Under stirring at room temperature, 2 N sodium hydroxide aqueous solution was added to a suspension of S-alanine (1.0 equivalent) in a mixture of dioxane and water (1:1, 100 mL). The resulting reaction mixture was transferred to an ice-water bath and cooled to 0 °C, then stirred for 15 min. A solution of (Boc)₂O (1.1 equivalent) in dioxane (10 mL) was then added to the reaction mixture, and the mixture was stirred at 0 °C for another 45 min. The ice bath was removed, and the reaction mixture was brought to room temperature. The completion of the reaction was monitored by TLC. After the reaction was complete, the reaction mixture was concentrated under reduced pressure, and the aqueous layer was acidified with citric acid (pH 2-3). The mixture was extracted three times with ethyl acetate, and all organic layers were combined and washed three times with brine. The organic layers were separated and dried on Na₂SO₄. The desiccant was removed by filtration, and the filtrate was concentrated under reduced pressure to obtain N-tert-butoxycarbonyl-L-alanine.
Figure: Synthetic Route of N-tert-Butoxycarbonyl-L-Alanine
