[OH:1][CH2:2][C@@H:3]([NH:6][C:7](=[O:16])[O:8][CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)[CH2:4][CH3:5].C(N(CC)CC)C.C(O)(=O)CC(CC(O)=O)(C(O)=O)O>CS(C)=O>[CH:2]([C@@H:3]([NH:6][C:7](=[O:16])[O:8][CH2:9][C:10]1[CH:11]=[CH:12][CH:13]=[CH:14][CH:15]=1)[CH2:4][CH3:5])=[O:1]A solution of benzyl [(1S)-1-(hydroxymethyl)propyl]carbamate (30.0 g) in dimethyl sulfoxide (260 mL) was ice-cooled under a nitrogen atmosphere, and triethylamine (56.9 mL) and a solution of sulfur trioxide pyridine complex (71.3 g) in dimethyl sulfoxide (260 mL) was successively added. The mixture was stirred at the same temperature for 1 hr, and at room temperature for 4 hr. A 1 mol/L aqueous citric acid solution (450 mL) was added to the reaction solution, and the mixture was extracted with diethyl ether. The obtained organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate/hexane=0→30%) to give the title compound as a colorless oil (yield: 16.3 g, 55%).
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