[Br:1][C:2]1[CH:30]=[CH:29][C:5]2[N:6]([C:16]([C:18]3[CH:19]=[CH:20][C:21]4[O:26][CH2:25][C:24](=[O:27])[NH:23][C:22]=4[CH:28]=3)=[O:17])[C@@H:7]([CH2:10][C:11]([O:13]CC)=[O:12])[CH2:8][O:9][C:4]=2[CH:3]=1.[OH-].[Li+].CCOC(C)=O>C1COCC1.O>[Br:1][C:2]1[CH:30]=[CH:29][C:5]2[N:6]([C:16]([C:18]3[CH:19]=[CH:20][C:21]4[O:26][CH2:25][C:24](=[O:27])[NH:23][C:22]=4[CH:28]=3)=[O:17])[C@@H:7]([CH2:10][C:11]([OH:13])=[O:12])[CH2:8][O:9][C:4]=2[CH:3]=1Ethyl 2-[(3S)-7-bromo-4-(3-oxo-4H-1,4-benzoxazine-6-carbonyl)-2,3-dihydro-1,4-benzoxazin-3-yl]acetate (Intermediate 28a, 173 mg, 0.37 mmol) was dissolved in THF (1.5 mL). Lithium hydroxide (52.5 mg, 2.19 mmol) dissolved in water (1.50 mL) was added. The reaction was stirred at rt for 2 h before addition of EtOAc (50 mL). The organic layer was washed with HCl (1M, 30 mL) and brine (30 mL). Dried through a phase separator and evaporated under reduced pressure. The title compound (160 mg, 98%) was obtained crude and used without further purification.
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