title: New artificial host compounds containing galactose end groups for binding chiral organic amine guests: chiral discrimination and their complex structures.
abstract: New linear host (1) and cyclic hosts (2 and 3), which have galactopyranose skeletons as chiral origins and oxyethylenes skeletons as binding sites, were designed based on the structural features extracted from the fructo-oligosaccharide derivatives, having a large chiral discrimination ability, and were then synthesized. These hosts showed chiral discrimination toward chiral organic ammonium salts. For example, the chiral discrimination ability (the ratio of association constants: K(R)/K(S)) of host 1, which has the highest value among them, was K(R)/K(S) = 3 for Trp-O-(i)Pr(+) and K(R)/K(S) = 0.7 for 1-(1-naphthyl)ethylammonium (NEA(+)) at 298 K in CHCl(3). It was clarified that host 1 changed the conformation from a linear structure to the pseudo-ring structure by complexation with cations such as alkali metallic ions and chiral organic ammonium ions. The (1)H NMR induced shifts of host 1 by adding the NEA(+) guests showed that the host-guest complex structures are clearly different, depending upon the chirality of the guest; in the complex with (R)-NEA(+), the naphthyl group of the guest is located above the oxyethylene skeleton of the host and in the complex with (S)-NEA(+), and the naphthyl group is located between the edges of the pseudo-ring of the host. The clearly different structure of the complex of host 1 with NEA(+) may be caused by the dynamic molecular recognition, thus the induced-fitting mechanism.
authors.affiliation: Technochemistry Department, Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan. shizuma@omtri.city.osaka.jp
authors.forename: Motohiro
authors.initials: M
authors.lastname: Shizuma
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kadoya
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Imamura
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Yamada
authors.forename: Tokuji
authors.initials: T
authors.lastname: Takeda
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Takahashi
authors.forename: Masami
authors.initials: M
authors.lastname: Sawada
mesh_terms: D001665:Binding Sites; D002625:Chemistry, Organic / Q000379:methods*; D003500:Cyclization; D005690:Galactose / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008968:Molecular Conformation; D015394:Molecular Structure; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D009844:Oligosaccharides; D000644:Quaternary Ammonium Compounds; D005690:Galactose