title: Chiral separation by a terminal chirality triggered P-helical quinoline oligoamide foldamer.
abstract: A P-helical quinoline oligoamide foldamer was grafted on silica and applied as an HPLC stationary phase for chiral separation. The P-handedness of the quinoline oligoamide foldamer was induced by a (1S)-camphanyl group, which was introduced at the N-terminus of a tetrameric quinoline oligoamide foldamer (Cmp-Q4). To immobilize the foldamer on porous silica particles, a trimethoxysilyl group was introduced at the opposing end of the foldamer. Elemental analysis indicated that the amount of foldamer on the silica surface was 0.57μmol/m(2). Circular dichroism and vibrational CD spectra of Cmp-Q4 and Cmp-Q4-immobilized silica (Sil-Q4-Cmp) suggested that the helical structure of Cmp-Q4 was altered on the silica surface whilst retaining a chiral structure. The chiral recognition ability of Sil-Q4-Cmp was evaluated with various aromatic enantiomers. Sil-Q4-Cmp showed enantio-selectivity for axially chiral molecules (e.g., αTrigger's base=1.26 and αBinaphthol=1.07). Sil-Q4-Cmp showed remarkable recognition of helical octameric quinoline oligoamides with isobutoxy and triethylene glycol side chains (α=10.35 and 14.98, respectively). In contrast, an (1S)-camphanyl group-immobilized porous silica showed no chiral recognition for any enantiomers tested in this study. To elucidate the chiral separation mechanism of Sil-Q4-Cmp, thermodynamic parameters were calculated using van't Hoff plots. HPLC results and thermodynamic parameters suggested that the chiral recognition of Sil-Q4-Cmp is based on the helical structure of Cmp-Q4 and other thermally dependent interactions such as hydrophobic effects associated with aromatic stacking. This work represents the first known application of aromatic foldamers in chiral separation.
authors.affiliation: Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Chuoku, Kurokami, Kumamoto 860-8555, Japan; University of Bordeaux, CBMN (UMR 5248), Institut Européen de Chimie Biologie, 2 rue Escarpit, 33600 Pessac, France; CNRS, CBMN (UMR 5248), 2 rue Escarpit, 33600 Pessac, France.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Noguchi
authors.affiliation: Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Chuoku, Kurokami, Kumamoto 860-8555, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Takafuji
authors.affiliation: University of Bordeaux, CBMN (UMR 5248), Institut Européen de Chimie Biologie, 2 rue Escarpit, 33600 Pessac, France; CNRS, CBMN (UMR 5248), 2 rue Escarpit, 33600 Pessac, France.
authors.forename: Victor
authors.initials: V
authors.lastname: Maurizot
authors.affiliation: University of Bordeaux, CBMN (UMR 5248), Institut Européen de Chimie Biologie, 2 rue Escarpit, 33600 Pessac, France; CNRS, CBMN (UMR 5248), 2 rue Escarpit, 33600 Pessac, France. Electronic address: i.huc@iecb.u-bordeaux.fr.
authors.forename: Ivan
authors.initials: I
authors.lastname: Huc
authors.affiliation: Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Chuoku, Kurokami, Kumamoto 860-8555, Japan; Kumamoto Institute for Photo-electro Organics (PHOENICS), 3-11-38 Higashimachi, Kumamoto, Japan. Electronic address: ihara@kumamoto-u.ac.jp.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ihara
mesh_terms: D000577:Amides / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D002942:Circular Dichroism; D011804:Quinolines / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000577:Amides; D011804:Quinolines
keywords: Aromatic foldamers; Chiral HPLC; Chiral stationary phase; Enantioselectivity; Helical structure