(+)-(1S, 5R, 7S)-7-Ethyl-5-methyl-6, 8-dioxabicyclo[3. 2. 1]oct-3-ene, an optically active form of the androgen-dependent pheromone of the adult male house mouse (Mus)___ (musculus)___, was synthesized from (+)-(R, R)-diethyl tartrate (via)___ highly site-selective olefination of the 6, 8-dioxabicyclo[3. 2. 1]octane intermediate.