Citric Acid → (2S,3S)-2-tert-butoxycarbonylamino-3-(2-nitro-phenylamino)-butyric acid

Participants

Reaction Steps

To a solution of (2S,3S)-2-tert-butoxycarbonylamino-3-(2-nitro-phenylamino)-butyric acid methyl ester (5.71 g, 16.2 mmol) in dioxane water (1:1, 100 ml) was added an aqueous solution of 2.5 M lithium hydroxide (31 ml) and the reaction was stirred at ambient temperature for 2 h. The reaction was made acidic with 10% aqueous citric acid, diluted with water (60 ml) and extracted with ethyl acetate (2×100 mL). The organic layers were combined, washed with water (1×50 mL), brine, dried over sodium sulfate, filtered and concentrated in vacuo to give (2S,3S)-2-tert-butoxycarbonylamino-3-(2-nitro-phenylamino)-butyric acid which was carried to the subsequent step without purification (5.48 g, 99%).

Provenance & Evidence