Prepn: Jackson, Manske, J. Am. Chem. Soc. 52, 5029 (1930); by heating indole, γ-butyrolactone, and sodium hydroxide, followed by acidification of the product: Fritz, US 3051723 (1962 to Union Carbide); by decarboxylation of 2-carboxyindole-3-butyric acid: Bowman, Islip, Chem. Ind. (London) 1971, 154. Toxicity studies: Anderson et al., Proc. Soc. Exp. Biol. Med. 34, 138 (1936); Pesonen, Acta Endocrinol. 5, 409 (1950). Hypoglycemic effect in rats: Mirsky et al., Endocrinology 59, 715 (1956).