A general and highly efficient asymmetric synthesis of optically active anthracyclinones

The title asymmetric synthesis has been developed by featuring bromolactonization of (−)-acetals, derived from 2-acetyl-3,4-dihydronaphthacene-6,11-diones and (2R,3R)-(+)-N,N,N′,N′-tetraalkyltartaric acid diamides, as a key diastereoselective reaction. The produced bromolactone mixtures could be readily converted to the highly optically active key synthetic intermediates of 4-demethoxy- and 11-deoxy-4-demethoxyanthracyclinones.     

Gravitational interaction of two spinning particles in general relativity. II

Within the framework of the previous paper, we complete the set of equations of motion by including the spin propagation equation at first order. We check this equation with the known result on the precession, which is obtained by means of slow motion approximation of our result. A new scheme of expanding equations of motion is also introduced. It will be useful to undertake higher-order calculations.     

Palladium-catalyzed dehydroarylation of triarylmethanols and their coupling with unsaturated compounds accompanied by C-C bond cleavage

Triarylmethanols are effectively dehydroarylated and reacted with some unsaturated compounds by using an appropriate palladium catalyst system such as Pd(OAc)2-P(1-Nap)3 (1-Nap = 1-naphthyl) to give the corresponding arenes and hydroarylation products, respectively, along with diaryl ketones.     

A nonisothermal study of the kinetics of the nanoporosity elimination in sonogels-derived silica xerogels

A nonisothermal study of the kinetics of the nanoporosity elimination in monolithic silica xerogels, prepared from acid and ultrasound catalyzed hydrolysis of tetraethylortosilicate (TEOS), has been carried out by means of in situ linear shrinkage measurements performed with different heating rates. The study could be applied up to almost alpha approximately 0.6 of the volume fraction alpha of eliminated pores. The activation energy was found increasing from about 3.2 x 10(2) kJ/mol for alpha approximately 0.06 up to about 4.4 x 10(2) kJ/mol for alpha approximately 0.44. The sintering process accompanying the nanopore elimination in this set of xerogels is in agreement with a viscous flux sintering process with the hydroxyl content diminishing with the volume fraction of eliminated pores. All the volume fraction of eliminated pores versus temperature (T) curves can be matched onto a unique curve with an appropriate rescaling of the T axis, independent of the heating rate. This scaling property suggests that the path of sintering seems the same, regardless of the heating rate; the difference is that the rate is faster at higher temperature.     

Characterization via liquid chromatography coupled to diode array detector and tandem mass spectrometry of supercritical fluid antioxidant extracts of Spirulina platensis microalga

Spirulina platensis microalga has been extracted on a pilot scale plant using supercritical fluid extraction (SFE) under various extraction conditions. The extraction yield and the antioxidant activity of the extracts were evaluated in order to select those extracts with both the highest antioxidant capacity and a good extraction yield. These extracts were characterized using LC coupled to diode array detection (DAD) and LC coupled to mass spectrometry (MS) with two different interfaces, atmospheric pressure chemical ionization (APCI) and electrospray (ESI) which allowed us to perform tandem MS by using an ion trap analyzer. The best extraction conditions were as follows: CO2 with 10% of modifier (ethanol) as extraction solvent, 55 degrees C (extraction temperature) and 220 bar (extraction pressure). Fractionation was achieved by cascade depressurization providing two extracts with different activity and chemical composition. Several compounds have been identified in the extracts, corresponding to different carotenoids previously identified in Spirulina platensis microalga along with chlorophyll a and some degradation products. Also, the structure of some phenolic compounds could be tentatively identified. The antioxidant activity of the extracts could be attributed to some of the above mentioned compounds.     

Quantification of sterols, 5α- and 5β-stanols in sewage sludge, manure and soils amended with these both potential fertilizers

A method for the quantitative determination of sterols, 5α- and 5β-stanols is proposed to characterize the lipid fraction of two potential organic fertilizers, like sewage sludge and manure, as well as soils amended by them. It was possible to determine the kind of fertilizer added to the soil. Further studies were conducted to determine the accumulative effects of steroids in soils treated with manure and different doses of sewage sludge.     

