Cycloaddition of 5-hexen-1-ol (I) with (II) in presence of NaHCO3 yields isoxazoline (III). Alternatively (III) can be obtained by treatment of (I) with diethyl nitromalonate (A) in mesitylene. Isoxazoline (III) is then oxidized by means of Jones reagent to provide acid (IV) which is coupled in presence of BOP with the imidazole derivative (V) and hydrolyzed with LiOH affording derivative (VI). Acid (VI) is coupled with derivative (IX) (obtained by reaction of diaminopropionate (VII) with (VIII) in presence of DIEA) by means of BOP, and finally hydrolyzed to afford the desired product.