Saccharide Recognition-Induced Transformation of Pyridine−Pyridone Alternate Oligomers from Self-Dimer to Helical Complex

Co-oligomers involving (1H)-4-pyridone and 4-alkoxypyridine rings were studied, and it was found that their supramolecular transformation was caused by saccharide recognition. In the co-oligomers, pyridone and pyridine rings are alternately linked at their 2,6-position with an acetylene bond. The pyridine rings behave as a hydrogen bonding acceptor, and the pyridone rings and tautomerized 4-pyridinol work as a donor. Pyridine−pyridone−pyridine 3-mer was found to self-dimerize on the basis of vapor pressure osmometry in CHCl3, and the association constant was obtained as 2.3 × 103 M−1 by 1H NMR titration. Longer 5-, 7-, 9-, and 11-mer oligomers showed considerable broadening and anisotropy in the 1H NMR spectra due to self-association. These longer oligomers recognized octyl β-d-glucopyranoside and changed their form into a chiral helical complex, showing characteristic circular dichroism.