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International audience; Myrtus communis L. grows wild all around the Mediterranean basin and on the islands. Myrtle leaf essential oil has a characteristic pleasant odour although various compositions, which differ by the content of monoterpene esters, have been reported. Fractionation of an essential oil sample from Corsica, followed by analysis of the chromatographic fractions by GC (RI) and 13 C NMR allowed the identification of four C8-C10 esters, first identified 20 years ago in a Spanish essential oil sample and since that time very scarcely reported, despite the tremendous amount of work carried out on the composition of myrtle leaf essential oil. Therefore, the composition of 63 samples of M. communis L. leaf essential oil isolated from myrtle growing wild in various Mediterranean countries (Corsica, Sardinia, Portugal, Morocco, Algeria and Tunisia) has been investigated by GC(RI) and 13 C NMR and the four C8-C10 esters have been identified in all the samples. The occurrence of these esters merits great attention, since they contribute to the pleasant odour of the myrtle essential oil. In parallel, 3,3,5,5,8,8-hexamethyl-7-oxabicyclo[4.3.0]non-1(6)-ene-2,4-dione has been identified in all the samples.

International audience; Introduction - In the course of on-going work on the characterisation of aromatic plants from the Ivory Coast we investigated the composition of the root oil from Xylopia aethiopica. Objectives - The aim of this work was to investigate the chemical composition of X. aethiopica root oil and elucidate the structure of two new compounds. Methodology - Analysis of the essential oil was carried out using a combination of chromatographic (CC, GC with retention indices) and spectroscopic techniques (MS, 13C-NMR, 2D-NMR). Results - Twenty seven components, accounting for 95.6% of the whole composition, were identified including various compounds for which spectroscopic data were absent on commercial computerised MS libraries. Three compounds are reported for the first time as natural compounds and the structure of two new compounds, ,4-dimethyl-2-vinylcyclohexenene and endo-5-methoxy-3-patchoulene, has been elucidated using extensive two-dimensional NMR spectroscopy. Conclusion - The composition of X. aethiopica root oil is dominated by two dimethylvinylcyclohexene isomers. It differs drastically from the composition of leaf and fruit oils of the same plant. The combination of analytical techniques appeared crucial for a fruitful analysis.

International audience; Leaves (16 samples) and stem bark (four samples) of Xylopia villosa were collected in two forests of south-eastern Côte d'Ivoire. The chemical composition of essential oils was investigated by gas chromatography (GC; in combination with retention indices) and 13C nuclear resonance (NMR). Thirty-three compounds accounting for 85.9-95.9% of the oil have been identified. Xylopia villosa produces a monoterpene-rich essential oil, whose composition was dominated by sabinene or (Z)-B-ocimene, one or the other compound being the major component. One atypycal leaf oil sample exhibited myrcene as major component.

International audience; The chemical composition of 48 essential-oil samples isolated from the leaves of Xylopia aethiopica harvested in six Ivoirian forests was investigated by GC-FID and 13C-NMR analyses. In total, 23 components accounting for 82.5-96.1% of the oil composition were identified. The composition was dominated by the monoterpene hydrocarbons b-pinene (up to 61.1%) and a-pinene (up to 18.6%) and the sesquiterpene hydrocarbon germacrene D (up to 28.7%). Hierarchical cluster and principal component analyses allowed the distinction of two groups on the basis of the b-pinene and germacrene D contents. The chemical composition of the oils of Group I (38 oil samples) was clearly dominated by bpinene, while those of Group II (10 samples) were characterized by the association of b-pinene and germacrene D. The leaves collected in the four inland forests produced b-pinene-rich oils (Group I), while the oil samples belonging to Group II were isolated from leaves harvested in forests located near the littoral.

International audience

Although numerous quantum calculations have been made over the years of the stabilities of the fluxional isomers of C4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{7}^{+}}}\end{equation*}\end{document}, none have been reported for other than the gas phase (which is unrealistic for these ionic species) that exhibit exceptional fluxional properties in solution. To be sure, quantum-mechanical calculations for solutions are subject to substantial uncertainties, but nonetheless it is important to see whether the trends seen for the gas-phase C4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{7}^{+}}}\end{equation*}\end{document} species are also found in calculations for polar solutions. Of the C4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{7}^{+}}}\end{equation*}\end{document} species, commonly designated bisected-cyclopropylcarbinyl 1, unsym-bicyclobutonium 2, sym-bicyclobutonium 3, allylcarbinyl 4, and pyramidal structure 6, the most advanced gas-phase calculations available thus far suggest that the order of stability is 1 ≥ 2 ≥ 3 ≫ 4 ≫ 6 with barriers of only ≈1 kcal/mol for interconversions among 1, 2, and 3. We report here that, when account is taken of solvation, 2 turns out to be slightly more stable than 1 or 3 in polar solvents. The pattern of the overall results is unexpected, in that despite substantial differences in structures and charge distributions between the primary players in the C4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{7}^{+}}}\end{equation*}\end{document} equilibria and the large differences in solvation energies calculated for the solvents considered, the differential solvent effects from species to species are rather small.