1: 2-Amino-5-hydroxy-benzoic acid; acetic anhydride Heating; 2: 3.4-diacetoxybenzaldehyde With toluene-4-sulfonic acid in toluene Heating; 3: With sodium salt of phosphorous acid Heating;

methanol; potassium hydroxide; dicyclohexyl-carbodiimide 1.) pyridine, 24 h, 3.) room temperature, 24 h; Yield given. Multistep reaction;

base hydrolysis;