To a stirred solution of tert-butyl 2-(benzyloxy)-1-formylethylcarbamate (3.29 g, 11.8 mmol) in anhydrous THF (12 mL) was added 4-fluorobenzylamine (2.03 mL, 17.7 mmol). After 10 min, sodium triacetoxyborohydride (3.99 g, 18.8 mmol) was added, and the reaction was stirred at ambient temperature under inert atmosphere for 30 min. Saturated aqueous NaHCO3 solution was added and the mixture stirred until gas evolution ceased. The aqueous layer was extracted with EtOAc, saturated with NaCl and again extracted with EtOAc. The combined organic extracts were washed with brine, dried over Na2SO4 and concentrated in vacuo. The resulting cloudy yellow oil was purified by silica gel chromatography (EtOAc to 10% MeOH/EtOAc) to afford the title compound as a pale yellow oil. 1H NMR (500 MHz, CDCl3) δ 7.37-7.23 (m, 7H), 7.03-6.96 (m, 2H), 5.04 (br s, 1H), 4.49 (dd, J=11.5, 18.0 Hz, 2H), 3.86 (br s, 1H), 3.76-3.70 (m, 2H), 3.60 (dd, J=3.0, 9.0 Hz, 1H), 3.53 (d, J=4.5 Hz, 1H), 2.83-2.80 (m, 1H), 2.76-2.72 (m, 1H), 1.44 (s, 9H). ES MS (M+1)=389.5.
