(1) Synthesis of benzyl [2-(tert-butyldiphenylmethoxysilyl)ethyl]carbamate [1515]: To a solution of 2-aminoethanol (2.0 g, 32.7 mmol) in dichloromethane (60 mL), benzyl chloroformate (5.6 mL, 41.3 mmol) and triethylamine (5.5 mL, 39.5 mmol) were sequentially added under ice bath conditions. The reaction mixture was stirred at room temperature for 1 hour. After completion of the reaction, the mixture was partitioned between ethyl acetate and saturated aqueous sodium chloride solution. The organic layer was dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with the eluent being toluene:acetonitrile (3:2) to afford benzyl (2-hydroxyethyl)carbamate (5.37 g, 84% yield) as a white solid. [1516] Subsequently, to a solution of benzyl (2-hydroxyethyl)carbamate (5.37 g, 27.5 mmol) in dimethylformamide (160 mL) was added tert-butyldiphenylmethylsilyl chloride (8.6 mL, 33.0 mmol) and imidazole (2.3 g, 33.8 mmol) under ice bath conditions. The mixture was stirred at room temperature overnight. After the reaction was complete, ethanol was added and stirring was continued for 2 hours. The reaction mixture was partitioned between ethyl acetate and saturated aqueous sodium bicarbonate. The organic layer was washed with saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with hexane:ethyl acetate (5:1) as eluent to give benzyl [2-(tert-butyldiphenylmethylsilylmethoxy)ethyl]carbamate (11.93 g, 100% yield) as a colorless transparent syrup. [1517] 1H-NMR (400 MHz, CDCl3): δ (ppm) 7.64 (4H, d, J = 6.8 Hz), 7.46-7.28 (12H, m), 5.10 (2H, s), 3.73 (2H, t, J = 4.9 Hz), 3.35 (2H, q, J = 4.9 Hz), 1.05 (9H, s).
