title: A facile synthesis of C-24 and C-25 oxysterols by in situ generated ethyl(trifluoromethyl)dioxirane.
abstract: Experiments were performed to compare the regioselective hydroxylation of the isopropyl C-H bond at C-25 in 5alpha-cholestan-3beta-yl acetate by in situ generated dimethyldioxirane, methyl(trifluoromethyl)dioxirane, hexafluoro(dimethyl)dioxirane or ethyl(trifluoromethyl)dioxirane (ETDO). The dioxiranes were generated from the corresponding ketones and potassium peroxymonosulfate in aq. NaHCO(3), pH 7.5-8.0. Of the four dioxiranes examined, partially fluorinated, sterically bulky ETDO displayed the highest reactivity and regioselectivity. Using in situ generated ETDO, a facile, synthesis was developed for two naturally occurring oxysterols, i.e., 25-hydroxycholesterol, as well as its 3-sulfate (overall yield of the sulfate, 24%) and 24-oxocholesterol (16%), starting from cholesterol.
authors.affiliation: Department of Chemistry, College of Humanities & Sciences, Nihon University, Sakurajousui, Setagaya, Tokyo 156-8550, Japan.
authors.forename: Shoujiro
authors.initials: S
authors.lastname: Ogawa
authors.forename: Genta
authors.initials: G
authors.lastname: Kakiyama
authors.forename: Akina
authors.initials: A
authors.lastname: Muto
authors.forename: Atsuko
authors.initials: A
authors.lastname: Hosoda
authors.forename: Kuniko
authors.initials: K
authors.lastname: Mitamura
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ikegawa
authors.forename: Alan F
authors.initials: AF
authors.lastname: Hofmann
authors.forename: Takashi
authors.initials: T
authors.lastname: Iida
mesh_terms: D002788:Cholesterol Esters / Q000138:chemical synthesis* / Q000737:chemistry; D005027:Ethylene Oxide / Q000737:chemistry; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry; D006888:Hydroxycholesterols / Q000138:chemical synthesis* / Q000737:chemistry; D007653:Ketocholesterols / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C534977:25-hydroxycholesterol 3-sulfate; D002788:Cholesterol Esters; D006845:Hydrocarbons, Fluorinated; D006888:Hydroxycholesterols; D007653:Ketocholesterols; D005027:Ethylene Oxide