[CH3:1][O:2][NH2:3].C([O-])(=O)C.[Na+].S([O-])([O-])(=O)=O.[Mg+2].[CH3:15][O:16]/[N:17]=[C:18](/[C:22]1([CH3:28])[O:27][CH2:26][CH2:25][CH2:24][O:23]1)\[C:19](=O)[CH3:20].[OH-].[Na+]>CO.O>[CH3:15][O:16][N:17]=[C:18]([C:22]1([CH3:28])[O:27][CH2:26][CH2:25][CH2:24][O:23]1)[C:19](=[N:3][O:2][CH3:1])[CH3:20]239 g (0.4 mol) of 14% strength methanolic methoxyamine solution, 50 g (0.6 mol) of sodium acetate (anhydrous), dissolved in 250 ml of methanol, 75 g of magnesium sulfate and 92 g of the ketal (Example 3), dissolved in 100 ml of methanol, were initially charged at room temperature. The pH meter showed a value of 6. The mixture was stirred for 10 minutes, during which the pH decreased to 5.2, and a pH of 4.2 was set by dropwise addition of sodium acetate. The mixture was stirred at room temperature for another 20 hours and the conversion was monitored by HPLC. 7% of starting material was left. After a further 4 hours of stirring, the reaction mixture was neutralized using dilute aqueous sodium hydroxide solution and diluted with water. The mixture was extracted with methyl tert-butyl ether. The combined organic phases were washed with dilute ammonium chloride solution, dried over magnesium sulfate and concentrated. This gave 92 g (89% yield) of the title compound.
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