Synthesis and biological activity of optically active phenylbutenoid dimers

Article abstract of DOI:10.1021/np100942e

The total synthesis of optically active phenylbutenoid dimers 1, 3, and ent-3 is described. The key step to access optically active cyclohexene rings was achieved by Diels-Alder reaction of chiral acryloyloxazolinone 9 and phenylbetadiene 10.

Full text of DOI:10.1021/np100942e

NOTE
pubs.acs.org/jnp
Synthesis and Biological Activity of Optically Active
Phenylbutenoid Dimers
Jeonghyun Chu,† Dong Hoon Suh,‡ Gehyung Lee,§ Ah-Reum Han,^ Song Wha Chae,^ Hwa Jeong Lee,^
Eun-Kyoung Seo,*,^ and Hee-Jong Lim*,§
†Department of Chemistry, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701, Korea
‡Department of Chemistry, Sogang University, 1 Sinsu-dong, Mapo-gu, Seoul 121-742, Korea
§Bio-Organic Science Division, Korea Research Institute of Chemical Technology, P.O. Box 107, Yusung-gu, Daejeon 305-600, Korea
^College of Pharmacy, Ewha Womans University, 11-1 Daehun-dong, Seodaemun-gu, Seoul 120-750, Korea
S Supporting Information
b
ABSTRACT: The total synthesis of optically active phenylbutenoid dimers 1, 3,
and ent-3 is described. The key step to access optically active cyclohexene rings was
achieved by DielsꢀAlder reaction of chiral acryloyloxazolinone 9 and phenylbeta-
diene 10.
everal phenylbutenoid dimers including 3-aryl-4-(E)-styrylcy-
clohexenes 1ꢀ6 and 1,2-bis((E)-styryl) cyclobutane were
(1) has inhibitory activity for NO production induced by LPS in
mouse macrophages.2 Also, (()-3-(3,4-dimethoxyphenyl)-4-
[(E)-3,4-dimethoxystyryl]cyclohex-1-ene (3) has been re-
ported to inhibit P-glycoprotein (P-gp) activity in a P-gp-over-
expressing human breast cancer cell line,3 cyclooxygenase-2
(COX-2) activity,1f,4 and cell proliferation in several human
tumor cell lines.5 One limitation in biological evaluation of
phenylbutenoid dimers is their low natural abundance. Thus,
for precise analysis of structureꢀactivity relationships, a new and
general synthesis of optically active phenylbutenoid dimers
became necessary. In an effort to further study the biological
activities of these molecules, we were interested in the synthesis
of optically active 3S-(3,4-dimethoxyphenyl)-4S-{(E)-3,4-dime-
thoxystyryl}cyclohex-1-ene (1), 3S-(3,4-dimethoxyphenyl)-4R-
{(E)-3,4-dimethoxystyryl}cyclohex-1-ene (3), and 3R-(3,4-dime-
thoxyphenyl)-4S-{(E)-3,4-dimethoxystyryl}cyclohex-1-ene
(ent-3).
S
isolated from the rhizomes of a tropical Zingiber cassumunar, which
has been used for the treatment of asthma, gastrointestinal distress,
and motion sickness.1 All of the phenylbutenoid dimers were
isolated as racemic mixtures, implying that they were produced
by a nonenzymatic process. Structure elucidations of these com-
pounds were based on analyses of their 1D and 2D NMR and
mass spectroscopic data, and configurations of the groups attached
to the cyclohexene ring of 1 and 3 were deduced to be cis
1
and trans, respectively, on the basis of the H NMR coupling
constants.1d
Thermal [4 + 2] dimerization of 1-phenylbutadiene was re-
ported to give cis- and trans-phenylbutenoid dimers in ratio of
1.4:1,6 and dimerization of 1-(3,4-dimethoxyphenyl)butadiene
(10) yielded the cis-isomer (1) in 23% yield as a racemic mix-
ture.7 In our synthetic strategy, optically active phenylbutenoid di-
mers 1 and 3 would arise from (1R,2S)-2-(3,4-dimethoxyphenyl)
There has been a growing interest in phenylbutenoid dimers
due to their diverse biological activities. For example, (()-3-(3,4-
dimethoxyphenyl)-4-[(Z)-3,4-dimethoxystyryl]cyclohex-1-ene
Received: December 24, 2010
Published: July 19, 2011
r
Copyright
2011 American Chemical Society and
