n-Butyllithium (1.6 M solution in hexane; 11.9 ml; 19 mmol) was added dropwise at 0° C. to a solution of 4-fluoroaniline (1.06 g; 9.5 mmol) in 10 ml THF. The mixture was allowed to come to RT and was subsequently stirred for 1 h. A solution of (4-dimethylamino-4-phenyl-cyclohexyl)-acetic acid ethyl ester (2.5 g; 8.6 mmol) in 15 ml THF was added dropwise at −78° C. The mixture was subsequently stirred for 1 h and then allowed to come to RT. It was hydrolysed with ammonium chloride solution and extracted with MC. After concentration, the crude product was taken up in ether. A solid then remained (less polar diastereoisomer; 1.37 g; 45%); the supernatant was chromatographed on silica gel (eluent:ether). 315 mg (10%) of the more polar diastereoisomer were obtained.
