Unravelling the scent of vetiver: identification of character-impact compounds.

Vetiver oil is a highly esteemed basic ingredient of modern perfumery, but the nature of the constituents that really impart its typical and most sought woody-earthy scent has remained controversial. Indeed, vetiver oil is considered as one of the most complex essential oils, being mostly composed of several hundreds of sesquiterpene derivatives with a large structural diversity. Its complexity has hindered the direct identification of its odoriferous components. We thus aimed at using a combination of GC×GC/MS and GC-Olfactometry in order to identify most of its odor-impact constituents. The olfactory analysis of vetiver oil and vetiveryl acetate revealed a huge variety of odors in both products. While khusimone has almost unanimously been recognized as the most characteristic vetiver odorant, we have identified several even more important contributors to the typical vetiver character.

Integrated comprehensive two-dimensional gas-chromatographic and spectroscopic characterization of vetiveryl acetates: Molecular identifications, quantification of constituents, regulatory and olfactory considerations.

Vetiveryl acetate is a common ingredient of the perfume industry highly prized by perfumers for its crisp vetiver note and thus often used in high-end perfume compositions. Vetiveryl acetate is currently manufactured from vetiver oil by means of various industrial processes that result in the conversion of the main vetiver alcohols into their corresponding acetates. Despite being used for decades as perfume ingredient, vetiveryl acetate has barely been studied in the past, therefore its chemical composition is poorly documented. While vetiveryl acetate is currently under investigation by regulation authorities, it was crucial to fill this gap of knowledge. We report here the first detailed investigation of different types of vetiveryl acetates, covering analytical, regulatory, and olfactory aspects. This study is based upon an integrated analytical methodology involving a full array of gas chromatographic techniques and spectroscopic/spectrometric methods. The principal objective was the identification of the main ester constituents contained in different samples of vetiveryl acetate, as well as linking their chemical composition with their manufacture process. Among the major esters detected in all samples, 23 ester constituents were either isolated by capillary preparative-gas chromatography or synthesized in order to provide their complete spectral characterization. The quantification of constituents in both commercial and laboratory-made vetiveryl acetates was carried out by internal calibration using comprehensive two-dimensional-gas chromatography and predicted relative response factors. The generated set of analytical data permitted to explore both the regulatory aspects and the olfactory properties associated with the substance. The manufacture of vetiveryl acetate modulates the initial scent of vetiver essential oil by suppressing the notes brought by the main fragrant alcohols. While the impact of undesired odorant molecules such as phenol derivatives and geosmin is lowered, the major odour-active ketones such as khusimone, ziza-6(13)-en-3-ones, and the two vetivones develop their own odor characters in vetiveryl acetate.

Odor-active constituents of Cedrus atlantica wood essential oil.

The main odorant constituents of Cedrus atlantica essential oil were characterized by GC-Olfactometry (GC-O), using the Aroma Extract Dilution Analysis (AEDA) methodology with 12 panelists. The two most potent odor-active constituents were vestitenone and 4-acetyl-1-methylcyclohexene. The identification of the odorants was realized by a detailed fractionation of the essential oil by liquid-liquid basic extraction, distillation and column chromatography, followed by the GC-MS and GC-O analyses of some fractions, and the synthesis of some non-commercial reference constituents.

Qualitative and quantitative analysis of vetiver essential oils by comprehensive two-dimensional gas chromatography and comprehensive two-dimensional gas chromatography/mass spectrometry.

Vetiver essential oils (VEO) are important raw ingredients used in perfume industry, entering the formula of numerous modern fragrances. Vetiver oils are considered to be among the most complex essential oils, resulting most of the time in highly coeluted chromatograms whatever the analytical technique. In this context, conventional gas chromatography has failed to provide a routine tool for the accurate qualitative and quantitative analysis of their constituents. Applying comprehensive two-dimensional gas chromatography techniques (GC×GC-FID/MS) afforded the mean to separate efficiently vetiver oil constituents in order to identify them in a more reliable way. Moreover, this is the first time that a complete true quantitation of each constituent is carried out on such complex oils by means of internal calibration. Finally, we have studied the influence of the injection mode on the determined chemical composition, and showed that several alcohols underwent dehydration under defined chromatographic conditions (splitless mode) usually recommended for quantitation purposes.

Bi(OTf)3-catalyzed cycloisomerization of aryl-allenes.

Intramolecular hydroarylation of allenes was achieved under very mild conditions using bismuth(III) triflate as the catalyst. Efficient functionalization of activated and nonactivated aromatic nuclei led to C-C bond formation through a formal Ar-H activation. A tandem bis-hydroarylation of the allene moiety was also developed giving access to various interesting polycyclic structures.