Abstract
The iminoketene-Claisen reaction serves as a key step in an efficient asymmetric synthesis of (+)-canadensolide, (+)-santolinolide B and (-)-santolinolide A: Starting from D-mannitol an optically active N-allylacetamide was generated which was rearranged to the corresponding diastereomeric nitrile. After cyclization two optically active 4,5-difunctionalized γ-butyrolactones with defined configuration at the chiral centers were obtained. The syn-4,5 disubstituted lactone was used for the synthesis of (2R,3S,4S)-(+)-canadensolide, the anti-4,5 difunctionalized lactone was employed in the synthesis of the (3R,4S,5S)-(+)-santolinolide B and the (3S,4S,5S)-(-)-santolinolide A.

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