C([O:5][C:6]([C:8]1[CH:21]=[CH:20][C:11]2[CH2:12][CH2:13][O:14][C:15](=[O:19])[N:16]([CH2:17][CH3:18])[C:10]=2[CH:9]=1)=[O:7])(C)(C)C>C(O)(C(F)(F)F)=O.C(Cl)Cl>[CH2:17]([N:16]1[C:10]2[CH:9]=[C:8]([C:6]([OH:7])=[O:5])[CH:21]=[CH:20][C:11]=2[CH2:12][CH2:13][O:14][C:15]1=[O:19])[CH3:18]A solution of 5-ethyl-6-oxo-5,6,8,9-tetrahydro-7-oxa-5-aza-benzocycloheptene-3-carboxylic acid tert-butyl ester (0.91 g, 3.12 mmol) was stirred in TFA/DCM (1:1, 3 mL) for 16 hours. The reaction was concentrated to provide 5-ethyl-6-oxo-5,6,8,9-tetrahydro-7-oxa-5-aza-benzocycloheptene-3-carboxylic acid (0.73 g).
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