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.     

Reversed-phase liquid chromatography on an amide stationary phase for the determination of the B group vitamins in baby foods

A liquid chromatographic method for the separation and determination of several water-soluble vitamins of the B group is proposed. The procedure is based on the use of a new amide-based stationary phase, which avoids the need of using the ion-pair technique, leading to narrower peaks and a simpler mobile phase. Analyses were performed by gradient elution with acetonitrile-phosphate buffer as mobile phase and using a photodiode array detector. Specificity was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity index with commercial standards. Linearity, precision, recovery and sensitivity were satisfactory. The vitamins are extracted from the baby food using a single digestion with hydrochloric acid followed by enzymatic digestion with taka-diastase. The method was successfully applied to the determination of nine vitamins: thiamine, riboflavin, nicotinamide, nicotinic acid, pyridoxine, pyridoxal, folic acid, cyanocobalamine and inosine in different baby foods as infant formulas, cereals and fruit products. Validation was performed using two certified reference materials.     

Surface modification of sepiolite in aqueous gels by using methoxysilanes and its impact on the nanofiber dispersion ability

Surface modification reactions on needle-like sepiolite using alkyl and functional silanes have been carried out in the form of aqueous gels. In contrast with modifications in organic solvents, reactions in water make it possible to modify the surface of almost-individual sepiolite fibers and produce either a continuous coating or a nanotexturization of the sepiolite fiber surface, depending on the reaction conditions. This clean procedure substitutes advantageously organic solvent surface modifications and allows the tuning of surface properties such as specific surface area, wetting behavior, and chemical functionalization. A consequence of such tuning is, for example, the excellent dispersion of modified sepiolite nanofibers in a great variety of polymers by routine compounding and processing techniques.     

Absorption and distribution of lupeol in CD‐1 mice evaluated by UPLC–APCI+–MS/MS

Lupeol is a dietary triterpene that shows limited water solubility, which affects its bioavailability. It is well known that poor oral bioavailability is one of the major causes of therapeutic variability. Lupeol has been reported to have multiple biological activities; however, there are no reports about its bioavailability. Therefore, the objective of this research was to evaluate the systemic bioavailability of lupeol. An experimental strategy with three groups of female CD‐1 strain mice was proposed (control, olive oil and lupeol in olive oil), at six experimental times (0.5, 2, 4, 8, 12 and 24 h) with four animals per experimental point. Mice were sacrificed for organs, urine, feces and blood collection. Lupeol was extracted from samples and analyzed by UPLC–APCI⁺–MS/MS, obtaining the pharmacokinetics parameters time to peak concentration 6.444 ± 0.851 h and peak concentration 8.071 ± 2.930 μg/mL. Study of direct digestion and absorption in various organs showed important concentrations of lupeol at earlier post‐administration times (stomach, 137.25 ± 19.94 ng/mg and small intestine, 99.00 ± 12.99 ng/mg). The main excretion route was fecal, with a peak at 12 h post‐administration (163.28 ± 9.83 μg/mg). Absorption of lupeol by the animals was better than expected despite its nonpolar nature (extent of absorption F = 0.645 ± 0.0581).     

Biaryl and Aryl Ketone Synthesis via Pd‐Catalyzed Decarboxylative Coupling of Carboxylate Salts with Aryl Triflates

A bimetallic catalyst system has been developed that for the first time allows the decarboxylative cross‐coupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non‐coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic cross‐coupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho‐substituted or otherwise activated derivatives to a broad range of ortho‐, meta‐, and para‐substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of Cu^I/1,10‐phenanthroline (10–15 mol %) and PdI₂/phosphine (2–3 mol %) in NMP for 1–24 h, the other involving Cu^I/1,10‐phenanthroline (6–15 mol %) and PdBr₂/Tol‐BINAP (2 mol %) in NMP using microwave heating for 5–10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non‐activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylative cross‐couplings are discussed.     

Well‐Defined Silica‐Supported Mo–Alkylidene Catalyst Precursors Containing One OR Substituent: Methods of Preparation and Structure–Reactivity Relationship in Alkene Metathesis

Silica supports : Well‐defined silica‐supported Mo–alkylidene complexes containing one alkoxy/aryloxy substituent are selectively obtained by grafting onto silica either well‐defined molecular bis(alkoxy) or alkoxyamido complexes (see scheme). These silica‐supported complexes are highly efficient catalyst precursors for the metathesis of acyclic alkenes. However, they display poor performances in ring‐closing metathesis reactions, possibly due to the relatively large siloxy ligand (silica) inducing a greater rigidity.

     

Infinitesimal adjunction and polar curves

The polar curves of foliations having a curve C of separatrices generalize the classical polar curves associated to hamiltonian foliations of C. As in the classical theory, the equisingularity type ℘() of a generic polar curve depends on the analytical type of , and hence of C. In this paper we find the equisingularity types ε(C) of C, that we call kind singularities, such that ℘() is completely determined by ε(C) for Zariski-general foliations . Our proofs are mainly based on the adjunction properties of the polar curves. The foliation-like framework is necessary, otherwise we do not get the right concept of general foliation in Zariski sense and, as we show by examples, the hamiltonian case can be out of the set of general foliations. The author was partially supported by the research projects MTM2007-66262 (Ministerio de Educación y Ciencia), MTM2006-15338-C02-02 (Ministerio de Educación y Ciencia),VA059A07 (Junta de Castilla y León) and PGIDITI06PXIB377128PR (Xunta de Galicia).