title: Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation.
abstract: We demonstrate two types of inversion of a helical preference upon the 1:1 complexation of a dynamic figure eight molecule with a guest molecule through the controlled transmission of point chirality. We designed a series of macrocycles that prefer a nonplanar conformation with figure eight chirality. These macrocycles are composed of a chirality-transferring unit (terephthalamide) and a structure-modifying unit (two o-phenylene rings spaced with a varying number of triple bonds). The former unit provides a binding site for capturing a guest molecule through the formation of hydrogen bonds. The attachment of chiral auxiliaries to the former unit induces a helical preference for a particular sense through the intramolecular transmission of point chirality. For relatively small-sized macrocycles, the preferred sense was reversed upon complexation with an achiral guest. Contrary preferences before and after complexation were both seen for chiral auxiliaries associated with a figure eight host through two-way intramolecular transmission of the single chiral source. Alternatively, the helical preference induced in relatively large-sized macrocycles was reversed only when a figure eight host formed a 1:1 complex with a particular enantiomeric guest through the supramolecular transmission of point chirality in the guest. This stereospecific inversion of a helical preference is rare.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Katoono
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kusaka
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Kenshu
authors.initials: K
authors.lastname: Fujiwara
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Suzuki