Effect of the fluid in the inclusions of cement paste on the ultrasonic velocity

The durability of cement composites significantly depends on the movement of the fluids into the material through the porous system. The aqueous phase contained in the pores can cause irreversible damage from the dimensional stability viewpoint. In this sense, methods for non-destructive characterization of both, the porous structure and water content should be investigated. In this work, the effect of the fluid in the inclusions of the cement paste on the ultrasonic velocity is studied. Firstly, a theoretical analysis based on the micromechanical model, considering the microstructural information of the matrix and the fluid filling the pores, is presented. Some experimental work is made later using cement paste samples, whose porous structure is maintained dry or saturate with water. In both cases, the ultrasonic velocity is measured and compared to the one predicted by the micromechanical model. Using this technique, the ultrasonic velocity can be predicted with errors below 2% in the cases of dry or water saturated cement paste.     

Spectrophotometric determination of iron(III) with o-hydroxyhydroquinonephthalein after preconcentration on a membrane filter

Application of xanthene derivatives in analytical chemistry. Part LXXXVIII. Part LXXXVII see ref. [1]     

Chemical functionalization of polysilicon microparticles for single-cell studies

In this work, two types of polycrystalline silicon (polysilicon) microparticles were modified with specific ligands in order to be selectively attached to chemical residues located at the plasma membrane and thus to be applied to study individual cells in culture. Two different functionalization approaches based on adsorption and covalent attachment were assayed. A comparative study of the efficiency of the ligand immobilization and stability of the modified particle in the culture medium was carried out using the selected ligands labeled with a fluorophore. Cylindrical microparticles (nonencoded microparticles) and shape-encoded microparticles (bar codes) were used with the aim of demonstrating the nondependence of the particle size and shape on the efficiency of the immobilization protocol. Fluorescence imaging and statistical analysis of the recorded fluorescence intensity showed that the covalent attachment of the ligand to the surface of the microparticle, previously modified with an aldehyde-terminated silane, gave the best results. As a proof of concept, Vero cells in culture were labeled with the covalently modified bar codes and successfully tracked for up to 1 week without observing any alteration in the viability of the cells. Bar code numbers could be easily read by eye using a bright-field optical microscope. It is anticipated that such modified microparticles could be feasible platforms for the introduction of other analytical functions of interest in single-cell monitoring and cell sorting in automatic analysis systems.     

Hydrogen reactivity of palladium nanoparticles coated with mixed monolayers of alkyl thiols and alkyl amines for sensing and catalysis applications

Palladium monolayer-protected clusters (MPCs) coated with octylamines (C8NH(2)), hexanethiolates (C6S), and mixed monolayers of C8NH(2) and C6S exhibit significantly different reactivities with hydrogen gas, depending on the relative amounts of the two ligands coating the Pd nanoparticle surface, as determined by UV-vis spectroscopy of Pd MPCs in solution and electronic measurements of films of Pd MPCs as a function of exposure time to hydrogen. The average estimated composition of the ~3.0 nm diameter Pd MPCs was Pd(919)(C6S)(192) or Pd(919)(C8NH(2))(177-x)(C6S)(x), where x was varied to be 0, 3, 10, 16, 32, or 81 by the synthesis of pure C8NH(2) Pd MPCs and subsequent liquid-phase place exchange with a varied amount of C6SH. When x = 0-10, the Pd MPCs react strongly with H(2), leading to aggregated particles in solution and large irreversible changes in the morphology of films accompanied by an increase in film conductivity by 2-5 orders of magnitude. Pd(919)(C6S)(192) MPCs are stable against significant aggregation in solution and do not exhibit large film morphology changes, but they are also not highly reactive to H(2), as determined by minimal changes in the optical properties of solutions and the small, irreversible changes in the conductivity of films in the presence of H(2). Finally, when x is 32 and 81, the Pd MPCs are fairly stable, exhibit minimal aggregation or morphology changes, and readily react with H(2) based on the significant, reversible changes in film conductivity in the presence of H(2). Pd MPCs with mixed monolayers have the benefit of high H(2) reactivity while maintaining the structural stability necessary for sensing and catalysis applications.