Glycosylation reaction is an important class of reactions in organic chemistry, and the development of the method contributes to the synthesis of many biologically active compounds containing various glycoside bonds. Is arguably the most important, albeit challenging, reaction in the field of carbohydrate chemistry. Examples of the products of glycosylation reactions are glycoproteins, glycolipids, glycosaminoglycans, oligosaccharides, and polysaccharides. Glycosylation types are classified according to the identity of the atom which binds the carbohydrate chain, i.e. C-linked, N-linked, O-linked or S-linked. In this short review, recent reports of the main glycosylation methods, basic mechanisms, factors influencing the stereoselectivity and their applications in the synthesis of bioactive molecules are described.

This paper proposes the development of a simple experiment with easily accessible and low cost materials, enabling its practice with or without laboratory infrastructure, with feasibility for computational theoretical study. On the other hand, the objective of the work is to develop a chemical experiment that demonstrates that the chromophore curcumin (natural indicator) is responsible for indicating the acidity or basicity of a given solution. The experiment has different applicability, being useful in the approach of different chemical contents, showing potential for multi and interdisciplinary approaches. Subjects such as tautomeric equilibrium, chromophoric compounds, hydrogen potential, UV-Vis electron absorption spectra analysis and molecular modeling are explored.

Amino sugars are chemical compounds that have a sugar backbone, in which one of the hydroxyl groups is replaced by an amino group. Derivatives of amine-containing sugars, such as N-acetylglucosamine, are also considered amino sugars. The synthetic introduction of amino functionalities in a regio- and stereoselective manner ontosugar scaffolds represents a substantial challenge. Most of the modern methods for the preparation of 1-, 2- and 3-amino sugars are those starting from glycals, 2,3-unsaturated O-glycosides epoxy-sugars, keto-sugars among others. This review summarizes recente developments in the current state of knowledge concerning the occurrence, biosynthesis, synthesis and application of amino sugars.

In carbohydrate chemistry, the O-glycoside is an organic molecule in which sugar is bound to another functional group via a glycosidic bond. In the last few years, considerable progress has been made in the synthesis and applications of O-glycosides. Despite their challenging chemistry, due to their versatility, O-glycosides play a pivotal role the development of the chemistry of novel materials and bioactive molecules. This review summarizes recent developments, in the last twenty years, about the Ferrier rearrangement reaction involving synthesis, mechanistic proposal and application of 2,3-unsaturated O-glycosides.

1,2,4-oxadiazoles are used in a wide range of applications, including medicinal chemistry and chemistry of materials. However, this kind of oxadiazoles is not usually prepared in an undergraduate organic teaching laboratory. This work describes a didactic sequence for the preparation of 1,2,4-oxadiazols, mediated by microwave irradiation, employing home-use microwave oven. For the development of this practice, one lecture and one laboratory session were used. At the end of this session, a questionnaire was applied to evaluate the didactic sequence. The conclusion was that this approach can be used for the preparation of 1,2,4-oxadiazoles as a pedagogical practice to make the process of teaching easier and enjoyable.

This article describes an experiment that involves the extraction and separation of the pigments of spinach extract by column chromatography using the silica obtained from rice husk ash as a stationary phase. The experimental procedure is very simple to apply in the chemistry laboratory, and allowed to illustrate some concepts of organic chemistry: structure of organic molecules, solubility, polarity, extraction, partition coefficient, adsorption and retention factor (Rf), as well as objectives and fundamentals of chromatographic methods. The experiment can be carried out in a 4 h period.

This is a report on an efficient and rapid synthesis of amidoximes using ultrasound irradiation with appropriate nitrile and hydroxylamine hydrochloride in water/ethanol. This new synthetic methodology is compared with previously known methods. The main advantages of the process reported are shorter reaction times, easier work-up, and good yield.

As dificuldades conceituais que alunos apresentam sobre o tema "isomerismo" são atribuídas a problemas básicos, como a compreensão de teorias estruturais, ligações químicas e representações de fórmulas estruturais. Este trabalho teve como objetivo avaliar a evolução da apren dizagem de estudantes do ensino médio sobre o fenômeno de isomeris mo. A metodologia utilizada se baseou nas concepções prévias dos estu dantes e na utilização do processo de construção do conceito de isome- ria. Os dados foram coletados de um grupo de 25 estudantes da terceira série por meio de pré e pós-teste e analisados segundo a técnica de análi se de conteúdo. Como conclusão, foi possível verificar uma evolução con- ceitual da maioria dos estudantes, objeto do estudo.

The conceptual difficulties faced by students on the theme "isomerism" are attributed to basic problems, such as the understanding of structural theories, chemical bonds and representations of structural formulas. This study was aimed at the evaluation of the High School stu dents' learning evolution on the isomerism phenomenon. Our strategy was based on the students' previous conceptions and on the use of the construction of concept isomers. The results have been collected from a group of twenty-five students from third grade through pre and post tri als, and were analyzed using contents analysis technique. As conclusions, it was possible to verify a conceptual evolution on the majority of the stu dents, object of this study.

A reação de tri-O-acetil-D-glucal (1) com cicloexanol (2) usando o método de Ferrier forneceu o glicosídeo cicloexílico insaturado 3, que por sua vez produziu o composto 12 através da seqüência envolvendo hidrólise, tritilação seletiva no oxigênio do C-6, oxidação alílica e cicloadição dipolar 1,3 com diazometano. O produto 17 foi obtido em quatro etapas a partir de 6. Cálculos semi-empíricos de orbitais moleculares (AM1) para o composto 12 forneceram a conformação estável e também apoiaram a existência do efeito anomérico. Foi feito um esforço para abrir o anel pirazolínico dos compostos 12 e 17, porém não tivemos sucesso. A carga negativa parcial no C-3 foi responsável pela falta de reatividade deste carbono frente a redução da ligação C=N.

Reaction of tri-O-acetyl-D-glucal (1) with cyclohexanol (2) using Ferrier's method provided the unsaturated cyclohexyl glucoside 3, which furnished the title compound 12 in a sequence involving hydrolysis, selective tritylation of oxygen at C-6, allylic oxidation with MnO2 and 1,3-dipolar cycloaddition with diazomethane. Starting from 6, product 17 was obtained in four steps. Semi-empirical molecular orbital calculations (AM1) were carried out for compound 12 which gave an idea about its stable conformation, and also supported the existence of the anomeric effect. Attempts to open the pyrazoline ring in 12 and 17 failed. Partial negative charge at C-3 was responsible for the lack of reactivity of 12 towards reduction of C=N bond.