This work describes the study of behavior of the δ-substituted and δ-non-substituted exo-cyclic double bond of γ-alkylidenebutenolides with dialkylcuprates. The addition reaction was found to be regioselective to afford the 1,6-conjugate adduct up to 87% yield.
A New, Highly Stereoselective Synthesis of β-Unsubstituted (<i>Z</i>)<i>-</i>γ-Alkylidenebutenolides Using Bromine as a Removable Stereocontrol Element
Several β-unsubstituted (Z)-γ-alkylidenebutenolides have been prepared in highly stereocontrolled fashion by implementing a steric directing group stratagem in the vinylogous aldol condensation of butenolides with aldehydes. Applications to the synthesis of the antitumor heptene (S)-melodorinol and a thiophenelactone from Chamaemelum nobile L. are described.