To a solution of tert-butyl (3-formylphenoxy)acetate (1.50 g) in dichloroethane (20.0 mL) were added tert-butyl glycinate (874 mg) and acetic acid (1.09 mL), and then sodium triacetoxyborohydride (2.69 g) was added thereto under ice-cooling. The reaction suspension was stirred at room temperature for 16 hours. To the reaction mixture was added a saturated aqueous sodium hydrogen carbonate solution, followed by extraction with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (chloroform-methanol) to obtain tert-butyl N-[3-(2-tert-butoxy-2-oxoethoxy)benzyl]glycinate (1.18 g).
