Highly Enantioselective Synthesis of β‐Aminophosphinates with Two Stereogenic Atoms and Their Conversion into Optically Pure Ethyl β‐Amino‐H‐phosphinates

β‐Amino acid analogues : The nucleophilic addition of ethyl (diethoxyethyl)methylphosphinate to a variety of (S)‐(tert‐butanesulfinyl)imines leads to the isolation of two enantioenriched β‐aminophosphinates (>95 % ee; see scheme). Subsequent removal of the protecting groups through pivotal metal‐catalyzed thiophenolysis leads to optically pure ethyl β‐amino‐H‐phosphinates.

     

Novel Indices for the Topological Complexity of Molecules

Abstract

The development of molecular complexity measures is reviewed. Two novel sets of indices termed topological complexities are introduced proceeding from the idea that topological complexity increases with the overall connectivity of the molecular graph. The latter is assessed as the connectivity of all connected subgraphs in the molecular graph, including the graph itself. First-order, second-order, third-order, etc., topological complexities ⁱ TC are defined as the sum of the vertex degrees in the connected subgraphs with one, two, three, etc., edges, respectively. Zero-order complexity is also specified for the simplest subgraphs–the graph vertices. The overall topological complexity TC is then defined as the sum of the complexities of all orders. These new indices mirror the increase in complexity with the increase in the number of atoms and, at a constant number of atoms, with the increase in molecular branching and cyclicity. Topological complexities compare favorably to molecular connectivities of Kier and Hall, as demonstrated in detail for the classical QSPR test-the boiling points of alkanes. Related to the wide application of molecular connectivities to QSAR studies, a similar importance of the new indices is anticipated.     

Intramolecular inverse electron-demand [4+2] cycloadditions of ynamidyl-tethered pyrimidines: Comparative studies in trifluorotoluene and sulfolane

Three representative 6,7-dihydro-5H-cyclopenta[b]pyridin-4-amines were synthesized using an intramolecular inverse electron demand hetero–Diels–Alder/retro–Diels–Alder sequence between pyrimidines (acting as azadienes) and ynamides (acting as dienophiles). Two solvents of this reaction, sulfolane and trifluorotoluene, were compared at 210 °C and the former consistently led to higher yields. In addition, these studies confirmed the importance of the steric bulk of the C5-position of the pyrimidinyl cycloaddition precursor.     

The influence of the modification of carbonaceous materials on their catalytic properties in SCR-NH3. A short review

Carbonaceous catalysts are promising materials for the low-temperature (< 523 K) process of NO reduction with ammonia. Based on literature and own experience of the authors, this review focuses on the possibilities to enhance their catalytic performance. It may be increased by the introduction of oxygen or nitrogen functionalities. So obtained materials may be used in SCR-NH₃ either as catalysts or supports for transition metals oxides/hydroxides. Oxygen functionalities increase activity only to a small extent, but are necessary to prepare an efficient MeO_x/AC catalyst. Nitrogen surface species lead to a considerable increase in DeNO_x activity, as well as stability towards their oxidation to CO₂. As the most efficient active components, oxides of V, Mn, Fe and Cu were found. H₂O leads to the decrease of activity but for some catalysts additionally to the increase in selectivity. The understanding of SO₂ influence needs more experimental data. There still are several open questions concerning more detailed mechanistic studies, and especially the role of nitrogen functionalities, H₂O and SO₂.     

多尺度科学的研究进展

近些年来,化学家们开始关注多尺度现象,而在更广泛的意义上是关注一门新学科-- 多尺度科学--研究具有广泛时空尺度耦合现象的科学.本文分析了包括化学在内 的各个学科中的多尺度现象,讨论了多尺度研究的几个主要内容和方法并展望了它的未来. 我们认为,多尺度科学应作为一门独立的科学来对待,多尺度现象将是21世纪科学家们面临的最大挑战.     

