Total Synthesis of (−)-Callystatin A

The enantioselective synthesis of callystatin A is described. The pivotal step in the synthesis is the stereoselective aldol reaction that generates the β-hydroxy ketone moiety. Utilizing the allylic strain within the ethyl ketone precursor, we were able to generate the all-syn configuration of callystatin A. For the construction of the two diene moieties, both a Heck coupling and a Wittig reaction were employed.