beta-D-Galactose pentaacetate → 2,3,4,6-tetra-O-acetyl-D-galactopyranose

Beteiligte Stoffe

Reaktionsschritte

Under nitrogen atmosphere, hydrazine acetate (197 mg, 2.19 mmol, 1.4 equiv) was added to a solution of β-D-galactopyranose pentaacetate (605 mg, 1.55 mmol) in anhydrous THF (10 mL) in presence of 4 Å molecular sieve. The reaction mixture was stirred at room temperature for 4 h 30, filtered, concentrated to dryness under reduced pressure and purified by chromatography on silica gel (25:1, dichloromethane/methanol) to afford 2,3,4,6-tetra-O-acetyl-D-galactopyranose (528 mg, 98%) as a yellow oil which was directly used in the next step. Under nitrogen atmosphere, trichloroacetonitrile (1.34 mL, 13.4 mmol, 8.8 equiv) and potassium carbonate (1.42 g, 10.3 mmol, 6.7 equiv) were added to a solution of 2,3,4,6-tetra-O-acetyl-D-galactopyranose (528 mg, 1.52 mmol) in anhydrous dichloromethane (20 mL) in presence of 4 Å molecular sieve. The reaction mixture was vigourously stirred at room temperature for 12 h, filtered and concentrated to dryness under reduced pressure to afford 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl trichloroacetamidate (707 mg, 95%) which was used without further purification.

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