N[C:2]1[NH:3][C:4](=[O:21])[C:5]2[S:10][C:9](=[O:11])[N:8]([C@@H:12]3[O:18][C@H:17]([CH2:19][OH:20])[C@@H:15]([OH:16])[C@H:13]3[OH:14])[C:6]=2[N:7]=1.N([O-])=[O:23].[Na+]>C(O)(=O)C.O>[C@@H:12]1([N:8]2[C:6]3[NH:7][C:2](=[O:23])[NH:3][C:4](=[O:21])[C:5]=3[S:10][C:9]2=[O:11])[O:18][C@H:17]([CH2:19][OH:20])[C@@H:15]([OH:16])[C@H:13]1[OH:14]To a suspension of 7 (0.76 g, 2.4 mmol) in glacial acetic acid (150 mL) was added dropwise a solution of sodium nitrite (1.5 g, 21.7 mmol) in water (15 mL) with stirring. After 30 min the suspension became clear and stirring was continued at room temperature overnight. The white solid which had separated was filtered, washed with cold water and dried. Recrystallization from hot water gave fine colorless crystals of 8: yield 0.3 g, 40%: mp 250° C. dec.: UV λmax (pH 1) 293 nm (ε5500): UV λmax (pH 7) 212 nm (ε14200), 301 (6100): UV λmax (pH 11) 204 nm (ε21900), 301 (5600). Anal. Calcd. for C10H11N3O7S: C, 37.86: H, 3.49: N, 13.24: S, 10.10. Found: C, 37.81: H, 3.42: N, 13.01: S, 10.01.
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