Acetic Anhydride → allyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-6-O-tolylsulfonyl-alpha-D-mannopyranoside

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Reaction Steps

A solution of allyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-mannopyranoside, prepared as described above, (6.46 g, 16.7 mmol) and methanolic NaOMe (2 mL; 1M solution) in MeOH (100 mL) was stirred for two hours at room temperature, and neutralized by addition of Dowex 50W-X8 [H+]. After the resin was filtered off, the filtrate was concentrated followed by coevaporation with pyridine. A solution of tolylsulfonyl chloride (3.50 g, 18.3 mmol) in pyridine (20 mL) and CH2Cl2 (30 mL) was added dropwise to a cooled solution of the residue in pyridine (30 mL) and CH2Cl2 (50 mL) at 0°-5° C. over 30 minutes, and the mixture was stirred for 10 hours at room temperature then cooled. Acetic anhydride (30 mL) was added to the mixture, and the mixture was stirred for five hours at room temperature. The mixture was concentrated, and the residue was chromatographed on silica gel, with toluene-EtOAc (1:2), to give allyl 2-acetamido-3,4-di-O-acetyl-2-deoxy-6-O-tolylsulfonyl-α-D-mannopyranoside (3.68 g, 44% );

Provenance & Evidence