[CH2:1]([C@@H:5]1[CH2:8][N:7]([O:9][CH2:10][C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)[C:6]1=[O:17])[CH2:2][CH2:3][CH3:4].[OH2:18].[OH-].[Li+]>C1COCC1.CO.O>[C:11]1([CH2:10][O:9][NH:7][CH2:8][C@@H:5]([CH2:1][CH2:2][CH2:3][CH3:4])[C:6]([OH:17])=[O:18])[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1To a solution of (3R)-3-butyl-1-[(phenylmethyl)oxy]-2-azetidinone (7) (52.8 g, 0.23 mol) in THF/MeOH (3:1, 1500 mL) at 0° C. was added Lithium hydroxide monohydrate (11.4 g, 0.27 mol) in water (375 mL). The mixture was warmed up to rt and stirred overnight. TLC indicated completion of the reaction. Organic solvents were removed under vacuum, and the aqueous solution was washed with DCM, acidified with 4 N HCl to pH ˜2.0, and extracted with DCM. The extracts were dried, filtered and concentrated to provide the title compound (40 g, 69%). LCMS: (M+H)+: 252.2.
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