In order to produce the citrate, the more nonpolar diastereoisomer of 1-(4-dimethylamino-4-phenylcyclohexylmethyl)-3-[2-(1H-indol-3-yl)-1-methylethyl]-thiourea (167 mg, 0.37 mmole) was dissolved in ethanol (4 ml) at RT and combined with a solution of citric acid (78.7 mg, 0.41 mmole) in ethanol (1 ml). After 1 h, a tacky precipitate could be seen on the flask wall and was detached mechanically. The batch was then combined with ether (35 ml) and stirred for 20 h. The resultant solid was filtered out, washed with ether (3×3 ml) and dried. The nonpolar diastereoisomer of 1-(4-dimethylamino-4-phenyl-cyclohexylmethyl)-3-[2-(1H-indol-3-yl)-1-methylethyl]thiourea citrate was obtained in this way as a colorless solid (Example 39) in a yield of 206 mg (87%).
