[CH3:1][O:2][CH:3]([O:23][CH3:24])[CH2:4][N:5]1[CH:10]=[CH:9][C:8](=[O:11])[C:7]([O:12][CH2:13][C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[C:6]1[C:20]([OH:22])=[O:21].[C:25]([O-])(O)=O.[Na+].CI>CN(C=O)C.CC(OC)(C)C.CCOC(C)=O>[CH3:24][O:23][CH:3]([O:2][CH3:1])[CH2:4][N:5]1[CH:10]=[CH:9][C:8](=[O:11])[C:7]([O:12][CH2:13][C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[C:6]1[C:20]([O:22][CH3:25])=[O:21]Crude 1-[2,2-bis(methyloxy)ethyl]-4-oxo-3-[(phenylmethyl)oxy]-1,4-dihydro-2-pyridinecarboxylic acid 22 obtained as above was dissolved in DMF (500 mL). To this solution was added NaHCO3(50.5 g, 0.6 mole). The suspension was stirred vigorously with a mechanic stirrer while CH3I in TBME (2.0M, 300 mL) was introduced by addition funnel over 30 minutes. After addition, the reaction was stirred overnight at room temperature. The reaction mixture was then diluted with EtOAc (˜1.5 L) and washed with water and brine. The organic layer was dried over anhydrous Na2SO4. Evaporation of solvents gave methyl 1-[2,2-bis(methyloxy)ethyl]-4-oxo-3-[(phenylmethyl)oxy]-1,4-dihydro-2-pyridinecarboxylate 23 as brown oil, which was used directly for the next step.
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