Synthetic duplex oligomers: optimizing interstrand affinity through the use of a noncovalent constraint

The covalent casting of a one-dimensional hydrogen-bonding motif permits the design of oligomers possessing a predetermined duplex mode of aggregation. In this account, studies on the hydrogen bond mediated self-assembly of dimeric duplex oligomers 2 in solution are described. Two-fold self-association in solution is established by H-1 NMR, and the intended mode of assembly is further corroborated via X-ray crystallographic analysis. An increase in interstrand affinity of over three orders of magnitude is observed upon substitution of nitrogen for oxygen in the oligomer backbone, owing to preorganization of the molecular strand in the binding effective conformation as directed by the formation of an internal hydrogen bond. These data provide insight into the structural and interactional features of the oligomers required for high affinity/specificity binding in organic media. (C) 2002 Elsevier Science Ltd. All rights reserved.