A doubly-convergent and regioselective synthesis of (±)-daunomycinone

The monoadduct of benzoquinone to 2,3,5,6-tetramethylidene-7-oxabicyclo[2.2. l]heptane (7) was transformed into (1RS,4RS,4aSR)-2,3-dimethylidene-l,4-epoxy-l,2,3,4,4a,10-hexahydro-8-methoxyanthracene (28). 3The exocyclic diene added to methy into (±)-7,9-dideoxydaunomycinone (54), a known precursor of(±)-daunomycinone     

From Pd nanoparticles to single crystals: 1,3-butadiene hydrogenation on well-defined model catalysts

Although 1,3-butadiene hydrogenation is known to be a structure-sensitive reaction, correlation of the catalytic activity with the exact Pd particle surface structure shows that the reaction is in fact particle size independent.     

Toeplitz operators on weighted Hardy and Besov spaces

We obtain estimates of the norm of Toeplitz operators on weighted Hardy and Besov spaces. As an application we give characterizations of some spaces of pointwise multipliers.     

A density functional theory study of the free-radical scavenging activity of aminoguanidine. Comparison with its reactive carbonyl compound and metal scavenging activities

Since protein glycation is related to several human diseases, it is very important to develop molecules that can inhibit its effects. This work adds the reaction of Aminoguanidine (AG) with the methoxy (˙OCH₃) and hydroperoxyl (˙OOH) radicals at the UM05-2X-SMD/6-311+G(d,p) level of theory in water and pentyl ethanoate to simulate the physiological aqueous and lipidic environments. At physiological pH, AG is an effective ˙OCH₃ and a moderate ˙OOH scavenger in nonpolar solvents (where AG is predominantly neutral), acting exclusively by hydrogen-atom transfer. However, reactions in a polar solvent (where AG is predominantly cationic) have smaller rate constants. Therefore, the ability of AG to scavenge free radicals seems to depend on the polarity of the environment. Taken together, the results reported herein and in previous works suggest that the scavenging of reactive carbonyl species is the main mechanism of action of aminoguanidine in the context of protein glycation inhibition.     

Isoform-specific quantification of endothelins in HUVEC culture supernatants by on-line high-performance liquid chromatography/electrospray mass spectrometry

A method for the quantitative analysis of endothelin peptides in human umbilical vein endothelial cell (HUVEC) culture supernatants is reported. The analysis is isoform-specific and employs solid-phase extraction and subsequent HPLC fractionation followed by HPLC-ESIMS analysis. The peptide vasoactive-intestinal-contractor (VIC) was used as internal standard for the HPLC-ESIMS analysis. Linearity of calibration curves was from 50 fmol to 25 pmol. The limit of detection of the HPLC-ESIMS step using a buffer matrix was estimated at 50 fmol (S/N > 3). The overall limit of detection for supernatants of HUVEC was 500 fmol/mL. In HUVEC culture supernatants only ions of endothelin-1 (ET1) were observed. Basal levels were determined to be 1.8 +/- 0.3 pmol/mL. Quantitative results obtained for ET1 were in agreement with those obtained by using a standard addition method and by an ELISA method.