Palladium-catalyzed coupling of methyl (3-bromophenyl)acetate (I) with 2-pyridyl triflate (II) furnished the pyridylphenylacetate ester (III), which was further hydrolyzed with LiOH to the corresponding carboxylic acid (IV). Coupling of acid (IV) with (3S)-3N-Boc-1,3-diamino-2-butanol (V) using HBTU produced amide (VI). After acid cleavage of the Boc protecting group of (VI), the resulting amine (VII) was coupled with N-Boc-leucine (VIII), yielding adduct (IX). Subsequent acidic deprotection of (IX) provided the intermediate amine (X).

Ether cleavage of methyl 5-methoxybenzofuran-2-carboxylate (XI) was achieved by treatment with aluminum chloride and ethanethiol to provide phenol (XII). Subsequent Mitsunobu coupling of the resulting phenol derivative (XII) with N-(2-hydroxyethyl)morpholine (XIII) gave ether (XIV). Basic hydrolysis of the ester group provided acid (XV), which was further coupled with the intermediate amine (X) to yield amide (XVI). Finally, oxidation of the alcohol function of (XVI) under Swern conditions gave rise to the title ketone derivative.