Mannitol → 1,2:5,6-di-O-isopropylidene-D-mannitol

Participants

Reaction Steps

To a stirring suspension of D-Mannitol (1.82 g, 10.0 mmol) in tetrahydrofuran (21 mL) and dimethylformamide (9 mL) was added p-toluenesulfonic acid monohydrate (0.02 g, 0.1 mmol,) at ambient temperature, followed by 2,2-dimethoxypropane (2.8 mL, 0.023 mol). The reaction mixture was stirred for 18 hours at room temperature, then additional 2,2-dimethoxypropane (0.3 mL, 2.4 mmol) was added. The suspension was heated to 40° C. to 45° C., and stirred for 2 hours. Sodium bicarbonate (1.8 g, 0.016 mol) was added to neutralize the acid and the mixture was stirred for 30 minutes. The excess Na2CO3 was filtered and washed with tetrahydrofuran (5 mL). The filtrate was concentrated. To the remaining light yellow oil was added toluene (15 mL) and the mixture was stirred at 3° C. to 5° C. until a light-yellow gelatinous solid formed. The solid was filtered and washed with hexane (2×5 mL). The product was dried in a vacuum oven for 18 hours to give 1,2:5,6-di-O-isopropylidene-D-mannitol (1.24 g, 47.3%) as an off-white solid, mp 110–113° C.

Provenance & Evidence