Stereoselective organozinc addition reactions to 1,2-dihydropyrans for the assembly of complex pyran structures.

[reaction: see text] Nucleophilic addition of organozincs to 1,2-dihydropyranyl acetates represents a new, broadly defined method for the stereocontrolled synthesis of alpha-substituted pyrans. The products obtained from this process are versatile materials that can be used to construct C-glycosides and other functionalized pyran structures of import. The occurrence of pyranyl groups in both natural products and therapeutically active agents confers added value to the studies described herein.