Amino­pyrimidine–carboxyl­(ate) interactions in trimethoprim maleate,an antifolate drug

In the title cocrystal, trimethoprim maleate [2,4‐di­amino‐5‐(3,4,5‐tri­methoxy­benzyl)­pyrimidin‐1‐ium maleate], C₁₄H₁₉­N₄O₃⁺·­C₄H₃O₄^?, the trimethoprim mol­ecule is protonated at N1. The carboxyl group of the maleate ion makes a specific double hydrogen bond of type N—H?O with the 2‐amino group and the protonated N1 atom of the trimethoprim cation which is similar to the carboxyl­ate–trimethoprim cation interaction observed in the complex of di­hydro­folate reductase with trimethoprim. The pyrimidine moieties of trimethoprim cations are centrosymmetrically paired through a pair of N—H?N hydrogen bonds involving the 4‐amino group and the pyridinium N3 atom of a symmetry‐related molecule. One of the O atoms at the maleate carboxyl­ate group bridges the 2‐­amino and 4‐amino groups on either side of the paired trimethoprim cations. The other O atom of the carboxyl­ate group forms an intramolecular O—H?O hydrogen bond with the carboxyl group. These characteristic hydrogen bonds result in infinite two‐dimensional aggregation of rings into a supramolecular ladder, which is further crosslinked through weak C—H?O interactions with methoxy groups of neighbouring trimethoprim mol­ecules to form a layered structure.     

From aerogels to compact glasses: effect of the density on the dynamical structure factor

The dynamical structure factor, S(Q,E), of a model system, based on a percolator and using the harmonic approximation, has been calculated using the moments method especially in the smaller Q region. With this particular growth algorithm we calculate systems with densities as small as few percent of the complete lattice. The variation of the width of the Brillouin peak with density and its dependence on the exchanged wavevector are compared with the experimental data available for amorphous silica at different densities. The results show that the dynamical properties of sparse materials, such as aerogels and xerogels, can be reproduced considering only the dynamic of their network neglecting the contribution of the elemental units forming the network.     

Determination of nuclear graphite impurities by prompt gamma activation analysis to support decommissioning operations

Journal of Radioanalytical and Nuclear Chemistry - Elemental composition of non-irradiated nuclear grade graphite was determined by Prompt Gamma Activation Analysis (PGAA) to quantitively assess...     

Synthesis of 2-alkylidene-cycloalkane-1,3-diols via enantioselective intramolecular carbolithiation

The lithiodestannylation and intramolecular anti-selective carbolithiation of α-lithiated ω-carbamoyloxy-1-alkynyl carbamates have been used to synthesize highly enantioenriched protected 2-alkylidene-cycloalkane-1,3-diols.     

The influence of polarization functions on electron density analysis of diborane

The experimental electron density in diborane is compared with the dynamic one derived from an SCF density calculated by an extended plus polarization basis set. The effect of the polarization functions is a lengthening of the BH bonds and the best agreement is now obtained for the experimental geometry.     

Thermally stable recyclable naphthalenediimide–siloxane polymers

We report here the synthesis and study of naphthalenediimide–siloxane polymers with high thermal stability. Two of the five polymers investigated could be developed into recyclable materials. We use solid-state ²⁹Si NMR to evaluate the degree of cross-linking and polymerisation in our materials.     

2′-Methyl taxanes: synthesis and NMR configurational assignment

Capitalizing on an oxidation-alkylation approach, a non-diastereoselective entry into 2′-methyl taxanes was developed. The issue of configurational assignment at the newly formed side-chain quaternary stereocenter was solved and put into a more general context by integrating information from an alternative diastereoselective synthesis of model compounds and from spectroscopic measurements, critically comparing the J-Based and the Universal NMR Database approaches.     

A new palladium nanoparticle catalyst on mesoporous silica prepared from a molecular cluster precursor

A promising approach to the controlled synthesis of supported nanoparticles involves the use of molecular carbonyl clusters as precursors. Molecular metal clusters consist of a defined number of structurally ordered atoms, and active monodisperse metal particles are formed after dispersing the molecules and removing the ligands. An octanuclear palladium cluster precursor with easily displaceable ligands was used to generate palladium nanoparticles on mesoporous MCM-41. The molecular cluster precursor, [Pd8(CO)8(PMe3)7], was directly adsorbed from solution onto MCM-41, followed by gentle thermolysis which yielded small metal nanoparticles. Compared to MCM-41-based catalysts prepared from palladium salts by conventional methods, this cluster-derived palladium catalyst has shown an efficient activity for liquid-phase hydrogenation of alkenes.     

Investigation of the aqueous transmetalation of pi-allylpalladium with indium salt: the use of the Pd(OAc)2-TPPTS catalyst

pi-Allylpalladium complexes could be generated in water by the palladium(0) water soluble catalyst prepared in situ from palladium acetate and TPPTS. These complexes were transmetalated with indium to react with benzaldehyde. The aqueous solution of Pd(0)(TPPTS)(n) could be reused without deterioration of the catalyst in the first and second recycling. The system proved to be efficient with primary and secondary allylic substrates. The stereochemical outcome of the allylation through umpolung of allylpalladium, was also studied using models with a restraint conformation.     

A Modular Flow Design for the meta-Selective C−H Arylation of Anilines

Described herein is an effective and practical modular flow design for the meta-selective C−H arylation of anilines. The design consists of four continuous-flow modules (i.e., diaryliodonium salt synthesis, meta-selective C−H arylation, inline copper extraction, and aniline deprotection) which can be operated either individually or consecutively to provide direct access to meta-arylated anilines. With a total residence time of 1 hour, the desired product could be obtained in high yield and excellent purity without the need for column chromatography, and the residual copper content meets the standards for parenterally administered pharmaceutical substances.