Chromatographic molecular recognition for catechol-related compounds using thiacalix[4]arene as an effective selector

Thiacalix[4]arene (5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxy-2,8,14,20-tetrathiacalix[4]arene) is an amphiphilic molecule comprising four p-tert-butylphenol-like groups ortho-linked by single sulfur atoms. This molecule has a high electron density area owing to the close proximity of the hydroxyl groups and sulfur atoms. We studied the applicability of this interesting compound as a selector for high-performance liquid chromatography (HPLC) thereby presumably exploiting this feature. Firstly, uniformly sized polymer particles were prepared by using a multi-step swelling and polymerization method with ethylene glycol dimethacrylate (EDMA) as a cross-linker. Methacrylic acid (MAA) was introduced onto the surface of the resulting polymer particles through a new modification method. Thiacalix[4]arene was chemically bonded through the MAA group by using 1,4-dibromobutane as a spacer to reduce steric hindrance around the MAA and the polymer particle itself. The performance of the prepared polymer-based thiacalix[4]arene-modified stationary phase was evaluated with HPLC. Specific chromatographic retention behavior was observed for catechol relative to positional isomers of xylene, cresol, and benzene-diol. Catecholamine and catechol showed specific chromatographic retention behavior.     

Organo-silanes and -germanes with chelated and/or non-chelated oxinato ligands

Several tri- and di-organo(oxinato)-silanes and -germanes have been prepared from corresponding organo-silazanes or -germazanes. The UV spectra indicate that the compounds involve either chelated or non-chelated oxinato groups or both depending on the number and kind of organic groups on the metal atom. The PMR spectra of RR′Si(OX)₂ (R = alkyl, R′ = vinyl or phenyl) are interpreted in terms of rapid exchanges between the two kinds of oxinato groups     

5-Fluorouracil derivatives with serum protein binding potencies

To develop an optimal delivery system for 5-fluorouracil (5FU) using serum protein as a drug carrier, a series of its benzyl derivatives was synthesized. Then their binding to the serum protein was investigated by equilibrium dialysis. The benzyl derivatives of 5FU were strongly bound to rat plasma protein or human serum albumin. The bound percentage increased with increasing hydrophobicity. It was suggested that the benzyl derivative of 5FU existed in the blood as a complex with serum albumin and circulated for a long time as a polymeric drug does.     

Alkenylation of thiophenes at the 2-position with magnesium alkylidene carbenoids

Treatment of magnesium alkylidene carbenoids, generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with 2-lithiothiophenes gave 2-alkenylated thiophenes in good to high yields. The intermediate of this reaction was found to be an alkenylmagnesium, which could be trapped with iodoalkanes and ethyl chloroformate. This procedure offers a novel and efficient one-pot synthesis of thiophenes having a disubstituted or a trisubstituted olefin at the 2-position from thiophenes in good yields.     

Micromachined Enzyme Reactor for FIA System

An enzyme reactor consisting of a 2.6-m-long silicon capillary with glucose oxidase immobilized on the inner surface was fabricated using micromachining techniques. A V-shaped groove of 100 μm width, formed by anisotropic etching, was anodically bonded to a glass plate to create the capillary. Glucose oxidase was covalently immobilized with 3-aminopropyltriethoxysilane and glutaraldehyde. The reactor was evaluated by connecting it to a Flow injection analysis system for glucose detection. Glucose concentrations were in the range of 10⁻³ to 5 × 10⁻²M with a volume of 0.2 μl of glucose solution.     

Electronic structures of exohedral lanthanide-C60 clusters

We have studied the electronic structures of several gas phase exohedral lanthanide (Ln)-C(60) clusters, Ln(n)C(60) (Ln=Pr, Ho, Tb, Tm, Eu, and Yb) with n=1-4, by photoionization spectroscopy of the neutrals and photoelectron spectroscopy of their anions. Both of the spectroscopic analyses reveal that most of the Ln atoms preferably take +3 oxidation states, while Eu atoms alone assume +2 oxidation states, and that C(60) accepts up to twelve donated electrons in Ln(n)C(60). An additional photoionization examination of the oxygen atom mixing into the Ln(n)C(60) clusters demonstrated that each oxygen atom reduces two electrons from C(60). This result implies that the number of accepted electrons in C(60) can be varied by a suitable choice of the number of Ln atoms and O atoms.     

Phase-Transfer Catalysis: Acylation of β-Dicarbonyl Compounds

The alkylation of β-dicarbonyl compounds under phase-transfer conditions has been studied in detail and, in virtually all of the reported examples, the C-alkylation products have been found to predominate.^1–6 Only when the reaction rate is slow is there any evidence for O-alkylation as, for example, when there is steric hindrance to the approach of the alkylating agent to the carbanionic centre.^1,7 There is no record, however, of the corresponding acylation reactions.     

Polymerization of Acrolein by Imidazole

Polymerization of acrolein(AL) in the presence of imidazole(Im) has been investigated in tetrahydrofuran or methanol below room temperature. The polymers obtained, white or pale yellow powders, were found to be composed of vinyl polymer with one Im group attached and having an aldehyde side chain, of which 70–80 mole % of the aldehyde revealed bridge structure. The number-average molecular weight (M _n) of these polymers was determined to be in the range of 317 to 691. The rate of polmerization R_p was expressed by the equation, R + k[Im] [AL]².

The addition of water or dimethyl sulfoxide accelerated the polymerization reaction, while the presence of benzaldehyde or N,N'-dimethylformamide decreased R_p. The structure of addition products in the initial polymerization step was confirmed by IR and NMR spectra, and the observations of polymerization system was carried out by UV and NMR spectra. The polymerization mechanisms were discussed on the basis of these results.     

Kinetics of the Copolymerization of Methyl Vinyl Ketone and Acrylamide Initiated by the Adduct of Methyl Vinyl Ketone and Imidazole

N-(Butyl-3-one)imidazole acts as an initiating adduct which is formed in the anionic polymerization of methyl vinyl ketone (MVK) induced by imidazole (Im) and is directly formed from Im and the MVK monomer. The kinetics of the anionic homopolymerization of MVK and acrylamide (AAm) under argon in the presence of the adduct were investigated in tetrahydrofuran (THF). The rate of polymerization for the MVK system is expressed as R_p = k[Adduct] [MVK], where k = 3.1 × 10^?6 L/(mol·s)in THF at 30°C. The overall activation energy, E_a , was found to be 5.34 kcal/mol. The R_p for the AAm system is expressed as R_p = k[Adduct] [AAm], where k = 6.8 × 10^?6 L/(mol·s) in THF at 30°C, with E_a 7.78 kcal/mol. The mechanism of the polymerization induced by the initiator adduct is discussed on the basis of these results.