The Facility of Formation of a Δ6Bond in Dihydromorphinone and Related Opiates

Hiroshi Nagase, Akira Abe, Philip S. Portoghese

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Treatment of naltrexone, dihydromorphinone, or related opiates that contain a 6-keto group with acetic anhydride or tert-butyldimethylsilyl chloride under mild conditions afforded enol derivatives having a Δ6bond. Naltrexone also was found to undergo the Robinson annelation reaction with methyl vinyl ketone with facility and in high yield to give the β-hydroxy ketone 3, whose stereochemistry was determined by means of 2D NMR spectroscopy. Upon acid treatment, 3 was dehydrated to the α,β-unsaturated ketone 4. Acid-catalyzed equilibration of 4 afforded the unconjugated olefin 5. These studies suggest that the Δ6bond is more stable than one that is exocyclic to ring C of the opiate because it permits ring flattening which may partially relieve torsional ring strain. The Δ6bond also may relieve an eclipsing interaction between a C-6 exocyclic substituent and the vicinal furan oxygen.

Original languageEnglish (US)
Pages (from-to)4120-4125
Number of pages6
JournalJournal of Organic Chemistry
Issue number17
StatePublished - Aug 1 1989


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