A comparative study of the epoxidation of 2‐substituted isoflavones by dimethyldioxirane,sodium hypochlorite,and alkaline hydrogen peroxide (weitz‐scheffer reaction)

The comparative epoxidation of 2‐substituted isoflavones 9–16 has been conducted by the utilization of three different protocols, viz. epoxidation with isolated dimethyldioxirane (Method A), with sodium hypochlorite (Method B), and with alkaline hydrogen peroxide (Method C), to afford epoxides 17–24 . Best results have been obtained with Method C (Weitz‐Scheffer epoxidation). The structures of epoxides have been assigned on the basis of nmr spectral and mass spectral data.     

Synthesis of Optically Active α-Methyl β-Hydroperoxy Esters by Diastereoselective Singlet Oxygen Ene Reaction and Horseradish Peroxidase Catalyzed Kinetic Resolution

Summary.  Optically active diastereomeric β-hydroperoxy esters 4 have been prepared by singlet oxygen ene reaction of β,γ-unsaturated esters 3 and subsequent horseradish peroxidase (HRP) catalyzed kinetic resolution of the ene product. The highest enantiomeric excess (up to 95%) has been obtained for the isopropyl ester threo-4c, which establishes that the size of the remote ester functionality exercises appreciable control in the enantioselectivity of the enzymatic kinetic resolution. Received December 20, 1999. Accepted (revised) February 11, 2000     

Advective transport in a multilayered system of aquifers

A three-dimensional model of transport in porous media, consisting of several aquifers and aquitards, is presented. In the solution procedure a two-dimensional flow model has been adapted to incorporate three-dimensional velocity components. This procedure enables to observe the way particles of a pollutant are being transported through the system of aquifers and aquitards, while maintaining the Dupuit assumption of zero vertical gradients of the hydraulic head in the aquifers. The governing equations are solved using a finite element technique. The transport of pollutants is restricted to advective transport and linear adsorption.     

Application of Raman Spectroscopy for Differentiation Among Cotton and Viscose Fibers Dyed with Several Dye Classes

The difference between natural and regenerated cellulose fibers caused by variations in the degree of polymerization and supramolecular structure, influences dyes adsorption properties. The aim of the study was to discriminate between cotton and viscose fibers, dyed with several dye classes, using Raman spectroscopy. 8 reactive and 6 direct dyes were used for colouring textiles under laboratory conditions. Spectra of fibers were obtained with the use of three excitation sources: 514, 633, and 785 nm. The obtained results allowed for the differentiation of studied types of cellulose fibers, dyed with the same dye, at the same or very similar concentrations.     

Synthesis of Resorcinarene Derivatives by the Catalyzed Mannich Reaction,Part 2: Resorcinarene Derivatives with Unsaturated Bonds

The conditions of a simple synthesis of alkenyloxymethyl and the alkynyloxymethyl derivatives of resorcinarene by the Mannich reaction catalyzed with iminodiacetic acid are described. The synthesis presented in this article is effective and uses readily available and inexpensive substrates.     

Hydrophilic Quaternary Ammonium Ionenes—Is There an Influence of Backbone Flexibility and Topology on Antibacterial Properties?

The antimicrobial properties of polycations are strongly affected by the structural features such as the backbone flexibility and topology (isomerism) through the polymer ability to attain proper conformation in interaction with the cell membrane. In this paper, a synthesis and biocidal properties evaluation of ionenes characterized by different backbone topology (isomerism) and flexibility are presented. The findings reveal influence of variation in topology on activity against different microorganisms, and general positive effect of improved flexibility. Furthermore, one of the obtained ionenes displays degradable properties in near physiological environment (phosphate‐buffered saline pH 7.4, 37 °C). The degradation proceeds via Hofmann elimination reaction and the products are not of acidic character. For the first time a new class of degradable ionenes with a high antimicrobial potential is presented.