Ammonium Chloride → Ethyl 4-benzyloxycarbonylamino-2,2-difluoro-3-hydroxy-5-phenylpentanoate

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Reaction Steps

To a mixture of the objective compound of step (10) (42.8 g, 0.151 mol), zinc dust (15.9 g, 0.243 mol) and THF (105 ml) was added ethyl bromodifluoroacetate (31.6 mL, 0.246 mol) with dropwise over 2 hours at 26˜49° C. The resulting mixture was stirred at room temperature for 2 hours. To this reaction mixture was added saturated ammonium chloride aqueous solution (110 mL), and the mixture was stirred for a few minutes. The obtained mixture was added to saturated ammonium chloride aqueous solution (650 mL) and extracted with ethyl acetate (500 mL, 2×300 mL). The extract was washed with saturated brine (400 mL), dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (2:1 hexane-ethyl acetate) to give 56.15 g of ethyl 4-benzyloxycarbonylamino-2,2-difluoro-3-hydroxy-5-phenylpentanoate as a light-yellow oil (a mixture of diastereomers, 75%).

Provenance & Evidence