A simple convergent synthesis of trans-fused six-membered polycyclic ethers

A highly convergent method for the synthesis of trans-fused polytetrahydropyrans was developed, which involves: (i) coupling of cyclic triflate with an acetylene unit; (ii) oxidation of acetylene to 1,2-diketone; (iii) formation of a trans-fused cyclic dihemiacetal; (iv) O-methylation of the dihemiacetal; and (v) stereoselective reduction of the diacetal to trans-fused oxane rings.