Amplification of local chirality within a folded dendrimer. An intramolecular ‘sergeants and soldiers’ experiment

Abstract

A series of pyridine-2,6-dicarboxamide dendrons having varying proportions of chiral and achiral termini have been prepared. Circular dichroism and X-ray crystallographic studies indicate that these folded dendrons propagate terminal chirality via a 'sergeants and soldiers' process. The extent of chiral amplification shows a dependence on dendron generation, but also is affected by the relative positioning of the chiral termini at the periphery of the dendron. Analysis of the crystal structures of the G1 dendrons, 4a-6a, reveals chain-chain and chain-dendron conformational communication, which is likely to be responsible for the chiral amplification observed in solution.

Chiral Amplification in Nature: Studying Cell‐Extracted Chiral Carotenoid Microcrystals via the Resonance Raman Optical Activity of Model Systems

“…According to this effect, a small number of chiral units (sergeants) force a large number of achiral ones (soldiers) to adopt a supramolecular structure and to display an intense chiral signal . This kind of chirality amplification has been observed for other supramolecular systems, such as foldamers, helical nanotubes and columns, as well as polymers and copolymers . The chirality of the model aggregates studied is due to chirality transfer between chiral αC or astaxanthin (AXT) molecules and achiral βC components, which together form a mixed supramolecular chiral system exhibiting resonance‐enhanced ROA (RROA).…”

Ligand Scaffold Optimization of a Supramolecular Hydrogenation Catalyst: Analyzing the Influence of Key Structural Subunits on Reactivity and Selectivity

“…10 We and others are exploring the use of these strategies to organize chirality and define the topography for supramolecular chemocatalysts 11-18 building on the studies of supramolecular chemistry 19-26 , especially in the context of ligands and organometallic catalysts constructed via self-assembly whether by metal complexation, 27-34 hydrogen bonding 35-46 or non-bonded interactions. 47 The concept is illustrated schematically by the bimetallic catalyst (i.e., structure 3 ) shown in Figure 1.…”

“…Hydrogen bonding and metal complexation are common structural motifs used in nature to direct the three-dimensional assembly of a protein framework so as to position the active site functionalities and create the chiral pocket for biocatalysts . We and others are exploring the use of these strategies to organize chirality and define the topography for supramolecular chemocatalysts − building on the studies of supramolecular chemistry, − especially in the context of ligands and organometallic catalysts constructed via self-assembly whether by metal complexation, − hydrogen bonding − or nonbonded interactions . The concept is illustrated schematically by the bimetallic catalyst (i.e., structure 3 ) shown in Figure .…”

The Structure of PAMAM DAB-dendr(NH2)4 – the First Crystal Structure of a PAMAM-Dendrimer

“…Searching the literature reveals a small number of crystal structures for dendrimers, but the majority of these are built from rigid branch cell units like Frechét-dendrons [9][10][11] , polyphenylenedendrimers 12 , pyridine carboxamide dendrons 13 , benzene-1,3,5-tris(carboxamide) dendrimers 14 , aromatic sulfonimides 15 , porphyrin-cored silane dendrimers 16 and a Mo 2 -cored poly(3,5dihydroxybenzoate) dendrimer 17 . Fewer are known for less rigid dendrimers with the structure of the tetrakis BOC-derivative of DAB-core poly(propyleneimine) G1 (Meijer-nomenclature but G0 according to the Tomalia-nomenclature) as a prominent example 18 .…”