In Search of Organic Zeolites – Does Modern Information Retrieval Inevitably Become a ‘Sieving‐the‐Desert' Exercise?

Information retrieval for planning and executing research projects and for publishing results is considered a routine task that is usually neither mentioned explicitly in a scientific publication nor described in any detail. In the information searches for the preceding publication (‘Building an Organic Zeolite from a Macrocyclic TADDOL Derivative or How to Teach an Old Dog New Tricks'), we were confronted with so many problems during retrieval of the desired information about related work that we decided to deviate from this tradition. We had to use the Cambridge Structural Database, the Chemical Abstracts structure and literature databases, and the Beilstein database to the full extent of their contents, indexing, and search facilities to retrieve the necessary information about ‘organic zeolites'. In the process, we found important limitations and deficiencies in any one of these databases, and we had to conceive search procedures that we considered rather unusual even after more than 20 years of experience in searching chemistry databases. The results and, particularly, the problems encountered underline the necessity for enhanced integration of individual compound and property databases and improved standardization as a prerequisite for this.     

The Even/Odd Disparity in Organic Compounds

There are more organic compounds with an even number of carbon atoms than with an odd number. This disparity could result mainly from the methods used in synthetic chemistry to build large molecules from smaller ones. Samples of C₂₈, C₄₇ and C₄₈ compounds have been examined in this context.     

Chlorophyll Catabolites in Fall Leaves of the Wych Elm Tree Present a Novel Glycosylation Motif

Fall leaves of the common wych elm tree (Ulmus glabra) were studied with respect to chlorophyll catabolites. Over a dozen colorless, non‐fluorescent chlorophyll catabolites (NCCs) and several yellow chlorophyll catabolites (YCCs) were identified tentatively. Three NCC fractions were isolated and their structures were characterized by spectroscopic means. Two of these, Ug‐NCC‐27 and Ug‐NCC‐43, carried a glucopyranosyl appendage. Ug‐NCC‐53, the least polar of these NCCs, was identified as the formal product of an intramolecular esterification of the propionate and primary glucopyranosyl hydroxyl groups of Ug‐NCC‐43. Thus, the glucopyranose moiety and three of the pyrrole units of Ug‐NCC‐53 span a 20‐membered ring, installing a bicyclo[17.3.1]glycoside moiety. This structural motif is unprecedented in heterocyclic natural products, according to a thorough literature search. The remarkable, three‐dimensional bicyclo[17.3.1]glycoside architecture reduces the flexibility of the linear tetrapyrrole. This feature of Ug‐NCC‐53 is intriguing, considering the diverse biological effects of known bicyclo[n.3.1]glycosidic natural products.     

Simultaneous determination of rabeprazole and its two active metabolites in human urine by liquid chromatography with tandem mass spectrometry and its application in a urinary excretion study

A simple and rapid liquid chromatography with tandem mass spectrometry method has been developed and validated for the determination of rabeprazole and its two active metabolites, rabeprazole thioether and desmethyl rabeprazole thioether, in human urine using donepezil as the internal standard. The sample preparation procedure involved a simple dilution of urine sample with methanol (1:3, v/v). The chromatographic separation was achieved on a Hedera ODS‐2 C₁₈ column using a mixture of methanol/10 mmol/L ammonium acetate solution (containing 0.05% formic acid; 55:45, v/v) as the mobile phase. The method was validated over the concentration ranges of 0.15–100 ng/mL for rabeprazole, 0.30–400 ng/mL for rabeprazole thioether, and 0.05–100 ng/mL for desmethyl rabeprazole thioether. The established method was highly sensitive with a lower limit of quantification of 0.15 ng/mL for rabeprazole, 0.30 ng/mL for rabeprazole thioether, and 0.05 ng/mL for desmethyl rabeprazole thioether. The intra‐ and interbatch precision was <4.5% for the low, medium, and high quality control samples of all the analytes. The recovery of the analytes was in the range 95.4–99.0%. The method was successfully applied to a urinary excretion profiles after intravenous infusion administration of 20 mg rabeprazole sodium in healthy volunteers.     

First correlation of nanoparticle size-dependent formation with the ionic liquid anion molecular volume

Stable silver nanoparticles are obtained reproducibly by hydrogen reduction of different inorganic precursors from AgIX salts (X = BF4, PF6, OTf) dissolved in the ionic liquids BMim+BF4-, BMim+PF6-, BMim+OTf-, or BtMA+NTf2- [BMim+ = n-butylmethylimidazolium, BtMA+ = n-butyltrimethylammonium, NTf2 = N(O2SCF3)2, and OTf = O3SCF3] in the presence of n-butylimidazole (Bim) as the scavenger for the HX acid byproduct and with a narrow size distribution in the diameter range of 2.8-26.1 nm, which increases linearly with the molecular volume of the ionic liquid anion (transmission electron microscopy characterization).     

Synthesis,Stabilization, Functionalization and,DFT Calculations of Gold Nanoparticles in Fluorous Phases (PTFE and Ionic Liquids)

Gold nanoparticles (Au‐NPs) were reproducibly obtained by thermal, photolytic, or microwave‐assisted decomposition/reduction under argon from Au(CO)Cl or KAuCl₄ in the presence of n‐butylimidazol dispersed in the ionic liquids (ILs) BMIm⁺BF₄^?, BMIm⁺OTf^?, or BtMA⁺NTf₂^? (BMIm⁺=n‐butylmethylimidazolium, BtMA⁺=n‐butyltrimethylammonium, OTf^?=^?O₃SCF₃, NTf₂^?=^?N(O₂SCF₃)₂). The ultra small and uniform nanoparticles of about 1–2 nm diameter were produced in BMIm⁺BF₄^? and increased in size with the molecular volume of the ionic liquid anion used in BMIm⁺OTf^? and BtMA⁺NTf₂^?. Under argon the Au‐NP/IL dispersion is stable without any additional stabilizers or capping molecules. From the ionic liquids, the gold nanoparticles can be functionalized with organic thiol ligands, transferred, and stabilized in different polar and nonpolar organic solvents. Au‐NPs can also be brought onto and stabilized by interaction with a polytetrafluoroethylene (PTFE, Teflon) surface. Density functional theory (DFT) calculations favor interactions between IL anions instead of IL cations. This suggests a Au???F interaction and anionic Au_n stabilization in fluorine‐containing ILs. The ¹⁹F NMR signal in BMIm⁺BF₄^? shows a small Au‐NP concentration‐dependent shift. Characterization of the dispersed and deposited gold nanoparticles was done by transmission electron microscopy (TEM/HRTEM), transmission electron diffraction (TED), dynamic light scattering (DLS), UV/Vis absorbance spectroscopy, scanning electron microscopy (SEM), electron spin resonance (ESR), and electron probe micro analyses (EPM, SEM/EDX).