4-[2-(3,5-Dimethoxyphenyl)ethenyl]-1,2-benzenediol
2465
and dry benzene (5 ml). After the reaction mixture
had been stirred for 2 h at rt, it was poured into ice
cooled water, and the product was extracted with
ether. The ethereal extract was washed with brine,
dried over sodium sulfate, and the solvent was evapo-
rated. The crude product obtained was dissolved in
dry benzene (20 ml) and treated with triphenyl
phosphine (2.0 g, 7.6 mmol). The reaction mixture
was then heated under re‰ux for 3 h, and cooled and
sulfate. The residue obtained after removing the
solvent was further puriˆed by column chro-
matography in a silica gel column with a mixture of
chloroform-methanol (98:2) as the eluent to give 7
(150 mg, 60
z
), mp 122–123
9 9
C (lit.5) mp 72–74
C);
UV lmax (MeOH) nm (
e
): 327 (2,62,325); IR (KBr)
n
max cm-1: 3499, 3327, 1599, 1514, 1312, 1282, 1152,
1064, 960, 814; NMR
d
H (400 MHz, DMSO-
d
6): 3.78
(6H, s, 3
?
,5
?
-OCH3), 6.37 (1H, s, H-4
,6 ), 6.73 (1H, d,
16.3 Hz,
Hz, H-5), 6.99 (1H, s, H-3), 7.08 (1H, d,
-H), 8.91 (1H, br s, OH), 9.08 (1H, br s, OH);
NMR dC (100 MHz, DMSO- 6): 160.63 (C-3 ,5 ),
145.52 (C-1), 145.24 (C-2), 139.60 (C-1 ), 129.27
(C- ), 128.62 (C-4), 125.15 (C- ), 118.96 (C-5),
115.76 (C-6), 113.25 (C-3), 104.05 (C-2 ,6 ), 99.28
(C-4 ), 55.15 (3 ,5 -OCH3); MS (ESI, neg. scan): m z
271 (M-1). Elemental analysis. Found; C, 70.56; H,
5.93 . Calcd. for C16H16O4: C, 70.58; H, 5.92
?), 6.72 (2H, d,
ˆltered to give 4 (3.7 g, 91
z
), mp 236–240
9
C; IR
J
=
1.9 Hz, H-2
?
?
J
=
9.0 Hz, H-6),
max cm-1: 1603, 1587, 1515, 1436, 1266, 1138,
6.85 (1H, d,
J
b
-H), 6.88 (1H, d,
J
9.0
=
=
(KBr)
n
=
16.3 Hz,
1111, 1017, 742, 694.
J
a
5-[2-(3,4-Dibenzyloxyphenyl)etheny1]-1,3-dimeth-
d
? ?
oxybenzene (
5
and
6
). To a solution of 3,4-diben-
?
zyloxybenzyltriphenylphosphonium bromide (4,
2.52 g, 3.9 mmol) in THF (15 ml) was added -butyl
lithium (3 ml, 4.8 mmol, 1.6 in hexane) at 0 C, and
a
b
n
9
? ?
M
?
? ?
W
the mixture stirred for 90 min. A solution of 3,5-
dimethoxybenzaldehyde (0.5 g, 3.0 mmol) in THF
(5 ml) was added to the reaction mixture, which was
allowed to warm to rt and further stirred for 16 h.
z
z
.
