Bufadienolides. 8. 12 (13å14)abeo Skeletal Rearrangements

George Pettit, T. R. Kasturi, John C. Knight, John Occolowitz

Research output: Contribution to journalArticle

18 Scopus citations


Several methods were developed for converting isodigitoxigenin (2a) into methyl acetals 4b and 4c. Of these, methanolysis (followed by acétylation) of isodigitoxigenin in the presence of p-toluenesulfonic acid proved most useful. Each isomer reached an equilibrium corresponding to ca. 3:1 acetal 4c to 4b within 15 min in benzene containing p-toluenesulfonic acid. Addition of dihydropyran to the equilibrium mixture resulted in excellent conversion into vinyl ether 5a. Heating either acetal 4b or 4c in benzene containing p-toluenesulfonic acid led to a skeletal rearrangement culminating in formation of C-norcardenolide 6. In addition to results of physical measurements, the structure of spiran 6 was confirmed by degradation to methyl ketone 8. Similar rearrangement of isodigitoxigenin gave spiran 9 accompanied by C-norcardenolide 6. Treating lactone 9 with p-toluene-sulfonic acid in methanol-water provided acetals 10a and 10b, which on further contact with p-toluenesulfonic acid in refluxing benzene gave lactone 9 and cardenolide 6. Evidence underlying the stereochemical assignments noted for structures 4, 9, and 10 was also discussed.

Original languageEnglish (US)
Pages (from-to)1404-1410
Number of pages7
JournalJournal of Organic Chemistry
Issue number5
StatePublished - May 1 1970

ASJC Scopus subject areas

  • Organic Chemistry

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