A diastereoselective synthesis of (1SR,3SR,7RS)-3-methyl-α-himachalene, the sex pheromone of the sandfly, Lutzomyia longipalpis (Diptera: Psychodidae)

The sandfly, Lutzomyia longipalpis, vectors the causative agent of visceral leishmaniasis in the New World. The male-produced pheromone, (1S,3S,7R)-3-methyl-α-himachalene provides an opportunity for pest managing this pest problem by influencing the behaviour of the biting female. Previous syntheses of the pheromone have all focused on a late stage Diels–Alder cyclisation to generate the bicyclic cis-himachalene skeleton. By adopting a new retrosynthetic analysis that depends on an early stage Diels–Alder cyclisation, the number of steps has been reduced to ten, of which five are catalytic and so provides access to quantities suitable for field-scale experiments.