Dichloromethane → 2,3,4-tri-O-acetyl-6-chloro-6-deoxy-alpha-D-galactopyranose

Beteiligte Stoffe

Reaktionsschritte

To a solution of tetra-O-acetyl-6-chloro-6-deoxy-D-galactopyranose (compound 54) (6.36 g, 17.3 mmol) in DMF (60 mL) was added hydrazine acetate (2.4 g, 26.0 mmol). The mixture was stirred for 1 hour at room temperature and then 1 L of dichloromethane was added and the resulting solution washed 4 times with water. The organic layer was dried over anhydrous sodium sulfate and evaporated. Flash column chromatography using hexane-ethyl acetate (1:1) as the eluent gave 2,3,4-tri-O-acetyl-6-chloro-6-deoxy-α-D-galactopyranose (5.79 g). This material was dissolved in 50 mL of dichloromethane and cooled to 0° C. Trichloroacetonitrile (8.93 mL, 89.2 mmol) was added followed by DBU (1.33 mL, 8.9 mmol). This solution was stirred for 1.5 hours and then evaporated. The residue was chromatographed on a silica gel column, eluting with hexane-ethyl acetate (2:1), to provide compound 55 (4.1 g, 51%) as a foam.

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