合成路线1

Coupling of N-Cbz-tyrosine (I) with n-pentylamine (II) afforded amide (III). Subsequent alkylation of the phenol group of (III) with diethyl chloromalonate (IV) gave phenoxy malonate (V). Hydrogenolytical deprotection of the N-Cbz group of (V) provided the corresponding amine, which was isolated as the hydrochloride salt (VI). Conversion of (VI) to isocyanate (VII) was effected by treatment with diphosgene in the presence of Proton Sponge(r). Addition of phenylalanine ethyl ester (VIII) to isocyanate (VII) furnished urea (IX). Finally, the ethyl ester groups of (IX) were saponified with LiOH to yield the title compound.