As described for Example 235, a cis/trans mixture of N,N-dimethyl-1-phenylcyclohexane-1,4-diamine (800 mg) was reacted with 0.95 mg 4-phenoxybutyryl chloride and the crude product (1.48 g) was isolated analogously. By chromatography on silica gel (3.0×19 cm) with 100 ml diethyl ether followed by 400 ml diethyl ether/methanol (v:v=2:1), 450 mg of the more polar diastereoisomer of N-(4-dimethylamino-4-phenylcyclohexyl)-4-phenoxybutyramide were obtained and, as a solution in 5 ml 2-butanone and 5 ml ethyl acetate, were converted into the corresponding hydrochloride by addition of 21.3 μl water and 150 μl chlorotrimethylsilane (420 mg of a white solid, m.p. 191-192° C.).
