Kahee Fujita

6A6B, 6A6C, and 6A6D-ditosylates of β-cyclodextrin

Abstract Regio-isomers, 6A6B, 6A6C, and 6A6D-ditosylates of β-cyclodextrin prepared by the reaction of β-cyclodextrin with tosyl chloride were easily and effectively separated through reversed phase column chromatography and assigned.

Guest-induced conformational change of β-cyclodextrin capped with an environmentally sensitive chromophore

Abstract A capped cyclodextrin, 6-deoxy-6-( p -hydroxy- m -nitrophenacylthio)-β-cyclodextrin, was prepared in order to detect any conformational change of the host upon the guest binding. The association constant between the cyclodextrin and 1-adamantanecarboxylate, cyclohexanecarboxylate, p -methylbenzoate, 3,3-dimethylbutyrate, or 2,2-dimethylpropionate was enhanced 20, 5.3, 3.7, 2.3, or 2.0 times, respectively, by chromophore capping. The changes in the electronic, NMR, and circular dichroism spectra as well as p K a of this cyclodextrin upon binding of the guest strongly indicate a conformational change around the chromophoric moiety of the cyclodextrin.

Convenient preparation and effective separation of the C-2 and C-3 tosylates of α-cyclodextrin

Abstract Secondary tosylates of α-cyclodextrin were conveniently prepared by the reaction of the cyclodextrin with tosyl chloride in alkaline water where pH of the mixture should be allowed to decrease as the proceeding of reaction, and were effectively separated by reversed-phase column chromatography.

A complete set of β -cyclodextrins 6A, 6X-diactivated by two different sulfonyl groups

Each of 6A-O-(p-nitrobenzenesulfonyl)-6X-O-(β-naphthalenesulfonyl)-β-cyclodextrins (X= B-G) was prepared by the reaction of 6-O-(β -naphthalenesulfonyl)-β -cyclodextrin with p-nitrobenzenesulfonyl chloride, isolated, and structurally determined through selective chemical conversion.

Selectivity variation in hydrolysis of phenyl acetates by simple modifications of β-cyclodextrin.

Abstract By reaction of β-cyclodextrin 6-monotosylate with alkyl mercaptans, 6-deoxy-6-alkylthio-β-cyclodextrins, 2 , 3 , and 4 , were prepared. Studies of the hydrolyses of m - and p -substituted phenyl acetates showed that the well-known meta-selectivity effect occurred with 2 , while none was observed with 4 . This variation in selectivity was due to a change in the catalytic rate constant caused by the substituent on β-cyclodextrin.

Enzyme-based discrimination between clockwise and counterclockwise isomers of unsymmetrically disubstituted β-cyclodextrins. 6A,6B- and 6A,6G-derivatives

Abstract 6A,6X-Dideoxy-6A-phenylthio-6X-[(β-naphthylsulfonyl)oxyl]-β-cyclodextrins (X=G and B) (5 and 6) were prepared together with the other isomers (X=C, D, E, and F) (1–4), isolated by reversed-phase column chromatography, and structurally assigned by use of Taka amylolysis.

Selective recognition of alkanoates by a β-cyclodextrin flexibly capped with a chromophore

Abstract The association between 6-deoxy-6-( p -hydroxy- m -nitrophenacylthio)-β-cyclodextrin 1 and sodium n -alkanoate, sodium 2,2-dimethylpropionate, or sodium 3,3-dimethylbutyrate was investigated. Host-guest association was measured by means of electronic spectroscopy and circular dichroism spectroscopy and ascertained to be 1:1. The inclusion of 2,2-dimethylpropionate or butanoate marginally affected the circular dichroism spectrum of 1. The inclusion of 3,3-dimethylbutyrate, hexanoate, octanoate, decanoate, or dodecanoate, however, dramatically affected the spectrum of 1. The plots of molecular ellipticities of the inclusion complexes against the carbon number of the n -alkanoates were sigmoid. From these observations, the effective size of the guest molecule to push the chromophore in the cavity to the capping position was estimated. From the similarity of the spectrum of the octanoate- 1 complex to that of 1-adamantanecarboxylate- 1 complex, the carbon chain of octanoate appears to be folded in the cavity of the cyclodextrin.

Laser-assisted field-desorption mass spectrometry of cyclomalto-hexaose and -heptaose and some 6-alkylthio derivatives

Abstract The use of laser-assisted field-desorption mass spectrometry for determination of molecular weight, elucidation of structure, and control of purity is demonstrated for cyclomalto-hexaose and -heptaose and their derivatives. Each compound gave an abundant [M + Na] + ion. The [Na] + ions originate from traces (∼0.1%) of salts in the authentic samples. The fragmentation obtained is structurally highly significant, as the sequential loss of 1–5 sugar subunits is observed. Under these conditions, the elimination of water is negligible, but can be induced by applying higher thermal stress, e.g. , using higher laser power. When fragmentation was induced, the cyclic oligosaccharides substituted at positions 6 lost substituted sugar units, thus confirming the synthesis pathway.

Meta/para-selectivity variation by sulfide/sulfoxide conversion of 6-substituted β-cyclodextrin. Hydrolyses of nitrophenyl acetates. ag

Abstract Hydrolyses of m- and p-nitrophenyl acetates by 6-deoxy-6-alkylthio-β-cyclodextrins and the corresponding sulfoxides were studied to show that the small chemical conversion from the sulfides to the sulfoxides led to a change of meta/para-selectivity in the hydrolysis of the β-cyclodextrin moiety.

Synthesis and structure determination of 3A,6X-Di-O-arenesulfonyl-∝-cyclodextrins

Abstract A regioisomeric mixture of 3 A -O-(β-naphthylsulfonyl)-6 X -O- mesitylsulfonyl-∝-cyclodextrins (X = A−F) was prepared by the reaction of 3- O-(β-naphthylsulfonyl)-α-cyclodextrin with mesitylenesulfonyl chloride in pyridine. Each isomer was isolated and assigned.