Synthesis and evaluation of the catalytic properties of semicarbazides derived from N-triphenylmethyl-aziridine-2-carbohydrazides

A straightforward synthesis of a series of new catalysts derived from N-triphenylmethyl-aziridine-2-carbohydrazides is described. The new compounds have been tested for the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, which afforded the corresponding chiral alcohols in high chemical yields (up to 92%) and with excellent ee’s of approximately 90%.     

Stepwise Stress-Induced Transformations of Metal-Organic Polyhedral Cluster-Based Assemblies: Where Conformational and Supramolecular Features Meet

Understanding the factors governing the formation of supramolecular structures and phase transitions between various forms of molecular crystals is pivotal for developing dynamic, stimuli-responsive materials and polymorph-controlled syntheses. Here, we investigate the pressure-induced dynamic of both the intrinsic molecular structure and the supramolecular network of a predesigned polyhedral oxo-centered zinc cluster incorporating monoanionic N,N’-diphenylformamidinate and featuring N-bonded phenyl groups in close proximity to the primary coordination sphere. We demonstrate that the model oxo cluster is prone to undergoing pressure-induced conformational transformations of the secondary coordination sphere and simultaneous stepwise (initially every second polyhedral molecule undergoes the conformational transformations) and reversible transitions from an ambient phase α to high-pressure phases β and γ, as single-crystal-to-single-crystal events. The observed phase transitions illustrate the key role of an interplay between the low-energy conformation perturbations and cooperative intra- and intermolecular noncovalent interactions.     

Highly enantioselective asymmetric reactions involving zinc ions promoted by chiral aziridine alcohols

Enantiomerically pure, chiral secondary and tertiary aziridine alcohols (including the aziridine analogue of ProPhenol—AziPhenol) have proven to be highly effective catalysts for enantioselective asymmetric reactions in the presence of zinc ions, including arylation of aromatic aldehydes, epoxidation of chalcone and addition of diethylzinc to aldehydes, leading to the desired chiral products in high chemical yields (up to 90%) and with ee’s up to 90%. A higher catalytic activity of Prophenol-type bis(aziridine alcohol) in the aforementioned asymmetric transformations has been demonstrated.     

Betaine and Carnitine Derivatives as Herbicidal Ionic Liquids

This study focused on the synthesis and subsequent characterization of herbicidal ionic liquids based on betaine and carnitine, two derivatives of amino acids, which were used as cations. Four commonly used herbicides (2,4‐D, MCPA, MCPP and Dicamba) were used as anions in simple (single anion) and oligomeric (two anions) salts. The obtained salts were subjected to analyzes regarding physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles and solubility) as well as evaluation of their herbicidal activity under greenhouse and field conditions, toxicity towards rats and biodegradability. The obtained results suggest that the synthesized herbicidal ionic liquids displayed low toxicity (classified as category 4 compounds) and showed similar or improved efficacy against weed compared to reference herbicides. The highest increase was observed during field trials for salts containing 2,4‐D as the anion, which also exhibited the highest biodegradability (>75 %).     

Absolute continuity and local limit theorems for homogeneous functionals of point processes

Lithuanian Mathematical Journal - We study the absolute continuity and local limit theorems for homogeneous functionals defined on configurations of point processes (p.p.s). For empirical p.p.s, we...     

Direct Chromatographic Resolution of P-Chiral Organophosphorus Compounds at Analytical and Preparative Levels

Abstract

High-performance liquid chromatography utilizing chiral stationary phases (CSPs) is well established as a very simple and efficient method for obtaining discrete amounts of optically active compounds with high e.e., as well as for determining their enantiomeric composition We wish to demonstrate in the present work that a totally synthetic brush-type π-acidic CSP based on a bis(N,N′-3,5-dinitrobenzoyl) derivative of (R,R)- or (S,S)-trans-1,2-diaminocyclohexane as selector can be used successfully to resolve variety of chiral organophosphorus compounds containing stereogenic centers at phosphorus     

A new class of stereoregular vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain

A synthesis of a new macromolecular class of vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain is presented. Two transition‐metal‐catalyzed processes, which is silylative‐coupling copolycondensation (SCC) and ADMET copolymerization of divinyl‐substituted double‐decker silsesquioxanes (DDSQ‐2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ‐silylene‐vinylene‐arylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1044–1055     

Vitamin B12 Phosphate Conjugation and Its Effect on Binding to the Human B12‐Binding Proteins Intrinsic Factor and Haptocorrin

The binding of vitamin B₁₂ derivatives to human B₁₂ transporter proteins is strongly influenced by the type and site of modification of the cobalamin original structure. We have prepared the first cobalamin derivative modified at the phosphate moiety. The reaction conditions were fully optimized and its limitations examined. The resulting derivatives, particularly those bearing terminal alkyne and azide groups, were isolated and used in copper‐catalyzed alkyne–azide cycloaddition reactions (CuAAC). Their sensitivity towards light revealed their potential as photocleavable molecules. The binding abilities of selected derivatives were examined and compared with cyanocobalamin. The interaction of the alkylated derivatives with haptocorrin was less affected than the interaction with intrinsic factor. Furthermore, the configuration of the phosphate moiety was irrelevant to the binding process.