Furanyl Cyclic Ethers: Single and Double Diastereoselectivity in the Synthesis of 2,4-Di and 2,4,5-Trisubstituted Tetrahydropyrans.

Combining the desymmetrization of a prochiral bis-hydroxymethyl group with the epimerization of a chiral furanyl ether in a single transformation, high levels of double diastereoselectivity have been achieved in a synthesis of 2,4,5-trisubstituted tetrahydropyrans, which proceeds under thermodynamic control.