[CH2:1]([O:3][C:4](=[O:12])[C:5]([S:8][C:9](=O)[CH3:10])([CH3:7])[CH3:6])[CH3:2].[F:13][C:14]([F:29])([F:28])CCOS(C1C=CC(C)=CC=1)(=O)=O.C[O-].[Na+]>C(O)C>[CH2:1]([O:3][C:4](=[O:12])[C:5]([CH3:7])([S:8][CH2:9][CH2:10][C:14]([F:29])([F:28])[F:13])[CH3:6])[CH3:2]A solution of 2-acetylsulfanyl-2-methyl-propionic acid ethyl ester (1.7 g, 8.72 mmol), toluene-4-sulfonic acid 3,3,3-trifluoro-propyl ester (2.3 g, 8.72 mmol) and sodium methoxide (1.9 g, 34.9 mmol) in ethanol (13 mL) are heated to 130° C. in a sealed tube for 4 h. The reaction is cooled to room temperature and concentrated under reduced pressure. The residue is diluted with DCM and washed with saturated aqueous NaHCO3 solution and brine. The organic layer is dried (Na2SO4), filtered and the filtrate concentrated under reduced pressure to afford 1.76 g of title compound as a brown solid. 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 1.28 (3H, t, J=7 Hz), 1.51 (3H, s), 2.26-2.42 (2H, m), 2.76-2.85 (2H, m), 4.18 (2H, q, J=6.96 Hz)
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