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

Participants

Reaction Steps

A mixture of 2-keto-L-gulonic acid (250 g, 1.15 mol, content: 89.6%, water: 8.6%) and trimethylcetylammonium chloride (0.275 g) was stirred in toluene (960 ml), and 36% conc. hydrochloric acid (30.0 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 (30.0 g) in ethylene glycol dimethyl ether (130 g) was added, and the mixture was stirred at the same temperature for 5 hours. Then, about 1200 g of the solvent was distilled away under reduced pressure while continuously introducing toluene (850 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 high performance liquid chromatography (HPLC) showed that the solution contained L-ascorbic acid (191.1 g, yield: 94.1%) and 2-keto-L-gulonic acid (2.7 g, residual ratio: 1.2%).

Provenance & Evidence