Acetic Anhydride → Tri-O-acetyl-D-glucal

Participants

Reaction Steps

The procedure used to synthesize hexa-O-acetyl maltal (not commercially available) is described below. This procedure has the advantage of using the same solvent for the entire workup. Maltose monohydrate (1.000 g 90% maltose, 10% glucose and maltatriose) was suspended in a solution of acetic acid (10 mL) and acetic anhydride (2.833 g, 10.0 equiv) and 1.000 g 31% HBr/acetic acid solution added. The reaction mixture was allowed to stir for 1 h, after which 9.000 g more 31% HBr/acetic acid solution was added and allowed to stir overnight. The reaction mixture was then poured into a suspension containing pulverized CuSO4 ·5H2O (0.182 g), zinc (7.290 g), water (10 mL), sodium acetate (5.470 g), and acetic acid (5 mL) and the resultant reaction mixture was stirred vigorously for 1.5 h. The solution was then filtered and the solid washed with ethyl acetate (100 mL) and water (100 mL). The organic layer of the filtrate was then washed with NaHCO3 (100 mL) and brine (50 mL), dried (Na2SO4), filtered and the solvent removed under reduced pressure to provide a colorless oil which was purified by silica gel chromatography (50% ethyl acetate/hexanes) to give hexa-O-acetyl-maltal (1.210 g, 86%) as a colorless solid and tri-O-acetyl-D-glucal (0.132 g, 88%) as a colorless oil. Regarding the maltose starting material, a more pure commercial sample would be preferred, obviating the need for the aforementioned chromatographic separation.

Provenance & Evidence