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dx.doi.org/10.1021/np100942e J. Nat. Prod. 2011, 74, 1817–1821
American Society of Pharmacognosy
|

Journal of Natural Products
NOTE
Scheme 1. Retrosynthetic Analysis
cyclohex-3-enecarbaldehyde (7), which in turn could be derived
from the optically active compound (S)-4-benzyl-3-((1R,2S)-
2-(3,4-dimethoxy phenyl)cyclohex-3-enecarbonyl)oxazolidin-
2-one (8) via DielsꢀAlder cyclization between (S)-3-acryloyl-4-
benzyloxazolidin-2-one (9) and 1-(3,4-dimethoxyphenyl)butadiene
(10) with high regio- and stereoselectivity (Scheme 1).8 The
starting compound 9 was prepared from (S)-4-benzyloxazolidin-
2-one by the reported method.9 Compound 10 was obtained
from 3,4-dimethoxyaldehyde by modification of the previous
method in 57% yield.1c Diethylaluminum chloride mediated
asymmetric cycloaddition reaction of 9 and 10 afforded 8 as
a single stereoisomer in quantitative yield. Reduction of 8 with
lithium borohydride in THF afforded the corresponding com-
pound ((1R,2S)-2-(3,4-dimethoxyphenyl)cyclohex-3-enyl)metha-
nol (11), which was then oxidized to 7 by Swern oxidation.
Compound 7 was converted to 3S-(3,4-dimethoxyphenyl)-
4S-{(E)-3,4-dimethoxystyryl}cyclohex-1-ene (1) by Hornerꢀ
WadsworthꢀEmmons condensation with dimethyl 3,4-di-
methoxybenzylphosphonate (12) in 50% yield with high E/Z-
selectivity in a ratio of 95:5 (Scheme 2).10 For the synthesis of
trans-isomer 3, compound 7 was epimerized with K2CO3 in
MeOH to thermodynamically more stable 13. However, when
olefination of 13 was carried out under the same conditions, 3S-
(3,4-dimethoxyphenyl)-4R-{(E)-3,4-dimethoxystyryl}cyclohex-
1-ene (3) was obtained in 24% yield.
dimethoxystyryl}cyclohex-1-ene (3) and 3S-(3,4-dimethoxy-
phenyl)-4R-{(Z)-3,4 dimethoxystyryl}cyclohex-1-ene (17) in
59% and 15% isolated yields, respectively, after separation by
HPLC using a chiral OD-H column.13 With the same synthetic
route described above, 3R-(3,4-dimethoxyphenyl)-4S-{(E)-
3,4-dimethoxystyryl}cyclohex-1-ene (ent-3) was prepared
starting with (R)-3-acryloyl-4-benzyloxazolidin-2-one (ent-7)
obtained by modification of the previous method.8 Optically
active phenylbutenoid dimers 3, ent-3, and 17 were evaluated
for their P-gylocoprotein inhibitory effect in a P-gp-overexpres-
sing multidrug-resistant (MDR) human breast cancer cell line,
MCF-7/ADR, using a previously reported protocol.3 Phenyl-
butenoids 3 and 17, with 3S, 4R configurations, were found to
have more potent P-gp inhibitory activity compared to ent-3,
with 3R, 4S configuration (Table 1). Further biological studies
of these optically active phenylbutenoid dimers will be reported
elsewhere.
In conclusion, phenylbutenoid dimer 1 and the structurally
related congeners 3, 17, and ent-3 have been successfully
synthesized from key intermediate 8 by employing asymmetric
DielsꢀAlder reactions with Evans chiral oxazolidinone 9. The
successful synthesis of phenylbutenoid dimers via a route that
readily gives entry to analogues will allow for further investiga-
tions of their pharmacological properties and structureꢀactivity
relationships.
Therefore, an alternative route involving stereoselective
vinylstannylation from 13 and Stille coupling to improve the
yield of 3 was attempted. Compound 13 was treated with PPh3
and carbon tetrabromide to afford the dibromide, then con-
verted to 4-((1S,6S)-6-ethynylcyclohex-2-enyl)-1,2-dimethox-
ybenzene (14) by Corey Fuch alkyne synthesis.11 Hydro-
stannylation of 14 with tributyltin hydride led to an 80% E
and 20% Z mixture of tributyl((E/Z)-2-((1S,2S)-2-(3,4-dime-
thoxyphenyl)cyclohex-3-enyl)vinyl)stannane (15).12 The E/Z
mixture (15) was used directly without separation, as a single
purification was planned for the final step of the synthesis.
