[CH2:1]([O:8][C:9]1[C:10]([C:20]([OH:22])=[O:21])=[C:11]([CH3:19])[C:12]([O:15][CH:16]([CH3:18])[CH3:17])=[N:13][CH:14]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[Si](C=[N+]=[N-])(C)(C)[CH3:24]>C(Cl)Cl.CO>[CH2:1]([O:8][C:9]1[C:10]([C:20]([O:22][CH3:24])=[O:21])=[C:11]([CH3:19])[C:12]([O:15][CH:16]([CH3:18])[CH3:17])=[N:13][CH:14]=1)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1To a solution of 5-(benzyloxy)-3-methyl-2-(propan-2-yloxy)pyridine-4-carboxylic acid (131a, 1.4 g, 4.7 mmol) in dry CH2Cl2 (50 mL) and dry MeOH (5 mL) was added dropwise TMSCHN2 (2.6 mL, 5.1 mmol, 2M in hexane) at 0° C. under N2. The reaction mixture was stirred at room temperature for 2 hours then concentrated under vacuum. The residue was purified by column chromatography (petroleum ether/EtOAc, 10/1) to give methyl 5-(benzyloxy)-3-methyl-2-(propan-2-yloxy)pyridine-4-carboxylate (131b, 1.1 g, 75%) as a colorless oil.
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