Synthesis of 2-substituted 1,3-butadienyl compounds by palladium-catalyzed regioselective 1,2-elimination reaction of methylvinylcarbinol acetates

Alkylation of the dianion of 3-methyl-3-buten-2-ol, followed by acetylation and palladium-catalyzed 1,2-elimination reaction of the so obtained methylvinylcarbinol acetates allows to synthesize regioselectively 2-substituted 1,3-butadienyl compounds having high isomeric purity.     

SERS studies of the adsorption of guanine derivatives on gold colloidal nanoparticles

Surface enhanced Raman scattering spectra of guanine, guanosine and 2'-deoxyguanosine adsorbed on gold colloidal nanoparticles were obtained. From the striking similarity of the SERS spectra of these compounds, it can be evidenced that guanosine and 2'-deoxyguanosine adsorb on gold nanoparticles through the guanine moiety. The molecular sites involved in the interaction with the gold surface are the same for the 3 compounds: the oxygen of the carbonilic group and the N(7) atom. Guanine, guanosine and 2'-deoxyguanosine adsorb on the gold substrates with a tilted orientation with respect to the metal surface. SERS data were interpreted taking into account density functional theoretical (DFT) calculations of guanine.     

A partial least squares regression study with antioxidant flavonoid compounds

The quantitative structure-activity relationship of a set of 19 flavonoid compounds presenting antioxidant activity was studied by means of PLS (Partial Least Squares) regression. The optimization of the structures and calculation of electronic properties were done by using the semiempirical method AM1. A reliable model (r ²=0.806 and q ²=0.730) was obtained and from this model it was possible to consider some aspects of the structure of the flavonoid compounds studied that are related with their free radical scavenging ability. The quality of the PLS model obtained in this work indicates that it can be used in order to design new flavonoid compounds that present ability to scavenge free radicals.     

Electrospray mass spectrometry in the differentiation of some isomeric trimethylfurocoumarins

Electrospray mass spectrometry (ES-MS) was successfully employed for the structural differentiation of six isomeric trimethylfurocoumarins of possible pharmaceutical interest. Two different approaches were employed. The first was based on MS(n) experiments of MH(+) ions. Although the product ion spectra of MH(+) of the isomers are very similar, the MS(3) spectra of the collisionally generated [MH[bond]CO](+) ions show some characteristic differences. The second approach was based on complexation of the molecules with Li(+), Na(+) and K(+) using ESI-MS of sample solutions containing alkali ions in a 100:1 molar ratio with respect to the analyte. Significant differences were observed in complex production yields, and these were related to the dimension of the alkali ion and to the steric availability of chelating groups in the different isomers.     

Conformation of three tetrahydropyridinyl oxime cognition activators

The conformational features of three tetrahydropyridinyl oxime cognition activators 1-(1-methyl-1,2,5,6-tetrahydro-3-pyridinyl)ethanone oxime·HCl (I), 1-(1-methyl-1,2,3,6-tetrahydro-4-pyridinyl)ethanone oxime·HCl (II), and 1-(1,2,5,6-tetrahydro-3-pyridinyl)ethanone O-methyloxime HCl(III) were analyzed by X-ray diffraction and the quantum mechanical semiempirical PM3 methods. Results indicate that in the solid state the drugs exhibit anti-syn isomerism, with the substituent at the oxime oxygen atomanti oriented in respect to C=N. This arrangement also represents a low-energy situationin vacuo, as confirmed at the PM3 level, although another low-energy conformation (clinal-anti) could be of significance in the conformational energetics of the drugs.     

The order of the QCD transition with two light flavors

We report on the status of our analysis on the order of the finite temperature transition in QCD with two light flavors. Our new simulations on larger lattices give preliminary evidence of the first order nature of the transition also at small non-zero quark masses.     

pH and Charge Effects Behind the Interaction of Artepillin C,the Major Component of Green Propolis,With Amphiphilic Aggregates: Optical Absorption and Fluorescence Spectroscopy Studies

Brazilian green propolis is one of the bee products most consumed in the world to prevent diseases, owing antioxidant, antimicrobial, anti‐inflammatory and antitumor activities. The major component of Brazilian green propolis is Artepillin C (ArtC), a cinnamic acid derivative with two prenylated groups that improve the affinity of the compound for lipophilic environment. Here, we have employed optical absorption and fluorescence techniques to draw conclusions on how ArtC interacts with amphiphilic aggregates commonly used as model membranes having different charges in the polar head group. Optical absorption spectra were representative of the protonation state of ArtC, dictated by the local pH at the surface of micelles and lipid vesicles. Fluorescence results showed that, in the presence of micelles and vesicles, the polarizability around ArtC was modified, compared to the value in aqueous medium, and the molecule should be located preferentially on the surface region of the model membranes, with an enhanced interaction with the less ordered state of the lipid vesicles.     

Highly Efficient Micro-Scale Liquid-Liquid In-Flow Extraction of 99mTc from Molybdenum

The trend to achieve even more compact-sized systems is leading to the development of micro-scale reactors (lab-on-chip) in the field of radiochemical separation and radiopharmaceutical production. Technetium-99m extraction from both high and low specific activity molybdenum could be simply performed by MEK-driven solvent extraction if it were not for unpractical automation. The aim of this work is to develop a solvent extraction and separation process of technetium from molybdenum in a micro-scale in-flow chemistry regime with the aid of a capillary loop and a membrane-based separator, respectively. The developed system is able to extract and separate quantitatively and selectively (91.0 ± 1.8% decay corrected) the [^99mTc]TcO₄Na in about 20 min, by using a ZAIPUT separator device. In conclusion, we demonstrated for the first time in our knowledge the high efficiency of a MEK-based solvent extraction process of ^99mTc from a molybdenum-based liquid phased in an in-flow micro-scale regime.