Article

Dynamic molecular propeller: supramolecular chirality sensing by enhanced chiroptical response through the transmission of point chirality to mobile helicity.

Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 Japan.
Journal of the American Chemical Society (impact factor: 9.91). 10/2009; 131(46):16896-904. DOI:10.1021/ja906810b pp.16896-904
Source: PubMed

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.

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    Article: Intelligent chiral sensing based on supramolecular and interfacial concepts.
    Katsuhiko Ariga, Gary J Richards, Shinsuke Ishihara, Hironori Izawa, Jonathan P Hill
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    ABSTRACT: Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized.
    Sensors 01/2010; 10(7):6796-820. · 1.74 Impact Factor
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Keywords

aryl blades
 
chiral auxiliaries
 
chiral ditopic guest
 
chiral guests
 
chiral recognition
 
chirality biasing
 
chirality generation
 
chirality generation-chirality biasing protocol
 
conformational change
 
ditopic guests
 
dynamic propeller host 1a-H results
 
mobile helicity
 
nonpropeller anti-form
 
p-xylylenediammonium derivatives
 
propeller-shaped host
 
propeller-shaped syn-form
 
secondary terephthalamide host 1a-H
 
simple point chiralities
 
stronger chiroptical signals
 
Suzuki-Miyaura coupling
 

Ryo Katoono