To a solution of trichloromethyl chloroformate (0.35 ml) THF (40 ml) was dropwise added a solution of 4-chlorobenzylamine (0.71 ml) and triethylamine (0.81 ml) in THF (20 ml) under ice-cooling, and the mixture was stirred at room temperature for 1.5 hours. A suspension of (2S)-2-[2-(4-chlorophenoxy)-1-hydroxyethyl]-1-(L-prolyl)pyrrolidine hydrochloride which had been obtained by treating (2S)-1-[N-(tert-butoxycarbonyl)-L-prolyl]-2-[2-(4-chlorophenoxy)-l-hydroxyethyl]pyrrolidine (2.13 g) with 4N hydrochloric acid in 1,4-dioxane (20 ml), and triethylamine (0.81 ml) in methylene chloride (20 ml) was dropwise added to the reaction mixture, followed by stirring at room temperature for 1 hour. The reaction mixture was poured into ice-water and extracted with ethyl acetate. The organic layer was washed with 1N hydrochloric acid, saturated aqueous solution of sodium bicarbonate and saturated brine, dried over anhydrous magnesium sulfate, and concentrated. The residue was purified by silica gel column chromatography (eluate: chloroform-methanol) to give 2.09 g of the title compound.
