Aromatic Amide Foldamers: Structures, Properties, and Functions

Synthesis of 1,8-diazaanthracenes as building blocks for internally functionalized aromatic oligoamide foldamers

The synthesis of a variety of 9-functionalized 1,8-diazaanthracene diesters and amino acids is described. Derivatization at the 9-position relies on facile reactions performed on the 9-chloro and 9-bromomethyl precursors. This has allowed the incorporation of nucleophilic or sensitive functional groups that otherwise cannot be incorporated under standard methods for synthesizing these compounds. Additionally, the synthesis of the protected amino acids via a high-yielding monosaponification and subsequent Curtius rearrangement has been accomplished on a multigram scale. These units, together with the functionalized derivatives, should prove to be useful monomers in the synthesis of aromatic oligoamide foldamers.

Conformation of a terminally protected βγ hybrid dipeptide Boc-Ant-Gpn-OMe stabilized by C6/C7 hydrogen bonds

The hybrid βγ dipeptide, methyl 2-[1-({2-[(tert-butoxycarbonyl)amino]benzamido}methyl)cyclohexyl]acetate (Boc-Ant-Gpn-OMe), C22H32N2O5, adopts a folded conformation stabilized by intramolecular six- (C6) and seven-membered (C7) hydrogen-bonded rings, together with weak C-H...O and C-H...π interactions, resulting in a ribbon-like structure.

Palladium-catalyzed carbonylation of allylamines via C–N bond activation leading to β,γ-unsaturated amides

Pd(Xantphos)Cl₂ has been identified as an efficient catalyst for the direct carbonylation of allylamines via C–N bond activation.

Mechanistic and dynamic insights into ligand encapsulation by helical arylamide foldamers

A hydrazine molecule encapsulated in an arylamide helical foldamer escaping from the “top” (top) and “side” (bottom) of the capsule in the aqueous and methanol solution, respectively.

Spontaneous formation of organic helical architectures through dynamic covalent chemistry

Using dynamic covalent chemistry, achiral and chiral building blocks are capable of self-organizing into organic helical structures, accompanied with chiral amplification.

Size-dependent patterned recognition and extraction of metal ions by a macrocyclic aromatic pyridone pentamer

A macrocyclic aromatic pyridine pentamer was found to exhibit patterned recognition of metal ions and efficiently extract larger ions, such as Cs⁺, Ba²⁺, Tl⁺, Au⁺, K⁺ and Rb⁺ preferentially over the other 18 smaller metal ions from the aqueous phase into the chloroform layer.

An insight into the extraction of transition metal ions by picolinamides associated with intramolecular hydrogen bonding and rotational isomerization

Disruption of intramolecular H-bonding via N-substitution leads to rotational isomerization and much improvement in extraction of Hg²⁺.

Novel ortho-OPE metallofoldamers: binding-induced folding promoted by nucleating Ag(i)–alkyne interactions

Ag(i)–alkyne interactions induce the folding of o-OPE foldamers, yielding a new class of metallofoldamers.

A conformationally switchable fluorescent oligophenol foldamer for selective sensing of copper(ii) ions

A stimuli-responsive hexameric oligophenol host undergoes amine-induced co-operative folding and fluorescence quenching, enabling easy classification of the bound metal ion guests as well as selective sensing of Cu²⁺ ions.

Intramolecular C–H⋯F hydrogen bonding-induced 1,2,3-triazole-based foldamers

Intramolecular C–H⋯F hydrogen bonding has been utilized to induce 1,2,3-triazole oligomers to fold into stable artificial secondary structures.

Ultrastructure of metallopeptide-based soft spherical morphologies

Metal-mediated modification of soft spherical assemblies is reportedviaintroduction of a coordinating linker for FF dipeptide. Single crystal data, microscopy and reversal of soft structure coalescence is described.

Quadruply hydrogen-bonded heteroduplexes based on imide and urea units arrayed with ADDA/DAAD sequences

A new class of imide- and urea-based hetero-strands with a quadruple ADDA/DAAD hydrogen-bond array was designed and synthesized from easily accessible starting materials. The molecular recognition between the two different strands depends highly on the substituents and the linker between neighboring hydrogen-bonds, which results in the stability of these heteroduplexes varying from 10(3) to >10(5) M(-1) in apolar solvents. In particular, an increase of the association constant by up to one order of magnitude was observed by derivatizing the ADDA arrays at the termini with electron-withdrawing groups. Molecular modelling of the representative complementary complexes reveals the binding mode of four hydrogen-bond arrays that agrees with the matched pair.

End-to-end conformational communication through a synthetic purinergic receptor by ligand-induced helicity switching

The long-range communication of information, exemplified by signal transduction through membrane-bound receptors, is a central biochemical function. Reversible binding of a messenger ligand induces a local conformational change that is relayed through the receptor, inducing a chemical effect typically several nanometres from the binding site. We report a synthetic receptor mimic that transmits structural information from a boron-based ligand binding site to a spectroscopic reporter located more than 2 nm away. Reversible binding of a diol ligand to the N-terminal binding site induces a screw-sense preference in a helical oligo(aminoisobutyric acid) foldamer, which is relayed to a reporter group at the remote C-terminus, communicating information about the structure and stereochemistry of the ligand. The reversible nature of boronate esterification was exploited to switch the receptor sequentially between left- and right-handed helices, while the exquisite conformational sensitivity of the helical relay allowed the reporter to differentiate even between purine and pyrimidine nucleosides as ligands.