To a stirring suspension of 3.5 g (0.021 mole) of 1-methyl-4-amino-1-azaspiro[4.5]decane of Example 2 and 150 ml of 10% NaOH was added dropwise 3.8 g (0.022 mole) of p-anisoyl chloride. The reaction was stirred vigorously for 5 hours, the aqueous solution was decanted and the remaining oil was dissolved in ethyl acetate and dried over Na2SO4. The solvent was then evaporated to give a solid which was recrystallized from hexane to give 4.4 g. The solid was dissolved in 20 ml of acetonitrile and 1.7 g of fumaric acid was added. The suspension was stirred until the amine salt precipitated from solution. The compound was filtered and recrystallized twice from ethanol-ether to give 1.2 g (15.8%) of 1-methyl-4-(4-methoxybenzamido)-1-azaspiro[4.5]decane hemifumarate, m.p. (softens at 110° C.) 152°-155° C.
