To a stirred solution of acetic acid (2R,3R,4R,5S)-3,4,5-triacetoxy-6-[4-bromo-3-(2,3-dihydro-benzo[1,4]dioxin-6-ylmethyl)-phenyl]-tetrahydro-pyran-2-ylmethyl ester (Intermediate 1, 10.0 g, 15.74 mmol) in toluene (200 mL) was added tricyclohexylphosphine (1.76 g, 6.29 mmol), a solution of potassium phosphate tribasic (13.3 g, 62.9 mmol) in water (15 mL), and ethylboronic acid (3.4 g, 47.2 mmol). The reaction mixture was degassed for 45 min then palladium (II) acetate (529 mg, 2.3 mmol) was added. After refluxing overnight, the reaction mixture was cooled to room temperature, and water was added. The resulting mixture was extracted with ethyl acetate, (2×200 mL), washed with water and brine, then dried over sodium sulfate, concentrated and purified by column chromatography to furnish acetic acid (2R,3R,4R,5S)-3,4,5-triacetoxy-6-[3-(2,3-dihydro-benzo[1,4]dioxin-6-ylmethyl)-4-ethyl-phenyl]-tetrahydro-pyran-2-ylmethyl ester (5.4 g).
