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Step 2: Synthesis of methyl 2-methylquinoline-6-carboxylate: 2-methyl-6-quinolinecarboxylic acid (3.0 g, 16.20 mmol) was dissolved in methanol (30 mL) at 0°C and concentrated sulfuric acid (3 mL) was added slowly and dropwise. Subsequently, the reaction mixture was warmed to 65°C and stirred continuously for 12 hours. Upon completion of the reaction, the reaction mixture was concentrated under reduced pressure. The concentrated residue was extracted by adding dichloromethane and aqueous sodium carbonate to the concentrated residue. The organic layer was separated, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford methyl 2-methylquinoline-6-carboxylate as a brown solid (1.9 g, 59% yield).