Asymmetric Dihydroxylation of β,γ‐Unsaturated Carboxylic Esterswith Trisubstituted C=C Bonds – Enantioselective Syntheses of Trisubstituted γ‐Butyrolactones

Abstract β,γ‐Unsaturated esters with stereodefined trisubstitued C=C double bonds were prepared by the Arndt–Eistert homologation of α,β‐unsaturated carboxyl halides, by two‐step methoxycarbonylation of allylbarium reagents, by deconjugation of α,β‐unsaturated esters, and by Horner–Wadsworth–Emmons variants of the Stobbe condensation. Sharpless asymmetric dihydroxylation of the β,γ‐unsaturated esters, followed by spontaneous cyclization, afforded β‐hydroxy‐γ‐lactones in moderate to good yields and with enantiomeric excesses of up to 97 %. Similarly, tetrahydroxy‐γ‐lactones were obtained from diunsaturated esters; these lactones were converted into a bislactone and an unsaturated β‐hydroxy γ‐lactone. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)