Stereoselective synthesis of (E)-hydroxystilbenoids by ruthenium-catalyzed cross-metathesis

An efficient and highly stereoselective synthetic procedure is reported for the construction of symmetrical and unsymmetrical (E)-polymethoxystilbene and (E)-polyhydroxystilbene derivatives. The strategy rests on a cross-metathesis reaction catalyzed by stable, well-defined (alkylidene)ruthenium complexes, in particular the second-generation Grubbs catalyst [RuCl2(=CHPh)(SlMes)(PCY3)1 [SIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene]. The metathesis of unprotected phenolic styrenes is illustrated by the synthesis of the important phytoalexins (E)-3,4',5-trihydroxystilbene (resveratrol) and (E)-3,3',4,5'-tetrahydroxystilbene (piceatannol). (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheirn, Germany, 2005).