Acid-Induced Rearrangement of Epoxygermacranolides: Synthesis of Furanoheliangolides and Cadinanes from Nobilin
by
Maria De Mieri 1,*, Martin Smieško 2
, Isidor Ismajili 1, Marcel Kaiser 3,4 and Matthias Hamburger 1,*
Maria De Mieri 1,*, Martin Smieško 2, Isidor Ismajili 1, Marcel Kaiser 3,4 and Matthias Hamburger 1,*
1
Pharmaceutical Biology, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
2
Molecular Modeling, Pharmazentrum, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
3
Department of Medical Parasitology & Infection Biology, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4000 Basel, Switzerland
4
University of Basel, Petersplatz 1, 4001 Basel, Switzerland
*
Authors to whom correspondence should be addressed.
Molecules 2017, 22(12), 2252; https://doi.org/10.3390/molecules22122252
Received: 16 November 2017 / Revised: 13 December 2017 / Accepted: 13 December 2017 / Published: 18 December 2017
(This article belongs to the Special Issue Diversity of Terpenoids)
The acid-induced rearrangement of three epoxyderivatives of nobilin 1, the most abundant sesquiterpene lactone in Anthemis nobilis flowers, was investigated. From the 1,10-epoxyderivative 2, furanoheliangolide 5 was obtained, while the 4,5-epoxy group of 3 did not react. Conversely, when the 3-hydroxy function of nobilin was acetylated (12), the 4,5-epoxy derivative did cyclize into cadinanes (15 and 16) under Lewis acid catalysis. The reactivity of the 4,5- and 1,10-epoxy derivatives of nobilin (2 and 3) was compared with that of parthenolide, and rationalized on the basis of quantum chemical calculations. All isolated reaction products were fully characterized by spectroscopic and computational methods, and their in vitro anti-protozoal activity was evaluated. The paper could provide new insights into the biosynthesis of this class of natural products.
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Keywords:
sesquiterpene lactones; epoxygermacranolides; acid-catalyzed rearrangement; mechanism of reaction; anti-protozoal activity
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MDPI and ACS Style
De Mieri, M.; Smieško, M.; Ismajili, I.; Kaiser, M.; Hamburger, M. Acid-Induced Rearrangement of Epoxygermacranolides: Synthesis of Furanoheliangolides and Cadinanes from Nobilin. Molecules 2017, 22, 2252.
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