Tandem Double-Cross-Coupling/Hydrothiolation Reaction of 2-Sulfenyl Benzimidazoles with Boronic Acids.

A new tandem palladium-catalyzed reaction involving a Suzuki-Miyaura coupling, a desulfenylative coupling, and a hydrothiolation of a triple bond is reported. Notably, the desulfenylative coupling occurs without copper(I) assistance and the hydrothiolation is totally regioselective and stereoselective. The overall process results in the double incorporation of the boronic acid and the reincorporation of the sulfenyl moiety into the product structure. Starting from 2-(bromobenzylsulfenyl)-1-propargyl benzimidazoles, the transformation led to variously substituted benzimidazoles bearing a stereodefined alkenyl sulfide.

Functionalization of 2H-1,2,3-Triazole C-Nucleoside Template via N(2) Selective Arylation.

C-Nucleosides are an underexplored and important class of nucleosides with antiviral and anticancer activity. In addition, triazole heterocycles are well employed as a strategy to modify nucleobase in nucleoside analogues, although rare examples were described for triazoyl C-nucleosides. N(2)-Aryl-1,2,3-triazole C-nucleoside compounds that could be obtained by selective 1,2,3-triazole heterocycle N(2) arylation in 1-ß-d-ribofuranosyl-2H-1,2,3-triazole substrate were designed in this study. The optimized condition used AdBrettPhos/[PdCl(allyl)]2 as the catalyst system. This transformation was accomplished by aryl halides bearing an electron donor and withdrawing groups, as well as by heterocyclic halides in good to excellent yields. The transformation developed in this study represents a significant contribution to the nucleoside field, once it allows for the synthesis of unexplored scaffolds through selective functionalization of triazole nucleosides.

Characterization of amide bond conformers for a novel heterocyclic template of N-acylhydrazone derivatives.

Herein we describe NMR experiments and structural modifications of 4-methyl-2-phenylpyrimidine-N-acylhydrazone compounds (aryl-NAH) in order to discover if duplication of some signals in their ¹H- and ¹³C-NMR spectra was related to a mixture of imine double bond stereoisomers (E/Z) or CO-NH bond conformers (syn and anti-periplanar). NMR data from NOEdiff, 2D-NOESY and ¹H-NMR spectra at different temperatures, and also the synthesis of isopropylidene hydrazone revealed the nature of duplicated signals of a 4-methyl-2-phenylpyrimidine-N-acylhydrazone derivative as a mixture of two conformers in solution. Further we investigated the stereoelectronic influence of substituents at the ortho position on the pyrimidine ring with respect to the carbonyl group, as well as the electronic effects of pyrimidine by changing it to phenyl. The conformer equilibrium was attributed to the decoplanarization of the aromatic ring and carbonyl group (generated by an ortho-alkyl group) and/or the electron withdrawing character of the pyrimidine ring. Both effects increased the rotational barrier of the C-N amide bond, as verified by the DG(≠) values calculated from dynamic NMR. As far as we know, it is the first description of aryl-NAH compounds presenting two CO-NH bond- related conformations.

Composiçäo química e protéico-molecular da farinha de resíduos de camaräo-sete-barbas (Xiphopenaeus kroyeri) / Chemical and proteic-molecular composition of shrimp \"ste barbas\" residues flour

Caracterizou-se a farinha de resíduos de camaräo-sete-barbas quanto aos aspectos físico-químicos e análise molecular de proteínas. O corpo do camaräo foi utilizado como parâmetro comparativo. Realizou-se estudo das proteínas pela quantificaçäo de N-total, análise colorimétrica e avaliaçäo molecular. Os resíduos apresentaram potencialem relaçäo a dois nichos alimentares: nutricional (mineral) edietético (alto teor de fibra alimentar e baixo conteúdo lipídico. Verificou-se neste resíduo de baixo teor protéico solúvel pela extraçäo e quantificaçäo em método colorimétrico. Nos extratos analisados por eletroforese em gel de poliacrilamida contendo dodecil sulfato de sódio (SDS-PAGEO) foi observada baixa diversidade protéica, devido ao menor número de cadeias polipeptídicas identificadas. A presença de uma banda de 74 kDa, resistente ao tratamento térmico, pode ser utilizadas como marcador de padräo de identidade molecular desta família