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(c) Synthesis of methyl 2-amino-3-methoxybenzoate: To a solution of 2-amino-3-methoxybenzoic acid (34.5 g, 206 mmol) in methanol (250 mL) was slowly added concentrated sulfuric acid (50 mL). The reaction mixture was heated to 95 °C and kept reacting overnight. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently concentrated under vacuum. The resulting residue was a beige-colored slurry, which was mixed with ether and slowly poured into a mixture of ether and a cold saturated aqueous sodium carbonate solution containing an excess of sodium carbonate. The ether layer is separated and the aqueous layer is extracted twice more with ether. The ether extracts were combined, washed sequentially with dilute sodium hydroxide solution (twice), brine, dried with anhydrous sodium sulfate, filtered through a short silica gel column, and finally concentrated in vacuum to give methyl 2-amino-3-methoxybenzoate (34.0 g, 91% yield) as a brown solid.LC-MS (ES) m/z = 182 [M + H]+.