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Frustrated Helicity: Joining the Diverging Ends of a Stable Aromatic Amide Helix to Form a Fluxional Macrocycle
Author(s) -
Urushibara Ko,
Ferrand Yann,
Liu Zhiwei,
Masu Hyuma,
Pophristic Vojislava,
Tanatani Aya,
Huc Ivan
Publication year - 2018
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.201802159
Subject(s) - helicity , amide , degenerate energy levels , helix (gastropod) , chemistry , crystallography , stereochemistry , physics , organic chemistry , quantum mechanics , ecology , snail , biology
Macrocyclization of a stable two‐turn helical aromatic pentamide, that is, an object with diverging ends that are not prone to cyclization, was made possible by the transient introduction of disruptors of helicity in the form of acid‐labile dimethoxybenzyl tertiary amide substituents. After removal of the helicity disruptors, NMR, X‐ray crystallography, and computational studies show that the macrocycle possesses a strained structure that tries to gain as high a helical content as possible despite being cyclic. Two points of disruption of helicity remain, in particular a cis amide bond. This point of disruption of helicity can propagate along the cycle in a fluxional manner according to defined trajectories to produce ten degenerate conformations.