Synthesis and Characterization of a Series of Homooligopeptide Peroxyesters

Abstract

A homologous series of stable N(alpha)-phthaloyl peptide peroxyesters based on alpha-aminoisobutyric acid residues was prepared. In each of the six oligomers synthesized, the chain of alpha-amino acids is separated from the peroxyester function by a beta-amino acid. [structure: see text]

Insights into the Distance Dependence of Electron Transfer through Conformationally Constrained Peptides

“…Third, in each solvent the E° shifts significantly as the peptide length increases, although not linearly. These observations point to the peptide secondary structure as unaffected by the solvent, which confirms the structural study that we described previously …”

“…As the insertion of two carbon atoms between the carbonyl group and the nitrogen atom could have imparted undesired flexibility to the backbone, we decided to use the trans ‐2‐aminocyclohexane carboxylic acid. The structural rigidity of the peptides was previously demonstrated by NMR and IR absorption spectroscopy studies . Noteworthy, addition of the very good H‐bond acceptor dimethyl sulfoxide to the NMR solution (CDCl 3 ) did not affect the peptide secondary structure.…”

“…The synthesis of the D‐B‐A systems 1 0 – 5 (Scheme ) was described previously . The insertion of a perester acceptor at the carboxylic side of the oligo‐Aib peptide requires using a β ‐amino acid, otherwise the resulting perester is unstable and undergoes spontaneous decarbonylation to form a dialkylperoxide .…”

“…Scheme compares the two phathalimide donor D‐B‐A systems. The peptide‐bridge length was modulated by changing the number of Aib units separating D and A ( n H in Scheme ) from 0 to 5. n H also represents the number of intramolecular hydrogen bonds in the Aib‐peptide structure . In addition to assessing the intramolecular ET kinetics and its distance dependence, we also tested the reaction for possible solvent effects.…”

“…The peptide-bridge length was modulated by changing the number of Aib units separating D and A (n H in Scheme 2) from 0 to 5. n H also represents the number of intramolecular hydrogen bonds in the Aib-peptide structure. [41] In addition to assessing the intramolecular ET kinetics and its distance dependence, we also tested the reaction for possible solvent effects. The results showed that the addition of one single methylene unit before the A group has the effect of virtually isolating the latter from the H-bond network, thereby making the mechanism follow a quite regular superexchange mechanism.…”