In order to produce the citrate, the more polar diastereoisomer of 1-(4-dimethylamino-4-phenylcyclohexylmethyl)-3-[2-(1H-indol-3-yl)-1-methylethyl]-thiourea (140 mg, 0.31 mmole) was dissolved in ethanol (4 ml) and combined with a solution of citric acid (65.9 mg, 0.34 mmole) in ethanol (1 ml). Only a little precipitate formed. The mixture was thus combined with ether (50 ml). After 20 h stirring at RT, the resultant solid was filtered out. The more polar diastereoisomer of 1-(4-dimethylamino-4-phenylcyclohexylmethyl)-3-[2-(1H-indol-3-yl)-1-methylethyl]thiourea citrate was obtained in this manner as a colorless solid (Example 40) in a yield of 185.5 mg (93%).
