Synthesis of Optically Active Butenolides and γ‐Lactones by the Sharpless Asymmetric Dihydroxylation of β,γ‐Unsaturated Carboxylic Esters

Deconjugated esters 1 and AD mix α or AD mix β give cis-configured γ-alkyl-β-hydroxy-γ-lactones 2. They are versatile precursors for γ-chiral butenolides and γ-chiral butyrolactones of moderate to high enantiomeric purity, as shown through their conversion into the natural products 3 (92% ee), 4 (95% ee), 5 (97% ee), and 6 (78% ee).