A concise formal stereoselective total synthesis of (−)-swainsonine

A short formal stereoselective synthesis of (−)-swainsonine (1) is described. Our synthesis started with the versatile building block (R)-3-benzyloxyglutarimide 5. Through controlled regioselective reduction, Ley's-sulfone chemistry (N-α-sulfonylation and ZnCl2-catalyzed N-α-amidovinylation), an RCM reaction, and an amide reduction, the synthesis of unsaturated indolizidine (8R,8aS)-3 has been achieved in five steps. The indolizidine (8R,8aS)-3 is an advanced intermediate toward the synthesis of (−)-swainsonine (1).

Graphical abstractThe synthesis of unsaturated indolizidine (8R,8aS)-3, an advanced intermediate toward the synthesis of (−)-swainsonine (1), has been achieved in five steps from the versatile building block (R)-3-benzyloxyglutarimide 5, via Ley's-sulfone-based α-amidovinylation and the RCM reaction as the key steps.Figure optionsDownload full-size imageDownload as PowerPoint slide