Highly stereoselective generation of α-pyrones displaying four contiguous stereogenic centers

We report here an efficient one-pot diastereoselective procedure which transforms silylated vinyloxiranes 2 into enantiomerically pure tetrasubstituted δ-lactones 7, 10. This transformation includes four steps: palladium(0)-catalyzed rearrangement/alkylation-lactonization/1,4-conjugated addition/electrophilic trapping of the intermediary enolate. These reactions allow efficient control of four contiguous stereogenic centers, and even of a fifth one when the electrophile is the prochiral benzaldehyde.