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Several Substrates (several + substrate)
Selected AbstractsThe addition reaction of diamides to 1,2,5-thiadiazole 1,1-dioxide derivatives,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2004José A. Caram Abstract The reactions of several derivatives of 1,2,5-thiadiazole 1,1-dioxide [3,4-diphenyl-(1a), 3,4-bis(p -methoxyphenyl)-(1b), phenanthro[9,10- c]-(1c) and acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide (1d), 3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2a) and 4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2b)], with reagents possessing two nucleophilic nitrogen atoms (urea, N,N,-dimethylurea, thiourea, N -methylthiourea, N -ethylthiourea, N -allylthiourea, N,N,-diethylthiourea, N,N,-diphenylthiourea, dithioxamide and sulfamide), were followed by cyclic voltammetry (CV) and UV,visible spectrophotometry in aprotic solvent solution. The products were isolated, characterized by IR, 1H NMR and 13C NMR methods and their structure was confirmed by single-crystal x-ray diffraction. Several substrate,nucleophile combinations (1a,d and 2a with some ureas and thioureas) reacted to give good yields of new compounds formed by the addition reaction of the two nitrogen atoms of the nucleophile to the two >CN, double bonds of the 1,2,5-thiadiazole 1,1-dioxide ring. Some systems (1a,dithioxamide and 2b,thiourea) did not react, whereas in others (e.g. 1a,sulfamide) a monoaddition equilibrium reaction was observed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Foxo1 regulates marginal zone B-cell developmentEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2010Jing Chen Abstract A fundamental component of signaling initiated by the BCR and CD19 is the activation of phosphoinositide 3-kinase. Downstream of phosphoinositide 3-kinase, the protein kinase AKT phosphorylates several substrates, including members of the forkhead box subgroup O (Foxo) transcription factor family. Among the Foxo proteins, Foxo1 has unique functions in bone marrow B-cell development and peripheral B-cell function. Here, we report a previously unrecognized role for Foxo1 in controlling the ratio of mature B-cell subsets in the spleen. Conditional deletion of Foxo1 in B cells resulted in an increased percentage of marginal zone B cells and a decrease in follicular (FO) B cells. In addition, Foxo1 deficiency corrected the absence of marginal zone B cells that occurs in CD19-deficient mice. These findings show that Foxo1 regulates the balance of mature B-cell subsets and is required for the marginal zone B-cell deficiency phenotype of mice lacking CD19. [source] Homogeneous Hydrogenation of Tri- and Tetrasubstituted Olefins: Comparison of Iridium-Phospinooxazoline [Ir-PHOX] Complexes and Crabtree Catalysts with Hexafluorophosphate (PF6) and Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) as CounterionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2008Bettina Wüstenberg Abstract Four iridium complexes with achiral phosphino-oxazoline (PHOX) ligands were readily prepared in two steps starting from commercially available phenyloxazolines. The air-stable complexes with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) as counterion showed high reactivity in the hydrogenation of a range of tri- and tetrasubstituted olefins. The best results were obtained with an iridium complex (11) derived from a dicyclohexylphosphino-oxazoline ligand bearing no additional substituents in the oxazoline ring. With several substrates, which gave only low conversion with the Crabtree catalyst, [Ir(Py)(PCy3)(COD)]PF6, full conversion was observed. The productivity of the Crabtree catalyst could be strongly increased by replacing the hexafluorophosphate anion with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. In one case, in the hydrogenation of a tetraalkyl-substituted CC bond, [Ir(Py)(PCy3)(COD)]BArF gave higher conversion than catalyst 11. However, with several other substrates complex 11 proved to be superior. [source] Crystallization and preliminary X-ray diffraction data analysis of stenodactylin, a highly toxic type 2 ribosome-inactivating protein from Adenia stenodactylaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 1 2010Giovanna Tosi Ribosome-inactivating proteins (RIPs) inhibit protein synthesis and induce cell death by removing a single adenine from a specific rRNA loop. They can be divided into two main groups: type 1 and type 2 RIPs. Type 1 RIPs are single-chain enzymes with N-glycosidase activity. Type 2 RIPs contain two chains (A and B) linked by a disulfide bond. The A chain has RIP enzymatic activity, whereas the B chain shows lectin activity and is able to bind to glycosylated receptors on the cell surface. Stenodactylin is a type 2 RIP from the caudex of Adenia stenodactyla from the Passifloraceae family that has been recently purified and characterized. It shows a strong enzymatic activity towards several substrates and is more cytotoxic than other toxins of the same type. Here, the crystallization and preliminary X-ray diffraction data analysis of stenodactylin are reported. This RIP forms crystals that diffract to high resolution (up to 2.15,Å). The best data set was obtained by merging data collected from two crystals. Stenodactylin crystals belonged to the centred monoclinic space group C2 and contained two molecules in the asymmetric unit. [source] Active Transport of Amino Acids by a Guanidiniocarbonyl,Pyrrole ReceptorCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2010Christian Urban Dr. Abstract Herein we report the synthesis and characterization of a transporter 9 for N-acetylated amino acids. Transporter 9 is a conjugate of a guanidiniocarbonyl pyrrole cation, one of the most efficient carboxylate binding motifs reported so far, and a hydrophobic tris(dodecylbenzyl) group, which ensures solubility in organic solvents. In its protonated form, 9 binds N-acetylated amino acid carboxylates in wet organic solvents with association constants in the range of 104,M,1 as estimated by extraction experiments. Aromatic amino acids are preferred due to additional cation-,-interactions of the amino acid side chain with the guanidiniocarbonyl pyrrole moiety. U-tube experiments established efficient transport across a bulk liquid chloroform phase with fluxes approaching 10,6,mol,m,2,s,1. In experiments with single substrates, the release rate of the amino acid from the receptor,substrate complex at the interface with the receiving phase is rate determining. In contrast to this, in competition experiments with several substrates, the thermodynamic affinity to 9 becomes decisive. As 9 can only transport anions in its protonated form and has a pKa value of approximately 7, pH-driven active transport of amino acids is also possible. Transport occurs as a symport of the amino acid carboxylate and a proton. [source] Screening of a Modular Sugar-Based Phosphite,Oxazoline Ligand Library in Asymmetric Pd-Catalyzed Heck ReactionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2007Yvette Mata Abstract We have synthesised a library of phosphite,oxazoline ligands derived from readily available D -glucosamine. These ligands have been successfully screened in the palladium-catalysed Heck reaction of several substrates with high regio- (up to 99,%) and enantioselectivities (ee's up to 99,%) as well as with improved activities under standard thermal conditions. The results indicate that the catalytic performance is highly affected by the oxazoline and biarylphosphite substituents and the axial chirality of the biaryl moiety of the ligand. The Heck reactions were also performed under microwave irradiation conditions, allowing a considerably shorter reaction time (full conversion in minutes) maintaining the excellent regio- and enantioselectivities. [source] | ||||||||||