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The Effect of Backbone Stereochemistry on the Folding of Acyclic β 2, 3 ‐Aminoxy Peptides
Author(s) -
Zhang YuHui,
Song Kesheng,
Zhu NianYong,
Yang Dan
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901471
Subject(s) - chemistry , intramolecular force , foldamer , hydrogen bond , stereochemistry , folding (dsp implementation) , circular dichroism , crystallography , cyclic peptide , peptide , molecule , organic chemistry , biochemistry , electrical engineering , engineering
As a new type of foldamer, β‐aminoxy peptides have the ability to adopt novel β NO turns or β NO helices in solution. Herein, we describe a new subclass of β‐aminoxy peptide, that is, peptides of acyclic β 2, 3 ‐aminoxy acids (NH 2 OCHR 1 CHR 2 COOH), in which the presence of two chiral centers provides insight into the effect of backbone stereochemistry on the folding of β‐aminoxy peptides. Acyclic β 2, 3 ‐aminoxy peptides with syn and anti configurations have been synthesized and their conformations investigated by NMR, IR, and circular dichroism (CD) spectroscopic, and X‐ray crystallographic analysis. The β NO turns or β NO helices, which feature nine‐membered rings with intramolecular hydrogen bonds and have been identified previously in peptides of β 3 ‐ and β 2, 2 ‐aminoxy acids, are also predominantly present in the acyclic β 2, 3 ‐aminoxy peptides with a syn configuration and NO bonds gauche to the C α C β bonds in both solution and the solid state. In the acyclic β 2, 3 ‐aminoxy peptides with an anti configuration, an extended strand (i.e., non‐hydrogen‐bonded state) is found in the solid state, and several conformations including non‐hydrogen‐bonded and intramolecular hydrogen‐bonded states are present simultaneously in nonpolar solvents. These results suggest that the backbone stereochemistry does affect the folding of the acyclic β 2, 3 ‐aminoxy peptides. Theoretical calculations on the conformations of model acyclic β 2, 3 ‐aminoxy peptides with different backbone stereochemistry were also conducted to elucidate structural characteristics. Our present work may provide useful guidelines for the design and construction of new foldamers with predicable structures.