Pivaloyl chloride (3.66 g, 30 mM) was added dropwise at -5° C. to compound 655 (8.62 g, 28.7 mM) and triethylamine (4.2 ml, 30 mM) dissolved in tetrahydrofuran (50 ml), then the mixture was stirred for 30 minutes. Chloroform (30 ml) in solution with 2-fluoroethylamine hydrochloride (3.48 g) and triethylamine (4.2 ml) was added dropwise thereto with cooling at 0° to -5° C. then the mixture was stirred for 1 hour with ice cooling and 4 hours at room temperature. Dilute aqueous potassium carbonate was added to the reaction mixture and the mixture was extracted three times with chloroform. The extract was dried with anhydrous magnesium sulfate, and concentrated in vacuo. The residue was charged on a column of silica gel (C-200, 175 g) and eluted successively with benzene and benzene-ethyl acetate (5:1) to obtain the product. (9.21 g, yield: 88.8%).
