A new synthesis of (-)-frontalin, the bark beetle pheromone

Abstract

(-)-Frontalin [(1S,5R)-1,5-dimethyl-6,8-dioxabicyclo[3.2.1]-octane (1)] was synthesized from ethyl 2-oxocyclopentane-1-carboxylate (2) as the starting material. Baker's yeast was used for the asymmetric reduction of 2 to 3. The S configuration at C-1 of 1 was generated by diastereoselective methylation of the dianion derived from 3 to give 4. The present process furnished about 10 g of 1 with enantiomeric purity of 89.1% e.e.