Regioselective oxidative coupling of 4-hydroxystilbenes:: Synthesis of resveratrol and ε-viniferin (E)-dehydrodimers

Treatment of 5-[2-(4-hydroxyphenyl)vinyl]benzene-1,3-diol (resveratrol) with an equimolar amount of silver(I) acetate in dry MeOH at 50 degreesC for I h followed by chromatographic purification with a short silica gel column allowed the isolation of its (E)-dehydrodimer, 5-{5-[2-(3,5-dihydroxyphenyl)vinyl]-2-(4-hydroxyphenyl)-2,3-dihydrobenzofuran-3-yl}benzene-1, 3-diol, as a racemic mixture in high yield. The present method was applicable to the oxidative dimerization of 4-hydroxystilbenes such as trans-styrylphenol and 5-{6-hydroxy-2-(4-hydroxyphenyl)-4-[2-(4-hydroxyphenyl)vinyl]-2,3-dihydrobenzofuran-3-yl}benzene-1,3-diol (epsilon-viniferin) leading to the corresponding 2-(4-hydroxyphenyl)-2,3-dihydrobenzofurans possessing various types of biological activities.