Biosynthesis-inspired intramolecular oxa-conjugate cyclization of α,β-unsaturated thioesters: stereoselective synthesis of 2,6-cis-substituted tetrahydropyrans.

Intramolecular oxa-conjugate cyclization of α,β-unsaturated thioesters under Brønsted acid catalysis, inspired by biosynthesis of polyketide natural products, provides a variety of 2,6-cis-substituted tetrahydropyran derivatives with excellent diastereoselectivities. An added bonus of this methodology is that the product tetrahydropyrans could be readily elaborated to various derivatives by exploiting the unique reactivity of the thioester group.