Search

To unambiguously identify their structures and to evaluate their organoleptic properties, several constitutional und configurational isomers of dialkyl-tetrathianes and dialkyl-pentathiepanes were synthesized by two different synthetic protocols, and separated by preparative gas chromatography. Raman and NMR spectroscopy were used to differentiate between the constitutional 3,6-dialkyl-1,2,4,5-tetrathiane and the 4,6-dialkyl-1,2,3,5-tetrathiane isomers. Furthermore, cis- and trans-isomers of 3,6-dialkyl-1,2,4,5-tetrathianes were distinguished by temperature-dependent NMR experiments. Static, quantum-chemical simulations of the NMR spectra for these cis- and trans-isomers were calculated in the gas layer in order to confirm our experimental assignments. In addition, the assignment of 4,7-alkyl-1,2,3,5,6-pentathiepanes were deducted from their Raman spectra. Dialkyl-tetrathianes and dialkyl-pentathiepanes are interesting components to be used in flavor applications due to their unique olfactory impact and facets.

Cyclic polysulfides such as trithiolanes, tetrathianes and their derivatives are found in natural sources like archaea, mushrooms and vegetables. They gained interest for research and industrial applications because of their pronounced flavors and biological activity. This study compares Raman spectra of reference compounds and cyclic polysulfides which were synthesized in-house and separated by preparative gas chromatography. The data show that the positions of the Raman bands due to S S stretching vibrations in the wavenumber region from 550 to 450 cm −1 can determine the relative stereochemistry of 2,5-dialkyl trithiolanes and 4,6-dialkyl tetrathianes. Configurational cis isomers were distinguished from their corresponding trans isomers. In addition, 4,6-dialkyl-1,2,4,5-tetrathiane with disulfide bonds were distinguished from the constitutive isomer 3,6-dialkyl-1,2,3,5-tetrathiane with trisulfide bonds.

Knowledge of the difference in character and intensity of organoleptically important enantiomeric flavor and fragrance components has initiated the development of new analytical and preparative methods for the separation of optical isomers. In recent years, progress in the area of chirospecific analysis has been especially achieved by the development of modified cyclodextrins as a new type of chiral stationary phase. The state of the art in research on inclusion gas chromatography for separating flavor and fragrance substances is presented. Furthermore, this review reports on new results and recent research developments in enantioselective GC analysis.

This study describes the identification of six allyl esters in a garlic cheese preparation and in a commercial cream cheese. The extracts were prepared by liquid/liquid extraction and concentrated by the SAFE process. The identification of the allyl esters of acetic, butyric, hexanoic, heptanoic, octanoic, and decanoic acids is based on the correlation of their mass spectrometric data and chromatographic retention time data obtained from the extracts with those of authentic standards. In addition to the gas chromatography (GC)/mass spectrometry analysis, the flavor ingredients were characterized by GC sniffing by a trained flavorist. Some of the esters were isolated by preparative GC.