The Syntheses of δ-NCS-Butyl α-l-Fucosides and Fucobiosides and Their Clustering to Traintennary Glycomimetics

Abstract

L-Fucose is an especially important monosaccharide constituent in eukaryotic glycoconjugates. Its recognition by fucose specific lectins might play an important role in embryonic development, cancer development and metastasis. Therefore it is of great interest to develop potent inhibitors of fucose specific lectins, both to investigate as well as to manipulate the respective interactions. A promising approach to high affinity fucoside ligands is the synthesis of oligovalent fucosyl clusters. The synthesis of isothiocyanato-functionalized spacer α-fucosides and fucobiosides is described together with their clustering on tris(2-aminoethyl)amine giving rise to the first thiourea bridged cluster fucosides 14 and 16 in excellent yields.     

Galactosidase-Assisted Synthesis En Route to Type I And Type II Structures of Chitooligomers

ABSTRACT

Transgalactosylation of chitobiose and chitotriose led to formation of terminally (β1-3)- and (β1-4)-galactosylated chitooligosaccharides ready for fucosylation to give Lewis^a and Lewis^x motifs. Their structures could be assigned employing HPAECPAD, methylation, ESI-MS/MS and NMR analyses.     

Meeting Report: Australia's First Users Workshop

The Australian Synchrotron Research Program (ASRP) and the Australian Synchrotron (AS) held their first joint Users Workshop over three days in December 2005. The ASRP has been providing access for Australian users to the APS, NSRRC and the Photon Factory since 1996; the AS is under construction in Melbourne and at press time was scheduled to open in early 2007. The joint user workshop is one of an increasing number of collaborative projects between the two programs as they move forward towards an eventual combined Australian user program.     

Effects of graphene and carbon nanotube fillers on the shear properties of epoxy

The effects of quantity of graphene and carbon nanotube‐based fillers and their pendant functional groups on the shear properties of a thermoset epoxy were investigated. Two novel functionalized graphenes, one with epoxy functionality and the other with an amine, are synthesized for this purpose. Nanocomposites are prepared at concentrations of 0.5, 1, 2, 3, 5, and 10 wt % and the effects of functionalization on the homogeneity of dispersion and the shear mechanical properties are investigated. The properties of the epoxy nanocomposites containing epoxy‐ and amine‐functionalized graphene are compared with those containing graphene oxide, Claisen‐functionalized graphene, neat multiwalled carbon nanotubes (MWNTs), three types of epoxy‐functionalized MWNT (EpCNT), and the unfilled epoxy. One of the EpCNT ( EpCNT3 ) was found to increase the plateau shear storage modulus by 136% (1.67–3.94 MPa) and the corresponding loss modulus by almost 400% at a concentration of 10 wt %. Several other fillers were also found to increase shear properties at certain concentrations. A hybrid system of EpCNT3 and graphite was also studied, which improved the storage modulus by up to 51%. SEM images reveal a correlation between thorough dispersion of the additive and enhancement of shear modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 997–1006     

Multiple Triplet Metal-Centered Jahn-Teller Isomers Determine Temperature-Dependent Luminescence Lifetimes in [Ru(bpy)3]2+

Understanding the factors that determine the luminescence lifetime of transition metal compounds is key for applications in photocatalysis and photodynamic therapy. Here we show that for (bpy = 2,2’-bipyridine), the generally accepted idea that emission lifetimes can be controlled optimizing the energy barrier from the emissive triplet metal-to-ligand charge-transfer (³MLCT) state to the thermally-activated triplet metal-centered (³MC) state or the energy gap between both states is a misconception. Further, we demonstrate that considering a single relaxation pathway determined from the minimum that is lowest in energy leads to wrong temperature-dependent emission lifetimes predictions. Instead, we obtain excellent agreement with experimental temperature-dependent lifetimes when an extended kinetic model that includes all the pathways related to multiple Jahn–Teller isomers and their effective reaction barriers is employed. These concepts are essential to correctly design other luminescent transition metal complexes with tailored emission lifetimes based on theoretical predictions.