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Gold–mesoporous silica Janus nanoparticles were prepared through a masking strategy and further employed as building blocks for the preparation of bienzyme biosensors through toposelective immobilization of the corresponding enzymes. The system was evaluated by immobilizing glucose oxidase and horseradish peroxidase on the Au and mesoporous silica faces, respectively. The anisotropic nanoparticles were deposited on glassy carbon electrodes coated with single-walled carbon nanotubes in order to construct an amperometric biosensor for glucose detection. The enzymatic electrode showed excellent electroanalytical performance with a fast response in about 6 s, a linear range of 490 nM–600 μM, a high sensitivity of 4.3 mA M−1 , and a low detection limit of 360 nM for glucose. This biosensor was successfully employed to determine the content of this monosaccharide in commercial soft drink samples.

A novel hybrid nanomaterial was synthesised by covalent attachment of O-carboxymethylcellulose to reduced graphene oxide. Graphene oxide was first anchored with (3-aminopropyl)triethoxysilane moieties to provide reactive primary amino groups at the basal plane. Periodate-oxidised O-carboxymethylcellulose was further covalently attached to this aminated nanomaterial through reductive alkylation with NaBH4. Stable aqueous dispersions were obtained with the resulting hybrid nanomaterial, which was used to coat glassy carbon electrodes. Furthermore, the enzyme tyrosinase was covalently immobilised and the nanostructured enzyme electrode was successfully employed for the amperometric detection of catechol in the 20 nM–56 μM range. The biosensor showed excellent analytical performance with a high sensitivity of 270 mA M−1 and a low detection limit of 0.2 nM.

The electron ionization (EI) mass spectra of some new bridgehead 7,7-dimethylnorbornane-based β-amino alcohols have been studied and their fragmentation patterns compared with those of isomeric 3,3-dimethyl derivatives described by us previously. The dimethyl substitution at C7 results in a significant complication of the spectra, although all compounds show a C1–C2 bond cleavage with charge location at the nitrogen atom that leads to the base peak. Thus, two main fragmentation patterns dominated by cyclopentenylimmonium or methyleneimmonium ions are described depending on the position of the amino group in the norbornane framework (C1 or C2, respectively), as well as other secondary routes that can explain the appearance of the less noticeable fragments. Copyright © 2005 John Wiley & Sons, Ltd.

The electron impact mass spectra of several 3,3-dimethyl-1, 2-norbornanediols, diamines, amino alcohols and related derivatives have been studied and their fragmentation pathways discussed. Different fragmentation patterns were observed, depending not only on the nature of the substituents, but also on their relative positions on the norbornane framework. In general, the dominant peaks in the spectra of these compounds originate from initial C1-C2 bond cleavage (alpha-cleavage) with charge retention on the heteroatom (oxygen or nitrogen) attached at the bridgehead position, followed by hydride shift and loss of the C2-C3 fragment by homolytic cleavage of the C3-C4 bond. This fragmentation pathway leads to a highly stabilized cyclopentenylimmonium or cyclopentenyloxonium ion, which constitutes the base peak in the spectra in most of the studied compounds. Copyright 1999 John Wiley & Sons, Ltd.

The reaction of 2-norbornanones bearing an amine derivative in the bridgehead position with formamide and formic acid yields enantiomerically pure 1,2-norbornane diamides. These compounds are excellent precursors of chiral vicinal diamines, which have been increasingly used due to their numerous applications in medicinal chemistry and asymmetric synthesis. The rigid structure of the norbornane framework allows the study of conformational equilibrium in the formamide groups and its dependence on other substituents in the molecule.

The synthesis of chiral amine norbornane derivatives has been achieved by means of the Leuckart reaction of various 2-norbornanones. We propose an ionic mechanism for this process in which the formation of a 2-formylamino-2-norbornyl cation is the common initial step. The reaction pathway and the isolated products are strongly dependent on the nature of the bridgehead substituents; hydrogen and alkyl groups yield only enantiopure 2-norbornyl formamides with structural retention, whereas O-acyl or N-acyl groups favour a pinacol-type skeleton rearrangement through a cascade of Wagner−Meerwein rearrangements and intramolecular transamidations.