[C:1]([C:4]1([O:17][CH3:18])[CH2:9][CH2:8][N:7]([C:10]([O:12][C:13]([CH3:16])([CH3:15])[CH3:14])=[O:11])[CH2:6][CH2:5]1)(=[O:3])[CH3:2].C(NC(C)C)(C)C.[Li].[CH:27](=[O:30])[CH2:28][CH3:29].[Cl-].[NH4+]>O1CCCC1>[OH:30][CH:27]([CH2:28][CH3:29])[CH2:2][C:1]([C:4]1([O:17][CH3:18])[CH2:9][CH2:8][N:7]([C:10]([O:12][C:13]([CH3:14])([CH3:16])[CH3:15])=[O:11])[CH2:6][CH2:5]1)=[O:3]To a solution of tert-butyl 4-acetyl-4-methoxypiperidine-1-carboxylate (0.589 g, 2.29 mmol) from Step A in tetrahydrofuran (20 mL) at −78° C. was added lithium diisopropylamine (0.650 mL, 0.974 mmol) followed by propionaldehyde (0.266 g, 0.330 mL, 4.58 mmol). After 5 min, the reaction mixture was poured into saturated ammonium chloride, and extracted three times with diethyl ether. The organic layers were combined, washed with saturated sodium chloride solution, dried over sodium sulfite, filtered, and concentrated. The residue was purified by flash chromatography eluting with 40% ethyl acetate/hexanes to afford the title compound (0.404 g). MS/EI (acetonitrile/water): m/z 216.1 (M+1−BOC) retention time=2.69 min.
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