Water → tert-butyl 4-[(2R)-3-benzyloxycarbonylamino-2-hydroxy-propyl]piperazine-1-carboxylate

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Reaction Steps

The crude compound tert-butyl 4-[(2R)-3-amino-2-hydroxy-propyl]piperazine-1-carboxylate 20b (4.50 g, 17.40 mmol) was dissolved in 80 mL of dichloromethane in an ice-water bath followed by the addition of diisopropylethylamine (2.50 g, 19.10 mmol) and dropwise addition of 20 mL of a solution of carbobenzoxy chloride (2 g, 19.10 mmol) in dichloromethane successively, stirred for 12 hours. The resulting mixture was added with 20 mL of water and stirred for 10 minutes. The reaction solution was concentrated under reduced pressure, added with 100 mL of water and extracted with ethyl acetate (100 mL×3). The combined organic phase was washed with saturated sodium chloride solution (50 mL×3), then dried over anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound tert-butyl 4-[(2R)-3-benzyloxycarbonylamino-2-hydroxy-propyl]piperazine-1-carboxylate 20c (1.80 g, yield: 26.0%) as a light yellow oil.

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