High diastereoselection in the claisen rearrangement of enantiomerically pure butyrolactones

The Claisen rearrangement permits the stereoselective formation of butyrolactone $\text{5b,c}$ or $\text{13b,c}$ through the utilization of enantiomeric lactone $\text{1a}$ and enantiomeric alcohols $\text{2b}$, ent-$\text{2b}$, $\text{2c}$, and ent-$\text{2c}$.