A normal mammalian metabolite of cortisone: Schneider, J. Biol. Chem. 183, 365 (1950). Prepn by microbial reduction using a Streptomyces sp.: Barkemeyer et al., Appl. Microbiol. 8, 237 (1960). Prepn of the triacetate: GB 737291 (1955 to Merck & Co.). Prepn of the 21-acetate: Julian et al., US 2752339 (1956 to Glidden).