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The addition of a precisely positioned chiral center in the tether of a constrained peptide is reported, yielding two separable peptide diastereomers with significantly different helicity, as supported by circular dichroism (CD) and NMR spectroscopy. Single crystal X-ray diffraction analysis suggests that the absolute configuration of the in-tether chiral center in helical form is R, which is in agreement with theoretical simulations. The relationship between the secondary structure of the short peptides and their biochemical/biophysical properties remains elusive, largely because of the lack of proper controls. The present strategy provides the only method for investigating the influence of solely conformational differences upon the biochemical/biophysical properties of peptides. The significant differences in permeability and target binding affinity between the peptide diastereomers demonstrate the importance of helical conformation. [ABSTRACT FROM AUTHOR]

A precisely positioned sulfilimine chiral center in the tether of a stabilized peptide would determine the peptide's secondary structure. Peptide sulfilimines could be prepared by a facile chloramine T oxidation and the two resulting peptide diastereomers showed significant differences in their secondary structures, which were supported by circular dichroism spectroscopy and NMR. [ABSTRACT FROM AUTHOR]

Recently, our group reported that a precisely positioned chiral center on a thioether tether could dominate the backbone peptides' secondary structures and modulate the peptides' biophysical properties. Helical peptides constructed with this chirality induced helicity (CIH) method were named as CIH peptide. In this work, we examined the effects of substituting the thioether tether with an all hydrocarbon tether for the biophysical property differences. Two peptide epimers were prepared and showed distinct secondary structures and the R epimer is helical. Comparing with its thioether counterpart, the all‐hydrocarbon R epimer showed slightly higher helical content, modest improved binding affinity with mammal double minute 2 (MDM2), while similar cell permeability and slightly higher membrane toxicity. [ABSTRACT FROM AUTHOR]