Preparation of a cyclodextrin dimer linked with a bis(picolinyl)cystine moiety and its intra- and intermolecular inclusion behavior

A novel cyclodextrin (CD) dimer linked with a bis(picolinyl)cystine (Cys) moiety was prepared by the coupling of Boc-protected Cys with amino-modified CDs, followed by deprotection of the Boc groups and bispicolinylation. The dimer showed less affinity to an organic guest molecule compared to that of a native CD monomer. It was attributed to an intramolecular inclusion of the pyridine moiety into CD cavity. The dimer caused significant increase of its organic guest affinity by an addition of a copper ion. The included pyridine group may come out of a CD cavity to bind the copper ion and the two CDs included cooperatively and intermolecularly a guest molecule with high affinity.     

Analysis of traces of polycyclic aromatic hydrocarbons by adsorption on cobalt phthalocyanine and barium salts of sulphophthalocyanines followed by thermal desorption gas chromatograph

Small amounts of polycyclic aromatic hydrocarbons (PAHs) in aqueous solution were almost completely adsorbed on barium salts of copper (II) sulphophthalocyanines and cobalt (II) phthalocyanine, which were precipitated from the solution. Recoveries of the PAHs from the precipitates by thermal desorption gas chromatography were 71–95%. The method is useful for the concentration and analysis of medium molecular weight, thermally stable PAHs.     

Stereochemistry and mechanism of catalytic hydrogenation of substituted cyclohexanones

Substituted alkylcyclohexanones were hydrogenated over several transition metal catalysts. The hydrogenation with freshly prepared Raney Ni gave predominantly the axial alcohols but catalyst to which sodium hydroxide was added or aged catalyst increased the stereoselectivity. In contrast to the PtO₂ hydrogenation in which the equatorial alcohols were favoured, more axial alcohols were obtained than the equatorial counterparts on Pt-black. On Pd catalyst the isomeric ratios of the cyclohexanols changed as the reaction progressed. This may be due to a decrease in the amount of hydrogen available caused by the strong adsorption of ketones on the catalyst. Rh catalyst gave more of the axial alcohols than any other catalyst used in the present study.     

A novel ring transformation of uracil into the benzene ring system

Reaction of 5-formyl-1,3-dimethyluracil with some active methylene compounds in the presence of base causes novel ring transformations to give the p-hydroxybenzoates and the nicotinate.     

Current-potential curves for facilitated ion transfer across oil/water interfaces in the presence of successive complex formation

A theoretical analysis of the current-potential curves for facilitated ion transfer across an oil/water interface is presented for the case where two complex species having an ion-to-ligand ratio of 1:1 and 1:2 are allowed to exist in the oil phase. Cyclic voltammograms are calculated numerically by using a finite difference method assuming that the ion transfer is reversible and the complex formation equilibria are maintained throughout the oil phase. When the ligand concentration in the oil phase is much smaller than the ion concentration in the aqueous phase and the former limits the ion-transfer current, two well separated peaks may develop even under the assumption of equilibrium conditions for the complex formation. The shape of the voltammogram is determined primarily by the ratio of the two reduced stability constants: b₁ = K₁^bc_L^O and b₂ = K₁K₂(^bc^O_L)², where K₁ and K₂ are the stability constants for 1:1 and 1:2 complexes in the oil phase and ^bc^O_L the ligand concentration in the bulk of the oil phase. The degree of peak separation thus depends not only on K₂/K₁ but also on ^bc^O_L. A method for estimating the two stability constants from the voltammograms is proposed.     

Structures of 1,4-benzodioxane derivatives from the seeds of Phytolacca americana and their neuritogenic activity in primary cultured rat cortical neurons

The methanol extract of the seeds of Phytolacca americana was reinvestigated to yield three new 1,4-benzodioxane-type compounds, americanoic acid methyl ester (1), isoamericanoic acid A methyl ester (2), and 9'-O-methylamericanol A (3) along with the previously isolated neolignans 6-9. The structures of 1-3 were characterized by 2D NMR and long-range selective proton-decoupling (LSPD) techniques. The neuritogenic effects of compounds 1-3, and dicarboxilic acids 4 and 5, which had been previously synthesized with horseradish peroxidase-catalyzed oxidative coupling of caffeic acid, were examined in primary cultured rat cortical neurons. Americanoic acid A methyl ester (1) exhibited neurite outgrowth-promoting activity at concentration of 0.01-1.0 microM, whereas dicarboxilic acids 4 and 5 were found to induce neuritogenesis dose dependently at the concentrations from 0.1 microM to 10 microM.     

Synthesis of the enantiomers of cis-2-methyl-5-hexanolide,the major component of the sex pheromone of the carpenter bee

(2R,5S)-2-Methyl-5-hexanolide and its antipode were synthesized in highly optically pure state (?98–99% e.e.) starting from ethyl (S)-lactate and the enantiomers of methyl β-hydroxyisobutyrate. The specific rotations of our samples were [α]_D±91.0-93.5° (CHCl₃), while the reported values of the samples prepared by resolution or asymmetric synthesis were ±64.5–65.6°.