Stereostructure of mycoheptin A2

The absolute configurations of all the stereogenic centers of the antibiotic mycoheptin A₂ were established upon previously elaborated general procedure, consisting of DQF‐COSY, NOESY, ROESY, HSQC and HMBC experiments as major tools. The structure of mycoheptin A₂ without stereochemistry of its aglycone has been reported before. Copyright © 2012 John Wiley & Sons, Ltd.     

The Cubical Cohomology Ring: An Algorithmic Approach

A cohomology ring algorithm in a dimension-independent framework of combinatorial cubical complexes is developed with the aim of applying it to the topological analysis of high-dimensional data. This approach is convenient in the cup-product computation and motivated, among others, by interpreting pixels or voxels in digital images as cubes. The S-complex theory and so called co-reductions are adopted to build a cohomology ring algorithm speeding up the algebraic computations.     

Pseudodifferential parabolic equations in uniform spaces

The paper is devoted to local and global solvability in locally uniform spaces and to the existence of a global attractor for a parabolic problem containing fractional power of the minus Laplace operator. Several useful technical tools and estimates are also collected in this paper.     

Characterization of CaTi0.9Fe0.1O3/La0.98Mg0.02NbO4 composite

A composite of CaTi_0.9Fe_0.1O₃ and electrolyte material, i.e. magnesium doped La_0.98Mg_0.02NbO₄ was prepared and studied. The phase content and the sample microstructure was examined by an X-ray diffraction method and scanning electron microscopy. EDS measurements were done both for composite samples and the diffusion couple. The electrical properties were studied by four terminal DC method. The high-temperature interaction between the two components of the composite has been observed. It has been suggested that lanthanum diffused into the perovskite phase and substituted for calcium whereas calcium and niobium formed the Ca₂Nb₂O₇ pyrochlore phase. At 1500°C very large crystallites of the pyrochlore were observed. Regardless of strong interaction between the composite components, its total conductivity was weakly dependent on the sintering temperature.     

Functionalization of some benzylthioarylboronic acids by benzylic lithiation of their N‐butyldiethanolamine esters or lithium (triisopropoxy)borates

The reaction of benzylthioarylboronic acids protected as N‐butyldiethanolamine esters or as triisopropoxyborates with organolithium bases or lithium diisopropylamide (LDA) has been investigated. The benzylic lithiation occurs selectively using LDA at − 68 °C. The stability of the resultant borio‐lithio intermediates is strongly influenced by the position of the boron atom in the phenyl ring. The reaction with various electrophiles affords new arylboronic acids substituted in the benzylic position. Copyright © 2011 John Wiley & Sons, Ltd.     

Calixarene complexes with metal ions

Selected complexes of metal ions are presented showing their syntheses and possible applications, an attention was paid to their usefulness in chemosensors design and in the environmental protection.     

Synthesis of new thiazole-2, -4, and -5-yl-(amino)methylphosphonates and phosphinates: unprecedented cleavage of thiazole-2 derivatives under acidic conditions

An efficient and reliable synthesis of new thiazole-(amino)methylphosphonic, phosphinic acids, and phosphine oxides is reported. The synthetic protocol is based on nucleophilic addition of phosphorous species to thiazole derived imines. Unexpectedly, it was discovered that heating of thiazole-2-yl-(amino)methylphosphonates and phosphinates with aqueous HCl leads to their decomposition resulting in a rupture of the C-P bond, rejecting of the phosphorus containing fragment and formation of the corresponding secondary N-(thiazole-2-yl-methyl)-alkylamines. Two alternative mechanisms for this cleavage are postulated.     

5‐Carboxymethyl‐2‐(4‐methylthiophenyl)‐1,3,2‐dioxaborolan‐4‐one: synthesis,characterization and application in enantioselective reduction of ketones

The reaction of arylboronic acids with L ‐O‐benzoyl‐tartaric acid and D ,L ‐malic acid has been studied. The obtained (acyloxy)boranes are moderately stable in solution and decompose to give boroxines. 5‐Carboxymethyl‐2‐(4‐methylthiophenyl)‐1,3,2‐dioxaborolan‐4‐one was obtained in the reaction of 4‐methylthiophenylboronic acid with D ,L ‐malic acid and characterized by X‐ray structural analysis. The use of L ‐(−)‐malic acid afforded the optically pure product which can be used as the powerful chiral reagent in the enantioselective reduction of ketones. Copyright © 2011 John Wiley & Sons, Ltd.     

Fast deterministic approximation for the multicommodity flow problem

In this paper we consider an optimization version of the multicommodity flow problem which is known as the maximum concurrent flow problem. We show that an approximate solution to this problem can be computed deterministically using O(k(ε ⁻² + logk) logn) 1-commodity minimum-cost flow computations, wherek is the number of commodities,n is the number of nodes, andε is the desired precision. We obtain this bound by proving that in the randomized algorithm developed by Leighton et al. (1995) the random selection of commodities can be replaced by the deterministic round-robin without increasing the total running time. Our bound significantly improves the previously known deterministic upper bounds and matches the best known randomized upper bound for the approximation concurrent flow problem. A preliminary version of this paper appeared inProceedings of the 6th ACM-SIAM Symposium on Discrete Algorithms, San Francisco CA, 1995, pp. 486–492.