Solution-phase synthesis of 2-cyano and 2-amido aziridinyl peptides

Starting from a library of 2-l-α-amino acyl (E)-acrylonitriles, different short 2-cyano and 2-amido aziridinyl peptides, potential protease inhibitors, were obtained under parallel solution-phase conditions. The transformations include careful selection of conditions for aziridine deprotection and cyano group partial hydrolysis.     

Straightforward Access to Pyrazine-(2,3)-diones through Sequential Three-Component Reaction

A novel protocol for the assembly of polysubstituted 2,3-dioxo-1,4,5,6-tetrahydropyrazines and 2,3-dioxo-hydro-1H-cycloalkyl[b]pyrazines has been developed by the sequential three-component reaction of primary aliphatic amines, 1,2-diaza-1,3-dienes (DDs) and oxalyl chloride. This synthetic sequence proceeds by initial aza-Michael addition of the amine to the azo-ene compounds and subsequent ring closure involving the oxalyl chloride. The ready availability of the starting materials as well as the high level of practicability of the reaction and work-up make this approach an attractive opportunity towards these uncommon systems.     

Regularized Quadratic Penalty Methods for Shape from Shading

Shape from shading (SFS) denotes the problem of reconstructing a 3D surface, starting from a single shaded image which represents the surface itself. Minimization techniques are commonly used for solving the SFS problem, where the objective function is a weighted combination of the brightness error, plus one or more terms aiming to obtain a valid solution. We present a regularized quadratic penalty method where quadratic penalization is used to adaptively adjust the smoothing weights, and regularization improves the robustness and reliability of the procedure. A nonmonotone Barzilai–Borwein method is employed to efficiently solve the arising subproblems. Numerical results are provided showing the reliability of the proposed approach.     

Acid‐catalysed glucose dehydration in the gas phase: a mass spectrometric approach

Understanding on a molecular level the acid‐catalysed decomposition of the sugar monomers from hemicellulose and cellulose (e.g. glucose, xylose), the main constituent of lignocellulosic biomass is very important to increase selectivity and reaction yields in solution, key steps for the development of a sustainable renewable industry. In this work we reported a gas‐phase study performed by electrospray triple quadrupole mass spectrometry on the dehydration mechanism of d ‐glucose. In the gas phase, reactant ions corresponding to protonated d ‐glucose were obtained in the ESI source and were allowed to undergo collisionally activated decomposition (CAD) into the quadrupole collision cell. The CAD mass spectrum of protonated d ‐glucose is characterized by the presence of ionic dehydrated daughter ion (ionic intermediates and products), which were structurally characterized by their fragmentation patterns. In the gas phase d ‐glucose dehydration does not lead to the formation of protonated 5‐hydroxymethyl‐2‐furaldehyde, but to a mixed population of m/z 127 isomeric ions. To elucidate the d ‐glucose dehydration mechanism, 3‐O‐methyl‐d ‐glucose was also submitted to the mass spectrometric study; the results suggest that the C3 hydroxyl group plays a key role in the reaction mechanism. Furthermore, protonated levulinic acid was found to be formed from the monodehydrated d ‐glucose ionic intermediate, an alternative pathway other than the known route consisting of 5‐hydroxymethyl‐2‐furaldehyde double hydration. Copyright © 2015 John Wiley & Sons, Ltd.     

Multidimensional preparative liquid chromatography to isolate flavonoids from bergamot juice and evaluation of their anti‐inflammatory potential

Important objectives of a high‐performance liquid chromatography preparative process are: purity of products isolated, yield, and throughput. The multidimensional preparative liquid chromatography method used in this work was developed mainly to increase the throughput; moreover purity and yield are increased thanks to the automated collection of the molecules based on the intensity of a signal generated from the mass spectrometer detector, in this way only a specific product can be targeted. This preparative system allowed, in few analyses both in the first and second dimensions, the isolation of eight pure compounds present at very different concentration in the original sample with high purity (>95%) and yield, which showed how the system is efficient and versatile. Pure molecules were used to validate the analytical method and to test the anti‐inflammatory and antiproliferative potential of flavonoids. The contemporary presence, in bergamot juice, of all the flavonoids together increases the anti‐inflammatory effect with respect to the single compound alone.     

Oscillatory asymptotic expansion for semilinear wave equation

We study oscillatory properties of the solution to semilinear wave equation, assuming oscillatory terms in initial data have sufficiently small amplitude. The main result gives an a priori estimate of the remainder in the approximation by means of the method of geometric optics. The method of establishing this estimate is based on a combination between energy type estimates for transport equation and Sobolev embedding. Copyright © 2001 John Wiley & Sons, Ltd.     

Optimizing analytical methods using sequential response surface methodology. Application to the pararosaniline determination of formaldehyde

Sequential response surface methodology is a general procedure to re-optimize common analytical methods on the basis of the application of the response surface methodology and of a new approach to the steepest ascent method. This procedure, which is easy to apply, consists of estimating an analytical function relating the response with the experimental parameters by means of a second-degree polynomial. Thus, a 2nd order design covering the total experimental domain is used and when a maximum is obtained, the characteristics of the response surface are confirmed using a new design, which is obtained contracting the first one. In the proposed methodology, Box-Behnken designs are used because they offer advantages in comparison with second order designs more frequently used in the steepest ascent method (central composite designs), i.e. fewer experiments are needed, they are more efficient, they can be moved through the experimental domain and they can even be easily contracted or expanded.     

Non-rigid liquid crystalline networks based on linear,segmented-chain mesogenic polymers

Five linear mesogenic polyesters, containing terephthalic groups, and bearing different amounts of unsaturated substituents were prepared and their phase behaviour characterised by calorimetric and X-ray diffraction means. Networks based on these polymers were obtained by thermally activated radical polymerisation. Some optical and structural features of these networks were investigated both in the bulk and in the swollen state.     

Synthesis of new 2,2′‐disubstituted 5,5′‐dimethyl‐4,4′‐bitriazoles and 2‐(4‐Triazolyl)quinoxalines

Thermal rearrangement of 3‐acylisoxazole arylhydrazones allowed facile preparation of 2H‐1,2,3‐triazoles which were firstly reacted with isoamyl nitrite and then with an opportune arylhydrazine to produce the corresponding α‐hydroxyiminohydrazones 8a‐h . The reaction of compounds 8a‐h with phosphorus pentachloride afforded the desired 4,4′‐bitriazoles 1a‐h . The α‐hydroxyiminoketone derivative 7 or the α‐diketone 14 reacted easily with 1,2‐phenylenediamine to afford 1,2,3‐triazoles 2a‐c bearing the quinoxaline moiety at position 4. Improved yields of the quinoxalines 2a‐c were obtained when 1,2‐phenylenediamine was reacted with the dioxime 15.