Cyclic peroxides by intramolecular peroxymercuration of unsaturated hydroperoxides

Lewis Acids and Heteropoly Acids in the Synthesis of Organic Peroxides

Organic peroxides are an important class of compounds for organic synthesis, pharmacological chemistry, materials science, and the polymer industry. Here, for the first time, we summarize the main achievements in the synthesis of organic peroxides by the action of Lewis acids and heteropoly acids. This review consists of three parts: (1) metal-based Lewis acids in the synthesis of organic peroxides; (2) the synthesis of organic peroxides promoted by non-metal-based Lewis acids; and (3) the application of heteropoly acids in the synthesis of organic peroxides. The information covered in this review will be useful for specialists in the field of organic synthesis, reactions and processes of oxygen-containing compounds, catalysis, pharmaceuticals, and materials engineering.

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

The synthesis of complex cyclic compounds is extremely challenging for organic chemists. Many transition-metal-salt-mediated cyclizations are reported in literature. Hg(II) salts have been successfully employed in cyclizations to form complex heterocyclic and carbocyclic structures that are impossible to synthesize with other transition metal salts. In this review, we have summarized cyclization reactions that are performed with Hg(II) salts. These salts are also successfully applied in stoichiometric or catalytic amounts to form complex cyclic structures and natural products.

Beyond prostaglandins--chemistry and biology of cyclic oxygenated metabolites formed by free-radical pathways from polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs) are important constituents in all organisms. They fulfil many functions, ranging from modulating the structure of membranes to acting as precursors of physiologically important molecules, such as the prostaglandins, which for a long time were the most prominent cyclic PUFA metabolites. However, since the beginning of the 1990s a large variety of cyclic metabolites have been discovered that form under autoxidative conditions in vivo to a much larger extent than do prostaglandins. These compounds--isoprostanes, neuroprostanes, phytoprostanes, and isofurans--proved subsequently to be ubiquitous in nature. They display a wide range of biological activities, and isoprostanes have become the currently most reliable indicators of oxidative stress in humans. In a relatively short time, the structural variety, properties, and applications of the autoxidatively formed cyclic PUFA derivatives have been uncovered.

Discovery of lipid peroxidation products formed in vivo with a substituted tetrahydrofuran ring (isofurans) that are favored by increased oxygen tension

Free radicals have been implicated in the pathogenesis of an increasing number of diseases. Lipids, which undergo peroxidation, are major targets of free radical attack. We report the discovery of a pathway of lipid peroxidation that forms a series of isomers in vivo that are characterized by a substituted tetrahydrofuran ring structure, termed isofurans (IsoFs). We have proposed two distinct pathways by which IsoFs can be formed based on 18O2 and H2 18O labeling studies. Measurement of F2-isoprostanes (IsoPs), prostaglandin F2-like compounds formed nonenzymatically as products of lipid peroxidation, is considered one of the most reliable approaches for assessing oxidative stress status in vivo. However, one limitation with this approach is that the formation of IsoPs becomes limited at high oxygen tension. In contrast, the formation of IsoFs becomes increasingly favored as oxygen tension increases. IsoFs are present at readily detectable levels in normal fluids and tissues, and levels increase dramatically in CCl4-treated rats, an animal model of oxidant injury. The ratio of IsoFs to IsoPs in major organs varies according to normal steady-state tissue oxygenation. In addition, IsoFs show a marked increase early in the course of hyperoxia-induced lung injury, whereas IsoPs do not significantly increase. We propose that combined measurement of IsoFs and IsoPs should provide a more reliable index of oxidant stress severity than quantification of either alone because of the opposing modulation of the two pathways by oxygen tension, which can vary widely in different organs and disease states.