[F:1][C:2]([F:19])([F:18])[C:3]1[N:7]([C:8]2[CH:17]=[CH:16][C:11]([C:12]([O:14]C)=[O:13])=[CH:10][CH:9]=2)[N:6]=[N:5][N:4]=1.[OH-].[Li+].Cl>C1COCC1.CO.O>[F:19][C:2]([F:1])([F:18])[C:3]1[N:7]([C:8]2[CH:17]=[CH:16][C:11]([C:12]([OH:14])=[O:13])=[CH:10][CH:9]=2)[N:6]=[N:5][N:4]=1To a solution of the compound (5.2 g) obtained in step 1 in THF/methanol/water (6.0/18/9.5 mL) was added 4N aqueous lithium hydroxide solution (9.5 mL), and the mixture was stirred at room temperature for 4 hr. The mixture was acidified with 1N hydrochloric acid, concentrated under reduced pressure, diluted with water, and extracted with ethyl acetate. The extract was washed with water and saturated brine, dried, filtered through silica gel (eluted with ethyl acetate). The filtrate was concentrated under reduced pressure, and crystallized from ethyl acetate/hexane to give the title compound (4.3 g, 86%) as a pale-yellow powder.
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