042, 928. H NMR (acetone−d6, 500 MHz) δ: 1.90−2.01 (m,
2H, 2 × ArCH2CH), 2.57−2.62 (m, 4H, 2 × ArCH2CH), 3.41 (dd, 2H,
J = 11.0, 3.5 Hz, CH2OH), 3.52 (dd, 2H, J = 11.0, 6.5 Hz, CH2OH),
3.75 (s, 6H, 2 × OCH3), 6.62−6.74 (m, 6H,ArH).13C NMR (acetone−d6,
125 MHz) δ: 33.2 (C-7, C-7′), 44.6 (C-8, C-8′), 55.3 (2 × OCH3), 62.2
(C-9, C-9′), 112.5 (C-2, C-2′), 114.5 (C-5, C-5′), 121.6 (C-6, C-6′),
132.7 (C-1, C-1′), 144.6 (C-4, C-4′), 147.3 (C-3, C-3′). HRMS Calcd
for C20H30NO6(M+NH4+): 380.2068. Found: 380.2073.
1
153 °C. IR (KBr, cm−1) v: 3350, 2900, 1740, 1496, 1241, 1042. H
NMR (CDCl3, 500 MHz) δ: 3.78 (s, 6H, 2 × OCH3), 5.16 (s, 4H, 2 ×
ArCH2O), 6.78−7.44 (m, 16H, ArH), 7.96 (s, 2H, 2 × ArCH=C). 13
C
NMR (CDCl3, 125 MHz) δ: 55.7 (2 × OCH3), 70.7 (2 ×ArCH2), 112.7,
113.1, 123.3, 124.9, 127.2, 127.3, 128.0, 128.6 (2 × ArCH=C), 136.4
(2 × ArCH=C), 144.2, 149.2, 150.1, 172.7 (2 × C=O). EI−MS (m/z,
%): 566 (M+, 2.1), 549 (4.3), 325 (11), 175 (35), 151 (5.2), 91 (100).
HRMS Calcd for C34H31O8 (M+H+): 567.2014. Found: 567.2012.
Trans-(E)-dimethyl 2,3-bis(4′-benzyloxy-3′-methoxybenzylidene)su
ccinate (9): Following the procedure described for the preparation of
7, and starting with the diacid 8 (28.3 g, 50 mmol), gave a light-yellow
solid which was purified by recrystallisation from 10% hexane in
EtOAc to yield the diester 9 (28.0 g, 94%). m.p. 143−146 °C. IR (KBr,
Threo-( )-secoisolariciresinol 6b: M.p. 127−128°C. IR (KBr/
1
cm−1): 3354, 2910, 1512, 1240, 1032, 928. H NMR (acetone−d6,
125 MHz) δ: 1.86−1.91 (m, 2H, ArCH2CH), 2.58−2.70 (m, 4H, 2 ×
ArCH2CH), 3.49 (dd, 2H, J = 11.0, 4.5 Hz, CH2OH), 3.62 (dd, 2H,
J = 11.0, 3.5 Hz, CH2OH), 3.71 (s, 6H, 2 × OCH3), 6.55−6.68 (m, 6H,
ArH).13C NMR (acetone-d6, 125 MHz) δ: 36.2 (C-7, C-7′), 44.8 (C-8,
C-8′), 56.3 (2 × OCH3), 61.4 (C-9, C-9′), 113.5 (C-2, C-2′), 115.6
(C-5, C-5′), 122.5 (C-6, C-6′), 133.8 (C-1, C-1′), 145.6 (C-4, C-4′),
148.3 (C-3, C-3′). HRMS Calcd for C20H30NO6(M+NH4+): 380.2068.
