CS(C)=O.[C:5](Cl)(=[O:9])[C:6](Cl)=[O:7].C(Cl)Cl.C(NO)([O:16][C:17]([CH3:20])([CH3:19])[CH3:18])=O.C([N:25](CC)CC)C>C(Cl)Cl.C1COCC1>[C:6]([C:5]([NH2:25])=[O:9])([O:16][C:17]([CH3:20])([CH3:19])[CH3:18])=[O:7]DMSO (6.3 mL, 88 mmol) was added dropwise to a 2M solution of oxalyl chloride in CH2Cl2 (24.3 mL, 48.6 mmol) at −78° C. After 15 min, amino alcohol 22a (9.6 g, 44 mmol) in 80 mL CH2Cl2/THF (1:1) was added dropwise followed by dropwise addition of triethylamine (30.8 mL, 220 mmol) The reaction mixture was warmed to rt and stirred for 2. The reaction mixture was partitioned between EtOAc and sat KH2PO4, separated, and the organic layer was washed with brine, dried over MgSO4, filtered, and concentrated by rotary evaporator. The residue was purified by silica gel chromatography to give 8.0 g (85% yield) of Boc-amino ketone 22b.
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