SYNTHESIS OF PTEROSTILBENE
3221
[(NH4)6Mo7O24 ꢂ 4H2O] (48.5 g, 39.2 mmol) was added portionwise to this mixture.
Sodium acetate (11.5 g, 140 mmol) was added to the resulting solution and stirred
at room temperature. After 24 h, the mixture was concentrated, diluted with water
(100 mL), extracted with EtOAc (3 ꢃ 50 mL), dried over anhydrous Na2SO4,
filtered, and concentrated under reduced pressure to give crude residue, which was
purified by silica-gel column chromatography (20% of EtOAc in hexane) to give white
crystalline sulfone 5 5.2 g) in 95% yield. IR (cmꢁ1) 2963, 2908, 1592, 1430, 1315, 780.
1H NMR (400 MHz, CDCl3) d 8.22 (d, J ¼ 8.1 Hz, 1H), 7.90 (d, J ¼ 7.9 Hz, 1H),
7.63–7.58 (m, 1H), 7.56–7.51 (m, 1H), 6.33 (d, J ¼ 4.1 Hz, 3H), 4.66 (s, 2H), 3.55 (s,
6H). 13C NMR (101 MHz, CDCl3) d 165.19, 161.97, 160.87, 128.08, 127.73, 125.38,
122.33, 108.87, 101.78, 61.30, 55.25. HRMS-ESI calcd. C16H16NO4S2 350.0512;
found 350.0511.
(E)-1,2-Bis(3,5-dimethoxyphenyl)ethane (8)
LiHMDS (5.0 mL of 1.0 M solution in THF) was added to a solution of sulfone
5 (1.75 g, 5.0 mmol) in anhydrous THF (20 mL) at 0 ꢀC and stirred for 30 min at the
same temperature, and then a solution of aldehyde 7b (930 mg, 4.5 mmol) in THF
(30 mL) was added. Stirring continued for 3 h at 0 ꢀC. After completion of the reac-
tion, the reaction mixture was quenched with saturated NH4Cl solution and
extracted with EtOAc, and the solvent was evaporated under reduced pressure to
give a crude residue. The residue was purified by silica-gel column chromatography
to give compound 8 with 90% yield (1.35 g). IR (cmꢁ1) 2915, 1600, 1515, 1468, 1235,
1185, 960. 1H NMR (400 MHz, CDCl3) d 7.01 (s, 2H), 6.66 (d, J ¼ 2.3 Hz, 4H), 6.31
(t, J ¼ 2.3 Hz, 2H), 3.82 (s, 12H). 13C NMR (101 MHz, CDCl3) d 160.91, 139.07,
129.11, 104.56, 100.05, 55.28. HRMS-ESI calcd. C18H21O4 301.1440; found
301.1442.
(E)-4-(3,5-Dimethoxystyryl)phenol (Pterostilbene) (1)
LiHMDS (17.1 mL of 1.0 M solution in THF, 10.3 mmol) was added to a sol-
ution of sulfone 5 (3.0 g, 8.5 mmol) in anhydrous THF (30 mL) at ꢁ78 ꢀC and stirred
for an additional 30 min at the same temperature. To this cold solution, aldehyde 7a
(1.75 g, 10.63 mmol) in THF (20 mL) was added and stirring continued at ꢁ78 ꢀC.
After 3 h, the mixture was quenched with saturated NH4Cl solution and extracted
with EtOAc (3 ꢃ 25 mL). The combined organic layers were washed with water and
saturated NaCl, dried over anhydrous Na2SO4, and concentrated under reduced
pressure to yield the crude product. The residue was purified by silica-gel column
chromatography using EtOAc (5–20%) in hexanes to give 4-acetyl pterostilbene
(1.35 g, 53% yield) and pterostilbene (0.42 g, 19% yield). Alternatively, the crude pro-
duct obtained in Julia olefination was subjected to saponification without further
purification using K2CO3 (18.45 mmol) in methanol (20 mL) at room temperature,
followed by purification on silica-gel column chromatography (5–25% EtOAc in hex-
anes) to yield pure 1 in 69% yield (two steps) (1.52 g). IR (cmꢁ1) 3393, 2989, 2941,
1
1661, 1581, 1140, 827. H NMR (400 MHz, CDCl3) d 7.41–7.38 (m, 2H), 7.03 (d,
J ¼ 16.2 Hz, 1H), 6.89 (dd, J ¼ 16.4, 1.6 Hz, 1H), 6.84 (d, J ¼ 8.7 Hz, 2H), 6.66 (t,
J ¼ 1.8 Hz, 2H), 6.41–6.38 (m, 1H), 3.83 (d, J ¼ 1.6 Hz, 6H). 13C NMR (101 MHz,