[N-:1]=[N+:2]=[N-:3].[Na+].[CH2:5]([O:12][CH2:13][C@@H:14](OS(C)(=O)=O)[C@@H:15]1[CH2:19][C@@H:18]([CH3:20])[C:17](=[O:21])[O:16]1)[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1>CN1C(=O)N(C)CCC1>[N:1]([C@H:14]([C@H:15]1[O:16][C:17](=[O:21])[C@H:18]([CH3:20])[CH2:19]1)[CH2:13][O:12][CH2:5][C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1)=[N+:2]=[N-:3]2.93 g of sodium azide (45.1 mmol) was added to a solution of 9.90 g of methanesulfonic acid (R)-2-benzyloxy-1-[(2S,4R)-4-methyl-5-oxotetrahydrofuran-2-yl]ethyl ester obtained in Example (76d) (30.1 mmol) in N,N′-dimethylpropyleneurea (100 ml) at room temperature, and the mixture was stirred at 60° C. for three days. The reaction mixture was cooled and then poured into ice water, followed by extraction with diethyl ether. Then, the organic layer was washed with water and brine and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (elution solvent:n-hexane/ethyl acetate=5/1) to obtain 7.56 g of the title compound (yield: 91%).
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