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

Participants

Reaction Steps

A mixture of 2-keto-L-gulonic acid (125 g, 0.584 mol, content: 90.7%, water: 8.5%) and trimethylcetylammonium chloride (0.084 g) was stirred in diisopropyl ether (500 ml), and 36% conc. hydrochloric acid (18.0 g) was added. At this time, the amount of water in the reaction system was calculated as 2.1 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 (17.2 g) in diisopropyl ether (88 g) was added, and the mixture was stirred at the same temperature for 5 hours. Then, about 900 g of the solvent was distilled away under reduced pressure while continuously introducing diisopropyl ether (1000 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 (95.8 g, yield: 93.1%) and 2-keto-L-gulonic acid (0.9 g, residual ratio: 0.8%). Quantitative analysis of diisopropyl ether in the distillate and filtrate showed that the recovery ratio was not less than 99%.

Provenance & Evidence