Hydroxyl-directed ruthenium-catalyzed C-H bond functionalization: versatile access to fluorescent pyrans

Hydroxyl-assisted oxidative annulations of alkynes were accomplished with an inexpensive ruthenium(II) complex, delivering fluorescent pyrans via highly site selective as well as chemo- and regioselective C-H/O-H bond functionalizations.     

An alternative-conditional functional equation and the orthogonally additive functionals

Let X be a real inner product space of dimension greater than 2 and f be a real functional defined on X. Applying some ideas from the recent studies made on the alternative-conditional functional equation

On the convergence of an inexact Gauss–Newton trust-region method for nonlinear least-squares problems with simple bounds

We introduce an inexact Gauss–Newton trust-region method for solving bound-constrained nonlinear least-squares problems where, at each iteration, a trust-region subproblem is approximately solved by the Conjugate Gradient method. Provided a suitable control on the accuracy to which we attempt to solve the subproblems, we prove that the method has global and asymptotic fast convergence properties. Some numerical illustration is also presented.     

Capturing Linear Intermediates and C-Terminal Variants during Maturation of the Thiopeptide GE2270

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A redox-driven multicomponent molecular shuttle

A multicomponent [2]rotaxane designed to operate as a molecular shuttle driven by light energy has been constructed, and its properties have been investigated. The system is composed of (1) a light-fueled power station, capable of using the photon energy to create a charge-separated state, and (2) a mechanical switch, capable of utilizing such a photochemically generated driving force to bring about controllable molecular shuttling motions. The light-fueled power station is, in turn, a dyad comprising (i) a pi-electron-accepting fullerene (C60) component and (ii) a light-harvesting porphyrin (P) unit which acts as an electron donor in the excited state. The mechanical switch is a redox-active bistable [2]rotaxane moiety that consists of (i) a tetrathiafulvalene (TTF) unit as an efficient pi-electron-donor station, (ii) a dioxynaphthalene (DNP) unit as a second pi-electron-rich station, and (iii) a tetracationic cyclobis(paraquat-p-phenylene) (CBPQT4+) pi-electron-acceptor cyclophane, which encapsulates the better pi-electron-donating TTF station. Diethylene glycol spacers were conveniently introduced between the electroactive components in the dumbbell-shaped thread to facilitate the template-directed synthesis of the [2]rotaxane. A modular synthetic approach was undertaken for the overall synthesis of this multicomponent bistable [2]rotaxane, beginning with the syntheses of the P-C60 dyad unit and the two-station TTF-DNP-based [2]rotaxane separately, using conventional synthetic methodologies. These two components were finally stitched together by an esterification to afford the target rotaxane. Its structure was characterized by 1H NMR spectroscopy and mass spectrometry as well as by UV-vis-NIR absorption spectroscopy and voltammetry. The observations reflect remarkable electronic interactions between the various units, pointing to the existence of folded conformations in solution. The redox-driven shuttling process of the CBPQT4+ ring between the two competitive electron-rich recognition units, namely, TTF and DNP, was investigated by electrochemistry and spectroelectrochemistry as a means to verify its operational behavior prior to the photophysical studies related to light-driven operation. The oxidation process of the TTF unit is dramatically hampered in the rotaxane, thereby reducing the efficiency of the shuttling motion. These results confirm that, as the structural complexity increases, the overall function of the system no longer depends simply on its "primary" structure but also on higher-level effects which are reminiscent of the secondary and tertiary structures of biomolecules.     

The Gieseker-Petri divisor in {\mathcal{M}_g} for g ≤ 13

The Gieseker-Petri locus GP _g is defined as the locus inside ${\mathcal{M}_g}$ consisting of curves which violate the Gieseker-Petri Theorem. It is known that GP _g has always some divisorial components and it has been conjectured that it is of pure codimension 1 inside ${\mathcal{M}_g}$ . We prove that this holds true for genus up to 13.     

Nero d’Avola and Perricone cultivars: determination of polyphenols,flavonoids and anthocyanins in grapes and wines

In 2011 vintage, the evolution of monomer and total anthocyanins, as well as of total flavonoids and polyphenols of grapes and wine of Nero d’Avola and Perricone, varieties cultivated in Sicily, was studied. Anthocyanin profiles are commonly used for grapevine cultivar identification because it is currently accepted that this trait is closely related to their genetic characteristics. The concentration of Nero d’Avola and Perricone anthocyanins was determined by HPLC-DAD.     

On the number of equations defining certain varieties

The present paper deals with the problem of determining the minimal number of equations needed to define the variety associated to a monomial ideal. This problem is open in general: we develop some techniques which allow us to settle it for many particular classes of ideals. The author was supported by funds of the Italian Ministry for Education and Scientific Research (M.U.R.S.T.)     

The bottom-up approach to molecular-level devices and machines

The macroscopic concepts of a device and a machine can be extended to the molecular level. Molecular-level devices and machines are constructed by a bottom-up approach. The atom-by-atom bottom-up approach is unrealistic from the chemical viewpoint. The bottom-up approach molecule-by-molecule following the guidelines of supramolecular (multicomponent) chemistry has proved to be successful. The extension of the concepts of a device and a machine to the molecular level is of interest not only for basic research, but also for the growth of nanoscience and the development of nanotechnology.