SYNTHÈSE ET RÉACTIVITÉ DES 2-PHOSPHONOMETHYLBENZIMIDAZOLES N-ETHOXYCARBONYLES: NOUVELLE VOIE D'ACCÈS AUX 2-PHOSPHONOMETHYL N-AMIDOBENZIMIDAZOLES ET AUX 2-PHOSPHONOMETHYL N-HYDRAZIDOBENZIMIDAZOLES

Abstract

A variety of 2-phosphonomethyl N-amidobenzimidazoles and 2-phosphonomethyl N-hydrazidobenzimidazoles has been efficiently synthesized by treatment of 2-phosphonométhyl N-ethoxycarbonylbenzimidazoles respectively with the appropriate prim amines and hydrazines. The structure of these products was confirmed by IR, NMR(¹H, ¹³C, ³¹P) spectroscopy and mass spectra.     

Nouveau Modele d'Electrode Modifiee a Base de Carbone et de Polymere

Abstract

A new type of modified electrode is proposed, based on the thermosealing of carbon and a polymer in different proportions. The mode of preparation and the performances of this new model of polymer electrode are described in details. The potential range is larger than with other electrodes, particularly in the anodic range. Some performances realized on the behaviour of pharmaceutical compounds are described.     

Elimination De L'Interference Des Salicyles Dans Le Dosage U. V. Du Paracetamol Sanguin

Abstract

Authors propose a simple method for U. V. determination of blood paracetamol in emergency toxicology. First, diethy1-ether extraction allows salicylate elimination (especially salicylic acid which is the most frequently used in therapy). Secondly paracetamol is extracted by ethyl-acetate and measured by U. V. spectrophotometry at 244 nm. The method provides good repeta-bility (C V=3.3 %) and reproducibility (C V u 4.3 %) with a detection limit of 2 mg L^?1 in plasma.     

风险认知偏差与风险语境中的媒体

风险认知既取决于物理性一面,也取决于精神性的一面,后者往往作用力更大。风险认知能否客观、真实,受制于认知主体所具备的认知条件和认知能力。在信息“过载”和风险情境下,人的信息感知机理愈加复杂,不确定性加大,风险的认知难度也更大,容易产生认知偏差。复杂性是现代性的伴生物。在几何级扩张的复杂性面前,人类的智性和理性捉襟见肘。作为社会系统的传播、沟通、整合机制,媒体是人类社会风险控制和复杂性管控的有效架构,以其专业化努力给复杂世界带来明确的描述和确定性。但是,在网络社会和风险语境中,媒体系统面临双重“复杂性”,难以胜任风险认知和复杂性管理的重任。     

Sorption de biomolécules par membrane échangeuse d’ions : étude expérimentale et modélisation

Microporous membranes are an alternative to conventional packed columns chromatography. They offer the main advantage compared to bulk material to reduce diffusion phenomena, reduce residence time and pressures drops, and thus, facilitate rapid purification of large quantities of molecules. A wide range of chromatographic membranes involving different molecules retention mechanism (ion exchange, affinity, etc…) is now commercialized. Despite their success, the influence of the geometry of the membrane chromatography devices remains relatively unexplored from a theoretical point of view.This study on the sorption of bovine serum albumin (BSA) on a chromatographic ion exchange membrane (type Sartobind Q from Sartorius Stedim Biotech-Goettingen, Germany), aims to experimentally evaluate the influence of operating conditions (fluid flowrate, initial concentrations) on the breakthrough curves. Two types of geometries (plane module or spiral module) were used and helped to highlight the influence of the type of flow (axial or radial) on separation. The experimental study was conducted on an Akta Prime chromatography system (General Electrics, France). In order to understand the observed phenomena, to predict the performance of different modules and to develop a tool for improving the design of membrane chromatography capsule, a mathematical model was developed in CFD (Computational Fluid Dynamics) and successfully simulated.     

Synthese simplifiee de sondes mixtes avec des triazolo-nucleosides

The incorporation of triazolo-nucleosides during the synthesis of a specific sequence yields, after treatment with a mixture of pyridine aldoximate—tetramethyl guanidine— concentrated ammonia, mixed probes oligonucleotides with practically equimolecular amounts of T/^MeC and G/^NH2A at the degenerate sites.     

