RESUMO
A homologous series of 4-mercapto-2-alkanols (C5-C10) was used to investigate the impact of the stereochemistry on the sensory properties of a class of naturally occurring polyfunctional thiols having a 1,3-oxygen-sulfur functionality. Stereoisomers were obtained via syntheses of racemic mixtures and subsequent lipase-catalyzed kinetic resolutions. Analytical separations of the stereoisomers were achieved by capillary gas chromatography (GC) using chiral stationary phases. The absolute configurations were assigned via NMR analysis. Sensory evaluations by means of GC/olfactometry revealed odor threshold minima for the medium-chain homologues (C7-C9) of the 4-mercapto-2-alkanol stereoisomers. Except for the C5 homologue, the lowest odor thresholds were determined for the (2R,4R)-configured stereoisomers. The variability in odor qualities was mainly determined by the chain length. None of the 4-mercapto-2-alkanol stereoisomers showed consistent odor qualities for all homologues.
Assuntos
Odorantes/análise , Cromatografia Gasosa-Espectrometria de Massas , Estrutura Molecular , Olfatometria , Olfato , EstereoisomerismoRESUMO
4-Mercapto-2-heptanol, previously described in cooked bell pepper, was used to determine the impact of the stereochemistry on the sensory properties of a thiol with a 1,3-oxygen-sulfur functionality. In addition, the acetyl-derivatives 4-acetylthio-2-heptanol, 4-mercapto-2-heptyl acetate and 4-acetylthio-2-heptyl acetate were investigated. The synthesized stereoisomers were separated via capillary gas chromatography (GC) using chiral stationary phases. The GC orders of elution were determined by assigning the absolute configurations via NMR analysis in combination with lipase-catalyzed kinetic resolutions. Odor thresholds and odor properties were determined by means of GC/Olfactometry. The data revealed that the sensory properties of the investigated compounds are not only significantly influenced by the acetylation but also by the configurations of the two asymmetric centers.