C[O:2][C:3]([C:5]1([CH3:19])[CH2:9][O:8][C:7]([CH3:11])([CH3:10])[N:6]1[C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])=[O:4].O[Li].O>C1COCC1.O>[C:15]([O:14][C:12]([N:6]1[C:5]([CH3:19])([C:3]([OH:4])=[O:2])[CH2:9][O:8][C:7]1([CH3:11])[CH3:10])=[O:13])([CH3:18])([CH3:16])[CH3:17]To a stirring solution of 4 (9.392 g, 34 mmol) in THF (65 mL) and H2O (35 mL) under an inert atmosphere was added solid LiOH—H2O (1.426 g, 34 mmol) in one portion. The reaction mixture was heated to 90° C. and stirred 8 h at which point the reaction mixture was cooled to rt. The crude reaction mixture was washed with Et2O (3×50 mL) and the Et2O extracts were discarded. The aqueous solution was then acidified with 2M KHSO4 until a white precipitate began to form on addition, pH=5. The acid was added dropwise until the precipitate persisted and the aqueous solution was extracted with Et2O (50 mL). After extraction, two addition drops of acid were added to the aqueous layer and it was again extracted with Et2O (25 mL). The Et2O extracts were combined and quickly back extracted with 1M NaOH (15 mL). The organic phase was then dried over sodium sulfate and concentrated in vacuo to give 5 (7.458 g, 85%) as a white solid which was used without further purification. Compound was observed as an uneven mixture of rotomers.
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