General approach to epipolythiodiketopiperazine alkaloids: total synthesis of (+)-chaetocins A and C and (+)-12,12'-dideoxychetracin A.

A highly stereoselective and systematic strategy for the introduction of polysulfides in the synthesis of epipolythiodiketopiperazines is described. We report the first total synthesis of dimeric epitri- and epitetrathiodiketopiperazines.