Optically active (4E, 6S)-(+)-4, 6-dimethyloct-4--en-3-one (1021), manicone, and (3E, 5S)-(+)- 3, 5-dimethylhept-3-en-2-one (l0b), normanicone, the biologically active stereoisomers of mandibular gland alarm pheromone components of Manica ants, were synthesized by three dillcrcnt routes starting from (S)-(-)-2-methyl butan-1-ol (1).