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Light‐Controlled Conformational Switch of an Aromatic Oligoamide Foldamer
Author(s) -
Gole Bappaditya,
Kauffmann Brice,
Maurizot Victor,
Huc Ivan,
Ferrand Yann
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201902378
Subject(s) - foldamer , conformational isomerism , helix (gastropod) , chemistry , stereochemistry , crystallography , beta sheet , protein structure , molecule , organic chemistry , ecology , snail , biology , biochemistry
An aromatic oligoamide sequence composed of a light‐responsive diazaanthracene‐based aromatic β‐sheet flanked by two variable diameter helical segments was prepared. Structural investigations revealed that such oligomers adopt two distinct conformations: a canonical symmetrical conformation with the two helices stacked above and below the sheet, and an unanticipated unsymmetrical conformation in which one helix has flipped to directly stack with the first helix. Photoirradiation of the foldamer led to the quantitative, and thermally reversible, formation of a single photoproduct resulting from the [4+4] cycloaddition of two diazaanthracenes within the aromatic β‐sheet. NMR and crystallographic studies revealed a parallel arrangement of the diazaanthracene photoproduct and a complete conversion into a symmetrical conformation requiring a rearrangement of all unsymmetrical conformers. These results highlight the potential of foldamers, with structures more complex than isolated helices, for the design of photoswitches showing nontrivial nanometer scale shape changes.