کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2028461 | 1070419 | 2009 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: A facile synthesis of C-24 and C-25 oxysterols by in situ generated ethyl(trifluoromethyl)dioxirane A facile synthesis of C-24 and C-25 oxysterols by in situ generated ethyl(trifluoromethyl)dioxirane](/preview/png/2028461.png)
Experiments were performed to compare the regioselective hydroxylation of the isopropyl C–H bond at C-25 in 5α-cholestan-3β-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. NaHCO3, 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.
Journal: Steroids - Volume 74, Issue 1, January 2009, Pages 81–87