[S:1](Cl)(Cl)=[O:2].[OH:5][CH:6]([CH3:17])[CH2:7][CH2:8][NH:9][C:10](=[O:16])[O:11][C:12]([CH3:15])([CH3:14])[CH3:13].N1C=CC=CC=1.C(OCC)(=O)C>C(#N)C.CN(C1C=CN=CC=1)C>[CH3:17][CH:6]1[O:5][S:1](=[O:2])[N:9]([C:10]([O:11][C:12]([CH3:13])([CH3:15])[CH3:14])=[O:16])[CH2:8][CH2:7]1A stirred solution of thionyl chloride (2.0 mL, 27.9 mmol) in acetonitrile (15 mL) is cooled down to −45° C. and a solution of tert-butyl (3-hydroxybutyl)carbamate (2.1 g, 11.2 mmol) in acetonitrile (20 mL) is added by syringe over about 10 min, keeping the internal temperature below −40° C. Then DMAP (136 mg, 1.1 mmol) is added followed by the dropwise addition of pyridine (4.5 mL, 55.8 mmol) by syringe, keeping the temperature below −40° C. The addition takes 1.5 h. Ethyl acetate (50 mL) is added to the suspension. The mixture is filtered at −35° C. to remove the solid and the solid is washed with EtOAc before it is discarded. Then the filtrates are combined, and sat. Na2HPO4 solution (20 mL) is added. Again the mixture is stirred vigorously for 30 min. Then the organic layer is separated, washed with 1M NaHSO4 to remove residual pyridine, dried (MgSO4) and concentrated to afford the title compound as an oil (2.52 g, 96%) which is used in the next step without purification.
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