Smiles rearrangements in Ugi- and Passerini-type couplings: new multicomponent access to O- and N-arylamides

The use of Smiles rearrangement in Ugi- and Passerini-type couplings with electron-deficient phenols allows very straightforward multicomponent formation of O-aryl- and N-arylamides. Best yields were observed with the highly activated o- and p-nitrophenols, salicylic derivatives giving adducts in lower yields. The scope of these new reactions is further increased by the successful couplings of heterocyclic phenols such as hydroxypyridines and hydroxypyrimidines.     

Development of special optical fibers for evanescent-wave chemical sensing

The paper summarizes results achieved in the Institute of Radio Engineering and Electronics in the field of investigation and fabrication of novel fiber-optic structures for evanescent-wave chemical sensing. Several approaches for increasing the evanescent-wave sensitivity of multimode silica optical fibers to gaseous and liquid chemicals are shown. These approaches make use of the decrease of the core diameter in sectorial and capillary sectorial fibers, modification of trajectories of optical rays in the cores of inverted-graded-index fibers, tailoring of the refractive index of porous layers applied on silica cores, an output mode filter preventing the detection of rays propagating at low axial angles or fibers bent in single or multiple turns. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998. This work was supported by the Grant Agency of the Czech Republic (projects No. 102/96/0939 and No. 102/98/1358) and by joint project No. 4104 of AS CR and CNRS, France.     

Er-doped twin-core fibre coupler as a saturable-absorber-based narrow-band filter for fibre lasers

We have proposed and demonstrated experimentally that an Er-doped twin-core fibre (ErTCF) can be employed as a tracking narrow-band filter in fibre ring lasers for line narrowing and enhancement of the spectral stability. The device mimics a saturable absorber with inhomogeneous broadening. The slow erbium ion saturation dynamics in the ErTCF prevents wavelength hopping whilst it enables the filter to track the operation wavelength on its tuning. We have improved the device operation by utilizing the inherent filtering effect of a twin-core fibre coupler. Presented at the 1st Czech-Chinesse Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998 This research has been in part supported by the Commission of the European Union in the frame of Copernicus programme, Project # 7882 and by the Ministry of Education of the Czech Republic under Contract OC 241.10/1998.     

Synthesis of [3-<Superscript>14</Superscript>C]-L-tryptophan and 5′-hydroxy-[3-<Superscript>14</Superscript>C]-L-tryptophan

The synthesis of selectively labeled [3-¹⁴C]-L-tryptophan and its derivative 5′-hydroxy-[3-¹⁴C]-L-tryptophan using chemical and multienzymatic methods is reported. The key intermediate for this synthesis, [3-¹⁴C]-DL-alanine was obtained from ¹⁴CH₃I as a result of its condensation with N-(diphenylmethylene)glycine tert-butyl ester. Next, the mixture containing [3-¹⁴C]-DL-alanine, indole or 5-hydroxyindole has been converted to [3-¹⁴C]-L-tryptophan or 5′-hydroxy-[3-¹⁴C]-L-tryptophan, respectively, in a one-pot multienzymatic reaction using four enzymes: D-amino acid oxidase, catalase, glutamic-pyruvic transaminase and tryptophanase.     

Synthesis of an AIE-active fluorogen and its application in cell imaging

A fluorogen named 1-decyl-1-methyl-2,5-bis{4-[(N,N-diethylamino)methyl]phenyl}-3,4-diphenylsilole (3) was synthesized. It emitted weakly as isolated molecule but strongly as supramolecular aggregate, showing a characteristic behavior of aggregation-induced emission (AIE). The molecules of 3 formed highly emissive nanoparticles in aqueous media, which quickly and selectively marked cytoplasm of HeLa cells and posed no toxicity to the living cells. The fluorogen is thus a promising candidate material for cell imaging as a sensitive, selective and cytocompatible biosensor. Supported by the Research Grants Council of Hong Kong (Grant Nos. 603008, 601608 and 602707), the National Natural Science Foundation of China (Grant No. 20634020) and the CAO GuangBiao Foundation of Zhejiang University.     

Pd‐PEPPSI‐IPent: An Active,Sterically Demanding Cross‐Coupling Catalyst and Its Application in the Synthesis of Tetra‐Ortho‐Substituted Biaryls

Incredible Bulk : A series of N‐heterocyclic carbene catalysts (see picture) were prepared and evaluated in the Suzuki–Miyaura reaction. A variety of sterically encumbered tetra‐ortho‐substituted biaryl products were formed from unreactive aryl chlorides using the isopentyl‐substituted catalyst at temperatures ranging from 65 °C to room temperature. The cyclopentyl‐substituted catalyst was virtually inactive, demonstrating that “flexible bulk” is essential to promote these transformations.

     

Separation of tryptic peptides of native and glycated BSA using open‐tubular CEC with salophene–lanthanide–Zn2+ complex as stationary phase

Open‐tubular CEC (OT‐CEC) with a new stationary phase, salophene–lanthanide–Zn²⁺ complex, has been applied to the separation of tryptic peptides of native BSA and BSA glycated by glucose and ribose. Glycation of proteins (non‐enzymatic modification by sugars) significantly affects their properties and it is of great importance from a physiological point of view. Separation of tryptic peptides of glycated BSA by CZE was poor because of their strong adsorption to the bare fused silica capillary. An improved separation of tryptic peptides of both native and glycated BSA was achieved by OT‐CEC in the fused silica capillary non‐covalently coated with salophene–lanthanide–Zn²⁺ complex, which suppressed the adsorption of peptides to the capillary and via specific interactions with some (glyco)peptides enhanced selectivity of the separation. Significant differences have been found in OT‐CEC analyses of tryptic hydrolysates of native and glycated BSA. In OT‐CEC‐UV profile of tryptic peptides of native BSA, 44 peaks could be resolved, whereas a reduced number of 38 peaks were observed in the profile of tryptic peptides of glucose‐glycated BSA and only 30 peaks were found in the case of ribose‐glycated BSA. The developed OT‐CEC can be potentially used for monitoring of protein glycation.     

Affine images of compact convex sets and maximal measures

Let be an affine continuous mapping of a compact convex set X onto a compact convex set Y. We show that the induced mapping φ_? need not map maximal measures on X to maximal measures on Y even in case φ maps extreme points of X to extreme points of Y. This disproves Théorème 6 of [S. Teleman, Sur les mesures maximales, C. R. Acad. Sci. Paris Sér. I Math. 318 (6) (1994) 525-528]. We prove the statement of Théorème 6 under an additional assumption that extY is Lindelöf or Y is a simplex. We also show that under either of these two conditions injectivity of φ on extX implies injectivity of φ_? on maximal measures. A couple of examples illustrate the results.     

Observation of some elastic networks

We consider a network of vibrating elastic strings. Using a generalized Poisson formula and some Tauberian theorem, we give a Weyl formula with optimal remainder estimate. As a consequence we prove some observability and stabilization results. To cite this article: K. Ammari, M. Dimassi, C. R. Acad. Sci. Paris, Ser. I 347 (2009).