α‐Amino‐iso‐Butyric Acid Foldamers Terminated with Rhodium(I) N‐Heterocyclic Carbene Catalysts

Abstract

To investigate how remotely induced changes in ligand folding might affect catalysis by organometallic complexes, dynamic α‐amino‐iso‐butyric acid (Aib) peptide foldamers bearing rhodium(I) N‐heterocyclic carbene (NHC) complexes have been synthesized and studied. X‐ray crystallography of a foldamer with an N‐terminal azide and a C‐terminal Rh(NHC)(Cl)(diene) complex showed a racemate with a chiral axis in the Rh(NHC) complex and a distorted 310 helical body. Replacing the azide with either one or two chiral L‐α‐methylvaline (L‐αMeVal) residues gave diastereoisomeric foldamers that each possessed point, helical and axial chirality. NMR spectroscopy revealed an unequal ratio of diastereoisomers for some foldamers, indicating that the chiral conformational preference of the N‐terminal residue(s) was relayed down the 1 nm helical body to the axially chiral Rh(NHC) complex. Although the remote chiral residue(s) did not affect the stereoselectivity of hydrosilylation reactions catalysed by these foldamers, these studies suggest a potential pathway towards remote conformational control of organometallic catalysts.

A Chiral 19F NMR Reporter of Foldamer Conformation in Bilayers

“…The development of synthetic oligomers able to mimic the function of transmembrane proteins will provide insights into key cellular processes, such as the transit of molecules and information across membranes. , The ability to transmit molecular information across multinanometer distances (i.e., the width of a membrane) could also provide technology for new fields like molecular robotics, for example, by transferring instructions to a catalytic centre . Synthetic folded oligomers, foldamers, have shown great promise for mimicking the behavior of biological folded oligomers, such as proteins and oligosaccharides.…”

Advances in the Synthesis and Applications of N-Heterocyclic Carbene Metal Complexes with a Focus on the Weak Base Route

“…As a last relevant example in this context, we have chosen the work recently published by Webb and co-workers . With the aim of evaluating the effect of remotely induced changes in ligand folding on the catalytic activity of transition metal complexes, the authors prepared a selection of rhodium­(I)-NHC complexes bearing dynamic α-aminoisobutyric acid (Aib) peptide foldamers.…”