Efficient Intramolecular Asymmetric Reductions of α-, β-, and γ-Keto Acids with Diisopinocampheylborane 1

[figure: see text] 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.