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

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Reaction Steps

A mixture of 2-keto-L-gulonic acid (250 g, content: 89.6%, water: 8.6%) and trimethylcetylammonium chloride (0.275 g) was stirred in a mixed solvent of toluene (960 ml) and acetone (24 ml), and 35% conc. hydrochloric acid (30.0 g) was added. This mixture was stirred at 60° C. for 1 hour, a solution of hydrogen chloride gas (30.0 g) in acetone (116 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 HPLC showed that the solution contained L-ascorbic acid (190.0 g, yield: 93.5%) and 2-keto-L-gulonic acid (2.7 g, residual ratio: 1.2%).

Provenance & Evidence