[Li+].[OH-].[CH3:3][C:4]([O:7][C:8]([NH:10][C@@H:11]([CH2:18][CH3:19])/[CH:12]=[CH:13]/[C:14]([O:16]C)=[O:15])=[O:9])([CH3:6])[CH3:5].O>C1COCC1.CO>[CH3:6][C:4]([O:7][C:8]([NH:10][C@@H:11]([CH2:18][CH3:19])/[CH:12]=[CH:13]/[C:14]([OH:16])=[O:15])=[O:9])([CH3:3])[CH3:5]LiOH (2.95 g, 123 mmol) was added to a solution of methyl (2E,4S)-4-({[(1,1-dimethylethyl)oxy]carbonyl}amino)-2-hexenoate (6 g, 24.66 mmol) in THF (50 mL), MeOH (10.00 mL), and water (50.0 mL). The reaction was stirred overnight at RT. After 18.5 h, the reaction mixture was concentrated under reduced pressure to remove the THF and MeOH. Water (40 mL) was added, and aqueous mixture was adjusted to pH=3 with 6 M aq. HCl, as measured by pH paper. EtOAc (80 mL) was added, the layers were separated, and the aqueous layer was extracted with EtOAc (2×40 mL). The combined organic layers were dried over Na2SO4, concentrated under reduced pressure, and dried under high vacuum, giving 6.09 g of the title compound. LC-MS m/z 230 (M+H)+, 0.77 min (ret time).
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