1.00 g of the polar diastereomer of N,N-dimethyl-1-phenyl-N′-propyl-cyclohexane-1,4-diamine (see example 6) were dissolved in 15 ml methylene chloride, and 560 μl triethylamine and approx. 10 mg DMAP were added. 468 μl benzoyl chloride were added dropwise, while cooling in an ice/methanol bath, and the reaction mixture was then stirred overnight, while warming to room temperature. For working up, 12 ml five molar KOH solution and 12 ml water were added, the mixture was stirred for ten minutes and extracted three times with 25 ml methylene chloride each time, the combined extracts were dried over magnesium sulfate and filtered and the filtrate was concentrated. From the product obtained (1.29 g), 752 mg of the polar diastereomer of N-(4-benzyl-4-dimethylamino-cyclohexyl)-N-propyl-benzamide hydrochloride were prepared as described for example 1 with water and chlorotrimethylsilane in 2-butanone.
