Isoln from savoy cabbage juice: Procházka, Sanda, Collect. Czech. Chem. Commun. 25, 270 (1960). Prepn from l-ascorbic acid + glucobrassicin: Gmelin, Virtanan, Suom. Kemistil. B 34, 15 (1961), C.A. 55, 17774f (1961); from l-ascorbic acid + gramine methiodide: Procházka, Collect. Czech. Chem. Commun. 28, 544 (1963). Prepn from l-ascorbic acid + 3-hydroxymethylindole; forms two diastereoisomers: ascorbigen A as the main product and ascorbigen B as a minor product: Kiss, Neukom, Helv. Chim. Acta 49, 989 (1966); Kiss, Angew. Chem. 78, 1066 (1966).