The starting material can be prepared, for example, as follows: 2.89 g of 4-methoxycarbonyl-4-methyl-pentanoic acid chloride are added to a solution of 2.50 g of N-(2'-cyanobiphenyl-4-ylmethyl)-N-propyl-amine and 2.09 ml of triethylamine in 100 ml of CH2Cl2, and the mixture is stirred for 1 hour. The reaction mixture is washed twice with 50 ml of water each time and the combined aqueous phases are extracted with 50 ml of CH2Cl2. The crude product obtained from the organic phase by the customary procedure is purified by chromatography on silica gel 60 (40-63 μm) using CH2Cl2 /CH3OH (98:2) as eluant to yield pure 4-methoxycarbonyl-4-methyl-pentanoic acid N-(2'-cyanobiphenyl-4-ylmethyl)-N-propyl-amide that has an Rf value of 0.56 [CH2Cl2 /CH3OH (95:5)].
