2-(Trifluoromethyl)propionaldehyde (0.0724 g; 0.574 mmole) was dissolved in tetrahydrofurane (3 ml) and sulfuric acid (4 M; 0.041 ml; 0.164 mmole) was added under stirring, followed by addition of 3-{4-[2-(4-aminophenyl)ethoxy]phenyl}-(S)-2-ethoxypropanoic acid hydro chloride (described in Example 56a) (0.2 g; 0.547 mmole) dissolved in tetrahydrofurane (2 ml). The reaction mixture was stirred for 10 minutes, then cooled to 0° C in an ice-bath and sodium borohydride (0.042 g; 1.10 mmole) was added. After addition, the cooling bath was removed. The mixture was stirred overnight and then evaporated to remove tetrahydrofurane. Ethyl acetate and water were added into the residue and the organic phase was separated, washed with brine, dried with magnesium sulfate. The solvent was then evaporated. Chromatography on silica gel(Isolute, SI ) using dichloromethane and then 1% methanol in dichloromethane as eluant gave 0.13 g (40% yield) of (S)-2-ethoxy-3-(4-{2-[4-(3,3,3-trifluoro-2-methyl-(R/S)-propylamino)phenyl]ethoxy}phenyl)propanoic acid.
