Prepd by ozonolysis of vitamin D3, q.v. Preparative method: A. Windaus, W. Grundmann, Ann. 524, 295 (1936). Prepn: H. H. Inhoffen et al., Ber. 90, 664 (1957). Synthetic applications: H. Nemoto et al., J. Org. Chem. 51, 5311 (1986); P. Bovicelli et al., ibid. 57, 5052 (1992); M. C. Clasby, D. Craig, Synth. Commun. 24, 481 (1994); R. R. Sicinski, H. F. DeLuca, Bioorg. Med. Chem. Lett. 5, 159 (1995); W. H. Okamura et al., J. Org. Chem. 67, 1637 (2002).