Kazuko Ohta

Preparation and solution properties of pullulan fractions as standard samples for water-soluble polymers

Abstract A series of pullulan fractions with molecular weights in the range 5 × 10 3 to 8 × 10 5 were prepared. The weight-average molecular weight (M w ) of all the samples was determined by sedimentation equilibrium. The hydrodynamic properties of pullulan in aqueous solution were investigated by viscometry and ultracentrifugation. The experimental results indicate that pullulan molecules in water are fairly stable and behave as expanded random coils when M w is above 2 × 10 4 . The molecular weight distributions of the fractions were measured by gel filtration. The ratio M w /M n was close to 1·1, except for a sample with the highest M w . It is concluded that the pullulan fractions prepared by the present work are well characterized and have a narrow molecular weight distribution. They may be useful as standard samples for studies of water-soluble polymers.

General method for preparing altrosides from 2,3-manno-epoxides and its application to synthesis of alternative β-cyclodextrin with an altroside as the constituent of macrocyclic structure

Abstract A general and convenient method for preparing altrosides from 2,3-manno-epoxides is described and as the application, 2A(S),3A(R)-β-Cyclodextrin which has an altroside as the constituent was prepared and assigned;the altroside part has 1C4 conformation predominantly.

A simple and sensitive chemiluminescence method for the determination of tiopronin for a pharmaceutical formulation

Here we report a rather simple and convenient chemiluminescence (CL) method for the determination of tiopronin. It was based that tiopronin could greatly enhance CL between H2O2 and luminol in a basic alkaline solution. Light emission is intense, and even with a simple setup a high sensitivity could be achieved. The linear range was 3 mM-500 nM with a detection limit of 200 nM. Singlet oxygen and hydroxyl radical were suggested to be produced in this reaction and was responsible for the CL of tiopronin. As a preliminary application, this simple method has been successfully applied into the determination of tiopronin in a pharmaceutical formulation.

Synthesis of a ‘head-to-tail’ type cyclodextrin dimer linked by a disulfide bridge

A ‘head-to-tail’ type cyclodextrin dimer, where C-3 of one cyclodextrin and C-6 of the other are linked by a disulfide bond, is synthesized using 2,2′-dipyridyl disulfide, which is widely applicable to the preparation of other dimers.

Fluorescence derivatizing procedure for 5-hydroxytryptamine and 5-hydroxyindoleacetic acid using 1,2-diphenylethylenediamine reagent and their sensitive liquid chromatographic determination

A pre-column derivatization method using a fluorogenic reagent, 1,2-diphenylethylenediamine (DPE) was studied for the sensitive HPLC determination of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), which are biosubstances used in the diagnosis of several diseases. For the quantitative determination, the biogenic indole compounds were converted to their corresponding fluorescent derivatives with DPE in the presence of potassium hexacyanoferrate (III) at room temperature, and then the derivatives were separated by reversed-phase liquid chromatography with fluorescence detection. The chromatographic detection limits of the fluorescent peaks at a signal-to-noise ratio of 3 were 0.3 fmol for 5-HT and 0.2 fmol for 5-HIAA. The proposed method permits the simultaneous quantification of 5-HT and 5-HIAA at concentrations higher than 2.4 nM in human urine without a clean-up procedure.

An efficient resolution of 3-trifluoromethyl-γ-butyrolactone and its conversion to 5,5,5-trifluoroleucinol

Abstract 3-Trifluoromethyl-γ-butyrolactone( 2 ) was effectively resolved via its diastereomeric amide( 3 ). 5,5,5-Trifluoroleucinol hydrochloride( 8 ) were prepared in enatiomerically pure form and the absolute configurations were determined by CD spectra of dibenzoyl derivatives ( 9 ) and X-ray analysis of the N-benzoyl derivative ( 11 ).

DEPENDENCE OF GUEST-BINDING ABILITY ON CAVITY SHAPE OF DEFORMED CYCLODEXTRINS

Abstract Guest-binding ability of some β-cyclodextrin derivatives with deformed cavities were dependent on the cavity shapes, where 2,3′-anhydro-β-cyclodextrin 3 bound methyl orange about 2.8 times stronger than native β-cyclodextrin at 10°C.

Capped cyclofructan, preparation and structure determination of 6A,6C,di-O-(biphenyl-4,4'-disulfonyl)-cycloinulohexaose

Abstract A capped cyclofructan, 6 A ,6 C -di- O -(biphenyl-4,4′-disulfonyl)-cycloinulohexaose was selectively prepared by the reaction of cycloinulohexaose with biphenyl-4,4′-disulfonyl chloride in pyridine.

A NEW SYNTHETIC STRATEGY OF CYCLOOLIGOSACCHARIDES. CYCLODEXTRIN-DERIVED CYCLOALTRINS MADE UP FROM ALPHA (14)-LINKED ALTROPYRANOSES

An effective synthetic strategy for preparing a new type of cyclooligosaccharide is proposed and along this plan, α-, β-, and γ-cycloaltrins, made up from six to eight α(1→4)-linked D-altropyranoses, have been prepared in 36, 52, and 37% overall yields from the corresponding cyclodextrins.

6-O-sulfonates of cycloinulohexaose (cyclofructan-6)

Abstract Mono-, di-, and tri-6- O -sulfonylated cycloinulohexaoses were prepared and regiochemistry of di- and tri-sulfonates was determined by the extended Korner method.