title: The preparation of (1alpha,3beta)-3-hydroxycholestane-4,6-diene- 1,25-diol diacetate from a 5,7-diene precursor: a new method for the synthesis of heteroannular dienes.
abstract: Starting from the 7alpha-bromide 5a, a regioselective synthesis of (1alpha,3beta)-3-hydroxycholestane-4,6-diene-1,25-diol diacetate (2) is described. The preparative removal of contaminating 5,7-diene 9 was accomplished by the formation of the corresponding Diels-Alder adduct 11. Acetylation of the diacetate 2 followed by acid-catalyzed elimination and rearrangement yielded styrene 13.
authors.affiliation: Pharmaceutical Process Development, Hoffmann-La Roche, 340 Kingsland Avenue, Nutley, New Jersey 07110, USA. svanarnum@rcsb.rutgers.edu
authors.forename: Susan D
authors.initials: SD
authors.lastname: Van Arnum
authors.forename: Barry K
authors.initials: BK
authors.lastname: Carpenter
authors.forename: David R
authors.initials: DR
authors.lastname: Parrish
authors.forename: Archibald
authors.initials: A
authors.lastname: MacIntrye