Glassy carbon electrode modified with hemin and new melamine compounds for H<Subscript>2</Subscript>O<Subscript>2</Subscript> amperometric detection

In an attempt to increase the stability and efficiency of hemin-modified electrodes, the present work reports the preparation of a new modified glassy carbon electrode obtained by immobilization of hemin (Hm) on the electrode surface together with a new N-substituted melamine (2,4,6-triamino-1,3,5-triazine) based G-2 dendrimer comprising p-aminophenol as peripheral unit (Den) or with one of its analogues, a melamine G-0 dimer (Dim). Basic structural features, able to determine intimate relationships between Hm and Dim (or Den) at room temperature in solid state, were evidenced with the use of vibrational analysis carried out by FT-IR. This method revealed contacts between Hm and Dim or Den respectively as H-bond interactions, proton-interchange, and π-π stacking interactions. The new modified electrodes were characterized by cyclic voltammetry and electrochemical impedance spectroscopy and tested for amperometric detection of H₂O₂. In this purpose, GC/Hm-Dim electrode exhibited better catalytic properties than GC/Hm-Den electrode, but lower stability.     

InCl3 and ZrCl4 catalyzed regioselective reaction of 2,2′-dihydroxybiphenyl with terminal alkynes: synthesis of new dibenzo[d,f][1,3]dioxepines

The regioselective reaction of 2,2′-dihydroxybiphenyl with terminal alkynes was found to be rapidly catalyzed by InCl₃ and ZrCl₄. The chemoselectivity of catalysts and alkynes for biphenol over water, together with the reaction mechanism are discussed in details.     

Facile Entry to 4‐ and 5‐Hydroxybenzofuran and to Their Amino Derivatives

An innovative one‐step procedure for the synthesis of 4‐hydroxybenzofuran and an improved synthesis of 5‐hydroxybenzofuran is reported. Such compounds were also transformed into their amino derivatives via Smiles rearrangement with good to high overall yields.     

A hybrid method for pricing European options based on multiple assets with transaction costs

The problem of pricing European options based on multiple assets with transaction costs is considered. These options include, for example, quality options and options on the minimum of two or more risky assets. The value of these options is the solution of a nonlinear parabolic partial differential equation subject to a final condition given by the payoff function associated with the option. A computationally efficient method to solve this final-value problem is proposed. This method is based on an asymptotic expansion of the required solution with respect to the parameters related to the transaction costs followed by the numerical solution of the linear partial differential equations obtained at each order in perturbation theory. The numerical solution of these linear problems involves an implicit finite-difference scheme for the parabolic equation and the use of the fast Fourier sine transform to solve the resulting elliptic problems. Numerical results obtained on test problems with the method proposed here are shown and discussed.     

Electron ionization-induced fragmentation of some new dibenzo(d, f)(1,3)dioxepine derivatives

The mass spectrometric behaviour of a series of 6,6-disubstituted dibenzo(d,f)(1,3)dioxepine derivatives have been studied. The fragmentation patterns were described and discussed in detail with the aid of labelled compounds, accurate mass measurements and collisionally induced dissociation experiments performed using an ion trap.     

Ligand exchange capillary electrophoresis by cyclodextrin derivatives, a powerful tool for enantiomeric separations

Five pure CD derivatives synthesized in our laboratory were used as chiral selectors in the presence of copper(II) ion. Three enantiomeric pairs of amino acids were submitted to separation experiments in CE, by exploiting the ligand exchange mechanism. The results obtained in the investigated systems, together with those of the analogous systems previously studied, clearly show the usefulness of this technique in chiral separations. By comparing the ligand exchange CE results with potentiometric results, either reported elsewhere or studied here for the first time (system Cu/CDampy/tyrosine), it has been possible to rationalise the separation results. The importance of the availability of pure selectors, and to characterise them both spectroscopically and thermodynamically is discussed.     

Intramolecular Inclusion of L-tryptophan within 3-functionalized Cyclodextrins

Abstract

The synthesis of L-tryptophan attached to the C3 group of a β-cyclodextrin through amide linkages with ethylenediamine or propylenediamine is reported. Circular dichroism and fluorescence investigations were carried out showing great differences between the two derivatives. The derivative containing the propylenediamine chain shows clear self-inclusion and exhibits spectral variations upon guest inclusion detected both by circular dichroism or by fluorescence. The difference in conformation of the two derivatives could be explained on the basis of the chain length.