title: Dynamic molecular propeller: supramolecular chirality sensing by enhanced chiroptical response through the transmission of point chirality to mobile helicity.
abstract: The secondary terephthalamide host 1a-H attached to four aryl blades was prepared from tetrabromide 2a by Suzuki-Miyaura coupling and undergoes a conformational change from a nonpropeller anti-form to a propeller-shaped syn-form upon complexation with ditopic guests such as p-xylylenediammonium derivatives (R,R)/(S,S)-3 (chirality generation). Through transmission of the point chiralities attached on the nitrogens in the chiral guests to the mobile helicity in 1a-H, the propeller-shaped host in the complex is biased to prefer a particular handedness (chirality biasing). While chiral guests with simple point chiralities such as (R,R)/(S,S)-3 exhibit only very weak CD activity, complexation with the dynamic propeller host 1a-H results in much stronger chiroptical signals (chiroptical enhancement). The chirality generation-chirality biasing protocol was successfully applied to a neurotransmitter, (-)-phenylephrine 4, acting as a chiral ditopic guest. When the chiral auxiliaries are attached to the host as in (R,R)-1b-H, complexation with (S,S)-3 causes CD enhancement but not with (R,R)-3, due to chiral recognition.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Katoono
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kawai
authors.forename: Kenshu
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Takanori
authors.initials: T
authors.lastname: Suzuki