Cl.[Br:2][C:3]1[CH:8]=[CH:7][C:6]([C@@H:9]([NH:11][S@@](C(C)(C)C)=O)[CH3:10])=[C:5]([CH3:18])[CH:4]=1>C(OCC)(=O)C>[Br:2][C:3]1[CH:8]=[CH:7][C:6]([C@@H:9]([NH2:11])[CH3:10])=[C:5]([CH3:18])[CH:4]=1Hydrochloric acid (4 mol/L in 1,4-dioxane, 46 mL) was added to a solution of (R)-2-methyl-propane-2-sulfinic acid [(S)-1-(4-bromo-2-methyl-phenyl)-ethyl]-amide (crude from Step 2, 8.85 g, ca. 75% pure) in ethyl acetate (80 mL) at room temperature. The solution was stirred at room temperature for 1 h and then concentrated. The residue was taken up in water and the resulting mixture was washed with diethyl ether. The aqueous phase was basified using aqueous 1 M NaOH solution and extracted with dichloromethane. The combined extracts were washed with brine, dried (MgSO4), and concentrated to afford the title compound.
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