Synthesis,mesogenic and dielectric properties of fluorosubstituted isothiocyanatoterphenyls

The synthesis, mesomorphic and physical properties of 14 homologous series of laterally fluorinated 4?-alkyl-4-isothiocyanatoterphenyls were described. Influence of the number of fluorine atoms and their position in the terphenyl core on the phase transition temperatures, nematic range, dielectric and optic anisotropy as well as bulk viscosity were discussed. The compounds with the most optimal properties for formulation of nematic mixtures were selected, and mixture examples with low viscosity and medium or high birefringence were presented.     

Resonant equations with the Neumann p-Laplacian plus an indefinite potential

We consider a nonlinear Neumann problem driven by the p  -Laplacian plus an indefinite potential and a Carathéodory reaction which at ±∞ is resonant with respect to any nonprincipal variational eigenvalue of the differential operator. Using critical point theory and Morse theory (critical groups), we show that the problem has at least three nontrivial smooth solutions, two of which have constant sign. In the process we prove some results of independent interest concerning the unique continuation property of eigenfunctions and the critical groups at infinity of a C¹$C^1$-functionals.     

Chimera Spectrum Diagnostics for Peptides Using Two-Dimensional Partial Covariance Mass Spectrometry

The rate of successful identification of peptide sequences by tandem mass spectrometry (MS/MS) is adversely affected by the common occurrence of co-isolation and co-fragmentation of two or more isobaric or isomeric parent ions. This results in so-called `chimera spectra’, which feature peaks of the fragment ions from more than a single precursor ion. The totality of the fragment ion peaks in chimera spectra cannot be assigned to a single peptide sequence, which contradicts a fundamental assumption of the standard automated MS/MS spectra analysis tools, such as protein database search engines. This calls for a diagnostic method able to identify chimera spectra to single out the cases where this assumption is not valid. Here, we demonstrate that, within the recently developed two-dimensional partial covariance mass spectrometry (2D-PC-MS), it is possible to reliably identify chimera spectra directly from the two-dimensional fragment ion spectrum, irrespective of whether the co-isolated peptide ions are isobaric up to a finite mass accuracy or isomeric. We introduce ‘3-57 chimera tag’ technique for chimera spectrum diagnostics based on 2D-PC-MS and perform numerical simulations to examine its efficiency. We experimentally demonstrate the detection of a mixture of two isomeric parent ions, even under conditions when one isomeric peptide is at one five-hundredth of the molar concentration of the second isomer.     

Two-Parameter Fuzzy-Valued Stochastic Integrals and Equations

This article is concerned with notions of fuzzy-valued stochastic integrals driven by two-parameter martingales and increasing processes. We present their main properties and formulate next two-parameter fuzzy-valued stochastic integral equations. We establish the existence and uniqueness of solutions to such equations as well as their additional properties.     

Can 2‐acylpyrroles form an intramolecular hydrogen bond?

The formation of intramolecular hydrogen bonding by certain N‐substituted 2‐acylpyrroles has been demonstrated by B3LYP/aug‐cc‐pVDZ calculations, the quantum theory of atoms in molecules, and the natural bond orbital method. Total electron energy densities H_BCP at the bond critical point of the H?O bond were applied to analyze the strength of these interactions. The relations between quantum theory of atoms in molecules, carbonyl stretching vibrational modes ν_{C = O}, and natural bond orbital parameters associated with the formation of the C–H?O interaction have been established. The short contacts were found experimentally in the crystal structure of a new 2‐acylpyrrole derivative 5‐chloro‐2‐oxopentyl‐1‐(5‐chloro‐2‐oxopentyl)pyrrolo‐2‐carboxylate. The influence of 2‐ and N‐substitution of 2‐acylpyrroles on C‐H?O interaction energy is discussed. It was found that the methylene group may act as a proton donor leading to a red‐shift or blue‐shift phenomenon of the ν_C–H stretching mode. Copyright © 2015 John Wiley & Sons, Ltd.     

Chiral Sulfinimines in Asymmetric Synthesis of Enantiomeric Aminophosphonic Acids

Abstract

Aminophosphonic acids have become important in different fields of chemistry, medicine and agriculture. In this review article, we highlight a new strategy developed in the author's laboratory of asymmetric synthesis of enantiomeric aminophosphonic acid that users chiral sulfinimines as reagents. A key reaction in the synthesis of enantiopure α-, β- and γ-aminophosphonic acids is a highly or fully diastereoselective addition of trivalent phosphorus nucleophiles and α-phosphonate carbanions to enantiopure sulfinimines. The steric course of these addition reactions is rationalized. The usefulness of the sulfinimine methodology is demonstrated by the synthesis of biologically active enantiopure 2-amino-3-phosphonopropanoic acid (AP3), 2-amino-4-phosphonobutanoic acid (AP4) and phosphoemeriamine.     

Hydrogen‐Bonding in Aminocatalysis: From Proline and Beyond

This Concept article summarizes recent progress in the field of hydrogen‐bonding aminocatalysis using proline‐derived systems. The aminocatalysts available in the literature are categorized by the incorporated hydrogen‐bonding scaffold and its mode of recognition. Both mono‐ and double‐hydrogen‐bonding motifs are discussed and examples of their application in asymmetric synthesis are given.