Reaction of enaminonitriles with isocyanates. Synthesis of new 2-oxo- and 6-oxopyrimidines

The reaction of enaminonitriles 1 with aryl or benzyl isocyanates afforded C- 3–5 or N-adducts 6–8 or a mixture of both depending on the substitution pattern of the considered enaminonitrile. The one-step synthesis of 6-oxopyrimidines 9–11 and 2-oxopyrimidines 12–14 by cyclization of compounds 3–5 and 6–8 respectively is also described.     

New synthesis of 2(1H)-pyridone derivatives

The reaction of N¹-acyl-2-ethoxycarbonylacetamidrazones 1 with diethyl ethoxymethylenemalonate (EMME) is reported. By refluxing equimolecular amounts of 1 and EMME in DMSO/toluene (or ethanol) solution, the 1-acylamino-2(1H)-pyridones 2 were obtained in good yield. When the reaction was performed in ethanolic solution in the presence of triethylamine, the 6-acylhydrazino-2(1H)-pyridones 3 were obtained.     

NMR-based metabolic study of leaves of three species of Actinidia with different degrees of susceptibility to Pseudomonas syringae pv. actinidiae

Abstract

Bacterial canker of Actinidia, caused by the bacterium Pseudomonas syringae pv. actinidiae (Psa), is the most serious disease of these plants worldwide. Leaves of three species of Actinidia, namely A. chinensis var. chinensis, A. chinensis var. deliciosa and A. arguta, having different degrees of tolerance to Psa, were analyzed by Nuclear Magnetic Resonance spectroscopy. Aqueous extracts of leaves were studied and several metabolites, classified as organic acids, amino acids, carbohydrates, phenols and other metabolites, were identified by 1D and 2D NMR experiments and quantified. The metabolic profiles of these species were compared through univariate statistical analysis ANOVA and multivariate PCA. Levels of metabolites with known antibacterial activity, such as caffeic and chlorogenic acids, were observed to be higher in the A. arguta samples. Moreover, these metabolites have different Pearson correlation patterns among the three Actinidia species, suggesting a difference at the phenylpropanoid biosynthetic pathway.     

Crystallite size effect of Pd/charcoal catalysts for benzene hydrogenation

The dispersity, calculated from the particle size distribution functions obtained by Small Angle X-ray Scattering (SAXS) measurements, when related to the chemical behavior of Pd/charcoal catalysts in benzene hydrogenation, points out that this reaction is mildly structure-sensitive below the range of 40 Å, whereas no dependence on particle size is observed above this limit.

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, , (SAXS), Pd/ , , 40 Å .

     

Core-shell photoabsorption and photoelectron spectra of gas-phase pentacene: experiment and theory

The C K-edge photoabsorption and 1s core-level photoemission of pentacene (C22H14) free molecules are experimentally measured, and calculated by self-consistent-field and static-exchange approximation ab initio methods. Six nonequivalent C atoms present in the molecule contribute to the C 1s photoemission spectrum. The complex near-edge structures of the carbon K-edge absorption spectrum present two main groups of discrete transitions between 283 and 288 eV photon energy, due to absorption to pi* virtual orbitals, and broader structures at higher energy, involving sigma* virtual orbitals. The sharp absorption structures to the pi* empty orbitals lay well below the thresholds for the C 1s ionizations, caused by strong excitonic and localization effects. We can definitely explain the C K-edge absorption spectrum as due to both final (virtual) and initial (core) orbital effects, mainly involving excitations to the two lowest-unoccupied molecular orbitals of pi* symmetry, from the six chemically shifted C 1s core orbitals.     

Significance of minor components of milk fat

In order to establish criteria for the evaluation of the genuineness of milk fat and its derivatives, research has been carried out on some minor components (mono- and diglycerides and cholestrol esters). Most determinations of milk fat diglycerides showed significant qualitative and quantitative differences compared with other fat sources, and especially with tallow. In particular, the milk fat diglycerides C30–C32–C34–C36 showed characteristic fingerprints. Moreover, the sterol fractions (free and esterified) have also been evaluated. The cholesterol ester profile in milk lipids includs fatty acides from 10 to 18 carbon atoms, while tallow basically showed only C14–C16–C18. In comparison, phytosteral esters with C16 and C18 fatty acids have been found in vegetable fats. These results lead to the hypothesis of possible use of these methods in addition to those most commonly applied (TG-FAME). Furthermore, the natural variability of milk fat components makes a final evaluation of these methodologies difficult unless experimental work is extended to more samples and performed by several research groups.     

