[C:1]([O:5][C:6]([NH:8][C:9]([CH3:19])([CH3:18])[CH2:10]/[CH:11]=[CH:12]/[C:13]([O:15]CC)=[O:14])=[O:7])([CH3:4])([CH3:3])[CH3:2].[OH-].[Li+]>O1CCOCC1.O>[C:1]([O:5][C:6]([NH:8][C:9]([CH3:19])([CH3:18])[CH2:10]/[CH:11]=[CH:12]/[C:13]([OH:15])=[O:14])=[O:7])([CH3:4])([CH3:2])[CH3:3]Ethyl (2E)-5-(tert-butoxycarbonylamino)-5-methylhex-2-enoate (1.233 g, 4.54 mmol) was dissolved in dioxane (20 ml). Lithium hydroxide (0.120 g, 5.00 mmol) was added as a solid. Water (10 ml) was added, until a clear solution was reached. The solution was stirred 16 h at room temperature. The solution was diluted with water (70 ml) and was extracted with tert-butyl methyl ether (2×100 ml). The aqueous phase was acidified with 1N sodium hydrogensulfate solution (pH=1) and was extracted with tert-butylmethylether (3×70 ml). The organic phases were combined and dried over magnesium sulfate. The solvent was removed in vacuo to give 1.05 g of (2E)-5-(tert-butoxycarbonylamino)-5-methylhex-2-enoic acid. The crude product was used for further syntheses.
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