From ergosterol or lumisterol by ultraviolet irradiation: Windaus et al., Ann. 492, 226 (1932); Ann. 499, 188 (1932); Dimroth, Ber. 70, 1631 (1937). From calciferol by adsorption on acid clay: Thibaudet, Compt. Rend. 220, 751 (1945). From precalciferol: Velluz, Goffinet, US 2847426 (l958 to UCLAF). Structure: Grundmann, Z. Physiol. Chem. 252, 151 (1938); Thibaudet, loc. cit. Stereochemistry of the tachysterol system: Inhoffen, Ber. 88, 1424 (1955); Verloop, Rec. Trav. Chim. 76, 689 (1957); Delaroff et al., Bull. Soc. Chim. Fr. 1963, l739.