The alkylation of N-[1(S)-(5-oxotetrahydrofuran-2(R)-yl)-2-phenylethyl]carbamic acid tert-butyl ester (I) with benzaldehyde (II) by means of LDA in THF, followed by a treatment with Ac2O and TEA at 120 C, gives the benzylidene derivative (III), which is hydrogenated with H2 over Pd/C in methanol/ethyl acetate to yield N-[1(S)-[4(R)-benzyl-5-oxotetrahydrofuran-2(R)-yl]-2-phenylethyl]carbamic acid tert-butyl ester (IV). The hydrolysis of (IV) with NaOH in dimethoxyethane/water affords the hexanoic acid (V), which is finally condensed with the dipeptide L-leucyl-L-phenylalaninamide (VI) by means of EDC and HOBT in DMF to provide the target acylated dipeptide.