Stille coupling of 15 with 3,4-dimethoxyphenyl triflate (16) led
to a 4:1 mixture of 3S-(3,4-dimethoxyphenyl)-4R-{(E)-3,4
’ EXPERIMENTAL SECTION
General Experimental Procedures. All reagents were purchased
from Aldrich Chemical Co. and Alfa Aesar Chemical Co. and used as
obtained unless otherwise noted. RPMI 1640 cell culture medium and
antibiotic-antimycotic agent were obtained from Invitrogen (Carlsbad,
CA, USA), and fetal bovine serum (FBS) was from Hyclone (South
Logan, UT, USA). Daunomycin, verapamil, and sulfo-rhodamine B (SRB)
were supplied by Sigma-Aldrich (St. Louis, MO, USA). Anhydrous THF
and CH2Cl2 were prepared by a solvent purification system. Melting
points were obtained on a Thomas Scientific melting point apparatus and
are uncorrected. Flash chromatography was carried out using silica gel
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Journal of Natural Products
NOTE
Scheme 2. Synthesis of Optically Active Phenybutenoid Dimers 1, 3, and ent-3a
a Reagents and conditions: (a) Et2AlCl, CH2Cl2, ꢀ78 ꢀC, 99%; (b) LiBH4, H2O, THF, 0 ꢀC 78%; (c) DMSO, (ClCO)2, Et3N, CH2Cl2, ꢀ78 ꢀC to rt,
94%; (d) 12, n-BuLi, THF, ꢀ78 ꢀC, 10 min, then 7, ꢀ78 ꢀC to rt, 2 h, 50%; (e) K2CO3, MeOH, rt, 73%; (f) PPh3, CBr4, CH2Cl2, 0 ꢀC, 99%; (g) n-BuLi,
THF, ꢀ78 ꢀC, 90%; (h) Bu3SnH, AIBN, toluene, 80 ꢀC, 83%; (i) Pd(PPh3)4, NMP, 90 ꢀC, 74%.
Table 1. Effects of Phenylbutenoid Dimers on Daunomycin
400 MHz (1H NMR) and 75 or 100 MHz (13C NMR), referenced to an
internal standard (TMS) or residual solvent protons, and signals are
reported in ppm (δ). High-resolution mass spectra (HRMS) were
recorded on an AEI MS3074 spectrometer and Agilent 6220 Accu-
rate-Mass TOF LC/MS system. Circular dichroism measurements were
performed using a Jasco J-715 CD/ORD spectropolarimeter.
(S)-4-Benzyl-3-[(1R,2S)-2-(3,4-dimethoxyphenyl)cyclohex-3-
enecarbonyl)]oxazolidin-2-one (8).To a solution of (S)-3-acryloyl-4-
benzyloxazolidin-2-one (9)9 (1.30 g, 5.62 mmol) in CH2Cl2 (50 mL) was
added sequentially 1-(3,4-dimethoxyphenyl)butadiene (10) (1.50 g, 7.87
mmol) and diethylaluminum chloride (4.37 mL, 7.87 mmol) at ꢀ78 ꢀC.
The resulting solution was stirred for an additional 5 min at ꢀ78 ꢀC
and then poured into a stirred solution of 1 N HCl (40 mL). The organic
layer was separated, and the aqueous layer was extracted with CH2Cl2
(2 ꢁ 50 mL). The combined organic layer was washed with H2O (50 mL),
dried over MgSO4, and concentrated. The crude product was purified by
(DNM) Cytotoxicitya
compound
IC50 (μM)
daunomycin
verapamil
14.33 ( 1.39
1.90 ( 0.30
1.44 ( 0.48
3S-(3,4-dimethoxyphenyl)-4R-{(E)-3,
4-dimethoxystyryl}cyclohex-1-ene (3)
3S-(3,4-dimethoxyphenyl)-4R-{(Z)-3,
4-dimethoxystyryl}cyclohex-1-ene (17)
3R-(3,4-dimethoxyphenyl)-4S-{(E)-3,
4-dimethoxystyryl}cyclohex-1-ene (ent-3)
1.74 ( 0.33
3.19 ( 1.08
a IC50 values of DNM were determined in MCF-7/ADR cells after 2 h of
incubation with three phenylbutenoids and verapamil at a final concen-
tration of 50 μM. Each data point is expressed as mean ( SD from three
different experiments. Daunomycin: negative control; verapamil: posi-
tive control.
