Engineering Chiral Induction in Centrally Functionalized -Phenylenes.

Work on foldamers, nonbiological oligomers that mimic the hierarchical structure of biomacromolecules, continues to yield new architectures of ever increasing complexity. -Phenylenes, a class of helical aromatic foldamers, are well-suited to this area because of their structural simplicity and the straightforward characterization of their folding in solution. However, control of structure requires, by definition, control over folding handedness.

Guest-Driven Control of Folding in a Crown-Ether-Functionalized -Phenylene.

A crown-ether-functionalized -phenylene tetramer has been synthesized and coassembled with monotopic and ditopic, achiral and chiral secondary ammonium ion guests. NMR spectroscopy shows that the -phenylene forms both 1:1 and 1:2 complexes with monotopic guests while remaining well-folded. Binding of an elongated ditopic guest, however, forces the -phenylene to misfold by pulling the terminal rings apart.

Fluorine Labeling of -Phenylenes to Facilitate Conformational Analysis.

H NMR spectroscopy is a powerful tool for the conformational analysis of -phenylene foldamers in solution. However, as -phenylenes are integrated into ever more complex systems, we are reaching the limits of what can be analyzed by H- and C-based NMR techniques. Here, we explore fluorine labeling of -phenylene oligomers for analysis by F NMR spectroscopy.

Biomedically Relevant Applications of Bolaamphiphiles and Bolaamphiphile-Containing Materials.

Bolaamphiphiles (BAs) are structurally segmented molecules with rich assembly characteristics and diverse physical properties. Interest in BAs as standalone active agents or as constituents of more complex therapeutic formulations has increased substantially in recent years. The preorganized amphiphilicity of BAs allows for a range of biological activities including applications that rely on multivalency.

Twist sense control in terminally functionalized -phenylenes.

Many abiotic foldamers are based on achiral repeat units but adopt chiral geometries, especially helices. In these systems, there is no inherent preference for one handedness of the fold; however, it is well-established that the point chirality of substituents can be communicated to the helix. This capability represents a basic level of control over folding that is necessary for applications in molecular recognition and in the assembly of higher-order structures.

Solvent effects on the folding of o-phenylene oligomers.

ortho-Phenylene oligomers fold into compact helical conformations in solution, and have therefore recently emerged as a class of foldamers. Previous work has shown that their folding is controlled by arene-arene stacking interactions parallel to the helical axis. Such interactions might reasonably be expected to be sensitive to solvent, but little is known of solvent effects in this system.