[CH2:1]([OH:13])[C@H:2]([OH:12])[C@@H:3]([OH:11])[C@H:4]([OH:10])[C:5]([C:7]([OH:9])=[O:8])=[O:6].OCC([C@H]([C@@H]([C@H](CO)O)O)O)=O.S(=O)(=O)(O)O.[Mn]([O-])(=O)(=O)=O>OC1[C@@H]([C@@H](O)CO)OC(=O)C=1O.CC(C)=O>[O:8]=[C:7]([OH:9])[C@H:5]([C@H:4]([C@@H:3]([C@H:2]([CH2:1][OH:13])[OH:12])[OH:11])[OH:10])[OH:6]2-keto-L-gulonic acid is an important intermediate in vitamin C manufacture. Condensation of L-sorbose with acetone in the presence of sulfuric acid followed by oxidation with permanganate and hydrolysis of the diisopropylidene derivative by boiling yields 2 keto-L-gulonic acid as described in Helv. Chim. Acta., 17, 311 (1934) and U.S. Pat. No. 2,301,811. The preparation of 2-keto-L-gulonic acid by careful oxidation of L-sorbose with nitric acid is claimed in British Pat. No. 443,901 and Dutch Pat. No. 59,584. The selective reduction of 2,5-diketogluconic acid to yield a mixture of 2-ketogluconic acid and 2-ketogulonic acid is described in co-pending application, Ser. No. 749,509 filed Oct. 10, 1976.
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