Preparation and characteristic odour of optically active 3‐hydroxy‐2‐octanone

Abstract

ABSTRACTThe preparation of optically active 3‐hydroxy‐2‐octanone was examined by Sharpless asymmetric dihydroxylation of a silyl enol ether derived from 2‐octanone. (R)‐3‐Hydroxy‐2‐octanone was obtained in 68% yield and 87.8% ee when AD‐mix‐β was used as an oxidant, while the (S)‐enantiomer was produced in 69% yield and 77.3% ee from AD‐mix‐α. The characteristic odour of the optically active products was evaluated by chiral gas chromatography–olfactometry. (R)‐3‐Hydroxy‐2‐octanone has a mushroom‐like, fresh grass odour, while the (S)‐enantiomer presents a mushroom‐like, earthy note. Aroma extract dilution analysis was applied to determine the flavour dilution factors of the two enantiomers. The flavour dilution factor of the (R)‐enantiomer was 1024, which is much higher than that of (S)‐enantiomer (256). They obviously differ in odour intensity. Copyright © 2012 John Wiley & Sons, Ltd.