Asymmetric Total Synthesis of (+)‐6‐epi‐castanospermine by the Stereoselective Formation of a Syn,anti Acetylenic 2‐amino‐1,3‐diol Stereotriad

The asymmetric total synthesis of (+)-6-epi-castanospermine (1) is described herein. In this synthesis the diastereoselective addition of a racemic allenylzinc reagent to an enantiopure alpha-alkoxy-tert-butylsulfinylimine is the key step and is followed by the formation of a piperidine ring by ring-closing metathesis and subsequent syn-dihydroxylation of an alkene.