The general procedure for the synthesis of N-tert-butoxycarbonyl-2-aminoacetaldehyde from N-BOC-gly-N'-methoxy-N'-methylamide was as follows: under argon protection, Boc-Gly-N-methoxy-N-methylamide (19) (4.37 g, 20 mmol) was dissolved in 150 mL of anhydrous THF and stirred in an ice-water bath for 30 min. An ether solution of LAH (1 M, 30 mL, 30 mmol) was slowly added to the above well-stirred solution through a cannula under argon protection. The reaction solution continued to be stirred for 30 minutes. Subsequently, aqueous potassium bisulfate solution (4.77 g, 35 mmol dissolved in 60 mL of water) was slowly added to the reaction solution and stirred for 10 minutes. The organic solvent was removed by evaporation under reduced pressure. To the remaining aqueous phase, 60 mL of water was added and then extracted with dichloromethane (DCM, 100 mL x 4). The DCM extracts were combined and washed sequentially with 1 M hydrochloric acid solution (100 mL x 4), saturated sodium bicarbonate solution (100 mL x 2), and saturated sodium chloride solution (100 mL), dried overnight with 4 g of anhydrous magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure to give light yellow oil 20 (2.83 g), which could be used in the next reaction without further purification. Yield: 89%. Thin layer chromatography (TLC) Rf = 0.44 (Expanding agent: hexane-ethyl acetate = 1:1). 1H-NMR (90 MHz, CDCl3) δppm: 9.60 (s, 1H), 5.26 (s, br, 1H), 4.04 (d, 2H, J = 5.1 Hz), 1.46 (s, 9H).
