Synthesis, Characterization, and Folding Behavior of β‐Amino Acid Derived Polyisocyanides

Abstract

Helical polymers of isocyanopeptides derived from beta-amino acids have been synthesized and their architectures have been studied in detail. Similar to their alpha-amino acid analogues, the helical conformation in these macromolecules is stabilized by internal hydrogen-bonding arrays along the polymeric backbone. Unexpectedly, the flexibility of the beta-peptide side arms results in a rearrangement of the initial macromolecular architecture, leading to a more stable helical structure possessing a better defined hydrogen-bonding pattern, as was concluded from IR and temperature-dependent circular dichroism studies. Based on these results we propose a dynamic helical model for the beta-amino acid derived polyisocyanopeptides; this model is in contrast to the kinetically stable helical macromolecules that are formed upon polymerization of alpha-amino acid based isocyanopeptides.

Unexpected Thermally Stable, Cholesteric Liquid‐Crystalline Helical Polyisocyanides with Memory of Macromolecular Helicity

“…Similar hydrogen‐bonding‐assisted helix formation and stabilization was reported by Nolte and co‐workers for poly(isocyanopeptide)s, although the helices unfold irreversibly at high temperature 3d. 9a,b, 15…”

Tuning the properties of PS–PIAT block copolymers and their assembly into polymersomes

“…43 Polyisocyanides derived from b-amino acids were also reported to revert, on standing in solution, from a kinetically determined structure to a thermodynamically more stable one, as reflected in the CD spectra. 44 Interestingly, for these polymers it was observed that both the helical arrangement and the hydrogen-bonding network remained intact and only minor changes occurred in the corresponding spectra. For PIAG during polymerization, a transition was already observed to a state with only little secondary structure.…”

Poly(isocyanide)s, Poly(quinoxaline‐2,3‐diyl)s, and Related Helical Polymers Used as Chiral Polymer Catalysts in Asymmetric Synthesis

“…Helical poly(isocyanopeptide)s 15 and 16 derived from b-amino acids were synthesized ( Figure 8.3) [22]. Like their a-amino acid analogs, the helical conformation in these polymers is stabilized by internal hydrogen-bonding arrays.…”