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Derivatives Bearing (derivative + bearing)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Synthesis and Photochromism of Novel Chromene Derivatives Bearing a Monoazacrown Ether Moiety

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2003
Saleh A. Ahmed
Abstract Crowned chromenes , four novel naphthopyrans (chromenes) bearing monoaza-12-crown-4, -15-crown-5, -18-crown-6, and a noncyclic analogue at the 5-position , were synthesized, and their photochromism in acetonitrile was examined in the presence of alkali and alkaline-earth metal ions. Incorporation of crown ether units to chromene moieties facilitated to a great extent both the thermal isomerization and photoisomerization of the chromene moiety, reflecting the metal-ion-binding ability of the crown ether moiety. Comparison of the crowned chromenes with the corresponding crowned spirobenzopyrans reveals that photochromism of the crowned chromene reflects an interaction between the metal ion and the crown ether moiety that is stronger than that of the crowned spirobenzopyran, and shows only positive photochromism with significant red-shifts in the UV/Vis absorption spectra, in contrast to the crowned spirobenzopyrans reported previously. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Synthesis and Structure of Spirocyclic Tetrahydrothiophene Derivatives Bearing a "Cage" Residue.

CHEMINFORM, Issue 47 2005
J. Romanski
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

First Synthesis of Phosphatidylcholine and Cholesteryl Derivatives Bearing an Unsaturated Aldehyde Residue

CHEMINFORM, Issue 2 2003
Arnold N. Onyango
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Physical Hydrogels of Poly(vinyl alcohol) with Different Syndiotacticity Prepared in the Presence of Lactosilated Chitosan Derivatives

MACROMOLECULAR BIOSCIENCE, Issue 9 2003
Giancarlo Masci
Abstract Poly(vinyl alcohol) (PVA) physical hydrogels were prepared by repeated freeze,thawing cycles using aqueous solutions of two PVA samples having different degrees of syndiotacticity, a-PVA and s-PVA with 55% and 61% of syndiotactic diads, respectively. The hydrogels were prepared in the presence of different amounts of lactosilated chitosan derivatives (LC) of different molecular weight. The PVA stereoregularity was found to have a dramatic effect on the amount of PVA incorporated into the hydrogels, leading to remarkable differences in the swelling degree and porosity of a-PVA and s-PVA hydrogels. A significant amount of LC was retained in the hydrogels after equilibrium swelling. The swelling of the a-PVA hydrogels was found to increase significantly by increasing the amount of LC while it was only slightly increased in the case of s-PVA hydrogels. The amount of LC released after equilibrium swelling was lower when chitosan derivatives with higher molecular weights were used. Increased initial concentrations of LC resulted in much higher porosity of the hydrogels. TGA and DSC studies showed that LC is stabilized by the incorporation in the PVA hydrogels. The melting temperature of the crystalline regions of PVA was not significantly influenced by LC. Conversely, the extension of the crystalline domains increased in the presence of LC. The retention of a chitosan derivative bearing , - D -galactose side chain residues makes these hydrogels potentially useful as scaffolds for hepatocytes culture. Scanning electron micrographs of PVA-LC hydrogels: (a) a-PVA; (b) a-PVA/LC150 80:20; (c) a-PVA/LC150 50:50. [source]