The synthesis of D-16120 can be achieved by several methods: 1) Aminolysis of 3-cyclohexylpropionyl chloride (I) with 2-ethoxyphenylpiperazine (II) in the presence of triethylamine yields D-16120. 2) Reaction of ethyl 3-cyclohexylpropionate (III) with 2-ethoxyphenylpiperazine (IV) also gives D-16120.