Found: 380.2065. The data are consistent with the literature.21
Meso-2,3-bis(4′-benzyloxy-3′-methoxybenzyl)-1,4-butanediol
(10a): Following the procedure described for the preparation of 3, and
starting with the diol 6a (3.62 g, 10 mmol), compound 10a was
obtained as a yellow oil (4.9 g, 90%). IR (KBr/cm−1): 3293, 2925,
1488, 1246, 1037, 931. 1H NMR (CDCl3, 500 MHz) δ: 2.01−2.10 (m,
2H, 2 × ArCH2CH), 2.69−2.76 (m, 4H, 2 × ArCH2CH), 3.54−3.56 (m,
2H, CH2OH), 3.60−3.62 (m, 2H, CH2OH), 3.84 (s, 6H, 2 × OCH3),
5.10 (s, 4H, 2 × ArCH2O), 6.62−6.80 (m, 6H, ArH) , 7.27−7.39
(m, 10H, ArH). 13C NMR (CDCl3, 125 MHz) δ: 33.4 (C-3, C-4), 43.9
(C-7′, C-7″), 56.1 (2 × OCH3), 60.9 (C-1, C-4), 71.3 (2 × ArCH2O),
73.3 (C-2, C-5), 113.0 (C-2′, C-2″), 114.4 (C-5′, C-5″), 121.0 (C-6′,
C-6″), 127.3, 127.8, 128.5, 133.7 (C-1′, C-1″), 137.4, 146.6 (C-4′,
C-4″), 149.7 (C-3′, C-3″). HRMS Calcd for C34H42NO6(M+NH4+):
560.3007. Found: 560.3012.
1
cm−1) v: 3010, 2951, 2842, 1710, 1600, 1513, 1427, 916. H NMR
(CDCl3, 500 MHz) δ: 3.67 (s, 6H, 2 × OCH3), 3.75 (s, 6H, 2 ×
COOCH3), 5.15 (s, 4H, 2 × ArCH2O), 6.79−7.41 (m, 16H, ArH), 7.87
(s, 2H, 2 ×ArCH=C).13C NMR (CDCl3, 125 MHz) δ: 52.5 (2 × OCH3),
55.8 (2 × OCH3), 70.8 (2 × ArCH2), 112.4, 113.2, 124.5, 124.6, 127.3,
127.9, 128.1, 128.7 (2 × ArCH=C), 136.6 (2 × ArCH=C), 142.4,
149.3, 149.7, 167.8 (2 × C=O). HRMS Calcd for C36H35O8 (M+H+):
595.2327. Found: 595.2325.
Trans-(E)-dimethyl 2,3-bis(4′-benzyloxy-3′-methoxybenzylidene)
-1,4-butanediol (5): Diester 9 (17.8 g, 30 mmol) in dry THF was
added dropwise during 1 h to a mixture of LiAlH4/AlCl3(3:1, 6.0 g), in
dry THF and stirred under nitrogen at room temperature. Then the
reaction was quenched by ice water and filtered. The filtrate was dried
by MgSO4 and concentrated in vacuo. Flash column chromatography
of the residue gave trans-(E)-diol 5 (13.7 g, 85%). IR (KBr, cm−1)
v: 3320, 2931, 1512, 1247, 1032. 1H NMR (CDCl3, 500 MHz) δ: 3.74
(s, 6H, 2 × OCH3), 4.12−4.13 (d, 4H, 2 × CH2OH), 5.12 (s, 4H,
2 × ArCH2O), 6.63 (s, 2H, 2 × ArCH), 6.79−7.44 (m, 16H, ArH) . 13
C
Threo-( )-2,3-bis(4′-benzyloxy-3′-methoxybenzyl)-1,4-butanediol
(10b): Following the procedure described for the preparation of 3, and
starting with the diester 6b (3.6 g, 10 mmol), compound 10b was
obtained as a yellow oil (4.8 g, 89%). IR (KBr/cm−1): 3383, 2921,1521,
NMR (CDCl3, 125 MHz) δ: 55.7 (2 × OCH3), 66.6 (2 × CH2OH), 70.8
(2 × ArCH2O), 111.5 (C-2, C-2′), 113.6 (C-5, C-5′), 121.1 (C-6, C-6′),
127.2, 127.4, 127.8, 128.5, 128.8 (2 × ArCH=C), 129.8, 136.9 (2 ×
ArCH=C), 137.5 (C-1, C-1′), 147.7 (C-4, C-4′), 149.3 (C-3, C-3′).
