Increasing the Functional Group Diversity in Helical beta-Peptoids: Achievement of Solvent- and pH-Dependent Folding

Isabelle Wellhofer, Janina Beck, Karla Frydenvang, Stefan Brase, Christian A. Olsen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

2 Citations (Scopus)

Abstract

We report the synthesis of a series of bis-functionalized beta-peptoid oligomers of the hexamer length. This was achieved by synthesizing and incorporating protected amino- or azido-functionalized chiral building blocks into precursor oligomers by a trimer segment coupling strategy. The resulting hexamers were readily elaborated to provide target compounds displaying amino groups, carboxy groups, hydroxy groups, or triazolo-pyridines, which should enable metal ion binding. Analysis of the novel hexamers by circular dichroism (CD) spectroscopy and H-1-C-13 heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) spectroscopy revealed robust helical folding propensity in acetonitrile. CD analysis showed a solvent-dependent degree of helical content in the structural ensembles when adding different ratios of protic solvents including an aqueous buffer. These studies were enabled by a substantial increase in solubility compared to previously analyzed beta-peptoid oligomers. This also allowed for the investigation of the effect of pH on the folding propensity of the amino- and carboxy-functionalized oligomers, respectively. Interestingly, we could show a reversible effect of sequentially adding acid and base, resulting in a switching between compositions of folded ensembles with varying helical content. We envision that the present discoveries can form the basis for the development of functional peptidomimetic materials responsive to external stimuli.

Original languageEnglish
JournalJournal of Organic Chemistry
Volume85
Issue number16
Pages (from-to)10466-10478
Number of pages13
ISSN0022-3263
DOIs
Publication statusPublished - 2020

Keywords

  • SOLID-PHASE SYNTHESIS
  • ASYMMETRIC-SYNTHESIS
  • CHIRAL AMINES
  • SIDE-CHAIN
  • CIRCULAR-DICHROISM
  • FOLDAMERS
  • PEPTIDE
  • BACKBONE
  • SUBSTITUENTS
  • STABILITY

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