Isomerisation of Z-stilbene
5 to E-stilbene 6. To a
After the usual workup, the residue (E Z. 1.2:1 by
solution of -stilbene 5 (10 mg) in toluene (5 ml) was
Z
W
HPLC) was chromatographed in a silica gel column
using a mixture of pet. ether and ethyl acetate (95:5)
added a catalytic amount of iodine, and the mixture
was heated to re‰ux for 4 h. The reaction mixture
was diluted with diethyl ether (20 ml) and successive-
ly washed with saturated aqueous sodium bisulˆte
(10 ml) and brine (10 ml). The organic layer was
dried over sodium sulfate. The residue obtained after
evaporating the solvent was chromatographed in a
silica gel column, using hexane-EtOAc (95:5) as the
as the eluent to give 5 (
an oil; UV lmax (MeOH) nm (
(26, 243); IR(neat)
max cm-1: 1590, 1510, 1259, 1204,
1155, 1065, 1019, 868, 737, 696; NMR H (200 MHz,
CDCl3): 3.64 (6H, s), 4.91 (2H, s), 5.12 (2H, s), 6.31
Z
-isomer, 500 mg, 38
z
) as
e
): 206 (42,180), 280
n
d
=
=
2.2 Hz), 6.44
(1H, t,
J
2.3 Hz), 6.41 (2H, d,
J
(2H, s), 6.76–6.82 (2H, m), 6.89 (1H, m), 7.30–7.43
eluent, to give
180–182 C; IR (neat)
1151, 1061, 1019, 958, 772, 735, 695.
E
-stilbene 6 (9.0 mg, 90
z), mp
(10H, m); MS (ESI, positive scan): m z 453 (M
+
1).
9
n
max cm-1: 1590, 1510, 1261,
W
Further elution of the column with pet. ether and
EtOAc (95:5) as the eluent gave 6 (E-isomer, 550 mg,
42
z
), mp180–182
9
C; UV lmax (MeOH) nm (
e
): 202
Superoxide free radical-scavenging activity. The
superoxide free radical-scavenging activity was deter-
mined by the NBT method.13,14) The reaction mixture
(43,180), 324 (32,253); IR (neat)
n
max cm-1: 1590,
1510, 1261, 1151, 1061, 1019, 958, 772, 735, 695;
NMR dH (400 MHz, CDCl3): 3.83 (6H, s), 5.18 (2H,
contained EDTA (6.6 m
(2 ), NBT (50 ), various concentrations of the
test drug in ethanol, and a phosphate buŠer (58 m
M
), NaCN (3 mg), ribo‰avin
s), 5.20 (2H, s), 6.38 (1H, t,
J
=
2.1 Hz), 6.63 (2H, d,
=
16.2 Hz), 6.92 (1H, d,
16.2 Hz), 7.02 (1H, dd,
1.7 Hz), 7.31–7.40
m
M
m
M
=
=
=
J
J
J
2.1 Hz), 6.84 (1H, d,
8.3 Hz), 6.97 (1H, d,
J
M
,
=
J
pH 7.8) in a ˆnal volume of 3 ml. The optical density
was measured at 560 nm. The test tubes were uni-
formly illuminated with an incandescent lamp for
15 min, after which the optical density was measured
again at 560 nm. The percentage inhibition of su-
peroxide radical generation was measured by com-
paring the absorbance value of the control and that
of each test compound. IC50 values were obtained
1.7 & 8.3 Hz), 7.14 (1H, d, J
=
(6H, m), 7.44–7.49 (4H, m); MS (ESI, positive scan):
m z 453 (M 1).
+
W
4-[2-(3,5-Dimethoxyphenyl)ethenyl]-1,2-ben-
zenediol ( ). To a mixture of 6 ( -isomer, 400 mg,
0.91 mmol) and -dimethylaniline (1.0 ml,
8.2 mmol) in dichloromethane (25 ml) was added
aluminum chloride (0.73 g, 5.46 mmol) at 0 C, this
7
E
N, N
from a plot of the concentration in
percentage inhibition.
mg against the
9
temperature being maintained for a further 30 min.
The reaction mixture was allowed to warm to room
temperature and stirring continued for a further 2 h.
The reaction mixture was quenched with 1 N HCl
Acknowledgments
We thank Sri G. Ganga Raju, the chairman, and
Mr. G. Rama Raju, the managing director, of Laila
Impex for encouragement, and Dr. M. Vanisree of
Taiwan for providing some of the NMR spectra.
×
(25 ml) and extracted with ethyl acetate (3 25 ml).
The organic layer was successively washed with
sodium carbonate and brine, and dried over sodium