Montmorellonite Clays Catalysis Ix1: A Mild and Efficient Method for Removal of Tetrahydropyranyl Ethers

From Conventional Lewis Acids to Heterogeneous Montmorillonite K10: Eco-Friendly Plant-Based Catalysts Used as Green Lewis Acids

The concept of green chemistry began in the USA in the 1990s. Since the publication of the 12 principles of this concept, many reactions in organic chemistry have been developed, and chemical products have been synthesized under environmentally friendly conditions. Lewis acid mediated synthetic transformations are by far the most numerous and best studied. However, the use of certain Lewis acids may cause risks to environmental and human health. This Review discusses the evolution of Lewis acid catalyzed reactions from a homogeneous liquid phase to the solid phase to yield the expected organic molecules under green, safe conditions. In particular, recent developments and applications of biosourced catalysts from plants are highlighted.

Effect of isouronium/guanidinium substitution on the efficacy of a series of novel anti-cancer agents

Considering our hypothesis that the guanidinium moiety in the protein kinase type III inhibitor 1 interacts with a phosphate of ATP within the hinge region, the nature of the interactions established between a model isouronium and the phosphate groups of ATP was computationally analysed indicating that an isouronium derivative of 1 will interact in a similar manner with ATP. Thus, a number of compounds were prepared to assess the effect of the guanidinium/isouronium substitution on cancer cell growth; additionally, the molecular shortening and conformational change induced by replacing the di-substituted guanidine-linker of 1 by an amide was explored. The effect of these compounds on cell viability was tested in human leukaemia, breast cancer and cervical cancer cell lines and the resulting IC50 values were compared with those of the lead compound 1. Replacement of the di-substituted guanidine-linker by an amide results in the loss of cytotoxicity; however, substitution of the mono-substituted guanidinium by an isouronium cation seems to be beneficial for cell growth inhibition. Additionally, the effect of these compounds on the MAPK/ERK pathway was studied by means of Western blotting and the results indicate that the isouronium derivative 2 decreases the levels of phosphorylated, and thus activated, ERK (pERK) both in leukaemia and breast cancer cells, whereas lead compound 1 only shows an effect on pERK levels in breast cancer cells. This confirms that both compounds could interfere with the MAPK/ERK pathway although other targets cannot be ruled out.

Acid-Washed Bentonite: A New Reagent for the Deprotection of Tetrahydropyranyl Ethers

Acid-washed (pH 4 and pH 6) bentonite earth cleaves the tetrahydropyranyl ethers to the corresponding alcohols in good yield under mild conditions.