[C:1]([O:5][C:6](=[O:22])[CH2:7][C:8]([C:12]1[CH:17]=[CH:16][N:15]=[C:14]([O:18]C)[C:13]=1[O:20][CH3:21])([OH:11])[CH2:9][CH3:10])([CH3:4])([CH3:3])[CH3:2].[I-].[K+]>C(O)(=O)C>[C:1]([O:5][C:6](=[O:22])[CH2:7][C:8]([OH:11])([C:12]1[CH:17]=[CH:16][NH:15][C:14](=[O:18])[C:13]=1[O:20][CH3:21])[CH2:9][CH3:10])([CH3:3])([CH3:2])[CH3:4]The mixture of 3-(2,3-dimethoxy-pyridin-4-yl)-3-hydroxy-pentanoic acid tert-butyl ester (6) (3.6 g; 11.56 mmol) and potassium iodide (8 g) in acetic acid (10 mL) was stirred at 60° C. for 16 hours. Reaction was checked by TLC and was not completed. The mixture was then heated at 73° C. for 2 days. The acetic acid was removed by evaporation under reduced pressure and dichloromethane (50 mL) was added. The solution was then washed with saturated sodium bicarbonate solution, dried over sodium sulfate and concentrated under reduced pressure. Purification by column chromatograph over silica gel (10 to 50% ethyl acetate/hexanes) provided 1.9 g of the ester, 3-hydroxy-3-(3-methoxy-2-oxo-1,2-dihydro-pyridin-4-yl)-pentanoic acid tert-butyl ester (7), as a white solid.
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