[NH2:1][C:2]1[CH:14]=[CH:13][C:5]([CH2:6][C@H:7]2[CH2:11][O:10][C:9](=[O:12])[NH:8]2)=[CH:4][CH:3]=1.[N:15]([O-])=O.[Na+]>Cl>[NH:1]([C:2]1[CH:14]=[CH:13][C:5]([CH2:6][C@H:7]2[CH2:11][O:10][C:9](=[O:12])[NH:8]2)=[CH:4][CH:3]=1)[NH2:15]In an embodiment, (S)-4-(4-aminobenzyl)-1,3-oxazolidin-2-one of formula (II), which was prepared using prior art methods was treated with an aqueous solution of sodium nitrite in concentrated hydrochloric acid at −5 to 10° C. After completion of reaction based on HPLC, the resulting diazonium salt was treated with stannous chloride in hydrochloric acid at −15 to 10° C. to give (S)-4-(4-hydrazinobenzyl)-1,3-oxazolidin-2-one of formula (III).
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