Xylose Incorporated in Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes: Synthesis, Characterization and Antibacterial Activity.

A series of Au(I) complexes containing unsymmetrical N-heterocyclic carbene (imidazolylidene and benzimidazolylidene) functionalized with a xyloside group and an alkyl moiety (methyl and mesityl) was prepared using efficient procedures from D-xylose. Their characterization was carried out in solution by multinuclear NMR, HR-MS spectrometry and cyclic voltammetry, as well as in the solid state by means of single crystal X-ray diffraction analysis for two of them. Evaluation of their ability to inhibit bacterial growth showed a preference for a Gram-positive strain, Staphylococcus aureus, over a Gram-negative strain, Pseudomonas aeruginosa.

Organocatalyzed Asymmetric Allylic Alkylation Enables Synthesis of Chiral γ-Lactones Bearing Vicinal Tertiary and Quaternary Stereocenters.

The synthesis of enantioenriched α-aryl-α'-allyl-γ-butyrolactones bearing vicinal tertiary and quaternary stereocenters through organocatalyzed asymmetric allylic alkylation is reported. The process demonstrated that weakly stabilized enolates derived from α-aryl-γ-butyrolactones can undergo regio-, diastereo-, and enantioselective allylation using the proper activation of Morita-Baylis-Hillman (MBH) carbonates.

Electron-Beam-Induced Grafting of Chitosan onto HDPE/ATZ Composites for Biomedical Applications.

The surface functionalisation of high-density polyethylene (HDPE) and HDPE/alumina-toughened zirconia (ATZ) surfaces with chitosan via electron-beam (EB) irradiation technique was exploited for preparing materials suitable for biomedical purposes. ATR-FTIR analysis and wettability measurements were employed for monitoring the surface changes after both irradiation and chitosan grafting reaction. Interestingly, the presence of ATZ loadings beyond 2 wt% influenced both the EB irradiation process and the chitosan functionalisation reaction, decreasing the oxidation of the surface and the chitosan grafting. The EB irradiation induced an increase in Young's modulus and a decrease in the elongation at the break of all analysed systems, whereas the tensile strength was not affected in a relevant way. Biological assays indicated that electrostatic interactions between the negative charges of the surface of cell membranes and the -NH3+ sites on chitosan chains promoted cell adhesion, while some oxidised species produced during the irradiation process are thought to cause a detrimental effect on the cell viability.

Evidence of chitosan-mediated reduction of Au(III) to Au(0) nanoparticles under electron beam by using OH˙ and e⁻(aq) scavengers.

Selective scavengers of e(-)(aq) and OH˙ radicals were used to investigate the radiolytic synthesis of gold nanoparticles from Au(III) solutions in the presence of chitosan. This reaction does not exclusively follow the direct reduction by solvated electrons. Irradiation generates short-lived and long-lived reductive species derived from chitosan that efficiently convert Au(III) into Au(0) which aggregates to form clusters.