(R)-2-[4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy]propionic acid is prepared as follows: A suspension of ethyl (R)-2-mesyloxypropionate (0.392 g, 2.0 mmol), 4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenol (0.578 g, 2.0 mmol) and potassium carbonate (0.276 g, 2.0 mmo.) in 8 ml of DMSO is heated at 80° for 24 hours. The reaction mixture is cooled and worked up to give ethyl (R)-2-[4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy]propionate. The propionate is hydrolyzed by stirring it (0.80 g, 2.22 mmol) in 10 ml of ethanol with sodium hydroxide (0.10 g, 2.50 mmol) in 1 ml of water overnight. The ethanol is then removed in vacuo from the reaction mixture. The residue is acidified with HCl and extracted with ether. The organic fraction is washed with brine until neutral and dried over sodium sulfate. Solvent is removed to give (R)-2-[4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy]propionic acid.
