Yasuhisa Kuroda

A,B,D,F-tetrasubstituted β-cyclodextrin as artificial channel compound

Abstract As a channel forming compound, β-cyclodextrin having four hydrophobic tails and three metal binding sites, 1, [A,C,D,F,-tetra-6-(6-n-butyrylamino-n-hexylsulfenyl)-β-cyclodextrin] was synthesized as a “half channel”. Artificial liposome modified with 1 transported Co ++ efficiently with the rate, 4.5 × 10 −4 sec −1 for 55 μM 1, much faster tahn the rate for the unmodified liposome.

A STUDY OF THE KINETICS OF INCLUSION OF HALONAPHTHALENES WITH ß-CYCLODEXTRIN VIA TIME CORRELATED PHOSPHORESCENCE

Abstract— The phosphorescence of 1‐bromonaphthalene and 1‐chloronaphthalene is readily observable in nitrogen purged aqueous solutions containing ß‐cyclodextrin. Addition of acetonitrile increases both the phosphorescence intensity and lifetime. The quenching of halonaphthalene phosphorescence in aqueous solution by nitrite is substantially inhibited upon addition of ß‐cyclodextrin, as a result of a guest‐host complex. The rate constants for formation and dissociation of the l‐bromonaphthalene/ß‐cyclodextrin complex are evaluated from an analysis of the dependence of phosphorescence lifetimes on nitrite concentration.

A new route for meso-substituted porphyrin

Abstract A new synthetic route of meso-substituted porphyrins was established. The method presented here shows wide applicability for the preparation of aryl and alkyl meso-substituted porphyrins.

Cyclodextrins and Cyclophanes as Enzyme Models

Publisher Summary This chapter discusses cyclodextrins and cyclophanes as enzyme models. Cyclodextrins are doughnut-shaped, macrocyclic oligosaccharides constructed of glucose units linked by a α( 1 → 4) bond. Cyclodextrin has the following apparent merits as an enzyme model: (1) its chemical and physical properties are well known, (2) its crystal structures (free and complexed) are satisfactorily established, (3) the stoichiometry of the inclusion processes is easily defined, and (4) a new strategy was found recently by the authors for the specific introduction of desired catalytic functional group(s) on cyclodextrins. The term “cyclophane” is the general name and means a macrocyclic compound containing aromatic moieties within its cyclic skeleton. Cyclophanes has several great advantages in use as enzyme models. First, the design of the preparation of substituted cyclophanes is well established. Second, they are very stable, even more by stable comparison with corresponding cyclodextrins. Moreover, a cyclophane of certain cavity size isreadily available. Because of these advantages, cyclophanes attract increasing attention from chemists.

Self-induced porphyrin dimer formation via unusual atropisomerization of tetraphenylporphyrin derivative

Abstract Atropisomerization of meso-tetrakis( 2 -carboxy-4-nonylphenyl)porphyrin 1 , in nonpolar solvents such as CHCl 3 gives the αααα isomer exclusively, while the same isomerization in polar solvents such as DMSO proceeds normally. Spectroscopic investigations of 1 suggest that the porphyrin exists as a cofacial dimer in nonpolar solvents, where eight hydrogen bonds among tour pairs of carboxylic acids in 1 are formed.

Highly Fluorescent Slipped-Cofacial Phthalocyanine Dimer as a Shallow Inclusion Complex with α-Cyclodextrin

Supramolecular control of the π-stacked configuration of aqueous phthalocyanine (Zn[Pc(SO(3))(4)]) was achieved, allowing organization of a J-type slipped-cofacial dimer with per-O-methylated α-cyclodextrin (TMe-α-CDx) by the aid of host-guest interactions. Pristine Zn[Pc(SO(3))(4)] forms nonfluorescent face-to-face aggregates in water. The π-stacked configuration was controlled in the slipped-cofacial dimer, which was formed as a shallow inclusion complex with TMe-α-CDx, giving remarkably enhanced fluorescence with a very small Stokes shift. Organization of the J-type slipped-cofacial dimer as a 2:2 Zn[Pc(SO(3))(4)]-TMe-α-CDx complex was achieved through π-stacking of the unencapsulated segment of Zn[Pc(SO(3))(4)] shallowly encapsulated by a small TMe-α-CDx cavity.

Adamantyl amino acid as γ-turn inducer for peptide

Abstract The structures of six peptide mimics having different bulkiness and/or rigidity of the amino acids were investigated spectroscopically. Comparison of 1 H NMR, IR spectra and H-D exchange rate of the amide protons reveals that 2-amino-2-carboxyadamantane induces the high population of γ-turn conformation in the room temperature region and may be utilized as a promising γ-turn inducer for synthetic peptides.

A.C; A′.C′-doubly capped δ-cyclodextrin. Direct evidence for the capping structure

Abstract Doubly capped β-cyclodextrin was firstly prepared in good yield by the treatment of β- cyclodextrin with an excess amount (2.6/1 mol/mol) of benzophenone-3,3′-disulfonyl chloride. This successful double capping demonstrates that benzophenone-3,3′-disulfonyl capping takes place on A,C rings. The present double cap is a useful key intermediate for the preparation of regiospecifically tetrasubstituted cyclodextrins.

Construction of porphyrin-cyclodextrin self-assembly with molecular wedge

A new host porphyrin bearing four permethyl-beta-cyclodextrin moieties for multi-porphyrin assembly forms a unique 2 : 2 assembly with the tetra-anion of tetrakis(p-sulfonylphenyl)porphyrin (TPPS) in aqueous solution.

Synthetic strategies of multifunctional porphyrins as receptors

A series of multi-functional porphyrins 1-10 were prepared as a model receptor to clarify the mechanism of electron transfer reaction mediated by molecular recognition between reductase and mobile ubiquinone in membrane. Formation of complementary face-to-face complex is performed by multi-point hydrogen bonding between benzoquinones substituted with methoxy groups and particular porphyrins. Fluorescence from photo-chemically excited porphyrin is efficiently quenched by quinone derivative in the face-to-face adduct. Binding constants and thermodynamic parameters are discussed with structural changes in both quinones and host porphyrins. Newly prepared intrinsic chiral porphyrins with C2 symmetry have been examined as a model receptor for amino acid esters. Thermodynamic investigation on the intermolecular interaction of chiral and reference porphyrins with amino acids enables us to estimate contribution of the respective interactions such as hydrogen bonding, coordination to the metal, and van der Waals contact. The host having the chiral cavity above and below the porphyrin plane shows high diastereomeric selectivity towards amino acids with bulky residue.