L-(-)-Sorbose → alpha-L-Sorbofuranose, 2,3:4,6-bis-o-(1-methylethylidene)-

Participants

Reaction Conditions

Reaction Steps

A mixture of 20 g (111 millimoles) of L-sorbose, 200 μl (2.3 millimoles) of trifluoromethanesulfonic acid (TFMSA) and 400 ml of acetone (H2O content 0.1%) was refluxed for 4.5 hours. 40 g of a molecular sieve (3 Å) were present in a Soxhlet extractor between the reaction flask and the reflux condenser. When the reaction was complete, the reaction mixture was cooled to -10° C. and 10 ml of aqueous NaHCO3 solution were added. Thereafter, the acetone was distilled off under reduced pressure, the residue was taken up in 35 ml of H2O and the solution was extracted with 3 times 110 ml of toluene at 70° C. The combined toluene phases were washed with 7.5 ml of H2O and dried over Na2SO4, and the toluene was distilled off under reduced pressure to give 24.7 g (85.5%) of 2,3:4,6-di-O-isopropylidene-α-L-sorbofuranose (DAS). After the product had been recrystallized from toluene, its melting point was measured as 78°-79° C.

Provenance & Evidence