Tandem Stereospecific Radical Cation-Mediated Syntheses of Oligostilbenoid Dimers

Protected trihydroxystilbenes have been synthesized by Heck coupling methodology in three steps. Treatment of 3,4-dimethoxy-12-benzyloxymethyl stilbene with ferric chloride in dichloromethane (room temperature), gave catechol analogues of ampelopsin F and of restrytisol C, while 3,4-dimethoxy-12- acetoxymethyl stilbene treated in the same conditions yielded two other analogues of restrytisol C (but no trace of ampelopsin F analogues). All the structures were unambiguously confirmed by 1D- and 2D- homo- and heteronuclear nmr experiments. All transformations were stereospecific. The ampelopsin F-type compounds are the result of radical cation pathways. By contrast, the restrytisol Ctype compounds are the products of pericyclic pathways.