To a solution of (5-Bromo-2-chlorobenzyloxy)triisopropylsilane (compound 4, 97 g, 257 mmol) from Step 3 in tetrahydrofuran (1 L) at −78° C. under an atmosphere of nitrogen was added dropwise n-butyllithium (2.5 M in hexanes, 103 mL, 257 mmol), and the mixture was stirred for 1.5 h at the same temperature. Then a solution of 2,3,4,6-tetra-O-benzyl-D-glucopyranone (compound 2, 106 g, 198 mmol) from Step 1 in tetrahydrofuran (500 mL) was added dropwise, and the mixture was stirred for 3 h at the same temperature. The reaction mixture was quenched by addition of saturated ammonium chloride solution. After complete addition, the solution was gradually raised to room temperature. The organic layer was separated and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with brine, dried over magnesium sulfate, filtered and concentrated in vacuo to yield the title compound as a yellow oil which was used without further purification.
