C([O:3][C:4]([C:6]1[S:7][C:8]2[CH2:9][CH2:10][O:11][C:12]3[CH:19]=[C:18]([Br:20])[CH:17]=[CH:16][C:13]=3[C:14]=2[N:15]=1)=[O:5])C.[OH-].[Na+].CO.Cl>O1CCCC1.O>[Br:20][C:18]1[CH:17]=[CH:16][C:13]2[C:14]3[N:15]=[C:6]([C:4]([OH:5])=[O:3])[S:7][C:8]=3[CH2:9][CH2:10][O:11][C:12]=2[CH:19]=1To a solution of 8-bromo-4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulene-2-carboxylic acid ethyl ester from Example 21 (518 mg) in tetrahydrofuran (10 ml) was added a solution of sodium hydroxide (117 mg) in water (2 mL). Methanol (5 mL) was also added to aid dissolution. After 2 hours, the reaction mixture was acidified with HCl (2M) and the reaction mixture was then extracted with dichloromethane, dried (MgSO4) and the solvent removed in vacuo to yield 8-bromo-4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulene-2-carboxylic acid.
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