Total Synthesis of Both Spiroketal Diastereomers of the Reported Structure of Cephalosporolide H

A total synthesis of both spiroketal diastereomers of the reported structure of cephalosporolide H is accomplished in 12 steps and 9% overall yield. The key steps involve Keck's allylation, cross metathesis (to get the desired beta,gamma-unsaturated ester), Sharpless asymmetric dihydroxylation (to install the eta-hydroxy-gamma-lactone moiety), and spiroketalization to access both spiroketal diastereomers of the reported structure of the natural product