The core steroid from which all others are derived by biological modification. From wool fat of sheep: Windaus, Tschesche, Z. Physiol. Chem. 190, 51 (1930). Identity with kryptosterol: Ruzicka et al., Helv. Chim. Acta 28, 759 (1945). Structure: Voser et al., ibid. 35, 2414 (1952); Barnes et al., J. Chem. Soc. 1953, 571. Stereochemistry: eidem, ibid. 1953, 576. Prepn from isocholesterol: Bloch, Urech, Biochem. Prep. 6, 32 (1958). Prepn by cyclization of squalene: Cornforth et al., Ciba Found. Symp. Terpenes Sterols 1958, 119; van Tamelen et al., J. Am. Chem. Soc. 88, 4752 (1966). Mechanism of the squalene to lanosterol conversion: eidem, ibid. 104, 6479, 6480 (1982).