crystallization from EtOAc and hexane to give 8 (2.37 g, 99%) as a white
1
solid: mp 132 ꢀC; [R]25 +307 (c 1.0, MeOH); H NMR (300 MHz,
D
CDCl3) δ 7.31ꢀ7.23 (3H, m), 7.12ꢀ7.09 (2H, m), 6.78ꢀ6.75 (3H, m),
5.98ꢀ5.94 (1H, m,), 5.78ꢀ5.73 (1H, m), 4.55ꢀ4.47 (1H, m), 4.15ꢀ4.03
(4H, m), 3.86 (3H, s), 3.77 (3H, s), 2.98ꢀ2.92 (1H, m), 2.35ꢀ2.05
(4H, m), 1.81ꢀ1.75 (1H, m); 13C NMR (75 MHz, CDCl3) δ 171.1, 150.8,
146.0, 145.7, 133.2, 130.8, 126.6, 126.4, 126.1, 124.7, 124.6, 119.1, 110.5,
108.2, 74.9, 74.5, 74.1, 53.4, 53.4, 53.0, 41.2, 39.0, 35.7, 21.5, 18.0; HREIMS
m/z 421.1888 [M]+ (calcd for C25H27NO5, 421.1889).
60 (230ꢀ400 mesh) using various solvent mixtures. High-performance
liquid chromatography (HPLC) was carried out on an Acme 9000 HPLC
system (Younglin, Korea) equipped with a Chiragel OD-H column
(250 mm ꢁ 10 mm i.d., Daicel Chemical Industries, Tokyo, Japan).
Optical rotation measurements were performed on a Rudolph Autopol
IV (automatic polarimeter). NMR spectra were recorded at 300 or
1819
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Journal of Natural Products
NOTE
(1R,2S)-2-[(3,4-Dimethoxyphenyl)cyclohex-3-enyl)]methanol
(11). To a suspension of LiBH4 (535 mg, 24.6 mmol) in THF (28 mL) and
H2O (7 mL) was added 8 (3.45 g, 8.2 mmol) at ꢀ20 ꢀC. The reaction
mixture was stirred for 5 h at 0 ꢀC, diluted with 0.1 N HCl (100 mL), and
extracted with EtOAc (2 ꢁ 100 mL). The combined organic layer was
washed with H2O (100 mL ꢁ 2), dried over MgSO4, and concentrated. The
crude product was purified by flash column chromatography (EtOAc/hexane,
4-[(1S,6S)-6-Ethynylcyclohex-2-enyl]-1,2-dimethoxyben-
zene (14). Compound 14 was prepared from 13 in two steps (81%) by
a reported method:11 white solid; mp 55 ꢀC; [R]25 ꢀ187 (c 1.0,
D
1
MeOH); H NMR (300 MHz, CDCl3) δ 6.79 (3H, d, J = 9.3 Hz),
5.91ꢀ5.87 (1H, m), 5.66ꢀ5.62 (1H, m), 3.87 (6H, d, J = 3 Hz),
3.40ꢀ3.36 (1H, m), 2.55ꢀ2.47 (1H, m), 2.20ꢀ2.18 (2H, m),
2.06ꢀ1.95 (2H, m), 1.82ꢀ1.70 (1H, m); 13C NMR (300 MHz, CDCl3)
δ 148.6, 147.7, 136.4, 128.9, 127.6, 120.2, 111.4, 110.7, 87.4, 77.4, 77.2,
77.0, 76.6, 69.3, 55.8, 47.1, 34.5, 27.3, 23.8; HREIMS m/z 242.1304
[M]+ (calcd for C16H18O2, 242.1307).
1:3ꢀ1:2) to give 11 (1.6 g, 78%) as a colorless oil: [R]25 +242 (c 1.0,
D
MeOH); 1H NMR (300 MHz, CDCl3) δ 6.83ꢀ6.77 (3H, m), 5.94ꢀ5.90
(1H, m), 5.77ꢀ5.72 (1H, m), 3.86 (6H, s), 3.58 (1H, br s), 3.30ꢀ3.26 (2H,
m), 2.20ꢀ2.15 (2H, m), 2.12ꢀ2.07 (1H, m), 1.60ꢀ1.41 (3H, m); 13C
NMR (75 MHz, CDCl3) δ 148.4, 147.6, 133.6, 129.1, 127.8, 121.6, 113.0,
110.7, 77.4, 77.0, 76.6, 65.1, 55.8, 42.1, 40.8, 24.7, 20.7; HREIMS m/z
248.1413 [M]+ (calcd for C15H20O3, 248.1412).
