2.6.4. Other Carbohydrate-Based Catalysts 3976 2.7. Carbocyclic Ketones 3977 2.8. Ketones with an Attached Chiral Moiety 3979 3. Chiral Iminium Salt-Catalyzed Epoxidation 3979 3.

Organocatalytic Oxidation. Asymmetric Epoxidation of Olefins Catalyzed by Chiral Ketones and Iminium Salts

An efficient ketone-catalyzed asymmetric epoxidation using hydrogen peroxide (H 2 O 2 ) as primary oxidant

Epoxides are very important building blocks in organic synthesis.1 Dioxiranes, either isolated or generated in situ, have been shown to be extremely versatile epoxidation reagents.2-6 In nearly every case, the generation of dioxiranes uses potassium peroxomonosulfate (KHSO5) as oxidant (Scheme 1).7,8 During our recent study on asymmetric epoxidation using the fructose-derived ketone (1), we found that hydrogen peroxide (H2O2) could be used as primary oxidant in combination with acetonitrile (eq 1).6l High yields and ee’s were obtained for a number of

An efficient ketone-catalyzed epoxidation using hydrogen peroxide as oxidant.

Asymmetric epoxidation using hydrogen peroxide (H2O2) as primary oxidant

Cortisol detection in saliva is of great interest for the diagnosis of various disease states and the monitoring of stress in humans. Currently, measurements are performed predominantly by radioimmunoassay (RIA) which is expensive, labour intensive, uses hazardous radioisotopes and involves extensive delays in obtaining results. A rationally designed cortisol-linker conjugate allowing high assay sensitivity was employed as a coating antigen in a microfluidic surface plasmon resonance (SPR) biosensor immunoassay for the ultrasensitive and rapid detection of salivary cortisol. Detection of cortisol is by competitive immunoassay using a secondary antibody for signal enhancement. The method requires no chemical extraction or complex sample pre-treatment despite high saliva viscosity. The cortisol assay was optimized for maximum sensitivity in buffer before being adapted for the salivary matrix, where it showed a limit of detection of 49 pg/mL. The results showed good correlation to RIA (r = 0.94). The biosensor assays showed an inter-assay coefficient of variation (CV) of 13.5% and recoveries close to 100%. The covalently immobilized sensor surface provided stable responses for more than 140 binding and regeneration cycles, enabling re-use. Cortisol in saliva was detected across the physiologically relevant range using the SPR immunobiosensor by employing a rationally designed assay format including signal enhancement for maximum sensitivity. The system can handle saliva matrix effects by use of chemical treatment during the assay to reduce non-specific binding to sensor surfaces. This sensor system provides an automated, high sensitivity analytical tool capable of yielding results in approximately 15 min. This biosensor could potentially be used for active stress-monitoring and in the diagnosis of disease.

Rapid ultrasensitive measurement of salivary cortisol using nano-linker chemistry coupled with surface plasmon resonance detection

Diastereoselective epoxidation of olefins by organo sulfonic peracids, II

Sulfonic peracids — III. Heteroatom oxidation and chemoselectivity

The reaction of ketones (acetone, 1,1,1-trifluoropropan-2-one) with the oxidation system (arenesulfonyl)imidazole (2)/H(2)O(2)/NaOH permits the in situ generation of the corresponding dimethyl- and methyl(trifluoromethyl)dioxirane in various solvents. This has been established by the chemoselective oxidation of azomethines 6, the diastereoselective oxidation of cholesterol (12), and (18)O-labeling experiments. Because only 5 equiv of ketone are used, the dioxirane oxidation pathway appears to be virtually exclusive one in this system. One example for the nonaqueous in situ generation of dimethyldioxirane (1a) is given.

S. Liebsch

Papers

Diastereoselective epoxidation of olefins by organo sulfonic peracids, II

Sulfonic peracids — III. Heteroatom oxidation and chemoselectivity

Organo Sulfonic Peracids. 4.(1) The Reaction of Arenesulfonylimidazoles with H(2)O(2) in the Presence of Ketones. A New Entry to Dioxiranes.

Diastereoselective epoxidation and bishydroxylation of cyclic tert-butyl allyl peroxides

New principles in metallomesogen structure–magnetism correlations