On some invariants of a mixed product of ideals

We compute some invariants (e.g., dimension, multiplicity, depth, the Castelnuovo–Mumford regularity and the Hilbert–Poincaré series) of mixed products of arbitrary homogeneous ideals.     

New and practical method for synthesis of 1- and 1,3-substituted xanthines.

[reaction: see text] A new and practical method for the synthesis of 1- and 1,3-substituted xanthines is reported. Direct base-promoted condensation of the imidazole precursor 1 with carbamates 2 gives 1-substituted 7-PMB xanthines 7 in good yields. Alkylation of these derivatives or their potassium salts proceeds under mild conditions to give functionalized 1,3-substituted 7-PMB xanthines 9 in good to excellent yields. The obtained 7-PMB-protected derivatives can be readily deprotected to give the parent 1- and 1,3-substituted xanthines.     

Comparison of reversed-phase liquid chromatographic methods for the separation of new quinolones

Reversed-phase high-performance liquid chromatography is widely used in the analysis of drug substances and their metabolites. The interaction of quinolones with residual silanol in a silica-based C18 stationary phase causes peak broadening and bad peak shapes and makes it hard to resolve the peak separations. This unusual interaction is studied and finally can be removed by masking the residual silanol of a silica-based C18 stationary phase, then good peak separation is achieved. We have chosen four new quinolones and ciprofloxacin and improved the peak shapes by optimizing the pH of the eluent and the quantity of the additive (N,N-dimethyloctylamine, approximately 0-40 mM) in the monomeric C18 stationary phase. The elution behavior of quinolones in the polymeric C18 stationary phase is compared with that in the monomeric C18 stationary phase under the same eluent condition. Good peak symmetry and a high plate number are achieved by this technique, which are hardly obtained with the conventional silica-based C18 stationary phase. Based on these results, we present data of the influence of the eluent composition such as pH, buffer, and additive concentration on the peak shape.     

Simple generation of tunable near-infrared picosecond dye-laser pulses using spectro-temporal selection

The spectral and temporal processes in broadband pulsed-laser emissions of near-infrared dyes generated from low-Q and short laser cavities have been investigated with a rate equation model extended to a multiwavelength analysis. A very fast spectral evolution is proved, and this leads to the intrinsic presence of a single short pulse on the short-wavelength wing of the broadband IR dye laser spectrum. From the results, the direct generation of picosecond (≈90 ps)infrared dye-laser pulses adjustable in the 700–850 nm spectral range is successfully demonstrated with spectro-temporal selection, in a compact and simple device, using a nitrogen laser (337.1 nm, 8 ns) or a Q-switched ruby laser (694.3 nm, 25 ns) as a pumping source. Received: 6 October 1998 / Revised version: 14 April 1999 / Published online: 11 August 1999     

Liquid chromatographic determination of novel aminithiazolecarboxamide fungicide residues in soil and crops using online solid-phase extraction

A simple and convenient liquid chromatographic method has been developed and applied to the analysis of the novel aminothiazolecarboxamide fungicide, ethaboxam, in soil and crops. After the isolation and concentration of analyte from soil and crops, clean-up and separation of sample solutions are performed by high-performance liquid chromatography with online solid-phase extraction. Good linearity (r2 > 0.9995), recovery [for soil, 95.3-98.4%, and crops (grape, red pepper), 92.9-95.9%], and repeatability are achieved in the calibration range of 0.1-10.3 microg/mL. The limit of detection is the 2.5 parts per billion (ppb) (40 g of soil) and the 20 ppb (25 g of crops), respectively. This assay method shows the suitability for the residual analysis of ethaboxam in soil and crops.     

Preparation of porous materials with ordered hole structure

This review paper investigates the synthesis of porous structures with controlled hole pattern and provides an overall view of the various factors involved when synthesizing such porous materials. The following factors are discussed: 1) various methods of synthesis to produce the porous structures; 2) materials which the porous structures are made of; 3) control of the pore structure; 4) various applications of such porous materials. The materials of the porous structures and the control of the pore structure will also be discussed separately under each different method, as these two factors are closely dependent on the method of fabrication.     

Debenzylation using catalytic hydrogenolysis in trifluoroethanol, and the total synthesis of (−)-raumacline

N-Debenzylations using catalytic hydrogenolysis often fail to take place unless alcoholic solvents are used, but this can lead to N-alkylation as a side reaction; using trifluoroethanol as the solvent overcomes this problem, and leads to highly reliable hydrogenolyses for a wide range of substrates, including the final deprotection step in our total synthesis of (−)-raumacline.     

Asymptotic behavior of reduction numbers

It is shown that the reduction number and the big reduction number of are linear functions of for all large . Here is a homogeneous ideal of a polynomial ring .

     

Using the 1,2‐dihydro‐1,2‐diphosphinine ring as a template for the synthesis of new bicyclic structures and new trans‐chelating bis‐phosphines

The 1,2‐dihydro‐1,2‐diphosphinine decacarbonylditungsten complex 1 has been used as a synthetic equivalent of the corresponding 1,2‐dianion 2 . These two 1,2‐positions can be linked by a (CH₂)₄ bridge to yield a [4.4.0] bicyclic structure 6 whose identity has been confirmed by X‐ray crystal structure analysis. Alternatively, two ω‐iodohexyl chains can be grafted onto these positions and the resulting diiodo derivative 9 transformed into a long‐chain bis‐phosphine 10 by reaction with lithium diphenylphosphide. This bis‐phosphine gives a chelate complex with PdCl₂ whose trans‐stereochemistry was established by X‐ray crystal structure analysis. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:44–48, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20073