Stereoselective Synthesis of 1,2-Annulated Sugars Having Substituted Tetrahydropyran/(-furan) Scaffolds Using the Prins-Reaction

Lewis acid catalyzed silyl-Prins/alkyne-Prins reactions are utilized for the stereoselective synthesis of 1,2-annulated sugars having substituted tetrahydropyran (or tetrahydrofuran) scaffolds from appropriately substituted sugar derived alkenyl (or alkynyl) alcohols. These annulated molecules having stereochemical/substitution dispositions similar to those of marine toxins such as maitotoxin could act as useful building blocks for the synthesis of these natural products. Further, the utility of the silyl-Prins reaction is extended to the synthesis of cis-sugar fused 4H-naptho[1,2-b]pyran and cis-sugar fused pyrano[3,2-c][1]benzopyran derivatives.