Stabilization of Chiral Helices for Saccharide-Linked Ethynylpyridine Oligomers Possessing a Conformationally Well-Defined Linkage

Tetrameric and octameric 2,6-pyridylene ethynylene oligomers linked to a β-D-glucopyranoside template through an o-phenylene linker were prepared and studied for their higher-order structure. These oligomers formed chiral helical structures through intramolecular hydrogen bonding between the ethynylpyridine moiety and the glucoside template. The rigidity of the o-phenylene linker stabilizes the helical structure to improve its CD activity and resistance against protic surroundings. Furthermore, the helical stabilization was enhanced by the addition of Cu(OTf)2 and Zn(NO3)2 salts.