The reaction of N-(tert-butoxycarbonyl)-L-(2-naphthyl)alanine (I) with N-methylbenzyamine (II) by means of isobutyl chloroformate and NMM in dichloromethane gives the corresponding amide (III), which is deprotected with HCl in dioxane yielding (IV) with a free amino group. Finally, this compound is condensed with 1-[N-(2-nitrophenyl)carbamoyl]-L-proline (V) by means of HOBT and DCC in THF. The intermediate 1-[N-(2-nitrophenyl)carbamoyl]-L-proline (V) has been obtained by reaction of L-proline (VI) with 2-nitrophenyl isocyanate (VII) by means of NMM in THF/water.