Characterization of Carbonyl–Phenol Adducts Produced by Food Phenolic Trapping of 4-Hydroxy-2-hexenal and 4-Hydroxy-2-nonenal
摘要:
4-Hydroxy-2-alkenals disappear in the presence of food phenolics (i.e., cathechin or quercetin), and the corresponding carbonyl-phenol adducts are produced. In an attempt to identify structure(s) of formed adducts, the reactions between model phenolics (resorcinol, 2-methylresorcinol, orcinol, and 2,5-dimethylresorcinol) and hydroxyalkenals (4-hydroxy-2-hexenal and 4-hydroxy-2-nonenal) were studied and the produced adducts were isolated by column chromatography and unambiguously characterized by one- and two-dimensional nuclear magnetic resonance and mass spectrometry as dihydrobenzofuranols (1), chromane-2,7-diols (2), and 2H-chromen-7-ols (3). These compounds were mainly produced at slightly basic pH values and moderate temperatures. Their activation energies (E-a) of formation were similar to 25 kJ mol(-1) for adducts 1,similar to 32 kJ mol(-1) for adducts 2, and similar to 38 kJ mol(-1) for adducts 3. A reaction pathway that explains their formation is proposed. All of these results confirm that, analogously to other lipid-derived carbonyl compounds, phenolics can trap 4-hydroxy-2-alkenals in an efficient way. Obtained results provide the basis for the potential detection of carbonyl-phenol adducts derived from hydroxyalkenals in food products.
Design of and Mechanistic Studies on a Biomimetic Iron-Imidazole Catalyst System for Epoxidation of Olefins with Hydrogen Peroxide
作者:Kristin Schröder、Stephan Enthaler、Bianca Bitterlich、Thomas Schulz、Anke Spannenberg、Man Kin Tse、Kathrin Junge、Matthias Beller
DOI:10.1002/chem.200802731
日期:2009.5.25
One step further in bio‐inspired catalytic epoxidation reactions was made in investigations on iron/imidazole catalyst systems (see the crystal of one example) with hydrogenperoxide as the terminal oxidant, in which it was shown for the first time that defined iron–imidazole complexes are capable of epoxidizing challenging aliphatic olefins. X‐ray studies, UV/Vis titrations, and NMR studies were carried
An improved methyltrioxorhenium-catalyzed epoxidation of alkenes with hydrogen peroxide
作者:Shigekazu Yamazaki
DOI:10.1039/b705276f
日期:——
Methyltrioxorhenium (MTO)-catalyzed epoxidation of alkenes with H(2)O(2) has been significantly improved by using 3-methylpyrazole as an additive. A system consisting of 35% H(2)O(2) and MTO-3-methylpyrazole in CH(2)Cl(2) catalyzes the epoxidation of various alkenes in excellent yields. The catalytic activity of MTO-3-methylpyrazole surpasses MTO-pyrazole and MTO-pyridine catalysts. Quantitative yields
An efficient organic solvent-free methyltrioxorhenium-catalyzed epoxidation of alkenes with hydrogen peroxide
作者:Shigekazu Yamazaki
DOI:10.1016/j.tet.2008.07.033
日期:2008.9
an efficient catalyticsystem for epoxidation of alkenes with aqueous 35% H2O2 in excellent yields under organic solvent-free conditions. The yields of epoxides by the organic solvent-free epoxidation are comparable to those using CH2Cl2 as the organic solvent. The epoxidations of simple alkenes under organic solvent-free conditions are slower than those in CH2Cl2, while the epoxidations of alkenols
Boronic acid-catalysed C-3 selective ring opening of 3,4-epoxy alcohols with thiophenols and thiols
作者:Hongqing Yao、Jiawei Liu、Chuan Wang
DOI:10.1039/c8ob02141d
日期:——
In this protocol we described a boronic acid-catalysed C-3selectiveringopening of 3,4-epoxy alcohols with thiophenols and thiols as nucleophiles. This diastereo- and enantiospecific reaction provides an efficient entry to prepare a variety of hydroxyl sulfides. Through the directing effect of the hydroxyl group, nucleophilic attack on the C-3 position of the epoxide moiety is favoured. It can be