L-Phenylalanine → tert-butyl (2S)-2-amino-3-phenylpropanoate

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Reaction Steps

A solution of L-phenylalanine (62.6 g; 379 mol) in tert-butyl acetate (320 mL) cooled on an ice bath and stirred vigorously is slowly added with 70% aqueous HClO4 (35 mL, 407 mol). After stirring for 11 days at room temperature, the mixture is diluted with 100 mL of water and cooled on an ice bath. The mixture is basified with 5 N NaOH to precipitate a white solid (unreacted phenylalanine) which is filtered off. The mixture is then extracted with EtOAc (4×200 mL), the organic phases are combined and washed with water (2×200 mL) and 5% Na2CO3 (300 mL). After drying over Na2SO4 and carefully removing the solvent under vacuum, the desired compound is obtained as a colourless oil (53.53 g; 242 mol), which needs no further purifications and is stored at −18° C.

Provenance & Evidence