C) Synthesis of 3,4-dibenzyloxybenzoic acid: Sodium hydroxide (1.2 g) was dissolved in methanol (100 mL) to prepare a methanolic solution of sodium hydroxide. This solution was added to a solution of methanol (50 mL) containing methyl 3,4-dibenzyloxybenzoate (4.64 g), and the reaction mixture was heated under reflux for 4 hours. After completion of the reaction, the methanol was evaporated under reduced pressure. The residue was dissolved in water (100 mL) and the aqueous layer was washed with ethyl acetate (2 x 50 mL). Subsequently, the aqueous layer was acidified to pH 2 with 2N hydrochloric acid, whereupon 3,4-dibenzyloxybenzoic acid precipitated as a precipitate. The precipitate was collected by filtration and dried under vacuum to give 2.4 g of 3,4-dibenzyloxybenzoic acid in 74% yield. The product was characterized by 1H NMR (CDCl3): δ 7.7 (2H, br s), 7.27-7.5 (10H, m), 6.98 (1H, d, J=8 Hz), 5.26 (2H, s), 5.22 (2H, s).
