Etude et application synthétique d'une nouvelle méthode de spiroannélation

Synthèse générale des noyaux spiranniques Au cours de ce travail, nous avons développé une méthode générale permettant d'assembler rapidement les noyaux spiro[4,4+n]alcanones (5) et spiro[5,4+n]alcanones (6). Durant l'étape de condensation, les ß-cétocétals (4) et (7) ont été obtenus avec de bons rendements grâce à l'emploi de dichlorure de zinc comme acide de Lewis. Différentes bases ont été testées dans l'étape de spiroannélation. Les meilleurs résultats ont été obtenus en utilisant du tert-butanolate de potassium dans le THF en présence d'un équivalent d'eau. La sélectivité de notre méthodologie a également été examinée lors de la génération des composés spiranniques substitués (10), (11), (13) et (15). Durant cette étude, nous avons notamment montré que la condensation et la cyclisation sont complètement diastéréosélectives au départ des éthers d'énols silylés (12) et des orthoesters (2) et (3). Applications En utilisant notre séquence réactionnelle, nous avons synthétisé la spirocétone (18). La fonctionnalisation de ce dérivé spirannique (18), nous a conduit à l'intermédiaire (19) qui pourrait être ultérieurement utilisé pour la synthèse de produits naturels tel que (20), appartenant à la classe des spirovétivanes La spirodicétone (23) a été employée dans la synthèse total de l'Erythrodiène (24) et du Spirojatamol (25) par Fukumoto. Notre méthodologie nous a permis de générer cet intermédiaire clef (23) en seulement trois étapes.(CHIM 3)--UCL, 200

A quick-check artefact and procedure for coordinate measuring machines

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Mild and neutral deprotections catalyzed by cerium(IV) ammonium nitrate.

The development of a novel, chemoselective, and catalytic deprotection methodology that proceeds under mild and neutral conditions is described, and its mechanism of action is analyzed in some detail. The scope, limitations, and advantages of this protocol are discussed. Selected applications in synthesis are also highlighted

Interaction between workpiece and CMM during geometrical quality control in non-standard thermal conditions

Industrial quality demands have resulted in increasing attention towards the thermal behavior of coordinate measuring machines. The influence of the workpiece on the measurement accuracy is hereby often disregarded. This can lead to significant measurement errors. The described research examines the interaction between the measurement device and the measured object. Four distinct measurement error types that result from non-standard temperatures are listed. Temperature variations during the measurement lead to the most challenging situation. The key to measurement accuracy lies in linking the measurement time to the accompanying temperature variation. The possibilities of this methodology are indicated by an experiment on a reference object. © 2001 Elsevier Science Inc. All rights reserved.status: publishe

A method for squareness error verification on a Coordinate measuring machine

The face diagonal method for squareness error measurement is already well established. Because it is easy to apply, this method is widely used in CMMs (coordinate measuring machines). This paper introduces a new method, which reduces the set-up and measuring time for squareness error by applying four volumetric diagonal measurements instead of six face diagonal measurements. The method also makes it possible to use a single properly sized artefact, which fits the machine's rectangular volume. The choice of artefacts used in the method is wide, and they need not be precalibrated before measurements.status: publishe

Linear regression and neural net models applied to thermal error compensation in machine tools

Thermal effects still remain an important source of errors in machining accuracy. Research indicates that temperature variations can affect the tool tip position and induce machining errors. Thermal error compensation by software method through the NC controller is considered a useful strategy to counteract these effects. Multiple Input and Multiple Output (MIMO) algorithms can be used to model the thermal behavior of machine tools. In this paper, Multiple Variable Linear Regression (MVLR) and Neural Network (NN) algorithms are used to build thermal deformation models for a big milling machine. The experiments and calculations illustrate that multiple variable models can predict the majority of thermal errors. This confirms the possibility of software compensation on machine tools. The potential of the two algorithms for calculating thermal errors is compared according to the results presented in the paper.status: publishe

Cerium(IV)-Catalyzed Deprotection of Acetals and Ketals under Mildly Basic Conditions.

Smooth and quantitative deprotection of a wide range of acetals and ketals [Eq. (a); R, R(1)=alkyl, aryl, H] under neutral to mildly basic conditions was achieved with catalytic quantities of cerium ammonium nitrate (CAN). The reaction conditions are compatible with a variety of sensitive functional groups, and aldehydes can be liberated from acetals without being oxidized to the corresponding carboxylic acids

Activation of TRPM3 by a potent synthetic ligand reveals a role in peptide release

Transient receptor potential (TRP) cation channel subfamily M member 3 (TRPM3), a member of the TRP channel superfamily, was recently identified as a nociceptor channel in the somatosensory system, where it is involved in the detection of noxious heat; however, owing to the lack of potent and selective agonists, little is known about other potential physiological consequences of the opening of TRPM3. Here we identify and characterize a synthetic TRPM3 activator, CIM0216, whose potency and apparent affinity greatly exceeds that of the canonical TRPM3 agonist, pregnenolone sulfate (PS). In particular, a single application of CIM0216 causes opening of both the central calcium-conducting pore and the alternative cation permeation pathway in a membrane-delimited manner. CIM0216 evoked robust calcium influx in TRPM3-expressing somatosensory neurons, and intradermal injection of the compound induced a TRPM3-dependent nocifensive behavior. Moreover, CIM0216 elicited the release of the peptides calcitonin gene-related peptide (CGRP) from sensory nerve terminals and insulin from isolated pancreatic islets in a TRPM3-dependent manner. These experiments identify CIM0216 as a powerful tool for use in investigating the physiological roles of TRPM3, and indicate that TRPM3 activation in sensory nerve endings can contribute to neurogenic inflammation.status: publishe