The condensation of tert-butoxycarbonyl-L-leucinal (I) with 1-benzylimidazole (II) by means of BuLi in THF gives 1-benzyl-2-[2(S)-(tert-butoxycarbonylamino)-1-hydroxy-4-methylpentyl]imidazole (III), which is hydrolyzed with HCl in dioxane yielding 2-(2(S)-amino)-1-hydroxy-4-methylpentyl]-2-benzylimidazole (IV). The condensation of (IV) with tert-butoxycarbonyl-L-leucine (V) by means of dicyclohexylcarbodiimide (DCC) and hydroxybenzotriazole (HOBT) in TFA/dichloromethane affords the protected seudo-dipeptide (VI), which is debenzylated with H2 over Pd/C giving the expected seudo-peptide (VII): Finally, this compound is oxidizad with the Dess-Martin oxidant.