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

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

Research output: Contribution to journalArticle

4 Citations (Scopus)

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 1H 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

Fingerprint

Guaiane Sesquiterpenes
Lactones
Nuclear magnetic resonance spectroscopy
Magnetic Resonance Spectroscopy
Nuclear magnetic resonance
nuclear magnetic resonance
seats
Temperature
spectroscopy
Heptanes
heptanes
Thermodynamics
Ion exchange
Chemical activation
activation
thermodynamics
optimization
Geometry
rings
geometry

Keywords

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

ASJC Scopus subject areas

  • Structural Biology
  • Chemistry(all)

Cite this

Conformational analysis of guaianolide-type sesquiterpene lactones by low-temperature NMR spectroscopy and semiempirical calculations. / Milosavljević, Slobodan; Juranić, Ivan; Bulatović, Vanja; Macura, Slobodan I; Juranić, Nenad; Limbach, Hans Heinrich; Weisz, Klaus; Vajs, Vlatka; Todorović, Nina.

In: Structural Chemistry, Vol. 15, No. 3, 06.2004, p. 237-245.

Research output: Contribution to journalArticle

Milosavljević, S, Juranić, I, Bulatović, V, Macura, SI, Juranić, N, Limbach, HH, Weisz, K, Vajs, V & Todorović, N 2004, 'Conformational analysis of guaianolide-type sesquiterpene lactones by low-temperature NMR spectroscopy and semiempirical calculations', Structural Chemistry, vol. 15, no. 3, pp. 237-245. https://doi.org/10.1023/B:STUC.0000021533.65546.57
Milosavljević, Slobodan ; Juranić, Ivan ; Bulatović, Vanja ; Macura, Slobodan I ; Juranić, Nenad ; Limbach, Hans Heinrich ; Weisz, Klaus ; Vajs, Vlatka ; Todorović, Nina. / Conformational analysis of guaianolide-type sesquiterpene lactones by low-temperature NMR spectroscopy and semiempirical calculations. In: Structural Chemistry. 2004 ; Vol. 15, No. 3. pp. 237-245.
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AB - 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 1H 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.

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