C([O:3][C:4](=[O:18])[C:5]([CH3:17])([S:7]([CH2:10][CH:11]1[CH2:16][CH2:15][O:14][CH2:13][CH2:12]1)(=[O:9])=[O:8])[CH3:6])C.[OH-].[Na+].CC(OC)(C)C>C1COCC1>[CH3:17][C:5]([S:7]([CH2:10][CH:11]1[CH2:12][CH2:13][O:14][CH2:15][CH2:16]1)(=[O:9])=[O:8])([CH3:6])[C:4]([OH:18])=[O:3]To 123 g (0.44 mol) of 2-methyl-2-(tetrahydro-pyran-4-ylmethanesulfonyl)-propionic acid ethyl ester in THF (450 mL) are added 663 mL of 2M aq. NaOH solution (1.33 mol). The reaction is stirred at RT for 1 h. To the reaction mixture is added TBME (1.25 L) and the layers are separated. The aq. layer is cooled in an ice bath and then acidified with 37% aq. HCl solution (123 mL). The resulting precipitate is isolated by filtration, washed with water (200 mL) and dried under reduced pressure at 50° C. to afford 101 g of 2-methyl-2-(tetrahydro-pyran-4-ylmethanesulfonyl)-propionic acid. Yield: 91%; ESI-MS: 251 [M+H]+
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