Isotope ratio analysis by HRGC-MS of monoterpene hydrocarbons from citrus essential oils
The isotope ratio of monoterpene hydrocarbons in citrus essential oils of different origins was measured by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). The isotope ratio (Ir) was determined by the ratio of the isotope peak intensity (m/z 137) to the molecular mass peak intensity (m/z 136) of the monoterpene hydrocarbons. The accuracy of Ir was examined by measuring monoterpene hydrocarbon standards and 13C-labeled compounds. The isotope fingerprints based on the values of monoterpene hydrocarbons from lemon, lime and yuzu essential oils were determined. These citrus essential oils were also discriminated by a principal component analysis of their Ir data. The characteristic vectors showed that α-terpinene, β-pinene and β-phellandrene were important components for distinguishing between the citrus species. It is suggested that this technique will be applicable to evaluate the quality, genuineness and origin of citrus fruits and their products.
γ-Alkylation of α,β-Unsaturated Ketones. γ-Arylsulfonyl Groups as Regioselective Control Elements
A reaction sequence for γ-alkylation of α,β-unsaturated ketones has been proposed and tested with some success. γ-(Phenylsulfonyl) groups are (1) introduced into the substrate; (2) present during alkylation of the resulting highly delocalized carbanions; (3) finally removed to leave the otherwise inaccessible γ-alkylation product.
Lansbury, Peter T.,Erwin, Robert W.,Jeffrey David A.
p. 1602 - 1608
(2007/10/02)
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