Determination continue du carbone-14 et du soufre-35 en milieu aqueux par un dispositif a scintillation: Application aux effluents chromatographiques

A recording apparatus is described for determining soft radiations (¹⁴C,³⁵S) in aqueous medium, especially adapted for continuous analysis of Chromatographie effluents It is based upon the spreading of the liquid in a thin layer in contact with a plastic scintillator coupled to a coincidence circuit The efficiency is comparable to that of a thin end-window GM counter in the absence of auto-absorption.     

A mass spectral investigation of derivatives of kanamycin A

The high and low resolution mass spectra of the N-acetyl-N,O-methyl and N-acetyl-O-trimethylsilyl derivatives of kanamycin A have been determined and interpreted, along with those of deuterated analogs under conditions of electron impact. In addition, the chemical ionization mass spectrum of the N-acetyl-N,O-methyl derivative is presented. The use of these spectra for recognizing structural features, such as the sequence of the sugar units, is discussed. The characteristics of the two types of derivatives are compared. The value of the chemical ionization spectrum and the complementary nature of the data obtained from it are emphasized.     

Intramolecular cyclization of cycloalkene carboxylic acid chlorides

Thermal cyclization of cyclooctene-4-yl-carboxylic acid chloride (5) and cycloheptene-4-yl-carboxylic acid chloride (10) yielded mixtures of mainly endo and exo 2-chlorobicyclo[3.3.1]nonane-9-one (7 and 8), and mixtures of endo and exo 2-chlorobicyclo[3.2.1]octane-8-one (12 and 13), respectively. AlCl₃-catalyzed cyclization of 10 gave the same product composition as the uncatalyzed reaction. In the AlCl₃-catalyzed cyclization of 5 considerable amounts of bicyclo[3.3.1]non-2-en-9-one (6) and exo 3-chlorobicyclo[3.3.1]nonane-9-one (9) were obtained in addition to 7 and 8.     

Dehydration of methanol to dimethyl ether over modified vermiculites

Vermiculite materials pillared with alumina and modified with titanium were tested as catalysts for methanol dehydration to dimethyl ether. The different samples were characterized by powder XRD, TG, nitrogen adsorption, and pyridine adsorption followed by FTIR. Catalytic activity was evaluated in the temperature range 250–450 °C using different hourly space velocities, in the absence and in the presence of water in the feed. Modified vermiculites were shown to be active and selective in methanol dehydration. Al pillaring was found to result in more active catalysts than in the case of the modification with TiO₂. The influence of methanol hourly space velocity did not have a significant effect on methanol conversion, but it changed drastically selectivity to dimethyl ether at the beginning of the reaction. The addition of water had a negative effect on the catalysts’ activity and led to a faster catalyst deactivation.     

Utilisation des Plans d'Expériences Pour la Modélisation de l'Élaboration d'un Phosphate de Calcium de Propriétés Antiseptiques à Usage Biomédical

La synthèse d'une apatite oxygénée phosphocalcique de rapport molaire Ca/P égal à 1.575 a été étudiée par un plan composite centré orthogonal. Cette étude nous a permis d'établir un modèle mathématique qui décrit l'influence des variables: pH, concentration de la solution du chlorure de calcium ([Ca ²⁺ ]), durée de maturation (D) et température (T), sur la réponse: rapport molaire Ca/P. L'exploitation de ce modèle permet de définir des conditions d'obtention d'un solide de rapport molaire Ca/P égal à 1.575.

The synthesis of phosphocalcic oxygenated apatite of Ca/P ratio equal to 1.575 was studied by an orthogonal central composite design. This study checks the effect of certain variables on the reaction, pH, concentration of the calcium chloride solution ([Ca ²⁺ ]), ripening time (D) and temperature (T) on the response, and Ca/P ratio with a mathematical model. The exploitation of this model allowed us to define conditions for obtaining a solid of Ca/P ratio equal to 1.575.