The Horner-Wadsworth-Emmons olefination of N-(tert-butoxycarbonyl)-L-homophenylalaninal (I) with phosphonate (II) by means of NaH in THF gives the vinylsulfonate (III), which is treated with tetrabutylammonium iodide and triphosgene to yield the sulfonyl chloride (IV). The reaction of (IV) with O-benzylhydroxylamine in dichloromethane affords the N-sulfonylhydroxylamine derivative (V), which is deprotected with TFA in dichloromethane, providing compound (VI) with a free amino group. Finally, this compound is condensed with N-(morpholin-4-ylcarbonyl)-L-phenylalanine (VII) by means of HOBt, EDC and NMM in DMF, giving rise to the target amide.