Frustrated Helicity: Joining the Diverging Ends of a Stable Aromatic Amide Helix to Form a Fluxional Macrocycle |
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| Authors: | Ko Urushibara Dr Yann Ferrand Dr Zhiwei Liu Prof Hyuma Masu Prof Vojislava Pophristic Prof Aya Tanatani Prof Ivan Huc |
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| Institution: | 1. Department of Chemistry, Faculty of Science, Ochanomizu University, Tokyo, Japan;2. CBMN (UMR5248), Univ. Bordeaux—CNRS—IPB, Institut Européen de Chimie et Biologie, Pessac, France;3. Department of Chemistry &Biochemistry, University of the Sciences, Philadelphia, PA, USA;4. Center for Analytical Instrumentation, Chiba University, Chiba, Japan;5. Department Pharmazie, Ludwig-Maximilians-Universit?t, München, Germany |
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| Abstract: | 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. |
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| Keywords: | cis amides fluxionality frustrated helicity macrocycles strained structures |
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