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Self-assembly of secondary structural elements represent an intriguing approach for non-covalent synthesis that can potentially offer greater selectivity and orthogonality than existing methods. To this end, the ability of aromatic oligamide foldamers to hybridize into multiple helices can be seen as a powerful tool for the formation of discrete molecular cages or even networks. Still, the spontaneity of this process complicates synthetic aspects of the incorporation of multi-helical segments into larger scaffolds. In this poster we describe the synthesis of a series of diazaiptycene based aromatic monomers via Diels-Alder reaction and show that their incorporation into longer oligomers leads to structural distortions that prevent aggregation between multiple strands. Importantly the use of a TAD (triazoledione) group as dienophile opens a way to the control the oligomer topology via a Diels-Alder / retro Diels-Alder strategy and the use of thermal stimulus to trigger double helix formation. Perspectives for using this approach for the design and synthesis of larger molecular architectures formed via double helix driven self-assembly are also discussed.

This project seeks to develop a method to control Aromatic Oligoamide Foldamer (AOF) self-assembly in solution by providing a method to prevent multi-stranded helix formation using a reversible synthetic modification. To this end, a Diels-Alder strategy was designed by screening 1,8-diazaanthracene aromatic monomers, acting as dienes, with a range of dienophiles to that would break the extended conjugation in the monomer and could also add steric constraints to further disfavor multi-stranded helix formation [1]. By incorporating this unit into longer sequences, we showed, based on structural studies, that the Diels-Alder modification is sufficient to prevent multi-helix formation. Finally, by applying retro-Diels-Alder conditions to the oligomer, it is possible to remove the dienophile and induce multi-helix formation. Together, these reactions provide a new tool for controlling multi-helix formation in AOF and expand their potential use in the broader area of self-assembly.

This project seeks to develop a method to control Aromatic Oligoamide Foldamer (AOF) self-assembly in solution by providing a method to prevent multi-stranded helix formation using a reversible synthetic modification. To this end, a Diels-Alder strategy was designed by screening 1,8-diazaanthracene aromatic monomers, acting as dienes, with a range of dienophiles to that would break the extended conjugation in the monomer and could also add steric constraints to further disfavor multi-stranded helix formation [1]. By incorporating this unit into longer sequences, we showed, based on structural studies, that the Diels-Alder modification is sufficient to prevent multi-helix formation. Finally, by applying retro-Diels-Alder conditions to the oligomer, it is possible to remove the dienophile and induce multi-helix formation. Together, these reactions provide a new tool for controlling multi-helix formation in AOF and expand their potential use in the broader area of self-assembly.

Diversification of the structures and applications possible for foldamers relies on expansion of the building block library available for their synthesis. In this work, we describe the synthesis of a range of three dimensional heteroaromatic monomers, based on iptycene scaffolds, that are suitable for the synthesis of aromatic oligoamide foldamers. These units can be obtained in gram quantities in up to 80% yield through [4+2] cycloaddition between diester, diamine, and amino acid derivatives of 1,8-diazaanthracenes and a variety of dienophiles. X-ray structural studies of the monomers and an oligomer show that the new motif orients the two heterocyclic rings and attached groups at an angle of approximately 120° to each other, opening new geometric considerations for the design of this class of foldamer.