C([O:5][C:6](=[O:14])[NH:7][C@H:8]([CH2:12][CH3:13])[CH2:9][C:10]#N)(C)(C)C.CCCCCC.CC(C[AlH]CC(C)C)C.Cl.CC[O:33]CC>>[CH2:12]([C@@H:8]([NH:7][C:6](=[O:14])[OH:5])[CH2:9][CH:10]=[O:33])[CH3:13]To a solution of ((R)-2-cyano-1-ethyl-ethyl)-carbamic acid tert-butyl ester (10 mmol; 1.98 g) in Et2O (50 mL) is slowly added a 0.97 M n-hexane solution (40 mmol; 41 mL) of DIBAL under nitrogen at −78° C. The reaction mixture is warmed to −40° C. and stirred for an additional 3.5 hours. Another 1.00 M n-hexane solution (30 mmol; 30 mL) of DIBAL is added to the suspension at the same temperature. After stirring for additional 1.5 hours, the solution is quenched by careful addition of 1 ml of MeOH then immediately poured into 25 ml of saturated aqueous ammonium chloride solution in a separatory funnel. Shake mixture and leave until it reaches room temperature. Aqueous 1M HCl is added to reach a pH of 3-4. The solution is extracted three times with EtOAc and the combined organic layer is washed with an aqueous 1M HCl/brine (1:1) solution and twice with a saturated aqueous NaHCO3/brine (1:1) solution, dried over Na2SO4, filtered and concentrated under reduced pressure and purified by column chromatography on silica gel (eluent; n-hexane/EtOAc) to give ((R)-1-ethyl-3-oxo-propyl)-carbamic acid tent-butyl ester (590 mg, 29%); ESI-MS m/z: 146 [M+−tBu+2], Retention time 2.17 min (condition A).
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