PURPOSE: To obtain an optically active ketone with high enanethio selectivity easily in high yield, by subjecting an optically active sulfonyloxy alcohol as a raw material to the pinacol rearrangement in the presence of an organoaluminum compound in a solvent.

CONSTITUTION: An optically active vic-diol of formula1(R is 2W20C hydrocarbon group; R' is 1W20C hydrocarbon group; hydrocarbon groups R and R' may contain functional groups which will not affect the reaction; * is asymmetric carbon atom; R is a group having more improved electron donative property than R' including the case where R is the same as R') is sulfonylated with a compound of formula II (R" is the same as R') to give an optically active sulfonyloxyalcohol of formula III, which is then subjected to the pinacol rearrangement reaction in the presence of an organoaluminum compound, e.g. a trialklaluminum, in a solvent at room temperature W-80°C for 0.05W5hr to afford the aimed compound, having [S] or [R] absolute configuration, which is an alarm pheromone of ants.