[CH3:1][O:2][C:3](=[O:27])[CH:4]([C:16]1[CH:21]=[CH:20][C:19]([S:22]([CH3:25])(=[O:24])=[O:23])=[C:18]([Cl:26])[CH:17]=1)[CH2:5][CH:6]1[CH2:15][CH2:14][C:9]2(OCC[O:10]2)[CH2:8][CH2:7]1.Cl>CC(C)=O.O>[CH3:1][O:2][C:3](=[O:27])[CH:4]([C:16]1[CH:21]=[CH:20][C:19]([S:22]([CH3:25])(=[O:24])=[O:23])=[C:18]([Cl:26])[CH:17]=1)[CH2:5][CH:6]1[CH2:15][CH2:14][C:9](=[O:10])[CH2:8][CH2:7]1A solution of 2-(3-chloro-4-methylsulfonyl-phenyl)-3-(1,4-dioxa-spiro[4.5]dec-8-yl)-propionic acid methyl ester (667 mg, 1.60 mmol) in acetone (15 mL) was treated with a 10% aqueous hydrochloric acid solution (1.8 mL). The reaction mixture was stirred at 25° C. for 24 h. The reaction mixture was then diluted with water (50 mL) and extracted with ethyl acetate (100 mL). The organic layer was dried over sodium sulfate, filtered, and concentrated in vacuo to afford pure 2-(3-chloro-4-methylsulfonyl-phenyl)-3-(4-oxo-cyclohexyl)-propionic acid methyl ester (600 mg, 100%) as a colorless gum which was used without further purification: EI-HRMS m/e calcd for C17H21ClO5S (M+Na)+ 395.0690, found 395.0692.
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