One-pot formation of large macrocycles with modifiable peripheries and internal cavities.

The shape of things to come: Aromatic oligohydrazide macrocycles with planar backbones enforced by three-center hydrogen bonds are formed in high yield from monomeric diacid chlorides and dihydrazides. Macrocycles consisting of six meta-linked pyridine and benzene residues have an internal cavity of about 10 A diameter, while those with alternating meta- and para-linked benzene residues are larger and contain multiple convergent sites (see picture).

Efficient kinetic macrocyclization.

In this article, the highly efficient formation of a series of recently discovered aromatic oligoamide macrocycles consisting of six meta-linked residues is first discussed. The macrocycles, with their backbones rigidified by three-center hydrogen bonds, were found to form in high yields that deviate dramatically from the theoretically allowed value obtained from kinetic simulation of a typical kinetically controlled macrocyclization reaction. The folding of the uncyclized six-residue oligomeric precursors, which belong to a class of backbone-rigidified oligoamides that have been demonstrated by us to adopt well-defined crescent conformations, plays a critical role in the observed high efficiency.

Sequence-specific, dynamic covalent crosslinking in aqueous media.

This article describes an associating system that integrates the specificity of multiple hydrogen bonding and the strength of dynamic covalent interactions. Linear oligoamides that sequence-specifically pair into H-bonded duplexes in nonpolar solvents were modified with S-trityl groups, allowing the reversible formation of disulfide bonds. The disulfide-crosslinking reactions of oligoamides capable of pairing via two, four, and six intermolecular H-bonds, along with several control strands, were examined using ESI, MALDI-TOF, reverse phase HPLC, and two-dimensional NMR.

Improving foldamer synthesis through protecting group induced unfolding of aromatic oligoamides.

The hydrogen bond rigidified backbones of aromatic oligoamides are temporarily interrupted by replacing the amide hydrogens with the acid-labile 2,4-dimethoxybenzyl (DMB) group, which allows the efficient preparation of long folding oligomers that, upon removal of the DMB groups, fold into multiturn helices. [structure: see text]

Sequence-specific association in aqueous media by integrating hydrogen bonding and dynamic covalent interactions.

Oligoamide strands that associate in a sequence-specific fashion into hydrogen-bonded duplexes in nonpolar solvents were converted into disulfide cross-linked duplexes in aqueous media. Thus, by incorporating trityl-protected thiol groups, which allows the reversible formation of disulfide bonds, into the oligoamide strands, only duplexes consisting of complementary hydrogen-bonding sequences were formed in aqueous solution as well as in methanol. The sequence-specific cross-linking of oligoamide strands was confirmed by MALDI-TOF, reverse-phase HPLC, and by isolating a cross-linked duplex.

Synthesis of crescent aromatic oligoamides.

[structures: see text] This article describes the synthetic procedures for the preparation of crescent (and helical) aromatic oligoamides developed in recent years in our laboratory. The large-scale preparation of a variety of monomers derived from various tetrasubstituted benzenes is presented. Three different strategies for constructing various oligomers consisting of meta- and meta/para-linked benzene residues are discussed.