Cycloadditions of chiral carbonyl ylides with imine dipolarophiles as a route to enantiomerically pure α-amino-β-hydroxy acids

The preparation of enantiomerically pure threo-β-amino-α-hydroxy acids via 1,3-dipolar cycloadditions of imine dipolarophiles with the chiral isomünchnone derived from (5R)-5-phenylmorpholin-3-one 1 is described. The cycloadducts were obtained with excellent diastereofacial- and exo-selectivity. Subsequent hydrolysis and chemoselective exocyclic amide cleavage afforded the threo-β-amino-α-hydroxy acids with recovery of the initial chiral auxiliary.