Hydrochloric Acid → (S)-tert-butyl 2-((tert-butoxycarbonyl)amino)-5-hydroxypentanoate

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Reaction Conditions

Reaction Steps

To a solution of N-(t-butoxycarbonyl)-L-glutamic acid t-butyl ester (6.0 g, 19.78 mmol) and triethylamine (2.83 mL, 20.27 mmol) in THF at −10° C. is added ethyl chloroformate (1.94 mL, 20.27 mmol) dropwise, via syringe, and the solution is stirred at −10° C. for 30 minutes. The solution is filtered to remove precipitate, and the filtrate is added into a solution of NaBH4 (2.3 g, 60.86 mmol) in THF (40 mL) and water (50 mL). This solution is then stirred for 4 hours, after which time the solution is acidified with 1 N HCl to pH=5, and THF is evaporated. The aqueous residue is extracted with EtOAc (3×200 mL), and the organic layers is then washed with 1 N NaOH (2×300 mL), water (300 mL) and brine (300 mL), dried over MgSO4, and evaporated. Chromatography (silica, 20% EtOAc/hexane) yields t-butyl (S)-5-hydroxy-2-(t-butoxycarbonylamino)-pentanoate as a thick oil.

Provenance & Evidence