[S:1](Cl)(Cl)=[O:2].[OH:5][CH:6]([CH3:17])[CH:7]([NH:9][C:10](=[O:16])[O:11][C:12]([CH3:15])([CH3:14])[CH3:13])[CH3:8].N1C=CC=CC=1.C(OCC)(=O)C>C(#N)C.CN(C)C1C=CN=CC=1>[CH3:8][CH:7]1[CH:6]([CH3:17])[O:5][S:1](=[O:2])[N:9]1[C:10]([O:11][C:12]([CH3:14])([CH3:13])[CH3:15])=[O:16]To a stirred solution of thionyl chloride (4.1 mL, 56.8 mmol) in acetonitrile (30 mL) cooled to −45° C. is added a solution of tert-butyl (3-hydroxybutan-2-yl)carbamate (4.30 g, 22.7 mmol) in acetonitrile (40 mL) by syringe over 10 min, keeping the internal temperature below −40° C. When the addition is complete, 4-dimethylamino pyridine (277.5 mg, 2.3 mmol) is added followed by the dropwise addition of pyridine (9.2 mL, 113.6 mmol), keeping the temperature below −40° C. The reaction mixture is stirred at −40° C. for 1 h. Ethyl acetate (70 mL) is added to the suspension and the mixture is filtered at −35° C. The solid is washed with EtOAc and the filtrates are combined. Saturated Na2HPO4 solution (40 mL) is added and the mixture is stirred vigorously for 30 min. The organic layer is separated, washed with 1M NaHSO4, dried (MgSO4) and concentrated to afford the title crude compound (4.83 g, 90%) as an oil.
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