反应详情

A solution of ManNAc (5.0 g, 2.6 mmol), Ac2O (10 mL) and pyridine (20 mL) was stirred for 10 hours at room temperature, and the mixture was concentrated, followed by coevaporation with toluene. A solution of the residue, benzyl alcohol (20 mL), BF3.OEt2 (1.6 g, 11.3 mmol) in CH3NO2 (150 mL) was gently refluxed for 2.5 hours. After cooling, the mixture was concentrated. The residue was chromatographed on silica gel, with toluene-EtOAc (1:2). The isolated benzyl 2-acetamido-4,5,6-tri-O-acetyl-2-deoxy-a-D-mannopyranoside and 0.15 g of NaOMe was dissolved in MeOH (100 mL) and the solution was stirred for 30 minutes 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 dimethylphosphinic chloride (1 g, 8.8 mmol) in DMF was added to a cold solution of benzyl 2-acetamido-2-deoxy-a-D-mannopyranoside (0.50 g, 1.6 mmol), 2,6-lutidine (0.34 g, 3.2 mmol) in anhydrous DMF (30 mL) in a dry ice-acetone bath, and the reaction was allowed to slowly warm to room temperature. The reaction was monitered by TLC with (1M NH4OAc/2-proponal/EtOAc, 1/2.4/3.4). After 10 hours, the reaction mixture was directly applied to silica gel chromatography, eluted with CHCl3 /EtOAc/MeOH (5/2/1) to give benzyl 2-acetamido-2-deoxy-6-(dimethyl-phosphinyl)-a-D-mannopyranoside (56 percent yield).

1. concentrationthe mixture was concentrated
2. temperatureAfter cooling
3. concentrationthe mixture was concentrated
4. customThe residue was chromatographed on silica gel, with toluene-EtOAc (1:2)
5. dissolutionThe isolated benzyl 2-acetamido-4,5,6-tri-O-acetyl-2-deoxy-a-D-mannopyranoside and 0.15 g of NaOMe was dissolved in MeOH (100 mL)
6. additionneutralized by addition of Dowex 50W-X8 (H+)
7. filtrationAfter the resin was filtered off
8. concentrationthe filtrate was concentrated
9. temperatureto slowly warm to room temperature
10. waitAfter 10 hours
11. washeluted with CHCl3 /EtOAc/MeOH (5/2/1)