HRMS Calcd for C34H38NO6(M+NH4+): 556.2694. Found: 556.2699.
Meso-secoisolariciresinol, 6a and threo-( )-secoisolariciresinol
(6b): Diol 5 (13.5 g, 25 mmol) in MeOH (250 mL) was stirred under
hydrogen atmosphere for 36 h in the presence of 10% Pd/C (5.6 g).
The reaction mixture was filtered through a pad of Celite. Then,
1
1245, 1037, 928. H NMR (CDCl3, 500 MHz) δ: 1.85−1.95 (m, 2H,
2 × ArCH2CH), 2.62−2.67 (m, 4H, 2 × ArCH2CH), 3.54−3.56 (m, 2H,
CH2OH), 3.60−3.62 (m, 2H, CH2OH), 3.80 (s, 6H, 2 × OCH3), 5.13
(s, 4H, 2 × ArCH2O), 6.61−6.71 (m, 6H, ArH) , 7.27−7.37 (m, 10H,
ArH). 13C NMR (CDCl3, 125 MHz) δ: 35.9 (C-3, C-4), 45.0 (C-7′,
C-7″), 56.1 (2 × OCH3), 63.4 (C-1, C-4), 71.3 (2 × ArCH2O), 113.0

JOURNAL OF CHEMICAL RESEARCH 2010 609
(C-2′, C-2″), 114.4 (C-5′, C-5″), 121.0 (C-6′, C-6″), 127.3, 127.8,
128.5, 133.9 (C-1′, C-1″), 137.4, 146.7 (C-4′, C-4″), 149.8 (C-3′,
C-3″). HRMS Calcd for C34H42NO6(M+NH4+): 560.3007. Found:
560.3012.
C-12,C-12′), 131.5 (s, C-1, C-1′), 133.0 (d, C-15, C-15′), 144.0 (s,
C-4,C-4′), 146.5 (s, C-3, C-3′), 166.5 (s, C-11, C-11′).
This work was financially supported by Taishan Scholar
Project of Shandong Province (NO.2005011036), Specialised
Research Fund for the Doctoral Program of Higher Education
of China (NO.20093719120004), and Open Foundation of
Chemical Engineering Subject, Qingdao University of Science
& Technology, China.
Meso-( )-9,9-dibenzoylsecoisolariciresinol (2): Benzoyl chloride
(0.9 g, 6 mmol) in dry dichloromethane (10 mL) was added dropwise
during 1 h to the mixture of diol 10a (1.6 g, 3 mmol), pyridine (0.5 g,
6 mmol) and dry dichloromethane (20 mL). The mixture was stirred
under nitrogen at room temperature for 5 h, and then filtered. The fil-
trate was concentrated in vacuo. Flash column chromatography of the
residue gave compound 2 as a white oil (1.5 g, 89%). IR (KBr/cm−1):
1
3448, 2928, 2842, 1712, 1605, 1515, 1450, 1265, 1035. H NMR
Received 24 June 2010; accepted 6 September 2010
Paper 1000221 doi: 10.3184/030823410X12869011963454
Published online 24 November 2010
(CDCl3, 500 MHz) δ: 2.28−2.37 (m, 2H, ArCH2CH), 2.67−2.75 (m,
4H, 2 × ArCH2CH), 3.76 (s, 6H, 2 × OCH3), 4.24 (m, 2H, H-9b,
H-9b′), 4.52 (m, 2H, H-9a, H-9a′), 6.53−6.78 (m, 6H, ArH), 7.45−8.05
(m, 10H, ArH). 13C NMR (CDCl3, 125 MHz) δ: 33.6 (C-7, C-7′), 40.5
(C-8, C-8′), 55.3 (2 × OCH3), 66.5 (C-9, C-9′), 110.6 (C-2, C-2′),
113.8 (C-5, C-5′), 120.7 (C-6, C-6′), 128.4 (C-13, C-13′, C-15, C-15′),
129.2 (C-12, C-12′, C-16, C-16′), 130.1 (C-11, C-11′), 130.5 (C-1,
C-1′), 133.2 (C-14, C-14′), 143.3 (C-4, C-4′), 145.8 (C-3, C-3′), 166.5
(C-10, C-10′). HRMS Calcd for C34H38NO8(M+NH4+): 588.2592.
