[CH3:1][O:2][C:3]([C:5]1[C:10]([CH:11](OC)[O:12]C)=[CH:9][CH:8]=[CH:7][N:6]=1)=[O:4].C1(C)C=CC(S(O)(=O)=O)=CC=1.C(=O)(O)[O-].[Na+]>O1CCOCC1.O>[CH3:1][O:2][C:3]([C:5]1[C:10]([CH:11]=[O:12])=[CH:9][CH:8]=[CH:7][N:6]=1)=[O:4]To a solution of 3-(dimethoxymethyl)-2-pyridinecarboxylic acid methyl ester (1.02 g) in dioxane (20 mL) was added water (20 mL), followed by p-toluenesulfonic acid (0.30 g). This solution was heated at 55°-60° C. for 24 hours. The reaction mixture was cooled, diluted with water (50 mL), treated with aqueous saturated sodium bicarbonate until the pH was 7.5-8.0, and extracted with methylene chloride (3×). The combined organic extracts were washed with dilute brine (3×), dried (K2CO3) and evaporated to afford a light yellow solid which yielded 540 mg (62.5%) of an almost pure product.
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