[O:1]1[C:5]2([CH2:10][CH2:9][N:8]([C:11]([NH:13][C:14]3[CH:23]=[CH:22][CH:21]=[CH:20][C:15]=3[C:16]([O:18]C)=[O:17])=[O:12])[CH2:7][CH2:6]2)[O:4][CH2:3][CH2:2]1.[OH-].[Na+].CCOC(C)=O.O>O1CCOCC1>[O:4]1[C:5]2([CH2:6][CH2:7][N:8]([C:11]([NH:13][C:14]3[CH:23]=[CH:22][CH:21]=[CH:20][C:15]=3[C:16]([OH:18])=[O:17])=[O:12])[CH2:9][CH2:10]2)[O:1][CH2:2][CH2:3]1A solution of methyl 2-(1,4-dioxa-8-azaspiro[4.5]decan-8-ylcarbonyl)aminobenzoate (2.00 g, 6.25 mmol) in dioxane (30 mL) was treated with 5 N NaOH (12.5 mL). After 1 h, the mixture was poured into EtOAc and water, and the aqueous layer was washed with EtOAc. The pH of the aqueous layer was then adjusted to 2–3 by addition of 5 N HCl and washed with EtOAc (3×). The combined organic layers were washed with brine, dried with sodium sulfate, and concentrated, yielding the title compound; which was used without further purification.
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