Efficient intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane

[GRAPHICS] alpha-, beta-, and gamma -Keto acids are reduced with diisopinocampheylborane at room temperature to the corresponding hydroxy acids with predictable stereochemistry in very high ee. The gamma -hydroxy acids produced were conveniently cyclized to the corresponding lactones, This provides a simple synthesis of 4-hexanolide, a component of the pheromone secreted by the female dermestid beetle Trogoderma glabrum.