The condensation of tert-butoxycarbonylproline (I) with methylamine (II), isovaleraldehyde (III) and ethyl isocyanoacetate (IV) in methanol gives Boc-Pro-Me-Leu-Gly-OEt (V), which is separated from its diastereoisomer by chromatography over silica gel. The reaction of (V) with ammonia in cold methanol yields the corresponding amide (VI). Finally this compound is deprotected by treatment with dry HCl in ethyl acetate