1,721,099 research outputs found
Impiego di un nuovo ed efficiente metodo di sintesi di 2-aril-2-oxoacetati di metile per la preparazione di (E)-O-metilossiimmino-2-arilacetati di metile aventi proprietà fungicide e degli stereoisomeri Z di tali sostanze
No full textInfluence of in vitro simulated gastroduodenal digestion on the metabolic profile of green tea (Camellia sinensis): an NMR investigation.
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Regiocontrolled synthesis of 1,2-diaryl-1H-imidazoles by palladium- and copper-mediated direct coupling of 1-aryl-1H-imidazoles with aryl halides under ligandless conditions
No full textA large variety of 1,2-diaryl-1H-imidazoles, including a selective COX-2 inhibitor, have been regioselectively synthesised in moderate to high yields by direct coupling of 1-aryl-1H-imidazoles with aryl iodides or bromides in DMF in the presence of CsF and catalytic amounts of Pd(OAC)(2) under ligandless conditions. A possible mechanism for this new highly regioselective C-2 arylation reaction, involving the formation of an organocopper(I) derivatives followed by a transmetallation reaction with an arylpalladium(II) halide species and a reductive elimination, is proposed, New one-step procedures for the synthesis of 1,2,5-triaryl-1H-imidazoles, based on palladium- and copper-mediated arylation of 1-aryl-1H-imidazoles, have also been developed. Interestingly, some imidazole derivatives prepared in this study have been found to exhibit significant cytotoxic activity against some human tumour cell lines. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006
Studies on the transition metal catalyzed synthesis of variously substituted (E)-3-[1-(aryl)methylidene]- and (E)-3-(1-alkylidene)-3H-furan-2-ones
No full text5-Aryl and 5-alkyl substituted (E)-3-[1-(aryl)methylidene]- and (E)-3-(1-alkylidene)-3H-furan-2-ones, (E)-9, have been selectively synthesized by cyclization of the corresponding (E)-2-(1-alkynyl)-3-aryl/alkylpropenoic acids, (E)-11, in the presence of AgNO(3) or Pd-catalysts such as trans-di(mu-acetato)bis[(di-o-tolylphosphino)benzyl] or that constituted of a mixture of Et(3)N and PdCl(2)(PhCN)(2) or PdCl(2)(CH(3)CN)(2). in a 3 : 1 molar ratio, respectively. A representative (E)-5-aryl-3-[1-(aryl)methylidene]-3H-furan-2-one, i.e. (E)-9i, has been also prepared by a tandem process involving a Pd(0)- and Cu(I)-catalyzed cross-coupling reaction between an 1-alkyne and a (Z)-3-aryl-2-bromopropenoic acid followed by a catalytic innamolecular oxypalladation of the resulting cross-coupled product. However, when this same approach was used to prepare an (E)-5-alkyl-3-[1-(aryl)methylidene]-3H-furan-2-one, i.e. (E)-9j, a mixture of (E)-9j and the corresponding (E)/(Z)-5-(1-alkylidene)-3-(aryl)methyl-5H-furan-2-one, i.e. (E)/(Z)-20, was obtained. Finally, in an attempt to prepare an (E)-4-alkyl-5-aryl-3-[1-(aryl)methylidene]-3H-furan-2-one, i.e. (E)-14a, by a tandem process involving the intramolecular oxypalladation of an (E)-enynoic acid, (E)-11, followed by a cross-coupling reaction of the resulting compound with an aryl iodide, a (Z)-5-(1-alkynyl)-4-aryl-3-arylmethyl-5H-furan-2-one, i.e. (Z)-22, has been stereoselectively obtained. (C) 1997 Elsevier Science Ltd. All rights reserved
Untargeted and targeted methodologies in the study of tea (Camellia sinensis L.)
No full textThe chemical composition of tea beverage is very complex and not yet completely elucidated. Many factors contribute to the chemical complexity of tea, from plant growth conditions (soil, climate, growth altitude and agricultural practices) and manufacturing processes (drying, steaming, fermentation and storage), to preparation methods (quality of water, infusion time and, not least, the time between tea preparation and consumption). Besides primary metabolites, tea leaves contain a number of secondary metabolites, belonging to many different classes of compounds (such as polyphenols, xanthines, proteic and nonproteic amino acids, sugars, volatile compounds) that are extracted during the infusion and transferred into the beverage. Epidemiological studies have suggested that tea consumption is inversely associated with the risk of developing chronic diseases such as cardiovascular diseases, stroke, some forms of cancer and diabetes. Thus, increasing interest in the health properties of tea resulted in a significant rise in scientific investigation on tea chemical composition. This review article highlights the recent results obtained in the tea beverage characterization using different analytical methodologies. The analytical approaches have been subdivided into two groups: targeted chromatographic and NMR techniques and untargeted NMR analytical approaches. Several examples of untargeted chromatographic techniques coupled with mass spectrometry methodologies are also reported. Advantages, drawbacks and significant applications of the different analytical approaches are discussed
Caratterizzazione chemiometrica di composti bioattivi nelle nuove cultivars di pomodori del Lazio: Bamano, Dolce Miele e Confettino Rosso.
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