[OH:1][C@H:2]1[C@@H:11]([O:12][CH2:13][CH2:14][O:15][CH3:16])[C:10]2[CH:9]=[CH:8][N:7]3[C:17]([CH3:21])=[C:18]([CH3:20])[N:19]=[C:6]3[C:5]=2[NH:4][C@@H:3]1[C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1.[C:28]([O-])(=[O:30])[CH3:29].[Na+].C(OC(=O)C)(=O)C.[OH-].[Na+]>>[C:28]([O:1][C@H:2]1[C@@H:11]([O:12][CH2:13][CH2:14][O:15][CH3:16])[C:10]2[CH:9]=[CH:8][N:7]3[C:17]([CH3:21])=[C:18]([CH3:20])[N:19]=[C:6]3[C:5]=2[NH:4][C@@H:3]1[C:22]1[CH:23]=[CH:24][CH:25]=[CH:26][CH:27]=1)(=[O:30])[CH3:29]A mixture of 1 g of (7S,8R,9R)-8-hydroxy-7-(2-methoxyethoxy)-2,3-dimethyl-9-phenyl-7,8,9,10-tetrahydroimidazo[1,2-h][1,7]naphthyridine, 0.1 g of sodium acetate (anhydrous) and 12 ml of acetic anhydride is stirred vigorously at room temperature for 4 h, then poured onto ice water, neutralized with 2 molar aqueous sodium hydroxide solution and extracted three times with 50 ml of ethyl acetate each time, the collected organic extracts are dried over potassium carbonate, the solvent is stripped off in vacuo and the residue is well dried in a high vacuum. 0.9 g of the title compound is obtained.
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