Tributyl{(E)-2-[(1S,2S)-2-(3,4-dimethoxyphenyl)cyclohex-
3-enyl]vinyl}stannane (15). 2,20-Azobisisobutyronitrile (3 mg) was
added to a solution of 14 (107 mg, 0.44 mmol) and tributyltin hydride
(0.185 mL, 0.70 mmol) in toluene (3 mL). The mixture was heated to
reflux for 6 h, diluted with EtOAc (10 mL), and washed with H2O
(10 mL). The organic layer was dried over MgSO4 and concentrated.
The residue was purified by flash column chromatography (EtOAc/
hexane, 1:10) to give 15 (197 mg, 83%) as an inseparable E/Z mixture
(1R,2S)-2-(3,4-Dimethoxyphenyl)cyclohex-3-enecarbal-
dehyde (7). To a solution of dimethyl sulfoxide (1.3 mL, 18.3 mmol)
in CH2Cl2 (20 mL) was added dropwise oxalyl chloride (1.6 mL, 18.3
mmol) at ꢀ78 ꢀC. The reaction mixture was stirred for 1 h, and 11 (1.5 g,
6.1 mmol) in CH2Cl2 (10 mL) wasadded. Afterstirring for 1 h atthesame
temperature, triethylamine was added. The reaction mixture was allowed
to warm to 0 ꢀC, stirred for an additional 30 min, diluted with H2O
(50 mL), and extracted with CH2Cl2 (2 ꢁ 50 mL). The combinedorganic
layer was washed with H2O (100 mL), dried over MgSO4, and concen-
trated. The residue was purified by flash column chromatography
(EtOAc/hexane, 1:4) to give 8 (1.41 g, 94%) as a white solid: mp
74 ꢀC; [R]25D +247 (c 1.0, MeOH); 1H NMR (300 MHz, CDCl3) δ 9.50
(1H, d, J = 2.1 Hz), 6.81ꢀ7.72 (3H, m), 6.00ꢀ5.97 (1H, m), 5.84ꢀ5.79
(1H, m), 3.92 (1H, s), 3.85 (6H, s), 2.77ꢀ2.70 (1H, m), 2.33ꢀ2.09 (2H,
m), 1.89ꢀ1.83 (2H, m); 13C NMR (75 MHz, CDCl3) δ 204.9, 148.7,
148.0, 132.5, 128.5, 128.0, 121.3, 122.5, 111.0, 55.8, 50.8, 41.1, 23.6, 18.8;
HREIMS m/z 246.1255 [M]+ (calcd for C15H18O3, 246.1256).
1
(E/Z = 4:1): H NMR (CDCl3, 300 MHz) δ 6.77ꢀ6.62 (2.8H, m),
6.51ꢀ6.44 (0.2H m), 5.96ꢀ5.78 (2H, m), 5.74ꢀ5.59 (2H, m), 3.86
(2.4H, s), 3.85 (3H, s), 3.83 (0.6H, s), 3.20ꢀ3.1.7(0.2H, m, for Z-17),
3.15ꢀ3.09 (0.8H, m, for E-17), 2.28ꢀ2.14 (3H, m), 1.90ꢀ1.82 (1H,
m), 1.68ꢀ1.61 (14H, m), 0.91ꢀ0.62 (14H, m); 13C NMR (75 MHz,
CDCl3) δ 152.3, 148.6, 147.2, 137.8, 130.5, 127.4, 126.3, 120.6, 111.3,
110.6, 55.8, 49.5, 47.4, 29.1, 27.3, 24.6, 13.7, 9.3; HREIMS m/z 478.1891
[M ꢀ C4H8 + 1]+ (calcd for C24H38O2Sn, 478.1894).
