Hydrazine, acetate (1:1) → 6-O-acetyl-2,3-di-O-benzoyl-4-chloro-4-deoxy-D-galactopyranose

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Reaction Steps

A solution of acetyl 6-O-acetyl-2,3-di-O-benzoyl-4-chloro-4-deoxy-D-galactopyranoside (68) (8.53 g, 17.4 mmol) and hydrazine acetate (2.4 g, 26.0 mmol, 1.5 eq) in 70 mL of DMF was stirred for 1 hour at room temperature. The reaction mixture was then evaporated, washed with water (5 times) and evaporated. The residue was chromatographed on a silica gel, eluting with hexane-ethyl acetate (2:1), to provide 6-O-acetyl-2,3-di-O-benzoyl-4-chloro-4-deoxy-D-galactopyranose (7.44 g, 95.3%). This material was dissolved in dichloromethane (50 mL) and the resulting solution was cooled to 0° C. Trichloroacetonitrile (8.3 mL, 82.9 mmol) was added and the mixture was stirred for 2 hours. The solvent was then evaporated and the residue was chromatographed on a silica gel column, eluting with hexane-ethyl acetate (3:1), to give imidate 69 (6.3 g, 64%).

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