Diastereoselective Organocatalytic Addition of α‑Angelica Lactone to β‑Halo-α-ketoesters

A quinidine-catalyzed diastereoselective addition of α-angelica lactone to β-halo-α-ketoesters is reported. The α-angelica lactone displays unusual regioselectivity in this reaction, acting as a nucleophile at the α-position to provide fully substituted glycolic esters with three contiguous stereocenters. Subsequent diastereoselective hydrogenation provides an additional stereocenter within the lactone.