The title compound was obtained by the solid-phase method using a peptide synthesizer. Starting from Fmoc-valine linked to Wang resin (I), cleavage of the Fmoc group with piperidine in DMF provided the deprotected valine-resin (II), which was then coupled with Fmoc-leucine (III) by means of 1-hydroxybenzotriazole and diisopropylcarbodiimide. The resulting dipeptide resin (IV) was deprotected with piperidine in DMF to give (V), and further coupling with protected serine (VI) yielded (VII). After Fmoc-deprotection, the tripeptide-resin (VIII) was coupled with phenyl isocyanate (IX), affording urea (X). Cleavage from the resin with simultaneous deprotection using trifluoroacetic acid furnished the tripeptide urea (XI). This was finally esterified by treatment with ethanolic HCl to provide the target ethyl ester.

The title compound was obtained by the solid-phase method using a peptide synthesizer. Starting from Fmoc-valine linked to Wang resin (I), cleavage of the Fmoc group with piperidine in DMF provided the deprotected valine-resin (II), which was then coupled with Fmoc-leucine (III) by means of 1-hydroxybenzotriazole and diisopropylcarbodiimide. The resulting dipeptide resin (IV) was deprotected with piperidine in DMF to give (V), and further coupling with protected serine (VI) yielded (VII). After Fmoc-deprotection, the tripeptide-resin (VIII) was coupled with phenyl isocyanate (IX), affording urea (X). Cleavage from the resin with simultaneous deprotection using trifluoroacetic acid furnished the tripeptide urea (XI). This was finally esterified by treatment with ethanolic HCl to provide the target ethyl ester.