Synthesis and evaluation of RGD peptidomimetics aimed at surface bioderivatization of polymer substrates

Several RGD peptidomimetics have been prepared, in a convergent way, from the common ortho-aminotyrosine template (O-substituted with an anchorage-arm or a methyl group, and alpha N-substituted with a fluorine tag for XPS analysis), and various omega-aminoacid derivatives. The most flexible compounds have shown a biological activity similar to that of the peptide reference (RGDS) in the platelet aggregation test. The compound 16a could be fitted (by modelisation) with DMP 728 and c(RGDfV), two cyclic peptides that are good ligands of integrins. The compound 16b has been covalently fixed on the surface of a poly(ethylene terephthalate) membrane used as support for mammalian cell cultivation

Bismuth derivatives of 2,3-dicarboxypyrazine and 3,5-dicarboxypyrazole as precursors for bismuth oxide based materials

Depending on the experimental conditions, different bismuth derivatives of 2,3-dicarboxypyrazine (2,3-H(2)pzdc) were obtained, corresponding to the compositions Bi(2,3-Hpzdc)(3). 2H(2)O (4) and Bi(2,3-Hpzdc)(2). OH (5). In line with the analytical results and the infrared spectra, high resolution NMR studies (DMSO - d(6)) of anhydrous Bi(2,3Hpzdc)(3) (4a) confirmed unequivocally the presence of one free carboxylic acid in the structure. Thermal degradation of 4a in air proceeds in three steps and results in the formation of alpha-Bi2O3 at moderate temperature (451 degrees C). A bismuth derivative of 3,5-dicarboxypyrazole (3,5-H(3)Dcp) corresponding to the formula Bi-2(3,5-Dcp)(2). nH(2)O (3) was obtained from bismuth nitrate and the dicarboxylic acid in hot water. It decomposes into alpha-Bi2O3 when heated in air at 385 degrees C. The starting compounds and their thermal degradation products were also examined with X-ray photoelectron spectroscopy

Proanthocyanidins of Barley - Separation and Identification

Proanthocyanidins of Barley - Separation and Identificatio

Reactive polymers incorporating silyl enol ether groups .1. Synthesis by radical polymerization of 2-(Trimethylsiloxy)-butadiene and 2-(tert-butyldimethylsiloxy)butadiene

2-(Trimethylsiloxy)butadiene (TMSBD) and 2-(tert-butyldimethylsiloxy)butadiene (TBMSBD) were copolymerized with styrene (St) and methyl methacrylate (MMA) under free-radical conditions. The obtained polymers were found to contain reactive silyl enol ether groups in a ratio identical to the TMSBD or TBMSBD molar fraction in the copolymer. All investigated samples displayed only 1,4- and 3,4-microstructures. The influence of several experimental factors on the yields, rates of polymerization, microstructures, and copolymer compositions were examined. Monomer reactivity ratios r(1) and r(2) at 60 degrees C were determined from copolymer composition curves at low conversions. The homopolymerization of TBMSBD was also investigated and results were compared with those previously obtained for TMSBD. A slight increase in rates was observed and was rationalized on the basis of the higher viscosity resulting from the structural change in the monomer. Thermal stabilities of the synthesized polymers were investigated by TGA and their glass transition temperatures were determined by DSC. All measurements are compatible with a possible use of TMSBD and TBMSBD copolymers as reactive polymers. (C) 1996 John Wiley & Sons, Inc

[4+2]cycloaddition of N-buta-1,3-dienylsuccinimide to gem-substituted vinyl phosphonates

Vinyl phosphonates or-substituted with carboxylate, nitrile, sulfone and phosphonate groups reacted with N-buta-1,3-dienylsuccinimide to give [4+2] ortho-cycloadducts as mixtures of endo/exo stereoisomers

Structure and Conformation of (3s-asterisk,4s-asterisk,6r-asterisk)-3,6-dimethyl-4-phenylsulphonyltetrahydropyran-2-ones and (3r-asterisk,4r-asterisk,6r-asterisk)-3,6-dimethyl-4-phenylsulphonyltetrahydropyran-2-ones

The nucleophilic ring opening of propylene oxide by the lithio derivative of the trioxabicyclic orthoester 1 leads, after acidic treatment, to the title lactones 3a and 3b with no evidence of delta-lactones 3c and 3d. The stereochemistry of these two lactones has been established by X-ray diffraction analysis. The ring conformations observed in the solid phase are similar in both lactones and are compared with those observed in related molecules, However, the NMR spectroscopic analysis shows that this similarity does not exist in solution; lactone 3a adopts a different conformation

Characterization of Sulfobetaine Monomers By Nuclear-magnetic-resonance Spectroscopy - a Note

A set of zwitterionic monomers bearing the 3-ammoniopropanesulfonate moiety is analysed in CDCl3, CD3OD and D2O by one- and two-dimensional H-1 n.m.r. and C-13 n.m.r. spectroscopy. Absolute and relative positions of the n.m.r, signals are determined depending on the solvent used; the refined assignments of the signals in the vicinity of the ammonium group deviate from previously proposed assignments based on standard n.m.r, shift tables. Still, there is no convincing evidence for a special ring current effect due to a six-membered ring conformation of the betaine moiety

Reductive cyclisation of Morita-Baylis-Hillman adducts. A simple approach towards substituted hydrindanones and decalones

A connective synthesis of substituted hydrindanones and decalones can be accomplished based upon a novel approach involving two key-steps: a Morita-Baylis-Hillman condensation and an intramolecular reductive cyclisation using lithium in ammonia. Decalones, akin to the middle core of the clerodane family of natural products and bearing a quaternary carbon centre, can be readily assembled via this protocol. (c) 2005 Elsevier Ltd. All rights reserved

Analyse des raies de résonance magnétique nucléaire. Étude d’un monocristal d’acide oxalique dihydraté

Les seconds moments des raies de RMN, pour toutes les orientations d’un monocristal dans le champ magnétique H0, peuvent être exprimés au moyen : 1o de deux angles situant H0 par rapport à des axes liés au cristal, 2° de quantités ne dépendant que de la position des noyaux magnétiques dans la maille cristalline (sommes réticulaires). Ces quantités peuvent également être déduites de la mesure expérimentale des seconds moments. Nous développons une méthode de détermination de la position des noyaux, dans laquelle on cherche à réduire progressivement l’écart entre sommes réticulaires expérimentales et sommes calculées pour une structure proposée. Cette méthode permet d’obtenir au maximum quinze paramètres structuraux. Contrairement à la méthode de Pake, elle permet de déterminer la géométrie de groupes contenant plus de 2 atomes en interaction. Elle a été appliquée à la recherche de la structure protonique de l’acide oxalique dihydraté. Les positions relatives des protons sont en bon accord avec celles obtenues par Garrett en diffraction de neutrons