Ingo Hardt

Preparative enantiomer separation with modified cyclodextrins as chiral stationary phases

Abstract Preparative gas chromatographic enantiomer separation was achieved by using a packed column with heptakis(2,6-di-O-methyl-3-O-pentyl)-β-cyclodextrin (2,6-Me-3-Pe-β-CD) as a chiral stationary phase. Depending on the selectivity factor up to milligram amounts of almost pure enantiomers or at least enantiomeric mixtures, sufficiently enriched to determine the sign of optical rotation, could be obtained with only one injection of a racemate. This technique may be very useful for stereochemical assignments, for attaining pure enantiomers for bioassays, pharmacokinetic and metabolic studies and investigations of fragrance and flavour compounds.

Enantioselective degradation of α-hexachlorocyclohexane and cyclodiene insecticides in roe-deer liver samples from different regions of Germany

Remarkably high concentrations of alpha-hexachlorocyclohexane (alpha-HCH), cis-heptachlorepoxide and oxychlordane were found in roe-deer liver samples both from the northern and southern German states Schleswig-Holstein and Baden-Württemberg, respectively. The data revealed no significant regional differences, but they showed some common characteristics: a preferential degradation of (+)-alpha-HCH, and a preferential enrichment of (+)-oxychlordane and of (+)-cis-heptachlorepoxide as determined by chiral capillary gas chromatography using modified cyclodextrin phases. Calculation of the spearman rank correlation coefficients rS supported the assumption that higher concentrations of alpha-HCH may result in a stronger decomposition of the (+)-enantiomer, while higher levels of cis-heptachlorepoxide and oxychlordane appear to lead to a faster decomposition of the respective (-)-enantiomer or a preferential formation of the respective (+)-enantiomer.

Sesquiterpene hydrocarbons in the essential oil of Meum athamanticum

The sesquiterpene hydrocarbons β-bazzanene and α- and β-barbatene, typical constituents of liverworts (Hepaticae), were identified for the first time as constituents of a higher plant in the roots of Meum athamanticum (L.) Jacq. In addition, isobazzanene and isobarbatene, together with a variety of common sesquiterpene hydrocarbons, were identified. For α- and β-barbatene and isobarbatene the opposite configurations from those in liverworts were determined by enantioselective GC using modified cyclodextrins as chiral stationary phases. The configuration of β-bazzanene and isobazzanene could not be assigned. Isobarbatene was found for the first time as a natural compound.

Identification of (+)-β-caryophyllene in essential oils of liverworts by enantioselective gas chromatography

Abstract A combination of capillary columns with conventional and chiral stationary phases in a double-oven gas chromatograph (2D-GC) was employed to investigate the enantiomeric composition of β-caryophyllene in several liverworts. By comparison with a synthetic standard of racemic β-caryophyllene, enantioselective gas chromatography using heptakis(2,6-di- O -methyl-3- O -pentyl)- β -cyclodextrin as a chiral stationary phase revealed the presence of up to 85% (+)-β-caryophyllene in some specimens of Pellia endiviifolia and P. epiphylla .

Gas chromatographic separation of the enantiomers of bromocyclen in fish samples

Abstract In muscle tissue of rainbow trouts from Danish fish farms and of three different fish species (orfe, bream, and pike) from the river Stor (northern Germany) remarkably high concentrations (between 0.09 and 1.23 mg/kg fat) of the chiral insecticide bromocyclen were found. For the first time, the separation of the bromocyclen enantiomers in environmental samples was achieved with the help of chiral capillary gas chromatography using modified cyclodextrin phases. A preferential enzymatic metabolism of the first eluting (−)-enantiomer was verified. The toxic implication of this result as well as the sources for the contamination are not yet known.

Isolepidozene, a diastereomer of bicyclogermacrene, in some liverworts

Isolepidozene, the diastereomer of the widespread sesquiterpene hydrocarbon, bicyclogermacrene, has been identified in several liverworts. This previously unknown sesquiterpene hydrocarbon is based on the rare trans-bicyclo[8.1.0]undecane skeleton.