<p>6-O-(2-keto-L-gulonoyl)-L-ascorbate substantially free from 2-keto-L-gulonic acid is produced by allowing an acid to act on 2-keto-L-gulonic acid in an inert organic solvent and recovering 6-O-(2-keto-L-gulonoyl)-L-ascorbate from the reaction mixture. 6-O-(2-keto-L-gulonoyl)-L-ascorbate is more fat-soluble than L-ascorbic acid and is expected of the use as a prodrug for L-ascorbic acid that can be absorbed from the intestinal tract.</p>
