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Keywords:

  • hydroxytheaspiranes;
  • theaspirones;
  • vitispiranes;
  • enantiodifferentiation;
  • multidimensional gas chromatography-mass spectrometry

Abstract

Two optically enriched theaspirone isomers, i.e. (2S,5S)-( − )-theaspirone 2b and (2S,5R)-( + )-theaspirone 2c (ee-values: 86% and 88% respectively), were obtained from quince juice by solvent extraction, flash chromatography and subsequent preparative high performance liquid chromatography (HPLC). Their absolute stereochemistry was assigned by circular dichroism spectroscopy. LiAlH4 reduction of 2b and 2c yielded 8-hydroxytheaspirane isomers 3b and 3c which were subjected to thermal treatment at pH 3 leading to vitispirane isomers 1b and 1c. In the same manner, vitispirane racemates 1a/1b and 1c/1d were obtained from the synthetic theaspirones 2a/2b and 2c/2d which had been separated by multi-layer coil countercurrent chromatography/HPLC. The optically enriched reference compounds were used to determine the order of elution in the course of enantio-separation of 1a-1d which was achieved by multidimensional gas chromatography (MDGC) using DB-Wax and 2,6-dimethyl-3-pentyl-β-cyclodextrin capillary columns. Using on-line coupled MDGC-mass spectrometry in the single ion monitoring mode, enantiodifferentiation of 1a-1d as well as 2a-2d from a number of natural sources was performed.