Selective oxidation of poly(4-methylstyrene)

A range of new functional copolymers bearing aldehyde and carboxylic acid groups have been prepared by functionalization of poly(4-methylstyrene). These polymers have molecular weights from 2,000 to 16,500 and contain up to 20% aldehyde and up to 90% carboxylic acid groups. The reaction proceeds by selective catalytic oxidations with molecular oxygen or air in acetic acid/organic cosolvent mixtures in presence of cobalt acetate and sodium bromide or hydrogen bromide. The effects of reaction temperature, catalyst, co-solvents and oxygen partial pressure on the reaction are described. © 1995 John Wiley & Sons, Inc.     

Dysinosin A: a novel inhibitor of Factor VIIa and thrombin from a new genus and species of Australian sponge of the family Dysideidae

A new marine natural product dysinosin A 1 has been isolated from a new genus and species of sponge of the family Dysideidae found near Lizard Island, North Queensland, Australia. Dysinosin A is a potent inhibitor of the blood coagulation cascade factor VIIa and an inhibitor of the serine protease thrombin. Among the distinctive features of dysinosin A are the presence of a 5,6-dihydroxy-octahydroindole-2-carboxylic acid, 3-amino-ethyl 1-N-amidino-Delta-3-pyrroline, a sulfated glyceric acid, and d-leucine, assembled through three peptidic linkages. Dysinosin A inhibited factor VIIa at a Ki of 108 nM and thrombin at a Ki of 452 nM. The identification of the 1-N-amidino-Delta-3-pyrroline and 5,6-dihydroxy-octahydroindole-2-carboxylic acid as P1 and P2 moieties respectively, should pave the way for the design and synthesis of new structure-based inhibitors.     

Amorphous aluminosilicates containing trivalent chromium in a non-octahedral coordination environment

Amorphous aluminosilicates containing up to 5.8 wt.% chromium have been prepared by cation exchange on an amorphous sodium aluminosilicate using Cr(III) salts. Electronic spectroscopy has shown that the ligand arrangement around the Cr(III) sites does not correspond to the octahedral geometry. No isomorphous substitution of Al³⁺ by Cr³⁺ in the aluminosilicate occurs, and it is not possible to exchange back chromium by Na⁺ ions. The amorphous chromium-substituted aluminosilicates (abbr. ACSAS) are slightly acidic and when heated in air at 800 °C no oxidation of Cr(III) takes place. The chromium species in the ACSAS undergoes ligand replacement reactions.

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Amorphe Alumosilicate mit dreiwertigem chrom in nicht-oktaedrischer Koordinationsumgebung

Zusammenfassung Bis zu 5,8 Gew.% Chrom enthaltende amorphe Alumosilicate wurden durch Kationenaustausch am amorphen Natriumalumosilicat unter Anwendung von Cr(III)-Salzen hergestellt. Elektronenspektroskopische Untersuchungen zeigten, daß die Ligandanordnung um die Cr(III)-Lagen nicht der oktaedrischen Geometrie entspricht. Im Alumosilicat erfolgt keine isomorphe Substitution von Al³⁺ durch Cr³⁺ und es ist nicht möglich, Chrom durch Na⁺ zurückzuersetzen. Die amorphen durch Chrom ersetzten Alumosilicate (abgekürzt ACSAS) sind schwach sauer und wenn sie in der Luft auf 800 °C aufgeheizt werden, erfolgt keine Oxydation von Cr(III). Das in den ACSAS vorliegende Chrom unterliegt Ligandaustauschreaktionen.

     

Etude conformationnelle du complexe η-(4-(trifluorométhoxy)aniline)tricarbonylchrome

Conformational study of η⁶-(4-(trifluoromethoxy)aniline)tricarbonylchromium shows in the solid state that the trifluoromethoxy group is nearly perpendicular to the arene ring (CF₃---C---O = 117°) and that the amino group is eclipsed by a chromium carbonyl bond, conformation which is also found in solution.     

Tailoring Atomoxetine Release Rate from DLP 3D-Printed Tablets Using Artificial Neural Networks: Influence of Tablet Thickness and Drug Loading

Various three-dimensional printing (3DP) technologies have been investigated so far in relation to their potential to produce customizable medicines and medical devices. The aim of this study was to examine the possibility of tailoring drug release rates from immediate to prolonged release by varying the tablet thickness and the drug loading, as well as to develop artificial neural network (ANN) predictive models for atomoxetine (ATH) release rate from DLP 3D-printed tablets. Photoreactive mixtures were comprised of poly(ethylene glycol) diacrylate (PEGDA) and poly(ethylene glycol) 400 in a constant ratio of 3:1, water, photoinitiator and ATH as a model drug whose content was varied from 5% to 20% (w/w). Designed 3D models of cylindrical shape tablets were of constant diameter, but different thickness. A series of tablets with doses ranging from 2.06 mg to 37.48 mg, exhibiting immediate- and modified-release profiles were successfully fabricated, confirming the potential of this technology in manufacturing dosage forms on demand, with the possibility to adjust the dose and release behavior by varying drug loading and dimensions of tablets. DSC (differential scanning calorimetry), XRPD (X-ray powder diffraction) and microscopic analysis showed that ATH remained in a crystalline form in tablets, while FTIR spectroscopy confirmed that no interactions occurred between ATH and polymers.     

Highly conductive molecular junctions based on direct binding of benzene to platinum electrodes

Highly conductive molecular junctions were formed by direct binding of benzene molecules between two Pt electrodes. Measurements of conductance, isotopic shift in inelastic spectroscopy, and shot noise compared with calculations provide indications for a stable molecular junction where the benzene molecule is preserved intact and bonded to the Pt leads via carbon atoms. The junction has a conductance comparable to that for metallic atomic junctions (around 0.1-1G0), where the conductance and the number of transmission channels are controlled by the molecule's orientation at different interelectrode distances.     

Generalization of a new parametric formulation of mechanics for systems with variable mass

In this paper a new parametric formulation of mechanics, formulated by the author himself and based on the separation of the double role of time (independent variable and a parameter) with the aid of a family of varied paths, is extended to the arbitrary rheonomic systems with variable mass. For such systems d'Alembert–Lagrange's principle, general Hamilton's principle, and the corresponding Hamiltonian formalism are formulated, as well as the energy relations with energy change law. The obtained results are illustrated by a simple, but characteristic example.