Tandem Alkylation-Michael Addition to Vinylogous Carbonates for the Stereoselective Construction of 2,3,3,6-Tetrasubstituted Tetrahydropyrans

A stereoselective method for the synthesis of substituted tetrahydropyran derivatives employing a tandem S(N)2-Michael addition sequence to vinylogous carbonates is developed. The method is extended to the synthesis of bicyclic ether motifs present in polyether ladder toxins.