Activation chemistry drives the emergence of functionalised protocells

The complexity of the simplest conceivable cell suggests that the chemistry of prebiotic mixtures needs to be explored to understand the intricate network of prebiotic reactions that led to the emergence of life. Early cells probably relied upon compatible and interconnected chemistries to link RNA, peptides and membranes. Here we show that several types of vesicles, composed of prebiotically plausible mixtures of amphiphiles, spontaneously form and sustain the methyl isocyanide-mediated activation of amino acids, peptides and nucleotides. Activation chemistry also drives the advantageous conversion of reactive monoacylglycerol phosphates into inert cyclophospholipids, thus supporting their potential role as major constituents of protocells. Moreover, activation of prebiotic building blocks within fatty acid-based vesicles yields lipidated species capable of localising to and functionalising primitive membranes. Our findings describe a potentially prebiotic scenario in which the components of primitive cells undergo activation and provide new species that might have enabled an increase in the functionality of protocells.

The complexity of the simplest conceivable cell suggests that the chemistry of prebiotic mixtures needs to be explored to understand the intricate network of prebiotic reactions that led to the emergence of life.     

Thermostable phytase production by Thermoascus aurantiacus in submerged fermentation

Phytases act on phytic acid, an antinutrient factor present in animal feeds, and release inorganic phosphate. We optimized the production parameters for phytase production using Thermoascus aurantiacus (TUB F 43), a thermophilic fungal culture, by submerged fermentation. A semisynthetic medium containing glucose, starch, peptone, and minerals supplemented with 3.75% (w/v) wheat bran particles was found to be the best production medium among the various combinations tried. Further supplementation of this medium with surfactants such as Tween-20 and Tween-80 considerably enhanced the enzyme yield. A maximum phytase activity (468.22 U/mL) was obtained using this production medium containing 2% (v/v) Tween-20 after 72 h of fermentation at 45°C in shake-flask cultures with a rotation of 150 rpm. Herein we present details of a few of the process parameter optimizations. The phytase enzyme was found to be thermostable, and the optimal temperature for phytase activity was found to be 55°C. However, 80% of the activity still remained when the temperature was shifted to 70°C.     

Porphyrin-fullerene C60 dyads with high ability to form photoinduced charge-separated state as novel sensitizers for photodynamic therapy

The photodynamic activities of a porphyrin-C60 dyad (P-C60) and its metal complex with Zn(II) (ZnP-C60) were compared with 5-(4-acetamidophenyl)-10,15,20-tris(4-methoxyphenyl)porphyrin (P), both in homogeneous medium-bearing photooxidizable substrates and in vitro on the Hep-2-human-larynx-carcinoma cell line. This study represents the first evaluation of dyads, with a high capacity to form a photoinduced charge-separated state, to act as agents to inactivate cells by photodynamic therapy (PDT). Absorption and fluorescence spectroscopic studies were performed in toluene and N,N-dimethylformamide (DMF). The emission of the porphyrin moiety in the dyads is strongly quenched by the attached fullerene C60 moiety. The singlet molecular oxygen, O2(1delta(g)), productions (phi(delta)) were determined using 9,10-dimethylanthracene (DMA). The values of phi(delta) were strongly dependent on the solvent's polarity. Comparable phi(delta) values were found for dyads and P in toluene, while O2(1delta(g)) production was significantly diminished for the dyads in DMF. In more polar solvent, the stabilization of charge-transfer state takes place, decreasing the efficiency of porphyrin triplet-state formation. Also, both dyads photosensitize the decomposition of L-tryptophan in DMF. In biological medium, no dark cytotoxicity was observed using sensitizer concentrations < or = 1 microM and 24 h of incubation. The uptake of sensitizers into Hep-2 was studied using 1 microM of sensitizer and different times of incubation. Under these conditions, a value of approximately 1.5 nmol/10(6) cells was found between 4 and 24 h of incubation. The cell survival after irradiation of the cells with visible light was dependent upon light-exposure level. A higher photocytotoxic effect was observed for P-C60, which inactivates 80% of cells after 15 min of irradiation. Moreover, both dyads keep a high photoactivity even under argon atmosphere. Thus, depending on the microenvironment where the sensitizer is localized, these compounds could produce biological photodamage through either an O2(1delta(g))-mediated photoreaction process or a free-radicals mechanism under low oxygen concentration. These results show that molecular dyads, which can form a photoinduced charge-separated state, are a promising model for phototherapeutic agents, with potential applications in cell inactivation by PDT.