Found: 588.2594.
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Threo-( )-9,9-dibenzoylsecoisolariciresinol (1): Following the
procedure described for the preparation of 2, and starting with the
diester 10b (1.6 g, 3 mmol), compound 1 was obtained as a white oil
(1.6 g, 92%). IR (KBr/cm−1): 3420, 2930, 2856, 1715, 1605, 1512,
1454, 1270, 1031. 1H NMR (CDCl3, 500 MHz) δ: 2.30−2.41 (m, 2H,
ArCH2CH), 2.75−2.88 (m, 4H, 2 ×ArCH2CH), 3.77 (s, 6H, 2 × OCH3),
4.33 (m, 2H, H-9b, H-9b′), 4.52 (m, 2H, H-9a, H-9a′), 6.53−6.80 (m,
6H, ArH), 7.43−8.05 (m, 10H, ArH). 13C NMR (CDCl3, 125 MHz)
δ: 35.2 (C-7, C-7′), 40.8 (C-8, C-8′), 55.6 (2 × OCH3), 65.1 (C-9,
C-9′), 111.4 (C-2, C-2′), 114.7 (C-5, C-5′), 121.5 (C-6, C-6′), 128.6
(C-13, C-13′, C-15, C-15′), 129.4 (C-12, C-12′, C-16, C-16′), 130.1
(C-11, C-11′), 131.6 (C-1, C-1′), 133.1 (C-14, C-14′), 144.0 (C-4,
C-4′), 146.5 (C-3, C-3′), 166.5 (C-10, C-10′). HRMS Calcd for
C34H38NO8(M+NH4+): 588.2592. Found: 588.2597. . The data are con-
sistent with the literature.12 The data of 1 in the literature:12jj IR (KBr/
cm−1): 2923, 2853, 2360, 2338, 1714, 1603, 1514, 1454, 1374, 1270,
7
8
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1
1115, 1031, 756, 712 cm-1; H NMR (CDCl3, 300MHz) δ: 2.36 (m,
2H, ArCH2CH), 2.81(m, 4H, 2 × ArCH2CH), 3.77 (s, 6H, 2 × OCH3),
4.35 (dd, 2H, J = 11.2, 4.3 Hz, H-9b, H-9b′), 4.54 (2H, dd, J = 11.2,
5.9 Hz, H-9a, H-9a′), 5.45(s, 2H, OH), 6.53 (d, 2H, J = 1.8 Hz, H-2,
H-2′), 6.61 (dd, 2H, J = 8.0, 1.8 Hz, H-6, H-6′), 6.79 (2H, dd, J = 8.0,
1.8 Hz, H-5, H-5′), 7.43 (t, 4H, J = 7.7 Hz, H-14, H-14′, H-16, H-16′),
7.57 (t, 2H, J = 6.5 Hz, H-15, H-15′), 8.01 (d, 4H, J = 8.0 Hz, H-13,
H-13′, H-17, H-17′). 13C NMR (CDCl3, 75MHz) δ: 35.1 (t, C-7, C-7′),
40.4 (d, C-8, C-8′), 55.6 (c, C-10, C-10′), 65.0 (t, C-9, C-9′), 111.2 (d,
C-2,C-2′), 114.2 (d, C-5, C-5′), 121.7 (d, C-6, C-6′), 128.4 (d, C-14,
C-14′;C-16, C-16′), 129.5 (d, C-13, C-13′; C-17, C-17′), 130.1 (s,
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