Prepd from ergosterol: Inhoffen, Ann. 497, 130 (1932); Windaus, Deppe, Ber. 70, 76 (1937); Mosettig, Scheer, J. Org. Chem. 17, 764 (1952). Stereochemistry: Steele et al., J. Am. Chem. Soc. 85, 1134 (1963).