2-keto-L-Gulonic acid → L-Ascorbic Acid

Participants

Reaction Steps

A mixture of 2-keto-L-gulonic acid (125 g, 0.579 mol, content: 89.9%, water: 8.7%) and trimethylcetylammonium chloride (0.137 g) was stirred in toluene (240 ml) and diisopropyl ether (170 ml), and 36% conc. hydrochloric acid (15.6 g) was added. At this time, the amount of water in the reaction system was calculated as 2.0 mol per mol of 2-keto-L-gulonic acid. This mixture was stirred at 60° C. for 1 hour, a solution of hydrogen chloride gas (15.5 g) in diisopropyl ether (70 ml) was added, and the mixture was stirred at the same temperature for 5 hours. Then, about 500 g of the solvent was distilled away under reduced pressure while continuously introducing toluene (720 ml). The residue was filtered to give crude crystals of L-ascorbic acid. The crude crystals were dissolved in water. Quantitative analysis of the solution by HPLC showed that the solution contained L-ascorbic acid (93.8 g, yield: 92.0%) and 2-keto-L-gulonic acid (0.3 g, residual ratio: 0.3%).

Provenance & Evidence