C([O:3][C:4](=[O:21])[CH:5]([CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)[CH2:6][S:7]([C:10]([CH3:13])([CH3:12])[CH3:11])(=[O:9])=[O:8])C.O.[OH-].[K+].Cl>C1COCC1>[CH2:14]([CH:5]([CH2:6][S:7]([C:10]([CH3:13])([CH3:12])[CH3:11])(=[O:9])=[O:8])[C:4]([OH:21])=[O:3])[C:15]1[CH:16]=[CH:17][CH:18]=[CH:19][CH:20]=1550 mg of 2-benzyl-3-tert.-butylsulphonyl-propionic acid ethyl ester are dissolved in 8 ml of THF and then reacted with 5 ml of water and 0.88 ml of 2N potassium hydroxide solution. The mixture is stirred overnight at room temperature, neutralised with 0.88 ml of 2N hydrochloric acid and concentrated by evaporation. The residue is purified by flash chromatography on 30 g of silica gel 60 (eluant H). Yellow oil; m/e 284; 1H-NMR (DMSO-d6): 1.27 ppm (s, 9H); 2.73-3.1 (m, 4H); 3.2-3.5 (m, 1H); 7.2-7.4 (m, 5H); 12.5 (s, 1H).
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