Bacterial resistance to commonly used antibiotics has been recognized as a significant global health issue. In this study, we carried out the screening of a family of allylic thiocyanates for their action against a diversity of bacteria and fungi with a view to developing new antimicrobial agents. Allylic thiocyanates bearing halogenated aryl groups, which were readily obtained in two steps from the Morita-Baylis-Hillman adducts, showed moderate-to-high activity against selective pathogens, including a methicillin-resistant S. aureus (MRSA) strain. In particular cases, methyl (Z)-3-(2,4-dichlorophenyl)-2-(thiocyanomethyl)-2-propenoate exhibited antimicrobial activity comparable to the reference antibiotic Imipenem.

The introduction of Mannich and Biginelli multicomponent reactions in a practical Organic Chemistry course is presented in this article. Procedures described in the literature were adapted for use under the simple conditions available in undergraduate laboratories and were selected on the basis of Green Chemistry principles and practicality of synthesis. The reactions are easy to carry out and all products are readily isolated as crystalline solids with yields ranging from moderate to high.

In recent years, the introduction of the Green Chemistry concepts in undergraduate chemistry classes has been intensively pursued. In this regard, the two-step preparation of Epoxone (an organocatalyst developed by Shi & col.) from commercial D-fructose, through ketalization of vicinal diols followed by oxidation of a sterically congested secondary alcohol, involves important topics in Organic Chemistry and employs inexpensive and nontoxic reagents. The reactions are easy to perform and the products from both steps are readily obtained as crystalline solids after simple procedures, thus facilitating their chemical characterization.

Este trabalho apresenta um método simples, rápido e eficiente para a desacetilação de ribonucleosídeos acetilados, a partir de metanólise catalisada por trietilamina em meio aquoso. As transformações assistidas por micro-ondas favoreceram sensivelmente a velocidade de reação e forneceram os nucleosídeos desprotegidos em altos rendimentos e sob condições brandas. Além de tolerar a presença de diversos grupos funcionais e de fornecer produtos com alto grau de pureza, esta nova metodologia utiliza reagentes de baixo custo e toxicidade.

A straightforward methodology for deacetylation of protected ribonucleosides was developed based on triethylamine-catalyzed solvolysis in aqueous methanol. Reactions are completed in a few minutes under microwave irradiation and the free nucleosides are obtained in high yield after simple evaporation of volatiles. Other important features include the involvement of readily available reagents and the compatibility with diverse functional groups, which make this process very attractive for broad application.

This article surveys a selection of the most recent advances in aziridine synthesis. Novel synthetic methods and new insights into existing methodologies for the selective construction of the title compounds reported in the past decade are discussed in terms of synthetic applicability and environmentally benign conditions. Mechanisms involving stereoselective preparation of structurally diverse aziridines are also presented in order to highlight the most important issues associated with the synthesis of these versatile building blocks.

This article provides an overview on the recent achievements to combat Gram-positive bacteria and the mechanisms related to antimicrobial activity and bacterial resistance. Selected synthetic methodologies to access structurally diverse bioactive compounds are presented in order to emphasize the most important substances currently developed to overcome multiresistant strains. The main properties of vancomycin and related glycopeptide antibiotics are also discussed as a background to understanding the design of new chemotherapeutic agents.

gamma-Hydroxy-alpha-diazo-beta-ketoesters are key intermediates in the chemistry of penicilin-based antibiotics and natural products. The method developed here for the synthesis of ethyl 2-diazo-4-hydroxy-3-oxo-butanoate 17 (in two steps from the diazo mercurial 2) compares very favorably with those reported in the literature for similar compounds. The Rh2(OAc)4-mediated intramolecular OH-insertion reaction of the diazo hydroxy ester 17 was investigated, furnishing the oxetan-3-one-2-carboxilate 18 in good yield. When the diazo ester lacks a free hydroxyl group as in the case of the phenoxy diazo ester 11 an intramolecular CH-insertion takes place, affording the 2H-chromene 20 in almost quantitative yield. The behavior of other functionalized diazo esters towards Rh2(OAc)4 was also investigated.

3(2H)-Furanona-2-carboxilatos têm sido preparadas em bons rendimentos e seletividade moderada (d.e. ca 60%), a partir da reação de inserção de O-H intramolecular de delta-hidroxi-alfa-diazoésteres catalisada por Rh2(OAc)4. Observou-se que as furanonas 2,5-cis substituídas são formadas inicialmente na reação, sofrendo epimerização quando submetidas à cromatografia em sílica gel, fornecendo os isômeros 2,5-trans correspondentes. A decomposição de gama-azido-delta-hidroxi-alfa-diazoestéres catalisada por Rh2(OAc)4 também forneceu 3(2H)-furanona-2-carboxilatos. Estes compostos são formados a partir de transformações sequenciais, envolvendo primeiramente uma reação de inserção de O-H intramolecular, seguido de um rearranjo sigmatrópico concertado [3,3] do intermediário alil azida.

The Rh2(OAc)4 catalyzed intramolecular O-H insertion reaction of delta-hydroxy-alpha-diazoesters affords 3(2H)-furanone-2-carboxylates in good yield but with moderate selectivity (d.e. ca 60%). The initially formed 2,5-substituted cis-furanones were found to epimerize to the corresponding 2,5-trans isomers when subjected to silica gel chromatography. The Rh2(OAc)4 catalyzed decomposition of gamma-azido-delta-hydroxy-alpha-diazoesters also furnished 3(2H)-furanone-2-carboxylates. These compounds are derived by a sequential O-H insertion reaction followed by a concerted [3,3]-sigmatropic shift of the allylic azide intermediate.