title: Chemoselective reduction of 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione by various hydride reagents.
abstract: The chemoselectivity of rigid cyclic alpha,beta-unsaturated carbonyl group on the reducing agents was influenced by the ring size and steric factor. Cholesterol (cholest-5-en-3beta-ol) and dehydroepiandrosterone (DHEA) were oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to form 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione. They were reduced with NaBH(4), lithium tri-sec-butylborohydride (l-Selectride), LiAlH(4), 9-borabicyclo[3.3.1]nonane (9-BBN), lithium triethylborohydride (Super-hydride), and BH(3) x (CH(3))(2)S in various conditions, respectively. Reduction of 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione by NaBH(4) (4 equiv.) produced 4,6-cholestadien-3beta-ol and 4,6-androstadiene-3beta,17beta-diol, respectively. Reduction by l-Selectride (12 equiv.) afforded 4,6-cholestadien-3alpha-ol and 4,6-androstadiene-3alpha,17beta-diol, chemoselectively. Reaction with Super-hydride (12 equiv.) produced 4,6-cholestadien-3-one and 3-oxo-4,6-androstadien-17beta-ol. Reduction of 1,4,6-cholestatrien-3-one by 9-BBN (14 equiv.) produced 1,4,6-cholestatrien-3alpha-ol, but 1,4,6-androstatriene-3,17-dione was not reacted with 9-BBN in the reaction conditions. Reaction of LiAlH(4) (6 equiv.) formed 4,6-cholestadien-3beta-ol and 3-oxo-1,4,6-androstatrien-17beta-ol. Reduction of 1,4,6-cholestatrien-3-one by BH(3) x (CH(3))(2)S (11 equiv.) gave cholestane as major compound and unlike reactivity of cholesterol, 1,4,6-androstatriene-3,17-dione by 8 equiv. of BH(3) x (CH(3))(2)S formed 3-oxo-1,4,6-androstatrien-17beta-ol. LiAlH(4) and BH(3) x (CH(3))(2)S showed relatively low chemoselectivity.
authors.affiliation: College of Pharmacy, Catholic University of Daegu, 330 Geumrak 1 ri, Hayang-eup, Gyongsan-si Gyongbook 712-702, Republic of Korea.
authors.forename: Eunjeong
authors.initials: E
authors.lastname: Kim
authors.forename: Eunsook
authors.initials: E
authors.lastname: Ma
mesh_terms: D000733:Androstatrienes / Q000737:chemistry*; D001671:Biochemistry / Q000379:methods*; D002782:Cholestenes / Q000737:chemistry; D002783:Cholestenones / Q000138:chemical synthesis*; D007202:Indicators and Reagents / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared
chemical_list: C520757:1,4,6-cholestatrien-3-one; D000733:Androstatrienes; D002782:Cholestenes; D002783:Cholestenones; D007202:Indicators and Reagents; C011658:androsta-1,4,6-triene-3,17-dione