Acetylenic derivatives of betulonic acid amide as a new type of compounds possessing spasmolytic activity

Efficient and versatile synthetic procedures towards novel derivatives of betulonic acid via Mannich reaction, Sonogashira cross-coupling, and copper(i)-catalyzed 1,3-dipolar cyclo-additions were developed. Introduction of secondary amines (Mannich reaction) into betulonic acid amides led to derivatives possessing marked spasmolytic activity, which is not characteristic of the triterpene fragment.     

Crystal associates of 18-crown-6 and polyfluoro(het)arylenediamines: structure,properties, and selectivity of formation

The new group of objects in crystal engineering, namely, 1 : 1 associates of polyfluoro(het)arylenediamines and 18-crown-6, being supramolecular 1D assemblies, is considered. Diamine isomerism is shown to serve as a design tool for control of the supramolecular architecture, and the nature of the aromatic framework and location and volume of substituents determine linear dimensions of the elementary unit in an assembly. A linear dependence of the enthalpy of melting of co-crystals on the length of the assembly unit is observed in the series of the meta-(het)arylenediamine and 18-crown-6 associates. The effect of selective co-crystallization of polyfluoroarylenediamines with crown ether is used in practice for the isolation of high-purity compounds from mixtures of products of the non-selective amination of basic polyfluoroarenes.     

Interaction of amorphous and crystalline nickel nanoparticles with hydrogen

Nickel nanoparticles were deposited on the surface of highly oriented pyrolytical graphite by laser electrodispersion and precipitation from a solution of reverse micelles. The particles were studied using scanning tunneling microscopy and spectroscopy as well as Auger spectroscopy. The elemental composition of the nanoparticles and specific features of the electronic structure of their surface were determined. Adsorption of molecular hydrogen was also studied.     

Reaction of 2,3-dibromo-3-nitroacrylates with N-amino-N″-nitroguanidine

Russian Journal of Organic Chemistry -     

Cooperative Lewis Pairs Based on Late Transition Metals: Activation of Small Molecules by Platinum(0) and B(C6F5)3

A Lewis basic platinum(0)–CO complex supported by a diphosphine ligand and B(C₆F₅)₃ act cooperatively, in a manner reminiscent of a frustrated Lewis pair, to activate small molecules such as hydrogen, CO₂, and ethene. This cooperative Lewis pair facilitates the coupling of CO and ethene in a new way.     

Structural Characterization of O‐ and C‐Glycosylating Variants of the Landomycin Glycosyltransferase LanGT2

The structures of the O‐glycosyltransferase LanGT2 and the engineered, C? C bond‐forming variant LanGT2S8Ac show how the replacement of a single loop can change the functionality of the enzyme. Crystal structures of the enzymes in complex with a nonhydrolyzable nucleotide‐sugar analogue revealed that there is a conformational transition to create the binding sites for the aglycon substrate. This induced‐fit transition was explored by molecular docking experiments with various aglycon substrates.     

Direct Catalytic Enantio‐ and Diastereoselective Ketone Aldol Reactions of Isocyanoacetates

A catalytic asymmetric aldol addition/cyclization reaction of unactivated ketones with isocyanoacetate pronucleophiles has been developed. A quinine‐derived aminophosphine precatalyst and silver oxide were found to be an effective binary catalyst system and promoted the reaction to afford chiral oxazolines possessing a fully substituted stereocenter with good diastereoselectivities and excellent enantioselectivities.     

Synthesis of potential inhibitors of glycosyltransferases representing UDP-GlcNAc

Based on rational design of the transition state analog inhibitors of glycosyltransferases, four model glycomimetics of this type, viz. benzyl 2-thio-α-dfructofuranoside 1-diethylphosphate (XIa), its β-anomer (XIb), and their ethyl 2-thio analogs — α-anomer (XIIa) and β-anomer (XIIb), were synthesized. In addition, fourteen precursors arising during the synthesis of the desired final model compounds (XI and XII), partially or fully acetylated benzyl and/or ethyl 2-thiofructofuranoside 1-diethyl phosphates, were isolated and characterized with the aim to prepare complete series of glycomimetics, representing donor UDP-GlcNAc designated for biological assays on human GnT’s, viz. GnT-I, Core2GnT, and GnT-V.     

Exact solutions to magnetogasdynamic equations in Lagrangian coordinates

The Lie group of point transformations, which leave the equations for a simplified model of one dimensional ideal gas in magnetogasdynamics invariant, are used to obtain some exact solutions for the governing system of hyperbolic partial differential equations (PDEs). Similarity variables which reduces the governing system of PDEs into system of ordinary differential equations (ODEs) are determined through the transformations. The resulting ODEs are solved analytically to obtain some exact solutions that exhibits space-time dependence. Further, we study the propagation of weak discontinuity through a state characterized by one of the solutions.