Racemic allylglycine (I) was protected as the N-Boc derivative (II) and then converted to the Weinreb amide (III) by treatment with N,O-dimethylhydroxylamine and BOP. Reduction of (III) with LiAlH4 afforded aldehyde (IV), which, upon treatment with acetone cyanohydrin (V), furnished the corresponding hydroxy nitrile (VI). Acid hydrolysis of the nitrile (VI) with concomitant Boc group deprotection provided hydroxy acid (VII), which was further reprotected as the N-Boc derivative (VIII). Coupling of hydroxy acid (VIII) with allylamine (IX) yielded amide (X). After Boc group cleavage with HCl in dioxan, the resulting amine (XI) was coupled with pentapeptide (XII) (obtained using a peptide synthesizer under standard conditions), to give the alpha-hydroxyamide (XIII).

This was converted to the keto amide (XIV) by Dess-Martin oxidation. Acidic deprotection of the tert-butyl groups of (XIV) then furnished the title compound.