L-Proline (I) is protected as its N-Boc derivative (II) with Boc2O/NaOH in a two-phase system. N-Boc-Proline (II) is further converted into diazo ketone (III) via activation with ethyl chloroformate, followed by condensation with diazomethane. Subsequent treatment of diazo ketone (III) with AcOH leads to the acetoxy ketone (IV). Then, acidic N-Boc group cleavage in (IV) furnishes amine (V). On the other side, L-proline (I) is acylated by 4-phenylbutyryl chloride to produce the corresponding amide (VI). Coupling between 2-(acetoxyacetyl)pyrrolidine (V) and N-(phenylbutyryl)proline (VI) via activation with pivaloyl chloride leads to the amide adduct (VII). Finally, methanolysis of the acetate ester group of (VII) provides the target hydroxyacetyl compound.