4-Methylmorpholine → (R)-(+)-3-Benzyloxy-2-(Boc-amino)-1-propanol

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(2S)-3-(benzyloxy)-2-[(tert-butoxycarbonyl)amino]propanoic acid (7.2 g, 24.4 mmole) was dissolved in ethylene glycol dimethyl ether (50 mL). N-Methylmorpholine (2.7 ml, 24.4 mmole) was added, and the resulting clear solution was cooled to −20° C. Isobutyl chloroformate (3.19 ml, 24.4 mmole) was added dropwise to cause N-methylmorpholine HCl salt precipitation. Stirring was continued for 15 min and the supernatant was then transferred via a filter-tipped funnel into a rapidly stirred solution of NaBH4 (2.93 g, 73.2 mmole) in ice water and washed with dry DME. After the mixture was stirred for 30 min, it was extracted with EtOAc and washed with H2O. The organic layers were combined, dried over Na2SO4, and concentrated in vacuo. Purification by chromatography (silica, 4/1: Hexane/EtOAc, Rf=0.2) afforded tert-butyl N-[(1R)-2-(benzyloxy)-1-(hydroxymethyl)ethyl]carbamate as a white solid (6.3 g, 92%).

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