Convenient Preparation of 5-Alkylidene-2,5-dihydropyrrol-2-ones by Ring-Transformations of (gamma)-Alkylidenebutenolides: Formal Synthesis of Pukeleimide A

The reaction of (gamma)-alkylidenebutenolides, readily available by cyclization of 1,3-bis-silyl enol ethers with oxalyl chloride, with amines in glacial acetic acid allows a convenient synthesis of 5-alkylidene-2,5-dihydropyrrol-2ones. This method was applied to a formal total synthesis of the natural product pukeleimide A.