To an acetic acid (150 mL) suspension of 14.9 g of 4-{3-[4-(3-{4-[amino(hydroxyimino)methyl]phenoxy}propyl)-1-piperidinyl]propoxy}-N′-hydroxybenzamidine was added 5.97 mL of acetic anhydride at room temperature, which was then stirred at room temperature for 1 hour and 20 minutes. To this mixture was added 1.50 g of 5% palladium-carbon, which was then stirred under hydrogen atmosphere for 4 hours and 40 minutes. Insoluble matter was filtered off, and 55 mL of 6.0 mol/L hydrochloric acid was then added. The solvent was distilled off under reduced pressure, and ethanol was added to the resultant residue. The solid matter was collected by filtration to provide 14.0 g of 4-{3-[4-(3-{4-[amino(imino)methyl]phenoxy}propyl)-1-piperidinyl]propoxy}benzamidine as white solid form.
