Cyclopentane Construction with Control of Side Chain Configuration: Enantioselective Synthesis of (+)-Brefeldin A

Intramolecular opening of an enantiomerically pure epoxide by an amide enolate (1 → 2) is shown to be an effective method for cyclopentane construction with control of both ring and side chain absolute configuration. This opening serves as the key step in a synthesis of the Golgi apparatus-blocking macrolide (+)-brefeldin A (3). Other features of the synthesis include improved procedures for the enantioselective hydrogenation of a β-keto ester to the corresponding β-hydroxy ester, and for the Julia-Lythgoe reduction of a β-acetoxy sulfone to the trans alkene.