Benzyl chloroformate (4.46 g, 24.8 mmol) was added at 0° C. to a mixture of (S)-2-(2,2-dimethoxy-ethylamino)-propionic acid methyl ester (4.75 g, 24.8 mmol) and sodium hydrogencarbonate (4.17 g, 49.7 mmol) in acetone (25 mL) and water (25 mL). The ice bath was removed, then after 2 h the reaction mixture was poured onto ice water and extracted with ethyl acetate. The organic layer was dried (MgSO4), filtered, and evaporated. Chromatography (SiO2; heptane-ethyl acetate gradient afforded the title compound (5.84 g, 72%). Yellow oil, MS (ISP)=348.2 (M+Na)+.
