NMR and x‐ray conformational study of artemisiifolin and three other related germacranolides

Abstract

From an acetone extract of Staehelina dubia, large quantities of the previously known germacranolide artemisiifolin were isolated. The conformations of the 10-membered germacra-1(10)E,4Z-diene ring system of this compound and those of its derivatives 11,13-dihydroartemisiifolin, isabelin and 6alpha-hydroxy-15-oxogermacra-1(10)E,4Z,11(13)-trien-12,8alpha-olide were studied by NMR spectroscopic methods. Low-energy conformations were obtained by quantum mechanical calculations. An x-ray diffraction analysis of artemisiifolin established that, in the crystalline state, it possesses a unique conformation that corresponds to the majority one existing in acetone-d6 solution.

Sesquiterpenoids from Common Ragweed (Ambrosia artemisiifolia L.), an Invasive Biological Polluter

“…Our results show that, in accordance with a previous genetic analysis,29 the European population of A. artemisiifolia is heterogeneous, and, at least as regards isoprenoids, different from the native American populations investigated before 6,25. A series of sesquiterpenoids, including compounds belonging to structural classes never identified before in this species, have been characterized, and some of them have been identified as highly reactive Michael acceptors and activators of TRPA1, a major player in the induction of inflammatory pathologies of the airways.…”

“…Because 10‐H showed no significant ROESY correlation, the relative configuration at C‐10 could not be assigned. Artemisiifolinic acid ( 15a ) is closely related to artemisiifolin, a compound isolated from an American collection of A. artemisiifolia ,25 from which it differs in the oxidation of Me‐14 to a carboxylic acid and in the hydrogenation of the Δ 1,10 double bond. The 1 H NMR spectrum of 15b was, however, characterized by sharp and well‐defined signals, showing a substantial difference from the conformational behavior of artemisifolin, a mixture of slowly interconverting rotamers at room temperature 26…”

Bioherbicidal activity of a germacranolide sesquiterpene dilactone fromAmbrosia artemisiifoliaL.

“…However, 13 C NMR multiple signals suggest the presence of two different conformers in the purified solution. Values obtained in 13 C NMR spectra matched with those assigned by Jimeno et al [21] for the two conformations of the sesquiterpene lactone…”

Structural Diversity from the Transannular Cyclizations of Natural Germacrone and Epoxy Derivatives: A Theoretical–Experimental Study

“…The two major conformers of the three products are represented in Figure 5. [30] To test the solvent effect, the calculations were performed also by applying the polarizable continuum model (PCM), [31] to reproduce the experimental conditions. [30] To test the solvent effect, the calculations were performed also by applying the polarizable continuum model (PCM), [31] to reproduce the experimental conditions.…”

“…These results are in agreement with the NMR spectroscopic studies performed for some germacranolides showing the existence of different conformer ratios depending on the solvent. [30] To test the solvent effect, the calculations were performed also by applying the polarizable continuum model (PCM), [31] to reproduce the experimental conditions. In this sense, THF was considered as a solvent.…”