The oxidation of a number of N-benzyl proline derivatives is described
. The oxidation proceeds with complete diastereoselectivity to give ho
mochiral amine oxides when a hydrogen bond donor group is located in t
he proline carboxylate side chain. The product amine oxides are highly
stable, crystalline compounds. In all eases, the amine oxide is forme
d syn to the hydrogen bonding donor group.