Akiko Ikuta

Preparation and Characterization of 61,6n-DI-O-(α-D-Galactopyranosyl)Cyclomaltooctaoses

ABSTRACT Four positional isomers of 61,6n-di-O-(D-galactopyranosyl)cyclomaltooctaoses (cG8s, γ-cyclodextrins) (n = 2−5) were chemically synthesized using the trichloroacetimidate method. The desired compounds having two α-(1→6)-linkages were isolated from a mixture of configurational isomers by HPLC, and their structures were confirmed by 13C NMR spectroscopy and FAB-high resolution mass spectra (HRMS). The elution behavior of their four positional isomers on an ODS column by HPLC is discussed.

Synthesis of Novel Heterobranched β-Cyclodextrins Having β-D-N-Acetylglucosaminyl-Maltotriose on the Side Chain

From a mixture of N-acetylglucosaminyl-β-cyclodextrin (GlcNAc-βCD) and lactose, β-D-galactosyl-GlcNAc-βCD (Gal-GlcNAc-βCD) was synthesized by the transfer action of β-galactosidase. GlcNAc-maltotriose (Glc3) and Gal-GlcNAc-Glc3 were produced with hydrolysis of GlcNAc-βCD by cyclodextrin glycosyltransferase, and Gal-GlcNAc-βCD by bacterial saccharifying α-amylase respectively. Finally, GlcNAc-Glc3-βCD and Gal-GlcNAc-Glc3-βCD were synthesized in 5.2% and 3.5% yield when Klebsiella pneumoniae pullulanase was incubated with the mixture of GlcNAc-Glc3 and βCD, or Gal-GlcNAc-Glc3 and βCD respectively. The structures of GlcNAc-Glc3-βCD and Gal-GlcNAc-Glc3-βCD were analyzed by FAB-MS and NMR spectroscopy and identified as 6-O-α-(63-O-β-D-N-acetylglucosaminyl-maltotriosyl)-βCD, and 6-O-α-(4-O-β-D-galactopyranosyl-63-O-β-D-N-acetylglucosaminyl-maltotriosyl)-βCD respectively.

Efficient Chemical Syntheses of Branched Cyclomalto‐Oligosaccharides Using the Trichloroacetimidate Method

Glycosylation using the trichloroacetimidate method was investigated in order to synthesize branched cyclomalto‐oligosaccharides (cyclodextrins, CDs). We examined the chemical syntheses of galactosyl CDs, directly β‐linked to the CD ring, which could not be synthesized by enzyme catalyzed reactions. We prepared 6‐O‐(d‐galactosyl)‐γCD and 6‐O‐(d‐mannosyl)‐γCD as basic model compounds using a combination of protecting groups on the glycosyl donor, catalysts to synthesize imidate derivatives, and catalysts for glycosylation. The configurational isomers were determined by HPLC and NMR spectroscopy.

Preparation and Characterization of Branched β-Cyclodextrins Having Manno-Oligosaccharide Side Chains Derived from Yeast Mannan and Study of Their Functions

Branched β-cyclodextrins (β-CDs) having manno-oligosaccharide side chains were investigated. Three kinds of monobranched β-CDs and five kinds of dibranched β-CDs were chemically synthesized using the trichloroacetimidate method. Their structures were analyzed by HPLC, MS, and NMR spectroscopies. The specific interaction between those compounds and mannose-binding lectins (Concanavalin A and Pisum sativum agglutinin) was investigated by inhibition tests of hemagglutinating activity and by using an optical biosensor of the IAsys apparatus with a resonant mirror detector. The results showed that all branched β-CDs interactedwith lectins. The binding affinity was 61,64-(Man3)2- ≫ 61,64-(Man2)2- > 61,64-(Man4)2-β-CD when the derivatives were compared on the basis of side chain length and 61,63- ≫ 61,64- > 61,62-(Man2)2-β-CD when compared on the basis of side chain position.

Preparation, Isolation and Characterization of all of the Regioisomeric 61, 6N-Bis-O-(Monomethoxytrityl) and-(Dimethoxytrityl) Derivatives of Cyclomalto-Olgosaccharides

Abstract Regioisomeric 61, 6n-bis-O-(monomethoxytrityl) or 61, 6n-bis-O-(dimethoxytrityl) cyclomaltohexaose, -cyclomaltoheptaose (n = 2-4), and -cyclomaltooctaose derivatives (n = 2-5) were prepared by the reaction of cyclomaltohexaose (1, cG6, αCD), cyclomaltoheptaose (11, cG7, βCD) or cyclomaltooctaose (21, cG8, γCD) and 4-monomethoxytrityl chloride or 4,4′-dimethoxytrityl chloride in pyridine. Products were isolated by HPLC. The regiochemical determination of these positional isomers was done by converting these compounds to the respective 61, 6n-bis-O-(tert-butyldimethylsilyl) derivatives1 whose structures have been already established.

Retention behavior of positional isomers of disubstituted cyclomalto-oligosaccharide (cyclodextrin) derivatives on an ODS column

The correlation between hydrophobic effects and structures of three and four positional isomers of 6(1),6n-di-O-triphenylmethyl (trityl)- or 6(1),6n-di-O-tert.- butyldimethylsilyl (tert.-BuMe2Si)-cyclomaltohexaoses (cG6s, alpha-cyclodextrin) (n = 2-4), -cyclomaltoheptaoses (cG7s, beta-cyclodextrin) (n = 2-4), and -cyclomaltooctaoses (cG8s, gamma-cyclodextrin) (n = 2-5) on an ODS column are discussed. Cyclodextrins with two hydrophobic-substituted groups bonded to hydroxyl groups tended to show low retention of positional isomers in which the binding positions of the two substituted groups on the cyclodextrin ring were far apart from each other.