3S-(3,4-Dimethoxyphenyl)-4R-[(E)-3,4-dimethoxystyryl]-
cyclohex-1-ene (3) and 17. To a solution of 15 (780 mg, 1.45 mmol),
1613 (504 mg, 1.75 mmol), and LiCl (74 mg, 1.75 mmol) in N-
methylpyrrolidone (5 mL) was added Pd(PPh3)4 (340 mg, 0.31 mmol).
The reaction mixture was heated for 3 h, diluted with H2O (30 mL), and
extracted with EtOAc (30 mL). The organic layer was washed with H2O
(2 ꢁ 20 mL), dried over MgSO4, and concentrated. The residue was
purified by flash column chromatography (EtOAc/hexane, 1:5) to give a
mixture of3and17 (430 mg, 74%). The mixtureof3and17(430mg) was
subjected to semipreparative HPLC, using an isocratic mixture of hexane/
2-propanol (9:1, 1.5 mL/min) as solvent system, to afford 17 (16 mg) and
3 (226 mg).
3S-(3,4-Dimethoxyphenyl)-4S-[(E)-3,4-dimethoxystyryl]-
cyclohex-1-ene (1). To a solution of dimethyl 3,4-dimethoxybenzyl-
phosphonate (12)10 (137 mg, 0.53 mmol) in dry THF (3 mL) was
added n-butyllithium (1.6 M in hexanes, 0.291 mL, 0.467 mmol) at
ꢀ78 ꢀC. The reaction mixture was allowed to warm to 0 ꢀC and stirred
for 20 min, and 7 (100 mg, 0.406 mmol) in THF (1 mL) was then added.
The mixture was stirred for an additional 2 h, diluted with saturated
NH4Cl (20 mL), and extracted with EtOAc (20 mL). The organic layer
was dried over MgSO4 and concentrated. The residue was purified by
flash column chromatography (EtOAc/hexane, 1:5) to give 1 (71 mg,
50%) as a white solid: mp 107 ꢀC (lit.1d mp 99ꢀ99.5 ꢀC); [R]25D +103
3S-(3,4-Dimethoxyphenyl)-4R-[(E)-3,4-dimethoxystyryl]-
cyclohex-1-ene (3): yellow gum; [R]25D +260 (c 0.13, MeOH); CD
(c 0.34 mM, MeOH) Δε230 +7.4, Δε255 +10.9, Δε267 +11.6, Δε283
+10.0; 1H NMR (CDCl3, 400 MHz) δ 6.81 (1H, br s, H-2000), 6.78 (1H,
dd, J = 9.1, 2.4 Hz, H- 6000), 6.77 (2H, d, J = 9.1 Hz, H-50 and H-5000), 6.72
(1H, dd, J = 9.1, 2.0 Hz, H-60), 6.70 (1H, d, J = 2.0 Hz, H-20), 6.10 (1H, d,
J = 16.0 Hz, H-200), 6.02 (1H, dd, J = 16.0, 6.8 Hz, H-100), 5.89 (1H, br d, J
= 10.0 Hz, H-1), 5.68 (1H, dd, J = 10.0, 2.6 Hz, H-2), 3.87 (3H, s,
OCH3), 3.84 (3H, s, OCH3), 3.83 (3H, s, OCH3), 3.82 (3H, s, OCH3),
3.18 (1H, dd, J = 8.4, 2.6 Hz, H-3), 2.35 (1H, br d, J = 8.4 Hz, H-4), 2.21
(2H, m, H-6), 1.93 (1H, dd, J = 12.8, 3.2 Hz, H-5), 1.66 (1H, m, H-5);
1
(c 1.0, CHCl3); H NMR (300 MHz, CDCl3) δ 6.82ꢀ6.69 (6H, m),
6.25 (1H, d, J = 15.7 Hz), 6.02ꢀ5.93 (1H, m), 5.84ꢀ5.76 (1H, m), 5.58
(1H, dd, J = 15.7, 9.1 Hz), 3.86 (3H, s) 3.85 (3H, s), 3.83 (3H, s), 3.75
(3H, s), 3.54ꢀ3.48 (1H, m), 2.96ꢀ2.64 (1H, m), 2.32ꢀ2.11 (2H, m),
1.72ꢀ1.57 (2H, m); 13C NMR (75 MHz, CDCl3) δ 149.1, 148.4, 148.2,
147.7, 133.9, 132.6, 131.2, 129.3, 128.6, 128.2, 122.0, 118.9, 113.7, 111.3,
110.5, 108.8, 56.0, 55.9, 55.9, 45.9, 42.7, 24.9, 24.4; HREIMS m/z
380.1988 [M]+ (calcd for C245H28O4, 380.1988).
