[CH2:1]1[O:9][C:8]2[CH:7]=[CH:6][C:5]([SH:10])=[CH:4][C:3]=2[O:2]1.[C:11]([O:15][C:16]([NH:18][C@H:19]([C:32]([O:34][CH3:35])=[O:33])[CH2:20]OS(C1C=CC(C)=CC=1)(=O)=O)=[O:17])([CH3:14])([CH3:13])[CH3:12].C(N(CC)CC)C>C(Cl)(Cl)Cl>[C:11]([O:15][C:16]([NH:18][C@H:19]([C:32]([O:34][CH3:35])=[O:33])[CH2:20][S:10][C:5]1[CH:6]=[CH:7][C:8]2[O:9][CH2:1][O:2][C:3]=2[CH:4]=1)=[O:17])([CH3:14])([CH3:12])[CH3:13]After 27.7 g of (3,4-methylenedioxy)thiophenol and 74 g of methyl N-(t-butoxycarbonyl)-O-tosyl-L-serinate were dissolved in 200 ml of chloroform, 20 g of triethylamine were added at room temperature, followed by stirring overnight. The reaction mixture was washed with water and then extracted with ethyl acetate. The extract so obtained was dried over anhydrous magnesium sulfate. After the solvent was distilled off, 49 g of crude oil were obtained. The crude oil was recrystallized from an ethyl acetatehexane system, whereby 42 g of methyl N-t-butoxycarbonyl-S-[(3,4-methylenedioxy)phenyl]cysteinate were obtained (yield: 66%).
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