[CH3:1][O:2][C:3](=[O:8])[C@@H:4]([CH3:7])[CH2:5][OH:6].C(N(CC)CC)C.[CH3:16][S:17](Cl)(=[O:19])=[O:18].C(OC(=O)CC(C)=O)C>ClCCl>[CH3:1][O:2][C:3](=[O:8])[C@@H:4]([CH3:7])[CH2:5][O:6][S:17]([CH3:16])(=[O:19])=[O:18]3 g (25.3 mmol) of (S)-3-hydroxy-2-methyl-propionic acid methyl ester was dissolved in dichloromethane 50 mL, then 5.3 mL (37.9 mmol) of triethylamine was dropwise added thereto. Thereafter, 2.16 mL (27.9 mmol) of methanesulfonyl chloride was added to the solution at 0° C. After 1 hour, 200 mL of ethylacetoacetate was added to the solution and then the reaction solution was washed with water and then an organic layer was dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure, then the residue was purified by column chromatography to give 4.97 g (25.3 mmol) of the title compound in a yield of 100%.
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