STEREOISOMERIC FLAVOR COMPOUNDS .73. 3-BUTYLPHTHALIDE - CHIROSPECIFICANALYSIS, STRUCTURE AND PROPERTIES OF THE ENANTIOMERS

Using enantioselective gas chromatography (GC) with an 6-di-O-tert-but yldimethylsilyl)-gamma-cyclodextrin column, the direct enantioselectiv e analysis of 3-butylphthalide enantiomers was achieved. Investigation s relating to their sensory characteristics and odour thresholds were carried out via enantioselective gas chromatography/olfactometry. In o rder to elucidate stereochemical features, the lactone structure of ra cemic 3-butylphthalide was hydrolysed and the carboxy function protect ed as an isopropylester: the hydroxy function at C-3 was esterified wi th (R)-2-phenylpropionic acid. The resulting diastereomeric esters wer e separated and isolated by high performance liquid chromatography. Ab solute configurations were derived from H-1-NMR studies according to t he Helmchen model, subsequently followed by ester cleavage and recylis ation to the corresponding 3-butylphthalide enantiomers. Investigation of the essential oil of celery seed show enantiomeric distributions i n the range of 95:5 in favour of the (3S)-enantiomer. This enantiomer shows a significantly lower GC odour threshold value than does the (3R )-enantiomer.