The above-obtained 2-(benzyloxymethyl)-4,6-bis(methoxymethoxy)benzaldehyde (0.80 g, 2.3 mmol) was dissolved in tert-butyl alcohol (20 mL) and the obtained solution was added with 2-methyl-2-butene (10 mL, 94 mmol), sodium chlorite (2.0 g, 22 mmol), sodium dihydrogen phosphate (2.0 g, 17 mmol) and water (5 mL), followed by stirring at a room temperature for 10 hours. The reaction mixture was extracted with chloroform 3 times. The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate. Then the solvent was evaporated under reduced pressure to obtain 2-(benzyloxymethyl)-4,6-bis(methoxymethoxy)benzoic acid (0.94 g, 100%).
