Asymmetric Synthesis of anti-1,2-Amino Alcohols via the Borono-Mannich Reaction:  A Formal Synthesis of (−)-Swainsonine

Chiral alpha-hydroxy aldehydes generated in situ by the ADH reaction of vinyl sulfones undergo a borono-Mannich reaction with beta-styrenyl boronic acid and primary amines to give anti-1,2-amino alcohols in high enantiomeric purities (83-95% ee). This new method allows much more rapid access to these valuable chiral building blocks that has been used in a short formal synthesis (10 synthetic steps from 4-penten-1-ol) of (-)-swainsonine.