CHIRAL COMPOUNDS OF ESSENTIAL OILS .21. (E,Z)-2,3-DIHYDROFARNESALS-CHIROSPECIFIC ANALYSIS AND STRUCTURE ELUCIDATION OF THE STEREOISOMERS

A synthetic racemic mixture of (E,Z)-2,3-dihydrofarnesal was oxidized to the corresponding carboxylic acids and converted to diastereomeric (S)-phenylglycinyl amides which were separated by high performance liq uid chromatography, Reductive amide cleavage yielded the enantiopure a ldehydes, Absolute configurations were derived from proton nuclear mag netic resonance spectroscopy studies of the diastereomeric amides or f rom enantioselective analysis of 4-methylhexanoic acid as a product of deoxygenation and oxidative decomposition of the corresponding enanti opure dihydrofarnesols, Using enantioselective multidimensional capill ary gas chromatography (column combination PS yl-6-O-tert-butyldimethy lsilyl)-beta-cyclodextrin) the direct enantioselective analysis of all four stereoisomers was achieved, The application of this method to th e scent of orchids (Aerides jarckianum) and to the blossom fragrance o f Citrus limon proves that genuine (E)-2,3-dihydrofarnesal has an enan tiomeric distribution in the range of 85:15 in favour of the (3S)-enan tiomer. (C) 1997 by John Wiley & Sons, Ltd.