Synthesis of Artificial Ladder-Shaped Polyethers Containing a 6/7 cis-Fused Ring System

Ladder-shaped tetracyclic and heptacyclic ethers containing a 6/7 cis-fused ring system have been synthesized. The synthesis features convergent coupling of monocyclic building blocks through esterification, ring-closing reaction using a low-valent titanium complex, and hydroxy dithioacetal cyclization. The double reaction strategy enabled expeditious synthesis of the heptacyclic ether in only thirteen steps from the building blocks.