Unified synthesis of eudesmanolides, combining biomimetic strategies with homogeneous catalysis and free-radical chemistry

[GRAPHIC] A general procedure for the synthesis of both 12,6- and 12,8-eudesmanolides has been developed. The key step is the titanocene-catalyzed radical cyclization of accessible epoxygermacrolides. The novel reagent 2,4,6-trimethyl-1-trimethylsilyipyridinium chloride, both compatible with oxiranes and capable of regenerating Cp2TiCl2 from Cp2Ti(Cl)H and Cp2Ti(Cl)OAc, played an important role in the catalytic cycle leading to exocyclic alkenes.