Alkylation of diphenylamine (I) with THP-protected 3-bromopropanol (II) using NaH in 15-crown-5 yields tertiary amine (III), which is then deprotected with HOAc/H2O to provide (IV). Alcohol (IV) is treated with PPh3 and CBr4 to afford alkyl bromide (V), which is then converted into amine (VII) by reaction with 2,6-dimethylpiperazine (VI) in DMF/H2O in the presence of K2CO3. Finally, (VII) is acylated with 3-phenylpropionyl chloride (VIII) and reduced with LAH.