Synthesis of Optically Active α-Alkylidene-β-hydroxy-γ-methylenebutyrolactones. Isoobtusilactones and Isomahubalactones (Isomahubanolide and Isomahubenolide)

The title compounds were prepared via stereoselective aldol reaction of α,β-unsaturated carboxylate α-anion equivalent, derived from optically active α-(arylsulfinyl)carboxylate and bromomagnesium diisopropylamide, with propargyl aldehyde as a key step.