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

The 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.