A mixture of ethyl 4-[4-[4-(6-methoxyhexyloxy)phenyl]piperazin-1-yl]benzoate (3.00 g) in ethanol (30 ml) was treated with 1N-sodium hydroxide aqueous solution (6.81 ml) then the mixture was refluxed for 24 hours, during which period tetrahydrofuran (20 ml) and 1N-sodium hydroxide aqueous solution (6.81 ml) was added. After cooling, water was added to the mixture, and the acidity of the mixture was adjusted to pH 1 with 1N-hydrochloric acid. The resulting precipitate was filtered, washed with water and dried under reduced pressure to give 4-[4-[4-(6-methoxyhexyloxy)phenyl]piperazin-1-yl]benzoic acid dihydrochloride (2.25 g) as an ocher solid.
