Photochemical behaviour of 5-formyl and 5-acetyl uracils in the presence of ethene

Atypically for uracils, 5-formyl and 5-acetyl uracils react photochemically with excess ethene to produce non-acylated cyclobutane adducts whose formation can be explained by a novel, tandem [2+2] cycloaddition/Norrish-I α-cleavage proces

Total synthesis of cyclotheonamide C using a tandem backbone-extension-coupling methodology

International audienceNo abstrac

Le cas chinois ultra ou non-phénomène culturel ?

La Chine, au-delà d’une sinité unificatrice est un pays d’une grande variété intraculturelle, hétérogénéité encore accentuée par l’ouverture. Or. ce phénomène est aujourd’hui largement sous-estimé, avec des analyses parfois contradictoires, que ce soit en Occident, mais aussi en Chine, où les Chinois cohabitent avec leurs différences en toute indifférence. Après avoir présenté les différentes situations intraculturelles, cet article s’interroge sur le paradoxe entre cette apparence de non-phénomène et l’ambivalence d’une réalité faite de sinité et d’intra-culturalité extrême (ultraphénomène). Il propose des pistes de recherches qui permettront aux entreprises de mieux aborder ce marché complexe par une segmentation plus fine des marchés et du management. Quant à cette indifférence chinoise, malgré tout efficace, elle doit nous conduire à nous réinterroger sur notre propre gestion de l’interculturel.Despite its confucian heritage which unifies the country : (hina is the motherland of extreme cultural heterogeneity, increased by the opening policy /ultra-phenomenon). Nevertheless, this question is underestimated or biased not only in Western countries, but also in China, where Chinese people don t even pay attention to their internal cultural gap (non-phenomenon) This article first presents the diversity of intra-cultural situations across China, underlining the paradox between the ambivalent ultra-cultural reality and the current trends towards its non-existence. Assessing the heterogeneous – even within the sinity or convergence models, it suggests a better segmentation of markets. The way Chinese people are succeeding in coping with their own cultural gaps should also lead us to rethink our own management of intercultural situations

A solution to the component instability problem in the preparation of peptides containing C2 substituted cis-cyclobutane b-aminoacids: synthesis of a stable rhodopeptin analogue.

Despite the inherent instability of C2-substituted cis-cyclobutane β-aminoacids, incorporation of such residues into peptides is shown to be possible through use of a 1-amino-2-(hydroxymethyl)cyclobutane derivative as a stable β-aminoacid surrogate. This synthetic strategy was validated by the synthesis of a rhodopeptin analogue

Maturation of B Cells in the Lamina Propria of Human Gut and Bronchi in the First Months of Human Life

Little is known of the maturation of the mucosae-associated lymphoid tissue (MALT) in man, because, for ethical reasons, tissues from newborns are not easy to obtain. We used the opportunity provided by autopsies systematically performed in infants who died of Sudden Infant Death Syndrome (SIDS) to study the maturation of the MALT after birth. Gut and bronchus samples of 90 infants from postpartum to 90 months and who died from SIDS were collected and studied by histological and immunofluorescence examination. Plasma cells, absent at birth, appeared within a few hours after birth and initially were of the IgM isotype. IgA plasma cells appeared at 12 days. These cells were first observed in gut and later in bronchi, indicating that maturation of the gut precedes that of bronchi. The number of plasma cells increased rapidly over time and IgA plasma cells became predominant after 3 weeks in the gut and 6 weeks in bronchi. At birth, only small IgM bearing B-cell foci were seen and organized germinal centers appeared to develop over a few days, first in the gut and only later in bronchi. These results confirm that, in man, the MALT organization at birth is still in its fetal form and that maturation depends on intestinal challenges and evolves over several weeks before IgA becomes the predominant isotype secreted

Chronic pneumonia with Pseudomonas aeruginosa and impaired alveolar fluid clearance

BACKGROUND: While the functional consequences of acute pulmonary infections are widely documented, few studies focused on chronic pneumonia. We evaluated the consequences of chronic Pseudomonas lung infection on alveolar function. METHODS: P. aeruginosa, included in agar beads, was instilled intratracheally in Sprague Dawley rats. Analysis was performed from day 2 to 21, a control group received only sterile agar beads. Alveolar-capillary barrier permeability, lung liquid clearance (LLC) and distal alveolar fluid clearance (DAFC) were measured using a vascular ((131)I-Albumin) and an alveolar tracer ((125)I-Albumin). RESULTS: The increase in permeability and LLC peaked on the second day, to return to baseline on the fifth. DAFC increased independently of TNF-α or endogenous catecholamine production. Despite the persistence of the pathogen within the alveoli, DAFC returned to baseline on the 5(th )day. Stimulation with terbutaline failed to increase DAFC. Eradication of the pathogen with ceftazidime did not restore DAFC response. CONCLUSIONS: From these results, we observe an adequate initial alveolar response to increased permeability with an increase of DAFC. However, DAFC increase does not persist after the 5(th )day and remains unresponsive to stimulation. This impairment of DAFC may partly explain the higher susceptibility of chronically infected patients to subsequent lung injury

Total synthesis of cyclotheonamide C by use of an alpha-keto cyanophosphorane methodology for peptide assembly

International audienceThe total synthesis of cyclotheonamide C (3), a macrocyclic pentapeptide incorporating an alpha-keto homoarginine (k-Arg) and a vinylogous dehydrotyrosine (V-deltaTyr) unit, has been achieved. For comparison of macrocyclisation feasibility, two linear pentapeptides bearing free ketone functions at the k-Arg units were prepared, by use of tandem oxidation/coupling reactions on alpha-keto cyanophosphorane precursors as the key processes for pentapeptide elaboration. Successful activation and coupling at the pentapeptide V-deltaTyr C terminus led to the target molecule core, and thus provided a short total synthesis of the target compoun

Cyclic b-peptoids

The first synthesis of functionalized -peptoid macrocycles is reported. X-ray crystallographic structure of tetramer 9 reveals a C2-symmetrical derivative with unexpected all-cis-amide bonds and spatial disposition of the appendages toward the two opposite faces of the ring. Quantum calculations suggest that 9 is locked in this layout. These macrocycles constitute novel promising templates for multimeric ligation of biologically active ligands. The concept was exemplified by chemical decoration of tetramer 9 via "click" reaction

Rapid assembly of the polyhydroxylated b-amino acid constituents of microsclerodermins C, D et E.

A very short and efficient synthesis of protected derivatives of APTO and AETD, the complex polyhydroxylated -amino acid residues present in microsclerodermins C, D, and E, is described. The targets are obtained in only five steps, in 23% and 16% overall yields, respectively. The key transformation involves the completely diastereoselective two-carbon homologation of appropriately selected intermediate chiral sulfinimine