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

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

Research output: Contribution to journalArticlepeer-review

19 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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