Confirmation of the Structure of Kessane by NMR Spectroscopy

In order to prove the correct relative and absolute stereochemistry of the sesquiterpene ether (−)-kessane that was recently synthesized by us, its chromatographic retention, mass and 1H-NMR spectrum and optical rotation were compared with that of natural kessane. Natural kessane was isolated by means of fractionated vacuum distillation and repeated medium-pressure liquid chromatography from the essential oil of Valeriana officinalis. The recorded data confirm that the two compounds are identical. Further, by means of one- and two-dimensional 1H- and 13C-NMR spectroscopy at 600 MHz, it was possible to assign all protons and determine all coupling constants in the 1H-NMR spectrum. The NMR data are in full agreement with the relative stereochemistry proposed in the original work on kessane.