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)(SIMes)(PCy3)] [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). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)