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1.
Emily K. Corlett Helen Blade Leslie P. Hughes Philip J. Sidebottom David Walker Richard I. Walton Steven P. Brown 《Magnetic resonance in chemistry : MRC》2020,58(11):1026-1035
Single-crystal X-ray diffraction structures of the 5-amino-2-methylpyridinium hydrogen fumarate salt have been solved at 150 and 300 K (CCDC 1952142 and 1952143). A base–acid–base–acid ring is formed through pyridinium-carboxylate and amine-carboxylate hydrogen bonds that hold together chains formed from hydrogen-bonded hydrogen fumarate ions. 1H and 13C chemical shifts as well as 14N shifts that additionally depend on the quadrupolar interaction are determined by experimental magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) and gauge-including projector-augmented wave (GIPAW) calculation. Two-dimensional homonuclear 1H-1H double-quantum (DQ) MAS and heteronuclear 1H-13C and 14N-1H spectra are presented. Only small differences of up to 0.1 and 0.6 ppm for 1H and 13C are observed between GIPAW calculations starting with the two structures solved at 150 and 300 K (after geometry optimisation of atomic positions, but not unit cell parameters). A comparison of GIPAW-calculated 1H chemical shifts for isolated molecules and the full crystal structures is indicative of hydrogen bonding strength. 相似文献
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Mario Culebras Mahboubeh Pishnamazi Gavin M. Walker Maurice N. Collins 《Molecules (Basel, Switzerland)》2021,26(6)
Nowadays, sustainable materials are receiving significant attention due to the fact that they will be crucial for the development of the next generation of products and devices. In the present work, hydrogels have been successfully synthesized using lignin which is non-valorized biopolymer from the paper industry. Hydrogels were prepared via crosslinking with Poly(ethylene) glycol diglycidyl ether (PEGDGE). Different crosslinker ratios were used to determine their influence on the structural and chemical properties of the resulting hydrogels. It has been found that pore size was reduced by increasing crosslinker amount. The greater crosslinking density increased the swelling capacity of the hydrogels due to the presence of more hydrophilic groups in the hydrogel network. Paracetamol release test showed higher drug diffusion for hydrogels produced with a ratio lignin:PEGDGE 1:1. The obtained results demonstrate that the proposed approach is a promising route to utilize lignocellulose waste for producing porous materials for advanced biomedical applications in the pharmacy industry. 相似文献
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Myriam Drouin Dr. Parvesh Wadhwani Dr. Stephan L. Grage Dr. Jochen Bürck Dr. Johannes Reichert Sébastien Tremblay Marie Sabine Mayer Christian Diel Alexander Staub Prof. Jean-François Paquin Prof. Dr. Anne S. Ulrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1511-1517
Solid-state 19F NMR is a powerful method to study the interactions of biologically active peptides with membranes. So far, in labelled peptides, the 19F-reporter group has always been installed on the side chain of an amino acid. Given the fact that monofluoroalkenes are non-hydrolyzable peptide bond mimics, we have synthesized a monofluoroalkene-based dipeptide isostere, Val-Ψ[(Z)-CF=CH]-Gly, and inserted it in the sequence of two well-studied antimicrobial peptides: PGLa and (KIGAKI)3 are representatives of an α-helix and a β-sheet. The conformations and biological activities of these labeled peptides were studied to assess the suitability of monofluoroalkenes for 19F NMR structure analysis. 相似文献
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Bodil Lousen Dr. Stephan K. Pedersen Pernille Bols Kasper H. Hansen Michelle R. Pedersen Prof. Ole Hammerich Dr. Sergey Bondarchuk Prof. Boris Minaev Dr. Glib V. Baryshnikov Prof. Hans Ågren Prof. Michael Pittelkow 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):4935-4940
This work describes a synthetic approach where a non-planar aromatic heterocyclic [7]helicene is compressed to yield a hetero[8]circulene containing an inner antiaromatic cyclooctatetraene (COT) core. This [8]circulene consists of four benzene rings and four heterocyclic rings, and it is the first heterocyclic [8]circulene containing three different heteroatoms. The synthetic pathway proceeds via a the flattened dehydro-hetero[7]helicene, which is partially a helicene and partially a circulene: it is non-planar and helically chiral as helicenes, and contains a COT motif like [8]circulenes. The antiaromaticity of the COT core is confirmed by nucleus independent chemical shift (NICS) calculations. The planarization from a helically π-conjugated [7]helicene to a fully planar heterocyclic [8]circulene significantly alters the spectroscopic properties of the molecules. Post-functionalization of the [7]helicenes and the [8]circulenes by oxygenation of the thiophene rings to the corresponding thiophene-sulfones allows an almost complete fluorescence emission coverage of the visible region of the optical spectrum (400–700 nm). 相似文献
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Pim R. Linnebank Stephan Falcão Ferreira Alexander M. Kluwer Prof. Dr. Joost N. H. Reek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(37):8214-8219
Regioselective catalytic transformations using supramolecular directing groups are increasingly popular as it allows for control over challenging reactions that may otherwise be impossible. In most examples the reactive group and the directing group are close to each other and/or the linker between the directing group is very rigid. Achieving control over the regioselectivity using a remote directing group with a flexible linker is significantly more challenging due to the large conformational freedom of such substrates. Herein, we report the redesign of a supramolecular Rh–bisphosphite hydroformylation catalyst containing a neutral carboxylate receptor (DIM pocket) with a larger distance between the phosphite metal binding moieties and the DIM pocket. For the first time regioselective conversion of internal and terminal alkenes containing a remote carboxylate directing group is demonstrated. For carboxylate substrates that possess an internal double bond at the Δ-9 position regioselectivity is observed. As such, the catalyst was used to hydroformylate natural monounsaturated fatty acids (MUFAs) in a regioselective fashion, forming of an excess of the 10-formyl product (10-formyl/9-formyl product ratio of 2.51), which is the first report of a regioselective hydroformylation reaction of such substrates. 相似文献