(2-(Trimethylsilyl)ethoxymethyl chloride (SEM-Cl, 3.10 mL, 17.5 mmol) was added to a mixture of methyl 3-(benzyloxy)-4-bromo-5-hydroxybenzoate (Example 22-1 Step 1, 5.36 g, 15.9 mmol) and potassium carbonate (5.49 g, 39.7 mmol) in DMF (53.0 mL), and the mixture was allowed to stir at room temperature for two days. An additional portion of SEM-Cl (3.10 mL, 17.5 mmol) was added and the mixture stirred an additional 4 hours. The reaction mixture was partitioned between saturated sodium bicarbonate and 1:1 ethyl acetate/diethyl ether. The organic phase was washed with water (5×), brine, dried over MgSO4, and concentrated to a light orange oil. The crude product was dissolved into 2:1 tetrahydrofuran/methanol (100 mL) and aqueous sodium hydroxide solution (2.0 M, 63.6 mL, 127 mmol) was added. The solution was stirred for 1 hour after which time volatiles were removed via rotary evaporation. The remaining solution was acidified to pH 3 by slow addition of concentrated hydrochloric acid, extracted with dichloromethane (1×), then with 1:1 ether/ethyl acetate (4×). The combined extracts were washed with brine, dried over MgSO4 and concentrated to a solid. The crude product was triturated with heptane and dried under vacuum to provide 3-(benzyloxy)-4-bromo-5-((2-(trimethylsilyl)ethoxy)methoxy)benzoic acid (6.36 g) as a white solid. MS (M+1)=453.4. 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 7.28-7.59 (m, 7H) 5.36 (s, 2H) 5.18-5.28 (m, 2H) 3.75-3.90 (m, 2H) 0.92-1.03 (m, 2H) 0.00 (s, 9H).
