Pergamon Tetrahedmn 55 (1999) 549-560 TETRAHEDRON Intramolecular Hydrogen Bonding Studies For a Series of Dipurinyl-2,6- pyridinedicarboxamides Geoffrey T. Crisp* and Yu-Lin Jiang Department of Chemistry,The Universityof Adelaide, Adelaide,South Australia, 5005 Received 25 August 1998; revised 21 October 1998; accepted 5 November 1998 Abstract: A series of potential receptor moleculesbased on the dipurinyl-2,6-pyridinediearboxsmide motif has been prepared and the intramolecularhydrogenbonding charecterised by ZH NMR and FT- IR spectroscopies. The hydrogenbondinggives rise to a preferential planar, cis conformationfor the molecules. The planar nature of the unit also gives rise to ~¢-~stacking as shownby IH NMR dilution experiments. © 1998Elsevier ScienceLtd. All fights reserved. INTRODUCTION Molecular recognition studies of nucleoside bases provide useful information in the search for pharmacologically active compounds 1'2 and the selective cleavage of DNA. 3 Specific hydrogen bonding interactions of the Hoogsteen-type and Watson-Crick type are the dominant interactions in the recognition 2, 4,6 of single base pairs, along with the g-g stacking of the aromatic base pairs.l, 7 Amide derivatives of pyridine-2,6-dicarboxylic acids have been used previously to study the intramolecular hydrogen bonding of amido carbohydrates, s the self assembly of macrocyclic porphyrins 9 and for the directed macrocyclisation of host molecules) ° In addition, such derivatives have been used to assist the synthesis of metallohelices based on Ni(II) and Cu(II) complexes where deprotonation of the amide nitrogens allows ready coordination of the metal.t= The intramoleeular hydrogen bonding between the pyridinyl nitrogen and the amide hydrogens enables the molecules to adopt a preferential cis conformation (Figure 1). l0 R" N,•" ',H.,.N~R Figure 1 Molecular modelling of simple dipurinyl-2,6-pyridinedicarboxamides showed that the planar conformation stabilised by the intramolecular hydrogen bonding would give rise to potential hosts for a 0040-4020/99/$ - see front matter © 1998 Elsevier Science Ltd. All rights reserved. Plh S0040-4020(98)01053-9