Synthesis of the sex pheromone of the obscure mealybug, the first example of a new class of monoterpenoids

The title compound was synthesized using a PPA-catalyzed cyclization, and diastereoselective quenching of a key intermediate to set up the relative stereochemistry of the methyl groups. A diastereoselective synthesis of (1 R ∗,2 R ∗,3 S ∗)-1-acetoxymethyl-2,3,4,4-tetramethylcyclopentane, the sex pheromone of the obscure mealybug Pseudococcus viburni, is described. Key steps included the polyphosphoric acid-catalyzed cyclization of isobutyl methacrylate to form the core five-membered ring, and diastereoselective quenching of an enolate intermediate to give the thermodynamically less favored cis orientation of vicinal methyl groups in a cyclopentanone intermediate.