Asymmetric oxidation of 2-(arylsulfenyl)pyrroles
The asymmetric oxidation of prochiral 2-(arylsulfenyl)pyrroles has been investigated. A marked electronic effect within the substrate significantly influenced the degree of enantioselectivity obtai...
Planar Chiral Flavinium Salts - Prospective Catalysts for Enantioselective Sulfoxidation Reactions
A novel planar chiral flavinium salt, 3-benzyl-5-ethyl-10-(8-phenylnaphthalen-1-yl)isoalloxazinium perchlorate (2b), which bears a phenyl cap that covers one side of the isoalloxazinium skeleton plane, has been prepared as a potential catalyst for the enantioselective H 2 O 2 oxidation of sulfides. The rate of H 2 O 2 oxidation of sulfides in the presence of racemic 2b is comparable to that of the reaction catalysed by 5-ethyl-3,10-dimethylisoalloxazinium perchlorate, which indicates that the bulky shielding substituent does not influence the catalytic activity of the flavinium unit. The turnover frequency for the oxidation of thioanisole with hydrogen peroxide with 2b is 870 h -1 . The enantiomerically pure salts (+)-2b and (―)-2b were prepared from the pure enantiomers (+)-3b and (―)-3b of 3-benzyl-10-(8-phenylnaphthalen-1-yl)isoalloxazine (3b) obtained by HPLC separation of racemic 3b on a chiral stationary phase. The enantiomerically pure salts (+)-2b and (―)-2b catalyse the H 2 O 2 oxidation of para-substituted thioanisoles with enantiomeric excesses of 34-44 %. The highest enantioselectivity (54 % ee) was observed in the oxidation of methyl naphthyl sulfide.
Essential Oil Profiles of 168 Perilla Cultivars by Head Space Solid Phase Micro-extraction Gas Chromatography Mass Spectrometry
Abstract In order to comprehensively elucidate the chemical biosynthesis in Perillla (commonly used in traditional herbal medicine), an untargeted analysis based on Gas chromatography-Mass spectrometry was done to reveal the metabolites from 168 different species of Perilla, with 73 components were identified. The results based on the 168 samples, which can be classified into five chemotypes, reveals that different genetic background have a significant influence on the metabolic synthesis of Perilla. The results of heat map for the components of different species and the principal component analysis are implying that the Perilla chemotypes are clustered for characteristic compounds. This study, which used optimized solid-phase microextraction conditions to investigate volatile oil composition, expanded our knowledge of metabolic pathways in Perilla. The differences between chemotypes provide a scientific basis for distinguishing between Perilla species, which not only can improve the testing standards for essential oils from Perilla herbs, but also can be beneficial to Perilla breeding.