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Aminomethylenehelicene Oligomers Possessing Flexible Two‐Atom Linker Form a Stimuli‐Responsive Double‐Helix in Solution
Author(s) -
Shigeno Masanori,
Sato Masahiko,
Kushida Yo,
Yamaguchi Masahiko
Publication year - 2014
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.201402065
Subject(s) - random hexamer , pentamer , chemistry , tetramer , helix (gastropod) , trifluoroacetic acid , crystallography , triple helix , linker , oligomer , stereochemistry , polymer chemistry , organic chemistry , biochemistry , enzyme , snail , computer science , biology , operating system , ecology
Aminomethylenehelicene oligomers up to the ( M )‐heptamer were synthesized by reductive amination from a formylhelicene building block. The oligomers containing more than three helicenes formed a double helix in 1,3‐dilfuorobenzene. The ( M )‐tetramer and ( M )‐pentamer unfolded into a random coil by heating to 60 °C, whereas the ( M )‐hexamer only slightly unfolded at the same temperature. A two‐sided thermal hysteresis was detected in the structural change of the ( M )‐tetramer and ( M )‐pentamer during cooling and heating. The ( M )‐pentamer and ( M )‐hexamer unfolded with the addition of trifluoroacetic acid and regenerated a double helix with the addition of triethylamine.