Cobalt-Catalyzed Diastereoselective Synthesis of C-Furanosides. Total Synthesis of (−)-Isoaltholactone

An array of C-aryl and C-vinyl furanosides were prepared in good yields and diastereoselectivities from C-halogeno furanosides either with aryl Grignard or with vinyl Grignard using the convenient Co(acac)3/TMEDA catalytic system. This method is illustrated by the total synthesis of the (-)-isoaltholactone.