N[C@@H:2]([C@H:6]([O:8][CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)[CH3:7])[C:3]([OH:5])=[O:4].N([O-])=[O:17].[Na+].[OH-].[Na+].C(OCC)(=O)C>S(=O)(=O)(O)O.O>[CH2:9]([O:8][C@H:6]([CH3:7])[C@H:2]([OH:17])[C:3]([OH:5])=[O:4])[C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1To a solution of (2S,3R)-2-amino-3-benzyloxy-butyric acid (1.1 g) in 2M sulfuric acid (6.31 mL) was added dropwise over 2 h a solution of sodium nitrite (0.65 g) in water (6 mL), keeping the internal temperature of the reaction below 0° C. The reaction mixture was stirred at −5° C. for 6 h then allowed to warm to room temperature overnight. The mixture was adjusted to pH 4 with 50% aqueous sodium hydroxide then ethyl acetate was added. The mixture was stirred vigorously and acidified to pH 2 with concentrated sulfuric acid. The layers were separated and the aqueous layer extracted with further ethyl acetate (×2). The combined organic extracts were washed with saturated aqueous sodium chloride, dried (MgSO4), filtered and evaporated to give the subtitle compound as a yellow crystalline solid which was used without further purification. Yield: 0.84 g.
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