Conformational analysis of guaianolide-type sesquiterpene lactones by low-temperature NMR spectroscopy and semiempirical calculations

Slobodan Milosavljević, Ivan Juranić, Vanja Bulatović, Slobodan Macura, Nenad Juranić, Hans Heinrich Limbach, Klaus Weisz, Vlatka Vajs, Nina Todorović

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Conformational analysis of 9α-acetoxycumambrine A 1 and 8-O-isobutiryl-9α-acetoxycumambrine B 2 was carried out by low-temperature NMR studies. Results suggested that lactones 1 and 2 are mixtures of two distinctive conformers, I and II. Based on low-temperature 1 H NMR spectra, in four solvents, the thermodynamic parameters of I ⇌ II exchange process were assessed. Energy of activation of I → II reaction was obtained by dynamic NMR simulations for both compounds. Results revealed that conformational exchange of lactones 1 and 2 occurs due to "chair ⇌ twisted chair" interconversion of a heptane ring. The same PM3 semiempirical method was applied for geometry optimization of lactones 1 and 2, as well as of 9α-hydroxycumambrine A 3, 9α-acetoxycumambrine B 4, and cumambrine B 5.

Original languageEnglish (US)
Pages (from-to)237-245
Number of pages9
JournalStructural Chemistry
Volume15
Issue number3
DOIs
StatePublished - Jun 2004

Keywords

  • Conformations
  • Cumambrine
  • Dynamic NMR
  • Guaianolides
  • Low-temperature NMR
  • PM3 semiempirical calculations

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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    Milosavljević, S., Juranić, I., Bulatović, V., Macura, S., Juranić, N., Limbach, H. H., Weisz, K., Vajs, V., & Todorović, N. (2004). Conformational analysis of guaianolide-type sesquiterpene lactones by low-temperature NMR spectroscopy and semiempirical calculations. Structural Chemistry, 15(3), 237-245. https://doi.org/10.1023/B:STUC.0000021533.65546.57