Isolation, identification and enantioselective synthesis of octane-1,3,7-triol: determination of its absolute configuration

Extracts obtained by solid-phase extraction from apples were separated by multilayer countercurrent chromatography. In the most polar fractions, the novel octane-1,3,7-triol was identified by 1H and 13C NMR as well as LC-MS and by comparison with the synthesized racemic reference compound. Resolution of the enantiomers was achieved after acetylation of the triol followed by GC separation. The enantioselective synthesis of the stereoisomers of octane-1,3,7-triol was performed using the building blocks (R)- and (R,S)-butane-1,3-diol and (S)- and (R,S)-butane-1,2,4-triol. Comparison with the isolated products indicated that the natural compound consisted of a mixture of (3R,7S)- and (3R,7R)-octane-1,3,7-triol in a ratio of 2:3. Since the C3 chiral center is enantiomerically pure, the triol might be biogenetically related to the known antimicrobial (R)-(+)-octane-1,3-diol, the major volatile compound of some apple cultivars.