13
C NMR (CDCl3, 100 MHz) δ 149.0 (C-40), 148.6 (C-4000), 148.3 (C-
3000), 147.4 (C-30), 137.6 (C-10), 132.2 (C-100), 131.0 (C-1000), 130.3 (C-
2), 129.0 (C-200), 127.6 (C-1), 120.5 (C-60), 118.9 (C-6000), 111.8 (C-
20), 111.3 (C-5000), 111.0 (C-50), 108.8 (C-2000), 56.0 (OCH3), 55.9
(OCH3), 55.8 (OCH3), 55.8 (OCH3), 48.1 (C-3), 45.5 (C-4), 28.0
(C-5), 24.6 (C-6); HRESIMS (positive mode) m/z 381.2060 [M + H]+
(calcd for C24H29O4, 381.2060).
(1S,2S)-2-(3,4-Dimethoxyphenyl)cyclohex-3-enecarbalde-
hyde (13). Potassium carbonate (493 mg, 3.57 mmol) was added to a
solution of 7 (0.8 g, 3.24 mmol) in MeOH (15 mL), and the reaction
mixture was stirred for 36 h at room temperature and then concentrated.
The residue was diluted with H2O (50 mL), extracted with EtOAc
(50 mL), dried over MgSO4, and concentrated. The residue was purified
by flash column chromatography (EtOAc/hexane, 1:10) to give 13 (650
mg, 81%) as a colorless oil: [R]25D +168 (c 1.0, MeOH); 1H NMR (300
MHz, CDCl3) δ 9.69 (1H, d, J = 1.2 Hz), 6.82ꢀ6.74 (3H, m), 5.92ꢀ5.86
(1H, m), 5.70ꢀ5.65 (1H, m), 3.86 (6H, d, J = 3 Hz), 3.74ꢀ3.69 (1H, m),
2.61ꢀ2.55 (1H, m), 2.18ꢀ2.17 (2H, m), 1.98ꢀ1.93 (1H, m), 1.81ꢀ1.71
(1H, m), 13C NMR (75 MHz, CDCl3) δ 204.0, 149.0, 147.8, 136.1,
129.1, 127.6, 120.2, 111.3, 111.2, 55.9, 55.8, 54.0, 41.0, 23.4, 21.0;
HREIMS m/z 246.1255 [M]+ (calcd for C15H18O3, 246.1256).
3S-(3,4-Dimethoxyphenyl)-4R-[(Z)-3,4-dimethoxystyryl]-
cyclohex-1-ene (17): yellow gum; [R]25 ꢀ24.3 (c 0.18, MeOH);
D
CD (c 0.47 mM, MeOH) Δε230 +4.4, Δε250 ꢀ6.6, Δε274 ꢀ4.4; 1H NMR
(CDCl3, 400 MHz) δ 6.73(1H, d, J = 8.0, H-50), 6.70 (1H, d, J = 8.0 Hz,
H-5000), 6.65 (1H, dd, J = 8.0, 2.2 Hz, H-60), 6.56 (1H, d, J = 2.2 Hz,
H-20), 6.43 (1H, br s, H-2000), 6.42 (1H, dd, J = 8.0, 1.6 Hz, H-6000), 6.27
(1H, d, J = 11.6 Hz, H-200), 5.84 (1H, br dd, J = 10.0, 3.0 Hz, H-1), 5.65
(1H, dd, J = 10.0, 2.3 Hz, H-2), 5.51 (1H, dd, J = 11.6, 10.8 Hz, H-100),
1820
dx.doi.org/10.1021/np100942e |J. Nat. Prod. 2011, 74, 1817–1821

Journal of Natural Products
NOTE
3.84 (3H, s, OCH3), 3.83 (3H, s, OCH3), 3.76 (3H, s, OCH3), 3.73 (3H,
s, OCH3), 3.14 (1H, dd, J = 8.6, 2.3 Hz, H-3), 2.84 (1H, ddd, J = 10.8,
8.6, 2.8 Hz, H-4), 2.17 (2H, m, H-6), 1.83 (1H, br dd, J = 12.8, 2.8 Hz,
H-5), 1.64 (1H, m, H-5); 13C NMR (CDCl3, 100 MHz) δ 149.1
(C-3000), 148.8 (C-40), 148.5 (C-4000), 147.5 (C-30), 137.8 (C-10), 135.9
(C-100), 130.6 (C-1000), 130.5 (C-2), 128.5 (C-200), 127.3 (C-1), 120.8
(C-6000), 120.3 (C-60), 111.7 (C-2000), 111.3 (C-20), 110.8 (C-50), 110.7
(C-5000), 56.9 (OCH3), 56.9 (OCH3), 56.8 (OCH3), 56.8 (OCH3), 48.1
Med. 2004, 70, 1095–1097. (g) Nakamura, S.; Iwami, J.; Matsuda, H.;
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Seo, E.-K.; Lee, H. J. Phytother. Res. 2009, 23, 472–476.
