Active polycondensation of diethyl 2,3,4,5-tetrahydroxyadipate with diamines

Polycondensation of diethyl 2,3,4,5-tetrahydroxyadipate with various diamines was carried out in solutions under mild conditions. The polycondensation reaction occurred rapidly even at room temperature in polar solvents such as alcohols, and in aqueous solution a cyclic product was obtained instead of linear polymers although the reaction with diamines was completed within several minutes. Polymers obtained from diethyl 2,3,4,5-tetrahydroxyadipate were a linear polyamide having pendant hydroxyl groups, which decomposed on heating at around 200°C. A solid-phase polycondensation of the precursor polyamide yielded a high molecular weight polyamide.     

A general and highly efficient asymmetric synthesis of optically active anthracyclinones

The title asymmetric synthesis has been developed by featuring bromolactonization of (−)-acetals, derived from 2-acetyl-3,4-dihydronaphthacene-6,11-diones and (2R,3R)-(+)-N,N,N′,N′-tetraalkyltartaric acid diamides, as a key diastereoselective reaction. The produced bromolactone mixtures could be readily converted to the highly optically active key synthetic intermediates of 4-demethoxy- and 11-deoxy-4-demethoxyanthracyclinones.     

Biosynthesis of citreothiolactone,citreopyrone and pyrenocine B

¹³C NMR spectroscopy using INADEQUATE pulse sequence method has been used to deduce the labelling patterns of the three metabolites of $\text{Penicillium citreo-viride}$ B. derived from [1,2-¹³C]acetate, indicating that their carbon skeletons consist of two different units [CH₃COCH₂COCH₂COS-Enzyme and CH₃COCH₂COS-Enzyme].     

A novel procedure for the synthesis of multifunctional ketones through the Fukuyama coupling reaction employing dialkylzincs

Treatment of thiol esters 1 with dialkylzincs 2 in the presence of zinc bromide, that was in situ prepared from zinc dust and bromine, provided various functionalized ketones 3 in high yields. The reaction mechanism, which may shift the Schlenk equilibrium from dialkylzincs 2 to reactive alkylzinc bromide 5, was postulated to account for the facile coupling reaction.     

Stereospecific analysis of loxoprofen in plasma by chiral column liquid chromatography with a circular dichroism-based detector

The chiral separation of loxoprofen was achieved on a chiral column with UV and circular dichroism (CD) detection. The good resolution of four loxoprofen stereoisomers was obtained. The column used for the chiral separation was Chiralcel OJ column (250 x 4.6 mm) using hexane-2-propanol-trifluoroacetic acid (95:5:0.1), as an eluent. The flow-rate was 1.0 ml/min and the detection was at 225 nm. In addition, CD and UV spectra were obtained by stopped flow scanning. The method allows the determination of the stereoisomers of loxoprofen in human plasma after the administration of therapeutic dose of the racemic drug, thus HPLC with CD detector is useful for the stereospecific determination of loxoprofen products in biological samples.     

Structure of alatol,a hydrolysis product of a sesquiterpene polyester,alatolin from Euonymus alatus forma striatus (Thunb.) Makino,and transformation of evoninol to alatol

Alatol 3, a new hexahydroxy C₁₅-compound was obtained by hydrolysis of alatolin 2, a new nonbasic polyester isolated from Euonymus alatus forma striatus (Thunb.) Makino. The structure of alatol 3 was determined mainly based on chemical and spectroscopic methods. An evoninol derivative 5, whose structure was previously elucidated was transformed into alatol 3 by ten steps: this conversion provided an unequivocal proof for the structure of alatol 3.     

Fluorimetric determination of reducing carbohydrates with malonamide

Samples are heated for 90 min with malonamide in carbonate buffer (pH 9.2) for measurement at 383 nm (excitation)/425 nm (emission). For D-glucose, relative standard deviations are 1–3% at the 10^-6–10^-9 mol level. Relative fluorescence intensities are reported for 36 carbohydrates.     

A bound for global solutions of semilinear heat equations

We show that global positive solutions of the initial-boundary value problem foru _t =u+u ^p are bounded, provided thatp>1 is subcritical. Our bound depends only on sup norm of the initial data and is useful to classify initial data by the asymptotic behavior of the solutions as time tend to infinity.Partially supported by the Sakkokai Foundation     

Structural and conformational studies on euphornin and related diterpenes

In addition to euphornin, three new toxic substances (euphornins A, B and C) have been isolated from the plant $\text{Euphorbia}$$\text{helioscopia}$ L., and their absolute stereostructures also been elucidated on the basis of their spectral data and some chemical evidence together with an X-ray crystallographic analysis of the p-bromobenzoate derived from euphornin. Furthermore, their conformations have also been discussed.