Saccharide-linked ethynylpyridine oligomers: Primary structures encode chiral helices

A series of glycoside-linked oligomeric 2,6-pyridylene-ethynylene (m-ethynylpyridine) compounds were prepared and studied for their intramolecular chiral induction. The primary structure of the oligomers, such as the lengths of ethynylpyridine moieties and linkers and the types of terminal groups and linked glycosides, was varied. From circular dichroism (CD) and H-1 NMR analyses, it was found that the intramolecular hydrogen bonds between the glycoside and ethynylpyridine moieties induced the formation of higher-order, chiral helices of the oligomers. The sign and strength of CD signals for the helices were found to depend strongly on the length of ethynylpyridines and the types of terminal groups and glycosides. These results showed that the oligomers encode their higher-order structures in their primary structures.