Convenient diastereospecific synthesis of a rociverine precursor and its resolution by lipase-catalyzed transesterification

(±)-1-Cyclohexyl-c-2-hydroxymethyl-r-1-cyclohexanol 3, a precursor of the antimuscarinic drug Rociverine 1, was obtained diastereospecifically in very high yield, from the Grignard reaction between C₆H₁₁MgCl and an appropriately protected 2-(hydroxymethyl)cyclohexanone. The preparation of enantiomerically enriched cis diol (+)-(1R,2S)-3 and the corresponding 2-acetoxymethyl derivative (+)-(1S,2R)-12 was achieved by lipase PPL-catalyzed transesterification of racemic diol (±)-3.     

Efficient and sustainable V-catalyzed oxidative desulfurization of fuels assisted by ionic liquids

Fuel desulfurization is an appealing topic for the chemical industry since severe environmental regulations regarding SO₂ emissions have been legislated in many countries. In order to reduce the amount of sulfur-containing compounds in fuels, responsible for high SO_x emission levels, a green chemistry approach is compulsory. In this paper, vanadium salen and salophen complexes were used in the oxidation of a model aromatic sulfide, such as dibenzothiophene (DBT), in the presence of H₂O₂ as green oxidant. The oxidative process was successfully coupled with the extraction of the oxidized compounds by ionic liquids. The system resulted highly selective for sulfide oxidation, showing poor reactivity toward the oxidation of alkenes and allowing a significant reduction of S content in a model benzine. To note, the use of microwave in place of standard heating allowed to obtain 98% of DBT oxidation and almost complete sulfur extraction in the model fuel in 1000 s. For these reasons, this system was considered an easy, rapid and clean process to achieve fuel desulfurization.     

New phosphorylating reagents for deoxyribonucleosides and oligonucleotides

New phosphorylating reagents 1 and 2 were prepared in three steps from 4-hydroxybenzaldehyde. They showed good efficiency in the solid phase synthesis of 5′-phosphate monoester nucleosides. End-phosphate DNA sequence synthesis demonstrated the efficiency of the new reagents (1 and 2) according to the general procedure of automated DNA synthesis. The oxidation of P(III) to P(V) and the removal of benzyl protecting groups were achieved in a single step by treatment with a 0.02 M I₂/pyridine/H₂O solution. Due to this one-pot treatment, it is possible to use the phosphorylating reagents (1 and 2) for the synthesis of base-sensitive ODNs. The reagents 1 and 2 are unique among phosphorylating reagents.     

Structural Inhomogeneity in Electrolyte Solutions: The Calcium Perchlorate–Water System

A new approach has been proposed to study the structure of aqueous electrolyte solutions. NIR, Raman and attenuated total reflectance, Fourier transform infra-red (ATR FTIR) spectra have been measured for aqueous calcium perchlorate solutions in the 0.22–4.3 mol·L^?1 (0.22–7.46 mol·kg^?1) concentration range at 25 °C. By the methods of principal component analysis (PCA) and multivariate curve resolution—alternating least squares (MCR-ALS) the number, spectra and concentration profiles have been determined for spectroscopically distinguishable forms of water and ClO ₄ ^? ion in solutions. The results have been analyzed using a phenomenological model, establishing thereby: concentration ranges for structural rearrangements of the solution, the nature of structural microirregularities and different states of the ClO ₄ ^? ion in the areas of domination of the natural water structure, and of cybotactic groups of calcium perchlorate hexa and tetra hydrates.     

A new subspace iteration method for the algebraic Riccati equation

We consider the numerical solution of the continuous algebraic Riccati equation A*X + XA ? XFX + G = 0, with F = F*,G = G* of low rank and A large and sparse. We develop an algorithm for the low‐rank approximation of X by means of an invariant subspace iteration on a function of the associated Hamiltonian matrix. We show that the sought‐after approximation can be obtained by a low‐rank update, in the style of the well known Alternating Direction Implicit (ADI) iteration for the linear equation, from which the new method inherits many algebraic properties. Moreover, we establish new insightful matrix relations with emerging projection‐type methods, which will help increase our understanding of this latter class of solution strategies. Copyright © 2014 John Wiley & Sons, Ltd.     

An alternating extragradient method with non euclidean projections for saddle point problems

In this work we analyze a first order method especially tailored for smooth saddle point problems, based on an alternating extragradient scheme. The proposed method is based on three successive projection steps, which can be computed also with respect to non Euclidean metrics. The stepsize parameter can be adaptively computed, so that the method can be considered as a black-box algorithm for general smooth saddle point problems. We develop the global convergence analysis in the framework of non Euclidean proximal distance functions, under mild local Lipschitz conditions, proving also the \(\mathcal {O}(\frac{1}{k})\) rate of convergence on the primal–dual gap. Finally, we analyze the practical behavior of the method and its effectiveness on some applications arising from different fields.     

Diversification limit of quantiles under dependence uncertainty

In this paper, we investigate the asymptotic behavior of the portfolio diversification ratio based on Value-at-Risk (quantile) under dependence uncertainty, which we refer to as “worst-case diversification limit”. We show that the worst-case diversification limit is equal to the upper limit of the worst-case diversification ratio under mild conditions on the portfolio marginal distributions. In the case of regularly varying margins, we provide explicit values for the worst-case diversification limit. Under the framework of dependence uncertainty the worst-case diversification limit is significantly higher compared to classic results obtained in the literature of multivariate regularly varying distributions. The results carried out in this paper bring together extreme value theory and dependence uncertainty, two popular topics in the recent study of risk aggregation.     

Minimal Blow-Up Solutions to the Mass-Critical Inhomogeneous NLS Equation

We consider the mass-critical focusing nonlinear Schrödinger equation in the presence of an external potential, when the nonlinearity is inhomogeneous. We show that if the inhomogeneous factor in front of the nonlinearity is sufficiently flat at a critical point, then there exists a solution which blows up in finite time with the maximal (unstable) rate at this point. In the case where the critical point is a maximum, this solution has minimal mass among the blow-up solutions. As a corollary, we also obtain unstable blow-up solutions of the mass-critical Schrödinger equation on some surfaces. The proof is based on properties of the linearized operator around the ground state, and on a full use of the invariances of the equation with an homogeneous nonlinearity and no potential, via time-dependent modulations.     

Relating Categorical Semantics for Intuitionistic Linear Logic

There are several kinds of linear typed calculus in the literature, some with their associated notion of categorical model. Our aim in this paper is to systematise the relationship between three of these linear typed calculi and their models. We point out that mere soundness and completeness of a linear typed calculus with respect to a class of categorical models are not sufficient to identify the most appropriate class uniquely. We recommend instead to use the notion of internal language when relating a typed calculus to a class of models. After clarifying the internal languages of the categories of models in the literature we relate these models via reflections and coreflections. Mathematics Subject Classifications (2000) 03G30, 03B15, 18C50, 03B20.