Intramolecular Versus Intermolecular Induction of Helical Handedness in Pyridinedicarboxamide Oligomers

A new convergent synthetic scheme has been developed to prepare oligoamides of 2,6-diaminopyridine and 4-decyloxy-2,6-pyridinedicarboxylic acid. These compounds adopt stable single helical conformations in solution. NMR and circular dichroism studies show that intramolecular and intermolecular chiral induction of handedness in these helices is possible. Intramolecular induction is effected by attaching a single chiral group to the end of an oligomer. Intermolecular induction results from various noncovalent interactions between chiral carboxylic or sulfonic acids and the terminal residues of the oligoamides. Intramolecular induction appears to be more efficient than intermolecular induction. When both effects compete, intramolecular induction prevails. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)