Unravelling the Enantiomeric Distribution of Key Sandalwood Sesquiterpenoids by Enantioselective Gas Chromatography and Molecular Rotational Resonance

The enantiomeric distribution of α- and β-santalol in various Santalum and Osyris species of different origins was determined by the combination of enantioselective gas chromatography and chiral tagging molecular rotational resonance spectroscopy, supported by the preparation of (+)- and (−)-α-santalol standards by total synthesis and isolation of (−)-β-santalol from Santalum album essential oil. (−)-β-Santalol was largely dominant in all Santalum essential oil samples (>99%) except for the mixtures of santalols produced by biotechnology. The enantiomeric distribution of α-santalol was much less in favor of the levorotatory enantiomer, contained in percentages up to 5 and 45% in some Santalum and Osyris samples, respectively. The olfactory evaluations of synthetic (+)- and (−)-α-santalol samples by a panel of 56 assessors showed that they were very weak to odorless for most panelists.