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13
(C-3), 40.7 (C-4), 28.6 (C-5), 24.4 (C-6); 1Hꢀ C HMBC correlations
(CDCl3, 400 MHz) H-50/C-60, C-10; C-40; H-5000/C-1000; H-60/C-20,
C-40, C-3; H-20/C-3,C-60, C-30, C-40; H-2000/C-6000, C-200, C-1000, C-3000,
C-4000; H-6000/ C-2000, C-4000; H-200/C-4, C-100, C-2000, C-6000, C-1000; H-1/
C-2; H-2/C-6, C-4, C-3, C-1; H-100/C-5, C-4, C-3, C-2, C-1000; OCH3/
C-4000; OCH3/C-30; OCH3/C-40; OCH3/C-3000; H-3/C-1, C-2; H-4/C-
200, C-100; H-6/C-1, C-2; H-5/C-1, C-100; HRESIMS (positive mode) m/
z 381.2060 [M + H]+ (calcd for C24H29O4, 381.2060).
Biological Assays. Biological assays were conducted according to
published protocols.3 In brief, MCF-7/ADR cells were cultured in RPMI
1640 supplemented with 10% FBS, 2 mM L-glutamine, 10 mM HEPES,
24 mM NaHCO3, and 1% antibioticꢀantimycotic agent and main-
tained at 37 ꢀC in a humidified 5% CO2 atmosphere. In order to examine
the effects of phenylbutenoid dimers on daunomycin cytotoxicity, the
cells (5000 cells/well) were seeded in 96-well plates and incubated for
24 h at 37 ꢀC. Then, daunomycin was added to each well to achieve final
concentrations of 1.0 ꢁ 10ꢀ7 to 1.0 ꢁ 10ꢀ4 M with and without 50 μM
phenylbutenoid dimers 3, ent-3, and 17, followed by incubation for 2 h.
Daunomycin containing 50 μM verapamil was used as the positive
control. After the cells were washed and maintained with 200 μL of fresh
media for 72 h, the cytotoxicity of daunomycin was determined using a
modification of a SRB staining assay.14
(11) (a) Ramirez, F.; Desal, N. B.; McKelvie, N. J. Am. Chem. Soc.
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36, 3769.
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^
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(13) Mori, A.; Mizusaki, T.; Ikawa, T.; Maegawa, T.; Monguchi, Y.;
Sajiki, H. Tetrahedron 2007, 63, 1270–1280.
(14) Skehan, P.; Storeng, R.; Scudiero, D.; Monks, A.; McMahon, J.;
Vistica, D.; Warren, J. T.; Bokesch, H.; Kenney, S.; Boyd, M. R. J. Natl.
Cancer Inst. 1990, 82, 1107–111.
’ ASSOCIATED CONTENT
S
Supporting Information. Experimental procedures for
b
the preparation of compounds ent-3, 10, 12, 14, 15, and 16,
copies of NMR spectra of 1, 3, ent-3, 7, 8, and 10ꢀ17, and CD
spectra of 3, ent-3, and 17. This material is available free of charge
via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*Tel: +82-42-860-7150 (H.-J.L.); +82-2-3277-3047 (E.-K.S.).
Fax: +82-42-861-1291 (H.-J.L.); +82-2-3277-3051 (E.-K.S.).
E-mail: heejong@krict.re.kr (H.-J.L.); Yuny@ewha.ac.kr (E.-K.S.).
’ ACKNOWLEDGMENT
This study was supported in part by the NCRC program of
MEST/KOSEF (Grant R15-2006-020) through the Center for
Cell Signaling and Drug Discovery Research at Ewha Womans
University.
’ REFERENCES
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