Kimiho Yamada

Functional organic gels Chirality induction through formation of highly-oriented structure

Abstract An L-glutamate derivative having one carboxylic and two dodecylamide groups form highly-oriented aggregates in benzene, which interact with a cationic achiral dye to produce extremely strong exciton coupling around the absorption band of the dye.

Specific bindings of methyl orange to chiral bilayer membranes with β-alanyl-L-glutamoyl head groups [1]

Abstract Interactions between methyl orange and cationic bilayer membranes constructed from a dialkyl amphiphile with a β-alanyl-L-glutamoyl head group were investigated. The chiral bilayers undergo a gel to liquid crystal phase transition to give rise to the reversible chirality change from - 8 × 104 to + 11 × 104 deg cm2 dmol−1 near the phase transition temperature. Methyl orange combines with the cationic membranes to give three kinds of spectra, belonging to the surface-oriented chiral dimer and the monomer and incorporated achiral monomer, in response to the phase transition of the bilayer membrane.

Functional organic gels. Enantioselective elution using chiral gels from amino acid-derived lipids

Abstract The L-glutamic acid-derived lipids form organic gels in benzene, which show enantioselective elution of N-dansyl L-phenylalanine from organic gels to aqueous phases. Differential scanning calorimetry and circular dichroism measurements demonstrate that this enantioselectivity occurred through highly-oriented structures of aggregated lipids like those of aqueous lipid membrane systems.

Chirally arranged monomeric dyes on helical bilayer membranes

Abstract Strong exciton coupling around the absorption band of monomeric dyes was induced by helical bilayer membranes formed from various L-glutamic acid-derived amphiphiles which contain three amides per molecule. The mirror-image of the circular dichroism spectra was observed by the corresponding D-isomers. No similar induction was observed by the corresponding ester-type amphiphiles which could not produce helices. It is assumed that dyes are helically arranged on helical bilayer membranes, resulting in an induction of chirality even in monomeric dyes.

Thermal isomerization process in benzene gels of l-glutamic acid-derived lipids with spiropyran head groups

First-order kinetic behaviour during the thermal isomerization process of lipids with photochromic spiropyran head groups in benzene strongly depends on the dispersion state of the lipids and this enables the determination of their critical aggregation concentrations.

Enantioselectively catalyzed oxidation of 3,4-dihydroxy-l-phenylalanine by N-lauroyl L or D-histidine-Cu(II) complex in CTABr micelles.

Abstract In order to investigate the enzyme model reaction the oxidation of 3,4-dihydihydroxy-L-phenylalanine(L-DOPA) was carried out using optically active catalyst, N-lauroyl L or D-histidine-Cu(II) complex(L or D-LauHis-Cu(II)), showing appreciable enantioselectivity in the presence of the mixed micelles with CTABr.

Lipid membrane analogues. Formation of highly-oriented structures and their phase separation behaviour in benzene

L-Glutamate derivatives 1 and 2 having two N-dodecylamide groups formed highly-oriented aggregates in benzene, which underwent phase transition and phase separation behaviours analogous to those of lipid membranes.

Enantioselectively catalyzed hydrolysis of p-nitrophenyl esters of N-protected L or D-amino acids by optically active hydroxamic acid and dipeptides

Abstract Catalyzed hydrolysis of p-nitrophenyl esters of N-protected L or D-phenylalanine by optically active hydroxamic acid or dipeptides in the presence of CTABr micelles showed high enantioselectivity (D/L=5.68 for L-ZLysZ(MHX)), demonstrating control of the direction of the enantioselectivity based on the balance of the structures of the nucleophile and substituent.

Enantioselectively catalyzed hydrolysis of p-nitrophenyl esters of N-protected L-amino acids by N-lauroyl L or D-histidine in CTABr micelles.

Abstract Remarkable dependencies of the rate constants and enantioselectivities on the substituents and protecting groups were demonstrated by the catalyzed hydrolysis of p-nitrophenyl esters of various N-protected L-amino acids by L or D-LauHis in the presence of mixed micelles with CTABr.

Planarity recognition of cationic dyes by anionic, crystalline bilayer aggregates

Abstract Steric selectivity in terms of molecular planarity of cationic dyes was investigated using anionic bilayer aggregates. Planar cationic dye (para-type stilbazolium) could be incorporated into the hydrophobic region of anionic crystalline bilayer aggregates, whereas structurally related, less planar dyes (ortho-type stilbazolium) could not be incorporated in spite of somewhat higher hydrophobicity resulting from lengthening of the N-alkyl group.