Ingrid Benecke

New Results in the gas chromatographic separation of enantiomers of hydroxy acids and carbohydrates

New chiral stationary phases for the gas chromatographic separation of the enantiomers of amines, amino alcohols, hydroxy acids and carbohydrates are described. Hydroxy acids can be separated on stationary phases prepared from S-2-hydroxyisopentanoic acid and S-2-hydroxyoctanoic acid by coupling with S-phenylethylamine. For the first time the separation of carbohydrate enantiomers could be achieved on a stationary phase obtained by connecting l-valine-S-phenylethylamide to the functionalized cyanoethyl side-chains of the polysiloxane XE-60.

Gas chromatographic enantiomer separation of chiral alcohols

Abstract A micro-scale procedure for the gas chromatographic enantiomer separation of chiral aliphatic, aromatic and monoterpene alcohols on glass capillary columns coated with XE-60-S-valine-S-α-phenylethylamide is described. By the formation of stable isopropyl urethanes in a facile derivatization step, the polarity of alcohols and their enantioselective intermolecular interaction with the chiral stationary phase is sufficiently enhanced to result in enantiomer separation with moderate retention times.

New procedure for gas chromatographic enantiomer separation : Application to chiral amines and hydroxy acids

Abstract By reaction with isopropyl isocyanate, chiral amines can be converted into urea derivatives. With the same reagent, urethane derivatives of chiral α-hydroxy acid esters are formed. The enantiomers of both types of derivatives are separated on XE-60- S -valine- S -α-phenylethylamide with high separation factors.

Isocyanates as reagents for enantiomer separation: Application to amino acids, N-methylamino acids and 3-hydroxy acids

Abstract The formation of N-alkylureido derivatives of amino acid esters increases the selectivity of a chiral stationary phase towards the enantiomers, resulting in complete separation, even for the proline and isovaline enantiomers. In the reaction of isocyanates with N-methylamino acids, N-alkylureido/N-alkylamide derivatives are formed in one step. In a similar way, 3-hydroxy acids are converted into N-alkylcarbamate/N-alkylamide derivatives. By this procedure, the enantiomers of N-methylamino and 3-hydroxy acids were separated on chiral stationary phases for the first time. The order of elution of the enantiomers of 3-hydroxy acids was determined with optically active reference compounds, obtained by stereoselective reduction of 3-keto acid esters with yeast.

The occurrence of l-galactose in snail galactans

Abstract The occurrence of l -galactose ( l -Gal) was investigated in twelve preparations of snail galactans from nine different species. l -Gal (11–15%) was found not only in members of the family Helicidae , a highly developed group among the Pulmonata , but was detected also in a galactan of the oldest phylogenetic subclass of snails in the Prosobranchiata . To determine the position of the l -Gal residues, the galactans of Arianta arbustorum , Cepaea nemoralis , and Helix pomatia were methylated and hydrolysed, and the partially methylated Gal derivatives were isolated. Each derivative was O -demethylated and the ratio of d - and l -galactose was determined by g.l.c. of the trifluoroacetylated methyl glycosides using a chiral stationary phase. l -Gal (22–34%) was detected only in the tetra- O -methyl fractions, and hence l -Gal occupies exclusively terminal non-reducing positions.