Treatment of N,N'-di-Cbz-lysine (I) with ethyl chloroformate and N-ethyl morpholine, followed by condensation of the resulting mixed anhydride with N,O-dimethylhydroxylamine provided the corresponding N-methoxyamide (II). This was reduced with LiAlH4 in cold Et2O to furnish aldehyde (III). The title compound was then obtained by reductive condensation of (III) with D-proline (IV) in the presence of NaBH3CN.