title: Stereoselective reduction of C-2 substituted steroid C-3 ketones with lithium tris-(R,S-1,2-dimethylpropyl)-borohydride and sodium borohydride.
abstract: The effect of C-2 substitution on the stereoselective reduction of steroid C-3 ketones with lithium tris-(R,S-1,2-dimethylpropyl)-borohydride and sodium borohydride was investigated. The C-2 mono- and di-substituted chloro and methyl derivatives were predominantly reduced to one of the epimeric alcohols. The 2 alpha-chloro and 2 alpha-methyl derivatives of 17 beta-acetoxy-5 alpha-androstan-3-one undergo stereoselective reduction with lithium tris-(R,S-1,2-dimethylpropyl)-borohydride to the axial (3 alpha) alcohol as observed in the unsubstituted compound, whereas sodium borohydride gives predominantly the equatorial (3 beta) alcohol. The 2 beta-chloro, 2 beta-methyl, 2,2-dichloro, and 2,2-dimethyl derivatives are reduced predominantly to the equatorial (3 beta) alcohol by both reagents.
authors.affiliation: Faculty of Pharmacy, University of Manitoba, Winnipeg, Canada.
authors.forename: J F
authors.initials: JF
authors.lastname: Templeton
authors.forename: V P
authors.initials: VP
authors.lastname: Kumar
authors.forename: R K
authors.initials: RK
authors.lastname: Gupta
authors.forename: A M
authors.initials: AM
authors.lastname: Friesen
mesh_terms: D001894:Borohydrides / Q000032:analysis*; D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D008094:Lithium / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D013256:Steroids / Q000032:analysis*
chemical_list: D001894:Borohydrides; D013256:Steroids; C025364:sodium borohydride; D008094:Lithium