Sodium borohydride → 5-(R)-(2-(S)-Amino-1-(S)-hydroxy-3-phenylpropyl)-2-(S)-(2-cyclohexylethyl)-morpholine-4-carboxylic acid tert-butyl ester

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Reaction Steps

Dissolve 2(S)-(2-cyclohexylethyl)-5-(R)-(1-(R)-hydroxy-2-(S)-nitro-3-phenylpropyl)-morpholine-4-carboxylic acid tert-butyl ester (152 mg, 0.32 mmol) in methanol (5 mL), and place in a room temperature oil bath. Add dry nickel (II) chloride (62 mg, 0.48 mmol) followed by sodium borohydride (30 mg, 0.80 mmol). After 3 minutes add a second portion of sodium borohydride (30 mg, 0.80 mmol). Quench with water (1 mL) then 0.1 N sodium hydroxide (3 mL). Dilute with ethyl acetate and extract (3×30 mL). Wash the combined extracts with saturated aqueous sodium chloride, filter through a pad of Celite®, dry (sodium sulfate) and concentrate to give the desired compound as a white solid which is used without further purification (140 mg, 99%).

Provenance & Evidence