The naturally occurring 3-oxohexanoyl-L-homoserinelactone (1a), a bacterial autoinducer, has been prepared in 47 % overall yield by condensing stable 3-oxohexanoic acid (2), prepared by hydrolysis from the corresponding ester (3), with L-homoserinelactone using hydroxybenzotriazole (HOBT) and dicyclohexylcarbodiimide (DCC) in non-aqueous media.