ISSN:
0075-4617
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Rose Bengal Sensitized Type-II Photooxygenation ('Singlet O2 Reaction') of 3β-Acetoxy Δ7-cholestene and 3β,7α-Diacetoxy-Δ8(14)-cholesteneRose bengal- or hematoporphyrin-sensitized type-II photooxygenation ('singlet O2 reaction') of 3β-acetoxy-Δ7-cholestene (1) in pyridine yields two bis-hydroperoxides by two consecutive ene-reactions: 3β-acetoxy-7α,8α-dihydroperoxy-Δ14-cholestene (14; main product) and 3β-acetoxy-7α,8β-dihydroperoxy-Δ14-cholestene (7; side product). Initially 1 is converted regio- and stereo-selectively into the monohydroperoxide 3β-acetoxy-7α-hydroxy-Δ8(14)- cholestene (4) which immediately transforms to the stereoisomeric bis-hydroperoxides 14 and 7, respectively. Similarly, photooxygenation of 3β,7α-diacetoxy-Δ8(14)-cholestene (2) yields two stereoisomeric hydroperoxides. The stereoselectivity in the case of 2 differs from that found in the case of 4. - The structures of the unstable hydroperoxides have been elucidated via their various reduction products.
Notes:
Die durch Bengalrosa oder Hämatoporphyrin sensibilisierte Typ-II-Photooxygenierung („Singulett-O2-Reaktion“) von 3β-Acetoxy-Δ7-cholesten (1) in Pyridin liefert zwei Bis-hydroperoxide in je zwei konsekutiven En-Reaktionen: 3β-Acetoxy-7α,8α-dihydroperoxy- Δl4-cholesten (14) als Hauptprodukt und 3β-Acetoxy-7α,8β-dihydroperoxy-Δ14-cholesten (7). Zuerst entsteht regio- und stereoselektiv das Monohydroperoxid 3β-Acetoxy-7α-dihydroperoxy-Δ8(14)-cholesten (4), das alsbald zu den stereoisomeren Bis-hydroperoxiden 14 und 7 umgesetzt wird. Die Photooxygenierung von 3β,7α-Diacetoxy-Δ8(14)hyphen;cholesten (2) liefert zwei Hydroperoxide mit einer von 4 verschiedenen Stereoselektivität. - Die Strukturen der leichtzersetzlichen Hydroperoxide wurden anhand ihrer Reduktionsprodukte aufgeklärt.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.197519750412
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